Toothed belt and method for manufacturing same

Abstract

The present invention relates to a toothed belt wherein an adhesive rubber layer contains a crosslinked product of a first rubber composition containing a first polymer component and silica, the first polymer component contains a first ethylene-α-olefin elastomer, the proportion of the silica is 50-130 parts by mass per 100 parts by mass of the first polymer component, a tooth rubber layer and a back rubber layer contain a crosslinked product of a second rubber composition containing a second ethylene-α-olefin elastomer, and the rubber hardness of the crosslinked product of the first rubber composition is greater than the rubber hardness of the crosslinked product of the second rubber composition.

Description

Toothed belt and method for manufacturing the same

[0001] The present invention relates to a toothed belt in which the tooth surface (inner circumferential surface or the side that meshes with a toothed pulley) is covered with toothed fabric, and to a method for manufacturing the same.

[0002] Power transmission belts are broadly classified into friction belts and meshing belts. Examples of friction belts include flat belts, V-belts, and V-ribbed belts, while an example of a meshing belt is a toothed belt. A toothed belt has a back portion with a core wire embedded approximately parallel to the belt's circumference, teeth arranged at predetermined intervals in the belt's circumference, and a toothed fabric covering the surface of the teeth. The teeth of a toothed belt transmit power by engaging with a pulley that has grooves opposite to the teeth. Toothed belts are used in industrial machinery, internal combustion engines in automobiles (such as for camshaft drives), and rear-wheel drives in motorcycles, taking advantage of their ability to reliably transmit power even under high loads without slippage between the pulley and the belt. For example, Japanese Patent Publication No. 2017-211084 (Patent Document 1) discloses a toothed belt in which an ethylene-α-olefin elastomer such as ethylene-propylene-diene terpolymer (EPDM) is used for the tooth rubber.

[0003] In recent years, there has been a growing need for toothed belts that can withstand even higher loads. An important factor in the durability of toothed belts is the rigidity (deformation resistance) of the teeth. When the teeth repeatedly deform due to contact with the toothed pulley during the meshing process, it can lead to malfunctions such as tooth skipping (jumping) causing poor meshing, or tooth chipping due to cracks at the tooth root. Tooth chipping is a type of failure in which a tooth falls off the belt body. It is thought that this occurs when repeated deformation of the teeth concentrates stress at the tooth root, causing a tiny crack to form at the tooth root, and then that crack to grow. In particular, when toothed belts are used under high load conditions, the stress concentrated at the tooth root becomes especially large, making it easy for cracks to form starting from the tooth root and leading to tooth chipping.

[0004] Therefore, to improve tooth chipping resistance, it is effective to increase the rigidity of the tooth (hardness and modulus, etc.) to suppress tooth deformation, and various formulations are being considered to increase the rigidity of the rubber composition (tooth rubber) that forms the tooth.

[0005] For example, Japanese Patent Publication No. 2023-018654 (Patent Document 2) discloses a toothed belt in which a balanced configuration is achieved that can achieve both rigidity (deformability) and flexibility (flexibility) of the teeth by using a rubber composition containing HNBR containing an unsaturated carboxylic acid metal salt in the tooth rubber.

[0006] Japanese Patent Publication No. 2017-211084 Japanese Patent Publication No. 2023-018654

[0007] The toothed belt disclosed in Patent Document 2 uses expensive materials to increase the rigidity of the teeth, resulting in high manufacturing costs, while using a less rigid material for the back to obtain flexibility. Therefore, the teeth and back must be manufactured independently, and the manufacturing process consists of two stages: a pre-forming process (a process in which only the teeth are formed in advance) and a main forming process, resulting in low productivity. Consequently, while the toothed belt in Patent Document 2 has excellent performance, it is not productive or economical. In other words, the rigidity required for the belt and the flexibility required for processability and bending are inversely related, and manufacturing a toothed belt with such characteristics inevitably leads to high material and manufacturing costs.

[0008] Therefore, the object of the present invention is to provide a toothed belt and a method for manufacturing the same that is highly productive and economical, and has excellent resistance to tooth breakage.

[0009] As a result of diligent research to achieve the above objectives, the present inventors have found that by adopting the following embodiment 1, the resistance of tooth breakage of toothed belts can be improved with high productivity and cost-effectiveness, and have completed the present invention.

[0010] The present invention includes the following embodiments.

[0011] Aspect 1 A toothed belt comprising: a back portion in which a core wire extending along a belt circumferential direction is embedded; and a plurality of tooth portions formed on an inner circumferential surface of the back portion at intervals in the belt circumferential direction, the toothed belt including a back rubber layer forming the back portion, a tooth rubber layer forming the tooth portions, tooth fabric formed on a surface of the tooth portions, and an adhesive rubber layer interposed between the tooth rubber layer and the tooth fabric, wherein the adhesive rubber layer includes a crosslinked product of a first rubber composition containing a first polymer component and silica, the first polymer component contains a first ethylene-α-olefin elastomer, a proportion of the silica is 50 to 130 parts by mass based on 100 parts by mass of the first polymer component, the tooth rubber layer and the back rubber layer include a crosslinked product of a second rubber composition containing a second ethylene-α-olefin elastomer, and a rubber hardness of the crosslinked product of the first rubber composition is higher than a rubber hardness of the crosslinked product of the second rubber composition.

[0012] Aspect 2 The toothed belt according to Aspect 1, wherein the rubber hardness of the crosslinked product of the first rubber composition is 50 or more in terms of type D hardness.

[0013] Aspect 3 The toothed belt according to Aspect 1 or 2, wherein a 5% modulus of the crosslinked product of the first rubber composition in the belt circumferential direction is 3 MPa or more.

[0014] Aspect 4 The toothed belt according to any one of Aspects 1 to 3, wherein the first ethylene-α-olefin elastomer contains an ethylene-α-olefin-diene terpolymer.

[0015] Aspect 5 The toothed belt according to any one of Aspects 1 to 3, wherein the first ethylene-α-olefin elastomer includes an ethylene-α-olefin-diene terpolymer and an ethylene-α-C ４－８ olefin copolymer.

[0016] Aspect 6 The toothed belt according to Aspect 5, wherein a mass ratio of the ethylene-α-olefin-diene terpolymer to the ethylene-α-C ４－８ olefin copolymer satisfies the following relationship: former / latter = 80 / 20 to 20 / 80.

[0017] Aspect 7 The ethylene-α-C４－８ The olefin copolymer has a specific gravity of 0.88 or higher, ethylene-α-C ５－８ A toothed belt according to embodiment 5 or 6, which is an olefin copolymer.

[0018] Embodiment 8: The toothed belt according to Embodiment 4 or 5, wherein the diene content of the ethylene-α-olefin-diene ternary copolymer is 3% by mass or more.

[0019] Embodiment 9 A toothed belt according to any one of Embodiments 1 to 8, wherein the first rubber composition contains an unsaturated carboxylic acid metal salt, and the proportion of the unsaturated carboxylic acid metal salt is 50 parts by mass or more per 100 parts by mass of the first polymer component.

[0020] Embodiment 10 A toothed belt according to any one of Embodiments 1 to 9, wherein the average thickness of the adhesive rubber layer is 0.3 to 1 mm.

[0021] Embodiment 11: A toothed belt according to any one of Embodiments 1 to 10, wherein the X value of the core wire arrangement density is 15% or more.

[0022] Embodiment 12 A method for manufacturing a toothed belt according to any one of Embodiments 1 to 11, comprising a crosslinking molding step of crosslinking an uncrosslinked molded body obtained by laminating a tooth cloth precursor, an adhesive rubber layer precursor, a core wire precursor, and precursors for the tooth rubber layer and the back rubber layer.

[0023] In this application, the numerical range represented by "A to B" means "A or greater and B or less," and is used to include the values ​​A and B at both ends of that range.

[0024] Furthermore, in this application, "inner surface" means the "inner surface of the belt" in each layer or belt, and "outer surface" means the "outer surface of the belt" in each layer or belt.

[0025] In this invention, the adhesive rubber layer interposed between the tooth cloth and the tooth rubber layer of a toothed belt, in which the polymer component includes ethylene-α-olefin elastomer and the rubber compositions of the back rubber layer and the tooth rubber layer are the same, is formed of a crosslinked rubber composition containing 50 to 130 parts by mass of silica per 100 parts by mass of the polymer component, and its rubber hardness is adjusted to be greater than that of the tooth rubber layer. Therefore, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency. In particular, the toothed belt of this invention can be manufactured by an inexpensive and highly productive method that does not require preforming, and also has excellent processability. Furthermore, the toothed belt of this invention also has excellent durability (running life).

[0026] Figure 1 is a schematic partial cross-sectional perspective view showing an example of the toothed belt of the present invention. Figure 2 is a schematic cross-sectional view of the toothed belt of Figure 1. Figure 3 is a schematic diagram illustrating the method for measuring the X value (%) of the arrangement density. Figure 4 is a schematic diagram illustrating the measurement method for the tooth chipping resistance test of the embodiment.

[0027] [Toothed Belt] Below, an example of a toothed belt of the present invention will be described in detail, with reference to the attached drawings as necessary. In the following description, the same reference numeral may be used for elements (or components) that are identical or have common functions.

[0028] Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt of the present invention, and Figure 2 is a schematic cross-sectional view of the toothed belt of Figure 1.

[0029] The toothed belt 1 in this example is an endless interlocking transmission belt, comprising a back portion 1c in which a core wire 5 extending in the belt circumferential direction (longitudinal direction) is embedded, and a plurality of teeth 1a provided at predetermined intervals on the inner circumferential surface of the back portion 1c and extending in the belt width direction, with the belt surface (inner circumferential surface) on the teeth side being made of tooth fabric 2. The back portion 1c is formed of a back rubber layer 6, and this back rubber layer 6 forms the outer circumferential surface of the belt. Furthermore, the teeth 1a are formed of a tooth rubber layer 4, an adhesive rubber layer 3 covering the inner circumferential surface of the tooth rubber layer 4, and the tooth fabric 2 covering the adhesive rubber layer 3 and forming the inner circumferential surface of the belt.

[0030] Between adjacent tooth portions 1a, there is a flat tooth root portion 1b, and the tooth portions 1a and tooth root portions 1b are formed alternately along the circumferential direction (belt longitudinal direction) on the inner surface of the belt. That is, the surface of the tooth portion 1a and the inner surface of the back portion 1c (i.e., the surface of the tooth root portion 1b) are made of a single continuous tooth fabric 2.

[0031] In the embodiment shown in Figure 1, the tooth fabric constituting the surface of the tooth portion is a constituent element of the tooth portion, while the tooth fabric constituting the surface of the tooth root portion is a constituent element of the back portion. Furthermore, each tooth fabric constituting the tooth portion is part of a continuous tooth fabric (part of tooth fabric 2 in Figure 2).

[0032] In this example, the tooth portion 1a has a roughly trapezoidal cross-sectional shape in the circumferential direction of the belt. In the tooth portion 1a, the tooth rubber layer 4 forms the main part of the tooth portion, and the adhesive rubber layer 3 is a thin layer formed along the tooth fabric 2.

[0033] Furthermore, in the tooth root portion 1b, an adhesive rubber layer acting as a surface rubber layer and a back rubber layer acting as an internal rubber layer are interposed between the tooth fabric 2 and the core wire 5 (not shown). The thickness of the adhesive rubber layer and the back rubber layer in the tooth root portion is extremely thin.

[0034] The core wires 5 extend in the longitudinal direction (circumferential direction) of the belt and are arranged at intervals in the width direction of the belt. The rubber composition constituting the back rubber layer 6 and the rubber composition constituting the tooth rubber layer 4 have the same composition, and the gaps between adjacent core wires 5 are also formed of the rubber composition constituting the back rubber layer 6.

[0035] Toothed belts are used in high-load power transmission applications such as industrial machinery, internal combustion engines in automobiles, and rear-wheel drives in motorcycles. For example, when a toothed belt is wrapped between a drive pulley (toothed pulley) and a driven pulley (toothed pulley), power is transmitted from the drive pulley to the driven pulley as the drive pulley rotates.

[0036] The toothed belt of the present invention is not limited to the form and structure shown in Figures 1 and 2. For example, the multiple teeth only need to be able to mesh with a toothed pulley, and the cross-sectional shape of the teeth (the cross-sectional shape of the toothed belt in the circumferential direction) is not limited to a substantially trapezoidal shape, but may be, for example, semicircular, semielliptical, polygonal [triangle, quadrilateral (rectangle, trapezoid, etc.)], etc. Of these, a trapezoidal or substantially trapezoidal shape is preferred from the viewpoint of meshing and power transmission.

[0037] In the toothed belt of the present invention, the average distance between the centers of adjacent teeth in the circumferential direction (tooth pitch, see Figure 2) can be selected from a range of approximately 2 to 25 mm, depending on the shape of the toothed pulley, etc. The tooth pitch value corresponds to the scale of the teeth (length of the teeth in the belt circumferential direction, and tooth height). That is, the larger the tooth pitch, the larger the scale of the teeth becomes. The tooth pitch is preferably 3 to 20 mm, more preferably 4 to 15 mm, more preferably 5 to 12 mm, and most preferably 6 to 10 mm.

[0038] Furthermore, the average tooth height of the teeth is, for example, 40-70%, preferably 50-65%, of the average value of the total belt thickness [thickness (distance or height) from the back surface (outer surface) to the tooth crown].

[0039] In this application, as shown in Figure 2, the average tooth height of the teeth refers to the average height of the protruding teeth on the inner circumferential surface of the belt [the average value of the thickness (distance or height) from the tooth root surface to the tooth apex].

[0040] In the toothed belt of the present invention, the teeth include a tooth cloth disposed on the surface side (inner surface side), a tooth rubber layer for forming the teeth, and an adhesive rubber layer interposed between the tooth cloth and the tooth rubber layer. In the toothed belt of the present invention, the polymer component contains an inexpensive ethylene-α-olefin elastomer, and the rubber composition of the back rubber layer and the tooth rubber layer are the same, and it can be manufactured by a simple and inexpensive method that does not require pre-forming. Nevertheless, because a high-hardness rubber composition is used for the adhesive rubber layer interposed between the tooth cloth and the tooth rubber, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency. Specifically, by forming the adhesive rubber layer with a crosslinked rubber composition that has been hardened by containing a large amount (50 to 130 parts by mass) of silica per 100 parts by mass of polymer component, the tooth chipping resistance of the toothed belt can be improved with high processability. In this invention, the crosslinked rubber composition of the adhesive rubber layer contains a large amount of silica (50 to 130 parts by mass) per 100 parts by mass of polymer component, thereby increasing the hardness (elastic modulus, modulus) of the adhesive rubber composition and improving the rigidity of the tooth surface. As a result, the resistance of tooth chipping of the toothed belt is improved. On the other hand, if the amount of silica exceeds 130 parts by mass, the processability is impaired, making it difficult to manufacture the toothed belt.

[0041] (Adhesive rubber layer) The adhesive rubber layer includes a crosslinked product of a first rubber composition containing a first polymer component and silica.

[0042] (1A) First polymer component The first polymer component includes an ethylene-α-olefin-diene terpolymer as the first ethylene-α-olefin elastomer, or an ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ It is preferable that the material contains an olefin copolymer.

[0043] In ethylene-α-olefin-diene terpolymers, the α-olefins used to form the α-olefin units include, for example, propylene, butene, pentene, methylpentene, hexene, octene, and other chain-like α-C ３－１２ Examples include olefins. Among these α-olefins, propylene, butene, and other α-C ３－４ Olefins are preferred.

[0044] As the diene monomer for forming a diene unit, non-conjugated diene monomers are usually used. Examples of non-conjugated diene monomers include dicyclopentadiene, methylene norbornene, ethylidene norbornene, 1,4-hexadiene, cyclooctadiene and the like. Among these diene monomers, ethylidene norbornene and 1,4-hexadiene (especially ethylidene norbornene) are preferred.

[0045] Representative ethylene-α-olefin-diene terpolymers include, for example, ethylene-propylene-non-conjugated diene terpolymer (EPDM), ethylene-1-butene-non-conjugated diene copolymer (EBDM), ethylene-1-octene-non-conjugated diene copolymer (EODM) and other ethylene-α-C ３－８ olefin-diene terpolymers.

[0046] These ethylene-α-olefin-diene terpolymers can be used alone or in combination of two or more. Among these, from the viewpoint of excellent heat resistance, cold resistance and weather resistance, ethylene-α-C ３－６ olefin-diene terpolymers such as EPDM and EBDM are preferred, and ethylene-α-C ３－４ olefin-diene terpolymer is particularly preferred. Therefore, the proportion of ethylene-α-C ３－４ olefin-diene terpolymer may be 50% by mass or more based on the total amount of the ethylene-α-olefin-diene terpolymer, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass or more), and may be 100% by mass (only ethylene-α-C ３－４ olefin-diene terpolymer).

[0047] In the ethylene-α-olefin-diene terpolymer, the ethylene content (percentage of ethylene units) may be 30% by mass or more, for example, 30 to 80% by mass, preferably 35 to 70% by mass, more preferably 40 to 65% by mass, more preferably 50 to 60% by mass, and most preferably 53 to 57% by mass. If the ethylene content is too low, the wear resistance of the toothed belt may decrease, and if it is too high, the processability may decrease.

[0048] In this application, the ethylene content refers to the mass ratio of ethylene units in the total units constituting the ethylene-α-olefin-diene ternary copolymer, and can be measured by conventional methods, but may also be a mass ratio based on ethylene as a monomer.

[0049] Furthermore, in this application, when there are multiple types of ethylene-α-olefin-diene ternary copolymers, the ethylene content refers to the average value based on the mass ratio (average ethylene content). That is, the average ethylene content is the sum of the products of the ethylene content and mass fraction of each ethylene-α-olefin-diene ternary copolymer.

[0050] In ethylene-α-olefin-diene terpolymers, ethylene and α-olefin (especially α-C ３－４ The ratio (mass ratio) of the olefin to the olefin is 30 / 70 to 90 / 10, preferably 40 / 60 to 80 / 20, more preferably 50 / 50 to 70 / 30, and more preferably 55 / 45 to 65 / 35.

[0051] In this application, the α-olefin content refers to the mass ratio of α-olefin units in the total units constituting the ethylene-α-olefin-diene ternary copolymer, and can be measured by conventional methods, but may also refer to the mass ratio based on α-olefin as a monomer.

[0052] Ethylene-α-olefin-diene terpolymer (especially ethylene-α-C ３－４The diene content (especially the ethylidene norbornene content) of the olefin-diene terpolymer may be 0.1% by mass or more (preferably 3% by mass or more, more preferably 4.5% by mass or more, and more preferably 6% by mass or more), for example, 0.1 to 15% by mass, preferably 1 to 12% by mass, more preferably 3 to 11% by mass, more preferably 4 to 10% by mass (especially 6 to 10% by mass), and most preferably 4.5 to 9% by mass (especially 8 to 9% by mass). If the diene content is too low, the crosslinking density of the rubber composition may decrease, which may reduce the rigidity (tooth surface hardness) of the tooth surface, and if it is too high, the wear resistance of the toothed belt may decrease.

[0053] In this application, the diene content refers to the mass ratio of diene monomer units in the total units constituting the ethylene-α-olefin-diene ternary copolymer, and can be measured by conventional methods, but may also be a ratio based on monomers.

[0054] The iodine value of the ethylene-α-olefin-diene ternary copolymer containing the diene monomer 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 becomes insufficient, making it prone to wear. Conversely, if the iodine value is too high, the scorch time of the rubber composition becomes shorter, making it difficult to handle and reducing its heat resistance.

[0055] In this application, the iodine value of the ethylene-α-olefin-diene ternary copolymer can be measured by conventional methods, such as infrared spectroscopy.

[0056] The Mooney viscosity [ML(1+4)125°C] of the uncrosslinked ethylene-α-olefin-diene terpolymer may be 10 or higher, for example, 10 to 80, preferably 15 to 75, more preferably 20 to 70, more preferably 25 to 68, and most preferably 30 to 65. If the Mooney viscosity is too low, the wear resistance of the toothed belt may decrease, and conversely, if it is too high, the processability may decrease.

[0057] In this application, Mooney viscosity can be measured by a method conforming to JIS K 6300-1 (2013), with test conditions being the use of an L-shaped rotor, a test temperature of 125°C, a preheating time of 1 minute, and a rotor operating time of 4 minutes. Mooney viscosity is used as an indicator of the fluidity (ease of processing) of rubber by filling a cavity with uncrosslinked ethylene-α-olefin-diene ternary copolymer so that it is in contact with a rotor having grooves on its surface, and measuring the torque required to rotate the rotor.

[0058] Furthermore, in this application, when there are multiple types of ethylene-α-olefin-diene ternary copolymers, Mooney viscosity refers to the average value based on mass ratio (average Mooney viscosity). That is, the average Mooney viscosity is the sum of the products of the Mooney viscosity and mass fraction of each ethylene-α-olefin-diene ternary copolymer.

[0059] Ethylene-α-C ４－８ In olefin copolymers, α-C ４－８ Examples of olefins include butene, pentene, methylpentene, hexene, and octene, which are chain-like α-C molecules. ４－８ Examples include olefins. These α-C ４－８ Among olefins, alpha-C olefins such as hexene and octene can improve tooth chipping resistance. ５－８ Olefins (especially α-C) ６－８ Olefins are preferred.

[0060] Typical ethylene-α-C ４－８ Examples of olefin copolymers include ethylene-butene rubber (EBM), ethylene-hexene rubber (EHM), and ethylene-octene rubber (EOM), which are ethylene-α-C ４－８ Examples include olefin binary copolymers.

[0061] These ethylene-α-C ４－８ Olefin copolymers can be used alone or in combination of two or more types. Among these, ethylene-C copolymers such as EHM and EOM can improve tooth chipping resistance. ５－８ Olefin copolymers are preferred, and ethylene-C ６－８Olefin copolymers are particularly preferred. Therefore, ethylene-C ５－８ The proportion of olefin copolymer is ethylene-α-C ４－８ It may be 50% by mass or more relative to the total olefin copolymer, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass or more), and 100% by mass (ethylene-C ５－８ (Olefin copolymer only) is also acceptable.

[0062] Ethylene-α-C ４－８ In olefin copolymers, ethylene and α-C ４－８ The ratio (mass ratio) of the olefin is former / latter = 99 / 1 to 1 / 99, preferably 95 / 5 to 5 / 95, and more preferably 90 / 10 to 10 / 90.

[0063] Furthermore, in this application, ethylene and α-C ４－８ The ratio with olefins can be measured by conventional methods, but it may also be a mass ratio based on monomers.

[0064] Ethylene-α-C ４－８ The specific gravity of the olefin copolymer may be 0.85 or higher (particularly 0.88 or higher), for example, 0.85 to 0.99, preferably 0.86 to 0.98, more preferably 0.88 to 0.97, more preferably 0.89 to 0.95, and most preferably 0.9 to 0.93. If the specific gravity is too low, there is a risk that the resistance to tooth chipping and the durability of running will decrease.

[0065] Ethylene-α-C ４－８ The melting point of the olefin copolymer may be 30°C or higher (particularly 50°C or higher), for example, 30 to 150°C, preferably 50 to 140°C, more preferably 70 to 130°C, more preferably 80 to 120°C, and most preferably 90 to 110°C. If the melting point is too low, there is a risk that the resistance to tooth chipping and the durability of the running gear will decrease.

[0066] Furthermore, in this application, ethylene-α-C ４－８ The melting point of olefin copolymers can be measured using a differential scanning calorimetry (DSC).

[0067] Ethylene-α-olefin-diene terpolymer and the ethylene-α-C４－８ The mass ratio with the olefin copolymer can be selected from a range of approximately 95 / 5 to 5 / 95, for example, 90 / 10 to 10 / 90 (particularly 80 / 20 to 30 / 70), preferably 80 / 20 to 20 / 80 (particularly 75 / 25 to 50 / 50), even more preferably 70 / 30 to 30 / 70, more preferably 70 / 30 to 40 / 60, and most preferably 60 / 40 to 45 / 55. If the ratio of ethylene-α-olefin-diene ternary copolymer is too low, the stability to temperature changes and processability may decrease, and if it is too high, the resistance to tooth chipping may decrease.

[0068] Ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ The total amount of the olefin copolymer may be 50% by mass or more in the first ethylene-α-olefin elastomer, preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. If the proportion of the total amount is too low, the first polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0069] The first ethylene-α-olefin elastomer is an ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ Examples of ethylene-α-olefin elastomers other than olefin copolymers (other ethylene-α-olefin elastomers) include, for example, ethylene-α-C ４－１２ Olefin-diene terpolymers and ethylene-α-C ９－１２ It may further contain olefin copolymers, etc.

[0070] The proportion of other ethylene-α-olefin elastomers is ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ The amount may be 100 parts by mass or less per 100 parts by mass of the total amount of the olefin copolymer, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 5 parts by mass or less.

[0071] The first ethylene-α-olefin elastomer is preferably substantially free of other ethylene-α-olefin elastomers, and more preferably is substantially free of them.

[0072] The proportion of the first ethylene-α-olefin elastomer may be 50% by mass or more of the first polymer component, preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. If the proportion of the first ethylene-α-olefin elastomer is too low, the first polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0073] The first polymer component may contain other polymer components besides the first ethylene-α-olefin elastomer.

[0074] Other polymer components include, for example, diene rubbers [natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), styrene-butadiene rubber (SBR), vinylpyridine-styrene-butadiene rubber, acrylonitrile-butadiene rubber (nitrile rubber: NBR), acrylonitrile-chloroprene rubber, hydrogenated nitrile rubber (HNBR), etc.], chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. These polymer components can be used individually or in combination of two or more.

[0075] The proportion of other polymer components may be 100 parts by mass or less per 100 parts by mass of the first ethylene-α-olefin elastomer, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 5 parts by mass or less.

[0076] The first polymer component is preferably substantially free of other polymer components, and more preferably free of expensive HNBR.

[0077] The proportion of the first polymer component may be 10% by mass or more in the first rubber composition, for example, 10 to 90% by mass, preferably 20 to 80% by mass, more preferably 30 to 60% by mass, more preferably 33 to 50% by mass, and most preferably 35 to 40% by mass. If the proportion of the first polymer component is too low, the flexibility of the toothed belt may decrease.

[0078] (1B) The first silica first rubber composition contains 50 parts by mass or more of silica (first silica) per 100 parts by mass of the first polymer component, thereby increasing the hardness (elastic modulus, modulus) of the crosslinked material of the first rubber composition, improving the rigidity of the tooth surface, and consequently improving the tooth chipping resistance of the toothed belt. Carbon black is more commonly used than silica as a filler (reinforcement) to increase the rigidity of rubber, but the inventors estimated that for the tooth chipping resistance of the toothed belt in this problem, the elastic modulus in the low strain region (e.g., 5% modulus) is more important than the elastic modulus in the high strain region (e.g., 100% modulus). By incorporating a large amount of silica, which has a higher elastic modulus in the low strain region than carbon black, the inventors succeeded in improving the tooth chipping resistance of the toothed belt.

[0079] The first type of silica includes dry silica, wet silica, and surface-treated silica. Silica can also be classified by its manufacturing method, for example, dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica. The silica may also be amorphous silica. These silicas can be used individually or in combination of two or more types. Among these silicas, silica having surface silanol groups (anhydrous silicic acid, hydrated silicic acid) is preferred, and hydrated silicic acid with many surface silanol groups exhibits strong chemical bonding with rubber components.

[0080] The first silica may be in particulate (powder) form. The average particle diameter (average primary particle diameter) of the first silica is, for example, 1 to 500 nm, preferably 3 to 300 nm, more preferably 5 to 100 nm, and more preferably 10 to 50 nm.

[0081] In this application, the average particle diameter of silica can be measured using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and can be calculated as the arithmetic mean particle diameter of an appropriate number of samples (e.g., 50 samples) by image analysis.

[0082] Furthermore, the BET specific surface area of ​​silica obtained by the BET method is, for example, 50 to 400 m². ２ / g, preferably 100 to 300m ２ / g, more preferably 150-270m ２ / g (especially 150-200m) ２ / g), more preferably 170 to 250m ２ It is / g.

[0083] In this application, the BET specific surface area of ​​filler compounding agents such as silica and carbon black refers to the specific surface area measured using nitrogen gas by the BET method.

[0084] The proportion of the first silica can be selected from a range of approximately 50 to 130 parts by mass (particularly 50 to 100 parts by mass) per 100 parts by mass of the first polymer component, for example, 55 to 120 parts by mass (particularly 70 to 110 parts by mass), preferably 60 to 100 parts by mass, more preferably 63 to 90 parts by mass, more preferably 65 to 85 parts by mass, and most preferably 70 to 80 parts by mass. Furthermore, in applications where tooth chipping resistance and durable running performance are important, the proportion of the first silica is preferably 65 to 130 parts by mass, more preferably 90 to 130 parts by mass, and more preferably 110 to 130 parts by mass per 100 parts by mass of the first polymer component. If the proportion of the first silica is too low, the tooth chipping resistance and durable running performance of the toothed belt will decrease, and if it is too high, the processability will be impaired, making it difficult to manufacture the toothed belt.

[0085] (1C) The first rubber composition contains a large amount of unsaturated carboxylic acid metal salt (first unsaturated carboxylic acid metal salt), which increases the crosslinking density in the crosslinked material of the first rubber composition, thereby improving the rigidity of the tooth surface (tooth surface hardness). In particular, by adjusting the proportion of the first silica to a specific range and adjusting the proportion of the first unsaturated carboxylic acid metal salt to a specific range, tooth chipping resistance and durable running performance can be greatly improved.

[0086] The first unsaturated carboxylate metal salt may be a compound in which an unsaturated carboxylic acid having one or more carboxyl groups is ionically bonded to a metal.

[0087] Examples of unsaturated carboxylic acids in the first unsaturated carboxylic acid metal salt include monocarboxylic acids such as (meth)acrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and monoalkyl esters of these dicarboxylic acids. These unsaturated carboxylic acids can be used alone or in combination of two or more. A preferred unsaturated carboxylic acid is (meth)acrylic acid.

[0088] Examples of metals used in the first unsaturated carboxylate metal salts include alkali metals such as sodium and potassium; polyvalent metals such as group 2 elements of the periodic table (magnesium, calcium, etc.), group 4 elements (titanium, zirconium, etc.), and group 8 to 14 elements of the periodic table (e.g., iron, cobalt, nickel, copper, zinc, aluminum, tin, lead, etc.). These metals can be used individually or in combination of two or more. Preferred metals are polyvalent metals such as group 2 elements of the periodic table (magnesium, etc.) and group 12 elements of the periodic table (zinc, etc.).

[0089] These unsaturated carboxylate metal salts can also be used individually or in combination of two or more.

[0090] As the primary unsaturated carboxylate metal salt, zinc (meth)acrylate and magnesium (meth)acrylate are preferred, zinc (meth)acrylate is more preferred, and zinc methacrylate is most preferred.

[0091] The proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 10 parts by mass or more (preferably 30 parts by mass or more, more preferably 50 parts by mass or more) per 100 parts by mass of the first polymer component, and can be selected from a range of approximately 10 to 130 parts by mass (particularly 50 to 100 parts by mass). The proportion is, for example, 55 to 120 parts by mass (particularly 70 to 110 parts by mass), preferably 60 to 100 parts by mass, more preferably 63 to 90 parts by mass, more preferably 65 to 85 parts by mass, and most preferably 70 to 80 parts by mass per 100 parts by mass of the first polymer component. Furthermore, in applications where resistance to tooth chipping and durable running performance are important, the proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) is preferably 50 to 130 parts by mass, more preferably 80 to 130 parts by mass, and more preferably 110 to 130 parts by mass per 100 parts by mass of the first polymer component. If the proportion of primary unsaturated carboxylate metal salt is too low, the tooth breakage resistance and durability of the toothed belt will decrease, and if it is too high, the processability will be impaired, making it difficult to manufacture toothed belts.

[0092] (1D) First Crosslinking Compound The first rubber composition preferably further contains a crosslinking compound (first crosslinking compound). Examples of the first crosslinking compound include a first crosslinking agent (vulcanizing agent) for crosslinking the first polymer component, as well as a first co-crosslinking agent, a first crosslinking accelerator (vulcanization accelerator), a first crosslinking retarder (vulcanization retarder), and so on. Of these, the first crosslinking compound preferably contains at least a first crosslinking agent and a first co-crosslinking agent (crosslinking aid), and a combination of a first crosslinking agent and a first co-crosslinking agent is particularly preferred.

[0093] As the first crosslinking agent, conventional components can be used depending on the type of the first polymer component, such as organic peroxides and sulfur-based crosslinking agents.

[0094] Examples of organic peroxides include diacyl peroxides (e.g., dilauroyl peroxide, dibenzoyl peroxide, etc.), peroxyketals [e.g., 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, etc.], and dialkyl peroxides [di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyl peroxide]. Examples include [n-3,1,3-bis(2-t-butylperoxyisopropyl)benzene, etc.], alkyl peroxyesters [t-butylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, etc.], dialkyl peroxides (dicumyl peroxide, t-butylcumyl peroxide, etc.), peroxycarbonates (t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethyl-hexyl carbonate, t-amylperoxy-2-ethyl-hexyl carbonate, etc.). Furthermore, the organic peroxide may be a peroxide that has a decomposition temperature of 150 to 250°C (e.g., 175 to 225°C) at which it obtains a half-life of 1 minute by thermal decomposition. These organic peroxides can be used individually or in combination of two or more.

[0095] Among these organic peroxides, dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene are preferred.

[0096] The proportion of the organic peroxide is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 5 to 18 parts by mass, more preferably 6 to 15 parts by mass, and most preferably 8 to 12 parts by mass, per 100 parts by mass of the first polymer component.

[0097] Examples of sulfur-based crosslinking agents include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and sulfur chloride (sulfur monochloride, sulfur dichloride, etc.). These sulfur-based crosslinking agents can be used individually or in combination of two or more.

[0098] Of these sulfur-based crosslinking agents, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur are preferred, with powdered sulfur being the most preferred.

[0099] The proportion of the sulfur-based crosslinking agent is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, more preferably 0.12 to 1 part by mass, more preferably 0.15 to 0.5 parts by mass, and most preferably 0.18 to 0.3 parts by mass, per 100 parts by mass of the first polymer component.

[0100] The proportion of the first crosslinking agent is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 5 to 18 parts by mass, more preferably 6 to 15 parts by mass, and most preferably 8 to 12 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0101] The first co-crosslinking agent (crosslinking aid or co-vulcanizing agent) is a known crosslinking aid, for example, polyfunctional (iso)cyanurates [e.g., triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), etc.], polydienes (e.g., 1,2-polybutadiene, etc.), oximes (e.g., quinone dioxime, etc.), guanidines (e.g., diphenylguanidine, etc.), polyfunctional (meth)acrylates [e.g., ethylene glycol di(meth)acrylate, alkanediol di(meth)acrylate such as butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, etc., alkane polyol poly(meth)acrylate] Examples include acrylates, bismaleimides (aliphatic bismaleimides, such as alkylene bismaleimides like N,N'-1,2-ethylenedimaleimide, N,N'-hexamethylenebismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane; arene bismaleimides or aromatic bismaleimides, such as N,N'-m-phenylenedimaleimide, 4-methyl-1,3-phenylenedimaleimide, 4,4'-diphenylmethanedimaleimide, 2,2-bis[4-(4-maleimoidphenoxy)phenyl]propane, 4,4'-diphenyletherdimaleimide, 4,4'-diphenylsulfonedimaleimide, 1,3-bis(3-maleimoidphenoxy)benzene, etc.). These cocrosslinking agents can be used alone or in combination of two or more.

[0102] Among these cocrosslinking agents, polyfunctional (iso)cyanurates, polyfunctional (meth)acrylates, and bismaleimides (arene bismaleimides such as N,N'-m-phenylenedimaleimide or aromatic bismaleimides) are preferred, with bismaleimides being particularly preferred.

[0103] The proportion of the first co-crosslinking agent (crosslinking aid) can be selected from a range of about 0.2 to 40 parts by mass per 100 parts by mass of the first polymer component, for example, 1 to 30 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, more preferably 8 to 17 parts by mass, and most preferably 10 to 15 parts by mass. If the proportion of the first co-crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0104] The proportion of the first crosslinking compound is, for example, 1 to 50 parts by mass, preferably 5 to 45 parts by mass, more preferably 10 to 40 parts by mass, more preferably 15 to 35 parts by mass, and most preferably 20 to 30 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first crosslinking compound is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0105] (1E) The first carbon black first rubber composition may further contain carbon black (first carbon black).

[0106] The first carbon black may be in particulate (powder) form. Carbon black can generally be classified into hard carbon black, which has a relatively small particle size, and soft carbon black, which has a relatively large particle size. While the classification of carbon black is sometimes based on the average particle size (average primary particle size) in the raw material state, in this application, it is based on the primary particle size of the carbon black contained in the rubber composition (particularly in the crosslinked material of the rubber composition). That is, in this application, the primary particle size is measured for each primary particle of carbon black contained in the rubber composition, and carbon black with a primary particle size of 1 nm or more and less than 40 nm is referred to as hard carbon black (or hard carbon), and carbon black with a primary particle size of 40 nm or more (e.g., 40 to 300 nm) is referred to as soft carbon black (or soft carbon).

[0107] The average primary particle size of hard carbon black is, for example, 10 to 38 nm, preferably 15 to 35 nm, more preferably 20 to 33 nm, and more preferably 25 to 30 nm. On the other hand, the average primary particle size of soft carbon black is, for example, 40 to 100 nm, preferably 50 to 80 nm, more preferably 60 to 70 nm, and more preferably 65 to 68 nm.

[0108] In this application, the average particle size of particulate fillers such as carbon black can be measured using, for example, a SEM or TEM, and can be calculated as the arithmetic mean particle size of an appropriate number of samples (e.g., 50 samples) by image analysis.

[0109] In this invention, the first carbon black may be either hard carbon black or soft carbon black, and can be appropriately selected depending on the application, or both may be combined.

[0110] The amount of iodine adsorbed by the first carbon black is, for example, 5 to 200 g / kg, preferably 15 to 150 g / kg, and more preferably 20 to 140 g / kg.

[0111] In this application, the amount of iodine adsorbed by carbon black can be measured in accordance with the standard test method of ASTM D1510-17.

[0112] The BET specific surface area of ​​the first carbon black by the BET method is, for example, 10 to 400 m². ２ / g, preferably 15 to 200m ２ / g, more preferably 20 to 150m ２ It is / g.

[0113] The proportion of the first carbon black is 50 parts by mass or less per 100 parts by mass of the first polymer component, 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. If the proportion of the first carbon black is too high, it may become difficult to improve the resistance to tooth breakage while maintaining the processability of the toothed belt.

[0114] The proportion of the first carbon black is, for example, 150 parts by mass or less (particularly 50 parts by mass or less) per 100 parts by mass of the first silica, for example, 1 to 150 parts by mass, preferably 2 to 100 parts by mass, more preferably 3 to 50 parts by mass, more preferably 5 to 20 parts by mass, and most preferably 10 to 15 parts by mass. If the proportion of the first carbon black is too high, it may become difficult to improve the resistance to tooth breakage while maintaining the processability of the toothed belt.

[0115] (1F) First Filling Compound The first rubber composition may further contain a filling compound (first filling compound). Examples of the first filling compound include a first filler and a first short fiber.

[0116] Examples of first fillers include metal oxides (magnesium oxide, zinc oxide, lead oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (barium sulfate, etc.), silicates (natural or synthetic silicates in which some of the silicon is replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, and aluminum magnesium silicate; minerals with silicates as the main component, such as clay containing aluminum silicate, and silicate minerals such as talc and mica containing magnesium silicate), silica, lithopone, and silica sand. These fillers can be used alone or in combination of two or more types.

[0117] Of these, metal oxides such as zinc oxide are preferred. As the first filler, commercially available powdered fillers used as rubber fillers can be used.

[0118] The average particle size (average primary particle size) of the first filler is, for example, 0.01 to 25 μm, preferably 0.2 to 20 μm, and more preferably 0.5 to 15 μm.

[0119] In this application, the average particle diameter of the first filler can be measured as the volume-average particle diameter using a laser diffraction particle size distribution analyzer. Furthermore, the average particle diameter of the nanometer-sized first filler can be calculated as the arithmetic mean particle diameter of an appropriate number of samples (e.g., 50 samples) by image analysis of electron microscope images, including scanning electron microscope images.

[0120] The proportion of the first filler is, for example, 0.3 to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and most preferably 3 to 7 parts by mass, per 100 parts by mass of the first polymer component.

[0121] The first short fibers can be oriented (arranged) in a predetermined direction during the process of preparing an uncrosslinked rubber sheet by rolling a rubber composition, which has been kneaded in a Banbury mixer or the like, using rolls or a calender. Preferably, the orientation direction of the first short fibers is towards the circumferential direction of the belt.

[0122] The fibers forming the first short fibers may be organic fibers or inorganic fibers. Examples of organic fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers (nylon fibers), aramid fibers, etc.], polyester fibers [polyalkylene arylate fibers (for example, polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.)] ２－４ Alkilen C ８－１４Synthetic fibers such as polyarylate fibers, fully aromatic polyester fibers including liquid crystal polyester fibers, vinylon fibers, polyvinyl alcohol fibers, acrylic fibers, poly(p-phenylene)benzobisoxazole (PBO) fibers, fluororesin fibers [polytetrafluoroethylene (PTFE) fibers, etc.], polyphenylene ether fibers, polyether ether ketone fibers, polyether sulfone fibers, polyurethane fibers, etc.; natural fibers such as cotton, linen, and wool; regenerated cellulose fibers such as rayon; and cellulose ester fibers. Examples of inorganic fibers include carbon fibers, glass fibers, and metal fibers (steel fibers). These fibers can be used individually or in combination of two or more types.

[0123] Of these, fibers with a high modulus, such as polyamide fibers, PBO fibers, glass fibers, and carbon fibers, are preferred, polyamide fibers such as aliphatic polyamide fibers (nylon fibers) and aramid fibers, PBO fibers are more preferred, and aramid fibers are most preferred.

[0124] The average fiber diameter of the first short fibers is, for example, 1 to 100 μm, preferably 3 to 70 μm, more preferably 5 to 50 μm, and more preferably 10 to 30 μm. The average fiber length of the first short fibers is, for example, 0.3 to 10 mm, preferably 0.5 to 7 mm, more preferably 1 to 5 mm, and more preferably 2 to 4 mm.

[0125] It is preferable to subject the first short fibers to a conventional bonding treatment (or surface treatment) to adhere an adhesive component to at least a portion of the surface. Examples of bonding treatments include treatment with adhesive components such as epoxy compounds (or epoxy resins), polyisocyanates, silane coupling agents, and RFL liquid.

[0126] The proportion of the first short fibers may be 50 parts by mass or less per 100 parts by mass of the first polymer component, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and more preferably 5 parts by mass or less (for example, 1 to 5 parts by mass).

[0127] The first rubber composition preferably contains substantially no first short fibers, and is particularly preferably free of first short fibers.

[0128] The proportion of the first filling compound is, for example, 0.3 to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and most preferably 3 to 7 parts by mass, per 100 parts by mass of the first polymer component.

[0129] (1G) First softener The first rubber composition may further contain a softener (first softener). The first softener (processing agent or processing aid) may include mineral oil-based softeners, vegetable oil-based softeners, synthetic softeners, etc.

[0130] Examples of mineral oil-based softeners include petroleum-based softeners [paraffinic oils, alicyclic oils (naphthenic oils), aromatic oils, etc.] and coal tar-based softeners (coal tar, coumarone-indene resin, etc.).

[0131] Examples of vegetable oil-based softeners include fatty oil-based softeners (such as stearic acid, fatty acids or their metal salts, fatty acid esters, fatty acid amides, and fatty oils).

[0132] Examples of synthetic softeners include synthetic resin softeners (phenol aldehyde resins, hydrocarbon synthetic oils such as liquid ethylene-α-olefin copolymers, liquid polybutene, liquid polybutadiene, liquid isoprene rubber, etc.), and synthetic plasticizers [aliphatic carboxylic acid plasticizers (adipate ester plasticizers, sebacate ester plasticizers, etc.), aromatic carboxylic acid ester plasticizers (phthalate ester plasticizers, trimellitic acid ester plasticizers, etc.), oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, ether ester plasticizers, etc.].

[0133] These softeners can be used individually or in combination of two or more. Of these, petroleum-based softeners such as paraffinic oils and vegetable oil-based softeners such as stearic acid are preferred, and a combination of petroleum-based and vegetable oil-based softeners is particularly preferred.

[0134] The proportion of the first softener is, 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 6 to 10 parts by mass, per 100 parts by mass of the first polymer component.

[0135] (1H) First Anti-aging Agent The first rubber composition may further contain an anti-aging agent (first anti-aging agent). Examples of the first anti-aging agent include benzimidazole-based anti-aging agents, diarylamine-based anti-aging agents, and p-phenylenediamine-based anti-aging agents.

[0136] Examples of benzimidazole-based antioxidants include 2-mercaptobenzimidazole (MBI), 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, 1,3-dihydro-1-phenyl-2H-benzimidazole-2-thion, and benzimidazole compounds such as mixtures of 2-mercaptobenzimidazole and phenol condensates. Benzimidazole-based antioxidants may also be in the form of metal salts such as zinc.

[0137] Examples of diarylamine-based antioxidants include bis(C) such as di(4-octylphenyl)amine (ODPA). ４－１８ Alkyl C ６－１０ Examples include aryl amines; bis(aralkyl-aryl)amines such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (DCD); and styrene-diphenylamine (SDPA).

[0138] Examples of p-phenylenediamine-based antioxidants include N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and N-(1,3-methylheptyl)-N'-phenyl-p-phenylenediamine (8PPD), which are N-linear or branched C-cells. １－１０ Alkyl-N'-C ６－１０Aryl-p-phenylenediamines; N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine (DNPD), and other N,N'-diC ６－１０ Examples include aryl-p-phenylenediamines.

[0139] These anti-aging agents can be used individually or in combination of two or more. Of these, benzimidazole-based anti-aging agents, particularly benzimidazole compounds having a sulfur atom, are preferred, and benzimidazole compounds having a thiol group such as MBI (mercaptobenzimidazole compounds) are especially preferred.

[0140] The proportion of the first antioxidant is, for example, 0.3 to 10 parts by mass, preferably 0.5 to 8 parts by mass, more preferably 1 to 5 parts by mass, and more preferably 1.5 to 3 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first antioxidant is too low, the resistance of the belt to tooth chipping may decrease, and if it is too high, the mechanical properties of the belt may decrease.

[0141] (1I) First Other Compounding Agents The first rubber composition may further contain, as other compounding agents (first other compounding agents), conventional additives used in rubber compositions for toothed belts. Examples of conventional additives include antioxidants, flex crack inhibitors, ozone degradation inhibitors, colorants, tackifiers, plasticizers, coupling agents (such as silane coupling agents), stabilizers (such as ultraviolet absorbers and heat stabilizers), flame retardants, and antistatic agents. The first rubber composition may also contain adhesion improvers (such as resorcinol-formaldehyde copolymers and amino resins) as needed. These additives can be used individually or in combination of two or more.

[0142] The total proportion of the first other compounding agent is, for example, 100 parts by mass or less, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and more preferably 10 parts by mass or less, per 100 parts by mass of the first polymer component.

[0143] (1J) Characteristics of the adhesive rubber layer The adhesive rubber layer has high hardness (elastic modulus and modulus) and can improve the rigidity of the tooth surface. The rubber hardness of the crosslinked material of the first rubber composition forming the adhesive rubber layer is a type D hardness and may be 50 or more, or 55 or more, for example 55 to 90 (or 50 to 80), preferably 57 to 85 (or 55 to 75), more preferably 60 to 80 (or 58 to 70), more preferably 63 to 75 (or 60 to 65), and most preferably 65 to 70 (or 62 to 64). If the rubber hardness is too low, the tooth chipping resistance of the toothed belt may decrease.

[0144] The crosslinked material of the first rubber composition has a greater rubber hardness than the crosslinked material of the second rubber composition that forms the tooth rubber layer. Specifically, the difference (H1-H2) between the rubber hardness (H1) of the crosslinked material of the first rubber composition and the rubber hardness (H2) of the crosslinked material of the second rubber composition may be 5 or more on the Type D hardness scale, for example, 5 to 45 (or 5 to 40), preferably 10 to 40 (or 8 to 35), more preferably 15 to 35 (or 10 to 30), more preferably 20 to 30 (or 15 to 25), and most preferably 22 to 28 (or 18 to 22). If this difference is too small, the effects of the present invention may be reduced.

[0145] In this application, the Type D or Type A hardness of the crosslinked rubber composition refers to the value measured using a Type D or Type A durometer in accordance with the spring durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Method for determining hardness), and may simply be referred to as rubber hardness. In detail, the Type D or Type A hardness of the crosslinked rubber composition can be measured by the method described in the examples below, and can be measured as the hardness of a rubber sheet obtained by crosslinking a rubber composition for forming a belt.

[0146] Typically, the rubber hardness of rubber compositions is measured using Type A hardness (a value measured using a Type A durometer). However, if the value measured using a Type A durometer exceeds 90, it is considered preferable to use a Type D durometer.

[0147] The 5% modulus (tensile stress at 5% elongation) of the crosslinked material of the first rubber composition may be 3 MPa or more (particularly 9 MPa or more), or 5 MPa or more (particularly 12 MPa or more) in the belt circumferential direction (longitudinal direction), for example, 5 to 35 MPa (or 3 to 30 MPa), preferably 8 to 30 MPa (or 5 to 20 MPa), more preferably 10 to 25 MPa (or 8 to 15 MPa), more preferably 12 to 20 MPa (or 10 to 13 MPa), and most preferably 13 to 18 MPa (or 11 to 12 MPa). If the 5% modulus is too small, the tooth breakage resistance of the toothed belt may decrease.

[0148] The crosslinked material of the first rubber composition has a 5% modulus greater than the crosslinked material of the second rubber composition that forms the tooth rubber layer in the belt circumferential direction (longitudinal direction). Specifically, the difference between the 5% modulus of the crosslinked material of the first rubber composition (modulus 1) and the 5% modulus of the crosslinked material of the second rubber composition (modulus 2) (modulus 1 - modulus 2) may be 2 MPa or more in type D hardness, for example, 2 to 30 MPa, preferably 3 to 20 MPa, more preferably 5 to 15 MPa, more preferably 7 to 12 MPa, and most preferably 9 to 11 MPa. If this difference is too small, the effect of the present invention may be reduced.

[0149] In this application, the 5% modulus (tensile modulus) of the crosslinked rubber composition can be measured by a method in accordance with JIS K 6251 (2017), and in detail, it can be measured by the method described in the examples below.

[0150] The average thickness of the adhesive rubber layer is, for example, 0.2 to 1.5 mm, preferably 0.3 to 1 mm, more preferably 0.4 to 0.9 mm, more preferably 0.5 to 0.8 mm, and most preferably 0.6 to 0.7 mm. If the average thickness is too thin, the tooth-breakage resistance of the toothed belt may decrease, and if it is too thick, it may become expensive and the effects of the present invention may be diminished.

[0151] In this application, the average thickness of the adhesive rubber layer is the average value of the thickness of the adhesive rubber layer at the top of any six teeth in an image of the cross-section of the toothed belt taken with a microscope.

[0152] (Tooth rubber layer and back rubber layer) As described later, the toothed belt of the present invention is manufactured in a single molding process without separately preparing and pre-forming the tooth rubber layer and the back rubber layer. Therefore, the tooth rubber layer and the back rubber layer contain a crosslinked product of the same rubber composition (second rubber composition containing a second polymer component).

[0153] (2A) Second Polymer Component The second polymer component includes a second ethylene-α-olefin elastomer. Examples of the second ethylene-α-olefin elastomer include the ethylene-α-olefin elastomer exemplified as the first ethylene-α-olefin elastomer. The second ethylene-α-olefin elastomer can be used alone or in combination of two or more types. Among the second ethylene-α-olefin elastomers, ethylene-α-C is selected because of its excellent heat resistance, cold resistance, and weather resistance. ３－４ Ethylene-α-olefin-diene terpolymers, such as olefin-diene terpolymers, are preferred. Therefore, the proportion of ethylene-α-olefin-diene terpolymer may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass or more), and may be 100% by mass (ethylene-α-olefin-diene terpolymer only) relative to the total amount of the second ethylene-α-olefin elastomer.

[0154] In the second ethylene-α-olefin elastomer, the ethylene content (percentage of ethylene units) in the ethylene-α-olefin elastomer may be 30% by mass or more, for example, 30 to 80% by mass, preferably 35 to 70% by mass, more preferably 40 to 60% by mass, more preferably 45 to 55% by mass, and most preferably 47 to 53% by mass.

[0155] In the second ethylene-α-olefin elastomer, the ratio (mass ratio) of ethylene to α-olefin is former / latter = 30 / 70 to 90 / 10, preferably 40 / 60 to 80 / 20, more preferably 50 / 50 to 60 / 40, and more preferably 50 / 50 to 55 / 45.

[0156] The diene content (especially the ethylidene norbornene content) of the secondary ethylene-α-olefin elastomer (especially ethylene-α-olefin-diene terpolymer such as EPDM) may be 8% by mass or less (preferably 7% by mass or less, more preferably 6% by mass or less), for example, 0.1 to 8% by mass, preferably 1 to 7.5% by mass, more preferably 2 to 7% by mass, more preferably 3 to 6% by mass, and most preferably 4 to 5% by mass. If the diene content is too high, the effects of the present invention may be reduced.

[0157] In the second polymer component, the iodine value of the second ethylene-α-olefin elastomer containing the diene monomer is, for example, 3 to 40, preferably 5 to 30, and more preferably 10 to 20.

[0158] In the second polymer component, the Mooney viscosity [ML(1+4)125°C] of the uncrosslinked second ethylene-α-olefin elastomer may be 10 or more, for example, 10 to 80, preferably 12 to 70, more preferably 13 to 50, more preferably 15 to 30, and most preferably 18 to 25.

[0159] In the second polymer component, the proportion of the second ethylene-α-olefin elastomer may be 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. If the proportion of the second ethylene-α-olefin elastomer is too low, the second polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0160] The second polymer component may contain polymer components other than the second ethylene-α-olefin elastomer.

[0161] Other polymer components include those exemplified as other polymer components in the first polymer component. These polymer components can be used alone or in combination of two or more.

[0162] In the second polymer component, the proportion of other polymer components may be 100 parts by mass or less per 100 parts by mass of the second ethylene-α-olefin elastomer, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 5 parts by mass or less.

[0163] The second polymer component is preferably substantially free of other polymer components, and more preferably free of expensive HNBR.

[0164] The proportion of the second polymer component may be 10% by mass or more in the second rubber composition, for example, 10 to 90% by mass, preferably 20 to 80% by mass, more preferably 30 to 60% by mass, more preferably 35 to 50% by mass, and most preferably 40 to 45% by mass. If the proportion of the second polymer component is too low, the flexibility of the toothed belt may decrease.

[0165] (2B) The second carbon black rubber composition may further contain carbon black (second carbon black). The second carbon black can be selected from the carbon blacks exemplified as the first carbon black, including preferred embodiments.

[0166] The average primary particle size, iodine adsorption amount, and BET specific surface area ranges of the second carbon black can also be selected from those ranges of the first carbon black, including preferred ranges.

[0167] The proportion of the second carbon black is 10 parts by mass or more (particularly 20 parts by mass or more) per 100 parts by mass of the second polymer component, for example, 10 to 200 parts by mass, preferably 30 to 150 parts by mass, more preferably 40 to 100 parts by mass, more preferably 50 to 80 parts by mass, and most preferably 60 to 70 parts by mass. If the proportion of the second carbon black is too low, the mechanical properties of the tooth portion may deteriorate.

[0168] (2C) The second silica second rubber composition may further contain silica (second silica). The second silica can be selected from the silicas exemplified as the first silica, including preferred embodiments.

[0169] The average particle size and BET specific surface area range of the second silica can also be selected from those ranges of the first silica, including preferred ranges.

[0170] The proportion of the second silica may be 50 parts by mass or less (particularly 30 parts by mass or less) per 100 parts by mass of the second polymer component, for example, 0 to 50 parts by mass, preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, more preferably 3 to 10 parts by mass, and most preferably 4 to 7 parts by mass. If the proportion of the second silica is too high, the effect of the present invention may be reduced.

[0171] (2D) The second rubber composition may further contain an unsaturated carboxylic acid metal salt (second unsaturated carboxylic acid metal salt). The second unsaturated carboxylic acid metal salt can be selected from the unsaturated carboxylic acid metal salts exemplified as the first unsaturated carboxylic acid metal salt, including preferred embodiments.

[0172] The proportion of the second unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 1 part by mass or more (preferably 5 parts by mass or more, more preferably 10 parts by mass or more) per 100 parts by mass of the second polymer component, for example, 1 to 100 parts by mass, preferably 10 to 70 parts by mass, more preferably 15 to 50 parts by mass, more preferably 20 to 40 parts by mass, and most preferably 25 to 35 parts by mass. If the proportion of the second unsaturated carboxylic acid metal salt is too low, the tooth chipping resistance of the toothed belt will decrease, and if it is too high, the processability will be impaired, making it difficult to manufacture the toothed belt.

[0173] (2E) Second Crosslinking Compound The second rubber composition may further contain a crosslinking compound (second crosslinking compound). Examples of the second crosslinking compound include a second crosslinking agent (vulcanizing agent) for crosslinking the second polymer component, as well as a second cocrosslinking agent, a second crosslinking accelerator (vulcanization accelerator), and a second crosslinking retarder (vulcanization retarder). Of these, the second crosslinking compound preferably contains at least a second crosslinking agent and a second cocrosslinking agent (crosslinking aid), and a combination of a second crosslinking agent and a second cocrosslinking agent is particularly preferred.

[0174] As the second crosslinking agent, conventional components can be used depending on the type of second polymer component, such as organic peroxides and sulfur-based crosslinking agents.

[0175] The organic peroxide can be selected from the organic peroxides exemplified as the first crosslinking agent, including preferred embodiments.

[0176] The ratio of organic peroxide to the second polymer component can be selected from a range of ratios of organic peroxide to the first polymer component, including a preferred range.

[0177] As the sulfur-based crosslinking agent, it can be selected from the sulfur-based crosslinking agents exemplified as the sulfur-based crosslinking agent of the first crosslinking agent, including preferred embodiments.

[0178] The ratio of the sulfur-based crosslinking agent to the second polymer component can be selected from a range of ratios of the sulfur-based crosslinking agent to the first polymer component, including a preferred range.

[0179] The ratio of the second crosslinking agent to the second polymer component can be selected from the range of the ratio of the first crosslinking agent to the first polymer component, including a preferred range.

[0180] The second co-crosslinking agent can be selected from the co-crosslinking agents exemplified as the first co-crosslinking agent, including preferred embodiments.

[0181] The proportion of the second co-crosslinking agent can be selected from a range of about 0.2 to 40 parts by mass per 100 parts by mass of the second polymer component, for example, 1 to 30 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, more preferably 7 to 15 parts by mass, and most preferably 8 to 12 parts by mass. If the proportion of the second co-crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0182] The proportion of the second crosslinking compound is, for example, 1 to 50 parts by mass, preferably 5 to 45 parts by mass, more preferably 10 to 40 parts by mass, more preferably 12 to 30 parts by mass, and most preferably 15 to 25 parts by mass, per 100 parts by mass of the second polymer component. If the proportion of the second crosslinking compound is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0183] (2F) Second Filling Compound The second rubber composition may further contain a filling compound (second filling compound). Examples of the second filling compound include a second filler and a second staple fiber.

[0184] The second filler can be selected from the fillers exemplified as the first filler, including preferred embodiments.

[0185] The average particle size range of the second filler and its ratio to the second polymer component can be selected from the respective ranges of the first filler, including preferred ranges.

[0186] The second short fiber can be selected from the short fibers exemplified as the first short fiber, including preferred embodiments.

[0187] The average fiber diameter and average fiber length of the second short fiber can be selected from the range of the average fiber diameter and average fiber length of the first short fiber, including a preferred range.

[0188] The proportion of the second short fibers may be 10 parts by mass or less per 100 parts by mass of the second polymer component, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and more preferably 1 part by mass or less.

[0189] The second rubber composition preferably contains substantially no second short fibers, and is particularly preferably free of second short fibers.

[0190] The ratio of the second filler compound to the second polymer component can be selected from the range of the ratio of the first filler compound to the first polymer component, including a preferred range.

[0191] (2G) Second softener The second rubber composition may further contain a softener (second softener). The second softener can be selected from the softeners exemplified as the first softener, including preferred embodiments.

[0192] The ratio of the second polymer component to the second softener can also be selected from the range of the ratio of the first softener to the first polymer component.

[0193] (2H) Second Anti-aging Agent The second rubber composition may further contain an anti-aging agent (second anti-aging agent). The second anti-aging agent can be selected from the anti-aging agents exemplified as the first anti-aging agent, including preferred embodiments.

[0194] The ratio of the second antioxidant to the second polymer component can also be selected from the range of the ratio of the first antioxidant to the first polymer component.

[0195] (2I) Second Other Compounding Agent The second rubber composition may further contain, as a second other compounding agent, conventional additives used in rubber compositions for toothed belts. Examples of conventional additives include the conventional additives exemplified as the first other compounding agent.

[0196] The ratio of the second other compounding agent to the second polymer component can also be selected from the range of the ratio of the first other compounding agent to the first polymer component.

[0197] (2J) Characteristics of the tooth rubber layer and back rubber layer The rubber hardness of the crosslinked material of the second rubber composition forming the tooth rubber layer and back rubber layer is a Type D hardness and may be 50 or less, for example 30 to 50, preferably 35 to 48, more preferably 40 to 47, more preferably 41 to 46, and most preferably 42 to 45. If the rubber hardness is too high, it may become expensive and the effects of the present invention may decrease.

[0198] The 5% modulus of the crosslinked product of the second rubber composition may be 3 MPa or less (particularly 2 MPa or less) in the belt circumferential direction (longitudinal direction), for example, 0.5 to 3 MPa, preferably 1 to 2.8 MPa, more preferably 1.2 to 2.5 MPa, more preferably 1.3 to 2.2 MPa, and most preferably 1.5 to 2 MPa. If the 5% modulus is too high, it may become expensive and the effects of the present invention may be reduced.

[0199] The average thickness of the tooth rubber layer is, for example, 1 to 10 mm, preferably 1.5 to 8 mm, more preferably 2 to 5 mm, more preferably 3 to 4 mm, and most preferably 3.3 to 3.7 mm.

[0200] The average thickness of the back rubber layer is, for example, 1 to 5 mm, preferably 1.3 to 4.5 mm, more preferably 1.5 to 4 mm, and most preferably 2 to 3.5 mm.

[0201] In this application, the thickness of the tooth rubber layer and the back rubber layer are values ​​measured from images of the cross-section of the toothed belt taken with a microscope. The average thickness of the tooth rubber layer is the average of the measurements taken at the tops of any six teeth. The average thickness of the back rubber layer is the average of the measurements taken at the roots of any six teeth.

[0202] (Tooth Fabric) The tooth fabric, which is laminated on the inner surface of the belt (tooth and tooth base), may be made of fabric such as woven fabric, knitted fabric, or nonwoven fabric. Conventionally, it is often woven fabric (canvas), and is composed of a fabric made by weaving warp threads extending in the belt width direction and weft threads extending in the belt circumference direction. The weave structure of the woven fabric is not particularly limited as long as the warp and weft threads intersect regularly in the vertical and horizontal directions, and may be any of plain weave, twill weave (or diagonal weave), satin weave, or a weave structure that combines these structures. Preferred woven fabrics have a twill weave and / or satin weave structure (especially a twill weave structure).

[0203] The fibers forming the weft and warp threads of the tooth cloth may be organic fibers or inorganic fibers. Examples of organic fibers include the organic fibers exemplified as the first short fibers. Examples of inorganic fibers include the inorganic fibers exemplified as the first short fibers. These fibers can be used individually or in combination of two or more types.

[0204] Of the aforementioned fibers, organic fibers are commonly used, with cellulose fibers such as cotton and rayon, polyester fibers (such as PET fibers), polyamide fibers (such as aliphatic polyamide fibers like polyamide 66 fibers, aramid fibers, etc.), and PBO fibers being preferred. Composite yarns of these fibers and elastic yarns with elasticity [for example, polyurethane elastic yarns with elasticity such as spandex made of polyurethane, processed yarns that have undergone stretch processing (for example, woolly processing, crimping processing, etc.)] are also preferred.

[0205] The form of the warp and weft threads is not particularly limited and may be monofilament yarn, which is a single long fiber; multifilament yarn, which is made by aligning or twisting filaments (long fibers); or spun yarn, which is made by twisting short fibers. The multifilament yarn or spun yarn may be a blended yarn or blended yarn using multiple types of fibers. The weft threads preferably contain elastic yarn, while the warp threads usually do not contain elastic yarn from the viewpoint of weaving. In order to ensure the elasticity of the tooth fabric in the circumferential direction of the belt, the weft threads containing elastic yarn extend in the circumferential direction of the belt, and the warp threads extend in the width direction of the belt.

[0206] The average diameter of the fibers is, for example, 1 to 100 μm (e.g., 3 to 50 μm), preferably 5 to 30 μm, and more preferably 7 to 25 μm. Regarding the average diameter (thickness) of the yarn (twisted yarn), the weft may be, for example, 100 to 1000 dtex (particularly 300 to 700 dtex), and the warp may be, for example, 50 to 500 dtex (particularly 100 to 300 dtex). The density of the weft (threads / cm) may be, for example, 5 to 50 (particularly 10 to 30), and the density of the warp (threads / cm) may be, for example, 10 to 300 (particularly 20 to 100).

[0207] The average thickness of the tooth fabric (the tooth fabric in the toothed belt) is, for example, 0.1 to 2 mm, preferably 0.2 to 1.5 mm, and more preferably 0.3 to 1.3 mm. The average thickness of the tooth fabric as raw material (the tooth fabric before molding) is, for example, 0.5 to 3 mm, preferably 0.75 to 2.5 mm, and more preferably 0.8 to 1.5 mm.

[0208] To improve the adhesion between the tooth cloth and the tooth rubber layer, the cloth forming the tooth cloth may be treated with an adhesive. Examples of adhesive treatments include immersing the cloth in an RFL treatment solution followed by heat drying; treating with an epoxy compound or isocyanate compound; and dissolving a rubber composition in an organic solvent to make a rubber glue, immersing the cloth in this rubber glue, and then heat drying. These methods can be performed individually or in combination, and the order and number of treatments are not limited. For example, after immersing in the RFL treatment solution, the cloth may be further immersed in the rubber glue and then heat dried.

[0209] (Tooth root) The tooth cloth constitutes the surface of the tooth and also forms the surface on the tooth side of the back (the surface of the tooth root).

[0210] In the dorsal portion corresponding to the tooth root, an adhesive rubber layer and a tooth rubber layer may be interposed between the tooth cloth and the core wire, but the tooth cloth and the core wire may be in contact without the interposition of the adhesive rubber layer and the tooth rubber layer. Even when an adhesive rubber layer and a tooth rubber layer are interposed in the dorsal portion corresponding to the tooth root, the thickness of the adhesive rubber layer and the tooth rubber layer is formed to be thinner than that of the tooth portion.

[0211] (Core wire) A core wire extending along the belt circumferential direction is embedded in the back portion on the inner circumference side of the back rubber layer. This core wire acts as a tensile body and can improve the running stability and strength of the toothed belt. Furthermore, in the back portion, core wires, which are twisted cords extending along the belt circumferential direction, are usually embedded at predetermined intervals in the belt width direction, and multiple core wires parallel to the longitudinal direction may be arranged, but from the viewpoint of productivity, they are usually embedded in a spiral shape. When arranged in a spiral shape, the angle of the core wire with respect to the longitudinal direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it is as close to 0° as possible.

[0212] More specifically, the core wires may be embedded at predetermined intervals (or pitches) (or at equal intervals) from one end to the other in the belt width direction on the back, as shown in Figure 1.

[0213] The core wire may be formed from a twisted cord made by twisting together multiple strands or multifilament threads. Of these, a twisted cord of strands is preferred, and one strand may be formed by bundling filaments (long fibers). There are no particular limitations on the thickness of the filaments forming the twisted cord, the number of filaments converged, the number of strands, and the twist configuration.

[0214] The twisted cord forming the core wire may be a single-strand, double-strand, or Lang-strand cord. By using a Lang-strand core wire, where the twist direction of the lower twist and the twist direction of the upper twist are the same, the bending stiffness is lower compared to double-strand or single-strand cords, resulting in excellent bending fatigue resistance.

[0215] The fibers forming the core may be organic fibers or inorganic fibers. Examples of organic fibers include the organic fibers exemplified as the first short fibers. Examples of inorganic fibers include the inorganic fibers exemplified as the first short fibers. The fibers can be used individually or in combination of two or more types.

[0216] Among the aforementioned fibers, synthetic fibers such as polyester fibers and polyamide fibers, and inorganic fibers such as glass fibers and carbon fibers are commonly used due to their low elongation and high strength, with carbon fibers being preferred.

[0217] The core wire may be subjected to an adhesive treatment to enhance its adhesion to the crosslinked material of the rubber composition. For example, the adhesive treatment may involve immersing the stranded cord in a resorcinol-formaldehyde-latex treatment solution (RFL treatment solution), followed by heating and drying to form a uniform adhesive layer on the surface of the stranded cord. The RFL treatment solution is a mixture of latex and an initial condensate of resorcinol and formalin. The latex may be, for example, chloroprene rubber, styrene-butadiene-vinylpyridine terpolymer (VP latex), nitrile rubber, or hydrogenated nitrile rubber. Furthermore, the adhesive treatment may involve pre-treating with an epoxy compound or isocyanate compound before treatment with the RFL treatment solution.

[0218] The average diameter of the core wire (or stranded cord) (core wire diameter D or average wire diameter) can be selected from a range of approximately 0.2 to 2.5 mm. If the core wire diameter D is too small, the core wire will stretch excessively, which may cause tooth chipping (loss of teeth). If the core wire diameter D is too large, the belt will become rigid and its flexibility will decrease. It is preferable to adjust the core wire diameter D according to the tooth pitch.

[0219] In particular, for toothed belts with a tooth pitch of 6 mm or more and less than 9.5 mm (for example, 7 to 9 mm, especially 8 mm), the core wire diameter D is, for example, 0.8 to 1.2 mm, preferably 0.9 to 1.1 mm, more preferably 0.9 to 1.05 mm, and more preferably 0.9 to 1 mm. If the core wire diameter D is too large, the belt may become rigid and its flexibility may decrease.

[0220] Furthermore, for toothed belts with a tooth pitch of 9.5 mm or more and less than 12.5 mm (for example, 10 to 12 mm, particularly 11 mm), the core wire diameter D is, for example, 1.3 to 1.8 mm, preferably 1.4 to 1.8 mm.

[0221] Furthermore, in toothed belts with a tooth pitch of 12.5 to 16 mm (for example, 13 to 15 mm, particularly 14 mm), the core wire diameter D is, for example, 1.7 to 2.4 mm, preferably 1.7 to 2.2 mm, more preferably 1.8 to 2.1 mm, and even more preferably 1.8 to 2 mm.

[0222] The core wire pitch P, which refers to the distance between the centers of adjacent core wires in the belt, may be 0.5 mm or more, and can be selected from a range of approximately 0.5 to 3.5 mm. The core wire pitch is usually selected from this range so that the core wires are arranged at equal intervals. If the core wire pitch is too small, it may become difficult to manufacture the belt using a simple method that does not require preforming.

[0223] In particular, for toothed belts with a tooth pitch of 6 mm or more and less than 9.5 mm (for example, 7 to 9 mm, especially 8 mm), the core wire pitch P is, for example, 0.5 to 2.2 mm, preferably 0.8 to 2 mm, more preferably 1.1 to 1.8 mm, and more preferably 1.3 to 1.6 mm.

[0224] Furthermore, in toothed belts with a tooth pitch of 9.5 mm or more and less than 12.5 mm (for example, 10 to 12 mm, particularly 11 mm), the core wire pitch P is, for example, 1.2 to 2.8 mm, preferably 1.4 to 2.6 mm, more preferably 1.6 to 2.4 mm, and more preferably 1.8 to 2.2 mm.

[0225] Furthermore, in toothed belts with a tooth pitch of 12.5 to 16 mm (for example, 13 to 15 mm, particularly 14 mm), the core wire pitch P is, for example, 1.8 to 3.5 mm, preferably 2 to 3.4 mm, more preferably 2.2 to 3.2 mm, and more preferably 2.4 to 3 mm.

[0226] In this invention, by adjusting the core wire diameter D and core wire pitch P and controlling the X value (%) of the core wire arrangement density, a toothed belt having the desired tooth shape can be manufactured in a single molding process without separately preparing and pre-forming the tooth rubber layer and the back rubber layer.

[0227] In this application, the X value (%) of the array density is defined as "the ratio of areas without core wires (total spacing d) to the belt width W," that is, "the ratio of the total spacing d between adjacent core wires to the belt width W," and a smaller X value indicates a higher density.

[0228] More specifically, Figure 3 is a diagram showing the belt width W, core wire diameter D, core wire spacing d, and core wire pitch P in the toothed belt of the present invention. As shown in Figure 3, in a belt equipped with tooth fabric 2, a plurality of core wires 5 are arranged in the back rubber layer 6 at predetermined intervals d in the belt width direction. This interval d includes not only the interval between adjacent core wires 5, but also the interval between the core wires 5 at both ends and the belt end (d at the left end in Figure 3). The belt end refers to the end on the line connecting the centers of the core wires 5 (the left or right end in Figure 3). In other words, in this application, the total value of the interval d means the value obtained by subtracting the value of "total core wire diameter D (core wire diameter D × number of core wires)" from the value of "belt width" W. Therefore, the X value (%) can be replaced by the relationship between core wire diameter D and core wire pitch P, as shown in the following formula.

[0229] X = (Sum of intervals d / Belt width W) × 100 = [(Belt width W - Sum of core wire diameters D) / Belt width W] × 100 = {[Belt width W - (Core wire diameter D × Number of core wires)] / Belt width W} × 100 = <{Belt width W - [Core wire diameter D × (Belt width W / Core wire pitch P)]} / Belt width W> × 100 = [1 - (Core wire diameter D / Core wire pitch P)] × 100

[0230] In this application, the belt width W, core wire diameter D, spacing d, and core wire pitch P are determined based on a cross-sectional view perpendicular to the length direction of the belt, and the core wire pitch P is the distance between the centers of adjacent core wires in the cross-sectional view, as shown in Figure 3.

[0231] The X value of the arrangement density in the core wires may be 15% or more, for example, 15 to 50%, preferably 20 to 45%, more preferably 22 to 40%, more preferably 23 to 38%, and most preferably 25 to 35%. If the X value is too small, the gap between adjacent core wires becomes small, which may hinder the flow of rubber during belt manufacturing and cause molding defects (symptoms in which teeth of a predetermined shape are not formed). On the other hand, if the X value is too large, the number of spiral core wires per belt width decreases, which may make it difficult to secure the desired belt strength.

[0232] [Method for Manufacturing Toothed Belts] The toothed belt of the present invention does not require preforming and is manufactured in an inexpensive and simple method in which the belt is molded in a single molding process. That is, the toothed belt of the present invention can be obtained by a method including a crosslinking molding process in which an uncrosslinked molded body is formed by laminating a tooth cloth precursor, an adhesive rubber layer precursor, a core wire precursor, and precursors for the tooth rubber layer and back rubber layer. More specifically, the method for manufacturing a toothed belt of the present invention may include a precursor preparation step of preparing each precursor, a molding step of obtaining an uncrosslinked molded body by laminating a tooth cloth precursor, an adhesive rubber layer precursor, a core wire precursor, and precursors for the tooth rubber layer and back rubber layer, a crosslinking molding step of crosslinking the uncrosslinked molded body to obtain a crosslinked molded body, and a cutting step of cutting the crosslinked molded body to obtain a toothed belt.

[0233] (Precursor preparation step) In the precursor preparation step, the tooth cloth precursor may be prepared by bonding it to a cloth for forming the tooth cloth, as described above.

[0234] The precursors for the adhesive rubber layer, the tooth rubber layer, and the back rubber layer are each uncrosslinked rubber sheets. The uncrosslinked rubber sheets may be prepared by conventional methods, such as rolling using rolls or calenders.

[0235] Furthermore, in the present invention, when the adhesive rubber layer is thin, it is preferable to use the tooth cloth precursor and the adhesive rubber layer precursor as a laminate in which both precursors are pre-integrated (hereinafter referred to as "tooth cloth and adhesive rubber layer precursor"). The method for manufacturing the tooth cloth and adhesive rubber layer precursor is not particularly limited, as long as the tooth cloth precursor and the uncrosslinked rubber sheet, which is the adhesive rubber layer precursor, can be laminated and integrated. For example, one method is to coat the tooth cloth precursor with a first rubber composition for forming the adhesive rubber layer.

[0236] As a method for coating the tooth cloth precursor with the first rubber composition, a method in which the rubber composition and the cloth are simultaneously passed between rolls rotating at the same speed and the rubber composition is pressed onto the cloth is preferred from the viewpoint of simplicity and other factors. In this method, the first rubber composition, which has been kneaded in a conventional way using a Banbury mixer or the like, and the tooth cloth precursor are simultaneously passed between rolls rotating at the same speed and pressed (compressed) using rolls or a calender, and the solid first rubber composition is pressed (coated) onto one surface of the tooth cloth precursor, and a tooth cloth and an adhesive rubber layer precursor can be obtained in which a sheet-like first rubber composition, which is an adhesive rubber layer precursor, is laminated on one surface of the tooth cloth precursor.

[0237] (Molding Process) In the molding process, tooth cloth and adhesive rubber layer precursors are wound around the outer surface of a cylindrical mold having multiple grooves (recesses) corresponding to the teeth, with the tooth cloth precursor facing the outer surface of the cylindrical mold (if separate tooth cloth precursors and adhesive rubber layer precursors are used, the tooth cloth precursor and adhesive rubber layer precursor are wound sequentially). Next, a twisted cord (core wire precursor) that will form the core wire is wound around its outer surface in a spiral pattern at a predetermined pitch (with a predetermined pitch in the axial direction of the cylindrical mold). Furthermore, tooth rubber layer and back rubber layer precursors (uncrosslinked rubber sheets) are wound around its outer surface to form an uncrosslinked belt molded body (uncrosslinked molded body).

[0238] (Crosslinking Molding Process) Next, in the crosslinking molding process, the uncrosslinked belt molded body is placed on the outer circumference of a cylindrical mold, and a rubber jacket, which is a vapor barrier, is then placed over its outer circumference. Subsequently, the belt molded body with the jacket and the cylindrical mold are housed inside a crosslinking molding device such as a vulcanizing can. When the belt molded body is heated and pressurized inside the crosslinking molding device, a portion of the uncrosslinked rubber sheet, which is a precursor to the softened tooth rubber layer and back rubber layer, is extruded (press-fitted) into the inner circumference through the gaps in the twisted cord. Due to the press-fitting, the tooth cloth is stretched to conform to the contour of the teeth and placed on the innermost circumference, the tooth rubber layer derived from the uncrosslinked rubber sheet is placed on its outer circumference along the contour of the teeth, the twisted cord is arranged on the outer circumference, and the remaining back rubber layer (back) derived from the uncrosslinked rubber sheet is placed on the outermost circumference, forming a layered structure. At the same time, the crosslinking reaction of the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body causes each component to be joined together, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve). Thus, in the press-fitting method, the uncrosslinked rubber sheet (a single uncrosslinked rubber sheet) wrapped around the outer circumference of the twisted cord during the molding process forms both the teeth and the back portion.

[0239] (Cutting process) Finally, in the cutting process, multiple toothed belts are obtained by cutting the bridging belt sleeve, which has been demolded from the cylindrical mold, to a predetermined width.

[0240] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0241] [Materials Used] EPDM1: Dow Chemical's "Nordel IP 4520", ethylene content 50% by mass, diene content (ethylidene norbornene content) 4.9% by mass, Mooney viscosity 20ML (1+4) 125℃, specific gravity 0.86 EPDM2: Dow Chemical's "Nordel 6530 XFC", ethylene content 55% by mass, diene content (ethylidene norbornene content) 8.5% by mass, Mooney viscosity 30ML (1+4) 125℃, specific gravity 0.86 EPDM3: Dow Chemical's "Nordel 6565 XFC", ethylene content 55% by mass, diene content (ethylidene norbornene content) 8.5% by mass, Mooney viscosity 65ML (1+4) 125℃ EPDM4: Dow Chemical's "Nordel IP 4640", ethylene content 55% by mass, diene content (ethylidene norbornene content) 4.9% by mass, Mooney viscosity 40ML (1+4) 125℃ EPDM5: Dow Chemical's "Nordel IP 3760P", ethylene content 67% by mass, diene content (ethylidene norbornene content) 2.2% by mass, Mooney viscosity 63ML (1+4) 125℃ EPDM6: Dow Chemical's "Nordel IP 3745P", ethylene content 70% by mass, diene content (ethylidene norbornene content) 0.5% by mass, Mooney viscosity 45ML (1+4) 125℃ EBDM: Mitsui Chemicals, Inc. "K-9330M", ethylene content 50% by mass, diene content (ethylidene norbornene content) 7.1% by mass, Mooney viscosity 30ML (1+4) 125℃ EOM1: Ethylene-octene copolymer, Dow Chemical Company "Engage 8480", melting point 99℃, specific gravity 0.90 EOM2: Ethylene-octene copolymer, Dow Chemical Company "Engage 8180", melting point 47℃, specific gravity 0.86 EBM: Ethylene-butene copolymer, Dow Chemical Company "Engage 7467", melting point 34℃, specific gravity 0.86 EHM: Ethylene-hexene copolymer, Sumitomo Chemical Co., Ltd. "Excellent" FX201, melting point 94°C, specific gravity 0.90 Carbon black: "Seas S" manufactured by Tokai Carbon Co., Ltd. Silica 1: "Toxil 255G" manufactured by Oriental Silicas Co., Ltd., specific surface area 176 m² ２ / g Silica 2: Evonik Industries AG "Ultrasil VN3", BET specific surface area 180 m² ２ / g Silica 3: Evonik Industries AG "Ultrasil 9100GR", BET specific surface area 235 m² ２ / g Anti-aging agent: "Nocrack MB-O" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., 2-mercaptobenzimidazole Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd. Stearic acid: "Tsubaki Stearic Acid" manufactured by NOF Corporation Zinc methacrylate: "R-20S" manufactured by Asada Chemical Industries, Ltd., 85% purity Paraffin-based oil: "Diana Process Oil PW90" manufactured by Idemitsu Kosan Co., Ltd. Organic peroxide: "Perbutyl P-40MB" manufactured by NOF Corporation, 1,3-bis(2-t-butylperoxyisopropyl)benzene, 40% by mass of active ingredient Co-crosslinking agent: "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., N,N'-m-phenylenedimaleimide Sulfur: "MIDAS" manufactured by Bigen Chemical Co., Ltd.

[0242] [Preparation of Uncrosslinked Rubber Compositions] As uncrosslinked rubber compositions for forming adhesive rubber layers (hereinafter referred to as "adhesive rubber compositions"), each rubber composition with the formulations shown in Tables 11 to 24 was kneaded in a Banbury mixer to obtain kneaded rubber (lump-shaped uncrosslinked rubber compositions). Similarly, as uncrosslinked rubber compositions for use in rubber glue, kneaded rubber (lump-shaped uncrosslinked rubber compositions) was obtained from the rubber compositions with the formulations shown in Table 3. Furthermore, as uncrosslinked rubber compositions for forming tooth rubber layers and back rubber layers, each rubber composition with the formulations shown in Table 4 was kneaded in a Banbury mixer, and the obtained kneaded rubber was rolled to a predetermined thickness using a calender roll to produce uncrosslinked rubber sheets.

[0243] For the adhesive rubber composition, in preparing samples to measure the rubber hardness and tensile properties of the crosslinked rubber composition, an uncrosslinked rubber sheet obtained by rolling compounded rubber with a calender roll was used.

[0244] [Rubber Hardness of Crosslinked Rubber Composition] A crosslinked rubber sheet (100 mm x 100 mm x 2 mm thickness) was prepared by press-heating an uncrosslinked rubber sheet at a temperature of 170°C, a pressure of 2 MPa, and a time of 15 minutes. A laminate of three crosslinked rubber sheets was used as a sample, and the rubber hardness of the crosslinked rubber sheet was measured using a Type D or Type A durometer in accordance with the spring-type durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Method for determining hardness -). The test temperature was 23°C.

[0245] [Tensile properties (5% modulus) of crosslinked rubber composition] A crosslinked rubber sheet (100 mm x 100 mm x 2 mm thickness) was prepared by press-heating an uncrosslinked rubber sheet at a temperature of 170°C, a pressure of 2 MPa, and a time of 15 minutes. Test specimens were taken by punching out dumbbell-shaped (Type 3) specimens in accordance with JIS K 6251 (2017). For samples containing short fibers, dumbbell-shaped test specimens were taken from the crosslinked rubber sheet so that the longitudinal direction of the short fibers (parallel to the direction of the rows) was the tensile direction, and the longitudinal direction of the test specimen was approximately parallel to the longitudinal direction of the short fibers. The tensile stress (5% modulus) at 5% elongation was then measured in accordance with JIS K 6251 (2017). The tensile speed was 500 mm / min, the test temperature was 23°C, and a Shimadzu Corporation "Autograph AG-5000A" tensile testing machine was used.

[0246] [Core wire] A carbon fiber cord (12K-1 / 0, tensile modulus 230 GPa) was prepared by twisting one strand of 12K multifilament yarn [Toray Industries, Inc. "Torayca T700SC-12000", single filament fineness 0.67 dtex, total fineness 800 tex] into a single strand, and then bonding treatment was performed with an EPDM-based overcoat treatment agent to obtain a core wire with a core wire diameter of 1.0 mm.

[0247] [Tooth Fabric and Treatment of Tooth Fabric] (Examples A1-27 and Comparative Examples A1-4) (Examples B1-38 and Comparative Examples B1-6) As the tooth fabric precursor for the belt, a woven fabric shown in Table 1 was used, which had been immersed in an RFL treatment solution and rubber glue. Specifically, the woven fabric was immersed in the RFL treatment solution shown in Table 2 and dried, and the dried woven fabric was further immersed in rubber glue (a solution obtained by dissolving the rubber composition for rubber glue shown in Table 3 in methyl ethyl ketone at a ratio of 10% by mass) and dried to obtain an adhesive-treated woven fabric (tooth fabric precursor). Furthermore, by performing the coating treatment described in the [Modes for Carrying Out the Invention] section using adhesive rubber compositions with the compositions shown in Tables 11-24, the adhesive rubber composition was laminated onto one side of the adhesive-treated woven fabric to obtain a tooth fabric and an adhesive rubber layer precursor. This precursor is a tooth fabric precursor (basis weight approximately 820 g / m²). ２ The composite consisted of a woven fabric (approximately 1.1 mm thick) laminated with an adhesive rubber layer precursor (an adhesive rubber composition with an average thickness of 0.65 mm). The rubber hardness of the rubber composition for the rubber adhesive used to process the tooth cloth is also shown in Table 3.

[0248] (Examples A28-31) Tooth cloth and adhesive rubber layer precursors (composites in which the adhesive rubber layer precursor is laminated onto the tooth cloth precursor) were prepared in the same manner as in Example A10, except that the average thickness of the adhesive rubber layer precursor was changed to 0.2 mm (Example A28), 0.3 mm (Example A29), 1.0 mm (Example A30), and 1.2 mm (Example A31).

[0249] (Examples B39-42) Tooth cloth and adhesive rubber layer precursors (composites in which the adhesive rubber layer precursor is laminated onto the tooth cloth precursor) were prepared in the same manner as in Example B15, except that the average thickness of the adhesive rubber layer precursor was changed to 0.2 mm (Example B39), 0.3 mm (Example B40), 1.0 mm (Example B41), and 1.2 mm (Example B42).

[0250]

[0251]

[0252]

[0253] [Preparation of Toothed Belts] In Examples A1 to 31 and Comparative Examples A1 to 4, an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 4 was used as the uncrosslinked rubber sheet (precursor for the tooth rubber layer and back rubber layer) for forming the tooth rubber layer and back rubber layer. A toothed belt with a total thickness of 5.6 mm, tooth type G8M, tooth height (including tooth cloth) of 3.5 mm, tooth pitch of 8 mm, number of teeth of 140, core wire pitch of 1.4 mm, X value of arrangement density of 29%, circumference of 1120 mm, and width of 17 mm was prepared by the manufacturing method described in the section [Modes for Carrying Out the Invention]. For each test toothed belt (Examples and Comparative Examples), the composition of the adhesive rubber composition was changed to the compositions shown in Tables 11 to 16 for comparison. The rubber composition of the uncrosslinked rubber sheet for forming the tooth rubber layer and back rubber layer is the same as that of the adhesive rubber composition used in Comparative Example A1.

[0254] In Examples B1 to 42 and Comparative Examples B1 to 6, an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 4 was used as the precursor for forming the tooth rubber layer and back rubber layer. A toothed belt with a total thickness of 5.6 mm, tooth type G8M, tooth height (including tooth cloth) of 3.5 mm, tooth pitch of 8 mm, number of teeth of 140, core wire pitch of 1.4 mm, X value of arrangement density of 29%, circumference of 1120 mm, and width of 17 mm was manufactured using the manufacturing method described in the section [Modes for Carrying Out the Invention]. For each test specimen of the toothed belt (Examples and Comparative Examples), the composition of the adhesive rubber composition was changed to the compositions shown in Tables 17 to 24 for comparison. The rubber composition of the uncrosslinked rubber sheet for forming the tooth rubber layer and back rubber layer is the same as that used in Comparative Example B1.

[0255] Furthermore, the average thickness of the adhesive rubber layer of the toothed belt remained the same as the average thickness of the adhesive rubber layer precursor.

[0256]

[0257] [Evaluation and Judgment] For each test specimen (examples, comparative examples), the machinability of the toothed belt (formation of tooth shape), the temperature dependence of E', tooth chipping resistance (life cycle of the tooth portion), and durable running performance were verified to determine whether or not the problem of the present invention could be solved.

[0258] [Processability] (Test Method) The tooth shape of the toothed belt of the test specimen was visually observed to confirm whether the specified tooth shape was formed, and judged according to the criteria shown in Table 5. In other words, if the specified tooth shape was not formed (defective shape), it was determined that the toothed belt could not be manufactured and was rejected.

[0259] (Judgment criteria)

[0260]

[0261] [Temperature Dependence of E'] (Test Method) The storage modulus (E') of each rubber composition at 25°C and 120°C was measured using the following method.

[0262] An uncrosslinked rubber sheet was press-crosslinked at a temperature of 170°C, a pressure of 2 MPa, and a time of 15 minutes to produce a crosslinked rubber sheet (100 mm x 100 mm x 2 mm thick). A test piece with a rectangular cross-section (2.0 mm thick, 4.0 mm wide) and a length of 40 mm was taken from the crosslinked rubber sheet. The test piece was then chucked and fixed in the chucks of a viscoelasticity measuring device (VR-7121, manufactured by Ueshima Seisakusho Co., Ltd.) with a chuck-to-chuck distance of 15 mm. An initial strain (static strain) of 1.0% was applied, and the temperature was increased at a frequency of 10 Hz, a dynamic strain of 0.2% (i.e., with the initial strain of 1.0% as the center or reference position, applying a strain of ±0.2% in the longitudinal direction), and a heating rate of 1°C / min. The storage modulus (E') at 25°C and 120°C was read. The ratio (E') of E' at 120°C to E' at 25°C was then calculated. １２０ / E' ２５ The E'(E') at 120°C was calculated and judged according to the criteria shown in Table 6. １２０ ) is E' at 25℃ (E' ２５ It was smaller than ).

[0263] The ratio of E' at 120°C to E' at 25°C (E' １２０ / E' ２５ The closer this value is to 1, the smaller the change in physical properties of the rubber composition with respect to temperature, which indicates that it is preferable.

[0264] (Judgment criteria)

[0265]

[0266] [Tooth Breakage Resistance (Life Cycle of Tooth)] (Test Method) As shown in Figure 4, the teeth of the toothed belt 1 were hooked onto the projection 21a of a tooth shearing jig (a rigid body simulating the tooth shape of a toothed pulley) 21, and one tooth was pressed down with a constant pressure (tightening torque of 19.6 cNm / 17 mm width). A servopulser (manufactured by Shimadzu Corporation) was used to repeatedly apply loads of two levels (Conditions 1 and 2) shown in Table 7 at 30 Hz (30 cycles per second). The number of cycles until tooth breakage occurred (life cycle) was compared. Of the comparison results, the results under the more severe condition, Condition 2, were judged according to the criteria shown in Table 8. From the viewpoint of tooth breakage resistance in actual use for this application, toothed belts with a rating of d or higher were considered acceptable.

[0267] (Load level)

[0268]

[0269] (Judgment criteria)

[0270]

[0271] [Durability] (Driving test conditions) A toothed belt was attached to a two-axis running test machine equipped with a drive pulley (number of teeth: 24) and a driven pulley (number of teeth: 59). The running time until a failure (loss of teeth) occurred in the toothed belt was measured as the running life and judged according to the criteria shown in Table 9. The mounting tension of the toothed belt was 400 N, the rotation speed of the drive pulley was 900 rpm, the load on the driven pulley was 6.0 kW, and the ambient temperature was 25°C (room temperature).

[0272] Furthermore, this driving life (driving time until failure) is set to 390 hours as 1.00, and the driving life of each example and comparative example is shown as a relative value.

[0273] (Judgment criteria)

[0274]

[0275] [Overall Assessment] Based on the assessment of each evaluation item, an overall assessment was made according to the criteria shown in Table 10.

[0276] (Judgment criteria)

[0277]

[0278] [Verification Results and Discussion 1] The verification results are shown in Tables 11 to 16.

[0279]

[0280] (Examples A1-7 and Comparative Examples A1-4) Comparative Example A1 is an example in which the adhesive rubber layer is formed from the same rubber composition as the tooth rubber layer and the back rubber layer. That is, the adhesive rubber layer contains 65 parts by mass of carbon black and 5 parts by mass of silica as a reinforcing filler per 100 parts by mass of polymer component. In Comparative Example A1, the hardness and 5% modulus of the adhesive rubber composition were small, and there was no reinforcing effect on the rigidity of the tooth portion, so the life cycle and running life were judged as d or e (fail), and the overall judgment was rank E.

[0281] Comparative Example A2 is an example in which the composition of the reinforcing filler contained in the adhesive rubber layer was changed compared to Comparative Example A1, with the amount of silica increased to 20 parts by mass and the amount of carbon black decreased to 10 parts by mass. In Comparative Example A2, although the proportion of silica, which has an excellent reinforcing effect in the low strain region of the rubber, was increased, the hardness and 5% modulus of the adhesive rubber layer did not improve, and the overall evaluation was E rank, the same as in Comparative Example A1.

[0282] Comparative Example A3, Examples A1-7, and Comparative Example A4 are examples in which the silica content was increased based on Comparative Example A2. As the silica content, which has excellent reinforcing effect in the low strain region, increased, the hardness and 5% modulus of the rubber composition improved, as did the rigidity of the teeth, and there was a tendency for the life cycle and running life to improve. In Comparative Example A3, in which the silica content was increased to 40 parts by mass, the hardness and 5% modulus of the rubber composition improved compared to Comparative Example A2, but the overall rating was E, similar to Comparative Example A2. In Examples A1-3, in which the silica content was 50-65 parts by mass, the life cycle and running life reached a practical acceptable level (C or D rating), and the overall rating improved to D. Furthermore, in Examples A4-7, in which the silica content was 75-130 parts by mass, the overall rating improved to C. However, in Comparative Example A4, where the silica content was further increased to 150 parts by mass, the adhesive rubber composition (uncrosslinked rubber sheet) in the tooth cloth precursor was too rigid, resulting in poor fluidity. This made it difficult to form the teeth, and the predetermined tooth shape could not be formed. Therefore, it was deemed unmanufacturable in terms of processability (e rating), and the overall rating was E.

[0283] In Examples A1 (50 parts by mass), A2 (60 parts by mass), A3 (65 parts by mass), A4 (75 parts by mass), A5 (80 parts by mass), A6 (100 parts by mass), and A7 (130 parts by mass), where the silica content was 50 to 130 parts by mass per 100 parts by mass of polymer component, using a rubber composition with a hardness (Type D) of 50 or higher and a 5% modulus of 3 MPa or higher as the adhesive rubber composition reinforced the rigidity of the tooth portion, resulting in a life cycle and running life of an acceptable level (rated d or higher).

[0284] From the above results, it was confirmed that when a rubber composition with a silica content of 50 to 130 parts by mass per 100 parts by mass of polymer component is applied to the adhesive rubber layer, a reinforcing effect on the rigidity of the tooth is observed, and tooth chipping resistance is improved. It was also found that a rubber composition with a hardness (Type D) of 50 or higher and a 5% modulus of 3 MPa or higher is preferably used to form the adhesive rubber layer.

[0285]

[0286] (Examples A8-12) Compared to Example A4 (75 parts by mass of silica, 30 parts by mass of zinc methacrylate), Examples A9 (50 parts by mass), A10 (75 parts by mass), A11 (100 parts by mass), and A12 (130 parts by mass) showed an increase in the amount of zinc methacrylate to 50 parts by mass or more. As the amount of zinc methacrylate increased, there was a tendency for the rigidity of the teeth (life cycle and running life) to improve. In these examples, where the ratio of zinc methacrylate to 100 parts by mass of polymer component was 50 parts by mass or more, compared to Example A4, the increased amount of zinc methacrylate improved the crosslinking density of the rubber component, resulting in a reinforcing effect on the rigidity of the teeth. The life cycle and running life improved to a very good a or b rating, and the overall rating was B.

[0287] On the other hand, in Example A8, in which the amount of zinc methacrylate was reduced to 10 parts by mass compared to Example A4, the life cycle and running life decreased, resulting in a c or d rating. However, it maintained a practical acceptable level, and the overall rating was D.

[0288]

[0289] (Examples A13-21) Examples A13-16 are examples in which the type of ethylene-α-olefin elastomer (EPDM) polymer component was changed compared to Example A2. Examples A13-16 showed that the higher the diene content of the EPDM, the better the hardness and 5% modulus of the rubber composition, as well as the longer life cycle and running life tended to improve.

[0290] Examples A17 to A21 are examples in which the type of polymer component (ethylene-α-olefin elastomer) is changed compared to Example A10. From Examples A10 and A17 to A21, it was observed that the higher the diene content of the EPDM, the greater the hardness and 5% modulus of the rubber composition, as well as the life cycle and running life tended to improve.

[0291] In detail, Examples A10 (diene content 4.9% by mass), A17 (diene content 8.5% by mass), A18 (diene content 8.5% by mass), and A19 (diene content 4.9% by mass), which used EPDM with a diene content of 3% by mass or more, all received an a or b rating for life cycle and running life, and the overall rating was B.

[0292] On the other hand, in Examples A20 (2.2 mass%) and A21 (0.5 mass%), which had a reduced diene content compared to Example A10, the life cycle and running life decreased (rated b, c, or d), but a practical acceptable level was maintained, and the overall rating was C or D.

[0293] Therefore, it can be said that EPDM with a diene content of 3% by mass or more is suitable for the rubber composition that forms the adhesive rubber layer.

[0294] (Example A22) Example A22 is an example in which the polymer component was changed from Example A10 to EBDM (diene content 7.1% by mass). Similar to Example A10, the life cycle and running life were judged as a or b, and the overall judgment was rank B. The same results as with EPDM were obtained even when using EBDM.

[0295]

[0296] (Examples A23-25) Example A23 is an example in which 2 parts by mass of para-aramid short fibers were added to Example A3. Example A24 is an example in which 2 parts by mass of para-aramid short fibers were added to Example A10. In both cases, no significant difference was observed due to the addition of para-aramid short fibers. Example A25 is an example in which the amount of co-crosslinking agent was increased to 15 parts by mass compared to Example A10. In this example as well, there was no difference from Example A10. In other words, the reinforcing effect of short fibers and co-crosslinking agents is small.

[0297]

[0298] (Examples A26 and A27) Examples A26 and A27 are examples in which the type of silica (BET specific surface area) is changed compared to Example A10. However, the life cycle and running life were judged as a or b, similar to Example A10, and the overall judgment was rank B.

[0299]

[0300] (Examples A28-31) Examples A28-31 are examples in which the average thickness of the adhesive rubber layer was changed compared to Example A10. As the average thickness of the adhesive rubber layer increased, the life cycle improved, but the durability life improved up to an average thickness of about 0.65 mm, and then tended to decrease beyond that. This is because, in the life cycle test, which is affected by tooth stiffness, the life cycle improves as the average thickness of the high-rigidity adhesive rubber layer increases, as tooth stiffness increases. However, for durability life, which is affected by the balance between tooth stiffness and flexibility, it is thought that if the average thickness of the adhesive rubber layer becomes too large, the flexibility of the belt decreases, and the running life decreases. As a result of this balance between tooth stiffness and flexibility, in Examples A29 (0.3 mm), A10 (0.65 mm), and A30 (1.0 mm), where the average thickness of the adhesive rubber layer is in the range of 0.3 to 1.0 mm, the life cycle and running life were judged as a or b, and the overall judgment was rank B. In Example A31 (1.2 mm), where the average thickness of the adhesive rubber layer was large, the durability life was rated as C due to the influence of flexibility, resulting in an overall rating of C. On the other hand, in Example A28 (0.2 mm), where the average thickness of the adhesive rubber layer was small, the life cycle and durability life were rated as C or D due to the influence of low tooth rigidity, resulting in an overall rating of D. In both average thicknesses, a practical acceptable level was maintained.

[0301] (Effects Obtained) From the above verification, it was found that the configuration of the present invention [a configuration in which the polymer component contains ethylene-α-olefin elastomer, and the adhesive rubber layer is formed with a crosslinked rubber composition that has been hardened by containing a large amount (50 to 130 parts by mass) of silica per 100 parts by mass of the polymer component] can be used to obtain a toothed belt that can improve tooth chipping resistance without increasing material costs or manufacturing costs.

[0302] [Verification Results and Discussion 2] Further verification results are shown in Tables 17-24.

[0303]

[0304] (Examples B1-7 and Comparative Examples B1-4) Examples B1-7 and Comparative Examples B1-4 are embodiments in which an adhesive rubber layer is formed using a crosslinked rubber composition in which the rubber component is a blend of EPDM and EOM, with a blend ratio (mass ratio) of EPDM / EOM = 50 / 50, and are examples in which the content of silica, which is a reinforcing filler, is varied.

[0305] In Examples B1 (50 parts by mass), B2 (60 parts by mass), B3 (65 parts by mass), B4 (75 parts by mass), B5 (80 parts by mass), B6 ​​(100 parts by mass), and B7 (130 parts by mass), which had relatively high silica content, as the silica content increased, the hardness and 5% modulus of the rubber composition increased, the rigidity of the teeth improved, and there was a tendency for the life cycle and running life to improve. The overall evaluation for Examples B1 (50 parts by mass) and B2 (60 parts by mass) was rank C, but in particular, for Examples B3 to B7, which had silica content of 65 to 130 parts by mass, the overall evaluation improved to rank B. However, in Comparative Example B4, in which the silica content was further increased to 150 parts by mass, the adhesive rubber composition (uncrosslinked rubber sheet) in the tooth cloth precursor was too rigid, resulting in poor fluidity, which made it difficult to form the teeth, and the predetermined tooth shape could not be formed. Therefore, it was deemed unmanufacturable due to its processability (rating e), resulting in an overall rating of E.

[0306] On the other hand, in Comparative Examples B1 (5 parts by mass), B2 (20 parts by mass), and B3 (40 parts by mass), which had relatively small silica content, the rigidity of the tooth portion was low, and the resistance to tooth chipping (life cycle) was rated as d or e, resulting in an overall rating of E.

[0307] From the above results, it was confirmed that when a rubber composition with a silica content of 50 to 130 parts by mass per 100 parts by mass of polymer component is applied to the adhesive rubber layer, a reinforcing effect on the rigidity of the tooth is observed, and tooth chipping resistance is improved. It was also found that a rubber composition with a hardness (Type D) of 55 or higher and a 5% modulus of 6 MPa or higher is preferably used to form the adhesive rubber layer.

[0308]

[0309] (Examples B8-11, Example A13, and Reference Example B6) Example A13 is an example in which the polymer component is changed to EPDM2 only, compared to Example B3 (65 parts by mass of silica, EPDM2 / EOM1 = 50 / 50).

[0310] On the other hand, in Reference Example B6, in which the rubber component was changed to EOM1 only compared to Example B3 (65 parts by mass of silica, EPDM2 / EOM1 = 50 / 50), the adhesive rubber composition (uncrosslinked rubber sheet) in the tooth fabric precursor was too rigid, making it difficult to form the teeth using a method without pre-forming, and the predetermined tooth shape could not be formed. Therefore, it was deemed unmanufacturable in terms of processability (e rating), and the overall rating was E rank.

[0311] Next, Examples B8 to B11 are examples in which the blend ratio (mass ratio) of EPDM2 and EOM1 is varied compared to Example B3 (65 parts by mass of silica, EPDM2 / EOM1 = 50 / 50). In these examples, the ratio of EOM1 increases in the order of Example B8, Example B9, Example B10, Example B3, and Example B11. As the ratio of EOM1, a polymer component, increases, tooth chipping resistance (life cycle) improves, while the temperature dependence of E' tends to decrease. Specifically, in Examples B9 (EPDM2 / EOM1 = 75 / 25), B10 (EPDM2 / EOM1 = 60 / 40), and B3 (EPDM2 / EOM1 = 50 / 50), both the tooth chipping resistance and the temperature dependence of E' were rated b or higher, resulting in an overall rating of B. However, in Example B8 (EPDM2 / EOM1 = 90 / 10), the tooth chipping resistance was rated c, and in Example B11 (EPDM2 / EOM1 = 25 / 75), the temperature dependence of E' was rated c, resulting in a C rating for both.

[0312] From these results, it was confirmed that by using a blend of EPDM and EOM as the polymer component, tooth chipping resistance (life cycle) can be increased to a practical level. Furthermore, it was found that a blend ratio of approximately 50 / 50 between EPDM and EOM (for example, approximately 40 / 60 to 70 / 30) is preferable in that it balances the conflicting relationship between tooth chipping resistance and the temperature dependence of E'.

[0313]

[0314] (Examples B12-17) In Examples B13 (50 parts by mass), B14 (55 parts by mass), B15 (75 parts by mass), B16 (100 parts by mass), and B17 (130 parts by mass), in which the amount of zinc methacrylate was increased to 50 parts by mass or more compared to Example B4 (EPDM2 / EOM1 = 50 / 50), a tendency was observed for the rigidity of the teeth (life cycle and running life) to improve as the amount of zinc methacrylate increased. In these examples, where the ratio of zinc methacrylate to 100 parts by mass of polymer component was 50 parts by mass or more, compared to Example B4, a reinforcing effect on the rigidity of the teeth was observed, possibly due to an improvement in the crosslinking density of the rubber component by increasing the amount of zinc methacrylate, resulting in a very good life cycle and running life rating of A, and an overall rating of A.

[0315] On the other hand, in Example B12, in which the amount of zinc methacrylate was reduced to 10 parts by mass compared to Example B4, the life cycle and running life decreased, resulting in a rating of b or c. However, it maintained a practically acceptable level, and the overall rating was C.

[0316]

[0317] (Examples B18-23) Examples B18-20 are examples in which the proportion of zinc methacrylate was varied in the embodiment of EPDM2 / EOM1 = 70 / 30. In Example B18, where the proportion of zinc methacrylate was 30 parts by mass, the life cycle and running life were rated as b, and the overall rating was B rank. However, in Examples B19 (50 parts by mass) and B20 (75 parts by mass), where the proportion was increased to 50 parts by mass or more, the life cycle and running life improved to rated as a, and the overall rating was A rank.

[0318] Examples B21 to B23 are examples in which the proportion of zinc methacrylate was varied in the embodiment where EPDM2 / EOM1 = 90 / 10. In Example B21, where the proportion of zinc methacrylate was 30 parts by mass, the life cycle and running life were judged as b or c, and the overall judgment was rank C. However, in Examples B22 (50 parts by mass) and B23 (75 parts by mass), where the proportion was increased to 50 parts by mass or more, the life cycle and running life improved to a judgment of a or b, and the overall judgment was rank B.

[0319]

[0320] (Examples B24-29) Examples B24-26 are examples in which the polymer components blended with EPDM2 were changed compared to Example B3 (EPDM2 / EOM1 = 50 / 50, 65 parts by mass of silica, 30 parts by mass of zinc methacrylate). In Example B24, which used EOM2 instead of EOM1, the rigidity of the teeth decreased slightly, and the life cycle and running life decreased to a b or c rating, with an overall rating of C. In Example B25, which used EBM instead of EOM1, the rigidity of the teeth also decreased slightly, and the life cycle and running life decreased to a b or c rating, with an overall rating of C. In Example B26, which used EHM instead of EOM1, the rating was B, the same as in Example B3.

[0321] Examples B27 to B29 are examples in which the polymer components blended with EPDM2 were changed compared to Example B15 (EPDM2 / EOM1 = 50 / 50, 75 parts by mass of silica, 75 parts by mass of zinc methacrylate). In Example B27, which used EOM2 instead of EOM1, and Example B28, which used EBM, the life cycle decreased to a B rating, and the overall rating was B. In Example B29, which used EHM instead of EOM1, the rating was A, equivalent to Example B15.

[0322] From these results, it was found that toothed belts of rank C or higher, which meet practically acceptable standards, can be obtained not only in EOM but also in EBM and EHM. Furthermore, based on comparisons in EOM, a specific gravity of 0.88 or higher and / or a melting point of 50°C or higher can be considered preferable.

[0323]

[0324] (Examples B30-34) Examples B30-34 are examples in which the type of ethylene-α-olefin elastomer (EPDM) polymer component was changed compared to Example B15. Examples B30-34 showed that the higher the diene content of the EPDM, the better the hardness and 5% modulus of the rubber composition, as well as the longer life cycle and running life tended to improve.

[0325] In detail, Examples B15 (diene content 8.5% by mass), B30 (diene content 4.9% by mass), B31 (diene content 8.5% by mass), and B32 (diene content 4.9% by mass), which used EPDM with a diene content of 3% by mass or more, all received an "a" rating for life cycle and running life, and the overall rating was A rank.

[0326] On the other hand, in Examples B33 (2.2 mass%) and B34 (0.5 mass%), which had a reduced diene content compared to Example B15, the life cycle decreased (rated B or C), but a practical acceptable level was maintained, and the overall rating was B or C.

[0327] Therefore, it can be said that EPDM with a diene content of 3% by mass or more is suitable for the rubber composition that forms the adhesive rubber layer.

[0328] (Example B35) Example B35 is an example in which the polymer component was changed from Example B15 to EBDM (diene content 7.1% by mass). The life cycle and running life were rated as "a" and the overall rating was A, the same as in Example B15. The same results as with EPDM were obtained even when using EBDM.

[0329]

[0330] (Examples B36 and B37) Examples B36 and B37 are examples in which the type of silica (BET specific surface area) is changed compared to Example B15. However, the life cycle and running life were rated as 'a', similar to Example B15, and the overall rating was A.

[0331] (Example B38) Example B38 is an example in which the proportion of the crosslinking agent (organic peroxide) was reduced to 5 parts by mass compared to Example B15. No significant difference was observed even when the amount of organic peroxide was reduced. It can be said that the reinforcing effect of the crosslinking agent is small.

[0332]

[0333] (Examples B39-42) Examples B39-42 are examples in which the average thickness of the adhesive rubber layer was changed compared to Example B15. As the average thickness of the adhesive rubber layer increased, the life cycle improved, and the durability life improved up to an average thickness of about 0.65 mm, but tended to decrease beyond that. This is because, in the life cycle test, which is affected by tooth stiffness, the life cycle improves as the average thickness of the high-rigidity adhesive rubber layer increases, as tooth stiffness increases. However, for durability life, which is affected by the balance between tooth stiffness and flexibility, it is thought that if the average thickness of the adhesive rubber layer becomes too large, the flexibility of the belt decreases, and the running life decreases. As a result of this balance between tooth stiffness and flexibility, in Examples B40 (0.3 mm), B15 (0.65 mm), and B41 (1.0 mm), where the average thickness of the adhesive rubber layer is in the range of 0.3 to 1.0 mm, the life cycle and running life were rated as A, and the overall rating was A rank. In Example B42 (1.2 mm), where the average thickness of the adhesive rubber layer was large, the durability life was rated as C due to the effect of flexibility, resulting in an overall rating of C. On the other hand, in Example B39 (0.2 mm), where the average thickness of the adhesive rubber layer was small, the life cycle and durability life were rated as C due to the effect of low tooth rigidity, resulting in an overall rating of C. In both average thicknesses, a practical acceptable level was maintained.

[0334] From the above examples, it can be seen that the polymer components constituting the adhesive rubber layer only need to have a blend ratio of EOM1 of EPDM2 / EOM1 = 90 / 10 or higher. In particular, from the viewpoint of balancing the rigidity of the teeth (life cycle and running life) with the temperature dependence of E', a blend ratio of EPDM2 / EOM1 = 70 / 30 to 40 / 60 is preferable. Furthermore, it was found that particularly excellent toothed belts can be obtained when the silica content is 65 parts by mass or more and the zinc methacrylate content is 50 parts by mass or more per 100 parts by mass of polymer components.

[0335] (Effects obtained) From the above verification, the composition of the present invention [polymer components are ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８It was found that a toothed belt with improved resistance to tooth breakage can be obtained without increasing material or manufacturing costs by forming an adhesive rubber layer with a crosslinked rubber composition containing an olefin copolymer and a large amount of silica (50 to 130 parts by mass) to increase hardness.

[0336] Although the present invention has been described in detail and with reference to specific embodiments, 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. This application is based on Japanese Patent Application No. 2025-056210, filed March 28, 2025, Japanese Patent Application No. 2025-056211, filed March 13, 2026, Japanese Patent Application No. 2026-041507, and filed March 13, 2026, Japanese Patent Application No. 2026-041508, the contents of which are incorporated herein by reference.

[0337] The toothed belt (meshing transmission belt or toothed transmission belt) of the present invention, when combined with a toothed pulley, can be used in various fields where synchronization between input and output is required, such as power transmission mechanisms in vehicles such as automobiles and motorcycles, power transmission mechanisms in industrial machinery such as motors and pumps, machinery such as automatic doors and automated machines, office automation (OA) equipment components, coin handling equipment, photocopiers, and printing presses. The toothed belt of the present invention can be used particularly in industrial machinery for high-load (high-horsepower) applications and as a power transmission belt (timing belt) for rear-wheel drive in motorcycles.

[0338] 1...Toothed belt 1a...Tooth portion 1b...Tooth base portion 1c...Back portion 2...Tooth fabric 3...Adhesive rubber layer 4...Tooth rubber layer 5...Core wire 6...Back rubber layer

Claims

1. A toothed belt comprising: a back portion in which a core wire extending along the circumferential direction of the belt is embedded; a plurality of teeth formed on the inner circumferential surface of the back portion at intervals in the circumferential direction of the belt; a back rubber layer forming the back portion; a tooth rubber layer forming the teeth; a tooth cloth formed on the surface of the teeth; and an adhesive rubber layer interposed between the tooth rubber layer and the tooth cloth, wherein the adhesive rubber layer comprises a crosslinked product of a first rubber composition comprising a first polymer component and silica; the first polymer component comprises a first ethylene-α-olefin elastomer; the proportion of silica is 50 to 130 parts by mass per 100 parts by mass of the first polymer component; the tooth rubber layer and the back rubber layer comprise a crosslinked product of a second rubber composition comprising a second ethylene-α-olefin elastomer; and the rubber hardness of the crosslinked product of the first rubber composition is greater than the rubber hardness of the crosslinked product of the second rubber composition.

2. The toothed belt according to claim 1, wherein the rubber hardness of the crosslinked product of the first rubber composition is 50 or more on a Type D hardness scale.

3. The toothed belt according to claim 1 or 2, wherein the 5% modulus of the crosslinked product of the first rubber composition is 3 MPa or more in the circumferential direction of the belt.

4. The toothed belt according to any one of claims 1 to 3, wherein the first ethylene-α-olefin elastomer comprises an ethylene-α-olefin-diene terpolymer.

5. The first ethylene-α-olefin elastomer is an ethylene-α-olefin-diene terpolymer and an ethylene-α-C ４－８ A toothed belt according to any one of claims 1 to 3, comprising an olefin copolymer.

6. The ethylene-α-olefin-diene terpolymer and the ethylene-α-C ４－８ The toothed belt according to claim 5, wherein the mass ratio of the olefin copolymer is former / latter = 80 / 20 to 20 / 80.

7. The aforementioned ethylene-α-C ４－８ The olefin copolymer has a specific gravity of 0.88 or higher, ethylene-α-C ５－８ The toothed belt according to claim 5 or 6, which is an olefin copolymer.

8. The toothed belt according to claim 4 or 5, wherein the diene content of the ethylene-α-olefin-diene ternary copolymer is 3% by mass or more.

9. The toothed belt according to any one of claims 1 to 8, wherein the first rubber composition contains an unsaturated metal carboxylate salt, and the proportion of the unsaturated metal carboxylate salt is 50 parts by mass or more per 100 parts by mass of the first polymer component.

10. The toothed belt according to any one of claims 1 to 9, wherein the average thickness of the adhesive rubber layer is 0.3 to 1 mm.

11. The toothed belt according to any one of claims 1 to 10, wherein the X value of the arrangement density of the core wires is 15% or more.

12. A method for manufacturing a toothed belt according to any one of claims 1 to 11, comprising a crosslinking molding step of crosslinking an uncrosslinked molded body obtained by laminating a tooth cloth precursor, an adhesive rubber layer precursor, a core wire precursor, and precursors for the tooth rubber layer and the back rubber layer.

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