Toothed belt, manufacturing method therefor, and toothed belt transmission mechanism

Abstract

The present invention pertains to a toothed belt comprising a back part in which core wires are embedded, and a plurality of tooth sections on the inner peripheral surface of the back part, and further comprising a back rubber layer forming the back part, a tooth rubber layer forming the tooth sections, and a tooth cloth formed on the surface of the tooth sections, wherein the tooth surface hardness of the tooth sections is D50 to D75 in the type D hardness, the tooth rubber layer and the back rubber layer include a crosslinked product of a first rubber composition containing a first polymer component, and the rubber hardness of the crosslinked product of the first rubber composition is lower than the tooth surface hardness.

Description

Toothed belt, method for manufacturing the same, and toothed belt transmission mechanism

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

[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 a belt and the flexibility required for processability and flexibility are inversely related, and manufacturing a toothed belt with such characteristics inevitably increases material costs and manufacturing costs. In particular, in high-load transmission applications such as rear-wheel drive for motorcycles, there is a high demand for resistance to tooth breakage, and it is especially difficult to achieve both high rigidity and flexibility while keeping material and manufacturing costs down.

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

[0009] Another object of the present invention is to provide a toothed belt, a method for manufacturing the same, and a toothed belt transmission mechanism that can improve resistance to tooth breakage, jumping resistance, and durable driving performance with high productivity and economy, even when applied to high-load transmission applications in rear-wheel drive of motorcycles.

[0010] As a result of intensive studies conducted by the present inventors to achieve the above object, they have found that by adjusting the tooth surface hardness in the tooth portion of a toothed belt whose surface is formed of tooth cloth and in which the rubber compositions of the back rubber layer and the tooth rubber layer are the same to D50 to D75 in terms of type D hardness, and adjusting the rubber hardness of a crosslinked product of the rubber composition (crosslinked rubber composition) to be lower than the tooth surface hardness, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency, and thus completed the present invention.

[0011] That is, the present invention includes the following aspects.

[0012] Aspect [1]: A toothed belt comprising: a back portion in which a core wire extending along the belt circumferential direction is embedded; a plurality of tooth portions formed on the inner circumferential surface of the back portion at intervals in the belt circumferential direction; a back rubber layer forming the back portion; a tooth rubber layer forming the tooth portions; and a tooth cloth formed on the surface of the tooth portions, wherein the tooth surface hardness of the tooth portions is D50 to D75 in terms of type D hardness, the tooth rubber layer and the back rubber layer comprise a crosslinked product of a first rubber composition containing a first polymer component, and the rubber hardness of the crosslinked product of the first rubber composition is lower than the tooth surface hardness.

[0013] Aspect [2]: The toothed belt according to aspect [1], wherein the tooth cloth comprises a crosslinked product of a second rubber composition containing a second polymer component.

[0014] Aspect [3]: The toothed belt according to aspect [1] or [2], wherein an adhesive rubber layer containing a crosslinked product of a third rubber composition containing a third polymer component is interposed between the tooth rubber layer and the tooth cloth.

[0015] Aspect [4]: The toothed belt according to aspect [3], wherein the first polymer component, the second polymer component and the third polymer component comprise an ethylene-α-olefin elastomer or a hydrogenated nitrile rubber.

[0016] Aspect [5]: The toothed belt according to any one of aspects [1] to [4], wherein the tooth surface hardness of the tooth portions is D60 or higher in terms of type D hardness.

[0017] Aspect [6]: The toothed belt according to any one of aspects [3] to [5], wherein the average thickness of the adhesive rubber layer is 0.3 to 1 mm.

[0018] Aspect [7]: The toothed belt according to any one of Aspects [1] to [6], wherein the X value of the arrangement density of the core wires is 15% or more.

[0019] Aspect [8]: A toothed belt transmission mechanism comprising the toothed belt according to any one of Aspects [1] to [7], and a pulley.

[0020] Aspect [9]: The toothed belt transmission mechanism according to Aspect [8], which is used for transmission applications in rear wheel drive of motorcycles.

[0021] Aspect

[10] : The method for producing a toothed belt according to any one of Aspects [1] to [7], comprising a crosslinking molding step of crosslinking an uncrosslinked molded article containing a tooth cloth precursor, a core wire precursor, and precursors of a tooth rubber layer and a back rubber layer.

[0022] In the present application, a numerical range represented by "A to B" means "from A to B inclusive", and is used to include the numerical values A and B at both ends thereof.

[0023] Also, in the present application, "inner circumferential surface" means "a surface on the inner circumferential side of the belt" in each layer or the belt, and "outer circumferential surface" means "a surface on the outer circumferential side of the belt" in each layer or the belt.

[0024] In the present invention, in the tooth portion of a toothed belt whose surface is formed of tooth cloth, and wherein the rubber compositions of the back rubber layer and the tooth rubber layer are identical, the tooth surface hardness of the tooth portion is adjusted to D50 to D75 on type D hardness scale, and the rubber hardness of a crosslinked product of the rubber composition (crosslinked rubber composition) is adjusted to be lower than the tooth surface hardness. Therefore, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency. In particular, the toothed belt of the present invention can be produced by an inexpensive method with high productivity that does not require pre-molding, and is also excellent in processability. Furthermore, by increasing the tooth surface hardness of the tooth portion, even when applied to high-load transmission applications in rear wheel drive of motorcycles, tooth chipping resistance, jumping resistance and durable running performance (running life) can be improved with high productivity and economic efficiency.

[0025] 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.

[0026] [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.

[0027] 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.

[0028] 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 surface of the back portion 1c and extending in the belt width direction, with the belt surface (inner surface) on the tooth side being made of tooth fabric 2. The back portion 1c is formed of a back rubber layer 6, which forms the outer surface of the belt. Furthermore, the teeth 1a are formed of a tooth rubber layer 4, an adhesive rubber layer 3 covering the inner surface of the tooth rubber layer 4, and the tooth fabric 2 covering the adhesive rubber layer 3 and forming the inner surface of the belt. 。

[0029] 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.

[0030] 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).

[0031] 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. 。

[0032] 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.

[0033] 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.

[0034] 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.

[0035] 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.

[0036] Alternatively, the tooth portion may be directly covered with tooth cloth to form the tooth rubber layer without interposing an adhesive rubber layer. However, interposing an adhesive rubber layer is preferable because it makes it easier to adjust the tooth surface hardness to a high range and is easily applicable to high-load transmission applications in rear-wheel drive systems of motorcycles.

[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] The toothed belt of the present invention has a tooth fabric arranged on the surface side (inner surface side), and while the tooth rubber layer and back rubber layer have low hardness (low modulus of elasticity), the surface of the teeth has high rigidity (high hardness). The toothed belt of the present invention is formed from a rubber composition containing the same low-hardness and inexpensive polymer component for both the back rubber layer and the tooth rubber layer, and can be manufactured by a simple and inexpensive method that does not require pre-forming. Furthermore, because the surface of the teeth has high hardness, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency. Specifically, since the tooth surface hardness of the teeth is D50 to D75 on the Type D hardness scale, the rigidity of the tooth surface is improved, and the tooth chipping resistance of the toothed belt can be improved.

[0041] The tooth surface hardness should be D50 to D75 on the Type D hardness scale, preferably D55 to D75, particularly preferably D60 to D75, even more preferably D65 to D75, more preferably D70 to D75, and most preferably D72 to D74. If the tooth surface hardness is too low, there is a risk of reduced resistance to tooth chipping, and if it is too high, there is a risk of reduced flexibility.

[0042] In this application, the tooth surface hardness (Type D hardness) of the tooth portion is expressed as the value measured using a Type D 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 -). As shown in Figure 1, the tooth surface hardness (Type D hardness) of the tooth portion can be directly measured by applying a hardness tester to the surface near the top of the tooth portion from the direction of arrow A.

[0043] The method for adjusting the tooth surface hardness to the above range is not particularly limited. If an adhesive rubber layer is interposed between the tooth cloth and the tooth rubber layer, the tooth surface hardness may be adjusted by adjusting the rubber hardness of this adhesive rubber layer. Alternatively, the tooth surface hardness may be adjusted by adjusting the rubber hardness of the crosslinked material in the rubber adhesive used for bonding the tooth cloth.

[0044] (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 (first rubber composition containing a first polymer component).

[0045] (1A) First Polymer Component Examples of the first polymer component include diene rubber [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.], ethylene-α-olefin elastomer (ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.), chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber, etc. These polymer components can be used alone or in combination of two or more. Of these, ethylene-α-olefin elastomer and hydrogenated nitrile rubber (HNBR) are preferred.

[0046] Ethylene-α-olefin elastomers may contain ethylene units and α-olefin units as constituent units, and may further contain diene units. Therefore, ethylene-α-olefin elastomers include ethylene-α-olefin-diene terpolymers and ethylene-α-olefin copolymers. Of these, ethylene-α-olefin-diene terpolymers are preferred.

[0047] 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.

[0048] Non-conjugated diene monomers are typically used as diene monomers to form diene units. Examples of non-conjugated diene monomers include dicyclopentadiene, methylenenorbornene, ethylidenenorbornene, 1,4-hexadiene, and cyclooctadiene. Of these diene monomers, ethylidenenorbornene and 1,4-hexadiene (especially ethylidenenorbornene) are preferred.

[0049] Typical ethylene-α-olefin-diene terpolymers include, for example, ethylene-propylene-diene terpolymer (EPDM), ethylene-1-butene-non-conjugated diene copolymer (EBDM), and ethylene-1-octene-non-conjugated diene copolymer (EODM), among others. ３－８ Examples include olefin-diene terpolymers.

[0050] These ethylene-α-olefin-diene ternary copolymers can be used individually or in combination of two or more. Among these, EPDM and EBDM, which have excellent heat resistance, cold resistance, and weather resistance, are used. ３－６ An olefin-diene terpolymer is preferred, and ethylene-α-C ３－４An olefin-diene terpolymer is more preferred, and EPDM is particularly preferred. Therefore, ethylene-α-C ３－４ The proportion of the olefin-diene terpolymer may be 50% by mass or more relative to the entire ethylene-α-olefin elastomer, 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 alone).

[0051] In the ethylene-α-olefin-diene terpolymer of the first polymer component, the content of ethylene (proportion of ethylene units) in the ethylene-α-olefin-diene terpolymer 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, still more preferably 45 to 55% by mass, and most preferably 47 to 53% by mass.

[0052] In the ethylene-α-olefin-diene terpolymer of the first polymer component, the ratio (mass ratio) of ethylene to α-olefin (particularly α-C ３－４ olefin) is former / latter = 30 / 70 to 90 / 10, preferably 40 / 60 to 80 / 20, more preferably 50 / 50 to 60 / 40, and still more preferably 50 / 50 to 55 / 45.

[0053] In the present application, the α-olefin content means the mass proportion of α-olefin units among all units constituting the ethylene-α-olefin-diene terpolymer, and can be measured by a conventional method, or may be the mass proportion based on α-olefin as a monomer.

[0054] The ethylene-α-olefin-diene terpolymer of the first polymer component (particularly, ethylene-α-C ３－４The diene content (particularly the ethylidene norbornene content) of the olefin-diene terpolymer 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.

[0055] 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.

[0056] In the first polymer component, 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.

[0057] In this application, the iodine value of the ethylene-α-olefin-diene ternary copolymer can be measured by conventional methods, such as infrared spectroscopy.

[0058] In the first polymer component, the Mooney viscosity [ML(1+4)125°C] of the uncrosslinked ethylene-α-olefin-diene ternary copolymer 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.

[0059] 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.

[0060] 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.

[0061] HNBR may be partially hydrogenated nitrile rubber or fully hydrogenated nitrile rubber. The hydrogenation rate of HNBR can be selected from a range of approximately 50 to 100%, and may be 70 to 100%. HNBR may be carboxylated.

[0062] In this application, HNBR refers to a type of rubber that maintains the oil resistance advantage of conventional nitrile rubber while preventing the deterioration of rubber elasticity due to sulfur recombination reactions during thermal aging. This is achieved by chemically hydrogenating the unsaturated bonds (carbon-carbon double bonds) present in conventional nitrile rubber, thereby making recombination reactions during thermal aging less likely to occur and improving heat resistance.

[0063] The iodine value (unit: mg / 100 mg) of HNBR is, for example, 5 to 60 (for example, 7 to 50), preferably 8 to 40 (for example, 8 to 35), and more preferably 10 to 30.

[0064] In this application, the iodine value is an indicator of the amount of unsaturated bonds; a higher iodine value indicates a greater amount of unsaturated bonds in the polymer molecular chain. The iodine value is determined by adding an excess of iodine to the sample and allowing it to react completely (reacting with unsaturated bonds), then quantifying the remaining amount of iodine by redox titration. If the iodine value of HNBR is low, the crosslinking reaction between HNBRs is insufficient, resulting in lower rigidity of the crosslinked rubber, which may reduce deformation resistance during belt operation. On the other hand, if the iodine value of HNBR is high, the amount of unsaturated bonds becomes excessively high, which may lead to thermal and oxidative degradation of the crosslinked rubber, shortening the belt life.

[0065] HNBR can be made from composite polymers or polymer alloys containing unsaturated carboxylate metal salts (hereinafter referred to as "HNBR containing unsaturated carboxylate metal salts"), for example, HNBR in which zinc methacrylate is highly finely dispersed as an unsaturated carboxylate metal salt (for example, Zeon Corporation's product name "Zeoforte (ZSC)").

[0066] Furthermore, HNBR containing an unsaturated carboxylate metal salt is preferably used as a mixture with hydrogenated nitrile rubber (HNBR) that does not contain an unsaturated carboxylate metal salt. The mass ratio of hydrogenated nitrile rubber to unsaturated carboxylate metal salt may be adjusted by mixing commercially available HNBR containing an unsaturated carboxylate metal salt with commercially available hydrogenated nitrile rubber. The modulus and hardness may be adjusted by changing the mixing ratio of the two.

[0067] When the first polymer component contains ethylene-α-olefin elastomer, the proportion of 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 ethylene-α-olefin elastomer is too low, the first polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0068] If the first polymer component contains ethylene-α-olefin elastomer, the first polymer component may also contain other polymer components besides ethylene-α-olefin elastomer. The proportion of the other polymer components may be 100 parts by mass or less per 100 parts by mass of 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.

[0069] When the first polymer component contains HNBR, the proportion of HNBR 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 HNBR is too low, the first polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0070] If the first polymer component contains HNBR, the first polymer component may also contain other polymer components besides HNBR. The proportion of the other polymer components may be 100 parts by mass or less per 100 parts by mass of HNBR, 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 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. If the first polymer component contains ethylene-α-olefin elastomer, the proportion of the first polymer component is preferably 30 to 60% by mass in the first rubber composition, more preferably 35 to 50% by mass, and most preferably 40 to 45% by mass. If the first polymer component contains HNBR, the proportion of the first polymer component is preferably 30 to 75% by mass in the first rubber composition, more preferably 40 to 70% by mass, and most preferably 50 to 60% by mass. If the proportion of the first polymer component is too low, the flexibility of the toothed belt may decrease.

[0072] (1B) The first carbon black first rubber composition may further contain carbon black (first carbon black).

[0073] 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).

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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.

[0080] The proportion of the first carbon black may be 200 parts by mass or less per 100 parts by mass of the first polymer component, and may be, for example, 1 to 200 parts by mass.

[0081] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first carbon black may be 10 parts by mass or more (particularly 20 parts by mass or more) per 100 parts by mass of the first 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 first carbon black is too low, the mechanical properties of the tooth portion may deteriorate.

[0082] When the first polymer component contains HNBR, the proportion of the first carbon black may be 100 parts by mass or less per 100 parts by mass of the first polymer component, for example, 0.1 to 100 parts by mass, preferably 0.3 to 50 parts by mass, more preferably 0.5 to 30 parts by mass, more preferably 1 to 10 parts by mass, and most preferably 1.5 to 5 parts by mass. If the proportion of the first carbon black is too high, the mechanical properties of the tooth portion may deteriorate.

[0083] (1C) The first silica first rubber composition may further contain silica (first silica).

[0084] 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.

[0085] 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.

[0086] 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) through image analysis.

[0087] 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 150-200m ２ It is / g.

[0088] 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.

[0089] The proportion of the first silica may be 50 parts by mass or less per 100 parts by mass of the first polymer component, for example, 0 to 50 parts by mass.

[0090] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first silica may be 30 parts by mass or less per 100 parts by mass of the first polymer component, for example, 1 to 30 parts by mass, preferably 2 to 20 parts by mass, more preferably 3 to 10 parts by mass, and more preferably 4 to 7 parts by mass. If the proportion of the first silica is too high, the effects of the present invention may be reduced.

[0091] When the first polymer component contains HNBR, the proportion of the first silica may be 30 parts by mass or less per 100 parts by mass of the first polymer component, preferably 20 parts by mass or less, more preferably 10 parts by mass or less, and more preferably 5 parts by mass or less. If the proportion of the first silica is too high, the effects of the present invention may be reduced.

[0092] (1D) 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.

[0093] 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 mainly composed of silicates, 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.

[0094] Of these, metal oxides such as zinc oxide and polyvalent metal carbonates such as calcium carbonate are preferred. If the first polymer component contains ethylene-α-olefin elastomer, metal oxides are preferred, and if the first polymer component contains HNBR, polyvalent metal carbonates are preferred. As the first filler, commercially available powdered fillers used as rubber fillers can be used.

[0095] Furthermore, metal oxides may be added as crosslinking agents depending on the type of polymer component. For example, if the polymer component is HNBR, they may be added as crosslinking agents.

[0096] 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.

[0097] 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.

[0098] The proportion of the first filler can be selected from a range of approximately 0.3 to 50 parts by mass per 100 parts by mass of the first polymer component.

[0099] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first filler is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and more preferably 3 to 7 parts by mass, per 100 parts by mass of the first polymer component.

[0100] When the first polymer component contains HNBR, the proportion of the first filler is, for example, 1 to 50 parts by mass, preferably 5 to 45 parts by mass, more preferably 10 to 40 parts by mass, and more preferably 15 to 30 parts by mass, per 100 parts by mass of the first polymer component.

[0101] 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.

[0102] 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 ８－１４ Synthetic 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.

[0103] 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.

[0104] 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.

[0105] It is preferable to subject the first short fibers to a conventional adhesive treatment (or surface treatment) to adhere an adhesive component to at least a portion of the surface. Examples of adhesive treatments include treatment with adhesive components such as epoxy compounds (or epoxy resins), polyisocyanates, silane coupling agents, and RFL liquid.

[0106] 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.

[0107] The first rubber composition preferably contains substantially no first short fibers, and is particularly preferably free of first short fibers.

[0108] The proportion of the first filling compound is, for example, 0.3 to 50 parts by mass, preferably 0.5 to 40 parts by mass, more preferably 1 to 35 parts by mass, more preferably 2 to 30 parts by mass, and most preferably 3 to 25 parts by mass, per 100 parts by mass of the first polymer component.

[0109] (1E) The first rubber composition may further contain an unsaturated carboxylic acid metal salt (first unsaturated carboxylic acid metal salt).

[0110] 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.

[0111] 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.

[0112] 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.).

[0113] These unsaturated carboxylate metal salts can also be used individually or in combination of two or more.

[0114] 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.

[0115] The proportion of the first unsaturated carboxylate 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 first polymer component, for example, 1 to 100 parts by mass, preferably 10 to 70 parts by mass, and more preferably 15 to 50 parts by mass.

[0116] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) is, for example, 20 to 40 parts by mass, preferably 25 to 35 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first unsaturated carboxylic acid metal salt is too low, the tooth breakage resistance of the toothed belt decreases, and if it is too high, the processability is impaired, making it difficult to manufacture the toothed belt.

[0117] When the first polymer component contains HNBR, the proportion of the first unsaturated carboxylate metal salt (particularly zinc methacrylate) is, for example, 20 to 50 parts by mass, preferably 30 to 40 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first unsaturated carboxylate metal salt is too low, the tooth breakage resistance of the toothed belt decreases, and if it is too high, the processability is impaired, making it difficult to manufacture the toothed belt.

[0118] (1F) First Crosslinking Compound The first rubber composition may further contain 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.

[0119] As the first crosslinking agent, conventional components can be used depending on the type of the first polymer component, such as organic peroxides, sulfur-based crosslinking agents, and metal oxides.

[0120] 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.

[0121] Among these organic peroxides, dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene are preferred.

[0122] The proportion of the organic peroxide is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, per 100 parts by mass of the first polymer component.

[0123] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the organic peroxide is, for example, 5 to 18 parts by mass, preferably 6 to 15 parts by mass, and more preferably 8 to 12 parts by mass, per 100 parts by mass of the first polymer component.

[0124] When the first polymer component contains HNBR, the proportion of organic peroxide is, for example, 1 to 10 parts by mass, preferably 1.2 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.

[0125] 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.

[0126] 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.

[0127] The proportion of the sulfur-based crosslinking agent may be, for example, 5 parts by mass or less per 100 parts by mass of the first polymer component.

[0128] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the sulfur-based crosslinking agent is, for example, 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.

[0129] When the first polymer component contains HNBR, the proportion of the sulfur-based crosslinking agent is, for example, 3 parts by mass or less, preferably 1 part by mass or less, per 100 parts by mass of the first polymer component.

[0130] Examples of metal oxides include magnesium oxide, zinc oxide, and lead oxide. These metal oxides can be used individually or in combination of two or more.

[0131] When the first polymer component contains HNBR, the proportion of the metal oxide is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and more preferably 3 to 7 parts by mass, per 100 parts by mass of the first polymer component.

[0132] The proportion of the first crosslinking agent is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, per 100 parts by mass of the first polymer component.

[0133] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first crosslinking agent is, for example, 5 to 18 parts by mass, preferably 6 to 15 parts by mass, and more preferably 8 to 12 parts by mass, per 100 parts by mass of the first polymer component.

[0134] When the first polymer component contains HNBR, the proportion of the first crosslinking agent is, for example, 2 to 15 parts by mass, preferably 3 to 13 parts by mass, and more preferably 5 to 10 parts by mass, per 100 parts by mass of the first polymer component.

[0135] 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.

[0136] 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.

[0137] The proportion of the first co-crosslinking agent (crosslinking aid) can be selected from a range of approximately 0.2 to 40 parts by mass per 100 parts by mass of the first polymer component.

[0138] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first cocrosslinking agent is, for example, 1 to 30 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, and more preferably 8 to 15 parts by mass, per 100 parts by mass of the first polymer component.

[0139] When the first polymer component contains HNBR, the proportion of the first cocrosslinking agent is, for example, 0.3 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 0.7 to 3 parts by mass, per 100 parts by mass of the first polymer component.

[0140] The proportion of the first crosslinking compound can be selected from a range of, for example, 1 to 50 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.

[0141] When the first polymer component contains an ethylene-α-olefin elastomer, the proportion of the first crosslinking compound is, for example, 5 to 45 parts by mass, preferably 10 to 40 parts by mass, more preferably 15 to 35 parts by mass, and more preferably 20 to 30 parts by mass, per 100 parts by mass of the first polymer component.

[0142] When the first polymer component contains HNBR, the proportion of the first crosslinking compound is, for example, 3 to 40 parts by mass, preferably 5 to 30 parts by mass, more preferably 8 to 20 parts by mass, and more preferably 10 to 15 parts by mass, per 100 parts by mass of the first polymer component.

[0143] (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.

[0144] 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.).

[0145] 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).

[0146] 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.].

[0147] 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. When the first polymer component contains ethylene-α-olefin elastomer, a combination of petroleum-based softener and vegetable oil-based softener is particularly preferred, and when the first polymer component contains HNBR, vegetable oil-based softener is particularly preferred.

[0148] The proportion of the first softening agent may be 0.1 parts by mass or more per 100 parts by mass of the first polymer component.

[0149] When the first polymer component contains an ethylene-α-olefin elastomer, 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.

[0150] When the first polymer component contains HNBR, the proportion of the first softener is, for example, 0.1 to 10 parts by mass, preferably 0.3 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, more preferably 0.7 to 2 parts by mass, and most preferably 1 to 1.5 parts by mass, per 100 parts by mass of the first polymer component.

[0151] (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.

[0152] 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.

[0153] 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).

[0154] 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 ６－１０ Aryl-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.

[0155] 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.

[0156] 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.

[0157] (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.

[0158] 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.

[0159] (1J) Characteristics of the tooth rubber layer and back rubber layer The rubber hardness of the crosslinked material of the first rubber composition forming the tooth rubber layer and back rubber layer is a type D hardness, and may be D50 or less, and can be selected from a range of approximately D30 to D50. If the rubber hardness is too high, it may become expensive and the effects of the present invention may be reduced.

[0160] When the first polymer component contains an ethylene-α-olefin elastomer, the rubber hardness is a Type D hardness, for example, D35 to D48, preferably D40 to D47, more preferably D41 to D46, and more preferably D42 to D45.

[0161] When the first polymer component contains HNBR, the rubber hardness is a Type D hardness, for example, D40 or more and less than D50, preferably D43 to D49, and more preferably D45 to D48.

[0162] 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.

[0163] 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 A90, it is considered preferable to use a Type D durometer.

[0164] The tooth surface hardness (H1) of the tooth portion is greater than the rubber hardness (H2) of the crosslinked material of the first rubber composition. Specifically, the difference (H1-H2) between the tooth surface hardness (H1) and the rubber hardness (H2) of the crosslinked material of the first rubber composition may be 5 or more on the Type D hardness scale, for example, 5 to 45, preferably 10 to 40, more preferably 15 to 35, more preferably 20 to 33, and most preferably 25 to 30.

[0165] The 5% modulus (tensile stress at 5% elongation) of the crosslinked product of the first 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 large, it may become expensive and the effects of the present invention may be reduced.

[0166] 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.

[0167] 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.

[0168] 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.

[0169] 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.

[0170] (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).

[0171] 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.

[0172] 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.

[0173] 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.

[0174] 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).

[0175] The woven fabric may have a multi-layered structure (such as a double-layered structure), and in a woven structure comprising warp and weft threads, at least some of the weft threads may be made of low-friction fibers (or low-friction fibers) such as fluororesin-containing fibers (such as composite yarns containing fibers formed from fluororesins such as PTFE). For example, the warp threads may be made of polyamide fibers such as nylon 66, polyester fibers, etc., and the weft threads may be made of fluororesin-formed fibers alone; composite yarns of fluororesin-formed fibers and second fibers such as polyamide fibers or polyurethane fibers (elastic yarns); or composite yarns of this composite yarn and a second composite yarn formed from a plurality of the second fibers.

[0176] In this embodiment, it is preferable to use a fluorine-based fiber (e.g., PTFE fiber) with a low coefficient of friction as the weft thread located on the surface side of the tooth fabric (the side that engages with the toothed pulley) (exposed) in order to reduce friction between the tooth fabric and the toothed pulley. On the other hand, by using a fiber other than a fluorine-based fiber for the weft thread located on the back side of the tooth fabric (the side that adheres to the rubber constituting the teeth or back), it is possible to increase the adhesive strength between the tooth fabric and the rubber constituting the teeth. In this embodiment of the tooth fabric, friction in the engagement between the tooth fabric and the toothed pulley can be reduced, and sound can be suppressed.

[0177] Furthermore, when using fluorine-based fibers, it is preferable that low-melting-point fibers having a melting point that melts at the crosslinking (vulcanization) temperature of the teeth and back, which are based on rubber, are arranged around the fluorine-based fibers. Specifically, the form of the composite yarn containing fluorine-based fibers includes forms in which fluorine-based fibers and low-melting-point fibers are mixed and twisted together, or forms in which fluorine-based fibers are covered by low-melting-point fibers. The crosslinking (vulcanization) conditions of the teeth and back are not particularly limited, but generally, the crosslinking (vulcanization) temperature is 100 to 200°C and the crosslinking (vulcanization) time is about 1 minute to 5 hours.

[0178] In an embodiment in which low-melting-point fibers are arranged around fluorine-based fibers, the low-melting-point fibers melt during crosslinking (vulcanization) of the teeth and back of the belt, flow into the spaces between the fibers constituting the tooth fabric, and then crystallize when cooled to below their melting point. Therefore, the fluorine-based fibers are prevented from being cut or scattered by the impact and abrasion generated on the surface of the tooth fabric when the belt engages with or disengages from a toothed pulley. When the weft of the above embodiment is used as the tooth fabric of a toothed belt, the teeth and back are protected for a longer period of time due to the above effect, preventing chipping of the belt teeth and enabling a longer lifespan during high-load operation.

[0179] 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.

[0180] To enhance the adhesion between the tooth cloth and the tooth rubber layer, it is preferable to apply an adhesive treatment to the cloth forming the tooth cloth. Examples of adhesive treatments include immersing the cloth in an RFL treatment solution and then heating and drying it; treating it with an epoxy compound or isocyanate compound; or dissolving a rubber composition in an organic solvent to make a rubber glue, using this rubber glue to bond the cloth, and then heating and drying it. These methods can be performed individually or in combination, and the order and number of treatments are not limited. Of these methods, it is preferable to include a method of bonding the cloth using rubber glue; for example, the cloth may be immersed in an RFL treatment solution and then further bonded using rubber glue.

[0181] Adhesion methods using rubber cement include methods of immersing the fabric in rubber cement to adhere the rubber composition (second rubber composition) to the interior and / or surface of the fabric, and methods of coating the surface (one or both sides) of the fabric with rubber cement to adhere the rubber composition (second rubber composition) to the interior and / or surface of the fabric. Of these, when adjusting the tooth surface hardness by increasing the rubber hardness of the crosslinked material in the rubber cement, the method of coating the surface (one or both sides) of the fabric with rubber cement to adhere the rubber composition (second rubber composition) to the interior and / or surface of the fabric is preferred because it is easier to increase the tooth surface hardness.

[0182] (Rubber composition for rubber adhesive) When the bonding treatment of tooth cloth includes bonding treatment using rubber adhesive, the tooth cloth obtained by bonding treatment includes a crosslinked product of a second rubber composition containing a second polymer component as a rubber composition derived from rubber adhesive.

[0183] (2A) Second polymer component The second polymer component can be selected from the polymer components exemplified as the first polymer component, including preferred embodiments. The second polymer component may be the same as the first polymer component. Furthermore, if the first polymer component contains ethylene-α-olefin elastomer, it is preferable that the second polymer component also contains ethylene-α-olefin elastomer, and if the first polymer component contains HNBR, it is preferable that the second polymer component also contains HNBR.

[0184] 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 30 to 80% by mass, more preferably 40 to 70% by mass, more preferably 50 to 65% by mass, and most preferably 55 to 60% by mass. If the proportion of the second polymer component is too low, the flexibility of the toothed belt may decrease.

[0185] (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 in preferred embodiments.

[0186] The average primary particle size, iodine adsorption capacity, BET specific surface area, and ratio to the second polymer component of the second carbon black can be selected from those ranges of the first carbon black, including preferred ranges.

[0187] (2C) The second silica rubber composition may further contain silica (second silica). The second silica can be selected from the silicas exemplified as the first silica, including in preferred embodiments.

[0188] The average particle size and BET specific surface area range of the second silica can be selected from those ranges of the first silica, including preferred ranges.

[0189] The proportion of the second silica may be 1 part by mass or more per 100 parts by mass of the second polymer component, for example, 1 to 100 parts by mass.

[0190] When the second polymer component contains an ethylene-α-olefin elastomer, the proportion of the second silica is, for example, 1 to 30 parts by mass, preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, and more preferably 8 to 12 parts by mass, per 100 parts by mass of the second polymer component.

[0191] When the second polymer component contains HNBR, the proportion of the second silica is, for example, 10 to 90 parts by mass, preferably 20 to 70 parts by mass, more preferably 30 to 60 parts by mass, and more preferably 40 to 50 parts by mass, per 100 parts by mass of the second polymer component.

[0192] (2D) 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.

[0193] Examples of the second filler include the fillers exemplified as the first filler. The fillers can be used alone or in combination of two or more. When the second polymer component of the fillers contains an ethylene-α-olefin elastomer, a metal oxide such as zinc oxide is preferred.

[0194] Furthermore, metal oxides may be added as crosslinking agents depending on the type of the second polymer component. For example, if the second polymer component is HNBR, metal oxides may be added as crosslinking agents.

[0195] The average particle size of the second filler can be selected from the range of the average particle size of the first filler, including a preferred range.

[0196] The proportion of the second filler can be selected from a range of about 50 parts by mass or less (particularly 10 parts by mass or less) per 100 parts by mass of the second polymer component. When the second polymer component contains ethylene-α-olefin elastomer, the proportion is 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.

[0197] The second short fiber can be selected from the short fibers exemplified as the first short fiber, including preferred embodiments. The second rubber composition preferably contains substantially no second short fibers, and is particularly preferably free of second short fibers.

[0198] The proportion of the second filling compound can be selected from a range of about 50 parts by mass or less (particularly 10 parts by mass or less) per 100 parts by mass of the second polymer component. When the second polymer component contains ethylene-α-olefin elastomer, the proportion is 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.

[0199] (2E) The second rubber composition may further contain an unsaturated carboxylic acid metal salt (second unsaturated carboxylic acid metal salt).

[0200] The second unsaturated carboxylate metal salt can be selected from the unsaturated carboxylate metal salts exemplified as the first unsaturated carboxylate metal salt, including preferred embodiments.

[0201] The proportion of the second unsaturated carboxylate metal salt may be 100 parts by mass or less (particularly 30 parts by mass or less) per 100 parts by mass of the second polymer component, and if the second polymer component contains HNBR, it is preferably 1 to 50 parts by mass, more preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, and most preferably 7 to 15 parts by mass.

[0202] (2F) The second polyisocyanate rubber composition may further contain polyisocyanate. In particular, when adjusting the tooth surface hardness by increasing the rubber hardness of the crosslinked material of the rubber adhesive, it is preferable for the second rubber composition to contain polyisocyanate because it is easier to increase the tooth surface hardness.

[0203] Examples of polyisocyanates include aliphatic polyisocyanates [aliphatic diisocyanates such as propylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate (HDI), trimethylhexamethylene diisocyanate (TMDI), lysine diisocyanate (LDI), and aliphatic triisocyanates such as 1,6,11-undecane triisocyanate methyloctane and 1,3,6-hexamethylene triisocyanate], alicyclic polyisocyanates [cyclohexane 1,4-diisocyanate, isophorone diisocyanate (IPDI), hydrogenated xylylene diisocyanate, hydrogenated bis(iso) Examples include alicyclic diisocyanates such as cyanatophenyl)methane and alicyclic triisocyanates such as bicycloheptane triisocyanate, and aromatic polyisocyanates such as phenylene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), naphthalene diisocyanate (NDI), bis(isocyanatophenyl)methane (MDI), toluidine diisocyanate (TODI), and aromatic diisocyanates such as 1,3-bis(isocyanatophenyl)propane; and polymeric polyphenyl polyisocyanates such as polymeric MDI.

[0204] These polyisocyanates may also be derivatives such as polymers (dimers, trimers, tetramers, etc.), adducts, modified forms (biuret modified forms, alohanate modified forms, urea modified forms, etc.), or urethane oligomers having multiple isocyanate groups.

[0205] As modified or derivative forms of polyisocyanates, for example, adducts of polyisocyanates (such as aliphatic polyisocyanates like HDI) and polyhydric alcohols (such as trimethylolpropane or pentaerythritol), biuret forms of the polyisocyanates, and polymers of the polyisocyanates can be preferably used.

[0206] Among these polyisocyanates, aliphatic polyisocyanates or their derivatives (e.g., HDI or its trimers), aromatic polyisocyanates (TDI, MDI, etc.) or their derivatives are preferred, and aromatic polyisocyanates or their derivatives [4,4'-diphenylmethane diisocyanate (pure MDI), polymeric MDI (crude MDI), etc.] are particularly preferred due to their excellent reactivity and anchoring effect of the isocyanate group.

[0207] The proportion of polyisocyanate is 200 parts by mass or less (particularly 100 parts by mass or less) per 100 parts by mass of the second polymer component, and may be 0 to 10 parts by mass. However, when adjusting the tooth surface hardness by increasing the rubber hardness of the crosslinked material of the rubber adhesive, it is preferably 10 to 200 parts by mass, more preferably 30 to 150 parts by mass, even more preferably 50 to 120 parts by mass, and most preferably 70 to 100 parts by mass.

[0208] (2G) 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), a second crosslinking retarder (vulcanization retarder), and so on. 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.

[0209] As the second crosslinking agent, conventional components can be used depending on the type of second polymer component, such as organic peroxides, sulfur-based crosslinking agents, and metal oxides.

[0210] The organic peroxide can be selected from the organic peroxides exemplified as the first crosslinking agent, including preferred embodiments.

[0211] The proportion of organic peroxide may be, for example, 30 parts by mass or less (particularly 10 parts by mass or less) per 100 parts by mass of the second polymer component, and if the second polymer component contains HNBR, it is preferably 1 to 10 parts by mass, more preferably 3 to 8 parts by mass, and more preferably 4 to 7 parts by mass.

[0212] The sulfur-based crosslinking agent can be selected from the sulfur-based crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments.

[0213] The proportion of the sulfur-based crosslinking agent may be, for example, 10 parts by mass or less (particularly 3 parts by mass or less) per 100 parts by mass of the second polymer component. When the second polymer component contains an ethylene-α-olefin elastomer, the proportion is preferably 0.1 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2 parts by mass, and most preferably 0.7 to 1.5 parts by mass.

[0214] The second cocrosslinking agent can be selected from the cocrosslinking agents exemplified as the first cocrosslinking agent, including preferred embodiments.

[0215] The proportion of the second co-crosslinking agent may be 30 parts by mass or less (particularly 10 parts by mass or less) per 100 parts by mass of the second polymer component, and if the second polymer component contains HNBR, it is preferably 0.5 to 10 parts by mass, more preferably 1 to 5 parts by mass, and more preferably 2 to 3 parts by mass.

[0216] (2H) Second Other Compounding Agents The second rubber composition may further contain, as other compounding agents (second other compounding agents), conventional additives used in rubber compositions for toothed belts, in addition to the antioxidant exemplified as the first antioxidant. Examples of conventional additives include the additives exemplified as the first other compounding agents. These second other compounding agents can be used alone or in combination of two or more.

[0217] The total proportion of the second 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 second polymer component.

[0218] (2I) Characteristics of the second rubber composition The rubber hardness of the crosslinked product of the second rubber composition is a type A hardness, and may be A50 or higher, for example A60 to A95, preferably A70 to A90, and more preferably A80 to A85. When adjusting the tooth surface hardness by increasing the rubber hardness of the crosslinked product of the rubber adhesive, the rubber hardness of the crosslinked product of the second rubber composition is a type D hardness, and may be D40 or higher, for example D40 to D80, preferably D45 to D70, and more preferably D50 to D60.

[0219] (Adhesive Rubber Layer) The toothed belt of the present invention may have an adhesive rubber layer interposed between the tooth rubber layer and the tooth fabric. In the toothed belt of the present invention, it is preferable to interpose an adhesive rubber layer containing a crosslinked product of a third rubber composition containing a third polymer component between the tooth rubber layer and the tooth fabric, as this makes it easier to adjust the tooth surface hardness to D50 to D75 by adjusting the rubber hardness of the adhesive rubber layer.

[0220] (3A) Third polymer component Examples of the third polymer component include the polymer component exemplified as the first polymer component. The polymer component can be used alone or in combination of two or more. Among the polymer components, ethylene-α-olefin elastomer and HNBR are preferred. Furthermore, if the first polymer component contains ethylene-α-olefin elastomer, it is preferable that the third polymer component also contains ethylene-α-olefin elastomer, and if the first polymer component contains HNBR, it is preferable that the third polymer component also contains HNBR.

[0221] The ethylene-α-olefin elastomer preferably contains an ethylene-α-olefin-diene terpolymer, and from the standpoint of easily increasing tooth surface hardness, the ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ It is particularly preferable that the mixture contains an olefin copolymer.

[0222] 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 ３－１２Examples include olefins. Among these α-olefins, propylene, butene, and other α-C ３－４ Olefins are preferred.

[0223] In ethylene-α-olefin-diene ternary copolymers, non-conjugated diene monomers are typically used as diene monomers to form diene units. Examples of non-conjugated diene monomers include dicyclopentadiene, methylenenorbornene, ethylidenenorbornene, 1,4-hexadiene, and cyclooctadiene. Of these diene monomers, ethylidenenorbornene and 1,4-hexadiene (especially ethylidenenorbornene) are preferred.

[0224] Typical ethylene-α-olefin-diene terpolymers include, for example, ethylene-propylene-ethylidene norbornene terpolymer (EPDM), ethylene-1-butene-non-conjugated diene copolymer (EBDM), and ethylene-1-octene-non-conjugated diene copolymer (EODM), among others. ３－８ Examples include olefin-diene terpolymers.

[0225] These ethylene-α-olefin-diene ternary copolymers can be used individually or in combination of two or more. Among these, EPDM and EBDM, which have excellent heat resistance, cold resistance, and weather resistance, are used. ３－６ An olefin-diene terpolymer is preferred, and ethylene-α-C ３－４ An olefin-diene terpolymer is preferred. Therefore, ethylene-α-C ３－４ The proportion of the olefin-diene terpolymer may be 50% by mass or more of the total 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 100% by mass (ethylene-α-C ３－４ It may also be olefin-diene terpolymer only.

[0226] In the ethylene-α-olefin-diene terpolymer, which is the third polymer component, the ethylene content (percentage of ethylene units) in the ethylene-α-olefin-diene terpolymer 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.

[0227] 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.

[0228] 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.

[0229] In the third polymer component, the ethylene-α-olefin-diene ternary copolymer, the ratio (mass ratio) of ethylene to α-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.

[0230] 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.

[0231] The third polymer component is an ethylene-α-olefin-diene terpolymer (especially ethylene-α-C ３－４The diene content (particularly 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 (particularly 6 to 10% by mass), and most preferably 4.5 to 9% by mass (particularly 8 to 9% by mass). If the diene content is too low, the crosslinking density of the rubber composition will decrease, which may reduce the rigidity of the tooth surface (tooth surface hardness), and may also make it difficult to increase the tooth surface hardness. If the diene content is too high, the wear resistance of the toothed belt may decrease.

[0232] 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.

[0233] In the third polymer component, 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.

[0234] In this application, the iodine value of the ethylene-α-olefin-diene ternary copolymer can be measured by conventional methods, such as infrared spectroscopy.

[0235] In the third polymer component, the Mooney viscosity [ML(1+4)125°C] of the uncrosslinked ethylene-α-olefin-diene ternary copolymer 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.

[0236] 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-propylene-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.

[0237] 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.

[0238] 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, α-C such as hexene and octene can improve tooth chipping resistance, jumping resistance, and durable running performance. ５－８ Olefins (especially α-C) ６－８ Olefins are preferred.

[0239] 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.

[0240] 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.

[0241] 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.

[0242] 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.

[0243] 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, jumping resistance, and durability of running will decrease.

[0244] 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 140°C, preferably 50 to 135°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, jumping resistance, and durability during running will decrease.

[0245] Furthermore, in this application, ethylene-α-C ４－８ The melting point of olefin copolymers can be measured using a differential scanning calorimetry (DSC).

[0246] The ethylene-α-olefin elastomer may contain an ethylene-α-olefin-diene terpolymer. That is, the ethylene-α-olefin elastomer may consist only of the ethylene-α-olefin-diene terpolymer, or it may contain an ethylene-α-olefin-diene terpolymer and an ethylene-α-C ４－８ It may also include combinations with olefin copolymers.

[0247] Ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ The mass ratio of the olefin copolymer can be selected from a range of approximately 100 / 0 to 5 / 95, and is preferably 100 / 0 to 25 / 75, as this improves resistance to tooth chipping, jumping resistance, and durable running performance. If the ratio of ethylene-α-olefin-diene ternary copolymer is too low, there is a risk that the stability against temperature changes and processability will decrease.

[0248] Furthermore, ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ When combined with olefin copolymers, it becomes easier to improve the rigidity of the tooth surface and adjust the rubber hardness of the adhesive rubber layer to easily improve tooth surface hardness. Therefore, ethylene-α-olefin-diene terpolymer and ethylene-α-C ４－８ When combined with an olefin copolymer, the mass ratio is, for example, former / latter = 95 / 5 to 5 / 95, preferably 90 / 10 to 10 / 90, more preferably 80 / 20 to 20 / 80, more preferably 70 / 30 to 30 / 70, and most preferably 75 / 25 to 25 / 75.

[0249] 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 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 third polymer component will be expensive, and the effects of the present invention may be reduced.

[0250] The HNBR can be selected from the HNBRs exemplified as the first polymer component, including preferred embodiments. When improving tooth surface hardness by adjusting the rubber hardness of the adhesive rubber layer, it is preferable to use an HNBR containing an unsaturated carboxylate metal salt.

[0251] When the third polymer component contains ethylene-α-olefin elastomer, the proportion of ethylene-α-olefin elastomer may be 50% by mass or more of the third 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 ethylene-α-olefin elastomer is too low, the third polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0252] If the third polymer component contains ethylene-α-olefin elastomer, the third polymer component may also contain other polymer components besides ethylene-α-olefin elastomer. The proportion of the other polymer components may be 100 parts by mass or less per 100 parts by mass of 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.

[0253] When the third polymer component contains HNBR, the proportion of HNBR may be 50% by mass or more of the third 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 HNBR is too low, the third polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0254] If the third polymer component contains HNBR, the third polymer component may also contain other polymer components besides HNBR. The proportion of the other polymer components may be 100 parts by mass or less per 100 parts by mass of HNBR, 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.

[0255] The proportion of the third polymer component may be 10% by mass or more in the third rubber composition, for example, 10 to 90% by mass, preferably 20 to 80% by mass, and more preferably 20 to 50% by mass, more preferably 25 to 40% by mass, and most preferably 30 to 35% by mass, from the viewpoint of easily improving tooth surface hardness. If the proportion of the third polymer component is too low, the flexibility of the toothed belt may decrease.

[0256] (3B) Third Carbon Black The third rubber composition may further contain carbon black (third carbon black). The third carbon black can be selected from the carbon blacks exemplified as the first carbon black, including preferred embodiments.

[0257] The average primary particle size, iodine adsorption capacity, and BET specific surface area of ​​the third carbon black can be selected from those ranges of the first carbon black, including preferred ranges.

[0258] The proportion of the third carbon black may be 200 parts by mass or less per 100 parts by mass of the third polymer component, and may be, for example, 1 to 200 parts by mass. If the proportion of the third carbon black is too high, it may become difficult to improve the tooth chipping resistance while maintaining the processability of the toothed belt.

[0259] When the third polymer component contains an ethylene-α-olefin elastomer, the proportion of the third carbon black 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 8 to 12 parts by mass, per 100 parts by mass of the third polymer component.

[0260] When the third polymer component contains HNBR, the proportion of the third carbon black is, for example, 0.1 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 2 to 15 parts by mass, more preferably 3 to 10 parts by mass, and most preferably 4 to 7 parts by mass, per 100 parts by mass of the third polymer component.

[0261] (3C) The third silica third rubber composition may further contain silica (third silica). The third silica can be selected from the silicas exemplified as the first silica, including in preferred embodiments.

[0262] The average particle size and BET specific surface area range of the third silica can be selected from those ranges of the first silica, including preferred ranges.

[0263] The proportion of the third silica may be 200 parts by mass or less per 100 parts by mass of the third polymer component, and may be, for example, 0 to 150 parts by mass.

[0264] When the third polymer component contains an ethylene-α-olefin elastomer, the proportion of the third silica may be 30 to 200 parts by mass per 100 parts by mass of the third polymer component. Preferably, it is 40 to 150 parts by mass, more preferably 50 to 130 parts by mass, more preferably 60 to 120 parts by mass, and most preferably 70 to 100 parts by mass, in order to improve tooth surface hardness. Furthermore, in applications where resistance to tooth chipping, jumping resistance, and durable running are important, the proportion of the third silica is preferably 65 to 130 parts by mass, more preferably 75 to 130 parts by mass, more preferably 90 to 130 parts by mass, and most preferably 110 to 130 parts by mass per 100 parts by mass of the third polymer component. When a large amount of silica is blended with the ethylene-α-olefin elastomer, the hardness (modulus) of the adhesive rubber composition increases, and the rigidity of the tooth surface can be improved.

[0265] When the third polymer component contains HNBR, the proportion of the third silica is 100 parts by mass or less, 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 1 part by mass or less, per 100 parts by mass of the third polymer component.

[0266] (3D) Third Filling Compound The third rubber composition may further contain a filling compound (third filling compound). Examples of the third filling compound include a third filler and a third staple fiber.

[0267] The third filler can be selected from the fillers exemplified as the first filler, including preferred embodiments. The average particle size and the ratio of the third filler to the third polymer component can also be selected from those ranges of the first filler, including preferred ranges.

[0268] The third short fiber can be selected from the short fibers exemplified as the first short fiber, including preferred embodiments. The third rubber composition preferably contains substantially no third short fibers, and is particularly preferably free of third short fibers.

[0269] The range of the ratio of the third filler compound to the third 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.

[0270] (3E) The third rubber composition may further contain an unsaturated carboxylic acid metal salt (third unsaturated carboxylic acid metal salt). Increasing the proportion of the third unsaturated carboxylic acid metal salt can increase the crosslinking density in the crosslinked product of the third rubber composition, thereby improving the rigidity of the tooth (tooth surface hardness). In particular, the tooth surface hardness can be easily adjusted by adjusting the proportion of the third silica to a specific range and the proportion of the third unsaturated carboxylic acid metal salt to a specific range.

[0271] The third unsaturated carboxylate metal salt can be selected from the unsaturated carboxylate metal salts exemplified as the first unsaturated carboxylate metal salt, including in preferred embodiments.

[0272] The proportion of the third unsaturated carboxylate metal salt (particularly zinc methacrylate) may be 10 parts by mass or more per 100 parts by mass of the third polymer component, preferably 30 parts by mass or more, and more preferably 50 parts by mass or more.

[0273] When the third polymer component includes an ethylene-α-olefin elastomer, the proportion of the third unsaturated carboxylic acid metal salt can be selected from a range of, for example, 10 to 130 parts by mass (particularly 50 to 100 parts by mass) per 100 parts by mass of the third 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 jumping resistance, tooth chipping resistance, and durable running performance are important, the proportion of the third unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 30 parts by mass or more per 100 parts by mass of the third polymer component, preferably 50 to 130 parts by mass, more preferably 75 to 130 parts by mass, more preferably 90 to 130 parts by mass, and most preferably 110 to 130 parts by mass.

[0274] When the third polymer component contains HNBR, the proportion of the third unsaturated carboxylic acid metal salt is, for example, 40 to 200 parts by mass, preferably 50 to 180 parts by mass, more preferably 80 to 150 parts by mass, and more preferably 100 to 130 parts by mass, per 100 parts by mass of the third polymer component.

[0275] (3F) Third Crosslinking Compound The third rubber composition may further contain a crosslinking compound (third crosslinking compound). Examples of third crosslinking compounds include a third crosslinking agent (vulcanizing agent) for crosslinking the third polymer component, as well as a third co-crosslinking agent, a third crosslinking accelerator (vulcanization accelerator), and a third crosslinking retarder (vulcanization retarder). Of these, the third crosslinking compound preferably contains at least a third crosslinking agent and a third co-crosslinking agent (crosslinking aid), and a combination of a third crosslinking agent and a third co-crosslinking agent is particularly preferred.

[0276] The third crosslinking agent can be selected from the crosslinking agents exemplified as the first crosslinking agent, including preferred embodiments. The range of the ratio of the third crosslinking agent to the third polymer component can be selected from the range of the ratio of the first crosslinking agent to the first polymer component, including preferred ranges.

[0277] The third cocrosslinking agent can be selected from the cocrosslinking agents exemplified as the first cocrosslinking agent, including preferred embodiments.

[0278] The proportion of the third crosslinking agent can be selected from a range of approximately 0.2 to 40 parts by mass per 100 parts by mass of the third polymer component.

[0279] When the third polymer component contains an ethylene-α-olefin elastomer, the ratio of the third co-crosslinking agent to the third polymer component can be selected from the range of the ratio of the first co-crosslinking agent to the first polymer component, including a preferred range.

[0280] When the third polymer component contains HNBR, the proportion of the third cocrosslinking agent may be, for example, 0.3 to 30 parts by mass per 100 parts by mass of the third polymer component, and is preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, and more preferably 10 to 15 parts by mass, in order to improve tooth surface hardness.

[0281] The proportion of the third crosslinking compound can be selected from a range of approximately 1 to 50 parts by mass per 100 parts by mass of the third polymer component. If the proportion of the third crosslinking compound is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0282] When the third polymer component includes an ethylene-α-olefin elastomer, the range of the ratio of the third crosslinking compound to the third polymer component can be selected from the range of the ratio of the first crosslinking compound to the first polymer component, including a preferred range.

[0283] When the third polymer component contains HNBR, the proportion of the third crosslinking compound is, for example, 3 to 40 parts by mass, preferably 5 to 30 parts by mass, more preferably 10 to 25 parts by mass, and more preferably 15 to 20 parts by mass, per 100 parts by mass of the third polymer component.

[0284] (3G) Third Softener The third rubber composition may further contain a softener (third softener). The third softener can be selected from the softeners exemplified as the first softener, including preferred embodiments. The range of the ratio of the third softener to the third polymer component can be selected from the range of the ratio of the first softener to the first polymer component, including preferred ranges.

[0285] (3H) Third Anti-aging Agent The third rubber composition may further contain an anti-aging agent (third anti-aging agent). The third anti-aging agent can be selected from the anti-aging agents exemplified as the first anti-aging agent, including preferred embodiments. The range of the ratio of the third anti-aging agent to the third polymer component can be selected from the range of the ratio of the first anti-aging agent to the first polymer component, including preferred ranges.

[0286] (3I) Third Other Compounding Agent The third rubber composition may further contain, as other compounding agents (third other compounding agents), conventional additives used in rubber compositions for toothed belts. Examples of conventional additives include those exemplified as the first other compounding agents. The additives can be used alone or in combination of two or more. The range of the ratio of the third other compounding agent to the third polymer component can be selected from the range of the ratio of the first other compounding agent to the first polymer component, including a preferred range.

[0287] (3J) Characteristics of the adhesive rubber layer The rubber hardness of the crosslinked material of the third rubber composition for forming the adhesive rubber layer may be less than D50 (for example, D40 to D48) on a Type D hardness scale, and may be D50 or higher when the rubber hardness of the crosslinked material of the third rubber composition is increased to adjust the tooth surface hardness.

[0288] When the third polymer component contains an ethylene-α-olefin elastomer, the rubber hardness is a Type D hardness of, for example, D50 to D80, preferably D55 to D78, more preferably D60 to D75, more preferably D65 to D73, and most preferably D68 to D72.

[0289] When the third polymer component contains HNBR, the rubber hardness is, for example, D50 to D85 on the Type D hardness scale, preferably D60 to D83, more preferably D65 to D80, more preferably D68 to D77, and most preferably D70 to D75.

[0290] The 5% modulus of the crosslinked product of the third rubber composition may be 5 MPa or more (particularly 12 MPa or more) in the belt circumferential direction (longitudinal direction), for example, 5 to 35 MPa, preferably 10 to 30 MPa, more preferably 12 to 25 MPa, more preferably 15 to 20 MPa, and most preferably 16 to 18 MPa. If the 5% modulus is too small, the tooth breakage resistance of the toothed belt may decrease.

[0291] 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.

[0292] 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.

[0293] (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).

[0294] In the dorsal portion corresponding to the tooth root, a tooth rubber layer (or a tooth rubber layer and an adhesive rubber layer) may be interposed between the tooth cloth and the core wire, but the tooth cloth and the core wire may also be in contact without the interposition of a tooth rubber layer (or a tooth rubber layer and an adhesive rubber layer). Even when a tooth rubber layer (or a tooth rubber layer and an adhesive rubber layer) is interposed in the dorsal portion corresponding to the tooth root, the thickness of the tooth rubber layer (or a tooth rubber layer and an adhesive rubber layer) is formed to be thinner than that of the tooth portion.

[0295] (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.

[0296] 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.

[0297] 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.

[0298] 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.

[0299] 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.

[0300] 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.

[0301] In particular, when the toothed belt of the present invention is used for high-load transmission applications in the rear-wheel drive of motorcycles, a core wire containing high modulus fibers is preferred because it can increase the belt modulus and improve jumping resistance. Examples of high modulus fibers include carbon fibers, aramid fibers, PBO fibers, and metal fibers (steel fibers). These high modulus fibers can be used alone or in combination of two or more types. Among these high modulus fibers, carbon fibers and aramid fibers are preferred, and carbon fibers are particularly preferred. The proportion of high modulus fibers may be 10% by mass or more of the total fibers constituting the core wire, preferably 50% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass.

[0302] The core wire may further contain other fibers in addition to the high modulus fibers, as long as the effects of the present invention are not impaired. Examples of other fibers include synthetic fibers such as polyester fibers (polyalkylene arylate fibers, poly(p-phenylene naphthalate) fibers), polybenzoxazole fibers, acrylic fibers, and aliphatic polyamide fibers; and inorganic fibers such as glass fibers. The proportion of other fibers may be 50% by mass or less of the total fibers constituting the core wire, preferably 20% by mass or less, and more preferably 10% by mass or less.

[0303] The core wire may contain the high modulus fibers, may be a core wire formed of high modulus fibers, or may be a core wire formed of high modulus fibers and low modulus fibers.

[0304] The core wires formed from high-modulus fibers and low-modulus fibers may be, for example, core wires formed from twisted cords in which a plurality of sheath threads containing glass fibers are arranged around a core thread containing carbon fibers. In these core wires, the number of sheath threads per core thread is, for example, 10 to 20, preferably 11 to 19, and more preferably 13 to 18. The ratio of the average diameter D2 of the sheath threads to the average diameter D1 of the core threads (D2 / D1) is, for example, 0.2 to 0.4, preferably 0.25 to 0.38, and more preferably 0.3 to 0.36. The average diameter (average wire diameter) D1 of the core threads is, for example, 0.2 to 1 mm, preferably 0.3 to 0.8 mm, and more preferably 0.4 to 0.7 mm. The average diameter D2 of the sheath threads is, for example, 0.13 to 0.25 mm, preferably 0.15 to 0.23 mm, and more preferably 0.19 to 0.22 mm.

[0305] Of these, for high-load transmission applications in the rear-wheel drive of motorcycles, a core wire made of the high modulus of elasticity fiber is preferred, and a core wire made of carbon fiber is particularly preferred.

[0306] Examples of carbon fibers include pitch-based carbon fibers, polyacrylonitrile (PAN)-based carbon fibers, phenolic resin-based carbon fibers, cellulose-based carbon fibers, and polyvinyl alcohol-based carbon fibers. Commercially available carbon fibers include, for example, "Torayca®" manufactured by Toray Industries, Inc., "Tenax®" manufactured by Toho Tenax Co., Ltd., and "Dialead®" manufactured by Mitsubishi Chemical Corporation. These carbon fibers can be used individually or in combination of two or more types. Among these carbon fibers, pitch-based carbon fibers and PAN-based carbon fibers are preferred, with PAN-based carbon fibers being particularly preferred.

[0307] Furthermore, carbon fiber is suitably used as a multifilament yarn for high-load transmission applications in rear-wheel drive systems of motorcycles. Carbon fiber multifilament yarns can be selected from multifilament yarns with different filament counts, such as 6K and 12K. 6K represents a multifilament yarn with 6,000 filaments, and 12K represents a multifilament yarn with 12,000 filaments. The fineness of 6K multifilament yarn is approximately 400 tex, and the fineness of 12K multifilament yarn is approximately 800 tex.

[0308] Specific examples of carbon fiber cords used for the core wire include the carbon fiber cords (twisted cords) shown in Table 1.

[0309]

[0310] 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.

[0311] 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.

[0312] 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.

[0313] 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.

[0314] 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.

[0315] 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.

[0316] 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.

[0317] 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.

[0318] 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.

[0319] 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.

[0320] 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.

[0321] 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.

[0322] 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

[0323] 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.

[0324] 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.

[0325] [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.

[0326] (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.

[0327] 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.

[0328] 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 third rubber composition for forming the adhesive rubber layer.

[0329] As a method for coating a tooth cloth precursor with a third rubber composition, a method is preferred in which the rubber composition and the cloth are simultaneously passed between rolls rotating at the same speed, thereby pressing the rubber composition onto the cloth, from the viewpoint of simplicity and other factors. In this method, the third 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 compressed (compressed) using rolls or a calender, thereby pressing (coating) a solid third rubber composition onto one surface of the tooth cloth precursor, and obtaining a tooth cloth and an adhesive rubber layer precursor in which a sheet-like third rubber composition, which is an adhesive rubber layer precursor, is laminated on one surface of the tooth cloth precursor.

[0330] (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).

[0331] (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 method of the present invention, an 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.

[0332] (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.

[0333] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0334] [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 0.90HNBR containing unsaturated carboxylate metal salt: Zeon Corporation's "Zeoforte ZSC2295CX", base HNBR: unsaturated carboxylate metal salt (mass ratio) = 100:110, iodine value of base HNBR 28 mg / 100 mg HNBR: Zeon Corporation's "Zetpol 2010", iodine value 11 mg / 100 mg Carbon black: Tokai Carbon Co., Ltd.'s "Seasto S" Silica: Oriental Silicas Co., Ltd.'s "Toxil 255G", specific surface area 176 m² ２ / g Anti-aging agent: "Nocrack MB-O" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., 2-mercaptobenzimidazole Calcium carbonate: "Super #1500" manufactured by Maruo Calcium Co., Ltd., average particle size 1.5 μm 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., purity 85% Polymeric isocyanate (polymeric MDI): "Millionate (registered trademark) MR-200" manufactured by Tosoh Corporation, NCO content 30% by mass Paraffinic 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, active ingredient 40% by mass Co-crosslinking agent: "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., N,N'-m-phenylenedimaleimide sulfur: "MIDAS" manufactured by Migen Chemical Co., Ltd.

[0335] [Rubber Compositions] Tables 2 to 11 show rubber compositions for forming rubber glue for processing tooth cloth, rubber compositions for forming an adhesive rubber layer, and rubber compositions for forming a tooth rubber layer and a back rubber layer.

[0336]

[0337]

[0338]

[0339]

[0340]

[0341]

[0342]

[0343]

[0344]

[0345]

[0346] [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 2 to 11 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 Tables 2 and 11. Furthermore, as uncrosslinked rubber compositions for forming tooth rubber layers and back rubber layers, each rubber composition with the formulations shown in Tables 2 and 11 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.

[0347] 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.

[0348] [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.

[0349] [Tensile properties (5% modulus) of crosslinked rubber composition] Crosslinked rubber sheets (100 mm x 100 mm x 2 mm thickness) were 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. Then, the tensile stress (5% modulus) at 5% elongation was 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.

[0350] [Core wire 1] A carbon fiber cord (12K-1 / 0, tensile modulus of elasticity 230 GPa) was prepared by twisting one strand of 12K multifilament yarn [Toray Industries, Inc. "Torayca T700SC-12000", single yarn fineness 0.67 dtex, total fineness 800 tex] into a single strand, and then bonded with an EPDM-based overcoat treatment agent to obtain core wire 1 with a core wire diameter of 1.0 mm.

[0351] [Core wire 2] A carbon fiber cord (12K-1 / 0, tensile modulus of elasticity 230 GPa) was prepared by twisting one strand of 12K multifilament yarn [Toray Industries, Inc. "Torayca T700SC-12000", single yarn fineness 0.67 dtex, total fineness 800 tex] into a single strand, and then bonded with an HNBR-based overcoat treatment agent to obtain core wire 2 with a core wire diameter of 1.0 mm.

[0352] [Preparation of a lump-like kneaded material for forming an adhesive rubber layer precursor] Rubber compositions R1 to R65 shown in Tables 2 to 10 or rubber compositions R66 to R68 shown in Table 11 (lump-like uncrosslinked rubber compositions) were kneaded in a Banbury mixer to prepare a lump-like kneaded material for forming an adhesive rubber layer precursor.

[0353] [Preparation of a lump-shaped kneaded material for forming a rubber adhesive for tooth cloths] Rubber compositions RC1 to RC2 shown in Table 2 or rubber composition RC3 shown in Table 11 (lump-shaped uncrosslinked rubber compositions) were kneaded in a Banbury mixer to prepare a lump-shaped kneaded material for forming a rubber adhesive for processing tooth cloths (rubber adhesive for tooth cloths).

[0354] [Preparation of rubber adhesive for tooth cloth] (Rubber adhesive 1) 10 parts by mass of a lump of rubber composition RC1 shown in Table 2 was dissolved in 90 parts by mass of a solvent (methyl ethyl ketone) to prepare rubber adhesive 1 in solution.

[0355] (Rubber glue 2) Ten parts by mass of the lump-like kneaded rubber composition RC3 shown in Table 11 were dissolved in 90 parts by mass of a solvent (methyl ethyl ketone) to prepare a solution of rubber glue 2.

[0356] (Rubber glue 3) 40 parts by mass of the lump-like kneaded rubber composition RC1 shown in Table 2 was dissolved in 60 parts by mass of solvent (methyl ethyl ketone) to prepare a solution of rubber glue 3.

[0357] (Rubber glue 4) A composition (total 12 parts by mass) was prepared by mixing 10 parts by mass of a lump-like kneaded rubber composition RC1 shown in Table 2 with 2 parts by mass of polymeric MDI, and dissolving this mixture in 88 parts by mass of solvent (methyl ethyl ketone) to prepare a solution of rubber glue 4.

[0358] (Rubber glue 5) A composition (total 15 parts by mass) was prepared by mixing 10 parts by mass of a lump-like kneaded rubber composition RC2 shown in Table 2 with 5 parts by mass of polymeric MDI, and dissolving this mixture in 85 parts by mass of solvent (methyl ethyl ketone) to prepare a rubber glue 5 in solution form.

[0359] (Rubber glue 6) 40 parts by mass of the lump-like kneaded rubber composition RC2 shown in Table 2 was dissolved in 60 parts by mass of a solvent (methyl ethyl ketone) to prepare a rubber glue solution 6.

[0360] [Tooth Fabric and Treatment of Tooth Fabric] (Examples 1-62, 67-71 and Comparative Examples 1-7) As the tooth fabric precursor for the belt, a woven fabric (F1 or F2) shown in Table 12 was used, which had been immersed in RFL treatment solution and rubber glue. Specifically, the woven fabric was immersed in the RFL treatment solution shown in Table 13 and dried, and the dried woven fabric was further immersed in the aforementioned rubber glue and dried to obtain an adhesive-treated woven fabric (tooth fabric precursor).

[0361] Furthermore, by performing the lamination process (coating process) described in the section [Modes for Carrying Out the Invention] using adhesive rubber compositions with the compositions shown in Tables 18-28 and 30-31, a lump-shaped kneaded material for forming an adhesive rubber layer precursor was laminated onto one side of the bonded woven fabric, thereby obtaining a toothed cloth and an adhesive rubber layer precursor. This precursor is a toothed cloth precursor (basis weight approximately 820 g / m²). ２ It was a composite in which an adhesive rubber layer precursor (an adhesive rubber composition with an average thickness of 0.65 mm) was laminated onto a woven fabric with a thickness of approximately 1.1 mm.

[0362] (Examples 63-66) 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 10, except that the average thickness of the adhesive rubber layer precursor was changed to 0.2 mm (Example 63), 0.3 mm (Example 64), 1.0 mm (Example 65), and 1.2 mm (Example 66).

[0363]

[0364]

[0365] [Preparation of Toothed Belts] In Examples 1 to 71 and Comparative Examples 1 to 7, toothed belts with a total thickness of 5.6 mm, tooth type G8M, tooth height (including tooth fabric) of 3.5 mm, tooth pitch of 8 mm, number of teeth of 140, core wire pitch of 1.4 mm, X value of array density of 29%, circumference of 1120 mm, and width of 17 mm were prepared using the method described in the section [Modes for Carrying Out the Invention]. For toothed belts in Tables 18 to 30 where the rubber type is EPDM, core wire 1 was used as the core wire precursor, and for toothed belts in Table 31 where the rubber type is HNBR, core wire 2 was used as the core wire precursor.

[0366] 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.

[0367] [Evaluation and Judgment] For each test specimen (example and comparative example), the tooth surface hardness, tooth chipping resistance (life cycle of the tooth portion), jumping resistance, and durability of the toothed belt were verified to determine whether or not the problem of the present invention could be solved.

[0368] [Tooth Surface Hardness] The fabricated toothed belt was placed on a measuring stand with the teeth facing upwards (back facing downwards). 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 tooth surface hardness (Type D) of the tooth surface was measured using a Type D durometer, as indicated by arrow A in Figure 1. The test temperature was 23°C.

[0369] [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 load of 425 N (25 N / mm) was repeatedly applied at 30 Hz (30 cycles per second) by a servopulser (manufactured by Shimadzu Corporation). The number of cycles until tooth breakage occurred (life cycle) was compared and judged according to the criteria shown in Table 14. From the viewpoint of tooth breakage resistance in actual use for this application, toothed belts with a rating of c or higher were considered acceptable.

[0370] (Judgment criteria)

[0371]

[0372] [Jumping Resistance (Jumping Test)] (Running Test Conditions) Using a two-axis torque measuring test machine, a toothed belt was wrapped between a drive pulley (number of teeth: 24) and a driven pulley (number of teeth: 59), and the distance between the pulleys was adjusted so that the belt tension was 400N. Then, the drive pulley was rotated at 900 rpm, and the load on the driven pulley was continuously increased while the belt was running. The load torque applied to the driven pulley when jumping (tooth skipping) occurred was measured as the jumping torque. The jumping torque value was used as an indicator of jumping resistance, and the larger the jumping torque value, the better the toothed belt is in that it is less prone to tooth skipping.

[0373] The jumping torque value was determined by setting the jumping torque value (110 N·m) to 1.00, converting the jumping torque values ​​of each example and comparative example to relative values, and then judging them according to the criteria shown in Table 15. A larger value indicates improved rigidity (deformation resistance) of the tooth section.

[0374] (Judgment criteria)

[0375]

[0376] [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 16. 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).

[0377] 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.

[0378] (Judgment criteria)

[0379]

[0380] [Overall Assessment] Based on the assessment of each evaluation item, an overall assessment was made according to the criteria shown in Table 17.

[0381] (Judgment criteria)

[0382]

[0383] [Verification Results and Discussion] The verification results are shown in Tables 18 to 31.

[0384]

[0385] (Comparative Examples 1-2 and Examples 1-7) Comparative Example 1 is an example in which the adhesive rubber layer is formed from the same rubber composition (R1) 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 rubber component. In Comparative Example 1, the hardness and 5% modulus of the adhesive rubber composition were small, the tooth surface hardness was D43, and the life cycle, jumping torque, and running life were all rated as d, resulting in an overall rating of D rank.

[0386] Comparative Example 2 is an example in which the composition of the reinforcing filler contained in the adhesive rubber layer was changed from that of Comparative Example 1, with the amount of silica increased to 40 parts by mass and the amount of carbon black decreased to 10 parts by mass, and a rubber composition (R2) was used. As a result, in Comparative Example 2, the hardness and 5% modulus of the rubber composition improved compared to Comparative Example 1, and the tooth surface hardness improved slightly to D46, but the life cycle, jumping torque, and running life were all rated as d, and the overall rating remained at rank D.

[0387] In Examples 1 to 7, which used rubber compositions (R3 to R9) with increased silica content based on Comparative Example 2, an improvement in the hardness and 5% modulus of the rubber composition was observed as the silica content increased, possibly due to the increased silica content, which is excellent in reinforcing the low-strain region of rubber. As a result, tooth surface hardness improved to D50 or higher, and life cycle, jumping torque, and running life also improved, reaching a practical acceptable level (B or C rank).

[0388]

[0389] (Examples 8-12) Regarding the adhesive rubber layer, in Example 9 (R11), where the amount of zinc methacrylate was increased to 50 parts by mass compared to Example 4 (rubber composition R6; 75 parts by mass of silica, 30 parts by mass of zinc methacrylate), Example 10 (R12), where it was increased to 75 parts by mass, Example 11 (R13), where it was increased to 100 parts by mass, and Example 12 (R14), where it was increased to 130 parts by mass, a tendency was observed for tooth surface hardness, life cycle, jumping torque, and running life to improve as the amount of zinc methacrylate increased. It is possible that the crosslinking density of the rubber component improved with the increase in the amount of zinc methacrylate, resulting in a reinforcing effect on the rigidity of the tooth portion, and the overall evaluation was A rank.

[0390] On the other hand, in Example 8 (R10), where the amount of zinc methacrylate was reduced to 10 parts by mass, the tooth surface hardness decreased to D53, and the life cycle, jumping torque, and running life were rated as C. However, it maintained a practically acceptable level, and the overall rating was C.

[0391]

[0392] (Examples 13-21) Regarding the adhesive rubber layer, Examples 13-16 are examples in which the type of polymer component (EPDM) was changed compared to Example 3 (R5; 65 parts by mass of silica, 30 parts by mass of zinc methacrylate). From Examples 13-16, it was observed 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, jumping torque, and running life tended to improve.

[0393] Examples 10 and 17-21 are examples in which the type of polymer component (EPDM) was changed from Example 10 (R12; 75 parts by mass of silica, 75 parts by mass of zinc methacrylate). From Examples 10 and 17-21, it was observed that the higher the diene content of the EPDM, the better the hardness and 5% modulus of the rubber composition, as well as the tooth surface hardness, life cycle, jumping torque, and running life tended to improve.

[0394] In detail, in Examples 10 (R12; diene content 4.9% by mass), 17 (R19; diene content 8.5% by mass), 18 (R20; diene content 8.5% by mass), and 19 (R21; diene content 4.9% by mass), which used EPDM with a diene content of 3% by mass or more, the life cycle, jumping torque, and running life all received an "a" rating, and the overall rating was A rank.

[0395] On the other hand, in Examples 20 (R22; 2.2 mass%) and 21 (R23; 0.5 mass%), which had a reduced diene content compared to Example 10, the life cycle, jumping torque, and running life decreased (rated B or C), but a practical acceptable level was maintained, and the overall rating was B or C.

[0396] 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.

[0397] (Example 22) In this example, the polymer component of the adhesive rubber layer was changed from Example 10 (R12; 75 parts by mass of silica, 75 parts by mass of zinc methacrylate) to EBDM (diene content 7.1% by mass). The life cycle, jumping torque, and running life were all rated as 'a', similar to Example 10, and the overall rating was A. The same results as with EPDM were obtained even when using EBDM.

[0398]

[0399] (Examples 23-25) Regarding the adhesive rubber layer, Example 23 is an example in which 2 parts by mass of para-aramid short fibers were added to Example 3 (R5; 65 parts by mass of silica, 30 parts by mass of zinc methacrylate). Also, Example 24 is an example in which 2 parts by mass of para-aramid short fibers were added to Example 10 (R12; 75 parts by mass of silica, 75 parts by mass of zinc methacrylate). In both cases, no significant difference was observed due to the addition of para-aramid short fibers. Furthermore, Example 25 is an example in which the amount of co-crosslinking agent was increased to 15 parts by mass compared to Example 10. In this example as well, there was no difference from Example 10. In other words, the reinforcing effect of short fibers and co-crosslinking agents is small.

[0400]

[0401] (Examples 26-27) Example 26 is a belt in which the rubber adhesive treatment was omitted in the bonding treatment of the tooth cloth, as in Example 3 (rubber composition R5 of the adhesive rubber layer; 65 parts by mass of silica, 30 parts by mass of zinc methacrylate). Comparing Example 3 and Example 26, there is no difference in tooth surface hardness or tooth chipping resistance depending on whether or not the rubber adhesive treatment is performed. Therefore, the improvement in tooth surface hardness and tooth chipping resistance in Example 3 can be attributed to the effect of increasing the hardness of the adhesive rubber layer.

[0402] Furthermore, Example 27 is a belt in which the woven fabric used for the tooth cloth was changed to F2 compared to the belt in Example 26 (tooth surface hardness D53). However, the tooth surface hardness decreased to D51, and the resistance to tooth chipping (life cycle) also decreased slightly. Because F2 is a bulky woven fabric composed of a double-weave structure, the tooth surface hardness is slightly lower due to the flexibility of the tooth cloth, but it maintains a practical acceptable level (C rank).

[0403]

[0404] (Comparative Examples 3 to 5 and Examples 28 to 34) In Comparative Examples 1 to 2 and Examples 1 to 27, the rubber component of the adhesive rubber layer is EPDM, while in Comparative Examples 3 to 5 and Examples 28 to 34, the rubber component of the adhesive rubber layer is a blend of EPDM and EOM.

[0405] Comparative Example 3 is an example using rubber composition R28 in which the blend ratio (mass ratio) of EPDM2 / EOM1 is 50 / 50 and the content of silica, which is a reinforcing filler, is 5 parts by mass. In this example, the hardness and 5% modulus of the adhesive rubber composition were low, the tooth surface hardness was D39, all of the life cycle, jumping torque and running life were rated d, and the overall evaluation was Rank D.

[0406] In Comparative Examples 4 to 5 and Examples 28 to 34, which used rubber compositions (R29 to R37) obtained by increasing the amount of silica based on Comparative Example 3, the hardness and 5% modulus of the rubber composition tended to improve as the silica content increased. In Comparative Example 4 (R29), the tooth surface hardness increased to D44, and in Comparative Example 5 (R30), the tooth surface hardness increased to D49, but the overall evaluation of both cases was Rank D. In Examples 28 (R31) to 29 (R32), the tooth surface hardness increased to D50 or higher, and the life cycle, jumping torque and running life were also improved, reaching a practical pass level (Rank B). Furthermore, in Examples 30 (R33) to 34 (R37), the tooth surface hardness further increased, all of the life cycle, jumping torque and running life were rated a, and the overall evaluation was Rank A.

[0407]

[0408] (Examples 35 to 38) Regarding the adhesive rubber layer, Examples 35 to 38 are examples in which the blend ratio (mass ratio) of EPDM2 to EOM1 is varied based on Example 13 (R15; EPDM2 / EOM1 = 100 / 0) and Example 30 (R33; EPDM2 / EOM1 = 50 / 50). In these examples, the proportion of EOM1 increases in the order of Example 35, Example 36, Example 37, Example 30, and Example 38, and it was observed that as the proportion of EOM1 in the polymer component increases, all of the life cycle, jumping torque, and running life tend to be improved.

[0409] In Example 13, where EOM1 is not blended, the tooth surface hardness was D54, whereas in Example 35 (EPDM2 / EOM1 = 90 / 10), the tooth surface hardness was improved to D57. Furthermore, in Example 36 (EPDM2 / EOM1 = 75 / 25), Example 37 (EPDM2 / EOM1 = 60 / 40), Example 30 (EPDM2 / EOM1 = 50 / 50), and Example 38 (EPDM2 / EOM1 = 25 / 75), the tooth surface hardness reached D60 or higher, and the overall evaluation obtained rank A.

[0410] From the above results, it was confirmed that by using a blend of EPDM and EOM as the rubber component, the tooth surface hardness increases, and all of the life cycle, jumping torque, and running life can be improved.

[0411]

[0412] (Examples 39-44) Compared to Example 31 (R34; 75 parts by mass of silica, 30 parts by mass of zinc methacrylate) where EPDM2 / EOM1 = 50 / 50, in Examples 40 (R43; 50 parts by mass), 41 (R44; 55 parts by mass), 42 (R45; 75 parts by mass), 43 (R46; 100 parts by mass), and 44 (R47; 130 parts by mass), where the amount of zinc methacrylate was increased to 50 parts by mass or more, a tendency for tooth surface hardness to improve was observed as the amount of zinc methacrylate increased. It is possible that the crosslinking density of the rubber component improved with the increase in the amount of zinc methacrylate, resulting in a reinforcing effect on the rigidity of the tooth, with tooth surface hardness reaching D60 or higher, and especially when increased to 75 parts by mass or more, tooth surface hardness reached D70 or higher. In these examples, the life cycle, jumping torque, and driving life all improved to an excellent A rating, resulting in an overall A rank.

[0413] On the other hand, in Example 39, in which the amount of zinc methacrylate was reduced to 10 parts by mass compared to Example 31, the life cycle, jumping torque, and running life decreased to a B rating, but a practical acceptable level was maintained, and the overall rating was B.

[0414]

[0415] (Examples 45-50) Regarding the adhesive rubber layer, Examples 45-47 are examples in which the proportion of zinc methacrylate was varied in the embodiment of EPDM2 / EOM1 = 70 / 30. In Example 45, where the proportion of zinc methacrylate was 30 parts by mass, the overall evaluation was rank A, but in Examples 46 (50 parts by mass) and 47 (75 parts by mass), where the amount was increased to 50 parts by mass or more, tooth surface hardness improved, and the levels of life cycle, jumping torque, and running life also improved.

[0416] Examples 48 to 50 are examples in which the proportion of zinc methacrylate was varied in the embodiment of EPDM2 / EOM1 = 90 / 10. In Example 48, where the proportion of zinc methacrylate was 30 parts by mass, the overall evaluation was rank B. However, in Examples 49 (50 parts by mass) and 50 (75 parts by mass), where the proportion was increased to 50 parts by mass or more, the tooth surface hardness improved, and the life cycle, jumping torque, and running life also improved to an A rating, resulting in an overall evaluation of rank A.

[0417]

[0418] (Examples 51-56) Regarding the adhesive rubber layer, Examples 51-53 are examples in which the polymer components blended with EPDM2 were changed compared to Example 30 (R33; EPDM2 / EOM1 = 50 / 50, 65 parts by mass of silica, 30 parts by mass of zinc methacrylate). In Example 51, which used EOM2 instead of EOM1, and Example 52, which used EBM, the rigidity of the tooth portion was slightly reduced, and the overall evaluation was rank B. In Example 53, which used EHM instead of EOM1, it was rank A, equivalent to Example 30.

[0419] Examples 54 to 56 are examples in which the polymer components blended with EPDM2 were changed compared to Example 42 (R45; EPDM2 / EOM1 = 50 / 50, 75 parts by mass of silica, 75 parts by mass of zinc methacrylate). In all three examples, Example 54, which used EOM2 instead of EOM1, Example 55, which used EBM, and Example 56, which used EHM, were ranked A, the same as in Example 42.

[0420] From these results, it was found that toothed belts meeting practically acceptable standards can be obtained not only for EOM but also for EBM and EHM. Furthermore, based on comparisons with EOM, it can be said that a specific gravity of 0.88 or higher and / or a melting point of 50°C or higher are preferable.

[0421]

[0422] (Examples 57-62) Regarding the adhesive rubber layer, Examples 57-62 are examples in which the type of ethylene-α-olefin elastomer (EPDM2) of the polymer component was changed compared to Example 42 (R45; EPDM2 / EOM1 = 50 / 50, 75 parts by mass of silica, 75 parts by mass of zinc methacrylate). From Examples 57-62, it was observed that the higher the diene content of EPDM, the more the tooth surface hardness improved, as well as the life cycle, jumping torque, and running life tended to improve.

[0423] In detail, in Examples 57 (R60; diene content 4.9 mass%), 42 (R45; diene content 8.5 mass%), 58 (R61; diene content 8.5 mass%), and 59 (R62; diene content 4.9 mass%), which used EPDM with a diene content of 3 mass% or more, the life cycle, jumping torque, and running life all received an "a" rating, and the overall rating was A rank.

[0424] On the other hand, in Example 60 (R63; 2.2 mass%), which had a reduced diene content compared to Example 42, the overall rating was A, although the level was lower. Similarly, in Example 61 (R64; 0.5 mass%), a practically acceptable level was maintained, and the overall rating was B.

[0425] Furthermore, Example 62 (R65; diene content 7.1% by mass) using EBDM also received an "a" rating for life cycle, jumping torque, and running life, resulting in an overall rating of A.

[0426] Based on these results, it was confirmed that by adjusting the blend ratio of polymer components, silica content, and zinc methacrylate content in the rubber composition forming the adhesive rubber layer to increase hardness, a reinforcing effect on the rigidity of the tooth surface was observed, resulting in increased tooth surface hardness, improved life cycle, jumping torque, and running life.

[0427]

[0428] (Examples 63-66) These are examples in which the average thickness of the adhesive rubber layer was changed compared to Example 10 (R12; 75 parts by mass of silica, 75 parts by mass of zinc methacrylate). 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 Example 64 (0.3 mm), Example 10 (0.65 mm), and Example 65 (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, jumping torque, and running life all received an "a" rating, and the overall rating was A rank. In Example 66 (1.2 mm), where the average thickness of the adhesive rubber layer was large, the running life was rated as C due to the effect of flexibility, resulting in an overall rating of C. On the other hand, in Example 63 (0.2 mm), where the average thickness of the adhesive rubber layer was small, the life cycle, jumping torque, and running life were all 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.

[0429]

[0430] (Comparative Examples 1, 6 and Examples 67-69) As described above, Comparative Example 1 is an example in which the adhesive rubber layer is formed from the same rubber composition (R1) as the tooth rubber layer and back rubber layer. As the hardness and 5% modulus of the adhesive rubber composition are low and the tooth surface hardness is low at D43, the life cycle, jumping torque and running life were judged as d, and the overall judgment was rank D.

[0431] Examples 67 to 69 are examples in which the rubber adhesive used for bonding the tooth cloth was changed compared to Comparative Example 1. In Comparative Example 1, rubber adhesive 1 [rubber composition RC1 (hardness A80), solid content concentration 10%) was used for immersion treatment, whereas in Example 67, rubber adhesive 3 [rubber composition RC1 (hardness A80), solid content concentration 40%) was used for coating treatment on both sides of the cloth (200 g / m²). ２ This is an example of application. Specifically, by increasing the solid content concentration (40% by mass) relative to the rubber adhesive (1 unit), and increasing the amount of solid component adhering (difference in treatment method between immersion and double-sided coating), the amount of solid component derived from the rubber adhesive remaining on the tooth fabric after belt cross-linking is increased. As a result, the tooth surface hardness increased to D50, and the life cycle, jumping torque, and running life were rated as C, reaching a practical acceptable level (C rank).

[0432] Example 68 is an example using rubber adhesive 4. Rubber adhesive 4 is a rubber adhesive obtained by mixing polymeric MDI with rubber adhesive 1. The solid component remaining on the tooth fabric after belt crosslinking molding contains isocyanate, which increases the hardness of the solid component derived from the rubber adhesive. In Comparative Example 1, which was treated with immersion treatment using rubber adhesive 1 [rubber composition RC1 (hardness A80), solid content concentration 10% by mass], in Example 68, as a result of immersion treatment with rubber adhesive 4 [rubber composition RC1 (hardness A80), solid content concentration 10% by mass] containing isocyanate, the tooth surface hardness increased to D50, and the life cycle, jumping torque, and running life were judged as C, which is a practical acceptable level (C rank).

[0433] Example 69 is an example using rubber cement 5. Rubber cement 5 is also a rubber cement obtained by mixing polymeric MDI with rubber cement 1. Compared to Example 68, in which rubber cement 4 [rubber composition RC1 (hardness A80), solid content concentration 10% by mass, MDI concentration 2% by mass] was used for immersion treatment, in Example 69, in which rubber cement 5, which has a low hardness (hardness A70) rubber composition (RC2) but a high MDI concentration of 5% by mass, was used for immersion treatment, the tooth surface hardness increased to D50, and the life cycle, jumping torque, and running life were judged as C, reaching a practical acceptable level (C rank).

[0434] Comparative Example 6, similar to Example 67, is an example in which the solid content derived from rubber paste remaining in the tooth canvas after belt crosslinking molding was increased by using a high solid content concentration (solid content concentration of 40% by mass) for rubber paste 1 and increasing the adhesion amount of solid components (due to the difference in treatment method between dipping and double-sided coating). However, in contrast to rubber paste 3 [rubber composition RC1 (hardness A80), solid content concentration 40%] used in Example 67, rubber paste 6, whose rubber composition (RC2) had low hardness (hardness A70), was subjected to dipping treatment. Therefore, although the amount of solid components derived from rubber paste remaining in the tooth canvas increased, the hardness of the solid components was insufficient, the tooth surface hardness remained at D43 and did not increase, the life cycle, jumping torque, and running life all received a d judgment, and the overall judgment was rank D.

[0435] From the above results, it was confirmed that for rubber paste used for adhesion treatment of tooth canvas, adjusting the amount of solid components derived from rubber paste remaining in the tooth canvas after belt crosslinking molding by methods such as increasing the solid content concentration, increasing the adhesion amount of solid components, and increasing the hardness of solid components has a reinforcing effect on the rigidity of the tooth part, increases tooth surface hardness, and improves tooth crack resistance.

[0436]

[0437] (Comparative Example 7 and Examples 70 to 71) Comparative Example 7 is an example in which the adhesive rubber layer was formed from the same rubber composition (R66) as the tooth rubber layer and the back rubber layer. In Comparative Example 7, the hardness of the adhesive rubber composition was low, the tooth surface hardness was D47, the life cycle, jumping torque, and running life all received a d judgment, and the overall judgment was rank D.

[0438] Example 70 is an example in which, compared to Comparative Example 7, a rubber composition (R67) with a changed configuration of the rubber component contained in the adhesive rubber layer was used. As a result, in Example 70, compared to Comparative Example 7, the hardness of the rubber composition improved, the tooth surface hardness increased to D67, the life cycle, jumping torque, and running life all received an a judgment, and the overall judgment improved to rank A.

[0439] Example 71 is an example in which R68 was used as the rubber composition for forming the adhesive rubber layer, compared to Example 70. As a result, in Example 71, the tooth surface hardness increased further to D73, the overall rating was A rank, and the levels of life cycle, jumping torque, and running life also improved.

[0440] From these results, it was confirmed that, similar to EPDM-based toothed belts, adjusting the compound composition of the rubber composition forming the adhesive rubber layer in HNBR-based toothed belts to increase hardness provides a reinforcing effect on the rigidity of the teeth, resulting in increased tooth surface hardness and improved resistance to tooth chipping.

[0441] From the above verification, it was found that by increasing the hardness (high modulus of elasticity) only near the surface of the tooth (without hardening the tooth rubber) so that the "tooth surface hardness" falls within a specific numerical range (D50 to D75), it is possible to obtain a toothed belt that can improve resistance to tooth chipping without increasing material costs or manufacturing costs.

[0442] 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.

[0443] 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. 2025-056212 filed on 28 March 2025 and Japanese Patent Application No. 2026-041509 filed on 13 March 2026, the contents of which are incorporated herein by reference.

[0444] 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; and a tooth cloth formed on the surface of the teeth, wherein the tooth surface hardness of the teeth is D50 to D75 on a Type D hardness scale; the tooth rubber layer and the back rubber layer contain a crosslinked product of a first rubber composition containing a first polymer component; and the rubber hardness of the crosslinked product of the first rubber composition is lower than the tooth surface hardness.

2. The toothed belt according to claim 1, wherein the tooth cloth comprises a crosslinked product of a second rubber composition containing a second polymer component.

3. The toothed belt according to claim 1 or 2, wherein an adhesive rubber layer containing a crosslinked product of a third rubber composition containing a third polymer component is interposed between the tooth rubber layer and the tooth cloth.

4. The toothed belt according to claim 3, wherein the first polymer component, the second polymer component, and the third polymer component each contain ethylene-α-olefin elastomer or hydrogenated nitrile rubber.

5. The toothed belt according to any one of claims 1 to 4, wherein the tooth surface hardness of the tooth portion is D60 or higher on a Type D hardness scale.

6. The toothed belt according to any one of claims 3 to 5, wherein the average thickness of the adhesive rubber layer is 0.3 to 1 mm.

7. The toothed belt according to any one of claims 1 to 6, wherein the X value of the arrangement density of the core wires is 15% or more.

8. A toothed belt transmission mechanism comprising a toothed belt according to any one of claims 1 to 7 and a pulley.

9. The toothed belt transmission mechanism according to claim 8, used for transmission purposes in the rear-wheel drive of a motorcycle.

10. A method for manufacturing a toothed belt according to any one of claims 1 to 7, comprising a crosslinking molding step of crosslinking an uncrosslinked molded body comprising a tooth cloth precursor, a core wire precursor, and precursors for the tooth rubber layer and the back rubber layer.

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