Toothed belt and method for manufacturing the same

Abstract

To provide a toothed belt that is highly productive, economical, and has excellent resistance to tooth breakage. [Solution] A toothed belt 1 comprises a back portion 1c in which a core wire 5 extending along the circumferential direction of the belt is embedded, and a plurality of teeth 1a formed on the inner circumferential surface of the back portion 1c at intervals in the circumferential direction of the belt, the back rubber layer 6 forming the back portion 1c, a tooth rubber layer forming the teeth 1a, a tooth cloth formed on the surface of the teeth 1a, and an adhesive rubber layer interposed between the tooth rubber layer and the tooth cloth, wherein the adhesive rubber layer comprises a crosslinked product of a first rubber composition containing a first polymer component and silica. The first polymer component comprises a first ethylene-α-olefin elastomer, and the proportion of silica is 50 to 130 parts by mass per 100 parts by mass of the first polymer component. The tooth rubber layer and the back rubber layer 6 comprise a crosslinked product of a second rubber composition containing a second ethylene-α-olefin elastomer. The rubber hardness of the crosslinked product of the first rubber composition is greater than the rubber hardness of the crosslinked product of the second rubber composition.

Description

[Technical Field]

[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 toothed fabric, and to a method for manufacturing the same. [Background technology]

[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 (deformation resistance) and flexibility (flexibility) of the teeth by using a rubber composition containing HNBR containing an unsaturated carboxylic acid metal salt in the tooth rubber. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2017-211084 [Patent Document 2] Japanese Patent Publication No. 2023-018654 [Overview of the Initiative] [Problems that the invention aims to solve]

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

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

[0009] Another object of the present invention is to provide a toothed belt with high productivity and economy, excellent chipping resistance and endurance running performance, and a method for manufacturing the same.

Means for Solving the Problems

[0010] As a result of intensive studies to achieve the above problems, the present inventors have found that an adhesive rubber layer interposed between the tooth cloth of a toothed belt in which the polymer component contains an ethylene-α-olefin elastomer and the rubber compositions of the back rubber layer and the tooth rubber layer are the same, is formed of a cross-linked product (cross-linked rubber composition) of a rubber composition containing 50 to 130 parts by mass of silica with respect to 100 parts by mass of the polymer component, and by adjusting the rubber hardness to be greater than that of the tooth rubber layer, it is possible to improve the chipping resistance of the toothed belt with high productivity and economy, and thus the present invention has been completed.

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

[0012] Aspect [1]: A back portion in which a core wire extending along the belt circumferential direction is embedded, a plurality of tooth portions formed at intervals in the belt circumferential direction on the inner peripheral surface of the back portion, a back rubber layer forming the back portion, a tooth rubber layer forming the tooth portions, a tooth cloth formed on the surface of the tooth portions, a toothed belt including an adhesive rubber layer interposed between the tooth rubber layer and the tooth cloth, where the adhesive rubber layer includes a cross-linked product of a first rubber composition containing a first polymer component and silica, the first polymer component includes a first ethylene-α-olefin elastomer, the ratio of the silica is 50 to 130 parts by mass with respect to 100 parts by mass of the first polymer component, the tooth rubber layer and the back rubber layer include a cross-linked product of a second rubber composition containing a second ethylene-α-olefin elastomer, and A toothed belt in which the rubber hardness of the crosslinked product of the first rubber composition is greater than the rubber hardness of the crosslinked product of the second rubber composition.

[0013] Aspect [2]: The toothed belt according to Aspect [1], wherein the rubber hardness of the crosslinked product of the first rubber composition is 50 or more in terms of type D hardness.

[0014] Aspect [3]: The toothed belt according to Aspect [1] or [2], wherein the 5% modulus in the crosslinked product of the first rubber composition is 3 MPa or more in the belt circumferential direction.

[0015] Aspect [4]: The first ethylene-α-olefin elastomer includes an ethylene-α-olefin-diene terpolymer, The toothed belt according to any one of Aspects [1] to [3], wherein the diene content of the ethylene-α-olefin-diene terpolymer is 3% by mass or more.

[0016] Aspect [5]: The first rubber composition includes a metal salt of an unsaturated carboxylic acid, and the proportion of the metal salt of the unsaturated carboxylic acid is 50 parts by mass or more with respect to 100 parts by mass of the first polymer component. The toothed belt according to any one of Aspects [1] to [4].

[0017] Aspect [6]: The toothed belt according to any one of Aspects [1] 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 wire is 15% or more.

[0019] Aspect [8]: A method for manufacturing a toothed belt according to any one of Aspects [1] to [7], including a crosslinking molding step of crosslinking an uncrosslinked molded body in which a tooth cloth precursor, an adhesive rubber layer precursor, a core wire precursor, and precursors of a tooth rubber layer and a back rubber layer are laminated.

[0020] In this application, the numerical range represented by "A~B" means "A or greater and B or less," and is used to include the values ​​A and B at both ends of that range.

[0021] Furthermore, in this application, "inner surface" means the "inner surface of the belt" in each layer or belt, and "outer surface" means the "outer surface of the belt" in each layer or belt. [Effects of the Invention]

[0022] In this invention, the adhesive rubber layer interposed between the tooth cloth and the tooth rubber layer of a toothed belt, in which the polymer component contains ethylene-α-olefin elastomer and the rubber compositions of the back rubber layer and the tooth rubber layer are the same, is formed of a crosslinked rubber composition containing 50 to 130 parts by mass of silica per 100 parts by mass of the polymer component, and its rubber hardness is adjusted to be greater than that of the tooth rubber layer. Therefore, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency. In particular, the toothed belt of this invention can be manufactured by an inexpensive and highly productive method that does not require preforming, and also has excellent processability. Furthermore, the toothed belt of this invention also has excellent durability (running life). [Brief explanation of the drawing]

[0023] [Figure 1] Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt according to the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of the toothed belt shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram illustrating the method for measuring the X value (%) of the array density. [Figure 4] Figure 4 is a schematic diagram illustrating the measurement method for the tooth chipping resistance test in the embodiment. [Modes for carrying out the invention]

[0024] [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, identical or functionally common elements (or components) may be denoted by the same reference numeral.

[0025] 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.

[0026] 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.

[0027] Between adjacent tooth portions 1a, there is a flat tooth root portion 1b, and the tooth portions 1a and tooth root portions 1b are alternately formed 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 composed of a single continuous tooth fabric 2.

[0028] 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).

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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), the rotation of the drive pulley transmits power from the drive pulley side to the driven pulley side.

[0033] It should be noted that 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.

[0034] 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.

[0035] 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].

[0036] 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 surface of the belt [the average value of the thickness (distance or height) from the tooth root surface to the tooth apex].

[0037] In the toothed belt of the present invention, the teeth include a tooth cloth disposed on the surface side (inner surface side), a tooth rubber layer for forming the teeth, and an adhesive rubber layer interposed between the tooth cloth and the tooth rubber layer. In the toothed belt of the present invention, the polymer component contains an inexpensive ethylene-α-olefin elastomer, and the rubber composition of the back rubber layer and the tooth rubber layer are the same, and it can be manufactured by a simple and inexpensive method that does not require pre-forming. Nevertheless, because a high-hardness rubber composition is used for the adhesive rubber layer interposed between the tooth cloth and the tooth rubber, the tooth chipping resistance of the toothed belt can be improved with high productivity and economic efficiency. Specifically, by forming the adhesive rubber layer with a crosslinked rubber composition that has been hardened by containing a large amount (50 to 130 parts by mass) of silica per 100 parts by mass of polymer component, the tooth chipping resistance of the toothed belt can be improved with high processability. In this invention, the crosslinked rubber composition of the adhesive rubber layer contains a large amount of silica (50 to 130 parts by mass) per 100 parts by mass of polymer component. This increases the hardness (elastic modulus, modulus) of the adhesive rubber composition, improving the rigidity of the tooth surface. As a result, the resistance of tooth chipping in the toothed belt is improved. On the other hand, if the amount of silica exceeds 130 parts by mass, the processability is impaired, making it difficult to manufacture the toothed belt.

[0038] (Adhesive rubber layer) The adhesive rubber layer includes a crosslinked material of a first rubber composition containing a first polymer component and silica.

[0039] (1A) First polymer component The first polymer component includes a first ethylene-α-olefin elastomer. Preferably, the first ethylene-α-olefin elastomer includes an ethylene-α-olefin-diene ternary copolymer.

[0040] 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, etc. 3-4 Olefins are preferred.

[0041] 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.

[0042] Typical ethylene-α-olefin-diene terpolymers include, for example, ethylene-propylene-nonconjugated diene terpolymer (EPDM), ethylene-1-butene-nonconjugated diene terpolymer (EBDM), and ethylene-1-octene-nonconjugated diene terpolymer (EODM), among others. 3-8 Examples include olefin-diene terpolymers.

[0043] These ethylene-α-olefin-diene ternary copolymers can be used individually or in combination of two or more. Among these, EPDM and EBDM, among others, are used due to their excellent heat resistance, cold resistance, and weather resistance. 3-6 An olefin-diene terpolymer is preferred, and ethylene-α-C 3-4 An olefin-diene terpolymer is particularly preferred. Therefore, ethylene-α-C 3-4The proportion of the olefin-diene ternary copolymer may be 50% by mass or more of the total ethylene-α-olefin-diene ternary 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-α-C 3-4 It may also be olefin-diene terpolymer only.

[0044] In the ethylene-α-olefin-diene terpolymer, the ethylene content (percentage of ethylene units) may be 30% by mass or more, for example, 30-80% by mass, preferably 35-70% by mass, more preferably 40-65% by mass, more preferably 50-60% by mass, and most preferably 53-57% 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.

[0045] In this application, the ethylene content refers to the mass ratio of ethylene units in the total number of 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.

[0046] 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.

[0047] In ethylene-α-olefin-diene terpolymers, ethylene and α-olefin (especially α-C 3-4 The ratio (mass ratio) of the olefin to the olefin is 30 / 70 to 90 / 10, preferably 40 / 60 to 80 / 20, more preferably 50 / 50 to 70 / 30, and more preferably 55 / 45 to 65 / 35.

[0048] In the present application, the α-olefin content means the mass ratio of α-olefin units in all units constituting the ethylene-α-olefin-diene terpolymer, and can be measured by a conventional method, but may also be the mass ratio based on the α-olefin as a monomer.

[0049] The diene content (particularly, the ethylidene norbornene content) of the ethylene-α-olefin-diene terpolymer (especially, the ethylene-α-C 3-4 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, still 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, still 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 small, the crosslinking density of the rubber composition may decrease and the rigidity (tooth surface hardness) of the tooth part surface may decrease. If it is too large, the abrasion resistance of the toothed belt may decrease.

[0050] In the present application, the diene content means the mass ratio of diene monomer units in all units constituting the ethylene-α-olefin-diene terpolymer, and can be measured by a conventional method, but may also be the ratio based on the monomer.

[0051] The iodine value of the ethylene-α-olefin-diene terpolymer containing a diene monomer is, for example, 3 to 40, preferably 5 to 30, and more preferably 10 to 20. If the iodine value is too small, the crosslinking of the rubber composition becomes insufficient and abrasion is likely to occur. Conversely, if the iodine value is too large, the scorch time of the rubber composition becomes short, making it difficult to handle, and the heat resistance tends to decrease.

[0052] In the present application, the iodine value of the ethylene-α-olefin-diene terpolymer can be measured by a conventional method, for example, by infrared spectroscopy.

[0053] The Mooney viscosity [ML(1+4)125℃] 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.

[0054] 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.

[0055] 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.

[0056] The proportion of the ethylene-α-olefin-diene terpolymer may be 50% by mass or more relative to the total amount of the first 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 also be 100% by mass (ethylene-α-olefin-diene terpolymer only).

[0057] The proportion of the first ethylene-α-olefin elastomer may be 50% by mass or more of the first polymer component, preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. If the proportion of the first ethylene-α-olefin elastomer is too low, the first polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0058] The first polymer component may contain other polymer components besides the first ethylene-α-olefin elastomer.

[0059] Other polymer components include, for example, diene rubbers [natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), styrene-butadiene rubber (SBR), vinylpyridine-styrene-butadiene rubber, acrylonitrile-butadiene rubber (nitrile rubber: NBR), acrylonitrile-chloroprene rubber, hydrogenated nitrile rubber (HNBR), etc.], chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. These polymer components can be used individually or in combination of two or more.

[0060] The proportion of other polymer components may be 100 parts by mass or less per 100 parts by mass of the first ethylene-α-olefin elastomer, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 5 parts by mass or less.

[0061] The first polymer component is preferably substantially free of other polymer components, and more preferably free of expensive HNBR.

[0062] The proportion of the first polymer component may be 10% by mass or more in the first rubber composition, for example, 10 to 90% by mass, preferably 20 to 80% by mass, more preferably 30 to 60% by mass, more preferably 33 to 50% by mass, and most preferably 35 to 40% by mass. If the proportion of the first polymer component is too low, the flexibility of the toothed belt may decrease.

[0063] (1B) Silica No. 1 The first rubber composition contains 50 parts by mass or more of silica (first silica) per 100 parts by mass of the first polymer component, thereby increasing the hardness (elastic modulus, modulus) of the crosslinked material in the first rubber composition, improving the rigidity of the tooth surface, and consequently improving the tooth chipping resistance of the toothed belt. While carbon black is more commonly used than silica as a filler (reinforcement) to increase the rigidity of rubber, the inventors estimated that for the tooth chipping resistance of the toothed belt in this problem, the elastic modulus in the low-strain region (e.g., 5% modulus) is more important than the elastic modulus in the high-strain region (e.g., 100% modulus). By incorporating a large amount of silica, which has a higher elastic modulus in the low-strain region than carbon black, the inventors succeeded in improving the tooth chipping resistance of the toothed belt.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] Furthermore, the BET specific surface area of ​​silica using the BET method is, for example, 50 to 400 m². 2 / g, preferably 100-300m 2 / g, more preferably 150-270m 2 / g (especially 150-200m) 2 ( / g), more preferably 170-250m 2 It is / g.

[0068] 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.

[0069] The proportion of the first silica can be selected from a range of approximately 50 to 130 parts by mass (particularly 50 to 100 parts by mass) per 100 parts by mass of the first polymer component, for example, 55 to 120 parts by mass (particularly 70 to 110 parts by mass), preferably 60 to 100 parts by mass, more preferably 63 to 90 parts by mass, more preferably 65 to 85 parts by mass, and most preferably 70 to 80 parts by mass. Furthermore, in applications where tooth chipping resistance and durable running performance are important, the proportion of the first silica is preferably 75 to 130 parts by mass, more preferably 90 to 130 parts by mass, and more preferably 110 to 130 parts by mass per 100 parts by mass of the first polymer component. If the proportion of the first silica is too low, the tooth chipping resistance and durable running performance of the toothed belt will decrease, and if it is too high, the processability will be impaired, making it difficult to manufacture the toothed belt.

[0070] (1C) Monounsaturated carboxylic acid metal salt The first rubber composition contains a large amount of unsaturated carboxylic acid metal salt (first unsaturated carboxylic acid metal salt), which increases the crosslinking density in the crosslinked product of the first rubber composition, thereby improving the rigidity (tooth surface hardness) of the tooth surface. In particular, by adjusting the proportion of the first silica and the proportion of the first unsaturated carboxylic acid metal salt to a specific range, tooth chipping resistance and durable running performance can be greatly improved.

[0071] 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.

[0072] Examples of unsaturated carboxylic acids in the primary unsaturated carboxylic acid metal salts 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.

[0073] Examples of metals used in the primary 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.).

[0074] These unsaturated carboxylate metal salts can also be used individually or in combination of two or more.

[0075] 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.

[0076] The proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 10 parts by mass or more (preferably 30 parts by mass or more, more preferably 50 parts by mass or more) per 100 parts by mass of the first polymer component, and can be selected from a range of approximately 10 to 130 parts by mass (particularly 50 to 100 parts by mass). The proportion is, for example, 55 to 120 parts by mass (particularly 70 to 110 parts by mass), preferably 60 to 100 parts by mass, more preferably 63 to 90 parts by mass, more preferably 65 to 85 parts by mass, and most preferably 70 to 80 parts by mass per 100 parts by mass of the first polymer component. Furthermore, in applications where resistance to tooth chipping and durable running are important, the proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) is preferably 50 to 130 parts by mass, more preferably 80 to 130 parts by mass, and more preferably 110 to 130 parts by mass per 100 parts by mass of the first polymer component. If the proportion of primary unsaturated carboxylate metal salts is too low, the tooth breakage resistance and durability of the toothed belt will decrease, and if it is too high, the processability will be impaired, making it difficult to manufacture toothed belts.

[0077] (1D) First cross-linking compound The first rubber composition preferably further contains a crosslinking compound (first crosslinking compound). Examples of the first crosslinking compound include a first crosslinking agent (vulcanizing agent) for crosslinking the first polymer component, as well as a first co-crosslinking agent, a first crosslinking accelerator (vulcanization accelerator), and a first crosslinking retarder (vulcanization retarder). 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.

[0078] As the first crosslinking agent, conventional components can be used depending on the type of the first polymer component, such as organic peroxides and sulfur-based crosslinking agents.

[0079] 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 [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 150-250°C (e.g., 175-225°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.

[0080] Among these organic peroxides, dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene are preferred.

[0081] The proportion of the organic peroxide is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 5 to 18 parts by mass, more preferably 6 to 15 parts by mass, and most preferably 8 to 12 parts by mass, per 100 parts by mass of the first polymer component.

[0082] 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.

[0083] 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.

[0084] The proportion of the sulfur-based crosslinking agent is 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, more preferably 0.12 to 1 part by mass, more preferably 0.15 to 0.5 parts by mass, and most preferably 0.18 to 0.3 parts by mass, per 100 parts by mass of the first polymer component.

[0085] The proportion of the first crosslinking agent is, for example, 0.5 to 30 parts by mass, preferably 1 to 20 parts by mass, more preferably 5 to 18 parts by mass, more preferably 6 to 15 parts by mass, and most preferably 8 to 12 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0086] 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, and 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, and 1,3-bis(3-maleimoidphenoxy)benzene). These cocrosslinking agents can be used alone or in combination of two or more.

[0087] 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.

[0088] The proportion of the first co-crosslinking agent (crosslinking aid) can be selected from a range of about 0.2 to 40 parts by mass per 100 parts by mass of the first polymer component, for example, 1 to 30 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, more preferably 8 to 17 parts by mass, and most preferably 10 to 15 parts by mass. If the proportion of the first co-crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0089] The proportion of the first crosslinking compound is, for example, 1 to 50 parts by mass, preferably 5 to 45 parts by mass, more preferably 10 to 40 parts by mass, more preferably 15 to 35 parts by mass, and most preferably 20 to 30 parts by mass, per 100 parts by mass of the first polymer component. If the proportion of the first crosslinking compound is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0090] (1E) Carbon Black No. 1 The first rubber composition may further contain carbon black (first carbon black).

[0091] 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).

[0092] 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.

[0093] In this application, the average particle size of particulate fillers such as carbon black can be measured using, for example, 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.

[0094] 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.

[0095] 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.

[0096] 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.

[0097] The BET specific surface area of ​​carbon black using the BET method is, for example, 10 to 400 m². 2 / g, preferably 15-200m 2 / g, more preferably 20-150m 2 It is / g.

[0098] The proportion of the first carbon black is 50 parts by mass or less per 100 parts by mass of the first polymer component, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, more preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, and most preferably 8 to 12 parts by mass. If the proportion of the first carbon black is too high, it may become difficult to improve the resistance to tooth breakage while maintaining the processability of the toothed belt.

[0099] The proportion of the first carbon black is, for example, 150 parts by mass or less (particularly 50 parts by mass or less) per 100 parts by mass of the first silica, for example, 1 to 150 parts by mass, preferably 2 to 100 parts by mass, more preferably 3 to 50 parts by mass, more preferably 5 to 20 parts by mass, and most preferably 10 to 15 parts by mass. If the proportion of the first carbon black is too high, it may become difficult to improve the resistance to tooth chipping while maintaining the processability of the toothed belt.

[0100] (1F) First filling system compounding agent The first rubber composition may further contain a filler compound (first filler compound). Examples of the first filler compound include a first filler and a first short fiber.

[0101] 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 atoms are replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, and aluminum magnesium silicate; minerals with silicates as the main component, such as clay containing aluminum silicate, and silicate minerals such as talc and mica containing magnesium silicate), silica, lithopone, and silica sand. These fillers can be used alone or in combination of two or more.

[0102] Of these, metal oxides such as zinc oxide are preferred. As the first filler, commercially available powdered fillers used as rubber fillers can be used.

[0103] 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.

[0104] 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.

[0105] The proportion of the first filler is, for example, 0.3 to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and most preferably 3 to 7 parts by mass, per 100 parts by mass of the first polymer component.

[0106] 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 toward the circumferential direction of the belt.

[0107] The fibers forming the first short fibers may be organic fibers or inorganic fibers. Examples of organic fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers (nylon fibers), aramid fibers, etc.], polyester fibers [polyalkylene arylate fibers (for example, polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.)] 2-4 Alkilen C 8-14Synthetic fibers such as arylate fibers (including polyarylate fibers, liquid crystal polyester fibers, and other fully aromatic polyester fibers), vinylon fibers, polyvinyl alcohol fibers, acrylic fibers, poly(p-phenylene) benzobisoxazole (PBO) fibers, fluororesin fibers (such as polytetrafluoroethylene (PTFE) fibers), polyphenylene ether fibers, polyether ether ketone fibers, polyether sulfone fibers, and polyurethane fibers; natural fibers such as cotton, linen, and wool; regenerated cellulose fibers such as rayon; and cellulose ester fibers are also examples. Inorganic fibers include, for example, carbon fibers, glass fibers, and metal fibers (steel fibers). These fibers can be used individually or in combination of two or more types.

[0108] 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, and PBO fibers are more preferred, with aramid fibers being the most preferred.

[0109] 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.

[0110] It is preferable to subject the first short fibers to a conventional bonding treatment (or surface treatment) to adhere an adhesive component to at least a portion of the surface. Examples of bonding treatments include treatment with adhesive components such as epoxy compounds (or epoxy resins), polyisocyanates, silane coupling agents, and RFL liquid.

[0111] The proportion of the first short fibers may be 50 parts by mass or less per 100 parts by mass of the first polymer component, preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and more preferably 5 parts by mass or less (for example, 1 to 5 parts by mass).

[0112] The first rubber composition preferably contains substantially no first short fibers, and is particularly preferably free of first short fibers.

[0113] The proportion of the first filling compound is, for example, 0.3 to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 1 to 20 parts by mass, more preferably 2 to 10 parts by mass, and most preferably 3 to 7 parts by mass, per 100 parts by mass of the first polymer component.

[0114] (1G) First softening agent The first rubber composition may further contain a softening agent (first softening agent). The first softening agent (processing agent or processing aid) may include mineral oil-based softening agents, vegetable oil-based softening agents, synthetic softening agents, etc.

[0115] 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.).

[0116] 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).

[0117] 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.].

[0118] These softeners can be used individually or in combination of two or more. Of these, petroleum-based softeners such as paraffinic oils and vegetable oil-based softeners such as stearic acid are preferred, and a combination of petroleum-based and vegetable oil-based softeners is particularly preferred.

[0119] 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.

[0120] (1H) First Anti-aging Agent The first rubber composition may further contain an antioxidant (first antioxidant). Examples of the first antioxidant include benzimidazole-based antioxidants, diarylamine-based antioxidants, and p-phenylenediamine-based antioxidants.

[0121] Examples of benzimidazole-based antioxidants include benzimidazole compounds such as 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 mixtures of 2-mercaptobenzimidazole and phenol condensates. Benzimidazole-based antioxidants may also be in the form of metal salts such as zinc.

[0122] Examples of diarylamine-based antioxidants include bis(C) such as di(4-octylphenyl)amine (ODPA). 4-18 Alkyl C 6-10 Examples include arylamines; bis(aralkyl-aryl)amines such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (DCD); and styrene-diphenylamine (SDPA).

[0123] 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-phenylenediamine; N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine (DNPD), etc., N,N'-diC 6-10 Examples include aryl-p-phenylenediamines.

[0124] These anti-aging agents can be used individually or in combination of two or more. Of these, benzimidazole-based anti-aging agents are preferred, particularly benzimidazole compounds having a sulfur atom, and especially benzimidazole compounds having a thiol group such as MBI (mercaptobenzimidazole compounds).

[0125] 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.

[0126] (1I) 1 Other Combination Agents The first rubber composition may further contain other compounding agents (first other compounding agents) that are commonly used in rubber compositions for toothed belts. Examples of commonly used additives include antioxidants, flex crack inhibitors, ozone degradation inhibitors, colorants, tackifiers, plasticizers, coupling agents (such as silane coupling agents), stabilizers (such as UV absorbers and heat stabilizers), flame retardants, and antistatic agents. The first rubber composition may also optionally contain adhesion improvers (such as resorcinol-formaldehyde cocondensates and amino resins). These additives can be used individually or in combination of two or more.

[0127] 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.

[0128] (1J) Characteristics of the adhesive rubber layer The adhesive rubber layer has high hardness (elastic modulus and modulus), which can improve the rigidity of the tooth surface. The rubber hardness of the crosslinked material of the first rubber composition forming the adhesive rubber layer is a type D hardness and may be 50 or higher, for example, 50 to 80, preferably 55 to 75, more preferably 58 to 70, more preferably 60 to 65, and most preferably 62 to 64. If the rubber hardness is too low, the tooth chipping resistance of the toothed belt may decrease.

[0129] The crosslinked material of the first rubber composition has a greater rubber hardness than the crosslinked material of the second rubber composition that forms the tooth rubber layer. Specifically, the difference (H1-H2) between the rubber hardness (H1) of the crosslinked material of the first rubber composition and the rubber hardness (H2) of the crosslinked material of the second rubber composition may be 5 or more on the Type D hardness scale, for example, 5 to 40, preferably 8 to 35, more preferably 10 to 30, more preferably 15 to 25, and most preferably 18 to 22. If this difference is too small, the effects of the present invention may be reduced.

[0130] 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.

[0131] Typically, the rubber hardness of rubber compositions is measured using Type A hardness (a value measured using a Type A durometer). However, if the value measured using a Type A durometer exceeds 90, it is considered preferable to use a Type D durometer.

[0132] The 5% modulus (tensile stress at 5% elongation) of the crosslinked material of the first rubber composition may be 3 MPa or more (particularly 9 MPa or more) in the belt circumferential direction (longitudinal direction), for example, 3 to 30 MPa, preferably 5 to 20 MPa, more preferably 8 to 15 MPa, more preferably 10 to 13 MPa, and most preferably 11 to 12 MPa. If the 5% modulus is too small, the tooth breakage resistance of the toothed belt may decrease.

[0133] The crosslinked material of the first rubber composition has a 5% greater modulus in the belt circumferential direction (longitudinal direction) than the crosslinked material of the second rubber composition that forms the tooth rubber layer. Specifically, the difference between the 5% modulus of the crosslinked material of the first rubber composition (modulus 1) and the 5% modulus of the crosslinked material of the second rubber composition (modulus 1 - modulus 2) may be 2 MPa or more in type D hardness, for example, 2 to 30 MPa, preferably 3 to 20 MPa, more preferably 5 to 15 MPa, more preferably 7 to 12 MPa, and most preferably 9 to 11 MPa. If this difference is too small, the effect of the present invention may be reduced.

[0134] 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.

[0135] 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-breaking 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.

[0136] 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.

[0137] (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 (a second rubber composition containing a second polymer component).

[0138] (2A) Second polymer component The second polymer component includes a second ethylene-α-olefin elastomer. The second ethylene-α-olefin elastomer may include the ethylene-α-olefin-diene ternary copolymer exemplified as the first ethylene-α-olefin elastomer, as well as ethylene-α-C 4-8 Olefin copolymers (e.g., ethylene-butene rubber (EBM), ethylene-hexene rubber (EHM), ethylene-octene rubber (EOM), etc.) 4-8 Examples include olefin binary copolymers. Secondary ethylene-α-olefin elastomers can be used alone or in combination of two or more. Among the secondary ethylene-α-olefin elastomers, ethylene-α-C is selected due to its excellent heat resistance, cold resistance, and weather resistance.3-4 Ethylene-α-olefin-diene terpolymers, such as olefin-diene terpolymers, are preferred. Therefore, the proportion of ethylene-α-olefin-diene terpolymer may be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass or more), and may be 100% by mass (ethylene-α-olefin-diene terpolymer only) relative to the total amount of the secondary ethylene-α-olefin elastomer.

[0139] In the second ethylene-α-olefin elastomer, the ethylene content (percentage of ethylene units) in the ethylene-α-olefin elastomer may be 30% by mass or more, for example, 30-80% by mass, preferably 35-70% by mass, more preferably 40-60% by mass, more preferably 45-55% by mass, and most preferably 47-53% by mass.

[0140] In the second ethylene-α-olefin elastomer, 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 60 / 40, and more preferably 50 / 50 to 55 / 45.

[0141] The diene content (especially the ethylidene norbornene content) of the secondary ethylene-α-olefin elastomer (especially ethylene-α-olefin-diene ternary copolymer such as EPDM) may be 8% by mass or less (preferably 7% by mass or less, more preferably 6% by mass or less), for example, 0.1 to 8% by mass, preferably 1 to 7.5% by mass, more preferably 2 to 7% by mass, more preferably 3 to 6% by mass, and most preferably 4 to 5% by mass. If the diene content is too high, the effects of the present invention may be reduced.

[0142] In the second polymer component, the iodine value of the second ethylene-α-olefin elastomer containing the diene monomer is, for example, 3 to 40, preferably 5 to 30, and more preferably 10 to 20.

[0143] In the second polymer component, the Mooney viscosity [ML(1+4)125℃] of the uncrosslinked second ethylene-α-olefin elastomer may be 10 or more, for example, 10 to 80, preferably 12 to 70, more preferably 13 to 50, more preferably 15 to 30, and most preferably 18 to 25.

[0144] In the second polymer component, the proportion of the second ethylene-α-olefin elastomer may be 50% by mass or more, preferably 70% by mass or more, more preferably 80% by mass or more, more preferably 90% by mass or more, and most preferably 100% by mass. If the proportion of the second ethylene-α-olefin elastomer is too low, the second polymer component will become expensive, which may reduce the effectiveness of the present invention.

[0145] The second polymer component may contain polymer components other than the second ethylene-α-olefin elastomer.

[0146] Other polymer components include those exemplified as other polymer components in the first polymer component. These polymer components can be used alone or in combination of two or more.

[0147] In the second polymer component, the proportion of other polymer components may be 100 parts by mass or less per 100 parts by mass of the second ethylene-α-olefin elastomer, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 5 parts by mass or less.

[0148] The second polymer component is preferably substantially free of other polymer components, and more preferably free of expensive HNBR.

[0149] The proportion of the second polymer component may be 10% by mass or more in the second rubber composition, for example, 10 to 90% by mass, preferably 20 to 80% by mass, more preferably 30 to 60% by mass, more preferably 35 to 50% by mass, and most preferably 40 to 45% by mass. If the proportion of the second polymer component is too low, the flexibility of the toothed belt may decrease.

[0150] (2B) Second Carbon Black The second rubber composition may further contain carbon black (secondary carbon black). The secondary carbon black can be selected from the carbon blacks exemplified as the first carbon black, including preferred embodiments.

[0151] The average primary particle size, iodine adsorption amount, and BET specific surface area ranges of the second carbon black can also be selected from those ranges of the first carbon black, including preferred ranges.

[0152] The proportion of the second carbon black is 10 parts by mass or more (particularly 20 parts by mass or more) per 100 parts by mass of the second polymer component, for example, 10 to 200 parts by mass, preferably 30 to 150 parts by mass, more preferably 40 to 100 parts by mass, more preferably 50 to 80 parts by mass, and most preferably 60 to 70 parts by mass. If the proportion of the second carbon black is too low, the mechanical properties of the tooth portion may deteriorate.

[0153] (2C) Silica II The second rubber composition may further contain silica (secondary silica). The secondary silica can be selected from the silica exemplified as the first silica, including preferred embodiments.

[0154] The average particle size and BET specific surface area range of the second silica can also be selected from those ranges of the first silica, including preferred ranges.

[0155] The proportion of the second silica may be 50 parts by mass or less (particularly 30 parts by mass or less) per 100 parts by mass of the second polymer component, for example, 0 to 50 parts by mass, preferably 1 to 30 parts by mass, more preferably 2 to 20 parts by mass, more preferably 3 to 10 parts by mass, and most preferably 4 to 7 parts by mass. If the proportion of the second silica is too high, the effect of the present invention may be reduced.

[0156] (2D) Deuteransaturated carboxylic acid metal salt The second rubber composition may further contain an unsaturated carboxylate metal salt (second unsaturated carboxylate metal salt). 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.

[0157] The proportion of the secondary unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 1 part by mass or more (preferably 5 parts by mass or more, more preferably 10 parts by mass or more) per 100 parts by mass of the second polymer component, for example, 1 to 100 parts by mass, preferably 10 to 70 parts by mass, more preferably 15 to 50 parts by mass, more preferably 20 to 40 parts by mass, and most preferably 25 to 35 parts by mass. If the proportion of the secondary unsaturated carboxylic acid metal salt is too low, the tooth breakage resistance of the toothed belt will decrease, and if it is too high, the processability will be impaired, making it difficult to manufacture the toothed belt.

[0158] (2E) Second crosslinking compound The second rubber composition may further contain a crosslinking compound (second crosslinking compound). Examples of the second crosslinking compound include a second crosslinking agent (vulcanizing agent) for crosslinking the second polymer component, as well as a second co-crosslinking agent, a second crosslinking accelerator (vulcanization accelerator), and a second crosslinking retarder (vulcanization retarder). Of these, the second crosslinking compound preferably contains at least a second crosslinking agent and a second co-crosslinking agent (crosslinking aid), and a combination of a second crosslinking agent and a second co-crosslinking agent is particularly preferred.

[0159] As the second crosslinking agent, conventional components can be used depending on the type of second polymer component, such as organic peroxides and sulfur-based crosslinking agents.

[0160] The organic peroxide can be selected from the organic peroxides exemplified as the first crosslinking agent, including preferred embodiments.

[0161] The ratio of organic peroxide to the second polymer component can be selected from a range of ratios of organic peroxide to the first polymer component, including a preferred range.

[0162] As the sulfur-based crosslinking agent, it can be selected from the sulfur-based crosslinking agents exemplified as the sulfur-based crosslinking agent of the first crosslinking agent, including preferred embodiments.

[0163] The ratio of the sulfur-based crosslinking agent to the second polymer component can be selected from a range of ratios of the sulfur-based crosslinking agent to the first polymer component, including a preferred range.

[0164] The ratio of the second crosslinking agent to the second polymer component can be selected from the range of the ratio of the first crosslinking agent to the first polymer component, including a preferred range.

[0165] The second cocrosslinking agent can be selected from the cocrosslinking agents exemplified as the first cocrosslinking agent, including preferred embodiments.

[0166] The proportion of the second co-crosslinking agent can be selected from a range of about 0.2 to 40 parts by mass per 100 parts by mass of the second polymer component, for example, 1 to 30 parts by mass, preferably 3 to 25 parts by mass, more preferably 5 to 20 parts by mass, more preferably 7 to 15 parts by mass, and most preferably 8 to 12 parts by mass. If the proportion of the second co-crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0167] The proportion of the second crosslinking compound is, for example, 1 to 50 parts by mass, preferably 5 to 45 parts by mass, more preferably 10 to 40 parts by mass, more preferably 12 to 30 parts by mass, and most preferably 15 to 25 parts by mass, per 100 parts by mass of the second polymer component. If the proportion of the second crosslinking compound is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0168] (2F) Second filling system compounding agent The second rubber composition may further contain a filler compound (second filler compound). Examples of the second filler compound include a second filler and a second staple fiber.

[0169] The second filler can be selected from the fillers exemplified as the first filler, including preferred embodiments.

[0170] The average particle size range of the second filler and its ratio to the second polymer component can be selected from the respective ranges of the first filler, including preferred ranges.

[0171] The second staple fiber can be selected from the staple fibers exemplified as the first staple fiber, including preferred embodiments.

[0172] The average fiber diameter and average fiber length of the second short fiber can be selected from the range of the average fiber diameter and average fiber length of the first short fiber, including a preferred range.

[0173] The proportion of the second short fibers may be 10 parts by mass or less per 100 parts by mass of the second polymer component, preferably 5 parts by mass or less, more preferably 3 parts by mass or less, and more preferably 1 part by mass or less.

[0174] The second rubber composition preferably contains substantially no second short fibers, and is particularly preferably free of second short fibers.

[0175] The ratio of the second filler compound to the second polymer component can be selected from the range of the ratio of the first filler compound to the first polymer component, including a preferred range.

[0176] (2G) Second softening agent The second rubber composition may further contain a softening agent (second softening agent). The second softening agent can be selected from the softening agents exemplified as the first softening agent, including preferred embodiments.

[0177] The ratio of the second polymer component to the second softener can also be selected from the range of the ratio of the first softener to the first polymer component.

[0178] (2H) Second Anti-aging Agent The second rubber composition may further contain an antioxidant (second antioxidant). The second antioxidant can be selected from the antioxidants exemplified as the first antioxidant, including preferred embodiments.

[0179] The ratio of the second antioxidant to the second polymer component can also be selected from the range of the ratio of the first antioxidant to the first polymer component.

[0180] (2I) Second Other Combination 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. Examples of conventional additives include those exemplified as the first other compounding agent.

[0181] The ratio of the second other compounding agent to the second polymer component can also be selected from the range of the ratio of the first other compounding agent to the first polymer component.

[0182] (2J) Characteristics of the tooth rubber layer and back rubber layer The rubber hardness of the crosslinked material of the second rubber composition forming the tooth rubber layer and the back rubber layer is a Type D hardness, and may be 50 or less, for example, 30 to 50, preferably 35 to 48, more preferably 40 to 47, more preferably 41 to 46, and most preferably 42 to 45. If the rubber hardness is too high, it may become expensive and the effects of the present invention may be reduced.

[0183] The 5% modulus of the crosslinked product of the second rubber composition may be 3 MPa or less (particularly 2 MPa or less) in the belt circumferential direction (longitudinal direction), for example, 0.5 to 3 MPa, preferably 1 to 2.8 MPa, more preferably 1.2 to 2.5 MPa, more preferably 1.3 to 2.2 MPa, and most preferably 1.5 to 2 MPa. If the 5% modulus is too high, it may become expensive and the effects of the present invention may be reduced.

[0184] 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.

[0185] 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.

[0186] 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.

[0187] (Tooth cloth) The tooth fabric laminated on the inner surface of the belt (tooth portion and tooth base portion) 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 woven from 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).

[0188] 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.

[0189] 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, and processed yarns that have undergone stretch processing (for example, woolly processing, crimping processing, etc.)] are also preferred.

[0190] 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.

[0191] 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).

[0192] 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.

[0193] To improve the adhesion between the tooth cloth and the tooth rubber layer, the cloth forming the tooth cloth may be treated with an adhesive. Examples of adhesive treatments include immersing the cloth in an RFL treatment solution followed by heat drying; treating with an epoxy compound or isocyanate compound; or dissolving a rubber composition in an organic solvent to make a rubber glue, immersing the cloth in this rubber glue, and then heat drying. These methods can be performed individually or in combination, and the order and number of treatments are not limited. For example, after immersion in an RFL treatment solution, the cloth may be further immersed in rubber glue and then heat dried.

[0194] (Tooth root) The tooth fabric constitutes the surface of the tooth, as well as the surface on the tooth side of the back (the surface of the tooth root).

[0195] In the dorsal portion corresponding to the tooth root, an adhesive rubber layer and a tooth rubber layer may be interposed between the tooth cloth and the core wire, but the tooth cloth and the core wire may be in contact without the interposition of the adhesive rubber layer and the tooth rubber layer. Even when an adhesive rubber layer and a tooth rubber layer are interposed in the dorsal portion corresponding to the tooth root, the thickness of the adhesive rubber layer and the tooth rubber layer is formed to be thinner than that of the tooth portion.

[0196] (Core wire) On the back of the belt, a core wire extending along the belt circumferential direction is embedded on the inner circumference side of the back rubber layer. This core wire acts as a tensile body, improving the running stability and strength of the toothed belt. Furthermore, on the back, the core wire, which is usually a twisted cord extending along the belt circumferential direction, is embedded at predetermined intervals in the belt width direction. 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.

[0197] 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 width direction of the belt on the back, as shown in Figure 1.

[0198] 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] The core wire may be treated with 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.

[0203] 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.

[0204] In particular, for toothed belts with a tooth pitch of 6 mm or more and less than 9.5 mm (e.g., 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.

[0205] 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, especially 11 mm), the core wire diameter D is, for example, 1.3 to 1.8 mm, preferably 1.4 to 1.8 mm.

[0206] Furthermore, for toothed belts with a tooth pitch of 12.5 to 16 mm (e.g., 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 more preferably 1.8 to 2 mm.

[0207] 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.

[0208] In particular, for toothed belts with a tooth pitch of 6 mm or more and less than 9.5 mm (e.g., 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.

[0209] 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 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.

[0210] Furthermore, in toothed belts with a tooth pitch of 12.5 to 16 mm (e.g., 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.

[0211] 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.

[0212] 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.

[0213] 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, multiple 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 with the relationship between core wire diameter D and core wire pitch P, as shown in the following formula.

[0214] X = (Sum of intervals d / Belt width W) × 100 =[(Total of belt width W - core wire diameter 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-(wire diameter D / wire pitch P)]×100

[0215] 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 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.

[0216] The X value of the arrangement density in the core wires may be 15% or more, for example, 15-50%, preferably 20-45%, more preferably 22-40%, more preferably 23-38%, and most preferably 25-35%. 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 (a symptom 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.

[0217] [How to manufacture a toothed belt] 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 the 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.

[0218] (Precursor preparation process) 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.

[0219] 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.

[0220] Furthermore, in the present invention, when the adhesive rubber layer is thin, it is preferable to use the tooth cloth precursor and the adhesive rubber layer precursor as a laminate in which both precursors are pre-integrated (hereinafter referred to as "tooth cloth and adhesive rubber layer precursor"). The method for manufacturing the tooth cloth and adhesive rubber layer precursor is not particularly limited, as long as the tooth cloth precursor and the uncrosslinked rubber sheet, which is the adhesive rubber layer precursor, can be laminated and integrated. For example, one method is to coat the tooth cloth precursor with a first rubber composition for forming the adhesive rubber layer.

[0221] As a method for coating the tooth cloth precursor with the first rubber composition, a method in which the rubber composition and the cloth are simultaneously passed between rolls rotating at the same speed and the rubber composition is pressed onto the cloth is preferred from the viewpoint of simplicity and other factors. In this method, the first rubber composition, which has been kneaded in a conventional way using a Banbury mixer or the like, and the tooth cloth precursor are simultaneously passed between rolls rotating at the same speed and pressed (compressed) using rolls or a calender, and the solid first rubber composition is pressed (coated) onto one surface of the tooth cloth precursor, and a tooth cloth and an adhesive rubber layer precursor can be obtained in which a sheet-like first rubber composition, which is an adhesive rubber layer precursor, is laminated on one surface of the tooth cloth precursor.

[0222] (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 precursors facing the outer surface of the cylindrical mold (if separate tooth cloth precursors and adhesive rubber layer precursors are used, they 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).

[0223] (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 apparatus such as a vulcanizing can. When the belt molded body is heated and pressurized inside the crosslinking molding apparatus, 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 further on the outer circumference, and the back rubber layer (back portion) derived from the remaining uncrosslinked rubber sheet is placed on the outermost circumference, forming a layered structure. At the same time, the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body undergo a crosslinking reaction, and each component is integrally joined, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve). Thus, in the press-fitting method, the uncrosslinked rubber sheet (a single uncrosslinked rubber sheet) wrapped around the outer circumference of the twisted cord during the molding process forms both the teeth and the back portion.

[0224] (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. [Examples]

[0225] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples.

[0226] [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℃ 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℃ 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℃ Para-aramid short fibers: "Twaron®" manufactured by Teijin Limited, average fiber length 3mm Carbon Black: "Seast S" manufactured by Tokai Carbon Co., Ltd. Silica 1: Toxil 255G manufactured by Oriental Silicas Co., Ltd., specific surface area 176 m² 2 / g Silica 2: Ultrasil VN3 manufactured by Evonik Industries AG, BET specific surface area 180 m² 2 / g Silica 3: Ultrasil 9100GR manufactured by Evonik Industries AG, BET specific surface area 235 m² 2 / g Anti-aging agent: "Nocrack MB-O" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., 2-mercaptobenzimidazole Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd. Stearic acid: "Stearic acid Tsubaki" manufactured by NOF Corporation. Zinc methacrylate: "R-20S" manufactured by Asada Chemical Industries, Ltd., purity 85% Paraffin-based oil: "Diana Process Oil PW90" manufactured by Idemitsu Kosan Co., Ltd. Organic peroxide: NOF Corporation's "Perbutyl P-40MB", 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.

[0227] [Preparation of uncrosslinked rubber composition] 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 9 to 14 was kneaded in a Banbury mixer to obtain kneaded rubber (lump-shaped uncrosslinked rubber compositions). Similarly, as uncrosslinked rubber compositions for use in rubber glue, kneaded rubber (lump-shaped uncrosslinked rubber compositions) was obtained from the rubber compositions with the formulations shown in Table 3. Furthermore, as uncrosslinked rubber compositions for forming tooth rubber layers and back rubber layers, each rubber composition with the formulations shown in Table 4 was kneaded in a Banbury mixer, and the resulting kneaded rubber was rolled to a predetermined thickness using a calender roll to produce uncrosslinked rubber sheets.

[0228] 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.

[0229] [Rubber hardness of crosslinked rubber compositions] Crosslinked rubber sheets (100 mm × 100 mm × 2 mm thick) 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. 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.

[0230] [Tensile properties of crosslinked rubber compositions (5% modulus)] Crosslinked rubber sheets (100mm x 100mm x 2mm thick) were prepared by press-heating an uncrosslinked rubber sheet at a temperature of 170°C, a pressure of 2MPa, and a time of 15 minutes. Test specimens were punched out in a dumbbell shape (Type 3) 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 fibers) was in 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 500mm / min, the test temperature was 23°C, and a Shimadzu Corporation "Autograph AG-5000A" tensile testing machine was used.

[0231] [Heart wire] A carbon fiber cord (12K-1 / 0, tensile modulus 230 GPa) was prepared by twisting one strand of 12K multifilament yarn [Toray Industries, Inc.'s "Torayca T700SC-12000", single filament fineness 0.67 dtex, total fineness 800 tex] into a single strand. This cord was then bonded with an EPDM-based overcoat to obtain a core wire with a diameter of 1.0 mm.

[0232] [Tooth cloth and tooth cloth processing] (Examples 1-27 and Comparative Examples 1-4) As the belt tooth fabric precursor, a woven fabric shown in Table 1 was used, which had been immersed in an RFL treatment solution and rubber adhesive. Specifically, the woven fabric was immersed in the RFL treatment solution shown in Table 2 and dried, and the dried woven fabric was further immersed in rubber adhesive (a solution obtained by dissolving the rubber composition for rubber adhesive shown in Table 3 in methyl ethyl ketone at a ratio of 10% by mass) and dried to obtain an adhesive-treated woven fabric (tooth fabric precursor). Furthermore, by performing the coating treatment described in the [Modes for Carrying Out the Invention] section using adhesive rubber compositions with the compositions shown in Tables 9 to 13, the adhesive rubber composition was laminated onto one side of the adhesive-treated woven fabric to obtain a tooth fabric and an adhesive rubber layer precursor. This precursor is a tooth fabric precursor (basis weight approximately 820 g / m²). 2 The composite consisted of a woven fabric (approximately 1.1 mm thick) laminated with an adhesive rubber layer precursor (an adhesive rubber composition with an average thickness of 0.65 mm). The rubber hardness of the rubber composition for the rubber adhesive used to process the tooth cloth is also shown in Table 3.

[0233] (Examples 28-31) Except for changing the average thickness of the adhesive rubber layer precursor to 0.2 mm (Example 28), 0.3 mm (Example 29), 1.0 mm (Example 30), and 1.2 mm (Example 31), tooth cloth and adhesive rubber layer precursors (composites in which the adhesive rubber layer precursor is laminated onto the tooth cloth precursor) were prepared in the same manner as in Example 10.

[0234] [Table 1]

[0235] [Table 2]

[0236] [Table 3]

[0237] [Manufacturing of toothed belts] In Examples 1-31 and Comparative Examples 1-4, an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 4 was used as the precursor for forming the tooth rubber layer and back rubber layer. A toothed belt with a total thickness of 5.6 mm, tooth type G8M, tooth height (including tooth cloth) of 3.5 mm, tooth pitch of 8 mm, number of teeth of 140, core wire pitch of 1.4 mm, X value of arrangement density of 29%, circumference of 1120 mm, and width of 17 mm was manufactured using the manufacturing method described in the section [Modes for Carrying Out the Invention]. For each test specimen of the toothed belt (Examples and Comparative Examples), the composition of the adhesive rubber composition was changed to the compositions shown in Tables 9-14 for comparison. The rubber composition of the uncrosslinked rubber sheet for forming the tooth rubber layer and back rubber layer was the same as that used in Comparative Example 1.

[0238] 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.

[0239] [Table 4]

[0240] [Evaluation and Judgment] For each test specimen (examples and comparative examples), the machinability (formation of tooth shape), resistance to tooth chipping (life cycle of the teeth), and durability of the toothed belt were verified to determine whether or not the problem of the present invention could be solved.

[0241] [Workability] (Test method) The tooth shape of the toothed belt in the test specimen was visually observed to confirm whether the specified tooth shape was formed, and judged according to the criteria shown in Table 5. In other words, if the specified tooth shape was not formed (defective shape), it was determined that the toothed belt could not be manufactured and it was rejected.

[0242] (Judgment criteria)

[0243] [Table 5]

[0244] [Tooth chipping resistance (tooth part life cycle)] (Test method) As shown in Fig. 4, the tooth part of the toothed belt 1 was hooked on the protrusion 21a of the tooth shearing jig (a rigid body assuming the tooth shape of the toothed pulley) 21, and with one tooth pressed under a constant pressure (clamping torque 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 servo pulsar (manufactured by Shimadzu Corporation). The number of cycles (life cycle) until tooth chipping occurred was compared and judged according to the criteria shown in Table 6. From the perspective of the actual use tooth chipping resistance of this application, a toothed belt with a c judgment or higher was regarded as qualified.

[0245] (Judgment criteria)

[0246]

Table 6

[0247] [Endurance running performance] (Running test conditions) The toothed belt was attached to a two-axis running test machine equipped with a driving pulley (number of teeth: 24) and a driven pulley (number of teeth: 59), and the running time until a failure (tooth part loss) occurred in the toothed belt was measured as the running life and judged according to the criteria shown in Table 7. The attachment tension of the toothed belt was 400 N, the rotational speed of the driving pulley was 900 rpm, the load of the driven pulley was 6.0 kW, and the ambient temperature was 25 °C (room temperature).

[0248] Regarding this running life (running time until failure), 390 hours was taken as 1.00, and the running lives of each example and comparative example were converted into relative values and shown.

[0249] (Judgment criteria)

[0250]

Table 7

[0251] [Overall assessment] Based on the evaluation of each evaluation item, an overall evaluation was performed according to the criteria shown in Table 8.

[0252] (Judgment criteria)

[0253] [Table 8]

[0254] [Verification Results and Discussion] The verification results are shown in Tables 9-14.

[0255] [Table 9]

[0256] (Examples 1-7 and Comparative Examples 1-4) Comparative Example 1 is an example in which the adhesive rubber layer is formed from the same rubber composition as the tooth rubber layer and the back rubber layer. Specifically, the adhesive rubber layer contains 65 parts by mass of carbon black and 5 parts by mass of silica as a reinforcing filler per 100 parts by mass of polymer component. In Comparative Example 1, the hardness and 5% modulus of the adhesive rubber composition were low, and there was no reinforcing effect on the rigidity of the tooth, resulting in a life cycle rating of d (failure) and an overall rating of D.

[0257] Comparative Example 2 is an example in which the composition of the reinforcing filler contained in the adhesive rubber layer was changed compared to Comparative Example 1, with the amount of silica increased to 20 parts by mass and the amount of carbon black decreased to 10 parts by mass. In Comparative Example 2, although the proportion of silica, which has an excellent reinforcing effect in the low strain region of the rubber, was increased, the hardness and 5% modulus of the adhesive rubber layer did not improve, and the overall evaluation was a D rank, similar to Comparative Example 1.

[0258] Comparative Example 3, Examples 1-7, and Comparative Example 4 are examples in which the silica content was increased based on Comparative Example 2. As the silica content, which has excellent reinforcing effect in the low strain region, increased, the hardness and 5% modulus of the rubber composition improved, as did the rigidity of the teeth, and there was a tendency for the life cycle and running life to improve. In Comparative Example 3, in which the silica content was increased to 40 parts by mass, the hardness and 5% modulus of the rubber composition improved compared to Comparative Example 2, but the overall rating was D, similar to Comparative Example 2. In Examples 1-3, in which the silica content was 50-65 parts by mass, the life cycle and running life reached a practical acceptable level (C rating), and the overall rating improved to C. Furthermore, in Examples 4-7, in which the silica content was 75-130 parts by mass, the overall rating improved to B. However, in Comparative Example 4, where the silica content was further increased to 150 parts by mass, the adhesive rubber composition (uncrosslinked rubber sheet) in the tooth cloth precursor was too rigid, resulting in poor fluidity and making it difficult to form the teeth. Consequently, the desired tooth shape could not be formed, making it unmanufacturable in terms of processability (rating d), and the overall rating was rank D.

[0259] In Examples 1 (50 parts by mass), 2 (60 parts by mass), 3 (65 parts by mass), 4 (75 parts by mass), 5 (80 parts by mass), 6 (100 parts by mass), and 7 (130 parts by mass), where the silica content was 50 to 130 parts by mass per 100 parts by mass of polymer components, using a rubber composition with a hardness (Type D) of 50 or higher and a 5% modulus of 3 MPa or higher as the adhesive rubber composition reinforced the rigidity of the tooth portion, resulting in a life cycle and running life of an acceptable level (rating of C or higher).

[0260] From these results, it was confirmed that when a rubber composition with a silica content of 50 to 130 parts by mass per 100 parts by mass of polymer component is applied to the adhesive rubber layer, a reinforcing effect on the rigidity of the tooth is observed, improving resistance to tooth chipping. It was also found that a rubber composition with a hardness (Type D) of 50 or higher and a 5% modulus of 3 MPa or higher is preferably used to form the adhesive rubber layer.

[0261]

Table 10

[0262] (Examples 8 to 12) In Examples 9 (50 parts by mass), Example 10 (75 parts by mass), Example 11 (100 parts by mass), and Example 12 (130 parts by mass) in which the amount of zinc methacrylate was increased to 50 parts by mass or more with respect to Example 4 (75 parts by mass of silica and 30 parts by mass of zinc methacrylate), as the amount of zinc methacrylate increased, the rigidity (life cycle and running life) of the tooth portion tended to improve. In these examples where the ratio of zinc methacrylate to 100 parts by mass of the polymer component was 50 parts by mass or more, compared with Example 4, due to the increase in the amount of zinc methacrylate, the crosslinking density of the rubber component was improved, and a reinforcing effect on the rigidity of the tooth portion was observed. The life cycle and running life were improved to a very excellent a judgment, and the comprehensive judgment was A rank.

[0263] On the other hand, in Example 8 in which the amount of zinc methacrylate was reduced to 10 parts by mass with respect to Example 4, although the life cycle and running life decreased to a c judgment, the practical passing level was maintained, and the comprehensive judgment was C rank.

[0264]

Table 11

[0265] (Examples 13 to 21) Examples 13 to 16 are examples in which the type of ethylene-α-olefin elastomer (EPDM) of the polymer component was changed with respect to Example 2. From Examples 13 to 16, as the diene content of EPDM was higher, the hardness and 5% modulus of the rubber composition were improved, and the life cycle and running life tended to improve.

[0266] Examples 17-21 are examples in which the type of polymer component (ethylene-α-olefin elastomer) was changed compared to Example 10. From Examples 10 and 17-21, it was observed that the higher the diene content of the EPDM, the greater the hardness and 5% modulus of the rubber composition, as well as the improved life cycle and running life.

[0267] In detail, Examples 10 (diene content 4.9% by mass), 17 (diene content 8.5% by mass), 18 (diene content 8.5% by mass), and 19 (diene content 4.9% by mass), which used EPDM with a diene content of 3% by mass or more, all received an "a" rating for life cycle and running life, and the overall rating was A.

[0268] On the other hand, in Examples 20 (2.2 mass%) and 21 (0.5 mass%), which had a reduced diene content compared to Example 10, the life cycle and running life decreased (rated B or C), but a practical acceptable level was maintained, and the overall rating was B or C.

[0269] 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.

[0270] (Example 22) Example 22 is an example in which the polymer component was changed from Example 10 to EBDM (diene content 7.1% by mass). However, the life cycle and running life were rated as "a" and the overall rating was A, the same as in Example 10. Results equivalent to those obtained with EPDM were obtained even when using EBDM.

[0271] [Table 12]

[0272] (Examples 23-25) Example 23 is an example in which 2 parts by mass of para-aramid short fibers were added to Example 3. Similarly, Example 24 is an example in which 2 parts by mass of para-aramid short fibers were added to Example 10. 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.

[0273] [Table 13]

[0274] (Examples 26 and 27) Examples 26 and 27 are examples in which the type of silica (BET specific surface area) was changed compared to Example 10. However, the life cycle and running life were rated as 'a', similar to Example 10, and the overall rating was A.

[0275] [Table 14]

[0276] (Examples 28-31) Examples 28-31 are examples in which the average thickness of the adhesive rubber layer was changed compared to Example 10. 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-stiffness adhesive rubber layer increases, as tooth stiffness increases. However, for durability life, which is affected by the balance between tooth stiffness and flexibility, it is thought that if the average thickness of the adhesive rubber layer becomes too large, the flexibility of the belt decreases, and the running life decreases. As a result of this balance between tooth stiffness and flexibility, in Examples 29 (0.3 mm), 10 (0.65 mm), and 30 (1.0 mm), where the average thickness of the adhesive rubber layer is in the range of 0.3 to 1.0 mm, the life cycle and running life were rated as 'a', and the overall rating was A. In Example 31 (1.2 mm), where the average thickness of the adhesive rubber layer was large, the durability life was rated as 'c' due to the effect of flexibility, and the overall rating was C. On the other hand, in Example 28 (0.2 mm), where the average thickness of the adhesive rubber layer was small, the life cycle and durability life were rated as C due to the effect of low tooth rigidity, resulting in an overall rating of C. In all average thicknesses, a practical acceptable level was maintained.

[0277] (Effects obtained) From the above verification, it was found that the configuration of the present invention [a configuration in which the polymer component contains ethylene-α-olefin elastomer, and the adhesive rubber layer is formed with a crosslinked rubber composition that has been hardened by containing a large amount (50 to 130 parts by mass) of silica per 100 parts by mass of the polymer component] can be used to obtain a toothed belt that can improve tooth chipping resistance without increasing material costs or manufacturing costs. [Industrial applicability]

[0278] 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. [Explanation of symbols]

[0279] 1…Toothed belt 1a...teeth part 1b...Root of the tooth 1c...back 2… Toothcloth 3…Adhesive rubber layer 4…Tooth rubber layer 5… Core wire 6... Back rubber layer

Claims

1. The back portion has a core wire embedded in it that extends along the circumference of the belt, The inner circumferential surface of the back portion is provided with a plurality of teeth formed at intervals in the circumferential direction of the belt, The back rubber layer that forms the back portion, The tooth rubber layer that forms the tooth portion, The tooth cloth formed on the surface of the tooth portion, A toothed belt comprising an adhesive rubber layer interposed between the tooth rubber layer and the tooth cloth, The adhesive rubber layer comprises a crosslinked product of a first rubber composition containing a first polymer component and silica. The first polymer component comprises a first ethylene-α-olefin elastomer, The proportion of silica is 50 to 130 parts by mass per 100 parts by mass of the first polymer component. The tooth rubber layer and the back rubber layer contain a crosslinked product of a second rubber composition containing a second ethylene-α-olefin elastomer, and A toothed belt in which the rubber hardness of the crosslinked product of the first rubber composition is greater than the rubber hardness of the crosslinked product of the second rubber composition.

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

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

4. The first ethylene-α-olefin elastomer comprises an ethylene-α-olefin-diene terpolymer, The toothed belt according to claim 1 or 2, wherein the diene content of the ethylene-α-olefin-diene ternary copolymer is 3% by mass or more.

5. The toothed belt according to claim 1 or 2, wherein the first rubber composition contains an unsaturated metal carboxylate salt, and the proportion of the unsaturated metal carboxylate salt is 50 parts by mass or more per 100 parts by mass of the first polymer component.

6. The toothed belt according to claim 1 or 2, wherein the average thickness of the adhesive rubber layer is 0.3 to 1 mm.

7. The toothed belt according to claim 1 or 2, wherein the X value of the arrangement density of the core wires is 15% or more.

8. A method for manufacturing a toothed belt according to claim 1 or 2, comprising a crosslinking molding step of crosslinking an uncrosslinked molded body obtained by laminating a tooth cloth precursor, an adhesive rubber layer precursor, a core wire precursor, and precursors for the tooth rubber layer and the back rubber layer.

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