Belt, belt transmission mechanism, and method for improving adhesiveness

Abstract

The present invention relates to a transmission belt which comprises a core wire extending along the belt circumferential direction and an outer peripheral rubber layer formed on the belt outer peripheral side with respect to the core wire, and which is for conveying an article on the outer peripheral surface of the outer peripheral rubber layer, wherein: the outer peripheral rubber layer has a layered structure including a first rubber layer forming a conveyance surface serving as the outer peripheral surface and a second rubber layer positioned on the belt inner peripheral side of the first rubber layer; the first rubber layer is formed from a crosslinked product of a first rubber composition including silicone rubber; the second rubber layer is formed from a crosslinked product of a second rubber composition including at least one selected from among an ethylene-ɑ-olefin elastomer and a hydrogenated nitrile rubber; and the outer peripheral rubber layer includes an unsaturated carboxylic acid metal salt.

Description

Transmission belt, method for manufacturing a transmission belt, belt transmission mechanism, and method for improving adhesion

[0001] The present invention relates to a power transmission belt for transmitting power and transporting articles using the back surface of the belt, a method for manufacturing a power transmission belt, a belt transmission mechanism, and a method for improving adhesion.

[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 examples of meshing belts include toothed belts. These transmission belts consist of a rubber layer and a core (core wire) embedded in the rubber layer. The polymer component that makes up the rubber layer is increasingly made of ethylene-α-olefin elastomers, including ethylene-propylene-diene terpolymer (EPDM). Ethylene-α-olefin elastomers have the advantage of excellent heat resistance because they do not have double bonds in their main chain, and it is relatively easy to incorporate a large amount of filler, making it easy to improve the mechanical properties of the transmission belt. In addition, it is possible to adjust the viscosity and hardness by changing the ratio of the ethylene component to the α-olefin component, and it is possible to adjust the physical properties of the rubber composition according to the application. On the other hand, ethylene-α-olefin elastomers exhibit properties closer to those of resins compared to conventionally used materials such as chloroprene rubber. They are brittle and lack adhesiveness, resulting in problems with processability such as mixing and sheet rolling, and poor adhesion to other materials. For example, Japanese Patent Publication No. 2002-81506 (Patent Document 1) and Japanese Patent Publication No. 2017-211084 (Patent Document 2) disclose V-ribbed belts and toothed belts using EPDM. Another example of a polymer component constituting a rubber layer is hydrogenated nitrile rubber (HNBR). Hydrogenated nitrile rubber is a highly saturated rubber in which the butadiene unit of nitrile rubber is hydrogenated, and it is an elastomer that combines oil resistance due to the nitrile group with heat resistance due to hydrogenation. For example, Japanese Patent Publication No. 8-118507 (Patent Document 3) and Japanese Patent Publication No. 2014-70644 (Patent Document 4) disclose toothed belts and V-belts using HNBR.

[0003] A power transmission belt is wrapped around the shafts of a drive pulley and a driven pulley and rotates to transmit power. However, depending on the application, it may also serve to transport goods using the back surface of the belt in addition to transmitting power.

[0004] Generally, conveying surfaces for transporting goods require appropriate grip (coefficient of friction) and non-stick properties in relation to the transported object, and are therefore formed from a polymer layer containing a silicone component. For example, as a flat conveying belt for use in a belt conveyor, Japanese Patent Publication No. 2016-183049 (Patent Document 5) discloses a conveying belt in which the conveying surface is formed from a thermoplastic resin or thermoplastic elastomer containing a silicone component. Furthermore, Japanese Patent Publication No. 2016-37338 (Patent Document 6) discloses a conveying belt including a peroxide-vulcanized rubber layer made of a peroxide-vulcanized rubber other than silicone rubber, and a peroxide-vulcanized thermosetting silicone rubber layer laminated on the surface of this peroxide-vulcanized rubber layer via a silane coupling agent layer.

[0005] Japanese Patent Publication No. 2002-81506, Japanese Patent Publication No. 2017-211084, Japanese Patent Publication No. Hei 8-118507, Japanese Patent Publication No. 2014-70644, Japanese Patent Publication No. 2016-183049, Japanese Patent Publication No. 2016-37338

[0006] The flat conveying belts described in Patent Documents 5 and 6 are belts intended solely for conveying articles, and have a relatively small overall thickness, with the silicone component layer also being a thin film. On the other hand, in the case of a power transmission belt that also serves to convey articles using the back surface of the belt, it is necessary to add a conveying surface layer to a base structure for power transmission, so the thickness is greater than that of a flat conveying belt. When the power transmission structure is formed from a rubber layer using the aforementioned ethylene-α-olefin elastomer or hydrogenated nitrile rubber, it is necessary to laminate a polymer layer containing a silicone component (for example, a silicone rubber layer) that forms the conveying surface.

[0007] However, silicone components such as silicone rubber are known as difficult-to-adhere materials having low adhesion to other components, as they are commonly used as release agents and non-adhesive materials. Furthermore, ethylene-α-olefin elastomers are also known as rubber components with low adhesion among synthetic rubbers used in power transmission belts. Therefore, the combination of silicone rubber and ethylene-α-olefin elastomer is a combination of components that are difficult to adhere to each other. In particular, silicone rubber is selected as a rubber with low adhesion from the aspect of the function requiring non-adhesiveness to conveyed objects, and there is a trade-off relationship between the function of silicone rubber required as a conveying surface and adhesion. It is extremely difficult to adhere (join) a silicone rubber layer to an ethylene-α-olefin elastomer layer or a hydrogenated nitrile rubber layer. Therefore, in the conveyor belt of Patent Document 6, a silane coupling agent layer is interposed as an adhesive layer between the peroxide-vulcanized rubber layer and the thermosetting silicone rubber layer, but the adhesion is not sufficient.

[0008] Accordingly, an object of the present invention is to provide a power transmission belt excellent in adhesion (joint strength) between a silicone rubber layer on a conveying surface and an ethylene-α-olefin elastomer layer or a hydrogenated nitrile rubber layer laminated on the inner circumferential surface of the silicone rubber layer, and a method for producing the same.

[0009] Another object of the present invention is to provide a method for producing a power transmission belt that has a simple structure, high productivity, transmits power, and conveys articles using the back surface thereof.

[0010] Still another object of the present invention is to provide a power transmission belt having a long durable running life and a method for producing the same.

[0011] The inventors of the present invention have conducted intensive studies to achieve the above object, and found that by blending an unsaturated carboxylic acid metal salt into an outer peripheral rubber layer including a silicone rubber layer that forms a conveying surface of a power transmission belt, the adhesion (joint strength) with the silicone rubber layer can be improved, and completed the present invention.

[0012] In other words, the present invention includes the following embodiments: [1] A transmission belt for conveying articles on the outer surface of the outer rubber layer, comprising a core wire extending along the circumferential direction of the belt and an outer rubber layer formed on the outer circumferential side of the belt with respect to the core wire, wherein the outer rubber layer has a laminated structure including a first rubber layer that forms a conveying surface which is the outer surface and a second rubber layer located on the inner circumferential side of the belt of the first rubber layer, the first rubber layer is formed of a crosslinked product of a first rubber composition including silicone rubber, the second rubber layer is formed of a crosslinked product of a second rubber composition including at least one selected from ethylene-α-olefin elastomer and hydrogenated nitrile rubber, and the outer rubber layer contains an unsaturated carboxylic acid metal salt. [2] The transmission belt according to [1], wherein the second rubber layer is laminated on the inner circumferential surface of the first rubber layer, and the unsaturated carboxylic acid metal salt is contained in at least one of the first rubber composition and the second rubber composition. [3] The transmission belt according to [1] or [2], wherein the unsaturated carboxylic acid metal salt comprises a first unsaturated carboxylic acid metal salt contained in the first rubber composition, and the proportion of the first unsaturated carboxylic acid metal salt is 0.5 parts by mass or more per 100 parts by mass of the silicone rubber. [4] The transmission belt according to any one of [1] to [3], wherein the second rubber composition comprises an ethylene-α-olefin elastomer. [5] The transmission belt according to [4], wherein the unsaturated carboxylic acid metal salt comprises a second unsaturated carboxylic acid metal salt contained in the second rubber composition, and the proportion of the second unsaturated carboxylic acid metal salt is 3 parts by mass or more per 100 parts by mass of the ethylene-α-olefin elastomer. [6] The transmission belt according to [4] or [5], wherein the peel strength between the first rubber layer and the second rubber layer is 10 N / 25 mm or more. [7] The transmission belt according to any one of [1] to [3], wherein the second rubber composition comprises hydrogenated nitrile rubber. [8] The transmission belt according to [7], wherein the unsaturated metal carboxylate salt comprises a second unsaturated metal carboxylate salt contained in the second rubber composition, and the amount of the second unsaturated metal carboxylate salt is 3 parts by mass or more per 100 parts by mass of the hydrogenated nitrile rubber.[9] The transmission belt according to [7] or [8], wherein the peel strength between the first rubber layer and the second rubber layer is 30 N / 25 mm or more.

[10] The transmission belt according to [1], wherein the outer peripheral rubber layer further includes an intermediate layer, the intermediate layer is laminated on the inner peripheral surface of the first rubber layer, the second rubber layer is laminated on the inner peripheral surface of the intermediate layer, and the intermediate layer includes a crosslinked binder component containing the unsaturated carboxylic acid metal salt.

[11] The transmission belt according to

[10] , wherein the intermediate layer is an intermediate layer formed of a crosslinked binder component, and the binder component consists of the unsaturated carboxylic acid metal salt.

[12] The basis weight of the binder component is 50 g / m. ２The power transmission belt according to

[11] , wherein the intermediate layer is an intermediate layer formed of a crosslinked product of the binder component, or an intermediate layer formed of a cloth containing a crosslinked product of the binder component, and the binder component is a third rubber composition comprising a rubber component and the unsaturated carboxylic acid metal salt.

[14] The power transmission belt according to

[13] , wherein the second rubber composition comprises an ethylene-α-olefin elastomer, and the rubber component comprises a silicone rubber and / or an ethylene-α-olefin elastomer.

[15] The power transmission belt according to

[13] or

[14] , wherein the rubber component comprises an ethylene-α-olefin elastomer, and the proportion of the unsaturated carboxylic acid metal salt is 3 parts by mass or more per 100 parts by mass of the rubber component.

[16] The power transmission belt according to any one of

[10] to

[15] , wherein the peel strength between the first rubber layer and the intermediate layer is 10 N / 25 mm or more.

[17] The transmission belt according to

[13] , wherein the second rubber composition comprises hydrogenated nitrile rubber, and the rubber component comprises silicone rubber and / or hydrogenated nitrile rubber.

[18] The transmission belt according to

[13] or

[17] , wherein the rubber component comprises hydrogenated nitrile rubber, and the proportion of the unsaturated carboxylic acid metal salt is 3 parts by mass or more per 100 parts by mass of the rubber component.

[19] The transmission belt according to any one of

[10] to

[13] ,

[17] to

[18] , wherein the peel strength between the first rubber layer and the intermediate layer is 30 N / 25 mm or more.

[20] The transmission belt according to any one of

[13] to

[19] , wherein the average thickness of the cloth is 0.05 to 1 mm, the cloth is formed of a woven fabric made of warp threads extending in the belt width direction and weft threads extending in the belt circumferential direction, and the woven fabric contains polyamide fibers, and the average diameter of the warp threads is 0.3 times or more the average diameter of the weft threads.

[21] A power transmission belt according to any one of [1] to

[20] , wherein the unsaturated carboxylic acid metal salt comprises zinc methacrylate.

[22] A power transmission belt according to any one of [1] to

[21] , wherein the average thickness of the first rubber layer is 50 to 80% of the average thickness of the outer rubber layer.

[23] A power transmission belt according to any one of [1] to

[22] , which is a toothed belt.

[24] A method for manufacturing a power transmission belt according to any one of [1] to

[23] , comprising a joining step of joining the first rubber layer and the second rubber layer by crosslinking a first rubber layer precursor formed of the first rubber composition and a second rubber layer precursor formed of the second rubber composition.

[25] The method for manufacturing a power transmission belt according to

[24] , wherein in the joining step, the first rubber layer and the second rubber layer are joined without interposing an adhesive between the first rubber layer and the second rubber layer by laminating and crosslinking the first rubber layer precursor and the second rubber layer precursor in this order.

[26] The method for manufacturing a power transmission belt according to

[24] , wherein in the joining step, the first rubber layer and the second rubber layer are joined by interposing an intermediate layer between the first rubber layer and the second rubber layer by crosslinking the first rubber layer precursor, the intermediate layer precursor containing the binder component, and the second rubber layer precursor in this order.

[27] A transmission belt comprising a core wire extending along the circumferential direction of the belt and an outer peripheral rubber layer formed on the outer peripheral side of the belt relative to the core wire, wherein the outer peripheral rubber layer has a laminated structure comprising a first rubber layer that forms a conveying surface which is the outer peripheral surface and a second rubber layer located on the inner peripheral side of the belt relative to the first rubber layer, wherein the first rubber layer is formed of a crosslinked product of a first rubber composition containing silicone rubber, and the second rubber layer is formed of a crosslinked product of a second rubber composition containing at least one selected from ethylene-α-olefin elastomer and hydrogenated nitrile rubber, and the adhesion between the first rubber layer and the second rubber layer is improved by compounding an unsaturated carboxylic acid metal salt into the outer peripheral rubber layer.

[28] The method according to

[27] , wherein the second rubber layer is laminated on the inner peripheral surface of the first rubber layer, and the unsaturated carboxylic acid metal salt is contained in at least one of the first rubber composition and the second rubber composition.

[29] The method according to

[27] , wherein the outer peripheral rubber layer further includes an intermediate layer, the intermediate layer is laminated on the inner peripheral surface of the first rubber layer, the second rubber layer is laminated on the inner peripheral surface of the intermediate layer, and the intermediate layer includes a crosslinked product of a binder component containing the unsaturated carboxylic acid metal salt.

[30] A belt transmission mechanism for transporting articles, comprising a transmission belt as described in any of [1] to

[23] and a pulley.

[0013] In this application, the numerical range represented by "A to B" means "A or greater and B or less," and is used to include the values ​​A and B at both ends of that range.

[0014] 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.

[0015] In the present invention, the outer periphery rubber layer, which includes a silicone rubber layer forming the conveying surface of the power transmission belt, contains an unsaturated carboxylic acid metal salt, thereby improving adhesion (bonding strength) with the silicone rubber layer. In one aspect of the present invention, at least one of the silicone rubber layer forming the conveying surface of the power transmission belt and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer laminated on the inner periphery of the silicone rubber layer contains an unsaturated carboxylic acid metal salt, thereby improving adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer. In particular, since the silicone rubber layer and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer can be bonded without using an adhesive, the structure of the power transmission belt, which transmits power and conveys articles using the back surface of the belt, can be simplified, and it can be manufactured with high productivity. In another aspect of the present invention, an intermediate layer containing a crosslinked binder component containing an unsaturated carboxylic acid metal salt is interposed between the silicone rubber layer forming the conveying surface of the transmission belt and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer. This improves the adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer, even though they are a combination of materials that are difficult to bond. Furthermore, the transmission belt of the present invention has a long service life, and in particular, it can suppress failures due to long-term use (cracks on the back surface, peeling of the back layer).

[0016] Figure 1 is a schematic partial cross-sectional perspective view showing an example of the toothed belt of the present invention. Figure 2 is a schematic cross-sectional view of the toothed belt of Figure 1. Figure 3 is a schematic partial cross-sectional perspective view showing another example of the toothed belt of the present invention. Figure 4 is a schematic cross-sectional view of the toothed belt of Figure 3. Figure 5 is a schematic diagram illustrating the measurement method for the adhesion test of Examples A and C. Figure 6 is a schematic diagram illustrating the measurement method for the adhesion test of Examples B and D.

[0017] [Power Transmission Belt] The power transmission belt (power transmission belt) of the present invention is not particularly limited as long as it is a power transmission belt that transmits power and can transport articles using the back surface (outer surface) of the belt. The type of power transmission belt of the present invention is not particularly limited as long as it is a belt that transmits power by contacting a pulley, and may be a friction transmission belt or a meshing transmission belt.

[0018] Examples of friction transmission belts include flat belts, V-belts (wrapped V-belts, raw edge V-belts, raw edge cogged V-belts with cogs formed on the inner circumference, raw edge double cogged V-belts with cogs formed on both the inner and outer circumferences), and V-ribbed belts.

[0019] Examples of interlocking power transmission belts include toothed belts and double-sided toothed belts.

[0020] In the present invention, in these power transmission belts, the outer rubber layer formed on the outer circumference side of the belt relative to the core wire has a laminated structure including a first rubber layer (silicone rubber layer) that forms the conveying surface which becomes the outer circumference, and a second rubber layer (ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer) located on the inner circumference side of the belt relative to the first rubber layer, and the adhesion (bonding strength) between the silicone rubber layer and the outer rubber layer can be improved by including an unsaturated carboxylic acid metal salt in the outer rubber layer. In one aspect of the present invention, the outer rubber layer formed on the outer circumference side of the belt relative to the core wire has a laminated structure including a first rubber layer (silicone rubber layer) that forms the conveying surface which becomes the outer circumference, and a second rubber layer (ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer) laminated on the inner circumference side of the first rubber layer and in contact with the first rubber layer, and the adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer can be improved by including an unsaturated carboxylic acid metal salt in the first rubber layer and the second rubber layer. While it is possible to some extent to bond an ethylene-α-olefin elastomer layer or a hydrogenated nitrile rubber layer to a silicone rubber layer using a resin-based adhesive, the presence of a non-elastic resin component between the layers can reduce flexibility and create bending stress between the layers, making delamination more likely. In contrast, in one aspect of the present invention, by utilizing an "unsaturated carboxylic acid metal salt" in an integral crosslinking molding method without using a (resin-based) adhesive, the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer and the silicone rubber layer can be firmly bonded through a chemical crosslinking reaction. In another aspect of the present invention, the outer rubber layer formed on the outer circumference side of the belt relative to the core wire has a laminated structure comprising a first rubber layer (silicone rubber layer) that forms the conveying surface which is the outer circumference, an intermediate layer laminated on the inner circumference surface of the first rubber layer, and a second rubber layer (ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer) laminated on the inner circumference surface of the intermediate layer, and by including a crosslinked binder component containing an unsaturated carboxylic acid metal salt in the intermediate layer, the adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer or hydrogenated nitrile rubber layer can be improved.

[0021] In the power transmission belt of the present invention, the outer periphery rubber layer may include the first rubber layer and the second rubber layer, or it may include the first rubber layer, the intermediate layer and the second rubber layer. One or more other rubber layers (for example, an adhesive rubber layer to improve the adhesion between the second rubber layer and the core wire) may be further interposed between the second rubber layer and the core wire. As the adhesive rubber layer, an adhesive rubber layer commonly used in power transmission belts can be used, depending on the type of rubber. Of these, in one embodiment of the present invention, the outer periphery rubber layer is preferably a combination of the first rubber layer, the second rubber layer and the third rubber layer (particularly the adhesive rubber layer), a combination of the first rubber layer and the second rubber layer (an outer periphery rubber layer consisting only of the first rubber layer and the second rubber layer), and the combination of the first rubber layer and the second rubber layer is particularly preferred. Furthermore, in other embodiments of the present invention, the outer periphery rubber layer may be a combination of a first rubber layer, an intermediate layer, a second rubber layer, and a third rubber layer (particularly an adhesive rubber layer), or a combination of a first rubber layer, an intermediate layer, and a second rubber layer (an outer periphery rubber layer consisting only of the first rubber layer, an intermediate layer, and a second rubber layer), with the combination of a first rubber layer, an intermediate layer, and a second rubber layer being particularly preferred. In the power transmission belt of the present invention, the details of the first rubber layer, the intermediate layer, and the second rubber layer are as follows.

[0022] (First rubber layer) The first rubber layer is formed of a crosslinked product of the first rubber composition containing silicone rubber.

[0023] (1A) Silicone rubber The silicone rubber may be conventional silicone rubber, for example, polyorganosiloxane. Polyorganosiloxane is a linear, branched, or network compound having Si-O bonds (siloxane bonds), and is of formula: R ａ SiO （４－ａ）／２ It may be composed of units represented by the formula (wherein R is a substituent and a is a number from 0 to 3).

[0024] Furthermore, since silicone rubber is mainly composed of two-dimensional siloxane bonds (D units), it is superior in flexibility compared to silicone resins which are mainly composed of three-dimensional siloxane bonds (T units). On the other hand, the silicone-modified resin disclosed in Patent Document 5 is a thermoplastic resin or thermoplastic elastomer that melts when heated, and thus can be relatively easily bonded to other rubbers, whereas silicone rubber is thermosetting, does not melt when heated, and has extremely low adhesion to other rubbers. Therefore, among polymers containing a silicone component that are generally used as release agents and non-adhesive materials, silicone rubber is a polymer with particularly low adhesion.

[0025] In the above formula, examples of the substituent R include C １－１０ alkyl groups, halogenated C １－１０ alkyl groups such as 3-chloropropyl group and 3,3,3-trifluoropropyl group, C ２－１０ alkenyl groups such as vinyl group, allyl group and butenyl group, C ６－２０ aryl groups such as phenyl group, tolyl group and naphthyl group, C ３－１０ cycloalkyl groups such as cyclopentyl group and cyclohexyl group, C ６－１２ aryl-C １－４ alkyl groups, and the like. These substituents can be used alone or in combination of two or more kinds. Among these, preferred R are methyl group, phenyl group, alkenyl groups (such as vinyl group), and fluoro C １－６ alkyl groups.

[0026] Examples of the polyorganosiloxane include polydialkylsiloxanes (polydi C １－１０ alkylsiloxanes such as polydimethylsiloxane), polyalkylalkenylsiloxanes (poly C １－１０ alkyl C ２－１０ alkenylsiloxanes such as polymethylvinylsiloxane), polyalkylarylsiloxanes (poly C １－１０ alkyl C ６－２０Arylsiloxanes, polydiarylsiloxanes (polydiphenylsiloxanes, etc.) ６－２０ Examples include arylsiloxanes, copolymers composed of the polyorganosiloxane units [dimethylsiloxane-methylvinylsiloxane copolymer, dimethylsiloxane-methylphenylsiloxane copolymer, dimethylsiloxane-methyl(3,3,3-trifluoropropyl)siloxane copolymer, dimethylsiloxane-methylvinylsiloxane-methylphenylsiloxane copolymer; dimethylsiloxane-diphenylsiloxane copolymer, etc.]. These polyorganosiloxanes may be used individually or in combination of two or more types.

[0027] Polyorganosiloxanes may also be polyorganosiloxanes having substituents such as epoxy groups, hydroxyl groups, alkoxy groups, carboxyl groups, amino groups or substituted amino groups (such as dialkylamino groups), or (meth)acryloyl groups at the molecular ends or main chain. Furthermore, both ends of the polyorganosiloxane may have substituents such as trimethylsilyl groups, dimethylvinylsilyl groups, silanol groups, or tri-C groups. １－２ It may also be an alkoxysilyl group, etc.

[0028] Of these polyorganosiloxanes, polydiC is selected based on its mechanical properties and availability. １－１０ It is preferable that the material contains alkylsiloxanes, particularly polydimethylsiloxane (PDMS).

[0029] The polyorganosiloxane structure forming the silicone rubber may be branched or networked, but a linear structure is preferred from the viewpoint of mechanical properties. Examples of silicone rubbers include dimethyl silicone rubber (MQ), vinyl methyl silicone rubber (VMQ), phenyl methyl silicone rubber (PMQ), phenyl vinyl methyl silicone rubber (PVMQ), and fluorovinyl methyl silicone rubber (FVMQ). Of these, dimethyl silicone rubber composed of PDMS is preferred. Furthermore, the silicone rubber may be a combination of linear polyorganosiloxane (such as methyl silicone rubber) and branched or networked polyorganosiloxane (such as MQ resin).

[0030] The silicone rubber may be either room-temperature curing or thermosetting, and may be either one-component curing or two-component curing. Of these, thermosetting silicone rubber is preferred in terms of handling ease and heat resistance.

[0031] The rubber hardness of the silicone rubber (crosslinked silicone rubber) is a Type A hardness, for example A10 to A90 (particularly A10 to A75), preferably A20 to A80, even more preferably A25 to A75, more preferably A30 to A70, and most preferably A40 to A65 (particularly A40 to A60). If the rubber hardness of the silicone rubber is too low, the first rubber layer may wear down easily, and if it is too high, the friction with the conveyed material may be insufficient, and sufficient grip may not be obtained. From the viewpoint of improving the durability and running performance of the belt, the rubber hardness of the silicone rubber may be a Type A hardness, preferably A52 to A65, and even more preferably A53 to A63.

[0032] In this application, the Type A hardness of each rubber layer is expressed as the value measured using a 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).

[0033] If the outer rubber layer does not include an intermediate layer between the first and second rubber layers, the proportion of silicone rubber may be 50% by mass or more in the first rubber composition, for example 50 to 99.9% by mass, preferably 70 to 99.5% by mass, more preferably 80 to 99% by mass, more preferably 90 to 98% by mass, and most preferably 93 to 96% by mass. If the second rubber composition described later contains an unsaturated carboxylic acid metal salt (particularly zinc methacrylate), the proportion of silicone rubber may be 50% by mass or more in the first rubber composition (for example 50 to 99.9% by mass), for example 80 to 99.9% by mass, preferably 90 to 99.9% by mass, more preferably 95 to 99.8% by mass, more preferably 98 to 99.7% by mass, and most preferably 99 to 99.6% by mass. If the proportion of silicone rubber is too low, the transportability of the article may decrease.

[0034] When the outer rubber layer includes an intermediate layer between the first and second rubber layers, the proportion of silicone rubber may be 50% by mass or more (for example, 50 to 99.9% by mass) in the first rubber composition, for example, 80 to 99.9% by mass, preferably 90 to 99.9% by mass, more preferably 95 to 99.8% by mass, more preferably 98 to 99.7% by mass, and most preferably 99 to 99.6% by mass. If the proportion of silicone rubber is too low, the transportability of the article may decrease.

[0035] (1B) The first rubber composition contains an unsaturated carboxylic acid metal salt (first unsaturated carboxylic acid metal salt), which improves the adhesion between the first rubber layer and the second rubber layer. In the power transmission belt of the present invention, the unsaturated carboxylic acid metal salt only needs to be included in the outer rubber layer. In one embodiment of the present invention in which the outer rubber layer does not include an intermediate layer, the unsaturated carboxylic acid metal salt only needs to be included in at least one of the first rubber composition and the second rubber composition. Therefore, if the second rubber composition contains an unsaturated carboxylic acid metal salt (second unsaturated carboxylic acid metal salt), the first unsaturated carboxylic acid metal salt is not an essential component in the first rubber composition, and from the standpoint of economy, etc., the first rubber composition does not need to contain an unsaturated carboxylic acid metal salt. In an embodiment in which the outer rubber layer includes an intermediate layer, the first rubber composition and the second rubber composition do not need to contain an unsaturated carboxylic acid metal salt.

[0036] 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.

[0037] Examples of unsaturated carboxylic acids in the first unsaturated carboxylic acid metal salt include monocarboxylic acids such as (meth)acrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and monoalkyl esters of these dicarboxylic acids. These unsaturated carboxylic acids can be used alone or in combination of two or more. A preferred unsaturated carboxylic acid is (meth)acrylic acid.

[0038] Examples of metals used in the first unsaturated carboxylate metal salts include alkali metals such as sodium and potassium; polyvalent metals such as group 2 elements of the periodic table (magnesium, calcium, etc.), group 4 elements (titanium, zirconium, etc.), and group 8 to 14 elements of the periodic table (e.g., iron, cobalt, nickel, copper, zinc, aluminum, tin, lead, etc.). These metals can be used individually or in combination of two or more. Preferred metals are polyvalent metals such as group 2 elements of the periodic table (magnesium, etc.) and group 12 elements of the periodic table (zinc, etc.).

[0039] These unsaturated carboxylate metal salts can be used individually or in combination of two or more.

[0040] 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.

[0041] The proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 0.1 parts by mass or more (preferably 0.5 parts by mass or more, more preferably 3 parts by mass or more) per 100 parts by mass of silicone rubber, and can be selected from a range of approximately 0.1 to 30 parts by mass (particularly 0.5 to 20 parts by mass), preferably 1 to 15 parts by mass, more preferably 2 to 12 parts by mass, more preferably 3 to 10 parts by mass, and most preferably 4 to 7 parts by mass. If high bonding performance is required, the proportion may be 4 parts by mass or more per 100 parts by mass of silicone rubber, for example 5 to 30 parts by mass, preferably 8 to 20 parts by mass. If the proportion of the first unsaturated carboxylic acid metal salt is too low, the adhesion between the first rubber layer and the second rubber layer may decrease. From the viewpoint of improving the durability of the belt's running performance, the proportion may be preferably 3 to 15 parts by mass, more preferably 4 to 12 parts by mass, and more preferably 5 to 10 parts by mass per 100 parts by mass of silicone rubber.

[0042] If the second rubber composition contains a second unsaturated carboxylic acid metal salt (particularly zinc methacrylate), the proportion of the first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 10 parts by mass or less per 100 parts by mass of silicone rubber, for example, 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and most preferably 0 parts by mass.

[0043] (1C) The first rubber composition preferably further contains a crosslinking agent (first crosslinking agent). Examples of the first crosslinking agent include organic peroxides.

[0044] Examples of organic peroxides include diacyl peroxides (e.g., dilauroyl peroxide, dibenzoyl peroxide, etc.), peroxyketals [e.g., 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, etc.], and dialkyl peroxides [di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyl peroxide]. Examples include [n-3,1,3-bis(2-t-butylperoxyisopropyl)benzene, etc.], alkyl peroxyesters [t-butylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, etc.], dialkyl peroxides (dicumyl peroxide, t-butylcumyl peroxide, etc.), peroxycarbonates (t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethyl-hexyl carbonate, t-amylperoxy-2-ethyl-hexyl carbonate, etc.). Furthermore, the organic peroxide may be a peroxide that has a decomposition temperature of 150 to 250°C (e.g., 175 to 225°C) at which it obtains a half-life of 1 minute by thermal decomposition. These organic peroxides can be used individually or in combination of two or more.

[0045] Among these organic peroxides, dialkyl peroxides such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexane are preferred.

[0046] The proportion of the first crosslinking agent (especially organic peroxide) may be 0.05 parts by mass or more per 100 parts by mass of silicone rubber, for example, 0.05 to 5 parts by mass, preferably 0.1 to 3 parts by mass, more preferably 0.15 to 1 part by mass, more preferably 0.2 to 0.8 parts by mass, and most preferably 0.3 to 0.7 parts by mass. 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, and bloom (precipitation on the surface) may occur.

[0047] (1D) Other components The first rubber composition may further contain other components (first other components), such as rubber other than silicone rubber, and conventional additives used in rubber compositions for power transmission belts. Examples of conventional additives include crosslinking aids (cocrosslinking agents, crosslinking accelerators, crosslinking retarders, etc.), filling agents (fillers, short fibers, etc.), softeners, antioxidants, flex crack inhibitors, ozone degradation inhibitors, colorants, adhesion improvers, tackifiers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, and antistatic agents. These other components can be used individually or in combination of two or more.

[0048] The total proportion of the other components is 100 parts by mass or less, preferably 50 parts by mass or less, more preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and most preferably 1 part by mass or less, per 100 parts by mass of silicone rubber.

[0049] (Second rubber layer) The second rubber layer is formed of a crosslinked product of a second rubber composition containing ethylene-α-olefin elastomer or hydrogenated nitrile rubber.

[0050] (2A-1) Ethylene-α-olefin elastomer Ethylene-α-olefin elastomer is a rubber component with low adhesive properties among synthetic rubbers used in power transmission belts, and it is extremely difficult to improve the interlayer adhesion between the first rubber layer and the second rubber layer when combined with silicone rubber, which is a difficult-to-bond material that constitutes the first rubber layer.

[0051] Ethylene-α-olefin elastomers only need to contain ethylene units and α-olefin units as constituent units, and may further contain diene units. Therefore, ethylene-α-olefin elastomers include ethylene-α-olefin copolymer rubber and ethylene-α-olefin-diene ternary copolymer rubber.

[0052] Examples of α-olefins used to form α-olefin units include linear α-C such as propylene, 1-butene, 1-pentene, methylpentene, 1-hexene, and 1-octene. ３－１２Examples include olefins. Among these α-olefins, α-C ３－８ Olefins are preferred, and α-C ３－６ Olefins are more preferred, and α-C such as propylene ３－４ Olefins (especially propylene) are more preferred.

[0053] 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.

[0054] Typical ethylene-α-olefin elastomers include, for example, ethylene-α-olefin rubber [ethylene-propylene rubber (EPM), ethylene-butene rubber (EBM), ethylene-hexene copolymer (EHM), ethylene-octene rubber (EOM), etc.]. ３－８ [Olefin binary copolymers, etc.], ethylene-α-olefin-diene rubber [ethylene-propylene-non-conjugated diene terpolymer (EPDM), ethylene-1-butene-non-conjugated diene copolymer (EBDM), etc., ethylene-α-C ３－８ Examples include olefin-non-conjugated polyene terpolymers.

[0055] These ethylene-α-olefin elastomers can be used individually or in combination of two or more. Of these, ethylene-α-C is preferred due to its excellent heat resistance, cold resistance, and weather resistance. ３－４ Ethylene-α-olefin-non-conjugated diene terpolymer rubber, such as olefin-diene terpolymer rubber, is preferred, and EPDM is particularly preferred. Therefore, the proportion of EPDM may be 50% by mass or more of the total ethylene-α-olefin elastomer, preferably 80% by mass or more, more preferably 90% by mass or more (particularly 95% by mass or more), and may be 100% by mass (EPDM only).

[0056] In the ethylene-α-olefin elastomer, the ethylene content (percentage of ethylene units) may be 30% by mass or more, for example, 30 to 80% by mass, preferably 35 to 70% by mass, more preferably 40 to 60% by mass, and more preferably 45 to 55% by mass. The most preferred value is 48 to 52% by mass, as this can further improve the adhesion between the first rubber layer and the second rubber layer. If the ethylene content is too low, the wear resistance of the transmission belt may decrease, and if it is too high, the processability may decrease.

[0057] In this application, the ethylene content refers to the mass ratio of ethylene units in the total units constituting the ethylene-α-olefin elastomer, and can be measured by conventional methods, but may also be a mass ratio based on ethylene as a monomer.

[0058] Furthermore, in this application, when there are multiple types of ethylene-α-olefin elastomers, 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 elastomer.

[0059] In ethylene-α-olefin elastomers, the ratio (mass ratio) of ethylene to α-olefin is 30 / 70 to 90 / 10, preferably 40 / 60 to 80 / 20, more preferably 45 / 55 to 70 / 30, and more preferably 50 / 50 to 60 / 40.

[0060] In this application, the α-olefin content refers to the mass ratio of α-olefin units in the total units constituting the ethylene-α-olefin elastomer, and can be measured by conventional methods, but may also be a mass ratio based on α-olefin as a monomer.

[0061] The diene content (especially the ethylidene norbornene content) of the ethylene-α-olefin elastomer (particularly ethylene-α-olefin-diene ternary copolymer rubber such as EPDM) is, for example, 0.1 to 15% by mass, preferably 1 to 10% by mass, and more preferably 2 to 7% by mass, more preferably 3 to 6% by mass, and most preferably 4 to 5% by mass, in order to further improve the adhesion between the first rubber layer and the second rubber layer. If the diene content is too high, the heat resistance and abrasion resistance of the transmission belt may decrease, and if it is too low, the processability may decrease.

[0062] In this application, the diene content refers to the mass ratio of diene monomer units in the total units constituting the ethylene-α-olefin elastomer, and can be measured by conventional methods, but may also be a ratio based on monomers.

[0063] The iodine value of the ethylene-α-olefin elastomer containing diene monomer units is, for example, 3 to 40, preferably 5 to 30, and more preferably 10 to 20. If the iodine value is too low, the crosslinking of the rubber composition becomes insufficient, making it prone to wear. Conversely, if the iodine value is too high, the scorch time of the rubber composition becomes shorter, making it difficult to handle and reducing its heat resistance.

[0064] In this application, the iodine value of the ethylene-α-olefin elastomer can be measured by conventional methods, such as infrared spectroscopy.

[0065] The Mooney viscosity [ML(1+4)125°C] of the uncrosslinked ethylene-α-olefin elastomer may be 10 or higher, 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. If the Mooney viscosity is too low, the wear resistance of the transmission belt may decrease, and conversely, if it is too high, the processability may decrease.

[0066] 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 elastomer so as to be in contact with a rotor having grooves on its surface, and measuring the torque required to rotate the rotor.

[0067] Furthermore, in this application, when there are multiple types of ethylene-α-olefin elastomers, Mooney viscosity refers to the average value based on the 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 elastomer.

[0068] If the outer rubber layer does not contain an intermediate layer between the first and second rubber layers, the proportion of ethylene-α-olefin elastomer in the second rubber composition may be 10% by mass or more, for example, 10 to 95% by mass, preferably 20 to 90% by mass, more preferably 30 to 80% by mass, more preferably 40 to 60% by mass, and most preferably 45 to 55% by mass. If the proportion of ethylene-α-olefin elastomer is too low, the flexibility of the transmission belt may decrease.

[0069] When the outer rubber layer includes an intermediate layer between the first and second rubber layers, the proportion of ethylene-α-olefin elastomer may be 10% by mass or more in the second rubber composition, for example, 10 to 95% by mass, preferably 20 to 90% by mass, more preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and most preferably 50 to 60% by mass. If the proportion of ethylene-α-olefin elastomer is too low, the flexibility of the transmission belt may decrease.

[0070] (2A-2) Hydrogenated Nitrile Rubber Hydrogenated nitrile rubber (HNBR) may be partially hydrogenated nitrile rubber or fully hydrogenated nitrile rubber. The hydrogenation rate of the hydrogenated nitrile rubber can be selected from a range of about 50 to 100%, and may be 70 to 100%. The hydrogenated nitrile rubber may be carboxylated.

[0071] In this application, hydrogenated nitrile rubber refers to rubber that maintains the oil resistance, which is an advantage of conventional nitrile rubber, while preventing the deterioration of rubber elasticity due to sulfur recombination reactions during thermal aging. This is achieved by chemically hydrogenating the unsaturated bonds (carbon-carbon double bonds) present in conventional nitrile rubber, thereby making recombination reactions during thermal aging less likely to occur and improving heat resistance.

[0072] The iodine value (unit: mg / 100 mg) of hydrogenated nitrile rubber is, for example, 5 to 60 (for example, 7 to 50), preferably 8 to 40 (for example, 8 to 35), and more preferably 10 to 30.

[0073] In this application, the iodine value is an indicator of the amount of unsaturated bonds, and a higher iodine value indicates a greater amount of unsaturated bonds in the polymer molecular chain. The iodine value is determined by adding an excess of iodine to the sample and allowing it to react completely (reacting iodine with unsaturated bonds), and then quantifying the amount of remaining iodine by redox titration. If the iodine value of hydrogenated nitrile rubber is low, the crosslinking reaction between hydrogenated nitrile rubbers is insufficient, resulting in lower rigidity of the crosslinked rubber, which may reduce deformation resistance during belt operation. On the other hand, if the iodine value of hydrogenated nitrile rubber is high, the amount of unsaturated bonds becomes excessively high, which may lead to thermal and oxidative degradation of the crosslinked rubber, shortening the belt life.

[0074] If the outer rubber layer does not include an intermediate layer between the first and second rubber layers, the proportion of hydrogenated nitrile rubber in the second rubber composition may be 10% by mass or more, for example, 10 to 90% by mass, preferably 30 to 70% by mass, more preferably 40 to 65% by mass, more preferably 50 to 60% by mass, and most preferably 52 to 57% by mass. If the proportion of hydrogenated nitrile rubber is too low, the flexibility of the transmission belt may decrease.

[0075] When the outer rubber layer includes an intermediate layer between the first and second rubber layers, the proportion of hydrogenated nitrile rubber may be 10% by mass or more in the second rubber composition, for example, 10 to 90% by mass, preferably 30 to 80% by mass, more preferably 40 to 75% by mass, more preferably 50 to 70% by mass, and most preferably 60 to 65% by mass. If the proportion of hydrogenated nitrile rubber is too low, the flexibility of the transmission belt may decrease.

[0076] (2B) The second rubber composition, by containing the second unsaturated carboxylic acid metal salt, can improve the adhesion between the first rubber layer and the second rubber layer. If the first rubber composition contains the first unsaturated carboxylic acid metal salt, the second unsaturated carboxylic acid metal salt is not an essential component in the second rubber composition, and from the standpoint of economy, etc., the second rubber composition may not contain the second unsaturated carboxylic acid metal salt.

[0077] The second unsaturated carboxylate metal salt can be selected from the unsaturated carboxylate metal salts exemplified as the first unsaturated carboxylate metal salt, including in preferred embodiments.

[0078] If the second rubber composition contains hydrogenated nitrile rubber, the second unsaturated carboxylic acid metal salt may be used as a raw material in the form of a composite polymer of hydrogenated nitrile rubber and an unsaturated carboxylic acid metal salt. For example, a commercially available product in which zinc methacrylate is highly finely dispersed in hydrogenated nitrile rubber may be used.

[0079] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of the second unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 1 part by mass or more (preferably 3 parts by mass or more, more preferably 12 parts by mass or more) per 100 parts by mass of ethylene-α-olefin elastomer, and can be selected from a range of, for example, 1 to 50 parts by mass (particularly 3 to 40 parts by mass), preferably 5 to 38 parts by mass (particularly 13 to 35 parts by mass), more preferably 10 to 33 parts by mass (particularly 15 to 33 parts by mass), more preferably 15 to 30 parts by mass, and most preferably 20 to 27 parts by mass. If the proportion of the second unsaturated carboxylic acid metal salt is too low, the adhesion between the first rubber layer and the second rubber layer and the durability of the belt may decrease. From the viewpoint of improving the durability of the belt, the proportion may preferably be 10 to 40 parts by mass, and more preferably 15 to 35 parts by mass, per 100 parts by mass of ethylene-α-olefin elastomer.

[0080] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the second unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 1 part by mass or more (preferably 3 parts by mass or more, more preferably 12 parts by mass or more) per 100 parts by mass of hydrogenated nitrile rubber, and can be selected from a range of, for example, 1 to 50 parts by mass (particularly 3 to 40 parts by mass), for example 5 to 38 parts by mass (particularly 13 to 35 parts by mass), preferably 8 to 35 parts by mass, more preferably 10 to 33 parts by mass (particularly 15 to 33 parts by mass), more preferably 15 to 30 parts by mass, and most preferably 20 to 27 parts by mass. If the proportion of the second unsaturated carboxylic acid metal salt is too small, the adhesion between the first rubber layer and the second rubber layer and the durability of the belt may decrease. From the viewpoint of improving the durability of the belt, the proportion may preferably be 10 to 40 parts by mass, more preferably 15 to 35 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0081] If the first rubber composition contains a first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) and the second rubber composition contains an ethylene-α-olefin elastomer, the proportion of the second unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 10 parts by mass or less per 100 parts by mass of ethylene-α-olefin elastomer, for example, 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and most preferably 0 parts by mass.

[0082] If the first rubber composition contains a first unsaturated carboxylic acid metal salt (particularly zinc methacrylate) and the second rubber composition contains hydrogenated nitrile rubber, the proportion of the second unsaturated carboxylic acid metal salt (particularly zinc methacrylate) may be 10 parts by mass or less per 100 parts by mass of hydrogenated nitrile rubber, for example, 5 parts by mass or less, preferably 3 parts by mass or less, more preferably 1 part by mass or less, more preferably 0.5 parts by mass or less, and most preferably 0 parts by mass.

[0083] (2C) Second Crosslinking Agent The second rubber composition preferably further contains a second crosslinking agent. When the second rubber composition contains an ethylene-α-olefin elastomer, the second crosslinking agent may be an organic peroxide, a sulfur-based crosslinking agent, or the like. When the second rubber composition contains hydrogenated nitrile rubber, the second crosslinking agent may be an organic peroxide, a metal oxide, or the like. These crosslinking agents can be used individually or in combination of two or more.

[0084] Examples of organic peroxides include those exemplified as the organic peroxides of the first crosslinking agent.

[0085] 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.

[0086] Examples of metal oxides include magnesium oxide, zinc oxide, and lead oxide. These metal oxides can be used individually or in combination of two or more.

[0087] When the second rubber composition contains an ethylene-α-olefin elastomer, among the crosslinking agents, organic peroxides are preferred, and dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene are particularly preferred.

[0088] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of the second crosslinking agent (especially organic peroxide) may be 0.5 parts by mass or more per 100 parts by mass of ethylene-α-olefin elastomer, for example, 0.5 to 15 parts by mass, preferably 1 to 10 parts by mass, more preferably 1.5 to 8 parts by mass, more preferably 2 to 7 parts by mass, and most preferably 3 to 6 parts by mass. If the proportion of the second crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0089] When the second rubber composition contains hydrogenated nitrile rubber, among the crosslinking agents, organic peroxides and / or metal oxides are preferred, and a combination of organic peroxides (especially dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene) and metal oxides (especially zinc oxide) is particularly preferred. The crosslinking agents can be used alone or in combination of two or more.

[0090] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of organic peroxide may be 0.3 parts by mass or more per 100 parts by mass of hydrogenated nitrile rubber, for example, 0.3 to 10 parts by mass, preferably 0.5 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass. If the proportion of organic peroxide is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0091] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of metal oxide may be 0.3 parts by mass or more per 100 parts by mass of hydrogenated nitrile rubber, for example, 0.3 to 10 parts by mass, preferably 0.5 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass. If the proportion of metal oxide is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0092] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the second crosslinking agent may be 0.5 parts by mass or more per 100 parts by mass of hydrogenated nitrile rubber, for example, 0.5 to 15 parts by mass, preferably 1 to 10 parts by mass, more preferably 1.5 to 8 parts by mass, more preferably 2 to 7 parts by mass, and most preferably 3 to 5 parts by mass. If the proportion of the second crosslinking agent is too low, the rubber hardness may decrease, and if it is too high, the flexibility of the belt may decrease.

[0093] (2D) Second Co-crosslinking Agent If the second rubber composition contains hydrogenated nitrile rubber, the second rubber composition may further contain a second co-crosslinking agent (crosslinking aid or co-vulcanizing agent). Examples of the second co-crosslinking agent include 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)acrylates such as butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, etc.] Examples include bismaleimides [for example, alkylene bismaleimides such as N,N'-1,2-ethylenedimaleimide, N,N'-hexamethylenebismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane; N,N'-m-phenylenedimaleimide (MPBM), 4-methyl-1,3-phenyledimaleimide, 4,4'-diphenylmethanedimaleimide, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 4,4'-diphenyletherdimaleimide, 4,4'-diphenylsulfonedimaleimide, and arene bismaleimides such as 1,3-bis(3-maleimidophenoxy)benzene].

[0094] These cocrosslinking agents can be used individually or in combination of two or more. Of these, bismaleimides such as MPBM are preferred because they can improve abrasion resistance and lateral pressure resistance.

[0095] The proportion of the second co-crosslinking agent may be 0.3 parts by mass or more per 100 parts by mass of hydrogenated nitrile rubber, for example, 0.3 to 10 parts by mass, preferably 0.5 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass. If the proportion of the 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.

[0096] (2E) The second rubber composition may further contain a second filler. The second filler includes reinforcing inorganic fillers, non-reinforcing fillers, and the like.

[0097] Examples of reinforcing inorganic fillers include carbon black and silica. The reinforcing inorganic filler may also be in particulate (powder) form.

[0098] 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, the classification is based on the primary particle size of the carbon black contained in the rubber composition (particularly in the crosslinked rubber composition). That is, in this application, the primary particle size of each primary particle of carbon black contained in the rubber composition is measured, 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).

[0099] The average primary particle size of hard carbon black may be, 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 may be, for example, 40 to 100 nm, preferably 50 to 80 nm, more preferably 60 to 70 nm, and more preferably 65 to 68 nm.

[0100] In this application, the average particle diameter of particulate fillers such as carbon black can be measured using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and the arithmetic mean particle diameter of an appropriate number of samples (for example, any 50 samples) can be calculated by image analysis.

[0101] In this invention, the 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.

[0102] The amount of iodine adsorbed by carbon black is, for example, 5 to 200 g / kg, preferably 15 to 150 g / kg, and more preferably 20 to 140 g / kg.

[0103] 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.

[0104] The BET specific surface area of ​​carbon black using the BET method is, for example, 10 to 400 m². ２ / g, preferably 15 to 200m ２ / g, more preferably 20 to 150m ２ It is / g.

[0105] In this application, the BET specific surface area of ​​a filler such as carbon black refers to the specific surface area measured using nitrogen gas by the BET method.

[0106] Silica includes dry silica, wet silica, and surface-treated silica. Furthermore, silica can be classified by its manufacturing method into, for example, dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated 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 a high number of surface silanol groups is particularly preferred due to its strong chemical bonding ability with rubber components.

[0107] The average particle diameter (average primary particle diameter) of 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.

[0108] Furthermore, the specific surface area for nitrogen adsorption of silica by the BET method is, for example, 50 to 400 m². ２ / g, preferably 100 to 300m ２ / g, more preferably 150-200m ２ It is / g.

[0109] Examples of non-reinforcing fillers include metal oxides other than metal oxides as crosslinking agents (magnesium oxide, zinc oxide, lead oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (barium sulfate, etc.), silicates (natural or synthetic silicates in which some of the silicon is replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, and aluminum magnesium silicate; minerals mainly composed of silicates, such as clay containing aluminum silicate, and silicate minerals such as talc and mica containing magnesium silicate), lithopone, and silica sand. These non-reinforcing fillers can be used alone or in combination of two or more. Of these, metal oxides are preferred, and zinc oxide is particularly preferred.

[0110] These fillers can be used alone or in combination of two or more. When the second rubber composition contains ethylene-α-olefin elastomer, the second filler preferably contains carbon black, more preferably contains carbon black and silica, and a combination of carbon black, silica and a metal oxide is particularly preferred. When the second rubber composition contains hydrogenated nitrile rubber, the second filler preferably contains carbon black and / or silica, more preferably contains carbon black and silica, and a combination of carbon black and silica is particularly preferred.

[0111] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of carbon black (especially soft carbon black) is, for example, 10 to 150 parts by mass, preferably 20 to 100 parts by mass, more preferably 30 to 90 parts by mass, more preferably 40 to 80 parts by mass, and most preferably 50 to 70 parts by mass, per 100 parts by mass of ethylene-α-olefin elastomer.

[0112] When the second rubber composition contains ethylene-α-olefin elastomer, the amount of silica is, for example, 0.5 to 50 parts by mass, preferably 1 to 30 parts by mass, more preferably 1.5 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 ethylene-α-olefin elastomer.

[0113] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of metal oxide is, for example, 0.5 to 50 parts by mass, preferably 1 to 30 parts by mass, more preferably 1.5 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 ethylene-α-olefin elastomer.

[0114] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of the second filler is, 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 90 parts by mass, and most preferably 60 to 80 parts by mass, per 100 parts by mass of ethylene-α-olefin elastomer.

[0115] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of carbon black (especially soft carbon black) is, for example, 0.3 to 50 parts by mass, preferably 0.5 to 30 parts by mass, more preferably 1 to 10 parts by mass, more preferably 1.2 to 5 parts by mass, and most preferably 1.5 to 3 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0116] When the second rubber composition contains hydrogenated nitrile rubber, the amount of silica is, for example, 1 to 150 parts by mass, preferably 5 to 100 parts by mass, more preferably 10 to 80 parts by mass, more preferably 20 to 70 parts by mass, and most preferably 30 to 50 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0117] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the second filler is, for example, 5 to 200 parts by mass, preferably 10 to 150 parts by mass, more preferably 20 to 100 parts by mass, more preferably 30 to 80 parts by mass, and most preferably 35 to 60 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0118] (2F) Second softener The second rubber composition may further contain a second softener (processing agent or processing aid) as it can improve the flexibility of the belt. The second softener includes mineral oil-based softeners, vegetable oil-based softeners, synthetic softeners, and the like.

[0119] 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.).

[0120] 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).

[0121] 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.].

[0122] These softeners can be used individually or in combination of two or more. When the second rubber composition contains ethylene-α-olefin elastomer, petroleum-based softeners such as paraffinic oil and vegetable oil-based softeners such as stearic acid are preferred, with petroleum-based softeners being particularly preferred. When the second rubber composition contains hydrogenated nitrile rubber, petroleum-based softeners such as paraffinic oil, vegetable oil-based softeners such as stearic acid, and synthetic plasticizers such as ether ester plasticizers are preferred, with vegetable oil-based softeners and synthetic plasticizers being particularly preferred.

[0123] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of the second 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 ethylene-α-olefin elastomer.

[0124] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the vegetable oil-based softener is, for example, 0.1 to 10 parts by mass, preferably 0.2 to 5 parts by mass, more preferably 0.3 to 3 parts by mass, more preferably 0.5 to 2 parts by mass, and most preferably 0.8 to 1.5 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0125] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the synthetic plasticizer is, for example, 1 to 100 parts by mass, preferably 2 to 50 parts by mass, more preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, and most preferably 8 to 15 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0126] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the second softener is, for example, 1 to 100 parts by mass, preferably 3 to 50 parts by mass, more preferably 5 to 40 parts by mass, more preferably 8 to 30 parts by mass, and most preferably 10 to 20 parts by mass, per 100 parts by mass of hydrogenated nitrile rubber.

[0127] (2G) Second Anti-aging Agent The second rubber composition may further contain a second anti-aging agent, as this can improve heat aging resistance. Examples of the second anti-aging agent include benzimidazole-based anti-aging agents, diarylamine-based anti-aging agents, and p-phenylenediamine-based anti-aging agents.

[0128] Examples of benzimidazole-based antioxidants include 2-mercaptobenzimidazole (MBI), 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, 1,3-dihydro-1-phenyl-2H-benzimidazole-2-thion, and benzimidazole compounds such as mixtures of 2-mercaptobenzimidazole and phenol condensates. Benzimidazole-based antioxidants may also be in the form of salts with metals such as zinc.

[0129] Examples of diarylamine-based antioxidants include bis(C) such as di(4-octylphenyl)amine (ODPA). ４－１８ Alkyl C ６－１０ Examples include aryl amines; bis(aralkyl-aryl)amines such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (DCD); and styrene-diphenylamine (SDPA).

[0130] Examples of p-phenylenediamine-based antioxidants include N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and N-(1,3-methylheptyl)-N'-phenyl-p-phenylenediamine (8PPD), which are N-linear or branched C-cells. １－１０ Alkyl-N'-C ６－１０ Aryl-p-phenylenediamines; N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine (DNPD), and other N,N'-diC ６－１０ Examples include aryl-p-phenylenediamines.

[0131] These anti-aging agents can be used individually or in combination of two or more. When the second rubber composition contains an ethylene-α-olefin elastomer, among these, benzimidazole-based anti-aging agents, particularly benzimidazole compounds having a sulfur atom, are preferred, and benzimidazole compounds having a thiol group such as MBI (mercaptobenzimidazole compounds) are particularly preferred. When the second rubber composition contains hydrogenated nitrile rubber, diarylamine-based anti-aging agents, particularly bis(C) such as ODPA, are preferred. ４－１８ Alkyl C ６－１０ Arylamines are preferred.

[0132] When the second rubber composition contains ethylene-α-olefin elastomer, the proportion of the second 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 ethylene-α-olefin elastomer. When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the second 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 hydrogenated nitrile rubber. If the proportion of the second antioxidant is too low, the crack resistance of the belt may decrease, and if it is too high, the mechanical properties of the belt may decrease.

[0133] (2H) Second Other Component If the second rubber composition contains ethylene-α-olefin elastomer, the second rubber composition may further contain, as a second other component, rubber other than ethylene-α-olefin elastomer, and conventional additives used in rubber compositions for power transmission belts. Examples of conventional additives include crosslinking aids (co-crosslinking agents, crosslinking accelerators, crosslinking retarders, etc.), short fibers, antioxidants, flex crack inhibitors, ozone degradation inhibitors, colorants, adhesion improvers, tackifiers, coupling agents (silane coupling agents, etc.), stabilizers (ultraviolet absorbers, heat stabilizers, etc.), flame retardants, and antistatic agents. These other components can be used individually or in combination of two or more.

[0134] When the second rubber composition contains ethylene-α-olefin elastomer, the total proportion of the second other component is 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 ethylene-α-olefin elastomer.

[0135] If the second rubber composition contains hydrogenated nitrile rubber, the second rubber composition may further contain, as a second other component, rubber other than hydrogenated nitrile rubber, and conventional additives used in rubber compositions for power transmission belts. Examples of conventional additives include crosslinking accelerators, crosslinking retarders, short fibers, antioxidants, flex crack inhibitors, ozone degradation inhibitors, colorants, adhesion improvers, tackifiers, coupling agents (such as silane coupling agents), stabilizers (such as UV absorbers and heat stabilizers), flame retardants, and antistatic agents. These other components can be used individually or in combination of two or more.

[0136] When the second rubber composition contains hydrogenated nitrile rubber, the total proportion of the second other component is 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 hydrogenated nitrile rubber.

[0137] (Intermediate Layer) The outer rubber layer of the present invention may include a first rubber layer and a second rubber layer, but may also include an intermediate layer. The intermediate layer is interposed between the first rubber layer and the second rubber layer and can firmly bond the first rubber layer and the second rubber layer by including a crosslinked binder component containing an unsaturated carboxylic acid metal salt. Preferred embodiments for including the crosslinked binder component in the intermediate layer include an embodiment in which the intermediate layer is formed by a crosslinked binder component consisting of an unsaturated carboxylic acid metal salt (first embodiment), an embodiment in which the intermediate layer is formed by a crosslinked binder component which is a third rubber composition containing a rubber component and an unsaturated carboxylic acid metal salt (second embodiment), and an embodiment in which the intermediate layer is formed by a cloth containing the crosslinked binder component which is the third rubber composition (third embodiment).

[0138] (First Embodiment) In the first embodiment, the binder component consists of an unsaturated carboxylate metal salt, and the intermediate layer consists of a crosslinked product of the binder component. The unsaturated carboxylate metal salt, which is the binder component, exists in the transmission belt primarily in the form of a self-crosslinked product of the unsaturated carboxylate metal salt, and it can be presumed that at the boundaries between the first rubber layer and the second rubber layer, it is partially crosslinked with the silicone rubber and the ethylene-α-olefin elastomer or hydrogenated nitrile rubber at each boundary.

[0139] The metal salt of an unsaturated carboxylate may be a compound in which an unsaturated carboxylic acid having one or more carboxyl groups is ionically bonded to a metal.

[0140] Examples of unsaturated carboxylic acids in metal salts of unsaturated carboxylic acids 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.

[0141] Examples of metals used in 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.).

[0142] These unsaturated carboxylate metal salts can be used individually or in combination of two or more.

[0143] As unsaturated carboxylate metal salts, zinc (meth)acrylate and magnesium (meth)acrylate are preferred, zinc (meth)acrylate is more preferred, and zinc methacrylate is most preferred.

[0144] In the intermediate layer of the first embodiment, the basis weight of the binder component (unsaturated carboxylic acid metal salt) is 10 g / m². ２ (especially 50 g / m) ２ The above may also be the case, for example, 10 to 300 g / m ２ Preferably 30 to 250 g / m² ２ More preferably 50 to 200 g / m² ２ More preferably 70 to 150 g / m² ２ Most preferably 90 to 120 g / m² ２ When high bonding strength is required, the basis weight is 80 g / m². ２ It may be greater than or equal to 80 to 300 g / m², preferably 80 to 300 g / m². ２ More preferably 100 to 270 g / m² ２ More preferably 150 to 250 g / m² ２ Most preferably 180 to 220 g / m² ２ Therefore, if the basis weight of the binder component is too low, there is a risk that the adhesion between the first rubber layer and the second rubber layer will decrease.

[0145] (Second Embodiment) In the second embodiment, the binder component is a third rubber composition comprising a rubber component and an unsaturated carboxylic acid metal salt.

[0146] (3A) Rubber components Examples of rubber components include 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.], ethylene-α-olefin elastomers (ethylene-propylene copolymer (EPM), ethylene-propylene-diene terpolymer (EPDM), etc.), chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, fluororubber, etc. These rubber components can be used individually or in combination of two or more.

[0147] When the second rubber composition contains ethylene-α-olefin elastomer, the rubber component of the third rubber composition is preferably silicone rubber and / or ethylene-α-olefin elastomer, more preferably ethylene-α-olefin elastomer, and most preferably ethylene-α-olefin elastomer alone, from the viewpoint of adhesion to the first and second rubber layers.

[0148] When the second rubber composition contains hydrogenated nitrile rubber, the rubber component of the third rubber composition preferably contains silicone rubber and / or hydrogenated nitrile rubber, more preferably hydrogenated nitrile rubber, and most preferably hydrogenated nitrile rubber alone, from the viewpoint of adhesion to the first and second rubber layers.

[0149] The silicone rubber can be selected from the silicone rubbers exemplified as the first rubber layer, including in preferred embodiments. Furthermore, the ethylene-α-olefin elastomer can be selected from the ethylene-α-olefin elastomers exemplified as the second rubber layer, including in preferred embodiments. Furthermore, the hydrogenated nitrile rubber can be selected from the hydrogenated nitrile rubbers exemplified as the second rubber layer, including in preferred embodiments.

[0150] When the rubber component includes silicone rubber and / or ethylene-α-olefin elastomer, the total amount of silicone rubber and ethylene-α-olefin elastomer may be 50% by mass or more of the rubber component, preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass.

[0151] When the rubber component includes silicone rubber and / or hydrogenated nitrile rubber, the total amount of silicone rubber and hydrogenated nitrile rubber may be 50% by mass or more of the rubber component, preferably 80% by mass or more, more preferably 90% by mass or more, more preferably 95% by mass or more, and most preferably 100% by mass.

[0152] If the second rubber composition contains ethylene-α-olefin elastomer, the proportion of the rubber component may be 10% by mass or more in the third rubber composition, for example, 10 to 95% by mass, preferably 20 to 90% by mass, more preferably 30 to 80% by mass, more preferably 40 to 60% by mass, and most preferably 45 to 55% by mass. If the proportion of the rubber component is too low, the flexibility of the transmission belt may decrease.

[0153] If the second rubber composition contains hydrogenated nitrile rubber, the proportion of the rubber component may be 10% by mass or more in the third rubber composition, for example, 10 to 95% by mass, preferably 20 to 90% by mass, more preferably 30 to 80% by mass, more preferably 50 to 70% by mass, and most preferably 53 to 60% by mass. If the proportion of the rubber component is too low, the flexibility of the transmission belt may decrease.

[0154] (3B) Metal unsaturated carboxylate salt The metal unsaturated carboxylate salt can be selected from the metal unsaturated carboxylate salts exemplified in the first embodiment, including preferred embodiments.

[0155] When the second rubber composition contains an ethylene-α-olefin elastomer, the proportion of the unsaturated carboxylic acid metal salt (particularly zinc methacrylate) should be 1 part by mass or more (preferably 3 parts by mass or more, more preferably 12 parts by mass or more, and more preferably 15 parts by mass or more) per 100 parts by mass of the rubber component (particularly ethylene-α-olefin elastomer) of the third rubber composition. For example, it can be selected from a range of about 1 to 50 parts by mass (particularly 3 to 40 parts by mass), preferably 5 to 35 parts by mass, more preferably 10 to 33 parts by mass, more preferably 15 to 30 parts by mass, and most preferably 20 to 27 parts by mass. If the proportion of the unsaturated carboxylic acid metal salt is too low, the adhesion between the first rubber layer and the second rubber layer may decrease.

[0156] When the second rubber composition contains hydrogenated nitrile rubber, the proportion of the unsaturated carboxylic acid metal salt (particularly zinc methacrylate) should be 1 part by mass or more (preferably 3 parts by mass or more, more preferably 8 parts by mass or more, more preferably 10 parts by mass or more, and most preferably 12 parts by mass or more) per 100 parts by mass of the rubber component (particularly hydrogenated nitrile rubber) of the third rubber composition. For example, it can be selected from a range of about 1 to 50 parts by mass (particularly 3 to 40 parts by mass), preferably 5 to 35 parts by mass, more preferably 8 to 30 parts by mass, more preferably 10 to 25 parts by mass, and most preferably 12 to 20 parts by mass. If the proportion of the unsaturated carboxylic acid metal salt is too low, the adhesion between the first rubber layer and the second rubber layer may decrease.

[0157] (3C) Third Crosslinking Agent The third rubber composition may further contain a third crosslinking agent. Examples of the third crosslinking agent include organic peroxides, sulfur-based crosslinking agents, and metal oxides.

[0158] Examples of organic peroxides include the organic peroxides exemplified as the first crosslinking agent. These organic peroxides can be used alone or in combination of two or more types.

[0159] When the second rubber composition contains an ethylene-α-olefin elastomer, examples of sulfur-based crosslinking agents include the sulfur-based crosslinking agents exemplified as the second crosslinking agent. The sulfur-based crosslinking agents can be used alone or in combination of two or more types.

[0160] When the second rubber composition contains an ethylene-α-olefin elastomer, examples of metal oxides include magnesium oxide, zinc oxide, and lead oxide. These metal oxides can be used individually or in combination of two or more.

[0161] When the second rubber composition contains an ethylene-α-olefin elastomer, among the crosslinking agents, organic peroxides are preferred, and dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene are particularly preferred.

[0162] When the second rubber composition contains an ethylene-α-olefin elastomer, the range of the ratio of the third crosslinking agent (including organic peroxides) to the rubber component can be selected from the range of the ratio of the second crosslinking agent to the ethylene-α-olefin elastomer, including a preferred range.

[0163] When the second rubber composition contains hydrogenated nitrile rubber, examples of metal oxides include those exemplified as the first crosslinking agent. These metal oxides can be used alone or in combination of two or more.

[0164] When the second rubber composition contains hydrogenated nitrile rubber, 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 alone or in combination of two or more.

[0165] When the second rubber composition contains hydrogenated nitrile rubber, the crosslinking agent can be used alone or in combination of two or more. Among the crosslinking agents, organic peroxides and / or metal oxides are preferred, and a combination of organic peroxides (especially dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene) and metal oxides (especially zinc oxide) is particularly preferred.

[0166] When the second rubber composition contains hydrogenated nitrile rubber, the range of the ratio of the third crosslinking agent (including organic peroxides and metal oxides) to the rubber component can be selected from the range of the ratio of the second crosslinking agent to the hydrogenated nitrile rubber, including a preferred range.

[0167] (3D) Third Filler The third rubber composition may further contain a third filler. The third filler can be selected from the fillers exemplified as the second filler, including preferred embodiments. If the second rubber composition contains an ethylene-α-olefin elastomer, the range of the ratio of the third filler (including carbon black, silica, and metal oxides) to the rubber component can also be selected from the range of the ratio of the second filler to the ethylene-α-olefin elastomer, including preferred embodiments. If the second rubber composition contains hydrogenated nitrile rubber, the range of the ratio of the third filler (including carbon black and silica) to the rubber component can also be selected from the range of the ratio of the second filler to the hydrogenated nitrile rubber, including preferred embodiments.

[0168] (3E) Third softener The third rubber composition may further contain a third softener. The third softener can be selected from the softeners exemplified as the second softener, including preferred embodiments. If the second rubber composition contains an ethylene-α-olefin elastomer, the range of the ratio of the third softener to the rubber component can also be selected from the range of the ratio of the second softener to the ethylene-α-olefin elastomer, including preferred embodiments. If the second rubber composition contains hydrogenated nitrile rubber, the range of the ratio of the third softener to the rubber component can also be selected from the range of the ratio of the second softener to the hydrogenated nitrile rubber, including preferred embodiments.

[0169] (3F) Third Anti-aging Agent The third rubber composition may further contain a third anti-aging agent. The third anti-aging agent can be selected from the anti-aging agents exemplified as the second anti-aging agent, including preferred embodiments. If the second rubber composition contains an ethylene-α-olefin elastomer, the range of the ratio of the third anti-aging agent to the rubber component can also be selected from the range of the ratio of the second anti-aging agent to the ethylene-α-olefin elastomer, including preferred embodiments. If the second rubber composition contains hydrogenated nitrile rubber, the range of the ratio of the third anti-aging agent to the rubber component can also be selected from the range of the ratio of the second anti-aging agent to the hydrogenated nitrile rubber, including preferred embodiments.

[0170] (3G) Third Other Component The third rubber composition may further contain, as a third other component, conventional additives used in rubber compositions for power transmission belts. Examples of conventional additives include those exemplified as the second other component. The total proportion of the third other component is 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 rubber component.

[0171] (Third Embodiment) In the third embodiment, by interposing an intermediate layer formed of a cloth containing a crosslinked binder component of the third rubber composition (hereinafter referred to as "intermediate cloth") between the first rubber layer and the second rubber layer, the first rubber layer and the second rubber layer can be firmly bonded together. In addition, in the toothed belt, it is possible to suppress the flow of the first rubber layer into the teeth from the back side through the space between the core wires during the manufacturing process. As a result, it is possible to suppress the occurrence of appearance defects and a decrease in tooth shear strength in the toothed belt. The intermediate cloth only needs to contain the third rubber composition, and may usually be a cloth to which the third rubber composition is attached (a cloth to which the third rubber composition is attached to the surface of the fibers constituting the cloth).

[0172] Examples of fabrics (cloths or fabric materials) include woven fabrics, knitted fabrics, and nonwoven fabrics. The fabric is conventionally often woven (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. It may be plain weave, twill weave (or diagonal weave), satin weave, or a combination of these structures. Preferred woven fabrics have a twill weave and / or satin weave structure (especially a twill weave structure). The twill weave structure may be a random twill weave structure.

[0173] The fibers forming the fabric may be organic or inorganic. Examples of organic fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers (nylon fibers), aramid fibers, etc.], polyester fibers [polyalkylene arylate fibers (for example, polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.)]. ２－４ Alkilen C ８－１４ Synthetic fibers include: arylate fibers; polyarylate fibers, fully aromatic polyester fibers such as liquid crystal polyester fibers, vinylon fibers, polyvinyl alcohol fibers, poly(p-phenylenebenzobisoxazole) (PBO) fibers, polyphenylene ether fibers, polyether ether ketone fibers, polyether sulfone fibers, polyurethane fibers, etc.; natural fibers such as cotton, linen, and wool; regenerated cellulose fibers such as rayon; and cellulose ester fibers. Inorganic fibers include, for example, carbon fibers and glass fibers. These fibers can be used individually or in combination of two or more types.

[0174] Of these fibers, organic fibers are commonly used, with cellulose fibers such as cotton and rayon, polyester fibers (such as PET fibers), polyamide fibers (such as polyamide 6 fibers, polyamide 66 fibers, and other aliphatic polyamide fibers, as well as aramid fibers), and PBO fibers being preferred, with aliphatic polyamide fibers being more preferred, and polyamide 66 fibers being even more preferred. Furthermore, composite yarns of these fibers and elastic yarns with elasticity [for example, elastic polyurethane-based elastic yarns such as spandex made of polyurethane, and processed yarns that have undergone stretch processing (for example, woolly processing, crimping processing, etc.)] are also preferred.

[0175] If the fabric is woven, 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 intermediate fabric in the belt circumferential direction, the weft threads containing elastic yarn extend in the belt circumferential direction, and the warp threads extend in the belt width direction.

[0176] The average diameter of the fibers is, for example, 1 to 100 μm (for example, 3 to 50 μm), preferably 5 to 30 μm, and more preferably 7 to 25 μm.

[0177] Regarding the average diameter (thickness) of the yarn (twisted yarn), if the fabric is woven, the average diameter of the warp threads can be selected from a range of about 10 to 1000 dtex, for example, 30 to 700 dtex, preferably 50 to 500 dtex, more preferably 100 to 400 dtex, more preferably 150 to 350 dtex, and most preferably 200 to 300 dtex. If the average diameter of the warp threads is too small, the unevenness of the woven fabric surface may decrease, reducing the anchoring effect, and if it is too large, the amount of rubber component that penetrates between the fibers may decrease, reducing the bonding strength.

[0178] The average diameter of the weft yarn can be selected from a range of approximately 10 to 1000 dtex, for example, 20 to 500 dtex, preferably 30 to 300 dtex, more preferably 35 to 200 dtex, more preferably 40 to 100 dtex, and most preferably 40 to 70 dtex. If the average diameter of the weft yarn is too small, the surface irregularities of the woven fabric may become smaller, reducing the anchoring effect, and if it is too large, the amount of rubber component that penetrates between the fibers may decrease, reducing the bonding strength.

[0179] The average diameter of the warp threads may be 0.3 times or more the average diameter of the weft threads, for example, 0.3 to 30 times, preferably 0.5 to 20 times, more preferably 1 to 15 times, more preferably 3 to 10 times, and most preferably 4 to 7 times.

[0180] The warp density (threads / 3cm) can be selected from a range of approximately 30 to 500, for example, 40 to 300, preferably 50 to 200, more preferably 60 to 150, more preferably 70 to 110, and most preferably 80 to 100. If the warp density is too low, there is a risk that the silicone rubber will penetrate the intermediate fabric, and if it is too high, there is a risk that the amount of rubber component that penetrates between the fibers will decrease, reducing the bonding strength.

[0181] The density of the warp threads may be five times or less the density of the weft threads, for example, 0.3 to 3 times, preferably 0.4 to 2 times, more preferably 0.5 to 1 time, more preferably 0.6 to 0.9 times, and most preferably 0.7 to 0.8 times.

[0182] (Characteristics of the outer rubber layer) In the power transmission belt of the present invention, although the first rubber layer and the second rubber layer constituting the outer rubber layer are a combination of silicone rubber with low adhesion and ethylene-α-olefin elastomer or hydrogenated nitrile rubber, the outer rubber layer can be firmly bonded because it contains an unsaturated carboxylic acid metal salt.

[0183] When the outer rubber layer does not contain an intermediate layer and the second rubber composition contains an ethylene-α-olefin elastomer, the peel strength between the first rubber layer and the second rubber layer may be 10 N / 25 mm or more, preferably 50 N / 25 mm or more, and more preferably 100 N / 25 mm or more.

[0184] When the outer rubber layer includes an intermediate layer and the second rubber composition includes an ethylene-α-olefin elastomer, the peel strength between the first rubber layer and the intermediate layer may be 10 N / 25 mm or more, preferably 50 N / 25 mm or more, and more preferably 100 N / 25 mm or more.

[0185] When the outer rubber layer does not include an intermediate layer and the second rubber composition includes hydrogenated nitrile rubber, the peel strength between the first rubber layer and the second rubber layer may be 30 N / 25 mm or more, preferably 50 N / 25 mm or more, and more preferably 100 N / 25 mm or more.

[0186] When the outer rubber layer includes an intermediate layer and the second rubber composition includes hydrogenated nitrile rubber, the peel strength between the first rubber layer and the intermediate layer may be 30 N / 25 mm or more, preferably 50 N / 25 mm or more, and more preferably 100 N / 25 mm or more.

[0187] In this application, the peel strength between the first rubber layer and the second rubber layer, and between the first rubber layer and the intermediate layer, can be measured by the method described in the examples below.

[0188] In the present invention, if the outer rubber layer of the power transmission belt does not include an intermediate layer, it is sufficient that at least one of the first rubber composition and the second rubber composition contains an unsaturated carboxylate metal salt, and both rubber compositions may contain an unsaturated carboxylate metal salt. However, from the viewpoint of economy and other factors, it is preferable that one of the first and second rubber compositions contains an unsaturated carboxylate metal salt. Furthermore, it is more preferable that the second rubber composition contains an unsaturated carboxylate metal salt from the viewpoint of excellent processability and improved belt productivity, and it is more preferable that the first rubber composition contains an unsaturated carboxylate metal salt from the viewpoint of improved adhesion with a small amount of unsaturated carboxylate metal salt. In the embodiment in which the outer rubber layer includes an intermediate layer, since the intermediate layer contains an unsaturated carboxylate metal salt, the unsaturated carboxylate metal salt is an optional component in the first and second rubber compositions.

[0189] (Toothed Belt) The transmission belt of the present invention is not particularly limited as long as it has the outer rubber layer described above, but among the transmission belts, a toothed belt is preferred because a thick outer layer is required on the conveying surface, and the effects of the present invention are greatly enhanced.

[0190] Below, an example of a power transmission belt of the present invention will be described in detail, with reference to the attached drawings as necessary. In the following description, elements (or components) that are the same or have common functions may be denoted by the same reference numeral.

[0191] Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt of the present invention, in which the outer rubber layer does not include an intermediate layer. Figure 2 is a schematic cross-sectional view of the toothed belt of Figure 1. Figure 3 is a schematic partial cross-sectional perspective view showing another example of a toothed belt of the present invention, in which the outer rubber layer includes an intermediate layer. Figure 4 is a schematic cross-sectional view of the toothed belt of Figure 3.

[0192] The toothed belt 1 in this example is an endless interlocking transmission belt, comprising a back portion 1c in which a core wire 3 extending in the belt circumferential direction (longitudinal direction) is embedded, and a plurality of teeth 1a provided at predetermined intervals on the inner circumferential surface of the back portion 1c and extending in the belt width direction, with the belt surface (inner circumferential surface) on the tooth portion side being made of tooth fabric 5. The back portion 1c has a back rubber layer (outer rubber layer) 2 disposed on the outer circumferential side of the belt of the core wire 3. In the example of Figure 1 in which the outer rubber layer does not include an intermediate layer, this back rubber layer 2 consists of a first rubber layer 2a that forms the belt outer circumferential surface (conveying surface) and a second rubber layer 2b located on the inner circumferential side of the first rubber layer 2a. On the other hand, in the example shown in Figure 3, where the outer rubber layer includes an intermediate layer, the back rubber layer 2 consists of a first rubber layer 2a that forms the outer surface (conveying surface) of the belt, an intermediate layer 2c located on the inner side of the first rubber layer 2a, and a second rubber layer 2b located on the inner side of the intermediate layer 2c. Furthermore, the toothed belt 1 has a tooth rubber layer (rubber layer that forms the teeth) 4 between the tooth fabric 5 and the core wire 3 on the inner side of the belt of the core wire 3.

[0193] 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 made of the continuous tooth fabric 5.

[0194] In the embodiments shown in Figures 1 and 3, the tooth fabric 5 that constitutes the surface of the tooth portion is a constituent element of the tooth portion, while the tooth fabric 5 that constitutes the surface of the tooth root portion is a constituent element of the back portion. Furthermore, each tooth fabric 5 that constitutes the tooth portion is a part of a continuous tooth fabric 5 (a part of the tooth fabric 5 in Figures 2 and 4).

[0195] In this example, the tooth portion 1a has a substantially trapezoidal cross-sectional shape in the circumferential direction of the belt. Furthermore, the tooth portion 1a with a substantially trapezoidal cross-section has a circumferential surface formed of the tooth fabric 5, and its interior is formed of a tooth rubber layer 4 interposed between the tooth fabric 5 and the core wire 3.

[0196] Furthermore, in the tooth root portion 1b, a tooth rubber layer 4 is interposed between the tooth fabric 5 and the core wire 3 (not shown). The thickness of the tooth rubber layer 4 in the tooth root portion 1b is extremely thin compared to the thickness of the tooth rubber layer 4 in the tooth portion 1a.

[0197] The core wires 3 extend in the longitudinal direction (circumferential direction) of the belt and are arranged at intervals in the width direction of the belt. The gaps between adjacent core wires 3 may be formed by crosslinked rubber compositions (particularly the rubber compositions constituting the back rubber layer 2) and / or the tooth rubber layer 4.

[0198] The toothed belt of the present invention is not limited to the form and structure shown in Figures 1 to 4. 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 belt 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.

[0199] 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.

[0200] (Back rubber layer) The back portion has the teeth and tooth roots formed on its inner circumferential surface, and on its outer circumferential side, it has a back rubber layer that forms the outer surface of the belt.

[0201] In a toothed belt, the back rubber layer corresponds to the outer rubber layer; therefore, the back rubber layer can be selected from the outer rubber layer, including preferred embodiments.

[0202] In the cross-section of the toothed belt shown in Figures 1 and 2, cut along the circumferential direction of the belt, the interface (interface shape) between the first rubber layer 2a and the second rubber layer 2b is a gentle wave shape (wavy shape) corresponding to the uneven shape of the teeth 1a and tooth roots 1b, but it may also be a flat shape along the length direction of the belt. The toothed belt of the present invention can usually be manufactured by the first method (a method in which the teeth are not formed in advance during the molding process) or the second method (a method in which the teeth are formed in advance during the molding process), as described later. In the first method, a toothed belt with a wave-shaped interface is obtained, and in the second method, a toothed belt with a flat interface is obtained. Since the interface of the toothed belt obtained by the first method is a gentle wave shape, the adhesion between the first rubber layer and the second rubber layer can be considered the same for the toothed belt obtained by the first method and the toothed belt obtained by the second method.

[0203] In the toothed belt of the present invention, if the outer rubber layer does not include an intermediate layer, the average thickness of the back rubber layer (outer rubber layer) is, for example, 1 to 9 mm, preferably 2 to 8 mm, more preferably 3 to 7 mm, and most preferably 3 to 6 mm.

[0204] If the outer rubber layer does not include an intermediate layer, the average thickness of the first rubber layer is, for example, 0.8 to 6 mm (particularly 0.8 to 5 mm), preferably 0.9 to 4.5 mm, more preferably 1 to 4 mm, more preferably 1.5 to 3.5 mm, and most preferably 2 to 3.3 mm (particularly 2.2 to 3.2 mm).

[0205] In addition, in the cross-section of the toothed belt shown in Figures 3 and 4, when cut along the belt circumferential direction, the layer shape of the intermediate layer 2c interposed at the interface between the first rubber layer 2a and the second rubber layer 2b is a gentle wave shape (wavy shape) corresponding to the uneven shape of the teeth 1a and tooth roots 1b, but it may also be a flat shape along the belt length direction. The toothed belt of the present invention can usually be manufactured by the first method (a method in which the teeth are not formed in advance during the molding process) or the second method (a method in which the teeth are formed in advance during the molding process), as described later. In the first method, a toothed belt with a wave-shaped intermediate layer is obtained, and in the second method, a toothed belt with a flat layer shape is obtained. Since the layer shape of the intermediate layer of the toothed belt obtained by the first method is a gentle wave shape, the adhesion between the first rubber layer and the second rubber layer can be considered the same for the toothed belt obtained by the first method and the toothed belt obtained by the second method.

[0206] In the toothed belt of the present invention, when the outer rubber layer includes an intermediate layer, the average thickness of the back rubber layer (outer rubber layer) is, for example, 1 to 9 mm, preferably 2 to 8 mm, more preferably 3 to 7.5 mm, and most preferably 4 to 7.2 mm.

[0207] When the outer rubber layer includes an intermediate layer, the average thickness of the first rubber layer is, for example, 0.8 to 7 mm (particularly 0.8 to 5 mm), preferably 0.9 to 4.5 mm, more preferably 1 to 4 mm, more preferably 1.5 to 3.8 mm, and most preferably 1.7 to 3.5 mm (particularly 2.3 to 3.2 mm).

[0208] The average thickness of the first rubber layer is, for example, 35 to 90%, preferably 40 to 85%, of the average thickness of the outer rubber layer, and more preferably 50 to 80%, in order to greatly improve the durability and running performance of the belt. If the ratio of the average thickness of the first rubber layer to the average thickness of the outer rubber layer (back rubber layer) is too small, the hardness of the second rubber layer will become dominant throughout the outer rubber layer, and the overall hardness of the outer rubber layer will increase, which may result in insufficient grip (coefficient of friction) on the conveyed object. On the other hand, if the ratio of the average thickness of the first rubber layer to the average thickness of the outer rubber layer (back rubber layer) is too large, the second rubber layer will be too thin, which may result in insufficient mechanical strength of the belt.

[0209] If the outer rubber layer does not include an intermediate layer, the average thickness of the second rubber layer is, for example, 0.2 to 4 mm (particularly 1 to 4 mm), preferably 0.3 to 3.5 mm, more preferably 0.5 to 3 mm, more preferably 0.7 to 2.5 mm, and most preferably 0.8 to 2 mm.

[0210] When the outer rubber layer includes an intermediate layer, the average thickness of the second rubber layer is, for example, 0.2 to 4 mm (particularly 1 to 4 mm), preferably 0.3 to 3.5 mm, more preferably 0.4 to 3 mm, more preferably 0.5 to 2.5 mm, and most preferably 0.8 to 2 mm.

[0211] When the outer rubber layer includes an intermediate layer, the average thickness of the intermediate layer in the second embodiment is, for example, 0.05 to 2 mm, preferably 0.1 to 1 mm, more preferably 0.2 to 0.8 mm, more preferably 0.3 to 0.7 mm, and most preferably 0.4 to 0.6 mm.

[0212] When the outer rubber layer includes an intermediate layer, the average thickness of the intermediate fabric (intermediate fabric in the transmission belt) in the third embodiment is, for example, 0.05 to 1 mm, preferably 0.08 to 0.8 mm, more preferably 0.1 to 0.6 mm, more preferably 0.12 to 0.4 mm, and most preferably 0.15 to 0.35 mm.

[0213] In this application, the average thickness of each layer is the average of the measured thicknesses at any six points in an image of the cross-section of the transmission belt taken with a microscope. Furthermore, if the interface between the first rubber layer and the second rubber layer is corrugated, or if the intermediate layer is corrugated, the average thickness of the first and second rubber layers is the average of the measured thicknesses at three arbitrarily selected peaks and three bottoms of the corrugated shape.

[0214] The toothed belt of the present invention only needs to have a back rubber layer formed from the outer rubber layer, and conventional core wires and teeth can be used, but for example, the following core wires and teeth may be used.

[0215] (Core wire) A core wire extending along the belt circumferential direction is embedded in the back portion on the inner circumference side of the back rubber layer. This core wire acts as a tensile body and can improve the running stability and strength of the toothed belt. Furthermore, in the back portion, core wires, which are twisted cords extending along the belt circumferential direction, are usually embedded at predetermined intervals in the belt width direction, and multiple core wires parallel to the longitudinal direction may be arranged, but from the viewpoint of productivity, they are usually embedded in a spiral shape. When arranged in a spiral shape, the angle of the core wire with respect to the longitudinal direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it is as close to 0° as possible.

[0216] More specifically, the core wires may be embedded at predetermined intervals (or pitches) (or at equal intervals) from one end to the other in the belt width direction on the back, as shown in Figure 1. The spacing (spinning pitch), which is the distance between the centers of adjacent core wires, should be greater than the core wire diameter, and depending on the core wire diameter, it may be, for example, 0.5 to 3.5 mm, preferably 0.8 to 3 mm, and more preferably 1 to 2.8 mm.

[0217] 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.

[0218] 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.

[0219] The fibers forming the core are not particularly limited, and examples include synthetic fibers such as polyester fibers (polyalkylelelate fibers, poly(p-phenylene naphthalate) fibers), poly(p-phenylene benzobisoxazole) (PBO) fibers, acrylic fibers, and polyamide fibers (aliphatic polyamide fibers, aramid fibers, etc.), as well as inorganic fibers such as glass fibers, carbon fibers, and metal fibers (steel fibers). These fibers can be used individually or in combination of two or more types. As fibers forming the core, 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.

[0220] The core wire may be subjected to an adhesive treatment to enhance its adhesion to the crosslinked material of the rubber composition. For example, the adhesive treatment may involve immersing the stranded cord in a resorcinol-formaldehyde-latex treatment solution (RFL treatment solution), followed by heating and drying to form a uniform adhesive layer on the surface of the stranded cord. The RFL treatment solution is a mixture of latex and an initial condensate of resorcinol and formalin. The latex may be, for example, chloroprene rubber, styrene-butadiene-vinylpyridine terpolymer (VP latex), nitrile rubber, or hydrogenated nitrile rubber. Furthermore, the adhesive treatment may involve pre-treating with an epoxy compound or isocyanate compound before treatment with the RFL treatment solution.

[0221] The average diameter (average wire diameter) of the stranded cord (or core wire) is, for example, 0.2 to 2.5 mm, preferably 0.5 to 2.3 mm, and more preferably 0.7 to 2.2 mm. If the core wire diameter is too small, the elongation of the core wire will increase, which may cause tooth breakage (loss of teeth). If the core wire diameter is too large, the fatigue resistance of the core wire will decrease, which may cause the core wire to break.

[0222] (Tooth Rubber Layer) The tooth portion includes a tooth rubber layer positioned on the inner circumference side of the core wire. In the embodiments shown in Figures 1 and 3, the surface of the tooth rubber layer is covered with tooth cloth, but the tooth rubber layer may not be covered with tooth cloth, and the inner circumference of the belt may be formed of the tooth rubber layer.

[0223] The tooth rubber layer may be formed of a crosslinked material of a fourth rubber composition containing ethylene-α-olefin elastomer or hydrogenated nitrile rubber. When the second rubber composition contains ethylene-α-olefin elastomer, the crosslinked material of the fourth rubber composition preferably contains the same or similar ethylene-α-olefin elastomer as the ethylene-α-olefin elastomer of the second rubber composition, and is particularly preferably the same ethylene-α-olefin elastomer, in order to improve the adhesion between the back rubber layer and the tooth rubber layer.

[0224] If the second rubber composition contains ethylene-α-olefin elastomer, the fourth rubber composition may further contain, in addition to the ethylene-α-olefin elastomer, a crosslinking agent exemplified as the second crosslinking agent of the second rubber composition, a filler exemplified as the second filler, a softener exemplified as the second softener, an anti-aging agent exemplified as the second anti-aging agent, and other components exemplified as the second other component. The fourth rubber composition may be the same rubber composition as the second rubber composition.

[0225] When the second rubber composition contains hydrogenated nitrile rubber, the crosslinked material of the fourth rubber composition is preferably the same as or of the same type as the hydrogenated nitrile rubber of the second rubber composition, and is particularly preferably the same as the hydrogenated nitrile rubber, since it can improve the adhesion between the back rubber layer and the tooth rubber layer.

[0226] If the second rubber composition contains hydrogenated nitrile rubber, the fourth rubber composition may further contain, in addition to hydrogenated nitrile rubber, a crosslinking agent exemplified as the second crosslinking agent of the second rubber composition, a filler exemplified as the second filler, a softener exemplified as the second softener, an antioxidant exemplified as the second anti-aging agent, and other components exemplified as the second other component. The fourth rubber composition may be the same rubber composition as the second rubber composition.

[0227] The tooth rubber layer is not limited to a single-layer tooth rubber layer as shown in Figures 1 and 3, but may also be a tooth rubber layer having a laminated structure of two or more layers.

[0228] (Tooth Fabric) When the teeth include tooth fabric, the tooth fabric laminated on the inner circumferential surface of the belt (tooth and tooth base) may be formed from a fabric (fabric material or cloth) 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 circumferential 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 plain weave, twill weave (or diagonal weave), satin weave, etc., 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). The woven fabric can be selected from the woven fabrics exemplified as intermediate fabrics, including preferred embodiments.

[0229] The fibers forming the weft and warp threads of the toothed fabric may be organic or inorganic fibers. Examples of organic and inorganic fibers include those exemplified as organic and inorganic fibers forming the intermediate layer of fabric. These fibers can be used individually or in combination of two or more types.

[0230] Of the aforementioned fibers, organic fibers are commonly used, and preferred are cellulose fibers such as cotton and rayon, polyester fibers (PET fibers, etc.), polyamide fibers (aliphatic polyamide fibers such as polyamide 66 fibers, aramid fibers, etc.), PBO fibers, and fluororesin fibers [polytetrafluoroethylene (PTFE) fibers, etc.]. Also preferred are composite yarns of these fibers and elastic yarns with elasticity [for example, polyurethane elastic yarns with elasticity such as spandex made of polyurethane, processed yarns that have undergone stretch processing (for example, woolly processing, crimping processing, etc.)].

[0231] 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.

[0232] 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).

[0233] The woven fabric may have a multi-layered weave structure (such as a double weave structure), and in a woven structure comprising warp and weft threads, at least some of the weft threads may be made of low-friction fibers (or low-friction fibers) such as fluororesin-containing fibers (such as composite yarns containing fibers formed from fluororesins such as PTFE). For example, the warp threads may be made of polyamide fibers such as polyamide 66, polyester fibers, etc., and the weft threads may be made of fluororesin-formed fibers alone; composite yarns of fluororesin-formed fibers and second fibers such as polyamide fibers or polyurethane fibers (elastic yarns); or composite yarns of this composite yarn and a second composite yarn formed from a plurality of the second fibers.

[0234] In woven fabrics with a multi-layered structure, it is preferable to use fluorine-based fibers (e.g., PTFE fibers) with a low coefficient of friction as the weft threads located on the surface side of the toothed fabric (the side that engages with the toothed pulley) (exposed side) in order to reduce friction between the toothed fabric and the toothed pulley. On the other hand, by using fibers other than fluorine-based fibers for the weft threads located on the back side of the toothed fabric (the side that adheres to the first rubber layer), it is possible to increase the adhesive strength between the toothed fabric and the rubber constituting the teeth.

[0235] Furthermore, when using fluorine-based fibers, it is preferable that low-melting-point fibers that melt at the cross-linking (vulcanization) temperature of the teeth and back, with rubber as the base material, be arranged around the fluorine-based fibers. Specifically, the form of the composite yarn containing fluorine-based fibers includes forms in which fluorine-based fibers and low-melting-point fibers are mixed and twisted together, or forms in which fluorine-based fibers are covered by low-melting-point fibers. The cross-linking (vulcanization) conditions of the teeth and back are not particularly limited, but generally, the cross-linking (vulcanization) temperature is 100 to 200°C and the cross-linking (vulcanization) time is 1 minute to 5 hours.

[0236] In an embodiment in which low-melting-point fibers are arranged around fluorine-based fibers, the low-melting-point fibers melt during crosslinking (vulcanization) of the teeth and back portions, flow into the spaces between the fibers constituting the tooth fabric, and then crystallize when cooled to below their melting point. Therefore, the cutting and scattering of fluorine-based fibers due to impact and abrasion on the surface of the tooth fabric during engagement with or disengagement from a toothed pulley is suppressed.

[0237] 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. 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.

[0238] To improve the adhesion between the tooth cloth and the tooth rubber layer, the cloth forming the tooth cloth may be treated with an adhesive. Examples of adhesive treatments include immersing the cloth in an RFL treatment solution followed by heat drying; treating with an epoxy compound or isocyanate compound; and dissolving a rubber composition in an organic solvent to make a rubber glue, immersing the cloth in this rubber glue, and then heat drying. These methods can be performed individually or in combination, and the order and number of treatments are not limited. For example, after immersing in the RFL treatment solution, the cloth may be further immersed in the rubber glue and then heat dried.

[0239] Furthermore, to enhance the adhesion between the tooth cloth and the tooth rubber layer, an uncrosslinked rubber sheet, formed by rolling a rubber composition, may be laminated onto the back surface (the side that adheres to the tooth rubber layer) of the cloth forming the tooth cloth. This rubber composition can be appropriately selected from the rubber compositions exemplified above as the fourth rubber composition for forming the tooth rubber layer, or it may be a conventional adhesive rubber composition. In addition, the uncrosslinked rubber sheet made of this rubber composition may form an adhesive rubber layer interposed between the tooth cloth and the tooth rubber layer in the toothed belt.

[0240] The average tooth height of the teeth is, for example, 25 to 70%, preferably 30 to 50%, and more preferably 35 to 40%, of the average value of the total belt thickness [thickness (distance or height) from the back surface (outer surface) to the tooth crown].

[0241] In this application, as shown in Figure 2, the average tooth height of the teeth refers to the average height of the protruding teeth on the inner circumferential surface of the belt [the average value of the thickness (distance or height) from the tooth root surface to the tooth apex].

[0242] (Tooth root) When the tooth portion includes a tooth cloth, the tooth cloth constitutes the surface of the tooth portion and also forms the surface on the tooth side of the back (the surface of the tooth root).

[0243] If the tooth portion includes a tooth cloth, a tooth rubber layer may be interposed between the tooth cloth and the core wire in the dorsal portion corresponding to the tooth root, or the tooth cloth and core wire may be in contact without the tooth rubber layer being interposed. Even if a tooth rubber layer is interposed in the dorsal portion corresponding to the tooth root, the thickness of the tooth rubber layer is formed to be thinner than that of the tooth portion.

[0244] If the tooth portion does not include a tooth cloth, the dorsal portion corresponding to the tooth root may be formed of a tooth rubber layer. In the dorsal portion corresponding to the tooth root, the thickness of the tooth rubber layer is formed to be thinner than that of the tooth portion.

[0245] [Method for Manufacturing a Power Transmission Belt] The method for manufacturing a power transmission belt of the present invention is not particularly limited, and conventional methods can be used depending on the type of belt. In the case of a toothed belt, it can be manufactured by a first method that does not involve pre-forming only the teeth, or by a second method that does involve the aforementioned pre-forming. Specifically, a toothed belt having a toothed fabric and whose outer rubber layer consists of a first rubber layer and a second rubber layer may be manufactured, for example, by the method shown below.

[0246] (a) First method (method in which teeth are not formed in advance during the molding process) A toothed belt can be obtained by a method that includes a crosslinking molding step in which an uncrosslinked molded body is formed by laminating precursors of tooth cloth, core wire, tooth rubber layer and back rubber layer (outer rubber layer). Specifically, the method includes a precursor preparation step in which each precursor is prepared, a molding step in which an uncrosslinked molded body is formed by laminating precursors of tooth cloth, core wire, tooth rubber layer and back rubber layer, a crosslinking molding step in which the uncrosslinked molded body is crosslinked to obtain a crosslinked molded body, and a cutting step in which the crosslinked molded body is cut to obtain a toothed belt.

[0247] (Precursor preparation step) In the precursor preparation step, the core wire precursor and the tooth cloth precursor may be prepared by bonding treatment as described above.

[0248] The precursors for the tooth rubber layer and the back rubber layer (the first and second rubber layers that form the outer periphery) are uncrosslinked rubber sheets. The uncrosslinked rubber sheets are prepared by conventional methods, for example, by kneading a rubber composition in a Banbury mixer and rolling it with a roll or calender to prepare uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and uncrosslinked rubber sheet B for forming the first rubber layer.

[0249] (Molding Process) In the molding process, a tooth cloth precursor for forming the tooth cloth is wound around the outer surface of a cylindrical mold having multiple grooves (recesses) corresponding to the teeth. Subsequently, a twisted cord for forming 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, an uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and an uncrosslinked rubber sheet B for forming the first rubber layer are sequentially wound around its outer surface to form an uncrosslinked belt molded body (uncrosslinked molded body).

[0250] (Crosslinking Molding Process) Next, in the crosslinking molding process, the uncrosslinked belt molded body is placed on the outer circumference of the cylindrical mold, and a rubber jacket, which is a vapor barrier, is then placed over its outer circumference. Subsequently, the belt molded body with the jacket and the cylindrical mold are housed inside a crosslinking molding device such as a vulcanizing can. When the belt molded body is heated and pressurized inside the crosslinking molding device, a portion of the softened uncrosslinked rubber sheet A is extruded (press-fitted) into the inner circumference through the gaps in the twisted cord.

[0251] By press-fitting, the tooth cloth precursor is stretched to conform to the contour of the tooth and positioned on the innermost circumference, a rubber layer derived from the uncrosslinked rubber sheet A is positioned on its outer circumference along the contour of the tooth, twisted cords are arranged on the outer circumference of the rubber layer, the remaining rubber layer is positioned on the outer circumference of the twisted cords, and a rubber layer derived from the uncrosslinked rubber sheet B (back) is positioned on the outermost circumference, forming a layered structure.

[0252] Simultaneously with the formation of this layered structure, the cross-linking reaction of the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body causes each component to be integrally joined together, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0253] Thus, in the first method, which does not involve pre-forming, the uncrosslinked rubber sheet A (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. In other words, in the first method, a portion of the rubber composition for forming the second rubber layer and the teeth (tooth rubber layer) flows from the back side through the space between the core wires to the teeth side to form the teeth.

[0254] (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.

[0255] (b) Second method (method of forming teeth in advance during the molding process) The first method may be manufactured by adding a step of preparing a pre-formed body in which only the teeth are formed during the molding process.

[0256] (Precursor preparation step) In the precursor preparation step, the core wire precursor and the tooth cloth precursor may be prepared by bonding treatment as described above.

[0257] The precursors for the tooth rubber layer and the back rubber layer (the first and second rubber layers that form the outer periphery) are uncrosslinked rubber sheets. The uncrosslinked rubber sheets are prepared by conventional methods, for example, by rolling a rubber composition kneaded in a Banbury mixer or the like, using rolls or a calender, to prepare an uncrosslinked rubber sheet a for forming the tooth rubber layer, an uncrosslinked rubber sheet b for forming the second rubber layer, and an uncrosslinked rubber sheet c for forming the first rubber layer.

[0258] (Molding Process) In the molding process, a tooth cloth precursor for forming the tooth cloth is wrapped around the outer surface of a cylindrical mold having multiple grooves (recesses) corresponding to the teeth of a toothed belt. Subsequently, a laminate is formed by wrapping an uncrosslinked rubber sheet a around its outer surface. While heating the laminate to a temperature (for example, about 70 to 90°C) that softens the rubber composition using a predetermined device, the laminate is pressurized from the outer side to press-fit the rubber composition of the uncrosslinked rubber sheet a and the tooth cloth precursor into the grooves (recesses) of the cylindrical mold to form the teeth and obtain a semi-crosslinked pre-molded body (pre-laminated body). During this press-fitting process to form the teeth, the tooth cloth is stretched to a shape that follows the contour of the teeth and positioned on the outermost surface, and a layer structure is formed on the outer side where the rubber layer is positioned along the contour of the teeth.

[0259] Alternatively, instead of using a cylindrical mold, a flat press mold (flat mold) having multiple grooves (recesses) corresponding to the teeth may be used to form the teeth by press-fitting the rubber composition of an uncrosslinked rubber sheet and a tooth cloth precursor into the grooves (recesses) of the flat mold using the above procedure. In this method, after demolding the preformed body from the flat mold, the preformed body is wrapped around and attached to a cylindrical mold having multiple grooves (recesses) corresponding to the teeth (fitting the teeth and grooves).

[0260] In either method, a stranded cord forming the core is wound spirally around the outer surface of the obtained preformed body at a predetermined pitch (with a predetermined pitch in the axial direction of the cylindrical mold). Furthermore, an uncrosslinked rubber sheet b forming the second rubber layer and an uncrosslinked rubber sheet c forming the first rubber layer are sequentially wound around its outer surface to form an uncrosslinked belt molded body (uncrosslinked laminate).

[0261] (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 vessel. When the belt molded body is heated and pressurized inside the crosslinking molding apparatus, the desired shape is formed, and the crosslinking reaction of the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body causes each component to be joined together integrally, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0262] (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.

[0263] A toothed belt, which has a toothed fabric and whose outer rubber layer consists of a first rubber layer, an intermediate layer, and a second rubber layer, may be manufactured, for example, by the following method.

[0264] (c) First method (method in which teeth are not formed in advance during the molding process) A toothed belt can be obtained by a method that includes a crosslinking molding step in which an uncrosslinked molded body is formed by laminating precursors of tooth cloth precursor, core wire precursor, intermediate layer precursor, tooth rubber layer, and back rubber layer (outer rubber layer). Specifically, the method includes a precursor preparation step in which each precursor is prepared, a molding step in which an uncrosslinked molded body is formed by laminating precursors of tooth cloth precursor, core wire precursor, intermediate layer precursor, tooth rubber layer, and back rubber layer, a crosslinking molding step in which the uncrosslinked molded body is crosslinked to obtain a crosslinked molded body, and a cutting step in which the crosslinked molded body is cut to obtain a toothed belt.

[0265] (Precursor preparation step) In the precursor preparation step, the core wire precursor, the tooth cloth precursor, and the intermediate layer precursor for forming the third intermediate layer (third intermediate layer precursor) may be prepared by bonding treatment as described above.

[0266] The precursors for the tooth rubber layer and the back rubber layer (the first and second rubber layers that form the outer periphery) are uncrosslinked rubber sheets. The uncrosslinked rubber sheets are prepared by conventional methods, for example, by kneading a rubber composition in a Banbury mixer and rolling it with a roll or calender to prepare uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and uncrosslinked rubber sheet B for forming the first rubber layer.

[0267] In forming the intermediate layer according to the first embodiment, the intermediate layer may be formed by pre-laminating an intermediate layer precursor (first intermediate layer precursor) onto one side of the obtained uncrosslinked rubber sheet A and then subjecting it to the next step. Methods for laminating the first intermediate layer precursor include scattering powdered unsaturated carboxylate metal salt and applying a solution containing the unsaturated carboxylate metal salt to one side of the obtained uncrosslinked rubber sheet A. Of these, the method of applying a solution containing the unsaturated carboxylate metal salt is preferred because it easily forms a uniform intermediate layer and improves interlayer adhesion.

[0268] Furthermore, when forming the intermediate layer of the second embodiment, an uncrosslinked rubber sheet C (second intermediate layer precursor) for forming the intermediate layer is prepared in the same manner as uncrosslinked rubber sheets A and B.

[0269] Furthermore, when forming an intermediate layer (intermediate cloth) according to the third embodiment, an uncrosslinked third rubber composition is attached to the cloth. Methods for attaching the uncrosslinked third rubber composition to the cloth include, for example, a method of soaking (immersing) the cloth in a rubber glue made by dissolving the uncrosslinked rubber composition in a solvent to form a rubber glue adhesive layer (soaking method), a method of applying (coating) the rubber glue to the cloth to form a rubber glue adhesive layer (coating method), and a method of friction-adhesive rubber layer being formed by friction-rubbing (rubbing) the solid uncrosslinked rubber composition into the cloth (frictioning method). Of these, the soaking method and the coating method are preferred.

[0270] In soaking and coating methods, solvents for preparing rubber adhesive include, for example, aromatic hydrocarbons (e.g., aliphatic hydrocarbons such as hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene), ketones (e.g., aliphatic ketones such as acetone, diacetone alcohol, methyl ethyl ketone, and methyl isobutyl ketone; alicyclic ketones such as cyclohexanone and isophorone), ethers (e.g., dioxane and tetrahydrofuran), and esters (e.g., acetate esters such as methyl acetate, ethyl acetate, isopropyl acetate, butyl acetate, and amyl acetate). These solvents can be used individually or in combination of two or more. Of these, aromatic hydrocarbons and aliphatic ketones are commonly used.

[0271] In the soaking method, the proportion of solvent may be 50% by mass or more in the rubber adhesive, for example, 50 to 99% by mass, preferably 70 to 98% by mass, and more preferably 80 to 95% by mass. In the coating method, the proportion of solvent may be 10% by mass or more in the rubber adhesive, for example, 10 to 90% by mass, preferably 50 to 85% by mass, and more preferably 70 to 80% by mass.

[0272] In the soaking method, after immersing the cloth in rubber cement, the cloth impregnated with rubber cement may be passed between rollers to remove excess rubber cement and allow the rubber cement to penetrate into the fabric. The cloth impregnated with rubber cement may be dried by heating at a temperature of 50°C or higher (for example, 60-100°C).

[0273] In the coating method, rubber adhesive may be applied to the surface of the fabric using a coater or similar device, and then dried by heating at a temperature of 50°C or higher (for example, 60-100°C).

[0274] To improve the adhesion between the intermediate fabric and the first and second rubber layers, the fabric forming the intermediate fabric may be subjected to an adhesive treatment as a pretreatment before applying the third rubber composition. Examples of adhesive treatments include immersing the fabric in an RFL treatment solution followed by heat drying; and treating it with an epoxy compound or isocyanate compound. These methods can be performed individually or in combination, and the order and number of treatments are not limited.

[0275] (Molding Process) In the molding process, a tooth cloth precursor for forming the tooth cloth is wound around the outer surface of a cylindrical mold having multiple grooves (recesses) corresponding to the teeth. Subsequently, a twisted cord for forming 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, an uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and an uncrosslinked rubber sheet B for forming the first rubber layer are sequentially wound around its outer surface to form an uncrosslinked belt molded body (uncrosslinked molded body).

[0276] When forming the intermediate layer according to the first embodiment, an uncrosslinked rubber sheet A is used, in which the first intermediate layer precursor is laminated on one side, and the first intermediate layer precursor is arranged in contact with the uncrosslinked rubber sheet B.

[0277] On the other hand, when forming the intermediate layer of the second embodiment, an uncrosslinked rubber sheet C is wrapped between the uncrosslinked rubber sheet A and the uncrosslinked rubber sheet B. Similarly, when forming the intermediate layer of the third embodiment, a third intermediate layer precursor (intermediate fabric precursor) is wrapped between the uncrosslinked rubber sheet A and the uncrosslinked rubber sheet B.

[0278] (Crosslinking Molding Process) Next, in the crosslinking molding process, the uncrosslinked belt molded body is placed on the outer circumference of the cylindrical mold, and a rubber jacket, which is a vapor barrier, is then placed over its outer circumference. Subsequently, the belt molded body with the jacket and the cylindrical mold are housed inside a crosslinking molding device such as a vulcanizing can. When the belt molded body is heated and pressurized inside the crosslinking molding device, a portion of the softened uncrosslinked rubber sheet A is extruded (press-fitted) into the inner circumference through the gaps in the twisted cord.

[0279] By press-fitting, the tooth cloth precursor is stretched to conform to the contour of the tooth and positioned on the innermost circumference, a rubber layer derived from the uncrosslinked rubber sheet A is positioned on its outer circumference along the contour of the tooth, twisted cords are arranged on the outer circumference of the rubber layer, the remaining rubber layer is positioned on the outer circumference of the twisted cords, an intermediate layer is positioned further on its outer circumference, and a rubber layer derived from the uncrosslinked rubber sheet B (back) is positioned on the outermost circumference, forming a layered structure.

[0280] Simultaneously with the formation of this layered structure, the cross-linking reaction of the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body causes each component to be integrally joined together, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0281] Thus, in the first method, which does not involve pre-forming, the uncrosslinked rubber sheet A (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. In other words, in the first method, a portion of the rubber composition for forming the second rubber layer and the teeth (tooth rubber layer) flows from the back side through the space between the core wires to the teeth side to form the teeth.

[0282] (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.

[0283] (d) Second method (method of forming teeth in advance during the molding process) The first method may be manufactured by adding a step of preparing a pre-formed body in which only the teeth are formed during the molding process.

[0284] (Precursor preparation step) In the precursor preparation step, the core wire precursor, tooth cloth precursor, and third intermediate layer precursor may be prepared by bonding treatment as described above.

[0285] The precursors for the tooth rubber layer and the back rubber layer (the first and second rubber layers that form the outer periphery) are uncrosslinked rubber sheets. The uncrosslinked rubber sheets are prepared by conventional methods, for example, by rolling a rubber composition kneaded in a Banbury mixer or the like, using rolls or a calender, to prepare an uncrosslinked rubber sheet a for forming the tooth rubber layer, an uncrosslinked rubber sheet b for forming the second rubber layer, and an uncrosslinked rubber sheet c for forming the first rubber layer.

[0286] Furthermore, when forming the intermediate layer according to the first embodiment, the intermediate layer may be formed by pre-laminating an intermediate layer precursor onto one side of the obtained uncrosslinked rubber sheet b and then subjecting it to the next step.

[0287] Furthermore, when forming the intermediate layer of the second embodiment, an uncrosslinked rubber sheet d for forming the intermediate layer is prepared in the same manner as the uncrosslinked rubber sheets a to c.

[0288] (Molding Process) In the molding process, a tooth cloth precursor for forming the tooth cloth is wrapped around the outer surface of a cylindrical mold having multiple grooves (recesses) corresponding to the teeth of a toothed belt. Subsequently, a laminate is formed by wrapping an uncrosslinked rubber sheet a around its outer surface. While heating the laminate to a temperature (for example, about 70 to 90°C) that softens the rubber composition using a predetermined device, the laminate is pressurized from the outer side to press-fit the rubber composition of the uncrosslinked rubber sheet a and the tooth cloth precursor into the grooves (recesses) of the cylindrical mold to form the teeth and obtain a semi-crosslinked pre-molded body (pre-laminated body). During this press-fitting process to form the teeth, the tooth cloth is stretched to a shape that follows the contour of the teeth and positioned on the outermost surface, and a layer structure is formed on the outer side where the rubber layer is positioned along the contour of the teeth.

[0289] Alternatively, instead of using a cylindrical mold, a flat press mold (flat mold) having multiple grooves (recesses) corresponding to the teeth may be used to form the teeth by press-fitting the rubber composition of an uncrosslinked rubber sheet and a tooth cloth precursor into the grooves (recesses) of the flat mold using the above procedure. In this method, after demolding the preformed body from the flat mold, the preformed body is wrapped around and attached to a cylindrical mold having multiple grooves (recesses) corresponding to the teeth (fitting the teeth and grooves).

[0290] In either method, a stranded cord forming the core is wound spirally around the outer surface of the obtained preformed body at a predetermined pitch (with a predetermined pitch in the axial direction of the cylindrical mold). Furthermore, an uncrosslinked rubber sheet b forming the second rubber layer and an uncrosslinked rubber sheet c forming the first rubber layer are sequentially wound around its outer surface to form an uncrosslinked belt molded body (uncrosslinked laminate).

[0291] (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 vessel. When the belt molded body is heated and pressurized inside the crosslinking molding apparatus, the desired shape is formed, and the crosslinking reaction of the uncrosslinked and semi-crosslinked rubber components contained in the belt molded body causes each component to be joined together integrally, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0292] When forming the intermediate layer according to the first embodiment, an uncrosslinked rubber sheet b is used, which has an intermediate layer precursor (first intermediate layer precursor) laminated on one side, and is arranged so that the intermediate layer precursor is in contact with the uncrosslinked rubber sheet c.

[0293] On the other hand, when forming the intermediate layer of the second embodiment, an uncrosslinked rubber sheet d (second intermediate layer precursor) is wrapped between the uncrosslinked rubber sheet b and the uncrosslinked rubber sheet c. Similarly, when forming the intermediate layer of the third embodiment, a third intermediate layer precursor (intermediate fabric precursor) is wrapped between the uncrosslinked rubber sheet b and the uncrosslinked rubber sheet c.

[0294] (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.

[0295] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The present invention was implemented in four embodiments: Example A, Example B, Example C, and Example D.

[0296] [Example A] Example A is an embodiment in which the outer rubber layer does not contain an intermediate layer, and the second rubber composition contains an ethylene-α-olefin elastomer. The raw materials used, the preparation method, the method for producing the measurement laminate (crosslinked molded body), and the evaluation method for the measurement laminate are shown below.

[0297] [EPDM Composition] Table 1 shows the formulation of the second rubber composition (EPDM composition) for forming the second rubber layer.

[0298]

[0299] [Materials for EPDM Composition] EPDM1: Nordel IP 4520 manufactured by Dow Chemical Company, ethylene content 50% by mass, diene content (ethylidene norbornene content) 4.9% by mass, Mooney viscosity 20ML (1+4) 125℃ EPDM2: Nordel IP 3640 manufactured by Dow Chemical Company, ethylene content 55% by mass, diene content (ethylidene norbornene content) 1.8% by mass, Mooney viscosity 40ML (1+4) 125℃ Zinc methacrylate: R-20S manufactured by Asada Chemical Industries, Ltd., purity 85% by mass Paraffin-based oil: Diana Process Oil PW90 manufactured by Idemitsu Kosan Co., Ltd. Anti-aging agent: "Nocrack MB-O" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., 2-mercaptobenzimidazole. Carbon black: "Seasto S" manufactured by Tokai Carbon Co., Ltd., average particle size 66 nm, iodine adsorption capacity 26 mg / g. Silica: "Ultrazil VN3" manufactured by Evonik Degussa Japan Co., Ltd., BET specific surface area 175 m². ２ / g Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.55 μm Organic peroxide: "Perbutyl P-40MB" manufactured by NOF Corporation, 1,3-bis(2-t-butylperoxyisopropyl)benzene, active ingredient 40% by mass

[0300] [Silicone Rubber Composition] Table 2 shows the formulation of the first rubber composition (silicone rubber composition) for forming the first rubber layer.

[0301]

[0302] [Materials for the silicone rubber composition] Silicone rubber 1: "TSE270-5U" manufactured by Momentive Performance Materials Japan LLC Silicone rubber 2: "TSE261-6U" manufactured by Momentive Performance Materials Japan LLC Zinc methacrylate: "R-20S" manufactured by Asada Chemical Industries, Ltd., purity 85% by mass Organic peroxide: "TC-8" manufactured by Momentive Performance Materials Japan LLC

[0303] [Tooth Fabric] A 2 / 2 twill canvas was woven using 155 dtex nylon 66 yarn as the warp and a composite yarn of 155 dtex nylon 66 yarn and 122 dtex urethane elastic yarn as the weft. The warp density was 137 threads / 3cm and the weft density was 81 threads / 3cm. The woven canvas was immersed in the RFL treatment solution shown in Table 3 and dried. Then, the dried canvas was further immersed in a rubber adhesive prepared by dissolving the uncrosslinked EPDM composition for rubber adhesive shown in Table 4 in methyl ethyl ketone at a ratio of 10% by mass, and dried to obtain a bonded canvas (tooth fabric precursor) with a thickness of 0.85 mm.

[0304]

[0305]

[0306] [Reinforcement fabric] 0.5 mm thick nylon canvas

[0307] [Core wire (processed cord)] Three strands of 200 E glass filaments with a diameter of 9 μm (a strand designated ECG150 as described in JIS R 3413 (2012)) were arranged together and immersed in the RFL solution (18-23°C) shown in Table 3 for 3 seconds. After that, they were heated and dried at 200-280°C for 3 minutes to form an RFL adhesive coating. After this bonding treatment, the three strands were twisted in the S direction with 8 twists / 10 cm to prepare a pre-twisted yarn (pre-twisted yarn S), and the same number of twists were twisted in the Z direction to prepare a pre-twisted yarn (pre-twisted yarn Z). Next, 13 pre-twisted yarns S were arranged together and twisted in the Z direction with 8 twists / 10 cm to obtain a multi-twisted cord (multi-twisted cord Z). Similarly, thirteen strands of under-twisted yarn Z were aligned and twisted in the S direction at a twist rate of 8 times / 10 cm to obtain a multi-twisted cord (multi-twisted cord S). Each multi-twisted cord was passed through an overcoat solution (rubber glue prepared by dissolving the uncrosslinked rubber composition shown in Table 4 in methyl ethyl ketone at a ratio of 10% by mass) and then dried to produce treated cords (treated cord S and treated cord Z) with an adhesive film of the rubber composition. The total fineness of the treated cords was 1300-1400 tex, and the outer diameter was 1.2 mm.

[0308] [Preparation of Uncrosslinked Rubber Sheets] For the toothed belts to be made in the examples and comparative examples, an uncrosslinked rubber sheet A having the composition shown in Table 1 was used to form the toothed rubber layer and the second rubber layer, and for the uncrosslinked rubber sheet B having the composition shown in Table 2 was used to form the first rubber layer. The rubber compositions were kneaded in a Banbury mixer and rolled with calender rolls to produce uncrosslinked rubber sheets.

[0309] [Adhesion (peel strength) test on test specimens] The reinforcing cloth, uncrosslinked rubber sheet for the first rubber layer (uncrosslinked silicone rubber sheet, which is uncrosslinked rubber sheet B, thickness 2 mm, width 30 mm, length 150 mm), uncrosslinked rubber sheet for the second rubber layer (uncrosslinked EPDM sheet, which is uncrosslinked rubber sheet A, thickness 2 mm, width 30 mm, length 150 mm), and reinforcing cloth were stacked in that order, and crosslinking molding was performed in a press die (surface pressure 2 MPa, 165°C) for 30 minutes to produce a laminate (crosslinked molded body) 15 in which the reinforcing cloth 11, silicone rubber sheet 12, sheet 13, and reinforcing cloth 14 were joined together to form an integrated structure, as shown in Figure 5. In Example A, sheet 13 is an EPDM sheet.

[0310] In this laminate 15, the interface between the silicone rubber sheet 12 and the sheet 13 was joined over a length of 120 mm, while one end of each uncrosslinked rubber sheet was not joined, as shown in Figure 5, in order to be used as gripping portions A and B (30 mm each) for the tensile force measurement described later. The resulting laminate 15 was cut to a width of 25 mm to produce a sample with a width of 25 mm, a length of 150 mm (joining length 120 mm), and a thickness of 4 mm.

[0311] The Autograph (AGS-J10kN, manufactured by Shimadzu Corporation) was used to grip portion A (a laminate of reinforcing fabric 11 and silicone rubber sheet 12) with its upper grip and grip portion B (a laminate of sheet 13 and reinforcing fabric 14) with its lower grip. The upper grip was raised at a speed of 50 mm / min according to JIS K 6256 (2013) to separate the bonding interface, and the tensile strength (tensile force) at that time was recorded as the peel strength (peel force). The measurement time was set to 2 minutes so that the movement distance of the upper grip and the peeled portion were approximately 100 mm. The test temperature (ambient temperature) was 23°C, and the sample was measured after being left at the test temperature for 16 hours or more. The tensile force showed a wavy curve, and its average value was calculated according to Method E of JIS K 6274 (2018). In other words, ignoring the initial upward curve at the start of the test, we calculated the average of the maximum and minimum values ​​among all the peaks of the wave curve.

[0312] Then, based on the obtained peel strength (peeling force), the bonding strength (adhesion) between the first rubber layer (silicone rubber composition) and the second rubber layer (EPDM composition) was determined according to the following criteria.

[0313] (Judgment Criteria) a: Peel strength (peeling force) per 25 mm width is 100 N or more b: Peel strength (peeling force) per 25 mm width is 10 N or more but less than 100 N c: Peel strength (peeling force) per 25 mm width is less than 10 N

[0314] [Manufacturing of Toothed Belts] In Comparative Examples A1 to A2 and Examples A1 to A30, an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 1 was used as the uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 2 was used as the uncrosslinked rubber sheet B for forming the first rubber layer. A toothed belt with a tooth profile G8M, tooth height (including tooth cloth) 3.35 mm, tooth pitch 8 mm, number of teeth 100, core wire pitch 1.45 mm, and circumference 800 mm was manufactured by the first manufacturing method without pre-forming as described in the manufacturing method (a) in the section [Modes for Carrying Out the Invention]. The width of the toothed belt used for measuring the bonding strength (peel strength) was 36.0 mm, and the width of the toothed belt used for the durability running test was 15.0 mm.

[0315] (Comparative Example A1) Uncrosslinked rubber composition RA1 was used as uncrosslinked rubber sheet A, and uncrosslinked rubber composition RA9 was used as uncrosslinked rubber sheet B. In the molding process, an uncrosslinked belt molded body (uncrosslinked molded body) was formed. This was crosslinked to form a sleeve-shaped crosslinked molded body (crosslinked belt sleeve), and a toothed belt was produced by cutting it to a predetermined width. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0316] (Comparative Example A2) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that uncrosslinked rubber sheet A and uncrosslinked rubber sheet B were bonded together with an epoxy resin adhesive. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0317] (Example A1) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that an uncrosslinked rubber composition RA2 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0318] (Example A2) A toothed belt was manufactured in the same manner as in Example A1, except that an uncrosslinked rubber composition RA3 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0319] (Example A3) A toothed belt was manufactured in the same manner as in Example A1, except that an uncrosslinked rubber composition RA4 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0320] (Example A4) A toothed belt was manufactured in the same manner as in Example A1, except that an uncrosslinked rubber composition RA5 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0321] (Example A5) A toothed belt was manufactured in the same manner as in Example A1, except that an uncrosslinked rubber composition RA6 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0322] (Example A6) A toothed belt was manufactured in the same manner as in Example A1, except that an uncrosslinked rubber composition RA7 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0323] (Example A7) A toothed belt was manufactured in the same manner as in Example A3, except that an uncrosslinked rubber composition RA8 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0324] (Example A8) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 1.6 mm and the average thickness of the second rubber layer was 2.5 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 39.0%.

[0325] (Example A9) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 2.2 mm and the average thickness of the second rubber layer was 1.9 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 53.7%.

[0326] (Example A10) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 3.2 mm and the average thickness of the second rubber layer was 0.9 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.0%.

[0327] (Example A11) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 3.4 mm and the average thickness of the second rubber layer was 0.7 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.9%.

[0328] (Example A12) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 2.0 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 62.5%.

[0329] (Example A13) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 4.5 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.9%.

[0330] (Example A14) A toothed belt was manufactured in the same manner as in Example A3, except that the average thickness of the first rubber layer was 5.5 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.1%.

[0331] (Example A15) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that an uncrosslinked rubber composition RA10 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A51, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0332] (Example A16) A toothed belt was manufactured in the same manner as in Example A15, except that an uncrosslinked rubber composition RA11 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A52, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0333] (Example A17) A toothed belt was manufactured in the same manner as in Example A15, except that an uncrosslinked rubber composition RA12 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A53, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0334] (Example A18) A toothed belt was manufactured in the same manner as in Example A15, except that an uncrosslinked rubber composition RA13 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A55, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0335] (Example A19) A toothed belt was manufactured in the same manner as in Example A15, except that an uncrosslinked rubber composition RA14 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A63, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0336] (Example A20) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 1.6 mm and the average thickness of the second rubber layer was 2.5 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 39.0%.

[0337] (Example A21) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 2.2 mm and the average thickness of the second rubber layer was 1.9 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 53.7%.

[0338] (Example A22) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 3.2 mm and the average thickness of the second rubber layer was 0.9 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.0%.

[0339] (Example A23) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 3.4 mm and the average thickness of the second rubber layer was 0.7 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.9%.

[0340] (Example A24) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 2.0 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 62.5%.

[0341] (Example A25) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 4.5 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.9%.

[0342] (Example A26) A toothed belt was manufactured in the same manner as in Example A17, except that the average thickness of the first rubber layer was 5.5 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.1%.

[0343] (Example A27) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that uncrosslinked rubber composition RA2 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RA11 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A52, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0344] (Example A28) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that uncrosslinked rubber composition RA4 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RA12 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A53, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0345] (Example A29) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that uncrosslinked rubber composition RA3 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RA11 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A52, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0346] (Example A30) A toothed belt was manufactured in the same manner as in Comparative Example A1, except that uncrosslinked rubber composition RA8 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RA14 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A63, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0347] [Measurement of bonding strength (peel strength) of toothed belts] A 15 cm section was cut from the fabricated endless toothed belt in the length direction to obtain a sample for measurement, which was used as a sample in an unrunned state. Similarly, a sample was also taken from the endless toothed belt after it had been run, which was used as a sample in a runned state. A two-axis running test machine consisting of a drive (Dr.) pulley with a diameter of 56.02 mm and a driven (Dn.) pulley with a diameter of 56.02 mm was used to run the toothed belt. On the two-axis running test machine, a toothed belt with a width of 36.0 mm was mounted on each pulley, the shaft load was set to 128 N, the rotation speed of the drive pulley was set to 3600 rpm, and the load of the driven pulley was set to 4.86 N·m, and the belt was run for 720 hours at an ambient temperature of 100°C.

[0348] The peel strength of each sample was measured as follows: On the end face of a sample taken from an endless belt, an incision was made with a cutting tool at the interface between the first and second rubber layers to create gripping portions A and B. Then, gripping portion A (first rubber layer) was gripped with the upper gripper of an Autograph (AGS-J10kN, manufactured by Shimadzu Corporation), and gripping portion B (second rubber layer, laminated tooth portion) was gripped with the lower gripper. In the same manner as in the "Measurement of bonding strength (peel strength) using a test piece" described above, gripping portion A and gripping portion B were pulled apart (peel angle of 180°, i.e., gripping portion A was folded back 180° relative to gripping portion B), and the tensile strength (tensile force) when the interface was peeled was recorded as the peel strength (peel force). The peel strength was calculated by converting the measured tensile force to a value per 25 mm width.

[0349] Based on the obtained peel strength (peel force), the bonding strength (adhesion) between the first rubber layer (silicone rubber composition) and the second rubber layer (EPDM composition) was determined according to the following criteria.

[0350] (Judgment Criteria) a: Peel strength (peeling force) per 25 mm width is 40 N or more b: Peel strength (peeling force) per 25 mm width is 30 N or more but less than 40 N c: Peel strength (peeling force) per 25 mm width is 10 N or more but less than 30 N d: Peel strength (peeling force) per 25 mm width is less than 10 N, or peeling occurs during driving

[0351] [Durability Running Test] To confirm the transport performance on the reverse side, the superiority or inferiority of the belts was verified using the belt's durability running life as an indicator. In other words, since transport performance is lost due to failure during durable running (cracks on the reverse side, delamination of the reverse layer), the durability running life (running time until failure occurs) was used as an indicator of "sustainability of transport performance" to determine the superiority or inferiority of the belts.

[0352] The durability running test was conducted using the same two-axis running test machine used for measuring joint strength (peel strength). A toothed belt with a width of 15.0 mm was used, with an axle load of 442 N, a drive pulley rotation speed of 3600 rpm, a driven pulley load of 10.33 N·m, and an ambient temperature of 100°C. The running time until failure occurred in the toothed belt was measured as the running life.

[0353] The travel time until this failure occurs (hereinafter referred to as "travel time") is shown as a relative value, with the travel time of Comparative Example A1 set to 1.0. If this relative value is greater than 1.0, it indicates a longer travel life than the toothed belt of Comparative Example A1 (i.e., superior sustained transport performance), and if it is 1.0 or less, it indicates that it is equivalent to or less than the toothed belt of Comparative Example A1.

[0354] (Criteria for judging endurance driving tests) a: Driving time (relative value) until failure is 18 or more b: Driving time (relative value) until failure is 10 or more but less than 18 c: Driving time (relative value) until failure is greater than 1.0 but less than 10 d: Driving time (relative value) until failure is 1.0 or less

[0355] [Overall Evaluation] Considering three items for toothed belts—bonding strength in the non-running state (bonding strength between the first and second rubber layers), bonding strength after running (maintainability from the non-running state), and durable running life (maintenance of conveying performance)—the overall superiority or inferiority was determined (ranked) according to the following criteria. From the perspective of product practicality, ranks A, B, and C were deemed acceptable, and rank D was deemed unacceptable.

[0356] (Criteria for overall evaluation) A rank: All three of the above items are judged as 'a' B rank: The above three items include a 'b' judgment (but do not include 'c' or 'd' judgments) C rank: The above three items include a 'c' judgment (but do not include 'd' judgment) D rank: The above three items include a 'd' judgment

[0357] The evaluation results for Comparative Examples A1-A2 and Examples A1-A30 are shown in Tables 5-9.

[0358]

[0359]

[0360]

[0361]

[0362]

[0363] <Verification Results in Table 5> (Comparative Examples A1 and A2) Comparative Example A1 is an example of a toothed belt in which a first rubber layer (RA9) without zinc methacrylate and a second rubber layer (RA1) without zinc methacrylate are joined together. Comparative Example A2 is an example of a toothed belt in which the first rubber layer (RA9) and the second rubber layer (RA1) of Comparative Example A1 are joined together with an epoxy resin adhesive.

[0364] In all cases, the bonding strength between the first and second rubber layers was low (rated d) in the undriven belt state, and the bonding strength after driving could not be measured (rated d) because the first and second rubber layers separated during driving. It was confirmed that sufficient bonding strength could not be obtained without using zinc methacrylate.

[0365] Furthermore, in the durability driving test, the driving life (driving time until failure (relative value)) was also low (rated D) due to early delamination between the first and second rubber layers, resulting in an overall rating of D (fail).

[0366] (Examples A1 to A6) Examples A1 to A6 are examples of toothed belts in which zinc methacrylate was added to the second rubber layer (EPDM composition) compared to the configuration of Comparative Example A1. When the amount of zinc methacrylate added was varied to 5 parts by mass (Example A1: RA2), 10 parts by mass (Example A2: RA3), 15 parts by mass (Example A3: RA4), 25 parts by mass (Example A4: RA5), 30 parts by mass (Example A5: RA6), and 35 parts by mass (Example A6: RA7), the bonding strength between the first rubber layer and the second rubber layer in the undriven belt state improved to a passing level of c in Examples A1 and A2, and to an a passing level of a in Examples A3 to A6. Furthermore, this bonding strength was maintained even after driving.

[0367] Furthermore, regarding the running life, in Example A1, delamination between the first and second rubber layers occurred, resulting in failure (end of lifespan) at a running time (relative value) of 10 (judgment b). In other words, it can be said that it can run 10 times longer than Comparative Example A1 (conveying performance is maintained). The running time (relative value) until failure was 12 in Example A2 (judgment b), and in Examples A3 to A6, delamination between the first and second rubber layers did not occur during running, and tooth chipping occurred at a running time (relative value) of 20, resulting in failure (end of lifespan) (judgment a). In the overall judgment, the toothed belts of Examples A1 and A2 were ranked C (pass), and the toothed belts of Examples A3 to A6 were ranked A (pass).

[0368] From these results, it was confirmed that adding zinc methacrylate improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and improves the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0369] <Verification Results in Table 6> (Example A7) Example A7 is an example of a toothed belt in which the type of EPDM in the second rubber layer was changed (the composition was changed from RA4 to RA8) compared to the configuration of Example A3. The bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example A3, and the overall evaluation was A rank (pass).

[0370] (Examples A8 to A11) Examples A8 to A11 are based on the configuration of Example A3, but while keeping the total belt thickness (and back thickness of 4.1 mm) constant, the ratio of the thickness of the second rubber layer (EPDM composition) to the first rubber layer (silicone rubber composition) is varied, thereby changing the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 39.0% (Example A8), 53.7% (Example A9), 70.7% (Example A3), 78.0% (Example A10), and 82.9% (Example A11). As a result, the bonding strength between the first rubber layer and the second rubber layer was the same as in Example A3 in all cases. Regarding durability and running life (maintenance of conveying function), in Example A8, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the high proportion of EPDM composition in the outer rubber layer increased rigidity and made it difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 12 (rating b). On the other hand, in Example A11, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the high proportion of silicone rubber composition in the outer rubber layer reduced rigidity near the teeth, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 16 (rating b). In Examples A9 and A10, no delamination between the first and second rubber layers or back surface cracking occurred during running, but tooth chipping occurred and failure (end of life) occurred (rating a). The overall rating was B rank (pass) for the toothed belts in Examples A8 and A11, and A rank (pass) for the toothed belts in Examples A9 and A10.

[0371] (Examples A12 to A14) Examples A12 to A14 are based on the configuration of Example A3, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (EPDM composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 62.5% (Example A12), 70.7% (Example A3), 78.9% (Example A13), and 82.1% (Example A14). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example A3. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples A12 and A13, no delamination between the first and second rubber layers or back cracks occurred during running, but tooth chipping occurred, resulting in failure (end of life) (rating a). In Example A14, which had the largest total belt thickness, cracks occurred on the back after a running time (relative value) of 14, resulting in failure (end of life) (rating b). The overall rating was B rank (pass) for the toothed belt in Example A14, and A rank (pass) for the toothed belts in Examples A12 and A13.

[0372] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0373] <Verification Results in Table 7> (Examples A15-A18) Examples A15-A18 are examples of toothed belts in which zinc methacrylate was added to the first rubber layer (silicone rubber composition) compared to the configuration of Comparative Example A1. When the amount of zinc methacrylate added was varied to 1 part by mass (Example A15: RA10), 2.5 parts by mass (Example A16: RA11), 5 parts by mass (Example A17: RA12), and 10 parts by mass (Example A18: RA13), the bonding strength between the first rubber layer and the second rubber layer in the state of an undriven belt improved to a passing level of c for Examples A15 and A16, and to an a passing level of a for Examples A17 and A18. Furthermore, this bonding strength was maintained even after driving.

[0374] Furthermore, regarding the running life, in Example A15, the first and second rubber layers separated and the belt failed (reached the end of its lifespan) at a running time (relative value) of 12 (rated b). In other words, it can be said that it can run 12 times longer than Comparative Example A1 (conveying performance is maintained). The running time (relative value) until failure was 16 in Example A16 (rated b), and in Examples A17 and A18, no separation of the first and second rubber layers occurred during running, and tooth chipping occurred at a running time (relative value) of 20, resulting in failure (reached the end of its lifespan) (rated a). In the overall evaluation, the toothed belts in Examples A15 and A16 were rated C (pass), and the toothed belts in Examples A17 and A18 were rated A (pass).

[0375] From these results, it was confirmed that adding zinc methacrylate to the first rubber layer (silicone rubber composition) also improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and improves the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0376] <Verification Results in Table 8> (Example A19) Example A19 is an example of a toothed belt in which the type of silicone rubber in the first rubber layer was changed (the composition was changed from RA12 to RA14) compared to the configuration of Example A17. The bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example A17, and the overall evaluation was A rank (pass).

[0377] (Examples A20 to A23) Examples A20 to A23 are based on the configuration of Example A17, but while keeping the total belt thickness (and back thickness of 4.1 mm) constant, the ratio of the thickness of the second rubber layer (EPDM composition) to the first rubber layer (silicone rubber composition) is varied, thereby changing the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 39.0% (Example A20), 53.7% (Example A21), 70.7% (Example A17), 78.0% (Example A22), and 82.9% (Example A23). As a result, the bonding strength between the first rubber layer and the second rubber layer was the same as in Example A17 in all cases. Regarding durability and running life (maintenance of conveying function), in Example A20, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the rigidity of the outer rubber layer increased, making it difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 12 (rating b). On the other hand, in Example A23, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the rigidity near the teeth was reduced due to the high proportion of silicone rubber composition in the outer rubber layer, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 16 (rating b). In Examples A21 and A22, tooth chipping occurred without delamination between the first and second rubber layers or cracking on the back surface during running (rating a). The overall rating was B rank (pass) for the toothed belts in Examples A20 and A23, and A rank (pass) for the toothed belts in Examples A21 and A22.

[0378] (Examples A24 to A26) Examples A24 to A26 are based on the configuration of Example A17, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (EPDM composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 62.5% (Example A24), 70.7% (Example A3), 78.9% (Example A25), and 82.1% (Example A26). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example A17. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples A24 and A25, no delamination between the first and second rubber layers or back cracks occurred during running, but tooth chipping occurred, resulting in failure (end of life) (rating a). In Example A26, which had the largest total belt thickness, cracks occurred on the back after a running time (relative value) of 14, resulting in failure (end of life) (rating b). The overall rating was B rank (pass) for the toothed belt in Example A26, and A rank (pass) for the toothed belts in Examples A24 and A25.

[0379] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0380] <Verification Results in Table 9> (Examples A27 to A30) Examples A27 to A30 are examples of toothed belts in which zinc methacrylate is added to both the first rubber layer (silicone rubber composition) and the second rubber layer (EPDM composition) compared to the configuration of Comparative Example A1.

[0381] Example A27 is a combination of the second rubber layer of Example A1 (composition RA2, 5 parts by mass of zinc methacrylate) and the first rubber layer of Example A16 (composition RA11, 2.5 parts by mass of zinc methacrylate). In Examples A1 and A16, the bonding strength between the first and second rubber layers was at a low level (rating C), and the overall rating was C (pass). In Example A27, no significant improvement in bonding strength was observed, and it was also rated C (pass).

[0382] Example A28 is a combination of the second rubber layer of Example A3 (composition RA4, 15 parts by mass of zinc methacrylate) and the first rubber layer of Example A17 (composition RA12, 5 parts by mass of zinc methacrylate). In Examples A3 and A17, the bonding strength between the first and second rubber layers was at a high level (rating a), and the overall rating was A rank (pass). However, in Example A28, the bonding strength was equivalent to that of Examples A3 and A17, and no significant improvement was observed.

[0383] Example A29 is a combination of the second rubber layer of Example A2 (composition RA3, 10 parts by mass of zinc methacrylate) and the first rubber layer of Example A16 (composition RA11, 2.5 parts by mass of zinc methacrylate). In Examples A2 and A16, the bonding strength between the first and second rubber layers was at a low level (rating c), and the overall rating was rank C (pass). However, in Example A29, the bonding strength was slightly improved compared to Examples A2 and A16, and the overall rating was rank B (pass).

[0384] Example A30 is a combination of the second rubber layer of Example A7 (composition RA8, 15 parts by mass of zinc methacrylate) and the first rubber layer of Example A19 (composition RA14, 5 parts by mass of zinc methacrylate). In Examples A7 and A19, the bonding strength between the first and second rubber layers was at a high level (rating a), and the overall rating was A rank (pass). In Example A30, the bonding strength was equivalent to that of Examples A7 and A19, and no significant improvement was observed.

[0385] Based on these results, it can be said that adding zinc methacrylate to either the first rubber layer (silicone rubber composition) or the second rubber layer (EPDM composition) improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and tends to improve the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0386] [Example B] Example B is an embodiment in which the outer rubber layer includes an intermediate layer, and the second rubber composition includes an ethylene-α-olefin elastomer. The raw materials used, the preparation method, the method for producing the measurement laminate (crosslinked molded body), and the evaluation method for the measurement laminate are shown below.

[0387] [EPDM Composition] Table 10 shows the formulations of the EPDM compositions (RB1, RB6) as the second rubber composition for forming the second rubber layer and the EPDM compositions (RB2 to RB5) as the third rubber composition for forming the intermediate layer.

[0388]

[0389] [Materials for EPDM Composition] EPDM1: Nordel IP 4520 manufactured by Dow Chemical Company, ethylene content 50% by mass, diene content (ethylidene norbornene content) 4.9% by mass, Mooney viscosity 20ML (1+4) 125℃ EPDM2: Nordel IP 3640 manufactured by Dow Chemical Company, ethylene content 55% by mass, diene content (ethylidene norbornene content) 1.8% by mass, Mooney viscosity 40ML (1+4) 125℃ Zinc methacrylate: R-20S manufactured by Asada Chemical Industries, Ltd., purity 85% by mass Paraffin-based oil: Diana Process Oil PW90 manufactured by Idemitsu Kosan Co., Ltd. Anti-aging agent: "Nocrack MB-O" manufactured by Ouchi Shinko Chemical Industry Co., Ltd., 2-mercaptobenzimidazole. Carbon black: "Seasto S" manufactured by Tokai Carbon Co., Ltd., average particle size 66 nm, iodine adsorption capacity 26 mg / g. Silica: "Ultrazil VN3" manufactured by Evonik Degussa Japan Co., Ltd., BET specific surface area 175 m². ２ / g Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.55 μm Organic peroxide 1: "Perbutyl P-40MB" manufactured by NOF Corporation, 1,3-bis(2-t-butylperoxyisopropyl)benzene, active ingredient 40% by mass

[0390] [Silicone Rubber Composition] The formulation of the first rubber composition (silicone rubber composition) for forming the first rubber layer is shown in Table 11.

[0391]

[0392] [Materials for the silicone rubber composition] Silicone rubber 1: "TSE270-5U" manufactured by Momentive Performance Materials Japan LLC Silicone rubber 2: "TSE261-6U" manufactured by Momentive Performance Materials Japan LLC Organic peroxide 2: "TC-8" manufactured by Momentive Performance Materials Japan LLC

[0393] [Tooth Fabric] A 2 / 2 twill canvas was woven using 155 dtex nylon 66 yarn as the warp and a composite yarn of 155 dtex nylon 66 yarn and 122 dtex urethane elastic yarn as the weft. The warp density was 137 threads / 3cm and the weft density was 81 threads / 3cm. The woven canvas was immersed in the RFL treatment solution shown in Table 12 and dried. Then, the dried canvas was further immersed in a rubber adhesive prepared by dissolving the uncrosslinked EPDM composition for rubber adhesive shown in Table 13 in methyl ethyl ketone at a ratio of 10% by mass, and dried to obtain a bonded canvas (tooth fabric precursor) with a thickness of 0.85 mm.

[0394]

[0395]

[0396] [Intermediate Fabric] A 2 / 2 twill canvas was woven using 235 dtex nylon 6 yarn as the warp and 44 dtex woolly processed nylon 6 yarn as the weft. The warp density was 90 threads / 3 cm and the weft density was 120 threads / 3 cm. The uncrosslinked EPDM composition for rubber adhesive shown in Table 14 was kneaded in a Banbury mixer, and 100 parts by mass of the EPDM composition was dissolved in 900 parts by mass of toluene to prepare the rubber adhesive. The woven canvas was immersed in the RFL solution shown in Table 12 and dried, and then immersed in the rubber adhesive and dried to obtain an adhesive-treated intermediate fabric (intermediate fabric precursor) with a thickness of 0.75 mm.

[0397]

[0398] [Reinforcement fabric] 0.5 mm thick nylon canvas

[0399] [Core wire (processed cord)] Three strands of 200 E glass filaments with a diameter of 9 μm (a strand designated ECG150 as described in JIS R 3413 (2012)) were aligned and immersed in the RFL solution (18-23°C) shown in Table 12 for 3 seconds. After that, they were heated and dried at 200-280°C for 3 minutes to form an RFL adhesive coating. After this bonding treatment, the three strands were twisted in the S direction with 8 twists per 10 cm to prepare a pre-twisted yarn (pre-twisted yarn S), and twisted in the Z direction with the same number of twists (pre-twisted yarn Z). Next, 13 pre-twisted yarns S were aligned and twisted in the Z direction with 8 twists per 10 cm to obtain a multi-twisted cord (multi-twisted cord Z). Similarly, thirteen strands of under-twisted yarn Z were aligned and twisted in the S direction at a twist rate of 8 times / 10 cm to obtain a multi-twisted cord (multi-twisted cord S). Each multi-twisted cord was passed through an overcoat solution (rubber glue prepared by dissolving the uncrosslinked rubber composition shown in Table 13 in methyl ethyl ketone at a ratio of 10% by mass) and then dried to produce treated cords (treated cord S and treated cord Z) with an adhesive film of the rubber composition. The total fineness of the treated cords was 1300-1400 tex, and the outer diameter was 1.2 mm.

[0400] [Preparation of Uncrosslinked Rubber Sheets] For the toothed belts produced in the examples and comparative examples, an uncrosslinked rubber sheet A having the composition shown in Table 10 was used to form the toothed rubber layer and the second rubber layer, and for the uncrosslinked rubber sheet B having the composition shown in Table 11 was used to form the first rubber layer. The rubber compositions were kneaded in a Banbury mixer and rolled with a calender roll to produce uncrosslinked rubber sheets.

[0401] Furthermore, as an uncrosslinked rubber sheet C for forming the intermediate layer of the second embodiment, an uncrosslinked rubber sheet (thickness 0.5 mm) was prepared using a rubber composition having the composition shown in Table 10.

[0402] [Lamination of Intermediate Layer Precursors] (Examples B1 to B14) A zinc methacrylate-containing solution was prepared by dissolving zinc methacrylate (R-20S, manufactured by Asada Chemical Industries, Ltd., purity 85% by mass) in toluene. The obtained solution was then applied with a brush to the entire surface of the uncrosslinked rubber sheet A (the surface that will be joined to the uncrosslinked rubber sheet B) to form the second rubber layer, and dried to produce an uncrosslinked rubber sheet A with the intermediate layer precursors laminated on top. In Example B1, the amount of zinc methacrylate attached was 70 g / m². ２ In Example B2, the concentration was 100 g / m². ２ In Example B3, the concentration was 150 g / m². ２ In Example B4, the concentration was 200 g / m². ２ In Examples B5 to B14, the concentration was 100 g / m². ２ The amount applied was adjusted to achieve this result.

[0403] (Examples B15 to B28) Using the prepared uncrosslinked rubber sheet C as an intermediate layer precursor, the uncrosslinked rubber sheet C was placed on the surface of the uncrosslinked rubber sheet A (the surface that joins with the uncrosslinked rubber sheet B) to produce an uncrosslinked rubber sheet A in which the intermediate layer precursor was laminated. The zinc methacrylate content in the rubber composition forming the uncrosslinked rubber sheet C was 5 parts by mass in Example B15 (RB2), 10 parts by mass in Example B16 (RB3), 15 parts by mass in Example B17 (RB4), 25 parts by mass in Example B18 (RB5), and 15 parts by mass in Examples B19 to B28 (RB4).

[0404] (Examples B29 to B42) Using the produced intermediate fabric precursor (adhesion-treated intermediate fabric) as an intermediate layer precursor, the intermediate fabric precursor was superimposed on the surface of uncrosslinked rubber sheet A (the surface to be bonded to uncrosslinked rubber sheet B), to produce an uncrosslinked rubber sheet A with the intermediate layer precursor laminated thereon. The content of zinc methacrylate in the rubber paste (rubber composition) used for the adhesion treatment of this intermediate fabric was 5 parts by mass in Example B29 (RB9), 10 parts by mass in Example B30 (RB10), 15 parts by mass in Example B31 (RB11), 25 parts by mass in Example B32 (RB12), and 15 parts by mass in Examples B33 to B42 (RB11).

[0405] [Adhesion (peeling force) test using test piece] A reinforcing fabric, an uncrosslinked rubber sheet for a first rubber layer (an uncrosslinked silicone rubber sheet which is uncrosslinked rubber sheet B, having a thickness of 2 mm, a width of 30 mm, and a length of 150 mm), an uncrosslinked rubber sheet for a second rubber layer with an intermediate layer precursor laminated in advance (an uncrosslinked EPDM sheet which is uncrosslinked rubber sheet A, having a thickness of 2 mm, a width of 30 mm, and a length of 150 mm), and a reinforcing fabric were stacked in this order (Comparative Example B1 had no intermediate layer precursor), and crosslinking molding was performed for 30 minutes in a press mold (surface pressure 2 MPa, 165°C). As shown in Fig. 6, a laminated body (crosslinked molded body) 26 in which a reinforcing fabric 21, a silicone rubber sheet 22, an intermediate layer 23, a sheet 24, and a reinforcing fabric 25 are bonded and integrated was produced. In Example B, the sheet 24 is an EPDM sheet.

[0406] In this laminated body 26, the interface between the silicone rubber sheet 22 and the sheet 24 is bonded over a length of 120 mm via the intermediate layer 23, and one end of each uncrosslinked rubber sheet was not bonded as shown in Fig. 6 to be used as gripping portions A and B (each having a length of 30 mm) in the tensile force measurement described later. The obtained laminated body 26 was cut into a width of 25 mm, thereby preparing a sample having a width of 25 mm, a length of 150 mm (bonding length 120 mm), and a thickness of 4 mm.

[0407] A grip portion A (a laminate of a reinforcing cloth 21 and a silicone rubber sheet 22) is gripped by the upper gripper of an autograph ("AGS-J10kN" manufactured by Shimadzu Corporation), and a grip portion B (a laminate of an intermediate layer 23, a sheet 24 and a reinforcing cloth 25) is gripped by the lower gripper. In accordance with JIS K 6256 (2013), the bonding interface is peeled by lifting the upper gripper at a speed of 50 mm / min, and the tensile strength (tensile force) at this time is recorded as peel strength (peel force). The measurement time was set to 2 minutes so that the moving distance of the upper gripper and the peeled portion were about 100 mm. The test was performed at a test temperature (atmospheric temperature) of 23°C, and the measurement was carried out after the sample was left to stand at the test temperature for 16 hours or more. Although the tensile force exhibits a wavy curve, the average value was obtained in accordance with Method E of JIS K 6274 (2018). Specifically, ignoring the initial rising curve at the start of the test, the average value of the maximum and minimum values among all peaks of the wavy curve was obtained.

[0408] Then, from the obtained peel strength (peel force), the bonding strength (adhesive force) between the first rubber layer (silicone rubber composition) and the intermediate layer was evaluated according to the following criteria.

[0409] (Judgment Criteria) a: Peel strength (peel force) per 25 mm width is 100 N or more b: Peel strength (peel force) per 25 mm width is 10 N or more and less than 100 N c: Peel strength (peel force) per 25 mm width is less than 10 N

[0410] As shown in Fig. 6, in this test, peeling occurs at the interface between the silicone rubber sheet and the intermediate layer. This interface is easier to peel than the interface between the EPDM sheet and the intermediate layer, and is the weakest portion, so it is a dominant factor for the durable life of the belt.

[0411] [Preparation of Toothed Belts] In Comparative Examples B1 to B2 and Examples B1 to B42, an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 10 was used as the uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 11 was used as the uncrosslinked rubber sheet B for forming the first rubber layer. A toothed belt with a tooth profile G8M, tooth height (including tooth cloth) 3.35 mm, tooth pitch 8 mm, number of teeth 100, core wire pitch 1.45 mm, and circumference 800 mm was manufactured by the first manufacturing method without pre-forming (c) described in the [Modes for Carrying Out the Invention] section. The width of the toothed belt used for measuring bonding strength (peel strength) was 36.0 mm, and the width of the toothed belt used for the durability running test was 15.0 mm.

[0412] (Comparative Example B1) Uncrosslinked rubber composition RB1 was used as uncrosslinked rubber sheet A, and uncrosslinked rubber composition RB7 was used as uncrosslinked rubber sheet B. In the molding process, an uncrosslinked belt molded body (uncrosslinked molded body) was formed without using an intermediate layer precursor. This was crosslinked to form a sleeve-shaped crosslinked molded body (crosslinked belt sleeve), and a toothed belt was produced by cutting it to a predetermined width. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0413] (Comparative Example B2) A toothed belt was manufactured in the same manner as in Comparative Example B1, except that uncrosslinked rubber sheet A and uncrosslinked rubber sheet B were bonded together with an epoxy resin adhesive. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0414] (Examples B1 to B4) Toothed belts were manufactured in the same manner as in Comparative Example B1, except that the laminated sheet described in the section [Lamination of Intermediate Layer Precursors] (uncrosslinked rubber sheet A with intermediate layer precursors laminated) was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0415] (Example B5) A toothed belt was manufactured in the same manner as in Example B2, except that an uncrosslinked rubber composition RB6 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0416] (Example B6) A toothed belt was manufactured in the same manner as in Example B2, except that an uncrosslinked rubber composition RB8 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A60, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0417] (Example B7) A toothed belt was manufactured in the same manner as in Example B2, except that uncrosslinked rubber composition RB6 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RB8 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A60, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0418] (Examples B8 to B14) Toothed belts were manufactured in the same manner as in Example B2, except that the average thickness of the first rubber layer and the second rubber layer (and consequently the thickness ratio of the first rubber layer to the outer rubber layer) was adjusted to the values ​​shown in Table 16.

[0419] (Examples B15 to B18) Toothed belts were manufactured in the same manner as in Comparative Example B1, except that the laminated sheet described in the section on [Lamination of Intermediate Layer Precursors] (uncrosslinked rubber sheet A with uncrosslinked rubber sheet C as an intermediate layer precursor laminated on top) was used as the uncrosslinked rubber sheet A. The average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.4 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 64.4%.

[0420] (Example B19) A toothed belt was manufactured in the same manner as in Example B17, except that an uncrosslinked rubber composition RB6 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.4 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 64.4%.

[0421] (Example B20) A toothed belt was manufactured in the same manner as in Example B17, except that an uncrosslinked rubber composition RB8 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A60, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.4 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 64.4%.

[0422] (Example B21) A toothed belt was manufactured in the same manner as in Example B17, except that uncrosslinked rubber composition RB6 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RB8 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A60, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.4 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 64.4%.

[0423] (Examples B22 to B28) Toothed belts were manufactured in the same manner as in Example B17, except that the average thickness of the first rubber layer and the second rubber layer (and consequently the thickness ratio of the first rubber layer to the outer rubber layer) was adjusted to the values ​​shown in Table 18.

[0424] (Examples B29 to B32) Toothed belts were manufactured in the same manner as in Comparative Example B1, except that the laminated sheet described in the section on [Lamination of Intermediate Layer Precursors] (uncrosslinked rubber sheet A with an intermediate cloth precursor laminated as an intermediate layer precursor) was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.2 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 67.4%.

[0425] (Example B33) A toothed belt was manufactured in the same manner as in Example B31, except that an uncrosslinked rubber composition RB6 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.2 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 67.4%.

[0426] (Example B34) A toothed belt was manufactured in the same manner as in Example B31, except that an uncrosslinked rubber composition RB8 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A60, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.2 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 67.4%.

[0427] (Example B35) A toothed belt was manufactured in the same manner as in Example B31, except that uncrosslinked rubber composition RB6 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RB8 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A60, the average thickness of the first rubber layer was 2.9 mm, the thickness of the intermediate layer was 0.2 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 67.4%.

[0428] (Examples B36 to B42) Toothed belts were manufactured in the same manner as in Example B31, except that the average thickness of the first rubber layer and the second rubber layer (and consequently the thickness ratio of the first rubber layer to the outer rubber layer) was adjusted to the values ​​shown in Table 20.

[0429] [Measurement of bonding strength (peel strength) of toothed belts] A 15 cm section was cut from the fabricated endless toothed belt in the length direction to obtain a sample for measurement, which was used as a sample in an unrunned state. Similarly, a sample was also taken from the endless toothed belt after it had been run, which was used as a sample in a runned state. A two-axis running test machine consisting of a drive (Dr.) pulley with a diameter of 56.02 mm and a driven (Dn.) pulley with a diameter of 56.02 mm was used to run the toothed belt. On the two-axis running test machine, a toothed belt with a width of 36.0 mm was mounted on each pulley, the shaft load was set to 128 N, the rotation speed of the drive pulley was set to 3600 rpm, and the load of the driven pulley was set to 4.86 N·m, and the belt was run for 720 hours at an ambient temperature of 100°C.

[0430] The peel strength of each sample was measured as follows: On the end face of a sample taken from an endless belt, an incision was made with a cutting tool at the interface between the first rubber layer and the intermediate layer to create gripping portions A and B. Then, gripping portion A (first rubber layer) was gripped with the upper gripper of an Autograph (AGS-J10kN, manufactured by Shimadzu Corporation), and gripping portion B (laminated structure of intermediate layer, second rubber layer, and teeth) was gripped with the lower gripper. In the same manner as in the "Measurement of bonding strength (peel strength) using a test piece" described above, gripping portion A and gripping portion B were pulled apart (peel angle of 180°, i.e., gripping portion A was folded back 180° relative to gripping portion B), and the tensile strength (tensile force) when the interface was peeled was recorded as the peel strength (peel force). The peel strength was calculated by converting the measured tensile force to a value per 25 mm width.

[0431] Based on the obtained peel strength (peel force), the bonding strength (adhesion) between the first rubber layer (silicone rubber composition) and the intermediate layer was determined according to the following criteria.

[0432] (Judgment Criteria) a: Peel strength (peeling force) per 25 mm width is 40 N or more b: Peel strength (peeling force) per 25 mm width is 30 N or more but less than 40 N c: Peel strength (peeling force) per 25 mm width is 10 N or more but less than 30 N d: Peel strength (peeling force) per 25 mm width is less than 10 N, or peeling occurs during driving

[0433] [Durability Running Test] To confirm the transport performance on the reverse side, the superiority or inferiority of the belts was verified using the belt's durability running life as an indicator. In other words, since transport performance is lost due to failure during durable running (cracks on the reverse side, delamination of the reverse layer), the durability running life (running time until failure occurs) was used as an indicator of "sustainability of transport performance" to determine the superiority or inferiority of the belts.

[0434] The durability running test was conducted using the same two-axis running test machine used for measuring joint strength (peel strength). A toothed belt with a width of 15.0 mm was used, with an axle load of 442 N, a drive pulley rotation speed of 3600 rpm, a driven pulley load of 10.33 N·m, and an ambient temperature of 100°C. The running time until failure occurred in the toothed belt was measured as the running life.

[0435] The travel time until this failure occurs (hereinafter referred to as "travel time") is shown as a relative value, with the travel time of Comparative Example B1 set to 1.0. If this relative value is greater than 1.0, it indicates a longer travel life than the toothed belt of Comparative Example B1 (i.e., superior sustained transport performance), and if it is 1.0 or less, it indicates that it is equivalent to or less than the toothed belt of Comparative Example B1.

[0436] (Criteria for judging endurance driving tests) a: Driving time (relative value) until failure is 18 or more b: Driving time (relative value) until failure is 10 or more but less than 18 c: Driving time (relative value) until failure is greater than 1.0 but less than 10 d: Driving time (relative value) until failure is 1.0 or less

[0437] [Overall Evaluation] Considering three items for toothed belts—bonding strength in the non-running state (bonding strength between the first and second rubber layers), bonding strength after running (maintainability from the non-running state), and durable running life (maintenance of conveying performance)—the overall superiority or inferiority was determined (ranked) according to the following criteria. From the perspective of product practicality, ranks A, B, and C were deemed acceptable, and rank D was deemed unacceptable.

[0438] (Judgment Criteria for Comprehensive Judgment) Rank A: All judgments of the above three items are judgment a Rank B: Judgments of the above three items include judgment b (do not include judgments c or d) Rank C: Judgments of the above three items include judgment c (do not include judgment d) Rank D: Judgments of the above three items include judgment d

[0439] The evaluation results of Comparative Examples B1 to B2 and Examples B1 to B42 are shown in Tables 15 to 20.

[0440]

[0441]

[0442]

[0443]

[0444]

[0445]

[0446] <Verification Results of Table 15> (Comparative Examples B1 and B2) Comparative Example B1 is an example of a toothed belt obtained by joining a first rubber layer not containing zinc methacrylate (RB7) and a second rubber layer not containing zinc methacrylate (RB1). Comparative Example B2 is an example of a toothed belt obtained by joining the first rubber layer (RB7) and the second rubber layer (RB1) of Comparative Example B1 with an epoxy resin adhesive.

[0447] In all of the examples, the bonding strength between the first rubber layer and the second rubber layer was low in the state of an unused belt (judgment d), and since the first rubber layer and the second rubber layer peeled off during running, the bonding strength after running could not be measured (judgment d). It was confirmed that sufficient bonding strength could not be obtained when zinc methacrylate was not used.

[0448] In addition, regarding the running life (running time to failure (relative value)) in the durability running test, peeling occurred between the first rubber layer and the second rubber layer at an early stage, resulting in a low level (judgment d), and the comprehensive judgment was Rank D (unacceptable).

[0449] (Examples B1-B4) Examples B1-B4 are examples of toothed belts in which zinc methacrylate is sprayed at the bonding interface between the first rubber layer and the second rubber layer to perform crosslinking and bond the first rubber layer and the second rubber layer. The amount of zinc methacrylate sprayed at the bonding interface was 70 g / m ２ (Example B1), 100 g / m ２ (Example B2), 150 g / m ２ (Example B3), 200 g / m ２ As a result of the variation in (Example B4), the bonding strength between the first rubber layer and the second rubber layer in the unused belt state improved to a passing level (rating b) in Example B1 and to an passing level (rating a) in Examples B2 to B4. Furthermore, this bonding strength was maintained even after use.

[0450] Furthermore, regarding the running life, in Example B1, the first and second rubber layers separated and the belt failed (reached the end of its lifespan) at a running time (relative value) of 14 (judgment b). In other words, it can be said that it can run 14 times longer than Comparative Example B1 (conveying performance is maintained). In Examples B2 to B4, the running time (relative value) until failure was 20, when tooth breakage occurred and the belt failed (reached the end of its lifespan) without any separation of the first and second rubber layers during running (judgment a). In the overall judgment, the toothed belt in Example B1 was ranked C (pass), and the toothed belts in Examples B2 to B4 were ranked A (pass).

[0451] From these results, it was confirmed that spraying zinc methacrylate on the bonding interface improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and improves the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0452] (Examples B5 to B7) Example B5 is an example of a toothed belt in which the type of EPDM in the second rubber layer is changed from that of Example B2 (the composition is changed from RB1 to RB6). Example B6 is an example of a toothed belt in which the type of silicone rubber in the first rubber layer is changed from that of Example B2 (the composition is changed from RB7 to RB8). Example B7 is an example of a toothed belt in which the type of EPDM in the second rubber layer is changed from that of Example B2 (the composition is changed from RB1 to RB6) and the type of silicone rubber in the first rubber layer is changed (the composition is changed from RB7 to RB8). In all of these toothed belts, the bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example B2, and the overall evaluation was A rank (pass).

[0453] <Verification Results in Table 16> (Examples B8 to B11) Examples B8 to B11 are based on the configuration of Example B2, and while keeping the total belt thickness (and back thickness of 4.1 mm) constant, the ratio of the thickness of the second rubber layer (EPDM composition) to the first rubber layer (silicone rubber composition) was varied, thereby changing the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". In other words, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 39.0% (Example B8), 53.7% (Example B9), 70.7% (Example B2), 78.0% (Example B10), and 82.9% (Example B11). As a result, the bonding strength between the first rubber layer and the second rubber layer was the same as in Example B2 in all cases. Regarding durability and running life (maintenance of conveying function), in Example B8, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the high proportion of EPDM composition in the outer rubber layer increased rigidity and made it difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 14 (rating b). On the other hand, in Example B11, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the high proportion of silicone rubber composition in the outer rubber layer reduced rigidity near the teeth, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 16 (rating b). In Examples B9 and B10, no delamination between the first and second rubber layers or back surface cracking occurred during running, but tooth chipping occurred and failure (end of life) occurred (rating a). The overall rating was B rank (pass) for the toothed belts in Examples B8 and B11, and A rank (pass) for the toothed belts in Examples B9 and B10.

[0454] (Examples B12 to B14) Examples B12 to B14 are based on the configuration of Example B2, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (EPDM composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 62.5% (Example B12), 70.7% (Example B2), 78.9% (Example B13), and 82.1% (Example B14). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example B2. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples B12 and B13, tooth breakage occurred during running without delamination between the first and second rubber layers or cracking on the back surface (a rating). However, in Example B14, which had the largest total belt thickness, cracks occurred on the back surface after a running time (relative value) of 14, resulting in failure (b rating). The overall rating was B rank (pass) for the toothed belt in Example B14, and A rank (pass) for the toothed belts in Examples B12 and B13.

[0455] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0456] <Verification Results in Table 17> (Examples B15-B18) Examples B15-B18 are examples of toothed belts in which an uncrosslinked rubber sheet containing zinc methacrylate is interposed at the interface between the first rubber layer and the second rubber layer, and the two layers are joined by crosslinking. When the amount of zinc methacrylate added to the uncrosslinked rubber sheet was varied to 5 parts by mass (Example B15), 10 parts by mass (Example B16), 15 parts by mass (Example B17), and 25 parts by mass (Example B18), the bonding strength between the first rubber layer and the second rubber layer in the belt before use improved to a passing level (e.g., a c rating for Examples B15 and B16, and an a rating for Examples B17 and B18). Furthermore, this bonding strength was maintained even after use.

[0457] Furthermore, regarding the running life, the toothed belts in Examples B15 and B16 failed (reached the end of their lifespan) at a running time (relative value) of 12 and 14 respectively (judgment b). In other words, Example B15 can run 12 times longer than Comparative Example B1, and Example B16 can run 14 times longer than Comparative Example B1 (conveying performance is maintained). In Examples B17 and B18, the running time (relative value) until failure was 20, with no separation of the first and second rubber layers during running, and tooth chipping occurred, resulting in failure (reached the end of their lifespan) (judgment a). In the overall judgment, the toothed belts in Examples B15 and B16 were ranked C (pass), and the toothed belts in Examples B17 and B18 were ranked A (pass).

[0458] From the above results, it was confirmed that by placing a crosslinked rubber composition containing zinc methacrylate at the bonding interface, the bonding strength between the first rubber layer and the second rubber layer is improved (peeling between the first and second rubber layers becomes less likely), and the durability life of the toothed belt is improved (the sustainability of conveying performance is improved).

[0459] (Examples B19 to B21) Example B19 is an example of a toothed belt in which the type of EPDM in the second rubber layer is changed from that of Example B17 (the composition is changed from RB1 to RB6). Example B20 is an example of a toothed belt in which the type of silicone rubber in the first rubber layer is changed from that of Example B17 (the composition is changed from RB7 to RB8). Example B21 is an example of a toothed belt in which the type of EPDM in the second rubber layer is changed from that of Example B17 (the composition is changed from RB1 to RB6) and the type of silicone rubber in the first rubber layer is changed (the composition is changed from RB7 to RB8). The bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example B17, and the overall evaluation was A rank (pass).

[0460] <Verification Results in Table 9> (Examples B22 to B25) Examples B22 to B25 are based on the configuration of Example B17, but with the total belt thickness (and back thickness of 4.5 mm) kept constant, and the ratio of the thickness of the second rubber layer (EPDM composition) to the first rubber layer (silicone rubber composition) is varied, thereby changing the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". In other words, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 35.6% (Example B22), 51.1% (Example B23), 64.4% (Example B17), 71.1% (Example B24), and 82.2% (Example B25). As a result, the bonding strength between the first rubber layer and the second rubber layer was the same as in Example B17 in all cases. Regarding durability and running life (maintenance of conveying function), in Example B22, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the high proportion of EPDM composition in the outer rubber layer increased rigidity and made it difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 12 (rating b). On the other hand, in Example B25, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the high proportion of silicone rubber composition in the outer rubber layer reduced rigidity near the teeth, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 14 (rating b). In Examples B23 and B24, no delamination between the first and second rubber layers or back surface cracking occurred during running, but tooth chipping occurred and failure (end of life) occurred (rating a). The overall rating was B rank (pass) for the toothed belts in Examples B22 and B25, and A rank (pass) for the toothed belts in Examples B23 and B24.

[0461] (Examples B26 to B28) Examples B26 to B28 are based on the configuration of Example B17, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (EPDM composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 55.6% (Example B26), 64.4% (Example B17), 77.5% (Example B27), and 81.4% (Example B28). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example B17. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples B26 and B27, no delamination between the first and second rubber layers or back cracks occurred during running, but tooth chipping occurred, resulting in failure (end of life) (rating a). In Example B28, which had the largest total belt thickness, cracks occurred on the back after a running time (relative value) of 14, resulting in failure (end of life) (rating b). The overall rating was B rank (pass) for the toothed belt in Example B28, and A rank (pass) for the toothed belts in Examples B26 and B27.

[0462] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0463] <Verification Results in Table 10> (Examples B29-B32) Examples B29-B32 are examples of toothed belts in which the first and second rubber layers are joined by cross-linking with an intermediate cloth to which zinc methacrylate is attached at the bonding interface between the first and second rubber layers. The zinc methacrylate content in the rubber adhesive used to bond the intermediate cloth was varied to 5 parts by mass (Example B29), 10 parts by mass (Example B30), 15 parts by mass (Example B31), and 25 parts by mass (Example B32). As a result, the bonding strength between the first and second rubber layers in the undriven belt state improved to a passing level of c in Examples B29 and B30, and to an a in Examples B31 and B32. Furthermore, this bonding strength was maintained even after driving.

[0464] Furthermore, regarding the running life, the toothed belts in Example B29 failed (reached the end of their lifespan) at a running time (relative value) of 12 in Example B29 and at a running time (relative value) of 14 in Example B30 (judgment b). In other words, Example B29 can run 12 times longer than Comparative Example B1, and Example B30 can run 14 times longer than Comparative Example B1 (conveying performance is maintained). In Examples B31 and B32, the running time (relative value) until failure was 20 minutes, during which tooth chipping occurred and the belt failed (reached the end of its lifespan) without any separation between the first and second rubber layers during running (judgment a). In the overall judgment, the toothed belts in Examples B29 and B30 were ranked C (pass), and the toothed belts in Examples B31 and B32 were ranked A (pass).

[0465] From these results, it was confirmed that by placing an intermediate cloth with zinc methacrylate attached at the bonding interface, the bonding strength between the first rubber layer and the second rubber layer is improved (delamination between the first and second rubber layers becomes less likely), and the durability life of the toothed belt is improved (the sustainability of conveying performance is improved).

[0466] (Examples B33 to B35) Example B33 is an example of a toothed belt in which the type of EPDM in the second rubber layer is changed from that of Example B31 (the composition is changed from RB1 to RB6). Example B34 is an example of a toothed belt in which the type of silicone rubber in the first rubber layer is changed from that of Example B31 (the composition is changed from RB7 to RB8). Example B35 is an example of a toothed belt in which the type of EPDM in the second rubber layer is changed from that of Example B31 (the composition is changed from RB1 to RB6) and the type of silicone rubber in the first rubber layer is changed (the composition is changed from RB7 to RB8). The bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example B31, and the overall evaluation was A rank (pass).

[0467] <Verification Results in Table 11> (Examples B36 to B39) Examples B36 to B39 are based on the configuration of Example B31, and while keeping the total belt thickness (and back thickness of 4.3 mm) constant, the ratio of the thickness of the second rubber layer (EPDM composition) to the first rubber layer (silicone rubber composition) was varied, thereby changing the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 37.2% (Example B36), 53.5% (Example B37), 67.4% (Example B31), 74.4% (Example B38), and 86.0% (Example B39). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example B31. Regarding durability and running life (maintenance of conveying function), in Example B36, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the high proportion of EPDM composition in the outer rubber layer increased rigidity and made it difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 14 (rating b). On the other hand, in Example B39, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the high proportion of silicone rubber composition in the outer rubber layer reduced rigidity near the teeth, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 16 (rating b). In Examples B37 and B38, no delamination between the first and second rubber layers or back surface cracking occurred during running, but tooth chipping occurred and failure (end of life) occurred (rating a). The overall rating was B rank (pass) for the toothed belts in Examples B36 and B39, and A rank (pass) for the toothed belts in Examples B37 and B38.

[0468] (Examples B40 to B42) Examples B40 to B42 are based on the configuration of Example B31, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (EPDM composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 58.8% (Example B40), 67.4% (Example B31), 79.7% (Example B41), and 83.3% (Example B42). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example B31. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples B40 and B41, tooth breakage occurred during running without delamination between the first and second rubber layers or cracking on the back surface (rated a). However, in Example B42, which had the largest total belt thickness, cracks occurred on the back surface after a running time (relative value) of 14, resulting in failure (rated b). The overall rating was B rank (pass) for the toothed belt in Example B42, and A rank (pass) for the toothed belts in Examples B40 and B41.

[0469] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0470] From the above, it was confirmed that the adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer can be improved by interposing an intermediate layer formed of a binder component containing an unsaturated carboxylic acid metal salt between the silicone rubber layer forming the conveying surface of the transmission belt and the ethylene-α-olefin elastomer layer.

[0471] [Example C] Example C is an embodiment in which the outer rubber layer does not contain an intermediate layer, and the second rubber composition contains hydrogenated nitrile rubber. The raw materials used, the preparation method, the method for producing the measurement laminate (crosslinked molded body), and the evaluation method for the measurement laminate are shown below.

[0472] [HNBR Composition] The formulation of the second rubber composition (HNBR composition) for forming the second rubber layer is shown in Table 21.

[0473]

[0474] [Materials for HNBR composition] HNBR1: Zetpol 2010 manufactured by Nippon Zeon Co., Ltd., iodine value 11 mg / 100 mg HNBR2: Therban 3446 manufactured by Arlanxeo, residual double bond amount 5.5% Zinc methacrylate: R-20S manufactured by Asada Chemical Industries, Ltd., purity 85% by mass Stearic acid: Tsubaki stearic acid manufactured by NOF Corporation Carbon black: Seest S manufactured by Tokai Carbon Co., Ltd., average particle size 66 nm, iodine adsorption amount 26 mg / g Silica: Ultrazil VN3 manufactured by Evonik Degussa Japan Co., Ltd., BET specific surface area 175 m² ２ / g Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.55 μm Anti-aging agent: p,p'-dioctyldiphenylamine, "Nonflex OD3" manufactured by Seiko Chemical Co., Ltd. Organic peroxide: "Perbutyl P-40MB" manufactured by NOF Corporation, 1,3-bis(2-t-butylperoxyisopropyl)benzene, active ingredient 40% by mass Co-crosslinking agent: N,N'-m-phenylenedimaleimide, "Balnok PM" manufactured by Ouchi Shinko Chemical Co., Ltd. Plasticizer: "ADEKA Sizer RS700" manufactured by ADEKA Corporation

[0475] [Silicone Rubber Composition] The formulation of the first rubber composition (silicone rubber composition) for forming the first rubber layer is shown in Table 22.

[0476]

[0477] [Materials for the silicone rubber composition] Silicone rubber 1: "TSE270-5U" manufactured by Momentive Performance Materials Japan LLC Silicone rubber 2: "TSE261-6U" manufactured by Momentive Performance Materials Japan LLC Zinc methacrylate: "R-20S" manufactured by Asada Chemical Industries, Ltd., purity 85% by mass Organic peroxide: "TC-8" manufactured by Momentive Performance Materials Japan LLC

[0478] [Tooth Fabric] A 2 / 2 twill canvas was woven using 155 dtex nylon 66 yarn as the warp and a composite yarn of 155 dtex nylon 66 yarn and 122 dtex urethane elastic yarn as the weft. The warp density was 137 threads / 3 cm and the weft density was 81 threads / 3 cm. The woven canvas was immersed in the RFL treatment solution shown in Table 23 and dried. Then, the dried canvas was further immersed in a rubber adhesive prepared by dissolving the uncrosslinked HNBR composition for rubber adhesive shown in Table 24 in methyl ethyl ketone at a ratio of 10% by mass, and dried to obtain a bonded canvas (tooth fabric precursor) with a thickness of 0.85 mm.

[0479]

[0480]

[0481] [Reinforcement fabric] 0.5 mm thick nylon canvas

[0482] [Core wire (processed cord)] Three strands of 200 E glass filaments with a diameter of 9 μm (a strand designated ECG150 as described in JIS R 3413 (2012)) were aligned and immersed in the RFL solution (18-23°C) shown in Table 23 for 3 seconds. After that, they were heated and dried at 200-280°C for 3 minutes to form an RFL adhesive coating. After this bonding treatment, the three strands were twisted in the S direction with 8 twists per 10 cm to prepare a pre-twisted yarn (pre-twisted yarn S), and twisted in the Z direction with the same number of twists (pre-twisted yarn Z). Next, thirteen pre-twisted yarns S were aligned and twisted in the Z direction with 8 twists per 10 cm to obtain a multi-twisted cord (multi-twisted cord Z). Similarly, thirteen strands of under-twisted yarn Z were aligned and twisted in the S direction at a twist rate of 8 times / 10 cm to obtain a multi-twisted cord (multi-twisted cord S). Each multi-twisted cord was passed through an overcoat solution (rubber glue prepared by dissolving the uncrosslinked rubber composition shown in Table 24 in methyl ethyl ketone at a ratio of 10% by mass) and then dried to produce treated cords (treated cord S and treated cord Z) with an adhesive film of the rubber composition. The total fineness of the treated cords was 1300-1400 tex, and the outer diameter was 1.2 mm.

[0483] [Preparation of Uncrosslinked Rubber Sheets] For the toothed belts to be made in the examples and comparative examples, an uncrosslinked rubber sheet A having the composition shown in Table 21 was used to form the toothed rubber layer and the second rubber layer, and for the uncrosslinked rubber sheet B having the composition shown in Table 22 was used to form the first rubber layer. The rubber compositions were kneaded in a Banbury mixer and rolled with calender rolls to produce uncrosslinked rubber sheets.

[0484] [Adhesion (peel strength) test on test specimens] The reinforcing cloth, uncrosslinked rubber sheet for the first rubber layer (uncrosslinked silicone rubber sheet, which is uncrosslinked rubber sheet B, thickness 2 mm, width 30 mm, length 150 mm), uncrosslinked rubber sheet for the second rubber layer (uncrosslinked HNBR sheet, which is uncrosslinked rubber sheet A, thickness 2 mm, width 30 mm, length 150 mm), and reinforcing cloth were stacked in that order, and crosslinking molding was performed in a press die (surface pressure 2 MPa, 165°C) for 30 minutes to produce a laminate (crosslinked molded body) 15 in which the reinforcing cloth 11, silicone rubber sheet 12, sheet 13, and reinforcing cloth 14 were joined together to form an integrated structure, as shown in Figure 5. In Example C, sheet 13 is an HNBR sheet.

[0485] In this laminate 15, the interface between the silicone rubber sheet 12 and the sheet 13 was joined over a length of 120 mm, while one end of each uncrosslinked rubber sheet was not joined, as shown in Figure 5, in order to be used as gripping portions A and B (30 mm each) for the tensile force measurement described later. The resulting laminate 15 was cut to a width of 25 mm to produce a sample with a width of 25 mm, a length of 150 mm (joining length 120 mm), and a thickness of 4 mm.

[0486] The Autograph (AGS-J10kN, manufactured by Shimadzu Corporation) was used to grip portion A (a laminate of reinforcing fabric 11 and silicone rubber sheet 12) with its upper grip and grip portion B (a laminate of sheet 13 and reinforcing fabric 14) with its lower grip. The upper grip was raised at a speed of 50 mm / min according to JIS K 6256 (2013) to separate the bonding interface, and the tensile strength (tensile force) at that time was recorded as the peel strength (peel force). The measurement time was set to 2 minutes so that the movement distance of the upper grip and the peeled portion were approximately 100 mm. The test temperature (ambient temperature) was 23°C, and the sample was measured after being left at the test temperature for 16 hours or more. The tensile force showed a wavy curve, and its average value was calculated according to Method E of JIS K 6274 (2018). In other words, ignoring the initial upward curve at the start of the test, we calculated the average of the maximum and minimum values ​​among all the peaks of the wave curve.

[0487] Then, based on the obtained peel strength (peeling force), the bonding strength (adhesion) between the first rubber layer (silicone rubber composition) and the second rubber layer (HNBR composition) was determined according to the following criteria.

[0488] (Judgment Criteria) a: Peel strength (peeling force) per 25 mm width is 100 N or more b: Peel strength (peeling force) per 25 mm width is 50 N or more but less than 100 N c: Peel strength (peeling force) per 25 mm width is less than 50 N

[0489] [Preparation of Toothed Belts] In Comparative Examples C1 to C2 and Examples C1 to C30, an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 21 was used as the uncrosslinked rubber sheet A for forming the tooth rubber layer and the second rubber layer, and an uncrosslinked rubber sheet formed from a rubber composition having the composition shown in Table 22 was used as the uncrosslinked rubber sheet B for forming the first rubber layer. A toothed belt with tooth type G8M, tooth height (including tooth cloth) 3.35 mm, tooth pitch 8 mm, number of teeth 100, core wire pitch 1.45 mm, and circumference 800 mm was manufactured by the first manufacturing method without pre-forming as described in the [Modes for Carrying Out the Invention] section (a). The width of the toothed belt used for measuring bonding strength (peel strength) was 36.0 mm, and the width of the toothed belt used for the durability running test was 15.0 mm.

[0490] (Comparative Example C1) Uncrosslinked rubber composition RC1 was used as uncrosslinked rubber sheet A, and uncrosslinked rubber composition RC9 was used as uncrosslinked rubber sheet B. In the molding process, an uncrosslinked belt molded body (uncrosslinked molded body) was formed. This was crosslinked to form a sleeve-shaped crosslinked molded body (crosslinked belt sleeve), and a toothed belt was produced by cutting it to a predetermined width. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0491] (Comparative Example C2) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that uncrosslinked rubber sheet A and uncrosslinked rubber sheet B were bonded together with an epoxy resin adhesive. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0492] (Example C1) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that an uncrosslinked rubber composition RC2 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0493] (Example C2) A toothed belt was manufactured in the same manner as in Example C1, except that an uncrosslinked rubber composition RC3 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0494] (Example C3) A toothed belt was manufactured in the same manner as in Example C1, except that an uncrosslinked rubber composition RC4 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0495] (Example C4) A toothed belt was manufactured in the same manner as in Example C1, except that an uncrosslinked rubber composition RC5 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0496] (Example C5) A toothed belt was manufactured in the same manner as in Example C1, except that an uncrosslinked rubber composition RC6 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0497] (Example C6) A toothed belt was manufactured in the same manner as in Example C1, except that an uncrosslinked rubber composition RC7 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0498] (Example C7) A toothed belt was manufactured in the same manner as in Example C3, except that an uncrosslinked rubber composition RC8 was used as the uncrosslinked rubber sheet A. The back hardness of the first rubber layer was A50, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0499] (Example C8) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 1.6 mm and the average thickness of the second rubber layer was 2.5 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 39.0%.

[0500] (Example C9) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 2.2 mm and the average thickness of the second rubber layer was 1.9 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 53.7%.

[0501] (Example C10) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 3.2 mm and the average thickness of the second rubber layer was 0.9 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.0%.

[0502] (Example C11) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 3.4 mm and the average thickness of the second rubber layer was 0.7 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.9%.

[0503] (Example C12) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 2.0 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 62.5%.

[0504] (Example C13) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 4.5 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.9%.

[0505] (Example C14) A toothed belt was manufactured in the same manner as in Example C3, except that the average thickness of the first rubber layer was 5.5 mm. The back hardness of the first rubber layer was A50, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.1%.

[0506] (Example C15) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that an uncrosslinked rubber composition RC10 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A51, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0507] (Example C16) A toothed belt was manufactured in the same manner as in Example C15, except that an uncrosslinked rubber composition RC11 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A52, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0508] (Example C17) A toothed belt was manufactured in the same manner as in Example C15, except that an uncrosslinked rubber composition RC12 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A53, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0509] (Example C18) A toothed belt was manufactured in the same manner as in Example C15, except that an uncrosslinked rubber composition RC13 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A55, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0510] (Example C19) A toothed belt was manufactured in the same manner as in Example C15, except that an uncrosslinked rubber composition RC14 was used as the uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A63, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0511] (Example C20) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 1.6 mm and the average thickness of the second rubber layer was 2.5 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 39.0%.

[0512] (Example C21) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 2.2 mm and the average thickness of the second rubber layer was 1.9 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 53.7%.

[0513] (Example C22) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 3.2 mm and the average thickness of the second rubber layer was 0.9 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.0%.

[0514] (Example C23) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 3.4 mm and the average thickness of the second rubber layer was 0.7 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.9%.

[0515] (Example C24) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 2.0 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 62.5%.

[0516] (Example C25) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 4.5 mm. The back hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 78.9%.

[0517] (Example C26) A toothed belt was manufactured in the same manner as in Example C17, except that the average thickness of the first rubber layer was 5.5 mm. The back surface hardness of the first rubber layer was A53, and the thickness ratio of the first rubber layer to the outer rubber layer was 82.1%.

[0518] (Example C27) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that uncrosslinked rubber composition RC2 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RC11 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A52, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0519] (Example C28) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that uncrosslinked rubber composition RC4 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RC12 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A53, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0520] (Example C29) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that uncrosslinked rubber composition RC2 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RC10 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A52, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0521] (Example C30) A toothed belt was manufactured in the same manner as in Comparative Example C1, except that uncrosslinked rubber composition RC8 was used as uncrosslinked rubber sheet A and uncrosslinked rubber composition RC14 was used as uncrosslinked rubber sheet B. The back hardness of the first rubber layer was A63, the average thickness of the first rubber layer was 2.9 mm, the average thickness of the second rubber layer was 1.2 mm, and the thickness ratio of the first rubber layer to the outer rubber layer was 70.7%.

[0522] [Measurement of bonding strength (peel strength) of toothed belts] A 15 cm section was cut from the fabricated endless toothed belt in the length direction to obtain a sample for measurement, which was used as a sample in an unrunned state. Similarly, a sample was also taken from the endless toothed belt after it had been run, which was used as a sample in a runned state. A two-axis running test machine consisting of a drive (Dr.) pulley with a diameter of 56.02 mm and a driven (Dn.) pulley with a diameter of 56.02 mm was used to run the toothed belt. On the two-axis running test machine, a toothed belt with a width of 36.0 mm was mounted on each pulley, the shaft load was set to 128 N, the rotation speed of the drive pulley was set to 3600 rpm, and the load of the driven pulley was set to 4.86 N·m, and the belt was run for 720 hours at an ambient temperature of 100°C.

[0523] The peel strength of each sample was measured as follows: On the end face of a sample taken from an endless belt, an incision was made with a cutting tool at the interface between the first and second rubber layers to create gripping portions A and B. Then, gripping portion A (first rubber layer) was gripped with the upper gripper of an Autograph (AGS-J10kN, manufactured by Shimadzu Corporation), and gripping portion B (second rubber layer, laminated tooth portion) was gripped with the lower gripper. In the same manner as in the "Measurement of bonding strength (peel strength) using a test piece" described above, gripping portion A and gripping portion B were pulled apart (peel angle of 180°, i.e., gripping portion A was folded back 180° relative to gripping portion B), and the tensile strength (tensile force) when the interface was peeled was recorded as the peel strength (peel force). The peel strength was calculated by converting the measured tensile force to a value per 25 mm width.

[0524] Based on the obtained peel strength (peel force), the bonding strength (adhesion) between the first rubber layer (silicone rubber composition) and the second rubber layer (HNBR composition) was determined according to the following criteria.

[0525] (Judgment Criteria) a: Peel strength (peeling force) per 25 mm width is 40 N or more b: Peel strength (peeling force) per 25 mm width is 30 N or more but less than 40 N c: Peel strength (peeling force) per 25 mm width is 10 N or more but less than 30 N d: Peel strength (peeling force) per 25 mm width is less than 10 N, or peeling occurs during driving

[0526] [Durability Running Test] To confirm the transport performance on the reverse side, the superiority or inferiority of the belts was verified using the belt's durability running life as an indicator. In other words, since transport performance is lost due to failure during durable running (cracks on the reverse side, delamination of the reverse layer), the durability running life (running time until failure occurs) was used as an indicator of "sustainability of transport performance" to determine the superiority or inferiority of the belts.

[0527] The durability running test was conducted using the same two-axis running test machine used for measuring joint strength (peel strength). A toothed belt with a width of 15.0 mm was used, with an axle load of 442 N, a drive pulley rotation speed of 3600 rpm, a driven pulley load of 10.33 N·m, and an ambient temperature of 100°C. The running time until failure occurred in the toothed belt was measured as the running life.

[0528] The travel time until this failure occurs (hereinafter referred to as "travel time") is shown as a relative value, with the travel time of Comparative Example C1 set to 1.0. If this relative value is greater than 1.0, it indicates a longer travel life than the toothed belt of Comparative Example C1 (i.e., superior sustained transport performance), and if it is 1.0 or less, it indicates that it is equivalent to or less than the toothed belt of Comparative Example C1.

[0529] (Criteria for judging endurance driving tests) a: Driving time (relative value) until failure is 18 or more b: Driving time (relative value) until failure is 10 or more but less than 18 c: Driving time (relative value) until failure is greater than 1.0 but less than 10 d: Driving time (relative value) until failure is 1.0 or less

[0530] [Overall Evaluation] Considering three items for toothed belts—bonding strength in the non-running state (bonding strength between the first and second rubber layers), bonding strength after running (maintainability from the non-running state), and durable running life (maintenance of conveying performance)—the overall superiority or inferiority was determined (ranked) according to the following criteria. From the perspective of product practicality, ranks A, B, and C were deemed acceptable, and rank D was deemed unacceptable.

[0531] (Criteria for overall evaluation) A rank: All three of the above items are judged as 'a' B rank: The above three items include a 'b' judgment (but do not include 'c' or 'd' judgments) C rank: The above three items include a 'c' judgment (but do not include 'd' judgment) D rank: The above three items include a 'd' judgment

[0532] The evaluation results for Comparative Examples C1-C2 and Examples C1-C30 are shown in Tables 25-29.

[0533]

[0534]

[0535]

[0536]

[0537]

[0538] <Verification Results in Table 25> (Comparative Examples C1 and C2) Comparative Example C1 is an example of a toothed belt in which a first rubber layer (RC9) that does not contain zinc methacrylate and a second rubber layer (RC1) that does not contain zinc methacrylate are joined together. Comparative Example C2 is an example of a toothed belt in which the first rubber layer (RC9) and the second rubber layer (RC1) of Comparative Example C1 are joined together with an epoxy resin adhesive.

[0539] In all cases, the bonding strength between the first and second rubber layers was low in the undriven belt (rating c), and because the first and second rubber layers separated during driving, the bonding strength after driving could not be measured (rating d). It was confirmed that sufficient bonding strength could not be obtained without using zinc methacrylate.

[0540] Furthermore, in the durability driving test, the driving life (driving time until failure (relative value)) was also low (rated D) due to early delamination between the first and second rubber layers, resulting in an overall rating of D (fail).

[0541] (Examples C1-C6) Examples C1-C6 are examples of toothed belts in which zinc methacrylate was added to the second rubber layer (HNBR composition) compared to the configuration of Comparative Example C1. When the amount of zinc methacrylate added was varied to 5 parts by mass (Example C1: RC2), 10 parts by mass (Example C2: RC3), 15 parts by mass (Example C3: RC4), 25 parts by mass (Example C4: RC5), 30 parts by mass (Example C5: RC6), and 35 parts by mass (Example C6: RC7), the bonding strength between the first rubber layer and the second rubber layer in the unused belt state improved to a passing level (rating c) in Example C1 and a passing level (rating a) in Examples C2-C6. Furthermore, this bonding strength was maintained even after use.

[0542] Furthermore, regarding the running life, in Example C1, the first and second rubber layers separated and the belt failed (reached the end of its lifespan) at a running time (relative value) of 12 (rated b). In other words, it can run 12 times longer than Comparative Example C1 (conveying performance is maintained). The running time (relative value) until failure was 16 in Example C2 (rated b), and in Examples C3 to C6, no separation of the first and second rubber layers occurred during running, and tooth chipping occurred at a running time (relative value) of 20, resulting in failure (reached the end of its lifespan) (rated a). In the overall evaluation, the toothed belt in Example C1 was ranked C (pass), the toothed belt in Example C2 was ranked B (pass), and the toothed belts in Examples C3 to C6 were ranked A (pass).

[0543] From these results, it was confirmed that adding zinc methacrylate improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and improves the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0544] <Verification Results in Table 26> (Example C7) Example C7 is an example of a toothed belt in which the type of HNBR in the second rubber layer was changed (the composition was changed from RC4 to RC8) compared to the configuration of Example C3. The bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example C3, and the overall evaluation was A rank (pass).

[0545] (Examples C8 to C11) Examples C8 to C11 are based on the configuration of Example C3, but with the total belt thickness (and back thickness of 4.1 mm) kept constant, and the ratio of the thickness of the second rubber layer (HNBR composition) to the first rubber layer (silicone rubber composition) is varied, thereby changing the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 39.0% (Example C8), 53.7% (Example C9), 70.7% (Example C3), 78.0% (Example C10), and 82.9% (Example C11). As a result, the bonding strength between the first rubber layer and the second rubber layer was the same as in Example C3 in all cases. Regarding durability and running life (maintenance of conveying function), in Example C8, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the high proportion of HNBR composition in the outer rubber layer increased rigidity and made it difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 14 (rating b). On the other hand, in Example C11, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the high proportion of silicone rubber composition in the outer rubber layer reduced rigidity near the teeth, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 14 (rating b). In Examples C9 and C10, no delamination between the first and second rubber layers or back surface cracking occurred during running, but tooth chipping occurred and failure (end of life) occurred (rating a). The overall rating was B rank (pass) for the toothed belts in Examples C8 and C11, and A rank (pass) for the toothed belts in Examples C9 and C10.

[0546] (Examples C12-C14) Examples C12-C14 are based on the configuration of Example C3, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (HNBR composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 62.5% (Example C12), 70.7% (Example C3), 78.9% (Example C13), and 82.1% (Example C14). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example C3. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples C12 and C13, tooth breakage occurred during running without delamination between the first and second rubber layers or cracking on the back surface (rated a). However, in Example C14, which had the largest total belt thickness, cracks occurred on the back surface after a running time (relative value) of 14, resulting in failure (rated b). The overall rating was B rank (pass) for the toothed belt in Example C14, and A rank (pass) for the toothed belts in Examples C12 and C13.

[0547] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0548] <Verification Results in Table 27> (Examples C15-C18) Examples C15-C18 are examples of toothed belts in which zinc methacrylate was added to the first rubber layer (silicone rubber composition) compared to the configuration of Comparative Example C1. When the amount of zinc methacrylate added was varied to 1 part by mass (Example C15: RC10), 2.5 parts by mass (Example C16: RC11), 5 parts by mass (Example C17: RC12), and 10 parts by mass (Example C18: RC13), the bonding strength between the first rubber layer and the second rubber layer in the state of an unused belt improved to a passing level of a rating (c) for Example C15 and an a rating (a) for Examples C16-C18. Furthermore, this bonding strength was maintained even after use.

[0549] Furthermore, regarding the running life, in Example C15, the first and second rubber layers separated and the belt failed (reached the end of its lifespan) at a running time (relative value) of 12 (rated b). In other words, it can run 12 times longer than Comparative Example C1 (the transport performance is maintained). The running time (relative value) until failure was 16 in Example C16 (rated b), and in Examples C17 and C18, no separation of the first and second rubber layers occurred during running, and tooth chipping occurred at a running time (relative value) of 20, resulting in failure (reached the end of its lifespan) (rated a). In the overall evaluation, the toothed belts in Examples C15 and C16 were ranked C (pass), the toothed belt in Example C17 was ranked B (pass), and the toothed belt in Example C18 was ranked A (pass).

[0550] From these results, it was confirmed that adding zinc methacrylate to the first rubber layer (silicone rubber composition) also improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and improves the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0551] <Verification Results in Table 28> (Example C19) Example C19 is an example of a toothed belt in which the type of silicone rubber in the first rubber layer was changed (the composition was changed from RC12 to RC14) compared to the configuration of Example C17. The bonding strength between the first rubber layer and the second rubber layer, and the durable running life (maintenance of conveying function) were equivalent to that of Example C17, and the overall evaluation was A rank (pass).

[0552] (Examples C20-C23) Examples C20-C23 are based on the configuration of Example C17, but with the total belt thickness (and back thickness of 4.1 mm) kept constant. By changing the ratio of the thickness of the second rubber layer (HNBR composition) to the first rubber layer (silicone rubber composition), the "thickness ratio of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" was varied. Specifically, the thickness ratio of the first rubber layer to the outer rubber layer was varied to 39.0% (Example C20), 53.7% (Example C21), 70.7% (Example C17), 78.0% (Example C22), and 82.9% (Example C23). In all cases, the bonding strength between the first and second rubber layers was equivalent to that of Example C17. Regarding durability and running life (maintenance of conveying function), in Example C20, where the thickness ratio of the first rubber layer was small (the first rubber layer was thin), the rigidity of the outer rubber layer increased and it became difficult to bend, resulting in a crack on the back surface and failure (end of life) after a running time (relative value) of 14 (rating b). On the other hand, in Example C23, where the thickness ratio of the first rubber layer was large (the first rubber layer was thick), the rigidity near the teeth was reduced due to the high proportion of silicone rubber composition in the outer rubber layer, resulting in tooth chipping and failure (end of life) after a running time (relative value) of 16 (rating b). In Examples C21 and C22, tooth chipping occurred and failure (end of life) occurred without delamination between the first and second rubber layers or cracking on the back surface during running (rating a). The overall rating was B rank (pass) for the toothed belts in Examples C20 and C23, and A rank (pass) for the toothed belts in Examples C21 and C22.

[0553] (Examples C24-C26) Examples C24-C26 are based on the configuration of Example C17, but vary the thickness of the first rubber layer (silicone rubber composition) laminated onto a second rubber layer (HNBR composition) of a constant thickness (1.2 mm), thereby varying the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)". Specifically, the ratio of the thickness of the first rubber layer to the outer rubber layer was varied to 62.5% (Example C24), 70.7% (Example C3), 78.9% (Example C25), and 82.1% (Example C26). In all cases, the bonding strength between the first rubber layer and the second rubber layer was equivalent to that of Example C17. Regarding durable running life (maintenance of conveying function), as the thickness ratio of the first rubber layer increased, the total belt thickness (and back thickness) increased, making it more difficult for the outer rubber layer to bend, which tended to decrease the durable running life. In Examples C24 and C25, tooth breakage occurred during running without delamination between the first and second rubber layers or cracking on the back surface (rated a). However, in Example C26, which had the largest total belt thickness, cracks occurred on the back surface after a running time (relative value) of 16, resulting in failure (rated b). The overall rating was B rank (pass) for the toothed belt in Example C26, and A rank (pass) for the toothed belts in Examples C24 and C25.

[0554] Based on these results, it can be said that the preferred range for the "ratio of the thickness of the first rubber layer to the total thickness of the outer rubber layer (back rubber layer)" is 50-80%.

[0555] <Verification Results in Table 29> (Examples C27-C30) Examples C27-C30 are examples of toothed belts in which zinc methacrylate is added to both the first rubber layer (silicone rubber composition) and the second rubber layer (HNBR composition) compared to the configuration of Comparative Example C1.

[0556] Example C27 is a combination of the second rubber layer of Example C1 (composition RC2, 5 parts by mass of zinc methacrylate) and the first rubber layer of Example C16 (composition RC11, 2.5 parts by mass of zinc methacrylate). In Examples C1 and C16, the bonding strength between the first and second rubber layers was at a low level (rating C), and the overall rating was C (pass). In Example C27, no significant improvement in bonding strength was observed, and it was also rated C (pass).

[0557] Example C28 is a combination of the second rubber layer of Example C3 (composition RC4, 15 parts by mass of zinc methacrylate) and the first rubber layer of Example C17 (composition RC12, 5 parts by mass of zinc methacrylate). In Examples C3 and C17, the bonding strength between the first and second rubber layers was at a high level (rating a), and the overall rating was A rank (pass). However, in Example C28, the bonding strength was equivalent to that of Examples C3 and C17, and no significant improvement was observed.

[0558] Example C29 is a combination of the second rubber layer of Example C1 (composition RC2, 5 parts by mass of zinc methacrylate) and the first rubber layer of Example C15 (composition RC10, 1 part by mass of zinc methacrylate). In Examples C1 and C15, the bonding strength between the first and second rubber layers was at a low level (rating C), and the overall rating was rank C (pass). In Example C29, the results were equivalent to those of Examples C1 and C15, and no significant improvement was observed.

[0559] Example C30 is a combination of the second rubber layer of Example C7 (composition RC8, 15 parts by mass of zinc methacrylate) and the first rubber layer of Example C19 (composition RC14, 5 parts by mass of zinc methacrylate). In Examples C7 and C19, the bonding strength between the first and second rubber layers was at a high level (rating a), and the overall rating was A rank (pass). In Example C30, the bonding strength was equivalent to that of Examples C7 and C19, and no significant improvement was observed.

[0560] Based on these results, it can be said that adding zinc methacrylate to either the first rubber layer (silicone rubber composition) or the second rubber layer (HNBR composition) improves the bonding strength between the first and second rubber layers (making delamination between the first and second rubber layers less likely) and tends to improve the durability and lifespan of the toothed belt (improving the sustainability of conveying performance).

[0561] [Example D] Example D is an embodiment in which the outer rubber layer includes an intermediate layer, and the second rubber composition includes hydrogenated nitrile rubber. The raw materials used, the preparation method, the method for producing the measurement laminate (crosslinked molded body), and the method for evaluating the measurement laminate are shown below.

[0562] [HNBR Composition] Table 30 shows the formulations of HNBR compositions (RD1, RD6) as second rubber compositions for forming the second rubber layer and HNBR compositions (RD2 to RD5) as third rubber compositions for forming the intermediate layer.

[0563]

[0564] [Materials for HNBR composition] HNBR1: Zetpol 2010 manufactured by Nippon Zeon Co., Ltd., iodine value 11 mg / 100 mg HNBR2: Therban 3446 manufactured by Arlanxeo, residual double bond amount 5.5% Zinc methacrylate: R-20S manufactured by Asada Chemical Industries, Ltd., purity 85% by mass Stearic acid: Tsubaki stearic acid manufactured by NOF Corporation Carbon black: Seest S manufactured by Tokai Carbon Co., Ltd., average particle size 66 nm, iodine adsorption amount 26 mg / g Silica: Ultrazil VN3 manufactured by Evonik Degussa Japan Co., Ltd., BET specific surface area 175 m² ２ / g Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.55 μm Anti-aging agent: p,p'-dioctyldiphenylamine, "Nonflex OD3" manufactured by Seiko Chemical Co., Ltd. Organic peroxide 1: "Perbutyl P-40MB" manufactured by NOF Corporation, 1,3-bis(2-t-butylperoxyisopropyl)benzene, active ingredient 40% by mass Co-crosslinking agent: N,N'-m-phenylenedimaleimide, "Balnok PM" manufactured by Ouchi Shinko Chemical Co., Ltd. Plasticizer: "ADEKA Sizer RS700" manufactured by ADEKA Corporation

[0565] [Silicone Rubber Composition] The formulation of the first rubber composition (silicone rubber composition) for forming the first rubber layer is shown in Table 31.

[0566]

[0567] [Materials for the silicone rubber composition] Silicone rubber 1: "TSE270-5U" manufactured by Momentive Performance Materials Japan LLC Silicone rubber 2: "TSE261-6U" manufactured by Momentive Performance Materials Japan LLC Organic peroxide 2: "TC-8" manufactured by Momentive Performance Materials Japan LLC

[0568] [Tooth Fabric] A 2 / 2 twill canvas was woven using 155 dtex nylon 66 yarn as the warp and a composite yarn of 155 dtex nylon 66 yarn and 122 dtex urethane elastic yarn as the weft. The warp density was 137 threads / 3cm and the weft density was 81 threads / 3cm. The woven canvas was immersed in the RFL treatment solution shown in Table 32 and dried. Then, the dried canvas was further immersed in a rubber adhesive prepared by dissolving the uncrosslinked HNBR composition for rubber adhesive shown in Table 33 in methyl ethyl ketone at a ratio of 10% by mass, and dried to obtain a bonded canvas (tooth fabric precursor) with a thickness of 0.85 mm.

[0569]

[0570]

[0571] [Intermediate Fabric] A 2 / 2 twill canvas was woven using 235 dtex nylon 6 yarn as the warp and 44 dtex woolly processed nylon 6 yarn as the weft. The warp density was 90 threads / 3cm and the weft density was 120 threads / 3cm. The uncrosslinked HNBR composition for rubber adhesive shown in Table 34 was kneaded in a Banbury mixer, and 100 parts by mass of the HNBR composition was dissolved in 900 parts by mass of toluene to prepare the rubber adhesive. The woven canvas was immersed in the RFL solution shown in Table 3 and dried, and then immersed in the rubber adhesive and dried to obtain an adhesive-treated intermediate fabric (intermediate fabric precursor) with a thickness of 0.75 mm.

[0572]

[0573] [Reinforcement fabric] 0.5 mm thick...

Claims

1. A power transmission belt comprising a core wire extending along the circumferential direction of the belt and an outer rubber layer formed on the outer circumferential side of the belt relative to the core wire, wherein the outer rubber layer has a laminated structure including a first rubber layer that forms a conveying surface which is the outer circumferential surface and a second rubber layer located on the inner circumferential side of the belt relative to the first rubber layer, wherein the first rubber layer is formed of a crosslinked product of a first rubber composition including silicone rubber, the second rubber layer is formed of a crosslinked product of a second rubber composition including at least one selected from ethylene-α-olefin elastomer and hydrogenated nitrile rubber, and the outer rubber layer is a power transmission belt containing an unsaturated carboxylic acid metal salt.

2. The power transmission belt according to claim 1, wherein in the outer peripheral rubber layer, the second rubber layer is laminated on the inner peripheral surface of the first rubber layer, and the unsaturated carboxylic acid metal salt is contained in at least one of the first rubber composition and the second rubber composition.

3. The transmission belt according to claim 1 or 2, wherein the unsaturated metal carboxylate salt comprises a first unsaturated metal carboxylate salt contained in the first rubber composition, and the proportion of the first unsaturated metal carboxylate salt is 0.5 parts by mass or more per 100 parts by mass of the silicone rubber.

4. The transmission belt according to any one of claims 1 to 3, wherein the second rubber composition comprises an ethylene-α-olefin elastomer.

5. The transmission belt according to claim 4, wherein the unsaturated metal carboxylate salt comprises a second unsaturated metal carboxylate salt contained in the second rubber composition, and the amount of the second unsaturated metal carboxylate salt is 3 parts by mass or more per 100 parts by mass of the ethylene-α-olefin elastomer.

6. The transmission belt according to claim 4 or 5, wherein the peel strength between the first rubber layer and the second rubber layer is 10 N / 25 mm or more.

7. The transmission belt according to any one of claims 1 to 3, wherein the second rubber composition comprises hydrogenated nitrile rubber.

8. The transmission belt according to claim 7, wherein the unsaturated metal carboxylate salt comprises a second unsaturated metal carboxylate salt contained in the second rubber composition, and the amount of the second unsaturated metal carboxylate salt is 3 parts by mass or more per 100 parts by mass of the hydrogenated nitrile rubber.

9. The transmission belt according to claim 7 or 8, wherein the peel strength between the first rubber layer and the second rubber layer is 30 N / 25 mm or more.

10. The power transmission belt according to claim 1, wherein the outer peripheral rubber layer further comprises an intermediate layer, the intermediate layer being laminated on the inner circumferential surface of the first rubber layer, the second rubber layer being laminated on the inner circumferential surface of the intermediate layer, and the intermediate layer comprising a crosslinked binder component containing the unsaturated carboxylic acid metal salt.

11. The transmission belt according to claim 10, wherein the intermediate layer is formed of a crosslinked product of the binder component, and the binder component is the unsaturated carboxylic acid metal salt.

12. The basis weight of the binder component is 50 g / m². ２ The transmission belt according to claim 11, as described above.

13. The transmission belt according to claim 10, wherein the intermediate layer is an intermediate layer formed of a crosslinked product of the binder component, or an intermediate layer formed of a cloth containing a crosslinked product of the binder component, and the binder component is a third rubber composition containing a rubber component and the unsaturated carboxylic acid metal salt.

14. The transmission belt according to claim 13, wherein the second rubber composition comprises an ethylene-α-olefin elastomer, and the rubber component comprises silicone rubber and / or an ethylene-α-olefin elastomer.

15. The transmission belt according to claim 13 or 14, wherein the rubber component comprises an ethylene-α-olefin elastomer, and the proportion of the unsaturated carboxylic acid metal salt is 3 parts by mass or more per 100 parts by mass of the rubber component.

16. The transmission belt according to any one of claims 10 to 15, wherein the peel strength between the first rubber layer and the intermediate layer is 10 N / 25 mm or more.

17. The transmission belt according to claim 13, wherein the second rubber composition comprises hydrogenated nitrile rubber, and the rubber component comprises silicone rubber and / or hydrogenated nitrile rubber.

18. The power transmission belt according to claim 13 or 17, wherein the rubber component includes hydrogenated nitrile rubber, and the proportion of the unsaturated carboxylic acid metal salt is 3 parts by mass or more per 100 parts by mass of the rubber component.

19. The transmission belt according to any one of claims 10 to 13, 17 to 18, wherein the peel strength between the first rubber layer and the intermediate layer is 30 N / 25 mm or more.

20. A transmission belt according to any one of claims 13 to 19, wherein the average thickness of the fabric is 0.05 to 1 mm, the fabric is made of a woven fabric formed of warp threads extending in the belt width direction and weft threads extending in the belt circumferential direction, the woven fabric contains polyamide fibers, and the average diameter of the warp threads is 0.3 times or more the average diameter of the weft threads.

21. The transmission belt according to any one of claims 1 to 20, wherein the unsaturated carboxylic acid metal salt comprises zinc methacrylate.

22. The transmission belt according to any one of claims 1 to 21, wherein the average thickness of the first rubber layer is 50 to 80% of the average thickness of the outer peripheral rubber layer.

23. A power transmission belt according to any one of claims 1 to 22, which is a toothed belt.

24. A method for manufacturing a power transmission belt according to any one of claims 1 to 23, comprising a joining step of joining the first rubber layer and the second rubber layer by crosslinking a first rubber layer precursor formed from the first rubber composition and a second rubber layer precursor formed from the second rubber composition.

25. The manufacturing method according to claim 24, wherein in the bonding step, the first rubber layer precursor and the second rubber layer precursor are laminated and crosslinked to bond the first rubber layer and the second rubber layer without interposing an adhesive between the first rubber layer and the second rubber layer.

26. The manufacturing method according to claim 24, wherein in the bonding step, the first rubber layer precursor, the intermediate layer precursor containing the binder component, and the second rubber layer precursor are bonded together by crosslinking them in this order, thereby interposing an intermediate layer between the first rubber layer and the second rubber layer.

27. A transmission belt comprising a core wire extending along the circumferential direction of the belt and an outer rubber layer formed on the outer circumferential side of the belt relative to the core wire, and for conveying articles on the outer circumferential surface of the outer rubber layer, wherein the outer rubber layer has a laminated structure including a first rubber layer that forms a conveying surface which is the outer circumferential surface and a second rubber layer located on the inner circumferential side of the belt relative to the first rubber layer, the first rubber layer is formed of a crosslinked product of a first rubber composition containing silicone rubber, the second rubber layer is formed of a crosslinked product of a second rubber composition containing at least one selected from ethylene-α-olefin elastomer and hydrogenated nitrile rubber, and the adhesion between the first rubber layer and the second rubber layer is improved by compounding an unsaturated carboxylic acid metal salt into the outer rubber layer.

28. The method according to claim 27, wherein in the outer peripheral rubber layer, the second rubber layer is laminated on the inner peripheral surface of the first rubber layer, and the unsaturated carboxylic acid metal salt is included in at least one of the first rubber composition and the second rubber composition.

29. The method according to claim 27, wherein the outer peripheral rubber layer further comprises an intermediate layer, the intermediate layer being laminated on the inner circumferential surface of the first rubber layer, the second rubber layer being laminated on the inner circumferential surface of the intermediate layer, and the intermediate layer comprising a crosslinked product of a binder component containing the unsaturated carboxylic acid metal salt.

30. A belt transmission mechanism for transporting articles, comprising a transmission belt according to any one of claims 1 to 23 and a pulley.

Images