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

Abstract

The present invention provides a transmission belt with excellent adhesion (bonding strength) between the silicone rubber layer on the conveying surface and the ethylene α-olefin elastomer layer laminated on the inner circumferential surface of the silicone rubber layer. [Solution] A transmission belt 1 for transporting articles, comprising a core wire 3 extending along the circumferential direction of the belt and an outer peripheral rubber layer 2 formed on the outer peripheral side of the belt relative to the core wire 3, wherein the outer peripheral surface of the outer peripheral rubber layer 2 is used for transporting articles. The outer periphery rubber layer 2 has a laminated structure including a first rubber layer 2a that forms the transport surface which is the outer periphery, and a second rubber layer 2b laminated on the inner periphery of the first rubber layer 2a. The first rubber layer 2a is formed from a crosslinked product of a first rubber composition containing silicone rubber, The second rubber layer 2b is formed of a crosslinked product of the second rubber composition containing ethylene-α-olefin elastomer, and The first rubber composition and / or the second rubber composition are blended with an unsaturated carboxylic acid metal salt.

Description

[Technical Field]

[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. [Background technology]

[0002] Power transmission belts are broadly classified into friction belts and meshing belts. Examples of friction belts include flat belts, V-belts, and V-ribbed belts, while 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.

[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 Application Publication No. 2016-183049 (Patent Document 3) 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 Application Publication No. 2016-37338 (Patent Document 4) 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. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2002-81506 [Patent Document 2] Japanese Patent Publication No. 2017-211084 [Patent Document 3] Japanese Patent Publication No. 2016-183049 [Patent Document 4] Japanese Patent Publication No. 2016-37338 [Overview of the project] [Problems that the invention aims to solve]

[0006] The flat conveying belts described in Patent Documents 3 and 4 are belts intended solely for conveying articles, and their overall thickness is relatively small, with the layer containing the silicone component 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 layer that serves as the conveying surface to a base frame for power transmission, so the thickness is greater than that of a flat conveying belt. When the frame portion for power transmission is formed from a rubber layer using the aforementioned ethylene-α-olefin elastomer, it is necessary to laminate a polymer layer containing the silicone component (for example, a silicone rubber layer) that forms the conveying surface.

[0007] However, silicone components such as silicone rubber are widely used as release agents and non-stick materials, and are known as difficult-to-bond materials with low adhesion to other components. Furthermore, ethylene-α-olefin elastomer is also known as a rubber component 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 bond. In particular, silicone rubber is selected as a rubber with low adhesion from the standpoint of the function that requires non-stickness to the conveyed object, and there is a trade-off relationship between the function of silicone rubber required as a conveying surface and its adhesion, making it extremely difficult to bond (join) the silicone rubber layer and the ethylene-α-olefin elastomer layer. For this reason, in the conveying belt of Patent Document 4, 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] Therefore, the object of the present invention is to provide a transmission belt and a method for manufacturing the same that have excellent adhesion (bonding strength) between the silicone rubber layer on the conveying surface and the ethylene α-olefin elastomer layer laminated on the inner circumferential surface of the silicone rubber layer.

[0009] Another object of the present invention is to provide a method for manufacturing a power transmission belt that transmits power and transports articles using its back surface, with a simple structure and high productivity.

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

Means for Solving the Problems

[0011] As a result of intensive studies to achieve the above problems, the inventors of the present invention have found that by blending an unsaturated carboxylic acid metal salt with at least one of a silicone rubber layer forming a conveying surface of a transmission belt and an ethylene-α-olefin elastomer layer laminated on an inner peripheral surface of the silicone rubber layer, the adhesiveness (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer can be improved, and thus the present invention has been completed.

[0012] That is, the present invention includes the following aspects.

[0013] Aspect [1]: A transmission belt including a core wire extending along the belt circumferential direction and an outer peripheral rubber layer formed on the outer peripheral side of the core wire, and conveying an article on an outer peripheral surface of the outer peripheral rubber layer, wherein the outer peripheral rubber layer has a laminated structure including a first rubber layer forming a conveying surface serving as an outer peripheral surface and a second rubber layer laminated on an inner peripheral surface of the first rubber layer, the first rubber layer is formed of a crosslinked product of a first rubber composition containing silicone rubber, <000^0102>the second rubber layer is formed of a crosslinked product of a second rubber composition containing an ethylene-α-olefin elastomer, the first rubber composition and / or the second rubber composition contains an unsaturated carboxylic acid metal salt.

[0014] Aspect [2]: The transmission belt according to Aspect [1], wherein the unsaturated carboxylic acid metal salt contains zinc methacrylate.

[0015] Embodiment [3]: The transmission belt according to Embodiment [1] or [2], wherein the unsaturated metal carboxylic acid salt comprises a first unsaturated metal carboxylic acid salt contained in the first rubber composition, and the proportion of the first unsaturated metal carboxylic acid salt is 0.5 parts by mass or more per 100 parts by mass of the silicone rubber.

[0016] Embodiment [4]: ​​A transmission belt according to any one of Embodiments [1] to [3], 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.

[0017] Embodiment [5]: A transmission belt according to any of Embodiments [1] to [4], wherein the average thickness of the first rubber layer is 50 to 80% of the average thickness of the outer rubber layer.

[0018] Embodiment [6]: A transmission belt according to any of Embodiments [1] to [5], wherein the peel strength between the first rubber layer and the second rubber layer is 10 N / 25 mm or more.

[0019] Embodiment [7]: A transmission belt according to any of Embodiments [1] to [6], which is a toothed belt.

[0020] Embodiment [8]: A method for manufacturing a power transmission belt according to any one of Embodiments [1] to [7], comprising a joining step of joining the first rubber layer and the second rubber layer without interposing an adhesive between the first rubber layer and the second rubber layer by laminating and crosslinking a first rubber layer precursor formed of the first rubber composition and a second rubber layer precursor formed of the second rubber composition.

[0021] Embodiment [9]: 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, wherein the outer surface of the outer rubber layer is used to transport articles, The outer periphery rubber layer has a laminated structure including a first rubber layer that forms the transport surface which is the outer periphery, and a second rubber layer laminated on the inner periphery of the first rubber layer. The first rubber layer is formed from 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 ethylene-α-olefin elastomer, and A method for improving the adhesion between the first rubber layer and the second rubber layer by incorporating an unsaturated carboxylic acid metal salt into the first rubber composition and / or the second rubber composition.

[0022] Embodiment

[10] : A belt transmission mechanism for transporting articles, comprising a transmission belt according to any of Embodiments [1] to [7] and a pulley.

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

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

[0025] In 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 laminated on the inner circumferential surface of the silicone rubber layer contains an unsaturated carboxylic acid metal salt, thereby improving the adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer. In particular, since the silicone rubber layer and the ethylene-α-olefin elastomer layer can be bonded without using an adhesive, the structure of the power transmission belt that transmits power and conveys goods using the back surface of the belt can be simplified, and it can be manufactured with high productivity. Furthermore, the power transmission belt of the present invention has a long durable running life, and in particular, failures due to durable running (cracks on the back surface, peeling of the back surface layer) can be suppressed. [Brief explanation of the drawing]

[0026] [Figure 1]Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt according to the present invention. [Figure 2] Figure 2 is a schematic cross-sectional view of the toothed belt shown in Figure 1. [Figure 3] Figure 3 is a schematic diagram illustrating the measurement method for the adhesion test in the example. [Modes for carrying out the invention]

[0027] [Transmission belt] The 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 also 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.

[0028] 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.

[0029] Examples of interlocking power transmission belts include toothed belts and double-sided toothed belts.

[0030] In the present invention, these power transmission belts have a laminated structure in which the outer rubber layer formed on the outer circumference side of the belt relative to the core wire includes a first rubber layer (silicone rubber layer) that forms the conveying surface which is the outer circumference, and a second rubber layer (ethylene-α-olefin elastomer layer) laminated on the inner circumference surface of the first rubber layer and in contact with the first rubber layer. By including an unsaturated carboxylic acid metal salt in the first rubber layer and / or the second rubber layer, the adhesion (bonding strength) between the silicone rubber layer and the ethylene-α-olefin elastomer layer can be improved. While some degree of adhesion is possible between the ethylene-α-olefin elastomer layer and the silicone rubber layer using a resin-based adhesive, the presence of a non-elastic resin component between the layers reduces flexibility and generates bending stress between the layers, making delamination more likely. In contrast, in 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 and the silicone rubber layer can be strongly bonded by a chemical crosslinking reaction.

[0031] 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, and 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, adhesive rubber layers commonly used in power transmission belts can be used depending on the type of rubber. Of these, the outer periphery rubber layer is preferably a combination of the first rubber layer, the second rubber layer and the third rubber layer (especially 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. In the power transmission belt of the present invention, the details of the first rubber layer and the second rubber layer are as follows.

[0032] (First rubber layer) The first rubber layer is formed of a crosslinked product of the first rubber composition containing silicone rubber.

[0033] (1A) Silicone rubber The silicone rubber may be a conventional silicone rubber, for example, a polyorganosiloxane. The polyorganosiloxane is a linear, branched or network compound having Si—O bonds (siloxane bonds), and has the formula: R a SiO (4-a) / 2 (where R is a substituent and a is a number from 0 to 3).

[0034] Since the silicone rubber mainly has two-dimensional siloxane bonds (D units), it is superior in flexibility compared to silicone resins mainly having three-dimensional siloxane bonds (T units). On the other hand, the silicone-modified resin disclosed in Patent Document 3 is a thermoplastic resin or a thermoplastic elastomer and melts by heating, so it can be bonded to other rubbers relatively easily. In contrast, since the silicone rubber is thermosetting, it does not melt by heating and has extremely low adhesiveness to other rubbers. Therefore, the silicone rubber is a polymer containing a silicone component that is widely used as a release agent or a non-sticking material, and is a polymer having particularly low adhesiveness.

[0035] In the above formula, as the substituent R, for example, C 1-10 alkyl groups such as methyl group, ethyl group, propyl group, butyl group, halogenated C 1-10 alkyl groups such as 3-chloropropyl group, 3,3,3-trifluoropropyl group, C 2-10 alkenyl groups such as vinyl group, allyl group, butenyl group, C 6-20 aryl groups such as phenyl group, tolyl group, naphthyl group, C 3-10 cycloalkyl groups such as cyclopentyl group, cyclohexyl group, C 6-12 aryl-C 1-4 alkyl groups and the like can be mentioned. These substituents can be used alone or in combination of two or more. Among these, as R, a methyl group, a phenyl group, an alkenyl group (such as a vinyl group), and a fluoro C 1-6 alkyl group are preferred.

[0036] Examples of polyorganosiloxanes include polydialkylsiloxanes (such as polydimethylsiloxanes). 1-10 Alkylsiloxanes, polyalkylalkenylsiloxanes (such as polymethylvinylsiloxanes) 1-10 Alkyl C 2-10 Alkenylsiloxanes, polyalkylarylsiloxanes (such as polymethylphenylsiloxanes) 1-10 Alkyl C 6-20 Arylsiloxanes, 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.

[0037] 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.

[0038] Of these polyorganosiloxanes, polydiC is chosen based on its mechanical properties and availability. 1-10 It is preferable that the material contains alkylsiloxanes, particularly polydimethylsiloxane (PDMS).

[0039] 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).

[0040] 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.

[0041] 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. In order to improve 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.

[0042] 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).

[0043] The proportion of silicone rubber in the first rubber composition may be 50% by mass or more, 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 in the first rubber composition may be 50% by mass or more (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.

[0044] (1B) Unsaturated carboxylic acid metal salt The first rubber composition can improve the adhesion between the first rubber layer and the second rubber layer by including an unsaturated carboxylic acid metal salt (first unsaturated carboxylic acid metal salt). In the power transmission belt of the present invention, 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 and other factors, the first rubber composition may not contain an unsaturated carboxylic acid metal salt.

[0045] 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.

[0046] Examples of unsaturated carboxylic acids in the primary unsaturated carboxylic acid metal salts include monocarboxylic acids such as (meth)acrylic acid and crotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and monoalkyl esters of these dicarboxylic acids. These unsaturated carboxylic acids can be used alone or in combination of two or more. A preferred unsaturated carboxylic acid is (meth)acrylic acid.

[0047] Examples of metals used in the primary unsaturated carboxylate metal salts include alkali metals such as sodium and potassium; polyvalent metals such as group 2 elements of the periodic table (magnesium, calcium, etc.), group 4 elements (titanium, zirconium, etc.), and group 8 to 14 elements of the periodic table (e.g., iron, cobalt, nickel, copper, zinc, aluminum, tin, lead, etc.). These metals can be used individually or in combination of two or more. Preferred metals are polyvalent metals such as group 2 elements of the periodic table (magnesium, etc.) and group 12 elements of the periodic table (zinc, etc.).

[0048] These unsaturated carboxylate metal salts can be used individually or in combination of two or more.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] (1C) First crosslinking agent The first rubber composition preferably further contains a crosslinking agent (first crosslinking agent). Examples of the first crosslinking agent include organic peroxides.

[0053] Examples of organic peroxides include diacyl peroxides (e.g., dilauroyl peroxide, dibenzoyl peroxide, etc.), peroxyketals [e.g., 1,1-di(t-butylperoxy)cyclohexane, 2,2-di(t-butylperoxy)butane, 1,1-di(t-butylperoxy)-3,3,5-trimethylcyclohexane, etc.], and dialkyl peroxides [di-t-butyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyl peroxide]. Examples include [1,3-bis(2-t-butylperoxyisopropyl)benzene, etc.], alkyl peroxyesters [t-butylperoxybenzoate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, etc.], dialkyl peroxides (dicumyl peroxide, t-butylcumyl peroxide, etc.), peroxycarbonates (t-butylperoxyisopropyl carbonate, t-butylperoxy-2-ethyl-hexyl carbonate, t-amylperoxy-2-ethyl-hexyl carbonate, etc.). Furthermore, the organic peroxide may be a peroxide that has a decomposition temperature of 150-250°C (e.g., 175-225°C) at which it obtains a half-life of 1 minute by thermal decomposition. These organic peroxides can be used individually or in combination of two or more.

[0054] Among these organic peroxides, dialkyl peroxides such as 2,5-dimethyl-2,5-di(t-butylperoxy)hexane are preferred.

[0055] 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.

[0056] (1D) Other ingredients 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.

[0057] 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.

[0058] (Second rubber layer) The second rubber layer is formed of a crosslinked product of the second rubber composition containing ethylene-α-olefin elastomer.

[0059] (2A) Ethylene-α-olefin elastomer Ethylene-α-olefin elastomer is also 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 and second rubber layers when combined with silicone rubber, which is a difficult-to-bond material that constitutes the first rubber layer.

[0060] 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.

[0061] 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. 3-12 Examples 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.

[0062] 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.

[0063] 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.

[0064] 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 rubbers, such as olefin-diene terpolymer rubber, are 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).

[0065] In the ethylene-α-olefin elastomer, the ethylene content (percentage of ethylene units) may be 30% by mass or more, for example, 30-80% by mass, preferably 35-70% by mass, more preferably 40-60% by mass, and more preferably 45-55% by mass. The most preferred value is 48-52% 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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 refer to the mass ratio based on α-olefin as a monomer.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] In this application, the iodine value of the ethylene-α-olefin elastomer can be measured by conventional methods, such as infrared spectroscopy.

[0074] The Mooney viscosity [ML(1+4)125℃] 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.

[0075] 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.

[0076] 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.

[0077] 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 60% by mass, and most preferably 45 to 55% by mass. If the proportion of ethylene-α-olefin elastomer is too low, the flexural strength of the transmission belt may decrease.

[0078] (2B) Metal salts of deuteransaturated carboxylic acids The second rubber composition can improve the adhesion between the first rubber layer and the second rubber layer by including a second unsaturated carboxylic acid metal salt. If the first rubber composition contains a 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 and other factors, the second rubber composition may not contain a second unsaturated carboxylic acid metal salt.

[0079] 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.

[0080] The proportion of the secondary 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) per 100 parts by mass of ethylene-α-olefin elastomer. 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 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 secondary 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.

[0081] If the first rubber composition contains a first unsaturated carboxylic acid metal salt (particularly zinc methacrylate), 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] (2C) Second crosslinking agent The second rubber composition preferably further contains a second crosslinking agent. Examples of the second crosslinking agent include organic peroxides and sulfur-based crosslinking agents. These crosslinking agents can be used individually or in combination of two or more.

[0083] Examples of organic peroxides include those exemplified as organic peroxides for the first crosslinking agent.

[0084] 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.

[0085] Among the crosslinking agents, organic peroxides are preferred, and dialkyl peroxides such as 1,3-bis(2-t-butylperoxyisopropyl)benzene are particularly preferred.

[0086] 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.

[0087] (2D) Second filler The second rubber composition may further contain a second filler. The second filler includes reinforcing inorganic fillers, non-reinforcing fillers, and the like.

[0088] Examples of reinforcing inorganic fillers include carbon black and silica. The reinforcing inorganic filler may also be in particulate (powder) form.

[0089] 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).

[0090] 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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.

[0095] The BET specific surface area of ​​carbon black using the BET method is, for example, 10 to 400 m². 2 / g, preferably 15-200m 2 / g, more preferably 20-150m 2 It is / g.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] Furthermore, the specific surface area for nitrogen adsorption of silica by the BET method is, for example, 50 to 400 m². 2 / g, preferably 100-300m 2 / g, more preferably 150-200m 2 It is / g.

[0100] Examples of non-reinforcing fillers include metal oxides (magnesium oxide, zinc oxide, lead oxide, calcium oxide, barium oxide, iron oxide, copper oxide, titanium oxide, aluminum oxide, etc.), polyvalent metal carbonates (calcium carbonate, magnesium carbonate, etc.), polyvalent metal hydroxides (aluminum hydroxide, etc.), polyvalent metal sulfates (barium sulfate, etc.), silicates (natural or synthetic silicates in which some of the silicon atoms are replaced by polyvalent metal atoms, such as aluminum silicate, magnesium silicate, and aluminum magnesium silicate; minerals 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.

[0101] These fillers can be used individually or in combination of two or more. 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.

[0102] 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.

[0103] 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.

[0104] The proportion of the 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.

[0105] 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.

[0106] (2E) Second softening agent The second rubber composition may further contain a second softening agent (processing agent or processing aid) to improve the flexibility of the belt. The second softening agent may include mineral oil-based softening agents, vegetable oil-based softening agents, synthetic softening agents, and the like.

[0107] 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.).

[0108] 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).

[0109] 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.].

[0110] These softening agents can be used individually or in combination of two or more. Of these, petroleum-based softening agents such as paraffinic oils and vegetable oil-based softening agents such as stearic acid are preferred, with petroleum-based softening agents being particularly preferred.

[0111] The proportion of the second softening agent 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.

[0112] (2F) Second Anti-aging Agent The second rubber composition may further contain a second antioxidant, as this can improve its heat aging resistance. Examples of the second antioxidant include benzimidazole-based antioxidants, diarylamine-based antioxidants, and p-phenylenediamine-based antioxidants.

[0113] Examples of benzimidazole-based antioxidants include benzimidazole compounds such as 2-mercaptobenzimidazole (MBI), 2-mercapto-5-methylbenzimidazole, 2-mercapto-5-methoxybenzimidazole, 2-mercapto-5-carboxybenzimidazole, 2-mercapto-5-nitrobenzimidazole, 1,3-dihydro-1-phenyl-2H-benzimidazole-2-thion, and mixtures of 2-mercaptobenzimidazole and phenol condensates. Benzimidazole-based antioxidants may also be in the form of salts with metals such as zinc.

[0114] Examples of diarylamine-based antioxidants include bis(C) such as di(4-octylphenyl)amine (ODPA). 4-18 Alkyl C 6-10 Examples include arylamines; bis(aralkyl-aryl)amines such as 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (DCD); and styrene-diphenylamine (SDPA).

[0115] Examples of p-phenylenediamine-based antioxidants include N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), and N-(1,3-methylheptyl)-N'-phenyl-p-phenylenediamine (8PPD), which are N-linear or branched C-cells. 1-10 Alkyl-N'-C 6-10 Aryl-p-phenylenediamine; N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine (DNPD), etc., N,N'-diC 6-10 Examples include aryl-p-phenylenediamines.

[0116] These anti-aging agents can be used individually or in combination of two or more. Of these, benzimidazole-based anti-aging agents are preferred, particularly benzimidazole compounds having a sulfur atom, and especially benzimidazole compounds having a thiol group such as MBI (mercaptobenzimidazole compounds).

[0117] 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. 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.

[0118] (2G) Second Other Component 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.

[0119] 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.

[0120] (Characteristics of the outer rubber layer) In the power transmission belt of the present invention, the first rubber layer and the second rubber layer constituting the outer periphery rubber layer are a combination of silicone rubber and ethylene-α-olefin elastomer, which have low adhesive properties, yet they can be firmly joined together without the need for an adhesive layer.

[0121] 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.

[0122] In this application, the peel strength between the first rubber layer and the second rubber layer can be measured by the method described in the examples below.

[0123] The power transmission belt of the present invention may contain an unsaturated carboxylate metal salt in at least one of the first and second rubber compositions, 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.

[0124] (Toothed belt) The transmission belt of the present invention is not particularly limited as long as it has the outer rubber layer, but among the transmission belts, a toothed belt is preferred because it requires an outer layer with a large thickness on the conveying surface and offers greater benefits from the present invention.

[0125] 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, identical or functionally common elements (or components) may be denoted by the same reference numeral.

[0126] Figure 1 is a schematic partial cross-sectional perspective view showing an example of a toothed belt of the present invention, and Figure 2 is a schematic cross-sectional view of the toothed belt of Figure 1.

[0127] 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 side being made of tooth fabric 5. The back portion 1c has a back rubber layer (outer circumferential rubber layer) 2 disposed on the outer circumferential side of the belt of the core wire 3, and this back rubber layer 2 consists of a first rubber layer 2a that forms the outer circumferential surface (conveying surface) of the belt and a second rubber layer 2b located on the inner circumferential side of the first rubber layer 2a. Furthermore, the toothed belt 1 has a tooth rubber layer (rubber layer forming the teeth) 4 between the tooth fabric 5 and the core wire 3 on the inner circumferential side of the belt of the core wire 3.

[0128] 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.

[0129] In the embodiment shown in Figure 1, 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 part of a continuous tooth fabric 5 (part of the tooth fabric 5 in Figure 2).

[0130] 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.

[0131] Furthermore, in the tooth root portion 1b, a tooth rubber layer 4 is interposed between the tooth cloth 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.

[0132] 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.

[0133] The toothed belt of the present invention is not limited to the form and structure shown in Figures 1 and 2. For example, the multiple teeth only need to be able to mesh with a toothed pulley, and the cross-sectional shape of the teeth (the cross-sectional shape of the toothed belt in the circumferential direction) is not limited to a substantially trapezoidal shape, but may be, for example, semicircular, semielliptical, polygonal [triangle, quadrilateral (rectangle, trapezoid, etc.)], etc. Of these, a trapezoidal or substantially trapezoidal shape is preferred from the viewpoint of meshing and power transmission.

[0134] 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.

[0135] (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.

[0136] 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.

[0137] 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.

[0138] In the toothed belt of the present invention, 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.

[0139] 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).

[0140] The average thickness of the first rubber layer is, for example, 35-90%, preferably 40-85%, of the average thickness of the outer rubber layer, and more preferably 50-80% from the standpoint of significantly improving the belt's durability and running performance. 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, increasing the overall hardness of the outer rubber layer, 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 may become too thin, which may result in insufficient mechanical strength for the belt.

[0141] 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.

[0142] In this application, the average thickness of each layer is the average of the measured values ​​obtained by measuring the thickness 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, the average thickness is the average of the measured values ​​obtained by measuring at three arbitrarily selected peaks and three bottoms of the corrugated surface.

[0143] 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.

[0144] (Core wire) On the back of the belt, a core wire extending along the belt circumferential direction is embedded on the inner circumference side of the back rubber layer. This core wire acts as a tensile body, improving the running stability and strength of the toothed belt. Furthermore, on the back, the core wire, which is usually a twisted cord extending along the belt circumferential direction, is embedded at predetermined intervals in the belt width direction. Multiple core wires parallel to the longitudinal direction may be arranged, but from the viewpoint of productivity, they are usually embedded in a spiral shape. When arranged in a spiral shape, the angle of the core wire with respect to the longitudinal direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it is as close to 0° as possible.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] The core wire may be treated with an adhesive treatment to enhance its adhesion to the crosslinked material of the rubber composition. For example, the adhesive treatment may involve immersing the stranded cord in a resorcinol-formaldehyde-latex treatment solution (RFL treatment solution), followed by heating and drying to form a uniform adhesive layer on the surface of the stranded cord. The RFL treatment solution is a mixture of latex and an initial condensate of resorcinol and formalin. The latex may be, for example, chloroprene rubber, styrene-butadiene-vinylpyridine terpolymer (VP latex), nitrile rubber, or hydrogenated nitrile rubber. Furthermore, the adhesive treatment may involve pre-treating with an epoxy compound or isocyanate compound before treatment with the RFL treatment solution.

[0150] 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.

[0151] (Tooth rubber layer) The teeth include a tooth rubber layer positioned on the inner circumference of the core wire. In the embodiment shown in Figure 1, 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.

[0152] The tooth rubber layer may be formed of a crosslinked product of a third rubber composition containing an ethylene-α-olefin elastomer. In the crosslinked product of the third rubber composition, the ethylene-α-olefin elastomer is preferably the same as or of the same type as the ethylene-α-olefin elastomer in 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.

[0153] The third 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 antioxidant exemplified as the second anti-aging agent, and other components exemplified as the second other component. The third rubber composition may also be the same rubber composition as the second rubber composition.

[0154] The tooth rubber layer is not limited to a single-layer tooth rubber layer as shown in Figure 1, but may also be a tooth rubber layer having a laminated structure of two or more layers.

[0155] (Tooth cloth) If the teeth include tooth fabric, the tooth fabric laminated on the inner circumferential surface of the belt (teeth and tooth base) may be formed from a 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 any of 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).

[0156] The fibers forming the weft and warp threads of the tooth fabric may be organic or inorganic fibers. Examples of organic fibers include polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers [aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers (nylon fibers), aramid fibers, etc.], polyester fibers [polyalkylene arylate fibers (e.g., polyethylene terephthalate (PET) fibers, polytrimethylene terephthalate (PTT) fibers, polybutylene terephthalate (PBT) fibers, polyethylene naphthalate (PEN) fibers, etc.)] 2-4 Alkilen C 8-14Synthetic fibers include: arylate fibers (such as polyarylate fibers and fully aromatic polyester fibers like liquid crystal polyester fibers), vinylon fibers, polyvinyl alcohol fibers, 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.

[0157] 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 aliphatic polyamide fibers like polyamide 66 fibers, aramid fibers, etc.), PBO fibers, and fluororesin fibers [such as polytetrafluoroethylene (PTFE) fibers] being preferred. 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.

[0158] 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.

[0159] 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).

[0160] The woven fabric may have a multi-layered structure (such as a double-layered structure), and in a woven structure comprising warp and weft threads, at least some of the weft threads may be made of low-friction fibers (or low-friction fibers) such as fluororesin-containing fibers (such as composite yarns containing fibers formed from fluororesins such as PTFE). For example, the warp threads may be made of polyamide fibers such as 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 aforementioned second fibers.

[0161] In woven fabrics with a multi-layered weave 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 that constitutes the teeth.

[0162] 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.

[0163] In an embodiment in which low-melting-point fibers are arranged around fluorine-based fibers, the low-melting-point fibers melt during cross-linking (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.

[0164] 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.

[0165] To improve the adhesion between the tooth cloth and the tooth rubber layer, the cloth forming the tooth cloth may be treated with an adhesive. Examples of adhesive treatments include immersing the cloth in an RFL treatment solution followed by heat drying; treating with an epoxy compound or isocyanate compound; or dissolving a rubber composition in an organic solvent to make a rubber glue, immersing the cloth in this rubber glue, and then heat drying. These methods can be performed individually or in combination, and the order and number of treatments are not limited. For example, after immersion in an RFL treatment solution, the cloth may be further immersed in rubber glue and then heat dried.

[0166] 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 third 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.

[0167] The average tooth height of the teeth is, for example, 25-70%, preferably 30-50%, and more preferably 35-40%, of the average value of the total belt thickness [thickness (distance or height) from the back surface (outer surface) to the tooth crown].

[0168] In this application, as shown in Figure 2, the average tooth height of the teeth refers to the average height of the protruding teeth on the inner surface of the belt [the average value of the thickness (distance or height) from the tooth root surface to the tooth apex].

[0169] (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).

[0170] 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.

[0171] 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.

[0172] [Manufacturing method for power transmission belts] The method for manufacturing the 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.

[0173] (a) Method 1 (Method in which the 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.

[0174] (Precursor preparation process) In the precursor preparation step, the core wire precursor and the tooth cloth precursor may be prepared by bonding treatment as described above.

[0175] 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.

[0176] (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 spirally around its outer surface 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).

[0177] (Crosslinking molding process) Next, in the cross-linking molding process, the uncrosslinked belt molded body is placed on the outer circumference of the cylindrical mold, and a rubber jacket, which acts as 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 cross-linking molding device such as a vulcanizing can. When the belt molded body is heated and pressurized inside the cross-linking 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.

[0178] 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.

[0179] 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, forming a sleeve-shaped crosslinked molded body (crosslinked belt sleeve).

[0180] 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.

[0181] (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.

[0182] (b) Second method (a method in which the teeth are formed in advance during the molding process) The first method described above may also be manufactured by adding a step to prepare a pre-formed body in which only the teeth are formed during the molding process.

[0183] (Precursor preparation process) In the precursor preparation step, the core wire precursor and the tooth cloth precursor may be prepared by bonding treatment as described above.

[0184] 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 uncrosslinked rubber sheet a for forming the tooth rubber layer, uncrosslinked rubber sheet b for forming the second rubber layer, and uncrosslinked rubber sheet c for forming the first rubber layer.

[0185] (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 sufficient to soften the rubber composition (for example, about 70-90°C) using a predetermined device, pressure is applied to the laminate from the outer side, causing the rubber composition of the uncrosslinked rubber sheet a and the tooth cloth precursor to be pressed into the grooves (recesses) of the cylindrical mold to form the teeth and obtain a semi-crosslinked pre-molded body (pre-laminated body). In this process of pressing to form the teeth, the tooth cloth is stretched to a shape that follows the contour of the teeth and is 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.

[0186] 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 fabric 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).

[0187] 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).

[0188] (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 acts as 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).

[0189] (cutting process) Finally, in the cutting process, multiple toothed belts are obtained by cutting the bridging belt sleeve, which has been demolded from the cylindrical mold, to a predetermined width. [Examples]

[0190] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. The raw materials used, preparation methods, methods for producing the measurement laminate (crosslinked molded body), and evaluation methods for the measurement laminate are shown below.

[0191] [EPDM composition] Table 1 shows the formulation of the second rubber composition (EPDM composition) for forming the second rubber layer.

[0192] [Table 1]

[0193] [Materials for EPDM composition] EPDM1: Dow Chemical's "Nordel IP 4520," ethylene content 50% by mass, diene content (ethylidene norbornene content) 4.9% by mass, Mooney viscosity 20ML (1+4) 125℃ EPDM2: Dow Chemical's "Nordel IP 3640," 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: "Seas 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: NOF Corporation's "Perbutyl P-40MB", 1,3-bis(2-t-butylperoxyisopropyl)benzene, active ingredient 40% by mass

[0194] [Silicone rubber composition] Table 2 shows the formulation of the first rubber composition (silicone rubber composition) for forming the first rubber layer.

[0195] [Table 2]

[0196] [Materials for 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.

[0197] [Tooth cloth] 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 cloth precursor) with a thickness of 0.85 mm.

[0198] [Table 3]

[0199] [Table 4]

[0200] [Reinforcement fabric] 0.5mm thick nylon canvas

[0201] [Core wire (processing code)] 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 treatment 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 film. 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 strands of pre-twisted yarn S were arranged together and twisted in the Z direction with 8 twists per 10 cm to obtain a multi-twisted cord (multi-twisted cord Z). Similarly, 13 strands of pre-twisted yarn Z were arranged together and twisted in the S direction with 8 twists per 10 cm to obtain a multi-twisted cord (multi-twisted cord S). Each multi-ply cord was passed through an overcoat solution (a rubber adhesive 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 rubber coating. The total fineness of the treated cords was 1300-1400 tex, and the outer diameter was 1.2 mm.

[0202] [Preparation of uncrosslinked rubber sheets] For the toothed belts produced in the examples and comparative examples, a rubber composition having the composition shown in Table 1 was used as the uncrosslinked rubber sheet A for forming the toothed rubber layer and the second rubber layer, and for the uncrosslinked rubber sheet B for forming the first rubber layer, a rubber composition having the composition shown in Table 2 was used. The rubber compositions were kneaded in a Banbury mixer and rolled with a calender roll to produce uncrosslinked rubber sheets.

[0203] [Adhesion (peel strength) test on test specimens] The reinforcing fabric, an uncrosslinked rubber sheet for the first rubber layer (an uncrosslinked silicone rubber sheet, which is uncrosslinked rubber sheet B, with a thickness of 2 mm, a width of 30 mm, and a length of 150 mm), an uncrosslinked rubber sheet for the second rubber layer (an uncrosslinked EPDM sheet, which is uncrosslinked rubber sheet A, with a thickness of 2 mm, a width of 30 mm, and a length of 150 mm), and the reinforcing fabric were stacked in that order, and crosslinking molding was performed in a press mold (surface pressure of 2 MPa, 165°C) for 30 minutes to produce a laminate (crosslinked molded body) 15 in which the reinforcing fabric 11, silicone rubber sheet 12, EPDM sheet 13, and reinforcing fabric 14 were joined together to form an integrated structure, as shown in Figure 3.

[0204] In this laminate 15, the interface between the silicone rubber sheet 12 and the EPDM sheet 13 was joined over a length of 120 mm. One end of each uncrosslinked rubber sheet was not joined, as shown in Figure 3, in order to be used as gripping sections 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.

[0205] The Autograph (Shimadzu Corporation, "AGS-J10kN") was used to grip section A (a laminate of reinforcing fabric 11 and silicone rubber sheet 12) with its upper grip and grip section B (a laminate of EPDM 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 area 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.

[0206] 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.

[0207] (Judgment criteria) a: Peel strength (peeling force) of 100N or more per 25mm width b: Peel strength (peel force) per 25mm width is 10N or more and less than 100N c: Peel strength (peel force) per 25mm width is less than 10N

[0208] [Manufacturing of toothed belts] In Comparative Examples 1-2 and Examples 1-30, 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 using the first manufacturing method described in the section [Modes for Carrying Out the Invention], which does not go through (a) pre-forming. 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.

[0209] (Comparative Example 1) Uncrosslinked rubber composition R1 was used as uncrosslinked rubber sheet A, and uncrosslinked rubber composition R9 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%.

[0210] (Comparative Example 2) A toothed belt was fabricated in the same manner as in Comparative Example 1, 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%.

[0211] (Example 1) A toothed belt was prepared in the same manner as in Comparative Example 1, except that an uncrosslinked rubber composition R2 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%.

[0212] (Example 2) A toothed belt was manufactured in the same manner as in Example 1, except that an uncrosslinked rubber composition R3 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%.

[0213] (Example 3) A toothed belt was manufactured in the same manner as in Example 1, except that an uncrosslinked rubber composition R4 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%.

[0214] (Example 4) A toothed belt was manufactured in the same manner as in Example 1, except that an uncrosslinked rubber composition R5 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%.

[0215] (Example 5) A toothed belt was manufactured in the same manner as in Example 1, except that an uncrosslinked rubber composition R6 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%.

[0216] (Example 6) A toothed belt was manufactured in the same manner as in Example 1, except that an uncrosslinked rubber composition R7 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%.

[0217] (Example 7) A toothed belt was manufactured in the same manner as in Example 3, except that an uncrosslinked rubber composition R8 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%.

[0218] (Example 8) A toothed belt was manufactured in the same manner as in Example 3, 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%.

[0219] (Example 9) A toothed belt was manufactured in the same manner as in Example 3, 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%.

[0220] (Example 10) A toothed belt was manufactured in the same manner as in Example 3, 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%.

[0221] (Example 11) A toothed belt was manufactured in the same manner as in Example 3, 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%.

[0222] (Example 12) A toothed belt was manufactured in the same manner as in Example 3, except that the average thickness of the first rubber layer was set to 2.0 mm. The back surface 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%.

[0223] (Example 13) A toothed belt was manufactured in the same manner as in Example 3, except that the average thickness of the first rubber layer was set to 4.5 mm. The back surface 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%.

[0224] (Example 14) A toothed belt was manufactured in the same manner as in Example 3, except that the average thickness of the first rubber layer was set to 5.5 mm. The back surface 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%.

[0225] (Example 15) A toothed belt was prepared in the same manner as in Comparative Example 1, except that an uncrosslinked rubber composition R10 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%.

[0226] (Example 16) A toothed belt was manufactured in the same manner as in Example 15, except that an uncrosslinked rubber composition R11 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%.

[0227] (Example 17) A toothed belt was manufactured in the same manner as in Example 15, except that an uncrosslinked rubber composition R12 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%.

[0228] (Example 18) A toothed belt was fabricated in the same manner as in Example 15, except that an uncrosslinked rubber composition R13 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%.

[0229] (Example 19) A toothed belt was manufactured in the same manner as in Example 15, except that an uncrosslinked rubber composition R14 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%.

[0230] (Example 20) A toothed belt was manufactured in the same manner as in Example 17, 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%.

[0231] (Example 21) A toothed belt was manufactured in the same manner as in Example 17, 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%.

[0232] (Example 22) A toothed belt was manufactured in the same manner as in Example 17, 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%.

[0233] (Example 23) A toothed belt was manufactured in the same manner as in Example 17, 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%.

[0234] (Example 24) A toothed belt was manufactured in the same manner as in Example 17, except that the average thickness of the first rubber layer was set to 2.0 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 62.5%.

[0235] (Example 25) A toothed belt was manufactured in the same manner as in Example 17, except that the average thickness of the first rubber layer was set to 4.5 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 78.9%.

[0236] (Example 26) A toothed belt was manufactured in the same manner as in Example 17, except that the average thickness of the first rubber layer was set to 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%.

[0237] (Example 27) An toothed belt was produced in the same manner as in Comparative Example 1, except that unvulcanized rubber composition R2 was used as the unvulcanized rubber sheet A and unvulcanized rubber composition R11 was used as the unvulcanized rubber sheet B. The Shore hardness of the back surface 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 peripheral rubber layer was 70.7%.

[0238] (Example 28) An toothed belt was produced in the same manner as in Comparative Example 1, except that unvulcanized rubber composition R4 was used as the unvulcanized rubber sheet A and unvulcanized rubber composition R12 was used as the unvulcanized rubber sheet B. The Shore hardness of the back surface 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 peripheral rubber layer was 70.7%.

[0239] (Example 29) An toothed belt was produced in the same manner as in Comparative Example 1, except that unvulcanized rubber composition R3 was used as the unvulcanized rubber sheet A and unvulcanized rubber composition R11 was used as the unvulcanized rubber sheet B. The Shore hardness of the back surface 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 peripheral rubber layer was 70.7%.

[0240] (Example 30) An toothed belt was produced in the same manner as in Comparative Example 1, except that unvulcanized rubber composition R8 was used as the unvulcanized rubber sheet A and unvulcanized rubber composition R14 was used as the unvulcanized rubber sheet B. The Shore hardness of the back surface 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 peripheral rubber layer was 70.7%.

[0241] [Measurement of Bonding Strength (Peel Strength) in Toothed Belt] A 15cm section was cut from the fabricated endless toothed belt in the length direction to obtain a sample for measurement, representing the belt in its unrunned state. Similarly, a sample was also taken from the endless toothed belt after it had been run, representing the belt in its runned state. A two-axis running test machine consisting of a drive (Dr.) pulley with a diameter of 56.02mm and a driven (Dn.) pulley with a diameter of 56.02mm was used to run the toothed belt. On the two-axis running test machine, a toothed belt with a width of 36.0mm was mounted on each pulley, the shaft load was set to 128N, the drive pulley rotation speed to 3600rpm, and the driven pulley load to 4.86N·m. The belt was run for 720 hours at an ambient temperature of 100°C.

[0242] 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 grip of an Autograph (Shimadzu Corporation "AGS-J10kN"), and gripping portion B (second rubber layer, laminated tooth portion) was gripped with the lower grip. 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.

[0243] 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.

[0244] (Judgment criteria) a: Peel strength (peeling force) of 40N or more per 25mm width b: Peel strength (peel force) per 25mm width is 30N or more and less than 40N c: Peel strength (peel force) per 25mm width is 10N or more and less than 30N d: Peeling strength (peeling force) per 25mm width is less than 10N, or peeling occurs during driving.

[0245] [Endurance driving test] To verify the conveying performance on the back, we evaluated its superiority or inferiority using the belt's durability and running life as an indicator. Specifically, since conveying performance is lost due to failures caused by durable running (cracks on the back, delamination of the back layer), we used the durability and running life (running time until failure occurs) as an indicator of "sustainability of conveying performance" to determine its superiority or inferiority.

[0246] 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, and the machine was run 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.

[0247] 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 1 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 1 (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 1.

[0248] (Criteria for judging endurance driving tests) a: Driving time until breakdown (relative value) is 18 or more b: Driving time until breakdown (relative value) is 10 or more, but less than 18. c: Driving time until failure (relative value) is greater than 1.0 and less than 10. d: Driving time until failure (relative value) is 1.0 or less

[0249] [Overall assessment] Considering the three items of the joint strength in the non-running state (the joint strength between the first rubber layer and the second rubber layer), the joint strength after running (maintenance from the non-running state), and the endurance running life (maintenance of conveying performance) in the toothed belt, the overall superiority and inferiority were judged (ranked) according to the criteria shown below. From the perspective of the practicality of the product, grades A, B, and C were considered qualified, and grade D was considered unqualified.

[0250] (Criteria for comprehensive judgment) Grade A: All three items are judged as a Grade B: The judgment includes b (c and d judgments are not included) Grade C: The judgment includes c (d judgment is not included) Grade D: The judgment includes d

[0251] The evaluation results of Comparative Examples 1-2 and Examples 1-30 are shown in Tables 5-9.

[0252]

Table 5

[0253]

Table 6

[0254]

Table 7

[0255]

Table 8

[0256]

Table 9

[0257] <Verification results of Table 5> (Comparative Examples 1 and 2) Comparative Example 1 is an example of a toothed belt in which a first rubber layer (R9) that does not contain zinc methacrylate and a second rubber layer (R1) that does not contain zinc methacrylate are joined together. Comparative Example 2 is an example of a toothed belt in which the first rubber layer (R9) and the second rubber layer (R1) of Comparative Example 1 are joined together with an epoxy resin adhesive.

[0258] 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.

[0259] Furthermore, in the durability driving test, the driving life (driving time until failure (relative value)) was also low (rated D) due to delamination between the first and second rubber layers at an early stage, resulting in an overall rating of D (fail).

[0260] (Examples 1-6) Examples 1 to 6 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 1. When the amount of zinc methacrylate added was varied to 5 parts by mass (Example 1: R2), 10 parts by mass (Example 2: R3), 15 parts by mass (Example 3: R4), 25 parts by mass (Example 4: R5), 30 parts by mass (Example 5: R6), and 35 parts by mass (Example 6: R7), the bonding strength between the first rubber layer and the second rubber layer in the unused belt state improved to a passing level (grade c) in Examples 1 and 2, and to a passing level (grade a) in Examples 3 to 6. Furthermore, this bonding strength was maintained even after use.

[0261] Furthermore, regarding the running life, in Example 1, the belt failed (reached the end of its lifespan) due to delamination between the first and second rubber layers at a running time (relative value) of 10 (rating b). In other words, it can run 10 times longer than Comparative Example 1 (conveying performance is maintained). The running time (relative value) until failure was 12 in Example 2 (rating b), and in Examples 3 to 6, no delamination between 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) (rating a). In the overall evaluation, the toothed belts in Examples 1 and 2 were rated C (pass), and the toothed belts in Examples 3 to 6 were rated A (pass).

[0262] 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).

[0263] <Verification results in Table 6> (Example 7) Example 7 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 R4 to R8) compared to the configuration of Example 3. 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 those of Example 3, and the overall evaluation was A rank (pass).

[0264] (Examples 8-11) Examples 8 to 11 are based on the configuration of Example 3, 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 (EPDM 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 8), 53.7% (Example 9), 70.7% (Example 3), 78.0% (Example 10), and 82.9% (Example 11). In all cases, the bonding strength between the first and second rubber layers was equivalent to that of Example 3. Regarding durability and running life (maintenance of conveying function), in Example 8, 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 11, 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 9 and 10, no delamination between the first and second rubber layers or cracking on the back surface 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 8 and 11, and A rank (pass) for the toothed belts in Examples 9 and 10.

[0265] (Examples 12-14) Examples 12 to 14 are based on the configuration of Example 3, 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 12), 70.7% (Example 3), 78.9% (Example 13), and 82.1% (Example 14). In all cases, the bonding strength between the first and second rubber layers was equivalent to that of Example 3. 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 12 and 13, 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). However, in Example 14, which had the largest total belt thickness, cracks occurred on the back after 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 14, and A rank (pass) for the toothed belts in Examples 12 and 13.

[0266] 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%.

[0267] <Verification results in Table 7> (Examples 15-18) Examples 15-18 are toothed belts in which zinc methacrylate was added to the first rubber layer (silicone rubber composition) compared to the configuration of Comparative Example 1. By varying the amount of zinc methacrylate added (1 part by mass (Example 15: R10), 2.5 parts by mass (Example 16: R11), 5 parts by mass (Example 17: R12), and 10 parts by mass (Example 18: R13)), the bonding strength between the first and second rubber layers in an unused belt state improved to a passing level (grade c) in Examples 15 and 16, and to a passing level (grade a) in Examples 17 and 18. Furthermore, this bonding strength was maintained even after use.

[0268] Furthermore, regarding the running life, in Example 15, the belt failed (reached the end of its lifespan) due to delamination between the first and second rubber layers at a running time (relative value) of 12 (rating b). In other words, it can be said that it can run 12 times longer than Comparative Example 1 (conveying performance is maintained). The running time (relative value) until failure was 16 in Example 16 (rating b), while in Examples 17 and 18, no delamination between 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) (rating a). In the overall evaluation, the toothed belts in Examples 15 and 16 were rated C (pass), and the toothed belts in Examples 17 and 18 were rated A (pass).

[0269] 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).

[0270] <Verification results in Table 8> (Example 19) Example 19 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 R12 to R14) compared to the configuration of Example 17. The bonding strength between the first and second rubber layers, and the durable running life (maintenance of conveying function) were equivalent to those of Example 17, and the overall evaluation was A rank (pass).

[0271] (Examples 20-23) Examples 20 to 23 are based on the configuration of Example 17, 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 (EPDM 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 20), 53.7% (Example 21), 70.7% (Example 17), 78.0% (Example 22), and 82.9% (Example 23). In all cases, the bonding strength between the first and second rubber layers was equivalent to that of Example 17. Regarding durability and running life (maintenance of conveying function), in Example 20, 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 23, 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 21 and 22, 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 20 and 23, and A rank (pass) for the toothed belts in Examples 21 and 22.

[0272] (Examples 24-26) Examples 24 to 26 are based on the configuration of Example 17, 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 24), 70.7% (Example 3), 78.9% (Example 25), and 82.1% (Example 26). In all cases, the bonding strength between the first and second rubber layers was equivalent to that of Example 17. 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 24 and 25, 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). However, in Example 26, 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 26, and A rank (pass) for the toothed belts in Examples 24 and 25.

[0273] 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%.

[0274] <Verification results in Table 9> (Examples 27-30) Examples 27-30 are 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 1.

[0275] Example 27 is a combination of the second rubber layer of Example 1 (composition R2, 5 parts by mass of zinc methacrylate) and the first rubber layer of Example 16 (composition R11, 2.5 parts by mass of zinc methacrylate). In Examples 1 and 16, 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 27, no significant improvement in bonding strength was observed, and it was also rated C (pass).

[0276] Example 28 is a combination of the second rubber layer of Example 3 (composition R4, 15 parts by mass of zinc methacrylate) and the first rubber layer of Example 17 (composition R12, 5 parts by mass of zinc methacrylate). In Examples 3 and 17, 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 28, the bonding strength was equivalent to that of Examples 3 and 17, and no significant improvement was observed.

[0277] Example 29 is a combination of the second rubber layer of Example 2 (composition R3, 10 parts by mass of zinc methacrylate) and the first rubber layer of Example 16 (composition R11, 2.5 parts by mass of zinc methacrylate). In Examples 2 and 16, 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 29, the bonding strength was slightly improved compared to Examples 2 and 16, and the overall rating was rank B (pass).

[0278] Example 30 is a combination of the second rubber layer of Example 7 (composition R8, 15 parts by mass of zinc methacrylate) and the first rubber layer of Example 19 (composition R14, 5 parts by mass of zinc methacrylate). In Examples 7 and 19, 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 30, the bonding strength was equivalent to that of Examples 7 and 19, and no significant improvement was observed.

[0279] 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). [Industrial applicability]

[0280] The power transmission belt of the present invention is not particularly limited as long as it is a power transmission belt that transmits power and transports articles using the back surface of the belt. For example, it can be used as a friction transmission belt such as a flat belt, V-belt, or V-ribbed belt; or as a toothed transmission belt such as a toothed belt or a double-sided toothed belt. In particular, it can be suitably used as a toothed belt that transports articles using the back surface of the belt.

[0281] Preferred toothed belts include those used for transporting goods such as daily necessities, industrial products, agricultural products, and food products (for example, toothed belts for office automation (OA) equipment parts, coin handling equipment, photocopiers, and printing presses), and are particularly suitable as toothed belts for transporting paper products (paper, corrugated cardboard, etc.). [Explanation of Symbols]

[0282] 1…Toothed belt 1a...teeth part 1b...Root of the tooth 1c...back 2... Back elastic layer 2a...First rubber layer 2b...Second rubber layer 3… Core wire 4…Tooth rubber layer 5... Toothcloth

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 surface of the outer rubber layer is used to transport articles, The outer periphery rubber layer has a laminated structure including a first rubber layer that forms the transport surface which is the outer periphery, and a second rubber layer laminated on the inner periphery of 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 ethylene-α-olefin elastomer, A power transmission belt comprising the first rubber composition and / or the second rubber composition containing an unsaturated carboxylic acid metal salt.

2. The transmission belt according to claim 1, wherein the unsaturated carboxylic acid metal salt comprises zinc methacrylate.

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 claim 1 or 2, 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.

5. The transmission belt according to claim 1 or 2, wherein the average thickness of the first rubber layer is 50 to 80% of the average thickness of the outer rubber layer.

6. The transmission belt according to claim 1 or 2, 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 claim 1 or 2, which is a toothed belt.

8. A method for manufacturing a power transmission belt according to claim 1 or 2, comprising a joining step of joining a first rubber layer precursor formed of the first rubber composition and a second rubber layer precursor formed of the second rubber composition by laminating and crosslinking them, thereby joining the first rubber layer and the second rubber layer without interposing an adhesive between the first rubber layer and the second rubber layer.

9. 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 circumference side of the belt relative to the core wire, wherein the outer surface of the outer rubber layer is used to transport articles, The outer periphery rubber layer has a laminated structure including a first rubber layer that forms the transport surface which is the outer periphery, and a second rubber layer laminated on the inner periphery of the first rubber layer. The first rubber layer is formed from 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 ethylene-α-olefin elastomer, and A method for improving the adhesion between the first rubber layer and the second rubber layer by incorporating an unsaturated carboxylic acid metal salt into the first rubber composition and / or the second rubber composition.

10. A belt transmission mechanism for transporting articles, comprising a transmission belt according to claim 1 or 2 and a pulley.

Images