Rubber composition, reinforcing fabric, power transmission belt, and method for manufacturing a power transmission belt

Abstract

To improve the wear resistance and productivity of power transmission belts. [Solution] A rubber composition containing an ethylene-long-chain α-olefin-non-conjugated polyene copolymer, in which the long-chain α-olefin units have 4 or more carbon atoms, in a proportion of 25% by mass or more in the rubber component is compounded with the fabric of the transmission belt. The rubber composition may further contain silica, hard carbon black, aliphatic oil, tackifier, etc. At least a portion of the belt surface may be covered with a composite of the crosslinked rubber composition and the fabric to produce the transmission belt. This transmission belt may be a wrapped V-belt.

Description

[Technical Field]

[0001] The present invention relates to a rubber composition used in power transmission belts, a reinforcing fabric, a power transmission belt containing this rubber composition, and a method for manufacturing the same. [Background technology]

[0002] Power transmission belts are broadly classified into friction belts and meshing belts. Examples of friction belts include flat belts, V-belts, and V-ribbed belts, while examples of meshing belts include toothed belts. V-belts include raw-edge type (raw-edge V-belts), where the rubber layer with the friction transmission surface (V-shaped side) is exposed, and wrapped type (wrapped V-belts), where the friction transmission surface is covered with an outer fabric (cover fabric). These V-belts are used differently depending on the application, based on the surface properties of the friction transmission surface (coefficient of friction between the rubber layer and the cover fabric).

[0003] Many of these power transmission belts have at least a portion of their surface covered with reinforcing fabric to increase their strength and abrasion resistance. The reinforcing fabric is formed as a composite of fabric and rubber composition by impregnating woven, knitted, or nonwoven fabric with rubber adhesive, or by rubbing or laminating a rubber composition into it. By making the reinforcing fabric a composite of fabric and rubber composition, strength and abrasion resistance are improved, and tackiness (adhesion) is also imparted, which also improves the processability when forming the belt.

[0004] For example, the manufacturing process of a wrapped V-belt includes a friction process in which a rubber composition is rubbed into the canvas, a lap joint process in which the reinforcing fabric is cut diagonally and then the ends are overlapped and joined together, and a covering process in which the belt body is covered with the reinforcing fabric. Therefore, the reinforcing fabric used in a wrapped V-belt is required to have not only strength and abrasion resistance, but also properties that allow for good processability in each of the above processes.

[0005] For example, Japanese Patent Publication No. 2024-58593 (Patent Document 1) discloses a friction transmission belt formed from a reinforcing fabric containing a rubber composition in which the minimum viscosity of Mooney scorch at 125°C in the uncrosslinked portion is 21 or less, and the rubber hardness in the crosslinked portion is 55 or more, for the purpose of improving friction workability and wear resistance.

[0006] Furthermore, International Publication No. 2015 / 194116 (Patent Document 2) discloses a wrapped V-belt made of a rubber composition containing an ethylene-α-olefin elastomer with an ethylene content of 40% by mass or more and 56% by mass or less as a rubber component (polymer component), with the aim of realizing a transmission belt with excellent wear resistance and processability. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] Japanese Patent Publication No. 2024-58593 [Patent Document 2] International Publication No. 2015 / 194116 [Overview of the project] [Problems that the invention aims to solve]

[0008] However, the wrapped V-belts disclosed in Patent Documents 1 and 2 did not sufficiently improve wear resistance and processability, and further improvements were needed.

[0009] Therefore, an object of the present invention is to provide a rubber composition, a reinforcing fabric, a transmission belt containing this rubber composition, and a method for manufacturing the same, which can improve the wear resistance and productivity of transmission belts. [Means for solving the problem]

[0010] In order to achieve the above object, the present inventors have found that by compounding a rubber composition containing an ethylene-long chain α-olefin-non-conjugated polyene copolymer having 4 or more carbon atoms in the long chain α-olefin unit at a ratio of 25% by mass or more in the rubber component, the abrasion resistance and productivity of the transmission belt can be improved, and thus the present invention has been completed.

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

[0012] Aspect [1]: A rubber composition for compounding with a fabric of a transmission belt, comprising a rubber component, wherein the rubber component contains an ethylene-long chain α-olefin-non-conjugated polyene copolymer having 4 or more carbon atoms in the long chain α-olefin unit, and the proportion of the ethylene-long chain α-olefin-non-conjugated polyene copolymer is 25% by mass or more in the rubber component.

[0013] s Aspect [2]: The rubber composition according to Aspect [1], further comprising silica.

[0014] Aspect [3]: The rubber composition according to Aspect [1] or [2], further comprising hard carbon black.

[0015] Aspect [4]: The rubber composition according to any one of Aspects [1] to [3], further comprising an aliphatic oil.

[0016] Aspect [5]: The rubber composition according to Aspect [4], wherein the proportion of the aliphatic oil is 10 to 40 parts by mass with respect to 100 parts by mass of the rubber component.

[0017] Aspect [6]: The rubber composition according to any one of Aspects [1] to [5], further comprising a tackifier.

[0018] Aspect [7]: The rubber composition according to Aspect [6], wherein the proportion of the tackifier is 10 parts by mass or more with respect to 100 parts by mass of the rubber component.

[0019] Embodiment [8]: The rubber composition according to any one of Embodiments [1] to [7], wherein the rubber component further comprises an ethylene-propylene-nonconjugated polyene copolymer, the ethylene-long-chain α-olefin-nonconjugated polyene copolymer is an ethylene-butene-nonconjugated diene copolymer, and the proportion of the ethylene-long-chain α-olefin-nonconjugated polyene copolymer is 55 to 90% by mass of the rubber component.

[0020] Embodiment [9]: The rubber composition according to any one of Embodiments [1] to [8], wherein the minimum viscosity Vm of Mooney scorch at 125°C in the uncrosslinked material is 30 or less.

[0021] Embodiment

[10] : The rubber composition according to any of Embodiments [1] to [9], wherein the crosslinked material has a rubber hardness of 55 or more.

[0022] Embodiment

[11] : A reinforcing cloth for covering at least a portion of the surface of a power transmission belt, comprising a composite of the cloth and a crosslinked rubber composition according to any of Embodiments [1] to

[10] .

[0023] Embodiment

[12] : A transmission belt comprising the reinforcing fabric described in Embodiment

[11] , wherein at least a portion of the surface of the transmission belt is covered with the reinforcing fabric.

[0024] Embodiment

[13] : The transmission belt according to Embodiment

[12] , which is a wrapped V-belt.

[0025] Embodiment

[14] : A method for manufacturing a transmission belt, comprising a compounding step to obtain an uncrosslinked composite for forming a reinforcing fabric by compounding a cloth with a rubber composition according to any of Embodiments [1] to

[10] .

[0026] Embodiment

[15] : A method for manufacturing a transmission belt according to Embodiment

[14] , wherein the composite step is a friction treatment, coating treatment, lamination treatment or soaking treatment.

[0027] Embodiment

[16] : A method for manufacturing a transmission belt according to Embodiment

[14] or

[15] , further comprising a lap joint step of cutting the uncrosslinked composite diagonally and overlapping and joining the ends to obtain a reinforcing fabric precursor.

[0028] Embodiment

[17] : A method for manufacturing a transmission belt according to Embodiment

[16] , further comprising a covering step of covering the belt body precursor with the reinforcing fabric precursor. [Effects of the Invention]

[0029] In this invention, a rubber composition containing an ethylene-long-chain α-olefin-non-conjugated polyene copolymer having 4 or more carbon atoms in the long-chain α-olefin units at a ratio of 25% by mass or more in the rubber component is compounded with the fabric of the transmission belt, thereby improving the abrasion resistance and productivity of the transmission belt. In particular, when the rubber composition is used as the reinforcing fabric for a wrapped V-belt, the processability and abrasion resistance during belt manufacturing, such as friction (the process of manufacturing the reinforcing fabric by rubbing the rubber composition onto the fabric), lap joint (the process of overlapping and joining the ends after cutting the reinforcing fabric diagonally), and covering (the process of covering the belt body with the reinforcing fabric), can be improved. [Brief explanation of the drawing]

[0030] [Figure 1] Figure 1 is a schematic partial cross-sectional perspective view of a cut wrapped V-belt. [Figure 2] Figure 2 is a graph showing the behavior of Mooney viscosity to illustrate the method for measuring the minimum Mooney scorch viscosity (Vm) and scorch time. [Figure 3] Figure 3 shows the layout of the wear resistance test for the wrapped V-belt obtained in the example. [Modes for carrying out the invention]

[0031] [Rubber composition] (Rubber component (A)) The rubber composition of the present invention is a rubber composition for compounding with a fabric for a power transmission belt, and comprises a rubber component (A). The rubber component (A) is characterized by comprising an ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) in which the long-chain α-olefin unit has 4 or more carbon atoms.

[0032] (Ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1)) The ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) comprises ethylene units, long-chain α-olefin units, and non-conjugated polyene units as constituent units, wherein the long-chain α-olefin units have 4 or more carbon atoms.

[0033] The number of carbon atoms in the long-chain α-olefin unit should be 4 or more, but for example, 4 to 20, preferably 4 to 10, more preferably 4 to 8, more preferably 4 to 6, and most preferably 4 to 5. If the number of carbon atoms is too large, the wear resistance of the transmission belt may decrease.

[0034] Examples of α-olefins for forming long-chain α-olefin units having 4 or more carbon atoms include linear α-C such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, 1-nonene, 1-decene, 1-nonadecene, and 1-eicosene. 4-20 Olefins; branched-chain α-C such as 4-methyl-1-pentene, 9-methyl-1-decene, 11-methyl-1-dodecene, and 12-ethyl-1-tetradecene. 4-20 Examples include olefins. These α-olefins can be used individually or in combination of two or more.

[0035] Among these α-olefins, α-C such as 1-butene, 1-hexene, and 1-octene 4-10 Olefins are preferred. Linear α-C is preferred because it can improve the productivity of transmission belts. 4-8 Olefins are even more preferred, and linear α-C 4-6 Olefins are more preferred, and linear α-C 4-5 Olefins are the most preferred.

[0036] Examples of non-conjugated polyene monomers for forming non-conjugated polyene units include linear non-conjugated diene monomers such as 1,4-hexadiene, 1,6-octadiene, 2-methyl-1,5-hexadiene, 6-methyl-1,5-heptadiene, and 7-methyl-1,6-octadiene; cyclohexadiene, dicyclopentadiene (DCPD), methyltetrahydroindene, 5-vinyl-2-norbornene (VNB), 5-ethylidene-2-norbornene (ENB), 5-methylene-2-norbornene, and 5-I Examples include cyclic non-conjugated diene monomers such as sopropylidene-2-norbornene and 6-chloromethyl-5-isopropenyl-2-norbornene; and non-conjugated triene monomers such as 2,3-diisopropylidene-5-norbornene, 2-ethylidene-3-isopropylidene-5-norbornene, 2-propenyl-2,5-norbornadiene, 1,3,7-octatriene, 1,4,9-decatriene, 4,8-dimethyl-1,4,8-decatriene, and 4-ethylidene-8-methyl-1,7-nonadien. These non-conjugated polyene monomers can be used individually or in combination of two or more.

[0037] Among these non-conjugated polyene monomers, linear non-conjugated diene monomers such as 1,4-hexadiene and cyclic non-conjugated diene monomers are preferred. Ethylidene norbornene such as ENB, vinyl norbornene such as VNB, and DCPD are even more preferred, with ENB being the most preferred, from the viewpoint of improving abrasion resistance.

[0038] Typical ethylene-long-chain α-olefin-non-conjugated polyene copolymers (A1) include, for example, ethylene-1-butene-1,4-hexadiene copolymer, ethylene-1-pentene-1,4-hexadiene copolymer, ethylene-1-hexene-1,4-hexadiene copolymer, ethylene-1-heptene-1,4-hexadiene copolymer, ethylene-1-octene-1,4-hexadiene copolymer, ethylene-1-nonene-1,4-hexadiene copolymer, ethylene-1-decene-1,4-hexadiene copolymer, and ethylene-1-butene-1-octene-1,4-hexadiene copolymer, among others, such as ethylene-α-C 4-20Olefin-linear non-conjugated diene copolymer; ethylene-1-butene-5-ethylidene-2-norbornene copolymer, ethylene-1-pentene-5-ethylidene-2-norbornene copolymer, ethylene-1-hexene-5-ethylidene-2-norbornene copolymer, ethylene-1-heptene-5-ethylidene-2-norbornene copolymer, ethylene-1-octene-5-ethylidene-2-norbornene copolymer, ethylene-1-nonene-5-ethylidene-2-norbornene copolymer, ethylene-1-decene-5-ethylidene-2-norbornene copolymer, ethylene-1-butene-1-octene-5-ethylidene-2-norbornene copolymer, etc. of ethylene-α-C 4-20 Examples include olefin-cyclic non-conjugated diene copolymers and the like.

[0039] These ethylene-long chain α-olefin-non-conjugated polyene copolymers can be used alone or in combination of two or more.

[0040] Among these, from the viewpoint of improving the productivity of the transmission belt, ethylene-α-C 4-10 olefin-non-conjugated diene copolymers are preferred, ethylene-α-C 4-8 olefin-non-conjugated diene copolymers are more preferred, ethylene-1-butene-non-conjugated diene copolymers (EBDM) are even more preferred, and ethylene-1-butene-cyclic non-conjugated diene copolymers (especially ethylene-1-butene-5-ethylidene-2-norbornene copolymers) are most preferred.

[0041] The ethylene content (ratio of ethylene units) in the ethylene-long chain α-olefin-non-conjugated polyene copolymer (A1) may be 30% by mass or more, for example, 30 to 80% by mass, preferably 35 to 70% by mass, more preferably 40 to 60% by mass, still more preferably 45 to 55% by mass, and most preferably 48 to 52% by mass. If the ethylene content is too low, the abrasion resistance of the transmission belt may decrease, and if the ethylene content is too high, the processability may decrease.

[0042] } In this application, the ethylene content refers to the mass ratio of ethylene units in the total units constituting the copolymer [including not only the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) but also the ethylene-propylene-non-conjugated polyene copolymer (A2) described later]. The ethylene content can be measured by conventional methods, but it may also be a ratio based on ethylene as a monomer.

[0043] Furthermore, in this application, when there are multiple types of copolymers [including not only ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) but also ethylene-propylene-non-conjugated polyene copolymer (A2) described later], the ethylene content refers to the average value based on 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-long-chain α-olefin-non-conjugated polyene copolymer.

[0044] In the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1), the ratio (mass ratio) of ethylene to long-chain α-olefin is, for example, 30 / 70~90 / 10, preferably 40 / 60~80 / 20, more preferably 45 / 55~70 / 30, and more preferably 50 / 50~60 / 40. If the ratio of long-chain α-olefin is too low, the effect of improving the productivity of the transmission belt may decrease, and if the ratio of long-chain α-olefin is too high, the wear resistance may decrease.

[0045] In this application, the long-chain α-olefin content refers to the mass ratio of long-chain α-olefin units in the total units constituting the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1). The long-chain α-olefin content can be measured by conventional methods, but it may also be a ratio based on long-chain α-olefin as a monomer.

[0046] The non-conjugated polyene content (particularly the non-conjugated diene content) of the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) is, for example, 0.1 to 15% by mass, preferably 1 to 12% by mass, more preferably 3 to 10% by mass, more preferably 5 to 9% by mass, and most preferably 6 to 8% by mass. If the non-conjugated polyene content is too low, the productivity of the transmission belt may decrease, and conversely, if the non-conjugated polyene content is too high, the wear resistance may decrease.

[0047] In this application, the non-conjugated polyene content refers to the mass ratio of diene monomer units in the total units constituting the copolymer [including not only the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) but also the ethylene-propylene-non-conjugated polyene copolymer (A2) described later]. The non-conjugated polyene content can be measured by conventional methods, but it may also be a ratio based on monomers.

[0048] The Mooney viscosity [ML(1+4)125℃] of the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) (uncrosslinked copolymer) is, for example, 3 to 100, preferably 3 to 70, and more preferably 3 to 30. If the Mooney viscosity is too low, the wear resistance of the transmission belt may decrease, and conversely, if the Mooney viscosity is too high, the effect of improving processability may decrease.

[0049] In this application, the Mooney viscosity of the copolymer [including not only the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) but also the ethylene-propylene-non-conjugated polyene copolymer (A2) described later] can be measured by a method conforming to the Mooney viscosity test of JIS K 6300-1 (2013). The test conditions are as follows: an L-shaped rotor is used, the test temperature is 125°C, preheating is 1 minute, and the rotor operating time is 4 minutes. Mooney viscosity is calculated by filling the cavity with an uncrosslinked copolymer so that it is in contact with a rotor having grooves on its surface, and measuring the torque required to rotate the rotor. It is used as an indicator of the fluidity (ease of processing) of the rubber.

[0050] Furthermore, in this application, when there are multiple types of copolymers [including not only the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) but also the ethylene-propylene-non-conjugated polyene copolymer (A2) described later], the 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 copolymer.

[0051] The proportion of ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) is 25% by mass or more (particularly 30% by mass or more) of the rubber component (A), for example, 25-100% by mass, preferably 30-98% by mass, more preferably 50-95% by mass, more preferably 55-90% by mass, even more preferably 55-70% by mass, and most preferably 55-65% by mass. If the proportion of copolymer (A1) is too low, the effect of improving the productivity of the transmission belt will decrease, and if the proportion of copolymer (A1) is too high, there is a risk that the economic efficiency will decrease.

[0052] (Other rubber components) The rubber component (A) may contain, in addition to the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1), other rubber components (other rubber components).

[0053] Other rubber components include, for example, diene rubbers [natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), chloroprene rubber (CR), butyl rubber (IIR), styrene-butadiene rubber (SBR), vinylpyridine-styrene-butadiene rubber, acrylonitrile-butadiene rubber (nitrile rubber: NBR), acrylonitrile-chloroprene rubber, hydrogenated nitrile rubber (HNBR), etc.], ethylene-α-olefin elastomers other than ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1), chlorosulfonated polyethylene rubber (CSM), alkylated chlorosulfonated polyethylene rubber (ACSM), epichlorohydrin rubber, acrylic rubber, silicone rubber, urethane rubber, and fluororubber. These other rubber components can be used individually or in combination of two or more.

[0054] Of these, ethylene-α-olefin elastomers other than ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) are preferred due to their superior heat resistance, weather resistance, and abrasion resistance. In other words, it is preferable that the rubber component (A) is an ethylene-α-olefin elastomer.

[0055] The proportion of other rubber components is 75% by mass or less (particularly 70% by mass or less) of rubber component (A), for example, 2 to 70% by mass, preferably 5 to 50% by mass, more preferably 10 to 45% by mass, more preferably 30 to 45% by mass, and most preferably 35 to 45% by mass.

[0056] Other ethylene-α-olefin elastomers include, for example, ethylene-propylene-non-conjugated polyene copolymer (A2) and ethylene-α-olefin rubber [ethylene-propylene rubber (EPM), ethylene-butene rubber (EBM), ethylene-octene rubber (EOM), etc.]. These other ethylene-α-olefin elastomers can be used individually or in combination of two or more.

[0057] Among these other ethylene-α-olefin elastomers, ethylene-propylene-non-conjugated polyene copolymer (A2) is preferred due to its excellent heat resistance, weather resistance, and abrasion resistance.

[0058] (Ethylene-propylene-nonconjugated polyene copolymer (A2)) Ethylene-propylene-non-conjugated polyene copolymer (A2) contains ethylene units, propylene units, and conjugated polyene units as constituent units.

[0059] As the non-conjugated polyene monomer for forming non-conjugated polyene units, it can be selected from the non-conjugated polyene monomers exemplified as non-conjugated polyene monomers of the ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1), including preferred embodiments.

[0060] Typical ethylene-propylene-nonconjugated polyene copolymers (A2) include, for example, ethylene-propylene-chain nonconjugated diene copolymers such as ethylene-propylene-1,4-hexadiene copolymer; and ethylene-propylene-cyclic nonconjugated diene copolymers such as ethylene-propylene-5-ethylidene-2-norbornene copolymer. The ethylene-propylene-nonconjugated polyene copolymer (A2) may also be an ethylene-propylene-diene ternary copolymer (EPDM).

[0061] The ethylene content (percentage of ethylene units) in the ethylene-propylene-non-conjugated polyene copolymer (A2) may be 30% by mass or more, for example, 30-80% by mass, preferably 35-70% by mass, more preferably 40-60% by mass, more preferably 45-55% by mass, and most preferably 48-52% by mass.

[0062] In the ethylene-propylene-non-conjugated polyene copolymer (A2), the ratio (mass ratio) of ethylene to propylene is, for example, 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.

[0063] In this application, the propylene content refers to the mass ratio of propylene units in the total units constituting the ethylene-propylene-non-conjugated polyene copolymer (A2). The propylene content can be measured by conventional methods, but it may also be a ratio based on propylene as a monomer.

[0064] The non-conjugated polyene content (particularly the non-conjugated diene content) of the ethylene-propylene-non-conjugated polyene copolymer (A1) is, for example, 0.1 to 15% by mass, preferably 1 to 13% by mass, more preferably 5 to 12% by mass, more preferably 6 to 10% by mass, and most preferably 7 to 9% by mass. If the non-conjugated polyene content is too low, the productivity of the transmission belt may decrease, and conversely, if the non-conjugated polyene content is too high, the wear resistance may decrease.

[0065] The Mooney viscosity [ML(1+4)125℃] of the ethylene-propylene-non-conjugated polyene copolymer (A2) (uncrosslinked copolymer) is, for example, 10 to 100, preferably 15 to 70, and more preferably 20 to 50. If the Mooney viscosity is too low, the wear resistance of the transmission belt may decrease, and conversely, if the Mooney viscosity is too high, the effect of improving processability may decrease.

[0066] When the rubber component (A) includes an ethylene-long-chain α-olefin-non-conjugated polyene copolymer (A1) and an ethylene-propylene-non-conjugated polyene copolymer (A2), the mass ratio of the two, for example, the former (A1) / latter (A2), is 100 / 0 to 25 / 75, preferably 98 / 2 to 30 / 70, more preferably 95 / 5 to 50 / 50, more preferably 90 / 10 to 55 / 45, even more preferably 70 / 30 to 55 / 45, and most preferably 65 / 35 to 55 / 45.

[0067] The proportion of rubber component (A) in the rubber composition is, for example, 20 to 80% by mass, preferably 30 to 75% by mass, more preferably 35 to 70% by mass, more preferably 40 to 60% by mass, and most preferably 45 to 50% by mass.

[0068] (Filler (B)) The rubber composition of the present invention preferably further contains a filler (B). The filler (B) includes a reinforcing filler (B1) and a non-reinforcing filler (B2) for improving strength such as hardness.

[0069] (Reinforcing filler (B1)) The reinforcing filler (B1) preferably contains carbon black (B1-1) and / or silica (B1-2), more preferably contains at least carbon black (B1-1), and particularly preferably contains carbon black (B1-1) and silica (B1-2).

[0070] (Carbon Black (B1-1)) It is preferable to include carbon black (B1-1) as a reinforcing filler (B1) in order to increase hardness.

[0071] The average particle size (average primary particle size) of carbon black (B1-1) is, for example, 5 to 200 nm, preferably 10 to 100 nm, more preferably 15 to 40 nm, more preferably 20 to 35 nm, and most preferably 25 to 30 nm. If the average particle size of carbon black (B1-1) is too small, workability may decrease, and conversely, if the average particle size of carbon black (B1-1) is too large, wear resistance may decrease.

[0072] In this application, the average particle size of carbon black (B1-1) can be measured using, for example, a scanning electron microscope (SEM) or a transmission electron microscope (TEM), and can be calculated as the arithmetic mean particle size of an appropriate number of samples (e.g., 50 samples) by image analysis.

[0073] Carbon black (B1-1) preferably contains hard carbon black with a relatively small particle size, as this can suppress the occurrence of adhesive wear (a type of wear in which highly adhesive wear particles aggregate and accelerate wear) and improve wear resistance. Generally, carbon black can be classified into hard carbon black with a relatively small particle size and soft carbon black with a relatively large particle size. While the classification of carbon black is sometimes based on the average particle size (average primary particle size) in the raw material state, in this application, it is based on the primary particle size of the carbon black contained in the rubber composition (particularly in the crosslinked 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 to 300 nm is referred to as soft carbon black (or soft carbon).

[0074] The average primary particle size of hard carbon black is, for example, 10 to 38 nm, preferably 15 to 35 nm, more preferably 20 to 33 nm, and more preferably 25 to 30 nm. On the other hand, the average primary particle size of soft carbon black is, for example, 42 to 100 nm, preferably 45 to 80 nm, more preferably 50 to 75 nm, and more preferably 60 to 70 nm.

[0075] The proportion of hard carbon black (percentage of particles) may be 10% or more of the carbon black (B1-1), preferably 50% or more, more preferably 80% or more, more preferably 90% or more, and most preferably 100%. If the proportion of hard carbon black is too low, the effect of suppressing the occurrence of adhesive abrasion may decrease.

[0076] In this application, the ratio of soft carbon black to hard carbon black particle numbers can be calculated based on the primary particle size measured using a transmission electron microscope.

[0077] The amount of iodine adsorbed by carbon black (B1-1) is, for example, 5 to 200 g / kg, preferably 10 to 150 g / kg, more preferably 50 to 130 g / kg, more preferably 60 to 100 g / kg, and most preferably 70 to 90 g / kg. If the amount of iodine adsorbed is too low, the effect of improving wear resistance may decrease, and conversely, if the amount of iodine adsorbed is too high, the productivity of the transmission belt may decrease.

[0078] In this application, the amount of iodine adsorbed by carbon black can be measured in accordance with the standard test method of ASTM D1510-17.

[0079] The proportion of carbon black (B1-1) may be 30 parts by mass or more per 100 parts by mass of rubber component (A), for example, 30 to 80 parts by mass, preferably 40 to 70 parts by mass, more preferably 45 to 65 parts by mass, and more preferably 50 to 60 parts by mass. Furthermore, if the crosslinking agent (F) described later is a sulfur-based crosslinking agent, the proportion of carbon black (B1-1) is, for example, 40 to 75 parts by mass, preferably 50 to 70 parts by mass, more preferably 55 to 65 parts by mass, more preferably 56 to 64 parts by mass, and most preferably 58 to 62 parts by mass per 100 parts by mass of rubber component (A). When the crosslinking agent (F) described later contains an organic peroxide, the proportion of carbon black (B1-1) is, for example, 30 to 60 parts by mass (particularly 43 to 58 parts by mass), preferably 44 to 57 parts by mass, more preferably 45 to 55 parts by mass, more preferably 46 to 54 parts by mass, and most preferably 48 to 52 parts by mass, per 100 parts by mass of rubber component (A). If the proportion of carbon black (B1-1) is too low, the hardness cannot be increased and the wear resistance may decrease. Conversely, if the proportion of carbon black (B1-1) is too high, the Vm may become too high, and the productivity of the transmission belt may decrease.

[0080] (Silica (B1-2)) The reinforcing filler (B1) preferably further contains silica (B1-2). By including silica (B1-2) in the rubber composition, both tackiness (adhesion) and abrasion resistance can be achieved, and in particular, abrasion resistance can be improved by suppressing the occurrence of adhesive abrasion.

[0081] Silica (B1-2) includes dry silica, wet silica, and surface-treated silica. Furthermore, silica can be classified by manufacturing method into, for example, dry-process white carbon, wet-process white carbon, colloidal silica, and precipitated silica. Silica (B1-2) may also be amorphous silica. These silicas can be used individually or in combination of two or more types. Among these silicas, silica having surface silanol groups (anhydrous silicic acid, hydrated silicic acid) is preferred, and hydrated silicic acid with many surface silanol groups has a strong chemical bonding force with rubber components.

[0082] The average particle diameter (average primary particle diameter) of silica (B1-2) 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.

[0083] In this application, the average particle diameter of silica (B1-2) can be measured using, for example, a scanning electron microscope or a transmission electron microscope, and can be calculated as the arithmetic mean particle diameter of an appropriate number of samples (e.g., 50 samples) by image analysis.

[0084] Furthermore, the specific surface area for nitrogen adsorption of silica (B1-2) by the BET method is, for example, 50-400 m². 2 / g, preferably 100-300m 2 / g, more preferably 150-200m 2 It is / g.

[0085] The proportion of silica (B1-2) is, for example, 1 to 50 parts by mass, preferably 3 to 30 parts by mass, more preferably 5 to 20 parts by mass, more preferably 7 to 15 parts by mass, and most preferably 8 to 12 parts by mass, per 100 parts by mass of rubber component (A). If the proportion of silica (B1-2) is too low, the effect of improving wear resistance may decrease, and conversely, if the proportion of silica (B1-2) is too high, the productivity of the transmission belt may decrease.

[0086] The proportion of the reinforcing filler (B1) is, for example, 30 to 100 parts by mass, preferably 35 to 80 parts by mass, more preferably 40 to 80 parts by mass, more preferably 45 to 75 parts by mass, and most preferably 50 to 70 parts by mass, per 100 parts by mass of the rubber component (A).

[0087] (Non-reinforcing filler (B2)) Examples of non-reinforcing fillers (B2) include metal compounds or synthetic ceramics (metal oxides such as magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, zinc oxide, titanium oxide, and aluminum oxide; metal silicates such as calcium silicate; metal carbides such as silicon carbide and tungsten carbide; metal nitrides such as titanium nitride, aluminum nitride, and boron nitride; metal carbonates such as magnesium carbonate and calcium carbonate; metal sulfates such as calcium sulfate and barium sulfate, etc.), and mineral materials (clay, zeolite, diatomaceous earth, calcined diatomaceous earth, activated clay, alumina, silica, talc, mica, sericite, bentonite, montmorillonite, smectite, etc.). Metal oxides such as zinc oxide may be used as crosslinking agents, crosslinking accelerators, or co-crosslinking agents.

[0088] Of these, metal oxides such as zinc oxide are preferred.

[0089] The average particle size (average primary particle size) of the non-reinforcing filler (B2) is, for example, 0.01 to 25 μm, preferably 0.1 to 20 μm, and more preferably 0.3 to 15 μm. If the average particle size of the non-reinforcing filler (B2) is too small, the productivity of the transmission belt may decrease, and conversely, if the average particle size of the non-reinforcing filler (B2) is too large, the wear resistance may decrease.

[0090] In this application, the average particle size of the non-reinforcing filler (B2) can be measured as the volume-average particle size using a laser diffraction particle size distribution analyzer.

[0091] The proportion of the non-reinforcing filler (B2) is, for example, 0.5 to 100 parts by mass, preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, more preferably 3 to 10 parts by mass, and most preferably 4 to 8 parts by mass, per 100 parts by mass of the rubber component (A).

[0092] (Plasticizer (C)) The rubber composition of the present invention is preferably further enriched with a plasticizer (C) because it can suppress adhesive wear while improving the productivity of transmission belts.

[0093] Examples of plasticizers (C) include oil-based plasticizers [aliphatic oils such as paraffinic oils, alicyclic oils (naphthenic oils), aromatic oils, etc.], aliphatic carboxylic acid plasticizers (adipate ester plasticizers, sebacate ester plasticizers, etc.), aromatic carboxylic acid ester plasticizers (phthalate ester plasticizers, trimellitic ester plasticizers, etc.), oxycarboxylic acid ester plasticizers, phosphate ester plasticizers, ether plasticizers, and ether ester plasticizers. These plasticizers can be used individually or in combination of two or more.

[0094] Of these, oil-based plasticizers are preferred, and aliphatic oils such as paraffinic oils are particularly preferred.

[0095] The proportion of plasticizer (C) (especially aliphatic oil) is, for example, 1 to 80 parts by mass, preferably 5 to 50 parts by mass, more preferably 10 to 40 parts by mass, more preferably 12 to 30 parts by mass, and most preferably 15 to 25 parts by mass, per 100 parts by mass of rubber component (A). In particular, from the viewpoint of improving the processability of the transmission belt (especially the processability of friction), the proportion of plasticizer (C) may be 5 parts by mass or more, preferably 10 parts by mass or more, and more preferably 13 parts by mass or more, per 100 parts by mass of rubber component (A). Furthermore, from the viewpoint of an excellent balance between wear resistance and productivity, the proportion of plasticizer (C) is preferably 2 to 25 parts by mass, more preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, and most preferably 8 to 12 parts by mass, per 100 parts by mass of rubber component (A). If the proportion of plasticizer (C) is too low, the effect of suppressing adhesive wear and improving the productivity of the transmission belt may be reduced. Conversely, if the proportion of plasticizer (C) is too high, the wear resistance may be reduced.

[0096] (Tackifier (D)) The rubber composition of the present invention preferably further contains a tackifier (D) because it can enhance tackiness and improve the productivity of transmission belts (particularly processability such as lap joint processing and covering processing).

[0097] Examples of tackifiers (D) include factis [sulfur factis (black sub) obtained by crosslinking oils and fats (vegetable oils such as linseed oil, rapeseed oil, castor oil, cottonseed oil, soybean oil, etc.) with sulfur or hydrogen sulfide, sulfur chloride factis (white sub) obtained by crosslinking the oils and fats with sulfur monochloride or sulfur dichloride, sulfur-free factis obtained by crosslinking the oils and fats with isocyanate compounds or organic peroxides, etc.], terpene resins (polyterpene resins or their hydrogenated products, terpene phenol resins or their hydrogenated products, etc.), rosin resins (natural rosin, cured rosin, disproportionated rosin, polymerized rosin, rosin esters, rosin phenol resins, etc.), petroleum resins (C 5-9Examples of tackifiers include aliphatic petroleum resins mainly composed of higher olefinic hydrocarbons such as fractions, dicyclopentadiene petroleum resins mainly composed of dicyclopentadiene or their hydrogenated products, aromatic petroleum resins mainly composed of aromatic hydrocarbons such as vinyltoluene or indene or their hydrogenated products, coumarone resins such as coumarone-indene resin and coumarone-indene-styrene copolymer or their hydrogenated products), and modified olefin polymers [ethylene-(meth)acrylic acid copolymer, ethylene-2-hydroxyethyl (meth)acrylate copolymer, ethylene-glycidyl (meth)acrylate copolymer, ethylene-vinyl acetate-(meth)acrylic acid copolymer, ethylene-ethyl (meth)acrylate-(meth)acrylic acid copolymer, partially saponified ethylene-vinyl acetate copolymer, etc.]. These tackifiers can be used alone or in combination of two or more.

[0098] Of these, petroleum resins and modified olefin polymers are preferred due to their excellent compatibility with rubber component (A), and aliphatic petroleum resins are particularly preferred.

[0099] The proportion of the tackifier (D) may be 50 parts by mass or less per 100 parts by mass of rubber component (A), for example, 1 to 50 parts by mass, preferably 2 to 40 parts by mass, more preferably 3 to 30 parts by mass, more preferably 5 to 25 parts by mass, and most preferably 8 to 20 parts by mass (particularly 10 to 20 parts by mass). In particular, from the viewpoint of improving the processability of the transmission belt (particularly the processability of the covering), the proportion of the tackifier (D) may be 5 parts by mass or more per 100 parts by mass of rubber component (A), preferably 10 parts by mass or more, and more preferably 13 parts by mass or more. Furthermore, from the viewpoint of an excellent balance between wear resistance and productivity, the proportion of the tackifier (D) is preferably 2 to 25 parts by mass, more preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, and most preferably 8 to 12 parts by mass per 100 parts by mass of rubber component (A). If the proportion of tackifier (D) is too low, the effect of improving the productivity of the transmission belt (especially the processability of the covering) may decrease, and conversely, if the proportion of tackifier (D) is too high, the wear resistance may decrease.

[0100] (Adhesion improving agent (E)) The rubber composition of the present invention may further contain an adhesion improver (E) as it can improve the adhesion of fabrics.

[0101] Examples of adhesion improvers (E) include phenolic resins [such as resorcinol-formaldehyde cocondensates (RF condensates)], amino resins [such as melamine resins like hexamethylolmelamine and hexalokoxymethylmelamine (hexamethoxymethylmelamine, hexasubtoxymethylmelamine, etc.); urea resins like methylolurea; benzoguanamine resins like methylolbenzoguanamine resin, etc.], epoxy compounds, and isocyanate compounds. These adhesion improvers can be used individually or in combination of two or more.

[0102] Of these, phenolic resin and amino resin are preferred, and melamine resin is particularly preferred.

[0103] The proportion of the adhesion improver (E) is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 8 parts by mass, more preferably 1 to 5 parts by mass, more preferably 2 to 4 parts by mass, and most preferably 2.5 to 3.5 parts by mass, per 100 parts by mass of the rubber component (A). If the proportion of the adhesion improver (E) is too low, the effect of improving the adhesion of the fabric may decrease, and conversely, if the proportion of the adhesion improver (E) is too high, the productivity of the transmission belt may decrease.

[0104] (Crosslinking agent (F)) The rubber composition of the present invention may further contain a crosslinking agent (F). The crosslinking agent (or vulcanizing agent) (F) may be a sulfur-based crosslinking agent and / or an organic peroxide.

[0105] 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. Powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur are preferred as sulfur-based crosslinking agents, with powdered sulfur being the most preferred.

[0106] Examples of organic peroxides include those commonly used for crosslinking rubber and resins. Such organic peroxides include, for example, diacyl peroxides, peroxyesters, and dialkyl peroxides (e.g., dicumyl peroxide, t-butylcumyl peroxide, 1,1-di-butylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexane, 1,3-bis(t-butylperoxy-isopropyl)benzene, and di-t-butyl peroxide). These organic peroxides can be used individually or in combination of two or more. Furthermore, organic peroxides with a decomposition temperature of approximately 150-250°C (e.g., 175-225°C) that yields a half-life of 1 minute by thermal decomposition are preferred.

[0107] Of these, sulfur-based crosslinking agents are preferred because they easily improve the wear resistance of the transmission belt, and organic peroxides are preferred because they easily improve the productivity of the transmission belt (especially the processability of the covering).

[0108] The proportion of the crosslinking agent (F) is, for example, 0.1 to 10 parts by mass, preferably 0.3 to 5 parts by mass, more preferably 0.5 to 3 parts by mass, and more preferably 0.7 to 2 parts by mass, per 100 parts by mass of the rubber component (A).

[0109] (Crosslinking accelerator (G)) The rubber composition of the present invention may further contain a crosslinking accelerator (G) in addition to the crosslinking agent (F) (particularly a sulfur-based crosslinking agent).

[0110] Examples of crosslinking accelerators (G) include thiram-based accelerators [e.g., tetramethylthiram monosulfide (TMTM), tetramethylthiram disulfide (TMTD), tetraethylthiram disulfide (TETD), tetrabutylthiram disulfide (TBTD), dipentamethylenethiram tetrasulfide (DPTT), N,N'-dimethyl-N,N'-diphenylthiram disulfide (MPTD), etc.], sulfenamide-based accelerators [e.g., N-cyclohexyl-2-benzothiadylsulfenamide (CBS), N,N'-dicyclohexyl-2-benzothiadylsulfenamide (DCBS), Nt-butyl-2-benzothiadylsulfenamide (TBBS), etc.], and thiomorpholine-based accelerators [e.g., 4,4'-dithiodimorpholine (DTDM), 2-(4 Examples include '(-morpholinodithio)benzothiazole (MBSS), etc.), thiazole-based promoters [e.g., 2-mercaptobenzothiazole (MBT), zinc salt of MBT (ZMBT), dibenzothiadyl disulfide (MBTS), etc.], urea-based or thiourea-based promoters [e.g., ethylenethiourea (ETU), trimethylthiourea (TMU), diethylthiourea (DETU), etc.], guanidine-based promoters [e.g., diphenylguanidine (DPG), di-o-tolylguanidine (DOTG), etc.], dithiocarbamate-based promoters [e.g., sodium dimethyldithiocarbamate (SDMC), zinc diethyldithiocarbamate (ZDEC), zinc dibutyldithiocarbamate (ZDBC), etc.], xanthogenic acid-based promoters [e.g., zinc isopropylxanthogenic acid (ZIX), etc.], etc.]. These crosslinking accelerators can be used individually or in combination of two or more. Among these, TMTD, TETD, DPTT, CBS, and MBTS are commonly used.

[0111] The proportion of the crosslinking accelerator (G) is, for example, 0.2 to 10 parts by mass, preferably 0.5 to 8 parts by mass, more preferably 1 to 7 parts by mass, more preferably 1.5 to 5 parts by mass, and most preferably 2 to 4 parts by mass, per 100 parts by mass of the rubber component (A).

[0112] (Other additives (H)) The rubber composition of the present invention may further contain, as other additives (H), conventional additives used in rubber formulations.

[0113] Commonly used additives include, for example, processing agents or processing aids (fatty acids or their metal salts such as stearic acid and metal stearic acid salts; fatty acid esters such as stearic acid esters; fatty acid amides such as stearate amides), antioxidants (antioxidants, heat aging inhibitors, flex crack inhibitors, ozone degradation inhibitors, etc.), co-crosslinking agents, crosslinking retarders, colorants, coupling agents (silane coupling agents, etc.), stabilizers (UV absorbers, heat stabilizers, etc.), lubricants, flame retardants, and antistatic agents. These additives can be used individually or in combination of two or more.

[0114] Among these, processing agents or processing aids, and antioxidants are commonly used.

[0115] The total proportion of other additives (H) is, for example, 0.01 to 30 parts by mass, preferably 0.1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and more preferably 3 to 10 parts by mass, per 100 parts by mass of rubber component (A).

[0116] (Properties of rubber compositions) The rubber composition of the present invention, by adjusting it to have a specific minimum viscosity and rubber hardness of Mooney scorch, allows the viscosity of the rubber composition subjected to friction treatment, lap joint treatment, etc., during the transmission belt manufacturing process to be adjusted to a specific range, and the hardness of the reinforcing fabric after crosslinking can also be adjusted to a range that satisfies the requirements for wear resistance. Generally, in order to produce a high-hardness crosslinked rubber composition, the viscosity of the raw material uncrosslinked rubber composition tends to increase, and there is a trade-off relationship between the high hardness of the crosslinked rubber and the viscosity of the raw material. In contrast, the present invention can improve the hardness of the crosslinked rubber composition while suppressing the increase in viscosity of the uncrosslinked rubber composition to an appropriate range, thus achieving both workability for friction treatment, etc., and wear resistance.

[0117] The minimum Mooney scorch viscosity (minimum Mooney viscosity Vm) of the rubber composition (uncrosslinked rubber composition) of the present invention, measured at 125°C, is, for example, 40 or less (particularly 30 or less), preferably 10 to 40 (particularly 10 to 30), more preferably 15 to 35 (particularly 15 to 28), more preferably 17 to 27, particularly preferably 18 to 25, and most preferably 20 to 24. If Vm is too high, problems such as difficulty in uniformly rubbing the rubber composition onto the cloth during friction and tearing of the cloth are likely to occur. On the other hand, it is difficult to strictly specify the lower limit of Vm, but if Vm is too low, it may be difficult to adjust the amount of adhesion to the cloth. For example, if Vm is too low, it may be difficult to reduce the amount of adhesion because sufficient shear force cannot be obtained during friction, which may reduce economic efficiency.

[0118] The scorch time t5 of the rubber composition (uncrosslinked rubber composition) of the present invention (total time from the start of the test through Vm until it rises 5 points above Vm) is, for example, 15 to 60 minutes, preferably 16 to 40 minutes, more preferably 18 to 30 minutes, more preferably 19 to 25 minutes, and most preferably 20 to 23 minutes. If the scorch time t5 is too short, there is a risk that "burning" will occur, where crosslinking proceeds unintentionally during the rubber mixing or friction treatment. On the other hand, if the scorch time t5 is too long, it will take a long time to complete the crosslinking, which may reduce the productivity of the transmission belt.

[0119] In this application, the minimum viscosity Vm and scorch time t5 of the Mooney scorch can be measured in accordance with the Mooney scorch test of JIS K 6300-1 (2013), and in detail, they can be measured by the method described in the examples below.

[0120] The rubber hardness of the rubber composition (crosslinked rubber composition) of the present invention may be 50 or higher (particularly 55 or higher), for example, 50 to 90 (particularly 55 to 90), preferably 53 to 80 (particularly 56 to 80), even more preferably 57 to 70, more preferably 58 to 67, and most preferably 60 to 65. If the rubber hardness of the crosslinked rubber composition is too low, the wear resistance may decrease. On the other hand, if the rubber hardness is too high, it becomes necessary to increase the amount of fillers and crosslinking agents to increase the hardness, and Vm tends to increase at the same time, which may reduce the productivity of the transmission belt.

[0121] In this application, the rubber hardness of the crosslinked rubber composition is expressed as the value (Type A hardness) 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 -), and may be simply described as hardness or rubber hardness. In detail, the rubber hardness of the crosslinked rubber composition can be measured by the method described in the examples below.

[0122] [Reinforcement fabric] The reinforcing fabric of the present invention is a reinforcing fabric for covering at least a portion of the surface of a power transmission belt, and is formed of a composite of the fabric and a crosslinked material of the rubber composition.

[0123] (cloth) Examples of fabrics (textiles or fabric materials) include woven fabrics, knitted fabrics (weft-knitted fabrics, warp-knitted fabrics), and nonwoven fabrics. Of these, woven fabrics produced in plain weave, twill weave, satin weave, etc., and woven fabrics and knitted fabrics produced with a wide angle between the warp and weft threads, where the intersection angle is greater than 90° but less than or equal to about 120° are preferred. Particularly preferred are woven fabrics commonly used as cover fabrics for transmission belts in general industrial and agricultural machinery [plain weave fabrics where the intersection angle between the warp and weft threads is right angles, and plain weave fabrics (wide-angle canvas) where the intersection angle between the warp and weft threads is greater than 90° but less than or equal to about 120°].

[0124] Commonly used fibers for fabrics include, for example, polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, aramid fibers, etc.), polyester fibers [polyalkylene arylate fibers such as polyethylene terephthalate (PET) fibers and polyethylene naphthalate (PEN) fibers], vinyl alcohol fibers (polyvinyl alcohol, ethylene-vinyl alcohol copolymer fibers, vinylon fibers, etc.), poly(p-phenylene benzobisoxazole) (PBO) fibers, and other synthetic fibers; cellulose fibers (cellulose fibers, cellulose derivative fibers, etc.), natural fibers such as wool; and inorganic fibers such as carbon fibers and glass fibers. These fibers may be used individually as single yarns or as blended yarns combining two or more types.

[0125] Of these fibers, it is preferable to include cellulose fibers because they readily support the rubber composition and are economically efficient. Composite yarns (especially blended yarns) of cellulose fibers and synthetic fibers are particularly preferred because they are economically efficient and have excellent abrasion resistance. From an economic standpoint, the proportion of cellulose fibers may be 50% by mass or more of the total fiber, preferably 80% by mass or more, more preferably 90% by mass or more, and may even be 100% by mass. Furthermore, from an economic standpoint and abrasion resistance, the proportion of cellulose fibers may be 10% by mass or more of the total fiber, for example, 10 to 80% by mass, preferably 20 to 50% by mass, and more preferably 30 to 40% by mass.

[0126] Cellulosic fibers include cellulose fibers (cellulose fibers derived from plants, animals, or bacteria, etc.) and cellulose derivative fibers. Examples of cellulose fibers include natural plant-derived cellulose fibers (pulp fibers) such as wood pulp (coniferous and hardwood pulp, etc.), bamboo fibers, sugarcane fibers, seed hair fibers (cotton fibers (cotton linters), kapok, etc.), ginseng fibers (hemp, paper mulberry, mitsumata, etc.), and leaf fibers (Manila hemp, New Zealand hemp, etc.); animal-derived cellulose fibers such as ascidian cellulose; bacterial cellulose fibers; and algal cellulose. Examples of cellulose derivative fibers include cellulose ester fibers and regenerated cellulose fibers (rayon, cupro, lyocell, etc.).

[0127] In composite yarns of cellulose fibers and synthetic fibers, the synthetic fiber is preferably polyolefin fiber, polyamide fiber, or polyester fiber, with polyester fiber being particularly preferred. The polyester fiber may also be polyalkylene arylate fiber. Examples of polyalkylene arylate fibers include PET fiber, polybutylene terephthalate (PBT) fiber, PEN fiber, and other polycrystalline C 2-4 Alkylene-C 8-14 Examples include arylate-based fibers.

[0128] In a composite yarn of cellulose fibers and synthetic fibers, the mass ratio of cellulose fibers to synthetic fibers (especially polyester fibers) is, for example, 90 / 10 to 10 / 90, preferably 80 / 20 to 15 / 85, more preferably 70 / 30 to 20 / 80, more preferably 50 / 50 to 25 / 75, and most preferably 40 / 60 to 30 / 70. If the proportion of cellulose fibers is too low, the effect of improving economic efficiency may decrease, and conversely, if the proportion of cellulose fibers is too high, the effect of improving abrasion resistance may decrease.

[0129] The average fineness of the fibers that make up the fabric is, for example, 5 to 30 count, preferably 10 to 25 count, and more preferably 10 to 20 count. If the fineness (count) is too low, it may be difficult to uniformly penetrate the rubber composition between the fibers, and if the fineness (count) is too high, the mechanical strength of the reinforcing fabric may decrease.

[0130] The weight of the fabric (raw material) is, for example, 100-500 g / m². 2 Preferably 200-400 g / m² 2 More preferably 250-350 g / m² 2 If the fabric weight is too large, the flexibility of the belt may decrease, and if the fabric weight is too small, the reinforcing effect of the reinforcing fabric may decrease.

[0131] If the fabric (raw material) is woven, the thread density of the fabric (density of warp and weft threads) is, for example, 60 to 100 threads / 50 mm, preferably 70 to 90 threads / 50 mm, and more preferably 75 to 85 threads / 50 mm. If the density is too high, it may be difficult to uniformly penetrate the rubber composition between the fibers, and conversely, if the density is too low, the amount of rubber composition adhering to the fabric may increase, potentially reducing abrasion resistance.

[0132] The fabric may be subjected to an adhesive treatment [for example, an adhesive treatment such as immersion in a resorcinol-formaldehyde-latex solution (RFL solution)].

[0133] The fabric may be single-layered or multi-layered (for example, 2 to 5 layers, preferably 2 to 4 layers, and even more preferably 2 to 3 layers), but from the viewpoint of productivity, a single layer (1 ply) or two layers (2 plies) is preferred, and two layers are particularly preferred.

[0134] (Characteristics of reinforcing fabric) The proportion of the rubber composition can be selected from a range of approximately 5 to 80% by mass in the reinforcing fabric. The proportion of the rubber composition in the reinforcing fabric is, for example, 10 to 70% by mass, preferably 20 to 60% by mass, more preferably 25 to 55% by mass, more preferably 30 to 50% by mass, and most preferably 35 to 45% by mass, in order to improve abrasion resistance by reinforcing the fabric and the rubber composition together. If the proportion of the rubber composition is too low, the fabric may become more exposed, which may reduce abrasion resistance (the fabric may wear down easily). On the other hand, if the proportion of the rubber composition is too high, there will be a large amount of "free and weak" rubber composition that is not embedded in the weave of the fabric, which may reduce abrasion resistance (the rubber may wear down easily).

[0135] A reinforcing fabric is preferred in which at least one side of the fabric is friction-treated with a rubber composition, and it is even more preferred in which both sides (front and back) of the reinforcing fabric are friction-treated with a rubber composition for reinforcing fabrics. Friction-treating both sides of the reinforcing fabric with a rubber composition for reinforcing fabrics makes it easier to achieve both productivity and wear resistance in the transmission belt. In particular, when the fabric is multi-layered, it is possible to improve the tackiness when winding multiple layers of friction-treated fabric and the adhesion between friction-treated fabrics.

[0136] The average thickness of the reinforcing fabric (or the total average thickness of all layers if the reinforcing fabric is multi-layered) is, for example, 0.4 to 2 mm, preferably 0.5 to 1.4 mm, and more preferably 0.6 to 1.2 mm. If the reinforcing fabric is too thin, the abrasion resistance may decrease, and if the reinforcing fabric is too thick, the flexibility of the belt may decrease.

[0137] In this specification and the claims, the average thickness of the reinforcing fabric can be measured based on scanning electron microscopy (SEM) images and is determined as the average value of the thickness obtained at five or more arbitrary locations through image analysis or the like.

[0138] [Transmission belt] The power transmission belt of the present invention is not particularly limited as long as at least a portion of the surface of the power transmission belt is covered with a reinforcing fabric, and may be a friction power transmission belt or a meshing power transmission belt.

[0139] 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), V-ribbed belts, and resin block belts.

[0140] Examples of interlocking power transmission belts include toothed belts and double-sided toothed belts.

[0141] Among these power transmission belts, those in which at least a portion of the surface that contacts the pulley (friction transmission surface) is covered with reinforcing fabric are preferred, such as V-belts, V-ribbed belts, and flat belts, as they are often required to balance wear resistance and productivity. Wrapped V-belts, which are often used in harsh conditions where thermal degradation is likely to occur, are particularly preferred in recent years. Wrapped V-belts will be described in detail below, with reference to Figure 1 as necessary.

[0142] As shown in Figure 1, the wrapped V-belt 1 is formed of an endless belt body and an outer covering fabric 5 (woven, knitted, nonwoven, etc.) that covers the belt body over its entire length in the circumferential direction. The belt body is formed of an elastic rubber layer (or upper core rubber layer) 2 on the outer circumference of the belt, a compression rubber layer (or V-core rubber layer) 4 on the inner circumference of the belt, and a core body 3 embedded between the elastic rubber layer 2 and the compression rubber layer 4 along the longitudinal direction of the belt (circumferential direction, direction A in Figure 1). In this example, the core body 3 is a core wire (twisted cord) arranged at predetermined intervals in the belt width direction (direction B in Figure 1), and is interposed between the elastic rubber layer 2 and the compression rubber layer 4, in contact with both layers. The wrapped V-belt is not limited to this structure; for example, an adhesive rubber layer may be interposed between the compression rubber layer 4 and the elastic rubber layer 2 to improve the adhesion between the core body 3 and the elastic rubber layer 2 or the compression rubber layer 4. The core 3 may be embedded between the stretchable rubber layer 2 and the compression rubber layer 4. For example, it may be embedded in the compression rubber layer 4, or it may be embedded in the compression rubber layer 4 while in contact with the stretchable rubber layer 2. Furthermore, the core 3 may be embedded in the adhesive rubber layer, or it may be embedded between the compression rubber layer 4 and the adhesive rubber layer, or between the adhesive rubber layer and the stretchable rubber layer 2.

[0143] In the wrapped V-belt 1 shown in Figure 1, the cross-sectional shape is an inverted trapezoid (V-shape), and the outer covering fabric 5 on both sides, which slope in a V-shape, forms a friction transmission surface that contacts the inner wall of the V-groove of the pulley. Therefore, in a wrapped V-belt, the reinforcing fabric only needs to be formed in at least a part of the friction transmission surface (for example, the entire friction transmission surface), but from the standpoint of productivity, it is preferable that the entire outer covering fabric is formed of reinforcing fabric.

[0144] The wrapped V-belt of the present invention only requires that the outer covering (reinforcement fabric) be made of the reinforcement fabric of the present invention, and the belt body can be a conventional belt body or the like. A conventional belt body, as described above, usually includes a compression rubber layer, a core, and an extension rubber layer.

[0145] (Compressed rubber layer) The compression rubber layer is formed from a rubber composition (rubber composition for compression rubber layer) containing rubber component (a). The average thickness of the compression rubber layer can be appropriately selected depending on the type of belt, for example, 1 to 30 mm, preferably 1.5 to 25 mm, and more preferably 2 to 20 mm.

[0146] (Rubber component (a)) Examples of rubber component (a) include other rubber components as exemplified in section (A). These other rubber components can be used individually or in combination of two or more types.

[0147] Of the aforementioned rubber components, ethylene-α-olefin elastomer is preferred, ethylene-propylene-unconjugated polyene copolymer is more preferred, and EPDM is even more preferred.

[0148] The proportion of rubber component (a) in the rubber composition for the compression rubber layer is, for example, 20 to 80% by mass, preferably 30 to 75% by mass, more preferably 40 to 70% by mass, more preferably 45 to 65% by mass, and most preferably 50 to 60% by mass.

[0149] (Filler (b)) The rubber composition for the compression rubber layer preferably further contains a filler (b). The filler (b) includes a reinforcing filler (b1) and a non-reinforcing filler (b2).

[0150] (Reinforcing filler (b1)) The reinforcing filler (b1) preferably contains carbon black (b1-1) and / or silica (b1-2), and is particularly preferably containing carbon black (b1-1) and silica (b1-2).

[0151] (Carbon Black (b1-1)) The average particle diameter (average primary particle diameter) of carbon black (b1-1) is, for example, 5 to 200 nm, preferably 10 to 150 nm, more preferably 20 to 100 nm, more preferably 30 to 80 nm, and most preferably 50 to 70 nm.

[0152] The carbon black (b1-1) preferably contains soft carbon black with relatively large particle size. The proportion of soft carbon black (percentage of particle number) may be 10% or more of the carbon black (b1-1), preferably 50% or more, more preferably 80% or more, more preferably 90% or more, and most preferably 100%.

[0153] The amount of iodine adsorbed by carbon black (b1-1) is, for example, 5 to 200 g / kg, preferably 10 to 100 g / kg, more preferably 15 to 80 g / kg, more preferably 20 to 50 g / kg, and most preferably 23 to 30 g / kg.

[0154] The proportion of carbon black (b1-1) is, for example, 0.5 to 60 parts by mass, preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, more preferably 3 to 20 parts by mass, and most preferably 5 to 15 parts by mass, per 100 parts by mass of rubber component (a).

[0155] (Silica (b1-2)) As silica (b1-2), it can be selected from the silica exemplified as silica (B1-2), including preferred embodiments.

[0156] The range of the nitrogen adsorption specific surface area of ​​silica (b1-2) by the BET method, including preferred embodiments, can be selected from the range described as the nitrogen adsorption specific surface area of ​​silica (B1-2).

[0157] The proportion of silica (b1-2) is, for example, 1 to 100 parts by mass, preferably 10 to 80 parts by mass, more preferably 30 to 70 parts by mass, more preferably 35 to 65 parts by mass, and most preferably 40 to 60 parts by mass, per 100 parts by mass of rubber component (a).

[0158] The proportion of the reinforcing filler (b1) is, for example, 30 to 100 parts by mass, preferably 35 to 80 parts by mass, more preferably 40 to 80 parts by mass, more preferably 45 to 75 parts by mass, and most preferably 50 to 70 parts by mass, per 100 parts by mass of the rubber component (a).

[0159] (Non-reinforcing filler (b2)) The non-reinforcing filler (b2) can be selected from the non-reinforcing fillers exemplified as non-reinforcing filler (B2), including preferred embodiments.

[0160] The range of average particle size of the non-reinforcing filler (b2) and its ratio to 100 parts by mass of rubber component (a) can also be selected from the range of average particle size of the non-reinforcing filler (B2) and its ratio to 100 parts by mass of rubber component (A), including preferred embodiments.

[0161] (Plasticizer (c)) The rubber composition for the compression rubber layer preferably further contains a plasticizer (c). The plasticizer (c) can be selected from the plasticizers exemplified as plasticizer (C), including preferred embodiments. The proportion of plasticizer (c) (especially aliphatic oils) is, for example, 0.5 to 80 parts by mass, preferably 1 to 50 parts by mass, more preferably 2 to 30 parts by mass, more preferably 3 to 20 parts by mass, and most preferably 5 to 15 parts by mass, per 100 parts by mass of rubber component (a).

[0162] (Crosslinking agent (d)) The rubber composition for the compression rubber layer preferably further contains a crosslinking agent (d). The crosslinking agent (d) can be selected from the crosslinking agents exemplified as crosslinking agent (F), including preferred embodiments. The ratio of crosslinking agent (d) to 100 parts by mass of rubber component (a) can also be selected from the ratio of crosslinking agent (F) to 100 parts by mass of rubber component (A), including preferred embodiments.

[0163] (Crosslinking promoter (e)) The rubber composition for the compression rubber layer preferably further contains a crosslinking accelerator (e). The crosslinking accelerator (e) can be selected from the crosslinking accelerators exemplified as crosslinking accelerator (G), including preferred embodiments. The ratio of crosslinking accelerator (e) to 100 parts by mass of rubber component (a) can also be selected from the ratio of crosslinking accelerator (G) to 100 parts by mass of rubber component (A), including preferred embodiments.

[0164] (Other additives (f)) The rubber composition for the compression rubber layer preferably further contains other additives (f). Examples of other additives (f) include conventional additives exemplified in the section on other additives (H), as well as tackifiers, adhesion improvers, and short fibers (cellulosic fibers such as cotton and rayon, polyester fibers such as polyethylene terephthalate fibers, and polyamide fibers such as nylon fibers and aramid fibers). The additives can be used individually or in combination of two or more.

[0165] Among these, processing agents or processing aids, and antioxidants are commonly used.

[0166] The total proportion of other additives (f), including preferred embodiments, can be selected from the total proportion of additive (H) relative to 100 parts by mass of rubber component (A).

[0167] (Stretchable rubber layer) The rubber composition forming the stretchable rubber layer (rubber composition for the stretchable rubber layer) may be a different rubber composition from the rubber composition for the compression rubber layer, or it may be the same rubber composition as the rubber composition for the compression rubber layer. From the viewpoint of productivity of the wrapped V-belt, it is preferable that the rubber composition for the compression rubber layer and the rubber composition for the stretchable rubber layer are the same rubber composition. Even if the rubber composition for the stretchable rubber layer is a different rubber composition from the rubber composition for the compression rubber layer, it is preferable that it is a rubber composition selected from preferred embodiments of the rubber composition for the compression rubber layer.

[0168] The average thickness of the stretchable rubber layer can be appropriately selected depending on the type of belt, but is, for example, 0.5 to 10 mm, preferably 0.6 to 5 mm, and more preferably 0.6 to 2 mm.

[0169] (Core body) The core is not particularly limited, but typically, stranded cords arranged at predetermined intervals in the belt width direction can be used. The strands are arranged extending in the length direction of the belt. The strands may be arranged in parallel at a predetermined pitch parallel to the length direction of the belt, but from the viewpoint of productivity, they are usually arranged spirally in parallel at a predetermined pitch approximately parallel to the length direction of the belt. When the strands are arranged spirally, the angle of the strands with respect to the length direction of the belt may be, for example, 5° or less, and from the viewpoint of belt running performance, it is preferable that it be as close to 0° as possible. In addition, the pitch or spacing (especially the spinning pitch of the strands), which is the distance between the centers of adjacent cores, is preferably set in the range of 1.5 to 2.5 mm, and more preferably in the range of 1.8 to 2.2 mm.

[0170] The fibers that make up the core include, for example, ethylene terephthalate and ethylene-2,6-naphthalate. 2-4 Alkylene-C 8-14 Polyester fibers (polyalkylene arylate fibers) with arylate as the main constituent unit, synthetic fibers such as aramid fibers, and inorganic fibers such as carbon fibers are commonly used. Polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers, etc.) and aramid fibers are preferred, and aramid fibers are particularly preferred.

[0171] These fibers may be used in the form of multifilament yarn containing multiple filaments. The fineness of the multifilament yarn may be, for example, around 1000 to 3000 dtex (particularly 1200 to 2000 dtex). The multifilament yarn may contain, for example, around 100 to 3000 filaments (particularly 500 to 2000 filaments), and preferably around 700 to 1300 filaments.

[0172] As the core wire, a twisted cord using multifilament yarn (e.g., multi-ply, single-ply, Lang-ply, etc., preferably multi-ply) can be used. The average wire diameter of the core wire (diameter of the twisted cord) may be, for example, 0.5 to 3 mm, preferably 0.6 to 2.5 mm, and more preferably about 0.7 to 2 mm. The total fineness of the twisted cord may be, for example, about 10,000 to 50,000 dtex (e.g., about 22,000 to 28,000 dtex). The twisted cord may contain, for example, about 1,000 to 30,000 filaments (e.g., about 5,000 to 25,000 filaments), preferably about 10,000 to 20,000 filaments (e.g., about 12,000 to 18,000 filaments). The twist coefficient of the lower twisted yarn in the twisted cord may be, for example, around 2 to 4 (for example, 2.5 to 3.5), and the twist coefficient of the upper twisted yarn may also be, for example, around 2 to 4 (for example, 2.5 to 3.5).

[0173] The core wire may be bonded (or surface-treated) using conventional methods (such as bonding with RFL solution, epoxy compounds, or isocyanate compounds) to improve adhesion with the rubber component.

[0174] [Manufacturing method for power transmission belts] The power transmission belt of the present invention can be manufactured by conventional manufacturing methods according to the type of power transmission belt, except that the rubber composition of the present invention is used as the rubber composition for manufacturing the reinforcing fabric.

[0175] The manufacturing method for the belt body precursor can be a conventional method depending on the type of belt. For example, in the case of a wrapped V-belt, the belt body precursor can be obtained through a winding process, a cutting process, and a skiving process. In the winding process, an uncrosslinked sheet for the compression rubber layer obtained by rolling is cut and set on the mantle, then a core is wound around it, and an uncrosslinked sheet for the stretchable rubber layer is further wound on top of the wound core. In the cutting process, the obtained annular laminate is cut (sliced) on the mantle. In the skiving process, the cut annular laminate is placed on a pair of pulleys and cut into a V shape while rotating. Furthermore, the obtained belt body precursor may be wrapped (covered) with the reinforcing fabric precursor and subjected to the crosslinking process. As a method for manufacturing such a wrapped V-belt, for example, the method described in Japanese Patent Application Publication No. 6-137381 and International Publication No. 2015 / 104778 can also be used.

[0176] In such a manufacturing method, the present invention includes a compounding step in which a cloth and the rubber composition of the present invention are compounded to obtain an uncrosslinked composite. Examples of methods for obtaining the uncrosslinked composite include friction treatment, coating treatment, lamination treatment, or soaking treatment. Of these, friction treatment is preferred because it has a significant effect in improving workability.

[0177] In the friction treatment, a friction method (friction) is used in which the rubber composition of the present invention is rubbed into at least one surface of the fabric. In the friction method, for example, a calender roll may be used to simultaneously pass the solid composition (such as an uncrosslinked rubber composition) and the fabric between rolls with different rotation speeds and apply pressure (compression) to rub the solid composition into the spaces between the fabric fibers. In the present invention, since the rubber composition of the present invention has an appropriate minimum viscosity Vm of Mooney scorch, processability in the friction treatment can be improved. The shape of the rubber composition for reinforcing fabric is not particularly limited, but it may be in the form of a sheet in order to be rubbed uniformly into the fabric. The number of friction treatments may be one friction treatment each on the front and back surfaces.

[0178] The uncrosslinked composite obtained by friction treatment is preferably subjected to a lap joint treatment in which the uncrosslinked composite is cut diagonally and the ends are overlapped and joined together to obtain a reinforcing fabric precursor. In the present invention, the rubber composition of the present invention can impart appropriate tackiness to the uncrosslinked composite, thereby improving the processability in the lap joint treatment. The obtained reinforcing fabric precursor may be cut to the desired size.

[0179] The uncrosslinked composite (reinforcement fabric precursor) obtained in this way is subjected to a conventional crosslinking process for manufacturing a power transmission belt. In the crosslinking process, it is sufficient to firmly integrate the belt body and the reinforcement fabric by covering (covering) at least a portion of the surface of the belt body precursor with the reinforcement fabric precursor and crosslinking it. The crosslinking process can be carried out by known or conventional methods, except for the use of reinforcement fabric. The crosslinking temperature can be selected according to the type of rubber component, for example, 120 to 200°C, preferably 150 to 180°C. In the present invention, the rubber composition of the present invention can impart appropriate tackiness to the uncrosslinked composite, thereby improving processability in the covering process. [Examples]

[0180] The present invention will be described in more detail below based on examples, but the present invention is not limited to these examples. Details of the materials used in the examples are shown below.

[0181] [Raw materials for rubber compositions] (Rubber component) EPDM: "EPT 4021" manufactured by Mitsui Chemicals, Inc., ethylene content 51% by mass, diene (ENB) content 8.1% by mass EBDM: "EBT K-9330M" manufactured by Mitsui Chemicals, Inc., ethylene content 50% by mass, diene (ENB) content 7.1% by mass Chloroprene rubber: "PM-40" manufactured by Denka Co., Ltd.

[0182] (Filler) Magnesium oxide: "Kyowa Mag 150" manufactured by Kyowa Chemical Co., Ltd. Zinc oxide: "Zinc Oxide Type 2" manufactured by Sakai Chemical Industry Co., Ltd. Carbon Black HAF: "Seas 3" manufactured by Tokai Carbon Co., Ltd., average primary particle size 28nm Carbon black SRF: "Seas S" manufactured by Tokai Carbon Co., Ltd., average primary particle size 66nm Silica: Ultrasil VN3 manufactured by Evonik Industries AG, BET specific surface area 180 m² 2 / g Calcium carbonate: "Super 1500" manufactured by Maruo Calcium Co., Ltd.

[0183] (Plasticizer) Paraffin-based oil: "Diana Process Oil PW-90" manufactured by Idemitsu Kosan Co., Ltd. Naphthenic oil: "SUNTHENE410" manufactured by Nippon Sun Oil Co., Ltd.

[0184] (Tackifiers and adhesion improvers) Tackifier A: "T-REZ RA100" manufactured by ENEOS Material Co., Ltd. Tackifier B: "Coumaron Indene Oil" manufactured by Kobe Oil Chemical Industry Co., Ltd. Adhesion improver: Cyretz 964RPC, manufactured by Cytec Industries, a mixture of hexamethoxymethylmelamine (65% by mass) and amorphous silica (35% by mass).

[0185] (Crosslinking agents and crosslinking aids) Sulfur: "MIDAS" manufactured by Migen Chemical Co., Ltd. Peroxide crosslinking agent: NOF Corporation's "Perbutyl P-40MB", active ingredient (1,3-bis(2-t-butylperoxyisopropyl)benzene) 40% by mass Crosslinking accelerator CBS: "Noxellar CZ" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Crosslinking accelerator MBTS: "Noxellar DM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Crosslinking accelerator TETD: "Noxellar TET" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Co-crosslinking agent MPBM: "Balnock PM" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0186] (Other additives) Stearic acid: "Stearic acid Tsubaki" manufactured by NOF Corporation. Processing aid: "Kuro Sub 21" manufactured by Tenma Sub Chemical Co., Ltd. Anti-aging agent ODPA: "Nocrack AD-F" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0187] [Core wire (processing code)] Three aramid fiber bundles with 1670 dtex (1000 filaments) were joined together and twisted in the S direction with a twist coefficient of 3.0 to produce a base twist yarn. Five of these base twist yarns were joined together and twisted in the Z direction with a twist coefficient of 3.0 to produce a twisted cord (multi-twisted yarn). The total fineness of the produced twisted cord (multi-twisted yarn) was 25050 dtex (15000 filaments), and the diameter was 1.9 mm. The produced twisted cord (multi-twisted yarn) was subjected to an adhesive treatment, and the resulting treated cord was used as the core wire. The twist coefficient TF is calculated using the following formula.

[0188] TF = TN × D 0.5 / 960

[0189] [In the formula, TF represents the twist coefficient, TN represents the number of twists per meter, and D represents the fineness (tex) of the yarn.]

[0190] [Preparation of compositions for compression rubber layers or stretchable rubber layers] Rubber compositions (compositions for compression or stretchable rubber layers) having the compositions shown in Table 1 were mixed in a Banbury mixer. The resulting mixed rubber was passed through a calender roll to produce an uncrosslinked rolled rubber sheet (a sheet for compression or stretchable rubber layer) of a predetermined thickness.

[0191] [Table 1]

[0192] [Reinforcement fabric] Reinforcement fabric: Cotton woven fabric (plain weave, composed of 20 count warp and 20 count weft threads, warp and weft thread density 75 threads / 50mm, weight 280g / m) 2 )

[0193] Examples 1-18 and Comparative Examples 1-4 [Preparation of friction rubber composition] Rubber compositions having the compositions shown in Tables 2-5 were mixed in a Banbury mixer to prepare friction rubber compositions (lump-type uncrosslinked rubber compositions).

[0194] [Mooney scorch minimum viscosity (Vm) and scorch time] The obtained friction rubber composition was used to measure the minimum Mooney scorch viscosity in accordance with the Mooney scorch test of JIS K 6300-1 (2013). An L-shaped rotor was used, and the test temperature was 125°C. A polyester film (Toray Industries, Inc.'s "Lumirror") with a thickness of approximately 0.04 mm was placed between the surface where the test piece (the friction rubber composition) and the die were in contact. After closing the die, the rotor was preheated for 1 minute, and then the change in Mooney viscosity was recorded. The recorded Mooney viscosity generally behaved as shown in Figure 2, and the value at which the Mooney viscosity reached its lowest point was adopted as the minimum Mooney scorch viscosity (Vm). The time it took for the Mooney viscosity to rise by 5 points after reaching its lowest value (time from the start of the test) was recorded as the scorch time (t5).

[0195] [Rubber hardness of cross-linked rubber] The obtained friction rubber composition was passed through a calender roll to prepare an uncrosslinked rolled rubber sheet of a predetermined thickness. Then, the obtained uncrosslinked rolled rubber sheet was press-heated at 153°C, 2 MPa, and for 20 minutes to produce a crosslinked rubber sheet (100 mm × 100 mm × 2 mm thickness). A laminate of three crosslinked rubber sheets was used as a sample, and the rubber hardness (Type A hardness) of the crosslinked rubber sheet was measured using a Type A durometer in accordance with the spring-type durometer hardness test specified in JIS K 6253 (2012) (Vulcanized rubber and thermoplastic rubber - Method for determining hardness -). The test temperature was 23°C.

[0196] [Preparation of reinforcing fabric precursor] Using a calender roll with three rolls (top roll, center roll, and bottom roll) arranged vertically, the obtained friction rubber composition was rolled by passing it between the top roll and the center roll to obtain a sheet-like rubber composition. The obtained sheet-like rubber composition was then continuously passed between the center roll and the bottom roll, which rotated at different speeds, simultaneously with the reinforcing fabric, and the rubber composition was rubbed into the fibers of the fabric to obtain an uncrosslinked composite. The rotation speeds were 15 rpm for the top roll, 20 rpm for the center roll, and 10 rpm for the bottom roll, and the clearance between the center roll and the bottom roll was 1 mm. The obtained uncrosslinked composite was cut diagonally and subjected to a lap joint process by overlapping the ends to obtain a reinforcing fabric precursor.

[0197] [Friction processing properties] In the fabrication of uncrosslinked composites by friction, the workability was evaluated according to the following criteria.

[0198] Grade A: Processed smoothly (had processability equivalent to or better than that of chloroprene rubber in Comparative Example 4). Grade B: Processing was possible, but it took a long time. C rating... Processing failed.

[0199] [Lap joint workability] In the preparation of reinforced fabric precursors by lap joint processing, workability was evaluated according to the following criteria.

[0200] Grade A: Processed smoothly (had processability equivalent to or better than that of chloroprene rubber in Comparative Example 4). Grade B: Processing was possible, but it took a long time. C rating... Processing failed.

[0201] [Fabrication of wrapped V-belts] A sheet for the compression rubber layer, a core wire, and a sheet for the stretching layer were sequentially laminated and attached to the outer surface of a cylindrical drum to form a cylindrical uncrosslinked sleeve in which the uncrosslinked rubber layer and the core wire were laminated. The resulting uncrosslinked sleeve was cut in the circumferential direction while it was positioned on the outer surface of the cylindrical drum to form an annular uncrosslinked rubber belt.

[0202] Next, the uncrosslinked rubber belt was removed from the drum, and both sides of the uncrosslinked rubber belt were cut (skived) at a predetermined angle to form a V-shaped cross-section. The V-shaped uncrosslinked rubber belt was then subjected to a cover-wrapping process (covering process) twice using the reinforcing fabric precursor to form an uncrosslinked belt molded body in which the belt body was double-covered with the reinforcing fabric precursor.

[0203] The obtained uncrosslinked belt molded body was inserted into the groove of the ring mold. Furthermore, with cylindrical rubber sleeves fitted onto the outer surfaces of the ring mold and the uncrosslinked belt molded body, they were placed in a vulcanizing vessel and crosslinked by pressurizing them to 0.9 MPa at a temperature of 180°C to obtain a crosslinked belt. The obtained crosslinked belt was removed from the ring mold to obtain a wrapped V-belt [ASABE standard HB type, belt length 1600 mm, average thickness of reinforcing fabric (2ply) 0.55 mm × 2 = 1.1 mm].

[0204] [Covering processability] In the production of wrapped V-belts by covering, workability was evaluated according to the following criteria.

[0205] Grade A: Processed smoothly (had processability equivalent to or better than that of chloroprene rubber in Comparative Example 4). Grade B: Processing was possible, but it took a long time. C rating... Processing failed.

[0206] [Abrasion resistance test (measurement of abrasion rate)] The wear resistance of a wrapped V-belt was evaluated by running it under the following conditions and calculating the wear rate from the change in mass of the wrapped V-belt before and after running. As shown in Figure 3, the wrapped V-belt was mounted on a two-axis running test machine consisting of a drive (Dr.) pulley with a diameter of 180 mm and a driven (Dn.) pulley with a diameter of 180 mm. The axial load was set to 1600 N, the rotation speed of the drive pulley to 1800 rpm, and the load on the driven pulley to 53 N·m, and the wrapped V-belt was run for 24 hours at an ambient temperature of 25 °C. The mass of the wrapped V-belt was measured before and after running, and the wear resistance was evaluated by calculating the rate of mass change (wear rate) using the following formula.

[0207] Wear rate (%) = [(Belt mass before use - Belt mass after use) / Belt mass before use] × 100

[0208] [Overall assessment] Based on the evaluation of each evaluation item, an overall evaluation was conducted according to the following criteria.

[0209] Rank A: No "c" ratings in the machinability assessment, and the wear rate is 0.80% or less (pass). Rank B: No C rating in the machinability assessment, and the wear rate is greater than 0.80% but less than or equal to 2.00% (Pass) Rank C: If the machinability evaluation results in a "c" rating, or if the wear rate is greater than 2.00% (failure).

[0210] The evaluation results for Examples 1 to 18 are shown in Tables 2 to 4, and the evaluation results for Comparative Examples 1 to 4 are shown in Table 5.

[0211] [Table 2]

[0212] [Table 3]

[0213] [Table 4]

[0214] [Table 5]

[0215] As is clear from the results in Tables 2-4, the wrapped V-belts of Examples 1-18 achieved both processability and wear resistance.

[0216] Examples 1-5 show variations in the proportion of EBDM, but Examples 3-5, with an EBDM proportion of 55 parts by mass or more, exhibited particularly good friction processability. Furthermore, Example 6, which had the same composition as Example 5 except for containing a large amount of tackifier, maintained relatively high wear resistance while improving covering processability. The overall evaluation for all examples was a B grade (pass).

[0217] Example 7 is an example that uses a peroxide crosslinking agent based on the composition of Example 4. The processability and wear resistance were equivalent to Example 4. Specifically, although the rubber hardness and wear resistance were slightly reduced, the covering processability was improved. The overall evaluation was a B grade (pass).

[0218] Examples 8-11 are examples of variations based on the composition of Example 4, with changes in the amount of tackifier. Examples 9-11, in which the proportion of tackifier was 10 parts by mass or more, exhibited excellent covering processability, and Example 11 also showed excellent lap joint processability. On the other hand, in Examples 8-11, there was a tendency for rubber hardness and abrasion resistance to decrease as the proportion of tackifier increased. The overall evaluation for all was a B grade (pass).

[0219] Examples 12-14 are examples of variations based on the composition of Example 4, with changes in the amount of plasticizer. As the proportion of plasticizer increased, the minimum viscosity Vm of Mooney scorch decreased, and Examples 4 and 13-14, with 20 parts by mass or more of plasticizer, exhibited excellent friction processability. On the other hand, as the proportion of plasticizer increased, there was a tendency for rubber hardness and wear resistance to decrease. The overall evaluation for all was a B grade (pass).

[0220] Example 15 is an example with the same composition as Example 4 except that it does not contain silica, but the friction processability and wear resistance were slightly reduced. Similarly, Example 16 is an example with the same composition as Example 4 except that the amount of carbon black was increased, but the wear resistance was slightly improved. The overall evaluation for all was a B grade (pass).

[0221] Example 17 is an example in which a tackifier was further added to Example 7, which used a peroxide crosslinking agent, and the amount of silica was increased while the amount of plasticizer was reduced. As a result, wear resistance was greatly improved while maintaining good processability. The overall evaluation was A (pass), and the balance between wear resistance and processability was particularly excellent.

[0222] Example 18 is an example based on the composition of Example 4, but with the use of a co-crosslinking agent, the addition of a tackifier, a reduction in the amount of plasticizer, and an increase in carbon black without the use of silica. As a result, wear resistance was greatly improved while maintaining good processability. The overall evaluation was A (pass), and the balance between wear resistance and processability was particularly excellent.

[0223] As is clear from the results in Table 5, compared to these examples, comparative example 1, which does not contain EBDM, was not suitable for friction processing, and the overall evaluation was a C (fail).

[0224] In Comparative Example 2, which did not include EBDM, friction processing was not possible even with the addition of a tackifier, and the overall evaluation was a C (fail).

[0225] In Comparative Example 3, the amount of EBDM was less than 30 parts by mass, friction processing was not possible, and the overall evaluation was a C (fail).

[0226] Comparative Example 4 is an example using chloroprene rubber. Although it has good processability, it has low abrasion resistance, and the overall evaluation was a C (fail). [Industrial applicability]

[0227] The power transmission belt of the present invention is not particularly limited as long as it is a power transmission belt containing a composite of cloth and a rubber composition, but a friction power transmission belt in which at least a part of the friction transmission surface is covered with reinforcing cloth is preferred. The power transmission belt of the present invention can be used for flat belts, V-belts (wrapped V-belts, raw edge V-belts, raw edge cogged V-belts, etc.), V-ribbed belts, etc., and is particularly useful for wrapped V-belts because it also offers improved processability. [Explanation of Symbols]

[0228] 1... Wrapped V-belt 2…Stretchable rubber layer 3... Core body 4…Compressed rubber layer 5…Outer cover fabric (reinforced fabric)

Claims

1. A rubber composition for compounding with fabric for a transmission belt, Contains rubber components, The rubber component includes an ethylene-long-chain α-olefin-non-conjugated polyene copolymer in which the long-chain α-olefin unit has 4 or more carbon atoms, and A rubber composition in which the proportion of the ethylene-long-chain α-olefin-non-conjugated polyene copolymer is 25% by mass or more in the rubber component.

2. The rubber composition according to claim 1, further comprising silica.

3. The rubber composition according to claim 1 or 2, further comprising hard carbon black.

4. The rubber composition according to any one of claims 1 to 3, further comprising an aliphatic oil.

5. The rubber composition according to claim 4, wherein the proportion of the aliphatic oil is 10 to 40 parts by mass per 100 parts by mass of the rubber component.

6. A rubber composition according to any one of claims 1 to 5, further comprising a tackifier.

7. The rubber composition according to claim 6, wherein the proportion of the tackifier is 10 parts by mass or more per 100 parts by mass of the rubber component.

8. The rubber component further comprises an ethylene-propylene-nonconjugated polyene copolymer. The ethylene-long-chain α-olefin-non-conjugated polyene copolymer is an ethylene-butene-non-conjugated diene copolymer, and The rubber composition according to any one of claims 1 to 7, wherein the proportion of the ethylene-long-chain α-olefin-non-conjugated polyene copolymer is 55 to 90% by mass of the rubber component.

9. The rubber composition according to any one of claims 1 to 8, wherein the minimum viscosity Vm of Mooney scorch at 125°C in the uncrosslinked material is 30 or less.

10. The rubber composition according to any one of claims 1 to 9, wherein the crosslinked material has a rubber hardness of 55 or more.

11. A reinforcing fabric for covering at least a portion of the surface of a power transmission belt, comprising a composite of the fabric and a crosslinked rubber composition according to any one of claims 1 to 10.

12. A transmission belt comprising the reinforcing fabric described in claim 11, A transmission belt in which at least a portion of the surface of the transmission belt is covered with the reinforcing fabric.

13. The transmission belt according to claim 12, which is a wrapped V-belt.

14. A method for manufacturing a power transmission belt, comprising a compounding step of compounding a cloth with a rubber composition according to any one of claims 1 to 10 to obtain an uncrosslinked composite for forming a reinforcing cloth.

15. The method for manufacturing a transmission belt according to claim 14, wherein the composite step is a friction treatment, coating treatment, lamination treatment or soaking treatment.

16. A method for manufacturing a transmission belt according to claim 14 or 15, further comprising a lap joint step of cutting the uncrosslinked composite diagonally and overlapping and joining the ends to obtain a reinforcing fabric precursor.

17. The method for manufacturing a power transmission belt according to claim 16, further comprising a covering step of covering the belt body precursor with the reinforcing fabric precursor.

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