Composition for transmission belt and use thereof

Abstract

To provide a composition for a transmission belt which is suitable for obtaining a transmission belt having high transmissibility and excellent low-temperature characteristics.SOLUTION: The composition for a transmission belt contains: at least one (B) selected from a nitrile rubber and a hydrogenated nitrile rubber; an ethylene / α-olefin / nonconjugated polyene copolymer (A) containing a structural unit derived from ethylene [A1], a structural unit derived from a C3-20 α-olefin [A2], and a structural unit derived from a nonconjugated polyene [A3]; carbon black (C); a plasticizer (D); and a crosslinking agent (E).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a composition for a transmission belt and its uses.

Background Art

[0002] Transmission belts are widely used for automobiles, motorcycles, and general industrial machines. High rubber elasticity and abrasion resistance are required for transmission belts. To manufacture a transmission belt that satisfies the above properties, chloroprene rubber is usually used for transmission belts. In view of the improvement of the heat resistance of transmission belts and the demand for weight reduction, it has been considered to use ethylene-propylene-non-conjugated polyene copolymer rubber instead of chloroprene rubber (see, for example, Patent Documents 1 and 2).

[0003] In addition, hydrogenated nitrile rubber is also widely used in applications that require oil resistance, such as transmission belts, because it is excellent in oil resistance, mechanical properties, abrasion resistance, and heat aging resistance (see, for example, Patent Documents 3 and 4).

[0004] Patent Documents 5 to 7 disclose a composition for a transmission belt that contains an ethylene-α-olefin-non-conjugated polyene copolymer having specific physical properties and can form a transmission belt excellent in heat resistance and abrasion resistance. Patent Documents 5 to 7 describe that the composition for a transmission belt may contain usually 100 parts by mass or less of nitrile rubber with respect to 100 parts by mass of the ethylene-α-olefin-non-conjugated polyene copolymer.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

[0006] For transmission belts containing hydrogenated nitrile rubber, improvement in transmission performance and low-temperature properties is required. Therefore, an object of the present invention is to provide a composition for a transmission belt suitable for obtaining a transmission belt having high transmission performance and excellent low-temperature properties. [Means for Solving the Problems]

[0007] The present invention relates to, for example, the following [1] to [8].

[0008] [1] At least one (B) selected from nitrile rubber and hydrogenated nitrile rubber, An ethylene·α-olefin·non-conjugated polyene copolymer (A) containing structural units derived from ethylene [A1], structural units derived from an α-olefin [A2] having 3 to 20 carbon atoms, and structural units derived from a non-conjugated polyene [A3], Carbon black (C), A plasticizer (D), A crosslinking agent (E) And a composition for a transmission belt containing the same.

[0009] [2] The composition for a transmission belt according to [1], wherein the non-conjugated polyene [A3] contains a non-conjugated polyene [A3-1] containing two or more partial structures selected from the group consisting of the following formulas (I) and (II) in one molecule. [Chemical Formula]

[0010] [3] The transmission belt composition according to [1] or [2], wherein the copolymer (A) satisfies any one or more of the following requirements (i) to (v). Requirement (i): When the total constitutional units contained in the copolymer (A) are 100 mol%, the ratio [(A1) / (A2)] of the molar fraction (A1) of the structural unit derived from ethylene [A1] to the molar fraction (A2) of the structural unit derived from the α-olefin [A2] having 3 to 20 carbon atoms is 40 / 60 to 99.9 / 0.1; Requirement (ii): The mass fraction of the structural unit derived from the non-conjugated polyene [A3] is 0.07 to 10% by mass in 100% by mass of the copolymer (A); Requirement (iii): The weight average molecular weight (Mw) of the copolymer (A), the mass fraction of the structural unit derived from the non-conjugated polyene [A3] ([mass fraction of [A3] (% by mass)]), and the molecular weight of the non-conjugated polyene [A3] ([molecular weight of [A3]]) satisfy the following formula (1); 4.5 ≦ Mw × mass fraction of [A3] / 100 / molecular weight of [A3] ≦ 80 ··· (1) Requirement (iv): The complex viscosity η * (ω=0.1) (Pa·s) at a frequency ω = 0.1 rad / s, obtained by linear viscoelastic measurement (190 °C) using a rheometer, and the complex viscosity η * (ω=100) (Pa·s) at a frequency ω = 100 rad / s, and the ratio P(η * (ω=0.1) / η * (ω=100) ) and the intrinsic viscosity [η] (dL / g) and the mass fraction of the structural unit derived from the non-conjugated polyene [A3] ([mass fraction of [A3] (% by mass)]) satisfy the following formula (2); P / ([η] 2.9 ) ≦ mass fraction of [A3] × 6 ··· (2) Requirement (v): The complex viscosity η * (ω=0.01)(Pa·s) and the complex viscosity η at a frequency ω = 10 rad / s * (ω=10) (Pa·s) and the apparent iodine value derived from the non-conjugated polyene [A3] satisfy the following formula (3). Log[η * (ω=0.01) / Log[η * (ω=10) ≤ 0.0753 × {apparent iodine value derived from non-conjugated polyene [A3]} + 1.42 ··· (3)

[0011] [4] The composition for a transmission belt according to any one of [1] to [3], wherein the non-conjugated polyene [A3] contains 5-vinyl-2-norbornene (VNB).

[0012] [5] The composition for a transmission belt according to any one of [1] to [4], wherein the α-olefin [A2] having 3 to 20 carbon atoms is propylene.

[0013] [6] With respect to a total of 100 parts by mass of at least one (B) selected from the nitrile rubber and the hydrogenated nitrile rubber and the copolymer (A), the content of the carbon black (C) is 0.1 to 200 parts by mass, the content of the plasticizer (D) is 0.1 to 50 parts by mass, The composition for a transmission belt according to any one of [1] to [5].

[0014] [7] A crosslinked molded body formed from the composition for a transmission belt according to any one of [1] to [6].

[0015] [8] A transmission belt having the crosslinked molded body according to [7]. [Advantages of the Invention]

[0016] According to the present invention, it is possible to provide a composition for a transmission belt suitable for obtaining a transmission belt having high transmissibility and excellent low-temperature characteristics.

BEST MODE FOR CARRYING OUT THE INVENTION

[0017] The present invention will be described in more detail. [Composition for Transmission Belt] The composition for a transmission belt of the present invention contains at least one (B) selected from nitrile rubber and hydrogenated nitrile rubber, an ethylene·α-olefin·non-conjugated polyene copolymer (A), carbon black (C), a plasticizer (D), and a crosslinking agent (E).

[0018] <At least one (B) selected from nitrile rubber and hydrogenated nitrile rubber> The composition for a transmission belt contains at least one (B) selected from nitrile rubber and hydrogenated nitrile rubber (hereinafter also referred to as "component (B)"). Examples of commercially available nitrile rubbers include DN219 (manufactured by JSR Corporation). Examples of commercially available hydrogenated nitrile rubbers include Zetpol 2020 (manufactured by Nippon Zeon Co., Ltd.). Component (B) is preferably a hydrogenated nitrile rubber from the viewpoints of heat resistance, oil resistance, and abrasion resistance of the composition for a transmission belt.

[0019] Hydrogenated nitrile rubber is obtained by hydrogenating a copolymer of acrylonitrile and 1,3-butadiene. During hydrogenation, hydrogen is added to the double bonds in the structural units derived from 1,3-butadiene.

[0020] The content of the structural unit derived from acrylonitrile in component (B) is preferably 15 to 60% by mass, more preferably 20 to 50% by mass, and still more preferably 30 to 40% by mass with respect to 100% by mass of component (B). The content of the structural unit derived from 1,3-butadiene in component (B), including the hydrogenated ones, is preferably 40 to 85% by mass, more preferably 50 to 80% by mass, and still more preferably 60 to 70% by mass with respect to 100% by mass of component (B).

[0021] The iodine value of component (B) is preferably 80 g / 100 g or less, more preferably 60 g / 100 g or less, still more preferably 40 g / 100 g or less, from the viewpoints of heat aging resistance and oil resistance of the crosslinked molded body formed from the composition for transmission belts. The Mooney viscosity ML(1+4) 100 °C of component (B) is preferably 20 to 150, more preferably 30 to 120, still more preferably 40 to 100, particularly preferably 60 to 90, from the viewpoints of processability during molding and mechanical strength of the resulting molded body. As long as it does not inhibit the effects of the present invention, component (B) may contain structural units derived from copolymerizable monomers other than acrylonitrile and 1,3-butadiene, but the content thereof is usually 10% by mass or less, preferably 5% by mass or less, based on 100% by mass of component (B).

[0022] <Ethylene·α-olefin·non-conjugated polyene copolymer (A)> The composition for transmission belts contains an ethylene·α-olefin·non-conjugated polyene copolymer (A) (hereinafter, also referred to as "copolymer (A)") containing structural units derived from ethylene [A1], structural units derived from an α-olefin [A2] having 3 to 20 carbon atoms, and structural units derived from a non-conjugated polyene [A3]. By the composition for transmission belts containing copolymer (A), the crosslinked molded body formed from the composition for transmission belts has improved transmissibility, excellent low-temperature characteristics, and a tendency to improve hardness.

[0023] 《α-olefin [A2] having 3 to 20 carbon atoms》 Examples of the α-olefin [A2] having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, and 1-eicosene. As the α-olefin [A2] having 3 to 20 carbon atoms, α-olefins having 3 to 8 carbon atoms such as propylene, 1-butene, 1-hexene, and 1-octene are preferable, and propylene is particularly preferable. Such an α-olefin is preferable because the raw material cost is relatively low, the obtained copolymer (A) exhibits excellent mechanical properties, and a molded article having rubber elasticity can be obtained. The α-olefin [A2] having 3 to 20 carbon atoms may be used alone or in combination of two or more.

[0024] 《Non-conjugated polyene [A3]》 Examples of the non-conjugated polyene [A3] include compounds containing two or more partial structures selected from the group consisting of the following formulas (I) and (II) in one molecule, and compounds containing only one partial structure selected from the group consisting of the following formulas (I) and (II) in one molecule. [Chemical formula] A compound containing two or more partial structures selected from the group consisting of the formulas (I) and (II) in one molecule is also referred to as "non-conjugated polyene [A3-1]", and a compound containing only one partial structure selected from the group consisting of the formulas (I) and (II) in one molecule is also referred to as "non-conjugated polyene [A3-2]".

[0025] Examples of the non-conjugated polyene [A3-1] include, for example, 5-vinyl-2-norbornene (VNB), norbornadiene, 1,4-hexadiene, 5-(2-propenyl)-2-norbornene, 5-(3-butenyl)-2-norbornene, 5-(1-methyl-2-propenyl)-2-norbornene, 5-(4-pentenyl)-2-norbornene, 5-(1-methyl-3-butenyl)-2-norbornene, 5-(5-hexenyl)-2-norbornene, 5-(1-methyl-4-pentenyl)-2-norbornene, 5-(2-ethyl-3-butenyl)-2-norbornene, 5-(6-heptenyl)-2-norbornene, 5-(3-methyl-5-hexenyl)-2-norbornene, 5-(3-ethyl-4-pentenyl)-2-norbornene, 5-(7-octenyl)-2-norbornene, 5-(2-methyl-6-heptenyl)-2-norbornene, 5-(1,2-dimethyl-5-hexenyl)-2-norbornene, and 5-(1,2,3-trimethyl-4-pentenyl)-2-norbornene, and dicyclopentadiene. Since it is highly available, has good reactivity with the crosslinking agent (E) during the crosslinking reaction after polymerization, and the heat resistance of the composition for the transmission belt is likely to be improved, preferably the non-conjugated polyene [A3] contains the non-conjugated polyene [A3-1], more preferably the non-conjugated polyene [A3] contains VNB, and even more preferably the non-conjugated polyene [A3] is VNB. The non-conjugated polyene [A3] may be used alone or in combination of two or more. The non-conjugated polyene [A3-1] may be used alone or in combination of two or more.

[0026] The non-conjugated polyene [A3] may contain only the non-conjugated polyene [A3-1], or may contain the non-conjugated polyene [A3-1] and the non-conjugated polyene [A3-2].

[0027] Examples of the non-conjugated polyene [A3-2] include 5-ethylidene-2-norbornene (ENB), 5-methylene-2-norbornene, 5-(2,3-dimethyl-3-butenyl)-2-norbornene, 5-(3,4-dimethyl-4-pentenyl)-2-norbornene, 5-(5-ethyl-5-hexenyl)-2-norbornene, and 5-(2-methyl-1-propenyl)-2-norbornene. Since the non-conjugated polyene [A3-2] is highly available, has high reactivity with a crosslinking agent during the crosslinking reaction after polymerization, can easily control the crosslinking rate, and can easily obtain good mechanical properties, the non-conjugated polyene [A3-2] is preferably ENB. The non-conjugated polyene [A3-2] may be used alone or in combination of two or more.

[0028] When the copolymer (A) contains structural units derived from ethylene [A1], an α-olefin [A2] having 3 to 20 carbon atoms, a non-conjugated polyene [A3-1], and a non-conjugated polyene [A3-2], the mass fraction of the structural units derived from the non-conjugated polyene [A3-2] is preferably 20% by mass or less, more preferably 8% by mass or less, and still more preferably 0.01 to 8% by mass. However, the total mass fraction of the structural units derived from ethylene [A1], the α-olefin [A2] having 3 to 20 carbon atoms, the non-conjugated polyene [A3-1], and the non-conjugated polyene [A3-2] is 100% by mass.

[0029] The copolymer (A) may each contain structural units derived from at least one or more biomass-derived monomers (biomass-derived ethylene [A1], an α-olefin [A2] having 3 to 20 carbon atoms, and a non-conjugated polyene [A3]).

[0030] 《Requirements (i) to (v)》 The copolymer (A) preferably satisfies any one or more of the following requirements (i) to (v), more preferably satisfies any two or more of the following requirements (i) to (v), still more preferably satisfies any three or more of the following requirements (i) to (v), even more preferably satisfies any four or more of the following requirements (i) to (v), and particularly preferably satisfies all of the following requirements (i) to (v).

[0031] Requirement (i): When the total constitutional units contained in the copolymer (A) are 100 mol%, the ratio [(A1) / (A2)] of the molar fraction (A1) of the structural unit derived from ethylene [A1] to the molar fraction (A2) of the structural unit derived from an α-olefin [A2] having 3 to 20 carbon atoms is 40 / 60 to 99.9 / 0.1. The ratio [(A1) / (A2)] is preferably 50 / 50 to 90 / 10, more preferably 55 / 45 to 85 / 15, still more preferably 55 / 45 to 80 / 20, and particularly preferably 60 / 40 to 75 / 25.

[0032] When the total constitutional units contained in the copolymer (A) are 100 mol%, the molar fraction (A1) of the structural unit derived from ethylene [A1] is preferably 50 to 85 mol%, more preferably 55 to 80 mol%, and still more preferably 60 to 75 mol%.

[0033] By using the copolymer (A) that satisfies requirement (i), a transmission belt excellent in rubber elasticity, mechanical strength, and flexibility can be obtained. The molar fraction (A1) of the structural unit derived from ethylene [A1], the molar fraction (A2) of the structural unit derived from an α-olefin [A2] having 3 to 20 carbon atoms, and the ratio [(A1) / (A2)] are determined under the apparatus and conditions described in the Examples section below. 13 They can be calculated by measuring the C-NMR spectrum.

[0034] Requirement (ii): The mass fraction of the structural unit derived from the non-conjugated polyene [A3] is 0.07 to 10 mass% in 100 mass% of the copolymer (A). The mass fraction of the structural unit derived from the non-conjugated polyene [A3] is preferably 0.1 to 8.0 mass%, more preferably 0.5 to 5.0 mass%, still more preferably 0.5 to 3.0 mass%, and particularly preferably 0.5 to 2.0 mass%.

[0035] The copolymer (A) satisfying requirement (ii) has sufficient hardness and excellent mechanical properties. Further, the composition for a transmission belt containing the copolymer (A) satisfying requirement (ii) tends to exhibit a high crosslinking rate. The mass fraction of the structural unit derived from the non-conjugated polyene [A3] can be calculated by measuring the 13C-NMR spectrum under the apparatus and conditions described in the Examples section below. 13 measuring the 13C-NMR spectrum.

[0036] Requirement (iii): The weight average molecular weight (Mw) of the copolymer (A), the mass fraction of the structural unit derived from the non-conjugated polyene [A3] ([mass fraction of [A3] (mass%)]), and the molecular weight of the non-conjugated polyene [A3] ([molecular weight of [A3]]) satisfy the following formula (1). 4.5 ≦ Mw × mass fraction of [A3] / 100 / molecular weight of [A3] ≦ 80 ··· (1)

[0037] The formula (1) of requirement (iii) is preferably the following formula (1'). 4.5 ≦ Mw × mass fraction of [A3] / 100 / molecular weight of [A3] ≦ 70 ··· (1')

[0038] Requirement (iii) represents the content of the structural unit derived from the non-conjugated polyene [A3] per weight average molecular weight (Mw) in the copolymer (A). When the copolymer (A) satisfies requirement (iii), since the content of the structural unit derived from the non-conjugated polyene [A3] in the copolymer (A) is appropriate, the composition for a transmission belt exhibits sufficient crosslinking performance and tends to have a high crosslinking rate. Furthermore, the crosslinked molded body formed from the composition for a transmission belt tends to have excellent mechanical properties and heat aging resistance in good balance.

[0039] The weight average molecular weight (Mw) of the copolymer (A) can be determined as a polystyrene-equivalent value measured by gel permeation chromatography (GPC) under the conditions described in the Examples section below.

[0040] Requirement (iv): The ratio P(η * (ω=0.1) / η * (ω=100) ) of the complex viscosity η * (ω=0.1) at a frequency ω = 0.1 rad / s and the complex viscosity η * (ω=100) at a frequency ω = 100 rad / s, obtained by linear viscoelastic measurement (at 190 °C) using a rheometer, the limiting viscosity [η] (dL / g), and the mass fraction of the structural unit derived from the non-conjugated polyene [A3] (mass fraction of [A3] (mass %)) satisfy the following formula (2). P / ([η] 2.9 ) ≤ mass fraction of [A3] × 6 ··· (2)

[0041] The formula (2) of requirement (iv) is preferably the following formula (2'). P / ([η] 2.9 ) ≤ mass fraction of [A3] × 5.7 ··· (2')

[0042] The ratio P(η * (ω=0.1) / η * (ω=100) ) of the complex viscosity η * (ω=0.1) at a frequency ω = 0.1 rad / s and the complex viscosity η * (ω=100) at a frequency ω = 100 rad / s (hereinafter also referred to as "P value") represents the frequency dependence of viscosity. Therefore, P / ([η] 2.9 ), which corresponds to the left side of formula (2) and formula (2'), tends to show a high value when there are many long-chain branches, although it is affected by short-chain branches and molecular weight. Generally, in ethylene·α-olefin·non-conjugated polyene copolymers, the more the structural unit derived from the non-conjugated polyene is contained, the more the long-chain branches tend to be contained. However, it is considered that the copolymer (A) can satisfy formula (2) or (2') because it has fewer long-chain branches than conventionally known ethylene·α-olefin·non-conjugated polyene copolymers.

[0043] The P value is obtained by using a viscoelasticity measuring device (for example, Ares (manufactured by Rheometric Scientific)) and calculating the ratio of the complex viscosity measured at 190 °C, a strain of 1.0%, and 0.1 rad / second, with only the measurement frequency changed, to the complex viscosity measured at 100 rad / second. The limiting viscosity [η] means the value measured in decalin at 135 °C.

[0044] Requirement (v): The complex viscosity η at a frequency ω = 0.01 rad / second obtained by linear viscoelasticity measurement (190 °C) using a rheometer * (ω=0.01) (Pa·s), and the complex viscosity η at a frequency ω = 10 rad / second * (ω=10) (Pa·s), and the apparent iodine value derived from the non-conjugated polyene [A3] satisfy the following formula (3). Log[η * (ω=0.01) / Log[η * (ω=10) ≤ 0.0753 × {apparent iodine value derived from non-conjugated polyene [A3]} + 1.42 ··· (3)

[0045] In formula (3), the left side represents the shear rate dependence which is an index of the long-chain branch content, and the right side represents an index of the content of non-conjugated polyene [A3] that has not been consumed as long-chain branches during polymerization. When the copolymer (A) satisfies formula (3), it is preferable because the degree of long-chain branching is not too high.

[0046] The complex viscosity η * (ω=0.01) and the complex viscosity η * (ω=10) can be measured in the same manner as the complex viscosity η * (ω=0.1) and the complex viscosity η * (ω=100) in requirement (iv), except for the measurement frequency. The apparent iodine value derived from the non-conjugated polyene [A3] is obtained by the following formula. Apparent iodine value derived from [A3] = mass fraction of [A3] × 253.81 / molecular weight of [A3]

[0047] The copolymer (A) preferably satisfies the following requirement (vi). Requirement (vi): The number of long-chain branches per 1000 carbon atoms (LCB 1000C ) obtained using 3D-GPC and the natural logarithm of the weight-average molecular weight [Ln(Mw)] satisfy the following formula (4). LCB 1000C ≦1 - 0.07 × Ln(Mw) ··· (4)

[0048] Formula (4) is more preferably the following formula (4’). LCB 1000C ≦1 - 0.071 × Ln(Mw) ··· (4’) According to formula (4) or (4’), the upper limit value of the number of long-chain branches per unit carbon atom in the copolymer (A) is specified.

[0049] When the copolymer (A) satisfies requirement (vi), since the proportion of long-chain branches contained in the copolymer (A) is small, the curing characteristics are excellent when crosslinking the composition for the transmission belt, and the crosslinked molded body formed from the composition for the transmission belt tends to have excellent heat aging resistance.

[0050] Mw and the number of long-chain branches per 1000 carbon atoms (LCB 1000C ) can be determined by a structural analysis method using 3D-GPC, and specifically, can be determined as follows.

[0051] First, use a GPC device (for example, 3D-high temperature GPC device PL-GPC220 type (manufactured by Polymer Laboratories)) to determine the absolute molecular weight distribution, and use a viscometer to determine the intrinsic viscosity. The main measurement conditions are as follows.

[0052] Detector: Differential refractometer / built-in GPC device Two-angle light scattering photometer PD2040 type (manufactured by Precison Detectors) Bridge type viscometer PL-BV400 type (manufactured by Polymer Laboratories) Column: TSKgel GMH HR -H(S)HT × 2 pieces + TSKgel GMH HR -M(S) × 1 piece (both with an inner diameter of 7.8 mmφ and a length of 300 mm per piece) Temperature: 140 °C Mobile phase: 1,2,4-trichlorobenzene (containing 0.025% BHT) Injection volume: 0.5 mL Sample concentration: ca 1.5 mg / mL Sample filtration: Filtered through a sintered filter with a pore size of 1.0 μm

[0053] The dn / dc value required for the determination of the absolute molecular weight is determined for each sample from the dn / dc value of standard polystyrene (molecular weight 190,000) of 0.053 and the response intensity of the differential refractometer per unit injected mass.

[0054] Next, from the relationship between the intrinsic viscosity obtained from the viscometer and the absolute molecular weight obtained from the light scattering photometer, the long-chain branching parameter g' for each eluted component i is calculated from the following formula (v-1). In formula (v-1), [η] = KM v , let v = 0.725. This formula is called the Mark-Houwink-Sakurada formula, where K represents the solvent constant and M represents the average molecular weight.

[0055]

Equation

[0056] Each average value of g' is calculated from the following formulas (v-2), (v-3) and (v-4). The Trendline assuming only short-chain branches is determined for each sample.

[0057]

Equation

[0058] Furthermore, g' wUsing this, the number of branch points per molecular chain BrNo, the number of long-chain branches per 1000 carbon atoms LCB 1000C , and the branching degree λ per unit molecular weight are calculated. The calculation of BrNo uses the following formula (v-5) of Zimm-Stockmayer, and for the calculation of LCB 1000C and λ, the following formulas (v-6) and (v-7) are used. g is the long-chain branching parameter obtained from the radius of gyration Rg, and the following simple correlation is made with g’ obtained from the intrinsic viscosity. Various values of ε have been proposed depending on the molecular shape. Here, the calculation is performed assuming ε = 1 (i.e., g’ = g).

[0059] [Number]

[0060] λ = BrNo / M ··· (v-6) LCB 1000C = λ × 14000 ··· (v-7) In formula (v-7), "14000" means the molecular weight of 1000 methylene (CH2) units.

[0061] The intrinsic viscosity [η] of the copolymer (A) is preferably 0.1 to 5.0 dL / g, more preferably 0.5 to 5.0 dL / g, still more preferably 1.0 to 4.0 dL / g, particularly preferably 1.5 to 3.5 dL / g, and even more preferably 2.0 to 3.0 dL / g.

[0062] The weight-average molecular weight (Mw) of the copolymer (A) is preferably 10,000 to 900,000, more preferably 30,000 to 550,000, still more preferably 50,000 to 530,000, particularly preferably 100,000 to 500,000, and even more preferably 200,000 to 490,000.

[0063] The intrinsic viscosity [η] and weight-average molecular weight (Mw) of the copolymer (A) are both preferably within the above ranges. The intrinsic viscosity [η] of the copolymer (A) can be measured by the apparatus and conditions described in the Examples section. The weight-average molecular weight (Mw) of the copolymer (A) can be measured by gel permeation chromatography (GPC) under the apparatus and conditions described in the Examples section.

[0064] In the copolymer (A), as described above, it is preferable that the non-conjugated polyene [A3] contains VNB, and it is more preferable that the non-conjugated polyene [A3] is VNB. That is, in Formula (1), Formula (2), etc., the "mass fraction of [A3]" is preferably the "mass fraction of the structural unit derived from VNB".

[0065] As described above, when the copolymer (A) contains structural units derived from ethylene [A1], an α-olefin [A2] having 3 to 20 carbon atoms, a non-conjugated polyene [A3-1], and a non-conjugated polyene [A3-2], the mass fraction of the structural unit derived from the non-conjugated polyene [A3-2] is preferably 20% by mass or less (however, the total mass fraction of the structural units derived from ethylene [A1], an α-olefin [A2] having 3 to 20 carbon atoms, the non-conjugated polyene [A3-1], and the non-conjugated polyene [A3-2] is 100% by mass). In this case, the copolymer (A) preferably satisfies the following requirement (vii).

[0066] Requirement (vii): The weight-average molecular weight (Mw) of the copolymer (A), the mass fraction of the structural unit derived from the non-conjugated polyene [A3-1] ([mass fraction of [A3-1]] (% by mass)), the mass fraction of the structural unit derived from the non-conjugated polyene [A3-2] ([mass fraction of [A3-2]] (% by mass)), the molecular weight of the non-conjugated polyene [A3-1] ([molecular weight of [A3-1]]), and the molecular weight of the non-conjugated polyene [A3-2] ([molecular weight of [A3-2]]) satisfy the following formula (5) (however, the total mass fraction of the structural units derived from ethylene [A1], an α-olefin [A2] having 3 to 20 carbon atoms, the non-conjugated polyene [A3-1], and the non-conjugated polyene [A3-2] is 100% by mass). 4.5 ≦ Mw × {([mass fraction of [A3-1]] / 100 / [molecular weight of [A3-1]]) + ([mass fraction of [A3-2]] / 100 / [molecular weight of [A3-2]])} ≦ 80 ··· (5) In formula (5), the total content of structural units derived from non-conjugated polyenes ([A3-1] and [A3-2]) per weight average molecular weight (Mw) in the copolymer (A) is specified.

[0067] When the copolymer (A) containing structural units derived from the non-conjugated polyene [A3-2] satisfies requirement (vii), a transmission belt excellent in mechanical properties and heat aging resistance can be obtained.

[0068] The copolymer (A) preferably satisfies the following requirement (viii). Requirement (viii): The mass fraction of the structural units derived from the non-conjugated polyene [A3] ([mass fraction of [A3]] (mass%)) and the weight average molecular weight (Mw) of the copolymer (A) satisfy the following formula (6). 6 - 0.45 × Ln(Mw) ≦ [mass fraction of [A3]] ≦ 10 ··· (6) When the copolymer (A) satisfies requirement (viii), the copolymer (A) contains a sufficient amount of structural units derived from the non-conjugated polyene [A3], which is preferable.

[0069] When the copolymer (A) contains structural units derived from the non-conjugated polyene [A3-1] and structural units derived from the non-conjugated polyene [A3-2], the copolymer (A) preferably satisfies the following requirement (ix) and the following requirement (x). Requirement (ix): The number (n A3-1 ) of structural units derived from the non-conjugated polyene [A3-1] per weight average molecular weight (Mw) in the copolymer (A) is 6 or more. n A3-1 is preferably 6 or more and 80 or less, more preferably 7 or more and 70 or less, and still more preferably 10 or more and 65 or less.

[0070] The copolymer (A) that satisfies requirement (ix) contains a sufficient amount of structural units derived from non-conjugated polyenes [A3-1] such as VNB, and has a low long-chain branching content. Therefore, the crosslinked molded body formed from the composition for the transmission belt is excellent in curing characteristics, has good moldability, is excellent in the balance of physical properties such as mechanical properties, and is particularly excellent in heat aging resistance.

[0071] Requirement (x): The number (n A3-2 ) of structural units derived from non-conjugated polyenes [A3-2] per weight average molecular weight (Mw) in the copolymer (A) is 29 or less. n A3-2 is preferably 10 or less, more preferably less than 1.

[0072] The copolymer (A) that satisfies requirement (x) has the content of structural units derived from non-conjugated polyenes [A3-2] such as ENB suppressed within a range not impairing the object of the present invention, is less likely to cause post-crosslinking, and has sufficient heat aging resistance.

[0073] n A3-1 can be determined by the following formula from the molecular weight of the non-conjugated polyene [A3-1], the mass fraction of the structural unit derived from the non-conjugated polyene [A3-1] ([mass fraction of [A3-1] (mass%)]), and the weight average molecular weight (Mw) of the copolymer (A). n A3-2 can be determined by the following formula from the molecular weight of the non-conjugated polyene [A3-2], the mass fraction of the structural unit derived from the non-conjugated polyene [A3-2] ([mass fraction of [A3-2] (mass%)]), and the weight average molecular weight (Mw) of the copolymer (A) (however, the total of the mass fractions of the structural units derived from ethylene [A1], α-olefins [A2] having 3 to 20 carbon atoms, non-conjugated polyene [A3-1], and non-conjugated polyene [A3-2] is 100 mass%).). (n A3-1 ) = Mw × mass fraction of [A3-1] / 100 / molecular weight of [A3-1] (n A3-2 ) = Mw × mass fraction of [A3-2] / 100 / molecular weight of [A3-2]

[0074] Since the copolymer (A) that satisfies requirement (ix) and requirement (x) has a low long-chain branching content, the crosslinked molded article formed from the composition for transmission belts has excellent curing characteristics, good moldability, excellent physical property balance such as mechanical properties, and is less likely to undergo post-crosslinking, and particularly tends to have excellent heat aging resistance.

[0075] The copolymer (A) preferably satisfies the following requirement (xi). Requirement (xi): The B value represented by the following formula (7) is 1.00 or more. B value = ([EX] + 2[Y]) / {2×[E]×([X] + [Y])} ··· (7) In formula (7), [E], [X], and [Y] respectively represent the molar fraction of the structural unit derived from ethylene [A1], the molar fraction of the structural unit derived from an α-olefin [A2] having 3 to 20 carbon atoms, and the molar fraction of the structural unit derived from a non-conjugated polyene [A3], and [EX] represents the ethylene-α-olefin having 3 to 20 carbon atoms diad chain fraction. The B value is preferably 1.00 to 1.80, more preferably 1.10 to 1.40.

[0076] The copolymer (A) that satisfies requirement (xi) tends to have an excellent balance between rubber elasticity at low temperatures and tensile strength at room temperature. The B value is an index indicating the randomness of the copolymer monomer chain distribution in the copolymer (A), and [E], [X], [Y], and [EX] in the formula (7) are 13 measured by measuring the C-NMR spectrum and can be determined based on the reports of J.C. Randall [Macromolecules, 15, 353 (1982)], J. Ray [Macromolecules, 10, 773 (1977)], etc.

[0077] The Mooney viscosity ML(1+4)125°C of the copolymer (A) is preferably in the range of 10 to 90, more preferably 40 to 80, still more preferably 50 to 75, and particularly preferably 60 to 75. The composition for a transmission belt containing the copolymer (A) with a Mooney viscosity ML(1+4) at 125°C within the above range is excellent in roll processability even in a high-hardness oil-free formulation, and also shows good post-treatment (ribbon handling property) and tends to have excellent rubber physical properties.

[0078] The glass transition temperature (Tg) of the copolymer (A) is preferably in the range of -80 to -40°C, more preferably in the range of -70 to -50°C, and even more preferably in the range of -60 to -40°C. When the glass transition temperature (Tg) of the copolymer (A) is within the above range, the transmission belt tends to have excellent low-temperature characteristics.

[0079] 《Preparation of Copolymer (A)》 The copolymer (A) is a copolymer obtained by copolymerizing ethylene [A1], an α-olefin [A2] having 3 to 20 carbon atoms, and a non-conjugated polyene [A3].

[0080] The copolymer (A) is preferably obtained by copolymerizing monomers in the presence of a metallocene compound, and more preferably obtained by copolymerizing monomers in the presence of a catalyst system containing a metallocene compound.

[0081] The copolymer (A) can be produced, for example, by a production method using a metallocene catalyst described in JP-A-2018-119096 and WO 2015 / 122495.

[0082] The copolymer (A) may be used alone or in combination of two or more.

[0083] The mass ratio of the content of the copolymer (A) to the content of the component (B) in the composition for a transmission belt (content of the copolymer (A) / content of the component (B)) is preferably 2 / 98 to 50 / 50, more preferably 4 / 96 to 45 / 55, even more preferably 6 / 94 to 40 / 60, and particularly preferably 8 / 92 to 35 / 65 from the viewpoints of the hardness, transmission property, and low-temperature characteristics of a transmission belt having a crosslinked molded body formed from the composition for a transmission belt. When the mass ratio of the content of the copolymer (A) to the content of the component (B) in the composition for the transmission belt (content of the copolymer (A) / content of the component (B)) is in the range of 5 / 95 to 25 / 75, the transmission belt is also excellent in fracture resistance and oil resistance. Even when the mass ratio of the content of the copolymer (A) to the content of the component (B) in the composition for the transmission belt is within the above range, the reason why the crosslinked molded body formed from the composition for the transmission belt is excellent in transmission properties and low-temperature properties is considered to be that the component (B) and the copolymer (A) are co-crosslinked by the crosslinking agent (E).

[0084] The total content of the component (B) and the copolymer (A) in the composition for the transmission belt is preferably 35% by mass or more, more preferably 45% by mass or more, still more preferably 50% by mass or more, and particularly preferably 55% by mass or more, based on 100% by mass of the composition for the transmission belt.

[0085] <Carbon black (C)> The composition for the transmission belt contains carbon black (C). Carbon black (C) is a component that contributes to, for example, the improvement of the mechanical strength, modulus, and abrasion resistance of the obtained crosslinked molded body.

[0086] Examples of the carbon black (C) include SRF, GPF, FEF, MAF, HAF, ISAF, SAF, FT, and MT. The surface of the carbon black (C) may be treated with a silane coupling agent. Examples of commercially available products of carbon black (C) include Asahi #55G, Asahi #50HG, Asahi #60G, Asahi #60UG, and Asahi #70 (manufactured by Asahi Carbon Co., Ltd.), and Seast V and Seast SO (manufactured by Tokai Carbon Co., Ltd.).

[0087] The carbon black (C) may be used alone or in combination of two or more.

[0088] The content of carbon black (C) in the composition for the transmission belt is preferably 0.1 to 200 parts by mass, more preferably 1 to 150 parts by mass, still more preferably 3 to 100 parts by mass, particularly preferably 5 to 50 parts by mass, and even more preferably 10 to 20 parts by mass, based on 100 parts by mass in total of component (B) and copolymer (A). When the content of carbon black (C) is within the above range, the mechanical strength of the obtained crosslinked molded body and the processability of the composition for the transmission belt tend to be excellent.

[0089] <Plasticizer (D)> The composition for the transmission belt contains a plasticizer (D). Examples of the plasticizer (D) include phthalate ester-based, aliphatic dibasic acid ester-based, trimellitic acid ester-based, ether ester-based, polyether ester-based, and polyester-based synthetic plasticizers; petroleum-based softeners such as process oil, lubricating oil, paraffin oil, liquid paraffin, petroleum asphalt, and petrolatum; coal tar-based softeners such as coal tar; fatty oil-based softeners such as castor oil, linseed oil, rapeseed oil, soybean oil, and coconut oil; waxes such as beeswax and carnauba wax; fatty acids or their salts such as ricinoleic acid, palmitic acid, stearic acid, barium stearate, and calcium stearate; naphthenic acid, pine oil, and rosin or its derivatives; synthetic polymer substances such as terpene resin, petroleum resin, and coumarone indene resin; ester-based softeners such as dioctyl phthalate and dioctyl adipate; and others such as microcrystalline wax, liquid polybutadiene, modified liquid polybutadiene, hydrocarbon-based synthetic lubricating oil, tall oil, and sulfonated oil (sulfonated oil). Examples of the phthalate ester-based synthetic plasticizer include dibutyl phthalate (DBP), di(2-ethylhexyl) phthalate (DOP), and diisononyl phthalate (DINP). Examples of the aliphatic dibasic acid ester-based synthetic plasticizer include di(2-ethylhexyl) adipate (DOA), dibutyl sebacate (DBS), and di(2-ethylhexyl) sebacate (DOS).

[0090] Examples of trimellitic acid ester - based synthetic plasticizers include tri - 2 - ethylhexyl trimellitate (TOTM) and tridecyl trimellitate (TDTM). Examples of polyether ester - based synthetic plasticizers include adipic acid ether ester. Examples of polyester - based synthetic plasticizers include adipic acid polyester and sebacic acid polyester.

[0091] Commercially available products can also be used as the plasticizer (D). Examples of commercially available polyether ester - based synthetic plasticizers include Adeka Stab RS - 700, RS - 735, RS - 966, and RS - 1000 (manufactured by ADEKA CORPORATION). The content of the plasticizer (D) is preferably 0.1 - 50 parts by mass, more preferably 0.5 - 40 parts by mass, still more preferably 1 - 30 parts by mass, and particularly preferably 2 - 10 parts by mass, based on 100 parts by mass in total of the component (B) and the copolymer (A).

[0092] <Cross - linking agent (E)> The composition for the transmission belt contains a cross - linking agent (E). Examples of the cross - linking agent (E) include peroxide - based cross - linking agents, sulfur - based compounds, phenolic resins, hydrosilicone - based compounds, amino resins, quinones or their derivatives, amine - based compounds, azo - based compounds, epoxy - based compounds, and isocyanate - based compounds. The cross - linking agent (E) is preferably a peroxide - based cross - linking agent. When the composition for the transmission belt contains a peroxide - based cross - linking agent, it is considered that the components (B) and the copolymer (A) can be cross - linked well, and the heat - aging resistance of the cross - linked molded body formed from the composition for the transmission belt can be improved.

[0093] As the peroxide crosslinking agent, an organic peroxide is preferred. Examples of the organic peroxide include dicumyl peroxide (e.g., Peroximon DC, manufactured by Elf Atochem), tert-butyl peroxide (e.g., Peroximon 801, manufactured by Elf Atochem), di-tert-butyl peroxide (e.g., Luperox DI, manufactured by Elf Atochem), 2,5-di-(tert-butylperoxy)hexane, 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexane (e.g., Luperox 231, manufactured by Elf Atochem), 2,5-dimethyl-2,5-di-(tert-butylperoxy)hexyne-3 (e.g., Luperox 130, manufactured by Elf Atochem), 1,4-bis(tert-butylperoxyisopropyl)benzene (e.g., Peroximon F, manufactured by Elf Atochem), 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane (e.g., Luperox 101, manufactured by Elf Atochem), n-butyl-4,4-bis(tert-butylperoxy)valerate (e.g., Luperox 230, manufactured by Elf Atochem), benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, tert-butyl peroxybenzoate, tert-butyl peroxyisopropyl carbonate, diacetyl peroxide, lauroyl peroxide, and tert-butyl cumyl peroxide.

[0094] When using a peroxide crosslinking agent as the crosslinking agent (E), the content of the peroxide crosslinking agent in the composition for the transmission belt is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, and still more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass in total of the component (B) and the copolymer (A). When the content of the peroxide crosslinking agent is within the above range, the crosslinking of the composition for the transmission belt proceeds well, and the resulting crosslinked molded body tends to be excellent in heat resistance and abrasion resistance. The peroxide crosslinking agent may be used alone or in combination of two or more.

[0095] Examples of the sulfur-based compound include sulfur, sulfur chloride, sulfur dichloride, morpholine disulfide, alkylphenol disulfide, tetramethylthiuram disulfide, and selenium dithiocarbamate.

[0096] When a sulfur-based compound is used as the crosslinking agent (E), the content of the sulfur-based compound in the composition for the transmission belt is preferably 0.3 to 10 parts by mass, more preferably 0.5 to 7.0 parts by mass, and still more preferably 0.7 to 5.0 parts by mass with respect to 100 parts by mass in total of the component (B) and the copolymer (A). The sulfur-based compound may be used alone or in combination of two or more.

[0097] <Other Components> The composition for the transmission belt may further contain at least one selected from a crosslinking aid, an inorganic filler other than carbon black (C), a reinforcing agent other than carbon black (C), an antioxidant, a processing aid, an activator, a moisture absorbent, an antistatic agent, a colorant, a lubricant, and a thickener. Each of the components described below may be used alone or in combination of two or more.

[0098] When an organic peroxide is used as the crosslinking agent (E), it is preferable to use a crosslinking aid in combination. Examples of the crosslinking aid include quinone dioxime-based crosslinking aids such as p-quinone dioxime; acrylic crosslinking aids such as ethylene glycol dimethacrylate and trimethylolpropane trimethacrylate; allyl crosslinking aids such as diallyl phthalate and triallyl isocyanurate; maleimide-based crosslinking aids; divinylbenzene; metal oxides such as zinc oxide (for example, ZnO#1 · zinc oxide 2 types (JIS standard (K-1410)), manufactured by Hakusuitech Co., Ltd.), zinc white (for example, META-Z102, manufactured by Inoue Sekkai Kogyo Co., Ltd.), zinc methacrylate (for example, Actar ZMA, manufactured by Kawaguchi Chemical Industry Co., Ltd.), and magnesium oxide. As the crosslinking aid, a crosslinking aid having two or more ethylenic double bonds in one molecule is preferable.

[0099] When the composition for the transmission belt contains a crosslinking aid, the total content of the crosslinking aid is usually 0.5 to 30 moles, preferably 0.5 to 25 moles, more preferably 1 to 20 moles, per 1 mole of the organic peroxide.

[0100] When a sulfur-based compound is used as the crosslinking agent (E), it is preferable to use a vulcanization accelerator in combination. Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-oxydiethylene-2-benzothiazole sulfenamide, N,N'-diisopropyl-2-benzothiazole sulfenamide, 2-mercaptobenzothiazole, 2-(4-morpholinodithio)benzothiazole, 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, and dibenzothiazyl disulfide; guanidine-based vulcanization accelerators such as diphenylguanidine, triphenylguanidine, and diorthotolylguanidine; aldehydeamine-based vulcanization accelerators such as acetaldehyde aniline condensate and butyraldehyde aniline condensate; imidazoline-based vulcanization accelerators such as 2-mercaptoimidazoline; thiourea-based vulcanization accelerators such as diethylthiourea and dibutylthiourea; thiuram-based vulcanization accelerators such as tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and dipentamethylene thiuram tetrasulfide; dithiocarbamate-based vulcanization accelerators such as zinc dimethyldithiocarbamate, zinc diethyldithiocarbamate, zinc dibutyldithiocarbamate, and tellurium diethyldithiocarbamate; thiourea-based vulcanization accelerators such as ethylene thiourea (e.g., Sanseler 22C, manufactured by Sanshin Chemical Industry Co., Ltd.), N,N'-diethylthiourea, and N,N'-dibutylthiourea; xanthate-based vulcanization accelerators such as zinc dibutylxanthate; and others, including zinc white.

[0101] When the composition for the transmission belt contains a vulcanization accelerator, the content of the vulcanization accelerator is preferably 0.1 to 20 parts by mass, more preferably 0.2 to 15 parts by mass, and still more preferably 0.5 to 10 parts by mass with respect to 100 parts by mass in total of component (B) and the copolymer (A).

[0102] The vulcanization aid can be preferably used when a sulfur-based compound is used as the crosslinking agent (E). Examples of the vulcanization aid include zinc oxide (for example, ZnO#1 · zinc oxide type 2 (JIS standard (K-1410)), manufactured by Hakusuitech Co., Ltd.), magnesium oxide, and zinc white (for example, META-Z102, manufactured by Inoue Sekka Kogyo Co., Ltd.).

[0103] When the composition for the transmission belt contains a vulcanization aid, the content of the vulcanization aid is preferably 1 to 20 parts by mass with respect to 100 parts by mass in total of component (B) and the copolymer (A).

[0104] 《Inorganic filler》 Examples of the inorganic filler include light calcium carbonate, heavy calcium carbonate, talc, and clay (however, carbon black (C) is excluded). Among these, heavy calcium carbonate is preferable.

[0105] When the composition for the transmission belt contains an inorganic filler, the content of the inorganic filler is preferably 2 to 50 parts by mass, more preferably 5 to 50 parts by mass with respect to 100 parts by mass in total of component (B) and the copolymer (A).

[0106] 《Reinforcing agent》 Examples of the reinforcing agent include silica, calcium carbonate, activated calcium carbonate, fine talc, and fine silicic acid (however, carbon black (C) is excluded).

[0107] When the composition for the transmission belt contains a reinforcing agent, the content of the reinforcing agent is preferably 0.1 to 100 parts by mass, more preferably 5 to 30 parts by mass with respect to 100 parts by mass in total of component (B) and the copolymer (A).

[0108] 《Anti-aging agent (stabilizer)》 By containing an anti-aging agent (stabilizer), the life of the crosslinked molded body formed from the composition for the transmission belt can be extended. Examples of the anti-aging agent include amine-based anti-aging agents, phenolic anti-aging agents, and sulfur-based anti-aging agents.

[0109] Examples of the amine-based anti-aging agents include aromatic secondary amine-based anti-aging agents such as phenylbutylamine, N,N-di-2-naphthyl-p-phenylenediamine, and 4,4'-bis(α,α-dimethylbenzyl)diphenylamine (for example, No Crack CD, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.). Examples of the phenolic anti-aging agents include dibutylhydroxytoluene and pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]. Examples of the sulfur-based anti-aging agents include thioether-based anti-aging agents such as bis[2-methyl-4-(3-n-alkylthiopropionyloxy)-5-t-butylphenyl]sulfide; dithiocarbamate-based anti-aging agents such as nickel dibutyldithiocarbamate; zinc salts of 2-mercaptobenzoyl imidazole, 2-mercaptobenzimidazole, 2-mercaptobenzimidazole (for example, No Crack MBZ, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), dilauryl thiodipropionate, and distearyl thiodipropionate.

[0110] When the composition for the transmission belt contains an anti-aging agent, the total content of the anti-aging agent is preferably 0.3 to 10 parts by mass, more preferably 1.0 to 7.0 parts by mass, still more preferably 2.0 to 6.0 parts by mass, and particularly preferably 3.0 to 5.0 parts by mass with respect to a total of 100 parts by mass of component (B) and the copolymer (A).

[0111] 《Processing aid》 As the processing aid, those generally compounded with rubber as a processing aid can be widely used. Examples of the processing aid include ricinoleic acid, stearic acid, palmitic acid, lauric acid, barium stearate, zinc stearate, calcium stearate, and esters. Among these, stearic acid is preferred.

[0112] When the composition for the transmission belt contains a processing aid, the content of the processing aid is preferably 10 parts by mass or less, more preferably 8.0 parts by mass or less, based on 100 parts by mass in total of component (B) and the copolymer (A).

[0113] <Activator> Examples of the activator include amines such as di-n-butylamine, dicyclohexylamine, and monoethanolamine; activators such as diethylene glycol, polyethylene glycol, lecithin, triallyl trimellitate, and zinc compounds of aliphatic carboxylic acids or aromatic carboxylic acids; zinc peroxide preparations; octadecyltrimethylammonium bromide, synthetic hydrotalcite, and special quaternary ammonium compounds.

[0114] When the composition for the transmission belt contains an activator, the content of the activator is preferably 0.2 to 10 parts by mass, more preferably 0.3 to 5 parts by mass, based on 100 parts by mass in total of component (B) and the copolymer (A).

[0115] <Humectant> Examples of the humectant include calcium oxide, silica gel, sodium sulfate, molecular sieve, zeolite, and white carbon.

[0116] When the composition for the transmission belt contains a humectant, the content of the humectant is preferably 0.5 to 15 parts by mass, more preferably 1.0 to 12 parts by mass, based on 100 parts by mass in total of component (B) and the copolymer (A).

[0117] <Preparation of the Composition for the Transmission Belt> The composition for the transmission belt can be prepared by kneading the above-described respective components at a desired temperature using a kneader such as a mixer, a kneader, and a roll.

[0118] The composition for the transmission belt is prepared, for example, as follows. The copolymer (A), the component (B), the carbon black (C), the plasticizer (D), and predetermined other components are put into a kneader and kneaded under predetermined heating conditions (for example, at 80 to 200°C for 3 to 30 minutes) to be homogenized (A kneading). In the A kneading, when heating to the heating temperature of the A kneading, the copolymer (A) is crosslinked, and a crosslinking agent (E) or the like is not added. Next, after lowering the temperature of the mixture kneaded in the A kneading to below the crosslinking temperature of the crosslinking agent (E) (for example, 130°C or lower), the crosslinking agent (E) or the like that was not added in the A kneading is added to the mixture, and further kneaded and homogenized under predetermined heating conditions (for example, at a roll temperature of 30 to 80°C for 1 to 30 minutes) (B kneading), and the composition for the transmission belt can be obtained.

[0119] The Mooney viscosity ML(1+4)125°C of the composition for the transmission belt is preferably 10 to 250, more preferably 20 to 100, still more preferably 30 to 70, and particularly preferably 40 to 50. The composition for the transmission belt having the Mooney viscosity within the above range exhibits good post-treatment quality and has excellent rubber physical properties. The specific gravity of the composition for the transmission belt is preferably 0.80 to 1.20, more preferably 0.90 to 1.17, still more preferably 1.00 to 1.15, and particularly preferably 1.05 to 1.13.

[0120] [Crosslinked molded body, transmission belt] A crosslinked molded body can be obtained from the composition for the transmission belt. Examples of the molding method of the composition for the transmission belt include extrusion molding, injection molding, press molding, calender molding, transfer molding, and foam molding. The crosslinking temperature of the composition for the transmission belt is preferably 140 °C or higher, more preferably 150 to 220 °C, and even more preferably 160 to 200 °C. The crosslinking reaction can also be carried out in air.

[0121] The crosslinked molded body can be suitably used as a constituent member of the transmission belt. For example, the composition for the transmission belt has a high adhesive force suitable for moldability and is excellent in belt processability. Further, by using the composition for the transmission belt, a constituent member of the transmission belt excellent in high rubber elasticity, abrasion resistance, heat resistance, cold resistance, and light weight can be manufactured.

[0122] The transmission belt according to the present invention has a crosslinked molded body formed from the composition for the transmission belt.

[0123] Examples of the transmission belt include friction transmission belts such as V-belts and V-ribbed belts; and meshing transmission belts such as timing belts. Examples of the V-belt include wrapped belts and low-edge belts. The transmission belt is particularly suitable for timing belts.

[0124] The transmission belt has, for example, an adhesive rubber portion in which a core wire is embedded, and may further have a bottom rubber portion formed on the lower surface of the adhesive rubber portion. The transmission belt can have an upper canvas formed on the adhesive rubber portion and / or a lower canvas formed under the bottom rubber portion, if necessary. The composition for the transmission belt is preferably used, for example, to form the adhesive rubber portion and / or the bottom rubber portion. Specifically, as the adhesive rubber portion and / or the bottom rubber portion, a crosslinked molded portion formed from the composition for the transmission belt is preferably used.

[0125] The core wire, which is the tensile member of the transmission belt, extends in the longitudinal direction of the belt in the adhesive rubber portion. Examples of the core wire include polyester cords. The adhesive rubber portion surrounds the core wire and is adhered to the core wire. In one embodiment, for example, the composition for the transmission belt is disposed around the core wire and crosslinked to form an adhesive rubber portion adhered to the core wire. Examples of the canvas include those made of cotton, those made of a blend of cotton and polyester, and those made of a blend of cotton and polyamide.

Examples

[0126] Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples.

[0127] 〔Physical properties of copolymer (A)〕 The physical properties of the ethylene·α-olefin·non-conjugated polyene copolymer (A) were measured as follows. <Composition of ethylene·α-olefin·non-conjugated polyene copolymer (A)> The content of each structural unit in the copolymer (A) was 13 calculated from the C-NMR spectrum. Using an ECX400P nuclear magnetic resonance apparatus (manufactured by JEOL Ltd.), the measurement temperature was 120 °C, the measurement solvent was ortho-dichlorobenzene / deuterated benzene = 4 / 1, and the number of integrations was 8000 times. The 13 C-NMR spectrum of the copolymer (A) was measured.

[0128] <Mooney viscosity> The Mooney viscosity ML(1+4) 125 °C of the copolymer (A) was measured in accordance with JIS K 6300 (1994) using a Mooney viscometer (SMV-301 type manufactured by Shimadzu Corporation).

[0129] The B value of the copolymer (A) was measured using o-dichlorobenzene-d4 / benzene-d6 (4 / 1 [v / v]) as the measurement solvent at a measurement temperature of 120 °C. 13 The C-NMR spectrum (100 MHz, ECX400P manufactured by JEOL Ltd.) was measured and calculated based on the following formula. B value = ([EX]+2[Y]) / 〔2×[E]×([X]+[Y])〕 (The meanings of [E], [X], [Y] and [EX] are as described above.)

[0130] <Intrinsic viscosity> The intrinsic viscosity [η] of the copolymer (A) was measured using a fully automatic intrinsic viscometer (manufactured by Rigo Co., Ltd.) at a temperature of 135° C. and in a measurement solvent of decalin.

[0131] <Weight average molecular weight (Mw)> The weight average molecular weight (Mw) of the copolymer (A) is a value calculated in terms of polystyrene measured by gel permeation chromatography (GPC). The measuring device and conditions are as follows. The molecular weight was calculated based on a conversion method using a calibration curve prepared using commercially available monodisperse polystyrene. Apparatus: Gel permeation chromatograph Alliance GP2000 (Waters) Analysis device: Empower2 (Waters) Column: TSKgel GMH6-HT x 2 + TSKgel GMH6-HTL x 2 (7.5 mm I.D. x 30 cm, Tosoh Corporation) Column temperature: 140℃ Mobile phase: o-dichlorobenzene (containing 0.025% BHT) Detector: Differential refractometer (RI) Flow rate: 1.0mL / min Injection volume: 400μL Sampling time interval: 1 second Column calibration: Monodisperse polystyrene (Tosoh Corporation) Molecular weight conversion: Old EPR conversion / Calibration method taking into account viscosity

[0132] <Complex viscosity η * > The rheometer used was the Ares viscoelasticity measuring device (manufactured by Rheometric Scientific), and the complex viscosity η at a frequency of ω = 0.01 rad / s was measured under the conditions of 190°C and 1.0% strain. * (ω=0.01), the complex viscosity η at a frequency ω = 0.1 rad / second * (ω=0.1) , the complex viscosity η at a frequency ω = 10 rad / second * (ω=10) , and the complex viscosity η at a frequency ω = 100 rad / second * (ω=100) were measured. From the obtained results, the P value (η * (ω=0.1) / η * (ω=100) ), which is the ratio of the complex viscosities of η * (ω=0.1) and η * (ω=100) ), and Log[η * (ω=0.01) / Log[η * (ω=10) were calculated.

[0133] <Glass transition temperature (Tg)> The glass transition temperature (Tg) of the copolymer (A) was determined by measuring with a DSC (differential scanning calorimeter) under the following conditions. Using a differential scanning calorimeter (RDC220, manufactured by SII), about 10 mg of the sample was heated from 30°C to 200°C at a heating rate of 50°C / min under a nitrogen atmosphere and held at 200°C for 10 minutes. Further, it was cooled to -100°C at a cooling rate of 10°C / min and held at -100°C for 5 minutes, and then heated to 200°C at a heating rate of 10°C / min. The temperature based on the glass transition at this time was taken as the glass transition temperature (Tg).

[0134] In the examples, the ethylene·α-olefin·non-conjugated polyene copolymer (A) produced below was used. <Production of ethylene·α-olefin·non-conjugated polyene copolymer (A)>

[0135] [Production Example 1] Using a continuous polymerization apparatus, an ethylene·propylene·5-vinyl-2-norbornene (VNB) copolymer (A-1) was produced as follows. Into a polymerization reactor with a volume of 300 L, a hexane solvent dehydrated and purified from line 1 was continuously supplied at 58.3 L / hr, triisobutylaluminum (TIBAL) from line 2 at 4.5 mmol / hr, (C6H5)3CB(C6F5)4 at 0.150 mmol / hr, and di(p-tolyl)methylene(cyclopentadienyl)(octamethyl octahydrodibenzofluorenyl)zirconium dichloride at 0.030 mmol / hr. At the same time, ethylene was continuously supplied into the polymerization reactor from separate lines at 6.6 kg / hr, propylene at 9.3 kg / hr, hydrogen at 18 L / hr, and VNB at 340 g / hr, and copolymerization was carried out under the conditions of a polymerization temperature of 87 °C, a total pressure of 1.6 MPaG, and a residence time of 1.0 hour. The solution of the ethylene·propylene·VNB copolymer produced in the polymerization reactor was continuously discharged at a flow rate of 88.0 L / hr and heated to 170 °C (the pressure increased to 4.1 MPaG) and supplied to a phase separator. At this time, ethanol, which is a polymerization inhibitor, was continuously introduced into the discharge line in an amount 0.1 mol times that of TIBAL in the liquid component withdrawn from the polymerization reactor.

[0136] In the phase separator, the solution of the ethylene·propylene·VNB copolymer was separated into a concentrated phase (lower phase part) containing most of the ethylene·propylene·VNB copolymer and a dilute phase (upper phase part) containing a small amount of polymer. The separated concentrated phase was led to a heat exchanger K at 85.4 L / hr and further led into a hopper to evaporate and separate the solvent, and an ethylene·propylene·VNB copolymer (A-1) was obtained in an amount of 7.8 kg / hr. The physical properties of the obtained ethylene·propylene·VNB copolymer (A-1) were evaluated as described above. The results are shown in Table 1.

[0137]

Table 1

[0138] [Example 1] Using a MIXTRON BB MIXER (manufactured by Kobe Steel, Ltd., model BB-2, volume 1.7 L, rotor 2WH), 25 parts by mass of a crosslinking aid (Acter ZMA, manufactured by Kawaguchi Chemical Industry Co., Ltd.), 5 parts by mass of a crosslinking aid (ZnO#1, manufactured by Hakusuitec Co., Ltd.), 2 parts by mass of an antioxidant (No Crack CD, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), 2 parts by mass of an antioxidant (No Crack MBZ, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.), 15 parts by mass of carbon black (Asahi #60UG, manufactured by Asahi Carbon Co., Ltd.), and 5 parts by mass of a plasticizer (Adeka Sizer RS-700, manufactured by Adeka Corporation) were blended with 90 parts by mass of hydrogenated nitrile rubber (Zetpol 2020, manufactured by Nippon Zeon Co., Ltd.) and 10 parts by mass of copolymer (A-1), and then kneaded to obtain Compound 1. The kneading conditions during the preparation of Compound 1 were as follows: the rotor rotation speed was 40 rpm, the floating weight pressure was 3 kg / cm 2 , the kneading time was 5 minutes, and the kneading discharge temperature was 144°C.

[0139] Next, after confirming that the temperature of Compound 1 reached 40°C, 8 parts by mass of a crosslinking agent (Peroximon F40, manufactured by Elf-Atochem) was added to Compound 1 and kneaded using a 6-inch roll to obtain Compound 2. The kneading conditions during the preparation of Compound 2 were as follows: the roll temperature was front roll / rear roll = 50°C / 50°C, the roll peripheral speed was front roll / rear roll = 18 rpm / 15 rpm, the roll gap was 3 mm, and the kneading time was 8 minutes for separation to obtain Compound 2. For the obtained Compound 2, the compound viscosity and specific gravity described below were measured.

[0140] A crosslinked sheet with a thickness of 2 mm was produced by performing a press treatment on Compound 2 at 170°C for 15 minutes using a press molding machine. For the obtained crosslinked sheet, the hardness test, tensile test, heat aging resistance test, gamma torsion test, DIN friction test, and oil resistance test described below were performed.

[0141] [Examples 2 to 3 and Comparative Example 1] The same procedure as in Example 1 was carried out except based on the composition and curing system described in Table 3. The materials used in the examples and comparative examples are shown in Table 2 below.

[0142]

Table 2

[0143] [Physical properties of the composition for transmission belt] The physical properties of the compositions of the examples and comparative examples were measured as follows.

[0144] [Compound viscosity (Mooney viscosity)] The Mooney viscosity ML(1+4) 125°C of Compound 2 was measured in accordance with JIS K 6300 (1994) using a Mooney viscometer (Model SMV-301 manufactured by Shimadzu Corporation).

[0145] [Specific gravity] A 1 g sample of Compound 2 was cut out to prepare a test piece. The test piece was attached to an automatic specific gravity meter (Model M-1 manufactured by Toyo Seiki Seisakusho Co., Ltd.) in an atmosphere of 25°C, and the specific gravity was measured from the difference in mass in air and pure water.

[0146] [Hardness test: Durometer A hardness] The hardness (Type A durometer) of the crosslinked sheet was measured in accordance with JIS K 6253 (2012) using six crosslinked sheets with a thickness of 2 mm having a smooth surface. The flat portions were stacked to a thickness of approximately 12 mm. However, those with foreign matter mixed in, those with air bubbles, and those with scratches were not used. The dimensions of the measurement surface of the test piece were set to a size such that the tip of the pressing needle could be measured at a position more than 12 mm away from the edge of the test piece.

[0147] [Tensile test: Modulus, tensile breaking point stress, tensile breaking point elongation] The cross-linked sheet with a thickness of 2 mm was punched out to produce a No. 3 dumbbell test piece described in JIS K 6251 (1993). Using this test piece, a tensile test was conducted in accordance with the method specified in Paragraph 3 of JIS K 6251 under the conditions of a measurement temperature of 25°C and a tensile speed of 500 mm / min. The tensile stress (25% modulus (M25)), tensile breaking point stress (TB), and tensile breaking point elongation (EB) were measured when the elongation rate was 25%. It can be judged that the higher the M25, the higher the transmissibility. It can be judged that the larger the tensile breaking point elongation (EB), the better the fracture resistance.

[0148] [Heat Aging Test] The cross-linked sheet with a thickness of 2 mm was subjected to a heat aging test in accordance with JIS K 6257 (2017) by holding it at 170°C for 168 hours. The hardness, TB, and EB of the sheet after the heat aging test were measured in the same manner as the items of the hardness test and the tensile test. AH (Duro-A) was obtained from the hardness difference before and after the heat aging test. From the tensile breaking point stress (TB) and tensile breaking point elongation (EB) before and after the heat aging test, the change rates after the test with respect to the values before the heat aging test were determined as Ac(TB) and Ac(EB), respectively.

[0149] [German Twisting Test (Low Temperature Twisting Test)] In the low temperature twisting test, in accordance with JIS K 6261 (1993), using a German twisting tester, T2, T5, T 10 and T 100 of the cross-linked sheet with a thickness of 2 mm were measured. These temperatures serve as indicators of the low temperature flexibility of the cross-linked rubber. It can be judged that the lower the T 100 , the better the low temperature characteristics.

[0150] [DIN Friction Test (DIN Abrasion Amount)] Using the crosslinked sheet with a thickness of 2 mm, a disc-shaped test piece with a diameter of 16.0 ± 0.2 mm and a thickness of 6 mm or more was prepared in accordance with JIS K 6264-2 (2005). For the test piece, using a DIN abrasion tester, a drum with a diameter of 150.0 ± 0.2 mm and a length of 500 mm was rotated at 40 revolutions per minute, and the abrasion amount (DIN abrasion amount) was measured 3 times when the abrasion distance was 40.0 ± 0.2 m with a load of 1 kgf. The average value is shown in Table 3.

[0151] [Oil Resistance Test] The crosslinked sheet with a thickness of 2 mm was cut out into a 10 cm square, and in accordance with JIS K 6258 (2016), after immersing the crosslinked sheet in IRM901 oil at 125 °C for 72 hours, the volume change rate (ΔV) (volume %) was measured as the oil resistance. The results are shown in Table 3. It can be judged that the smaller the value of the volume change rate, the better the oil resistance.

[0152] [Table 3]

Claims

1. At least one (B) selected from nitrile rubber and hydrogenated nitrile rubber, An ethylene-α-olefin-non-conjugated polyene copolymer (A) containing a structural unit derived from ethylene [A1], a structural unit derived from an α-olefin [A2] having 3 to 20 carbon atoms, and a structural unit derived from a non-conjugated polyene [A3], Carbon black (C), A plasticizer (D), A crosslinking agent (E) And a composition for a transmission belt containing the same.

2. The composition for a transmission belt according to claim 1, wherein the non-conjugated polyene [A3] contains a non-conjugated polyene [A3-1] containing two or more partial structures selected from the group consisting of the following formulas (I) and (II) in one molecule. 【Chemical 1】

3. The composition for a transmission belt according to claim 1, wherein the copolymer (A) satisfies any one or more of the following requirements (i) to (v). Requirement (i): When the total constitutional units contained in the copolymer (A) are 100 mol%, the ratio [(A1) / (A2)] of the molar fraction (A1) of the structural unit derived from ethylene [A1] to the molar fraction (A2) of the structural unit derived from the α-olefin [A2] having 3 to 20 carbon atoms is 40 / 60 to 99.9 / 0.1; Requirement (ii): The mass fraction of the structural unit derived from the non-conjugated polyene [A3] is 0.07 to 10% by mass in 100% by mass of the copolymer (A); Requirement (iii): The weight average molecular weight (Mw) of the copolymer (A), the mass fraction of the structural unit derived from the non-conjugated polyene [A3] (mass fraction of [A3] (% by mass)), and the molecular weight of the non-conjugated polyene [A3] ([A3] molecular weight) satisfy the following formula (1); 4.5 ≦ Mw × mass fraction of [A3] / 100 / [A3] molecular weight ≦ 80... (1) Requirement (iv): The ratio P(η * / η （ω＝０．１） ) of the complex viscosity η (Pa·s) at a frequency ω = 0.1 rad / s to the complex viscosity η (Pa·s) at a frequency ω = 100 rad / s obtained by linear viscoelasticity measurement (at 190°C) using a rheometer, the limiting viscosity [η] (dL / g), and the mass fraction of the structural unit derived from the non-conjugated polyene [A3] (mass fraction of [A3] (mass %)) satisfy the following formula (2); * （ω＝０．１） (Pa·s) and the complex viscosity η * * （ω＝１００） (Pa·s), and the limiting viscosity [η] (dL / g), and the mass fraction of the structural unit derived from the non-conjugated polyene [A3] (mass fraction of [A3] (mass %)) satisfy the following formula (2); ＊ （ω＝０．１） / η * * （ω＝１００） ) and the limiting viscosity [η] (dL / g), and the mass fraction of the structural unit derived from the non-conjugated polyene [A3] (mass fraction of [A3] (mass %)) satisfy the following formula (2); P / ([η] ２．９ ) ≤ mass fraction of [A3] × 6... (2) Requirement (v): The complex viscosity η at a frequency ω = 0.01 rad / s and the complex viscosity η at a frequency ω = 10 rad / s, obtained by linear viscoelastic measurement (at 190 °C) using a rheometer, and the apparent iodine value derived from the non-conjugated polyene [A3] satisfy the following formula (3). ＊ (ω＝０．０１) (Pa·s) and the complex viscosity η at a frequency ω = 10 rad / s ＊ (ω＝１０) (Pa·s) and the apparent iodine value derived from the non-conjugated polyene [A3] satisfy the following formula (3). Log[η ＊ (ω＝０．０１) / Log[η ＊ (ω＝１０) ≤ 0.0753 × {apparent iodine value derived from non-conjugated polyene [A3]} + 1.42... (3)

4. The composition for a transmission belt according to claim 1, wherein the non-conjugated polyene [A3] contains 5-vinyl-2-norbornene (VNB).

5. The composition for a transmission belt according to claim 1, wherein the α-olefin [A2] having 3 to 20 carbon atoms is propylene.

6. With respect to 100 parts by mass in total of at least one (B) selected from the nitrile rubber and the hydrogenated nitrile rubber and the copolymer (A), The content of the carbon black (C) is 0.1 to 200 parts by mass, The content of the plasticizer (D) is 0.1 to 50 parts by mass, The composition for a transmission belt according to claim 1.

7. A crosslinked molded body formed from the composition for a transmission belt according to any one of claims 1 to 6.

8. A transmission belt having the crosslinked molded body according to claim 7.

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