Rubber composition, metal-coated rubber, and tire

Abstract

The present invention addresses the problem of providing a rubber composition having excellent durability (in particular, crack propagation resistance and breaking elongation after deterioration) and a metal-coated rubber and a tire having excellent durability. The solution is a rubber composition containing a rubber component (A), carbon black (B), sulfur (C), and a peroxide (D), characterized by the mass ratio (C / D) of the sulfur (C) and the peroxide (D) being 0.5-2.5, and a metal-coated rubber comprising said rubber composition, and a tire equipped with said metal-coated rubber.

Description

Rubber composition, metal-coated rubber, and tire

[0001] The present invention relates to a rubber composition, a metal-coated rubber, and a tire.

[0002] Generally, in rubber articles requiring strength, such as hoses, rubber crawlers, and tires, composites of metal members and rubber (hereinafter referred to as "metal-rubber composites") are used to reinforce the rubber and improve its strength and durability. For example, Patent Document 1 listed below discloses a composite of steel wire and rubber formed by applying a solution containing a cobalt metal salt to a zinc-plated steel wire, then coating the wire with a rubber composition that does not contain a cobalt metal salt, and vulcanizing the resulting composite. Furthermore, Patent Document 2 listed below discloses an adhesion promoter made of a specific metal salt, a rubber composition containing such an adhesion promoter, and a tire having a steel cord / rubber composite made of the rubber composition and a steel cord.

[0003] Japanese Patent Application Laid-Open No. 10-324753 International Publication No. 2016 / 039375

[0004] On the other hand, in recent years, with the improvement in performance of rubber articles such as the above-mentioned tires, it has become necessary to prevent failures due to deterioration of the adhesive interface between the metal member and the rubber even when the rubber article is exposed to a deteriorating environment during actual use, and to meet such demands, improvement in the durability of the rubber itself is required. In response to this, Patent Documents 1 and 2 aim to improve the adhesiveness between the metal member and the rubber, but there is room for improvement in the durability of the rubber itself (particularly, crack propagation resistance and breaking elongation after deterioration).

[0005] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional art and to provide a rubber composition excellent in durability (particularly, crack propagation resistance and elongation at break after degradation).A further object of the present invention is to provide a metal-coated rubber and a tire excellent in durability using such a rubber composition.

[0006] The rubber composition, metal-coated rubber, and tire of the present invention that solve the above problems are outlined below.

[0007] [1] A rubber composition comprising a rubber component (A), carbon black (B), sulfur (C), and a peroxide (D), wherein the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is 0.5 to 2.5.

[0008] [2] The rubber composition according to [1], further comprising a metal acrylate or a derivative thereof (E).

[0009] [3] The rubber composition according to [1] or [2], further comprising zinc diacrylate or a derivative thereof (E1).

[0010] [4] The rubber composition according to [2], wherein the mass ratio (D / E) of the peroxide (D) to the metal acrylate or its derivative (E) is 0.5 or more.

[0011] [5] The rubber composition according to [3], wherein the mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or its derivative (E1) is 0.5 or more.

[0012] [6] The rubber composition according to any one of [1] to [5], wherein the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is 0.5 or more and less than 2.0.

[0013] [7] The rubber composition according to [2] or [4], wherein the mass ratio (D / E) of the peroxide (D) to the metal acrylate or its derivative (E) is 0.5 to 3.

[0014] [8] The rubber composition according to [3] or [5], wherein the mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or its derivative (E1) is 0.5 to 3.

[0015] [9] The rubber composition according to any one of [1] to [8], wherein the rubber component (A) contains an isoprene skeleton rubber (A1).

[0016]

[10] A metal-coated rubber comprising the rubber composition according to any one of [1] to [9].

[0017]

[11] A tire comprising the metal-coated rubber according to

[10] .

[0018] According to the present invention, it is possible to provide a rubber composition having excellent durability (particularly crack propagation resistance and elongation at break after degradation). Furthermore, according to the present invention, it is possible to provide a metal-coated rubber and a tire having excellent durability using such a rubber composition.

[0019] The rubber composition, metal-coated rubber, and tire of the present invention will be described in detail below with reference to examples based on embodiments thereof.

[0020] <Definitions> The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0021] <Rubber Composition> The rubber composition of this embodiment contains a rubber component (A), carbon black (B), sulfur (C), and a peroxide (D). The rubber composition of this embodiment is characterized in that the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is 0.5 to 2.5.

[0022] The rubber composition of this embodiment contains sulfur (C) and peroxide (D) as crosslinking agents, and after crosslinking, the rubber composition contains sulfur crosslinks and crosslinked structures (C-C bonds, etc.) resulting from the peroxide. The sulfur crosslinks and crosslinked structures resulting from the peroxide contribute to improving the durability of the rubber composition. The rubber composition of this embodiment also contains carbon black (B), which improves the reinforcing properties of the rubber composition and contributes to improving the durability of the rubber composition. In addition, the rubber composition of this embodiment has a mass ratio (C / D) of sulfur (C) to peroxide (D) of 0.5 to 2.5, which enables a high level of balance between the crack propagation resistance and the elongation at break after aging, both of which are durability indicators. Therefore, the rubber composition of this embodiment is excellent in durability, particularly in crack propagation resistance and elongation at break after aging.

[0023] -Rubber Component (A)- The rubber composition of this embodiment includes a rubber component (A), which provides rubber elasticity to the composition. The rubber component (A) is preferably a diene-based rubber. Examples of the diene-based rubber include isoprene-skeleton rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), halogenated butyl rubber (Cl-IIR, Br-IIR, etc.), and ethylene-propylene rubber (EPR, EPDM). The rubber component (A) may also include a non-diene-based rubber. Examples of the non-diene-based rubber include fluororubber, silicone rubber, and urethane rubber. These rubber components (A) may be used alone or as a blend of two or more.

[0024] The rubber component (A) of the rubber composition of this embodiment preferably contains an isoprene skeleton rubber (A1). The isoprene skeleton rubber (A1) is a rubber having an isoprene unit as the main skeleton, and specific examples thereof include natural rubber (NR) and synthetic isoprene rubber (IR). A rubber composition containing the isoprene skeleton rubber (A1) as the rubber component (A) has excellent adhesion to metal members and is suitable for metal-coated rubber. Furthermore, the inclusion of the isoprene skeleton rubber (A1) in the rubber component (A) can also improve the strength of the rubber composition. The proportion of the isoprene skeleton rubber (A1) in the rubber component (A) is preferably 50% by mass or more, more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0025] —Carbon Black (B)— The rubber composition of this embodiment contains carbon black (B). When the rubber composition contains carbon black (B), the reinforcing properties of the rubber composition are improved, and the durability of the rubber composition is improved.

[0026] Examples of the carbon black (B) include GPF, FEF, HAF, ISAF, and SAF grade carbon blacks. These carbon blacks (B) may be used alone or in combination of two or more.

[0027] The content of the carbon black (B) in the rubber composition is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, and preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of the rubber component (A). When the content of the carbon black (B) is 10 parts by mass or more per 100 parts by mass of the rubber component (A), the reinforcement property of the rubber composition is further improved, and the durability is further improved. Furthermore, when the content of the carbon black (B) is 120 parts by mass or less per 100 parts by mass of the rubber component (A), the workability in kneading the rubber composition is further improved.

[0028] —Sulfur (C)— The rubber composition of this embodiment contains sulfur (C). When the rubber composition contains sulfur (C), sulfur crosslinks are present in the rubber composition after crosslinking (also referred to as a “crosslinked rubber composition” or “crosslinked rubber”), improving the durability of the rubber composition.

[0029] The sulfur (C) is not particularly limited, and various types of sulfur can be used, such as ordinary sulfur (soluble sulfur (powdered sulfur) and the like), insoluble sulfur, and oil treat sulfur can also be used. Here, insoluble sulfur is sulfur insoluble in carbon disulfide (amorphous polymeric sulfur), and soluble sulfur (powdered sulfur) is sulfur soluble in carbon disulfide.

[0030] The content of sulfur (C) in the rubber composition is appropriately selected so that the mass ratio (C / D) of sulfur (C) to peroxide (D) is within the range of 0.5 to 2.5. In one embodiment, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and preferably 10 parts by mass or less, even more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less, per 100 parts by mass of the rubber component (A). When the content of sulfur (C) is 0.1 parts by mass or more per 100 parts by mass of the rubber component (A), the network density due to sulfur is improved, and the durability of the rubber composition is further improved. When the content of sulfur (C) is 10 parts by mass or less per 100 parts by mass of the rubber component (A), a crosslinked rubber having sufficient elastomeric properties is obtained, and the elongation at break of the rubber composition is improved. Furthermore, when the content of sulfur (C) is 4 parts by mass or less per 100 parts by mass of the rubber component (A), the breaking elongation after aging of the rubber composition is further improved.

[0031] -Peroxide (D)- The rubber composition of this embodiment contains peroxide (D). When the rubber composition contains peroxide (D), a crosslinked structure (C-C bond, etc.) resulting from the peroxide (D) is present in the rubber composition after crosslinking, improving the durability of the rubber composition.

[0032] The peroxide (D) may be either an organic peroxide or an inorganic peroxide, but is preferably an organic peroxide. Here, the organic peroxide is not particularly limited, but examples thereof include tert-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, diisopropylbenzene hydroperoxide, dicumyl peroxide, di-tert-butyl peroxide, di-tert-hexyl peroxide, diisopropylbenzene hydroperoxide, tert-butylcumyl peroxide, di(2-tert-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, perbenzoic acid, benzoyl peroxide, 1,1-bis(1,1-dimethylethylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-hexylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-hexylperoxy)cyclohexane, 2,2-bis(4,4-di-(tert-butylperoxy)cyclohexyl)propane, n-butyl-4,4-di-(tert-butylperoxy)valerate, tert-butylperoxylaurate, tert-butylperoxy-2-ethylhexanate, 1,1, Examples of the peroxide (D) include 3,3-tetramethylbutylperoxy-2-ethylhexanoate, tert-hexylperoxy-2-ethylhexanoate, tert-butylperoxy-2-ethylhexanoate, tert-butylperoxyacetate, cyclohexanone peroxide, acetylacetone peroxide, diisopropyl peroxydicarbonate, and di(4-tert-butylcyclohexyl)peroxydicarbonate. Examples of the inorganic peroxide include hydrogen peroxide, sodium persulfate, potassium persulfate, and ammonium persulfate. These peroxides (D) may be used singly or in combination of two or more.

[0033] The content of the peroxide (D) in the rubber composition is appropriately selected so that the mass ratio (C / D) of sulfur (C) to peroxide (D) is within the range of 0.5 to 2.5. In one embodiment, the content is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1 part by mass or more, and preferably 10 parts by mass or less, even more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less, per 100 parts by mass of the rubber component (A). When the content of the peroxide (D) is 0.1 parts by mass or more per 100 parts by mass of the rubber component (A), the network density of the crosslinked structure resulting from the peroxide (D) is improved, and the durability of the rubber composition is further improved. When the content of the peroxide (D) is 10 parts by mass or less per 100 parts by mass of the rubber component (A), a crosslinked rubber having sufficient elastomeric properties is obtained, and the elongation at break of the rubber composition is further improved.

[0034] In the rubber composition of this embodiment, the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is 0.5 to 2.5, preferably 0.5 or more and less than 2.0. If the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is less than 0.5, the crack propagation resistance of the rubber composition deteriorates, and if the mass ratio (C / D) of the sulfur (C) to the peroxide (D) exceeds 2.5, the elongation at break of the rubber composition after aging deteriorates. On the other hand, if the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is less than 2.0, the elongation at break of the rubber composition after aging improves. Therefore, a rubber composition having a mass ratio (C / D) of the sulfur (C) to the peroxide (D) of 0.5 or more and less than 2.0 has improved crack propagation resistance and further improved elongation at break after aging. Further, from the viewpoint of the breaking elongation after deterioration of the rubber composition, the mass ratio (C / D) of sulfur (C) to peroxide (D) is more preferably 1.99 or less, more preferably 1.98 or less, more preferably 1.97 or less, even more preferably 1.96 or less, and particularly preferably 1.95 or less.

[0035] -Metal acrylate or derivative thereof (E)- The rubber composition of this embodiment preferably further contains a metal acrylate or a derivative thereof (E). When the rubber composition contains a metal acrylate or a derivative thereof (E), the elastic modulus is improved, and the durability of the rubber composition can be further improved. Here, the metal acrylate is a metal salt of acrylic acid. Furthermore, the metal acrylate derivative is a compound in which the hydrogen atoms in the metal salt of acrylic acid are substituted with a substituent, and examples of the substituent include an alkyl group such as a methyl group. Examples of the metal acrylate derivative include a metal salt of methacrylic acid.

[0036] Examples of the metal constituting the metal acrylate or derivative thereof (E) include zinc, magnesium, calcium, etc. The valence of the metal ion in the metal acrylate or derivative thereof (E) is not particularly limited, and each element may have any valence, but is preferably divalent or greater.

[0037] Specific examples of the metal acrylate or derivative thereof (E) include zinc diacrylate, magnesium diacrylate, calcium diacrylate, zinc dimethacrylate, magnesium dimethacrylate, calcium dimethacrylate, etc. These metal acrylates or derivatives thereof (E) may be used alone or in combination of two or more.

[0038] The content of the metal acrylate or derivative thereof (E) in the rubber composition is preferably 0.1 part by mass or more, more preferably 0.3 part by mass or more, even more preferably 0.5 part by mass or more, and preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less, per 100 parts by mass of the rubber component (A). When the content of the metal acrylate or derivative thereof (E) is 0.1 part by mass or more per 100 parts by mass of the rubber component (A), the durability of the rubber composition is further improved. Furthermore, when the content of the metal acrylate or derivative thereof (E) is 10 parts by mass or less per 100 parts by mass of the rubber component (A), a crosslinked rubber having sufficient elastomeric properties is obtained, and the breaking elongation of the rubber composition is further improved.

[0039] Among the metal acrylates or derivatives thereof (E), zinc diacrylate or derivatives thereof (E1) is preferred. When the rubber composition contains zinc diacrylate or derivatives thereof (E1), the durability of the rubber composition can be further improved. Here, examples of the zinc diacrylate or derivatives thereof (E1) include the above-mentioned zinc diacrylate and zinc dimethacrylate (ZDMA), and among these, zinc dimethacrylate is preferred.

[0040] The content of the zinc diacrylate or its derivative (E1) in the rubber composition is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, per 100 parts by mass of the rubber component (A), and is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 4 parts by mass or less. When the content of the zinc diacrylate or its derivative (E1) is 0.1 parts by mass or more per 100 parts by mass of the rubber component (A), the durability of the rubber composition is further improved. Furthermore, when the content of the zinc diacrylate or its derivative (E1) is 10 parts by mass or less per 100 parts by mass of the rubber component (A), a crosslinked rubber having sufficient elastomeric properties is obtained, and the elongation at break is further improved.

[0041] The mass ratio (D / E) of the peroxide (D) to the metal acrylate or derivative thereof (E) is preferably 0.5 or more, and more preferably 0.5 to 3. A rubber composition having a mass ratio (D / E) of the peroxide (D) to the metal acrylate or derivative thereof (E) of 0.5 or more improves the balance between crack propagation resistance and elongation at break after aging. Furthermore, a rubber composition having a mass ratio (D / E) of the peroxide (D) to the metal acrylate or derivative thereof (E) of 0.5 to 3 further improves the balance between crack propagation resistance and elongation at break after aging.

[0042] Furthermore, when the metal acrylate or derivative thereof (E) is zinc diacrylate or a derivative thereof (E1), the mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or a derivative thereof (E1) is preferably 0.5 or more, and more preferably 0.5 to 3. A rubber composition having a mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or a derivative thereof (E1) of 0.5 or more improves the balance between crack propagation resistance and elongation at break after aging. Furthermore, a rubber composition having a mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or a derivative thereof (E1) of 0.5 to 3 further improves the balance between crack propagation resistance and elongation at break after aging.

[0043] Others—In addition to the rubber component (A), carbon black (B), sulfur (C), peroxide (D), and metal acrylate or its derivative (E) described above, the rubber composition of this embodiment may contain compounding agents commonly used in the rubber industry, such as fillers other than carbon black (silica, clay, talc, calcium carbonate, aluminum hydroxide, etc.), zinc oxide (zinc white), softeners, stearic acid, antioxidants, waxes, silane coupling agents, vulcanization accelerators, retarders (vulcanization retarders), etc., selected appropriately within the scope of the present invention. Commercially available products can be suitably used as these compounding agents.

[0044] The content of the zinc oxide (zinc white) is not particularly limited, and is preferably in the range of 0.1 to 20 parts by mass, more preferably 1 to 15 parts by mass, and even more preferably 2 to 10 parts by mass, relative to 100 parts by mass of the rubber component (A).

[0045] The content of the stearic acid is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably 0.3 to 4 parts by mass, and even more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component (A).

[0046] Examples of the antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6C) and 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ). These antioxidants may be used alone or in combination of two or more. The content of the antioxidant is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, and more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component (A).

[0047] Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators, guanidine vulcanization accelerators, thiazole vulcanization accelerators, thiuram vulcanization accelerators, and dithiocarbamate vulcanization accelerators. These vulcanization accelerators may be used alone or in combination of two or more. The content of the vulcanization accelerator is not particularly limited, and is preferably in the range of 0.1 to 5 parts by mass, more preferably 0.2 to 3 parts by mass, per 100 parts by mass of the rubber component (A).

[0048] The rubber composition preferably contains 0.01 parts by mass or less of a cobalt compound per 100 parts by mass of the rubber component (A), and more preferably contains no cobalt compound. Addition of a cobalt compound accelerates thermal degradation of the rubber composition, so it is desirable to not contain a cobalt compound from the viewpoint of degradation resistance. Although a cobalt compound (or cobalt metal or cobalt ions derived from a cobalt compound) may migrate from the outside to the application site of the rubber composition, it is preferable not to compound a cobalt compound at least when producing the rubber composition.

[0049] -Method for producing rubber composition- The method for producing the rubber composition is not particularly limited, but the rubber composition can be produced, for example, by blending various components appropriately selected as necessary with the above-mentioned rubber component (A), carbon black (B), sulfur (C), and peroxide (D), and kneading, heating, extruding, etc. Furthermore, the obtained rubber composition can be crosslinked by heating to form a crosslinked rubber.

[0050] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0051] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roller typically used for heat-in of a rubber composition.

[0052] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0053] The crosslinking device, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of devices for crosslinking include a molding vulcanizer using a mold used for crosslinking (vulcanization) of rubber compositions. The crosslinking temperature is, for example, about 100 to 190°C.

[0054] <Metal-coated rubber> The metal-coated rubber of this embodiment is a rubber for coating a metal member, characterized by comprising the rubber composition of this embodiment described above. The metal-coated rubber of this embodiment is excellent in durability because it is made of the rubber composition of this embodiment described above, which has excellent durability.

[0055] The metal to be coated is not particularly limited and can take various shapes. In one embodiment, the metal is a metal cord. The metal cord is preferably a cord made of a plurality of twisted metal wires (metal steel wires) or a single metal wire. The metal wire is not particularly limited, but examples include wire materials such as iron, steel (stainless steel), lead, aluminum, copper, brass, bronze, Monel metal alloys, nickel, and zinc. The metal is preferably a steel cord. Steel cords are easily deformed into a desired shape, allowing for superior productivity in producing composites of metal-coated rubber and metal.

[0056] The metal is preferably plated on its surface. While the plating is not particularly limited, examples of the plating include zinc plating, copper plating, and brass plating, among which brass plating is preferred from the viewpoint of adhesion between the metal and the metal-coated rubber. When the metal is brass-plated, the adhesion between the metal and the metal coating is further improved.

[0057] The metal-coated rubber of this embodiment can be suitably used in various rubber articles that use metal members as reinforcing materials, and specifically can be used in tires, hoses, rubber crawlers, and the like.

[0058] <Tire> The tire of this embodiment is characterized by including the metal-coated rubber of this embodiment described above. The tire of this embodiment is excellent in durability because it includes the metal-coated rubber of this embodiment described above, which has excellent durability.

[0059] The tire of the present embodiment preferably includes a composite of the above-described metal-coated rubber and a metal member (metal-rubber composite), and the application portion of the tire to the metal-rubber composite is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a carcass, a belt, and a bead core.

[0060] A conventional method can be used to manufacture the tire. For example, components typically used in tire manufacturing, such as a carcass and belt (metal-rubber composite) made of an unvulcanized rubber composition and metal cords, and a tread made of an unvulcanized rubber composition, are laminated on a tire building drum in this order, and the drum is removed to form a green tire. Next, the green tire is heated and vulcanized in a conventional manner to manufacture a desired tire (e.g., a pneumatic tire).

[0061] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0062] <Production and Evaluation of Rubber Compositions> Rubber compositions were produced using a conventional Banbury mixer according to the formulations shown in Table 1. The crack propagation resistance and elongation at break after aging of the resulting rubber compositions were measured and evaluated by the following methods. The results are shown in Table 1.

[0063] (1) Crack Growth Resistance A thermally crosslinked rectangular test piece with a hole drilled in the center was prepared from the rubber composition, and the number of times to break in a dc / dn test (a constant stress test (1.7 MPa) was carried out at a frequency of 5 Hz and 80°C using a "Servo Pulser" manufactured by Shimadzu Corporation) using the test piece was measured. The greater the number of times to break, the lower the crack growth rate and the more excellent the durability (crack growth resistance). In addition, the crack growth resistance was evaluated / classified according to the following criteria. A: Number of times to break is 300,000 or more B: Number of times to break is 150,000 or more but less than 300,000 C: Number of times to break is 100,000 or more but less than 150,000 D: Number of times to break is less than 100,000

[0064] (2) Breaking elongation after aging A 160 mm x 160 mm x 2 mm slab plate prepared by thermally crosslinking the rubber composition was set in a Gear aging tester (Gear oven) manufactured by Toyo Seiki Seisakusho, and aged in the air for 2 days at an internal temperature of 100°C. The aged slab plate was punched into a JIS-3 dumbbell shape to prepare a rubber sample, which was measured using a fully automatic tensile tester manufactured by Toyo Seiki Seisakusho, to measure the breaking elongation (%) after aging. The breaking elongation after aging was evaluated / classified according to the following criteria: A: Breaking elongation after aging is 200% or more; B: Breaking elongation after aging is 150% or more but less than 200%; C: Breaking elongation after aging is 100% or more but less than 150%; D: Breaking elongation after aging is less than 100%

[0065]

[0066] * 1 Carbon black: Asahi Carbon Co., Ltd., trade name "Asahi # 70L" * 2 Stearic acid: New Japan Chemical Co., Ltd., trade name "Stearic acid 50S" * 3 Vulcanization accelerator: Ouchi Shinko Chemical Industry Co., Ltd., trade name "Noccela CZ-G" * 4 Sulfur: Tsurumi Chemical Industry Co., Ltd., trade name "Powdered sulfur" * 5 Peroxide: NOF Corporation, trade name "Perkmyl D-40", containing dicumyl peroxide at a concentration of 40% by mass, the actual amount of peroxide blended is shown in the lower part * 6 Metal acrylate derivative: Zinc dimethacrylate, CRAY VALLEY, trade name "DYMALINK 708" * 7 Zinc oxide: Hakusui Tech, trade name "Zinc oxide type 2" * 8 Other chemicals: The total amount of two types of antioxidants and retarder, blended in the same ratio in all examples and comparative examples

[0067] It can be seen from Table 1 that the rubber compositions of the examples according to the present invention have high crack propagation resistance and high elongation at break after aging, and are excellent in durability. On the other hand, the rubber composition of Comparative Example 1, which did not contain peroxide, had low elongation at break after aging, and the rubber composition of Comparative Example 2, which did not contain sulfur, had poor crack propagation resistance.

[0068] The rubber composition and metal-coated rubber of the present invention can be used for tires, hoses, rubber crawlers, and the like.

Claims

1. A rubber composition comprising a rubber component (A), carbon black (B), sulfur (C), and a peroxide (D), wherein the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is 0.5 to 2.

5.

2. The rubber composition according to claim 1, further comprising a metal acrylate or a derivative thereof (E).

3. The rubber composition according to claim 1, further comprising zinc diacrylate or a derivative thereof (E1).

4. The rubber composition according to claim 2, wherein the mass ratio (D / E) of the peroxide (D) to the metal acrylate or its derivative (E) is 0.5 or more.

5. The rubber composition according to claim 3, wherein the mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or its derivative (E1) is 0.5 or more.

6. The rubber composition according to claim 1, wherein the mass ratio (C / D) of the sulfur (C) to the peroxide (D) is 0.5 or more and less than 2.

0.

7. The rubber composition according to claim 2, wherein the mass ratio (D / E) of the peroxide (D) to the metal acrylate or its derivative (E) is 0.5 to 3.

8. The rubber composition according to claim 3, wherein the mass ratio (D / E1) of the peroxide (D) to the zinc diacrylate or its derivative (E1) is 0.5 to 3.

9. The rubber composition according to claim 1, wherein the rubber component (A) contains an isoprene-based rubber (A1).

10. A metal-coated rubber comprising the rubber composition according to any one of claims 1 to 9.

11. A tire comprising the metal-coated rubber of claim 10.

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