Rubber composition for metal bonding

Abstract

The belt layer of tires is subjected to strong impacts and heavy loads, so steel cords are used as reinforcing material. The rubber covering these steel cords needs to maintain good adhesion to the steel cords even when exposed to humid heat for extended periods. Furthermore, there is a demand to switch to silica-based materials for the belt layer, but this presents challenges such as increased viscosity, decreased hardness, and deterioration of wire adhesion after moisture aging. [Solution] A rubber composition for metal bonding comprising 100 parts by mass of diene rubber, 40 to 80 parts by mass of carbon black and silica in total, and 0.2 to 20% by mass of a disulfide compound and / or a fatty acid having 12 to 20 carbon atoms relative to the silica, wherein the ratio of silica to carbon black is 1.0 or more.

Description

[Technical Field]

[0001] The present invention relates to a rubber composition for metal bonding, and more specifically, to a rubber composition for metal bonding that has sufficient hardness and tackiness for practical use, low viscosity, low rolling resistance, and excellent adhesion after moist heat aging. [Background technology]

[0002] A pneumatic tire is mainly composed of a pair of bead sections and sidewall sections, and a tread section that extends from both sidewall sections. A carcass layer is provided on the inside of the tire, and both ends of the carcass layer are folded back to enclose the bead core from the inside to the outside of the tire. The tread section consists of a cap tread and an under tread, with a belt layer positioned between the under tread and the carcass layer. Because this belt layer is subjected to strong impacts and heavy loads, steel wires coated with metal-plated compounds are used as reinforcing materials. The rubber covering these steel wires requires good adhesion to the steel wires.

[0003] On the other hand, from a carbon neutrality perspective, there is a demand for tires with reduced rolling resistance. The aforementioned belt layer is no exception, and there is a need to switch from conventional carbon-based materials to silica-based materials. However, silica-based materials have drawbacks such as increased viscosity, decreased hardness, and deterioration of wire adhesion after moisture aging, as well as poor tackiness (adhesion over time). In particular, regarding processability, sufficient tackiness improves splicing workability and facilitates the bonding of various components.

[0004] Furthermore, the following Patent Documents 1 to 4 disclose techniques for incorporating disulfide compounds into rubber compositions for the purpose of improving their processability. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 5248211 [Patent Document 2] Patent No. 4768521 [Patent Document 3] Patent No. 6147585 [Patent Document 4] Patent No. 6522091 [Overview of the project] [Problems that the invention aims to solve]

[0006] The object of the present invention is to provide a rubber composition for metal bonding that has sufficient hardness and tackiness for practical use, low viscosity, low rolling resistance, and excellent adhesion after moist heat aging. [Means for solving the problem]

[0007] The present invention provides a rubber composition for metal bonding, characterized in that, with respect to 100 parts by mass of a diene rubber containing 50 parts by mass or more of natural rubber and / or synthetic isoprene rubber, the composition contains 40 to 80 parts by mass of carbon black and silica in total, and at least one selected from the group consisting of a disulfide compound represented by the following formula (1) and a fatty acid having 12 to 20 carbon atoms in an amount of 0.2 to 20% by mass relative to the silica, wherein the ratio of silica to carbon black is 1.0 or more as the former / latter (mass ratio).

[0008] [ka]

[0009] (In formula (1), R1 and R2 each represent substituents that can independently form an amide bond with the NH group.) [Effects of the Invention]

[0010] The rubber composition for metal bonding of the present invention contains 100 parts by mass of diene rubber containing 50 parts by mass or more of natural rubber and / or synthetic isoprene rubber, 40 to 80 parts by mass of carbon black and silica in total, and at least one selected from the group consisting of disulfide compounds represented by formula (1) and fatty acids having 12 to 20 carbon atoms in an amount of 0.2 to 20% by mass relative to the silica, and the ratio of silica to carbon black is 1.0 or more as the former / latter (mass ratio). As a result, it has sufficient hardness and tackiness for practical use, low viscosity, low rolling resistance, and excellent adhesion after moist heat aging. [Modes for carrying out the invention]

[0011] The present invention will be described in more detail below. The diene rubber used in the metal adhesive rubber composition of the present invention is essentially composed of natural rubber (NR) and / or synthetic isoprene rubber (IR). The amount of NR and / or IR must be 50 parts by mass or more when the total diene rubber is 100 parts by mass. If the amount of NR and / or IR is less than 50 parts by mass, the tensile strength deteriorates, which is undesirable. In addition to NR and IR, other diene rubbers can be used, such as butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and acrylonitrile-butadiene copolymer rubber (NBR). These may be used alone or in combination of two or more. Furthermore, their molecular weight and microstructure are not particularly limited, and they may be end-modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl groups, etc., or epoxidized. The amount of NR and / or IR is preferably 80 parts by mass or more when the total diene rubber is 100 parts by mass. The weight-average molecular weight (Mw) of the diene rubber is not particularly limited, but for reasons that the effects of the present invention are superior, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight average molecular weight (Mw) and the number average molecular weight (Mn) are values in terms of standard polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0012] The rubber composition for metal adhesion in the present invention contains carbon black and silica. From the viewpoint of improving the effects of the present invention, the carbon black preferably has the following embodiments. (1) The CTAB specific surface area is preferably 75 to 95 g / m 2 and more preferably 80 to 90 g / m 2 (2) The compression DBP oil absorption amount (24M4DBP) is preferably 60 to 85 ml / 100 ml, and more preferably 70 to 80 ml / 100 ml. (3) The ratio of the nitrogen adsorption specific surface area N2SA (unit: m 2 / g) to the iodine adsorption amount IA (unit: mg / g), i.e., N2SA / IA, is preferably 1.10 or less, and more preferably 0.85 to 1.05. In this specification, the CTAB specific surface area is measured in accordance with JIS K6217-2, the compression DBP (24M4DBP) is measured as the 24M4-DBP oil absorption amount based on JIS K6217-4 (compressed sample), the nitrogen adsorption specific surface area N2SA is measured in accordance with JIS K6217-2, and the iodine adsorption amount IA is measured in accordance with JIS K6217-1

[0013] From the viewpoint of improving the effects of the present invention, the silica used in the present invention preferably has a nitrogen adsorption specific surface area N2SA of 100 to 200 m 2 / g. The silica that can be used is not particularly limited, and silica using biomass materials such as rice husks as raw materials may be used.

[0014] The rubber composition for metal adhesion in the present invention contains at least one selected from the group consisting of a disulfide compound represented by the following formula (1) and a fatty acid having 12 to 20 carbon atoms.

[0015]

Chemical formula

[0016] (In formula (1), R1 and R2 each represent substituents that can independently form an amide bond with the NH group.)

[0017] Among the disulfide compounds represented by formula (1), dibenzamide diphenyl disulfide represented by the following formula is particularly preferred.

[0018] [ka]

[0019] Dibenzamide diphenyl disulfide can be a commercially available product, such as dibenzamide diphenyl disulfide manufactured by Tokyo Chemical Industry Co., Ltd. or Noctizer SD manufactured by Ouchi Shinko Chemical Industry Co., Ltd. For example, dibenzamide diphenyl disulfide is commonly used as a deconjugate (mixing accelerator) during diene rubber compounding (see, for example, Patent Document 3: Japanese Patent No. 6147585). On the other hand, in a preferred embodiment of the present invention, it is preferable to have at least a mixing step in which the diene rubber, carbon black, silica, and the disulfide compound represented by formula (1) are mixed simultaneously. Adopting such a mixing step further improves hardness and adhesion after moist heat aging. After the mixing step is completed, it is preferable to add other components to the obtained mixture and mix to prepare a rubber composition for metal bonding.

[0020] The fatty acids having 12 to 20 carbon atoms used in the rubber composition for metal bonding in the present invention include saturated or unsaturated linear or branched fatty acids having 12 to 20 carbon atoms, preferably saturated linear fatty acids having 12 to 20 carbon atoms, and more preferably saturated linear fatty acids having 14 to 20 carbon atoms.

[0021] (Formulation ratio of rubber composition for metal bonding) The rubber composition for metal bonding in the present invention is characterized in that, with respect to 100 parts by mass of diene rubber, it contains 40 to 80 parts by mass of carbon black and silica in total, and at least one selected from the group consisting of disulfide compounds represented by formula (1) and fatty acids having 12 to 20 carbon atoms in an amount of 0.2 to 20% by mass relative to the silica, and the ratio of silica to carbon black as the former / latter (mass ratio) is 1.0 or more.

[0022] If the total amount of carbon black and silica is less than 40 parts by mass, the hardness and adhesion after aging due to moist heat will decrease, while if it exceeds 80 parts by mass, the viscosity will increase, resulting in poor workability. If the amount of at least one compound selected from the group consisting of the disulfide compound represented by formula (1) and fatty acids having 12 to 20 carbon atoms is less than 0.2% by mass relative to silica, the amount is too small to achieve the effects of the present invention. Conversely, if it exceeds 20% by mass, the adhesion after moist heat aging decreases. If the ratio of silica to carbon black (mass ratio) is less than 1.0, the adhesion after moist heat aging will decrease.

[0023] The total amount of carbon black and silica is preferably 50 to 70 parts by mass per 100 parts by mass of diene rubber. The amount of at least one compound selected from the group consisting of a disulfide compound represented by formula (1) and a fatty acid having 12 to 20 carbon atoms is preferably 0.2 to 15.0% by mass, and more preferably 2.0 to 13.0% by mass, relative to the silica. The ratio of silica to carbon black is preferably 1.2 to 5.0 as the former / latter (mass ratio), and more preferably 1.5 to 3.0.

[0024] (Other ingredients) In the rubber composition for metal adhesion in the present invention, in addition to the above-described components, a vulcanizing or crosslinking agent; a vulcanizing or crosslinking accelerator; zinc oxide; various fillers such as clay, talc, calcium carbonate, aluminum oxide, and titanium oxide; various oils; an antioxidant; various additives generally blended in rubber compositions such as a plasticizer and cobalt fatty acid can be blended. Such additives can be kneaded by a general method to form a composition and can be used for vulcanization or crosslinking. The blending amounts of these additives can also be set to conventional general blending amounts as long as they do not conflict with the object of the present invention.

[0025] Further, the rubber composition for metal adhesion in the present invention can exhibit the effects of the present invention well by having one or more of the following forms (A) to (H). (A) It contains 2 to 10% by mass of a silane compound represented by the following formula (11) with respect to the silica.

[0026]

Chemical formula

[0027] (In formula (11), R 1 and R 2 are hydrocarbon groups having 1 to 20 carbon atoms, and R 3 is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. R 1 to R 3 may contain heteroatoms (however, sulfur is not included). n represents a number from 0 to 2.)

[0028] (B) Stearic acid is used together with the disulfide compound represented by the above formula (1). (C) In a constant strain fatigue test at a strain of 60% and 400 rpm, the number of repetitions until fracture is 40,000 times or more. The constant strain fatigue test conforms to JIS K6251, uses a test piece punched out in the shape of a JIS No. 3 dumbbell, and performs a tensile constant strain fatigue test under the conditions of 20 °C, a strain of 60%, and a test frequency of 6.67 Hz (rotation speed 400 rpm) in reference to JIS K6270, and measures the number of repeated deformations until fracture. (D) In ​​the silane compound represented by formula (11) above, n is 0 and R 1 R is an alkyl group having 7 to 20 carbon atoms. 3 This is an ethyl group. (E) The metal bonding rubber composition further contains, per 100 parts by mass of the diene rubber, 0.1 to 1.5 parts by mass of organic acid cobalt salt as cobalt amount, 0.5 parts by mass or more and less than 3.0 parts by mass of phenolic resin, and 0.5 to 5.0 parts by mass of curing agent. Examples of organic cobalt acid salts include cobalt naphthenate, cobalt neodecanoate, cobalt stearate, cobalt rosinate, cobalt versatate, cobalt tollate, cobalt neodecanoate borate, and cobalt acetylacetonate. Examples of phenolic resins include cresol resins, resorcinol resins, alkylphenol resins, and modified phenolic resins. Examples of modified phenolic resins include cashew-modified phenolic resins, oil-modified phenolic resins, epoxy-modified phenolic resins, aniline-modified phenolic resins, and melamine-modified phenolic resins. Examples of curing agents include hexamethylenetetramine, hexamethoxymethylmelamine (HMMM), hexamethoxymethylolmelamine, pentamethoxymethylmelamine, hexaethoxymethylmelamine, polymers of para-formaldehyde, and N-methylol derivatives of melamine. (F) The silica content is 55-70% by mass relative to the total amount of carbon black and silica. (G) The metal bonding rubber composition contains 12 parts by mass or more, preferably 12 to 18 parts by mass, of zinc oxide per 100 parts by mass of the diene rubber. (H) As a vulcanization accelerator, 0.1 to 1.5 parts by mass of N,N-dicyclohexyl-2-benzothiazolyl sulfenamide (for example, Noxellar DZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) is added per 100 parts by mass of the diene rubber.

[0029] The rubber-metal composite of the present invention is obtained by embedding a wire in the rubber composition for metal bonding of the present invention. The wire may be a steel wire coated with a plating compound, and it is preferable that the plating compound is brass plating, copper-tin plating, copper plating, zinc plating, nickel plating, chromium plating, or copper-zinc-cobalt ternary plating. Furthermore, applications of the rubber-metal composite of the present invention include, for example, tires, belt conveyors, electric wires, hoses, and seismic isolation rubber. In the case of tire applications, the rubber-metal composite may include belts embedded in the undertread, carcasses, and beads (including bead cores and steel cords housed therein).

[0030] The rubber-metal composite of the present invention can be obtained, for example, by mixing the various components mentioned above using a general-purpose mixer such as a Banbury mixer or a roll mixer to prepare a rubber composition for metal bonding, embedding a wire in it, and then vulcanizing it according to a conventional method.

[0031] Furthermore, when the rubber-metal composite of the present invention is used for tire applications, the manufacturing method is not particularly limited, and tires can be manufactured according to known technologies. The tire is preferably a pneumatic tire, and can be filled with air, nitrogen or other inert gases, and other gases. [Examples]

[0032] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0033] Standard example, Examples 1-8, Comparative Examples 1-8 In the formulations (parts by mass) shown in Tables 1 and 2, diene rubber, carbon black, silica, and the disulfide compound represented by formula (1) were simultaneously mixed for 5 minutes using a 1.7-liter sealed Banbury mixer. The other components were then added to the resulting mixture and kneaded to prepare an unvulcanized metal-bonding rubber composition. Next, the unvulcanized rubber composition was vulcanized under vulcanization conditions of 170°C for 10 minutes to prepare vulcanized rubber test pieces. The various physical properties of the unvulcanized rubber composition were measured as follows. For the wire pull-out test (wire adhesion after hot water degradation), a wire was coated with the unvulcanized rubber composition, and a test piece vulcanized under the vulcanization conditions was immersed in hot water at 70°C for 4 weeks to perform a hot water degradation treatment. A test piece after hot water degradation was obtained and tested under the following conditions. Brass-plated steel wire was used as the wire.

[0034] Viscosity: The Mooney viscosity ML(1+4) at 100°C was determined for the unvulcanized rubber composition using an L-shaped rotor in accordance with JIS K6300. The results are expressed as an index, with the standard value set to 100. A smaller index indicates lower viscosity and better processability.

[0035] Heat generation: For the vulcanized rubber test specimens, tanδ(60°C) was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., under the conditions of initial strain 10%, amplitude ±2%, frequency 20Hz, and temperature 60°C. The results are shown exponentially, with the standard value set to 100. A smaller value indicates lower heat generation and lower rolling resistance.

[0036] Hardness Hs: The hardness of the vulcanized rubber test specimen was measured at 20°C using a Type A durometer in accordance with JIS K6253. The results are expressed as an index, with the standard value set to 100. A higher index indicates higher hardness.

[0037] Pull-out force: In accordance with ASTM D-2, steel wires were pulled from the test specimens after hot water degradation, and the pull-out force was measured. The results are expressed as an exponential value, with the standard example value set to 100. A higher value indicates better adhesion to rubber after hot water degradation.

[0038] Rubber Adhesion: In accordance with ASTM D-2229, the amount of rubber adhesion was measured by pulling out steel wires from the test specimens after hot water degradation. The results are expressed as an exponential value, with the standard example value set to 100. A higher value indicates better adhesion to rubber after hot water degradation.

[0039] Tackiness: The obtained unvulcanized rubber composition was molded into a sheet-like sample (10 mm wide x 200 mm long x 2 mm thick) without vulcanization, and this was set on a metal disc. Furthermore, a sample to be pressed (70 mm wide x 100 mm long x 2 mm thick) was molded from the same rubber composition without vulcanization. The sheet-like sample was pressed onto this sample to be pressed with 4.9 N of pressure, and after 3 hours, the attached sheet-like sample (unvulcanized) was peeled off, and the adhesive force required to peel it off was measured using a PICMA tack meter (manufactured by Toyo Seiki Seisakusho Co., Ltd.). The obtained results were expressed as an index with the standard value set to 100. A larger index indicates higher tackiness over time (adhesion over time), which makes it easier to bond each component and thus indicates superior processability.

[0040] Constant Strain Fatigue Test: The vulcanized rubber test specimens were punched into a JIS No. 3 dumbbell shape in accordance with JIS K6251, and a tensile constant strain fatigue test was performed on these specimens under the conditions of 20°C, 60% strain, and a test frequency of 6.67 Hz (rotation speed of 400 rpm), with reference to JIS K6270, and the number of repeated deformations until failure was measured. The results are shown in Tables 1 and 2.

[0041] [Table 1]

[0042] [Table 2]

[0043] *1: NR (RSS#3) *2: Carbon black CB (Tokai Carbon Co., Ltd. Seast 300, CTAB specific surface area = 86g / m²) 2, Compressed DBP oil absorption (24M4DBP)=75ml / 100ml, N2SA / IA=1.024) *3: Silica (Precipitated silica K160 manufactured by FengHai Rice Biotechnology) *4: Silane coupling agent 1 (Si69 manufactured by Evonik DeGussa, bis(3-triethoxysilylpropyl)tetrasulfide) *5: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *6: Disulfide compound (Dibenzamide diphenyl disulfide, manufactured by Tokyo Chemical Industry Co., Ltd.) *7: Stearic acid (YR bead stearic acid manufactured by NOF Corporation) *8: Anti-aging agent (Flexis 6PPD) *9: Organic cobalt acid salt (DICNATE NBC-II, manufactured by DIC Corporation; cobalt borate neodecanoate) *10: Sulfur (Crystex HT OT 20, manufactured by AkzoNobel Co., Ltd.) *11: Vulcanization accelerator 1 (Noxellar DZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *12: Vulcanization accelerator 2 (Noxellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *13: Silane compound (KBE-3083, manufactured by Shin-Etsu Chemical Co., Ltd., octyltriethoxysilane) *14: Silane coupling agent 2 (Si75 manufactured by Evonik DeGussa, bis(3-triethoxysilylpropyl) disulfide)

[0044] From the results in Table 1, it can be seen that the metal bonding rubber composition of each example contains 100 parts by mass of diene rubber containing 50 parts by mass or more of natural rubber and / or synthetic isoprene rubber, 40 to 80 parts by mass of carbon black and silica in total, and at least one selected from the group consisting of disulfide compounds represented by the following formula (1) and fatty acids having 12 to 20 carbon atoms, in an amount of 0.2 to 20% by mass relative to the silica, and the ratio of silica to carbon black as the former / latter (mass ratio) is 1.0 or more. Therefore, it can be seen that, compared to the standard example, it has sufficient hardness and tackiness for practical use, low viscosity, low rolling resistance, and excellent adhesion after moist heat aging. Comparative Example 1 showed reduced hardness and tensile strength because the total amount of carbon black and silica was below the lower limit specified in the present invention. In Comparative Example 2, the ratio of carbon black to silica was below the lower limit specified in the present invention, resulting in decreased heat generation, rubber adhesion, tackiness, and constant strain fatigue test results. In Comparative Example 3, the ratio of carbon black to silica was below the lower limit specified in the present invention, resulting in decreased heat generation, tensile strength, rubber adhesion, tackiness, and constant strain fatigue test results. Comparative Example 4 showed reduced heat generation, pull-out strength, rubber adhesion, and tackiness because the amount of disulfide compound and fatty acid with 12 to 20 carbon atoms exceeded the upper limit specified in the present invention. In Comparative Example 5, the total amount of carbon black and silica was below the lower limit specified in the present invention, resulting in reduced hardness and tensile strength. Comparative Example 6 yielded results equivalent to the standard example because the amount of fatty acids with 12 to 20 carbon atoms was below the lower limit specified in the present invention, and therefore the effects of the present invention could not be achieved. Comparative Example 7 showed reduced pull-out strength, rubber adhesion, and tackiness because the amount of fatty acids with 12 to 20 carbon atoms exceeded the upper limit specified in the present invention. Comparative Example 8 showed deterioration in viscosity and exothermic properties because the total amount of carbon black and silica exceeded the upper limit specified in the present invention.

[0045] The present invention encompasses the following embodiments. Embodiment 1: The diene rubber, containing 50 parts by mass or more of natural rubber and / or synthetic isoprene rubber, contains 40 to 80 parts by mass of carbon black and silica in total, and at least one selected from the group consisting of disulfide compounds represented by the following formula (1) and fatty acids having 12 to 20 carbon atoms, in an amount of 0.2 to 20% by mass relative to the silica, with the ratio of silica to carbon black being 1.0 or more in terms of former / latter mass ratio. A rubber composition for metal bonding characterized by the following features.

[0046] [ka]

[0047] (In formula (1), R1 and R2 each represent substituents that can independently form an amide bond with the NH group.) Embodiment 2: The metal adhesive rubber composition according to Embodiment 1, characterized in that the disulfide compound is dibenzamide diphenyl disulfide. Embodiment 3: The metal-adhesive rubber composition according to Embodiment 1 or 2, characterized in that the metal-adhesive rubber composition contains a silane compound represented by the following formula (11), and the amount of the silane compound is 2 to 10% by mass relative to the silica.

[0048] [ka]

[0049] (In formula (11), R 1 and R 2 R is a hydrocarbon group having 1 to 20 carbon atoms. 3 R is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. 1 ~R 3 (The compound may contain heteroatoms (but not sulfur). n represents a number between 0 and 2.) Embodiment 4: A metal adhesive rubber composition according to any one of Embodiments 1 to 3, characterized in that, in a constant strain fatigue test under conditions of 60% strain and 400 rpm, the number of cycles until the metal adhesive rubber composition is destroyed is 40,000 or more. Embodiment 5: In the silane compound represented by formula (11) above, n is 0, and R 1 R is an alkyl group having 7 to 20 carbon atoms. 3 The metal bonding rubber composition according to Embodiment 3, characterized in that the group is an ethyl group. Embodiment 6: A rubber-metal composite comprising a wire embedded in a metal-adhesive rubber composition according to any one of Embodiments 1 to 5. Embodiment 7: The rubber-metal composite according to Embodiment 6, characterized in that the wire is a steel wire coated with a plating compound. Embodiment 8: The rubber-metal composite according to Embodiment 7, characterized in that the plating compound is brass plating, copper-tin plating, copper plating, zinc plating, nickel plating, chromium plating, or copper-zinc-cobalt ternary plating. Embodiment 9: A tire, belt conveyor, electric wire, hose, or seismic isolation rubber using the rubber-metal composite described in any of Embodiments 6 to 8. Embodiment 10: A tire using a rubber-metal composite as described in any of embodiments 6 to 8.

Claims

1. The diene rubber contains 50 parts by mass or more of natural rubber and / or synthetic isoprene rubber, and in 100 parts by mass, it contains 40 to 80 parts by mass of carbon black and silica in total, and a disulfide compound represented by the following formula (1) in an amount of 0.2 to 20% by mass relative to the silica, with the ratio of silica to carbon black being 1.0 or more in terms of former / latter mass ratio. A rubber composition for metal bonding characterized by the following features. 【Chemistry 1】 (In formula (1), R1 and R2 each represent substituents that can independently form an amide bond with an NH group.)

2. The metal adhesive rubber composition according to claim 1, characterized in that the disulfide compound is dibenzamide diphenyl disulfide.

3. The metal-adhesive rubber composition according to claim 1, characterized in that the metal-adhesive rubber composition comprises a silane compound represented by the following formula (11), wherein the amount of the silane compound is 2 to 10% by mass relative to the silica. 【Chemistry 2】 (In formula (11), R １ and R ２ R is a hydrocarbon group having 1 to 20 carbon atoms. ３ R is a hydrocarbon group having 1 to 3 carbon atoms or hydrogen. １ ~R ３ It may contain heteroatoms (but not sulfur). n represents a number between 0 and 2.

4. The metal adhesive rubber composition according to claim 1, characterized in that, in a constant strain fatigue test under conditions of 60% strain and 400 rpm, the number of repetitions until the metal adhesive rubber composition is destroyed is 40,000 or more.

5. In the silane compound represented by formula (11) above, n is 0, and R １ R is an alkyl group having 7 to 20 carbon atoms. ３ The rubber composition for metal bonding according to claim 3, characterized in that the group is an ethyl group.

6. A rubber-metal composite comprising a wire embedded in the metal-adhesive rubber composition according to claim 1.

7. The rubber-metal composite according to claim 6, characterized in that the wire is a steel wire coated with a plating compound.

8. The rubber-metal composite according to claim 7, characterized in that the plating compound is brass plating, copper-tin plating, copper plating, zinc plating, nickel plating, chromium plating, or copper-zinc-cobalt ternary plating.

9. A tire, belt conveyor, electric wire, hose, or seismic isolation rubber using the rubber-metal composite described in claim 6.

10. A tire using the rubber-metal composite described in claim 6.

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