Rubber composition and rubber product

Abstract

To provide a rubber composition which has a low load on the environment, has higher ozone resistance than a conventional rubber composition, and can suppress discoloration of the surface of a rubber product.SOLUTION: A rubber composition comprising a rubber component and an anti-aging agent, wherein the anti-aging agent comprises an amine-based anti-aging agent (A) represented by a predetermined formula and an amine-based anti-aging agent (B) represented by a predetermined formula.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition and a rubber product. [Background technology]

[0002] Generally, rubber products made from natural rubber or diene-based synthetic rubber deteriorate over time when exposed to an ozone environment, and cracks may develop on their surfaces. These cracks progress further as the rubber product continues to be subjected to static and dynamic stresses, eventually leading to the destruction of the rubber product.

[0003] In order to prevent or inhibit the occurrence and progression of cracks caused by ozone, it has become common to apply a rubber composition containing an antioxidant such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) to rubber products, particularly tire tread rubber and sidewall rubber (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2010-509415 [Patent Document 2] Special Publication No. 2010-536952 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when an antioxidant such as 6PPD is used in a rubber product, the antioxidant migrates to the rubber surface over time, which can easily cause so-called blooming, which discolors and stains the rubber surface, and can impair the appearance of the rubber product. Furthermore, in recent years, there has been a demand for further improvement in the ozone resistance of rubber products. In particular, in tire manufacturing, efforts are being made to reduce the gauge thickness of each component in order to improve fuel efficiency and save resources. Under these circumstances, there is a demand for rubber compositions with even higher ozone resistance than conventional rubber compositions containing the above-mentioned antioxidants.

[0006] Furthermore, the antioxidant 6PPD may have an impact on the environment. Therefore, it is desirable to use antioxidants that have a lower environmental impact, taking into account the possibility of future restrictions in European regulations.

[0007] Therefore, an object of the present invention is to provide a rubber composition that is environmentally friendly, has higher ozone resistance than conventional rubber compositions, and is capable of suppressing discoloration of the surface of rubber products. Another object of the present invention is to provide a rubber product that has high ozone resistance and is inhibited from discoloring its surface. [Means for solving the problem]

[0008] As a result of intensive research to achieve the above object, the inventors have discovered that by blending at least two types of compounds, each having a specific structure, into the rubber component, a rubber composition can be obtained that has high ozone resistance and is capable of suppressing discoloration of the surface of a rubber product, and have thus completed the present invention. That is, the gist of the rubber composition and rubber product of the present invention that solve the above problems is as follows.

[0009] [1] A rubber composition containing a rubber component and an antioxidant, The antioxidant is represented by the following general formula (1): [ka] [In the formula, R 11 and R12 represents a phenyl group, and m represents an integer of 7 or more.], and The following general formula (2): [ka] [In the formula, R 21 and R 22 are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R 21 and R 22 and (B) an amine-based antioxidant represented by the following formula: wherein at least one of the formulas is an alkyl group having 7 or more carbon atoms.

[0010] [2] The rubber composition according to [1], wherein the content of the amine-based antioxidant (A) is 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0011] [3] The rubber composition according to [1] or [2], wherein the content of the amine-based antioxidant (B) is 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

[0012] [4] The rubber composition according to any one of [1] to [3], wherein the mass ratio (A / B) of the amine-based antioxidant (A) to the amine-based antioxidant (B) is 0.025 or more and 40 or less.

[0013] [5] The rubber composition according to any one of [1] to [4], wherein the rubber component contains natural rubber.

[0014] [6] The rubber composition according to [5], wherein the rubber component further contains at least one of a butadiene rubber and a styrene-butadiene rubber.

[0015] [7] R in the general formula (2) 21 and R 22 The rubber composition according to any one of [1] to [6], wherein the other is a phenyl group.

[0016] [8] R in the general formula (2) 21 and R 22 At least one of the above has 7 or 8 carbon atoms.

[0017] [9] The antioxidant further contains a quinoline-based antioxidant (C), The rubber composition according to any one of [1] to [8], wherein the proportion of the quinoline-based antioxidant (C) in the antioxidant is 5% by mass or more and 50% by mass or less.

[0018]

[10] The antioxidant further comprises a compound represented by the following general formula (3): [ka] [In the formula, R 31 and R 32 are each independently a monovalent saturated hydrocarbon group.] (excluding the amine-based antioxidant (B) represented by the above general formula (2), The rubber composition according to any one of [1] to [9], wherein the proportion of the amine-based antioxidant (D) in the antioxidant is 0.1% by mass or more and 80% by mass or less.

[0019]

[11] The rubber composition according to any one of [1] to

[10] , which is for use in a tire tread.

[0020]

[12] A rubber product selected from the group consisting of tires, rubber crawlers, and seismic isolation rubber, characterized in that it contains the rubber composition according to any one of [1] to

[10] . [Effects of the Invention]

[0021] According to the present invention, it is possible to provide a rubber composition that has a low environmental impact, is more ozone resistant than conventional rubber compositions, and is capable of suppressing discoloration of the surface of rubber products. Furthermore, according to the present invention, it is possible to provide a rubber product that has high ozone resistance and is inhibited from discoloring on the surface. DETAILED DESCRIPTION OF THE INVENTION

[0022] The rubber composition and rubber product of the present invention will be described in detail below by way of example based on embodiments thereof.

[0023] <Definition> The compounds described herein may be derived in part or in whole from fossil sources, biological sources such as plant sources, recycled sources such as used tires, or a mixture of two or more of fossil, biological, and recycled sources.

[0024] <Rubber composition> A rubber composition according to one embodiment of the present invention (hereinafter sometimes referred to as "the rubber composition of the present embodiment") contains a rubber component and an antioxidant, The antioxidant is represented by the following general formula (1): [ka] [In the formula, R 11 and R 12 represents a phenyl group, and m represents an integer of 7 or more.], and The following general formula (2): [ka] [In the formula, R 21 and R 22 are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R 21 and R 22 and (B) an amine-based antioxidant represented by the formula: wherein at least one of the formulas is an alkyl group having 7 or more carbon atoms.

[0025] In the rubber composition of the present embodiment, the amine-based antiaging agent (A) represented by the general formula (1) has a higher molecular weight than conventional antiaging agents, and as shown in the above formula (1), it has a bridge moiety having a specific and relatively long chain length, i.e., "-NH-CH(CH3)-(CH2) mIt is believed that the high molecular weight and the presence of specific bridge moieties of the amine-based antiaging agent (A) reduce the diffusion rate in the rubber composition, further suppressing migration to the rubber surface. Furthermore, the amine-based antiaging agent (A) has a moiety composed of "-CH(CH3)-(CH2)" in the above formula (1). m One hydrogen atom is bonded to each of the two nitrogen atoms at both ends of -CH(CH3)- (forming a so-called secondary amino group), and the presence of this bond in the structure represented by formula (1) is thought to contribute to the specific effect of improving ozone resistance (weather resistance). Furthermore, the amine-based antioxidant (A) represented by general formula (1) can suppress discoloration of the surface of rubber products.

[0026] Furthermore, in the rubber composition of the present embodiment, by using an amine-based antioxidant (B) (phenylenediamine-based) represented by the above general formula (2) in combination as a substitute for an antioxidant that may have an impact on the environment, it is possible to more effectively improve ozone resistance while suppressing discoloration of the surface of the rubber product, and further suppress the occurrence of cracks.

[0027] Therefore, the rubber composition of this embodiment has a low environmental impact, is more ozone resistant than conventional rubber compositions, and can also inhibit discoloration of the surface of rubber products.

[0028] (rubber component) The rubber component used in the rubber composition of the present invention may be a diene rubber. Examples of the diene rubber include natural rubber (NR) and diene synthetic rubber. Examples of the diene synthetic rubber include isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene rubber (SBR), and chloroprene rubber (CR). These rubber components may be used alone or in combination of two or more.

[0029] The rubber component preferably contains natural rubber (NR). The rubber component more preferably further contains at least one of butadiene rubber (BR) and styrene-butadiene rubber (SBR). In these cases, the mechanical properties of rubber products using the rubber composition can be improved.

[0030] (anti-aging agent) The rubber composition of this embodiment contains an antioxidant. The antioxidant has the effect of preventing aging of the rubber composition and rubber products using the same. The rubber composition of this embodiment essentially contains, as the antioxidant, an amine-based antioxidant (A) represented by a predetermined formula and an amine-based antioxidant (B) represented by a predetermined formula (phenylenediamine-based), and may further contain other antioxidants described below as necessary.

[0031] -Amine-based antioxidant (A) of formula (1)- The antioxidant is represented by the following general formula (1): [ka] [In the formula, R 11 and R 12 represents a phenyl group, and m represents an integer of 7 or more.] The amine-based antioxidant (A) represented by the formula (1) has an excellent antiaging effect on rubber components such as natural rubber and diene-based synthetic rubber, and can be used as an antioxidant for rubber components.

[0032] In general formula (1), R 11 and R 12 When is a phenyl group, it is possible to more effectively improve ozone resistance and prevent discoloration.

[0033] In general formula (1), when m is an integer of 7 or more, it is possible to more effectively improve ozone resistance and prevent discoloration. From the same viewpoint, m in general formula (1) is preferably an integer of 8 to 16, and more preferably an integer of 10 to 14.

[0034] Examples of the amine-based antioxidant (A) represented by formula (1) include N,N'-bis(4-anilinophenyl)dodecane-2,11-diamine, N,N'-bis(4-anilinophenyl)hexadecane-2,15-diamine, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine, and N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine.

[0035] The amine-based antioxidant (A) represented by formula (1) can be produced by the reaction shown in the following reaction formula-1. [ka] [In the formula, R 11 , R 12 and m are the same as above. 1 represents an alkylene group having 7 to 28 carbon atoms.]

[0036] According to Reaction Scheme-1, the amine-based antiaging agent (A) represented by formula (1) can be produced by treating the diamide compound represented by formula (a1) with a reducing agent in a solvent or by reducing the amide carbonyl bond by catalytic hydrogen reduction using a metal catalyst.

[0037] As the solvent to be used in the reaction using the reducing agent of Reaction Scheme-1, a wide variety of known solvents can be used as long as they are inert to the reaction, and examples thereof include ether solvents such as dimethyl ether, diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, dioxane, tetrahydropyran, 1,2-dimethoxyethane, etc., and halogen-based solvents such as dichloromethane and carbon tetrachloride, and in particular, for boron hydride-based reducing agents, examples of the solvent include alcohol-based solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, etc. These solvents can be used alone or in combination of two or more types as needed. These solvents may be used in an amount of usually about 1 to 500 parts by mass, and preferably about 1 to 20 parts by mass, per part by mass of the diamide compound represented by formula (a1).

[0038] Reducing agents used in the reaction of Reaction Formula 1 include boron hydrides such as sodium borohydride, lithium aluminum hydride, borane, diborane, etc. Lithium aluminum hydride may be used in combination with aluminum chloride, and sodium borohydride may be used in combination with a Lewis acid such as tin tetrachloride or boron trifluoride diethyl ether complex. Such a reducing agent may be used in an amount of usually 1.5 to 20.0 equivalents, preferably 1.5 to 6.0 equivalents, more preferably 1.5 equivalents, relative to the diamide compound represented by formula (a1).

[0039] As the solvent to be used in the catalytic hydrogen reduction reaction of Reaction Scheme-1, a wide variety of known solvents can be used as long as they are inert to the reaction, and examples thereof include alcoholic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, and n-butanol, organic acids such as acetic acid and propionic acid, hydrocarbon solvents such as cyclohexane, and ether solvents such as tetrahydrofuran. These solvents can be used alone or in combination of two or more as needed. These solvents may be used in an amount of usually about 1 to 500 parts by mass, and preferably about 1 to 20 parts by mass, per part by mass of the diamide compound represented by formula (a1).

[0040] Examples of metal catalysts used in the catalytic hydrogen reduction reaction of Reaction Scheme 1 include palladium on carbon, platinum black (platinum on carbon), a mixture of copper oxide, zinc oxide, and aluminum oxide, a mixture of copper oxide, chromium oxide, manganese trioxide, and barium oxide, a mixture of copper oxide and zinc oxide, Raney nickel, and Raney cobalt. Such a metal catalyst may be used in an amount of usually 0.0001 to 0.5 parts by mass, preferably 0.0001 to 0.1 parts by mass, and more preferably 0.0001 to 0.01 parts by mass, per part by mass of the diamide compound represented by formula (a1).

[0041] This reaction can usually be carried out within a temperature range of from -78°C to the boiling point of the solvent used, but is usually carried out at about -10 to 50°C, preferably around room temperature. The reaction time varies depending on the reaction temperature and the like, and cannot be generalized, but the reaction is usually completed within about 0.5 to 24 hours. This reaction is carried out under a hydrogen atmosphere, and the pressure is usually from atmospheric pressure to 10 MPa, preferably from atmospheric pressure to 1.0 MPa, and more preferably around atmospheric pressure.

[0042] The amine-based antioxidant (A) represented by formula (1) can also be produced by the reaction shown in the following reaction formula-2. [ka] [In the formula, R 11 , R 12 and m are the same as above. 13 and R 14 are the same or different and represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms; A 2 represents an alkylene group having 7 to 28 carbon atoms. 13 , R 14 and A 2 The total number of carbon atoms is 28 or less.

[0043] Examples of the alkyl group having 1 to 4 carbon atoms include linear or branched alkyl groups having 1 to 4 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, and a tert-butyl group.

[0044] According to Reaction Scheme-2, the compound represented by formula (I) can be produced by treating the diimino compound represented by formula (a2) with a reducing agent in a solvent, or by reducing the imino bond by catalytic hydrogen reduction using a metal catalyst.

[0045] As the solvent to be used in the reaction using the reducing agent of Reaction Scheme-2, a wide variety of known solvents can be used as long as they are inert to the reaction, and examples thereof include ether solvents such as dimethyl ether, diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, dioxane, tetrahydropyran, 1,2-dimethoxyethane, etc., and halogen-based solvents such as dichloromethane and carbon tetrachloride, and in particular, for boron hydride-based reducing agents, examples of the solvent include alcohol-based solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, etc. These solvents can be used alone or in combination of two or more types as needed. These solvents may be used in an amount of usually about 1 to 500 parts by mass, and preferably about 5 to 100 parts by mass, per part by mass of the diimino compound represented by formula (a2).

[0046] The reducing agent used in the reaction of Reaction Formula-2 includes borohydrides such as sodium borohydride, lithium borohydride, and sodium cyanoborohydride, lithium aluminum hydride, and lithium triethylborohydride. Such a reducing agent may be used in an amount of usually 0.5 to 10.0 equivalents, preferably 0.5 to 2.0 equivalents, more preferably 0.5 to 1.0 equivalents relative to the diimino compound represented by formula (a2).

[0047] As the solvent to be used in the catalytic hydrogen reduction reaction of Reaction Scheme-2, a wide variety of known solvents can be used as long as they are inert to the reaction, and examples thereof include alcoholic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, and n-butanol, organic acids such as acetic acid and propionic acid, hydrocarbon solvents such as cyclohexane, and ether solvents such as tetrahydrofuran. These solvents can be used alone or in combination of two or more as needed. These solvents may be used in an amount of usually about 1 to 500 parts by mass, and preferably about 1 to 20 parts by mass, per part by mass of the diimino compound represented by formula (a2).

[0048] Examples of the metal catalyst used in the catalytic hydrogen reduction reaction of Reaction Formula 2 include palladium carbon, platinum black (platinum carbon), platinum sulfur carbon, platinum oxide, Raney nickel, and Raney cobalt. Such a metal catalyst may be used in an amount of usually 0.0001 to 0.5 parts by mass, preferably 0.0001 to 0.1 parts by mass, and more preferably 0.0001 to 0.01 parts by mass per part by mass of the diimino compound represented by formula (a2).

[0049] This reaction can usually be carried out within a temperature range of from -78°C to the boiling point of the solvent used, but is usually carried out at about -10 to 50°C, preferably around room temperature. The reaction time varies depending on the reaction temperature and the like, and cannot be generalized, but the reaction is usually completed within about 0.5 to 24 hours. This reaction is carried out under a hydrogen atmosphere, and the pressure is usually from atmospheric pressure to 10 MPa, preferably from atmospheric pressure to 1.0 MPa, and more preferably around atmospheric pressure.

[0050] Here, the diamide compound represented by formula (a1) can be produced by a method such as the following reaction scheme-3. [ka] [In the formula, R 11 , R 12and A 1 is the same as above. X represents a halogen atom or an alkoxy group having 1 to 4 carbon atoms.

[0051] According to Reaction Scheme-3, an aniline compound represented by formula (a3) ​​is reacted with an acid derivative represented by formula (a4) to produce an amide compound represented by formula (a5), and then an aniline compound represented by formula (a6) is reacted in the same manner to produce a diamide compound represented by formula (a1). For the amidation in each of these reactions, known reactions for producing an amide by reacting a carboxylic acid ester or an acid halide with an amine can be applied. In this embodiment, the substituent R 11 and R 12 When these are the same, the aniline compound represented by formula (a3) ​​can be used in an amount of 2 or more equivalents relative to the acid derivative represented by formula (a4) to produce the diamide compound represented by formula (a1) in a one-step reaction.

[0052] The diimino compound represented by formula (a2) can be produced by a method such as the following reaction scheme-4. [ka] [In the formula, R 11 , R 12 , R 13 , R 14 and A 12 is the same as above.]

[0053] According to Reaction Scheme-4, an imino compound represented by formula (a8) is produced by reacting a dicarbonyl compound represented by formula (a7) with an aniline compound represented by formula (a3), and then an aniline compound represented by formula (a6) is reacted in the same manner to produce a diimino compound represented by formula (a2). For the imination in each of these reactions, known reactions for producing imines from amines and carbonyls can be applied. In this embodiment, the substituent R 11 and R 12When these are the same, the aniline compound represented by formula (a3) ​​can be used in an amount of 2 or more equivalents relative to the dicarbonyl compound represented by formula (a7) to produce the diimino compound represented by formula (a2) in a one-step reaction.

[0054] Furthermore, the amine antioxidant (A) represented by formula (1) can be directly produced by reacting a dicarbonyl compound represented by formula (a7) with two or more equivalents of an aniline compound represented by formula (a3) ​​in the presence of a reducing agent or a metal catalyst through catalytic hydrogen reduction to carry out a reductive amination reaction.

[0055] As the solvent to be used in the reductive amination reaction using a reducing agent, a wide variety of known solvents can be used as long as they are inert to the reaction, and examples thereof include ether solvents such as dimethyl ether, diethyl ether, diisopropyl ether, t-butyl methyl ether, tetrahydrofuran, dioxane, tetrahydropyran, 1,2-dimethoxyethane, etc., halogen-based solvents such as dichloromethane, carbon tetrachloride, etc., and particularly for boron hydride-based reducing agents, alcohol-based solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, n-butanol, etc. These solvents can be used alone or in combination of two or more as needed. These solvents may be used in an amount of usually about 1 to 500 parts by mass, and preferably about 5 to 100 parts by mass, per part by mass of the dicarbonyl compound represented by formula (a7).

[0056] The reducing agent used may be a borohydride such as sodium borohydride, lithium borohydride, sodium cyanoborohydride or lithium triethylborohydride, or lithium aluminum hydride. Such a reducing agent may be used in an amount of usually 0.5 to 10.0 equivalents, preferably 0.5 to 2.0 equivalents, more preferably 0.5 to 1.0 equivalents relative to the dicarbonyl compound represented by formula (a7).

[0057] As the solvent to be used in the catalytic hydrogen reduction reaction, a wide variety of known solvents can be used as long as they are inert to the reaction, and examples thereof include alcoholic solvents such as methanol, ethanol, n-propanol, isopropyl alcohol, and n-butanol, organic acids such as acetic acid and propionic acid, hydrocarbon solvents such as cyclohexane, and ether solvents such as tetrahydrofuran. These solvents can be used alone or in combination of two or more as needed. These solvents may be used in an amount of usually about 1 to 500 parts by mass, and preferably about 1 to 20 parts by mass, per part by mass of the diimino compound represented by formula (a2).

[0058] Examples of the metal catalyst used in the catalytic hydrogen reduction reaction include palladium carbon, platinum black (platinum carbon), platinum sulfur carbon, platinum oxide, Raney nickel, and Raney cobalt. Such a metal catalyst may be used in an amount of usually 0.0001 to 0.5 parts by mass, preferably 0.0001 to 0.1 parts by mass, and more preferably 0.0001 to 0.01 parts by mass per part by mass of the diimino compound represented by formula (a2).

[0059] This reaction can usually be carried out within a temperature range of from -78°C to the boiling point of the solvent used, but is usually carried out at about -10 to 50°C, preferably around room temperature. This reaction is carried out under a hydrogen atmosphere, and the pressure is usually from atmospheric pressure to 10 MPa, preferably from atmospheric pressure to 1.0 MPa, and more preferably around atmospheric pressure. The reaction time varies depending on the reaction temperature and the like, and cannot be generalized, but the reaction is usually completed within about 0.5 to 24 hours.

[0060] The content of the amine-based antiaging agent (A) represented by the formula (1) is preferably 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component. When the content of the amine-based antiaging agent (A) represented by the formula (1) is 0.2 parts by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition can be sufficiently improved and discoloration of the surface of the rubber product can be effectively suppressed. On the other hand, when the content of the amine-based antiaging agent (A) represented by the formula (1) is 10 parts by mass or less per 100 parts by mass of the rubber component, the consumption of the amine-based antiaging agent (A) represented by the formula (1) as an antiaging agent can be reduced while sufficiently improving the ozone resistance and suppressing discoloration, which is advantageous in terms of raw material costs for the rubber composition. From the same viewpoint, the content of the amine-based antiaging agent (A) represented by the formula (1) per 100 parts by mass of the rubber component is more preferably 0.5 parts by mass or more and more preferably 7.5 parts by mass or less.

[0061] -Amine-based antioxidant (B) of formula (2)- The antioxidant is represented by the following general formula (2): [ka] [In the formula, R 21 and R 22 are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R 21 and R 22 wherein at least one of them is an alkyl group having 7 or more carbon atoms. The amine-based antioxidant (B) represented by general formula (2) is a phenylenediamine-based antioxidant. The amine-based antioxidant (B) represented by general formula (2) has the effect of improving the ozone resistance of the rubber composition and can suppress the occurrence of cracks in rubber products to which the rubber composition is applied.

[0062] In the above general formula (2), R 21 and R 22 are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R 21 and R 22At least one of the groups is an alkyl group having 7 or more carbon atoms. Examples of the alkyl group having 7 or more carbon atoms include a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, a 1-methylhexyl group, a 2-methylhexyl group, an n-heptyl group, a 1,2-dimethylhexyl group, a 1,3-dimethylhexyl group, a 1,4-dimethylhexyl group, a 1,5-dimethylhexyl group, a 2,3-dimethylhexyl group, a 2,4-dimethylhexyl group, a 2,5-dimethylhexyl group, a 3,4-dimethylhexyl group, a 3,5-dimethylhexyl group, a 1-methylheptyl group, a 2-methylheptyl group, an n-octyl group, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group and a 1-methylheptyl group are preferred. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a cumenyl group, a mesyl group, an α-naphthyl group, a β-naphthyl group, an ethylphenyl group, an n-propylphenyl group, an isopropylphenyl group, an n-butylphenyl group, a t-butylphenyl group, various dimethylphenyl groups, various diethylphenyl groups, various methylethylphenyl groups, various trimethylphenyl groups, various dimethylethylphenyl groups, various methyldiethylphenyl groups, and various triethylphenyl groups, and among these, a phenyl group is preferred.

[0063] R in the above general formula (2) 21 and R 22 At least one of R is an alkyl group having 7 or more carbon atoms. 21 and R 22 The other of R is preferably a phenyl group. 21 and R 22 one of the groups is an alkyl group having 7 or more carbon atoms, and R 21 and R 22 The amine-based antioxidant (B), in which the other radical is a phenyl group, can further improve the ozone resistance of the rubber composition and can further suppress the occurrence of cracks in rubber products to which the rubber composition is applied.

[0064] R in the above general formula (2) 21 and R 22 At least one of R preferably has 7 or 8 carbon atoms. 21 and R 22 The amine-based antioxidant (B), at least one of which has 7 or 8 carbon atoms, can further improve the ozone resistance of the rubber composition and can further suppress the occurrence of cracks in rubber products to which the rubber composition is applied.

[0065] Specific examples of the amine-based antiaging agent (B) represented by the above general formula (2) include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine (8PPD), N-phenyl-N'-(1,4-dimethylpentyl)-p-phenylenediamine (7PPD), etc. These amine-based antiaging agents (B) may be used alone or in combination of two or more.

[0066] The content of the amine-based antioxidant (B) represented by the formula (2) is preferably 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component. When the content of the amine-based antioxidant (B) represented by the formula (2) is 0.2 parts by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition can be sufficiently improved. On the other hand, when the content of the amine-based antioxidant (B) represented by the formula (2) is 10 parts by mass or less per 100 parts by mass of the rubber component, the consumption of the amine-based antioxidant (B) represented by the formula (2) as an antioxidant can be reduced while sufficiently improving the ozone resistance, which is advantageous in terms of raw material costs for the rubber composition. From the same viewpoint, the content of the amine-based antioxidant (B) represented by the formula (2) per 100 parts by mass of the rubber component is more preferably 0.5 parts by mass or more and more preferably 8 parts by mass or less.

[0067] The mass ratio (A / B) of the amine-based antiaging agent (A) to the amine-based antiaging agent (B) is preferably 0.025 or more and 40 or less. Within this range, a better balance can be maintained between the effect of improving ozone resistance and the effect of suppressing discoloration. From the same viewpoint, the mass ratio (A / B) of the amine-based antiaging agent (A) to the amine-based antiaging agent (B) is more preferably 0.030 or more and more preferably 30 or less.

[0068] -Quinoline-based antioxidant (C)- The antioxidant preferably further contains a quinoline-based antioxidant (C). The quinoline-based antioxidant (C) is an antioxidant having a quinoline moiety or a derivative thereof (such as a dihydroquinoline moiety or a tetrahydroquinoline moiety). The quinoline-based antioxidant (C) has the effect of improving the ozone resistance of the rubber composition, and a rubber composition containing the amino-based antioxidant (A) represented by the above general formula (1), the amine-based antioxidant (B) represented by the above general formula (2), and the quinoline-based antioxidant (C) can further suppress the occurrence of cracks in rubber products.

[0069] The quinoline antioxidant (C) preferably has a dihydroquinoline moiety, more preferably a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant (C) include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and the like. The quinoline antioxidant (C) preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). The quinoline antioxidant (C) containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline is highly effective in improving the ozone resistance of the rubber composition and also has the advantage of being less likely to discolor the rubber composition. Therefore, a rubber composition containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline can further suppress the occurrence of cracks in rubber products and is less likely to discolor. Examples of the polymer of 2,2,4-trimethyl-1,2-dihydroquinoline include a dimer, trimer, and tetramer of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0070] The proportion of the quinoline-based antioxidant (C) in the antioxidant is preferably 5% by mass or more and 50% by mass or less. Within this range, ozone resistance can be further improved. From the same viewpoint, the proportion is more preferably 10% by mass or more and more preferably 40% by mass or less.

[0071] -Amine-based antioxidant (D) of formula (3)- The antioxidant may further be represented by the following general formula (3): [ka] [In the formula, R 31 and R 32 are each independently a monovalent saturated hydrocarbon group. It is preferable to include an amine-based antioxidant (D) represented by the formula (3) (excluding the amine-based antioxidant (B) represented by the formula (2) above). The amine-based antioxidant (D) represented by the formula (3) contains a phenylenediamine moiety, similar to the general-purpose antioxidant N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD), but differs from the antioxidant 6PPD in that it does not contain a double bond outside the phenylenediamine moiety. The amine-based antioxidant (D) represented by the formula (3) has the effect of improving the ozone resistance of the rubber composition.

[0072] In the above general formula (3), R 31 and R 32 R is independently a monovalent saturated hydrocarbon group. 31 and R 32 may be the same or different, but from the viewpoint of synthesis, they are preferably the same.

[0073] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 or 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, thereby increasing the anti-aging effect and further improving the ozone resistance of the rubber composition. R in the above general formula (3) 31 and R 32 From the viewpoint of further improving the ozone resistance of the rubber composition, it is preferable that each of the groups independently represents a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.

[0074] Examples of the monovalent saturated hydrocarbon group include an alkyl group and a cycloalkyl group. The alkyl group may be linear or branched, and the cycloalkyl group may further have an alkyl group or the like bonded thereto as a substituent. Examples of the alkyl group include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a 1,2-dimethylbutyl group, a 1,3-dimethylbutyl group, a 2,3-dimethylbutyl group, an n-pentyl group, an isopentyl group, a neopentyl group, a 1-methylpentyl group, a 2-methylpentyl group, a 3-methylpentyl group, a 4-methylpentyl group, a 1,2-dimethylpentyl group, a 1,3-dimethylpentyl group, a 1,4-dimethylpentyl group, a 2,3-dimethylpentyl group, a 2,4-dimethylpentyl group, a 3,4-dimethylpentyl group, an n-hexyl group, a 1-methylhexyl group, a 2-methylhexyl group, various octyl groups, various decyl groups, and various dodecyl groups. Of these, a 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, and a cyclooctyl group, and among these, a cyclohexyl group is preferred.

[0075] Specific examples of the amine-based antiaging agent (D) represented by the above general formula (3) include N,N'-dicyclohexyl-p-phenylenediamine, etc. The amine-based antiaging agent (D) represented by the above formula (3) may be used alone or in combination of two or more.

[0076] The proportion of the amine-based antioxidant (D) in the antioxidant is preferably 0.1% by mass or more and 80% by mass or less. Within this range, ozone resistance can be further improved. From the same viewpoint, the proportion is more preferably 1% by mass or more and more preferably 70% by mass or less.

[0077] -Other antioxidants (E)- The antioxidant may or may not contain an antioxidant (E) other than the amine-based antioxidant (A) of formula (1), the amine-based antioxidant (B) of formula (2), the quinoline-based antioxidant (C), and the amine-based antioxidant (D) of formula (3). Examples of the other antioxidant (E) include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and N,N'-diphenyl-p-phenylenediamine (DPPD). Commercially available antioxidants can be used, including those from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., and Flexis. These other antioxidants (E) may be used alone or in combination. However, in this embodiment, it is preferable that the antioxidant does not contain N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) among these. The content of the other antioxidant (E) in the antioxidant is preferably 0 to 20% by mass, more preferably 0 to 10% by mass.

[0078] (Other ingredients) The rubber composition of the present invention may contain carbon black, silica, or the like as a reinforcing filler. Any commercially available silica may be used, with wet silica, dry silica, or colloidal silica being preferred, and wet silica being more preferred. The amount of reinforcing filler compounded is preferably 5 to 200 parts by mass per 100 parts by mass of the rubber component. When silica is used as a reinforcing filler, the amount of silane coupling agent added is preferably about 1 to 20% by mass relative to the silica from the viewpoint of reinforcing properties, and more preferably 6 to 12% by mass from the viewpoint of heat buildup.

[0079] -Carbon black- Carbon black can reinforce a rubber composition and improve the abrasion resistance of the rubber composition. As the carbon black, plant-derived carbon black and recycled carbon black (also called "recycled carbon black") are preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Recycled carbon black will be described in detail below.

[0080] The content of carbon black (total of recycled carbon black and carbon black other than recycled carbon black) in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, from the viewpoint of further improving the abrasion resistance of the rubber composition and rubber products such as tires to which the rubber composition is applied. Also, from the viewpoint of workability of the rubber composition, the content of carbon black in the rubber composition is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of the rubber component.

[0081] --Recycled Carbon Black-- As used herein, "recycled carbon black" refers to carbon black recovered from recycled waste materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only waste generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process of scraping the tread portion remaining on the base tire during tire retreading, for example. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as waste tires generated when tires are replaced or scrapped, or ELT (End-of-Life Tires) that have reached the end of their lifespan as tires. Waste oil is not limited to oil generated when plastics or rubber are decomposed, but may also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are preferred. Furthermore, waste oils containing carbon black or rubber containing carbon black are preferred. "Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., non-recycled carbon black. Note that "used" here does not only include carbon black that has been discarded after actual use, but also carbon black that has been manufactured but discarded without actually being used.

[0082] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black is preferably obtained from the solid residue produced by pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from volatile components, it is possible to recover an oil fraction with a specific gravity suitable for carbon black production and use it to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixing of different grades. Furthermore, in the production of carbon black with a low environmental impact, various options are available, including oil obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oil and oil derived from waste plastics. However, edible resources such as vegetable oils are in demand for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, because oil derived from waste plastics is also used for other purposes, such as horizontal plastic recycling, supply issues remain. On the other hand, when using volatile components (oils) produced by the thermal decomposition of vulcanized rubber products, especially tires, the tire industry has a system in place to continue using existing materials, making it possible to continue using existing materials and reduce the consumption of new materials in new tire production, thereby contributing to a reduction in the environmental impact of the industry.The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0083] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. Therefore, recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for rubber products such as tires manufactured using recycled carbon black, the higher the carbon content of the recycled carbon black, the better. The carbon content of the recycled carbon black is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. Furthermore, the carbon content of the recycled carbon black is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0084] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residue obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0085] The recycled carbon black can also be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

[0027] ). Carbon black obtained from such pyrolysis processes typically lacks functional groups on its surface, as mentioned in paragraph

[0004] of Japanese Patent Publication No. 6856781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercially Available Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0086] The recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also encompasses these carbon blacks that have been treated to include functional groups on their surfaces.

[0087] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0088] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be carried out for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be carried out for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be carried out for each group. When the decomposition step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0089] Furthermore, when the crosslinked rubber product used in the degradation is derived from tires, the tires may be grouped in advance by tire type (e.g., tires for passenger cars, trucks, buses, large vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.), and the degradation step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the degradation step may be carried out for each group. Furthermore, the tires may be grouped both by tire type and by tire component, and the degradation step may be carried out for each group. When the degradation step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0090] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m by the BET method. 2 / g, and 50 to 90m 2 / g, and more preferably 55 to 75m 2 / g is particularly preferred. In this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black measured by the BET method is the statistical thickness specific surface area (STSA), which is determined in accordance with ASTM D6556.

[0091] The regenerated carbon black preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Herein, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0092] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. In this specification, the toluene color transmission of recycled carbon black is determined in accordance with ASTM D1618.

[0093] The heat loss of the recycled carbon black at 125° C. is preferably 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0094] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0095] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. In this specification, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0096] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. In this specification, the 325 mesh (44 μm) sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0097] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0098] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. In this specification, the amount of pellet fines of recycled carbon black is determined in accordance with ASTM D1508.

[0099] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. In this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming that the refractive index of water is 1.33 and the refractive index of the filler is 1.75.

[0100] The recycled carbon black preferably contains particles of 5 μm or less in volume percentage of 50% or more, more preferably 70% or more, and particularly preferably 80% or more.

[0101] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of rubber products using the rubber composition can be improved. In this specification, the ash content of recycled carbon black is determined in accordance with ASTM D8474-D1506.

[0102] The regenerated carbon black preferably has a dibutyl phthalate (DBP) absorption of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Herein, the DBP absorption of recycled carbon black is determined in accordance with ASTM D2414.

[0103] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption of recycled carbon black is determined in accordance with ASTM D3493.

[0104] Commercially available recycled carbon black can be used. For example, Enrestec's product "PB365" is a recycled carbon black produced by pyrolysis of used tires. PB365 has a nitrogen adsorption specific surface area of ​​73.6 m2 as measured by the BET method. 2 / g and contains approximately 17% by mass of ash.

[0105] The content of the recycled carbon black is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, even more preferably 5 to 50 parts by mass, still more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component. When the content of recycled carbon black is 5 parts by mass or more per 100 parts by mass of the rubber component, the effect of improving the proportion of sustainable materials in rubber products to which the rubber composition is applied is significant, and when the content is 50 parts by mass or less, the fracture resistance of the rubber composition can be more reliably maintained.

[0106] The rubber composition of the present invention may further contain compounding agents commonly used in the rubber industry, such as vulcanizing agents, vulcanization accelerators, scorch inhibitors, softeners, zinc oxide, and stearic acid, selected and blended as appropriate within the scope of the present invention. Commercially available compounds may be used as these compounding agents. The rubber composition may be produced by kneading, heating, extruding, or the like, the rubber component, the various antioxidants described above, and various compounding agents selected as appropriate as necessary.

[0107] (Uses of rubber compositions) The rubber composition of the present embodiment can be applied to various rubber products such as tires, rubber crawlers, seismic isolation rubber, etc. Among these rubber products, the rubber composition of the present embodiment is suitable for tires, and more particularly suitable for tire treads or sidewalls that are exposed to the outer surface, and particularly suitable for tire treads. By using the rubber composition of the present embodiment in the tread and / or sidewall of a tire, it is possible to suppress the occurrence of cracks on the tire surface and also to suppress discoloration of the tire surface.

[0108] <Rubber products> A rubber product of one embodiment of the present invention (hereinafter sometimes referred to as "the rubber product of this embodiment") is a rubber product selected from the group consisting of tires, rubber crawlers, and seismic isolation rubber, and is characterized by including the above-mentioned rubber composition. The rubber product of the present embodiment contains the above-described rubber composition, and therefore has high ozone resistance and is inhibited from discoloring the surface.

[0109] (tire) When the rubber product of the present embodiment is a tire, the application portion of the tire to the above-described rubber composition is not particularly limited and can be appropriately selected depending on the purpose. Examples include the tread, base tread, sidewall, side reinforcing rubber, bead filler, etc., and among these, the tread and sidewall are preferred, and the tread is more preferred. The tire can be manufactured by a conventional method. For example, components typically used in tire manufacturing, such as a carcass layer, a belt layer, and a tread layer, each composed of an unvulcanized rubber composition and / or cords, are laminated on a tire-building drum in this order, and the drum is removed to form a green tire. The green tire is then heated and vulcanized in a conventional manner to manufacture a desired tire (e.g., a pneumatic tire).

[0110] (rubber track) In one embodiment, when the rubber product of this embodiment is a rubber crawler, the rubber crawler includes steel cords, an intermediate rubber layer covering the steel cords, a core bar disposed on the intermediate rubber layer, and a main rubber layer surrounding the intermediate rubber layer and the core bar, and further includes a plurality of lugs on the contact surface side of the main rubber layer. Here, the above-mentioned rubber composition may be used in any part of the rubber crawler, but is preferably used in the main rubber layer, particularly the lugs.

[0111] (Seismic isolation rubber) When the rubber product of the present embodiment is a seismic isolation rubber, in one embodiment, the seismic isolation rubber includes a laminate in which soft layers and hard layers are alternately laminated, and a plug press-fitted into a hollow portion formed in the center of the laminate. In one embodiment, the above-mentioned rubber composition can be used for at least one of the soft layer and the plug. [Industrial Applicability]

[0112] According to the present invention, it is possible to provide a rubber composition that has a low environmental impact, is more ozone resistant than conventional rubber compositions, and is capable of suppressing discoloration of the surface of rubber products. Furthermore, according to the present invention, it is possible to provide a rubber product that has high ozone resistance and is inhibited from discoloring on the surface.

Claims

1. Contains a rubber component and an antioxidant, The antioxidant is represented by the following general formula (1): 【Chemistry 1】 [In the formula, R １１ and R １２ represents a phenyl group, and m represents an integer of 7 or more. The following general formula (2): 【Chemistry 2】 [In the formula, R ２１ and R ２２ are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and R ２１ and R ２２ and an amine-based antioxidant (B) represented by the following formula: wherein at least one of the groups is an alkyl group having 7 or more carbon atoms.

2. The rubber composition according to claim 1, wherein the amount of the amine-based antioxidant (A) is 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

3. The rubber composition according to claim 1, wherein the amount of the amine-based antioxidant (B) is 0.2 parts by mass or more and 10 parts by mass or less per 100 parts by mass of the rubber component.

4. The rubber composition according to claim 1, wherein a mass ratio (A / B) of the amine-based antioxidant (A) to the amine-based antioxidant (B) is 0.025 or more and 40 or less.

5. The rubber composition of claim 1 , wherein the rubber component comprises natural rubber.

6. The rubber composition according to claim 5, wherein the rubber component further contains at least one of a butadiene rubber and a styrene-butadiene rubber.

7. R in the general formula (2) ２１ and R ２２ The rubber composition according to claim 1 , wherein the other of the groups is a phenyl group.

8. R in the general formula (2) ２１ and R ２２ The rubber composition according to claim 1, wherein at least one of the above has 7 or 8 carbon atoms.

9. the antioxidant further contains a quinoline-based antioxidant (C), The rubber composition according to claim 1, wherein a proportion of the quinoline-based antioxidant (C) in the antioxidant is 5% by mass or more and 50% by mass or less.

10. The antioxidant may further comprise a compound represented by the following general formula (3): 【Transformation 3】 [In the formula, R ３１ and R ３２ are each independently a monovalent saturated hydrocarbon group.] (excluding the amine-based antioxidant (B) represented by the general formula (2) above), The rubber composition according to claim 1, wherein a proportion of the amine-based antioxidant (D) in the antioxidant is 0.1% by mass or more and 80% by mass or less.

11. The rubber composition according to claim 1, which is used for a tire tread.

12. A rubber product selected from the group consisting of tires, rubber crawlers, and seismic isolation rubber, characterized in that it comprises the rubber composition according to claim 1.

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