Tire rubber composition and tire

Abstract

The present invention addresses the problem of providing a tire rubber composition which can suppress the occurrence of cracks and which can increase the proportion of sustainable materials in a tire while maintaining high-temperature tensile strength following degradation and crack propagation resistance following thermal degradation. A means for solving this problem is a tire rubber composition characterized by containing a rubber component (A), a recycled carbon black (B), and an anti-aging agent (C), wherein: the recycled carbon black (B) is such that three or more lines (3) having lengths of 10 mm or more are observed when measurements are carried out using a grind gauge (1), and the particle size of the third largest particle among particles that bring about said lines (3) having lengths of 10 mm or more is 20 µm or less; and the anti-aging agent (C) includes at least one selected from the group consisting of phenylenediamine-based anti-aging agents (C1) having a specific structure and triphenylamine-based anti-aging agents (C2) having a specific structure.

Description

Rubber composition for tires, and tires

[0001] This invention relates to a rubber composition for tires and to tires.

[0002] Generally, the various rubber components that make up a tire can deteriorate under the influence of external environmental conditions such as the presence of ozone, and as this deterioration progresses, cracks and other problems may occur. To address this problem, rubber compositions containing antioxidants are often applied to the various rubber components that make up a tire. For example, Patent Document 1 below discloses that by applying a rubber composition containing a specific quinoline-based antioxidant and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD) to the rubber that makes up the surface of the tire, cracks and discoloration of the tire surface can be suppressed.

[0003] Furthermore, various rubber compositions are used for the various rubber components that make up a tire. In order to ensure the strength of the tire, carbon black is usually added as a reinforcing filler to the rubber composition that serves as its raw material.

[0004] On the other hand, in recent years, from the perspective of social sustainability, there has been a demand for the use of so-called sustainable materials in tires, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources. Therefore, there is a need to increase the proportion of sustainable materials in the rubber compositions applied to these tires. For example, recycled carbon black is known as a material derived from recycled resources (see Patent Document 2 below).

[0005] International Publication No. 2018 / 056384, European Patent Application Publication No. 3427975, Specification

[0006] However, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (anti-aging agent 6PPD) used in the above-mentioned Patent Document 1 may have environmental impacts, and it is desirable to use an anti-aging agent that has a lower environmental impact, including the possibility of future regulations under European laws. On the other hand, it is conceivable to not use or nearly not use the anti-aging agent 6PPD in the rubber that constitutes the surface of the tire, but the inventors have investigated and found that if the anti-aging agent 6PPD is not used or nearly not used, cracks are more likely to occur in the rubber that constitutes the surface of the tire.

[0007] Furthermore, when the inventors investigated the application of recycled carbon black as a reinforcing filler instead of unused carbon black in order to improve the proportion of sustainable materials in tires, they found that the high-temperature tensile strength and crack propagation resistance after thermal degradation of the rubber composition decreased.

[0008] Therefore, the object of the present invention is to provide a rubber composition for tires that can suppress the occurrence of cracks, maintain high-temperature tensile strength and crack propagation resistance after deterioration and after thermal deterioration, and improve the proportion of sustainable materials in the tire. Furthermore, the object of the present invention is to provide a tire in which the occurrence of cracks is suppressed, durability is maintained, and the proportion of sustainable materials is improved.

[0009] The basic structure of the rubber composition for tires and the tire of the present invention, which solves the above problems, is as follows.

[0010] [1] The material comprises a rubber component (A), recycled carbon black (B), and an anti-aging agent (C), wherein the recycled carbon black (B) is such that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that produce such lines with a length of 10 mm or more is 20 μm or less, and the anti-aging agent (C) is the following general formula (1): [In the formula, R １１ and R １２ Each is independently an alkyl group or aryl group having 7 or more carbon atoms, and R１１ and R １２ At least one of them is an alkyl group having 7 or more carbon atoms. ] The phenylenediamine-based antioxidant (C1) represented by, and the following general formula (2) or general formula (3): [In the formula, R ２１ , R ２２ and R ２３ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms. ] [In the formula, R ３１ and R ３２ each independently represents a linear or branched alkyl group having 1 to 12 carbon atoms or a cycloalkyl group having 5 to 8 carbon atoms. ] A tire rubber composition characterized by containing at least one selected from the group consisting of triphenylamine-based antioxidants (C2) represented by

[0011] [2] In the measurement of the grind gauge of the recycled carbon black (B), a paste of the recycled carbon black (B) is prepared as a measurement sample according to JIS K5101-1-5. The tire rubber composition according to [1].

[0012] [3] In the measurement of the grind gauge of the recycled carbon black (B), as a measurement sample, according to JIS K5101-1-5, the applied load is set to 0.4 to 0.5 kN and the rotation speed of the glass plate is set to 90 to 110 r / min, and a paste of the recycled carbon black (B) is prepared. The tire rubber composition according to [1] or [2].

[0013] [4] The recycled carbon black (B) contains one or more metal atoms selected from the group consisting of Zn, Cu, and Fe. The tire rubber composition according to any one of [1] to [3].

[0014] [5] The recycled carbon black (B) contains Zn. The tire rubber composition according to any one of [1] to [4].<00​​

[0016] [7] The tire rubber composition according to any one of [1] to [6], wherein the recycled carbon black (B) has an ash content of 20% by mass or less.

[0017] [8] The tire rubber composition according to any one of [1] to [7], wherein the anti-aging agent (C) further comprises a quinoline-based anti-aging agent (C3).

[0018] [9] The tire rubber composition according to [8], wherein the proportion of the quinoline-based antioxidant (C3) in the antioxidant (C) is 5 to 50% by mass.

[0019]

[10] The tire rubber composition according to any one of [1] to [9], wherein the content of the anti-aging agent (C) is 0.05 to 50 parts by mass per 100 parts by mass of the rubber component (A).

[0020]

[11] R in the general formula (1) １１ and R １２ The other of the two is a phenyl group, the tire rubber composition according to any one of [1] to

[10] .

[0021]

[12] R in the general formula (1) １１ and R １２ A tire rubber composition according to any one of [1] to

[11] , wherein at least one of the members has 7 or 8 carbon atoms.

[0022]

[13] The anti-aging agent (C) further comprises the following general formula (4): [In the formula, R ４１ and R ４２ Each of the above is an independently monovalent saturated hydrocarbon group. The tire rubber composition according to any one of [1] to

[12] , comprising an amine-based antioxidant (C4) represented by [ ] (excluding the phenylenediamine-based antioxidant (C1) represented by the above general formula (1)), wherein the proportion of the amine-based antioxidant (C4) in the antioxidant (C) is 0.1 to 80% by mass.

[0023]

[14] The anti-aging agent (C) further comprises the following general formula (5): [In the formula, R ５１ and R ５２The rubber composition for tires according to any one of [1] to

[13] , wherein is a phenyl group, and m5 represents an integer of 7 or more. The composition comprises an amine-based antioxidant (C5) represented by [ ], and the proportion of the amine-based antioxidant (C5) in the antioxidant (C) is 0.1 to 80% by mass.

[0024]

[15] R in the above general formula (2) ２１ , R ２２ and R ２３ , and also R in the above general formula (3) ３１ and R ３２ The tire rubber composition according to any one of [1] to

[14] , wherein each is independently an alkyl group selected from the group consisting of an isopropyl group, a 1,3-dimethylbutyl group, and a 1,4-dimethylpentyl group.

[0025]

[16] R in the above general formula (2) ２１ , R ２２ and R ２３ , and also R in the above general formula (3) ３１ and R ３２ Each of the following is an independent tire rubber composition, wherein each has 2 to 8 carbon atoms:

[0026]

[17] A tire rubber composition according to any one of [1] to

[16] , for use in tire treads.

[0027]

[18] A tire rubber composition according to any one of [1] to

[16] , for use in tire cases.

[0028]

[19] A tire characterized by comprising any one of the tire rubber compositions described in [1] to

[18] .

[0029] According to the present invention, it is possible to provide a tire rubber composition that can suppress the occurrence of cracks, maintain high-temperature tensile strength and crack propagation resistance after thermal degradation, and improve the proportion of sustainable materials in the tire. Furthermore, according to the present invention, it is possible to provide a tire in which the occurrence of cracks is suppressed, durability is maintained, and the proportion of sustainable materials is improved.

[0030] This is an explanatory diagram illustrating an example of measurement results using a grind gauge.

[0031] The rubber composition for tires and the tire of the present invention will be described in detail below, based on embodiments thereof.

[0032] <Definitions> The compounds described herein may be derived in part or in whole from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires. They may also be derived from a mixture of two or more of fossil resources, biological resources, or recycled resources.

[0033] In this specification, "sustainable material ratio" refers to the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) in the tire rubber composition and tire in question.

[0034] In this specification, the term "biomass resources" refers to carbon-neutral organic resources of biological origin, excluding fossil resources (such as petroleum, coal, and natural gas). These biological resources may be edible or inedible, but are preferably inedible, as they do not compete with food resources and are considered to be resources that can be used effectively.

[0035] In this specification, the term "recycled resources" refers to resources obtained by recycling products that have been used, collected without being used, or discarded. For example, recycled resources include resources obtained by recycling used rubber products such as used tires.

[0036] <Tire Composition> The tire rubber composition of this embodiment comprises a rubber component (A), recycled carbon black (B), and an anti-aging agent (C). In the tire rubber composition of this embodiment, the recycled carbon black (B) is such that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that produce such lines with a length of 10 mm or more is 20 μm or less, and the anti-aging agent (C) is the following general formula (1): [In the formula, R １１ and R１２ Each is independently an alkyl group or aryl group having 7 or more carbon atoms, and R １１ and R １２ At least one of them is an alkyl group having 7 or more carbon atoms. A phenylenediamine-based antioxidant (C1) represented by the following general formula (2) or general formula (3): [In the formula, R ２１ , R ２２ and R ２３ Each of these independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. [In the formula, R ３１ and R ３２ Each of these independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. The present invention is characterized by containing at least one selected from the group consisting of triphenylamine-based antioxidants (C2) represented by [ ].

[0037] In the tire rubber composition of this embodiment, recycled carbon black (B) is a material derived from recycled resources. Therefore, by incorporating recycled carbon black (B) into the rubber composition, the proportion of sustainable materials in the tire to which the rubber composition is applied can be improved. However, when general recycled carbon black is incorporated into the rubber composition, the high-temperature tensile strength and crack propagation resistance after thermal degradation of the rubber composition decrease. In contrast, in the tire rubber composition of this embodiment, by incorporating recycled carbon black (B) in which, when measured with a grind gauge, three or more lines with a length of 10 mm or more are confirmed, and the particle size of the third largest particle among the particles that produce such lines of 10 mm or more is 20 μm or less, the high-temperature tensile strength and crack propagation resistance after thermal degradation of the rubber composition can be maintained. Furthermore, the tire rubber composition of this embodiment contains at least one selected from the group consisting of a phenylenediamine-based antioxidant (C1) represented by the above general formula (1) and a triphenylamine-based antioxidant (C2) represented by the above general formula (2) or general formula (3), thereby ensuring sufficient ozone resistance and suppressing crack formation. Accordingly, the tire rubber composition of this embodiment makes it possible to suppress crack formation, maintain high-temperature tensile strength after degradation and crack propagation resistance after thermal degradation, and improve the proportion of sustainable materials in the tire.

[0038] "Rubber component (A)" The tire rubber composition of this embodiment contains rubber component (A), which provides rubber elasticity to the composition. The sustainability rate of rubber component (A) is preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of rubber component (A) is the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources in rubber component (A).

[0039] The rubber component (A) is preferably the rubber derived from biological resources and the rubber derived from recycled resources. Here, the proportion of the monomer component derived from biological resources in 100 mol% of the monomer component constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%. Furthermore, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer component constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may also be 100 mol%.

[0040] The rubber component (A) is a component that contributes to crosslinking, and typically has a weight-average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 5,000,000 or less, more preferably 2,000,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight (Mw) of the rubber component (A) can be determined, for example, by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC).

[0041] The rubber component (A) is preferably a diene-based rubber, and isoprene-based rubber and butadiene-based rubber are preferred as the diene-based rubber.

[0042] Examples of isoprene-based rubbers include natural rubber and synthetic isoprene rubber. The origin of natural rubber is not particularly limited; for example, it may be derived from the Para rubber tree, guayule, or Russian dandelion. Natural rubber may be modified or altered, and synthetic isoprene rubber may also be altered. These isoprene-based rubbers may be used individually or in combination of two or more. Natural rubber is preferred as the isoprene-based rubber.

[0043] Examples of the butadiene-based rubber include butadiene rubber and styrene-butadiene rubber. Here, it is preferable that the butadiene used as a raw material for the butadiene-based rubber is derived from biological resources or recycled resources.

[0044] Examples of the styrene-butadiene rubber include emulsion-polymerized styrene-butadiene rubber and solution-polymerized styrene-butadiene rubber.

[0045] The isoprene-based rubber and the butadiene-based rubber preferably have a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0046] Furthermore, in order to ensure that the overall sustainability rate of the rubber component (A) is within the aforementioned range, it is preferable to use natural rubber as the rubber component (A), or to use a polymer synthesized using monomer components derived from biological resources or recycled resources. It is also possible to use mass balance certified synthetic rubber to ensure that the sustainability rate is within the aforementioned range.

[0047] The ratio of each monomer unit (for example, units derived from isoprene, units derived from butadiene, and units derived from aromatic vinyl compounds) in the entire rubber component (A) can be appropriately adjusted depending on the member to which it is applied. The ratio of each monomer unit in the entire rubber component (A) can be adjusted, for example, by appropriately combining the isoprene-based rubber and butadiene-based rubber described above. The ratio of cis-bonded units in the butadiene-derived units can also be appropriately adjusted depending on the member to which it is applied. In this specification, "monomer unit" means a constituent unit of a polymer, "unit derived from isoprene" means a constituent unit in a polymer composed of isoprene, which is a monomer (including isoprene units in natural rubber), "unit derived from butadiene" means a constituent unit in a polymer composed of butadiene, which is a monomer, and "unit derived from aromatic vinyl compounds" means a constituent unit in a polymer composed of aromatic vinyl compounds, which are monomers. In this specification, the ratio of each monomer unit is measured by NMR.

[0048] The rubber component (A) may include, in addition to the isoprene-based rubber, butadiene rubber, and styrene-butadiene rubber mentioned above, diene-based rubbers such as acrylonitrile-butadiene rubber, chloroprene rubber, butyl rubber, and styrene-isoprene-butadiene copolymer rubber. These rubber components may be used individually or in combination of two or more.

[0049] The rubber component (A) may have functional groups that interact with fillers such as carbon black and silica introduced through modification. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups. These functional groups may also have substituents. These functional groups may be introduced into the rubber component individually or in combination of two or more. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred, and substituted amino groups in which the hydrogen atoms of the amino group are replaced by alkyl groups having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and alkoxysilyl groups having 1 to 6 carbon atoms are even more preferred.

[0050] The functional group can be introduced, for example, by reacting a compound having the functional group (modifier) ​​with the rubber component. The functional group is a modifying functional group that interacts with fillers such as silica and carbon black, and examples include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups. Examples of compounds having nitrogen-containing functional groups (modifiers) include amino group-containing compounds, examples of compounds having silicon-containing functional groups (modifiers) include silicon halides and hydrocarbyloxysilane compounds, and examples of compounds having oxygen-containing functional groups (modifiers) include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples include compounds described in International Publication No. 2016 / 194316 and International Publication No. 2019 / 117256. These modifiers may be used individually or in combination of two or more.

[0051] The aforementioned rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be manufactured, for example, using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources, in the same manner as conventional methods for manufacturing synthetic rubber derived from fossil resources.

[0052] For example, the method described in Japanese Patent Publication No. 2022-179158 can be used to prepare rubber derived from biological resources.

[0053] As the butadiene obtained from the aforementioned biological resources, butadiene derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadiene derived from alkenes (preferably ethylene), and butadiene derived from unsaturated carboxylic acids (preferably tigric acid) can be suitably used.

[0054] "Recycled Carbon Black (B)" The tire rubber composition of this embodiment contains recycled carbon black (B). Since recycled carbon black (B) is a material derived from recycled resources, by incorporating recycled carbon black (B) into the rubber composition, the proportion of sustainable materials in the tire to which the rubber composition is applied can be improved.

[0055] In this specification, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials submitted for recycling. Examples of such waste materials include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only rubber generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeling rubber. Buffing powder is fine rubber generated, for example, in the buffing process of retreading tires, where the tread portion remaining on the base tire is scraped off. Peeling rubber is long pieces of rubber, for example, 1 to 2 cm wide, that are peeled off from the surface of rubber products such as tires. Peeling rubber is generated by scraping the surface of rubber products such as tires using a U-shaped or V-shaped knife like a peeler. Furthermore, waste rubber includes not only cross-linked rubber but also unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, and rubber parts or components at the manufacturing stage of final products. Used tires may include, for example, those that have been retreaded, as well as tires that have been discarded for any reason, such as those resulting from tire replacement or vehicle scrapping, and End-of-Life Tires (ELTs) that have reached the end of their lifespan. Waste oil is not limited to that generated when plastics and rubber are decomposed, but also includes used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oil that does not contain any composition other than organic matter, such as those derived from silicone rubber or polyvinyl chloride, is desirable. Furthermore, waste oil that is mixed with carbon black or rubber containing carbon black is desirable. "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., carbon black that is not recycled. Note that "used" here includes not only those that have been discarded after being actually used, but also those that were manufactured but discarded without actually being used.

[0056] Furthermore, it is preferable that the recycled carbon black (B) is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by thermal decomposition of a vulcanized rubber product containing carbon black is readily available because a large amount of vulcanized rubber product containing carbon black exists and it can be easily obtained by thermal decomposition. Moreover, it is preferable that the recycled carbon black (B) is obtained from the solid residue generated by the thermal decomposition of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is thermally decomposed, solid residue and volatile components (oil) are obtained, and recycled carbon black (B) can be recovered from either. When recovering carbon black from volatile components, it is possible to recover oil with a specific gravity suitable for producing carbon black and use it to produce carbon black using an existing carbon black production method (for example, Japanese Patent Publication No. 2015-520259). In this case, unlike carbon black recovered from solid residue, there are advantages such as the absence of impurities and the absence of mixtures of different grades. Furthermore, in the production of environmentally friendly carbon black, there are various options besides the oil obtained by recovering volatile components from the thermal decomposition of rubber mentioned above, such as using vegetable oil or oil derived from waste plastics. However, edible resources such as vegetable oil present challenges in securing sufficient quantities due to other uses such as food, and the environmental impact associated with the expansion of cultivated land must also be considered. Similarly, oil derived from waste plastics is used for other purposes such as horizontal recycling of plastics, so supply issues are also a concern. On the other hand, when using volatile components (oil) produced by the thermal decomposition of vulcanized rubber products, particularly tires, the tire industry has a system for continuing to use existing materials, making it possible to continue using existing materials and reduce the consumption of new materials in new tire manufacturing, thereby contributing to reducing the environmental burden on the industry. The grade of carbon black is not particularly limited, but examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0057] The solid residue obtained by thermally decomposing waste materials such as used rubber and used tires contains ash in addition to carbon black. The ash originates from non-volatile components contained in rubber and tires. Therefore, the recycled carbon black obtained from this solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, a higher carbon content in recycled carbon black (B) is preferable. In the recycled carbon black (B), the carbon content 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 in the recycled carbon black (B) is preferably 97% by mass or less. Note that the carbon content does not include adsorbed water.

[0058] The aforementioned ash content specifically includes zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from solid residue obtained by thermal decomposition of waste, a certain amount of ash remains even after various processes to remove it. In this embodiment, the inclusion of ash in recycled carbon black (B) is permitted. In one embodiment, the lower limit of the ash content of the recycled carbon black (B) may be 0.5% by mass.

[0059] Furthermore, the recycled carbon black (B) can be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, states that it can be obtained by the 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 Surface Morphology and Chemistry of Pyrolysis Carbon Black and Commercial Carbon Black, Powder Technology 160 (2005) 190-193).

[0060] The recycled carbon black (B) may lack functional groups on its surface, or it may have been treated to include functional groups on its surface. 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. 3173251, carbon black obtained from a thermal decomposition process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl groups and / or carboxyl groups on its surface. In addition, in Japanese Patent Publication No. 6856781, carbon black obtained from a thermal decomposition process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The recycled carbon black according to this embodiment also includes carbon black treated to include functional groups on its surface.

[0061] Furthermore, for the thermal decomposition of cross-linked rubber products (vulcanized rubber products) such as used tires, one example is a thermal decomposition method at a temperature of 650°C or higher.

[0062] The cross-linked rubber products used in the aforementioned decomposition may be grouped by the type of rubber component they contain beforehand, and the decomposition process may be carried out for each group separately. Alternatively, they may be grouped by the type of filler they contain beforehand (for example, the type of carbon black, the type of silica, the mixing ratio of carbon black and silica, etc.), and the decomposition process may be carried out for each group separately. Furthermore, they may be grouped by both the type of rubber component and the type of filler, and the decomposition process may be carried out for each group separately. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again incorporated into the rubber component, a rubber composition with better performance can be obtained.

[0063] Furthermore, if the cross-linked rubber product used in the decomposition is derived from a tire, it may be grouped in advance by tire type (for example, for passenger cars, trucks and buses, heavy vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.) and then the decomposition process may be carried out for each group. Alternatively, it may be grouped in advance by tire component (for example, tread rubber, sidewall rubber, bead rubber, steel cord coated rubber, organic fiber coated rubber, pad rubber, cushion rubber, etc.) and then the decomposition process may be carried out for each group. Moreover, it may be possible to group by both tire type and tire component and then carry out the decomposition process for each group. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when it is again blended into the rubber component, a rubber composition with better performance can be obtained.

[0064] In the tire rubber composition of this embodiment, the recycled carbon black (B) is such that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that produce such lines is 20 μm or less. By incorporating recycled carbon black into the rubber composition, which is such that, when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that produce such lines is 20 μm or less, the dispersibility of the recycled carbon black in the rubber composition is improved, and the high-temperature tensile strength and crack propagation resistance after thermal degradation of the tire rubber composition can be maintained.

[0065] Methods for evaluating the dispersibility of carbon black using the aforementioned grind gauge are described in JIS K5101 (particularly regarding paste preparation) and JIS K5400 (particularly regarding evaluation methods based on the manner of linear mark formation). In evaluating recycled carbon black using a grind gauge, as described later, from the viewpoint of high-temperature tensile strength after degradation of the rubber composition and crack propagation resistance after thermal degradation, it is important whether the particle size of the third largest particle in the recycled carbon black being measured is 20 μm or less. Therefore, from the viewpoint of accurately measuring particle sizes around 20 μm and from the viewpoint of ease of measurement, it is preferable to use a grind gauge with a range of 0 to 25 μm. Note that any grind gauge with an upper limit of the range greater than 20 μm can be used, as it is possible to determine whether the particle size of the third largest particle is 20 μm or less. Furthermore, when used for other purposes (maintaining performance other than high-temperature tensile strength and crack propagation resistance after thermal degradation of rubber compositions containing recycled carbon black), the range of the grind gauge used can be appropriately selected according to the purpose.

[0066] As described above, JIS K5101-1-5 describes a method for preparing a paste of recycled carbon black as a measurement sample in grind gauge measurement. In evaluating the recycled carbon black used in the rubber composition of this embodiment, it is preferable to prepare the paste of recycled carbon black according to JIS K5101-1-5 as a measurement sample for measurement using a grind gauge. By preparing the paste of recycled carbon black according to JIS K5101-1-5, the evaluation accuracy of the recycled carbon black can be further improved. Furthermore, a rubber composition containing recycled carbon black evaluated using such a measurement sample can more reliably maintain high-temperature tensile strength after degradation and crack propagation resistance after thermal degradation. In one embodiment, the accuracy of grind gauge measurement can be further improved by appropriately adjusting the viscosity of the paste. In one embodiment, it is preferable to prepare a paste (measurement sample) containing recycled carbon black by blending recycled carbon black and zinc oxide with epoxidized soybean oil. Here, the mixing ratio of the paste is not particularly limited, but it is preferable to use about 8 to 12 g of recycled carbon black and about 160 to 200 g of zinc oxide per 100 mL of epoxidized soybean oil.

[0067] Furthermore, in the evaluation of recycled carbon black using the grind gauge, when preparing the paste of recycled carbon black in accordance with JIS K5101-1-5, it is preferable to apply a load of 0.4 to 0.5 kN and rotate the glass plate at a speed of 90 to 110 r / min, from the viewpoint of improving evaluation accuracy. A rubber composition containing recycled carbon black evaluated using a measurement sample prepared with the applied load and glass plate rotation speed within the above range can more reliably maintain high-temperature tensile strength and crack propagation resistance after thermal degradation.

[0068] Figure 1 shows an explanatory diagram of an example of measurement results using a grind gauge. In the measurement using grind gauge 1, several lines attributable to particles in the measurement sample are observed. In this embodiment, in accordance with JIS standards, lines 2 with a length of less than 10 mm are not considered, and lines 3 with a length of 10 mm or more are considered. Furthermore, among the lines 3 with a length of 10 mm or more, line 31 attributable to the largest particle and line 32 attributable to the second largest particle are judged to be abnormal values, and in this embodiment, from the viewpoint of improving measurement accuracy, attention is focused on line 33 attributable to the third largest particle. The scale 4 at the location where line 33 attributable to the third largest particle appears is read, and this reading is taken as the particle size of the third largest particle. If the particle size of the third largest particle is 20 μm or less, even if recycled carbon black is added, the decrease in the durability of the rubber composition, particularly the high-temperature tensile strength after degradation and the crack propagation resistance after thermal degradation, can be suppressed. In this specification, the measurement of recycled carbon black (B) using a grind gauge is performed by the method described in the examples.

[0069] In this embodiment, recycled carbon black in which, when measured with a grind gauge, three or more lines with a length of 10 mm or more are observed, and the particle size of the third largest particle among the particles that give rise to such lines of 10 mm or more is 20 μm or less, can be manufactured by various methods. For example, recycled carbon black with a particle size of 20 μm or less can be manufactured by further grinding the recycled carbon black produced by a general method from recycled waste by extending the grinding process for a longer time or increasing the grinding intensity.

[0070] The recycled carbon black (B) may contain one or more metal atoms selected from the group consisting of Zn, Cu, and Fe. Since recycled carbon black is obtained from recycled waste as raw material, it contains various elements other than carbon (C), and zinc (Zn), copper (Cu), and iron (Fe) are elements that are easily contained in recycled carbon black. Therefore, recycled carbon black containing at least one of the elements of Zn, Cu, and Fe does not require any special removal operations, and tire rubber compositions containing such recycled carbon black are easy to manufacture.

[0071] The recycled carbon black (B) may contain Zn (zinc). The Zn in the recycled carbon black is derived, for example, from zinc oxide used as a vulcanization aid. If the Zn content in the recycled carbon black exceeds a certain amount, the physical properties of the rubber composition will deteriorate, but if it is below a certain amount, the deterioration of the physical properties of the rubber composition can be suppressed. The Zn content in the recycled carbon black (B) is preferably 0% by mass or more and 2.5% by mass or less. A lower Zn content in the recycled carbon black is preferable, but if the Zn content is 2.5% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Zn content in recycled carbon black (B) is preferably 2.0% by mass or less, more preferably 1.5% by mass or less, even more preferably 1.0% by mass or less, still more preferably 0.5% by mass or less, even more preferably 0.4% by mass or less, even more preferably 0.3% by mass or less, particularly preferably 0.2% by mass or less, and most preferably 0.1% by mass or less. A rubber composition containing recycled carbon black with a Zn content of 1.0% by mass or less is more likely to maintain high-temperature tensile strength after deterioration and crack propagation resistance after thermal deterioration. Furthermore, the Zn content in recycled carbon black (B) may be 0.01% by mass or more, or 0.05% by mass or more. The above upper and lower limits can be combined as appropriate. Methods for adjusting the Zn content in the recycled carbon black (B) to within the above range include, for example, analyzing the amount of Zn contained in the raw rubber to be acid-treated and recycled in advance, and using some or all of the raw rubber with a low Zn content.

[0072] The recycled carbon black (B) may contain Fe (iron). The Fe is derived, for example, from the steel cords of tires. If the Fe content in the recycled carbon black exceeds a certain amount, the physical properties of the rubber composition will deteriorate, but if it is below a certain amount, the deterioration of the physical properties of the rubber composition can be suppressed. The Fe content in the recycled carbon black (B) is preferably 0% by mass or more and 0.1% by mass or less. A lower Fe content in the carbon black is preferable, but if the Fe content is 0.1% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Fe content is more preferably 0.09% by mass or less, even more preferably 0.08% by mass or less, still more preferably 0.07% by mass or less, even more preferably 0.06% by mass or less, even more preferably 0.05% by mass or less, particularly preferably 0.04% by mass or less, and most preferably 0.03% by mass or less. Furthermore, the Fe content may be 0.01% by mass or more, or 0.02% by mass or more. The upper and lower limits can be combined as appropriate. Methods for adjusting the Fe content in the recycled carbon black (B) to within the above range include, for example, pre-analyzing the amount of Fe contained in the raw rubber to be acid-treated and recycled, and using some or all of the raw rubber with a low Fe content.

[0073] The recycled carbon black (B) may contain Cu (copper). The Cu may be derived from plating such as steel cord. The Cu content in the recycled carbon black (B) is preferably 0% by mass or more and 0.05% by mass or less. A lower Cu content in the carbon black is preferable, but if the Cu content is 0.05% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed. From the viewpoint of suppressing the deterioration of the physical properties of the rubber composition, the Cu content is more preferably 0.04% by mass or less, even more preferably 0.03% by mass or less, even more preferably 0.02% by mass or less, and even more preferably 0.01% by mass or less. The Cu content may also be 0.01% by mass or more, or 0.02% by mass or more. The upper and lower limits can be combined as appropriate. Methods for adjusting the Cu content in the recycled carbon black (B) to within the above range include, for example, performing acid treatment and analyzing the amount of Cu contained in the raw rubber to be recycled in advance, and using some or all of the raw rubber with a low Cu content.

[0074] The recycled carbon black (B) may contain components other than Zn, Fe, and Cu as described above. "Components other than Zn, Fe, and Cu" refers to components other than Zn, Fe, and Cu in the ash. Examples of components other than Zn, Fe, and Cu in the ash include Si (silicon), S (sulfur), Ca (calcium), K (potassium), Br (bromine), Mg (magnesium), Cl (chlorine), P (phosphorus), Co (cobalt), Na (sodium), and Al (aluminum).

[0075] The recycled carbon black (B) may contain Si (silicon). In the recycled carbon black (B), the Si content is preferably 0% by mass or more and 1.0% by mass or less. A Si content of 1.0% by mass or less suppresses a decrease in the physical properties of the rubber composition. From a similar viewpoint, the Si content is more preferably 0.5% by mass or less, and even more preferably 0.3% by mass or less. It is also preferable that the Si content is 0% by mass, i.e., substantially Si-free. On the other hand, the Si content may be 0.01% by mass or more, or 0.05% by mass or more. The upper and lower limits can be combined as appropriate. Examples of methods for adjusting the Si content in the recycled carbon black (B) to within the above range include hydrofluoric acid treatment and base treatment.

[0076] The recycled carbon black (B) may contain sulfur (S). The S content in the recycled carbon black (B) is preferably 0.4% by mass or more, more preferably 0.5% by mass or more. Furthermore, the S content is preferably 2.0% by mass or less, more preferably 1.8% by mass or less, and even more preferably 1.0% by mass or less. The upper and lower limits can be combined as appropriate. A method for adjusting the S content in the recycled carbon black (B) to within the above ranges can be, for example, acid treatment.

[0077] The recycled carbon black (B) may contain Ca (calcium). In the recycled carbon black (B), the Ca content is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.7% by mass or more, and particularly preferably 0.8% by mass or more. Furthermore, the Ca content is preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and even more preferably 1.1% by mass or less. The upper and lower limits can be combined as appropriate. A method for adjusting the Ca content in the recycled carbon black (B) to within the above range can be, for example, acid treatment.

[0078] The recycled carbon black (B) may contain K, Br, Mg, Cl, P, Co, Na, and Al. Preferably, the content of K, Br, Mg, Cl, P, Co, Na, and Al in the recycled carbon black (B) is 0% by mass or more and 0.2% by mass or less. More preferably, the content of P, Co, Na, and Al in the recycled carbon black (B) is 0% by mass, i.e., P, Co, Na, and Al are substantially not contained in the recycled carbon black.

[0079] The recycled carbon black (B) has a nitrogen adsorption specific surface area of ​​40 to 100 m² obtained by the BET method. ２ It is preferable that the amount be / g, and 50 to 90 m ２ It is more preferable that the amount be / g, and 55 to 75 m ２ It is particularly preferable that the value be / g. Here, in this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black by the BET method is the statistical thickness specific surface area (STSA), which is determined according to ASTM D6556.

[0080] The recycled carbon black (B) preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Herein, in this specification, the pH of the recycled carbon black is determined according to ASTM D1512.

[0081] The recycled carbon black (B) preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, in this specification, the toluene color transmittance of recycled carbon black is determined according to ASTM D1618.

[0082] The recycled carbon black (B) preferably has a heating loss of 3% by mass or less at 125°C, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Here, in this specification, the heating loss of recycled carbon black at 125°C is determined according to ASTM D1509.

[0083] The recycled carbon black (B) preferably has a 35-mesh sieve residue of 20 ppm by mass or less, more preferably 15 ppm by mass or less, and particularly preferably 10 ppm by mass or less. Here, in this specification, the 35-mesh sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0084] The recycled carbon black (B) preferably has a 325-mesh (44 μm) sieve residue of 1,000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. Here, in this specification, the 325-mesh (44 μm) sieve residue of the recycled carbon black is determined according to ASTM D1514.

[0085] The recycled carbon black (B) preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Here, in this specification, the pellet hardness of the recycled carbon black is determined according to ASTM D5230.

[0086] The recycled carbon black (B) 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. Hereinafter, the pellet fine powder content of the recycled carbon black is determined according to ASTM D1508.

[0087] The recycled carbon black (B) preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Here, in this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size analyzer, with the refractive index of water being 1.33 and the refractive index of the filler being 1.75.

[0088] The recycled carbon black (B) preferably contains 50% or more by volume of particles 5 μm or smaller, more preferably 70% or more by volume, and particularly preferably 80% or more by volume.

[0089] The recycled carbon black (B) preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, even more preferably 10% by mass or less, and particularly preferably 6.0% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the various physical properties of the tire to which the rubber composition is applied can be improved. Furthermore, the recycled carbon black (B) preferably has an ash content of 20% by mass or less. A tire rubber composition containing recycled carbon black with an ash content of 20% by mass or less is more likely to maintain high-temperature tensile strength after degradation and crack propagation resistance after thermal degradation. Herein, in this specification, the ash content of recycled carbon black is determined according to ASTM D8474 / D1506.

[0090] The recycled carbon black (B) preferably has an oil absorption rate (OAN) 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, in this specification, the OAN of the recycled carbon black is determined according to ASTM D2414.

[0091] The recycled carbon black (B) preferably has an oil absorption rate (COAN) of 50 to 110 mL / 100 g of compressed sample, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Hereinafter, the COAN of the recycled carbon black is determined according to ASTM D3493.

[0092] The content of the recycled carbon black (B) 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, even 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 (A). When the content of recycled carbon black (B) is 5 parts by mass or more per 100 parts by mass of the rubber component (A), it has a great effect in improving the ratio of sustainable materials in the tire to which the rubber composition is applied, and when it is 50 parts by mass or less, the fracture resistance of the rubber composition can be maintained more reliably.

[0093] "Anti-aging agent (C)" The tire rubber composition of this embodiment contains an anti-aging agent (C), and the anti-aging agent (C) includes at least one selected from the group consisting of a phenylenediamine-based anti-aging agent (C1) represented by general formula (1) and a triphenylamine-based anti-aging agent (C2) represented by general formula (2) or general formula (3). By including at least one selected from the group consisting of a phenylenediamine-based anti-aging agent (C1) represented by general formula (1) and a triphenylamine-based anti-aging agent (C2) represented by general formula (2) or general formula (3), the tire rubber composition of this embodiment can sufficiently ensure ozone resistance and suppress the occurrence of cracks.

[0094] The content of the antioxidant (C) is preferably 0.05 to 50 parts by mass, more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 8 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the antioxidant (C) is 0.05 parts by mass or more per 100 parts by mass of the rubber component (A), sufficient ozone resistance of the rubber composition can be ensured. Furthermore, when the content of the antioxidant (C) is 50 parts by mass or less per 100 parts by mass of the rubber component (A), the adverse effects on rubber properties other than ozone resistance (such as heat generation) are reduced, making it suitable for tire applications. Therefore, a tire rubber composition in which the content of the antioxidant (C) is 0.05 to 50 parts by mass per 100 parts by mass of the rubber component (A) can sufficiently ensure ozone resistance while suppressing adverse effects on rubber properties other than ozone resistance (such as heat generation), and can further suppress the occurrence of cracks.

[0095] - Phenylenediamine-based antioxidant (C1) represented by formula (1) - The phenylenediamine-based antioxidant (C1) is represented by the following general formula (1): [In the formula, R １１ and R １２ Each is independently an alkyl group or aryl group having 7 or more carbon atoms, and R １１ and R １２ At least one of the members is an alkyl group having 7 or more carbon atoms. Represented by [ ]. The phenylenediamine-based antioxidant (C1) represented by general formula (1) has the effect of improving the ozone resistance of rubber compositions and can suppress the occurrence of cracks in tires to which the rubber composition is applied.

[0096] In the above general formula (1), R １１ and R １２ Each is independently an alkyl group or aryl group having 7 or more carbon atoms, and R １１ and R １２At least one of the groups is an alkyl group having 7 or more carbon atoms. Examples of alkyl groups having 7 or more carbon atoms include 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, 1-methylhexyl group, 2-methylhexyl group, n-heptyl group, 1,2-dimethylhexyl group, 1,3-dimethylhexyl group, 1,4-dimethylhexyl group, 1,5-dimethylhexyl group, 2,3-dimethylhexyl group, 2,4-dimethylhexyl group, 2,5-dimethylhexyl group, 3,4-dimethylhexyl group, 3,5-dimethylhexyl group, 1-methylheptyl group, 2-methylheptyl group, n-octyl group, various decyl groups, various dodecyl groups, etc., and among these, 1,4-dimethylpentyl group and 1-methylheptyl group are preferred. Examples of the aryl group include phenyl group, tolyl group, xylyl group, cumenyl group, mesyl group, α-naphthyl group, β-naphthyl group, ethylphenyl group, n-propylphenyl group, isopropylphenyl group, n-butylphenyl group, 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. Among these, the phenyl group is preferred.

[0097] In the above general formula (1), R １１ and R １２ At least one of them is an alkyl group having 7 or more carbon atoms, R １１ and R １２ The other side is preferably a phenyl group. １１ and R １２ One of them is an alkyl group having 7 or more carbon atoms, R １１ and R １２ A phenylenediamine-based antioxidant, in which the other side is a phenyl group, can further improve the ozone resistance of the rubber composition and further suppress the occurrence of cracks in tires to which the rubber composition is applied.

[0098] In the above general formula (1), R １１ and R １２At least one of them preferably has 7 or 8 carbon atoms. １１ and R １２ A phenylenediamine-based antioxidant in which at least one of the components has 7 or 8 carbon atoms can further improve the ozone resistance of the rubber composition and further suppress the occurrence of cracks in tires to which the rubber composition is applied.

[0099] Examples of the phenylenediamine-based antioxidant (C1) represented by the general formula (1) above include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine (8PPD), and N-phenyl-N'-(1,4-dimethylpentyl)-p-phenylenediamine (7PPD). These phenylenediamine-based antioxidants (C1) may be used individually or in combination of two or more.

[0100] The proportion of the phenylenediamine-based antioxidant (C1) represented by the general formula (1) in the antioxidant (C) is preferably 10 to 100% by mass, and more preferably 20 to 100% by mass. When the proportion of the phenylenediamine-based antioxidant (C1) represented by the general formula (1) in the antioxidant (C) is 10 to 100% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in tires to which the rubber composition is applied can be further suppressed.

[0101] - Triphenylamine-based antioxidant (C2) represented by formula (2) or formula (3) - The triphenylamine-based antioxidant (C2) is represented by the following general formula (2) or general formula (3): [In the formula, R ２１ , R ２２ and R ２３ Each of these independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. [In the formula, R ３１ and R ３２Each of these independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. The triphenylamine-based antioxidant (C2) represented by general formula (2) or (3) has the effect of improving the ozone resistance of rubber compositions and can suppress the occurrence of cracks in tires to which the rubber composition is applied.

[0102] In the above general formula (2), R ２１ , R ２２ and R ２３ , and also R in the above general formula (3) ３１ and R ３２ Each of these independently represents a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms, and is preferably a linear or branched alkyl group having 2 to 8 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms. Examples of the linear or branched alkyl group having 2 to 8 carbon atoms include an ethyl group, a propyl group (i.e., n-propyl group, isopropyl group), a butyl group (i.e., n-butyl group, sec-butyl group, isobutyl group, tert-butyl group), a pentyl group, a hexyl group, a heptyl group, and an octyl group. Examples of the cycloalkyl group having 5 to 8 carbon atoms include a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, and a cyclooctyl group, among which the cyclohexyl group is preferred.

[0103] The aforementioned triphenylamine-based antioxidant (C2) may be one of the following general formulas (2-1) or (3-1): Compounds represented by the above general formula (2-1) are preferred. ２１１ , R ２１２ , R ２２１ , R ２２２ , R ２３１ and R ２３２ Each of these is an alkyl group independently, however, R ２１１ and R ２１２ The total number of carbon atoms is 2 to 11, preferably 2 to 7, and R ２２１ and R ２２２ The total number of carbon atoms is 2 to 11, preferably 2 to 7, and R２３１ and R ２３２ The total number of carbon atoms of is 2 to 11, preferably 2 to 7. In the above general formula (3-1), R ３１１ , R ３１２ , R ３２１ and R ３２２ are each independently an alkyl group. However, the total number of carbon atoms of R ３１１ and R ３１２ is 2 to 11, preferably 2 to 7. Also, the total number of carbon atoms of R[[ID=​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​２１ , R ２２ and R ２３ A triphenylamine-based antioxidant having 2 to 8 carbon atoms, and R in the above general formula (3) ３１ and R ３２ Triphenylamine-based antioxidants having 2 to 8 carbon atoms can further improve the ozone resistance of rubber compositions and further suppress the occurrence of cracks in tires to which such rubber compositions are applied.

[0107] As the triphenylamine-based antioxidant represented by the above general formula (2), 4,4',4''-tris(isopropylamino)triphenylamine, 4,4',4''-tris(1,3-dimethylbutylamino)triphenylamine, and 4,4',4''-tris(1,4-dimethylpentylamino)triphenylamine are specifically preferred. As the triphenylamine-based antioxidant represented by the above general formula (3), 4,4'-bis(isopropylamino)triphenylamine, 4,4'-bis(1,3-dimethylbutylamino)triphenylamine, and 4,4'-bis(1,4-dimethylpentylamino)triphenylamine are specifically preferred. These triphenylamine-based antioxidants (C2) may be used individually or in combination of two or more.

[0108] The proportion of the triphenylamine-based antioxidant (C2) represented by the general formula (2) or (3) in the aforementioned antioxidant (C) is preferably 10 to 95% by mass, and more preferably 20 to 95% by mass. When the proportion of the triphenylamine-based antioxidant (C2) represented by the general formula (2) or (3) in the antioxidant (C) is 10 to 95% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in tires to which the rubber composition is applied can be further suppressed.

[0109] -Quinoline-based antioxidant (C3)- Preferably, the antioxidant (C) further comprises a quinoline-based antioxidant (C3). The quinoline-based antioxidant (C3) is an antioxidant having a quinoline portion or a derivative thereof (dihydroquinoline portion, tetrahydroquinoline portion, etc.). The quinoline-based antioxidant (C3) has the effect of improving the ozone resistance of the rubber composition, and a rubber composition containing both a quinoline-based antioxidant (C3) and at least one selected from the group consisting of a phenylenediamine-based antioxidant (C1) represented by the general formula (1) and a triphenylamine-based antioxidant (C2) represented by the general formula (2) or general formula (3) is possible to further suppress the occurrence of cracks in tires to which the rubber composition is applied.

[0110] The quinoline-based antioxidant (C3) preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant (C3) include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and the like. The quinoline-based antioxidant (C3) preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ). A quinoline-based antioxidant (C3) containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline has a high effect in improving the ozone resistance of the rubber composition and also has the advantage of being less likely to cause discoloration of the rubber composition. Therefore, rubber compositions containing polymers of 2,2,4-trimethyl-1,2-dihydroquinoline can further suppress the occurrence of cracks in tires and are also less prone to discoloration. Examples of polymers of 2,2,4-trimethyl-1,2-dihydroquinoline include dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0111] The proportion of the quinoline-based antioxidant (C3) in the antioxidant (C) is preferably 5 to 50% by mass, and more preferably 10 to 40% by mass. When the proportion of the quinoline-based antioxidant (C3) in the antioxidant (C) is 5 to 50% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in tires to which the rubber composition is applied can be further suppressed.

[0112] - Amine-based antioxidant (C4) represented by formula (4) - The antioxidant (C) is further represented by the following general formula (4): [In the formula, R ４１ and R ４２ Each of these is independently a monovalent saturated hydrocarbon group. Preferably, the composition contains an amine-based antioxidant (C4) represented by [ ] (excluding the phenylenediamine-based antioxidant (C1) represented by the general formula (1) above). The amine-based antioxidant (C4) represented by general formula (4) contains a phenylenediamine moiety, similar to the general-purpose antioxidant N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD), but differs from antioxidant 6PPD in that it does not have double bonds other than the phenylenediamine moiety. The amine-based antioxidant (C4) represented by general formula (4) has the effect of improving the ozone resistance of the rubber composition.

[0113] In the above general formula (4), R ４１ and R ４２ These are each independently monovalent saturated hydrocarbon groups. ４１ and R ４２ These may be the same or different, but from a synthesis standpoint, it is preferable that they be the same.

[0114] 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 and 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, which enhances the anti-aging effect and further improves the ozone resistance of the rubber composition. In the above general formula (4) R ４１ and R ４２From the viewpoint of further improving the ozone resistance of the rubber composition, it is preferable that each of these is independently a monovalent saturated hydrocarbon group having 1 to 20 carbon atoms in a chain or cyclic configuration.

[0115] Examples of the monovalent saturated hydrocarbon group include alkyl groups and cycloalkyl groups. Alkyl groups may be linear or branched, and cycloalkyl groups may have further alkyl groups or the like bonded to them as substituents. Examples of the alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, n-hexyl group, 1-methylhexyl group, 2-methylhexyl group, various octyl groups, various decyl groups, various dodecyl groups, etc., and among these, 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include cyclopentyl group, methylcyclopentyl group, cyclohexyl group, methylcyclohexyl group, cycloheptyl group, and cyclooctyl group.

[0116] The proportion of the amine-based antioxidant (C4) represented by the general formula (4) in the antioxidant (C) is preferably 0.1 to 80% by mass, and more preferably 1 to 70% by mass. When the proportion of the amine-based antioxidant (C4) of formula (4) in the antioxidant (C) is 0.1 to 80% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in tires to which the rubber composition is applied can be further suppressed.

[0117] - Amine-based antioxidant (C5) represented by formula (5) - The antioxidant (C) is further represented by the following general formula (5): [In the formula, R ５１ and R ５２It is preferable to include an amine-based antioxidant (C5) represented by the general formula (5) above. The amine-based antioxidant (C5) represented by the general formula (5) above has a higher molecular weight than conventional antioxidants, and as shown in the formula (5) above, it has a bridge moiety having a unique and relatively long chain portion, namely "-NH-CH(CH ３ )-(CH ２ ) ｍ５ -CH(CH ３ It has a moiety composed of "-CH(CH)" in formula (5). Furthermore, it is thought that such amine-based antioxidant (C5) has a reduced diffusion rate in the rubber composition due to its high molecular weight and the presence of a specific bridge moiety, and that its migration to the rubber surface is further suppressed. Moreover, the amine-based antioxidant (C5) has a moiety composed of "-CH(CH)" in formula (5) above. ３ )-(CH ２ ) ｍ５ -CH(CH ３ The two nitrogen atoms at both ends of the )-" are each bonded to one hydrogen atom (forming a so-called secondary amino group), and the presence of this bond in the structure represented by formula (5) is thought to contribute to the unique effect of improving ozone resistance (weather resistance).

[0118] In the above general formula (5), R ５１ and R ５２ This is a phenyl group. ５１ and R ５２ The presence of a phenyl group further improves the ozone resistance of the rubber composition and more reliably prevents discoloration of the rubber composition.

[0119] In the above general formula (5), m5 is an integer of 7 or more, and from the viewpoint of improving the ozone resistance of the rubber composition and preventing discoloration, it is preferably an integer between 8 and 16, and more preferably an integer between 10 and 14.

[0120] Examples of the amine-based antioxidant (C5) in formula (5) above include N,N'-bis(4-anilinophenyl)dodecane-2,11-diamine, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine, N,N'-bis(4-anilinophenyl)hexadecane-2,15-diamine, and N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine. Among these, N,N'-bis(4-anilinophenyl)tetradecane-2,13-diamine and N,N'-bis(4-anilinophenyl)octadecane-2,17-diamine are particularly preferred.

[0121] The proportion of the amine-based antioxidant (C5) represented by the general formula (5) in the antioxidant (C) is preferably 0.1 to 80% by mass, and more preferably 1 to 70% by mass. When the proportion of the amine-based antioxidant (C5) of formula (5) in the antioxidant (C) is 0.1 to 80% by mass, the ozone resistance of the rubber composition can be further improved, and the occurrence of cracks in tires to which the rubber composition is applied can be further suppressed.

[0122] -Other Anti-aging Agents (C6)- The tire rubber composition of this embodiment may or may not contain anti-aging agents (C6) other than the phenylenediamine-based anti-aging agent of formula (1) (C1), the triphenylamine-based anti-aging agent represented by formula (2) or (3) (C2), the quinoline-based anti-aging agent (C3), the amine-based anti-aging agent of formula (4) (C4), and the amine-based anti-aging agent of formula (5) (C5) described above. Examples of the other anti-aging agents (C6) include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and N,N'-diphenyl-p-phenylenediamine (DPPD), but among these, it is preferable not to include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD). Commercially available products can be used as the aforementioned antioxidants. Examples of commercially available antioxidants include those from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Corporation, Flexis Co., Ltd., and others. These antioxidants (C6) may be used individually or in combination of two or more types. The proportion of other antioxidants (C6) in the aforementioned antioxidant (C) is preferably 0 to 20% by mass, and more preferably 0 to 10% by mass.

[0123] "Resin" The tire rubber composition of this embodiment may contain a resin. Examples of the resin include at least one resin selected from terpene resins, phenolic resins, coumarone-indene resins, xylene resins, rosin-based resins, aromatic hydrocarbon resins, aliphatic hydrocarbon resins, alicyclic hydrocarbon resins, polyurethane resins, acrylic resins, and the like. The above resins can be those described in Japanese Patent Publication No. 2022-132289 or International Publication No. 2019 / 116656.

[0124] The resin preferably has a softening point of 30°C or higher, more preferably 60°C or higher, more preferably 90°C or higher, more preferably higher than 110°C, and more preferably 120°C or higher. Furthermore, the resin preferably has a softening point of 160°C or lower, more preferably 150°C or lower, more preferably 145°C or lower, and more preferably 140°C or lower. The softening point of the resin is measured in accordance with JIS-K2207-1996 (ring-sphere method).

[0125] The resin content is not particularly limited, but for example, the resin is preferably in the range of 1 to 100 parts by mass, and more preferably in the range of 5 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0126] "Silica" The tire rubber composition of this embodiment may contain silica. The type of silica is not particularly limited. Examples include wet silica, colloidal silica, calcium silicate, aluminum silicate, etc. Among the above, wet silica is preferred, and precipitated silica is more preferred. These silicas may be used individually or in combination of two or more types.

[0127] From the viewpoint of reducing environmental impact, silica derived from silicate plants is preferred. These silicate plants include, for example, mosses, ferns, horsetails, cucurbitaceae, nettleaceae, and grasses. Among these plants, grasses are preferred. Among grasses, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred from the viewpoint of availability. Further examples of silica include silica recycled from silicon wafer scraps used as raw materials for semiconductors, glass bottles, etc.

[0128] The silica is not particularly limited, but for example, if its CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) is 70 m², ２ / g or more, 250m ２Silica of 0.35 nm or less can be used. The CTAB specific surface area refers to the value measured in accordance with ASTM D3765-92. However, the adsorption cross-section per molecule of cetyltrimethylammonium bromide on the silica surface is 0.35 nm. ２ The specific surface area (m²) is calculated from the amount of adsorption of CTAB. ２ The CTAB specific surface area is defined as ( / g). The BET specific surface area of ​​the silica is 100 m². ２ / g or more, 250m ２ It can be less than or equal to / g. The BET specific surface area is the specific surface area obtained by the BET method, and in this invention, it can be measured in accordance with ASTM D4820-93.

[0129] Furthermore, the silica content is not particularly limited. For example, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, per 100 parts by mass of the rubber component (A). On the other hand, it is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 100 parts by mass or less.

[0130] "Silane Coupling Agent" When the tire rubber composition of this embodiment contains silica, it is preferable that the rubber composition contains a silane coupling agent in order to improve the effect of the silica. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl- Examples include N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropylbenzothiazolyl tetrasulfide. These silane coupling agents may be used individually or in combination of two or more.

[0131] Furthermore, bioethanol can also be used as a raw material for the silane coupling agent.

[0132] "Other Carbon Blacks" The tire rubber composition of this embodiment may also contain carbon blacks other than the recycled carbon black (B) described above. Plant-derived carbon blacks are particularly preferred as the other carbon blacks. Examples of plant-derived carbon blacks include those derived from castor oil and pine resin oil.

[0133] The other carbon blacks mentioned above are not particularly limited, but it is preferable to use carbon blacks of high, medium, or low structure in SAF, ISAF, IISAF, N339, HAF, FEF, GPF, and SRF grades, and especially SAF, ISAF, IISAF, N339, HAF, and FEF grades. Nitrogen adsorption specific surface area (N ２ (Measured in accordance with SA, JIS K6217-2:2001), 20m ２ Preferably 30 m ２ More preferably 50 m ２ More preferably 70 m ２ More preferably 250m / g or more, and also 250m ２ Preferably less than / g, 200m ２ More preferably less than / g, and 150m ２ A value of less than / g is even more preferable. The other carbon blacks may be used individually or in combination of two or more types.

[0134] The content of the other carbon black is not particularly limited, but is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component (A). Furthermore, it is preferably 150 parts by mass or less, more preferably 120 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 90 parts by mass or less.

[0135] The proportion of silica in the total content of the silica and carbon black is not particularly limited, but is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, even more preferably 40% by mass or more, and particularly preferably 50% by mass or more. It may also be 100% by mass, but is preferably 98% by mass or less, more preferably 95% by mass or less, even more preferably 90% by mass or less, even more preferably 80% by mass or less, and particularly preferably 70% by mass or less.

[0136] "Other" In addition to the components described above, the rubber composition for tires of this embodiment may further contain various additives used in rubber products, especially tires, such as liquid softeners like oil and liquid polymers, fillers such as zinc oxide, sulfur, vulcanization accelerators, wax, stearic acid, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica, organic peroxides, cellulose nanofibers, cellulose particles, solid fine particles such as eggshells, rice husks, and walnut powder, and rubber powder obtained by crushing used rubber products.

[0137] "Method for Manufacturing Tire Rubber Composition" The method for preparing the tire rubber composition of this embodiment is not particularly limited, and known methods can be used. For example, it can be obtained by kneading each component, including rubber component (A), recycled carbon black (B), and antioxidant (C), using a kneader such as a Banbury mixer, roll mixer, or internal mixer. Alternatively, components other than the crosslinking accelerator and crosslinking agent may be mixed in a non-production (non-pro) stage, and the crosslinking accelerator and crosslinking agent may be added to the mixture and mixed in a production (pro) stage to prepare the rubber composition. The tire rubber composition of this embodiment can be crosslinked or vulcanized. The conditions for crosslinking or vulcanizing the rubber composition can be adjusted as appropriate, for example, the temperature can be 120 to 200°C and the heating time can be 1 minute to 900 minutes.

[0138] "Applications" The tire rubber composition of this embodiment can be applied to various components of a tire, for example, the tread (cap tread, base tread, under tread), cushion rubber, shoulder, sidewall, bead filler, carcass coating rubber, belt coating rubber, insulation, chafer, inner liner, etc., and can also be used as a side reinforcement layer for run-flat tires.

[0139] As described above, the tire rubber composition of this embodiment is suitable for tire treads because it can suppress the occurrence of cracks and maintains high-temperature tensile strength and crack propagation resistance after thermal degradation. Since the tire tread constitutes a part of the tire surface and is susceptible to the effects of ozone in the air, the tire rubber composition of this embodiment, which can suppress the occurrence of cracks, can be suitably applied.

[0140] Furthermore, the tire rubber composition of this embodiment is also suitable for use in tire casings. The tire casing (especially the side rubber placed on the sidewall) also constitutes part of the tire surface and is susceptible to the effects of ozone in the air, so the tire rubber composition of this embodiment, which can suppress the occurrence of cracks, can be suitably applied to it.

[0141] <Tire> The tire of this embodiment is characterized by containing the above-described tire rubber composition. Because the tire of this embodiment contains the above-described tire rubber composition, the occurrence of cracks is suppressed, and the proportion of sustainable materials is improved while maintaining durability.

[0142] The tire of this embodiment can be manufactured by conventional methods using the rubber composition described above. For example, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process, and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and as the gas used to fill the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, inert gases such as nitrogen, argon, and helium can be used.

[0143] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0144] <Evaluation of Recycled Carbon Black> The physical properties of recycled carbon black 1 and 2 were evaluated using the following method.

[0145] (1) Grind gauge measurement: 3.75 g of zinc oxide, 0.20 g of the test carbon black, and 2.00 mL of epoxidized soybean oil were mixed to obtain a mixture. The obtained mixture was kneaded for 5 to 10 minutes to form a paste, and the sample paste was prepared. In accordance with JIS K5101-1-5, paste was prepared using a Toyo Seiki Co., Ltd. Huber Mahler (model: H3) under conditions of load 0.4536 kN and glass plate rotation speed 100 r / min. In accordance with JIS K5400, each sample paste was placed on a grind gauge and stretched with a scraper. A grind gauge with a range of 0 to 25 μm was used. It was confirmed that three or more continuous lines of 10 mm or more appeared, and the scale at the location where the line caused by the third largest particle among the particles that produced the continuous lines of 10 mm or more appeared was read, and this reading was taken as the particle size of the third largest particle. The average value of the particle size measured four times is shown in Table 1.

[0146] (2) Nitrogen adsorption specific surface area (N ２ SA) In accordance with ASTM D6556, calculate the specific surface area (N) of nitrogen adsorption of the tested carbon black. ２ SA was measured.

[0147] (3) Elemental analysis: The content of zinc (Zn), copper (Cu), and iron (Fe) was confirmed by X-ray fluorescence analysis (XRF).

[0148] (4) Ash content The ash content of the carbon black sample was measured according to ASTM D8474 and D1506.

[0149]

[0150] <Preparation and Evaluation of Rubber Compositions in Reference Examples 1 and 2> Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 2. Other chemicals included antioxidants, oils, fatty acids, sulfur, and vulcanization accelerators, and the same types and amounts were added in Reference Examples 1 and 2. Commercially available chemicals commonly used in the preparation of rubber compositions were used. The amounts added were the amounts commonly used in the preparation of rubber compositions. The total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources was calculated for the rubber composition to determine the sustainable material ratio. Furthermore, the high-temperature tensile strength after degradation and crack propagation resistance after thermal degradation were evaluated for the obtained rubber compositions using the following methods.

[0151] (5) Method for evaluating high-temperature tensile strength after degradation Each rubber composition was vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. The obtained vulcanized rubber was subjected to thermal degradation at 100°C for 48 hours in an air atmosphere. A tensile test was performed at 100°C in accordance with JIS K6251:2017 and the tensile strength was measured. The tensile strength of the test piece in Reference Example 1 was set to 100, and the high-temperature tensile strength (fracture resistance) after degradation was expressed as an index using the following formula: High-temperature tensile strength index after degradation = (Tensile strength of the test piece / Tensile strength of the test piece in Reference Example 1) × 100 The larger the high-temperature tensile strength index after degradation, the less the vulcanized rubber is likely to break, indicating superior performance after degradation (fracture resistance).

[0152] (6) Method for evaluating crack propagation resistance after thermal degradation The test rubber composition was degraded in advance at 100°C for 24 hours under a nitrogen atmosphere. Strip-shaped test pieces were prepared from the degraded rubber composition with a 0.5 mm hole drilled in the lengthwise direction in the center. A dc / dn test was performed using these test pieces (using a Shimadzu Servopulsa at a frequency of 5 Hz and 80°C, applying repeated fatigue with a strain of 30-100%), and the tear energy [J / m] at 1950 cycles was determined. ２ The crack propagation rate was calculated when the common logarithm of [ ] was 3.9. In the crack propagation rate obtained by the above process, the formulation data of Reference Example 1 was used as a control (index value 100), and the formula data of each example was normalized by the reciprocal of the formula data. A larger index value indicates a lower crack propagation rate and superior crack propagation resistance after thermal degradation.

[0153]

[0154] *1 Natural rubber: RSS#3 *2 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *3 New carbon black: Manufactured by Asahi Carbon, N550 *4 Recycled carbon black 1: Same as Table 1 *5 Recycled carbon black 2: Same as Table 1

[0155] Tables 1 and 2 show that even with rubber compositions containing recycled carbon black of the same ash content, the high-temperature tensile strength and crack propagation resistance after thermal degradation of the rubber composition vary significantly depending on the particle size of the third largest particle measured by the grind gauge of the blended recycled carbon black. It can be seen that blending recycled carbon black in which the third largest particle size measured by the grind gauge is 20 μm or less improves the high-temperature tensile strength and crack propagation resistance after thermal degradation. These results indicate that by blending recycled carbon black in which three or more lines of 10 mm or longer are observed when measured by grind gauge, and the third largest particle size among the particles producing these lines of 10 mm or longer is 20 μm or less, it is possible to improve the proportion of sustainable materials while maintaining the high-temperature tensile strength and crack propagation resistance after thermal degradation of the rubber composition.

[0156] <Preparation and Evaluation of Rubber Compositions for Standard Example 1 and Reference Examples 3-5> Carbon black (CB) and styrene-butadiene rubber with different ash, Zn, and S content were kneaded according to the formulations shown in Table 3 to prepare the rubber compositions for each example. The methods for measuring the component amounts and ash content in the carbon black used in each example, and the methods for evaluating the tensile strength and viscoelasticity of the prepared rubber compositions are as follows. The results are shown in Table 3.

[0157] (7) Amount of components in carbon black The amounts of components such as Zn, Fe, and S in carbon black were measured by X-ray fluorescence analysis.

[0158] (8) Ash Content The ash content of carbon black was measured by thermogravimetric analysis (TGA, RIGAKU Corporation). The sample was heated from room temperature to 550°C under a nitrogen atmosphere, and then heated to maintain 550°C under an air atmosphere, and the loss on heating was measured. The loss on heating (mass%) when the sample was heated from room temperature to 550°C under a nitrogen atmosphere was defined as "Loss on Heating 1," and the loss on heating (mass%) when heated to maintain 550°C under an air atmosphere was defined as "Loss on Heating 2." The ash content was calculated using the following formula: Ash content (mass%) = 100 - Loss on Heating 1 - Loss on Heating 2

[0159] (9) The rubber compositions of the standard example and reference example were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. Tensile tests were performed on each vulcanized rubber at room temperature in accordance with JIS K6301-1995 to measure its tensile strength. The tensile strength of the standard example specimen was set to 100, and the tensile strength was expressed as an index using the following formula: Tensile strength index = (Tensile strength of specimens other than the standard example / Tensile strength of the standard example specimen) × 100 A larger index indicates that the vulcanized rubber is less prone to breakage and has superior tensile strength.

[0160] (10) Viscoelasticity A viscoelasticity test was performed using "ARES-G2" manufactured by TA Instruments Inc. under the conditions of a frequency of 15 Hz, shear strain of 10%, and temperature of 50°C, and the storage modulus (G') of the rubber composition was measured. The evaluation results were indexed with the standard example as the control (index value 100). A higher index indicates a higher G', which in turn indicates superior rubber properties when applied to tires.

[0161]

[0162] *6 SBR: Styrene-butadiene rubber, manufactured by ENEOS Material Co., Ltd., product name "#1500" *7 CB1: Carbon Black 1, recycled carbon black equivalent to N330 *8 CB2: Carbon Black 2, recycled carbon black equivalent to N330 *9 CB3: Carbon Black 3, recycled carbon black equivalent to N330 *10 CB4: Carbon Black 4, new carbon black equivalent to N330

[0163] Table 3 shows that by using recycled carbon black with a Zn content of 1.0% by mass or less, or an ash content of 6.0% by mass or less, the deterioration of the physical properties (tensile strength, viscoelasticity) of the rubber composition can be suppressed.

[0164] <Preparation and Evaluation of Rubber Compositions for Standard Example 2 and Reference Example 6> A vulcanized rubber composition is prepared according to the formulation shown in Table 4. The heat resistance and ozone resistance are evaluated using the following method. The evaluation results are shown in Table 4.

[0165] (Heat Resistance) For the vulcanized rubber compositions in Table 4, tanδ (23°C) was measured using a dynamic tensile viscoelasticity measuring device (spectrometer manufactured by Ueshima Seisakusho) at a measurement temperature of 23°C, initial strain of 10%, dynamic strain of 2%, and frequency of 52 Hz. For evaluation, the case where tanδ of Reference Example 2 was set to 100 was used as a control, and the evaluation was performed according to the following criteria. A higher number indicates better heat resistance. A: 110 or more and 120 or less B: 100 or more and less than 110 C: 90 or more and less than 100

[0166] (Ozone Resistance) For the vulcanized rubber compositions in Table 4, a dynamic ozone degradation test (test with repeated straining) will be conducted in accordance with ISO 1431 (JIS K 6259), and the samples will be observed at 20x magnification using a microscope. For evaluation, the observed samples will be ranked according to the size and depth of the cracks, and classified according to the following criteria (1 to 5), with a smaller number indicating a better result. (Rank by size and depth of cracks) 1: Not visible to the naked eye but visible with a 10x magnifying glass. 2: Visible to the naked eye. 3: Cracks are deep and relatively large (less than 1 mm). 4: Cracks are deep and large (1 mm or more but less than 3 mm). 5: Cracks of 3 mm or more or likely to break.

[0167]

[0168] *11 Carbon black: LS-SAF, nitrogen adsorption specific surface area = 150 m² ２ / g *12 Silica: Manufactured by Tosoh Silica Co., Ltd., product name "NipSeal AQ" *13 Anti-aging agent-1: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" *14 Anti-aging agent-2: N-phenyl-N'-(1-methylheptyl)-p-phenylenediamine (8PPD), manufactured by Seiko Chemical Co., Ltd., product name "Ozonon 35" *15 Other chemicals: Total of vulcanization accelerator, stearic acid, and zinc oxide, etc.

[0169] <Preparation and Evaluation of Rubber Compositions for Standard Example 3 and Reference Example 7> A vulcanized rubber composition is prepared according to the formulation shown in Table 5. The heat resistance and ozone resistance are evaluated using the following method. The evaluation results are shown in Table 5.

[0170] (Heat Resistance) For the vulcanized rubber compositions in Table 5, tanδ (23°C) was measured using a dynamic tensile viscoelasticity measuring device (spectrometer manufactured by Ueshima Seisakusho) at a measurement temperature of 23°C, initial strain of 10%, dynamic strain of 2%, and frequency of 52 Hz. For evaluation, the case where tanδ of Reference Example 3 was set to 100 was used as a control, and the evaluation was performed according to the following criteria. A higher number indicates better heat resistance. A: 110 or more and 120 or less B: 100 or more and less than 110 C: 90 or more and less than 100

[0171] (Ozone Resistance) For the vulcanized rubber compositions in Table 5, a dynamic ozone degradation test (test with repeated strain) will be conducted in accordance with ISO 1431 (JIS K 6259), and the samples will be observed at 20x magnification using a microscope. For evaluation, the observed samples will be ranked according to the size and depth of the cracks, and classified according to the following criteria (1 to 5), with a smaller number indicating a better result. (Rank by size and depth of cracks) 1: Not visible to the naked eye but visible with a 10x magnifying glass. 2: Visible to the naked eye. 3: Cracks are deep and relatively large (less than 1 mm). 4: Cracks are deep and large (1 mm or more but less than 3 mm). 5: Cracks of 3 mm or more or likely to break.

[0172]

[0173] *11 Carbon black: LS-SAF, nitrogen adsorption specific surface area = 150 m² ２ / g *12 Silica: Manufactured by Tosoh Silica Co., Ltd., product name "NipSeal AQ" *13 Anti-aging agent-1: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (6PPD), manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" *15 Other chemicals: total of vulcanization accelerator, stearic acid, and zinc oxide, etc. *16 Anti-aging agent-3: 4,4'-bis(2-octylamino)triphenylamine, represented by general formula (3), R ３１ and R ３２ Triphenylamine-based antioxidants that have a 2-octyl group.

[0174] Tables 4 and 5 show that the sample in the reference example can maintain the same level of heat resistance as conventional methods even when using an environmentally friendly anti-aging agent.

[0175] Based on the above results, it can be said that by adopting the configuration of the present invention, it is possible to reduce the environmental burden while suppressing the occurrence of cracks, and to improve the proportion of sustainable materials in the tire while maintaining the high-temperature tensile strength and crack propagation resistance after thermal degradation.

[0176] 1: Grind gauge 2: Line less than 10 mm in length 3: Line 10 mm or longer 31: Line caused by the largest particle 32: Line caused by the second largest particle 33: Line caused by the third largest particle 4: Scale mark at the location where the line caused by the third largest particle appeared

Claims

1. A rubber composition (A), a recycled carbon black (B), and an anti-aging agent (C), wherein the recycled carbon black (B) has three or more lines with a length of 10 mm or more confirmed when measured by a grind gauge, and the particle size of the third largest particle among the particles that provide the lines with a length of 10 mm or more is 20 μm or less, and the anti-aging agent (C) is represented by the following general formula (1): [In the formula, R ３２ , ２３ , ３１ , ２１ , ２２ , and R １２ are each independently an alkyl group or an aryl group having 7 or more carbon atoms, and at least one of R １１ and R １２ is an alkyl group having 7 or more carbon atoms.], a phenylenediamine-based anti-aging agent (C1) represented by the following general formula (2) or general formula (3): [In the formula, R ２１ , R ２２ and R ２３ each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.] [In the formula, R ３１ and R ３２ each independently represent a linear or branched alkyl group having 1 to 12 carbon atoms, or a cycloalkyl group having 5 to 8 carbon atoms.], a tire rubber composition characterized by containing at least one selected from the group consisting of triphenylamine-based anti-aging agents (C2).

2. The tire rubber composition according to claim 1, wherein, in the measurement of the recycled carbon black (B) using a grind gauge, a paste of the recycled carbon black (B) is prepared as the measurement sample in accordance with JIS K5101-1-5.

3. The tire rubber composition according to claim 1, wherein, in the measurement of the recycled carbon black (B) using a grind gauge, the applied load is set to 0.4 to 0.5 kN and the rotation speed of the glass plate to 90 to 110 r / min, in accordance with JIS K5101-1-5, and the paste of the recycled carbon black (B) is prepared as the measurement sample.

4. The tire rubber composition according to claim 1, wherein the recycled carbon black (B) contains one or more metal atoms selected from the group consisting of Zn, Cu, and Fe.

5. The tire rubber composition according to claim 1, wherein the recycled carbon black (B) contains Zn.

6. The tire rubber composition according to claim 1, wherein the recycled carbon black (B) has a Zn content of 1.0% by mass or less.

7. The tire rubber composition according to claim 1, wherein the recycled carbon black (B) has an ash content of 20% by mass or less.

8. The tire rubber composition according to claim 1, wherein the anti-aging agent (C) further comprises a quinoline-based anti-aging agent (C3).

9. The tire rubber composition according to claim 8, wherein the proportion of the quinoline-based antioxidant (C3) in the antioxidant (C) is 5 to 50% by mass.

10. The tire rubber composition according to claim 1, wherein the content of the anti-aging agent (C) is 0.05 to 50 parts by mass per 100 parts by mass of the rubber component (A).

11. R in the general formula (1) １１ and R １２ The tire rubber composition according to claim 1, wherein the other of the two groups is a phenyl group.

12. R in the general formula (1) １１ and R １２ The tire rubber composition according to claim 1, wherein at least one of the atoms has 7 or 8 carbon atoms.

13. The aforementioned anti-aging agent (C) is further a general formula (4): [In the formula, R ４１ and R ４２ The rubber composition for tires according to claim 1, wherein each of the following is an independently monovalent saturated hydrocarbon group. The composition comprises an amine-based antioxidant (C4) represented by [ ] (excluding the phenylenediamine-based antioxidant (C1) represented by the general formula (1) above), and the proportion of the amine-based antioxidant (C4) in the antioxidant (C) is 0.1 to 80% by mass.

14. The aforementioned anti-aging agent (C) is further a general formula (5): [In the formula, R ５１ and R ５２ The tire rubber composition according to claim 1, wherein represents a phenyl group, and m5 represents an integer of 7 or more. The composition comprises an amine-based antioxidant (C5) represented by , and the proportion of the amine-based antioxidant (C5) in the antioxidant (C) is 0.1 to 80% by mass.

15. R in the above general formula (2) ２１ , R ２２ and R ２３ , and also R in the above general formula (3) ３１ and R ３２ The tire rubber composition according to claim 1, wherein each of the alkyl groups is independently selected from the group consisting of isopropyl group, 1,3-dimethylbutyl group, and 1,4-dimethylpentyl group.

16. R in the above general formula (2) ２１ , R ２２ and R ２３ , and also R in the above general formula (3) ３１ and R ３２ The tire rubber composition according to claim 1, wherein each of the carbon atoms independently has 2 to 8 carbon atoms.

17. The tire rubber composition according to claim 1, which is for use in tire treads.

18. The tire rubber composition according to claim 1, which is for use in tire cases.

19. A tire characterized by comprising the tire rubber composition described in any one of claims 1 to 18.

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