Rubber composition, tire internal member, and tire

Abstract

The present invention addresses the problem of providing a rubber composition that makes it possible to increase the proportion of sustainable materials in rubber products, does not significantly reduce crack resistance and wear resistance in comparison to when fresh carbon black is used, and has excellent tensile strength and crack propagation resistance. The means for solving the problem is a rubber composition containing a rubber component (A), recycled carbon black (B), and an age resistor containing a quinoline age resistor (C). When measured using a grind gauge, the recycled carbon black (B) includes three or more lines having a length of 10 mm or greater, and the recycled carbon black is such that the particle size of the third largest particle among the particles forming said lines having a length of 10 mm or greater is 20 μm or less.

Description

Rubber composition, tire internal components, and tire

[0001] This invention relates to a rubber composition, an internal component of a tire, and a tire.

[0002] Conventionally, various rubber compositions have been used in rubber products such as tires, rubber tracks, and seismic isolation rubber. Furthermore, in order to ensure the strength of these rubber products, carbon black is usually added as a reinforcing filler to the rubber compositions that serve as their raw materials.

[0003] 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 rubber products, 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 rubber products. For example, recycled carbon black is known as a material derived from recycled resources (see Patent Document 1 below).

[0004] European Patent Application Publication No. 3427975

[0005] However, in order to increase the proportion of sustainable materials in rubber products, using recycled carbon black instead of unused carbon black as a reinforcing filler can lead to a decrease in the crack resistance and abrasion resistance of the rubber composition, resulting in reduced crack resistance and abrasion resistance in rubber products to which the composition is applied. In particular, rubber compositions applied to the internal components of tires require crack resistance and abrasion resistance, so it is necessary to achieve both an increase in the proportion of sustainable materials and the maintenance of crack resistance and abrasion resistance. Furthermore, in addition to these, rubber compositions applied to the internal components of tires also require tensile strength and crack propagation resistance.

[0006] Therefore, the present invention aims to solve the problems of the above-mentioned prior art, provide a rubber composition that can improve the proportion of sustainable materials in rubber products, maintains crack resistance and abrasion resistance without a significant decrease compared to when unused carbon black is used, and exhibits excellent tensile strength and crack propagation resistance. Furthermore, the present invention aims to provide tire internal components and tires that have an improved proportion of sustainable materials, maintain crack resistance and abrasion resistance without a significant decrease compared to when unused carbon black is used, and exhibit excellent tensile strength and crack propagation resistance.

[0007] The gist of the present invention, which solves the above problems, is as follows.

[0008] [1] A rubber composition comprising a rubber component (A), recycled carbon black (B), and an antioxidant containing a quinoline-based antioxidant (C), wherein the recycled carbon black (B) is recycled carbon black that, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles that give rise to the lines with a length of 10 mm or more is 20 μm or less.

[0009] [2] The rubber composition according to [1], wherein, in the measurement using the grind gauge, the paste of recycled carbon black is prepared as the measurement sample in accordance with JIS K5101-1-5.

[0010] [3] The rubber composition according to [1] or [2], wherein, in the measurement using the grind gauge, 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 in accordance with JIS K5101-1-5, and the paste of the recycled carbon black is prepared.

[0011] [4] The rubber composition according to any one of [1] to [3], wherein the antioxidant is two types of antioxidants including the quinoline-based antioxidant (C).

[0012] [5] The rubber composition according to any one of [1] to [4], further comprising zinc oxide (D).

[0013] [6] The rubber composition according to any one of [1] to [5], wherein the total amount of styrene in the rubber component (A) is 5% by mass or less.

[0014] [7] The rubber composition according to [5], wherein the mass ratio of zinc oxide (D) to the quinoline-based antioxidant (C) [zinc oxide (D) / quinoline-based antioxidant (C)] is greater than 1.8 and less than or equal to 5.0.

[0015] [8] The rubber composition according to any one of [1] to [7], further comprising carbon black (E) other than the recycled carbon black (B).

[0016] [9] The rubber composition according to any one of [1] to [8], wherein the rubber component (A) comprises isoprene rubber.

[0017]

[10] The rubber composition according to [9], wherein the rubber component (A) further comprises butadiene rubber.

[0018]

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

[10] further contains at least one of rubber powder and recycled rubber.

[0019]

[12] The rubber composition according to

[11] , comprising at least one of rubber powder and recycled rubber in an amount of 10 parts by mass or less per 100 parts by mass of the rubber component (A).

[0020]

[13] The rubber composition according to [5], wherein the content of zinc oxide (D) is 4 parts by mass or less per 100 parts by mass of the rubber component (A).

[0021]

[14] The rubber composition according to [4], further comprising zinc oxide (D), wherein the mass ratio of the zinc oxide (D) to the total amount of the two anti-aging agents [zinc oxide (D) / total amount of the two anti-aging agents] is greater than 0.55 and less than or equal to 2.0.

[0022]

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

[14] , wherein the recycled carbon black (B) comprises one or more metal atoms selected from the group consisting of Zn, Cu, and Fe.

[0023]

[16] The rubber composition according to

[15] , wherein the recycled carbon black (B) contains Zn.

[0024]

[17] The rubber composition according to

[16] , wherein the recycled carbon black (B) has a Zn content of 0% by mass or more and 3% by mass or less.

[0025]

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

[17] , wherein the recycled carbon black (B) has an ash content of 20% by mass or less.

[0026]

[19] A tire internal member comprising the rubber composition according to any one of [1] to

[18] .

[0027]

[20] A tire comprising the tire internal member according to

[19] .

[0028] According to the present invention, it is possible to improve the ratio of sustainable materials in rubber products, and the crack resistance and abrasion resistance are maintained without significant reduction compared to the case of using unused carbon black, and a rubber composition excellent in tensile strength and crack growth resistance can be provided. Further, the present invention can provide a tire internal member and a tire in which the ratio of sustainable materials is improved, the crack resistance and abrasion resistance are maintained without significant reduction compared to the case of using unused carbon black, and the tensile strength and crack growth resistance are excellent.

[0029] It is an explanatory diagram of an example of the measurement result by a grind gauge. It is a cross-sectional view of an embodiment of the tire of the present invention.

[0030] Hereinafter, the rubber composition, tire internal member, and tire of the present invention will be specifically illustrated and described based on their embodiments.

[0031] The compounds described in this specification may be partially or entirely derived from fossil resources, may be derived from biological resources such as plant resources, or may be derived from recycled resources such as used tires. Further, it may be derived from a mixture of any two or more of fossil resources, biological resources, and recycled resources.

[0032] In this specification, the "ratio of sustainable materials" is the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) in the target rubber composition and tire.

[0033] <Rubber Composition> The rubber composition of this embodiment contains a rubber component (A), recycled carbon black (B), and an antioxidant containing a quinoline-based antioxidant (C). The recycled carbon black (B) is a recycled carbon black characterized in that, when measured with a grind gauge, there are three or more lines with a length of 10 mm or more, and among the particles that provide the lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less.

[0034] In the rubber composition of this embodiment, since the recycled carbon black (B) is a material derived from recycled resources, by blending the recycled carbon black (B) into the rubber composition, the ratio of the sustainable material of the rubber product to which the rubber composition is applied can be improved. However, as described above, when recycled carbon black is blended instead of ordinary unused carbon black, there is a problem that the crack resistance and wear resistance of the rubber composition may decrease depending on the recycled carbon black. To address this problem, in the rubber composition of this embodiment, a recycled carbon black (B) and a quinoline-based antioxidant (C) are blended, where the recycled carbon black (B) is a recycled carbon black characterized in that, when measured with a grind gauge, there are three or more lines with a length of 10 mm or more, and among the particles that provide the lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less. The quinoline-based antioxidant (C) has the effect of suppressing the deterioration of the rubber composition. Also, since the recycled carbon black (B) is a recycled carbon black with good dispersibility in the rubber composition because, when measured with a grind gauge, there are three or more lines with a length of 10 mm or more, and among the particles that provide the lines with a length of 10 mm or more, the particle size of the third largest particle is 20 μm or less, the rubber composition of this embodiment can improve the ratio of the sustainable material of the rubber product, and compared to the case of using unused carbon black, the crack resistance and wear resistance are maintained without significant reduction, and it is excellent in tensile strength and crack growth resistance.

[0035] (Rubber component) The rubber composition of this embodiment contains a rubber component (A), which provides rubber elasticity to the composition. The sustainability rate of the rubber component 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. Herein, in this specification, "sustainability rate" refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources in the material in question.

[0036] 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.

[0037] 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.

[0038] 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%.

[0039] 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 can be determined, for example, by converting it to standard polystyrene based on measurements obtained by gel permeation chromatography (GPC).

[0040] 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.

[0041] In one embodiment of the present invention, it is preferable that the rubber component (A) includes isoprene-based rubber. By including isoprene-based rubber in the rubber component (A), the fracture strength of the rubber composition can be increased, and its durability can be improved.

[0042] The rubber component (A) preferably contains butadiene rubber (BR). Butadiene rubber can contribute to maintaining the crack resistance and abrasion resistance of the rubber composition. Furthermore, it is particularly preferable that the rubber component (A) further contains butadiene rubber (BR) in addition to isoprene rubber. By using natural rubber and butadiene rubber in combination as rubber component (A), the crack resistance and abrasion resistance of the rubber composition can be maintained at a higher level.

[0043] 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.

[0044] 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.

[0045] Examples of the styrene-butadiene rubber include emulsion-polymerized styrene-butadiene rubber and solution-polymerized styrene-butadiene rubber.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] The rubber component (A) may include, in addition to the isoprene-based rubber, butadiene rubber, and styrene-butadiene copolymer 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.

[0050] In the rubber composition of this embodiment, the total amount of styrene in the rubber component (A) is preferably 5% by mass or less, more preferably 3.0% by mass or less, and may be 0% by mass. If the total amount of styrene in the rubber component (A) exceeds 5% by mass, the physical properties of the rubber composition may deteriorate, and it may not be possible to sufficiently maintain crack resistance and abrasion resistance. Furthermore, if the total amount of styrene in the rubber component (A) is 3.0% by mass or less, crack resistance and abrasion resistance can be maintained at a higher level. Furthermore, the total amount of styrene in the rubber component (A) may be greater than 0% by mass. In this specification, the total amount of styrene in the rubber component (A) is the total content of styrene contained in the total amount of rubber component (A) (unit: mass%), and can be calculated as Σ (content of each rubber component × amount of styrene in each rubber component / 100).

[0051] The rubber component (A) may have functional groups that interact with fillers such as carbon black and silica introduced into it 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 (A) 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.

[0052] The functional group can be introduced, for example, by reacting a compound having the functional group (modifier) ​​with the rubber component (A). The compound having the functional group (modifier) ​​is a modifying functional group that interacts with fillers such as silica and carbon black, and can be a nitrogen-containing functional group, a silicon-containing functional group, or an oxygen-containing functional group. Examples of nitrogen-containing functional groups include amino group-containing compounds, examples of silicon-containing functional groups include silicon halides and hydrocarbyloxysilane compounds, and examples of oxygen-containing functional groups include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples include compounds described in WO2016 / 194316 and WO2019 / 117256. These modifiers may be used individually or in combination of two or more.

[0053] 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.

[0054] For example, the method described in Japanese Patent Publication No. 2022-179158 can be used to prepare rubber derived from biological resources.

[0055] 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.

[0056] (Recycled Carbon Black (B)) The rubber composition of this embodiment contains recycled carbon black (B). Since recycled carbon black (B) is a material derived from recycled resources, incorporating recycled carbon black (B) into the rubber composition can improve the proportion of sustainable materials in rubber products to which the rubber composition is applied.

[0057] 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 that 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, rubber hoses, and rubber conveyor belts, as well as rubber parts or components at the manufacturing stage of final products. Used tires may include, for example, tires that have been retreaded, tires generated from tire replacement or vehicle scrapping, and End-of-Life Tires (ELTs) that have reached the end of their lifespan, or any other type of tire that has been discarded for any reason. 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 non-organic composition, such as those derived from silicone rubber or polyvinyl chloride, is preferable. Furthermore, waste oil that is mixed with carbon black or rubber containing carbon black is preferable. "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 actually used and then discarded, but also those that were manufactured but discarded without actually being used.

[0058] 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 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.

[0059] 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 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.

[0060] 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.

[0061] 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).

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] In the rubber composition of this embodiment, the recycled carbon black (B) is measured with a grind gauge to produce three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles producing the lines with a length of 10 mm or more is 20 μm or less. Measurement by grind gauge is related to the evaluation of the dispersibility of carbon black and is described in JIS K5101-1-5 (particularly concerning the preparation of paste) and JIS K5400 (particularly concerning the method of evaluation by the manner in which linear marks are generated).

[0067] From the viewpoint of the durability of the rubber composition, 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. However, 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 (performance other than durability of the rubber composition containing recycled carbon black), the range of the grind gauge used can be appropriately selected according to the purpose.

[0068] 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 this embodiment, it is preferable to prepare the paste of recycled carbon black in accordance with JIS K5101-1-5 as a measurement sample for measurement using a grind gauge. By preparing the paste of recycled carbon black in accordance with JIS K5101-1-5, the evaluation accuracy of the recycled carbon black can be further improved.

[0069] 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 blending 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.

[0070] Furthermore, when preparing the recycled carbon black paste in accordance with JIS K5101-1-5, it is preferable to apply a load of 0.4 to 0.5 kN and to rotate the glass plate at a speed of 90 to 110 r / min, from the viewpoint of improving evaluation accuracy.

[0071] 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, the deterioration of the durability of the rubber composition, particularly the performance after degradation, can be suppressed even when recycled carbon black is added. In this specification, the measurement of recycled carbon black (B) using a grind gauge is performed by the method described in the examples.

[0072] In this embodiment, recycled carbon black having three or more lines of 10 mm or longer in length, as measured by a grind gauge, and the particle size of the third largest particle among the particles that give rise to these lines of 10 mm or longer being 20 μm or less, can be produced by various methods. For example, recycled carbon black with a particle size of 20 μm or less can be produced 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.

[0073] The recycled carbon black (B) preferably contains one or more metal atoms selected from the group consisting of Zn, Cu, and Fe. Since recycled carbon black (B) 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 special removal operations, and rubber compositions containing such recycled carbon black are easy to manufacture. Furthermore, among the metal atoms, recycled carbon black (B) preferably contains Zn (zinc). The Zn in recycled carbon black (B) originates from, for example, zinc oxide used as a vulcanization aid. The presence of Zn in recycled carbon black (B) can be expected to suppress the deterioration of the physical properties of the rubber composition. From the viewpoint of the durability of the rubber composition, the Zn content in recycled carbon black (B) is usually 0.01 to 5% by mass, preferably 0.01 to 4 parts by mass, and more preferably 0.01 to 3% by mass. In one embodiment, the Zn content in recycled carbon black (B) is preferably 0% by mass or more and 3% by mass or less. In addition, the Cu content in recycled carbon black (B) is usually 0 to 0.5% by mass, preferably 0.01 to 0.1% by mass. In addition, the Fe content in recycled carbon black (B) is usually 0.01 to 0.5% by mass, preferably 0.01 to 0.3% by mass.

[0074] The recycled carbon black (B) may contain sulfur (S). Since sulfur (S) is an element that is readily found in recycled carbon black, recycled carbon black containing sulfur (S) does not require any special removal operations, and rubber compositions containing such recycled carbon black are easy to manufacture. The sulfur (S) content in the recycled carbon black (B) is usually preferably 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less. The sulfur (S) content may also be 0.5% by mass or more, or 1% by mass or more.

[0075] 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 (B) by the BET method is the statistical thickness specific surface area (STSA), which is determined according to ASTM D6556.

[0076] The recycled carbon black (B) preferably has a pH of 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. Hereinafter, the pH of the recycled carbon black (B) is determined according to ASTM D1512.

[0077] 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 (B) is determined according to ASTM D1618.

[0078] 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. Hereinafter, the heating loss of the recycled carbon black (B) at 125°C is determined according to ASTM D1509.

[0079] The recycled carbon black (B) preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0080] 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 (B) is determined according to ASTM D1514.

[0081] 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 (B) is determined according to ASTM D1514.

[0082] 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 (B) is determined according to ASTM D5230.

[0083] 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 (B) is determined according to ASTM D1508.

[0084] 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. Hereinafter, the particle size (D97) of the recycled carbon black (B) 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.

[0085] 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.

[0086] The recycled carbon black (B) preferably has an ash content of 25% by mass or less, and more preferably 20% by mass or less. When the ash content of the recycled carbon black (B) is 25% by mass or less, the various physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, in this specification, the ash content of the recycled carbon black (B) is determined according to ASTM D8474 / D1506.

[0087] The recycled carbon black (B) preferably has an oil adsorption capacity (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 oil adsorption capacity (OAN) of the recycled carbon black (B) is determined according to ASTM D2414.

[0088] The recycled carbon black (B) preferably has an oil adsorption capacity (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 oil adsorption capacity (COAN) of the compressed sample of recycled carbon black (B) is determined according to ASTM D3493.

[0089] Commercially available recycled carbon black (B) can be used. Examples of such commercially available products include "PB365" manufactured by Enrestec. PB365 is recycled carbon black produced by the thermal decomposition of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m² by the BET method. ２ It is 1 / g and also contains approximately 17% by mass of ash.

[0090] The content of 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 rubber component (A). When the content of recycled carbon black (B) is 5 parts by mass or more per 100 parts by mass of rubber component (A), it has a great effect in improving the ratio of sustainable materials in rubber products 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.

[0091] (Anti-aging agent) The rubber composition of this embodiment contains an anti-aging agent including a quinoline-based anti-aging agent (C). By including an anti-aging agent including a quinoline-based anti-aging agent (C), crack resistance and abrasion resistance can be maintained without significantly reducing them. Preferably, the anti-aging agent is two types of anti-aging agents including a quinoline-based anti-aging agent (C). By including two types of anti-aging agents, the anti-aging effects of each are complemented, and crack resistance and abrasion resistance can be maintained.

[0092] -Quinoline-based antioxidant (C)- Quinoline-based antioxidant (C) is an antioxidant having a quinoline portion or a derivative portion thereof (such as a dihydroquinoline portion). Quinoline-based antioxidant (C) has the effect of suppressing the deterioration of rubber compositions.

[0093] The quinoline-based antioxidant (C) preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant (C) include polymers of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Commercially available products can be used as the quinoline-based antioxidant (C), and examples of commercially available products of this antioxidant include those from Ouchi Shinko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Corporation, Flexis, and others. These antioxidants may be used individually or in combination of two or more. The quinoline-based antioxidant (C) preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ). A quinoline-based antioxidant containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline has a high effect in improving the degradation resistance of the rubber composition and also has the advantage of being less likely to cause discoloration of the rubber composition. Examples of polymers of 2,2,4-trimethyl-1,2-dihydroquinoline include dimers, trimers, tetramers, etc.

[0094] The content of the quinoline-based antioxidant (C) is preferably in the range of 0.1 to 5 parts by mass per 100 parts by mass of the rubber component (A). When the content of the quinoline-based antioxidant (C) is 0.1 parts by mass or more per 100 parts by mass of the rubber component (A), crack resistance and abrasion resistance can be maintained. Furthermore, when the content of the quinoline-based antioxidant (C) is 5 parts by mass or less per 100 parts by mass of the rubber component (A), the influence on other rubber properties such as heat generation is reduced, making it suitable for tire applications. The content of the quinoline-based antioxidant (C) is more preferably 0.3 parts by mass or more per 100 parts by mass of the rubber component (A), even more preferably 0.5 parts by mass or more, and from the viewpoint of influence on other rubber properties, it is more preferably 4 parts by mass or less per 100 parts by mass of the rubber component (A), and even more preferably 3 parts by mass or less. In other words, the content range of the quinoline-based antioxidant (C) is more preferably 0.3 parts by mass or more and 4 parts by mass or less, and even more preferably 0.5 parts by mass or more and 3 parts by mass or less, per 100 parts by mass of rubber component (A).

[0095] (Anti-aging agent (F) other than quinoline-based anti-aging agent (C)) As described above, it is preferable that the anti-aging agent consists of two types of anti-aging agents, including quinoline-based anti-aging agent (C). That is, it is preferable that the rubber composition of this embodiment contains anti-aging agent (F) other than the quinoline-based anti-aging agent (C). By including anti-aging agent (F) other than quinoline-based anti-aging agent (C) together with quinoline-based anti-aging agent (C), the anti-aging effects of each are complemented, and crack resistance and abrasion resistance can be maintained.

[0096] The proportion of the quinoline-based antioxidant (C) in the total amount of the two types of antioxidants is preferably 20 to 50% by mass, more preferably 25 to 45% by mass, and even more preferably 30 to 40% by mass. A proportion of 20 to 50% by mass of the quinoline-based antioxidant (C) in the total amount of the two types of antioxidants is preferable because it exhibits a high effect on crack resistance.

[0097] Other antioxidants (F) besides the quinoline-based antioxidant (C) include phenylenediamine-based antioxidants, diphenylamine-based antioxidants, phenol-based antioxidants, quinoline-based antioxidants, carbamate-based antioxidants, imidazole-based antioxidants, and among these, phenylenediamine-based antioxidants are preferred. In other words, the two antioxidants are preferably a quinoline-based antioxidant (C) and a phenylenediamine-based antioxidant. The phenylenediamine-based antioxidant has a phenylenediamine moiety (-NH-C ６ H ４ The antioxidant has a -NH-) or a derivative thereof. By including a phenylenediamine-based antioxidant together with a quinoline-based antioxidant (C), the anti-aging effects of each antioxidant are complemented, and crack resistance and abrasion resistance can be maintained at a higher level. Examples of the phenylenediamine-based antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine. Commercial products can be used as the phenylenediamine-based antioxidant, and examples of commercially available products of the antioxidant include those from Ouchi Shinko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Corporation, Flexis Co., Ltd., etc. These anti-aging agents may be used individually or in combination of two or more.

[0098] The content of the antioxidant (F) other than the quinoline-based antioxidant (C) is not particularly limited and can be appropriately adjusted depending on the tire category, tire components, target performance, etc. For example, the content of the antioxidant (F) other than the quinoline-based antioxidant (C) is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2 parts by mass or more, and also preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component (A). In other words, the range of the content of the antioxidant (F) is preferably 1 part by mass or more and 12 parts by mass or less, more preferably 1.5 parts by mass or more and 10 parts by mass or less, and even more preferably 2 parts by mass or more and 8 parts by mass or less.

[0099] (Zinc Oxide (D)) The rubber composition of this embodiment preferably further contains zinc oxide (zinc oxide) (D). The zinc oxide (D) is preferably obtained not only from zinc ingots but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available zinc oxide (D) can be used, and commercially available zinc oxide products from companies such as Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. can be used. These commercially available zinc oxide (D) products may be used individually or in combination of two or more types.

[0100] The content of zinc oxide (D) is not particularly limited and can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the content of zinc oxide (D) is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, even more preferably 1.8 parts by mass or more, preferably 10 parts by mass or less, more preferably 6 parts by mass or less, even more preferably 4 parts by mass or less, and particularly preferably 2.2 parts by mass or less, per 100 parts by mass of rubber component (A). When the content of zinc oxide (D) is 4 parts by mass or less per 100 parts by mass of rubber component (A), the crack resistance and abrasion resistance of the rubber composition are maintained at a high level. Furthermore, when the zinc oxide (D) content is in the range of 1.5 to 4 parts by mass per 100 parts by mass of the rubber component (A), the vulcanization properties of the rubber composition can be improved while maintaining a higher level of crack resistance and abrasion resistance. When the content is in the range of 1.8 to 2.2 parts by mass, the vulcanization properties of the rubber composition can be further improved while maintaining an even higher level of crack resistance and abrasion resistance.

[0101] In the rubber composition of this embodiment, the mass ratio of zinc oxide (D) to the quinoline-based antioxidant (C) [zinc oxide (D) / quinoline-based antioxidant (C)] is preferably greater than 1.8 and 5.0 or less, more preferably between 2.5 and 4.5, and even more preferably between 3 and 4.5. When the mass ratio of zinc oxide (D) / quinoline-based antioxidant (C) is 5.0 or less, sufficient crack resistance and abrasion resistance can be maintained. Furthermore, when the mass ratio of zinc oxide (D) / quinoline-based antioxidant (C) is 2.5 or more, the vulcanization properties of the rubber composition are further improved, and when it is 4.5 or less, crack resistance and abrasion resistance can be further maintained.

[0102] In the case where the rubber composition of this embodiment contains zinc oxide (D) and two types of antioxidants, the mass ratio of zinc oxide (D) to the total amount of the two types of antioxidants [zinc oxide (D) / total amount of the two types of antioxidants] is preferably greater than 0.55 and 2.0 or less, more preferably 1.0 or more and 1.8 or less, and even more preferably 1.4 or more and 1.7 or less. When the mass ratio of zinc oxide (D) to the total amount of the two types of antioxidants is 2.0 or less, crack resistance and abrasion resistance can be maintained at an even higher level. Furthermore, when the mass ratio of zinc oxide (D) to the total amount of the two types of antioxidants is 1.0 or more, the vulcanization properties of the rubber composition are further improved, and when it is 1.8 or less, crack resistance and abrasion resistance can be maintained at an even higher level.

[0103] (Resin) The 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. For the above resin, those described in Japanese Patent Application Publication No. 2022-132289 or WO2019 / 116656 can be used.

[0104] 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).

[0105] 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 (A).

[0106] (Silica) The rubber composition of this embodiment may contain silica. The type of the silica is not particularly limited. For example, wet silica, colloidal silica, calcium silicate, aluminum silicate, etc. may be mentioned. Among those described above, the silica is preferably wet silica, and more preferably precipitated silica. These silicas may be used alone or in combination of two or more.

[0107] From the viewpoint of reducing environmental impact, silica derived from silicate plants is preferable as the silica. The silicate plants exist, for example, in mosses, ferns, toxics, cucurbitaceae, urticaceae, gramineae plants, etc. Among these plants, gramineae plants are preferable. Among gramineae plants, silica derived from rice husks (hereinafter, also referred to as "rice husk silica") is particularly preferable from the viewpoint of easy availability. As the silica, furthermore, end materials of silicon wafers that are raw materials of semiconductors, silica manufactured by recycling silicon components from glass bottles, etc. may also be mentioned.

[0108] The silica is not particularly limited, but for example, silica having a CTAB specific surface area (cetyltrimethylammonium bromide adsorption specific surface area) of 70 m ２ / g or more and 250 m ２ / g or less can be used. The CTAB specific surface area means a value measured in accordance with ASTM D3765-92. However, taking the adsorption cross-sectional area per molecule of cetyltrimethylammonium bromide on the silica surface as 0.35 nm ２ and using the specific surface area (m ２ / g) calculated from the adsorption amount of CTAB as the CTAB specific surface area. Also, the BET specific surface area of the silica can be 100 m ２ / g or more and 250 m ２ / g or less. The BET specific surface area is the specific surface area determined by the BET method, and in the present invention, it can be measured in accordance with ASTM D4820-93.

[0109] Furthermore, the silica content is not particularly limited. For example, the silica content 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, the silica content 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, per 100 parts by mass of the rubber component (A).

[0110] (Silane Coupling Agent) If the 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.

[0111] Furthermore, bioethanol can also be used as a raw material for silane coupling agents.

[0112] (Carbon black other than recycled carbon black (B) (E)) The rubber composition of this embodiment may also contain carbon black other than recycled carbon black. By combining carbon black other than recycled carbon black (B) (E) with recycled carbon black (B), the crack resistance and abrasion resistance of the rubber composition can be maintained at a higher level.

[0113] Other than this recycled carbon black (B), there are no particular restrictions on the carbon black (E), but it is preferable to use, for example, SAF, ISAF, IISAF, N339, HAF, FEF, GPF, SRF grade carbon black of high, medium, or low structure, and especially SAF, ISAF, IISAF, N339, HAF, FEF grade carbon black. 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. These carbon blacks may be used individually or in combination of two or more types.

[0114] The content of carbon black (E) other than the recycled carbon black (B) 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, the content of carbon black (E) other than the recycled carbon black (B) 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, per 100 parts by mass of the rubber component (A). The range of carbon black (E) content is preferably 1 part by mass or more and 120 parts by mass or less, more preferably 5 parts by mass or more and 100 parts by mass or less, and even more preferably 10 parts by mass or more and 90 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0115] The proportion of silica in the total content of the silica, recycled carbon black (B), and carbon black other than recycled carbon black (E) 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. Furthermore, the proportion of silica in the total content of the silica, recycled carbon black (B), and carbon black other than recycled carbon black (E) may 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.

[0116] The proportion of recycled carbon black (B) in the total amount of recycled carbon black (B) and carbon black other than recycled carbon black (E) (i.e., the total amount of carbon black) is preferably 5 to 100% by mass, more preferably 10 to 100% by mass, even more preferably 15 to 100% by mass, and particularly preferably 20 to 100% by mass. When the proportion of recycled carbon black (B) in the total amount of carbon black is 5% by mass or more, it has a great effect of improving the tensile strength after degradation and crack propagation resistance while increasing the proportion of sustainable materials in the rubber composition and rubber products using the same. When the proportion of recycled carbon black (B) in the total amount of carbon black is 100% by mass or less, it is possible to greatly increase the proportion of sustainable materials.

[0117] (Rubber Powder and Recycled Rubber) The rubber composition of this embodiment may further contain at least one of rubber powder and recycled rubber. By including at least one of rubber powder and recycled rubber in the rubber composition, the proportion of sustainable materials in the rubber product can be further improved. Rubber powder and recycled rubber will be described in detail below. Note that in this specification, rubber powder and recycled rubber are not included in the rubber components described above.

[0118] The rubber composition of this embodiment may contain at least one of rubber powder and recycled rubber in an amount of 10 parts by mass or less per 100 parts by mass of the rubber component (A). The content of at least one of rubber powder and recycled rubber may be 5 parts by mass or less, or 3 parts by mass or less, per 100 parts by mass of the rubber component (A). Alternatively, the content of at least one of rubber powder and recycled rubber may be 1 part by mass or more per 100 parts by mass of the rubber component (A).

[0119] -Rubber Powder- The rubber powder may be obtained by crushing used rubber products such as used tires, and optionally removing reinforcing materials such as steel materials and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for the production of rubber powder and crushing it. For example, rubber powder can be obtained from vulcanized rubber by the method described in "Rubber Chemistry and Technology". In the process of crushing vulcanized rubber to obtain rubber powder, mechanical treatment or low-temperature treatment may be used. For example, in mechanical treatment, various crushing equipment such as cracker mills and granulators can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature treatment, the finely chopped vulcanized rubber is frozen at an extremely low temperature and then crushed into fine particles. In addition, a magnetic separator can be used to remove steel materials, and an air separator can be used to remove fibers. Commercially available rubber powders can be used, and examples of such commercially available rubber powders include those from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing environmental impact, it is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more types.

[0120] The composition of the rubber powder is not particularly limited and depends on the composition of the vulcanized rubber used as a raw material, such as used rubber products (used tires). In one embodiment, the rubber powder includes rubber components, carbon black, silica, etc. The rubber components, carbon black, silica, etc. contained in the rubber powder may be the same as or different from the rubber components, carbon black, silica, etc. that may be contained in the rubber composition of this embodiment described above.

[0121] The rubber powder preferably has a volume-average particle diameter of 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. Furthermore, the smaller the volume-average particle diameter of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume-average particle diameter is measured using a laser diffraction particle size distribution analyzer, for example, the "CAPA500" manufactured by Horiba, Ltd.

[0122] The rubber powder preferably has a residue of less than 1% by mass after sieving through a 60-mesh sieve, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit. Furthermore, the rubber powder preferably has a residue of less than 10% by mass after sieving through an 80-mesh sieve, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, with no particular lower limit. In this specification, the sieve residue is measured according to ASTM D5644-01.

[0123] The rubber powder preferably has an acetone extract content of 12% by mass or less, more preferably 11% by mass or less, even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extract content in the rubber powder refers to the acetone extract content (%) obtained by an acetone extraction method in accordance with JIS K6350.

[0124] The content of the rubber powder is not particularly limited and can be adjusted as appropriate depending on the tire category to which it is applied, the internal components of the tire, the target performance, etc. For example, the content of the rubber powder is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and also preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less.

[0125] -Recycled Rubber- The recycled rubber is obtained by recycling used rubber from rubber products such as tires. By including recycled rubber in the rubber composition, the proportion of sustainable materials in rubber products can be increased.

[0126] In the rubber composition of this embodiment, commercially available recycled rubber can be used as the recycled rubber. The recycled rubber can be, for example, recycled used rubber from automobile tires, tubes, and other rubber products as specified in JIS K6313-2012, or rubber having equivalent properties. The recycled rubber may also be desulfurized.

[0127] The type of recycled rubber can be selected from recycled tube rubber, recycled tire rubber, or other recycled rubber, and multiple types can be combined. Among these, recycled tire rubber is preferred. The method for manufacturing the recycled rubber is not particularly limited, and known methods such as the oil pan method and the liquemeter method can be used.

[0128] The rubber component in the recycled rubber preferably has a natural rubber content of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass. The natural rubber content in the recycled rubber can be determined by measurement using pyrolysis gas chromatography (PyGC).

[0129] The recycled rubber content can be adjusted as appropriate depending on the tire category, tire components, target performance, etc. For example, the recycled rubber content is preferably 0.1 to 40 parts by mass, more preferably 0.5 to 20 parts by mass, and even more preferably 1 to 10 parts by mass, per 100 parts by mass of rubber component (A).

[0130] (Other) In addition to the components described above, the rubber composition of this embodiment may further contain various additives used in rubber products, especially tires, such as liquid softeners like oil and liquid polymers, fillers like sulfur, vulcanization accelerators, wax, stearic acid, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica, organic peroxides, cellulose nanofibers, cellulose particles, eggshells, rice husks, walnut powder, and other solid fine particles.

[0131] (Method for producing the rubber composition) The method for preparing the rubber composition of this embodiment is not particularly limited, and known methods can be used. For example, it can be obtained by kneading a predetermined rubber component and each component including recycled carbon black using a kneader such as a Banbury mixer, roll mixer, or internal mixer. Alternatively, the 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 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.

[0132] (Applications) The 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. It can also be used as a side reinforcement layer for run-flat tires. In addition to tires, the rubber composition of this embodiment can also be applied to hoses, rubber tracks, seismic isolation rubber, etc.

[0133] <Tire Internal Components> The tire internal components of this embodiment are characterized by being made of the rubber composition described above. Because the tire internal components of this embodiment are made of the rubber composition described above, the proportion of sustainable materials is improved, and crack resistance and abrasion resistance are maintained without a significant decrease compared to when unused carbon black is used, and tensile strength and crack propagation resistance are excellent.

[0134] <Tire> The tire of this embodiment is characterized by comprising the tire internal components described above. Because the tire of this embodiment comprises the tire internal components described above, the proportion of sustainable materials is improved, and crack resistance and abrasion resistance are maintained without a significant decrease compared to when unused carbon black is used, and tensile strength and crack propagation resistance are excellent. The tire of this embodiment can be manufactured by a conventional method 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 to be filled into 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.

[0135] Next, an embodiment of the tire of the present invention will be described in detail with reference to the drawings. Figure 2 is a cross-sectional view of an embodiment of the tire of the present invention. The tire 21 of this embodiment shown in Figure 2 has a pair of bead portions 22, a pair of sidewall portions 23, and a tread portion 24 connected to both sidewall portions 23, and comprises a carcass 26 extending in a toroidal shape between bead cores 25 embedded in each of the pair of bead portions 22, and a belt 27 arranged on the radially outer side of the crown portion of the carcass 26.

[0136] The carcass 26 of the tire 21 shown in Figure 2 is composed of a single carcass ply made of multiple parallel-arranged cords covered with coating rubber, and the carcass 26 consists of a main body portion that extends in a toroidal shape between the pair of bead cores 25 and folded portions that are wound radially outward from the inside to the outside in the tire width direction around each bead core 25, but the number of plies and structure of the carcass 26 in the tire 21 of the present invention are not limited to this.

[0137] Furthermore, in the tire 21 shown in Figure 2, a belt 27 consisting of two belt layers is arranged on the radially outer side of the crown portion of the carcass 26. The belt layer is usually made of a rubberized layer of cords (preferably steel cords) that extend inclined with respect to the tire's equatorial plane, and the two belt layers are stacked so that the cords constituting the belt layers intersect each other with the tire's equatorial plane in between to form the belt 27. Although the belt 27 in the figure consists of two belt layers, in the tire 21 of the present invention, the number of belt layers constituting the belt 27 may be three or more. In addition, the tire 21 of this embodiment is provided with side rubber 28 on a pair of sidewall portions 23 and gum chafers 29 on a pair of bead portions 22. Since the gum chafers 29 are arranged on the contact portion of the bead portion 22 with the rim, the rubber composition of this embodiment described above can be suitably applied to them.

[0138] 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.

[0139] <Evaluation of Carbon Black> The physical properties of carbon black were evaluated using the following method.

[0140] (1) Grind gauge measurement: 3.75 g of zinc oxide, 0.20 g of the carbon black under test, 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 sample pastes were prepared. In accordance with JIS K5101-1-5, pastes were prepared using a Toyo Seiki Co., Ltd. Huber Mahler (model: H3) under conditions of a load of 0.4536 kN and a glass plate rotation speed of 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.

[0141] (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.

[0142] (3) Elemental analysis: The content of zinc (Zn), copper (Cu), and iron (Fe) was confirmed by X-ray fluorescence analysis (XRF).

[0143] (4) Ash content The ash content of the carbon black sample was measured according to ASTM D8474 and D1506.

[0144]

[0145] <Preparation and Evaluation of Rubber Composition (1)> Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 2. Other chemicals included oil, fatty acids, sulfur, and vulcanization accelerators, and the same types and amounts were added in Example 1 and Comparative Example 1. Commercially available chemicals commonly used in the preparation of rubber compositions were used. The amounts added were also the amounts commonly used in the preparation of rubber compositions. The tensile strength and crack propagation resistance of the obtained rubber compositions were evaluated using the following method.

[0146] (5) Tensile strength after degradation The rubber composition was vulcanized at 145°C for 33 minutes to obtain vulcanized rubber. The obtained vulcanized rubber was degraded at 100°C for 48 hours in an air atmosphere. A tensile test was performed at 100°C in accordance with JIS K 6251:2017 and the tensile strength was measured. The tensile strength of the test piece from Example 1 was set to 100, and the high-temperature tensile strength 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 from Example 1) × 100 A larger index indicates better high-temperature tensile strength after degradation.

[0147] (6) Evaluation method for crack propagation resistance after degradation The rubber composition to be tested was degraded in an air atmosphere at 100°C for 24 hours beforehand. Strip-shaped test pieces were prepared from the rubber composition with a 0.5 mm hole drilled in the lengthwise direction in the center, and a dc / dn test was performed using the test pieces (using a Shimadzu "Servopulsa" at a frequency of 5 Hz and 80°C, repeated fatigue was applied with a strain of 30-100%, and the tear energy [J / m] at 1950 cycles was measured. 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 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.

[0148]

[0149] *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 *6 Anti-aging agent: Manufactured by Shinko Chemical Industry, product name "Nocrac 224", quinoline-based anti-aging agent

[0150] Table 2 shows that the rubber composition of Example 1, which uses recycled carbon black and, as measured with a grind gauge, has three or more lines with a length of 10 mm or more, 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, has an improved proportion of sustainable materials and exhibits excellent tensile strength after degradation and crack propagation resistance.

[0151] <Preparation and Evaluation of Rubber Compositions (2)> Rubber compositions were prepared using a standard Banbury mixer according to the formulations shown in Table 3. Each of the obtained rubber compositions was evaluated using the evaluation method described below.

[0152] (7) 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 (mass%) 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

[0153] (8) Tensile Strength Tensile tests were conducted at room temperature in accordance with JIS K6301-1995, and the tensile strength of each rubber composition was measured. The evaluation results were expressed as an index using the following formula, with Reference Example 1 as the control (index value 100): Tensile strength index = (Tensile strength of test specimens other than Reference Example 1 / Tensile strength of test specimen of Reference Example 1) × 100 A larger index indicates that the rubber composition is less prone to fracture and has superior tensile strength.

[0154] (9) Viscoelasticity A viscoelasticity test was performed using "ARES-G2" manufactured by TA Instruments, Inc., under the conditions of a frequency of 15 Hz, a shear strain of 10%, and a temperature of 50°C, and the storage modulus (G') of the rubber composition was measured. The evaluation results were indexed with Reference Example 1 as the control (index value 100). A higher index indicates a higher G', which in turn indicates superior rubber properties when applied to products such as tires.

[0155]

[0156] *7 SBR: Styrene-butadiene rubber, product name "#1500" *8 CB3: Carbon Black 3, recycled carbon black equivalent to N330 *9 CB4: Carbon Black 4, recycled carbon black equivalent to N330 *10 CB5: Carbon Black 5, recycled carbon black equivalent to N330 *11 CB6: Carbon Black 6, new carbon black equivalent to N330

[0157] Table 3 shows that when recycled carbon black with a Zn content of 0% to 3% by mass is used, the deterioration of the physical properties of the rubber composition is suppressed.

[0158] <Preparation and Evaluation of Rubber Compositions (3)> Rubber compositions for each reference example were prepared according to the formulations shown in Table 4. For each obtained rubber composition, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources was calculated to determine the sustainable material ratio. Other chemicals included resin, wax, vulcanization accelerator, sulfur, and retarder, and the same type and amount were added in each reference example. Commercially available chemicals commonly used when preparing rubber compositions were used. The amounts added were the amounts commonly used when preparing rubber compositions. Furthermore, the crack resistance and abrasion resistance of the obtained rubber compositions were evaluated using the following method. The results are shown in Table 4.

[0159] (10) Evaluation of crack resistance The prepared rubber composition was pre-degraded for 24 hours, then subjected to a 20% static strain at 50 ppm ozone, 40°C, and 50% humidity, and left for 96 hours. The degree of cracking was evaluated to assess the crack resistance of the rubber composition. The level of cracking was evaluated visually and quantified based on the JSR Handbook (P394). A smaller number indicates better crack resistance. Crack resistance is considered to be maintained at a level of 8 or less.

[0160] (11) Evaluation of abrasion resistance In accordance with JIS K6264, the amount of abrasion at room temperature was measured using a pico abrasion tester to evaluate the abrasion resistance of the rubber composition. Reference Example 5 is expressed as an index of 100. A smaller value indicates better abrasion resistance. An index of 110 or less is considered to indicate that the abrasion resistance is maintained.

[0161]

[0162] *12 NR: Natural rubber *13 BR: Butadiene rubber, manufactured by UBE Elastomers, product name "BR150L" *14 Unused CB: Unused carbon black, manufactured by Asahi Carbon, product name "N550", nitrogen adsorption specific surface area (N ２ SA) = 40m ２ / g, OAN = 121 mL / 100 g *15 Recycled CB: Recycled carbon black, manufactured by Enrestec, product name "PB365", ash content = 17% by mass *16 Quinoline-based: Quinoline-based antioxidant, manufactured by Seiko Chemical Co., Ltd., product name "Nonflex RD", 2,2,4-trimethyl-1,2-dihydroquinoline polymer *17 Phenylenediamine-based: Phenylenediamine-based antioxidant, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C", N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine

[0163] Table 4 shows that the rubber compositions of Reference Examples 6 to 12 have an improved proportion of sustainable materials, and although their crack resistance and abrasion resistance are lower than that of Reference Example 5, which does not use recycled carbon black, they are maintained within an acceptable range without a significant decrease.

[0164] Two types of rubber compositions having the compound compositions shown in Table 5 were prepared, and these rubber compositions were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test specimens. The obtained vulcanized rubber test specimens were punched out into JIS-3 dumbbells, and the resulting samples were subjected to tensile tests at room temperature in accordance with JIS K 6251:2004, and the breaking strength (TB) before thermal degradation (initial) and after thermal degradation (100°C × 24 hours) was measured. The results are shown in Table 5. A higher value indicates better fracture resistance, i.e., better crack resistance.

[0165]

[0166] *18 Butadiene rubber: Manufactured by UBE Elastomers, product name "BR150L" *19 Carbon black: Manufactured by Asahi Carbon, product name "N550", nitrogen adsorption specific surface area (N ２ SA) = 40m ２ / g, OAN = 121 mL / 100 g *20 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *21 Quinoline-based: Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 224" *22 Phenylenediamine-based: Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrack 6C" *23 Oil: ENEOS, product name "A / Omix" *24 Fatty acid: Miyoshi Oil & Fat Co., Ltd., product name "MXST" *25 Other chemicals: Total amount of sulfur, vulcanization accelerator, resin, and wax, same ratio in each rubber composition

[0167] Table 5 shows that replacing carbon black (virgin carbon black) with commercially available recycled carbon black among the various materials contained in the rubber composition reduces the tensile strength (TB) and crack propagation resistance both before and after thermal degradation.

[0168] From Tables 2, 3, and 4, it can be seen that the rubber composition of the present invention is capable of increasing the proportion of sustainable materials, maintains crack resistance and abrasion resistance without a significant decrease compared to when unused carbon black is used, and exhibits excellent tensile strength and crack propagation resistance.

[0169] The rubber composition of the present invention can be used in rubber products such as tires, rubber tracks, and seismic isolation rubber.

[0170] 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 where the line caused by the third largest particle appears 21: Tire 22: Bead area 23: Sidewall area 24: Tread area 25: Bead core 26: Carcass 27: Belt 28: Side rubber 29: Gum chafer

Claims

1. A rubber composition comprising a rubber component (A), recycled carbon black (B), and an antioxidant containing a quinoline-based antioxidant (C), wherein the recycled carbon black (B) is recycled carbon black that, when measured with a grind gauge, has three or more lines with a length of 10 mm or more, and the particle size of the third largest particle among the particles that give rise to the lines with a length of 10 mm or more is 20 μm or less.

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

3. The rubber composition according to claim 1, wherein, in the measurement using the 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 is prepared.

4. The rubber composition according to claim 1, wherein the anti-aging agent is two types of anti-aging agents, including the quinoline-based anti-aging agent (C).

5. The rubber composition according to claim 1, further comprising zinc oxide (D).

6. The rubber composition according to claim 1, wherein the total amount of styrene in the rubber component (A) is 5% by mass or less.

7. The rubber composition according to claim 5, wherein the mass ratio of zinc oxide (D) to the quinoline-based antioxidant (C) [zinc oxide (D) / quinoline-based antioxidant (C)] is greater than 1.8 and less than or equal to 5.

0.

8. The rubber composition according to claim 1, further comprising carbon black (E) other than the recycled carbon black (B).

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

10. The rubber composition according to claim 9, wherein the rubber component (A) further comprises butadiene rubber.

11. The rubber composition according to claim 1, further comprising at least one of rubber powder and recycled rubber.

12. The rubber composition according to claim 11, comprising at least one of rubber powder and recycled rubber in an amount of 10 parts by mass or less per 100 parts by mass of the rubber component (A).

13. The rubber composition according to claim 5, wherein the content of zinc oxide (D) is 4 parts by mass or less per 100 parts by mass of the rubber component (A).

14. The rubber composition according to claim 4, further comprising zinc oxide (D), wherein the mass ratio of the zinc oxide (D) to the total amount of the two anti-aging agents [zinc oxide (D) / total amount of the two anti-aging agents] is greater than 0.55 and less than or equal to 2.

0.

15. The 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.

16. The rubber composition according to claim 15, wherein the recycled carbon black (B) contains Zn.

17. The rubber composition according to claim 16, wherein the recycled carbon black (B) has a Zn content of 0% by mass or more and 3% by mass or less.

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

19. An internal tire component comprising the rubber composition described in claim 1.

20. A tire comprising the tire internal member described in claim 19.

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