Rubber composition, tire internal member, and tire

Abstract

[Problem] To provide a rubber composition which is capable of improving the ratio of a sustainable material in a rubber product and retains elongation at break (EB) and air permeation resistance after thermal deterioration. [Solution] A rubber composition comprises: a rubber component (A); and a recovered carbon black (B), wherein the rubber component (A) contains 5-25 parts by mass of an isoprene rubber and 75-95 parts by mass of butyl rubber in 100 parts by mass of the rubber component (A).

Description

Rubber composition, tire internal component, and tire

[0001] The present invention relates to a rubber composition, a tire internal component, and a tire.

[0002] Conventionally, various rubber compositions have been used in rubber products such as tires, rubber crawlers, seismic isolation rubber, etc. In order to ensure the strength of these rubber products, the rubber compositions that are the raw materials thereof usually contain carbon black as a reinforcing filler.

[0003] On the other hand, recently, from the viewpoint of social sustainability, there has been a demand for rubber products to use so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, and there has also been a demand for an increase in the proportion of sustainable materials in rubber compositions used in such rubber products. For example, with regard to carbon black, recycled carbon black is known as a material derived from recycled resources (see Patent Document 1 below).

[0004] EP 3427975

[0005] However, if recycled carbon black is used as a reinforcing filler instead of virgin carbon black to increase the proportion of sustainable materials in rubber products, there is a problem that the elongation at break (EB) of the rubber composition after thermal aging decreases, and the durability of the rubber product using the rubber composition after thermal aging decreases. Furthermore, air permeability resistance may also be required for internal components of tires. Therefore, it is necessary to maintain durability and air permeability after thermal aging while improving the proportion of sustainable materials.

[0006] Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technology and to provide a rubber composition that can increase the proportion of sustainable materials in rubber products and maintain elongation at break (EB) and air permeation resistance after thermal aging. Another object of the present invention is to provide a tire internal member and a tire that have an increased proportion of sustainable materials and maintain durability and air permeation resistance after thermal aging.

[0007] The rubber composition, tire internal member, and tire of the present invention that solve the above problems are summarized as follows.

[0008] [1] A rubber composition comprising a rubber component (A) and recycled carbon black (B), wherein the rubber component (A) contains 5 to 25 parts by mass of an isoprene-based rubber and 75 to 95 parts by mass of a butyl rubber per 100 parts by mass of the rubber component (A).

[0009] [2] The rubber composition according to [1], wherein the recycled carbon black (B) is obtained by thermal decomposition of a vulcanized rubber product containing carbon black.

[0010] [3] The rubber composition according to [1] or [2], wherein the recycled carbon black (B) has an ash content of 25 mass% or less.

[0011] [4] The rubber composition according to any one of [1] to [3], further comprising a carbon black (C) other than the recycled carbon black (B).

[0012] [5] The rubber composition according to [4], wherein the proportion of the recycled carbon black (B) in the total amount of the recycled carbon black (B) and the carbon black (C) other than the recycled carbon black (B) is 5 to 35 mass%.

[0013] [6] The carbon black (C) other than the recycled carbon black (B) has a dibutyl phthalate (DBP) oil absorption of 50 to 150 mL / 100 g and a nitrogen adsorption specific surface area (N ２ SA) is 20 to 130 m ２ The rubber composition according to [4] or [5], wherein the elastic modulus is 1 / g.

[0014] [7] The rubber composition according to any one of [1] to [6], further comprising oil.

[0015] [8] The rubber composition according to any one of [1] to [7], further comprising a phenolic resin.

[0016] [9] The rubber composition according to any one of [1] to [8], further comprising 10 parts by mass or less of at least one of rubber powder and reclaimed rubber per 100 parts by mass of the rubber component (A).

[0017]

[10] The rubber composition according to any one of [1] to [9], further comprising clay.

[0018]

[11] A tire internal member made of the rubber composition according to any one of [1] to

[10] .

[0019]

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

[11] .

[0020] According to the present invention, it is possible to provide a rubber composition that can increase the proportion of sustainable materials in rubber products and maintain the elongation at break (EB) and air permeation resistance after thermal aging. Also, according to the present invention, it is possible to provide a tire internal member and a tire that have an increased proportion of sustainable materials and maintain the durability and air permeation resistance after thermal aging.

[0021] 1 is a cross-sectional view of one embodiment of a tire of the present invention.

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

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

[0024] In this specification, the "proportion of sustainable materials" refers to the total mass proportion of materials derived from biological resources (biomass resources) and materials derived from renewable resources (recycled resources) in the target rubber composition, tire internal components, and tire.

[0025] In this specification, the term "biological resources (biomass resources)" refers to carbon-neutral organic resources derived from living organisms, and includes, for example, materials stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and is a resource excluding fossil resources (petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but are preferably non-edible in order not to compete with food and from the viewpoint of effective resource utilization.

[0026] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock excrement, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, etc.), and the like. Examples of biological resources include: corn oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc.), carbohydrate crops (corn, wheat, rice, rice husks, rice bran, old rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue left after sugarcane juicing), soybeans, soybean pulp refuse, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, and algae. The biological resources may also be processed (i.e., biological resource-derived substances). Examples of processing methods include biological processing methods utilizing the activity of microorganisms, plants, animals, and their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, thermal energy, light energy, etc.; and physical processing methods such as pulverization, compression, microwave treatment, and electromagnetic wave treatment. The biological resources may also be extracted and purified from the biological resources or biological resources that have undergone the above-described processing (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the above-mentioned biological resources can also be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, with valine, leucine, isoleucine, arginine, and phenylalanine being preferred.The amino acids may be either L-amino acids or D-amino acids, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. Examples of the fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. Examples of the fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may contain various materials and impurities.

[0027] In this specification, the term "recycled resources" refers to resources obtained by regenerating (recycling) products that have been used once, or that have been collected without being used, or that have been discarded. For example, recycled resources include resources obtained by regenerating (recycling) used rubber products such as used tires.

[0028] <Rubber Composition> The rubber composition of this embodiment includes a rubber component (A) and recycled carbon black (B). The rubber component (A) is characterized in that it contains 5 to 25 parts by mass of an isoprene-based rubber and 75 to 95 parts by mass of a butyl rubber per 100 parts by mass of the rubber component (A).

[0029] In the rubber composition of this embodiment, the recycled carbon black (B) is a material derived from a recycled resource (recycled resource). Therefore, by incorporating recycled carbon black (B) into the rubber composition, the proportion of sustainable materials in rubber products using the rubber composition can be increased. However, as mentioned above, incorporating recycled carbon black instead of conventional virgin carbon black poses the problem of a decrease in the elongation at break (EB) of the rubber composition after thermal aging. It is also necessary to maintain the air permeability resistance of the rubber composition. Therefore, in the rubber composition of this embodiment, the rubber components are incorporated so that 5 to 25 parts by mass of isoprene-based rubber and 75 to 95 parts by mass of butyl rubber per 100 parts by mass of rubber component (A), thereby suppressing and maintaining the decrease in elongation at break (EB) and air permeability resistance after thermal aging. Therefore, the rubber composition of the present invention can increase the proportion of sustainable materials in rubber products, while maintaining the elongation at break (EB) and air permeability resistance after thermal aging.

[0030] (Rubber Component (A)) The rubber component (A) of this embodiment contains 5 to 25 parts by mass of an isoprene-based rubber and 75 to 95 parts by mass of a butyl rubber per 100 parts by mass of the rubber component (A). By containing 5 to 25 parts by mass of an isoprene-based rubber and 75 to 95 parts by mass of a butyl rubber per 100 parts by mass of the rubber component (A), the elongation at break (EB) and air permeation resistance after thermal aging can be maintained.

[0031] The rubber composition of this embodiment includes a rubber component (A), which provides rubber elasticity to the composition. The rubber component (A) preferably has 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, still more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of the rubber component (A) refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in the rubber component (A).

[0032] 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 components 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 even be 100 mol%. Furthermore, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer components 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 even be 100 mol%.

[0033] 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, and even more preferably 200,000 or more. The weight average molecular weight (Mw) of the rubber component (A) is preferably 5,000,000 or less, more preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,300,000 or less. In this specification, the weight average molecular weight (Mw) of the rubber component (A) can be determined, for example, in terms of standard polystyrene, based on measurements obtained using a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation; detector: differential refractometer; column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0034] The rubber component (A) contains 5 to 25 parts by mass of an isoprene-based rubber per 100 parts by mass of the rubber component (A). Isoprene-based rubber refers to a rubber containing units derived from isoprene as a monomer unit. When the rubber component (A) contains 5 to 25 parts by mass of an isoprene-based rubber per 100 parts by mass of the rubber component (A), the breaking strength of the rubber composition can be increased. As a result, the durability of rubber products using the rubber composition can be further improved. From the same viewpoint, the rubber component (A) preferably contains 5 to 22 parts by mass of an isoprene-based rubber per 100 parts by mass of the rubber component (A), more preferably 5 to 20 parts by mass, and even more preferably 8 to 20 parts by mass.

[0035] Examples of the isoprene-based rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). Examples of natural rubber (NR) that can be used include those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20). The origin of the natural rubber (NR) is not particularly limited, and examples include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of synthetic isoprene rubber (IR) are not particularly limited, and examples include those commonly used in the tire industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0036] The isoprene-based rubber preferably has a sustainability ratio 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. To achieve a sustainability ratio within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.).

[0037] The isoprene-based rubber preferably contains natural rubber (NR). The inclusion of natural rubber in the isoprene-based rubber further increases the proportion of sustainable materials and enhances the breaking strength of the rubber composition. As a result, the proportion of sustainable materials and durability of rubber products using the rubber composition can be further improved.

[0038] The rubber component (A) contains 75 to 95 parts by mass of butyl rubber per 100 parts by mass of the rubber component (A). Butyl rubber is a rubber obtained by copolymerizing isobutylene with isoprene and is also called isobutylene-isobutylene copolymer (IIR). Butyl rubber has extremely low gas permeability, and when the rubber component (A) contains 75 to 95 parts by mass of butyl rubber per 100 parts by mass of the rubber component (A), the air permeation resistance of the rubber composition can be maintained while suppressing a decrease in elongation at break (EB) after thermal aging. From the viewpoint of maintaining the elongation at break (EB) and air permeation resistance after thermal aging, the rubber component (A) preferably contains 78 to 95 parts by mass of butyl rubber per 100 parts by mass of the rubber component (A), more preferably 80 to 95 parts by mass, and even more preferably 80 to 92 parts by mass.

[0039] The rubber component (A) may contain a butadiene-based rubber in addition to an isoprene-based rubber and a butyl rubber. Here, the butadiene-based rubber refers to a rubber containing a unit derived from butadiene as a monomer unit. Examples of the butadiene-based rubber include butadiene rubber (BR) and aromatic vinyl compound-butadiene copolymer rubber (e.g., styrene-butadiene rubber (SBR)). Here, the butadiene used as a raw material for the butadiene-based rubber is preferably derived from a biological resource or a recycled resource.

[0040] Examples of the butadiene rubber (BR) include high-cis butadiene rubber, low-cis butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available butadiene rubbers can be used as the butadiene rubber (BR), and examples of commercially available butadiene rubbers include products from UBE Elastomers Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Corporation, and Zeon Corporation. These butadiene rubbers may be used alone or in combination of two or more.

[0041] Examples of the aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) include emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)) and solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)). In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, and divinylnaphthalene. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, SBR is preferred as the aromatic vinyl compound-butadiene copolymer rubber. The styrene may have a substituent. As the aromatic vinyl compound-butadiene copolymer rubber, commercially available products can be used, and examples of such commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Zeon Corporation, Sumitomo Chemical Co., Ltd. These aromatic vinyl compound-butadiene copolymer rubbers may be used alone or in combination of two or more.

[0042] The butadiene-based rubber preferably has 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. To achieve a sustainability rate within the above range, for example, a polymer synthesized using a bioresource-derived butadiene, a recycled resource-derived butadiene, a bioresource-derived aromatic vinyl compound (e.g., bioresource-derived styrene), or a recycled resource-derived aromatic vinyl compound (e.g., recycled resource-derived styrene) as a monomer component may be used. In this case, the synthesized polymer may be a homopolymer of a bioresource-derived monomer, a homopolymer of a recycled resource-derived monomer, a copolymer of a bioresource-derived monomer and a recycled resource-derived monomer, or a copolymer of a bioresource-derived monomer and / or a recycled resource-derived monomer and a fossil resource (e.g., petroleum)-derived monomer. Note that the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (for example, styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene or the like according to conventional methods, but also rubber obtained by reactions involving microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.") or enzymatic reactions.

[0043] The butadiene-based rubber preferably contains butadiene rubber (BR), which can improve physical properties such as elongation at break (EB) of the rubber composition.

[0044] Furthermore, the rubber component (A) may contain, as described above, butadiene rubber (BR) or aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) in addition to the above-mentioned isoprene-based rubber and butyl rubber (IIR). In addition to these, the rubber component (A) may also contain diene-based rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These rubber components may be used alone or in combination of two or more. However, in the rubber composition of this embodiment, the total styrene content in the rubber component (A) is preferably 5% by mass or less, more preferably 3% by mass or less, and may even be 0% by mass. If the total styrene content in the rubber component (A) exceeds 5% by mass, the physical properties of the rubber composition may be reduced, and the elongation at break (EB) after thermal aging may not be sufficiently maintained.

[0045] In order to set the sustainability rate of the entire rubber component (A) within the above range, it is preferable to use natural rubber (NR) as the rubber component (A) or a polymer synthesized using a monomer component derived from a biological resource or a monomer component derived from a recycled resource as a monomer component.

[0046] Generally, the raw materials for rubber compositions for tires (e.g., rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment and are therefore typically produced in large factories in specific regions, requiring significant amounts of energy for the storage and transportation of raw materials and finished products. In contrast, materials derived from biological resources (biomass resources) are derived from local agricultural products, forests, etc., and can be produced on a small scale through microbial fermentation and catalytic reactions. By utilizing local products and waste, the energy required for transporting and storing raw materials can be reduced, and the energy required for transporting and storing the produced materials to tire factories can also be reduced, making them environmentally friendly. Materials derived from recycled resources can be obtained, for example, by dismantling, downsizing, and pyrolyzing used tires to extract the tire-constituting materials, such as rubber, fillers, and steel cords. In addition, sulfur can be obtained from biological resources or processed products of biological resources by a method including a desulfurization step of desulfurizing biological resources or processed products of biological resources to remove sulfur-containing substances from the biological resources or processed products of biological resources, a recovery step of recovering sulfur from the desulfurization residue generated in the desulfurization step, and a processing step of processing the recovered sulfur into sulfur for vulcanization (for example, the method described in Japanese Patent Application No. 2022-140390), and raw materials for tire rubber compositions can be obtained from various waste products and used items. In this way, the use of sustainable materials (materials derived from biological resources or materials derived from recycled resources) can reduce the overall environmental impact of tire manufacturing, such as reducing carbon dioxide emissions (LCCO2) over the entire life cycle, reducing energy consumption (LCE) over the entire life cycle, reducing costs incurred over the entire life cycle (LCC), and reducing the use of fossil resources.

[0047] As a means of obtaining materials derived from recycled resources (recycled resources), recovered rubber products such as tires may be subjected to a "dismantling and downsizing" process, and rubber products such as tires manufactured using the rubber composition of this embodiment may further be subjected to "dismantling and downsizing." Dismantling and downsizing is a series of processes in which rubber products such as tires are crushed and separated into individual materials. Dismantling and downsizing may further include the processes of "separation," "cutting," "chipping," "crushing," and "pulverization" in this order. Separation is a process in which a rubber product is separated into individual materials (e.g., rubber and metal). Cutting is a process in which a rubber product is cut into pieces into individual parts (e.g., tread and sidewall). Chipping is a process in which a rubber product is scraped or drilled. Crushing is a process in which a rubber product is crushed into chips on the order of several inches. Crushing is a process in which a rubber product is crushed into granules.

[0048] Separation techniques include pull-out, induction heating, punch-cutting, magnetic separation, cutting separation, mechanical separation, cooling, and water jetting. Pull-out is a method of using a hook or similar tool to hook and pull the bead out of the tire. Induction heating is a method of using induction heating to reduce the adhesive force between the metal and rubber of the bead, separating them. Punch-cutting is a method of removing the bead from the tire by making a series of overlapping punch cuts (holes) in the tire sidewall around the bead. Magnetic separation is a method of using magnetic force to separate the metal and rubber of the bead. Cut-out is a method of cutting and separating the metal and rubber of the bead using a blade, cutter blade, knife, or rotary milling machine. Mechanical separation is a method of separating the metal and rubber by applying sufficient mechanical force to separate them. Cooling is a method of using liquid nitrogen or similar to cool the rubber, thereby embrittling it before separation. Water jetting is a method of separating the rubber and metal by spraying water at high pressure.

[0049] Cutting methods include rotary blades, blade cutters, L-knives, water jets, and pneumatic cutting. Rotary blades are a method of cutting by bringing a rotating blade (including blades and circular saws) into contact with an object. Blade cutters are a method of cutting using a blade or cutting edge. L-knives are a method of cutting using an L-shaped knife. Water jets are a method of cutting by spraying water (including water containing sand) at high pressure. Pneumatic cutting is a method of cutting using compressed air.

[0050] Chipping methods include punch cutting and filing. Punch cutting is a method of making holes using a punch blade. File filing is a method of scraping the tire using a file.

[0051] Crushing methods include rotary blades, blade cutters, and cut-off wheels. Rotary blades are a method of crushing materials by applying a rotating blade (including blades, circular saws, etc.) to the material. Blade cutters are a method of crushing materials using a blade or cutter blade. Cut-off wheels are a method of crushing materials by applying a cutting blade to a wheel-shaped crushing component and applying it to the material.

[0052] Pulverization methods include roller mills, pin mills, and water jets. Roller mills are a method of pulverizing materials by a "grinding and grinding action" that combines the compressive force caused by the centrifugal force of the rollers with the shearing force caused by the rotation of the rollers. Pin mills are a method of pulverizing materials by attaching dozens of pins to the surfaces of two opposing circular plates that are rotated at high speed. Water jets are a method of pulverizing materials by spraying water at high speed and causing it to collide with the object.

[0053] Furthermore, for separation, the following separation techniques may be selected depending on the material to be separated. When the material to be separated is metal, magnetic separation, "pulling, peeling, and tearing," melting, crushing, punching, high-pressure jet, cutting / machining, sedimentation, and centrifugal classification may be selected. Magnetic separation separates metal and rubber using magnetic force. Pulling, peeling, and tearing separate metal, such as bead wire, from the rubber by pulling, peeling, and tearing. Melting includes vibration melting, heated steam, and induction heating. Vibration melting separates metal components by vibrating the tire with ultrasound or the like to melt and separate the metal components. Heated steam melts the rubber by spraying heated steam, separating the metal cord. Induction heating heats the tire using electromagnetic induction to separate the metal cord. Crushing separates the metal cord from the rubber by crushing the tire with a roller or the like. Punching removes metal cord from the tire by creating a series of overlapping punching cuts in a circumferential pattern on the tire sidewall around the bead. High-pressure jetting separates metal and rubber by spraying water or other materials at high pressure. Cutting and milling separates the metal and rubber parts by mechanical cutting and milling. Sedimentation involves placing the wire in a water-soluble polyol at temperatures exceeding 160°C for several to several tens of hours, and separating the rubber and wire that settle to the bottom. Centrifugal classification is a type of air classification that uses centrifugal force to separate metal and rubber.

[0054] When the material to be separated is fiber, methods that may be selected include sieving, vibrating screen, melting, air classification, centrifugal classification, gravity classification, friction, "pulling, peeling, tearing," high-pressure jet, electrostatic separation, mechanical heat control, and cutting / milling. Sieving uses a sieve to separate fiber and rubber. Vibrating screens perform sieving by vibrating a sieve up and down. Melting includes heated steam and induction heating. Heated steam is sprayed onto the tire to melt the rubber and separate the metal cord. Induction heating uses electromagnetic induction to heat the tire and separate the metal cord. Air classification separates fiber and rubber powder by utilizing differences in the hydrodynamic behavior of particles (centrifugal force, gravity, inertia force, etc.). Centrifugal classification is a type of air classification that uses centrifugal force to separate fiber and rubber. Gravity classification is a type of air classification that uses gravity to separate fiber and rubber. Friction involves applying pressure to the tire to generate friction, forming agglomerates from the fibers, and then separating the agglomerates from the rubber granules using a sieve or similar. Pulling, peeling, and tearing involve pulling out, peeling, or tearing the fiber reinforcement parts to separate them from the rubber. High-pressure jets separate the fibers and rubber by spraying them at high pressure using water or similar. Electrostatic separation uses electrostatic force to charge particles, and then separates the fibers and rubber due to the difference in charge or electric field strength. Mechanical thermal control separates the rubber from the fiber reinforcement elements under controlled thermal conditions. Cutting and milling separates the fiber and rubber parts by mechanically cutting or milling them.

[0055] When the object to be separated is a sealant, mechanical lubrication after solidification or the use of a processing aid may be selected. Mechanical lubrication after solidification involves solidifying the sealant using liquid nitrogen or the like, and then removing the sealant layer by mechanical lubrication. The use of a processing aid involves removing the sealant layer using water or a soap solution.

[0056] When the object to be separated is resin, crushing, cutting, melting, or peeling may be selected. Crushing involves crushing the tire with a roller or the like to separate the resin from the rubber. Cutting involves cutting along the interface between the rubber layer and the resin to separate the resin. Melting includes vibration melting. Vibration melting involves vibrating the tire with ultrasound or the like to melt and separate the resin. Peeling involves foaming unfoamed rubber by heating, which applies a peeling force between the rubber and the resin component, thereby peeling the resin component from the rubber.

[0057] Furthermore, when producing the rubber composition, the ratios of monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources can be appropriately selected depending on the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food). By polymerizing the monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources, rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be obtained that has performance equivalent to that of conventional synthetic rubber. When using monomer components derived from recycled resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomers. In such cases, the environmental impact can be evaluated by adopting the mass balance approach.

[0058] The ratio of each monomer unit (e.g., units derived from isoprene, units derived from isobutylene, and units derived from an aromatic vinyl compound (if included)) in the entire rubber component (A) can be adjusted appropriately depending on the components to which the rubber component (A) is applied. The ratio of each monomer unit in the entire rubber component (A) can be adjusted, for example, by appropriately combining the above-mentioned isoprene-based rubber and butyl rubber. Furthermore, when the rubber component (A) contains a butadiene-based rubber, the ratio of cis-bond units in the butadiene-derived units can also be adjusted appropriately depending on the components to which the rubber component (A) is applied. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "isoprene-derived unit" refers to a structural unit in a polymer formed based on the isoprene monomer (including isoprene units in natural rubber), the term "isobutylene-derived unit" refers to a structural unit in a polymer formed based on the isobutylene monomer, and the term "aromatic vinyl compound-derived unit" refers to a structural unit in a polymer formed based on the aromatic vinyl compound monomer. In this specification, the ratio of each monomer unit is measured by NMR.

[0059] The rubber component (A) may be modified to have a functional group that interacts with fillers such as carbon black and silica. Examples of such functional groups include amino, amide, isocyanate, imino, imidazole, urea, ammonium, imide, hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, epoxy, ether, carbonyl, oxycarbonyl, silyl, alkoxysilyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, and thiocarbonyl groups. These functional groups may also have a substituent. These functional groups may be introduced into the rubber component either individually or in combination. Among these, an amino group, an alkoxy group, and an alkoxysilyl group are preferred, and a substituted amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxysilyl group having 1 to 6 carbon atoms are more preferred.

[0060] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component (A). The functional group is a modifying functional group that has interactivity with fillers such as silica and carbon black, and examples thereof include a nitrogen-containing functional group, a silicon-containing functional group, and an oxygen-containing functional group. Examples of compounds (modifiers) having a nitrogen-containing functional group include amino group-containing compounds. Examples of compounds (modifiers) having a silicon-containing functional group include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having an oxygen-containing functional group include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples of the compounds described in WO 2016 / 194316 and WO 2019 / 117256 include the compounds described in WO 2016 / 194316 and WO 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0061] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be produced in the same manner as conventional methods for producing synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources. Furthermore, the rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions using microorganisms or enzyme reactions.

[0062] Regarding the method for preparing bioresource-derived rubber from the above-mentioned bioresources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from a bioresource as the monomer component, it is possible to obtain a bioresource (biomass resource)-derived butadiene rubber (B-BR). Furthermore, by using styrene obtained from a bioresource and butadiene obtained from a bioresource as the monomer components, it is possible to obtain a bioresource (biomass resource)-derived styrene-butadiene rubber (B-SBR). Here, methods for obtaining B-BR and B-SBR from bioresources include artificial polymerization methods, in vivo polymerization methods, and polymerization methods using biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods depending on the desired tire performance.

[0063] Suitable butadienes obtained from biological resources include butadienes derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadienes derived from alkenes (preferably ethylene), and butadienes derived from unsaturated carboxylic acids (preferably tiglic acid). Two or more of these butadienes may be used in combination. Suitable styrenes obtained from biological resources include styrenes obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, and Apocynaceae families, more preferably plants belonging to the Liquidambar, Styrax, and Catharanthus roseus, and even more preferably sweetgum, Styrax rostrata, and Catharanthus roseus), and styrenes obtained from microorganisms (preferably microorganisms belonging to the Penicillium and Escherichia genera, more preferably P. citrinum, and transformed E. coli). Suitable styrenes may be used in combination.

[0064] Recently, biomass industrial complexes centered on bioethanol, bioethylene, and the like have been planned. However, bioethanol and bioethylene are produced primarily using sugars and / or cellulose as biological resources, and do not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources as the biological resource-derived monomer component, or to use a combination of monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources, and further adjust the ratios of these monomer components appropriately. This allows for the effective utilization of a wide range of biological resources, such as sugars, proteins, and lipids, as well as renewable resources, without relying on a single type of biological resource. It also allows for a stable supply of rubber derived from sustainable materials and further allows for environmental considerations depending on the production conditions. When multiple types of monomer components derived from biological resources are used, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadienes derived from multiple types of biological resources with different origins as the biological resource-derived butadiene, and / or to use a mixture of styrenes derived from multiple types of biological resources with different origins as the biological resource-derived styrene. This allows for effective use of multiple types of biological resources.

[0065] (Recycled Carbon Black (B)) The rubber composition of this embodiment contains recycled carbon black (B). The recycled carbon black (B) is a material derived from a recycled resource (recycled resource). Therefore, by blending the recycled carbon black (B) into the rubber composition, it is possible to increase the proportion of sustainable materials in rubber products to which the rubber composition is applied.

[0066] As used herein, "recycled carbon black" refers to carbon black recovered from recycled waste materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only waste generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process of scraping the tread portion remaining on the base tire during tire retreading, for example. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELTs (End-of-Life Tires) that have reached the end of their service life. Waste oils are not limited to those generated during the decomposition of plastics and rubber, but also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils containing carbon black or rubber containing carbon black are desirable. "Recycled carbon black" differs from carbon black produced directly from hydrocarbons such as petroleum, natural gas, and coal, i.e., non-recycled carbon black. Note that "used" here refers not only to waste oils discarded after actual use, but also to waste oils that were produced but discarded without actually being used.

[0067] The recycled carbon black (B) is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black (B) is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from the volatile component, the oil component with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixing of different grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0068] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. Therefore, recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, a higher carbon content in the recycled carbon black is preferable. The carbon content of the recycled carbon black (B) is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and even more preferably 89% by mass or more. The carbon content of the recycled carbon black (B) is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0069] Specific examples of the ash include 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 residues obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black (B) is allowed to contain ash. The lower limit of the ash content of the recycled carbon black (B) may be 0.5% by mass. Meanwhile, considering the various physical properties required for tires and the quality of the recycled carbon black, the ash content of the recycled carbon black (B) is preferably 25% by mass or less, more preferably 20% by mass or less, even more preferably 15% by mass or less, and particularly preferably 5.0% by mass or less. When the ash content of the recycled carbon black (B) is 25% by mass or less, the physical properties of rubber products using the rubber composition can be improved. Herein, the ash content of carbon black is determined in accordance with ASTM D8474 and D1506.

[0070] The recycled carbon black (B) can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3,427,975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black (B) can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

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

[0004] of Japanese Patent No. 6,856,781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercially Available Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0071] The recycled carbon black (B) may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of the recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks that have been treated to include functional groups on their surfaces.

[0072] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0073] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0074] Furthermore, when the crosslinked rubber product used in the degradation is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and the degradation step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the degradation step may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and the degradation step may be carried out for each group. When the degradation step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0075] The recycled carbon black (B) used in this embodiment has a nitrogen adsorption specific surface area (N ２ SA) is 40 to 100m ２ / g, and 50 to 90m ２ / g, and more preferably 55 to 75m ２ / g is particularly preferred. In addition, the DBP oil absorption is preferably 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Note that, as the recycled carbon black in this embodiment, a commercially available product can be used, and an example of such a commercially available product is "PB365" manufactured by Enrestec. PB365 is recycled carbon black produced through the thermal decomposition of used tires, and has an N ２ SA is 73.6m ２ / g. PB365 contains about 17% by mass of ash. In this specification, the nitrogen adsorption specific surface area (N ２ SA) is the statistical thickness specific surface area (STSA) and is determined in accordance with ASTM D6556. In addition, in this specification, the DBP oil absorption of carbon black is determined in accordance with ASTM D2414.

[0076] The recycled carbon black (B) preferably has an oil adsorption number (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, the OAN of the recycled carbon black (B) is determined in accordance with ASTM D2414.

[0077] The pH of the recycled carbon black is preferably 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. In this specification, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0078] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, the toluene color transmittance of recycled carbon black is determined in accordance with ASTM D1618.

[0079] The recycled carbon black preferably has a heat loss of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less at 125°C. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0080] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0081] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. Herein, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0082] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. Herein, the 325 mesh (44 μm) sieve residue of the recycled carbon black is determined in accordance with ASTM D1514.

[0083] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0084] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Herein, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0085] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Here, in this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming a refractive index of 1.33 for water and a refractive index of 1.75 for the filler.

[0086] The recycled carbon black preferably contains particles of 5 μm or less in a proportion of 50% by volume or more, more preferably 70% by volume or more, and particularly preferably 80% by volume or more.

[0087] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption capacity of the recycled carbon black is determined in accordance with ASTM D3493.

[0088] The compressed oil adsorption (COAN) of the recycled carbon black is preferably 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the COAN of the recycled carbon black is determined in accordance with ASTM D3493.

[0089] The content of the recycled carbon black (B) is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, more preferably 5 to 50 parts by mass, even more preferably 5 to 30 parts by mass, and still more preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the recycled carbon black (B) is 5 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of improving the proportion of sustainable materials in rubber products to which the rubber composition is applied is significant, and when the content is 50 parts by mass or less, the fracture resistance of the rubber composition can be more reliably maintained.

[0090] (Carbon Black (C) Other Than Recycled Carbon Black (B)) The rubber composition of this embodiment preferably further contains carbon black (C) other than the recycled carbon black (B). By combining the carbon black (C) other than the recycled carbon black (B) with the recycled carbon black (B), the elongation at break (EB) of the rubber composition after thermal aging can be maintained at a higher level. As the carbon black (C) other than the recycled carbon black (B), plant-derived carbon black is particularly preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. The grade of the carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. As the carbon black (C) other than the recycled carbon black (B), commercially available products can be used, and examples of commercially available carbon black (C) other than the recycled carbon black (B) include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Birla Carbon Co., Ltd., etc. These carbon blacks may be used alone or in combination of two or more.

[0091] The nitrogen adsorption specific surface area (N ２ The nitrogen adsorption specific surface area (N SA) of the carbon black (C) other than the recycled carbon black (B) is not particularly limited and can be adjusted as appropriate depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. ２ SA) is 20m ２ / g or more is preferable, and 50m ２ / g or more is more preferable, and 70m ２ / g or more is more preferable, and 90m ２ / g or more is more preferable. In addition, the nitrogen adsorption specific surface area (N ２ SA) is 200m ２ / g or less is preferable, and 150m ２ / g or less is more preferable, and 130m ２ / g or less is more preferable.

[0092] The carbon black (C) other than the recycled carbon black (B) preferably has a dibutyl phthalate (DBP) oil absorption of 50 to 150 mL / 100 g. The carbon black (C) other than the recycled carbon black (B) preferably has a dibutyl phthalate (DBP) oil absorption of 50 to 150 mL / 100 g and a nitrogen adsorption specific surface area (N ２ SA) is 20 to 130 m ２ / g, and it is more preferable that the dibutyl phthalate (DBP) oil absorption is 80 to 130 mL / 100 g and the nitrogen adsorption specific surface area (N ２ SA) is 20 to 60 m ２ It is more preferable that the dibutyl phthalate (DBP) oil absorption is 80 to 130 mL / 100 g and the nitrogen adsorption specific surface area (N ２ SA) is 20 to 60 m ２ By combining the carbon black (C) having a carbon black content of 0.15 wt. / g with the recycled carbon black (B), it is possible to maintain a higher elongation at break (EB) of the rubber composition after thermal aging.

[0093] The content of the carbon black (C) other than the recycled carbon black (B) is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the carbon black (C) other than the recycled carbon black (B) is more preferably 5 parts by mass or more and preferably 100 parts by mass or less per 100 parts by mass of the rubber component (A).

[0094] The proportion of the recycled carbon black (B) in the total amount of the recycled carbon black (B) and the carbon black (C) other than the recycled carbon black (B) (i.e., the total amount of carbon black) is preferably 5 to 35% by mass, and more preferably 5 to 21% by mass. When the proportion of recycled carbon black (B) in the total amount of carbon black is 5% by mass or more, the effect of improving the proportion of sustainable materials in the rubber composition and rubber products using it is significant. Furthermore, when the proportion of recycled carbon black (B) in the total amount of carbon black is 35% by mass or less, the elongation at break (EB) of the rubber composition after thermal aging can be maintained at an even higher level.

[0095] (Oil) The rubber composition of the present embodiment preferably further contains oil. When the rubber composition further contains oil, various physical properties of a rubber product to which the rubber composition is applied can be improved.

[0096] The oil is a general term for extender oils contained in rubber components and liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, and mixtures thereof. From the perspective of reducing environmental impact, vegetable oils and recycled oils are preferred. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil. Examples of process oils include paraffin-based process oils, aromatic process oils, and naphthenic process oils. As the oil, commercially available products can be used, and examples of commercially available oils that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0097] The content of the oil is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the oil is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, more preferably 3 parts by mass or more, more preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component (A). Furthermore, the content of the oil is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0098] (Phenol-based resin) The rubber composition of the present embodiment preferably further contains a phenol-based resin. When the rubber composition further contains a phenol-based resin, various physical properties of a rubber product to which the rubber composition is applied can be improved.

[0099] The phenolic resin is not particularly limited and can be appropriately selected depending on the required performance. For example, it can be produced by subjecting a phenol such as phenol, cresol, resorcinol, or tert-butylphenol, or a mixture thereof, to a condensation reaction with formaldehyde in the presence of an acid catalyst such as hydrochloric acid or oxalic acid. The phenolic resin may be unmodified or modified. The phenolic resin may be used alone or in combination of two or more.

[0100] Examples of unmodified phenolic resins include phenolic resins and phenol-formaldehyde resins.

[0101] Examples of modified phenolic resins include those having a structure in which unmodified phenolic resins are modified with oils such as rosin oil, tall oil, cashew oil, linoleic acid, oleic acid, and linolenic acid, and having substituents such as hydrocarbon groups (e.g., alkyl groups) on the phenolic skeleton of the phenolic resin.

[0102] The hydroxyl equivalent of the phenolic resin is preferably 100 g / eq to 300 g / eq, more preferably 100 g / eq to 200 g / eq, and even more preferably 100 g / eq to 150 g / eq. The hydroxyl equivalent is measured in accordance with JIS K0070:1992.

[0103] The content of the phenolic resin is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the phenolic resin is preferably 0.1 parts by mass or more and 3.5 parts by mass or less per 100 parts by mass of the rubber component (A).

[0104] (Rubber crumb and reclaimed rubber) The rubber composition of this embodiment preferably further contains at least one of rubber crumb and reclaimed rubber. By containing at least one of rubber crumb and reclaimed rubber in the rubber composition, the proportion of sustainable materials in the rubber product can be further increased. Rubber crumb and reclaimed rubber will be described in detail below.

[0105] The rubber composition of this embodiment preferably contains 10 parts by mass or less of at least one of rubber crumb and reclaimed rubber per 100 parts by mass of the rubber component (A). By containing 10 parts by mass or less of at least one of rubber crumb and reclaimed rubber per 100 parts by mass of the rubber component (A), the proportion of sustainable materials in the rubber product can be further improved without deteriorating the properties of the rubber composition. The amount of at least one of rubber crumb and reclaimed rubber may be 8 parts by mass or less, or 7 parts by mass or less, per 100 parts by mass of the rubber component (A). Furthermore, the amount of at least one of rubber crumb and reclaimed rubber may be 2 parts by mass or more per 100 parts by mass of the rubber component (A).

[0106] -Rubber Crumb- The rubber crumb may be obtained by crushing used rubber products such as used tires and, if desired, removing reinforcing materials such as steel and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for producing the rubber crumb and crushing the resulting product. For example, rubber crumb can be obtained from vulcanized rubber by the method described in "Rubber Chemistry and Technology." The process of crushing vulcanized rubber to obtain rubber crumb may involve mechanical treatment or low-temperature treatment. For example, in mechanical treatment, various crushing devices such as a cracker mill or a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature treatment, the finely chopped vulcanized rubber is frozen at a cryogenic temperature and then crushed into fine particles. In addition, a magnetic separator or the like can be used to remove steel, and an air separator or the like can be used to remove fibers. The rubber powder may be a commercially available product, such as those available from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the 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.

[0107] The composition of the rubber crumb is not particularly limited and depends on the composition of the vulcanized rubber from used rubber products (used tires) or the like that serve as the raw material. In one embodiment, the rubber crumb contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber crumb may be the same as or different from the rubber component, carbon black, silica, etc. that can be contained in the rubber composition of the present embodiment described above.

[0108] 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. 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 with a laser diffraction particle size distribution analyzer, for example, a "CAPA500" manufactured by Horiba, Ltd.

[0109] The rubber powder preferably has a 60-mesh sieve residue of less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit. The rubber powder preferably has an 80-mesh sieve residue of less than 10% by mass, 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 in accordance with ASTM D5644-01.

[0110] The rubber crumb preferably has an acetone extractable content of 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less. The rubber crumb preferably has an acetone extractable content of 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 extractable content in the rubber crumb refers to the acetone extractable content (%) determined by the acetone extraction method in accordance with JIS K6350.

[0111] The content of the rubber crumb is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the internal components of the tire, the target performance, etc. For example, the content of the rubber crumb is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component (A). Furthermore, the content of the rubber crumb is 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, still 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, per 100 parts by mass of the rubber component (A).

[0112] - Reclaimed Rubber - The reclaimed rubber is reclaimed from used rubber from rubber products such as tires. By including reclaimed rubber in the rubber composition, the proportion of sustainable materials in the rubber product can be increased. In the present invention, reclaimed rubber is not included in the rubber component (A).

[0113] The reclaimed rubber used in the rubber composition of this embodiment can be commercially available reclaimed rubber. The reclaimed rubber can be, for example, reclaimed rubber from used rubber such as automobile tires, tubes, and other rubber products specified in JIS K6313-2012, or rubber having properties equivalent thereto. The reclaimed rubber may also be subjected to a devulcanization treatment.

[0114] The type of reclaimed rubber may be selected from tube reclaimed rubber, tire reclaimed rubber, and other reclaimed rubber, or a combination of multiple types may be used. Among these, tire reclaimed rubber is preferred. The method for producing reclaimed rubber is not particularly limited, and known methods such as the oil pan method and the reclamation method can be used.

[0115] The rubber component in the reclaimed 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 reclaimed rubber can be determined by pyrolysis gas chromatography (PyGC).

[0116] The content of reclaimed rubber can be adjusted as appropriate depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of reclaimed rubber 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 the rubber component (A).

[0117] (Clay) The rubber composition of this embodiment preferably further contains clay. When the rubber composition contains clay, air permeation resistance can be maintained at a higher level. The clay is preferably flat, and more preferably has an aspect ratio of 3 to 30. When the aspect ratio of the clay is 3 or more, the air permeation resistance of the rubber composition can be improved, and when the aspect ratio of the clay is 30 or less, the processability of the rubber composition can be maintained at a high level.

[0118] The clay is not limited to, but examples thereof include kaolin clay, sericite clay, calcined clay, and surface-treated silane-modified clay. The clay may be used alone or in combination of two or more. Among these, kaolin clay is preferred from the viewpoint of maintaining air permeation resistance.

[0119] The content of the clay is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the clay is preferably 10 parts by mass or more, and more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the content of the clay is preferably 50 parts by mass or less, and more preferably 40 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0120] (Antiaging Agent) The rubber composition of this embodiment may contain an antioxidant. The antioxidant has the effect of improving the heat degradation resistance of the rubber composition and improving the elongation at break (EB) after heat degradation. The antioxidant may be used alone or in combination of two or more. When two or more antioxidants are used in combination, the antiaging effects of each antioxidant are complemented, the elongation at break (EB) after heat degradation is further improved, and the elongation at break (EB) after heat degradation can be maintained at a higher level.

[0121] Examples of the antioxidant include quinoline-based antioxidants, phenylenediamine-based antioxidants, diphenylamine-based antioxidants, phenol-based antioxidants, quinone-based antioxidants, carbamate-based antioxidants, and imidazole-based antioxidants. Among these, quinoline-based antioxidants and phenylenediamine-based antioxidants are preferred. Quinoline-based antioxidants are antioxidants having a quinoline moiety or a derivative thereof (such as a dihydroquinoline moiety). Furthermore, the phenylenediamine-based antioxidants are antioxidants having a phenylenediamine moiety (-NH-C ６ H ４ -NH-) or a derivative thereof.

[0122] The quinoline-based antioxidant preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Specific examples of the quinoline-based antioxidant include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Commercially available quinoline-based antioxidants can be used, including those from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis, and Lanxess. These antioxidants may be used alone or in combination of two or more. The quinoline-based antioxidant preferably contains a 2,2,4-trimethyl-1,2-dihydroquinoline polymer (antiaging agent TMDQ). Quinoline-based antioxidants containing a 2,2,4-trimethyl-1,2-dihydroquinoline polymer are highly effective in improving the heat degradation resistance of rubber compositions and also have the advantage of being less likely to discolor the rubber composition. Examples of the 2,2,4-trimethyl-1,2-dihydroquinoline polymer include a dimer, trimer, and tetramer of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0123] Examples of the phenylenediamine-based antiaging agents 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), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, and N,N'-dicyclohexyl-p-phenylenediamine (CCPD). Commercially available phenylenediamine-based antiaging agents can be used, and examples of commercially available antiaging agents that can be used include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis, and Lanxess. These antiaging agents may be used alone or in combination of two or more.

[0124] The content of the antioxidant is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the antioxidant is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the content of the antioxidant is 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).

[0125] (Zinc Oxide) The rubber composition of this embodiment may contain zinc oxide (zinc white). The zinc oxide is preferably obtained not only from zinc metal but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available zinc oxide can be used, and examples of commercially available zinc oxide include products from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0126] The content of the zinc oxide is not particularly limited and can be appropriately adjusted depending on, for example, the tire category, tire components, target performance, etc., to which the rubber composition is applied. For example, the content of zinc oxide is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 1.8 parts by mass or more, per 100 parts by mass of the rubber component (A). Furthermore, the content of zinc oxide is 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 the rubber component (A). When the content of zinc oxide is 4 parts by mass or less, per 100 parts by mass of the rubber component (A), the elongation at break (EB) of the rubber composition after thermal aging can be maintained at a high level. Furthermore, when the content of zinc oxide is in the range of 1.5 to 4 parts by mass relative to 100 parts by mass of the rubber component (A), the vulcanizability of the rubber composition can be improved while maintaining a higher elongation at break (EB) after thermal aging. When the content is in the range of 1.8 to 2.2 parts by mass, the vulcanizability of the rubber composition can be further improved while maintaining an even higher elongation at break (EB) after thermal aging.

[0127] (Resin) The rubber composition of the present embodiment may contain a resin other than a phenol-based resin. Examples of such a resin include a terpene-based resin, a rosin-based resin, and a C ５ based resin, C ５ -C ９ based resin, C ９ Examples of suitable resins include cyclopentadiene-based resins, aromatic resins, coumarone resins, indene resins, coumarone-indene-based resins, olefin-based resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene-based resins, rosin-based resins, and C ５ based resin, C ５ -C ９ based resin, C ９ Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins, and aromatic resins, with terpene-based resins and rosin-based resins being particularly preferred. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins that can further reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry roads, wet roads, snow-covered roads, and frozen roads. ５ based resin, C ９ based resin, C ５ -C ９ The cyclopentadiene-based resin and the cyclopentadiene-based resin can improve abrasion resistance and fuel economy in a balanced manner, while the aromatic resin can improve grip performance, abrasion resistance, and rubber strength in a balanced manner.

[0128] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). Furthermore, the resin may be modified to introduce a functional group that interacts with fillers such as carbon black and silica. 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.

[0129] The terpene resin is a solid resin obtained by blending turpentine, which is obtained simultaneously when rosin is obtained from pine trees, or a polymerization component separated therefrom, and polymerizing the blend using a Friedel-Crafts catalyst. Examples of such a resin include β-pinene resin and α-pinene resin. Terpene resins also include terpene-aromatic compound resins, and a representative example of such a terpene-aromatic compound resin is styrene-terpene resin. The styrene-terpene resin can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes used as raw materials are not particularly limited, and monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred.

[0130] Examples of the rosin-based resin include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil, and examples of modified rosins, rosin derivatives, and modified rosin derivatives include polymerized rosin and partially hydrogenated rosin thereof; glycerin ester rosin and partially hydrogenated rosin thereof and fully hydrogenated rosin thereof; pentaerythritol ester rosin and partially hydrogenated rosin thereof and polymerized rosin; and the like.

[0131] Said C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry. ５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate.５ The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene.

[0132] Said C ５ -C ９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ More specifically, copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, etc. as the main component may be mentioned. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0133] Said C ９ The C-based resin is ９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９ Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0134] The cyclopentadiene-based resin refers to a resin containing a unit derived from a cyclopentadiene-based monomer as a monomer unit. Examples of the cyclopentadiene-based resin include a homopolymer of a cyclopentadiene-based monomer, a copolymer of two or more cyclopentadiene-based monomers, and a copolymer of a cyclopentadiene-based monomer and another monomer. Here, examples of the cyclopentadiene-based monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a dicyclopentadiene-based resin. The dicyclopentadiene-based resin is, for example, a copolymer of AlCl ３ or BF ３ The term "dicyclopentadiene-based resin" refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as Benzene, etc. Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, copolymers of dicyclopentadiene and C ９ Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0135] The aromatic resin refers to a resin containing units derived from aromatic monomers as monomer units. Examples of the aromatic resin include homopolymers of aromatic monomers, copolymers of two or more aromatic monomers, and copolymers of aromatic monomers with other monomers. Examples of the aromatic monomer include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; naphthol-based monomers such as naphthol, alkylnaphthol, and alkoxynaphthol; and the like.

[0136] The softening point of the resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, more preferably 80 ° C. or higher, more preferably higher than 110 ° C., more preferably 116 ° C. or higher, more preferably 120 ° C. or higher, more preferably 123 ° C. or higher, and even more preferably 127 ° C. or higher. From the viewpoint of processability, the softening point of the resin is preferably 160 ° C. or lower, more preferably 150 ° C. or lower, more preferably 145 ° C. or lower, more preferably 141 ° C. or lower, and even more preferably 136 ° C. or lower. In this specification, the softening point of the resin is the temperature at which the ball drops when the softening point as defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0137] Commercially available resins can be used, and examples of commercially available resins include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Kraton Corporation, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Polymers, Inc., Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0138] The content of the resin is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the resin is preferably in the range of 5 to 100 parts by mass, more preferably in the range of 10 to 60 parts by mass, per 100 parts by mass of the rubber component (A).

[0139] (Silica) The rubber composition of this embodiment may contain silica. Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it contains a large number of silanol groups. These silicas may be used alone or in combination of two or more. Commercially available silicas can be used, and examples of commercially available silicas include products from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation.

[0140] From the viewpoint of reducing environmental impact, silica derived from siliceous plants is preferred as the silica. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making it easy to secure a sufficient supply. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs involved in transportation and storage, which is environmentally preferable from various viewpoints. The rice husk silica may be rice husk charcoal powder obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing the rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner is pulverized using a known pulverizer (e.g., a ball mill), and then sorted and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by the method described in JP 2019-38728 A. From the perspective of reducing environmental impact, it is also preferable to use silica obtained by extracting silicic acid components from silicon wafer scraps, glass bottles, etc., which are used as raw materials for semiconductors, and recycling the extracted silica.

[0141] The silica has a nitrogen adsorption specific surface area (N ２ SA) is 50m ２ / g or more, and ２ / g or more is more preferable, and 150m ２ / g or more. ２SA) is 350m ２ / g or less, and ２ / g or less is more preferable, and 230m ２ / g or less is more preferable, and 200m ２ / g or less. In this specification, the nitrogen adsorption specific surface area (N ２ SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0142] The content of silica can be appropriately adjusted depending on, for example, the tire category, tire components, target performance, etc. For example, the content of silica is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the content of silica is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0143] The proportion of silica in the total content of silica and carbon black is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the composition is applied, the tire components, the target performance, etc. For example, the proportion of silica in the total content of silica and carbon black may be any proportion from 0% by mass to 100% by mass, but is preferably 5% by mass or more in order to achieve a black color for the tire.

[0144] (Silane Coupling Agent) When the rubber composition of this embodiment contains silica, in order to improve the effect of the silica, the rubber composition preferably contains a silane coupling agent. 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-N,N-dimethylthiocarbamoyltetrasulfide, Examples of such tetrasulfides include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. As the silane coupling agent, commercially available products can be used, and examples of commercially available silane coupling agents that can be used include products from Evonik, Momentive, Shin-Etsu Silicones Co., Ltd., Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used alone or in combination of two or more.

[0145] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced primarily using sugars and / or cellulose as biological resources, and does not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of ethanol derived from biological resources (bioethanol) as a raw material for the silane coupling agent, or to use a combination of ethanol derived from biological resources (bioethanol), ethanol derived from renewable resources, and ethanol derived from fossil resources. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0146] The content of the silane coupling agent can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, relative to 100 parts by mass of the silica. In addition, the content of the silane coupling agent is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the silica.

[0147] (Liquid Polymer) The rubber composition of the present embodiment may contain a liquid polymer. The liquid polymer is a polymer that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid polymer may be used alone or in combination of two or more.

[0148] The liquid polymer is preferably a liquid diene-based polymer. Examples of the liquid diene-based polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or their terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0149] The content of the liquid polymer is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the liquid polymer is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, per 100 parts by mass of the rubber component (A). Furthermore, the content of the liquid polymer is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0150] (Wax) The rubber composition of this embodiment may contain a wax. Examples of the wax include natural waxes such as plant waxes and animal waxes; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available waxes can be used, and examples of commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0151] The content of the wax is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the wax is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the content of the wax is preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0152] (Stearic Acid) The rubber composition of the present embodiment may contain stearic acid. Commercially available stearic acid products are available, including those from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Chiba Fatty Acid Co., Ltd., and the like. These commercially available stearic acid products may be used alone or in combination of two or more.

[0153] The content of stearic acid is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more, and more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the content of stearic acid is preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0154] (Sulfur) The rubber composition of this embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or sulfur obtained by processing biological resource-derived materials. From the perspective of reducing environmental impact, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of methods for obtaining sulfur from waste derived from biological resources include the method described in the aforementioned Japanese Patent Application No. 2022-140390. Furthermore, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, or the like, which are commonly used as crosslinking agents in the rubber industry. Commercially available sulfur products can be used, including those from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, and the like. These sulfurs may be used alone or in combination of two or more.

[0155] The sulfur content is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the sulfur content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the sulfur content is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0156] (Vulcanization Accelerator) The rubber composition of this embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, renewable resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing the environmental impact. Vulcanization accelerators derived from biological resources can be obtained, for example, by the method disclosed in JP 2005-139239 A. Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolsulfenamide, and N,N'-diisopropyl-2-benzothiazolsulfenamide; 1,3-diphenylguanidine (DPG), 1,3-dibenzothiazolylsulfenamide, and the like. Examples of suitable vulcanization accelerators include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available vulcanization accelerators can be used, including those manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., and the like. These vulcanization accelerators may be used alone or in combination of two or more.

[0157] The content of the vulcanization accelerator is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, per 100 parts by mass of the rubber component (A). Moreover, the content of the vulcanization accelerator is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5.5 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0158] (Cellulose Nanofiber) The rubber composition of this embodiment may contain cellulose nanofiber (CNF). The cellulose nanofiber can be blended into the rubber composition to reinforce the rubber composition. The cellulose nanofiber is preferably a modified cellulose nanofiber, which is a fine fiber made from modified cellulose. The fiber diameter of the cellulose nanofiber is not particularly limited, but is approximately 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofiber can be obtained by averaging the fiber diameters and fiber lengths obtained from the observation of each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofiber can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment or defibration treatment.

[0159] The raw material for the cellulose nanofibers is not particularly limited as long as it contains cellulose, and examples thereof include plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), bleached kraft pulp (BKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., ascidians), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc. These cellulose raw materials may be used alone or in combination of two or more.

[0160] The content of the cellulose nanofibers is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the cellulose nanofibers is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 70 parts by mass, and even more preferably in the range of 10 to 40 parts by mass, per 100 parts by mass of the rubber component (A).

[0161] (Others) In addition to the above-mentioned components, the rubber composition of the present embodiment may further contain various additives commonly used in the tire industry, such as fillers such as calcium carbonate, talc, alumina, aluminum hydroxide, and mica; organic peroxides; etc. The content of these additives is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which they are applied, the tire components, the target performance, etc. For example, the content is preferably in the range of 0.1 to 200 parts by mass per 100 parts by mass of the rubber component (A).

[0162] (Method for Producing Rubber Composition) The method for producing the rubber composition of the present embodiment is not particularly limited, but the rubber composition can be produced, for example, by blending the rubber component (A) with recycled carbon black (B) and various components appropriately selected as necessary, followed by kneading, heating, extrusion, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0163] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0164] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0165] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0166] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of apparatuses for vulcanization include molding vulcanizers using molds used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0167] (Applications) The rubber composition of this embodiment can be applied to various tire components, such as treads (cap treads, base treads, undertreads), cushion rubbers, shoulders, side rubbers, clinches, bead fillers, carcass coating rubbers, insulation, gum chafers, inner liners, and the like, and can also be used for side reinforcing layers of run-flat tires. In addition to tires, the rubber composition of this embodiment can also be applied to rubber crawlers, seismic isolation rubber, hoses, and the like. Among these, the rubber composition of this embodiment maintains its elongation at break (EB) and air permeation resistance after thermal aging, and is therefore suitable for inner liners that require durability and air permeation resistance.

[0168] <Tire internal member> The tire internal member of this embodiment is characterized by being made of the above-described rubber composition. Because the tire internal member of this embodiment is made of the above-described rubber composition, the proportion of sustainable materials is improved and durability and air permeation resistance after thermal degradation are maintained.

[0169] <Tire> The tire of this embodiment is characterized by including the above-described tire internal component. Because the tire of this embodiment includes the above-described tire internal component, the tire has an increased proportion of sustainable materials and maintains durability and air permeation resistance after heat degradation.

[0170] Next, an embodiment of a tire of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of an embodiment of a tire of the present invention. The tire 1 of this embodiment shown in Fig. 1 has a pair of bead portions 2, a pair of sidewall portions 3, and a tread portion 4 continuous with both sidewall portions 3. The tire 1 also has a carcass 6 extending in a toroidal shape between bead cores 5 embedded in each of the pair of bead portions 2, and a belt 7 disposed radially outward of a crown portion of the carcass 6. The tire 1 of this embodiment also has side rubbers 8 in the pair of sidewall portions 3, and an inner liner 9 made of rubber disposed along the inner surface of the carcass 6.

[0171] The carcass 6 of the tire 1 shown in FIG. 1 is composed of one carcass ply made of a plurality of parallel-arranged cords covered with a coating rubber, and the carcass 6 is composed of a main body portion extending in a toroidal shape between the pair of bead cores 5 and a folded-up portion wound up radially outward from the inside toward the outside in the tire width direction around each bead core 5, but the number and structure of the carcass plies in the tire of the present invention are not limited to this.

[0172] 1, a belt 7 consisting of two belt layers is disposed on the radially outer side of the crown portion of the carcass 6, and the belt layer is usually made of a rubberized layer of cords (preferably steel cords) extending at an angle with respect to the tire equatorial plane, and the two belt layers are laminated such that the cords constituting the belt layers cross each other with the tire equatorial plane in between to constitute the belt 7. Note that although the belt 7 in the drawing consists of two belt layers, the number of belt layers constituting the belt in the tire of the present invention may be three or more.

[0173] The tire of this embodiment can be manufactured by a conventional method using the above-mentioned rubber composition for the tire internal components. For example, depending on the type of tire to be applied, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0174] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0175] <Preparation of Rubber Compositions> Rubber compositions of Examples and Comparative Examples were prepared according to the formulations shown in Table 1. For each rubber composition obtained, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) was calculated to calculate the sustainable material ratio. Furthermore, the air permeation resistance and elongation at break (EB) after thermal aging were evaluated for the obtained rubber compositions using the following methods. The results are shown in Table 1.

[0176] <Evaluation of Air Permeation Resistance> To evaluate air permeation resistance, the air permeability of the obtained rubber composition was measured at 60°C using an air permeation tester GTR-31ABSM (manufactured by GTR Tech Co., Ltd.). The air permeability (JIS K 6275-1:2009) was expressed as an index, with the air permeability of Comparative Example 1 set to 100. The smaller the index value, the more excellent the air permeation resistance.

[0177] <Evaluation of Elongation at Break (EB) After Thermal Aging> The rubber composition was vulcanized to prepare vulcanized rubber test pieces. Next, the vulcanized rubber test pieces were left at 100°C for 24 hours to allow for thermal aging. The thermally aged test pieces were subjected to a tensile test similar to JIS K 6251 at 100°C to measure the elongation at break (EB) after thermal aging. The results were expressed as an index, with the elongation at break (EB) after thermal aging of Comparative Example 1 being set at 100. A larger index value indicates a larger elongation at break (EB) after thermal aging. In this specification, an index value of 83 or higher is considered to be maintained for the elongation at break after thermal aging, and an index value of 90 or higher is considered to be good.

[0178]

[0179] *1 Brominated butyl rubber: ExxonMobil, trade name "Bromobutyl 2222" *2 Unused carbon black: Asahi Carbon, trade name "Asahi #55", nitrogen adsorption specific surface area (N ２ SA) = 26 m ２ / g, DBP oil absorption = 87 mL / 100 g * 3 Recycled carbon black: Enrestec, trade name "PB365", ash content = 17 mass% * 4 Oil: JXTG Energy, trade name "Super Oil Y22" * 5 Phenolic resin: Sumitomo Bakelite Co., Ltd., trade name "DUREZ 19900" * 6 Other chemicals: total amount of sulfur, vulcanization accelerator, fatty acid, wax, the same ratio for comparative examples and examples

[0180] From Table 1, it can be seen that the rubber compositions of the examples according to the present invention have an improved proportion of sustainable materials, and also maintain the elongation at break (EB) and air permeation resistance after heat degradation.

[0181] The rubber composition of the present invention can be used for rubber products such as tires, rubber crawlers, seismic isolation rubber, and hoses, and is particularly suitable as an inner liner for tires.

[0182] 1: Tire 2: Bead section 3: Sidewall section 4: Tread section 5: Bead core 6: Carcass 7: Belt 8: Side rubber 9: Inner liner

Claims

1. A rubber composition comprising a rubber component (A) and recycled carbon black (B), wherein the rubber component (A) contains 5 to 25 parts by mass of isoprene-based rubber and 75 to 95 parts by mass of butyl rubber per 100 parts by mass of the rubber component (A).

2. The rubber composition according to claim 1, wherein the recycled carbon black (B) is obtained by pyrolysis of a vulcanized rubber product containing carbon black.

3. The rubber composition according to claim 1, wherein the recycled carbon black (B) has an ash content of 25 mass% or less.

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

5. The rubber composition according to claim 4, wherein the proportion of the recycled carbon black (B) in the total amount of the recycled carbon black (B) and the carbon black (C) other than the recycled carbon black (B) is 5 to 35 mass%.

6. The carbon black (C) other than the recycled carbon black (B) has a dibutyl phthalate (DBP) oil absorption of 50 to 150 mL / 100 g and a nitrogen adsorption specific surface area (N ２ SA) is 20 to 130 m ２ The rubber composition according to claim 4, wherein the modulus is 1 / g.

7. The rubber composition according to claim 1, further comprising an oil.

8. The rubber composition according to claim 1, further comprising a phenolic resin.

9. The rubber composition according to claim 1, further comprising 10 parts by mass or less of at least one of rubber crumb and reclaimed rubber per 100 parts by mass of the rubber component (A).

10. The rubber composition of claim 1, further comprising clay.

11. A tire internal member comprising the rubber composition of claim 1.

12. A tire comprising an internal tire component according to claim 11.

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