Rubber composition

Abstract

To provide a rubber composition that exhibits superior low-loss performance and resistance to cracking, and that also contributes to sustainability enhancement.SOLUTION: A rubber composition comprises at least a rubber component, a carbon black (A), which is a reclaimed carbon black, and a carbon black (B) having a nitrogen adsorption specific surface area greater than that of the carbon black (A).SELECTED DRAWING: None

Description

[Technical field]

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

[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, in recent years, from the viewpoint of social sustainability, it has been required to use so-called sustainable materials such as materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycling resources) in rubber products, and it has also been required to increase the ratio of sustainable materials in the rubber compositions used in the rubber products. For example, recycled carbon black is known as a material derived from recycled resources (Patent Document 1 below). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] European Patent Application Publication No. 3427975 Summary of the Invention [Problem to be solved by the invention]

[0005] However, when recycled carbon black is used as a reinforcing filler instead of virgin carbon black in order to increase the proportion of sustainable materials in rubber products, there is a problem that the durability, particularly the crack resistance, of the rubber composition deteriorates.

[0006] Therefore, an object of the present invention is to provide a rubber composition that is excellent in low loss property and crack resistance and can contribute to improving sustainability. [Means for solving the problem]

[0007] That is, the essential features of the rubber composition of the present invention that solves the above problems are as follows.

[0008] [1] A rubber composition comprising at least a rubber component, carbon black (A) which is recycled carbon black, and carbon black (B) having a larger nitrogen adsorption specific surface area than the carbon black (A). The rubber composition of the present invention is excellent in low loss property and crack resistance, and can contribute to improving sustainability.

[0009] [2] The nitrogen adsorption specific surface area of ​​the carbon black (A) is 70 m 2 / g or more 90m 2 / g or less of the rubber composition according to [1]. In this case, the arrangement of the carbon black as a whole is further optimized, and thus the crack resistance is further improved.

[0010] [3] The nitrogen adsorption specific surface area of ​​the carbon black (B) is 110 m 2 / g or more 140m 2 / g or less of the rubber composition according to [1] or [2]. In this case, the arrangement of the carbon black as a whole is further optimized, and thus the crack resistance is further improved.

[0011] [4] In addition, the nitrogen adsorption specific surface area is 70m 2 / g or more 90m 2 The rubber composition according to any one of [1] to [3], containing carbon black (C), which has a molecular weight of 1000 or less and may be recycled carbon black or not. In this case, the crack resistance and low loss properties can be further improved.

[0012] [5] The rubber composition according to any one of [1] to [4], wherein the amount of the carbon black (A) is 15 parts by mass or less based on 100 parts by mass of the rubber component. In this case, the low loss characteristic can be maintained better.

[0013] [6] The rubber composition according to any one of [1] to [5], wherein the carbon black (A) is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. In this case, resources can be recycled, further contributing to improving sustainability.

[0014] [7] The rubber composition according to any one of [1] to [6], wherein the carbon black (A) has an ash content of 20 mass % or less. In this case, the various physical properties required for rubber products such as tires and the quality of the regenerated carbon black are improved. Effect of the Invention

[0015] According to the present invention, it is possible to provide a rubber composition that is excellent in low loss property and crack resistance and can contribute to improving sustainability. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] The rubber composition of the present invention will be described in detail below with reference to examples based on embodiments thereof.

[0017] <Definition> The compounds described herein may be derived in whole or in part from fossil sources, from biological sources such as plant sources, from recycled sources such as used tires, or from a mixture of two or more of fossil sources, biological sources, and / or renewable sources.

[0018] In this specification, the "sustainability rate" refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from renewable resources (recycled resources) in a target material.

[0019] In this specification, the biological resources (biomass resources) refer to carbon-neutral organic resources derived from living organisms, and include, for example, those 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 are resources other than fossil resources (petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but are preferably non-edible from the viewpoint of not competing with food and of effective resource utilization.

[0020] 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 waste, 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 ... Examples of the biological resources include crops (corn, wheat, rice, rice husks, rice bran, old rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue after squeezing juice from sugarcane), soybeans, soybean pulp, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, algae, etc. The biological resources may be processed (i.e., biological resource-derived substances). Examples of the processing methods include biological processing methods that utilize the functions of microorganisms, plants, animals, and tissue cultures thereof; chemical processing methods that utilize acids, alkalis, catalysts, thermal energy, light energy, etc.; physical processing methods such as micronization, compression, microwave processing, and electromagnetic wave processing; and the like. The biological resources may also be extracted and refined from the biological resources or biological resources that have been processed (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the biological resources can 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, and among these, valine, leucine, isoleucine, arginine, and phenylalanine are preferred.The amino acid may be either an L-amino acid or a D-amino acid, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. The fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. The fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may be contaminated with various materials and impurities.

[0021] 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.

[0022] <Rubber composition> A rubber composition according to one embodiment of the present invention (hereinafter, sometimes referred to as the "rubber composition of the present embodiment") is characterized by containing at least a rubber component, carbon black (A) which is recycled carbon black, and carbon black (B) having a larger nitrogen adsorption specific surface area than the carbon black (A).

[0023] In the rubber composition of the present embodiment, carbon black (A) which is recycled carbon black is used. In this regard, first, it has been surprisingly found that when virgin carbon black (general commercially available carbon black derived from fossils, etc.) is replaced with recycled carbon black, the low loss property tends to improve. On the other hand, since recycled carbon black inevitably contains impurities, ash, etc., when used alone, there is a risk of causing deterioration of crack resistance. In contrast, by blending carbon black (B) having a smaller particle size than carbon black (A) (i.e., a larger specific surface area than carbon black (A)) in addition to carbon black (A) which is recycled carbon black, the carbon black (B) is efficiently arranged between carbon black (A). Then, by optimizing such arrangement, the network property of carbon black is enhanced, and as a result, the collapse of the carbon black network due to fatigue can be significantly suppressed, and the crack resistance can be improved. Therefore, the rubber composition of the present embodiment has excellent low loss property and crack resistance.

[0024] Moreover, since the rubber composition of the present embodiment uses recycled carbon black, it can contribute to improving sustainability.

[0025] (Rubber component) The rubber composition of the present embodiment contains a rubber component, which provides rubber elasticity to the composition. The rubber component has a sustainability rate of preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass.

[0026] As the rubber component, the rubber derived from biological resources and the rubber derived from recycled resources are preferable. Here, the proportion of the monomer components 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, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. The proportion of monomer components derived from recycled resources in 100 mol% of 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, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0027] The rubber component 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, and preferably 5 million or less, more preferably 2 million or less, more preferably 1.5 million or less, and even more preferably 1.3 million or less. In this specification, the weight average molecular weight (Mw) of the rubber component can be determined, for example, by converting the weight average molecular weight (Mw) of the rubber component into a standard polystyrene equivalent based on a measurement value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0028] The rubber component is preferably a diene rubber, and the diene rubber is preferably an isoprene rubber or a butadiene rubber, where the isoprene rubber refers to a rubber containing units derived from isoprene as monomer units, and the butadiene rubber refers to a rubber containing units derived from butadiene as monomer units.

[0029] 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 the 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 of the natural rubber include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of the synthetic isoprene rubber (IR) are not particularly limited, and examples of the synthetic isoprene rubber that can be used include those commonly used in the tire industry, such as IR2200. Examples of the modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of the modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. The modified IR includes epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, grafted synthetic isoprene rubber, etc. 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.

[0030] The isoprene-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, still more preferably 60% by mass or more, still 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. In order to set the sustainability rate of the isoprene-based rubber 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 renewable 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 renewable resources, a copolymer of a monomer derived from biological resources and a monomer derived from renewable resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from renewable resources and a monomer derived from a fossil resource (petroleum, etc.).

[0031] Examples of the butadiene rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene rubber, is preferably derived from biological resources or recycled resources.

[0032] The rubber component preferably contains a butadiene rubber (BR), which can improve the physical properties of the rubber composition, such as elongation at break (EB). It is particularly preferable that the rubber component further contains a butadiene rubber (BR) in addition to the natural rubber (NR). By using a combination of the natural rubber and the butadiene rubber as the rubber component, the elongation at break (EB) after thermal aging of the rubber composition can be further improved. In the rubber composition of the present embodiment, the total amount of styrene in the rubber component is 5% by mass or less, preferably 3% by mass or less, and may be 0% by mass. If the total amount of styrene in the rubber component exceeds 5% by mass, the physical properties of the rubber composition are deteriorated, and the elongation at break (EB) after thermal aging cannot be sufficiently improved.

[0033] Examples of the butadiene rubber (BR) include high cis content butadiene rubber, low cis content butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available products 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 Co., Ltd., and Zeon Corporation. These butadiene rubbers may be used alone or in combination of two or more.

[0034] 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)), solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)), and the like. In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, divinylnaphthalene, and the like. 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, the aromatic vinyl compound-butadiene copolymer rubber is preferably SBR. The styrene may have a substituent. As the aromatic vinyl compound-butadiene copolymer rubber, commercially available products can be used, and examples of the commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Nippon Zeon Corporation, Sumitomo Chemical Co., Ltd., and the like. These aromatic vinyl compound-butadiene copolymer rubbers may be used alone or in combination of two or more.

[0035] The butadiene-based rubber has a sustainability rate of preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, still 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. In order to make the sustainability rate of the butadiene-based rubber fall within the above range, for example, a polymer synthesized using butadiene derived from biological resources, butadiene derived from renewable resources, aromatic vinyl compounds derived from biological resources (e.g., styrene derived from biological resources), and aromatic vinyl compounds derived from renewable resources (e.g., styrene derived from renewable resources) as monomer components may be used. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from renewable resources, a copolymer of a monomer derived from biological resources and a monomer derived from renewable resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from renewable resources and a monomer derived from a fossil resource (petroleum, etc.). In addition, the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (e.g., styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene, etc. according to a conventional method, but also rubber obtained by reactions or enzyme reactions caused by microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.").

[0036] In addition, in order to set the sustainability rate of the entire rubber component within the above range, it is preferable to use natural rubber (NR) as the rubber component or a polymer synthesized using monomer components derived from biological resources or monomer components derived from recycled resources as monomer components.

[0037] Generally, materials for rubber compositions for tires (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment for their production, and are therefore usually produced in large factories in specific regions, and a lot of energy is required for the storage and transportation of raw materials and products. In contrast, materials derived from biological resources (biomass resources) are derived from agricultural products, forests, etc. in each region, and can be produced on a small scale by fermentation of microorganisms and catalytic reactions, so by utilizing products and waste from each region, the energy required for the transportation and storage of raw materials can be reduced, and further the energy required for the transportation and storage of the produced materials to tire factories can also be reduced, making them environmentally friendly. In addition, materials derived from regenerated resources (recycled resources) can be obtained, for example, by dismantling, downsizing, and pyrolyzing used tires to extract materials that constitute tires, 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 materials for rubber compositions for tires can be obtained from various wastes and used items. In this way, by using sustainable materials (materials derived from biological resources or materials derived from recycled resources), it is possible to reduce the overall environmental load in 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 (LCC) incurred over the entire life cycle, and reducing the amount of fossil resources used.

[0038] As a means of obtaining materials derived from recycled resources (recyclable resources), a rubber product such as a recovered tire may be subjected to a process of "dismantling and downsizing", and a rubber product such as a tire manufactured using the rubber composition of the present embodiment may be further subjected to a process of "dismantling and downsizing". Dismantling and downsizing is a series of processes in which a rubber product such as a tire is 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 (rubber and metal, etc.). Cutting is a process in which a rubber product is cut into pieces into individual parts (tread and sidewall, etc.). Chipping is a process in which a rubber product is scraped or perforated. Crushing is a process in which a rubber product is crushed into chips of several inches in size. Crushing is a process in which a rubber product is crushed into granules.

[0039] The separation techniques include pulling, induction heating, punch cutting, magnetic separation, cutting separation, mechanical separation, cooling, and water jet. Pulling is a technique in which a bead is hooked and pulled out of the tire using a hook or the like. Induction heating is a technique in which the adhesive force between the metal of the bead and the rubber is reduced by induction heating, and the metal and rubber are separated. Punch cutting is a technique in which a series of overlapping punch cuts (holes are made) are made in the tire sidewall around the bead to remove the bead from the tire. Magnetic separation is a technique in which a metal such as a bead is separated from the rubber using magnetic force. Cutting separation is a technique in which a blade, a cutter blade, a knife, or a rotating milling machine is used to cut and separate the metal such as a bead from the rubber. Mechanical separation is a technique in which a metal and rubber are separated by applying a mechanical force sufficient to separate them. Cooling is a technique in which the rubber is cooled using liquid nitrogen or the like to embrittle the rubber before separation. Water jet is a technique in which rubber and metal are separated by spraying water at high pressure.

[0040] Cutting techniques include rotary blades, blade cutters, L-knives, water jets, and pneumatic cutting. Rotary blades are a method of cutting by applying a rotating blade (including blades, circular saws, etc.) to the object. Blade cutters are a method of cutting using a blade or cutter blade. 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.

[0041] The chipping techniques 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.

[0042] Crushing methods include rotating blades, blade cutters, and cut-off wheels. Rotating blades are a method of crushing objects by applying a rotating blade (including blades and circular saws) to the object. Blade cutters are a method of crushing objects using a blade or cutter blade. Cut-off wheels are a method of crushing objects by applying a cutting blade to a wheel-shaped crushing component and applying it to the object.

[0043] Pulverization techniques include roller mills, pin mills, and water jets. Roller mills use 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 use dozens of pins attached to the surfaces of two opposing disks that are rotated at high speed to pulverize. Water jets use a high-speed jet of water that collides with the target material to pulverize it.

[0044] Further, for separation, the following separation techniques may be selected depending on the object to be separated. When the object to be separated is metal, magnetic separation, "pulling, peeling, 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 rubber by pulling, peeling, and tearing. Melting includes vibration melting, heated steam, and induction heating. Vibration melting separates metal components while vibrating the tire with ultrasound or the like and melting them. Heated steam melts rubber by spraying heated steam and separates metal cord. Induction heating heats the tire by electromagnetic induction and separates metal cord. Crushing separates metal cord from rubber by crushing the tire with a roller or the like. Punching removes metal cord from tire by creating a series of overlapping punching cuts in a circumferential pattern on the tire sidewall around the bead. High-pressure jets use water or other materials to spray at high pressure to separate the metal and rubber. 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 have settled to the bottom. Centrifugal classification is a type of wind classification that uses centrifugal force to separate the metal and rubber.

[0045] When the material to be separated is fiber, the following methods may be selected: sieving, vibrating screen, melting, wind classification, centrifugal classification, gravity classification, friction, "pulling, peeling, tearing", high pressure jet, electrostatic separation, mechanical heat control, cutting and milling. Sieving uses a sieve to separate fiber and rubber. Vibrating screen performs sieving by vibrating a sieve up and down. Melting includes heated steam and induction heating. Heated steam is sprayed onto the rubber to melt it and separate the metal cord. Induction heating is heating the tire by electromagnetic induction and separating the metal cord. Wind classification separates fiber and rubber powder by utilizing the difference in the hydrodynamic behavior of particles (centrifugal force, gravity, inertia force, etc.). Centrifugal classification is a type of wind classification that separates fiber and rubber using centrifugal force. Gravity classification is a type of wind classification that separates fiber and rubber using gravity. Friction involves applying pressure to the tire to generate friction, forming aggregates from the fibers, and then separating the aggregates from the rubber granules using a sieve or similar. Pulling, peeling, and tearing involve pulling, peeling, or tearing the fiber reinforcement parts away from the rubber. High-pressure jets separate the fibers and rubber by spraying them at high pressure using water or similar. Electrostatic separation involves charging particles using electrostatic forces, and separating the fibers and rubber due to the difference in charge or electric field strength. Mechanical heat control separates the rubber from the fiber reinforcement elements under controlled thermal conditions. Cutting and milling involves mechanically cutting or milling to separate the fiber and rubber parts.

[0046] When the object to be separated is a sealant, mechanical lubrication after solidification or the use of a processing aid may be selected. In the mechanical lubrication after solidification, the sealant layer is removed by mechanical lubrication after solidification using liquid nitrogen or the like. In the use of a processing aid, the sealant layer is removed using water or a soap solution.

[0047] When the object to be separated is resin, crushing, cutting, melting, or peeling may be selected. Crushing separates the resin from the rubber by crushing the tire with a roller or the like. Cutting separates the resin by cutting along the boundary surface between the rubber layer and the resin. Melting includes vibration melting. Vibration melting separates the resin while melting by vibrating the tire with ultrasound or the like. Peeling foams unfoamed rubber by heating, and a peeling force acts between the rubber and the resin member to peel the resin member from the rubber.

[0048] In addition, when producing the rubber composition, the ratio of the monomer components derived from biological resources, the monomer components derived from renewable resources, and the monomer components derived from fossil resources can be appropriately selected according to 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), and the monomer components derived from biological resources, the monomer components derived from renewable resources, and the monomer components derived from fossil resources can be polymerized to obtain rubber derived from sustainable materials (materials derived from biological resources or materials derived from renewable resources) having performance equivalent to that of conventional synthetic rubber. When using monomer components derived from renewable resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomer. In that case, the impact on the environment can be evaluated by adopting the concept of mass balance.

[0049] The ratio of each monomer unit (e.g., unit derived from isoprene, unit derived from butadiene, unit derived from aromatic vinyl compound) in the entire rubber component can be adjusted appropriately depending on the component to which the rubber is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the above-mentioned isoprene-based rubber and butadiene-based rubber. In addition, the ratio of cis-bond units in the butadiene-based units can also be adjusted appropriately depending on the component to which the rubber is applied. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "unit derived from isoprene" refers to a structural unit in a polymer constituted based on the monomer isoprene (including the isoprene unit in natural rubber), the term "unit derived from butadiene" refers to a structural unit in a polymer constituted based on the monomer butadiene, and the term "unit derived from an aromatic vinyl compound" refers to a structural unit in a polymer constituted based on the monomer aromatic vinyl compound. In this specification, the ratio of each monomer unit is measured by NMR.

[0050] The rubber component may contain diene rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), etc., in addition to the above-mentioned isoprene-based rubber, butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR). These rubber components may be used alone or in combination of two or more.

[0051] The rubber component may be modified to introduce a functional group that interacts with a filler such as carbon black or silica. Examples of the functional group 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, and these functional groups may have a substituent. These functional groups may be introduced into the rubber component alone or in combination of two or more. 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.

[0052] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component. The functional group is a modified functional group having an interactive property with a filler such as silica or 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, and 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 include those described in International Publication No. 2016 / 194316 and International Publication No. 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0053] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from renewable resources) can be produced in the same manner as conventional synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from renewable resources, and, if necessary, monomer components derived from fossil resources. The rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions with microorganisms or enzyme reactions.

[0054] Regarding the method for preparing rubber derived from biological resources from the above-mentioned biological resources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from biological resources as a monomer component, it is possible to obtain butadiene rubber (B-BR) derived from biological resources (biomass resources), and by using styrene obtained from biological resources and butadiene obtained from biological resources as monomer components, it is possible to obtain styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources). Here, methods for obtaining B-BR and B-SBR from biological resources include, in addition to artificial polymerization methods, methods of polymerization in vivo, and methods of polymerization with 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 according to the target tire performance.

[0055] As the butadiene obtained from the biological resources, butadiene derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadiene derived from alkenes (preferably ethylene), and butadiene derived from unsaturated carboxylic acids (preferably tiglic acid) can be suitably used. Two or more of these butadienes may be used in combination. As the styrene obtained from the biological resources, styrene obtained from a plant (preferably a plant belonging to the family Hamamelidaceae, Styraxaceae, or Apocynaceae, more preferably a plant belonging to the genera Liquidamus, Styrax, or Catharanthus, and even more preferably Sweetgum, Styrax rosa, or Catharanthus roseus) or a microorganism (preferably a microorganism belonging to the genera Penicillium or Escherichia, more preferably P. citrinum or transformed E. coli) can be suitably used. Two or more of these styrenes may be used in combination.

[0056] Recently, biomass combinat mainly using bioethanol, bioethylene, etc. are planned, but bioethanol and bioethylene are mainly produced using sugars and / or cellulose as biological resources, and other biological resources such as proteins, lipids, and amino acids cannot be effectively utilized. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, it is preferable to use multiple types of monomer components derived from biological resources as the monomer components derived from the biological resources, or to use monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources in combination, and further to appropriately adjust the ratio of these monomer components. This makes it possible to effectively utilize a wide range of biological resources and renewable resources such as sugars, proteins, and lipids without relying on one type of biological resource, and to stably supply rubber derived from sustainable materials, and further to consider the environment depending on the situation at the time of production. In addition, when using multiple types of monomer components derived from biological resources, 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 butadiene derived from multiple types of biological resources with different origins as the butadiene derived from biological resources, and / or to use a mixture of styrene derived from multiple types of biological resources with different origins as the styrene derived from biological resources. This allows multiple types of biological resources to be effectively utilized.

[0057] (Carbon Black) The rubber composition of the present embodiment contains carbon black. More specifically, the rubber composition of the present embodiment contains at least carbon black (A) which is recycled carbon black, and carbon black (B) having a larger nitrogen adsorption specific surface area than the carbon black (A). In this specification, the nitrogen adsorption specific surface area (N 2SA) is calculated according to JIS K 6217-2:2017 (ISO 4652:2012).

[0058] In this specification, "recycled carbon black" refers to carbon black obtained by recovering raw materials that are waste materials provided for recycling. Examples of the waste materials include waste rubber, used tires, waste oil, and the like. Waste rubber refers to all discarded rubber, including unnecessary scraps generated from the production or repair of rubber products, and is not limited to that generated from rubber products. Examples of the scraps include buffing powder, peeled rubber, and the like. Buffing powder is fine rubber generated in a buffing process for scraping the tread portion remaining on the base tire, for example, in tire retreading. Peeling rubber is a long piece of rubber, for example, 1 to 2 cm wide, peeled off from the surface of a rubber product such as a tire. Peeling rubber is generated by scraping the surface of a rubber product such as a tire using a knife with a U-shaped or V-shaped tip like a peeler. In addition, 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, and rubber parts or components in the manufacturing stage of the final products. The used tires may be tires to be retreaded, or may be tires discarded for some reason, such as waste tires generated from tire replacement, scrapping, etc., and ELT (End-of-Life Tire) that has reached the end of its life as a tire. Waste oil is not limited to oil generated when decomposing plastics and rubber, but may include, for example, used oil discharged from industry, such as animal and vegetable oils, lubricating oil, insulating oil, cutting oil, etc. Among them, the waste oil is preferably one that does not have any composition other than organic matter, such as one derived from silicone rubber or polyvinyl chloride. In addition, the waste oil is preferably one that is mixed with carbon black or rubber containing carbon black. "Recycled carbon black" is different from carbon black that is directly manufactured using hydrocarbons such as petroleum, natural gas, and coal as raw materials, i.e., carbon black that is not recycled. Note that "used" here does not only include carbon black that has been actually used and then discarded, but also carbon black that has been manufactured but not actually used and then discarded.

[0059] In addition, the recycled carbon black (carbon black (A) and the like) used in this embodiment is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. In this case, it is possible to recycle resources, which can further contribute to improving sustainability. In addition, since it is easily obtained by pyrolysis, it is easy to obtain. Furthermore, the recycled carbon black used in this embodiment is preferably obtained from a solid residue generated by pyrolysis of a vulcanized rubber product containing the above 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. In addition, when recovering carbon black from a volatile component, it is possible to recover an oil component with a specific gravity suitable for producing carbon black, and use it to produce carbon black by an existing carbon black production method (for example, JP-A-2015-520259). In this case, unlike carbon black recovered from a solid residue, there are advantages such as no impurities and no mixture of different grades. In addition, in the production of carbon black with low environmental impact, there are various options, such as using vegetable oil, oil derived from waste plastic, etc., in addition to the oil obtained by recovering the volatile components obtained by the above-mentioned rubber pyrolysis. However, since edible resources such as vegetable oil are needed for other uses such as food, it is necessary to consider the issue of securing sufficient amounts and the impact on the environment due to the expansion of cultivated land. In addition, while those derived from waste plastics are used for other purposes such as horizontal recycling of plastics, there are still issues on the supply side. On the other hand, when using volatile components (oil) generated by the pyrolysis of vulcanized rubber products, especially tires, it is possible to continue using existing materials because of the system of continuing to use existing materials within the tire industry, and it is possible to reduce the consumption of new materials in the production of new tires and contribute to reducing the environmental impact of the industry. The grade of the carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0060] The solid residue obtained by pyrolysis of wastes such as used rubber and used tires contains ash in addition to carbon black. The ash is derived from non-volatile components contained in rubber and tires. For this reason, the recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, in consideration of the various physical properties required for tires manufactured using the recycled carbon black, the higher the carbon content in the recycled carbon black (such as carbon black (A)), the better. In the recycled carbon black used in this embodiment, the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, more preferably 87% by mass or more, and even more preferably 89% by mass or more. In the recycled carbon black used in this embodiment, the carbon content is preferably 97% by mass or less. The carbon content is a value that does not include adsorbed moisture.

[0061] Specific examples of 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 residue obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the inclusion of ash in the recycled carbon black is permitted. The lower limit of the ash content of the recycled carbon black (carbon black (A) and the like) used in this embodiment may be 0.5 mass %. On the other hand, in consideration of the various physical properties required for tires and the quality of the recycled carbon black, the ash content of the recycled carbon black (carbon black (A) and the like) is preferably 20 mass % or less, more preferably 15 mass % or less, and even more preferably 5.0 mass % or less. When the ash content of the recycled carbon black is 20 mass % or less, the various physical properties of the rubber product to which the rubber composition is applied can be improved. In this specification, the ash content of carbon black is calculated from the mass of unburned components (ash content) obtained by burning carbon black at 550° C.±25° C. to convert it to incineration.

[0062] Also, regenerated carbon black (such as carbon black (A)) can be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, referring to "Rubber Chemistry and Technology", Vol. 85, No. 3, pp. 408-449 (2012), in particular pp. 438, 440, and 442, describes that it can be obtained by pyrolysis of organic materials at 550-800°C with the exclusion of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

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

[0063] The regenerated carbon black (such as carbon black (A)) 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 regenerated carbon black can be carried out by a conventional method. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black having hydroxyl and / or carboxyl groups on its surface. In Japanese Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain carbon black with an activated surface. The regenerated carbon black according to the present embodiment also includes carbon black that has been treated to include functional groups on its surface.

[0064] Moreover, examples of the thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0065] The crosslinked rubber products used for the decomposition may be grouped according to the type of rubber component previously blended, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped according to the type of filler previously blended (e.g., the type of carbon black, the type of silica, the 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 according to both the type of rubber component and the 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 is obtained, and therefore, when the carbon black is blended again with the rubber component, a rubber composition with better performance is obtained.

[0066] In addition, when the crosslinked rubber product used for the decomposition is derived from tires, the tires may be grouped in advance by type (for example, for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and then the decomposition process may be performed for each group. In addition, the tires may be grouped in advance by tire components (for example, tread rubber, sidewall rubber, bead rubber, steel cord coated rubber, organic fiber coated rubber, pad rubber, cushion rubber, etc.), and then the decomposition process may be performed for each group. Furthermore, the tires may be grouped both by type and by tire components, and then the decomposition process may be performed for each group. When the decomposition process is performed for each group in this way, recycled carbon black with more uniform physical properties is obtained, so that when it is blended again into the rubber component, a rubber composition with better performance can be obtained.

[0067] The nitrogen adsorption specific surface area of ​​the carbon black (A) which is the regenerated carbon black is not particularly limited, but from the viewpoint of further optimizing the arrangement of the carbon black as a whole and further improving the crack resistance, it is preferably 70 m 2 / g or more, and 2 / g or more, and 2 / g or more is more preferable, and 2 / g or less, and 2 / g or less is more preferable, 2 It is more preferable that the molecular weight is not more than 1 / g.

[0068] The carbon black (A) which is a regenerated carbon black preferably has a pH of 4-12, more preferably 5-11, and particularly preferably 6-10. Herein, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0069] The carbon black (A) which is a regenerated carbon black preferably has a toluene coloring transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. In this specification, the toluene color transmission of the recycled carbon black is determined in accordance with ASTM D1618.

[0070] The carbon black (A) which is a recycled carbon black preferably has a heat loss at 125° C. of 3 mass % or less, more preferably 2.5 mass % or less, and particularly preferably 2 mass % or less. Herein, the heat loss of recycled carbon black at 125° C. is determined in accordance with ASTM D1509.

[0071] The carbon black (A) which is a recycled carbon black preferably has a sulfur content of 5 mass % or less, more preferably 3.5 mass % or less, and particularly preferably 3 mass % or less.

[0072] The carbon black (A) which is a recycled carbon black preferably has a 35 mesh sieve residue of 20 ppm by mass or less, more preferably 15 ppm by mass or less, and particularly preferably 10 ppm by mass or less. In this specification, the 35 mesh screen residue of recycled carbon black is determined in accordance with ASTM D1514.

[0073] The carbon black (A) which is a recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. In this specification, the 325 mesh (44 μm) sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0074] The carbon black (A) which is a 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.

[0075] The carbon black (A) which is a recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. In this specification, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0076] The carbon black (A) which is recycled carbon black preferably has a particle size (D97) of 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. In this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming that the refractive index of water is 1.33 and the refractive index of the filler is 1.75.

[0077] The carbon black (A) which is recycled carbon black preferably has a ratio of particles of 5 μm or less of 50 vol % or more, more preferably 70 vol % or more, and particularly preferably 80 vol % or more.

[0078] The recycled carbon black (A) preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of the rubber product to which the rubber composition is applied can be improved. In this specification, the ash content of the recycled carbon black is determined in accordance with ASTM D8474-D1506.

[0079] The carbon black (A) which is a regenerated carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption of recycled carbon black is determined in accordance with ASTM D3493.

[0080] As the carbon black (A) which is the recycled carbon black, a commercially available product can be used. For example, the product name "PB365" manufactured by Enrestec can be mentioned as such a commercially available product. PB365 is a recycled carbon black produced by pyrolysis of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m2 as measured by the BET method. 2 / g and contains about 17 mass% ash.

[0081] From the viewpoint of more efficient arrangement of the carbon black as a whole, the carbon black (A) which is the recycled carbon black preferably has a dibutyl phthalate (DBP) oil absorption of 50 mL / 100 g or more, more preferably 60 mL / 100 g or more, and even more preferably 70 mL / 100 g or more, and preferably 100 mL / 100 g or less, more preferably 90 mL / 100 g or less, and even more preferably 80 mL / 100 g or less. In this specification, the DBP oil absorption of carbon black is determined in accordance with JIS K 6217-4:2017.

[0082] The content of the carbon black (A), which is recycled carbon black, is preferably 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the rubber component. In this case, the crack resistance and low loss property can be more highly balanced, and further contribute to improving sustainability. From the same viewpoint, the content of the carbon black (A) is more preferably 15 parts by mass or less per 100 parts by mass of the rubber component.

[0083] The nitrogen adsorption specific surface area of ​​the carbon black (B) is not particularly limited as long as it is larger than that of the carbon black (A) which is the recycled carbon black. However, from the viewpoint of further optimizing the arrangement of the carbon black as a whole and further improving the crack resistance, it is preferable that the nitrogen adsorption specific surface area be 110 m 2 / g or more, and 2 / g or more, and 2 / g or more is more preferable, and 140m 2 / g or less, and 2 / g or less, and 2 It is more preferable that the molecular weight is not more than 1 / g.

[0084] From the viewpoint of more efficient arrangement of the carbon black as a whole, the carbon black (B) preferably has a dibutyl phthalate (DBP) oil absorption of 75 mL / 100 g or more, more preferably 80 mL / 100 g or more, and even more preferably 87 mL / 100 g or more, and preferably 110 mL / 100 g or less, more preferably 105 mL / 100 g or less, and even more preferably 97 mL / 100 g or less.

[0085] The carbon black (B) may or may not be recycled carbon black. That is, the carbon black (B) may be recycled carbon black or virgin carbon black. However, if the carbon black (B) is recycled carbon black like the carbon black (A), it can further contribute to improving sustainability.

[0086] The content of carbon black (B) is preferably 5 parts by mass or more per 100 parts by mass of the rubber component. In this case, crack resistance can be further improved. In addition, the content of carbon black (B) is preferably 70 parts by mass or less per 100 parts by mass of the rubber component. In this case, low loss properties can be better maintained. From the same viewpoint, the content of carbon black (B) per 100 parts by mass of the rubber component is more preferably 10 parts by mass or more and more preferably 60 parts by mass or less.

[0087] The rubber composition of the present embodiment further contains carbon black (A) and carbon black (B) having a nitrogen adsorption specific surface area of ​​70 m 2 / g or more 90m 2 It is preferable that the carbon black (C) contains a carbon black having a carbon content of 0.1 to 1.0 carbon / g or less. In this case, the crack resistance and low loss properties can be further improved. The carbon black (C) may or may not be recycled carbon black. That is, the carbon black (C) may be recycled carbon black or virgin carbon black. However, from the viewpoint of crack resistance, it is preferable that the carbon black (C) is virgin carbon black.

[0088] The total content of the carbon black (A) which is recycled carbon black and the carbon black (C) which may or may not be recycled carbon black is preferably 30 parts by mass or more per 100 parts by mass of the rubber component. In this case, it is possible to achieve a higher balance between crack resistance and low loss properties. In addition, the total content of the carbon black (A) and the carbon black (C) is preferably 80 parts by mass or less per 100 parts by mass of the rubber component. In this case, it is possible to better maintain low loss properties. From the same viewpoint, the total content of the carbon black (A) and the carbon black (C) per 100 parts by mass of the rubber component is more preferably 35 parts by mass or more, more preferably 60 parts by mass or less, and even more preferably 50 parts by mass or less.

[0089] In the rubber composition of the present embodiment, the proportion of carbon black (A) in the total content of carbon black (A) and carbon black (C) is preferably 20 mass% or more, and more preferably 30 mass% or more, which can further contribute to improving sustainability.

[0090] In particular, the nitrogen adsorption specific surface area of ​​carbon black (A) is 70 m 2 / g or more 90m 2 / g or less, and the nitrogen adsorption specific surface area of ​​carbon black (B) is 110 m 2 / g or more 140m 2 / g or less, the total content of carbon black (A) and carbon black (C) is preferably greater than the content of carbon black (B). That is, in the rubber composition of the present embodiment, the mass ratio of the content of carbon black (A) and carbon black (C) to the content of carbon black (B) (carbon black (A+C) / carbon black (B)) is preferably greater than 1.0. This allows carbon black (B) to be efficiently disposed between carbon black (A) and carbon black (C), and while maintaining the same low loss properties, it is possible to improve crack resistance. From the same viewpoint, the mass ratio of the content of carbon black (A) and carbon black (C) to the content of carbon black (B) (carbon black (A+C) / carbon black (B)) is more preferably 1.2 or more, even more preferably 1.5 or more, and even more preferably 2.0 or more.

[0091] From the viewpoint of more reliably obtaining the desired effects, the rubber composition of the present embodiment preferably does not contain carbon black having a smaller nitrogen adsorption specific surface area than the carbon black (A) which is the recycled carbon black.

[0092] In the rubber composition of the present embodiment, the total content of carbon black is preferably 50 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the rubber component. If the total content is 50 parts by mass or more, the crack resistance can be further improved, and if it is 70 parts by mass or less, the low loss property can be better maintained.

[0093] In the rubber composition of the present embodiment, the proportion of recycled carbon black (such as carbon black (A)) in the total carbon black content is preferably 40 mass % or more, more preferably 50 mass % or more, and even more preferably 60 mass % or more, which can further contribute to improving sustainability.

[0094] (silica) The rubber composition of the present embodiment may contain silica. Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and among these, wet silica is preferred because it has a large number of silanol groups. These silicas may be used alone or in combination of two or more. As the silica, a commercially available product may be used, and examples of the commercially available silica include products from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, Tokuyama Corporation, etc.

[0095] As the silica, silica derived from silicic acid plants is preferred from the viewpoint of reducing environmental load. The silicic acid plants are present, for example, in mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. Among these plants, Gramineae plants are preferred. In addition, the Gramineae plants include rice, bamboo grass, sugarcane, and the like, among which rice is preferred. Since rice is widely cultivated for food, it can be procured locally in a wide area, and since rice husks are generated in large quantities as industrial waste, it is easy to secure the amount. Therefore, from the viewpoint of easy availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. By using the rice husk silica, rice husks that become industrial waste can be effectively utilized, and since the raw material can be procured locally near the tire manufacturing plant, the energy and cost of transportation and storage can be reduced, which is environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet method 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 and extracting the rice husk ash with an alkali silicate aqueous solution. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husks can be pyrolyzed by steaming them in a kiln to obtain rice husk charcoal. The rice husk charcoal thus obtained is pulverized using a known pulverizer (for example, 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. Further examples of the silica include silica produced by recycling silicon components from scraps of silicon wafers, which are raw materials for semiconductors, glass bottles, etc.

[0096] 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 is more preferable, and 2 / g or less, and 2 / g or less is more preferable, 2 / g or less is more preferable, 2 It is even more preferable that the molecular weight is not more than 1 / g. 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.

[0097] The amount of the silica, relative to 100 parts by mass of the rubber component, is, for example, preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, and more preferably 70 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, even more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less.

[0098] (Silane coupling agent) When the rubber composition of the present 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, Examples of the silane coupling agent 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, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, etc. As the silane coupling agent, a commercially available product can be used, and examples of the commercially available silane coupling agent include products from Evonik, Momentive, Shin-Etsu Silicone 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.

[0099] 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, and 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.

[0100] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced mainly using sugars and / or cellulose as biological resources, and other biological resources such as proteins, lipids, and amino acids cannot be effectively utilized. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, it is preferable to use multiple types of monomer components derived from biological resources as the monomer components derived from the biological resources, or to use a monomer component derived from a biological resource, a monomer component derived from a renewable resource, and a monomer component derived from a fossil resource in combination, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (for example, the demand for biomass resources as food). This makes it possible to effectively utilize a wide range of biological resources and renewable resources such as sugars, proteins, and lipids without relying on one type of biological resource, and also to consider the environment depending on the situation during production.

[0101] (resin) The rubber composition of the present embodiment may contain a resin. Examples of the resin include terpene-based resins, rosin-based resins, C 5 based resin, C 5 -C 9 based resin, C 9 Examples of the resins include cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene resins, rosin resins, C 5 based resin, C 5 -C9 based resin, C 9 Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins and aromatic resins, and particularly preferred are terpene-based resins and rosin-based resins. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins, and therefore can reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry road surfaces, wet road surfaces, snowy road surfaces, and frozen road surfaces. 5 based resin, C 9 based resin, C 5 -C 9 The cyclopentadiene-based resin and the cyclopentadiene-based resin can improve abrasion resistance, fuel economy, and loss reduction in a well-balanced manner, while the aromatic resin can improve grip performance, abrasion resistance, and rubber strength in a well-balanced manner.

[0102] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). In addition, the resin may be modified to introduce a functional group that interacts with a filler such as carbon black or silica. Examples of the functional group include an amino group, an amide group, an isocyanate group, an imino group, an imidazole group, a urea group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, an ether group, a carbonyl group, an oxycarbonyl group, a silyl group, an alkoxysilyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, and a thiocarbonyl group.

[0103] The terpene resin is a solid resin obtained by blending turpentine obtained at the same time when rosin is obtained from pine trees, or a polymerization component separated therefrom, and polymerizing it using a Friedel-Crafts catalyst, and examples of the terpene resin include β-pinene resin and α-pinene resin. The terpene resin also includes terpene-aromatic compound resin, and representative examples of the terpene-aromatic compound resin include terpene-phenol resin and styrene-terpene resin. The terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing with formalin. The styrene-terpene resin can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes as the raw material are not particularly limited, and are preferably monoterpene hydrocarbons such as α-pinene and limonene, more preferably those containing α-pinene, and particularly preferably α-pinene.

[0104] 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. Examples of modified rosin, rosin derivatives, and modified rosin derivatives include polymerized rosin, partially hydrogenated rosin thereof, glycerin ester rosin, partially hydrogenated rosin thereof, and fully hydrogenated rosin thereof, pentaerythritol ester rosin, partially hydrogenated rosin thereof, and polymerized rosin, etc.

[0105] Said C 5 As for the resin, C is obtained by thermal cracking of naphtha in the petrochemical industry. 5 Examples include aliphatic petroleum resins obtained by (co)polymerizing the fraction. 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, and the like.

[0106] Said C 5 -C9 The resin is C 5 -C 9 C refers to synthetic petroleum resin. 5 -C 9 As a type of resin, for example, petroleum-derived C 5 -C 11 The fraction was dissolved in AlCl 3 , B.F. 3 More specifically, copolymers mainly composed of styrene, vinyl toluene, α-methyl styrene, indene, etc., can be mentioned. 5 -C 9 As for the resin, 9 Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. 9 "Less than 100% of the total resin content" means that 9 This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0107] Said C 9 The resin is C 9 This refers to synthetic petroleum resins, such as AlCl 3 Or BF 3 Using Friedel-Crafts type catalysts such as C 9 It refers to the solid polymer obtained by polymerizing the fraction. 9 Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, or the like as a main component.

[0108] The cyclopentadiene resin refers to a resin containing a unit derived from a cyclopentadiene monomer as a monomer unit. Examples of the cyclopentadiene resin include a homopolymer of a cyclopentadiene monomer, a copolymer of two or more cyclopentadiene monomers, and a copolymer of a cyclopentadiene monomer and another monomer. Examples of the cyclopentadiene monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred, that is, the cyclopentadiene resin is preferably a dicyclopentadiene resin. The dicyclopentadiene resin is, for example, AlCl 3 Or BF 3 It refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as . Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, and copolymers of dicyclopentadiene and C 9 Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0109] The aromatic resin refers to a resin containing a unit derived from an aromatic monomer as a monomer unit. Examples of the aromatic resin include a homopolymer of an aromatic monomer, a copolymer of two or more aromatic monomers, and a copolymer of an aromatic monomer and another monomer. Examples of the aromatic monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenolic monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0110] 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 defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0111] As the resin, commercially available products can be used, and examples of commercially available resin products that can be used include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Clayton, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Clayton Polymers, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0112] 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, tire components, target performance, etc. For example, the content of the resin is preferably in the range of 5 to 100 parts by mass, and more preferably in the range of 10 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0113] (rubber powder) The rubber composition of the present embodiment preferably contains rubber powder. The rubber powder may be obtained by crushing used rubber products such as used tires, and removing reinforcing materials such as steel materials and fibers, dust, glass, sand, stones, etc., as desired, or by preparing a new vulcanized rubber composition to produce rubber powder and crushing it. For example, rubber powder can be obtained from vulcanized rubber by the method described in "Rubber Chemistry And Technology". In the process of crushing vulcanized rubber to obtain rubber powder, mechanical treatment or low-temperature treatment may be used. For example, in mechanical treatment, various crushing devices such as cracker mills and granulators can be used to mechanically crush vulcanized rubber into fine particles. In low-temperature treatment, finely chopped vulcanized rubber is frozen at a very low temperature and then crushed into fine particles. In addition, a magnetic separator or the like can be used to remove steel materials, and an air separator or the like can be used to remove fibers. As the rubber powder, commercially available products can be used, and examples of commercially available rubber powder include products from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental load, 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 kinds.

[0114] The composition of the rubber powder is not particularly limited, and depends on the composition of vulcanized rubber such as used rubber products (used tires) that serve as a raw material. In one embodiment, the rubber powder contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber powder may be the same as or different from the rubber component, carbon black, silica, etc. contained in the rubber composition of the present embodiment described above.

[0115] The rubber powder has a volume average particle size of preferably 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 size of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle size is measured by a laser diffraction particle size distribution measuring device, for example, "CAPA500" manufactured by Horiba, Ltd.

[0116] The rubber powder has a 60 mesh sieve residue of preferably less than 1 mass%, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, with no particular lower limit. Also, the rubber powder has an 80 mesh sieve residue of preferably less than 10 mass%, more preferably 1 mass% or less, and even more preferably 0.5 mass% or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0117] The rubber powder has an acetone extractable content of preferably 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractables in the rubber powder refer to the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0118] The content of the rubber powder is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the tire components, the target performance, etc. For example, the content of the rubber powder is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and 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, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0119] (liquid softener) The rubber composition of the present embodiment may contain a liquid softener. Here, the "liquid softener" is a compounding agent that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid softener is not particularly limited, and examples thereof include oil and liquid polymer, among which oil is preferable. These liquid softeners may be used alone or in combination of two or more.

[0120] The oil is a general term for the extender oil contained in the rubber component and the liquid oil added as a compounding agent of the rubber composition, and examples thereof include vegetable oil, process oil, oil obtained by recycling vegetable oil or process oil, or a mixture thereof. From the viewpoint of reducing the environmental load, the oil is preferably vegetable oil or oil obtained by recycling. Examples of the vegetable oil include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut 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, coconut oil, etc. Examples of the process oil include paraffin-based process oil, aromatic process oil, naphthene-based process oil, etc. The oil may be a commercially available product, and examples of the commercially available oil include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi 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.

[0121] The liquid polymer is preferably a liquid diene polymer. Examples of the liquid diene 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 the 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.

[0122] The content of the liquid softener 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 liquid softener is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, and 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, relative to 100 parts by mass of the rubber component.

[0123] (Anti-aging agent) The rubber composition of the present embodiment may contain an antioxidant, such as 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, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. As the antiaging agent, commercially available products can be used, and examples of the commercially available antiaging agent include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis Co., Ltd., etc. These antiaging agents may be used alone or in combination of two or more.

[0124] The content of the antiaging agent 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 antiaging agent 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, and 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, relative to 100 parts by mass of the rubber component.

[0125] (wax) The rubber composition of the present embodiment may contain a wax. Examples of the wax include natural waxes such as vegetable wax and animal wax; 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 the commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0126] 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 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, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, based on 100 parts by mass of the rubber component.

[0127] (Stearic acid) The rubber composition of the present embodiment may contain stearic acid. Commercially available stearic acid may be used, and examples of the commercially available stearic acid include products from NOF Corp., Kao Corp., Fujifilm Wako Pure Chemical Corp., Chiba Fatty Acid Corp., etc. These commercially available stearic acid products may be used alone or in combination of two or more.

[0128] The content of the stearic acid 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 stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0129] (Zinc Oxide) The rubber composition of the present embodiment may contain zinc oxide (zinc white). The zinc oxide is preferably zinc oxide obtained by recycling (specifically, zinc oxide obtained from not only zinc metal but also regenerated zinc or zinc dross). Commercially available zinc oxide can be used, and examples of the 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., Toho Zinc Co., Ltd., and the like. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0130] The content of the zinc oxide 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 zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0131] (sulfur) The rubber composition of the present embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or materials derived from biological resources. From the viewpoint of reducing the environmental load, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of a method for obtaining sulfur from waste derived from biological resources include the method described in the above-mentioned Japanese Patent Application No. 2022-140390. In addition, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are generally used as crosslinking agents in the rubber industry. As the sulfur, commercially available products can be used, and examples of commercially available sulfur products include products from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Co., Ltd., etc. These sulfurs may be used alone or in combination of two or more types.

[0132] The sulfur content is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, tire components, 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, and is preferably 8 parts by mass or less, and more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0133] (Vulcanization accelerator) The rubber composition of the present embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, recycled resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing environmental load. The vulcanization accelerator derived from biological resources can be obtained by the method disclosed in, for example, JP-A-2005-139239. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; 1,3-diphenylguanidine (DPG), 1,3-diphenylguanidine (DPG), and 1,3-diphenylguanidine (DPG). Examples of the vulcanization accelerator 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 products can be used as the vulcanization accelerator, and examples of the commercially available vulcanization accelerators include products from Ouchi Shinko Chemical Industry Co., Ltd. and Sumitomo Chemical Co., Ltd. These vulcanization accelerators may be used alone or in combination of two or more.

[0134] The content of the vulcanization accelerator is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which it is applied, tire components, 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, and 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, relative to 100 parts by mass of the rubber component.

[0135] (Cellulose nanofiber) The rubber composition of the present embodiment may contain cellulose nanofibers (CNF). The cellulose nanofibers can reinforce the rubber composition by blending them with the rubber composition. The cellulose nanofibers are preferably modified cellulose nanofibers, which are fine fibers made from modified cellulose. The fiber diameter of the cellulose nanofibers is not particularly limited, but is about 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofibers can be obtained by averaging the fiber diameters and fiber lengths obtained from the results of observing each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofibers can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment and defibration treatment.

[0136] 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.

[0137] The content of the cellulose nanofibers is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the tire components, 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 weight, and even more preferably in the range of 10 to 40 parts by mass, relative to 100 parts by mass of the rubber component.

[0138] (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, clay, 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 the rubber composition is applied, the tire components, the target performance, etc., and is preferably in the range of 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0139] (Method of manufacturing rubber composition) The method for producing the rubber composition of the present embodiment is not particularly limited, but for example, the rubber composition can be produced by blending the carbon black (A) and the carbon black (B) with various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0140] 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 the 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.

[0141] The conditions of the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, heat-in equipment, etc. can be appropriately selected depending on the purpose. Examples of the heat-in equipment include a heat-in roller machine usually used for heat-in of a rubber composition.

[0142] 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 that is usually used for extruding a rubber composition. The extrusion temperature can be appropriately determined.

[0143] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected according to the purpose. As the vulcanization apparatus, a molding vulcanizer using a mold used for vulcanizing a rubber composition can be mentioned. As the vulcanization condition, the temperature is, for example, about 100 to 190°C.

[0144] (Application) The rubber composition of the present embodiment can be applied to various components of tires, for example, treads (cap treads, base treads, under treads), cushion rubbers, shoulders, sidewalls, clinches, bead fillers, organic fiber coating rubbers, steel cord coating rubbers, insulation, chafers, inner liners, etc., and can also be used for side reinforcing layers of run-flat tires. In addition to tires, the rubber composition of the present embodiment can also be applied to hoses, rubber crawlers, seismic isolation rubbers, etc. These rubber members or rubber products, including tires, can be excellent in low loss properties and crack resistance, and can contribute to improving sustainability by using the rubber composition of the present embodiment.

[0145] When a tire is manufactured using the rubber composition of the present embodiment, the tire can be manufactured by a normal method using the above-mentioned rubber composition. For example, the tire of the present 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, depending on the type of tire to be applied. The tire of the present embodiment is preferably a pneumatic tire, and the gas to be filled in 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. EXAMPLES

[0146] The present invention will be described in more detail below with reference to examples. However, the present invention is not limited to the following examples and can be modified as appropriate without departing from the gist of the present invention.

[0147] (Low rolling resistance (low loss)) Two types of rubber compositions having the compounding compositions shown in Table 1 were prepared, and these rubber compositions were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The loss tangent (tan δ) of the obtained vulcanized rubber test pieces was measured using a viscoelasticity measuring device (manufactured by Rheometrics Corporation) under conditions of a temperature of 60°C, a strain of 1%, and a frequency of 52Hz. The measurement result of rubber composition 1 containing conventional carbon black was set as 100, and the results are indexed in Table 1. A higher index indicates better low rolling resistance (i.e., low loss).

[0148] (Sustainable material ratio) Furthermore, the sustainable material ratio of the above-mentioned rubber composition was calculated by the following formula. The results are shown in Table 1. Sustainable material ratio = Total sustainable materials (B in Table 1) / Total of all materials (A in Table 1) x 100

[0149] [Table 1]

[0150] *1 Low Tg modified SBR: Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method, Tg = -65°C, SP value = 8.65 (cal / cm 3 ) 1 / 2 *2 High Tg modified SBR: Modified styrene-styrene-butadiene copolymer rubber synthesized by the following method, containing 10.0 parts by mass of oil per 100 parts by mass of rubber component, weight average molecular weight (Mw) = 85.2 x 104, ratio of molecular weight between 200 x 104 and 500 x 104 = 4.6%, shrinkage factor (g') = 0.59 *3 Carbon black: Asahi Carbon Co., Ltd., product name "#78" *4 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *5 Silica: Tosoh Silica Industries Co., Ltd., product name "Nipsil AQ" *6 Silane coupling agent: Evonik, product name "Si75" *7 Heidilight: Manufactured by Resonac, product name "Heidilight H-43M" *8 Other chemicals: Total amount of sulfur, vulcanization accelerator, retarder, adhesion inhibitor, antioxidant, wax, resin, and softener. The same ratio for each rubber composition.

[0151] <Synthesis method of low Tg modified SBR(*1)> A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-substituted 800 mL pressure-resistant glass container so that the amount of 1,3-butadiene was 67.5 g and styrene was 7.5 g, and 0.6 mmol of 2,2-ditetrahydrofurylpropane was added, and 0.8 mmol of n-butyllithium was added, and polymerization was carried out at 50 ° C for 1.5 hours. At this time, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier to the polymerization reaction system in which the polymerization conversion rate was almost 100%, and a modification reaction was carried out at 50 ° C for 30 minutes. Thereafter, 2 mL of a 5 mass % solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to stop the reaction, and the mixture was dried according to a conventional method to obtain a modified SBR (low Tg modified SBR). Measurement of the microstructure of the resulting modified SBR revealed that the bound styrene content was 10% by mass, and the glass transition temperature (Tg) was -65°C.

[0152] <Synthesis method of high Tg modified SBR(*2)> The polymerization reactor was a tank-type pressure vessel with an internal volume of 10 L, an internal height (L) to diameter (D) ratio (L / D) of 4.0, an inlet at the bottom, an outlet at the top, and a jacket for temperature control. 1,3-butadiene, which had been previously dehydrated, was mixed at 17.2 g / min, styrene at 10.5 g / min, and n-hexane at 145.3 g / min. In a static mixer installed in the middle of the piping supplying this mixed solution to the inlet of the reactor, n-butyllithium for inactivating remaining impurities was added at 0.117 mmol / min, mixed, and then continuously supplied to the bottom of the reactor. Furthermore, 2,2-bis(2-oxolanyl)propane as a polar substance at a rate of 0.019 g / min and n-butyllithium as a polymerization initiator at a rate of 0.242 mmol / min were fed to the bottom of the polymerization reactor, which was being vigorously mixed with a stirrer, to continue the polymerization reaction continuously. The temperature of the polymerization solution at the top outlet of the reactor was controlled to be 75°C. When the polymerization was sufficiently stabilized, a small amount of the polymer solution before the addition of the coupling agent was withdrawn from the top outlet of the reactor, and an antioxidant (BHT) was added in an amount of 0.2 g per 100 g of polymer, after which the solvent was removed, and the Mooney viscosity at 110°C and various molecular weights were measured. Next, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine (abbreviated as "A" in the table) diluted to 2.74 mmol / L as a coupling agent was continuously added to the polymer solution flowing out from the outlet of the reactor at a rate of 0.0302 mmol / min (n-hexane solution containing 5.2 ppm water), and the polymer solution to which the coupling agent was added was mixed by passing through a static mixer to undergo a coupling reaction. At this time, it took 4.8 minutes for the coupling agent to be added to the polymer solution flowing out from the outlet of the reactor, the temperature was 68°C, and the difference between the temperature in the polymerization process and the temperature before the modifier was added was 7°C. An antioxidant (BHT) was continuously added to the polymer solution that had undergone the coupling reaction at 0.055 g / min (n-hexane solution) so that the amount was 0.2 g per 100 g of polymer, and the coupling reaction was terminated. Simultaneously with the antioxidant, oil (JOMO Process NC140 manufactured by JX Nippon Oil & Energy Corporation) was continuously added so that the amount was 10.0 g per 100 g of polymer, and mixed with a static mixer. The solvent was removed by steam stripping to obtain a modified conjugated diene polymer (high Tg modified SBR). It was confirmed that the modified conjugated diene polymer obtained by the above method contained nitrogen atoms and silicon atoms. The modified conjugated diene polymer has a "degree of branching" of 8, which corresponds to the number of branches estimated from the number of functional groups of the coupling agent and the amount added (this can also be confirmed from the value of the shrinkage factor), and has a "number of SiO R residues" of 4, which corresponds to the total number of SiO R contained in one molecule of the coupling agent minus the number of SiO R reduced by the reaction.

[0153] From Table 1, it can be seen that by replacing carbon black (virgin carbon black) with recycled carbon black, among the various materials contained in the rubber composition, the low loss property can be improved. In addition, such replacement also contributes to improving sustainability.

[0154] (Breaking strength (crack resistance-1)) Two types of rubber compositions having the compounding compositions shown in Table 2 were prepared, and these rubber compositions were vulcanized at 145°C for 33 minutes to obtain vulcanized rubber test pieces. The obtained vulcanized rubber test pieces were punched into JIS No. 3 dumbbells, and the obtained samples were subjected to a tensile test at room temperature according to JIS K 6251:2004 to measure the breaking strength (TB) before heat aging (initial stage) and after heat aging (100°C x 24 hours). The results are shown in Table 2. A larger value indicates better fracture resistance, i.e., crack resistance.

[0155] [Table 2]

[0156] *11 Butadiene rubber: UBE Elastomers, product name "BR150L" *12 Carbon black: Asahi Carbon Co., Ltd., product name "N550", nitrogen adsorption specific surface area (N 2 SA)=40m 2 / g, DBP oil absorption = 121mL / 100g *13 Recycled carbon black: Enrestec, product name "PB365", ash content = 17% by mass *14 Anti-aging agent: Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C" *15 Oil: Manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 224" *16 Fatty acid: Manufactured by ENEOS, product name “A / Omix” *17 Wax: Miyoshi Oil Co., Ltd., product name "MXST" *18 Other chemicals: Total amount of sulfur, vulcanization accelerator, resin, and wax. The same ratio for each rubber composition.

[0157] From Table 2, it can be seen that by replacing carbon black (virgin carbon black) with recycled carbon black, among the various materials contained in the rubber composition, the breaking strength before and after thermal degradation decreases.

[0158] (Crack resistance-2) A rubber composition sample was prepared by adding the prescribed amounts of zinc oxide (made by Hakusui Tech), resin, sulfur (made by Eastman Chemical Japan), antioxidant (made by Daito Sangyo) and other chemicals to the composition shown in Table 3 and mixing and kneading in a conventional manner. Note that kneading was performed using a 3.0 L Banbury mixer.

[0159] Then, tires of size 275 / 80R22.5 were produced using each rubber composition. The peel resistance S0 (unit: N / 400 mm 2 Next, the tire was subjected to a drum running test at a speed of 60 km / h for 12 hours (actual running distance: 720 km), and the peel resistance S1 (unit: N / 400 mm 2 ) was measured in the same manner as above. The peel resistance S1 was indexed with the value of rubber composition 5 being 100. Furthermore, the reduction rate of peel resistance was calculated for each example by (S0-S1) / S0×100. The results are shown in Table 3. A larger peel resistance S1 and a smaller reduction rate of peel resistance indicate better crack resistance.

[0160] [Table 3]

[0161] *21 Rubber component: Natural rubber *22 Carbon black A: Asahi Carbon Co., Ltd., HAF, N 2 SA:81m 2 / g, DBP oil absorption: 80mL / 100g *23 Carbon black B: Asahi Carbon Co., Ltd., SAF, N 2 SA:127m 2 / g, DBP oil absorption: 97mL / 100g

[0162] Table 3 shows that rubber composition 6, which uses carbon black A in combination with carbon black B, which has a larger nitrogen adsorption specific surface area than carbon black A, has significantly improved crack resistance compared to rubber composition 5, which uses carbon black A only.

[0163] Based on these evaluations, it is expected that the crack resistance can be well maintained by replacing carbon black with recycled carbon black and using two specific types of carbon black. Therefore, the rubber composition of the present invention can contribute to improving sustainability and is expected to have low loss and excellent crack resistance. [Industrial Applicability]

[0164] According to the present invention, it is possible to provide a rubber composition that is excellent in low loss property and crack resistance and can contribute to improving sustainability.

Claims

1. A rubber composition comprising at least a rubber component, carbon black (A) which is recycled carbon black, and carbon black (B) having a larger nitrogen adsorption specific surface area than the carbon black (A).

2. The nitrogen adsorption specific surface area of ​​the carbon black (A) is 70 m ２ / g or more 90m ２ The rubber composition according to claim 1, wherein the elastic modulus is 0.1 / g or less.

3. The nitrogen adsorption specific surface area of ​​the carbon black (B) is 110 m ２ / g or more 140m ２ The rubber composition according to claim 1 or 2, wherein the elastic modulus is 0.1 to 1.0 μm.

4. Furthermore, the nitrogen adsorption specific surface area is 70m ２ / g or more 90m ２ 3. The rubber composition according to claim 2, further comprising carbon black (C), which may or may not be recycled carbon black, and has a viscosity of 100% or less than 100% by mass.

5. The rubber composition according to claim 1 or 2, wherein an amount of the carbon black (A) is 15 parts by mass or less based on 100 parts by mass of the rubber component.

6. 3. The rubber composition according to claim 1, wherein the carbon black (A) is obtained by thermal decomposition of a vulcanized rubber product containing carbon black.

7. The rubber composition according to claim 1 or 2, wherein the carbon black (A) has an ash content of 20 mass % or less.

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