Rubber composition and steel cord coating rubber

Abstract

To provide a rubber composition that exhibits superior resistance to cracking while maintaining low-loss performance.SOLUTION: A rubber composition comprises a rubber component, a carbon black (A) having a nitrogen adsorption specific surface area of 70 m2 / g or more and 90 m2 / g or less, and a carbon black (B) having a nitrogen adsorption specific surface area of 110 m2 / g or more and 140 m2 / g or less, wherein the content of the carbon black (A) is greater than the content of the carbon black (B).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition and a steel cord coating rubber. [Background technology]

[0002] Generally, a tire that requires strength may have a carcass layer inside the tire, which is made of cords embedded along the meridian direction of the ring-shaped tire body, and a belt disposed on the tire radially outside of the carcass layer. This belt is usually formed of multiple belt layers in which steel cords are covered with rubber (hereinafter referred to as "steel cord coating rubber"), and provides the tire with load-bearing properties, traction resistance, etc. The steel cord coating rubber is required to have high durability, especially high crack propagation resistance.

[0003] On the other hand, in recent years, from the viewpoint of improving fuel efficiency of automobiles, there has been an increasing demand for improved low loss properties of steel cord coating rubber in order to reduce the rolling resistance of tires.

[0004] In this regard, for example, when the amount of carbon black blended into the steel cord coating rubber is reduced in order to improve the low loss property, the crack resistance tends to deteriorate, and therefore, there has been a demand for the development of a technology that can achieve both low loss property and crack resistance.

[0005] As such a technique, for example, Patent Document 1 discloses a technique in which a wet masterbatch is prepared using a specific grade of carbon black, and a rubber composition is produced using the wet masterbatch to enhance the dispersibility of carbon black. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2016-037547 A Summary of the Invention [Problem to be solved by the invention]

[0007] The above-mentioned technology has made it possible to obtain a certain level of compatibility between low loss and crack growth resistance. However, in order to further improve tire performance and from a technical viewpoint other than the use of the wet masterbatch, it has been desired to achieve a higher level of compatibility between low loss and crack growth resistance.

[0008] Therefore, an object of the present invention is to provide a rubber composition that has excellent crack resistance while maintaining low loss properties. Another object of the present invention is to provide a steel cord coating rubber that has excellent crack resistance while maintaining low loss properties. [Means for solving the problem]

[0009] That is, the essential features of the rubber composition and steel cord coating rubber of the present invention that solve the above problems are as follows.

[0010] [1] Rubber component with a nitrogen adsorption specific surface area of ​​70m 2 / g or more 90m 2 / g or less, and carbon black (A) having a nitrogen adsorption specific surface area of ​​110 m 2 / g or more 140m 2 and carbon black (B) having a molecular weight of 1 / g or less, A rubber composition, characterized in that the content of the carbon black (A) is greater than the content of the carbon black (B). The rubber composition of the present invention has excellent crack resistance while maintaining low loss properties.

[0011] [2] The rubber composition according to [1], wherein the total amount of carbon black is 50 parts by mass or more and 70 parts by mass or less per 100 parts by mass of the rubber component. In this case, the crack resistance can be further improved and the low loss property can be better maintained.

[0012] [3] The rubber composition according to [1] or [2], wherein the amount of the carbon black (B) is 25 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] [4] A steel cord coating rubber, characterized by using the rubber composition according to any one of [1] to [3]. The steel cord coating rubber of the present invention has excellent crack resistance while maintaining low loss properties. Effect of the Invention

[0014] According to the present invention, it is possible to provide a rubber composition that has excellent crack resistance while maintaining low loss properties. Moreover, according to the present invention, it is possible to provide a steel cord coating rubber that has excellent crack resistance while maintaining low loss properties. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The rubber composition and the steel cord coating rubber of the present invention will be described in detail below with reference to examples based on the embodiments.

[0016] <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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] <Rubber composition> The rubber composition according to one embodiment of the present invention (hereinafter, may be referred to as the “rubber composition according to the present embodiment”) comprises a rubber component and a nitrogen adsorption specific surface area (N 2 SA) is 70m 2 / g or more 90m 2 / g or less, and carbon black (A) having a nitrogen adsorption specific surface area of ​​110 m 2 / g or more 140m 2 / g or less, and the content of the carbon black (A) is greater than the content of the carbon black (B).

[0022] The carbon black (A) used in the rubber composition of this embodiment has a nitrogen adsorption specific surface area of ​​70 m 2 / g or more 90m 2 / g or less, and has a relatively large particle size. Therefore, when carbon black (A) is blended alone in the rubber component, the distance between the carbon black particles is large, and relatively large gaps are generated. In contrast, when carbon black (A) having a relatively small particle size, i.e., a nitrogen adsorption specific surface area of ​​110 m or less is blended in addition to the above-mentioned carbon black (A), 2 / g or more 140m 2By blending a predetermined amount of carbon black (B) having a molecular weight of 0.1 to 1.0 μg or less, the carbon black (B) is efficiently arranged between the carbon blacks (A). By optimizing the arrangement, the network properties of the carbon black are improved, and the collapse of the carbon black network due to fatigue can be significantly suppressed, and the crack resistance can be improved while maintaining the same low loss properties.

[0023] (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.

[0024] 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%.

[0025] 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).

[0026] 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.

[0027] 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.

[0028] 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.).

[0029] 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.

[0030] 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 preferably 5% by mass or less, more preferably 3% by mass or less, and may be 0% by mass. If the total amount of styrene in the rubber component is 5% by mass or less, the deterioration of the physical properties of the rubber composition can be suppressed, and the elongation at break (EB) after thermal aging can be sufficiently improved.

[0031] 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.

[0032] 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.

[0033] 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.").

[0034] 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.

[0035] 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.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] 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.

[0053] 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.

[0054] 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.

[0055] (Carbon Black) The rubber composition of the present embodiment contains carbon black. More specifically, the rubber composition of the present embodiment has at least a nitrogen adsorption specific surface area (N 2 SA) is 70m 2 / g or more 90m 2 / g or less, and carbon black (A) having a nitrogen adsorption specific surface area of ​​110 m 2 / g or more 140m 2 / g or less. The carbon black (A) may be a single type or a combination of two or more types. The carbon black (B) may be a single type or a combination of two or more types. In this specification, the nitrogen adsorption specific surface area (N 2 SA) is calculated according to JIS K 6217-2:2017 (ISO 4652:2012).

[0056] In addition, in the rubber composition of this embodiment, the content of carbon black (A) is greater than the content of carbon black (B). That is, in the rubber composition of this embodiment, the mass ratio of the content of carbon black (A) to the content of carbon black (B) (carbon black (A) / carbon black (B)) is greater than 1.0. This allows carbon black (B) to be efficiently arranged between carbon blacks (A), 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) to the content of carbon black (B) (carbon black (A) / carbon black (B)) is preferably 1.2 or more, more preferably 1.5 or more, and even more preferably 2.0 or more.

[0057] The nitrogen adsorption specific surface area of ​​carbon black (A) is 70 m as mentioned above. 2 / g or more, and 2 / g or less, but from the viewpoint of more efficient arrangement of the carbon black as a whole, 2 / g or more, and 2 / g or more is more preferable, and 2 / g or less, and 2 It is more preferable that the molecular weight is not more than 1 / g.

[0058] From the viewpoint of more efficient arrangement of the carbon black as a whole, the carbon black (A) 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.

[0059] The content of carbon black (A) is preferably 25 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 content of carbon black (A) 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 content of carbon black (A) per 100 parts by mass of the rubber component is more preferably 30 parts by mass or more, more preferably 60 parts by mass or less, and further preferably 50 parts by mass or less.

[0060] The nitrogen adsorption specific surface area of ​​carbon black (B) is 110 m as mentioned above. 2 / g or more, and 140m 2 / g or less, but from the viewpoint of more efficient arrangement of the carbon black as a whole, 2 / g or more, and 2 / g or more is more preferable, and 2 / g or less, and 2 It is more preferable that the molecular weight is not more than 1 / g.

[0061] 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.

[0062] 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 25 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 22 parts by mass or less.

[0063] The rubber composition of the present embodiment may contain carbon black (referred to as carbon black (C)) other than the above-mentioned carbon black (A) and carbon black (B).

[0064] In addition, the rubber composition of the present embodiment preferably has a total content of carbon black (i.e., carbon black (A), carbon black (B) and optional carbon black (C)) of 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.

[0065] At least one of the carbon black (A) and the carbon black (B) used in this embodiment may be recycled carbon black, which can contribute to improving sustainability. In this specification, the term "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 and peeled rubber. 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.

[0066] In addition, the above-mentioned recycled carbon black 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 that can be used in this embodiment is preferably obtained from a solid residue generated by pyrolysis of a vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and it is possible to recover recycled carbon black 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.

[0067] 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, the better. In the recycled carbon black, the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. In addition, the carbon content in the recycled carbon black is preferably 97% by mass or less. The carbon content is a value that does not include adsorbed moisture.

[0068] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from a solid residue obtained by pyrolysis of waste, a certain amount of ash remains even after various steps for removing the ash. In this embodiment, the inclusion of ash in the recycled carbon black is permitted. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0069] The recycled carbon black can also be obtained from a 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), especially pp. 438, 440, and 442, describes that the recycled carbon black 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 (paragraph

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

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

[0070] The regenerated carbon black may lack a functional group on its surface, or may be treated to include a functional group on its surface. The treatment to include a functional group 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 a hydroxyl group and / or a carboxyl group on its surface. In Japanese Patent Publication 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 blacks treated to include functional groups on their surfaces.

[0071] Moreover, examples of the thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include a thermal decomposition method at a temperature of 650° C. or higher.

[0072] 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 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.

[0073] In addition, when the crosslinked rubber product used for the decomposition is derived from a tire, the tire 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 step may be performed for each group. In addition, the tire 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 step may be performed for each group. Furthermore, the tire may be grouped by type and by tire components, 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 it is blended again into the rubber component, a rubber composition with better performance is obtained.

[0074] The regenerated carbon black has a nitrogen adsorption specific surface area of ​​70 to 140 m by the BET method. 2 / g, and 73 to 136 m 2 / g is more preferable, and 76 to 134 m 2 It is particularly preferred that the molecular weight is / g. In this specification, the nitrogen adsorption specific surface area of ​​the recycled carbon black measured by the BET method is the statistical thickness specific surface area (STSA) and is determined in accordance with ASTM D6556.

[0075] The 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.

[0076] The recycled 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.

[0077] The recycled carbon black preferably has a heat loss at 125° C. of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less. Herein, the heat loss of recycled carbon black at 125° C. is determined in accordance with ASTM D1509.

[0078] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0079] The 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.

[0080] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 ppm by mass or less, more preferably 700 ppm by mass or less, and particularly preferably 300 ppm by mass or less. In this specification, the 325 mesh (44 μm) sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0081] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0082] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. In this specification, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0083] The 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.

[0084] The recycled carbon black preferably contains particles of 5 μm or less in volume percentage of 50% or more, more preferably 70% or more, and particularly preferably 80% or more.

[0085] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of a 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.

[0086] The regenerated carbon black preferably has a dibutyl phthalate (DBP) absorption of 50 to 110 mL / 100 g, more preferably 60 to 105 mL / 100 g, and particularly preferably 70 to 97 mL / 100 g. As used herein, the DBP absorption of recycled carbon black is determined in accordance with ASTM D2414.

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

[0088] As the recycled carbon black, a commercially available product can be used. For example, a commercially available product under the trade name "PB365" manufactured by Enrestec can be mentioned. PB365 is a recycled carbon black produced through the thermal decomposition 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.

[0089] (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.

[0090] 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.

[0091] 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.

[0092] The amount of the silica is, for example, preferably 1 part by mass or more, more preferably 3 parts by mass or more, and is preferably 40 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, based on 100 parts by mass of the rubber component.

[0093] (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.

[0094] 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.

[0095] 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.

[0096] (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 Resin, C 5 -C 9 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 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 further reduce the environmental load and further improve tire performance. 5 based resin, C 9 based resin, C 5 -C 9 The cyclopentadiene-based resin and the cyclopentadiene-based resin can more effectively improve the low loss property, while the aromatic resin can more effectively improve the rubber strength.

[0097] 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.

[0098] The amount of the resin is not particularly limited and can be appropriately adjusted. For example, the amount of the resin is preferably within a range of 0.5 to 10 parts by mass with respect to 100 parts by mass of the rubber component.

[0099] (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.

[0100] 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.

[0101] (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.

[0102] 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.

[0103] (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. Commercially available zinc oxide may 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. The zinc used for the zinc oxide may be not only zinc bullion, but also zinc obtained from recycled zinc or zinc dross.

[0104] 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.

[0105] (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.

[0106] 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.

[0107] (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.

[0108] 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.

[0109] (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.

[0110] (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 rubber component with carbon black including carbon black (A) and carbon black (B), and various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] (Application) The rubber composition of this embodiment can be applied to various components of tires other than the steel cord coating rubber described later, for example, treads (cap tread, base tread, under tread), cushion rubber, shoulders, sidewalls, clinches, bead fillers, organic fiber coating rubber, insulation, chafers, inner liners, etc., and can also be used for side reinforcing layers of run-flat tires, etc. The rubber composition of this embodiment can also be applied to hoses, rubber crawlers, seismic isolation rubber, etc., in addition to tires.

[0116] <Steel cord coated rubber> The steel cord coating rubber of the present invention is characterized by using the rubber composition of the present embodiment described above. In other words, the steel cord coating rubber of the present invention includes the rubber composition of the present embodiment described above. Since the steel cord coating rubber of the present invention uses the rubber composition of the present embodiment, it has excellent crack resistance while maintaining low loss properties.

[0117] In addition, by disposing a belt in which steel cords are covered with the above-mentioned steel cord coating rubber on the radially outer side of the carcass layer, the resulting tire has excellent crack resistance while maintaining low loss properties. EXAMPLES

[0118] 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.

[0119] The rubber composition samples were prepared by compounding the prescribed amounts of zinc oxide (made by Hakusui Tech), sulfur (made by Eastman Chemical Japan), antioxidant (made by Daito Sangyo) and other chemicals into the formulations shown in Table 1 and compounding and kneading them in a conventional manner. The kneading was performed using a Banbury mixer with a capacity of 3.0 L. Each rubber composition sample was vulcanized at 145°C for 40 minutes to obtain vulcanized rubber, and then the 100% modulus value (M100, tensile stress at 100% elongation) was measured in accordance with JIS K 6251 (2010). The M100 value of Comparative Example 1 was set to 100 and indexed. The results are shown in Table 1.

[0120] Each rubber composition was further evaluated as follows.

[0121] (1) Low loss Each rubber composition sample was vulcanized at 145°C for 40 minutes to obtain a vulcanized rubber. The loss tangent (tan δ) of the obtained vulcanized rubber was measured using a spectrometer (manufactured by Ueshima Seisakusho Co., Ltd.) under conditions of a temperature of 24°C, a strain of 1%, and a frequency of 52Hz. The tan δ value of Comparative Example 1 was then indexed to 100. The results are shown in Table 1. The smaller the index value, the better the low loss property.

[0122] (2) Crack resistance Using each rubber composition, a tire of size 275 / 80R22.5 was produced. 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 then indexed with the value of Comparative Example 1 being 100. Furthermore, the rate of decrease in peel resistance was calculated in each example by (S0-S1) / S0×100. The results are shown in Table 1. A larger peel resistance S1 and a smaller rate of decrease in peel resistance indicate better crack resistance.

[0123] [Table 1]

[0124] *1 Rubber component: Natural rubber *2 Carbon black A: Asahi Carbon Co., Ltd., HAF, N 2 SA:81m 2 / g, DBP oil absorption: 80mL / 100g *3 Carbon black B: Asahi Carbon Co., Ltd., SAF, N 2 SA:127m 2 / g, DBP oil absorption: 97mL / 100g

[0125] From Table 1, it can be seen that Example 1, in which carbon black A and carbon black B are used in combination in specified amounts, has significantly improved crack resistance while maintaining the same low loss properties as Comparative Example 1, in which only carbon black A is used. [Industrial Applicability]

[0126] According to the present invention, it is possible to provide a rubber composition that has excellent crack resistance while maintaining low loss properties. Moreover, according to the present invention, it is possible to provide a steel-coated rubber that has excellent crack resistance while maintaining low loss properties.

Claims

1. Rubber component and nitrogen adsorption specific surface area of ​​70m ２ / g or more 90m ２ / g or less, and carbon black (A) having a nitrogen adsorption specific surface area of ​​110 m ２ / g or more 140m ２ and carbon black (B) having a molecular weight of 100 / g or less, A rubber composition, characterized in that the content of the carbon black (A) is greater than the content of the carbon black (B).

2. The rubber composition according to claim 1, wherein a total content of the carbon black is 50 parts by mass or more and 70 parts by mass or less based on 100 parts by mass of the rubber component.

3. The rubber composition according to claim 1 or 2, wherein an amount of the carbon black (B) is 25 parts by mass or less based on 100 parts by mass of the rubber component.

4. A steel cord coating rubber, comprising the rubber composition according to claim 1 or 2.

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