Rubber composition for tread, and tire

Abstract

To provide a rubber composition for a tread which has an excellent balance between wear resistance and low rolling resistance and an excellent ratio of sustainable materials.SOLUTION: The rubber composition for a tread according to the present invention contains a rubber component, a resin, and carbon black. The resin contains at least one selected from the group consisting of terpene resins and rosin resins. The carbon black has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 130 m2 / g or more, a ratio (CTAB / IA) of the CTAB (m2 / g) to an iodine adsorption (IA) (mg / g) of 0.92 or more and 1.06 or less, and a hydrogen release amount of 3,500 mass ppm or more and 4,800 mass ppm or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a rubber composition for a tread and a tire. [Background technology]

[0002] In general, pneumatic tires are required to have high performance that can simultaneously satisfy multiple performance requirements. In particular, tire components such as treads are strongly desired to have excellent abrasion resistance while suppressing the rolling resistance of the tire. However, since these properties are in a trade-off relationship, much trial and error has been carried out up to now. For example, in rubber compositions to be applied to tire treads (hereinafter referred to as "rubber compositions for treads"), carbon black is often used as one of the reinforcing fillers. Generally, increasing the carbon black content increases the reinforcing properties of the tire, thereby improving the abrasion resistance, but tends to deteriorate the rolling resistance of the tire.

[0003] Therefore, in order to achieve both abrasion resistance and low rolling resistance, for example, Patent Document 1 discloses a technique in which a rubber composition containing a diene rubber and a silica-rich reinforcing agent made of silica and carbon black is blended with a predetermined amount of polystyrene-vinyl isoprene triblock copolymer. Patent Document 2 also describes a butadiene polymer having a relatively high cis content that is modified with a specific modifier, and a polymer having a nitrogen adsorption specific surface area of ​​100 m 2 A technique for combining carbon black with a sintered body having a molecular weight of more than 10000 / g has been disclosed.

[0004] However, the techniques of Patent Documents 1 and 2 both leave room for improvement in terms of achieving a high level of balance between wear resistance and low rolling resistance, particularly in terms of maintaining low rolling resistance well.

[0005] Furthermore, in recent years, from the perspective of social sustainability, there has been a demand for the use of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, for the various components used in tires, and there is also a desire to develop technology to increase the usage rate of sustainable materials (hereinafter sometimes referred to as the "proportion of sustainable materials"). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2004-010781 A [Patent Document 2] JP 2011-219612 A Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, an object of the present invention is to provide a rubber composition for a tread that has an excellent balance between abrasion resistance and low rolling resistance, and has an excellent ratio of sustainable materials. Another object of the present invention is to provide a tire that has an excellent balance between wear resistance and low rolling resistance, and has an excellent ratio of sustainable materials. [Means for solving the problem]

[0008] The present inventors have conducted intensive research into a rubber composition for treads, which contains a rubber component, a resin, and carbon black, in order to solve the above problems. They have found that by incorporating a specific amount of at least one selected from the group consisting of terpene resins and rosin resins, the rubber composition can achieve excellent low rolling resistance even when the currently used fossil resource-derived material is replaced with a sustainable material, and that by optimizing the ratio of the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) to the iodine adsorption amount (IA) and the amount of hydrogen released from the carbon black, the balance between the wear resistance and low rolling resistance can be improved.

[0009] That is, the gist of the present invention is as follows. [1] A rubber composition for a tread comprising a rubber component, a resin, and carbon black, The resin contains at least one selected from the group consisting of a terpene-based resin and a rosin-based resin, The carbon black has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 130 m 2 / g or more, the CTAB (m 2 / g) (CTAB / IA) is 0.92 or more and 1.06 or less, and the amount of hydrogen released is 3500 ppm by mass or more and 4800 ppm by mass or less. The rubber composition for treads of the present invention described in [1] above can improve the balance between abrasion resistance and low rolling resistance, and the ratio of sustainable materials.

[0010] [2] The rubber composition for treads according to [1], wherein the content of the resin is 0.5 to 20 parts by mass per 100 parts by mass of the rubber component. The rubber composition for treads of the present invention described in [2] above can further improve the balance between abrasion resistance and low rolling resistance.

[0011] [3] The rubber composition for a tread according to [1] or [2], characterized in that the rubber component contains an isoprene skeleton rubber. The rubber composition for treads of the present invention described in [3] above can further improve the balance between abrasion resistance and low rolling resistance.

[0012] [4] The carbon black CTAB is 135m 2 / g or more 150m 2 The rubber composition for a tread according to any one of [1] to [3], characterized in that: The rubber composition for treads of the present invention described in [4] above can further improve the balance between abrasion resistance and low rolling resistance.

[0013] [5] The rubber composition for treads according to [3], characterized in that the rubber component further contains at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber. The rubber composition for treads of the present invention described in [5] above can further improve the balance between abrasion resistance and low rolling resistance.

[0014] [6] The rubber composition for treads according to [5], wherein at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber is modified. The rubber composition for treads of the present invention described in [5] above can further improve the balance between abrasion resistance and low rolling resistance.

[0015] [7] A tire comprising the rubber composition for a tread according to any one of [1] to [6]. The tire of the present invention described in [7] above has an excellent balance between wear resistance and low rolling resistance, and has an excellent ratio of sustainable materials. Effect of the Invention

[0016] According to the present invention, it is possible to provide a rubber composition for treads that has an excellent balance between abrasion resistance and low rolling resistance, and has an excellent ratio of sustainable materials. Furthermore, according to the present invention, it is possible to provide a tire that has an excellent balance between wear resistance and low rolling resistance, and has an excellent ratio of sustainable materials. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, an embodiment of the present invention will be described. The compounds described in this specification may be derived partially or entirely from fossil resources, from biological resources such as plant resources, or from recycled resources such as used tires, or may be derived from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0018] In addition, in this specification, the "proportion of sustainable materials" refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from renewable resources (recycled resources) in the 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] As a means of obtaining materials derived from regenerated resources (recycled resources), a process of "dismantling and downsizing" may be carried out on collected rubber products such as tires, and a process of "dismantling and downsizing" may also be carried out on rubber products such as tires manufactured using the rubber composition of the present embodiment. Dismantling and downsizing is a series of processes in which rubber products such as tires are crushed and separated into individual materials. Dismantling and downsizing may further include the processes of "separation," "cutting," "chipping," "crushing," and "pulverization," in that order. Separating is the process of separating a rubber product into its individual materials (e.g. rubber and metal). Cutting is the process of cutting a rubber product into pieces into its individual parts (e.g. tread and sidewall). Chipping is the process of scraping or drilling holes in a rubber product. Shredding is the process of breaking a rubber product into chips on the order of several inches in size. Grinding is the process of crushing a rubber product into granules.

[0023] The separation methods include pulling out, induction heating, punch cutting, magnetic separation, cutting separation, mechanical separation, cooling, and water jet. Pulling out is a method of hooking a bead using a hook or the like and pulling it out of the tire. Induction heating is a method of reducing the adhesive force between the metal of the bead and the rubber by induction heating, and separating the metal and the rubber. Punch cutting is a method of removing the bead from the tire by making a series of overlapping punch cuts (holes) in the sidewall of the tire around the bead. Magnetic separation is a method of separating the metal of the bead from the rubber using magnetic force. Cutting separation is a method of cutting and separating the metal of the bead and the rubber using a blade, a cutter blade, a knife, a rotary milling machine, or the like. Mechanical separation is a method of separating the metal and the rubber by applying a mechanical force sufficient for separation. Cooling is a method of cooling using liquid nitrogen or the like to embrittle the rubber before separating it. Water jet is a method of separating the rubber and the metal by spraying water at high pressure.

[0024] The cutting methods 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 and circular saws) 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.

[0025] The chipping method includes 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.

[0026] The crushing method includes a rotating blade, a blade cutter, and a cutting wheel. The rotating blade is a method of crushing an object by applying a rotating blade (including a blade or a circular saw) to the object. The blade cutter is a method of crushing an object by using a blade or a cutter blade. The cutting wheel is a method of crushing an object by applying a cutting blade to a wheel-shaped crushing part.

[0027] The crushing techniques include roller mills, pin mills, and water jets. Roller mills crush materials by a "grinding and grinding action" that combines the compressive force caused by the centrifugal force of the rollers and the shearing force caused by the rotation of the rollers. Pin mills crush materials by attaching dozens of pins to the surfaces of two opposing disks and rotating them at high speed. Water jets crush materials by spraying water at high speed and colliding it with the target material.

[0028] Furthermore, the following separation methods may be selected for the separation according to 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 ultrasonic waves 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 rollers or the like. Punching removes metal cord from tires 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 separates the wire from the rubber that settles to the bottom by placing it in a water-soluble polyol for several to several tens of hours at temperatures exceeding 160°C. Centrifugal classification is a type of wind classification that uses centrifugal force to separate the metal and rubber.

[0029] 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 to melt the rubber 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.

[0030] When the object to be separated is a sealant, mechanical friction after solidification or the use of a processing aid may be selected. Mechanical friction after solidification involves solidifying the sealant using liquid nitrogen or the like, and then removing the sealant layer by mechanical friction. The use of a processing aid involves removing the sealant layer using water or a soap solution.

[0031] When the object to be separated is a resin, crushing, cutting, melting, or peeling may be selected. Crushing involves crushing the tire with a roller or the like to separate the resin from the rubber. Cutting involves cutting along the boundary surface between the rubber layer and the resin to separate the resin. Melting includes vibration melting. Vibration melting involves vibrating the tire with ultrasound or the like to separate the resin while melting it. Peeling involves foaming unfoamed rubber by heating, applying a peeling force between the rubber and the resin member, and peeling the resin member from the rubber.

[0032] <Rubber composition for tread>

[0033] The components constituting the rubber composition for treads (hereinafter, sometimes simply referred to as "rubber composition") of the present invention will be described below. The rubber composition for a tread of the present invention is a rubber composition for a tread used in the tread portion of a tire, and contains a rubber component, a resin, and carbon black.

[0034] (Rubber component) The rubber composition of the present invention includes a rubber component that provides rubber elasticity to the composition. The rubber component preferably contains 30% by mass or more of sustainable materials, more preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, still 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.

[0035] 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%. Furthermore, 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%.

[0036] 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).

[0037] 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.

[0038] The isoprene-based rubber includes natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), modified synthetic isoprene rubber (modified IR), etc. Natural rubber (NR) can be, for example, RSS#3, TSR20 (for example, SIR20 or STR20), etc., which are common in the tire industry. The origin of natural rubber (NR) is not particularly limited, and examples thereof include rubber derived from Hevea brasiliensis, guayule, and Russian dandelion. Synthetic isoprene rubber (IR) is not particularly limited, and examples thereof include rubber derived from IR2200, etc., which are common in the tire industry. Modified NR can include deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), etc. Modified NR can include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. 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.

[0039] The isoprene-based rubber preferably has a ratio of sustainable materials of 30% by mass or more, more preferably 40% by mass or more, even 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, even more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to set the ratio of sustainable materials in 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.).

[0040] 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.

[0041] 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.

[0042] 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.

[0043] The butadiene-based rubber preferably has a ratio of sustainable materials of 30% by mass or more, more preferably 40% by mass or more, even 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, even more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to make the ratio of sustainable materials of the butadiene-based rubber 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.). Note that butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (for example, styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene, etc. according to conventional methods, but also rubber obtained by reactions with microorganisms, plants, animals, and tissue cultures of these (hereinafter also referred to as "microorganisms, etc.") and enzymatic reactions.

[0044] In addition, in order to keep the ratio of sustainable materials in 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.

[0045] Among the rubber components described above, the rubber component preferably contains at least the isoprene skeleton rubber, because this can further improve the abrasion resistance and low rolling resistance of the rubber composition. Furthermore, the rubber component preferably further contains at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber in addition to the isoprene skeleton rubber, because this can further improve the balance between abrasion resistance and low rolling resistance.

[0046] 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 recycled resources (recycling resources) can be obtained, for example, by downsizing, dismantling, and pyrolysis of 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.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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.

[0051] 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.

[0052] In addition, when the rubber component contains at least one rubber selected from the group consisting of the butadiene rubber and the styrene-butadiene rubber, it is preferable that these rubbers are modified. This is because the dispersibility of the carbon black described below is improved, resulting in a better balance between abrasion resistance and garden rolling resistance.

[0053] At least one rubber component selected from the group consisting of the butadiene rubber and the styrene-butadiene rubber is modified with a functional group having one or more atoms other than carbon and hydrogen. By chemically bonding with the carbon black, it exhibits excellent reinforcing properties, thereby further improving the abrasion resistance.

[0054] The at least one rubber component selected from the group consisting of the modified butadiene rubber and the styrene-butadiene rubber may have the functional group at an end or in the main chain. The at least one rubber component selected from the group consisting of the modified butadiene rubber and the styrene-butadiene rubber may be obtained, for example, by modifying a butadiene rubber (unmodified butadiene rubber) with a modifying agent.

[0055] Further, the atoms other than carbon and hydrogen include nitrogen atoms, oxygen atoms, sulfur atoms, metalloid atoms, metal atoms, etc., and the functional group preferably has one or more atoms selected from these.Further, the metalloid atoms include boron, silicon, germanium, arsenic, antimony, tellurium, etc., among which, one or more atoms selected from boron, silicon, and germanium are more preferable, and silicon is particularly preferable.Further, the metal atoms include tin, titanium, zirconium, bismuth, and aluminum, etc., among which, one or more atoms selected from tin and titanium are more preferable, and tin is particularly preferable.

[0056] 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.

[0057] 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.

[0058] 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 Liquidambar, 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.

[0059] 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.

[0060] (resin) The rubber composition for treads of the present invention further contains at least one resin selected from the group consisting of terpene resins and rosin resins. By containing the resin, the processability of the rubber composition for treads of the present invention can be improved, and wet performance when applied to a tire can also be improved. In addition, when the rubber component contains a styrene-butadiene rubber, compatibility is increased, so that dispersibility of the resin and carbon black described later is improved, and a better balance between abrasion resistance and low rolling resistance can be obtained. Furthermore, the balance between the storage modulus E' and tan δ of the rubber composition can be controlled by varying the softening point of the resin contained.

[0061] 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 from the turpentine, and polymerizing the blend 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 the terpene 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.

[0062] 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.

[0063] In addition to the above-mentioned terpene resin, terpene-aromatic compound resin, and rosin resin, the resin may include C5 resin, C5-C9 resin, C9 resin, cyclopentadiene resin, aromatic resin, coumarone resin, indene resin, coumarone-indene resin, olefin resin, polyurethane resin, acrylic resin, etc. These resins may be used alone or in combination of two or more. Among these resins, C5 resin, C5-C9 resin, C9 resin, cyclopentadiene resin, and aromatic resin are preferred. C5 resin, C9 resin, C5-C9 resin, and cyclopentadiene resin can improve wear resistance and fuel economy in a well-balanced manner. In addition, aromatic resin can improve grip performance, wear resistance, and rubber strength in a well-balanced manner.

[0064] Furthermore, 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.

[0065] The C5 resins include aliphatic petroleum resins obtained by (co)polymerizing C5 fractions obtained by thermal cracking of naphtha in the petrochemical industry. C5 fractions usually include 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.

[0066] The C5-C9 resin refers to a C5-C9 synthetic petroleum resin. Examples of the C5-C9 resin include petroleum-derived C5-C 11 Examples of the solid polymers include those obtained by polymerizing the fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3, and more specifically, copolymers mainly composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. As the C5-C9 resin, a resin with a small amount of C9 or more components is preferred from the viewpoint of compatibility with the rubber component. Here, "a small amount of C9 or more components" means that the amount of C9 or more components in the total amount of the resin is less than 50 mass%, preferably 40 mass% or less.

[0067] The C9 resin refers to a C9 synthetic petroleum resin, for example, a solid polymer obtained by polymerizing a C9 fraction using a Friedel-Crafts catalyst such as AlCl3 or BF3. Examples of the C9 resin include copolymers mainly composed of indene, α-methylstyrene, vinyltoluene, etc.

[0068] 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. Here, examples of the cyclopentadiene monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene, and among these, dicyclopentadiene is preferred, that is, the cyclopentadiene resin is preferably a dicyclopentadiene resin. The dicyclopentadiene resin refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as AlCl3 or BF3. Examples of dicyclopentadiene resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, and copolymers of dicyclopentadiene and C9 fractions (vinyl toluene, indene, etc.).

[0069] 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.

[0070] 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.

[0071] 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 Corporation, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., Taoka Chemical Co., Ltd., and the like.

[0072] The content of the resin in the rubber composition for tread of the present invention is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the composition is applied, tire components, target performance, etc. For example, the content of the resin is preferably in the range of 0.5 to 20 parts by mass with respect to 100 parts by mass of the rubber component.

[0073] (Reinforcing filler) Moreover, it is preferable that the rubber composition for a tread of the present invention further contains a reinforcing filler. This is because the vulcanized rubber composition of the present invention can have improved properties such as breaking strength, abrasion resistance, low heat build-up, and wet performance. The reinforcing filler may be any reinforcing filler commonly used in the rubber field, such as carbon black, silica, talc, clay, aluminum hydroxide, titanium oxide, etc.

[0074] ·silica Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it has a large number of silanol groups. These silicas may be used alone or in combination of two or more. Commercially available products of the silica can be used, and examples of the commercially available silica products include products from Tosoh Silica Co., Ltd., Degussa, Rhodia, Solvay Japan Co., Ltd., Tokuyama Corporation, and the like.

[0075] 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.

[0076] The silica has a nitrogen adsorption specific surface area (N2SA) of 50 m 2 / g or more, and 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and 350m 2 / g or less, and 2 / g or less is more preferable, 2 / g or less is more preferable, 2It is even more preferable that the molecular weight is not more than 1 / g. In this specification, the nitrogen adsorption specific surface area (N2SA) of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0077] The content of the silica 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 silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, still more preferably 60 parts by mass or more, particularly preferably 110 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, relative to 100 parts by mass of the rubber component.

[0078] Carbon black The carbon black has a first physical property of having a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 130 m 2 The carbon black must have a CTAB of 130m / g or more. 2 / g or more, it is possible to enhance the reinforcing properties of the rubber component, which in turn contributes to improving the abrasion resistance. 2 / g or more, and from the viewpoint of maintaining low rolling resistance and processability, it is preferable that the thickness of the sintered body is 150 m 2 It is preferable that the molecular weight is not more than 1 / g. The CTAB of carbon black is measured in accordance with JIS K6217-3. The CTAB of carbon black can be adjusted, but is not limited to, by controlling various conditions during the production of carbon black, such as the raw material introduction conditions, air introduction conditions, fuel introduction conditions, and cooling water introduction conditions.

[0079] The carbon black preferably has an iodine adsorption (IA) of 150 mg / g or less. If the IA of the carbon black is 150 mg / g or less, the carbon black surface is suitably activated to enhance the interaction with the rubber component (such as modified butadiene rubber). In order to better maintain low rolling resistance and processability, the IA of the carbon black is preferably 130 mg / g or more. The IA of carbon black is measured in accordance with JIS K6217-1. The IA of carbon black can be adjusted, but is not limited to, by controlling various conditions during the production of carbon black, such as the raw material introduction conditions, air introduction conditions, fuel introduction conditions, and cooling water introduction conditions.

[0080] In addition, the carbon black has a second physical property, which is the ratio of the CTAB (m 2 The ratio (CTAB / IA) of the carbon black to the total carbon dioxide amount (g) must be 0.92 or more and 1.06 or less. If the CTAB / IA is less than 0.92, the abrasion resistance may deteriorate. If the CTAB / IA is more than 1.06, the abrasion resistance may deteriorate and the low rolling resistance may deteriorate. From the viewpoint of further improving the abrasion resistance, the CTAB / IA of the carbon black is preferably 0.95 or more and 1.05 or less.

[0081] Furthermore, the carbon black is required to have a third physical property of releasing hydrogen of 3500 ppm by mass or more and 4800 ppm by mass or less. If the amount of hydrogen released is less than 3500 ppm by mass, the desired activation of the carbon black surface and therefore the interaction with the rubber component may be insufficient, resulting in a risk of deterioration of abrasion resistance. If the amount of hydrogen released is more than 4800 ppm by mass, the abrasion resistance may be deteriorated due to excess hydrogen. If the amount of hydrogen released is more than 4800 ppm by mass, the low rolling resistance may be deteriorated. In order to further improve the abrasion resistance, the amount of hydrogen released from the carbon black is preferably 3700 ppm by mass or more, and is preferably 4500 ppm by mass or less, and more preferably 4300 ppm by mass or less. The amount of hydrogen released by carbon black refers to the amount of hydrogen gas released when heated in an argon atmosphere at 2000°C for 15 minutes, and is measured using a hydrogen analyzer. The amount of hydrogen released by carbon black can be adjusted, but is not limited to, by controlling various conditions during the production of carbon black, such as the conditions for introducing raw materials, air, fuel, and cooling water.

[0082] The carbon black has a dibutyl phthalate oil absorption (DBP) of 130 cm 3 / 100g or more 150cm 3 / 100g or less. DBP is 130cm 3 If it is more than 100g, the abrasion resistance will be improved. 3 If the weight ratio is 100 g or less, good processability can be maintained.

[0083] The method for producing the carbon black is not particularly limited as long as it can provide the above-mentioned predetermined physical properties. However, it is extremely difficult to adjust the above-mentioned physical properties of the carbon black, such as CTAB, IA, and hydrogen release amount, independently. The carbon black that can be used in the present embodiment can be produced, for example, by appropriately adjusting the conditions based on the production conditions of the examples described later.

[0084] The content of the carbon black in the rubber composition of the present invention is preferably 20 parts by mass or more and 60 parts by mass or less relative to 100 parts by mass of the rubber component. If the content of the carbon black is 20 parts by mass or more, the interaction with the rubber component is sufficiently increased, and the abrasion resistance can be effectively improved. If the content of the carbon black is 60 parts by mass or less, low rolling resistance and processability can be better maintained. From the same viewpoint, the content of the carbon black in the rubber composition is more preferably 25 parts by mass or more and more preferably 50 parts by mass or less relative to 100 parts by mass of the rubber component.

[0085] The carbon black having the above-mentioned physical properties may be used alone or in combination of two or more kinds. In addition, the rubber composition of the present embodiment may or may not contain other carbon blacks other than the carbon black having the above-mentioned physical properties. Examples of other carbon blacks include carbon blacks that satisfy only two of the above-mentioned first, second, and third physical properties, carbon blacks that satisfy only one, or carbon blacks that satisfy none of them. However, from the viewpoint of more reliably obtaining the effect of improving the abrasion resistance peculiar to the present invention, in the rubber composition of the present embodiment, the proportion of other carbon blacks in the total carbon black is preferably 20% by mass or less, more preferably 10% by mass or less, even more preferably 5% by mass or less, and particularly preferably 0% by mass (i.e., no other carbon blacks are contained).

[0086] When the carbon black contains other carbon black, the other carbon black is particularly preferably plant-derived carbon black or carbon black obtained by recycling. Examples of plant-derived carbon black include those derived from castor oil and rosin oil. Examples of carbon black obtained by recycling include carbon black obtained by pyrolysis of used tires and carbon black obtained from waste oil. The grade of the carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N660, and N762. As the carbon black, commercially available products can be used, and examples of commercially available carbon black products include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Co., Ltd., and the like. These carbon blacks may be used alone or in combination of two or more.

[0087] In the rubber composition of the present invention, the mass ratio of the content of the silica to the total content of the carbon black and the silica (silica / (carbon black+silica)) is preferably 0.15 or more. In this case, low rolling resistance can be maintained sufficiently well. From the same viewpoint, the mass ratio (silica / (carbon black+silica)) is more preferably 0.20 or more. In addition, the mass ratio of the content of the silica to the total content of the carbon black and the silica (silica / (carbon black+silica)) is preferably 0.80 or less. In this case, the abrasion resistance can be maintained at a sufficiently high level. From the same viewpoint, the mass ratio (silica / (carbon black+silica)) is more preferably 0.60 or less.

[0088] (Silane coupling agent) In addition, when the rubber composition for tread of the present invention contains silica, in order to improve the effect of the silica, the rubber composition for tread of the present invention preferably contains a silane coupling agent. The silane coupling agent is 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 Degussa, 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.

[0089] 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 3 parts by mass or more, and 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.

[0090] (rubber powder) In addition, the rubber composition for treads of the present invention 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 the mechanical treatment, various crushing devices such as a cracker mill and a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In the low-temperature treatment, the 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.

[0091] 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.

[0092] 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.

[0093] 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.

[0094] 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 crumb means the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0095] The content of rubber powder in the rubber component is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber component is applied, tire components, target performance, etc. For example, the content of 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.

[0096] (liquid softener) Furthermore, the rubber composition for tread of the present invention 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 preferred. These liquid softeners may be used alone or in combination of two or more.

[0097] 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., Showa Shell Sekiyu K.K., Nisshin Oillio Group Co., Ltd., Fuji Kosan Co., Ltd., etc. These oils may be used alone or in combination of two or more.

[0098] 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.

[0099] 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.

[0100] (Anti-aging agent) Furthermore, the rubber composition for tread of the present invention 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.

[0101] 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, tire components, target performance, etc. For example, the content of the antiaging agent is preferably 1 part by mass or more, and preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and further preferably 8 parts by mass or less, per 100 parts by mass of the rubber component.

[0102] (wax) The rubber composition for treads of the present invention may also 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 products can be used as the wax, and examples of the commercially available wax products 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.

[0103] 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.

[0104] (Stearic acid) The rubber composition for treads of the present invention 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.

[0105] The content of stearic acid is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, tire components, target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more, preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0106] (Zinc Oxide) The rubber composition for treads of the present invention may also contain zinc oxide (zinc white). The zinc oxide is preferably zinc oxide obtained by recycling. Commercially available products can be used as the zinc oxide, 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.

[0107] 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.

[0108] (sulfur) Furthermore, the rubber composition for treads of the present invention preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or materials derived from biological resources. From the viewpoint of reducing environmental load, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of methods for obtaining sulfur from waste derived from biological resources include the methods 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., Nippon Kanzuri Kogyo Co., Ltd., etc. These sulfurs may be used alone or in combination of two or more types.

[0109] The sulfur content is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber 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.

[0110] (Cellulose nanofiber) The rubber composition of the present invention 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.

[0111] 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.

[0112] 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.

[0113] (Porous cellulose particles) The rubber composition of the present invention may contain porous cellulose particles. The porous cellulose particles are preferably cellulose particles having a porous structure with a porosity of 75 to 95%, and by compounding them with the rubber composition, the performance on ice can be improved. When the porosity of the porous cellulose particles is 75% or more, the effect of improving the performance on ice is excellent, and when the porosity is 95% or less, the strength of the particles can be increased. The porosity is more preferably 80 to 90%. The porosity of the porous cellulose particles can be calculated by measuring the volume of a certain mass of a sample (i.e., the porous cellulose particles) with a measuring cylinder, calculating the bulk density, and using the following formula. Porosity (%) = {1-[bulk specific gravity of sample (g / mL)] / [true specific gravity of sample (g / mL)]} x 100 Here, the true specific gravity of cellulose is 1.5.

[0114] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, the average particle size is preferably 1000 μm or less. The lower limit of the average particle size is not particularly limited, but is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and further preferably 200 to 800 μm. The porous cellulose particles are preferably spherical particles having a major axis / minor axis ratio of 1 to 2. By using particles having such a spherical structure, the dispersibility in the rubber composition is improved, which contributes to improving performance on ice and maintaining abrasion resistance, etc. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and the long axis / short axis ratio of the porous cellulose particles are obtained as follows: That is, the porous cellulose particles are observed under a microscope to obtain an image, and the long axis and short axis of the particles (when the long axis and short axis are the same, the length in a certain axis direction and the length in an axis direction perpendicular to the long axis) are measured for 100 particles using the image, and the average particle size is obtained by calculating the average value, and the long axis / short axis ratio is obtained by averaging the values ​​obtained by dividing the long axis by the short axis.

[0115] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopearl" and are described in JP-A-2001-323095, JP-A-2004-115284, etc., and these can be suitably used.

[0116] The content of the porous cellulose particles 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 porous cellulose particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by weight, and further preferably in the range of 3 to 15 parts by mass, relative to 100 parts by mass of the rubber component.

[0117] (solid fine particles) The rubber composition of the present invention may contain solid fine particles. The solid fine particles can improve the performance on ice by blending them with the rubber composition. The solid fine particles preferably have an average particle diameter of 1 μm or more, and more preferably 1000 μm or less, and more preferably 300 μm or less. Examples of the solid fine particles include powders derived from plants, such as rice husks, walnut powder, and walnut shells; powders derived from animals, such as eggshells (eggshell powder) and bone powder; powders derived from natural minerals, such as whitebait; inorganic fine particles, such as graphite and zinc oxide whiskers; water-soluble metal salt fine particles, such as magnesium sulfate and metal salts of lignin sulfonate; non-metallic fibers, such as glass fibers; and the like. Among these, rice husks, walnut shells, eggshells, and whitebait are preferred.

[0118] The content of the solid fine particles 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 solid fine particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by weight, and further preferably in the range of 3 to 15 parts by mass, relative to 100 parts by mass of the rubber component.

[0119] (Other Ingredients) The rubber composition for treads of the present invention may contain, in addition to the above-mentioned components, compounding agents that are commonly used in the rubber industry as other components. As for the other components, for example, fillers other than the above-mentioned reinforcing fillers; organic peroxides; etc. may be further compounded. The content of these additives 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., and is preferably in the range of 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component.

[0120] (Method of manufacturing rubber composition for tread) The method for producing the rubber composition for tread of the present invention is not particularly limited, but for example, the rubber composition for tread of the present invention can be produced by blending various components appropriately selected as necessary with the rubber component, kneading, heating, extruding, etc. In addition, the obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] <Tires> The tire of the present invention is characterized by including the above-mentioned rubber composition for tread of the present invention. By using the rubber composition for tread of the present invention, a tire excellent in balance between abrasion resistance and low rolling resistance, and in the ratio of sustainable materials can be obtained. The tire of the present invention can be used, for example, as a tire for construction vehicles, a tire for trucks and buses, a tire for aircraft, and a tire for passenger cars.

[0126] In addition, when using the above-mentioned rubber composition for tread of the present invention, for example, it may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or it may be obtained by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process, etc., and then further vulcanizing it. The tire of this 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.

[0127] In addition, in the tire of the present invention, the above-mentioned rubber composition for tread of the present invention must be applied to the tread (base tread, cap tread, under tread), but it can also be applied to various other components. For example, it can be used for cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, insulation, chafer, inner liner, etc., and it can also be used for side reinforcing layers of run-flat tires, etc. In addition to tires, the rubber composition for tread of the present invention can also be applied to rubber crawlers, seismic isolation rubber, hoses, etc. EXAMPLES

[0128] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples in any way.

[0129] [Reference Example 1-1, Reference Comparative Example 1-1] Rubber composition samples were prepared by compounding and kneading in a conventional manner according to the formulation shown in Table 1. In Table 1, the compounding amount of each component is expressed as an integer. Others are expressed to one decimal place.

[0130] <Evaluation> Each of the obtained samples was subjected to a vulcanization treatment and then the following evaluations (1) and (2) were carried out. (1) Low rolling resistance For test pieces of vulcanized rubber obtained from each sample of the rubber composition for tread, tan δ was measured using a viscoelasticity measuring device at a temperature of 60° C., a strain of 2%, and a frequency of 52 Hz. The tan δ measured in each example was indexed with the tan δ of Reference Comparative Example 1-1 set at 100. The smaller the index value, the lower the heat build-up of the vulcanized rubber, and the lower the rolling resistance of the tire obtained from the vulcanized rubber (the better the low rolling resistance). The evaluation results are shown in Table 1.

[0131] (2) Quantity and ratio of sustainable materials For each sample of rubber composition for tread, the proportion of the sustainable material blended parts out of the total blended parts was calculated by the formula: sustainable material blended parts (parts by mass) ÷ total blended parts (parts by mass) × 100 (mass%), and expressed as an integer. The higher the score, the higher the rate of sustainable material usage and the better the product. The evaluation results are shown in Table 1.

[0132] [Table 1]

[0133] *1 TSR#20, SP value = 8.20 (cal / cm 3 ) 1 / 2 *2 Hydrocarbyloxysilane compound modified styrene-butadiene rubber synthesized by the following method, Tg = -65°C, SP value = 8.65 (cal / cm 3 ) 1 / 2 *3 Styrene-butadiene rubber obtained by using butyl lithium as an initiator, with a Tg of -38°C and modified ends with N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propaneamine, Tg=-38°C, SP value=8.95 (cal / cm 3 ) 1 / 2 *4 Asahi Carbon Co., Ltd., product name "#80" *5 Tosoh Silica Corporation, product name "Nipsil AQ" *6 Showa Denko K.K., product name "Hijilite H-43M", average particle size = 1.0μm *7 Evonik, product name "Si75" *8 Zeon Corporation, product name "Quinton (registered trademark) G100B" *9 Kraton, product name "SYLVATRAXX8125" *10 Sigma-Aldrich, product number "307564" *11 The total amount of antioxidant, vulcanization accelerator, and sulfur is the same in both the Reference Comparative Example and Reference Example.

[0134] (Synthesis method of low Tg modified SBR(*2)) 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.

[0135] [Reference Example 2-1, Reference Comparative Example 2-1] Rubber composition samples were prepared by compounding and kneading in a conventional manner according to the formulation shown in Table 3. In Table 3, the compounding amount of each component is expressed as an integer. Others are expressed to one decimal place. The carbon black (CB1, CB2) and modified butadiene rubber (modified BR) in Table 3 were prepared as follows.

[0136] (Preparation of Carbon Black) Carbon blacks CB1 and CB2 were produced. The physical properties of each carbon black were controlled by changing various conditions (such as the amount of raw material introduced, the amount of air introduced, the temperature, the pressure, and the reaction time) as shown in Table 1. The cetyltrimethylammonium bromide adsorption specific surface area (CTAB) [m 2 The iodine adsorption capacity (IA) [mg / g] was measured in accordance with JIS K6217-1. The amount of hydrogen gas released (amount of hydrogen released) when heated in an argon atmosphere at 2000°C for 15 minutes was measured for the prepared CB1 to CB4 using a hydrogen analyzer (HORIBA, "EMGA"). Furthermore, the dibutyl phthalate oil absorption capacity (DBP) was measured for the prepared CB1 to CB4. The results are shown in Table 2 together with the calculated value of CTAB / IA.

[0137] [Table 2]

[0138] (Preparation of Modified Butadiene Rubber (Modified BR)) 283g of cyclohexane, 50g of 1,3-butadiene, 0.0057mmol of 2,2-ditetrahydrofurylpropane, and 0.513mmol of hexamethyleneimine (HMI) were added to a dried, nitrogen-substituted pressure-resistant glass vessel of about 900mL, and 0.57mmol of n-butyllithium (BuLi) was further added, followed by polymerization for 4.5 hours in a 50°C warm water bath equipped with a stirrer. The polymerization conversion rate at this time was almost 100%. Next, 0.100mmol of tin tetrachloride was quickly added to this polymerization reaction system as a modifier (coupling agent), and the mixture was stirred at 50°C for 30 minutes to carry out a modification reaction. Thereafter, 0.5mL of an isopropanol solution of 2,6-di-t-butyl-p-cresol (BHT) (BHT concentration: 5% by mass) was added to the polymerization reaction system to stop the reaction, and the mixture was dried according to a conventional method to obtain a modified butadiene rubber (modified BR) having tin atoms. Regarding the obtained modified BR, 1The amount of vinyl bonds in the butadiene portion was measured from the integral ratio of the H-NMR spectrum to be 14%, the glass transition temperature (Tg) was calculated from the inflection point of the DSC curve to be -95°C, and the coupling rate was calculated from the ratio of the peak area on the highest molecular weight side to the entire area of ​​the molecular weight distribution curve by gel permeation chromatography (GPC) to be 65%.

[0139] <Evaluation> Each of the obtained samples was subjected to a vulcanization treatment at 145° C. for 33 minutes, and then the following evaluations (3) to (5) were carried out. (3) Abrasion resistance For the test pieces of the vulcanized rubber obtained from each sample of the rubber composition for tread, the wear amount was measured at a slip rate of 60% using a Lambourn wear tester. The wear amount was calculated by reciprocal and indexed with the value of Reference Comparative Example 2-1 set at 100. The larger the index value, the smaller the wear amount and the more excellent the wear resistance. The evaluation results are shown in Table 3.

[0140] (4) Low rolling resistance For the vulcanized rubber test pieces obtained from each rubber composition sample, tan δ was measured using a viscoelasticity measuring device (manufactured by Ueshima Seisakusho Co., Ltd.) at a temperature of 50° C., a strain of 0.1%, and a frequency of 52 Hz. The tan δ measured in each example was indexed with the tan δ of Reference Comparative Example 2-1 set at 100. The smaller the index value, the lower the heat build-up of the vulcanized rubber, and the lower the rolling resistance of the tire obtained from the vulcanized rubber (the better the low rolling resistance). The evaluation results are shown in Table 3. For test pieces of vulcanized rubber obtained from each sample of the rubber composition for tread, tan δ was measured using a viscoelasticity measuring device at a temperature of 60° C., a strain of 2%, and a frequency of 52 Hz. The reciprocal of tan δ measured in each example was calculated, and the reciprocal of Reference Comparative Example 2-1 was set as 100 to make an index. The larger the index value, the lower the heat buildup of the vulcanized rubber and the lower the rolling resistance of the tire obtained from the vulcanized rubber (the better the low rolling resistance). The evaluation results are shown in Table 3.

[0141] (5) Overall rating Using the index value of wear resistance and the index value of low rolling resistance in each example, a comprehensive evaluation was performed based on an index value calculated from the following formula. A larger index value indicates a better balance of wear resistance and low rolling resistance. Overall evaluation index = (wear resistance index value - 100) + (rolling resistance index value - 100)

[0142] [Table 3]

[0143] *1 NR:TSR♯20 *2 Silica: Tosoh Silica Corporation, "NIPSIL AQ" *3 Silane coupling agent: Bistriethoxysilylpropyl polysulfide, manufactured by Osaka Soda Co., Ltd. *4 Vulcanization accelerator: N-cyclohexyl-2-benzothiazylsulfenamide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., "Noccela CZ"

[0144] From the results in Table 1, it can be seen that the rubber composition of Reference Example 1-1 is excellent in low rolling resistance and also has a good sustainable material ratio. On the other hand, the rubber composition of Reference Comparative Example 1-1 shows inferior results to each of Reference Examples 1-1, and it can be seen that it is difficult to achieve both low rolling resistance and a sustainable material ratio. Moreover, it can be seen from the results in Table 3 that the rubber composition of Reference Example 2-1 has a higher overall rating than the rubber composition of Reference Comparative Example 2-1, and is excellent in the balance of abrasion resistance and low rolling resistance. Taking into account the results in Tables 1 and 3, the rubber composition for treads of the present invention is expected to have a better balance between abrasion resistance and low rolling resistance, and a better ratio of sustainable materials, compared to conventional rubber compositions. [Industrial Applicability]

[0145] According to the present invention, it is possible to provide a rubber composition for treads that has an excellent balance between abrasion resistance and low rolling resistance, and has an excellent ratio of sustainable materials. Furthermore, according to the present invention, it is possible to provide a tire that has an excellent balance between wear resistance and low rolling resistance, and has an excellent ratio of sustainable materials.

Claims

1. A rubber composition for a tread comprising a rubber component, a resin, and carbon black, The resin contains at least one selected from the group consisting of a terpene-based resin and a rosin-based resin, The carbon black has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) of 130 m ２ / g or more, the CTAB (m ２ / g) (CTAB / IA) is 0.92 or more and 1.06 or less, and an amount of hydrogen released is 3500 ppm by mass or more and 4800 ppm by mass or less.

2. The rubber composition for treads according to claim 1, wherein the content of the resin is 0.5 to 20 parts by mass based on 100 parts by mass of the rubber component.

3. The rubber composition for a tread according to claim 1 or 2, characterized in that the rubber component contains an isoprene skeleton rubber.

4. The CTAB of the carbon black is 135 mm ２ / g or more 150m ２ The rubber composition for a tread according to claim 1 or 2, wherein the modulus of elasticity is 0.1 to 1.0 g / g or less.

5. The rubber composition for a tread according to claim 3, wherein the rubber component further contains at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber.

6. The rubber composition for a tread according to claim 5, wherein at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber is modified.

7. A tire comprising the rubber composition for tread according to claim 1 or 2.

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