Rubber composition for tires, tread rubber, and tire

Abstract

To provide a rubber composition for tires which can improve the ratio of sustainable materials of tires and promote a reduction in environmental load from the viewpoint of production, use, and disposal of a synthetic rubber as a whole.SOLUTION: The rubber composition for tires contains a rubber component (A), silica (B), and carbon black (C). The rubber component (A) consists only of a synthetic rubber (A1). The synthetic rubber (A1) contains a synthetic rubber (A1-1) supplied in a mass balance approach.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] Generally, tires are required to have various performance characteristics such as fuel economy, wear resistance, fracture resistance, steering stability, and grip performance on various road surfaces. To meet these requirements, various rubber compositions are used for the components that make up tires. For example, Patent Documents 1 and 2 listed below disclose rubber compositions for tire treads that are blends of polybutadiene, styrene-butadiene rubber, and natural rubber and / or polyisoprene, and further contain fillers such as silica and carbon black, and a resin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2022-535367 [Patent Document 2] Special Publication No. 2022-535725 Summary of the Invention [Problem to be solved by the invention]

[0004] Meanwhile, from the perspective of social sustainability, there has been a recent demand for an increase in the proportion of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, in the components that make up tires. However, among the materials compounded into rubber compositions for tires, the use of sustainable materials for synthetic rubber has not been fully considered to date, and there is a need to promote the reduction of environmental impact from the overall production, use, and disposal of synthetic rubber.

[0005] Therefore, an object of the present invention is to provide a rubber composition for tires and a tread rubber that can increase the proportion of sustainable materials in tires and promote a reduction in the environmental load in the overall production, use, and disposal of synthetic rubber. Another object of the present invention is to provide a tire that can promote a reduction in the environmental impact in terms of the overall production, use, and disposal of synthetic rubber, and that increases the proportion of sustainable materials. [Means for solving the problem]

[0006] The rubber composition for a tire, tread rubber, and tire of the present invention that solve the above problems are outlined below.

[0007] [1] A rubber composition comprising a rubber component (A), silica (B), and carbon black (C), the rubber component (A) consists solely of synthetic rubber (A1), A rubber composition for tires, wherein the synthetic rubber (A1) comprises a synthetic rubber (A1-1) supplied by a mass balance method. The rubber composition for tires of the present invention described in [1] above can promote a reduction in the environmental load in the overall production, use, and disposal of synthetic rubber, and can also increase the proportion of sustainable materials in tires to which the rubber composition is applied.

[0008] [2] The rubber composition for tires according to [1], wherein the synthetic rubber (A1) comprises a synthetic rubber derived from at least one of plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials. The rubber composition for tires described in [2] above can significantly contribute to reducing the environmental load in the overall process of producing, using, and disposing of synthetic rubber.

[0009] [3] The rubber composition for tires according to [1] or [2], wherein the synthetic rubber (A1) contains 0.1 to 99% by mass of synthetic rubber derived from biological resources and 1 to 99.9% by mass of synthetic rubber derived from fossil resources. The rubber composition for a tire described in the above [3] has an excellent balance between reduced environmental load and productivity.

[0010] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the synthetic rubber (A1) contains a styrene-butadiene rubber. The rubber composition for a tire described in [4] above can improve the fuel economy and wear resistance of a tire to which the rubber composition is applied.

[0011] [5] The rubber composition for a tire according to [4], wherein the styrene-butadiene rubber is modified with a modifier having a nitrogen atom and a silicon atom. The rubber composition for tires described in [5] above can further improve the fuel economy and wear resistance of tires to which the rubber composition is applied.

[0012] [6] The rubber composition for a tire according to any one of [1] to [5], further comprising a resin (D). The rubber composition for tires described in [6] above can achieve both good steering stability on dry road surfaces and good wet grip performance for a tire to which the rubber composition is applied.

[0013] [7] The rubber composition for a tire according to [6], wherein the content of the resin (D) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A). The rubber composition for a tire according to the above item [7] can further improve the wet grip performance of a tire to which the rubber composition is applied.

[0014] [8] A tread rubber comprising the rubber composition for a tire according to any one of [1] to [7]. The tread rubber of the present invention described in [8] above can promote a reduction in the environmental impact in the overall production, use, and disposal of synthetic rubber, and can also increase the proportion of sustainable materials in tires to which the tread rubber is applied.

[0015] [9] A tire comprising the tread rubber described in [8]. The tire of the present invention described in [9] above can promote the reduction of environmental impact in the overall production, use, and disposal of synthetic rubber, and the proportion of sustainable materials is increased. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a rubber composition for tires and a tread rubber that can increase the proportion of sustainable materials in tires and promote a reduction in the environmental load when viewed overall from the production, use, and disposal of synthetic rubber. Furthermore, according to the present invention, it is possible to provide a tire that can promote reduction of the environmental load in terms of the overall production, use, and disposal of synthetic rubber, and that has an increased proportion of sustainable materials. [Brief explanation of the drawings]

[0017] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] The rubber composition for a tire, the tread rubber, and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0019] <Definition> The compounds described herein may be derived in part or in whole from fossil sources, biological sources such as plant sources, recycled sources such as used tires, or a mixture of two or more of fossil, biological, and recycled sources.

[0020] In this specification, the "proportion of sustainable materials" refers to the total mass proportion of materials derived from biological resources (biomass resources) and materials derived from renewable resources (recycled resources) in the target rubber composition for tires, tread rubber, and tire.

[0021] In this specification, the term "biological resources (biomass resources)" refers to carbon-neutral organic resources derived from living organisms, and includes, for example, materials stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and is a resource excluding fossil resources (petroleum, coal, natural gas, etc.). Such 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.

[0022] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock excrement, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, etc.), and the like. Examples of biological resources include: corn oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc.), carbohydrate crops (corn, wheat, rice, rice husks, rice bran, used rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue left after sugarcane juicing), soybeans, soybean pulp refuse, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, and algae. The biological resources may also be processed (i.e., biological resource-derived substances). Examples of processing methods include biological processing methods utilizing the activity of microorganisms, plants, animals, and their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, thermal energy, light energy, etc.; and physical processing methods such as pulverization, compression, microwave treatment, and electromagnetic wave treatment. Furthermore, the biological resources may also be extracted and purified from the biological resources or biological resources that have undergone the above-described processing (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the above-mentioned biological resources can also be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, with valine, leucine, isoleucine, arginine, and phenylalanine being preferred.The amino acids may be either L-amino acids or D-amino acids, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. Examples of the fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. Examples of the fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may contain various materials and impurities.

[0023] 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.

[0024] <Rubber composition for tires> The rubber composition for a tire of this embodiment contains a rubber component (A), silica (B), and carbon black (C), and the rubber component (A) consists solely of a synthetic rubber (A1). The rubber composition for a tire of this embodiment is characterized in that the synthetic rubber (A1) contains a synthetic rubber (A1-1) supplied by a mass balance method.

[0025] In the rubber composition for tires of this embodiment, the synthetic rubber (A1-1) supplied using the mass balance method is a synthetic rubber to which biological resource-derived characteristics or recycled resource-derived characteristics are assigned using the mass balance method. The rubber composition for tires of this embodiment contains the synthetic rubber (A1-1) supplied using the mass balance method as at least a portion of the synthetic rubber (A1), and therefore has a high proportion of sustainable materials. Therefore, by applying the rubber composition for tires of this embodiment to tires, it is possible to increase the proportion of sustainable materials in the tire. Furthermore, because the rubber composition for tires of this embodiment uses the synthetic rubber (A1-1) supplied using the mass balance method, it is possible to promote a reduction in the environmental impact of the overall production, use, and disposal of synthetic rubber. Note that even when a rubber composition in which at least a part of the synthetic rubber (A1) is the synthetic rubber (A1-1) supplied by the mass balance method is applied to a tire, tire performance such as fuel efficiency (low loss) and wet grip performance (grip performance on wet road surfaces) can be maintained at the same level.

[0026] (Rubber component (A)) The rubber composition for a tire of this embodiment contains a rubber component (A), which provides rubber elasticity to the composition. The rubber component (A) preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, 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, still more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of the rubber component (A) refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in the rubber component (A).

[0027] The rubber component (A) is preferably the rubber derived from biological resources or the rubber derived from recycled resources. 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 the monomer components derived from recycled resources in 100 mol% of the monomer components constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0028] The rubber component (A) is a component that contributes to crosslinking, and typically has a weight average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and is preferably 5,000,000 or less, more preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,300,000 or less. In this specification, the weight average molecular weight (Mw) of the rubber component (A) can be determined, for example, by converting it into standard polystyrene 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).

[0029] In the rubber composition for tires of this embodiment, the rubber component (A) is composed solely of a synthetic rubber (A1), and the synthetic rubber (A1) includes a synthetic rubber (A1-1) supplied using a mass balance method. The synthetic rubber (A1-1) supplied using a mass balance method is a synthetic rubber assigned a biological resource-derived characteristic or a recycled resource-derived characteristic using the mass balance method. By including a synthetic rubber assigned a biological resource-derived characteristic or a recycled resource-derived characteristic using the mass balance method, it is possible to contribute to reducing the environmental impact of the overall production, use, and disposal of the synthetic rubber.

[0030] The content of the synthetic rubber (A1-1) supplied by the mass balance method is preferably 20 to 70 parts by mass, and more preferably 30 to 60 parts by mass, per 100 parts by mass of the rubber component (A) (i.e., per 100 parts by mass of the synthetic rubber (A1)). When the content of the synthetic rubber (A1-1) supplied by the mass balance method is 20 parts by mass or more per 100 parts by mass of the rubber component (A), the proportion of sustainable materials in a tire using the rubber composition can be further improved.

[0031] An example of the mass balance method is the ISCC PLUS certification, which can certify bio-based raw materials, circular raw materials, and renewable raw materials, and circular raw materials can be classified into bio-circular and non-bio-circular.

[0032] The bio- or renewable feedstocks are derived from unused biomass from agriculture, forestry, fishing, aquaculture and related industries, such as fermented and biodegradable fractions of corn, sugarcane, rapeseed and other products.

[0033] Circular raw materials are materials at the beginning of the supply chain that are considered waste / processing residues but are not landfilled or used for energy production; instead, they are reused or recycled. Among circular raw materials, "biocirque" refers to waste and residues of biological origin from related industries, including agriculture, forestry, and fisheries / aquaculture, as well as biodegradable fractions of industrial and municipal waste. Examples include used cooking oil (UCO), tall oil (a mixture of fatty acids, resin acids, unsaponifiable matter, etc., produced as a by-product during the cooking and fiber separation of pulp raw materials), and food waste. Meanwhile, "non-biocirque" refers to raw materials derived from the mechanical and / or chemical processing of recyclable materials of non-biological origin (fossil-based), such as plastic waste and used tires.

[0034] Furthermore, the bio-based raw materials are preferably plant-derived raw materials, and the circular raw materials are preferably plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials. In other words, the synthetic rubber (A1) preferably contains a synthetic rubber derived from at least one of plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials. Plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials are available in large quantities, making them easy to secure in sufficient quantities. A rubber composition for tires containing a synthetic rubber derived from at least one of these raw materials as synthetic rubber (A1) can significantly contribute to reducing the environmental impact of the entire process of producing, using, and disposing of synthetic rubber.

[0035] The synthetic rubber (A1) preferably contains both a synthetic rubber derived from a biological resource and a synthetic rubber derived from a fossil resource. Here, the synthetic rubber (A1) preferably contains 0.1 to 99% by mass of the synthetic rubber derived from a biological resource and 99.9 to 1% by mass of the synthetic rubber derived from a fossil resource. When the synthetic rubber (A1) contains 0.1% by mass or more of the synthetic rubber derived from a biological resource, the proportion of sustainable materials in a tire using the rubber composition can be significantly increased. Furthermore, when the synthetic rubber (A1) contains 1% by mass or more of the synthetic rubber derived from a fossil resource, the flexibility of the origin of the synthetic rubber (A1) is improved, facilitating the production of the rubber composition. Therefore, a rubber composition for a tire containing a synthetic rubber (A1) containing 0.1 to 99% by mass of the synthetic rubber derived from a biological resource and 99.9 to 1% by mass of the synthetic rubber derived from a fossil resource provides an excellent balance between reduced environmental impact and productivity.

[0036] The rubber component (A) is preferably a diene synthetic rubber, and the diene synthetic rubber is preferably an isoprene synthetic rubber or a butadiene synthetic rubber. Here, the isoprene synthetic rubber refers to a synthetic rubber containing units derived from isoprene as a monomer unit, and the butadiene synthetic rubber refers to a synthetic rubber containing units derived from butadiene as a monomer unit.

[0037] Examples of the isoprene-based synthetic rubber include synthetic isoprene rubber (IR) and modified synthetic isoprene rubber (modified IR). The synthetic isoprene rubber (IR) is not particularly limited, and for example, IR2200 or other rubbers commonly used in the tire industry can be used. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0038] The isoprene-based synthetic rubber preferably has a sustainability rate 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, still more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to achieve a sustainability ratio of the isoprene-based synthetic rubber within the above range, it is preferable to use a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.).

[0039] Examples of the butadiene-based synthetic rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (e.g., styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene-based synthetic rubber, is preferably derived from biological resources or recycled resources.

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

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

[0042] The butadiene-based synthetic rubber preferably has a sustainability rate 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, still more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to make the sustainability rate of the butadiene-based synthetic rubber fall within the above range, for example, a polymer synthesized using butadiene derived from biological resources, butadiene derived from recycled resources, an aromatic vinyl compound derived from biological resources (e.g., styrene derived from biological resources), or an aromatic vinyl compound derived from recycled resources (e.g., styrene derived from recycled 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 recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.). 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 and the like according to conventional methods, but also rubber obtained by reactions involving microorganisms, plants, animals, and tissue cultures of these (hereinafter also referred to as "microorganisms, etc.") and enzymatic reactions.

[0043] In order to set the sustainability rate of the entire rubber component (A) within the above range, it is preferable to use a polymer synthesized using a monomer component derived from a biological resource or a monomer component derived from a recycled resource as the rubber component (A).

[0044] Generally, the raw materials for rubber compositions for tires (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment and are therefore typically produced in large factories in specific regions, requiring significant amounts of energy for the storage and transportation of raw materials and finished products. In contrast, materials derived from biological resources (biomass resources) are derived from local agricultural products, forests, etc., and can be produced on a small scale through microbial fermentation and catalytic reactions. By utilizing local products and waste, the energy required for transporting and storing raw materials can be reduced, and the energy required for transporting and storing the produced materials to tire factories can also be reduced, making them environmentally friendly. Materials derived from recycled resources can be obtained, for example, by dismantling and pyrolyzing used tires to extract the rubber, fillers, steel cords, and other tire-constituting materials. 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 (e.g., the method described in Japanese Patent Application No. 2022-140390), and raw materials for tire rubber compositions can be obtained from various waste products and used items. In this way, the use of sustainable materials (materials derived from biological resources or recycled resources) can reduce the overall environmental impact of tire manufacturing by reducing carbon dioxide emissions over the entire life cycle (LCCO2), reducing energy consumption over the entire life cycle (LCE), reducing life cycle costs (LCC), and reducing the use of fossil resources.

[0045] Furthermore, when producing the rubber composition, the ratios of monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources can be appropriately selected depending on the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food). By polymerizing the monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources, rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be obtained that has performance equivalent to that of conventional synthetic rubber. When using monomer components derived from recycled resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomer. In such cases, the environmental impact can be evaluated by adopting the mass balance approach.

[0046] 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 (A) can be adjusted appropriately depending on the component to which it 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 synthetic rubber and butadiene-based synthetic rubber. In addition, the ratio of cis-bond units in the butadiene-derived units can also be adjusted appropriately depending on the component to which it 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, 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.

[0047] The rubber component (A) 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 synthetic 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.

[0048] The rubber component (A) may be modified to incorporate functional groups that interact with fillers such as carbon black and silica. Examples of such functional groups include amino, amide, isocyanate, imino, imidazole, urea, ammonium, imide, hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, epoxy, ether, carbonyl, oxycarbonyl, silyl, alkoxysilyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, and thiocarbonyl groups. These functional groups may have a substituent. These functional groups may be incorporated into the rubber component singly or in combination of two or more. Among these, amino groups, alkoxy groups, and alkoxysilyl groups are preferred, and substituted amino groups in which the hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, alkoxy groups having 1 to 6 carbon atoms, and alkoxysilyl groups having 1 to 6 carbon atoms are more preferred.

[0049] 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 modifying functional group that interacts with fillers such as silica and carbon black, and examples thereof include a nitrogen-containing functional group, a silicon-containing functional group, and an oxygen-containing functional group. Examples of compounds (modifiers) having a nitrogen-containing functional group include amino group-containing compounds. Examples of compounds (modifiers) having a silicon-containing functional group include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having an oxygen-containing functional group include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples of the compounds described in WO 2016 / 194316 and WO 2019 / 117256 include the compounds described in WO 2016 / 194316 and WO 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0050] The rubber (particularly synthetic rubber (A1-1) supplied by the mass balance method) derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be produced, for example, using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, using monomer components derived from fossil resources, in the same manner as conventional methods for producing synthetic rubber derived from fossil resources. Furthermore, the rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions using microorganisms or the like or enzyme reactions. In addition, synthetic rubber (A1-1) supplied with biological or recycled resource properties assigned using the mass balance method can be treated as having a sustainable material ratio (the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources)) of 100% by mass, even if it contains a portion of monomer components derived from fossil resources. Because the mass balance method is used, even if synthetic rubber (A1-1) supplied with biological or recycled resource properties uses a portion of monomer components derived from fossil resources, synthetic rubbers that contain a portion of monomer components derived from biological resources or recycled resources, or that are assigned fossil resource properties and have a sustainable material ratio of 0% by mass, are supplied separately from the synthetic rubber (A1-1). Therefore, the use of the synthetic rubber (A1-1) can significantly contribute to reducing the environmental impact of the overall production, use, and disposal of synthetic rubber.

[0051] Regarding the method for preparing bioresource-derived rubber from the above-mentioned bioresources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from a bioresource as a monomer component, a bioresource (biomass resource)-derived butadiene rubber (B-BR) can be obtained. Furthermore, by using styrene obtained from a bioresource and butadiene obtained from a bioresource as monomer components, a bioresource (biomass resource)-derived styrene-butadiene rubber (B-SBR) can be obtained. Here, methods for obtaining B-BR and B-SBR from bioresources include artificial polymerization methods, in vivo polymerization methods, and polymerization methods using biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods depending on the desired tire performance.

[0052] Suitable butadienes obtained from biological resources include butadienes derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadienes derived from alkenes (preferably ethylene), and butadienes derived from unsaturated carboxylic acids (preferably tiglic acid). Two or more of these butadienes may also be used in combination. As the styrene obtained from the biological resources, styrene obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, and Apocynaceae families, more preferably plants belonging to the genus Liquidambar, Styrax rostrata, and Catharanthus roseus, and even more preferably Sweetgum, Styrax rosea, and Catharanthus roseus) or styrene obtained from microorganisms (preferably microorganisms belonging to the genus Penicillium or Escherichia, more preferably P. citrinum or transformed E. coli) can be suitably used. Two or more of these styrenes may also be used in combination.

[0053] Recently, biomass industrial complexes centered on bioethanol, bioethylene, and the like have been planned. However, bioethanol and bioethylene are produced primarily from sugars and / or cellulose as biological resources, and do not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources, or to combine monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources, and further adjust the ratios of these monomer components appropriately. This allows for the effective use of a wide range of biological resources, such as sugars, proteins, and lipids, as well as renewable resources, without relying on a single type of biological resource. It also allows for a stable supply of rubber derived from sustainable materials and further contributes to environmental considerations depending on the production conditions. When multiple types of monomer components derived from biological resources are used, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadienes derived from multiple types of biological resources with different origins as the biological resource-derived butadiene, and / or to use a mixture of styrenes derived from multiple types of biological resources with different origins as the biological resource-derived styrene. This allows for effective use of multiple types of biological resources.

[0054] -Styrene-butadiene rubber (SBR)- The synthetic rubber (A1) preferably contains styrene-butadiene rubber (SBR). When the rubber component (A) contains styrene-butadiene rubber as the synthetic rubber (A1), the fuel economy and wear resistance of a tire using the rubber composition can be improved.

[0055] It is more preferable that the synthetic rubber (A1) contains (1) a styrene-butadiene rubber (modified SBR) modified with a modifier containing at least one atom of nitrogen, silicon, and tin and having a glass transition temperature (Tg) of −50° C. or lower, and (2) an unmodified styrene-butadiene rubber (unmodified SBR) having a glass transition temperature (Tg) at least 30° C. higher than that of the styrene-butadiene rubber (modified SBR).

[0056] The inclusion of (1) modified SBR and (2) unmodified SBR in the rubber component (A) can improve the wet grip performance of the tire. In addition, the use of styrene-butadiene rubber (modified SBR) modified with a modifier containing at least one atom of nitrogen, silicon, and tin can improve the dispersibility of fillers such as silica in the rubber composition, resulting in significantly improved low heat buildup and filler dispersibility, which can also improve performance such as reinforcement, fuel economy, and abrasion resistance.

[0057] As described above, the (1) modified SBR is a modified styrene-butadiene rubber having a glass transition temperature of −50° C. or lower, which has been modified with a modifier having at least one atom of nitrogen, silicon, and tin.

[0058] The (1) modified SBR has a glass transition temperature of −50° C. or lower, preferably −55° C. or lower, and preferably higher than −90° C. When the modified SBR has a glass transition temperature of −50° C. or lower, the fuel economy and abrasion resistance of the tire can be sufficiently improved. In addition, modified styrene-butadiene rubber having a glass transition temperature higher than −90° C. is easy to synthesize.

[0059] The glass transition temperatures of the (1) modified SBR and the unmodified SBR described below can be measured, for example, as follows. Using each styrene-butadiene rubber as a sample, a DSC curve is recorded using a TA Instruments DSC250 while heating from -100°C at 20°C / min under a helium flow of 50 mL / min, and the peak top (inflection point) of the DSC differential curve is taken as the glass transition temperature.

[0060] The content of the (1) modified SBR in the rubber component (A) is preferably 15% by mass or more and less than 85% by mass, more preferably 20 to 85% by mass, more preferably 30 to 80% by mass, and even more preferably 40 to 80% by mass. When the content of the modified SBR in the rubber component (A) is 15% by mass or more and less than 85% by mass, the fuel economy and wet grip performance of the tire can be further improved.

[0061] The (1) modified SBR preferably has a bound styrene content of less than 15% by mass. The bound styrene content of the modified SBR refers to the proportion of styrene units contained in the styrene-butadiene rubber. If the bound styrene content of the styrene-butadiene rubber is less than 15% by mass, the glass transition temperature is likely to be low. The bound styrene content of the styrene-butadiene rubber is more preferably 14% by mass or less, more preferably 13% by mass or less, and even more preferably 12% by mass or less. Furthermore, from the viewpoint of the wear resistance of a tire using the rubber composition, the bound styrene content of the styrene-butadiene rubber is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 8% by mass or more. The amount of bound styrene in the styrene-butadiene rubber can be adjusted by the amount of monomers used in the polymerization of the styrene-butadiene rubber, the degree of polymerization, and the like.

[0062] As described above, the (1) modified SBR is modified with a modifier having at least one atom selected from nitrogen, silicon, and tin. From the viewpoint of achieving a higher level of fuel economy, wear resistance, and wet grip performance of a tire, the modified SBR is preferably modified with a modifier having a nitrogen atom and a silicon atom, and more preferably modified with a modifier having a nitrogen-containing functional group and an alkoxy group. When the modified SBR is modified with a nitrogen atom and a silicon atom, the balance between wet grip performance, fuel economy, and wear resistance of a tire using the rubber composition is further improved, and in particular, the fuel economy and wear resistance can be further improved. Furthermore, when the modified SBR is modified with a modifier having a nitrogen-containing functional group and an alkoxy group, the balance between wet grip performance, fuel economy, and wear resistance of a tire is further improved, and in particular, the fuel economy and wear resistance can be further improved.

[0063] Here, the modifying agent having a nitrogen atom-containing functional group and an alkoxy group is a general term for modifying agents having at least one nitrogen atom-containing functional group and at least one alkoxy group. The functional group containing a nitrogen atom is preferably selected from the following: The monovalent hydrocarbon group has a functional group selected from the group consisting of a primary amino group, a primary amino group protected with a hydrolyzable protecting group, an onium salt residue of a primary amine, an isocyanate group, a thioisocyanate group, an imine group, an imine residue, an amide group, a secondary amino group protected with a hydrolyzable protecting group, a cyclic secondary amino group, an onium salt residue of a cyclic secondary amine, an acyclic secondary amino group, an onium salt residue of an acyclic secondary amine, an isocyanuric acid triester residue, a cyclic tertiary amino group, an acyclic tertiary amino group, a nitrile group, a pyridine residue, an onium salt residue of a cyclic tertiary amine, and an onium salt residue of an acyclic tertiary amine, and is a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, or a monovalent hydrocarbon group having 1 to 30 carbon atoms and containing a straight-chain, branched, alicyclic, or aromatic ring, which may contain at least one heteroatom selected from an oxygen atom, a sulfur atom, and a phosphorus atom.

[0064] --Modified styrene-butadiene rubber of the first preferred embodiment-- The (1) modified styrene-butadiene rubber (modified SBR) is preferably modified with an aminoalkoxysilane compound, and more preferably has its terminals modified with an aminoalkoxysilane compound from the viewpoint of having a high affinity for fillers such as silica. When the terminals of the styrene-butadiene rubber are modified with an aminoalkoxysilane compound, the interaction between the modified styrene-butadiene rubber and the filler (particularly silica) becomes particularly strong.

[0065] The modified site of the styrene-butadiene rubber may be the molecular terminal as described above, but may also be the main chain. Styrene-butadiene rubber having modified molecular terminals can be produced by reacting various modifiers with the terminals of a styrene-butadiene copolymer having active terminals, for example, according to the methods described in WO 2003 / 046020 and JP 2007-217562 A. In a preferred embodiment, the styrene-butadiene rubber having modified molecular terminals can be produced in accordance with the methods described in WO 2003 / 046020 and JP 2007-217562 A by reacting an aminoalkoxysilane compound with the terminal of a styrene-butadiene copolymer having active terminals with a cis-1,4 bond content of 75% or more, and then reacting the resulting copolymer with a carboxylic acid partial ester of a polyhydric alcohol for stabilization.

[0066] The carboxylic acid partial ester of a polyhydric alcohol refers to an ester of a polyhydric alcohol and a carboxylic acid, which has one or more hydroxyl groups. Specifically, an ester of a sugar or modified sugar having 4 or more carbon atoms and a fatty acid is preferably used. More preferred examples of this ester include (1) a fatty acid partial ester of a polyhydric alcohol, particularly a partial ester (which may be a monoester, diester, or triester) of a saturated higher fatty acid or an unsaturated higher fatty acid having 10 to 20 carbon atoms and a polyhydric alcohol, and (2) an ester compound in which 1 to 3 partial esters of a polycarboxylic acid and a higher alcohol are bonded to a polyhydric alcohol. The polyhydric alcohol used as a raw material for the partial ester is preferably a sugar (which may or may not be hydrogenated) having 5 or 6 carbon atoms and at least three hydroxyl groups, glycol, polyhydroxy compound, etc. The raw material fatty acid is preferably a saturated or unsaturated fatty acid having 10 to 20 carbon atoms, such as stearic acid, lauric acid, or palmitic acid. Among the fatty acid partial esters of polyhydric alcohols, sorbitan fatty acid esters are preferred, and specific examples include sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan tristearate, sorbitan monooleate, and sorbitan trioleate.

[0067] The aminoalkoxysilane compound is not particularly limited, but is preferably an aminoalkoxysilane compound represented by the following general formula (i): R11 a -Si-(OR 12 ) 4-a (i)

[0068] In general formula (i), R 11 and R 12 each independently represents a monovalent aliphatic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and R 11 and R 12 At least one of the groups is substituted with an amino group, a is an integer of 0 to 2, and OR 12 If there are multiple, each OR 12 may be the same or different, and the molecule does not contain any active protons.

[0069] The aminoalkoxysilane compound is also preferably an aminoalkoxysilane compound represented by the following general formula (ii). [ka]

[0070] In the general formula (ii), n1+n2+n3+n4=4 (wherein n2 is an integer of 1 to 4, and n1, n3 and n4 are integers of 0 to 3). A 1 is at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group, an isocyanuric acid trihydrocarbyl ester group, a nitrile group, a pyridine group, a (thio)ketone group, an amide group, and a primary or secondary amino group having a hydrolyzable group. When n4 is 2 or more, A 1 may be the same or different, and A 1 may be a divalent group that bonds with Si to form a cyclic structure. R 21 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, may be the same or different. R 22is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, both of which may contain a nitrogen atom and / or a silicon atom. When n2 is 2 or more, R 22 may be the same or different from each other, or may be joined together to form a ring. R 23 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or greater, may be the same or different. R 24 represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n4 is 2 or more, may be the same or different. The hydrolyzable group in the hydrolyzable group-containing primary or secondary amino group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and particularly preferably a trimethylsilyl group.

[0071] The aminoalkoxysilane compound represented by the above general formula (ii) is preferably an aminoalkoxysilane compound represented by the following general formula (iii). [ka]

[0072] In the general formula (iii), p1+p2+p3=2 (wherein p2 is an integer of 1 or 2, and p1 and p3 are integers of 0 or 1). A 2 is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). R 25 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 26is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, any of which may contain a nitrogen atom and / or a silicon atom. 26 may be the same or different, or may be joined together to form a ring. R 27 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom. R 28 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. The hydrolyzable group is preferably a trimethylsilyl group or a tert-butyldimethylsilyl group, and particularly preferably a trimethylsilyl group.

[0073] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (iv) or (v). [ka]

[0074] In the general formula (iv), q1+q2=3 (wherein q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3). R 31 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 32 and R 33 are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 34 represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q1 is 2, may be the same or different. R 35represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when q2 is 2 or greater, may be the same or different.

[0075] [ka]

[0076] In the general formula (v), r1+r2=3 (where r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2). R 36 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 37 represents a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, they may be the same or different. R 38 represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r2 is 2, may be the same or different. A specific example of the aminoalkoxysilane compound represented by general formula (v) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine.

[0077] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (vi) or (vii). [ka]

[0078] In general formula (vi), R 40 is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 41 is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 42 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. Here, TMS represents a trimethylsilyl group (the same applies hereinafter).

[0079] [ka]

[0080] In general formula (vii), R 43 and R 44 are each independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 45 is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R 45 may be the same or different.

[0081] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (viii) or (ix). [ka]

[0082] In the general formula (viii), s1+s2 is 3 (wherein s1 is an integer of 0 to 2, and s2 is an integer of 1 to 3). R 46is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 47 and R 48 are each independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. 47 or R 48 may be the same or different.

[0083] [ka]

[0084] In the general formula (ix), X is a halogen atom. R 49 is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 50 and R 51 are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R 50 and R 51 are bonded to form a divalent organic group. R 52 and R 53 are each independently a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. R 50 and R 51 As the hydrolyzable group, a hydrolyzable group is preferred, and as the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0085] The aminoalkoxysilane compound represented by the above general formula (ii) is also preferably an aminoalkoxysilane compound represented by the following general formula (x), (xi), (xii), or (xiii): [ka]

[0086] In the general formulae (x) to (xiii), the symbols U and V are each an integer of 0 to 2 and satisfy U+V=2. R in general formulas (x) to (xiii) 54 ~ 92 may be the same or different and are monovalent or divalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms, or monovalent or divalent aromatic hydrocarbon groups having 6 to 18 carbon atoms. In the general formula (xiii), α and β are integers of 0 to 5.

[0087] Among the compounds satisfying general formula (x), general formula (xi), and general formula (xii), N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine, 2-((hexyl-dimethoxysilyl)methyl)-N1,N1,N3,N3-2-pentamethylpropane-1,3-diamine, N1-(3-(dimethylamino)propyl)-N3,N3-dimethyl-N1-(3-(trimethoxysilyl)propyl)propane-1,3-diamine, and 4-(3-(dimethylamino)propyl)-N1,N1,N7,N7-tetramethyl-4-((trimethoxysilyl)methyl)heptane-1,7-diamine are particularly preferred. Furthermore, among the compounds satisfying the general formula (xiii), N,N-dimethyl-2-(3-(dimethoxymethylsilyl)propoxy)ethanamine, N,N-bis(trimethylsilyl)-2-(3-(trimethoxysilyl)propoxy)ethanamine, N,N-dimethyl-2-(3-(trimethoxysilyl)propoxy)ethanamine, and N,N-dimethyl-3-(3-(trimethoxysilyl)propoxy)propan-1-amine are particularly preferred.

[0088] The method for producing the modified SBR is not particularly limited. In one embodiment, the method for producing the styrene-butadiene rubber may include: 1) polymerizing styrene-butadiene rubber in a hydrocarbon solvent in the presence of an organic alkali metal compound to produce an activated polymer having an alkali metal bonded to at least one end thereof; and 2) reacting the activated polymer with a modifier such as the aminoalkoxysilane compound.

[0089] Step 1) is a step for preparing an activated polymer having an alkali metal bonded to at least one end thereof, and can be carried out by polymerizing a styrene-based monomer and a butadiene-based monomer in a hydrocarbon solvent in the presence of an organic alkali metal compound.

[0090] The hydrocarbon solvent is not particularly limited, but may be, for example, one or more selected from the group consisting of n-pentane, n-hexane, n-heptane, isooctane, cyclohexane, toluene, benzene, and xylene.

[0091] The organic alkali metal compound can be used in an amount of 0.1 mmol to 1.0 mmol based on 100 g of the total monomers. The organic alkali metal compound is not particularly limited, and examples thereof include, but are not limited to, at least one selected from the group consisting of methyl lithium, ethyl lithium, propyl lithium, n-butyl lithium, s-butyl lithium, t-butyl lithium, hexyl lithium, n-decyl lithium, t-octyl lithium, phenyl lithium, 1-naphthyl lithium, n-eicosyl lithium, 4-butylphenyl lithium, 4-tolyl lithium, cyclohexyl lithium, 3,5-di-n-heptylcyclohexyl lithium, 4-cyclopentyl lithium, naphthyl sodium, naphthyl potassium, lithium alkoxide, sodium alkoxide, potassium alkoxide, lithium sulfonate, sodium sulfonate, potassium sulfonate, lithium amide, sodium amide, potassium amide, and lithium isopropyl amide.

[0092] The polymerization in step 1 may be carried out by further adding a polar additive, if necessary. The polar additive may be added in an amount of 0.001 to 1.0 part by weight relative to 100 parts by weight of the total monomers. Specifically, the polar additive may be added in an amount of 0.005 to 0.5 parts by weight, more specifically 0.01 to 0.3 parts by weight, relative to 100 parts by weight of the total monomers. Examples of the polar additive include at least one selected from the group consisting of tetrahydrofuran, ditetrahydrofurylpropane, diethyl ether, cycloamethyl ether, dipropyl ether, ethylene dimethyl ether, ethylene dimethyl ether, diethyl glycol, dimethyl ether, tert-butoxyethoxyethane, bis(3-dimethylaminoethyl)ether, (dimethylaminoethyl)ethyl ether, trimethylamine, triethylamine, tripropylamine, and tetramethylethylenediamine.

[0093] In addition, in the above-mentioned preparation method, when a butadiene-based monomer and a styrene-based monomer are copolymerized by using the polar additive, the difference in reaction rate between them can be compensated for, thereby guiding the formation of a random copolymer easily.

[0094] The polymerization in step 1 can be carried out via adiabatic polymerization or isothermal polymerization. Here, the adiabatic polymerization refers to a polymerization method that involves polymerizing the organic alkali metal compound by heat of self-reaction without adding any heat after adding the organic alkali metal compound, while the isothermal polymerization refers to a polymerization method that maintains a constant temperature of the polymer by adding or removing heat after adding the organic alkali metal compound.

[0095] Furthermore, the polymerization may be carried out in a temperature range of 20°C to 200°C, specifically in a temperature range of 0°C to 150°C, and more specifically in a temperature range of 10°C to 120°C.

[0096] The step 2) is a modification reaction step in which the activated polymer is reacted with a modifier such as the aminoalkoxysilane compound to produce modified SBR.

[0097] In this case, the modifying agent may be the same as those described above. The modifying agent can be used in a proportion of 0.1 to 2.0 moles per mole of the organic alkali metal compound. Furthermore, the reaction in the step 2) is a modification reaction for introducing a functional group into the polymer, and each of the reactions can be carried out at a temperature range of 0°C to 90°C for 1 minute to 5 hours.

[0098] In addition, the above-mentioned preparation method may further include, after step 2), one or more steps of recovering the solvent and unreacted monomer and drying, if necessary.

[0099] --Modified styrene-butadiene rubber of a second preferred embodiment-- The (1) modified styrene-butadiene rubber (modified SBR) is also preferably modified with a coupling agent represented by the following general formula (I), which can further improve the fuel economy and wear resistance of tires using the rubber composition. [ka]

[0100] In the above general formula (I), R 1 , R 2 and R 3 each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. R 4 , R 5 , R 6 , R 7 and R 9 are each independently an alkyl group having 1 to 20 carbon atoms. R 8 and R 11 are each independently an alkylene group having 1 to 20 carbon atoms. R 10represents an alkyl group or a trialkylsilyl group having 1 to 20 carbon atoms. m represents an integer of 1 to 3; p represents 1 or 2; R 1 ~R 11 When there are multiple , m and p, they are independent of each other. i, j, and k each independently represent an integer of 0 to 6, provided that (i+j+k) is an integer of 3 to 10. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen atoms, nitrogen atoms, silicon atoms, sulfur atoms, and phosphorus atoms, and having no active hydrogen. In general formula (I), the hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group without active hydrogen include organic groups without functional groups with active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH), and a sulfhydryl group (-SH).

[0101] The styrene-butadiene rubber modified with the coupling agent represented by the general formula (I) has a weight average molecular weight (Mw) of 20×10 4 ~300×10 4 and the molecular weight of the modified styrene-butadiene rubber is 200×10 4 ~500×10 4 It is preferable that the modified styrene-butadiene rubber contains 0.25 to 30 mass % of the modified styrene-butadiene rubber represented by the formula (I) and has a shrinkage factor (g') of less than 0.64.

[0102] Generally, a polymer having branches tends to have a smaller molecular size compared to a linear polymer having the same absolute molecular weight, and the shrinkage factor (g') is an index of the ratio of the molecular size to that of a linear polymer having the same absolute molecular weight. In other words, the larger the degree of branching of a polymer, the smaller the shrinkage factor (g') tends to be. In this embodiment, intrinsic viscosity is used as an index of molecular size, and a linear polymer has an intrinsic viscosity [η] = -3.883 M 0.771The shrinkage factor (g') for each absolute molecular weight of the modified styrene-butadiene rubber is calculated, and the absolute molecular weight is calculated as 100 x 10 4 ~200×10 4 The average value of the shrinkage factor (g') when the above formula is used is the shrinkage factor (g') of the modified styrene-butadiene rubber. Here, "branching" refers to a branch formed by direct or indirect bonding of one polymer to another polymer. Furthermore, the "degree of branching" refers to the number of polymers directly or indirectly bonded to one branch. For example, if five styrene-butadiene copolymer chains (described below) are indirectly bonded to each other via coupling residues (described below), the degree of branching is 5. The coupling residue is a structural unit of the modified styrene-butadiene rubber bonded to the styrene-butadiene copolymer chain, and is, for example, a structural unit derived from a coupling agent, which is generated by reacting the styrene-butadiene copolymer (described below) with a coupling agent. The styrene-butadiene copolymer chain is a structural unit of the modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer, which is generated by reacting the styrene-butadiene copolymer (described below) with a coupling agent. The shrinkage factor (g') is preferably less than 0.64, more preferably 0.63 or less, more preferably 0.60 or less, even more preferably 0.59 or less, and even more preferably 0.57 or less. The lower limit of the shrinkage factor (g') is not particularly limited and may be below the detection limit, but is preferably 0.30 or more, more preferably 0.33 or more, even more preferably 0.35 or more, and even more preferably 0.45 or more. By using a modified styrene-butadiene rubber having a shrinkage factor (g') in this range, the processability of the rubber composition is improved. Since the shrinkage factor (g') tends to depend on the degree of branching, it is possible to control the shrinkage factor (g') using the degree of branching as an index, for example. Specifically, when a modified styrene-butadiene rubber has a branching degree of 6, its shrinkage factor (g') tends to be 0.59 or more and 0.63 or less, and when a modified styrene-butadiene rubber has a branching degree of 8, its shrinkage factor (g') tends to be 0.45 or more and 0.59 or less.

[0103] The styrene-butadiene rubber modified with the coupling agent represented by the general formula (I) preferably has branches and a degree of branching of 5 or more. Furthermore, the modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and more preferably, the branches include branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 5 or more and the branches include branches in which five or more styrene-butadiene copolymer chains are bonded to one coupling residue, the contraction factor (g') can be more reliably reduced to less than 0.64. The number of styrene-butadiene copolymer chains bonded to one coupling residue can be confirmed from the value of the contraction factor (g'). The modified styrene-butadiene rubber preferably has branches, with a degree of branching of 6 or more. The modified styrene-butadiene rubber preferably has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and more preferably includes branches in which six or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 6 or more and the branch includes branches in which six or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be set to 0.63 or less. Furthermore, the modified styrene-butadiene rubber has branches, and the degree of branching is more preferably 7 or more, and even more preferably 8 or more. The upper limit of the degree of branching is not particularly limited, but is preferably 18 or less. The modified styrene-butadiene rubber has one or more coupling residues and styrene-butadiene copolymer chains bonded to the coupling residues, and more preferably the branches include branches in which 7 or more styrene-butadiene copolymer chains are bonded to one coupling residue, and particularly preferably the branches include branches in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue. By specifying the structure of the modified styrene-butadiene rubber so that the degree of branching is 8 or more and the branches include branches in which 8 or more styrene-butadiene copolymer chains are bonded to one coupling residue, the shrinkage factor (g') can be made 0.59 or less.

[0104] At least one end of the styrene-butadiene copolymer chain is preferably bonded to a silicon atom of the coupling residue. In this case, the ends of a plurality of styrene-butadiene copolymer chains may be bonded to a single silicon atom. Alternatively, an end of the styrene-butadiene copolymer chain and an alkoxy group or hydroxyl group having 1 to 20 carbon atoms may be bonded to a single silicon atom, and as a result, that single silicon atom may constitute an alkoxysilyl group or silanol group having 1 to 20 carbon atoms.

[0105] The modified styrene-butadiene rubber may be an oil-extended rubber obtained by adding an extender oil. The modified styrene-butadiene rubber may be either non-oil-extended or oil-extended, but from the viewpoint of abrasion resistance, the Mooney viscosity measured at 100°C is preferably 20 or more and 100 or less, more preferably 30 or more and 80 or less.

[0106] The weight average molecular weight (Mw) of the modified styrene-butadiene rubber is preferably 20×10 4 Over 300 x 10 4or less, more preferably 50×10 4 More preferably, 64×10 4 More preferably, it is 80×10 4 The weight average molecular weight is preferably 250×10 4 or less, and more preferably 180×10 4 or less, and more preferably 150×10 4 The weight average molecular weight is 20 × 10 4 When the weight average molecular weight is 300×10 or more, the low loss property and abrasion resistance of the rubber composition can be sufficiently improved. 4 When it is equal to or less than this, the processability of the rubber composition is improved.

[0107] The modified styrene-butadiene rubber has a molecular weight of 200×10 relative to the total amount (100% by mass) of the modified styrene-butadiene rubber. 4 Over 500 x 10 4 It is preferable that the modified styrene-butadiene rubber (hereinafter also referred to as "specific high molecular weight component") contains 0.25% by mass or more and 30% by mass or less of the specific high molecular weight component. When the content of the specific high molecular weight component is 0.25% by mass or more and 30% by mass or less, the low loss property and abrasion resistance of the rubber composition can be sufficiently improved. The modified styrene-butadiene rubber contains the specific high molecular weight component preferably at least 1.0% by mass, more preferably at least 1.4% by mass, even more preferably at least 1.75% by mass, still more preferably at least 2.0% by mass, particularly preferably at least 2.15% by mass, and extremely preferably at least 2.5% by mass. Furthermore, the modified styrene-butadiene rubber contains the specific high molecular weight component preferably at most 28% by mass, more preferably at most 25% by mass, even more preferably at most 20% by mass, and even more preferably at most 18% by mass. In this specification, the "molecular weight" of the rubber component refers to the molecular weight in terms of standard polystyrene obtained by GPC (gel permeation chromatography). In order to obtain a modified styrene-butadiene rubber having a content of a specific high molecular weight component within this range, it is preferable to control the reaction conditions in the polymerization step and reaction step described below. For example, in the polymerization step, the amount of an organic monolithium compound used as a polymerization initiator, described below, can be adjusted. In addition, in the polymerization step, whether the polymerization method is continuous or batchwise, it is preferable to use a method with a residence time distribution, that is, to widen the time distribution of the propagation reaction.

[0108] In the modified styrene-butadiene rubber, the molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), is preferably 1.6 to 3.0. If the molecular weight distribution of the modified styrene-butadiene rubber is in this range, the rubber composition will have good processability.

[0109] The method for producing the modified styrene-butadiene rubber is not particularly limited, but preferably includes a polymerization step of copolymerizing butadiene and styrene using an organic monolithium compound as a polymerization initiator to obtain a styrene-butadiene copolymer, and a reaction step of reacting an active terminal of the styrene-butadiene copolymer with a pentafunctional or higher reactive compound (hereinafter also referred to as a "coupling agent").

[0110] The polymerization step is preferably a propagation polymerization by living anionic polymerization, which makes it possible to obtain a styrene-butadiene copolymer having active terminals and a modified styrene-butadiene rubber with a high degree of modification. The styrene-butadiene copolymer is obtained by copolymerizing 1,3-butadiene and styrene.

[0111] The amount of the organic monolithium compound used as a polymerization initiator is preferably determined based on the target molecular weight of the styrene-butadiene copolymer or modified styrene-butadiene rubber. The amount of monomers, such as 1,3-butadiene and styrene, used relative to the amount of polymerization initiator is related to the degree of polymerization, i.e., the number average molecular weight and / or weight average molecular weight. Therefore, to increase the molecular weight, it is recommended to adjust the amount of polymerization initiator to decrease, and to decrease the molecular weight, it is recommended to adjust the amount of polymerization initiator to increase. The organic monolithium compound is preferably an alkyllithium compound from the viewpoints of industrial availability and ease of control of the polymerization reaction. In this case, a styrene-butadiene copolymer having an alkyl group at the polymerization initiation terminal is obtained. Examples of the alkyllithium compound include n-butyllithium, sec-butyllithium, tert-butyllithium, n-hexyllithium, benzyllithium, phenyllithium, and stilbenelithium. From the viewpoints of industrial availability and ease of control of the polymerization reaction, n-butyllithium and sec-butyllithium are preferred as the alkyllithium compound. These organic monolithium compounds may be used alone or in combination of two or more.

[0112] In the polymerization step, examples of the polymerization reaction mode include batch and continuous polymerization modes. In a continuous mode, one or more connected reactors can be used. Continuous reactors, for example, tank-type or tubular reactors equipped with a stirrer, are used. In a continuous mode, preferably, monomers, an inert solvent, and a polymerization initiator are continuously fed into the reactor, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is continuously discharged. Batch reactors, for example, tank-type reactors equipped with a stirrer, are used. In a batch mode, preferably, monomers, an inert solvent, and a polymerization initiator are fed, and if necessary, monomers are added continuously or intermittently during polymerization, a polymer solution containing a polymer is obtained in the reactor, and the polymer solution is discharged after the polymerization is completed. In this embodiment, in order to obtain a styrene-butadiene copolymer having a high proportion of active ends, a continuous mode is preferred, which allows the polymer to be continuously discharged and subjected to the next reaction in a short period of time.

[0113] The polymerization step is preferably carried out in an inert solvent. Examples of the solvent include hydrocarbon solvents such as saturated hydrocarbons and aromatic hydrocarbons. Specific hydrocarbon solvents include, but are not limited to, aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclopentane, and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene; and hydrocarbons consisting of mixtures thereof. Treating impurities such as allenes and acetylenes with an organometallic compound before subjecting the mixture to the polymerization reaction tends to produce a styrene-butadiene copolymer having a high concentration of active terminals, and thus tends to produce a modified styrene-butadiene rubber with a high modification rate, which is preferable.

[0114] In the polymerization step, a polar compound may be added. By adding a polar compound, styrene can be randomly copolymerized with 1,3-butadiene, and the polar compound also tends to be usable as a vinylating agent for controlling the microstructure of the 1,3-butadiene moiety. Examples of the polar compound that can be used include ethers such as tetrahydrofuran, diethyl ether, dioxane, ethylene glycol dimethyl ether, ethylene glycol dibutyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dimethoxybenzene, and 2,2-bis(2-oxolanyl)propane; tertiary amine compounds such as tetramethylethylenediamine, dipiperidinoethane, trimethylamine, triethylamine, pyridine, and quinuclidine; alkali metal alkoxide compounds such as potassium tert-amylate, potassium tert-butylate, sodium tert-butylate, and sodium tert-amylate; and phosphine compounds such as triphenylphosphine. These polar compounds may be used alone or in combination of two or more.

[0115] In the polymerization step, from the viewpoint of productivity, the polymerization temperature is preferably 0° C. or higher, more preferably 120° C. or lower, and particularly preferably 50° C. or higher and 100° C. or lower. By keeping the temperature within such a range, it tends to be possible to ensure a sufficient amount of the coupling agent to react with the active terminals after the completion of polymerization.

[0116] The amount of bound butadiene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably 40% by mass or more and 100% by mass or less, and more preferably 55% by mass or more and 80% by mass or less. Furthermore, the amount of bound styrene in the styrene-butadiene copolymer or modified styrene-butadiene rubber is not particularly limited, but is preferably more than 0 mass% and not more than 60 mass%, and more preferably 20 mass% or more and 45 mass% or less. When the bound butadiene amount and the bound styrene amount are within the above ranges, the low loss property and the wear resistance of the rubber composition can be further improved. The amount of bound styrene can be measured by ultraviolet absorption of the phenyl group, and the amount of bound butadiene can also be determined from this.

[0117] In the styrene-butadiene copolymer or modified styrene-butadiene rubber, the amount of vinyl bonds in the butadiene bond units is not particularly limited, but is preferably 10 mol % to 75 mol %, more preferably 20 mol % to 65 mol %. When the amount of vinyl bonds is within the above range, the low loss property and wear resistance of the rubber composition can be further improved. For modified styrene-butadiene rubber, the vinyl bond content (1,2-bond content) in the butadiene bond unit can be determined by Hampton's method [RR Hampton, Analytical Chemistry, 21, 923 (1949)].

[0118] The alkoxysilyl group of the coupling agent represented by the general formula (I) tends to react with, for example, the active terminal of a styrene-butadiene copolymer, dissociating the alkoxylithium and forming a bond between the terminal of the styrene-butadiene copolymer chain and the silicon of the coupling residue. The number of alkoxysilyl groups in the coupling residue is calculated by subtracting the number of SiO R from the total number of SiO R in one molecule of the coupling agent. Furthermore, the azasilacycle group in the coupling agent forms an >N-Li bond and a bond between the terminal of the styrene-butadiene copolymer and the silicon of the coupling residue. The >N-Li bond tends to easily become >NH and LiOH upon exposure to water or other factors during finishing. Furthermore, any remaining unreacted alkoxysilyl groups in the coupling agent tend to easily become silanols (Si-OH groups) upon exposure to water or other factors during finishing.

[0119] The reaction temperature in the reaction step is preferably the same as the polymerization temperature of the styrene-butadiene copolymer, more preferably from 0° C. to 120° C., and even more preferably from 50° C. to 100° C. The temperature change from the end of the polymerization step to the addition of the coupling agent is preferably 10° C. or less, more preferably 5° C. or less. The reaction time in the reaction step is preferably 10 seconds or more, more preferably 30 seconds or more. From the viewpoint of the coupling rate, the time from the end of the polymerization step to the start of the reaction step is preferably shorter, and more preferably within 5 minutes. The mixing in the reaction step may be performed by mechanical stirring, stirring with a static mixer, or the like. When the polymerization step is continuous, it is preferable that the reaction step is also continuous. The reactor used in the reaction step may be, for example, a tank type or a tubular type equipped with a stirrer. The coupling agent may be diluted with an inert solvent and continuously supplied to the reactor. When the polymerization step is batchwise, the coupling agent may be charged into the polymerization reactor, or may be transferred to a separate reactor and the reaction step may be carried out.

[0120] In the general formula (I), A is preferably represented by any one of the following general formulae (II) to (V): When A is represented by any one of the general formulae (II) to (V), a modified styrene-butadiene rubber having better performance can be obtained.

[0121] [ka] In the general formula (II), B 1 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 1 are each independent of each other.

[0122] [ka] In the general formula (III), B 2 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, B 3 represents an alkyl group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 2 and B 3 are each independent of each other.

[0123] [ka] In the general formula (IV), B 4 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 4 are each independent of each other.

[0124] [ka] In the general formula (V), B 5 represents a single bond or a hydrocarbon group having 1 to 20 carbon atoms, and a represents an integer of 1 to 10. When a plurality of B 5 are each independent of each other.

[0125] B in the general formulas (II) to (V) 1 , B 2 , B 4 , B 5 Regarding the above, examples of the hydrocarbon group having 1 to 20 carbon atoms include an alkylene group having 1 to 20 carbon atoms.

[0126] Preferably, in the general formula (I), A is represented by the general formula (II) or (III), and k is 0. More preferably, in the general formula (I), A is represented by the general formula (II) or (III), k represents 0, and in the general formula (II) or (III), a represents an integer of 2 to 10. More preferably, in the general formula (I), A is represented by the general formula (II), k represents 0, and in the general formula (II), a represents an integer of 2 to 10. Examples of such coupling agents include bis(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]amine, tris(3-trimethoxysilylpropyl)amine, tris(3-triethoxysilylpropyl)amine, tris(3-trimethoxysilylpropyl)-[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl). bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane, tris(3-trimethoxysilylpropyl)-methyl-1,3-propanediamine, bis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-(3-trismethoxysilylpropyl)-methyl-1,3-propanediamine, and the like are particularly preferred among these.

[0127] The amount of the compound represented by general formula (I) added as the coupling agent can be adjusted so that the moles of styrene-butadiene copolymer to the moles of coupling agent react in a desired stoichiometric ratio, which tends to achieve a desired degree of branching. Specifically, the moles of the polymerization initiator are preferably 5.0 times or more, more preferably 6.0 times or more, relative to the moles of the coupling agent. In this case, in general formula (I), the number of functional groups of the coupling agent ((m-1) x i + p x j + k) is preferably an integer of 5 to 10, more preferably an integer of 6 to 10.

[0128] In order to obtain a modified styrene-butadiene rubber having the specific polymer component, the molecular weight distribution (Mw / Mn) of the styrene-butadiene copolymer is preferably 1.5 or more and 2.5 or less, more preferably 1.8 or more and 2.2 or less. In addition, it is preferable that the obtained modified styrene-butadiene rubber is one in which a single peak is detected in the molecular weight curve by GPC. When the peak molecular weight of the modified styrene-butadiene rubber measured by GPC is Mp1 and the peak molecular weight of the styrene-butadiene copolymer is Mp2, the following formula preferably holds true. (Mp1 / Mp2)<1.8×10-12×(Mp2-120×10 4 ) 2 +2 Mp2 is 20 x 10 4 Over 80 x 10 4 Below, Mp1 is 30 x 10 4 Over 150 x 10 4 The following is more preferred: Mp1 and Mp2 are determined by the method described in the Examples below.

[0129] The modification rate of the modified styrene-butadiene rubber is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. When the modification rate is 30% by mass or more, the low loss property and abrasion resistance of the rubber composition can be further improved.

[0130] After the reaction step, a deactivator, neutralizer, etc. may be added to the copolymer solution as needed. Examples of deactivators include, but are not limited to, water; alcohols such as methanol, ethanol, and isopropanol; and examples of neutralizers include, but are not limited to, carboxylic acids such as stearic acid, oleic acid, and versatic acid (a highly branched carboxylic acid mixture having 9 to 11 carbon atoms, with the majority being 10 carbon atoms); aqueous solutions of inorganic acids; and carbon dioxide gas. Furthermore, from the viewpoint of preventing gel formation after polymerization and improving stability during processing, it is preferable to add an antioxidant such as 2,6-di-tert-butyl-4-hydroxytoluene (BHT), n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, or 2-methyl-4,6-bis[(octylthio)methyl]phenol to the modified styrene-butadiene rubber.

[0131] The modified styrene-butadiene rubber can be obtained from the polymer solution by any known method, including, for example, a method in which the solvent is separated by steam stripping or the like, the polymer is filtered, and then the polymer is dehydrated and dried to obtain the polymer, a method in which the polymer is concentrated in a flashing tank and then devolatilized using a vent extruder or the like, and a method in which the polymer is directly devolatilized using a drum dryer or the like.

[0132] The modified styrene-butadiene rubber obtained by reacting the coupling agent represented by the above general formula (I) with a styrene-butadiene copolymer is represented, for example, by the following general formula (VI). [ka]

[0133] In the general formula (VI), D represents a styrene-butadiene copolymer chain, and the weight average molecular weight of the styrene-butadiene copolymer chain is 10 × 10 4 ~100×10 4 The styrene-butadiene copolymer chain is a structural unit of a modified styrene-butadiene rubber, and is, for example, a structural unit derived from a styrene-butadiene copolymer, which is generated by reacting a styrene-butadiene copolymer with a coupling agent. R 12 , R 13 and R 14 each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. R 15 and R 18each independently represents an alkyl group having 1 to 20 carbon atoms. R 16 , R 19 , and R 20 each independently represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. R 17 and R 21 each independently represents an alkylene group having 1 to 20 carbon atoms. R 22 represents a hydrogen atom or an alkyl group having 1 to 20 carbon atoms. m and x represent integers of 1 to 3, with x≦m; p represents 1 or 2; y represents an integer of 1 to 3, with y≦(p+1); and z represents an integer of 1 or 2. D and R when there are multiple of each 12 ~R 22 , m, p, x, y, and z are each independent and may be the same or different. Furthermore, i represents an integer from 0 to 6, j represents an integer from 0 to 6, k represents an integer from 0 to 6, (i+j+k) is an integer from 3 to 10, and ((x×i)+(y×j)+(z×k)) is an integer from 5 to 30. A represents a hydrocarbon group having 1 to 20 carbon atoms, or an organic group having at least one atom selected from the group consisting of oxygen, nitrogen, silicon, sulfur, and phosphorus atoms, and having no active hydrogen. The hydrocarbon group represented by A includes saturated, unsaturated, aliphatic, and aromatic hydrocarbon groups. Examples of the organic group having no active hydrogen include organic groups having no functional groups having active hydrogen, such as a hydroxyl group (-OH), a secondary amino group (>NH), a primary amino group (-NH), or a sulfhydryl group (-SH).

[0134] In the general formula (VI), A is preferably represented by any one of the general formulae (II) to (V). When A is represented by any one of the general formulae (II) to (V), the low loss property and abrasion resistance of the rubber composition can be further improved.

[0135] --Third Preferred Embodiment of Modified Styrene-Butadiene Rubber-- It is also preferable that the (1) modified styrene-butadiene rubber (modified SBR) has at least one end modified with a modifier containing a compound (alkoxysilane) represented by the following general formula (1). [ka]

[0136] The use of a styrene-butadiene rubber modified with a modifier containing a compound represented by the general formula (1) containing an oligosiloxane and a tertiary amino group, which are filler affinity functional groups, as the rubber component (A) can enhance the dispersibility of fillers such as silica. As a result, the rubber composition of the present invention has improved filler dispersibility, which significantly improves low loss properties, reduces the rolling resistance of tires using the rubber composition, and improves fuel economy.

[0137] In the above general formula (1), R 1 ~R 8 are each independently an alkyl group having 1 to 20 carbon atoms; L 1 and L 2 are each independently an alkylene group having 1 to 20 carbon atoms; and n is an integer of 2 to 4.

[0138] Specifically, in formula (1), R 1 ~R 4 may each independently represent a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, and 1 ~R 4 When substituted, each independently may be substituted with one or more substituents selected from the group consisting of an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 3 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkoxy group having 4 to 10 carbon atoms, an aryl group having 6 to 12 carbon atoms, an aryloxy group having 6 to 12 carbon atoms, an alkanoyloxy group having 2 to 12 carbon atoms (Ra-COO-, where Ra is an alkyl group having 1 to 9 carbon atoms), an aralkyloxy group having 7 to 13 carbon atoms, an arylalkyl group having 7 to 13 carbon atoms, and an alkylaryl group having 7 to 13 carbon atoms. More specifically, the R 1 ~R 4 may be a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, and more specifically, 1 ~R 4 may each independently be a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms.

[0139] In addition, in formula (1), R 5 ~R 8 are each independently a substituted or unsubstituted alkyl group having 1 to 20 carbon atoms, specifically a substituted or unsubstituted alkyl group having 1 to 10 carbon atoms, more specifically a substituted or unsubstituted alkyl group having 1 to 6 carbon atoms, and when substituted, they are first 1 ~R 4 It may be substituted with substituents as described above. In addition, the above R 5 ~R 8 If is not an alkyl group but a hydrolyzable substituent, NR 5 R 6 and NR 7 R 8 The bond can be hydrolyzed to NH in the presence of moisture, adversely affecting the processability of the polymer.

[0140] More specifically, in the compound represented by the formula (1), R 1 ~R 4 is a methyl group or an ethyl group, and R 5 ~R 8 can be an alkyl group having 1 to 10 carbon atoms.

[0141] The amino group in the compound represented by the formula (1), i.e., NR 5 R 6 and NR 7 R 8 is preferably a tertiary amino group. The tertiary amino group provides the compound represented by formula (1) with better processability when used as a modifying agent. In addition, the above R 5 ~R 8If a protecting group for protecting the amino group is bonded to the terminal end of the polymer or if hydrogen is bonded to the terminal end of the polymer, it may be difficult to realize the effect of the compound represented by formula (1). If hydrogen is bonded, the anion reacts with hydrogen during the modification process, losing its reactivity and making the modification reaction impossible. If a protecting group is bonded, the modification reaction will occur, but the terminal end of the polymer will be deprotected by hydrolysis during post-processing to become a primary or secondary amino group. The deprotected primary or secondary amino group may cause the compound to become viscous during subsequent blending, potentially resulting in reduced processability.

[0142] In addition, L in the compound represented by the formula (1) 1 and L 2 are each independently a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms. More specifically, L 1 and L 2 may each independently be an alkylene group having 1 to 10 carbon atoms, more specifically, an alkylene group having 1 to 6 carbon atoms such as a methylene group, an ethylene group, or a propylene group.

[0143] L in the compound represented by formula (1) 1 and L 2 Regarding the above, the shorter the distance between the Si atom and the N atom in the molecule, the better the effect. However, if Si is directly bonded to N, there is a risk that the bond between Si and N will break during subsequent processing steps, and the secondary amino group generated in this case is likely to be washed away by water during post-processing. In the modified styrene-butadiene rubber produced, it is difficult for the amino group, which promotes bonding with fillers such as silica, to bond with the filler, and as a result, the effect of improving the dispersibility of the filler may be reduced. In this way, considering the improvement effect depending on the bond length between Si and N, the above L 1 and L 2 More preferably, each of L is independently an alkylene group having 1 to 3 carbon atoms, such as a methylene group, an ethylene group, or a propylene group, and more specifically, can be a propylene group. 1 and L 2 R first 1 ~R4 It may be substituted with substituents as described above.

[0144] The compound represented by the formula (1) is preferably, for example, any one of the compounds represented by the following structural formulas (1-1) to (1-5), because this allows for achieving even better low loss properties. [ka]

[0145] The compound represented by formula (1) has an alkoxysilane structure that bonds to the active terminal of the styrene-butadiene copolymer, while the Si-O-Si structure and three or more amino groups bonded to the terminals exhibit affinity for fillers such as silica. This promotes bonding between the filler and the modified styrene-butadiene rubber compared to conventional modifiers containing a single amino group per molecule. Furthermore, the degree of bonding at the active terminals of the styrene-butadiene copolymer is uniform, and when observing the change in molecular weight distribution before and after coupling, the molecular weight distribution remains constant without increasing compared to before coupling. This prevents a deterioration in the physical properties of the modified styrene-butadiene rubber itself, prevents filler aggregation within the rubber composition, and enhances filler dispersibility, thereby improving the processability of the rubber composition. These effects, particularly when the rubber composition is applied to tires, enable a balanced improvement in fuel economy and wet grip performance.

[0146] The compound represented by the formula (1) can be produced through a condensation reaction represented by the following reaction scheme. [ka]

[0147] In the above reaction scheme, R 1 ~R 8 , L 1 and L 2and n are the same as those defined in the above formula (1), and R′ and R″ are any substituents that do not affect the condensation reaction. For example, R′ and R″ are each independently R 1 ~R 4 It can be identical to any one of the following:

[0148] The reaction in the above reaction scheme proceeds in the presence of an acid, and any acid generally used in condensation reactions can be used without limitation. Those skilled in the art can select an optimal acid depending on various process variables such as the type of reactor in which the reaction is carried out, starting materials, and reaction temperature.

[0149] The styrene-butadiene rubber modified with a modifier containing the compound represented by formula (1) can have a narrow molecular weight distribution (Mw / Mn, also referred to as "polydispersity index (PDI)") of 1.1 to 3.0. If the molecular weight distribution of the modified styrene-butadiene rubber exceeds 3.0 or is less than 1.1, the tensile properties and viscoelasticity may be reduced when the modified styrene-butadiene rubber is applied to a rubber composition. Considering the remarkable effect of improving the tensile properties and viscoelasticity by controlling the molecular weight distribution of the modified styrene-butadiene rubber, the molecular weight distribution of the modified styrene-butadiene rubber is preferably in the range of 1.3 to 2.0. By using the modifier, the modified styrene-butadiene rubber has a molecular weight distribution similar to that of the styrene-butadiene copolymer before modification.

[0150] The molecular weight distribution of the modified styrene-butadiene rubber can be calculated from the ratio (Mw / Mn) of the weight average molecular weight (Mw) to the number average molecular weight (Mn). The number average molecular weight (Mn) is the common average of the molecular weights of individual polymers calculated by measuring the molecular weights of n polymer molecules, summing the molecular weights, and dividing by n. The weight average molecular weight (Mw) represents the molecular weight distribution of the polymer composition. The average of the total molecular weight can be expressed in grams per mole (g / mol). The weight average molecular weight and number average molecular weight are each a polystyrene-equivalent molecular weight analyzed by gel permeation chromatography (GPC).

[0151] The modified styrene-butadiene rubber satisfies the above-mentioned molecular weight distribution conditions and may have a number average molecular weight (Mn) of 50,000 g / mol to 2,000,000 g / mol, more specifically, 200,000 g / mol to 800,000 g / mol, and a weight average molecular weight (Mw) of 100,000 g / mol to 4,000,000 g / mol, more specifically, 300,000 g / mol to 1,500,000 g / mol. If the weight-average molecular weight (Mw) of the modified styrene-butadiene rubber is less than 100,000 g / mol or the number-average molecular weight (Mn) is less than 50,000 g / mol, the tensile properties may be reduced when the modified styrene-butadiene rubber is applied to a rubber composition. If the weight-average molecular weight (Mw) is greater than 4,000,000 g / mol or the number-average molecular weight (Mn) is greater than 2,000,000 g / mol, the processability of the modified styrene-butadiene rubber may be reduced, resulting in a deterioration in the workability of the rubber composition, making kneading difficult, and making it difficult to sufficiently improve the physical properties of the rubber composition. More specifically, when the modified styrene-butadiene rubber satisfies the conditions for weight average molecular weight (Mw) and number average molecular weight (Mn) as well as the molecular weight distribution, when the modified styrene-butadiene rubber is applied to a rubber composition, it can improve the viscoelasticity and processability of the rubber composition in a well-balanced manner.

[0152] The modified styrene-butadiene rubber preferably has a vinyl bond content in the butadiene moiety of 5% or more, more preferably 10% or more, and preferably 60% or less. By adjusting the vinyl bond content in the butadiene moiety to fall within the above range, the glass transition temperature can be adjusted to an appropriate range.

[0153] The modified styrene-butadiene rubber may have a Mooney viscosity (MV) at 100° C. of 40 to 140, specifically 60 to 100. When the modified styrene-butadiene rubber has a Mooney viscosity in the above range, it can exhibit better processability. The Mooney viscosity can be measured using a Mooney viscometer, such as Monsanto's MV2000E, at 100°C, a rotor speed of 2±0.02 rpm, and a large rotor. The sample used here is left at room temperature (23±3°C) for 30 minutes or more, and then 27±3 g of the sample is taken and filled into the die cavity, and the platen is operated to measure the viscosity.

[0154] As described above, the modified styrene-butadiene rubber is preferably modified at one end with a modifier containing a compound represented by the above general formula (1), and is preferably further modified at the other end with a modifier containing a compound represented by the following general formula (2). By modifying both ends of the modified styrene-butadiene rubber, the dispersibility of the filler in the rubber composition is further improved, and a tire using the rubber composition can achieve both low fuel consumption performance and wet grip performance at a higher level. [ka]

[0155] In the above general formula (2), R 9 ~R 11 are each independently hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms, a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms. In addition, in formula (2), R 12 represents a single bond; an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted; a cycloalkylene group having 5 to 20 carbon atoms which is substituted or unsubstituted; or an arylene group having 5 to 20 carbon atoms which is substituted or unsubstituted, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. In addition, in formula (2), R 13is an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; a heterocyclic group having 3 to 30 carbon atoms; or a functional group represented by the following general formula (2a) or general formula (2b), wherein m is an integer of 1 to 5, and R 13 At least one of the functional groups is represented by the following general formula (2a) or (2b), and when m is an integer of 2 to 5, a plurality of R 13 may be the same as or different from each other.

[0156] [ka]

[0157] In the above general formula (2a), R 14 represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2a), R 15 and R 16 are each independently an alkylene group having 1 to 20 carbon atoms which is substituted or unsubstituted with an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2a), R 17 is hydrogen; an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms; and X is an N, O, or S atom, provided that when X is O or S, R 17 does not exist.

[0158] [ka]

[0159] In the above general formula (2b), R 18 represents a substituted or unsubstituted alkylene group having 1 to 20 carbon atoms; a substituted or unsubstituted cycloalkylene group having 5 to 20 carbon atoms; or a substituted or unsubstituted arylene group having 6 to 20 carbon atoms, wherein the substituent is an alkyl group having 1 to 10 carbon atoms, a cycloalkyl group having 5 to 10 carbon atoms, or an aryl group having 6 to 20 carbon atoms. Also, in formula (2b), R 19 and R 20 are each independently an alkyl group having 1 to 30 carbon atoms; an alkenyl group having 2 to 30 carbon atoms; an alkynyl group having 2 to 30 carbon atoms; a heteroalkyl group having 1 to 30 carbon atoms; a heteroalkenyl group having 2 to 30 carbon atoms; a heteroalkynyl group having 2 to 30 carbon atoms; a cycloalkyl group having 5 to 30 carbon atoms; an aryl group having 6 to 30 carbon atoms; or a heterocyclic group having 3 to 30 carbon atoms.

[0160] In addition, in the compound represented by the general formula (2), R 9 ~R 11 are each independently hydrogen; an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; or an alkynyl group having 2 to 10 carbon atoms; and R 12 is a single bond; or an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 13 is an alkyl group having 1 to 10 carbon atoms; an alkenyl group having 2 to 10 carbon atoms; an alkynyl group having 2 to 10 carbon atoms; or a functional group represented by the above general formula (2a) or (2b), and in the above general formula (2a), R 14 is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 15 and R 16 are each independently an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 17is an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms, and in the above general formula (2b), R 18 is an unsubstituted alkylene group having 1 to 10 carbon atoms, and R 19 and R 20 may each independently be an alkyl group having 1 to 10 carbon atoms; a cycloalkyl group having 5 to 20 carbon atoms; an aryl group having 6 to 20 carbon atoms; or a heterocyclic group having 3 to 20 carbon atoms.

[0161] More specifically, the compound represented by the above general formula (2) can be a compound represented by the following structural formulas (2-1) to (2-3). [ka]

[0162] When the styrene-butadiene copolymer is modified with a modifying agent containing the compound represented by the general formula (2), the modifying agent containing the compound represented by the formula (2) is used as a modification initiator. Specifically, for example, by polymerizing a butadiene monomer and a styrene monomer in a hydrocarbon solvent in the presence of a modifying agent containing a compound represented by formula (2), a modifying group derived from the compound represented by formula (2) can be imparted to the styrene-butadiene copolymer.

[0163] Furthermore, the content of (1) modified SBR modified with a modifier such as the aminoalkoxysilane compound in the rubber component (A) is not particularly limited, but is preferably 15% by mass or more, more preferably 20% by mass or more, preferably less than 85% by mass, more preferably 60% by mass or less, and even more preferably 50% by mass or less. When the content of (1) modified SBR in the rubber component (A) is 15% by mass or more, the fuel economy and wear resistance of the tire can be further improved. On the other hand, when the content of (1) modified SBR in the rubber component (A) is 60% by mass or less, a sufficient amount of (2) unmodified SBR, described below, can be contained, and the wet grip performance of the tire can be maintained at a good level.

[0164] In addition to the (1) modified SBR, the rubber component (A) preferably further contains an unmodified styrene-butadiene rubber (unmodified SBR) having a glass transition temperature at least 30°C higher than that of the (2) modified SBR. By including (2) unmodified SBR having a high glass transition temperature as the rubber component (A), the wet grip performance of the tire can be improved.

[0165] Here, the glass transition temperature of the (2) unmodified SBR is preferably at least 30° C. higher than the glass transition temperature of the (1) modified SBR, and more preferably at least 35° C. higher. By including the (1) modified SBR and the (2) unmodified SBR, the flexibility of the tread rubber layer can be increased, and the fuel economy and wear resistance of the tire can be sufficiently improved.

[0166] Furthermore, the content of the (2) unmodified SBR in the rubber component (A) is not particularly limited, but is preferably 15% by mass or more, more preferably 20% by mass or more, and preferably less than 85% by mass, more preferably 80% by mass or less. When the content of the (2) unmodified SBR in the rubber component (A) is 15% by mass or more, the wet grip performance of the tire can be further improved. On the other hand, when the content of the (2) unmodified SBR in the rubber component (A) is less than 85% by mass, the fuel economy and wear resistance of the tire can be maintained at a good level. Therefore, when the rubber component (A) contains the (2) unmodified SBR in an amount of 15% by mass or more but less than 85% by mass, the wet grip performance can be further improved while maintaining good fuel economy and wear resistance.

[0167] Furthermore, from the viewpoint of achieving higher levels of wet grip performance, fuel economy, and wear resistance of the tire, it is preferable that the content ratio of the (2) unmodified SBR is greater than the content ratio of the (1) modified SBR [content ratio of the (2) unmodified SBR / content ratio of the (1) modified SBR>1].

[0168] -Butadiene rubber (BR)- The synthetic rubber (A1) preferably contains a butadiene rubber (BR). Butadiene rubber has a low glass transition temperature (Tg), and when the rubber component (A) contains a butadiene rubber as the synthetic rubber (A1), the fuel economy and wear resistance of a tire using the rubber composition can be improved.

[0169] The butadiene rubber may be modified or unmodified. From the viewpoint of further improving the fuel economy and wear resistance of a tire to which the rubber composition is applied, the butadiene rubber is preferably a modified butadiene rubber having a functional group having affinity for a filler.

[0170] Examples of the functional group having affinity with the filler include functional groups having one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, a metalloid atom, and a metal atom. The metalloid atoms are preferably one or more atoms selected from boron, silicon, germanium, arsenic, antimony, and tellurium, more preferably one or more atoms selected from boron, silicon, and germanium, and particularly preferably silicon. The metal atom is preferably one or more atoms selected from tin, titanium, zirconium, bismuth, and aluminum, more preferably one or more atoms selected from tin and titanium, and particularly preferably tin. The functional group having affinity for the filler preferably contains at least one atom selected from the group consisting of a nitrogen atom, an oxygen atom, and a silicon atom.

[0171] The functional group having one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, a metalloid atom, and a metal atom is a residue of a compound having one or more atoms selected from a nitrogen atom, an oxygen atom, a sulfur atom, a metalloid atom, and a metal atom (hereinafter, sometimes referred to as a "heteroatom-containing compound"). The modified butadiene rubber may be formed, for example, by polymerizing 1,3-butadiene to obtain polybutadiene having active ends and then reacting the active ends of the polybutadiene with a modifier, or by polymerizing 1,3-butadiene using a polymerization initiator having a functional group to form polybutadiene having a functional group at the polymerization initiation end. For example, the heteroatom-containing compound may act as a modifier and react with the active terminal of polybutadiene to form a modified butadiene rubber, or a nitrogen-containing compound as a heteroatom-containing compound may react with an alkali metal to form a polymerization initiator for anionic polymerization, thereby forming a modified butadiene rubber having a nitrogen-containing compound residue at the polymerization initiation terminal of polybutadiene.

[0172] The modifier that reacts with the active terminal of the polybutadiene may be one or more modifiers selected from the following: tin-containing compounds, nitrogen- and silicon-containing compounds, oxygen- and silicon-containing compounds, sulfur- and silicon-containing compounds, and silicon-free nitrogen-containing compounds.

[0173] Suitable examples of the tin-containing compound include at least one tin compound selected from tin tetrachloride and tributyltin chloride.

[0174] Examples of the nitrogen- and silicon-containing compounds include N,N-bis(trimethylsilyl)aminopropylmethyldimethoxysilane, 1-trimethylsilyl-2,2-dimethoxy-1-aza-2-silacyclopentane, N,N-bis(trimethylsilyl)aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N Suitable examples of silane compounds having a protected primary amino group selected from N-bis(trimethylsilyl)aminoethyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethylmethyldimethoxysilane and N,N-bis(trimethylsilyl)aminoethylmethyldiethoxysilane are N-methyl-N-trimethylsilylaminopropyl(methyl)dimethoxysilane, N-methyl-N-trimethylsilylaminopropyl(methyl)diethoxysilane, N-trimethylsilyl(hexamethoxy) ... N-Trimethylsilyl(hexamethyleneimin-2-yl)propyl(methyl)dimethoxysilane, N-Trimethylsilyl(hexamethyleneimin-2-yl)propyl(methyl)diethoxysilane, N-Trimethylsilyl(pyrrolidin-2-yl)propyl(methyl)dimethoxysilane, N-Trimethylsilyl(pyrrolidin-2-yl)propyl(methyl)diethoxysilane, N-Trimethylsilyl(piperidin-2-yl)propyl(methyl)dimethoxysilane, N-Trimethylsilyl(piperidin-2-yl)propyl(methyl)di Suitable examples include silane compounds having a protected secondary amino group selected from ethoxysilane, N-trimethylsilyl(imidazol-2-yl)propyl(methyl)dimethoxysilane, N-trimethylsilyl(imidazol-2-yl)propyl(methyl)diethoxysilane, N-trimethylsilyl(4,5-dihydroimidazol-5-yl)propyl(methyl)dimethoxysilane, and N-trimethylsilyl(4,5-dihydroimidazol-5-yl)propyl(methyl)diethoxysilane.

[0175] Suitable examples of the oxygen- and silicon-containing compound include epoxy group-containing hydrocarbyloxysilane compounds selected from one or more of 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane.

[0176] Suitable examples of the sulfur- and silicon-containing compound include thioepoxy-containing hydrocarbyloxysilane compounds in which the epoxy groups of the above-mentioned epoxy-containing hydrocarbyloxysilane compounds are substituted with thioepoxy groups.

[0177] Suitable examples of the silicon-free nitrogen-containing compound include one or more compounds selected from bis(diethylamino)benzophenone, dimethylimidazolidinone, N-methylpyrrolidone, and 4-dimethylaminobenzylideneaniline.

[0178] The polymerization method for the polybutadiene may be anionic polymerization or coordination polymerization.

[0179] When the polybutadiene is obtained by anionic polymerization, an alkali metal compound is used as the polymerization initiator, with lithium compounds being preferred. The lithium compound used as the polymerization initiator is not particularly limited, but hydrocarbyllithium and lithium amide compounds are preferably used. When the former hydrocarbyllithium is used, a polybutadiene having a hydrocarbyl group at the polymerization initiation terminal and a polymerization active site at the other terminal is obtained. When the latter lithium amide compound is used, a polybutadiene having a nitrogen-containing functional group at the polymerization initiation terminal and a polymerization active site at the other terminal is obtained.

[0180] The hydrocarbyllithium is preferably one having a hydrocarbyl group having 2 to 20 carbon atoms, and examples thereof include ethyllithium, n-propyllithium, isopropyllithium, n-butyllithium, sec-butyllithium, tert-octyllithium, n-decyllithium, phenyllithium, 2-naphthyllithium, 2-butyl-phenyllithium, 4-phenyl-butyllithium, cyclohexyllithium, cyclopentyllithium, and a reaction product of diisopropenylbenzene with butyllithium. Of these, n-butyllithium is particularly preferred.

[0181] Examples of the lithium amide compound include lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium dodecamethyleneimide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium-N-methylpiperazide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, lithium methylphenethylamide, etc. Among these, from the viewpoints of the interaction effect with carbon black and polymerization initiation ability, cyclic lithium amides such as lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, and lithium dodecamethyleneimide are preferred, and lithium hexamethyleneimide and lithium pyrrolidide are more suitable.

[0182] It is more preferable to use lithium hexamethyleneimide as the polymerization initiator, because this makes it possible to obtain a modified butadiene rubber having a hexamethyleneimino group, which is a nitrogen-containing compound residue, as a functional group having atoms other than carbon and hydrogen at the polymerization initiation terminal of polybutadiene. A modified butadiene rubber having a nitrogen-containing compound residue at the polymerization initiation terminal of polybutadiene and having one or more compound residues selected from a tin-containing compound residue, a nitrogen- and silicon-containing compound residue, an oxygen- and silicon-containing compound residue, a sulfur- and silicon-containing compound residue, and a silicon-free nitrogen-containing compound residue at the active terminal of polybutadiene is more preferred from the viewpoints of further reducing the rolling resistance of a tire, achieving excellent fuel economy performance, and further improving abrasion resistance and crack resistance.

[0183] The method for producing polybutadiene by anionic polymerization using the lithium compound as a polymerization initiator is not particularly limited, and any conventionally known method can be used. Specifically, the target polybutadiene can be obtained by anionically polymerizing 1,3-butadiene in an organic solvent inert to the reaction, for example, a hydrocarbon solvent such as an aliphatic, alicyclic, or aromatic hydrocarbon compound, using the lithium compound as a polymerization initiator, and optionally in the presence of a randomizer. The hydrocarbon solvent is preferably one having 3 to 8 carbon atoms, and examples thereof include propane, n-butane, isobutane, n-pentane, isopentane, n-hexane, cyclohexane, propene, 1-butene, isobutene, trans-2-butene, cis-2-butene, 1-pentene, 2-pentene, 1-hexene, 2-hexene, benzene, toluene, xylene, ethylbenzene, etc. These may be used alone or in combination of two or more.

[0184] The optional randomizer is a compound that controls the microstructure of polybutadiene, for example, by increasing the number of 1,2 bonds in polybutadiene. The randomizer is not particularly limited, and any compound can be appropriately selected from known compounds commonly used as randomizers. Specific examples include ethers and tertiary amines such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, 2,2-bis(2-tetrahydrofuryl)-propane, triethylamine, pyridine, N-methylmorpholine, N,N,N',N'-tetramethylethylenediamine, and 1,2-dipiperidinoethane. Potassium salts such as potassium tert-amylate and potassium tert-butoxide, and sodium salts such as sodium tert-amylate can also be used. These randomizers may be used alone or in combination. The amount of the randomizer used is preferably selected from the range of 0.01 to 1000 molar equivalents per mole of the lithium compound.

[0185] The temperature in the polymerization reaction is preferably selected in the range of 0 to 150°C, more preferably 20 to 130°C. The polymerization reaction can be carried out under generated pressure, but it is usually desirable to operate at a pressure sufficient to maintain the monomer 1,3-butadiene substantially in a liquid phase. That is, although the pressure depends on the individual substances to be polymerized, the polymerization medium used, the polymerization temperature, etc., a higher pressure can be used if desired, and such a pressure can be obtained by a suitable method such as pressurizing the reactor with a gas inert to the polymerization reaction.

[0186] On the other hand, when the polybutadiene is produced by coordination polymerization using a rare earth metal compound as a polymerization initiator, it is more preferable to use the following components (a), (b), and (c) in combination.

[0187] The component (a) used in the coordination polymerization is selected from rare earth metal compounds and complex compounds of rare earth metal compounds with Lewis bases. Examples of rare earth metal compounds include carboxylates, alkoxides, β-diketone complexes, phosphates, and phosphites of rare earth elements. Examples of Lewis bases include acetylacetone, tetrahydrofuran, pyridine, N,N-dimethylformamide, thiophene, diphenyl ether, triethylamine, organic phosphorus compounds, and monohydric or dihydric alcohols. Preferred rare earth elements in the rare earth metal compounds include lanthanum, neodymium, praseodymium, samarium, and gadolinium, with neodymium being particularly preferred. Specific examples of component (a) include neodymium tri-2-ethylhexanoate, its complex compound with acetylacetone, neodymium trineodecanoate, its complex compound with acetylacetone, and neodymium tri-n-butoxide. These components (a) may be used singly or in combination of two or more.

[0188] The component (b) used in the coordination polymerization is selected from organoaluminum compounds. Specific examples of the organoaluminum compound include trihydrocarbylaluminum compounds represented by the formula R3Al, hydrocarbylaluminum hydrides represented by the formula R2AlH or RAlH2 (wherein R is each independently a hydrocarbon group having 1 to 30 carbon atoms), and hydrocarbylaluminoxane compounds having a hydrocarbon group having 1 to 30 carbon atoms. Specific examples of the organoaluminum compound include trialkylaluminum, dialkylaluminum hydrides, alkylaluminum dihydrides, and alkylaluminoxanes. These compounds may be used alone or in combination of two or more. It is preferable to use an aluminoxane in combination with another organoaluminum compound as the component (b).

[0189] The component (c) used in coordination polymerization is selected from compounds containing hydrolyzable halogens or complexes of these with Lewis bases; organic halides containing tertiary alkyl halides, benzyl halides, or allyl halides; and ionic compounds consisting of non-coordinating anions and counter cations. Specific examples of the component (c) include alkylaluminum dichlorides, dialkylaluminum chlorides, silicon tetrachloride, tin tetrachloride, complexes of zinc chloride with Lewis bases such as alcohols, complexes of magnesium chloride with Lewis bases such as alcohols, benzyl chloride, t-butyl chloride, benzyl bromide, t-butyl bromide, and triphenylcarbonium tetrakis(pentafluorophenyl)borate. These components (c) may be used alone or in combination.

[0190] In addition to the above components (a), (b), and (c), the polymerization initiator may be preliminarily prepared using 1,3-butadiene, which is also a polymerization monomer, if necessary. Also, a portion or all of component (a) or component (c) may be supported on an inert solid before use. The amounts of the above components can be appropriately determined, but typically, component (a) is used in an amount of 0.001 to 0.5 millimoles (mmol) per 100 g of monomer. Furthermore, the molar ratio of component (b) / component (a) is preferably 5 to 1,000, and the molar ratio of component (c) / component (a) is preferably 0.5 to 10.

[0191] The polymerization temperature in coordination polymerization is preferably in the range of -80°C to 150°C, more preferably in the range of -20°C to 120°C. Furthermore, as the solvent used in coordination polymerization, the hydrocarbon solvents inert to the reaction exemplified in the anionic polymerization described above can be used, and the concentration of the monomer 1,3-butadiene in the reaction solution is the same as in the anionic polymerization. Furthermore, the reaction pressure in coordination polymerization is also the same as in the anionic polymerization, and it is desirable that reaction inhibitors such as water, oxygen, carbon dioxide, and protic compounds are substantially removed from the raw materials used in the reaction.

[0192] The modified butadiene rubber is preferably one obtained by anion polymerization using an organic alkali metal compound, particularly alkyl lithium.

[0193] In both anionic polymerization and coordination polymerization, the polybutadiene can be modified by a modification reaction between the polymerization active terminals and the above-mentioned modifier after the polymerization reaction to obtain a modified butadiene rubber. The modification reaction is preferably carried out at a temperature of 20°C or higher, but the polymerization temperature of polybutadiene can be used as is, with a more preferred range being 30°C to 120°C. Lower reaction temperatures tend to result in excessive increases in the viscosity of polybutadiene and poor dispersibility of the reaction product. On the other hand, higher reaction temperatures tend to result in the easy deactivation of polymerization active sites. The amount of modifier used is preferably 0.25 to 3.0 mol, more preferably 0.5 to 1.5 mol, per mol of polymerization initiator used in the production of polybutadiene.

[0194] (Silica (B)) The rubber composition for a tire of this embodiment contains silica (B). Examples of the silica (B) include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it contains a large number of silanol groups. These silicas may be used alone or in combination of two or more. Commercially available silicas can be used, including those from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation.

[0195] From the viewpoint of reducing environmental impact, silica (B) derived from siliceous plants is preferred. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Poaceae plants. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making it easy to secure. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste. Furthermore, since the raw material can be procured locally near tire manufacturing plants, the energy and costs for 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 process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner can be pulverized using a known pulverizer (e.g., a ball mill), 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 a method such as that described in JP 2019-38728 A. From the viewpoint of reducing the environmental load, it is also preferable to use, as the silica, silica obtained by extracting silicic acid components from scraps of silicon wafers, which are raw materials for semiconductors, glass bottles, etc., and recycling the extracted silica for use in the production.

[0196] The silica (B) preferably has a CTAB (cetyltrimethylammonium bromide) specific surface area of 50 m 2 / g~350m 2 / g. The CTAB specific surface area of silica is 50m 2 / g or more, the abrasion resistance is further improved, and the CTAB specific surface area of the silica is 350m 2 / g or less, the rolling resistance will be small.

[0197] The silica (B) has a nitrogen adsorption specific surface area (BET method) of 80 m 2 / g or more 330m 2 The nitrogen adsorption specific surface area (BET method) of silica is preferably less than 80 m 2 When the silica has a nitrogen adsorption specific surface area (BET method) of 330 m / g or more, the tread rubber layer can be sufficiently reinforced, and the fuel efficiency of the tire can be further improved. 2 When the modulus of elasticity of the tread rubber layer is less than 1 / g, the wet grip performance of the tire is further improved. From the viewpoint of further reducing the rolling resistance and further improving the wear resistance of the tire, the nitrogen adsorption specific surface area (BET method) of the silica is 130 m 2 / g or more, and 150m 2 / g or more, and 170m 2 / g or more is preferable, and 180m 2 / g or more is preferable, and 190m 2 / g or more is preferable, and 195m 2 From the viewpoint of further improving the wet grip performance of the tire, the nitrogen adsorption specific surface area (BET method) of the silica is preferably 300 m 2 / g or less, and 2 / g or less is more preferable, and 270m 2 It is more preferable that the saturation coefficient is 1 / g or less.

[0198] The content of the silica (B) is preferably 20 parts by mass or more and less than 100 parts by mass per 100 parts by mass of the rubber component (A). By optimizing the amount of silica, wet grip performance, fuel economy, and abrasion resistance can be achieved at higher levels, and when the silica content is 20 parts by mass or more, sufficient wet grip performance, fuel economy, and abrasion resistance are obtained, while when the silica content is less than 100 parts by mass, deterioration of the low heat buildup properties and processability of the rubber composition can be suppressed. Therefore, when the silica content is 20 parts by mass or more but less than 100 parts by mass per 100 parts by mass of the rubber component, deterioration of the low heat buildup properties and processability can be suppressed while sufficient wet grip performance, fuel economy, and abrasion resistance are obtained. From the same viewpoint, the content of the silica is more preferably 40 parts by mass or more, more preferably 50 parts by mass or more, even more preferably 62 parts by mass or more, still more preferably 65 parts by mass or more, and particularly preferably 68 parts by mass or more, per 100 parts by mass of the rubber component (A). In addition, the content of the silica is more preferably 90 parts by mass or less, even more preferably 85 parts by mass or less, and particularly preferably 82 parts by mass or less, per 100 parts by mass of the rubber component.

[0199] (Carbon black (C)) The rubber composition for a tire of this embodiment contains carbon black (C), which reinforces the rubber composition and can improve the abrasion resistance of the rubber composition. The carbon black is not particularly limited, and examples thereof include GPF, FEF, HAF, ISAF, and SAF grade carbon black. These carbon blacks may be used alone or in combination of two or more. The carbon black may also be recycled carbon black.

[0200] In this specification, "recycled carbon black" refers to carbon black obtained by recovering raw materials that are waste materials that have been recycled. Examples of the waste materials that have been recycled include rubber products (particularly vulcanized rubber products) containing carbon black, such as used rubber and used tires, and waste oil. "Recycled carbon black" differs from carbon black that is produced directly from hydrocarbons such as petroleum and natural gas, i.e., non-recycled carbon black. Note that "used" here refers not only to carbon black that has been discarded after actual use, but also to carbon black that has been produced but discarded without actually being used.

[0201] As the carbon black (C), plant-derived carbon black and recycled carbon black are particularly preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Commercially available carbon blacks can be used, and examples of commercially available carbon blacks include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Birla Carbon Co., Ltd., and the like. These carbon blacks may be used alone or in combination of two or more.

[0202] The nitrogen adsorption specific surface area (N2SA) of the carbon black (C) 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 nitrogen adsorption specific surface area (N2SA) of carbon black is 20 m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable, and 200m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 / g or less is more preferable. In this specification, the nitrogen adsorption specific surface area (N2SA) of carbon black is determined according to JIS K 6217-2:2017 (ISO 4652:2012).

[0203] The content of the carbon black (C) is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component (A).

[0204] The content of silica in the total amount of the silica and the carbon black is preferably 80% by mass or more but less than 100% by mass, more preferably 85% by mass or more but less than 100% by mass, and even more preferably 90% by mass or more but less than 100% by mass. When the content of silica in the total amount of the silica and the carbon black is 80% by mass or more, it is possible to suppress a decrease in fuel efficiency performance due to an increase in carbon black, and when it is less than 100% by mass, it is possible to reliably ensure the reinforcing effect of carbon black.

[0205] In the rubber composition for tires of this embodiment, in addition to the above-mentioned silica (B) and carbon black (C), other inorganic compounds represented by the following formula (I), for example, can also be used as fillers. nM xSiO y zH2O (I) (In the formula, M represents at least one metal selected from the group consisting of Al, Mg, Ti, Ca, and Zr, oxides or hydroxides of these metals, hydrates thereof, and carbonates of these metals; and n, x, y, and z represent an integer of 1 to 5, an integer of 0 to 10, an integer of 2 to 5, and an integer of 0 to 10, respectively.) When the filler contains other inorganic compounds, the content thereof is preferably about 5 to 30 parts by mass per 100 parts by mass of the rubber component (A).

[0206] Examples of inorganic compounds of the above formula (I) include alumina (Al2O3) such as γ-alumina and α-alumina; alumina monohydrate (Al2O3·H2O) such as boehmite and diaspore; aluminum hydroxide [Al(OH)3] such as gibbsite and bayerite; aluminum carbonate [Al2(CO3)3], magnesium hydroxide [Mg(OH)2], magnesium oxide (MgO), magnesium carbonate (MgCO3), talc (3MgO·4SiO2·H2O), attapulgite (5MgO·8SiO2·9H2O), titanium dioxide (TiO2), titanium black (TiO 2n-1 ), calcium oxide (CaO), calcium hydroxide [Ca(OH)2], magnesium aluminum oxide (MgO·Al2O3), clay (Al2O3·2SiO2), kaolin (Al2O3·2SiO2·2H2O), pyrophyllite (Al2O3·4SiO2·H2O), bentonite (Al2O3·4SiO2·2H2O), aluminum silicate (Al2SiO5, Al4·3SiO4·5H2O, etc.), magnesium silicate (Mg2SiO4, MgSiO3, etc.), ke Examples include calcium silicate (Ca2SiO4, etc.), calcium aluminum silicate (Al2O3·CaO·2SiO2, etc.), calcium magnesium silicate (CaMgSiO4), calcium carbonate (CaCO3), zirconium oxide (ZrO2), zirconium hydroxide [ZrO(OH)2·nH2O], zirconium carbonate [Zr(CO3)2], and crystalline aluminosilicates containing hydrogen, alkali metals, or alkaline earth metals to compensate for the charge, such as various zeolites.

[0207] The total content of the filler, including the silica (B) and carbon black (C), is not particularly limited, but is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, per 100 parts by mass of the rubber component (A). It is also preferably 150 parts by mass or less, more preferably 140 parts by mass or less, and even more preferably 120 parts by mass or less. By optimizing the amount of filler, wet grip performance, fuel economy, and abrasion resistance can be achieved at higher levels. When the filler content is 20 parts by mass or more, sufficient wet grip performance, fuel economy, and abrasion resistance can be obtained. When the filler content is 150 parts by mass or less, deterioration of low heat generation and processability can be suppressed.

[0208] (Resin (D)) The rubber composition for a tire of this embodiment preferably further contains a resin (D). By blending the resin (D) into the rubber composition, the elastic modulus of the rubber composition is improved, and a tire using the rubber composition can achieve both steering stability on dry road surfaces and wet grip performance.

[0209] The content of the resin (D) is preferably 1 to 50 parts by mass, and more preferably 5 to 30 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the resin (D) is 1 part by mass or more per 100 parts by mass of the rubber component (A), the wet grip performance of a tire using the rubber composition is further improved, and when the content is 50 parts by mass or less, a decrease in the elastic modulus of the rubber composition is more easily suppressed. Therefore, when the content of the resin (D) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A), the wet grip performance of a tire using the rubber composition can be further improved.

[0210] Examples of the resin (D) include C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins, and at least one selected from C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, rosin resins, and alkylphenol resins is preferred. When the resin (D) contains at least one of C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins, the wet grip performance of tires using the rubber composition can be further improved. The resin (D) may be used alone or in combination of two or more.

[0211] Among the resins (D), C5 resins, C5-C9 resins, and C9 resins are particularly preferred from the viewpoint of wet grip performance of tires. C5-C9 resins and C9 resins are highly effective in increasing the elastic modulus of the rubber composition in a low strain range and decreasing the elastic modulus of the rubber composition in a high strain range, and can further improve the wet grip performance of tires. Among the resins (D), terpene resins and rosin resins are particularly preferred from the viewpoint of reducing the environmental impact. Terpene resins and rosin resins are naturally derived, sustainable resins, and therefore can further reduce the environmental impact and further improve tire performance, such as grip performance on various road surface conditions, including dry roads, wet roads, snow-covered roads, and icy roads.

[0212] Resin (D) may be modified to introduce a functional group that interacts with fillers such as carbon black and silica. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups.

[0213] The C5 resin refers to a C5 synthetic petroleum resin, and examples of the C5 resin include aliphatic petroleum resins obtained by polymerizing a C5 fraction obtained by thermal cracking of naphtha in the petrochemical industry using a Friedel-Crafts catalyst such as AlCl3 or BF3. The C5 fraction typically includes 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. As the C5 resin, commercially available products can be used, and examples thereof include the "ESCOLETZ (registered trademark) 1000 series" aliphatic petroleum resins manufactured by ExxonMobil Chemical Corporation, "A100, B170, M100, R100" of the "QUINTONE (registered trademark) 100 series" aliphatic petroleum resins manufactured by Zeon Corporation, and "T-REZ RA100" manufactured by Tonen Chemical Industry Co., Ltd.

[0214] The C5-C9 resin refers to a C5-C9 synthetic petroleum resin. Examples of the C5-C9 resin include solid polymers obtained by polymerizing petroleum-derived C5 fractions and C9 fractions using a Friedel-Crafts catalyst such as AlCl3 or BF3. More specifically, examples include copolymers primarily composed of styrene, vinyltoluene, α-methylstyrene, indene, etc. As the C5-C9 resin, a resin with a low content of C9 or higher components is preferred from the viewpoint of compatibility with rubber components. Here, "low content of C9 or higher components" refers to a resin in which the content of C9 or higher components in the total resin is less than 50% by mass, preferably 40% by mass or less. Commercially available C5-C9 resins include those sold under the trade name "Quinton (registered trademark) G100B" (manufactured by Zeon Corporation), "ECR213" (manufactured by ExxonMobil Chemical Corporation), and "T-REZ RD104" (manufactured by Tonen Chemical Industry Co., Ltd.).

[0215] The C9 resin is a resin obtained by polymerizing aromatic compounds having 9 carbon atoms, the main monomers of which are vinyltoluene, alkylstyrene, and indene, which are C9 fractions by-produced together with petrochemical base materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. Specific examples of the C9 fraction obtained by thermal decomposition of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. The C9 resin is obtained by polymerizing aromatic compounds having 9 carbon atoms, the main monomers being vinyltoluene, alkylstyrene, and indene, which are C9 fractions by-produced together with petrochemical base materials such as ethylene and propylene by thermal decomposition of naphtha in the petrochemical industry. Specific examples of the C9 fraction obtained by thermal decomposition of naphtha include vinyltoluene, α-methylstyrene, β-methylstyrene, γ-methylstyrene, o-methylstyrene, p-methylstyrene, and indene. The C9 resin is obtained by polymerizing aromatic compounds having 9 carbon atoms, such as styrene and C8 fractions, together with the C9 fraction. 10 The fractions methylindene, 1,3-dimethylstyrene, etc., as well as naphthalene, vinylnaphthalene, vinylanthracene, p-tert-butylstyrene, etc. are used as raw materials, and these C8 to C 10The C9 resin can be obtained by copolymerizing the fractions as a mixture with, for example, a Friedel-Crafts catalyst. The C9 resin may also be a modified petroleum resin modified with a compound having a hydroxyl group, an unsaturated carboxylic acid compound, or the like. Commercially available C9 resins can be used. Examples of unmodified C9 petroleum resins include those under the trade names "Nippon Oil Neopolymer (registered trademark) L-90," "Nippon Oil Neopolymer (registered trademark) 120," "Nippon Oil Neopolymer (registered trademark) 130," and "Nippon Oil Neopolymer (registered trademark) 140" (manufactured by JX Nippon Oil & Energy Corporation).

[0216] The dicyclopentadiene resin is a petroleum resin produced primarily from dicyclopentadiene obtained by dimerizing cyclopentadiene. Commercially available dicyclopentadiene resins are available, including, for example, alicyclic petroleum resins manufactured by Zeon Corporation under the trade name Quinton (registered trademark) 1000 Series (product names: 1105, 1325, and 1340).

[0217] The terpene phenol resin can be obtained, for example, by reacting terpenes with various phenols using a Friedel-Crafts catalyst or by further condensing them with formalin. The terpenes used as raw materials are not particularly limited, but monoterpene hydrocarbons such as α-pinene and limonene are preferred, with α-pinene being more preferred, and α-pinene being particularly preferred. Commercially available terpene phenol resins include those sold under the trade names "Tamanol 803L" and "Tamanol 901" (manufactured by Arakawa Chemical Industries, Ltd.), and those sold under the trade names "YS Polystar® U" series, "YS Polystar® T" series, "YS Polystar® S" series, "YS Polystar® G" series, "YS Polystar® N" series, "YS Polystar® K" series, and "YS Polystar® TH" series (manufactured by Yasuhara Chemical Co., Ltd.).

[0218] The terpene resin is a solid resin obtained by blending turpentine oil, which is obtained simultaneously when rosin is obtained from pine trees, or a polymerization component separated from the turpentine oil, and polymerizing the blend using a Friedel-Crafts catalyst, and examples of the terpene resin include β-pinene resin and α-pinene resin. Commercially available terpene resins can be used, and examples include the "YS Resin" series (PX-1250, TR-105, etc.) manufactured by Yasuhara Chemical Co., Ltd. and the "Picolite" series (A115, S115, etc.) manufactured by Hercules.

[0219] The rosin resin is the residue remaining after collecting balsams such as pine resin (pine tar), which is the sap of plants in the Pinaceae family, and distilling turpentine essential oil. It is a natural resin whose main component is rosin acid (abietic acid, palustric acid, isopimaric acid, etc.), as well as modified and hydrogenated resins obtained by modifying, hydrogenating, or otherwise processing these. Examples of rosin resin include natural resin rosin, its polymerized rosin, and partially hydrogenated rosin; glycerin ester rosin, its partially hydrogenated rosin, fully hydrogenated rosin, and polymerized rosin; pentaerythritol ester rosin, its partially hydrogenated rosin, and polymerized rosin. Natural resin rosins include gum rosin, tall oil rosin, and wood rosin, which are contained in raw pine resin and tall oil. The rosin resin may be a commercially available product, such as "Neotol 105" (manufactured by Harima Chemical Co., Ltd.), "SN Tack 754" (manufactured by San Nopco Ltd.), "Lime Resin No. 1," "Pensel A," and "Pensel AD" (manufactured by Arakawa Chemical Industries, Ltd.), "Polypale" and "Pentalin C" (manufactured by Eastman Chemical Co., Ltd.), or "Hi-Rosin (registered trademark) S" (manufactured by Taisho Matsu Oil Co., Ltd.).

[0220] The alkylphenol resin can be obtained, for example, by condensation of alkylphenol and formaldehyde in the presence of a catalyst. Commercially available alkylphenol resins include those sold under the trade names "Hitanol 1502P" (an alkylphenol formaldehyde resin, manufactured by Hitachi Chemical Co., Ltd.), "Tackirol 201" (an alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-I" (a brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), "Tackirol 250-III" (a brominated alkylphenol formaldehyde resin, manufactured by Taoka Chemical Co., Ltd.), and "R7521P," "SP1068," "R7510PJ," "R7572P," and "R7578P" (manufactured by SI Group Inc.).

[0221] -Hydrogenated resin- The resin (D) is preferably at least partially hydrogenated, which further controls the mobility of the rubber component (A) and further improves the hysteresis loss (tan δ) in the low temperature range, thereby further improving the wet grip performance of a tire using the rubber composition.

[0222] The resin (D) preferably has a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol. By applying a rubber composition containing such resin (D) to a tire, the wear resistance of the tire can be further improved. Here, the softening point of the resin (D) is measured in accordance with JIS-K2207-1996 (ring and ball method). The weight average molecular weight of the resin (D) is measured by gel permeation chromatography (GPC) and calculated as a polystyrene equivalent value.

[0223] If the softening point of the resin (D) is higher than 110°C, the tire to which the rubber composition is applied can be sufficiently reinforced, and the wear resistance can be further improved. From the viewpoint of the wear resistance of the tire, the softening point of the resin (D) is 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. Furthermore, from the viewpoint of processability, the softening point of the resin (D) 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.

[0224] When the weight average molecular weight of the resin (D) in terms of polystyrene is 200 g / mol or more, the resin component is less likely to precipitate from the tire, and the effects of the resin (D) can be fully exhibited. When the weight average molecular weight is 1600 g / mol or less, the resin (D) is easily compatible with the rubber component (A). From the viewpoint of suppressing precipitation of the resin (D) from the tire and suppressing deterioration in the tire appearance, the polystyrene-equivalent weight average molecular weight of the resin (D) is preferably 500 g / mol or more, more preferably 550 g / mol or more, even more preferably 600 g / mol or more, still more preferably 650 g / mol or more, and still more preferably 700 g / mol or more. Furthermore, from the viewpoint of improving the compatibility of the resin (D) with the rubber component (A) and further enhancing the effects of the resin (D), the polystyrene-equivalent weight average molecular weight of the resin (D) is more preferably 1570 g / mol or less, more preferably 1530 g / mol or less, more preferably 1500 g / mol or less, more preferably 1470 g / mol or less, more preferably 1430 g / mol or less, more preferably 1400 g / mol or less, more preferably 1370 g / mol or less, more preferably 1330 g / mol or less, more preferably 1300 g / mol or less, more preferably 1200 g / mol or less, more preferably 1100 g / mol or less, more preferably 1000 g / mol or less, and even more preferably 950 g / mol or less.

[0225] The weight average molecular weight (Mw HR ) (unit: g / mol) of the resin (D) versus the softening point (Ts HR ) (unit: °C) ratio (Ts HR / Mw HR ) is preferably 0.07 or more, more preferably 0.083 or more, more preferably 0.095 or more, more preferably 0.104 or more, more preferably 0.125 or more, more preferably 0.135 or more, more preferably 0.14 or more, and even more preferably 0.141 or more. HR / Mw HR) is preferably 0.25 or less, more preferably 0.24 or less, more preferably 0.23 or less, more preferably 0.19 or less, more preferably 0.18 or less, and even more preferably 0.17 or less. The softening point and polystyrene-equivalent weight average molecular weight of the resin (D) can be determined by the method described in the examples below.

[0226] The above-mentioned at least partially hydrogenated resin means a resin obtained by reducing and hydrogenating a resin. Examples of resins that can be used as raw materials for the hydrogenated resin include the above-mentioned C5 resins, C5-C9 resins, C9 resins, dicyclopentadiene resins, terpene phenol resins, terpene resins, rosin resins, and alkylphenol resins. These resins may be used alone or in combination of two or more.

[0227] Furthermore, the resin that is the raw material for the hydrogenated resin may contain, for example, a resin obtained by copolymerizing a C5 fraction with dicyclopentadiene (DCPD) (C5-DCPD-based resin). Here, if the dicyclopentadiene-derived component is 50% by mass or more of the total resin, the C5-DCPD resin is considered to be included in the dicyclopentadiene resin. If the dicyclopentadiene-derived component is less than 50% by mass of the total resin, the C5-DCPD resin is considered to be included in the C5 resin. The same applies to cases where a small amount of a third component is also contained.

[0228] From the viewpoints of increasing the compatibility between the rubber component (A) and the resin (D), further improving the wet grip performance of a tire using the rubber composition, and further reducing rolling resistance, the resin (D) is preferably at least one selected from the group consisting of hydrogenated C5 resins, hydrogenated C5-C9 resins, hydrogenated dicyclopentadiene resins (hydrogenated DCPD resins), and hydrogenated terpene resins, more preferably at least one selected from the group consisting of hydrogenated C5 resins and hydrogenated C5-C9 resins, and even more preferably a hydrogenated C5 resin. Furthermore, the resin is preferably a resin having a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least one monomer.

[0229] (Silane coupling agent) The rubber composition for a tire of this embodiment preferably contains a silane coupling agent to improve the effect of the silica (B). The inclusion of the silane coupling agent in the rubber composition improves the dispersibility of the silica (B) contained as a filler, contributing to achieving wet grip performance, fuel economy, and abrasion resistance at the same time.

[0230] The silane coupling agent preferably contains at least (1) a silane coupling agent having a thiol group and (2) a silane coupling agent having a sulfide bond. (1) The silane coupling agent having a thiol group is highly effective in increasing the dispersibility of the silica (B) described above, but if the content is high, it may cause discoloration such as the occurrence of black luster on the tire over time. Therefore, by further including a silane coupling agent having a sulfide bond (2) as the silane coupling agent and adjusting the content of this silane coupling agent, it becomes possible to suppress discoloration such as black luster while achieving both wet grip performance of the tire and low fuel consumption and wear resistance (excellent discoloration resistance).

[0231] Here, the total content of the (1) silane coupling agent having a thiol group and the (2) silane coupling agent having a sulfide bond is preferably more than 1 part by mass and not more than 15 parts by mass per 100 parts by mass of the silica (B). When the total content of the silane coupling agents exceeds 1 part by mass per 100 parts by mass of the silica (B), wet grip performance of the tire can be sufficiently achieved along with fuel economy and wear resistance, and when the total content of the silane coupling agents is 15 parts by mass or less per 100 parts by mass of the silica (B), discoloration resistance can be sufficiently ensured. From the same viewpoint, the total content of the (1) silane coupling agent having a thiol group and the (2) silane coupling agent having a sulfide bond is preferably 2 to 14 parts by mass, more preferably 3 to 13 parts by mass, and even more preferably 5 to 12 parts by mass, relative to 100 parts by mass of the silica (B).

[0232] The content of the (1) silane coupling agent having a thiol group is 1 to 10 parts by mass relative to 100 parts by mass of the silica (B). When the content of the (1) silane coupling agent having a thiol group is 1 part by mass or more relative to 100 parts by mass of the silica (B), wet grip performance of the tire can be sufficiently achieved in combination with fuel economy and wear resistance, and when the content of the (1) silane coupling agent having a thiol group is 10 parts by mass or less relative to 100 parts by mass of the silica (B), discoloration resistance can be sufficiently ensured. From the same viewpoint, the content of the (1) silane coupling agent having a thiol group is preferably 2 to 9.5 parts by mass, more preferably 3 to 9 parts by mass, relative to 100 parts by mass of the silica (B). The content of the (2) silane coupling agent having a sulfide bond is appropriately selected within a range in which the content of the (1) silane coupling agent having a thiol group is 1 to 10 parts by mass per 100 parts by mass of the silica (B), and the total content of the (1) silane coupling agent having a thiol group and the (2) silane coupling agent having a sulfide bond is 15 parts by mass or less per 100 parts by mass of the silica (B). For example, the content of the (2) silane coupling agent having a sulfide bond is preferably 0.5 to 9.5 parts by mass, more preferably 1 to 9 parts by mass per 100 parts by mass of the silica (B).

[0233] Furthermore, from the viewpoint of achieving a good balance between wet grip performance, fuel economy, and abrasion resistance of the tire, as well as the effect of discoloration resistance, it is preferable that the mass ratio of the content of the silane coupling agent having a sulfide bond (2) to the content of the silane coupling agent having a thiol group ((2) silane coupling agent having a sulfide bond / (1) silane coupling agent having a thiol group) is 0.3 or more and less than 3.0. When the mass ratio of the silane coupling agents ((2) silane coupling agent having a sulfide bond / (1) silane coupling agent having a thiol group) is 0.3 or more, the effect of discoloration resistance is more reliably obtained, and when the mass ratio of the silane coupling agents ((2) silane coupling agent having a sulfide bond / (1) silane coupling agent having a thiol group) is less than 3.0, the compatibility of wet grip performance, fuel economy, and abrasion resistance is more reliably achieved. From the same viewpoint, the mass ratio of the silane coupling agents ((2) silane coupling agent having a sulfide bond / (1) silane coupling agent having a thiol group) is preferably 0.31 or more and 3.0 or less, and more preferably 0.32 or more and 2.9 or less.

[0234] The (1) silane coupling agent having a thiol group is not particularly limited as long as it has a thiol group (—SH). For example, (1) silane coupling agents having a thiol group include 3-(trimethoxysilyl)-1-propanethiol, 3-(triethoxysilyl)-1-propanethiol, 3-(methyldimethoxysilyl)-1-propanethiol, 2-(trimethoxysilyl)-1-ethanethiol, 2-(triethoxysilyl)-1-ethanethiol, 2-(methyldimethoxysilyl)-1-ethanethiol, (trimethoxysilyl)methanethiol, (triethoxysilyl)methanethiol, (methyldimethoxysilyl)methanethiol, 3-[ethoxybis(3,6,9,12,15-pentaoxaoctacosan-1-yloxy)silyl]-1-propanethiol {manufactured by Evonik Degussa, trade name "Si363"; [C 13 H 27 O(CH2CH2O)5]2(CH3CH2O)Si(CH2)3SH}.

[0235] Furthermore, among the above-mentioned silane coupling agents, the (1) thiol group-containing silane coupling agent preferably has a carbon number of 20 to 75. This is because when the silane coupling agent having a thiol group has a carbon number of 20 to 75, wet grip performance, fuel economy, and wear resistance of the tire can be more reliably achieved at the same time.

[0236] The silane coupling agent (2) having a sulfide bond is not particularly limited as long as it has a sulfide bond (-S-). In addition, the sulfide bond may be a polysulfide bond [-(S) n -, where n is a natural number of 2 or more)], but this excludes -SH in which hydrogen is directly bonded to sulfur (ie, the above-mentioned thiol group). For example, (2) silane coupling agents having a sulfide bond include bis(3-triethoxysilylpropyl) tetrasulfide, bis(3-triethoxysilylpropyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) tetrasulfide, bis(3-trimethoxysilylpropyl) tetrasulfide, bis(2-trimethoxysilylethyl) tetrasulfide, and 3-triethoxysilylpropyl-N,N-dimethylsilyl. thiocarbamoyl 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, and the like.

[0237] Bioethanol can also be used as a raw material for silane coupling agents. Bioethanol is produced primarily from sugars and / or cellulose as biological resources, preventing the effective use of other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources as the biological resource-derived monomer component, or to use a combination of a monomer component derived from a biological resource, a monomer component derived from a renewable resource, and a monomer component derived from a fossil resource. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0238] (rubber powder) The rubber composition for tires of this embodiment preferably also contains rubber crumb. The rubber crumb may be obtained by pulverizing used rubber products such as used tires and, if desired, removing reinforcing materials such as steel and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for the purpose of producing rubber crumb and pulverizing the pulverized rubber. For example, rubber crumb can be obtained from vulcanized rubber by the method described in "Rubber Chemistry and Technology." The process of pulverizing vulcanized rubber to obtain rubber crumb may involve mechanical processing or low-temperature processing. For example, in mechanical processing, various crushing devices such as a cracker mill or granulator can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature processing, the finely chopped vulcanized rubber is frozen at a cryogenic temperature and then crushed into fine particles. A magnetic separator or the like can be used to remove steel, and an air separator or the like can be used to remove fibers. The rubber crumb may also be commercially available, including 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 types.

[0239] The composition of the rubber crumb is not particularly limited and depends on the composition of the vulcanized rubber from used rubber products (used tires) or the like that serve as the raw material. In one embodiment, the rubber crumb contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber crumb may be the same as or different from the rubber component (A), carbon black, silica, etc. contained in the rubber composition of this embodiment described above.

[0240] The volume average particle diameter of the rubber powder is 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 diameter 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.

[0241] The rubber powder preferably has a 60-mesh sieve residue of less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit. Also, the rubber powder preferably has an 80-mesh sieve residue of less than 10% by mass, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0242] The rubber powder preferably has an acetone extractable content of 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, 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 refers to the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0243] The content of the rubber crumb is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component is applied, the tire components, the target performance, etc. For example, the content of the rubber crumb is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, 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, still 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 (A).

[0244] (liquid softener) The rubber composition for a tire of this embodiment may contain a liquid softener. Here, the "liquid softener" refers to 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.

[0245] The oil is a general term for extender oils contained in rubber components and liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, and mixtures thereof. From the perspective of reducing environmental impact, vegetable oils and recycled oils are preferred. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil. Examples of process oils include paraffin-based process oils, aromatic process oils, and naphthenic process oils. The oil may be a commercially available product, such as products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0246] The liquid polymer is preferably a liquid diene-based polymer. Examples of the liquid diene-based polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or their terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0247] The content of the liquid softener is not particularly limited and can be adjusted appropriately 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, still 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 (A).

[0248] (anti-aging agent) The rubber composition for a tire according to the present embodiment may contain an antioxidant, such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), or 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Commercially available products can be used as the antioxidant, and examples of commercially available antioxidants that can be used include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis Co., Ltd., etc. These antioxidants may be used alone or in combination of two or more.

[0249] The content of the antioxidant is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the antioxidant is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0250] (wax) The rubber composition for a tire of this embodiment may contain a wax. Examples of the wax include natural waxes such as vegetable wax and animal wax; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available waxes can be used, and examples of commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0251] The content of the wax is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the 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, per 100 parts by mass of the rubber component (A).

[0252] (stearic acid) The rubber composition for a tire of this embodiment may contain stearic acid. Commercially available stearic acid can be used, and examples of commercially available stearic acid include products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. These commercially available stearic acid products may be used alone or in combination of two or more.

[0253] The content of stearic acid is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0254] (zinc oxide) The rubber composition for a tire of this embodiment may contain zinc oxide (zinc white). The zinc oxide is preferably obtained not only from zinc metal but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available zinc oxide products can be used, including those from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0255] The content of the zinc oxide is not particularly limited and can be adjusted appropriately 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 (A).

[0256] (sulfur) The rubber composition for tires of this embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or sulfur obtained by processing biological resource-derived materials. From the perspective of reducing environmental impact, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of methods for obtaining sulfur from waste derived from biological resources include the method described in the aforementioned Japanese Patent Application No. 2022-140390. The sulfur may also be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, and the like, which are commonly used as crosslinking agents in the rubber industry. Commercially available sulfur products are available, including those from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., and Flexis Corporation. These sulfurs may be used alone or in combination of two or more.

[0257] The sulfur content is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the 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, more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0258] (Vulcanization accelerator) The rubber composition for a tire of this embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, recycled resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing environmental impact. Vulcanization accelerators derived from biological resources can be obtained, for example, by the method disclosed in JP 2005-139239 A. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; 1,3-diphenylguanidine (DPG), 1,3-diphenylguanidine (DPG), and 1,3-diphenylguanidine (DPG). Examples of suitable vulcanization accelerators include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available vulcanization accelerators can be used, including those from Ouchi Shinko Chemical Industry Co., Ltd. and Sumitomo Chemical Co., Ltd. These vulcanization accelerators can be used alone or in combination of two or more.

[0259] The content of the vulcanization accelerator is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the vulcanization accelerator is applied, the tire components, the target performance, etc. For example, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5.5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0260] (Cellulose nanofiber) The rubber composition for a tire according to this embodiment may contain cellulose nanofibers (CNF). The cellulose nanofibers can reinforce a 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 approximately 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 observation of 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 or defibration treatment.

[0261] 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 (e.g., unbleached softwood kraft pulp (NUKP), bleached softwood kraft pulp (NBKP), unbleached hardwood kraft pulp (LUKP), bleached hardwood kraft pulp (LBKP), bleached kraft pulp (BKP), unbleached softwood sulfite pulp (NUSP), bleached softwood 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.

[0262] The content of the cellulose nanofibers is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of the cellulose nanofibers is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 70 parts by mass, and even more preferably in the range of 10 to 40 parts by mass, per 100 parts by mass of the rubber component (A).

[0263] (porous cellulose particles) The rubber composition for a tire of this embodiment 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 a rubber composition, performance on ice can be improved. When the porosity of the porous cellulose particles is 75% or more, the effect of improving 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 sample (i.e., porous cellulose particles) with a measuring cylinder, determining 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.

[0264] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, an average particle size of 1000 μm or less is preferred. The lower limit of the average particle size is not particularly limited, but it is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm. The porous cellulose particles are preferably spherical particles with a major axis / minor axis ratio of 1 to 2. The use of particles with such a spherical structure improves dispersibility in the rubber composition, contributing to improved performance on ice and maintenance of abrasion resistance, etc. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and the ratio of major axis to minor axis of the porous cellulose particles are determined as follows: The porous cellulose particles are observed under a microscope to obtain an image, and the images are used to measure the major axis and minor axis of 100 particles (when the major axis and minor axis are the same, the length in a certain axis direction and the length in an axis direction perpendicular to the major axis) and calculate the average value to obtain the average particle size, and the ratio of major axis to minor axis is obtained by averaging the values obtained by dividing the major axis by the minor axis.

[0265] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopearl" and are also described in JP-A Nos. 2001-323095 and 2004-115284, and can be suitably used.

[0266] 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 composition 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 mass, and even more preferably in the range of 3 to 15 parts by mass, per 100 parts by mass of the rubber component (A).

[0267] (solid fine particles) The rubber composition for a tire according to this embodiment may contain solid fine particles. Blending the solid fine particles into the rubber composition can improve performance on ice. The solid fine particles preferably have an average particle diameter of 1 μm or more, preferably 1000 μm or less, and more preferably 300 μm or less. Examples of the solid fine particles include plant-derived powders obtained from plants, such as rice husks, walnut flour, and walnut shells; animal-derived powders obtained from animals, such as eggshells (eggshell powder) and bone meal; 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 lignosulfonic acid; and non-metallic fibers, such as glass fiber. Among these, rice husks, walnut shells, eggshells, and whitebait are preferred.

[0268] 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, the tire components, the 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 mass, and even more preferably in the range of 3 to 15 parts by mass, per 100 parts by mass of the rubber component (A).

[0269] (others) In addition to the above-mentioned components, the rubber composition for tires of this embodiment may further contain various additives commonly used in the tire industry, such as organic peroxides. The content of these additives is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which they are applied, the tire components, the target performance, etc. For example, the content is preferably in the range of 0.1 to 200 parts by mass per 100 parts by mass of the rubber component (A).

[0270] (Method of manufacturing rubber composition) The method for producing the rubber composition for tires of the present embodiment is not particularly limited, but can be produced, for example, by blending various components appropriately selected as necessary with the rubber component (A), followed by kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0271] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0272] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roller typically used for heat-in of a rubber composition.

[0273] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0274] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of vulcanization apparatus include a molding vulcanizer using a mold used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0275] (Application) The rubber composition for a tire of the present embodiment can be applied to various constituent parts of a tire, such as a tread (cap tread, base tread, undertread), cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, insulation, chafer, inner liner, etc., and can also be used as a side reinforcing layer of a run-flat tire, etc.

[0276] <Tread rubber> The tread rubber of this embodiment is characterized by being made of the above-mentioned rubber composition for tires. The tread rubber of this embodiment is made of the above-mentioned rubber composition for tires, and therefore has a high proportion of sustainable materials, and can promote a reduction in the environmental impact of the entire process of producing, using, and disposing of synthetic rubber. Therefore, by applying the tread rubber of this embodiment to tires, it is possible to increase the proportion of sustainable materials in the tire, and can promote a reduction in the environmental impact of the entire process of producing, using, and disposing of synthetic rubber.

[0277] The tread rubber of this embodiment may be applied to a new tire or a retread tire. The tread rubber of this embodiment may be applied to a pneumatic tire or a non-pneumatic tire.

[0278] <Tires> The tire of this embodiment is characterized by including the above-mentioned tread rubber. The tire of this embodiment includes the above-mentioned tread rubber, and therefore the proportion of sustainable materials is increased, and the manufacturing, use, and disposal of synthetic rubber can promote a reduction in the environmental impact as a whole. Furthermore, the tire of this embodiment does not impair performance.

[0279] Next, one embodiment of the tire of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire 1 of this embodiment shown in Fig. 1 has a pair of bead portions 2, a pair of sidewall portions 3, and a tread portion 4 continuous with both sidewall portions 3, and is equipped with a carcass 5 extending in a toroidal shape between the pair of bead portions 2 to reinforce these portions 2, 3, and 4, and a belt 6 disposed on the radially outer side of the crown portion of the carcass 5.

[0280] The carcass 5 of the tire 1 shown in FIG. 1 is composed of one carcass ply made of a plurality of parallel-arranged cords covered with a coating rubber, and the carcass 5 is composed of a main body portion extending in a toroidal shape between the bead cores 7 respectively embedded in the bead portions 2, and turned-up portions wound up radially outward around each bead core 7 from the inner side toward the outer side in the tire width direction, but the number of plies and structure of the carcass 5 in the tire of the present invention are not limited to this.

[0281] 1 is composed of two belt layers 6A and 6B, but in the tire of the present invention, the number of belt layers constituting the belt 6 is not limited to this and the number of belt layers may be three or more. Here, the belt layers 6A and 6B are usually composed of rubberized layers of cords (preferably steel cords) extending at an angle with respect to the tire equatorial plane, and the two belt layers 6A and 6B are laminated to constitute the belt 6 such that the cords constituting the belt layers 6A and 6B cross each other with the tire equatorial plane in between.

[0282] The tire 1 of this embodiment has tread rubber 8 on the outermost surface of the tread portion 4, and the above-described rubber composition for a tire of this embodiment is used for the tread rubber 8. Therefore, the tire 1 of this embodiment has an improved proportion of sustainable materials.

[0283] The tire of the present invention may have a tread rubber made of the rubber composition for a tire according to the present embodiment, and various modifications may be made to the tire. For example, a belt reinforcing layer may be disposed on the radially outer side of the belt 6 of the tire 1 shown in Fig. 1, or the tread rubber 8 may be divided into a cap rubber located on the outermost side and a base rubber located on the radially inner side of the cap rubber.

[0284] The tire of this embodiment can be manufactured by a conventional method using the above-mentioned rubber composition as the tread rubber. For example, depending on the type of tire to be applied, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. [Example]

[0285] 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.

[0286] <Analysis method for rubber components> The glass transition temperature (Tg) and bound styrene content of the styrene-butadiene rubber were measured by the following methods.

[0287] (1) Glass transition temperature (Tg) The synthesized styrene-butadiene rubber was used as a sample, and a DSC curve was recorded using a TA Instruments DSC250 while heating from -100°C at 20°C / min under a helium flow of 50 mL / min. The peak top (inflection point) of the DSC differential curve was taken as the glass transition temperature.

[0288] (2) Bound styrene content The synthesized styrene-butadiene rubber was used as a sample. 100 mg of the sample was diluted to 100 mL with chloroform and dissolved to prepare a measurement sample. The amount of bound styrene (mass%) relative to 100 mass% of the sample was measured based on the amount of absorption of ultraviolet light by the phenyl group of styrene (near 254 nm). A Shimadzu UV-2450 spectrophotometer was used as the measurement device.

[0289] <Resin analysis method> The softening point and weight average molecular weight of the resin were measured by the following methods.

[0290] (3) Softening point The softening point of the resin was measured in accordance with JIS-K2207-1996 (ring and ball method).

[0291] (4) Weight average molecular weight The average molecular weight of the resin was measured by gel permeation chromatography (GPC) under the following conditions, and the weight average molecular weight in terms of polystyrene was calculated. Column temperature: 40℃ ·Injection volume: 50μL Carrier and flow rate: Tetrahydrofuran 0.6mL / min Sample preparation: Dissolve approximately 2.5 mg of resin in 10 mL of tetrahydrofuran.

[0292] <Preparation and Evaluation of Rubber Compositions> The rubber compositions of the examples and comparative examples were prepared by blending and kneading the components according to the formulation shown in Table 1. The blending amounts of the rubber components shown in Table 1 are listed as values including the amount of oil extension. The blending parts of other components are listed to two significant digits.

[0293] (5) Sustainable material ratio For each rubber composition obtained, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) is calculated to calculate the sustainable material ratio. The results are shown in Table 1. The larger the value, the better the effect.

[0294] [Table 1]

[0295] *1 Low Tg modified SBR-1: Modified styrene-butadiene rubber (modified SBR) synthesized using the following method, glass transition temperature (Tg) = -65°C *2 Low Tg modified SBR-2: Modified styrene-butadiene rubber (modified SBR) supplied using the mass balance method of low Tg modified SBR-1, glass transition temperature (Tg) = -65°C, synthetic rubber derived from bio-based and / or circular raw materials using the mass balance method according to ISCC PLUS certification, the proportion of sustainable materials is 100% by mass, equivalent to sustainable materials. *3 High Tg unmodified SBR: ENEOS Materials, product name "HP755B", glass transition temperature (Tg) = -19°C, blending amount includes 37.5 parts by mass of oil added to 100 parts by mass of SBR. *4 Silica: Tosoh Silica Corporation, product name "Nipsil AQ" *5 Carbon black: Asahi Carbon Co., Ltd., product name "#80" *6 Inorganic filler: Aluminum hydroxide, manufactured by Showa Denko K.K., "Hijilite (registered trademark)" *7 Silane coupling agent-1: A silane coupling agent with a thiol group, manufactured by EVONIK, product name "Si 363" *8 Silane coupling agent-2: A silane coupling agent with a sulfide bond, manufactured by EVONIK, product name "S 2.5" *9 Hydrogenated C5 resin: Manufactured by Eastman, product name "Registered Trademark Impera E1780", softening point = 130℃, weight average molecular weight (Mw) = 909g / mol *10 Other ingredients: Total amount of stearic acid, oil, wax, antioxidant, zinc oxide, vulcanization accelerator, sulfur, retarder, and workability improver. In Comparative Example 1 and Example 1, all ingredients were blended in the same amounts.

[0296] (Synthesis of low Tg modified SBR-1(*1)) A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-purged 800 mL pressure-resistant glass vessel so that the total weight of the mixture was 67.5 g of 1,3-butadiene and 7.5 g of styrene. 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were then added, and polymerization was carried out at 50 °C for 1.5 hours. At this point, the polymerization reaction system reached a polymerization conversion rate of nearly 100%, and 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and the modification reaction was carried out at 50 °C for 30 minutes. The reaction was then terminated by adding 2 mL of a 5% by weight solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol. The mixture was then dried in the usual manner to obtain modified SBR. Measurement of the microstructure of the resulting modified SBR revealed that the bound styrene content was 10% by mass and the glass transition temperature (Tg) was -65°C.

[0297] From Table 1, it can be seen that the rubber compositions of the examples according to the present invention contain synthetic rubber supplied using the mass balance method, and therefore have an increased proportion of sustainable materials, and that by applying them to tires, the proportion of sustainable materials in the tires can be increased.

[0298] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is expected to be a technology that contributes to the achievement of "No. 13 - Take concrete measures against climate change." [Explanation of symbols]

[0299] 1: Tires 2: Bead part 3: Sidewall 4: Tread section 5: Carcass 6: Belt 6A, 6B: Belt layer 7: Bead core 8: Tread rubber

Claims

1. The rubber composition comprises a rubber component (A), silica (B), and carbon black (C), the rubber component (A) consists solely of synthetic rubber (A1), A rubber composition for tires, characterized in that the synthetic rubber (A1) contains a synthetic rubber (A1-1) supplied on a mass balance basis.

2. 2. The rubber composition for a tire according to claim 1, wherein the synthetic rubber (A1) comprises a synthetic rubber derived from at least one of plant-derived raw materials, plant-derived by-products, raw materials obtained by recycling plant-derived materials, and raw materials obtained by recycling fossil resource-derived materials.

3. 2. The rubber composition for a tire according to claim 1, wherein the synthetic rubber (A1) comprises 0.1 to 99% by mass of a synthetic rubber derived from biological resources and 1 to 99.9% by mass of a synthetic rubber derived from fossil resources.

4. 2. The rubber composition for a tire according to claim 1, wherein the synthetic rubber (A1) includes a styrene-butadiene rubber.

5. 5. The rubber composition for a tire according to claim 4, wherein the styrene-butadiene rubber is modified with a modifier having a nitrogen atom and a silicon atom.

6. The rubber composition for a tire according to claim 1 , further comprising a resin (D).

7. 7. The rubber composition for tires according to claim 6, wherein the content of the resin (D) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A).

8. A tread rubber comprising the rubber composition for tires according to any one of claims 1 to 7.

9. A tire comprising a tread rubber according to claim 8.

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