Rubber composition for tires, and tire

Abstract

The present invention addresses the problem of providing a rubber composition for tires which makes it possible to heighten the proportion of sustainable materials in tires. The rubber composition for tires comprises a rubber component (A), a filler (B), and a resin (C), and is characterized in that the rubber component (A) comprises two or more rubbers and the filler (B) includes plant-derived silica (B1) and has a content ratio of the plant-derived silica (B1) of 45 mass% or higher.

Description

Rubber composition for tires and tires

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

[0002] Conventionally, from the viewpoint of improving vehicle safety, various technologies have been studied to improve tire performance, such as grip performance on wet road surfaces as well as on dry road surfaces (hereinafter referred to as "wet grip performance"). Meanwhile, in connection with the recent global trend toward carbon dioxide emission regulations accompanying growing interest in environmental issues, there is an increasing demand for improved fuel economy in automobiles, and in order to meet such demands, there is a demand for improved fuel economy in tires (i.e., reduced rolling resistance).

[0003] In response to this, Patent Document 1 below proposes a rubber composition for tires that can provide tires with excellent wet grip performance and fuel efficiency (low loss), the rubber composition comprising a rubber component containing 50% by mass or more of at least one selected from styrene-butadiene rubber and polybutadiene rubber, a filler selected from carbon black and silica, and, per 100 parts by mass of the rubber component, 5 to 50 parts by mass of polybutene and 1 to 30 parts by mass of at least one phenolic resin selected from unmodified phenolic resins and modified phenolic resins, wherein the modified phenolic resin has a modifying group selected from a cyclic modifying group and an acyclic modifying group having 1 to 7 carbon atoms.

[0004] Japanese Patent Application Laid-Open No. 2019-218464

[0005] On the other hand, in recent years, from the viewpoint of social sustainability, there has been a demand for increasing the proportion of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, in various components used in tires. However, among the materials compounded in rubber compositions for tires, the use of sustainable materials for silica has not been considered until now.

[0006] Therefore, an object of the present invention is to provide a rubber composition for a tire that can increase the proportion of sustainable materials in the tire.A further object of the present invention is to provide a tire with an increased proportion of sustainable materials.

[0007] The rubber composition for a tire and the tire of the present invention that solve the above problems are outlined below.

[0008] [1] A rubber composition for a tire, comprising a rubber component (A), a filler (B), and a resin (C), wherein the rubber component (A) comprises two or more types of rubber, the filler (B) comprises plant-derived silica (B1), and a ratio of the plant-derived silica (B1) in the filler (B) is 45 mass% or more.

[0009] [2] The rubber composition for a tire according to [1], wherein the rubber component (A) contains an isoprene-skeleton rubber.

[0010] [3] The rubber composition for a tire according to [1] or [2], wherein the content of the resin (C) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A).

[0011] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the rubber component (A) contains a styrene-butadiene rubber.

[0012] [5] The rubber composition for a tire according to any one of [1] to [4], wherein the resin (C) is a hydrogenated resin having a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol.

[0013] [6] The rubber composition for a tire according to any one of [1] to [5], wherein the plant-derived silica (B1) is silica derived from a grass plant.

[0014] [7] The rubber composition for a tire according to [6], wherein the plant-derived silica (B1) is silica derived from rice husks.

[0015] [8] The rubber composition for a tire according to any one of [1] to [7], which is for use in a tire tread.

[0016] [9] A tire comprising a tread rubber made of the rubber composition for a tire according to any one of [1] to [8].

[0017] According to the present invention, it is possible to provide a rubber composition for a tire that can increase the proportion of sustainable materials in the tire. Also, according to the present invention, it is possible to provide a tire with an increased proportion of sustainable materials.

[0018] 1 is a cross-sectional view of one embodiment of a tire of the present invention.

[0019] The rubber composition for a tire and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0020] <Definitions> The compounds described herein may be derived in whole or in part from fossil resources, from biological resources such as plant resources, from recycled resources such as used tires, or from a mixture of two or more of fossil resources, biological resources, and recycled resources.

[0021] 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 a tire and tire.

[0022] In this specification, the term "biological resources (biomass resources)" refers to carbon-neutral organic resources derived from living organisms, and includes, for example, materials stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and is a resource excluding fossil resources (petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but are preferably non-edible in order not to compete with food and from the viewpoint of effective resource utilization.

[0023] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock excrement, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, etc.), and the like. Examples of biological resources include: corn oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc.), carbohydrate crops (corn, wheat, rice, rice husks, rice bran, old rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue left after sugarcane juicing), soybeans, soybean pulp refuse, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, and algae. The biological resources may also be processed (i.e., biological resource-derived substances). Examples of processing methods include biological processing methods utilizing the activity of microorganisms, plants, animals, and their tissue cultures; chemical processing methods utilizing acids, alkalis, catalysts, thermal energy, light energy, etc.; and physical processing methods such as pulverization, compression, microwave treatment, and electromagnetic wave treatment. The biological resources may also be extracted and purified from the biological resources or biological resources that have undergone the above-described processing (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the above-mentioned biological resources can also be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, with valine, leucine, isoleucine, arginine, and phenylalanine being preferred.The amino acids may be either L-amino acids or D-amino acids, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. Examples of the fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. Examples of the fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may contain various materials and impurities.

[0024] 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.

[0025] <Rubber Composition for Tire> The rubber composition for tire of this embodiment includes a rubber component (A), a filler (B), and a resin (C). The rubber composition for tire of this embodiment is characterized in that the rubber component (A) includes two or more types of rubber, the filler (B) includes plant-derived silica (B1), and the ratio of the plant-derived silica (B1) in the filler (B) is 45 mass% or more.

[0026] In the rubber composition for a tire of this embodiment, the plant-derived silica (B1) is a material derived from a biological resource (biomass resource), and the ratio of the plant-derived silica (B1) in the filler (B) is 45% by mass or more. Therefore, the rubber composition for a tire of this embodiment has a high ratio of sustainable materials. Therefore, by applying the rubber composition for a tire of this embodiment to a tire, it is possible to increase the ratio of sustainable materials in the tire. Note that in a rubber composition for a tire that includes a rubber component (A), a filler (B), and a resin (C), and the rubber component (A) includes two or more types of rubber, even if 45% by mass or more of the filler (B) is plant-derived silica (B1), performance such as wet grip performance (grip performance on wet road surfaces) and fuel efficiency (low loss) is not impaired.

[0027] (Rubber Component (A)) The rubber composition for a tire of this embodiment contains a rubber component (A), and the rubber component (A) provides rubber elasticity to the composition. The rubber component (A) preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. Here, the "sustainability rate" of the rubber component (A) refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in the rubber component (A).

[0028] The rubber component (A) is preferably the rubber derived from biological resources and the rubber derived from recycled resources. Here, the proportion of the monomer component derived from biological resources in 100 mol% of the monomer components constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may even be 100 mol%. Furthermore, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer components constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may even be 100 mol%.

[0029] 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 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 in terms of standard polystyrene based on measurements obtained using, for example, a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

[0030] The rubber component (A) is preferably a diene rubber, and the diene rubber is preferably an isoprene rubber or a butadiene rubber. Here, the isoprene rubber refers to a rubber containing units derived from isoprene as a monomer unit, and the butadiene rubber refers to a rubber containing units derived from butadiene as a monomer unit.

[0031] Examples of the isoprene-based rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). Examples of natural rubber (NR) that can be used include those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20). The origin of the natural rubber (NR) is not particularly limited, and examples include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of synthetic isoprene rubber (IR) are not particularly limited, and examples include those commonly used in the tire industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0032] The isoprene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve a sustainability rate within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.).

[0033] Examples of the butadiene-based rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene-based rubber, is preferably derived from biological resources or recycled resources.

[0034] 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.

[0035] Examples of the aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) include emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)) and solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)). In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, and divinylnaphthalene. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, SBR is preferred as the aromatic vinyl compound-butadiene copolymer rubber. The styrene may have a substituent. As the aromatic vinyl compound-butadiene copolymer rubber, commercially available products can be used, and examples of such commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Zeon Corporation, Sumitomo Chemical Co., Ltd. These aromatic vinyl compound-butadiene copolymer rubbers may be used alone or in combination of two or more.

[0036] The butadiene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve a sustainability rate within the above range, for example, a polymer synthesized using a bioresource-derived butadiene, a recycled resource-derived butadiene, a bioresource-derived aromatic vinyl compound (e.g., bioresource-derived styrene), or a recycled resource-derived aromatic vinyl compound (e.g., recycled resource-derived styrene) as a monomer component may be used. In this case, the synthesized polymer may be a homopolymer of a bioresource-derived monomer, a homopolymer of a recycled resource-derived monomer, a copolymer of a bioresource-derived monomer and a recycled resource-derived monomer, or a copolymer of a bioresource-derived monomer and / or a recycled resource-derived monomer and a fossil resource (e.g., petroleum)-derived monomer. Note that the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (for example, styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene or the like according to conventional methods, but also rubber obtained by reactions involving microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.") or enzymatic reactions.

[0037] In order to set the sustainability rate of the entire rubber component (A) within the above range, it is preferable to use natural rubber (NR) as the rubber component (A) or a polymer synthesized using a monomer component derived from a biological resource or a monomer component derived from a recycled resource as a monomer component.

[0038] Generally, the raw materials for rubber compositions for tires (e.g., rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment for their production, 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 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 tire-constituting materials, such as rubber, fillers, and steel cords. In addition, sulfur can be obtained from biological resources or processed products of biological resources by a method including a desulfurization step of desulfurizing biological resources or processed products of biological resources to remove sulfur-containing substances from the biological resources or processed products of biological resources, a recovery step of recovering sulfur from the desulfurization residue generated in the desulfurization step, and a processing step of processing the recovered sulfur into sulfur for vulcanization (for example, the method described in Japanese Patent Application No. 2022-140390), and raw materials for tire rubber compositions can be obtained from various waste products and used items. In this way, the use of sustainable materials (materials derived from biological resources or materials derived from recycled resources) can reduce the overall environmental impact of tire manufacturing, such as reducing carbon dioxide emissions (LCCO2) over the entire life cycle, reducing energy consumption (LCE) over the entire life cycle, reducing costs incurred over the entire life cycle (LCC), and reducing the use of fossil resources.

[0039] Furthermore, when producing the rubber composition, the ratios of monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources can be appropriately selected depending on the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food). By polymerizing the monomer components derived from biological resources, monomer components derived from recycled resources, and monomer components derived from fossil resources, rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be obtained that has performance equivalent to that of conventional synthetic rubber. When using monomer components derived from recycled resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomers. In such cases, the environmental impact can be evaluated by adopting the mass balance approach.

[0040] The ratio of each monomer unit (e.g., isoprene-derived unit, butadiene-derived unit, and aromatic vinyl compound-derived unit) 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 rubber and butadiene-based rubber. 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 "isoprene-derived unit" refers to a structural unit in a polymer formed based on the isoprene monomer (including isoprene units in natural rubber), the term "butadiene-derived unit" refers to a structural unit in a polymer formed based on the butadiene monomer, and the term "aromatic vinyl compound-derived unit" refers to a structural unit in a polymer formed based on the aromatic vinyl compound monomer. In this specification, the ratio of each monomer unit is measured by NMR.

[0041] 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 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.

[0042] The rubber component (A) may be modified to have a functional group that interacts with fillers such as carbon black and silica. Examples of such functional groups include amino 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. These functional groups may have a substituent. These functional groups may be introduced into the rubber component either individually or in combination. Among these, an amino group, an alkoxy group, and an alkoxysilyl group are preferred, and a substituted amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxysilyl group having 1 to 6 carbon atoms are more preferred.

[0043] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component. The functional group is a modified functional group that has interactivity with fillers such as silica and carbon black, and examples thereof include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups. Examples of compounds (modifiers) having nitrogen-containing functional groups include amino group-containing compounds, and examples of compounds (modifiers) having silicon-containing functional groups include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having oxygen-containing functional groups 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.

[0044] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be produced in the same manner as conventional methods for producing synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources. Furthermore, the rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions using microorganisms or enzyme reactions.

[0045] Regarding the method for preparing bioresource-derived rubber from the above-mentioned bioresources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from a bioresource as the monomer component, it is possible to obtain a bioresource (biomass resource)-derived butadiene rubber (B-BR). Furthermore, by using styrene obtained from a bioresource and butadiene obtained from a bioresource as the monomer components, it is possible to obtain a bioresource (biomass resource)-derived styrene-butadiene rubber (B-SBR). Here, methods for obtaining B-BR and B-SBR from bioresources include artificial polymerization methods, in vivo polymerization methods, and polymerization methods using biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods depending on the desired tire performance.

[0046] Suitable butadienes obtained from biological resources include butadienes derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadienes derived from alkenes (preferably ethylene), and butadienes derived from unsaturated carboxylic acids (preferably tiglic acid). Two or more of these butadienes may be used in combination. Suitable styrenes obtained from biological resources include styrenes obtained from plants (preferably plants belonging to the Hamamelidaceae, Styraxaceae, and Apocynaceae families, more preferably plants belonging to the Liquidambar, Styrax, and Catharanthus roseus, and even more preferably sweetgum, Styrax rostrata, and Catharanthus roseus), and styrenes obtained from microorganisms (preferably microorganisms belonging to the Penicillium and Escherichia genera, more preferably P. citrinum, and transformed E. coli). Suitable styrenes may be used in combination.

[0047] Recently, biomass industrial complexes centered on bioethanol, bioethylene, and the like have been planned. However, bioethanol and bioethylene are produced primarily using sugars and / or cellulose as biological resources, and do not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources as the biological resource-derived monomer component, or to use a combination of monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources, and further to appropriately adjust the ratios of these monomer components. This allows for the effective utilization of a wide range of biological resources, such as sugars, proteins, and lipids, as well as renewable resources, without relying on a single type of biological resource. It also allows for a stable supply of rubber derived from sustainable materials and further allows for environmental considerations depending on the production conditions. When multiple types of monomer components derived from biological resources are used, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadienes derived from multiple types of biological resources with different origins as the biological resource-derived butadiene, and / or to use a mixture of styrenes derived from multiple types of biological resources with different origins as the biological resource-derived styrene. This allows for effective use of multiple types of biological resources.

[0048] The rubber component (A) contains two or more types of rubber. When the rubber component (A) contains two or more types of rubber, it becomes easier to achieve desired physical properties, such as wet grip performance and fuel economy.

[0049] The rubber component (A) preferably contains an isoprene-skeleton rubber. The isoprene-skeleton rubber is a rubber having an isoprene unit as the main skeleton, and specific examples thereof include the above-mentioned natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). When the rubber component (A) contains an isoprene-skeleton rubber, the breaking strength of the rubber composition for tires can be increased. As a result, the durability of tires using the rubber composition can be improved.

[0050] From the viewpoints of improving the fuel economy performance of the tire (reducing rolling resistance) and improving the wear resistance of the tire, the content of the isoprene skeleton rubber in the rubber component (A) is preferably 10% by mass or more, more preferably 15% by mass or more, more preferably 20% by mass or more, more preferably 30% by mass or more, preferably 35% by mass or more, and even more preferably 41% by mass or more. The content of the isoprene skeleton rubber in the rubber component (A) is preferably 90% by mass or less, more preferably 70% by mass or less, more preferably 65% ​​by mass or less, more preferably 60% by mass or less, and even more preferably 57% by mass or less.

[0051] The rubber component (A) preferably contains styrene-butadiene rubber (SBR). By containing styrene-butadiene rubber, the affinity between the rubber component (A) and silica improves, and the dispersibility of silica improves, thereby achieving a good balance between wet grip performance and fuel economy of the tire.

[0052] The content of the styrene-butadiene rubber in the rubber component (A) is preferably 10% by mass or more, more preferably 20% by mass or more, more preferably 30% by mass or more, more preferably 35% by mass or more, and even more preferably 41% by mass or more. The content of the styrene-butadiene rubber in the rubber component (A) is preferably 90% by mass or less, more preferably 80% by mass or less, more preferably 70% by mass or less, more preferably 60% by mass or less, more preferably 58% by mass or less, and even more preferably 53% by mass or less.

[0053] The rubber component (A) preferably contains the isoprene skeleton rubber and the styrene-butadiene rubber. When the rubber component (A) contains the isoprene skeleton rubber and the styrene-butadiene rubber, the effect of improving the wet grip performance and fuel economy of the tire is enhanced. Here, the mass ratio of the isoprene skeleton rubber to the styrene-butadiene rubber (SBR) (isoprene skeleton rubber / SBR) is preferably in the range of 20 / 80 to 80 / 20, and more preferably in the range of 25 / 75 to 75 / 25. When the mass ratio of the isoprene skeleton rubber to the styrene-butadiene rubber (isoprene skeleton rubber / SBR) is in this range, the effects of both the isoprene skeleton rubber and the styrene-butadiene rubber are fully exhibited, further enhancing the effect of improving the wet grip performance and fuel economy of the tire.

[0054] The styrene-butadiene rubber (SBR) may be unmodified or modified. When the styrene-butadiene rubber (SBR) is modified, the styrene-butadiene rubber (SBR) is preferably modified with at least one selected from the group consisting of a hydrocarbyloxysilane compound represented by the following general formula (I), a hydrocarbyloxysilane compound represented by the following general formula (II), a hydrocarbyloxysilane compound represented by the following general formula (III), a coupling agent represented by the following general formula (IV), a coupling agent represented by the following general formula (V), a lithioamine represented by the following general formula (VI), and vinylpyridine.

[0055]

[0056] In the above general formula (I), q1+q2=3 (wherein q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3). １１ 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. １２ and R １３ 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. １４are monovalent aliphatic or alicyclic hydrocarbon groups having 1 to 20 carbon atoms or monovalent aromatic hydrocarbon groups having 6 to 18 carbon atoms, and when q1 is 2, they may be the same or different. １５ 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 q2 is 2 or more, may be the same or different.

[0057]

[0058] In the above general formula (II), r1+r2=3 (where r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2). ２１ 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. ２２ 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 ２３ 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.

[0059]

[0060] In the above general formula (III), A ３is a monovalent group having at least one functional group selected from (thio)epoxy, (thio)isocyanate, (thio)ketone, (thio)aldehyde, imine, amide, isocyanuric acid trihydrocarbyl ester, (thio)carboxylic acid ester, metal salt of (thio)carboxylic acid, carboxylic acid anhydride, carboxylic acid halide, and carbonic acid dihydrocarbyl ester. Here, "(thio)epoxy" refers to epoxy and thioepoxy, "(thio)isocyanate" refers to isocyanate and thioisocyanate, "(thio)ketone" refers to ketone and thioketone, "(thio)aldehyde" refers to aldehyde and thioaldehyde, "(thio)carboxylic acid ester" refers to carboxylic acid ester and thiocarboxylic acid ester, and "metal salt of (thio)carboxylic acid" refers to metal salt of carboxylic acid and metal salt of thiocarboxylic acid. R ３１ R is a single bond or a divalent inert hydrocarbon group, and the divalent inert hydrocarbon group preferably has 1 to 20 carbon atoms. ３２ and R ３３ 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, n is an integer of 0 to 2, R ３２ If there are multiple R ３２ may be the same or different, OR ３３ If there are multiple, multiple OR ３３ may be the same or different. The molecule of the hydrocarbyloxysilane compound represented by general formula (III) does not contain an active proton or an onium salt.

[0061] In general formula (III), A ３ Among the functional groups in R, imine includes ketimine, aldimine, and amidine, and (thio)carboxylic acid ester includes unsaturated carboxylic acid ester such as acrylate and methacrylate. In addition, examples of the metal in the metal salt of (thio)carboxylic acid include alkali metals, alkaline earth metals, Al, Sn, and Zn. ３１Among these, preferred divalent inert hydrocarbon groups are alkylene groups having 1 to 20 carbon atoms. The alkylene groups may be linear, branched, or cyclic, with linear groups being particularly preferred. Examples of linear alkylene groups include methylene, ethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene, decamethylene, and dodecamethylene. R ３２ and R ３３ Examples of the alkyl group include an alkyl group having 1 to 20 carbon atoms, an alkenyl group having 2 to 18 carbon atoms, an aryl group having 6 to 18 carbon atoms, and an aralkyl group having 7 to 18 carbon atoms. Here, the alkyl group and the alkenyl group may be linear, branched, or cyclic, and examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, a pentyl group, a hexyl group, an octyl group, a decyl group, a dodecyl group, a cyclopentyl group, a cyclohexyl group, a vinyl group, a propenyl group, an allyl group, a hexenyl group, an octenyl group, a cyclopentenyl group, and a cyclohexenyl group. The aryl group may have a substituent such as a lower alkyl group on the aromatic ring, and examples thereof include a phenyl group, a tolyl group, a xylyl group, and a naphthyl group. Furthermore, the aralkyl group may have a substituent such as a lower alkyl group on the aromatic ring, examples of which include a benzyl group, a phenethyl group, a naphthylmethyl group, etc. n is an integer of 0 to 2, preferably 0, and the molecule must be free of active protons and onium salts.

[0062] Examples of the hydrocarbyloxysilane compound represented by the general formula (III) include (thio)epoxy group-containing hydrocarbyloxysilane compounds such as 2-glycidoxyethyltrimethoxysilane, 2-glycidoxyethyltriethoxysilane, (2-glycidoxyethyl)methyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, (3-glycidoxypropyl)methyldimethoxysilane, and 2-(3,4-epoxycyclohexyl) Preferred examples include ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane, 2-(3,4-epoxycyclohexyl)trimethoxysilane, and compounds in which the epoxy groups are replaced with thioepoxy groups. Of these, 3-glycidoxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)trimethoxysilane are particularly suitable. Furthermore, examples of the imine group-containing hydrocarbyloxycyanide compound include N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine, N-(1-methylethylidene)-3-(triethoxysilyl)-1-propanamine, N-ethylidene-3-(triethoxysilyl)-1-propanamine, N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine, N-(4-N,N-dimethylaminobenzylidene)-3-(triethoxysilyl)-1-propanamine, N-(cyclohex ... Preferred examples of the triethoxysilyl compounds include N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine and trimethoxysilyl compounds, methyldiethoxysilyl compounds, ethyldiethoxysilyl compounds, methyldimethoxysilyl compounds, and ethyldimethoxysilyl compounds corresponding to these triethoxysilyl compounds. Of these, N-(1-methylpropylidene)-3-(triethoxysilyl)-1-propanamine and N-(1,3-dimethylbutylidene)-3-(triethoxysilyl)-1-propanamine are particularly preferred.

[0063]

[0064] In the above general formula (IV), R ４１ , R ４２ and R ４３ R each independently represents a single bond or an alkylene group having 1 to 20 carbon atoms. ４４ , R ４５ , R ４６ , R ４７ and R ４９ R each independently represents an alkyl group having 1 to 20 carbon atoms. ４８ and R ５１ R each independently represents an alkylene group having 1 to 20 carbon atoms. ５０ represents an alkyl group or a trialkylsilyl group having 1 to 20 carbon atoms, m represents an integer of 1 to 3, and p represents 1 or 2. R ４１ ~R ５１ When there are a plurality of m and p, each is independent, and each of i, j and k independently represents an integer of 0 to 6, provided that (i+j+k) is an integer of 3 to 10. ４ 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 an oxygen atom, a nitrogen atom, a silicon atom, a sulfur atom, and a phosphorus atom, and having no active hydrogen.

[0065] Here, the coupling agent represented by general formula (IV) is preferably at least one selected from the group consisting of tetrakis[3-(2,2-dimethoxy-1-aza-2-silacyclopentane)propyl]-1,3-propanediamine, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, and tetrakis(3-trimethoxysilylpropyl)-1,3-bisaminomethylcyclohexane.

[0066] (R ５ ) ａ ZX ｂ In the general formula (V), Z is tin or silicon, and X is chlorine or bromine. (R ５ ) is selected from the group consisting of alkyl having 1 to 20 carbon atoms, cycloalkyl having 3 to 20 carbon atoms, aryl having 6 to 20 carbon atoms, and aralkyl having 7 to 20 carbon atoms, wherein (R５ Specific examples of the alkyl group include a methyl group, an ethyl group, an n-butyl group, a neophyl group, a cyclohexyl group, an n-octyl group, and a 2-ethylhexyl group. a is an integer of 0 to 3, and b is an integer of 1 to 4, where a+b=4.

[0067] The coupling agent represented by the general formula (V) includes tin tetrachloride, (R ５ ) SnCl ３ , (R ５ ) ２ SnCl ２ , (R ５ ) ３ SnCl and the like are preferred, and among them, tin tetrachloride is particularly preferred.

[0068] (AM)Li(Q) ｙ ... (VI) In the above general formula (VI), y is 0 or 0.5 to 3, (Q) is a solubilizing component selected from the group consisting of hydrocarbons, ethers, amines, or mixtures thereof, and (AM) is a compound represented by the following formula (VII): [In formula (VII), R ７１ and R ７２ each independently represents an alkyl, cycloalkyl, or aralkyl group having 1 to 12 carbon atoms.] or the following formula (VIII): [In formula (VIII), R ８１ represents alkylene having 3 to 16 methylene groups, linear or branched alkyl having 1 to 12 carbon atoms, substituted alkylene having a cycloalkyl, bicycloalkyl, aryl or aralkyl as a substituent, oxydiethylene or an N-alkylamino-alkylene group.

[0069] The presence of Q of general formula (VI) above renders the lithioamine soluble in hydrocarbon solvents. Q also includes dienyl or vinyl aromatic polymers or copolymers having a degree of polymerization of 3 to about 300 polymerization units. These polymers and copolymers include polybutadiene, polystyrene, polyisoprene, and copolymers thereof. Other examples of Q include polar ligands [e.g., tetrahydrofuran (THF), tetramethylethylenediamine (TMEDA), etc.].

[0070] The lithioamine represented by the general formula (VI) can also be a mixture with an organic alkali metal. The organic alkali metal is preferably a lithioamine represented by the general formula: (R ９１ ) M, (R ９２ ) OM, (R ９３ )C(O)OM, (R ９４ ) (R ９５ ) NM and (R ９６ ) SO ３ M, wherein (R ９１ ), (R ９２ ), (R ９３ ), (R ９４ ), (R ９５ ) and (R ９６ ) are each selected from the group consisting of alkyl, cycloalkyl, alkenyl, aryl, and phenyl having from about 1 to about 12 carbon atoms. The metal component M is selected from the group consisting of Na, K, Rb, and Cs. Preferably, M is Na or K. The mixture may also contain the organo alkali metal, preferably in a mixing ratio of from about 0.5 to about 0.02 equivalents per equivalent of lithium in the lithioamine.

[0071] In addition, a chelating agent can be used in the mixture of the lithioamine and the organic alkali metal to help prevent non-uniform polymerization. Useful chelating agents include, for example, tetramethylethylenediamine (TMEDA), oxolanyl cyclic acetals, and cyclic oligomeric oxolanyl alkanes. Cyclic oligomeric oxolanyl alkanes are particularly preferred, and a specific example is 2,2-bis(tetrahydrofuryl)propane.

[0072] Examples of the vinylpyridine include 2-vinylpyridine and 4-vinylpyridine.

[0073] Among the various modifying agents mentioned above, N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine, N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine, 3-glycidoxypropyltrimethoxysilane, tetrakis(3-trimethoxysilylpropyl)-1,3-propanediamine, tin tetrachloride, a reaction product of hexamethyleneimine and n-butyllithium, 4-vinylpyridine, and 2-vinylpyridine are preferred.

[0074] A randomizer can also be used in synthesizing the styrene-butadiene rubber (SBR). The randomizer refers to a compound that has the effect of controlling the microstructure of a conjugated diene polymer, for example, by increasing the number of 1,2 bonds in the butadiene moiety in styrene-butadiene, or by controlling the composition distribution of monomer units in a conjugated diene compound-aromatic vinyl compound copolymer, for example, by randomizing the styrene units and butadiene units in styrene-butadiene rubber. When a randomizer is used in synthesizing the styrene-butadiene rubber, the ratio of the randomizer to the polymerization initiator [randomizer (mol) / polymerization initiator (mol)] is preferably 0.01 to 1.0, and more preferably 0.05 to 0.8. An organic lithium compound such as butyllithium can be used as the polymerization initiator. The randomizer can be appropriately selected from known compounds that have been commonly used as randomizers. Specific examples include ethers and tertiary amines such as dimethoxybenzene, tetrahydrofuran, dimethoxyethane, diethylene glycol dibutyl ether, diethylene glycol dimethyl ether, oxolanylpropane oligomers [particularly those containing 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.

[0075] The rubber composition for a tire according to this embodiment more preferably contains a styrene-butadiene rubber having a styrene bond content of 15% by mass or less as the styrene-butadiene rubber. By applying a rubber composition containing a styrene-butadiene rubber having a styrene bond content of 15% by mass or less to a tire, the wet grip performance of the tire can be significantly improved. The styrene bond content is preferably 1% by mass or more, more preferably 3% by mass or more, and is preferably 13% by mass or less, and more preferably 11% by mass or less. In this specification, the styrene bond content of the styrene-butadiene rubber is １ It can be determined from the integral ratio of the H-NMR spectrum.

[0076] (Filler (B)) The rubber composition for a tire of this embodiment contains filler (B). By including filler (B), the reinforcement properties of the rubber composition for a tire are improved. The content of filler (B) in the rubber composition for a tire is preferably in the range of 40 to 125 parts by mass per 100 parts by mass of the rubber component (A). When the content of filler (B) in the rubber composition for a tire is 40 parts by mass or more per 100 parts by mass of the rubber component (A), the reinforcement of the rubber composition for a tire is sufficient and the abrasion resistance of the tire can be improved. When the content of filler (B) in the rubber composition for a tire is 125 parts by mass or less, the modulus of elasticity of the rubber composition for a tire does not become too high and the wet grip performance of the tire is improved. Furthermore, from the viewpoint of improving the fuel economy performance of the tire, the content of filler (B) in the rubber composition for a tire is more preferably 45 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more per 100 parts by mass of the rubber component (A). From the viewpoint of improving the wet grip performance of the tire, the content of the filler (B) in the rubber composition for a tire is more preferably 110 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0077] -Silica- The filler (B) contains plant-derived silica (B1). The plant-derived silica (B1) is a material derived from biological resources (biomass resources). Therefore, the inclusion of plant-derived silica (B1) increases the proportion of sustainable materials in the rubber composition for tires, and applying the rubber composition to tires increases the proportion of sustainable materials in the tire and reduces the environmental impact.

[0078] From the viewpoint of reducing environmental impact, the plant-derived silica (B1) is preferably silica derived from silicic acid plants. Examples of such silicic acid plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Poaceae plants. Among these plants, grasses are preferred, i.e., the plant-derived silica (B1) is preferably silica derived from grasses. Grass-derived silica can be procured locally near tire manufacturing plants, reducing the energy and costs required for transportation and storage, making it environmentally preferable from various viewpoints. Examples of such grasses include rice, bamboo grass, and sugarcane, with rice being preferred. Rice is widely cultivated for food, making it possible to obtain it locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making it easy to secure a sufficient amount. Therefore, from the viewpoint of availability, rice husk-derived silica (hereinafter also referred to as "rice husk silica") is particularly preferred as the plant-derived silica (B1). The use of rice husk silica allows for the effective utilization of rice husks, which are industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs of transportation and storage, making it environmentally advantageous from various perspectives. The rice husk silica may be rice husk charcoal powder obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution obtained by extracting rice husk ash, which is generated when rice husks are burned as fuel in a biomass boiler, with an alkali. The method for producing 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 particles of a predetermined particle size range, to obtain rice husk charcoal powder. The precipitated silica derived from rice husks can be produced by the method described in JP-A-2019-38728.

[0079] The ratio of the plant-derived silica (B1) in the filler (B) is 45% by mass or more. By setting the ratio of the plant-derived silica (B1) in the filler (B) to 45% by mass or more, the ratio of sustainable materials in the rubber composition for tires is increased, and by applying the rubber composition to tires, it is possible to increase the ratio of sustainable materials in the tires.

[0080] The filler (B) may contain silica other than the plant-derived silica (B1). Examples of such silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it contains a large number of silanol groups. These silicas other than the plant-derived silica (B1) may be used alone or in combination of two or more. Commercially available silicas other than the plant-derived silica (B1) may be used, and examples of such commercially available silicas include products from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation.

[0081] 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.

[0082] The plant-derived silica (B1) 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 / g or more, the tire can be sufficiently reinforced and the rolling resistance can be sufficiently reduced. ２ From the viewpoint of further reducing the rolling resistance of a tire and improving the abrasion resistance, the nitrogen adsorption specific surface area (BET method) of the plant-derived silica (B1) is less than 100 m ２ / g or more is more preferable, and 130m ２ / g or more is more preferable, and 150m ２ / g or more, and 170m ２ / g or more is more preferable, and 180m ２ / g or more, and 190m ２ / g or more, and 195m ２ From the viewpoint of further improving the wet grip performance, the nitrogen adsorption specific surface area (BET method) of the plant-derived silica (B1) is more preferably 300 m ２ / g or less is more preferable, and ２ / g or less is more preferable, and 270m ２ / g or less. In this specification, the nitrogen adsorption specific surface area (N ２ SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0083] From the viewpoints of improving the mechanical strength of the tire and reducing the rolling resistance, the content of the plant-derived silica (B1) is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, per 100 parts by mass of the rubber component (A). Also, from the viewpoint of further improving wet grip performance, the content of the plant-derived silica (B1) is preferably 90 parts by mass or less, more preferably 85 parts by mass or less, and even more preferably 80 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0084] -Carbon Black- The filler (B) preferably contains carbon black. As the carbon black, plant-derived carbon black and carbon black obtained by recycling (i.e., recycled carbon black) are particularly preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Examples of recycled carbon black include carbon black obtained by decomposition (particularly thermal decomposition) of crosslinked rubber products such as used tires, and carbon black obtained from waste oil.

[0085] The crosslinked rubber products used for the decomposition may be grouped by the type of rubber component previously compounded, and then the decomposition step may be performed for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., type of carbon black, type of silica, mixing ratio of carbon black and silica, etc.), and then the decomposition step may be performed for each group. Furthermore, the crosslinked rubber products may be grouped by both type of rubber component and type of filler, and then the decomposition step may be performed for each group. When the decomposition step is performed for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0086] Furthermore, when the crosslinked rubber product used for the degradation is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, trucks, buses, large vehicles such as off-road vehicles, aircraft, agricultural vehicles, etc.), and the degradation step may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and the degradation step may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and the degradation step may be carried out for each group. When the degradation step is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0087] The grade of the carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks can be used, and examples of commercially available carbon blacks include those manufactured by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Birla Carbon Co., Ltd. These carbon blacks may be used alone or in combination of two or more.

[0088] The nitrogen adsorption specific surface area (N ２ The nitrogen adsorption specific surface area (N SA) of carbon black 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. ２ SA) is 20m ２ / g or more is preferable, and 50m ２ / g or more is more preferable, and 70m ２ / g or more is more preferable, ２ / g or more is more preferable, and 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 (N ２ SA) is determined according to JIS K 6217-2:2017 (ISO 4652:2012).

[0089] From the viewpoint of improving the abrasion resistance of the tire, 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). Also, from the viewpoint of workability of the rubber composition, the content of the carbon black is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0090] It is preferable that the silica content be 50% by mass or more and less than 100% by mass relative to the total amount of the silica and carbon black. By satisfying this range, it is possible to achieve a high level of balance between wet grip performance and fuel economy. Furthermore, from the viewpoint of further improving the balance between wet grip performance and fuel economy, it is more preferable that the silica content be 70% by mass or more and less than 100% by mass, more preferably 80% by mass or more and less than 100% by mass, and even more preferably 90% by mass or more and less than 100% by mass relative to the total amount of the silica and carbon black.

[0091] Examples of the filler (B) include calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, and the like, in addition to the above-mentioned silica and carbon black.

[0092] (Resin (C)) The rubber composition for a tire of this embodiment contains a resin (C). When the rubber composition for a tire contains the resin (C), the wet grip performance and fuel economy performance of the tire can be improved. Examples of the resin (C) include terpene-based resins, rosin-based resins, and C ５ based resin, C ５ -C ９ based resin, C ９ Examples of the resin (C) include cyclopentadiene-based resins, aromatic resins, coumarone resins, indene resins, coumarone-indene-based resins, olefin-based resins, polyurethane resins, and acrylic resins. These resins (C) may be used alone or in combination of two or more. Among these resins (C), terpene-based resins, rosin-based resins, and C ５ based resin, C ５ -C ９ based resin, C ９ Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins, and aromatic resins, with terpene-based resins and rosin-based resins being particularly preferred. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins that can further reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry roads, wet roads, snow-covered roads, and frozen roads. ５ based resin, C ９ based resin, C ５ -C９ The cyclopentadiene-based resin and the cyclopentadiene-based resin can improve abrasion resistance and fuel economy in a balanced manner, while the aromatic resin can improve grip performance, abrasion resistance, and rubber strength in a balanced manner.

[0093] The resin (C) may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). Furthermore, the resin (C) 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.

[0094] The terpene resin is a solid resin obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or a polymerization component separated therefrom, and polymerizing the blend using a Friedel-Crafts catalyst. Examples of such resins include β-pinene resin and α-pinene resin. Terpene resins also include terpene-aromatic compound resins, representative examples of which include terpene-phenol resin and styrene-terpene resin. Terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing the terpene with formalin. The styrene-terpene resin can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes used as raw materials are not particularly limited; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred.

[0095] Examples of the rosin-based resin include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil, and examples of modified rosins, rosin derivatives, and modified rosin derivatives include polymerized rosin and partially hydrogenated rosin thereof; glycerin ester rosin and partially hydrogenated rosin thereof and fully hydrogenated rosin thereof; pentaerythritol ester rosin and partially hydrogenated rosin thereof and polymerized rosin; and the like.

[0096] Said C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry. ５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate. ５ The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene.

[0097] Said C ５ -C ９ The C-based resin is ５ -C ９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ More specifically, copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, etc. as the main component may be mentioned. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0098] Said C ９ The C-based resin is９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９ Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0099] The cyclopentadiene-based resin refers to a resin containing a unit derived from a cyclopentadiene-based monomer as a monomer unit. Examples of the cyclopentadiene-based resin include a homopolymer of a cyclopentadiene-based monomer, a copolymer of two or more cyclopentadiene-based monomers, and a copolymer of a cyclopentadiene-based monomer and another monomer. Here, examples of the cyclopentadiene-based monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a dicyclopentadiene-based resin. The dicyclopentadiene-based resin is, for example, a copolymer of AlCl ３ or BF ３ The term "dicyclopentadiene-based resin" refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as Benzene, etc. Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, copolymers of dicyclopentadiene and C ９ Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0100] The aromatic resin refers to a resin containing units derived from aromatic monomers as monomer units. Examples of the aromatic resin include homopolymers of aromatic monomers, copolymers of two or more aromatic monomers, and copolymers of aromatic monomers with other monomers. Examples of the aromatic monomer include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenol-based monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol-based monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0101] The softening point of the resin (C) is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, more preferably 80 ° C. or higher, more preferably higher than 110 ° C., more preferably 116 ° C. or higher, more preferably 120 ° C. or higher, more preferably 123 ° C. or higher, and even more preferably 127 ° C. or higher. From the viewpoint of processability, the softening point of the resin (C) is preferably 160 ° C. or lower, more preferably 150 ° C. or lower, more preferably 145 ° C. or lower, more preferably 141 ° C. or lower, and even more preferably 136 ° C. or lower. In this specification, the softening point of the resin (C) is the temperature at which the ball drops when the softening point as defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0102] Commercially available resins can be used as the resin (C). Commercially available resins include, for example, products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Clayton, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Clayton Polymers, Inc., Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0103] The content of the resin (C) is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of the resin (C) is preferably in the range of 1 to 50 parts by mass, more preferably 10 to 40 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the resin (C) is 1 to 50 parts by mass per 100 parts by mass of the rubber component (A), the wet grip performance and fuel economy of the tire can be further improved, while resin precipitation from the tire can be suppressed, thereby suppressing deterioration in the tire appearance.

[0104] The resin (C) is preferably a hydrogenated resin (hereinafter sometimes referred to as "hydrogenated resin") having a softening point higher than 110°C and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol. When a rubber composition for a tire contains such a hydrogenated resin, the wet grip performance and fuel economy performance of the tire can be further improved. Resins that are raw materials for the hydrogenated resin include the above-mentioned C. ５ based resin, C ５ -C ９ based resin, C ９ These resins may be used alone or in combination of two or more.

[0105] If the softening point of the hydrogenated resin is higher than 110°C, the tire can be sufficiently reinforced and the rolling resistance can be reduced. From the viewpoint of further reducing rolling resistance, the softening point of the hydrogenated resin is preferably 115°C or higher, more preferably 118°C or higher, more preferably 123°C or higher, and even more preferably 127°C or higher. Furthermore, from the viewpoint of wet grip performance, the softening point of the hydrogenated resin is preferably 145°C or lower, more preferably 138°C or lower, and even more preferably 133°C or lower.

[0106] When the weight average molecular weight of the hydrogenated resin in terms of polystyrene is 200 g / mol or more, the hydrogenated resin is less likely to precipitate from the tire, and the effects of the hydrogenated resin can be fully exhibited. When the weight average molecular weight is 1600 g / mol or less, the hydrogenated resin can be fully compatible with the rubber component (A).

[0107] From the viewpoint of suppressing precipitation of the hydrogenated resin from the tire and suppressing deterioration in tire appearance, the polystyrene-equivalent weight average molecular weight of the hydrogenated resin is preferably 500 g / mol or more, more preferably 550 g / mol or more, still more preferably 600 g / mol or more, still more preferably 650 g / mol or more, still more preferably 700 g / mol or more, and still more preferably 750 g / mol or more. In addition, from the viewpoint of improving the compatibility of the hydrogenated resin with the rubber component (A) and further enhancing the effects of the hydrogenated resin, the polystyrene-equivalent weight average molecular weight of the hydrogenated resin is more preferably 1400 g / mol or less, more preferably 1350 g / mol or less, more preferably 1300 g / mol or less, more preferably 1250 g / mol or less, more preferably 1200 g / mol or less, more preferably 1150 g / mol or less, more preferably 1100 g / mol or less, more preferably 1050 g / mol or less, more preferably 1000 g / mol or less, and even more preferably 950 g / mol or less. The weight average molecular weight can be calculated by measuring the average molecular weight of the hydrogenated resin by gel permeation chromatography (GPC) under the following conditions, for example. Column temperature: 40°C Injection volume: 50 μL Carrier and flow rate: tetrahydrofuran 0.6 mL / min Sample preparation: Approximately 2.5 mg of resin component was dissolved in 10 mL of tetrahydrofuran

[0108] The softening point (TsHR) (unit: °C) of the hydrogenated resin relative to its polystyrene-equivalent weight average molecular weight (MwHR) (unit: g / mol) is preferably 0.15 or higher [0.15≦(TsHR / MwHR)]. The (TsHR / MwHR) is preferably 0.08 or higher, more preferably 0.09 or higher, more preferably 0.098 or higher, more preferably 0.102 or higher, more preferably 0.11 or higher, more preferably 0.12 or higher, more preferably 0.14 or higher, more preferably 0.155 or higher, more preferably 0.158 or higher, more preferably 0.160 or higher, and even more preferably 0.162 or higher. Furthermore, (TsHR / MwHR) is preferably 0.2 or less, more preferably 0.185 or less, more preferably 0.178 or less, more preferably 0.172 or less, more preferably 0.168 or less, and even more preferably 0.163 or less.

[0109] From the viewpoint of further enhancing the effect of the hydrogenated resin, the content of the hydrogenated resin is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 9 parts by mass or more, per 100 parts by mass of the rubber component (A). Also, from the viewpoint of suppressing precipitation of the hydrogenated resin from the tire and suppressing deterioration of the tire appearance, the content of the hydrogenated resin is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0110] The resin used as the raw material for the hydrogenated resin is, for example, C ５ A resin (C) copolymerized with the fraction and dicyclopentadiene (DCPD) ５ -DCPD-based resin). When the dicyclopentadiene-derived component is 50% by mass or more in the total amount of the resin, C ５ - DCPD-based resins are included in dicyclopentadiene-based resins. When the dicyclopentadiene-derived component is less than 50% by mass in the total amount of resin, C ５ -DCPD resin is C５ The same applies to the case where a small amount of a third component is copolymerized.

[0111] From the viewpoints of increasing the compatibility between the rubber component (A) and the hydrogenated resin, further improving the wet grip performance, and further reducing the rolling resistance, the hydrogenated resin is preferably a hydrogenated C ５ based resin, hydrogenated C ５ -C ９ and hydrogenated dicyclopentadiene resin (hydrogenated DCPD resin), ５ Resin and hydrogenated C ５ -C ９ It is more preferable that the resin is at least one selected from the group consisting of hydrogenated C ５ It is also preferable that the resin has a hydrogenated DCPD structure or a hydrogenated cyclic structure in at least one monomer.

[0112] (Nonionic Surfactant) The rubber composition for a tire of this embodiment may contain a nonionic surfactant. The nonionic surfactant improves the fuel economy and abrasion resistance of the resulting rubber composition for a tire. As the nonionic surfactant, at least one type selected from polyhydric alcohol type, polyoxyethylene alkyl ether type, polyoxyethylene alkyl phenyl ether type, polyoxyethylene polyoxypropylene glycol type, polyethylene glycol type, glycoside type, and fatty acid alkanolamide type is used. In the rubber composition for a tire of this embodiment, one type of nonionic surfactant may be used alone, or two or more types may be used in combination.

[0113] Examples of the polyhydric alcohol type nonionic surfactants include fatty acid esters of glycerin (glycerol), fatty acid esters of pentaerythritol, fatty acid esters of polyoxyethylene sorbitan, fatty acid esters of polyoxyethylene sorbit, and fatty acid esters of sorbitan. Specific examples include palm oil-derived hardened fatty acid glycerin, lipophilic glycerin monostearate, self-emulsifying glycerin monostearate, lipophilic glycerin monooleate, glycerin monocaprylate, propylene glycol monostearate, sorbitan monostearate, and monooleate. Examples thereof include sorbitan phosphate, sorbitan sesquioleate, sorbitan coconut oil fatty acid, sorbitan monopalmitate, sorbitan tristearate, sorbitan trioleate, polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan tristearate, polyoxyethylene sorbitan monooleate, polyoxyethylene sorbitan trioleate, polyoxyethylene sorbitan triisostearate, and polyoxyethylene sorbitan tetraoleate.

[0114] Examples of the polyoxyethylene alkyl ether type include mono- or di-alkyl or alkenyl ethers of polyoxyethylene, and specific examples thereof include polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, and polyoxyethylene octyldodecyl ether.

[0115] The polyoxyethylene alkylphenyl ether type may be at least one selected from polyoxyethylene benzyl phenyl ether, polyoxyethylene tribenzyl phenyl ether, polyoxyethylene distyrenated phenyl ether, and the like.

[0116] The polyoxyethylene polyoxypropylene glycol type includes at least one selected from polyoxyethylene polyoxypropylene glycol and its mono- or di-fatty acid esters.

[0117] The polyethylene glycol type includes mono- or di-fatty acid esters of polyethylene glycol, and specific examples thereof include polyethylene glycol monolaurate, polyethylene glycol monostearate, and polyethylene glycol distearate.

[0118] Examples of the glucoside type include alkylglucosides in which the alkyl group has 8 to 20 carbon atoms, and specific examples include decyl glucoside and lauryl glucoside.

[0119] Examples of the fatty acid alkanolamide type include fatty acid diethanolamides and fatty acid N-alkylethanolamides, and specific examples include palm kernel oil fatty acid diethanolamide, lauric acid diethanolamide, coconut oil fatty acid N-methylethanolamide, and the like.

[0120] In the rubber composition for a tire of this embodiment, other preferred nonionic surfactants include polyoxyethylene hydrogenated castor oil and isostearyl glyceryl ether.

[0121] Among these nonionic surfactants, glycerin fatty acid esters are preferred, and as the glycerin fatty acid esters, those in which the number of carbon atoms of the fatty acid is 8 to 28, which include a glycerin fatty acid monoester and a glycerin fatty acid diester, and in which the content of the glycerin fatty acid monoester is 40 to 100 mass% are more preferred.

[0122] From the viewpoint of sufficiently improving fuel economy and abrasion resistance, the content of the nonionic surfactant in the rubber composition for tires of the present embodiment is preferably 0.1 parts by mass or more and 7 parts by mass or less, more preferably 0.2 parts by mass or more and 6 parts by mass or less, and even more preferably 0.3 parts by mass or more and 5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0123] In the rubber composition for tires of this embodiment, the mass ratio of the hydrogenated resin to the nonionic surfactant (hydrogenated resin / nonionic surfactant) is preferably 0.7 to 500, more preferably 1 to 30, and even more preferably 5 to 20. By satisfying this range, it is possible to achieve both wet grip performance and fuel economy at an even higher level.

[0124] (Silane Coupling Agent) The rubber composition for a tire of this embodiment preferably contains a silane coupling agent to improve the effect of the plant-derived silica (B1). Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, Examples of such tetrasulfides include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. As the silane coupling agent, commercially available products can be used, and examples of commercially available silane coupling agents that can be used include products from Evonik, Momentive, Shin-Etsu Silicones Co., Ltd., Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used alone or in combination of two or more.

[0125] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced primarily using sugars and / or cellulose as biological resources, and does not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of ethanol derived from biological resources (bioethanol) as the raw material for the silane coupling agent, or to use a combination of ethanol derived from biological resources (bioethanol), ethanol derived from renewable resources, and ethanol derived from fossil resources. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0126] The content of the silane coupling agent can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire component, the target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and still more preferably 10 parts by mass or less, relative to 100 parts by mass of the plant-derived silica (B1) (or the total amount of silica).

[0127] (Rubber Crumb) The rubber composition for tires of this embodiment may contain 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 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 treatment or low-temperature treatment. For example, in mechanical treatment, various crushing devices such as a cracker mill or a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature treatment, the finely chopped vulcanized rubber is frozen at a cryogenic temperature and then crushed into fine particles. A magnetic separator or the like can be used to remove steel, and an air separator or the like can be used to remove fibers. The rubber powder may be a commercially available product, such as those from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental impact, it is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more types.

[0128] The composition of the rubber crumb is not particularly limited and depends on the composition of the vulcanized rubber of used rubber products (used tires) or the like that serves as the raw material. In one embodiment, the rubber crumb contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber crumb may be the same as or different from the rubber component, carbon black, silica, etc. that can be contained in the rubber composition for tires of the present embodiment described above.

[0129] The rubber powder preferably has a volume average particle diameter of 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. The smaller the volume average particle diameter of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle diameter is measured with a laser diffraction particle size distribution analyzer, for example, a "CAPA500" manufactured by Horiba, Ltd.

[0130] The rubber powder preferably has a 60-mesh sieve residue of less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit. The rubber powder preferably has an 80-mesh sieve residue of less than 10% by mass, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0131] The rubber crumb has an acetone extractable content of preferably 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractable content in the rubber crumb refers to the acetone extractable content (%) determined by the acetone extraction method in accordance with JIS K6350.

[0132] 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, still more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0133] (Liquid Softener) The rubber composition for a tire of this embodiment may contain a liquid softener. Here, the "liquid softener" is a compounding agent that is liquid at 25°C (room temperature) and has the effect of softening the rubber composition. The liquid softener is not particularly limited, and examples thereof include oil and liquid polymer, and among these, oil is preferred. These liquid softeners may be used alone or in combination of two or more.

[0134] The oil is a general term for extender oils contained in rubber components and liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, and mixtures thereof. From the perspective of reducing environmental impact, vegetable oils and recycled oils are preferred. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil. Examples of process oils include paraffin-based process oils, aromatic process oils, and naphthenic process oils. As the oil, commercially available products can be used, and examples of commercially available oils that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0135] 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.

[0136] 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).

[0137] (Antiaging Agent) The rubber composition for a tire of the present embodiment may contain an antioxidant. Examples of the antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. 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.

[0138] 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).

[0139] (Wax) The rubber composition for a tire of this embodiment may contain a wax. Examples of the wax include natural waxes such as plant 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.

[0140] The content of the wax is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the content of the wax is preferably 0.5 parts by mass or more, 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).

[0141] (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., and the like. These commercially available stearic acid products may be used alone or in combination of two or more.

[0142] The content of stearic acid is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more and is preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0143] (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 ores but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available zinc oxide can be used, and examples of commercially available zinc oxide include products from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0144] The content of the zinc oxide is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0145] (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. Furthermore, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, or the like, which are commonly used as crosslinking agents in the rubber industry. Commercially available sulfur products can be used, including those from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, and the like. These sulfurs may be used alone or in combination of two or more.

[0146] The sulfur content is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber component (A) is applied, the tire components, the target performance, etc. For example, the sulfur content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, 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).

[0147] (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, renewable resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing the environmental impact. Vulcanization accelerators derived from biological resources can be obtained, for example, by the method disclosed in JP 2005-139239 A. Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolsulfenamide, and N,N'-diisopropyl-2-benzothiazolsulfenamide; 1,3-diphenylguanidine (DPG), 1,3-dibenzothiazolylsulfenamide, and the like. Examples of suitable vulcanization accelerators include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available vulcanization accelerators can be used, including those manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., and the like. These vulcanization accelerators may be used alone or in combination of two or more.

[0148] 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).

[0149] (Cellulose Nanofiber) The rubber composition for a tire according to this embodiment may contain cellulose nanofiber (CNF). The cellulose nanofiber can reinforce the rubber composition by blending it with the rubber composition. The cellulose nanofiber is preferably a modified cellulose nanofiber, which is a fine fiber made from modified cellulose. The fiber diameter of the cellulose nanofiber is not particularly limited, but is approximately 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofiber can be obtained by averaging the fiber diameters and fiber lengths obtained from the observation of each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofiber can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment or defibration treatment.

[0150] The raw material for the cellulose nanofibers is not particularly limited as long as it contains cellulose, and examples thereof include plants (e.g., wood, bamboo, hemp, jute, kenaf, agricultural waste, cloth, pulp (softwood unbleached kraft pulp (NUKP), softwood bleached kraft pulp (NBKP), hardwood unbleached kraft pulp (LUKP), hardwood bleached kraft pulp (LBKP), bleached kraft pulp (BKP), softwood unbleached sulfite pulp (NUSP), softwood bleached sulfite pulp (NBSP), thermomechanical pulp (TMP), recycled pulp, waste paper, etc.), animals (e.g., ascidians), algae, microorganisms (e.g., acetic acid bacteria (Acetobacter)), microbial products, etc. These cellulose raw materials may be used alone or in combination of two or more.

[0151] 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).

[0152] (Porous Cellulose Particles) The rubber composition for tires 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, on-ice performance can be improved. When the porosity of the porous cellulose particles is 75% or more, the on-ice performance can be improved effectively, 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 specific gravity, and then using the following formula: Porosity (%) = {1 - [bulk specific gravity of sample (g / mL)] / [true specific gravity of sample (g / mL)]} × 100, where the true specific gravity of cellulose is 1.5.

[0153] 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 the maintenance of abrasion resistance. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and major axis / minor axis ratio of the porous cellulose particles can be determined as follows. That is, porous cellulose particles are observed under a microscope to obtain an image, and this image is used to measure the long and short diameters of the particles (if the long and short diameters are the same, the length in a certain axis direction and the length in an axis direction perpendicular to it) for 100 particles, and the average particle size is obtained by calculating the average value, and the long diameter / short diameter ratio is obtained by averaging the values ​​obtained by dividing the long diameter by the short diameter.

[0154] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopal" and are also described in JP-A Nos. 2001-323095 and 2004-115284, and can be suitably used.

[0155] 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 component (A) is applied, the tire component, 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).

[0156] (Solid Particles) The rubber composition for a tire according to this embodiment may contain solid particles. Blending the solid particles into the rubber composition can improve performance on ice. The solid 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 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 powder; powders derived from natural minerals, such as whitebait; inorganic particles, such as graphite and zinc oxide whiskers; water-soluble metal salt particles, such as magnesium sulfate and metal salts of lignosulfonic acid; and non-metallic fibers, such as glass fibers. Of these, rice husks, walnut shells, eggshells, and whitebait are preferred.

[0157] 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).

[0158] (Others) In addition to the above-described components, the rubber composition for tires of the present 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).

[0159] (Method for Producing Rubber Composition) The method for producing the rubber composition for tires of the present embodiment is not particularly limited, but the tire rubber composition can be produced, for example, by blending the plant-derived silica (B1), the resin (C), and various components appropriately selected as necessary with the rubber component (A), followed by kneading, heating, extrusion, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0160] 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.

[0161] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0162] 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.

[0163] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of apparatuses for vulcanization include molding vulcanizers using molds used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0164] (Uses) The rubber composition for a tire of this embodiment can be applied to various constituent members of a tire, such as 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 for side reinforcing layers of run-flat tires, etc. In addition to tires, the rubber composition of this embodiment can also be applied to rubber crawlers, seismic isolation rubber, hoses, etc. Among these, the rubber composition for a tire of this embodiment does not impair wet grip performance and fuel economy performance, and is therefore suitable for use in tire treads and rubber crawler treads.

[0165] <Tire> The tire of this embodiment is characterized by including a tread rubber made of the above-described rubber composition for a tire. Because the tire of this embodiment includes a tread rubber made of the above-described rubber composition for a tire, the proportion of sustainable materials is improved without compromising performance.

[0166] Next, an embodiment of a tire of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of an embodiment of a tire of the present invention. The tire 1 of this embodiment shown in Fig. 1 has a pair of bead portions 2, a pair of sidewall portions 3, and a tread portion 4 continuous with both sidewall portions 3. The tire 1 also has a carcass 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 radially outward of a crown portion of the carcass 5.

[0167] 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 the structure of the carcass 5 in the tire of the present invention are not limited to this.

[0168] 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 usually consist 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.

[0169] 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.

[0170] 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.

[0171] 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.

[0172] 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.

[0173] Each rubber composition was produced according to a conventional method using the formulation shown in Table 1. Details of Modified SBR-A and Modified SBR-B in Table 1 are as follows. For each rubber composition obtained, the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) was calculated to calculate the sustainable material ratio. The larger the value, the better the effect.

[0174] <Synthesis of SBR-A> SBR-A is a styrene-butadiene rubber (SBR) obtained using butyllithium as an initiator, and its terminals are modified with N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine, and its glass transition temperature is −62° C. The Tg was measured by the following method.

[0175] <Synthesis of SBR-B> This is a styrene-butadiene rubber (SBR) obtained using butyllithium as an initiator, and its terminals are modified with N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine. Its Tg is −38°C.

[0176] <Synthesis of glycerin fatty acid ester (nonionic surfactant)> A glycerin fatty acid ester was used, which was synthesized by replacing the fatty acid from octanoic acid with an equimolar amount of palm oil-derived hydrogenated fatty acid, and then subjected to molecular distillation according to the method described in Production Example 1 of WO 2014 / 098155 (glycerin fatty acid ester composition). The glycerin fatty acid monoester content of the obtained glycerin fatty acid ester was 97% by mass.

[0177] <Measurement of Glass Transition Temperature> A DSC curve was recorded using a TA Instruments DSC250 while raising the temperature from −100° C. at 20° C. / min under a helium flow of 50 mL / min, and the peak top of the DSC differential curve was taken as the glass transition temperature.

[0178]

[0179] *1 Carbon black: N234 *2 Mineral-derived silica: Tosoh Silica Corporation, cetyltrimethylammonium bromide (CTAB) adsorption specific surface area = 191 m ２ / g, nitrogen adsorption specific surface area (BET method) = 245 m ２ / g, average primary particle size = 5 to 25 nm *3 Plant-derived silica: Rice husk silica *4 Aluminum hydroxide: Showa Denko K.K., trade name "Higilite (registered trademark)", average primary particle size = 0.5 to 10 μm *5 Hydrogenated C ５ *6 Silane coupling agent: manufactured by Evonik, trade name "Si75" *7 Nonionic surfactant: manufactured by the above <Synthesis of glycerin fatty acid ester> *8 Other chemicals: wax, etc.

[0180] From Table 1, it can be seen that the rubber compositions of the examples according to the present invention have an improved proportion of sustainable materials, and when applied to tires, the proportion of sustainable materials in the tires can be improved.

[0181] 1: Tire 2: Bead portion 3: Sidewall portion 4: Tread portion 5: Carcass 6: Belt 6A, 6B: Belt layer 7: Bead core 8: Tread rubber

Claims

1. A rubber composition for tires comprising a rubber component (A), a filler (B), and a resin (C), wherein the rubber component (A) comprises two or more types of rubber, the filler (B) comprises plant-derived silica (B1), and the ratio of the plant-derived silica (B1) in the filler (B) is 45 mass% or more.

2. The rubber composition for tires according to claim 1, wherein the rubber component (A) contains an isoprene skeleton rubber.

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

4. The rubber composition for tires according to claim 1, wherein the rubber component (A) contains a styrene-butadiene rubber.

5. The rubber composition for tires according to claim 1, wherein the resin (C) is a hydrogenated resin having a softening point higher than 110° C. and a weight average molecular weight in terms of polystyrene of 200 to 1600 g / mol.

6. The rubber composition for tires according to claim 1, wherein the plant-derived silica (B1) is silica derived from a grass family plant.

7. The rubber composition for tires according to claim 6, wherein the plant-derived silica (B1) is silica derived from rice husks.

8. The rubber composition for tires according to claim 1, which is for use in tire treads.

9. A tire comprising a tread rubber made of the rubber composition for tires according to claim 1.

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