Tire rubber composition, tire vulcanized rubber, tread rubber, and tire

Abstract

The present invention addresses the problem of providing: a tire rubber composition capable of improving the proportion of sustainable materials of a tire; and a tire vulcanized rubber, a tread rubber, and a tire, to which the rubber composition is applied. The solution to the problem includes: a tire rubber composition containing a rubber component (A), a filler (B), and a void-introducing agent (C), the tire rubber composition being characterized in that the filler (B) contains a plant-derived silica (B1); a tire vulcanized rubber obtained by vulcanizing the tire rubber composition; a tread rubber (8) composed of the tire rubber composition or the tire vulcanized rubber; and a tire (1) comprising the tread rubber (8).

Description

Rubber composition for tires, vulcanized rubber for tires, tread rubber, and tires

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

[0002] Traditionally, studless tires with soft tread rubber have been used to allow safe driving on ice in addition to normal road surfaces, and it is known that softening the tread rubber improves the tire's performance on ice.

[0003] For example, Patent Document 1 listed below discloses a rubber composition capable of significantly improving the on-ice performance of a tire, which comprises at least three diene polymers that form a plurality of mutually incompatible polymer phases and silica, wherein the blending amount of the at least three diene polymers is 10% by mass or more of the total amount of the diene polymers, the blending amount of a diene polymer (A) having the lowest glass transition temperature (Tg) among the diene polymers whose blending amount is 10% by mass or more of the total amount of the diene polymers is 85% by mass or more of the blending amount of a diene polymer (A) having the largest blending amount among the diene polymers other than the diene polymer (A), and the blending amount of a diene polymer (A) having the largest blending amount among the diene polymers other than the diene polymer (A) is 10% by mass or more of the total amount of the diene polymers. The rubber composition is characterized in that the diene polymer (B) other than the diene polymer (A) has a lower glass transition temperature (Tg) than the diene polymer (C) having the highest glass transition temperature (Tg) among the diene polymers, and is modified with a compound containing a silicon atom, and the diene polymer (B) is a copolymer of a conjugated diene compound and styrene and satisfies the following relationship: St + Vi / 2 ≦ 33 [where St is the bound styrene content (% by mass) of the diene polymer (B), and Vi is the vinyl bond amount (% by mass) of the conjugated diene compound portion of the diene polymer (B)], and the blended amount of the silica is 25 parts by mass or more per 100 parts by mass of the total of the diene polymers.

[0004] International Publication No. 2017 / 126629

[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, and a vulcanized rubber for a tire and a tread rubber that use such a rubber composition.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, the vulcanized rubber for a tire, the tread rubber, and the tire of the present invention, which solve the above-mentioned problems, are outlined as follows.

[0008] [1] A rubber composition for a tire, comprising a rubber component (A), a filler (B), and a void-introducing agent (C), wherein the filler (B) comprises plant-derived silica (B1).

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

[0010] [3] The rubber composition for a tire according to [2], wherein the rubber component (A) further comprises at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber.

[0011] [4] The rubber composition for a tire according to any one of [1] to [3], wherein the content of the filler (B) is 50 to 90 parts by mass per 100 parts by mass of the rubber component (A).

[0012] [5] The rubber composition for a tire according to any one of [1] to [4], wherein the void-introducing agent (C) includes a foaming agent (C1).

[0013] [6] The rubber composition for a tire according to any one of [1] to [5], further comprising a composite fiber (D).

[0014] [7] The rubber composition for a tire according to any one of [1] to [6], wherein the plant-derived silica (B1) is silica derived from a grass family plant.

[0015] [8] The rubber composition for a tire according to [7], wherein the plant-derived silica (B1) is silica derived from rice husks.

[0016] [9] A vulcanized rubber for tires, obtained by vulcanizing the rubber composition for tires according to any one of [1] to [8].

[0017]

[10] The tire vulcanizate according to [9], having voids.

[0018]

[11] A tread rubber comprising the rubber composition for a tire according to any one of [1] to [8] or the vulcanized rubber for a tire according to [9] or

[10] .

[0019]

[12] A tire comprising the tread rubber according to

[11] .

[0020] 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, as well as a vulcanized rubber for a tire and a tread rubber that use the rubber composition.Furthermore, according to the present invention, it is possible to provide a tire with an increased proportion of sustainable materials.

[0021] 1 is a cross-sectional view (partially enlarged) of a silica particle in the inward direction. It is a schematic diagram of mercury intrusion-extrusion curves of silica measured using a mercury porosimeter based on the mercury intrusion method, with the vertical axis representing the differential mercury intrusion amount (-dV / d(log d)) for mercury intrusion curve C and the differential mercury extrusion amount (-dV / d(log d)) for mercury extrusion curve D, where V represents the mercury intrusion amount (cc) for mercury intrusion curve C and the mercury extrusion amount (cc) for mercury extrusion curve D, and d represents the diameter (nm) of the opening of the silica pores, with the horizontal axis representing this d (nm).

[0023] FIG. 1 is a cross-sectional view of an embodiment of a tire of the present invention.

[0022] The rubber composition for a tire, the vulcanized rubber for a tire, the tread rubber, and the tire of the present invention will be described in detail below by way of example based on embodiments thereof.

[0023] <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.

[0024] 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 rubber composition for tires, vulcanized rubber for tires, tread rubber, and tire of interest.

[0025] 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.

[0026] 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.

[0027] 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.

[0028] <Rubber composition for tire> The rubber composition for tire of this embodiment contains a rubber component (A), a filler (B), and a void-introducing agent (C). The rubber composition for tire of this embodiment is characterized in that the filler (B) contains plant-derived silica (B1).

[0029] 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 therefore the rubber composition for a tire of this embodiment has an increased proportion of sustainable materials. Therefore, by applying the rubber composition for a tire of this embodiment to a tire, it is possible to increase the proportion of sustainable materials in the tire. Note that in a rubber composition for a tire containing a rubber component (A), a filler (B), and a void-introducing agent (C), even if the filler (B) contains the plant-derived silica (B1), performance such as on-ice performance is not impaired.

[0030] (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).

[0031] 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%.

[0032] 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).

[0033] 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.

[0034] 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.

[0035] 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.).

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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 (A) 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.

[0044] 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.

[0045] 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.

[0046] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component (A). 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.

[0047] 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.

[0048] 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.

[0049] 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 genera, 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.

[0050] 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.

[0051] The rubber component (A) preferably contains natural rubber (NR). When the rubber component (A) contains natural 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.

[0052] Preferably, the rubber component (A) further contains at least one selected from the group consisting of butadiene rubber (BR) and styrene-butadiene rubber (SBR). When the rubber component (A) contains at least one selected from the group consisting of butadiene rubber (BR) and styrene-butadiene rubber (SBR) together with natural rubber (NR), the elastic modulus at low temperatures decreases, the hysteresis loss increases, and the tire's braking performance on ice can be improved. Here, SBR and BR are easily compatible due to their butadiene-derived structures, and SBR and BR are easily separated from NR, so the rubber component (A) is prone to phase separation into an NR-containing phase (hereinafter abbreviated as "NR phase") and an SBR and BR-containing phase (hereinafter abbreviated as "SB phase"). Since SBR has a rigid styrene-derived structure, the SB phase containing SBR is harder than the NR phase, and it is believed that the NR phase and the SB phase of the rubber component (A) form a soft-hard phase structure. Because the rubber component (A) has such a phase structure, it is believed that a tire using this rubber composition has a low elastic modulus at low temperatures, a high hysteresis loss, and improved braking performance on ice.

[0053] The rubber component (A) may be unmodified or modified. However, from the viewpoint of distributing more silica in the SB phase, it is preferable that one or both of the butadiene rubber (BR) and styrene-butadiene rubber (SBR) constituting the SB phase be modified with a modifying functional group having affinity for the plant-derived silica (B1). The modifying functional group is not particularly limited as long as it has affinity for the plant-derived silica (B1), but it is preferable that it contains at least one atom selected from the group consisting of a nitrogen atom, a silicon atom, an oxygen atom, and a tin atom. Examples of such functional groups include a nitrogen-containing functional group, a silicon-containing functional group, an oxygen-containing functional group, and a tin-containing functional group. These may be used alone or in combination of two or more. Among these, a nitrogen-containing functional group, a silicon-containing functional group, and an oxygen-containing functional group are preferred because they strongly interact with the plant-derived silica (B1).

[0054] The method for introducing a modifying functional group into the rubber component (A) is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include a method using a functional group-containing polymerization initiator, a method of copolymerizing a functional group-containing monomer with another compound, a method of reacting a modifier with the polymerization terminal of the rubber component (A), etc. These methods may be used alone or in combination of two or more.

[0055] The nitrogen atom-containing modifying functional group is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a substituted amino group represented by the following general formula (I) and a cyclic amino group represented by the following general formula (II).

[0056]

[0057] In general formula (I), R １ are each independently an alkyl group, a cycloalkyl group, or an aralkyl group having 1 to 12 carbon atoms. Here, the alkyl group is preferably a methyl group, an ethyl group, a butyl group, an octyl group, or an isobutyl group, the cycloalkyl group is preferably a cyclohexyl group, and the aralkyl group is preferably a 3-phenyl-1-propyl group. １ may be of the same kind or of different kinds.

[0058]

[0059] In general formula (II), R ２The alkylene group is an alkylene group, a substituted alkylene group, an oxy-alkylene group, or an N-alkylamino-alkylene group having 3 to 16 methylene groups. Here, the substituted alkylene group includes mono- to octa-substituted alkylene groups, and examples of the substituents include linear or branched alkyl groups, cycloalkyl groups, bicycloalkyl groups, aryl groups, and aralkyl groups having 1 to 12 carbon atoms. Here, the alkylene group is preferably a trimethylene group, a tetramethylene group, a hexamethylene group, or a dodecamethylene group. The substituted alkylene group is preferably a hexadecamethylene group. The oxyalkylene group is preferably an oxydiethylene group. The N-alkylamino-alkylene group is preferably an N-alkylazadiethylene group.

[0060] Examples of the cyclic amino group represented by general formula (II) are not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include 2-(2-ethylhexyl)pyrrolidine, 3-(2-propyl)pyrrolidine, 3,5-bis(2-ethylhexyl)piperidine, 4-phenylpiperidine, 7-decyl-1-azacyclotridecane, 3,3-dimethyl-1-azacyclotetradecane, 4-dodecyl-1-azacyclooctane, 4-(2-phenylbutyl)-1-azacyclooctane, 3-ethyl-5-cyclohexyl-1-azacycloheptane, 4-hexyl-1-azacycloheptane, 9-isoamyl-1-azacycloheptadecane, 2-methyl-1-azacyclopentane ... Examples include groups in which one hydrogen atom bonded to a nitrogen atom has been removed from cycloheptadec-9-ene, 3-isobutyl-1-azacyclododecane, 2-methyl-7-t-butyl-1-azacyclododecane, 5-nonyl-1-azacyclododecane, 8-(4'-methylphenyl)-5-pentyl-3-azabicyclo[5.4.0]undecane, 1-butyl-6-azabicyclo[3.2.1]octane, 8-ethyl-3-azabicyclo[3.2.1]octane, 1-propyl-3-azabicyclo[3.2.2]nonane, 3-(t-butyl)-7-azabicyclo[4.3.0]nonane, 1,5,5-trimethyl-3-azabicyclo[4.4.0]decane, etc. These may be used alone or in combination of two or more.

[0061] The silicon atom-containing modifying functional group is not particularly limited and can be appropriately selected depending on the purpose. For example, the silicon atom-containing modifying functional group may be a group represented by the following general formula (III): ３ ) ａ Z (R ４ ) ｂ . . (III) and the like.

[0062] In the general formula (III), Z is silicon, and R ３ are each independently selected from the group consisting of alkyl groups having 1 to 20 carbon atoms, cycloalkyl groups having 3 to 20 carbon atoms, aryl groups having 6 to 20 carbon atoms, and aralkyl groups having 7 to 20 carbon atoms; R ４ are each independently chlorine or bromine, a is 0 to 3, b is 1 to 4, and a+b=4. Here, the alkyl group is preferably a methyl group, an ethyl group, an n-butyl group, an n-octyl group, or a 2-ethylhexyl group, the cycloalkyl group is preferably a cyclohexyl group, the aryl group is preferably a phenyl group, and the aralkyl group is preferably a neophyl group. ３ may be the same or different. ４ may be of the same kind or of a different kind.

[0063] Chemically bonding the rubber component (A) constituting the SB phase with silicon via a silicon-carbon bond is preferable in that it increases the affinity between the SB phase and the filler (B) and allows a larger amount of filler (B) to be distributed to the SB phase. Generally, when silicon is simply mixed into a rubber composition, the reinforcing properties of the rubber composition are low due to its low affinity with the rubber component (A). However, chemically bonding the rubber component (A) constituting the SB phase with silicon via a silicon-carbon bond increases the affinity between the rubber component (A) constituting the SB phase with the filler (B), thereby enabling the hysteresis loss of the tire to be further increased.

[0064] When the objective is to enhance the interaction of the modified rubber with silica, examples of the modifier include a modifier having at least one of a compound represented by the following general formula (IV) and a compound represented by the following general formula (V).

[0065] R ５ ｃ -Si-(OR ６ ) ４－ｃ ... (IV) In general formula (IV), R ５ and R ６ 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, c is an integer of 0 to 2, and OR ６ If there are multiple, multiple OR ６ may be the same or different, and the molecule does not contain an active proton.

[0066] Specific examples of the compound (alkoxysilane compound) represented by the general formula (IV) include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane, tetraisobutoxysilane, tetra-sec-butoxysilane, tetra-tert-butoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltrippropoxysilane, methyltriisopropoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltrippropoxysilane, and ethyltriisopropoxysilane. Examples of suitable silanes include silane, propyltrimethoxysilane, propyltriethoxysilane, propyltripropoxysilane, propyltriisopropoxysilane, butyltrimethoxysilane, butyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, dimethoxydimethylsilane, methylphenyldimethoxysilane, dimethyldiethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, and divinyldiethoxysilane. Among these, tetraethoxysilane, methyltriethoxysilane, and dimethyldiethoxysilane are preferred. These may be used alone or in combination of two or more.

[0067]

[0068] In general formula (V), A is a monovalent group having at least one functional group selected from the group consisting of epoxy, glycidyloxy, isocyanate, imine, carboxylic acid ester, carboxylic acid anhydride, cyclic tertiary amine, non-cyclic tertiary amine, pyridine, silazane, and disulfide; R ７ is a single bond or a divalent hydrocarbon group, and R ８ and R ９ are each independently 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, and OR ９ If there are multiple, multiple OR ９ may be the same or different, and the molecule does not contain an active proton.

[0069] Specific examples of the compound represented by general formula (V) above include epoxy group-containing alkoxysilane compounds, such as 2-glycidyloxyethyltrimethoxysilane, 2-glycidyloxyethyltriethoxysilane, (2-glycidyloxyethyl)methyldimethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3-glycidyloxypropyltriethoxysilane, (3-glycidyloxypropyl)methyldimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltriethoxysilane, and 2-(3,4-epoxycyclohexyl)ethyl(methyl)dimethoxysilane. Among these, 3-glycidyloxypropyltrimethoxysilane and 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane are preferred.

[0070] Examples of the silicon-based coupling agent are not particularly limited and can be appropriately selected depending on the purpose. Examples include hydrocarbyloxysilane compounds, SiCl ４ (silicon tetrachloride), (R １０ ) SiCl ３ , (R １０ ) ２ SiCl ２ , (R １０ )３ SiCl, etc. １０ each independently represents an alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, or an aralkyl group having 7 to 20 carbon atoms. Among these, hydrocarbyloxysilane compounds are preferred from the viewpoint of their high affinity for silica.

[0071] The hydrocarbyloxysilane compound is not particularly limited and can be appropriately selected depending on the purpose. For example, hydrocarbyloxysilane compounds represented by the following general formula (VI) can be mentioned.

[0072]

[0073] In general formula (VI), n1+n2+n3+n4=4 (wherein n2 is an integer of 1 to 4, and n1, n3, and n4 are integers of 0 to 3). １ is at least one functional group selected from a saturated cyclic tertiary amine compound residue, an unsaturated cyclic tertiary amine compound residue, a ketimine residue, a nitrile group, a (thio)isocyanate group, an isocyanuric acid trihydrocarbyl ester group, a nitrile group, a pyridine group, a (thio)ketone group, an amide group, and a primary or secondary amino group having a hydrolyzable group. １ may be the same or different, and A １ may be a divalent group that bonds with Si to form a cyclic structure. ２１ represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when n1 is 2 or more, they may be the same or different. ２２ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, both of which may contain a nitrogen atom and / or a silicon atom. ２２ may be the same or different, or may be joined together to form a ring. ２３represents a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom, and when n3 is 2 or greater, may be the same or different. ２４ represents a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when n4 is 2 or greater. As the hydrolyzable group in the primary or secondary amino group having a hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0074] Furthermore, the hydrocarbyloxysilane compound represented by the above general formula (VI) is preferably a hydrocarbyloxysilane compound represented by the following general formula (VII).

[0075]

[0076] In general formula (VII), p1+p2+p3=2 (wherein p2 is an integer of 1 or 2, and p1 and p3 are integers of 0 or 1). ２ is NRa (Ra is a monovalent hydrocarbon group, a hydrolyzable group, or a nitrogen-containing organic group). ２５ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ２６ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a nitrogen-containing organic group, any of which may contain a nitrogen atom and / or a silicon atom. ２６ may be the same or different, or may be joined together to form a ring. ２７ R is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or a halogen atom. ２８is 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. As the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0077] Furthermore, the hydrocarbyloxysilane compound represented by the above general formula (VI) is also preferably a hydrocarbyloxysilane compound represented by the following general formula (VIII) or (IX).

[0078]

[0079] In general formula (VIII), q1+q2=3 (wherein q1 is an integer of 0 to 2, and q2 is an integer of 1 to 3). ３１ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３２ and R ３３ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３４ are 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. ３５ 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.

[0080]

[0081] In general formula (IX), r1+r2=3 (where r1 is an integer of 1 to 3, and r2 is an integer of 0 to 2). ３６ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ３７represents a dimethylaminomethyl group, a dimethylaminoethyl group, a diethylaminomethyl group, a diethylaminoethyl group, a methylsilyl(methyl)aminomethyl group, a methylsilyl(methyl)aminoethyl group, a methylsilyl(ethyl)aminomethyl group, a methylsilyl(ethyl)aminoethyl group, a dimethylsilylaminomethyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and when r1 is 2 or more, they may be the same or different. R ３８ represents a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and may be the same or different when r2 is 2. A specific example of the aminoalkoxysilane compound represented by general formula (IX) is N-(1,3-dimethylbutylidene)-3-triethoxysilyl-1-propanamine.

[0082] It is also preferable that the hydrocarbyloxysilane compound represented by the above general formula (VI) has two or more nitrogen atoms represented by the following general formula (X) or (XI).

[0083]

[0084] In general formula (X), R ４０ is a trimethylsilyl group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４１ R is a hydrocarbyloxy group having 1 to 20 carbon atoms, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４２ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms, where TMS represents a trimethylsilyl group (the same applies hereinafter).

[0085]

[0086] In general formula (XI), R ４３ and R ４４are each independently a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４５ is a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, and each R ４５ may be the same or different.

[0087] The hydrocarbyloxysilane compound represented by the above general formula (VI) is also preferably a hydrocarbyloxysilane compound represented by the following general formula (XII).

[0088]

[0089] In general formula (XII), s1+s2 is 3 (wherein s1 is an integer of 0 to 2, and s2 is an integer of 1 to 3). ４６ 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. ４７ and R ４８ are each independently a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ４７ or R ４８ may be the same or different.

[0090] Furthermore, the hydrocarbyloxysilane compound represented by the above general formula (VI) is also preferably a compound represented by the following general formula (XIII).

[0091]

[0092] In general formula (XIII), X is a halogen atom. ４９ is a divalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms or a divalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ５０ and R ５１ are each independently a hydrolyzable group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms, or R ５０ and R ５１are bonded to form a divalent organic group. ５２ and R ５３ are each independently a halogen atom, a hydrocarbyloxy group, a monovalent aliphatic or alicyclic hydrocarbon group having 1 to 20 carbon atoms, or a monovalent aromatic hydrocarbon group having 6 to 18 carbon atoms. ５０ and R ５１ As the hydrolyzable group, a hydrolyzable group is preferred, and as the hydrolyzable group, a trimethylsilyl group or a tert-butyldimethylsilyl group is preferred, and a trimethylsilyl group is particularly preferred.

[0093] The hydrocarbyloxysilane compounds represented by the above general formulas (VI) to (XIII) are preferably used when the modified rubber is produced by anionic polymerization. The hydrocarbyloxysilane compounds represented by the general formulas (VI) to (XIII) are preferably alkoxysilane compounds.

[0094] The modifier suitable for modifying a diene polymer by anionic polymerization is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include 3,4-bis(trimethylsilyloxy)-1-vinylbenzene, 3,4-bis(trimethylsilyloxy)benzaldehyde, 3,4-bis(tert-butyldimethylsilyloxy)benzaldehyde, 2-cyanopyridine, 1,3-dimethyl-2-imidazolidinone, 1-methyl-2-pyrrolidone, etc. These may be used alone or in combination of two or more.

[0095] The hydrocarbyloxysilane compound is preferably the amide moiety of a lithium amide compound used as a polymerization initiator in anionic polymerization. The lithium amide compound is not particularly limited and can be appropriately selected depending on the purpose. Examples include lithium hexamethyleneimide, lithium pyrrolidide, lithium piperidide, lithium heptamethyleneimide, lithium dodecamethyleneimide, lithium dimethylamide, lithium diethylamide, lithium dibutylamide, lithium dipropylamide, lithium diheptylamide, lithium dihexylamide, lithium dioctylamide, lithium di-2-ethylhexylamide, lithium didecylamide, lithium N-methylpiberazide, lithium ethylpropylamide, lithium ethylbutylamide, lithium ethylbenzylamide, and lithium methylphenethylamide. For example, the modifier that forms the amide moiety of lithium hexamethyleneimide is hexamethyleneimine, the modifier that forms the amide moiety of lithium pyrrolidide is pyrrolidine, and the modifier that forms the amide moiety of lithium piperidide is piperidine. These may be used alone or in combination of two or more.

[0096] The modifying functional group containing an oxygen atom is not particularly limited and can be appropriately selected depending on the purpose, and examples thereof include alkoxy groups such as methoxy, ethoxy, n-propoxy, isopropoxy, n-butoxy, sec-butoxy, and t-butoxy; alkoxyalkyl groups such as methoxymethyl, methoxyethyl, ethoxymethyl, and ethoxyethyl; alkoxyaryl groups such as methoxyphenyl and ethoxyphenyl; alkylene oxide groups such as epoxy and tetrahydrofuranyl; and trialkylsilyloxy groups such as trimethylsilyloxy, triethylsilyloxy, and t-butyldimethylsilyloxy. These may be used alone or in combination of two or more.

[0097] From the viewpoint of incorporating a larger amount of filler (B) into the SB phase, it is preferable that the butadiene rubber (BR) and the styrene-butadiene rubber (SBR) are each silane-modified. Specifically, it is preferable that the butadiene rubber (BR) and the styrene-butadiene rubber (SBR) are each rubbers modified with a hydrocarbyloxysilane compound represented by the above-mentioned general formulas (VI) to (XIII).

[0098] The mass n of the natural rubber in the rubber component (A) is preferably 40% by mass or more. The mass n of the natural rubber, the mass b of the butadiene rubber, and the mass s of the styrene-butadiene rubber preferably satisfy the relationship s≦b≦n (provided that when n=b, s<b). The units of mass n, mass b, and mass s are "% by mass." The mass n of the natural rubber and the mass b of the butadiene rubber may be the same, and it is preferable that the mass b of the butadiene rubber and the mass s of the styrene-butadiene rubber are different. When the mass n of the natural rubber in the rubber component (A) is 40% by mass or more, the resulting tire does not become too hard at low temperatures and can deform, and a low elastic modulus at low temperatures and high hysteresis loss at low temperatures can both be achieved, ensuring sufficient braking performance on ice. From the viewpoint of further improving the on-ice braking performance of the tire, the mass n of the natural rubber in the rubber component (A) is more preferably 45 mass % or more, more preferably 50 mass % or more, and even more preferably 55 mass % or more.

[0099] The ratio (b / s) of the mass b of the butadiene rubber to the mass s of the styrene-butadiene rubber is preferably 1.0 to 2.0. When the mass s of the styrene-butadiene rubber is equal to or less than the mass b of the butadiene rubber, the elastic modulus of the SB phase is prevented from becoming too high, and the elastic modulus of the tire in a low-temperature environment is easily reduced. The mass s of the styrene-butadiene rubber in the rubber component (A) is preferably 10 to 30% by mass, and more preferably 15 to 25% by mass.

[0100] The ratio [vi / a] of the vinyl bond content vi (%) of the rubber component (A) to the content a (parts by mass) of the rubber component (A) is preferably 8 or more. Here, the unit of the content a of the rubber component (A) is "parts by mass". [vi / a] is calculated by the following formula: [(a ｂ ×vi ｂ ) + (a ｓｂ ×vi ｓｂ )] / a where, a ｂ is the content of butadiene rubber (parts by mass), ｂ is the vinyl bond content (%) of the butadiene rubber, a ｓｂ is the content of styrene-butadiene rubber (parts by mass), ｓｂ is the vinyl bond content (%) of the styrene-butadiene rubber. ｂ , a ｓｂ The unit of is "parts by mass." When vi / a is 8 or more, the elastic modulus of the tire at low temperatures is further reduced, making the tire more susceptible to deformation, thereby increasing hysteresis loss at low temperatures and improving braking effectiveness.

[0101] Furthermore, it is preferable that the ratio (b / s) of the mass b of the butadiene rubber to the mass s of the styrene-butadiene rubber is 1.0 to 2.0, and the ratio [vi / a] of the vinyl bond content vi (%) of the rubber component (A) to the content a of the rubber component (A) is not less than 8. Here, the vinyl bond content vi (%) of the rubber component (A) can be determined by an infrared method (Morello method).

[0102] The ratio (st / s) of the styrene bond content st (%) of the rubber component (A) to the mass s of the styrene-butadiene rubber is preferably 1.0 or less, more preferably 0.7 or less, and even more preferably 0.6 or less. When st / s is 1.0 or less, the rigidity of the styrene-butadiene copolymer rubber is reduced, which makes it possible to further reduce the elastic modulus of the tire in low-temperature environments and facilitates improved braking performance on ice. Here, the styrene bond content st (%) of the rubber component (A) can be determined by an infrared method (Morello method).

[0103] (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 the filler (B) is preferably in the range of 50 to 90 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 50 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 90 parts by mass or less, the modulus of elasticity of the rubber composition for a tire does not become too high and the tire's performance on ice can be improved. Therefore, a rubber composition for a tire in which the content of filler (B) is 50 to 90 parts by mass per 100 parts by mass of the rubber component (A) can improve the abrasion resistance and ice performance of the tire. The content of the filler (B) relative to 100 parts by mass of the rubber component (A) is more preferably 55 parts by mass or more, and more preferably 65 parts by mass or more, and is more preferably 85 parts by mass or less, and more preferably 75 parts by mass or less.

[0104] -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.

[0105] 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.

[0106] The ratio of the plant-derived silica (B1) in the filler (B) is preferably 5% by mass or more, more preferably 10% by mass or more, more preferably 25% by mass or more, and even more preferably 45% by mass or more. By making the ratio of the plant-derived silica (B1) in the filler (B) 5% 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, the ratio of sustainable materials in the tires can be further increased.

[0107] 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.

[0108] 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.

[0109] The plant-derived silica (B1) has a nitrogen adsorption specific surface area (N ２ SA) is 50m ２ / g or more, and ２ / g or more is more preferable, and 150m ２ / g or more, and ２ / g or less, and ２ / g or less is more preferable, and 230m ２ / g or less is more preferable, and 200m ２ / g or less. In this specification, the nitrogen adsorption specific surface area (N ２SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0110] The content of the plant-derived silica (B1) 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 plant-derived silica (B1) is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 30 parts by mass or more, and is preferably 300 parts by mass or less, more preferably 200 parts by mass or less, even more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0111] When the rubber component (A) contains at least one of butadiene rubber and styrene-butadiene rubber, it is preferable that 50% by mass or more of the total content of the plant-derived silica (B1) is contained in the phase containing butadiene rubber and styrene-butadiene rubber (SB phase). When the amount of plant-derived silica (B1) contained in the SB phase is 50% by mass or more of the total silica, the elastic modulus of the tire at low temperatures can be reduced. The amount of plant-derived silica (B1) contained in the SB phase is more preferably greater than 50% by mass, more preferably 60% by mass or more, and even more preferably 70% by mass or more. The amount of filler containing plant-derived silica (B1) contained in the SB phase (filler distribution ratio) can be measured by the following method. The filler distribution ratio in a rubber composition is approximate to the filler distribution ratio in a vulcanized rubber, and the filler distribution ratio can be measured using a vulcanized rubber obtained by vulcanizing the rubber composition as a measurement sample.

[0112] For example, after cutting a sample in a direction forming an angle of 38° with respect to the top surface of the sample, the smooth surface of the sample formed by cutting is photographed from a direction perpendicular to the smooth surface using a scanning electron microscope (SEM) [e.g., Carl Zeiss, trade name "Ultra 55"] using a focused ion beam at an accelerating voltage of 1.8 to 2.2 V. The obtained SEM image can be processed and analyzed to measure the filler distribution ratio. There are several analytical methods, but the following analytical method can be applied in the present invention. For example, when measuring a system in which the rubber component (A) is separated into two phases, such as the NR phase and SB phase described above, one possible method is to convert the obtained SEM image into a ternary image of the two rubber components (A) and the filler (B) using a histogram, and then perform image analysis based on the resulting ternary image. In this case, the perimeter of the filler (B) contained in each of the two rubber component (A) phases is determined, and the proportion of filler (B) present in one of the rubber component (A) phases is calculated from the total amount of filler (B) within the measurement area. If filler (B) is present at the interface between the two rubber components (A), the two points where each rubber component (A) and filler (B) contact are connected to divide the perimeter of the filler (B). Note that particles of 20 pixels or less are considered noise and are not counted. Furthermore, the method for measuring the abundance rate of filler (B) and the image analysis method are not limited to those described above.

[0113] The plant-derived silica (B1) preferably has a CTAB (cetyltrimethylammonium bromide) adsorption specific surface area of ​​150 m ２ / g or more, more preferably 180m ２ / g or more, more preferably 190m ２ / g or more, more preferably 195m ２ / g or more, particularly preferably 197m ２ The CTAB adsorption specific surface area of ​​the plant-derived silica (B1) is preferably 600 m / g or more. ２ / g or less, more preferably 300m ２ / g or less, particularly preferably 250m ２ / g or less. The CTAB specific surface area of ​​the plant-derived silica (B1) is 180 m ２ / g or more, the abrasion resistance is further improved, and the CTAB specific surface area of ​​the plant-derived silica (B1) is 600 m ２ If the value is 0.1 / g or less, the rolling resistance is small.

[0114] The plant-derived silica (B1) has a cetyltrimethylammonium bromide adsorption specific surface area (CTAB) (m ２ / g) and the ink bottle-like pore index (IB) are determined by the following formula (Y): IB≦−0.36×CTAB+86.8 (Y) [In formula (Y), the ink bottle-like pore index (IB) is a value calculated by the following formula (Z): IB=M2−M1 (Z) In formula (Z), M1 is the diameter of 1.2×10 ５ For silica having pores with openings in the outer surface having a size in the range of 1 nm to 6 nm, M2 is the diameter (nm) of the openings that show the maximum amount of mercury intrusion when the pressure is increased from 1 PSI to 32,000 PSI in a measurement using a mercury porosimeter based on the mercury intrusion method, and M3 is the diameter (nm) of the openings that show the maximum amount of mercury emission when the pressure is decreased from 32,000 PSI to 1 PSI in the same measurement.

[0115] Here, in formula (Y), the cetyltrimethylammonium bromide adsorption specific surface area (CTAB) (m ２ / g) means a value measured in accordance with ASTM D3765-92. However, since ASTM D3765-92 is a method for measuring the CTAB of carbon black, in the present invention, the standard product IRB#3 (83.0 m ２ Instead of silica OT (di-2-ethylhexyl sodium sulfosuccinate) solution, a cetyltrimethylammonium bromide (hereinafter abbreviated as CE-TRAB) standard solution was separately prepared and used to standardize the silica OT (di-2-ethylhexyl sodium sulfosuccinate) solution. The adsorption cross section of one CE-TRAB molecule on the silica surface was determined to be 0.35 nm ２ and the specific surface area (m ２ / g) is taken as the value of CTAB. This is because the surfaces of carbon black and silica are different, and it is thought that even with the same surface area, there will be differences in the amount of CE-TRAB adsorbed.

[0116] In addition, in formula (Y), the ink bottle pore index (IB) is the number of holes in a diameter of 1.2 × 10 ５ The mercury porosimeter value is the value calculated by the above formula (Z) using the diameter (M1) (nm) of the opening that shows the maximum amount of mercury intrusion when the pressure is increased from 1 PSI to 32,000 PSI, and the diameter (M2) (nm) of the opening that shows the maximum amount of mercury discharge when the pressure is decreased from 32,000 PSI to 1 PSI, in measurements using a mercury porosimeter based on mercury intrusion porosimetry for silica having pores with openings on the outer surface that are in the range of 1 nm to 6 nm. Measurement using a mercury porosimeter based on mercury intrusion porosimetry is a useful method because it is simpler and more quantitative than measurements using an electron microscope, which has traditionally been widely used to evaluate pore morphology.

[0117] Generally, silica particles have a large number of concave pores with openings on their outer surface. Figure 1 shows a schematic diagram simulating the shape of these pores in a cross section of a silica particle in the direction of the center. The concave pores in the cross section of the particle in the direction of the center have various shapes, and the diameter M of the opening on the outer surface of the particle ａ and the pore diameter (inner diameter) R ａ In some cases, the pores A have substantially the same shape, i.e., are substantially cylindrical in the cross section of the particle in the inward direction, while the pore diameter (inner diameter) R ｂ The diameter M of the opening on the outer surface of the particle ｂ In some cases, the pores B have a shape in which the outer surface is narrower than the outer surface, i.e., the pores B have an ink bottle shape in the cross section along the inboard direction of the particle. However, if the pores B have an ink bottle shape in the cross section along the inboard direction of the particle, rubber molecular chains have difficulty penetrating from the outer surface to the interior of the particle, and therefore the rubber molecular chains cannot sufficiently adsorb silica when silica is blended into the rubber component. Therefore, by reducing the number of pores B having such ink bottle shapes and increasing the number of pores A having a substantially cylindrical shape in the cross section along the inboard direction of the particle, the penetration of rubber molecular chains can be efficiently promoted, and sufficient reinforcement can be exhibited without increasing tan δ, contributing to improved tire handling stability.

[0118] From the above viewpoint, in the present invention, the plant-derived silica (B1) blended into the rubber component (A) has an ink-bottle-shaped pore index (IB) specified to reduce the number of ink-bottle-shaped pores B in the particle's inward cross section. As described above, when pressure is increased in a measurement using a mercury porosimeter based on the mercury intrusion method, mercury is easily injected into the approximately cylindrical pores A because the openings on the outer surface are open, but mercury is difficult to inject into the ink-bottle-shaped pores B because the openings on the outer surface are closed. On the other hand, when pressure is decreased, for the same reason, mercury is easily expelled from the approximately cylindrical pores A to the outside, but almost no mercury is expelled from the ink-bottle-shaped pores B to the outside.

[0119] Therefore, in measurements using a mercury porosimeter based on the mercury intrusion method, hysteresis occurs in the mercury intrusion-extrusion curve C-D, as shown in Fig. 2. That is, under relatively low pressure, mercury is gradually injecting into the approximately cylindrical pore A, but once a certain pressure is reached, mercury is suddenly injecting into pores other than the approximately cylindrical pore, including the ink-bottle-shaped pore B, which had previously been difficult for mercury to penetrate, resulting in a sudden increase in the amount of intrusion, and a mercury intrusion curve C is drawn when the vertical axis represents the differential mercury intrusion amount (-dV / d(log d)) and the horizontal axis represents the diameter M (nm) of the opening of the silica pore. On the other hand, when the pressure is decreased after a sufficient increase, although the mercury remains difficult to expel under relatively high pressures, once a certain pressure is reached, the mercury that had been injected into the pores is expelled from the pores all at once, resulting in a sudden increase in the amount of mercury expelled. This results in a mercury expulsion curve D, where the vertical axis represents the differential mercury expulsion rate (-dV / d (log d)) and the horizontal axis represents the diameter M (nm) of the opening of the silica pore. Once mercury is injected into the pores, it tends to be difficult to expel it from the pores as the pressure decreases. Therefore, as the pressure decreases, an increase in the amount of mercury expelled is observed at a position of diameter (M2) that is larger than the position of diameter (M1), which indicates an increase in the amount of mercury expelled during pressure increase. The difference between these diameters (M2 - M1) corresponds to IB in Figure 2 . In particular, the tendency for the injected mercury to be difficult to expel from pore B, which has an ink-bottle shape, is particularly pronounced. While mercury is injected into pore B during pressure increase, almost no mercury is expelled from pore B during pressure decrease.

[0120] By employing such a measurement method and utilizing the mercury intrusion-extrusion curve C-D, which is drawn due to the properties of the pores, and in accordance with the above formula (Z), the difference IB between the diameter (M1) (nm) of the opening that exhibits the maximum amount of mercury intrusion when the pressure is increased from 1 PSI to 32,000 PSI in measurements using a mercury porosimeter based on the mercury intrusion method, and the diameter (M2) (nm) of the opening that exhibits the maximum amount of mercury extrusion when the pressure is decreased from 32,000 PSI to 1 PSI, is determined. Although this value apparently indicates the difference between these diameters (length: nm), it actually means a pore index that indicates the proportion of ink-bottle-shaped pores B present in the silica. That is, the smaller the proportion of pores B that have an ink-bottle shape and have sufficiently narrow openings, the more the amount of mercury injected and the amount of mercury released approach each other, the smaller the difference between the diameter (M1) of the opening that indicates the maximum amount of mercury injected and the diameter (M2) of the opening that indicates the maximum amount of mercury released, and the smaller the IB value.On the other hand, the greater the proportion of pores B that have an ink-bottle shape, the more the amount of mercury released becomes less than the amount of mercury injected, the larger the difference between the diameter (M1) of the opening that indicates the maximum amount of mercury injected and the diameter (M2) of the opening that indicates the maximum amount of mercury released, and the larger the IB value.

[0121] The IB has the property that it can vary depending on the value of the CTAB, and as the CTAB increases, the IB value tends to decrease. Therefore, it is preferable that the plant-derived silica (B1) used in the present invention satisfies the above formula (Y). When the IB and CTAB of silica satisfy the above formula (Y), the number of pores B having a narrow opening and exhibiting an ink bottle shape is effectively reduced, and the proportion of pores A having a substantially cylindrical shape is increased, so that rubber molecular chains can sufficiently penetrate and be adsorbed, and sufficient reinforcement is exhibited, making it possible to improve steering stability without increasing the rolling resistance of the tire.

[0122] -Carbon Black- The filler (B) preferably contains carbon black. The carbon black reinforces the rubber composition and can improve the abrasion resistance of the rubber composition. As the carbon black, plant-derived carbon black and recycled carbon black (also called "recycled carbon black") are preferred. Examples of plant-derived carbon black include those derived from castor oil and pine oil. Recycled carbon black will be described in detail below.

[0123] From the viewpoint of further improving the abrasion resistance of the rubber composition and a tire using the same, the content of carbon black (total of recycled carbon black and carbon black other than recycled carbon black) in the rubber composition 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 rubber component (A). Also, from the viewpoint of workability of the rubber composition, the content of carbon black in the rubber composition is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 70 parts by mass or less, per 100 parts by mass of rubber component (A).

[0124] --Recycled Carbon Black-- In this specification, "recycled carbon black" refers to carbon black recovered from recycled waste raw materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only that generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process, for example, in tire retreading, where the tread portion remaining on the base tire is scraped off. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELTs (End-of-Life Tires) that have reached the end of their service life. Waste oils are not limited to those generated during the decomposition of plastics and rubber, but also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils containing carbon black or rubber containing carbon black are desirable. "Recycled carbon black" differs from carbon black produced directly from hydrocarbons such as petroleum, natural gas, and coal, i.e., non-recycled carbon black. Note that "used" here refers not only to waste oils discarded after actual use, but also to waste oils that were produced but discarded without actually being used.

[0125] The recycled carbon black is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. Recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is readily available because vulcanized rubber products containing carbon black are readily available and can be easily obtained by pyrolysis. Furthermore, the recycled carbon black is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either of them. When recovering carbon black from the volatile component, the oil component with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixing of different grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0126] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in the rubber and tires. Therefore, recycled carbon black obtained from the solid residues has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, the higher the carbon content of the recycled carbon black, the better. The carbon content of the recycled carbon black is preferably 80% by mass or more, more preferably 85% by mass or more, even more preferably 87% by mass or more, and particularly preferably 89% by mass or more. Furthermore, the carbon content of the recycled carbon black is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0127] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residue obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. In one embodiment, the lower limit of the ash content of the recycled carbon black may be 0.5% by mass.

[0128] The recycled carbon black can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3,427,975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (paragraph

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

[0004] of Japanese Patent Publication No. 6,856,781 (Comparison of the Surface Morphology and Chemistry of Pyrolytic Carbon Black and Commercially Available Carbon Black, Powder Technology 160 (2005) pp. 190-193).

[0129] The recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained by a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent Publication No. 6,856,781, carbon black obtained by a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks treated to include functional groups on their surfaces.

[0130] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0131] 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.

[0132] Furthermore, when the crosslinked rubber product used in the degradation is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for 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.

[0133] The recycled carbon black has a nitrogen adsorption specific surface area of ​​40 to 100 m as measured by the BET method. ２ / g, and 50 to 90m ２ / g, and more preferably 55 to 75m ２ In this specification, the nitrogen adsorption specific surface area of ​​recycled carbon black measured by the BET method is a statistical thickness specific surface area (STSA) determined in accordance with ASTM D6556.

[0134] The pH of the recycled carbon black is preferably 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. In this specification, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0135] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, the toluene color transmittance of recycled carbon black is determined in accordance with ASTM D1618.

[0136] The recycled carbon black preferably has a heat loss of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less at 125°C. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0137] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0138] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. Herein, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0139] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. Herein, the 325 mesh (44 μm) sieve residue of the recycled carbon black is determined in accordance with ASTM D1514.

[0140] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0141] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Herein, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0142] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Here, in this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming a refractive index of 1.33 for water and a refractive index of 1.75 for the filler.

[0143] The recycled carbon black preferably contains particles of 5 μm or less in a proportion of 50% by volume or more, more preferably 70% by volume or more, and particularly preferably 80% by volume or more.

[0144] The recycled carbon black preferably has an ash content of 25% by mass or less, more preferably 20% by mass or less, and particularly preferably 15% by mass or less. When the ash content of the recycled carbon black is 25% by mass or less, the physical properties of the rubber product to which the rubber composition is applied can be improved. Herein, the ash content of the recycled carbon black is determined in accordance with ASTM D8474 and D1506.

[0145] The recycled carbon black preferably has a dibutyl phthalate (DBP) absorption of 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Herein, the DBP absorption of recycled carbon black is determined in accordance with ASTM D2414.

[0146] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption capacity of the recycled carbon black is determined in accordance with ASTM D3493.

[0147] Commercially available recycled carbon black can be used. For example, Enrestec's product name "PB365" can be mentioned as such a commercially available product. PB365 is a recycled carbon black produced through the thermal decomposition of used tires, and has a nitrogen adsorption specific surface area of ​​73.6 m2 as measured by the BET method. ２ / g and contains about 17% by mass of ash.

[0148] The content of the recycled carbon black is preferably 1 to 100 parts by mass, more preferably 5 to 80 parts by mass, even more preferably 5 to 50 parts by mass, still more preferably 5 to 30 parts by mass, and particularly preferably 5 to 20 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the recycled carbon black is 5 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of improving the proportion of sustainable materials in rubber products to which the rubber composition is applied is significant, and when the content is 50 parts by mass or less, the fracture resistance of the rubber composition can be more reliably maintained.

[0149] The proportion of silica in the total content of silica and carbon black is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, in the case of tread rubber for passenger car tires, the proportion of silica in the total content of silica and carbon black is preferably 50% by mass or more. Furthermore, the proportion of silica in the total content of silica and carbon black may be 100% by mass, but is preferably 98% by mass or less.

[0150] 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.

[0151] (Void-introducing agent (C)) The rubber composition for a tire of this embodiment contains a void-introducing agent (C). When the rubber composition contains a void-introducing agent, the vulcanized rubber has voids on the surface or inside, or on the surface and inside. This means that a tire using this vulcanized rubber has flexibility and can easily adhere to an icy road surface. In addition, water on the road surface is absorbed into the voids on the tire surface, making it easy to remove water from the icy or snowy road surface, thereby improving braking performance on ice.

[0152] The content of the void-introducing agent (C) in the rubber composition is not particularly limited, but from the viewpoint of obtaining a desired void ratio and maintaining abrasion resistance, etc., it is preferably 0.1 to 20 parts by mass, more preferably 0.3 to 15 parts by mass, and even more preferably 0.5 to 10 parts by mass, per 100 parts by mass of the rubber component (A).

[0153] Examples of the void-introducing agent (C) include foaming agents, metal sulfates, thermally expandable microcapsules, porous cellulose particles, and lignin derivatives, and these may be used alone or in combination of two or more.

[0154] The rubber composition for a tire of this embodiment preferably contains a foaming agent (C1) as the void-introducing agent (C). A rubber composition containing the foaming agent (C1) can further improve the on-ice performance of a tire.

[0155] - Foaming Agent (C1) - When the rubber composition for tires contains a foaming agent (C1) as the void-introducing agent (C), the foaming agent generates bubbles in the vulcanized rubber during vulcanization of the rubber composition, turning the vulcanized rubber into foamed rubber. Because foamed rubber has flexibility, tire surfaces using vulcanized rubber can easily adhere to icy road surfaces. Furthermore, the bubbles create bubbles-derived holes (foam pores) on the vulcanized rubber surface and the tire surface, which function as water channels for draining water.

[0156] Specific examples of the blowing agent (C1) include inorganic blowing agents such as azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), dinitrosopentastyrenetetramine, benzenesulfonylhydrazide derivatives, p,p'-oxybisbenzenesulfonylhydrazide (OBSH), carbonates such as ammonium carbonate, sodium carbonate, and potassium carbonate, bicarbonates (hydrogencarbonates) such as ammonium bicarbonate, sodium bicarbonate, and potassium bicarbonate, nitrogen-generating nitrososulfonyl azo compounds, N,N'-dimethyl-N,N'-dinitrosophthalamide, toluenesulfonylhydrazide, p-toluenesulfonylsemicarbazide, and p,p'-oxybisbenzenesulfonylsemicarbazide. Among these, from the viewpoint of manufacturing processability, azodicarbonamide (ADCA), dinitrosopentamethylenetetramine (DPT), and inorganic blowing agents are preferably used. These blowing agents (C1) may be used alone or in combination of two or more.

[0157] The content of the foaming agent (C1) in the rubber composition is not particularly limited, but is preferably 1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, per 100 parts by mass of the rubber component (A).

[0158] -Metal Sulfate- When the rubber composition for tires contains a metal sulfate as the void-introducing agent (C), the metal sulfate protrudes from the tire surface obtained by vulcanizing the rubber composition, performing a claw function without the disadvantage of being abrasive. Subsequently, the metal sulfate gradually leaves the rubber matrix, creating cavities that function as storage volumes and passages for discharging the water film on the ice surface. Under these conditions, contact between the tire surface (e.g., the tread surface) and ice is no longer lubricated, and therefore, examples of metal sulfates that improve the coefficient of friction include magnesium sulfate.

[0159] The metal sulfate is preferably in the form of micrometer-sized particles. Specifically, the average particle size and median particle size (both expressed by mass) are preferably 1 μm to 1 mm, and the median particle size is more preferably 2 μm to 800 μm. When the average particle size and median particle size are 1 μm or more, the desired technical effect (i.e., the formation of an appropriate micro-roughness) is easily achieved. Furthermore, when the rubber composition is used as a tread, when the average particle size and median particle size are 1 mm or less, deterioration in aesthetics is suppressed (the appearance of too obvious particles on the tread surface can be suppressed) and grip performance on melting ice is less likely to be impaired.

[0160] For all these reasons, the median particle size of the metal sulfate is preferably 2 μm to 500 μm, more preferably 5 to 200 μm. This particularly preferred particle size range appears to represent an optimum compromise between the desired surface roughness on the one hand and good contact between the rubber composition and ice on the other hand.

[0161] Furthermore, for the same reason as above, the content of the metal sulfate in the rubber composition is preferably 5 to 40 parts by mass, more preferably 10 to 35 parts by mass, per 100 parts by mass of the rubber component (A).

[0162] Various known methods for analyzing particle size and calculating the median particle size of microparticles (or the average diameter of microparticles assuming a substantially spherical shape), for example by laser diffraction, can be applied (see, for example, standard ISO-8130-13 or standard JIS K5600-9-3). Particle size analysis by mechanical sieving can also be used simply and preferably. The procedure consists of: sieving a defined amount of sample (for example 200 g) for 30 minutes on a vibrating table through various sieve diameters (for example through meshes of 1000, 800, 630, 500, 400, ..., 100, 80 and 63 μm according to a progressive ratio equal to 1.26); weighing the oversize particles collected on each sieve on a precision balance; estimating the percentage of oversize particles at each mesh diameter relative to the total mass of the substance from the weighing; finally, calculating the median particle size (or median diameter) or mean particle size (or mean diameter) from a histogram of the particle size distribution in a known manner.

[0163] -Thermal-Expandable Microcapsules- The thermally expandable microcapsules are configured by encapsulating a thermally expandable substance within a shell material made of a thermoplastic resin. The shell material of the thermally expandable microcapsules can be formed from a nitrile-based polymer. The thermally expandable substance encapsulated within the shell material of the microcapsules has the property of vaporizing or expanding upon heat, and is exemplified by at least one type selected from the group consisting of hydrocarbons such as isoalkanes and normal alkanes. Examples of isoalkanes include isobutane, isopentane, 2-methylpentane, 2-methylhexane, and 2,2,4-trimethylpentane. Examples of normal alkanes include n-butane, n-propane, n-hexane, n-heptane, and n-octane. These hydrocarbons may be used alone or in combination. A preferred form of the thermally expandable substance is one in which a hydrocarbon that is gaseous at room temperature is dissolved in a hydrocarbon that is liquid at room temperature. By using such a hydrocarbon mixture, sufficient expansion force can be obtained from low to high temperature ranges within the vulcanization molding temperature range (150°C to 190°C) of an unvulcanized tire.

[0164] Examples of such thermally expandable microcapsules include those manufactured by Expancel AB in Sweden under the trade names "EXPANCEL 091DU-80" or "EXPANCEL 092DU-120" and those manufactured by Matsumoto Yushi Seiyaku Co., Ltd. under the trade names "Matsumoto Microsphere F-85D" or "Matsumoto Microsphere F-100D."

[0165] The content of the thermally expandable microcapsules in the rubber composition is preferably 0.1 to 10 parts by mass, and more preferably 0.5 to 5 parts by mass, per 100 parts by mass of the rubber component (A).

[0166] -Porous Cellulose Particles- When the rubber composition for tires contains porous cellulose particles as the void-introducing agent (C), if the porous cellulose particles are exposed on the surface of a tire obtained by vulcanizing the rubber composition, water on the icy or snowy road surface can be absorbed by the porous cellulose particles, thereby removing water from between the tire and the road surface. Furthermore, the presence of cellulose, which is a polysaccharide, causes an interaction between the tire and water on the icy or snowy road surface, which can further enhance the interaction between the tire and water by the modified polyoxyalkylene glycol.

[0167] The porous cellulose particles have a porous structure with a porosity of 75 to 95%, and when incorporated into a rubber composition, they can significantly improve performance on ice. A porosity of 75% or more in the porous cellulose particles provides excellent performance improvement on ice, while a porosity of 95% or less enhances particle strength. The porosity is more preferably 80 to 90%. The porosity of the porous cellulose particles can be calculated by measuring the volume of a given mass of sample (i.e., porous cellulose particles) with a measuring cylinder, determining the bulk density, and then using the following formula: Porosity [%] = {1 - (bulk density of sample [g / ml]) / (true specific gravity of sample [g / ml])} × 100, where the true specific gravity of cellulose is 1.5.

[0168] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, particles having an average particle size of 1,000 μm or less are preferably used. 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. Spherical particles having a major axis / minor axis ratio of 1 to 2 are preferably used as the porous cellulose particles. 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 axial direction and the length in an axial 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.

[0169] 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.

[0170] The content of the porous cellulose particles in the rubber composition is preferably 0.3 to 20 parts by mass per 100 parts by mass of the rubber component (A). A content of 0.3 parts by mass or more can enhance the effect of improving performance on ice, and a content of 20 parts by mass or less can prevent the rubber hardness from becoming too high and suppress a decrease in abrasion resistance. The content of the porous cellulose particles is more preferably 1 to 15 parts by weight, and even more preferably 3 to 15 parts by mass.

[0171] -Lignin Derivative- When the rubber composition for a tire contains a lignin derivative as the void-introducing agent, the effect of improving performance on ice can be enhanced. Here, lignin sulfonate is preferably used as the lignin derivative. Examples of lignin sulfonate include alkali metal salts, alkaline earth metal salts, ammonium salts, and alcoholamine salts of lignin sulfonic acid, and at least one of these can be used. Preferred are alkali metal salts and / or alkaline earth metal salts of lignin sulfonic acid, such as potassium salt, sodium salt, calcium salt, magnesium salt, lithium salt, and barium salt, and mixed salts thereof are also acceptable.

[0172] (Foaming Aid) When the rubber composition for tires contains the foaming agent (C1) as the void-introducing agent (C), it is preferable that the rubber composition further contains a foaming aid. Examples of the foaming aid include urea, zinc stearate, zinc benzenesulfinate, zinc oxide, etc. These may be used alone or in combination of two or more. By using the foaming aid in combination, it is possible to promote the foaming reaction, increase the degree of completion of the reaction, and suppress unnecessary deterioration over time.

[0173] Furthermore, the total content of the foaming agent (C1) and the foaming aid is preferably 1 to 30 parts by mass per 100 parts by mass of the rubber component (A). When the total content of the foaming agent and the foaming aid is 1 part by mass or more, the rubber composition can be sufficiently foamed during vulcanization, and the foaming rate of the vulcanized rubber can be maintained high. On the other hand, even when the total content of the foaming agent and the foaming aid is 30 parts by mass or less, a decrease in the foaming rate can be suppressed. From the viewpoint of suppressing a decrease in the foaming rate as described above, the total content of the foaming agent (C1) and the foaming aid is preferably 2 parts by mass or more, more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component (A). From the viewpoint of suppressing a decrease in the foaming rate as described above, the total content of the foaming agent and the foaming aid is preferably 25 parts by mass or less, more preferably 20 parts by mass or less, per 100 parts by mass of the rubber component (A).

[0174] In addition, in the rubber composition, the mass ratio of the foaming agent (C1) to the foaming aid (foaming agent:foaming aid) is preferably 1:0.2 to 1:3.0. If the mass ratio (foaming agent:foaming aid) is less than 1:0.2, the rubber composition may not foam sufficiently during vulcanization, which may result in a decrease in the foaming rate of the vulcanized rubber. On the other hand, if the mass ratio (foaming agent:foaming aid) exceeds 1:3.0, the foaming rate may also decrease. From the viewpoint of suppressing the decrease in the foaming rate as described above, the mass ratio of the foaming agent (C1) to the foaming aid (foaming agent:foaming aid) is preferably 1:3.0 or less, more preferably 1:2.7 or less, even more preferably 1:2.4 or less, even more preferably 1:2.1 or less, even more preferably 1:1.8 or less, and particularly preferably 1:1.5 or less.

[0175] From the viewpoints of the foaming rate of the vulcanized rubber and the on-ice performance of the tire, the content of the foaming aid is preferably in the range of 1 to 20 parts by mass, and more preferably in the range of 2 to 15 parts by mass, per 100 parts by mass of the rubber component (A).

[0176] (Composite Fiber (D)) The rubber composition for a tire of this embodiment preferably further contains a composite fiber (D). By containing the composite fiber (D), affinity with water can be sufficiently ensured, and excellent drainage properties and performance on ice can be imparted, particularly when used for a tire.

[0177] The composite fiber (D) is preferably made of a hydrophilic resin having a coating layer formed on the surface. This is because providing a coating layer on the surface of the composite fiber improves the dispersibility of the composite fiber in the rubber composition. The hydrophilic resin is preferably insoluble in water. By using a water-insoluble hydrophilic resin, dissolution of the composite fiber can be suppressed even when the composite fiber is exposed on the surface of a product (e.g., a tire).

[0178] The hydrophilic resin is not particularly limited as long as it is a resin that can exhibit affinity with water, that is, a resin that has a hydrophilic group in the molecule. Specifically, it is preferably a resin that contains an oxygen atom, a nitrogen atom, or a sulfur atom, such as —OH, —C(═O)OH, —OC(═O)R (R is an alkyl group), —NH ２, —NCO, and —SH. Among these groups, the most preferred are resins containing at least one group selected from the group consisting of —OH, —C(═O)OH, —OC(═O)R, —NH ２ , —NCO are preferred. More specific examples of the hydrophilic resin include ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, poly(meth)acrylic acid resins or ester resins thereof (hereinafter, copolymers containing structural units derived from (meth)acrylic acid and (co)polymers containing structural units derived from (meth)acrylic acid esters are collectively referred to as (meth)acrylic resins), polyamide resins, polyethylene glycol resins, carboxyvinyl copolymers, styrene-maleic acid copolymers, polyvinylpyrrolidone resins, vinylpyrrolidone-vinyl acetate copolymers, polyester resins, and cellulose-based resins. Among these, ethylene-vinyl alcohol copolymers, vinyl alcohol homopolymers, poly(meth)acrylic acid resins, polyamide resins, aliphatic polyamide-based resins, aromatic polyamide-based resins, polyester resins, polyvinyl alcohol-based resins, cellulose-based resins, and (meth)acrylic resins are preferred, with ethylene-vinyl alcohol copolymers being more preferred.

[0179] The surface of the fiber made of the hydrophilic resin is preferably coated with a coating layer made of a low-melting-point resin (hereinafter also referred to as "low-melting-point resin") that has affinity for the rubber component (A) and preferably has a melting point lower than the maximum vulcanization temperature. By forming such a coating layer, the hydrophilic resin can effectively maintain its affinity for water while exhibiting good affinity with the rubber component (A) near the composite fiber. It also captures the hydrophilic resin, which is difficult to melt during vulcanization (foaming), and promotes the formation of cavities within the composite fiber. That is, it ensures good dispersion of the composite fiber in the rubber component (A), fully exhibiting the drainage effect due to the hydrophilic resin, while also fully exhibiting the on-ice performance improvement effect due to the voids present within the composite fiber. Furthermore, the low-melting-point resin melts during vulcanization to form a fluid coating layer, contributing to improved adhesion between the rubber component and the composite fiber, thereby imparting good on-ice performance and abrasion resistance. The thickness of the coating layer may vary depending on the amount of the hydrophilic resin blended, the average diameter of the composite fiber, and other factors, but is preferably 0.001 to 10 μm, and more preferably 0.001 to 5 μm. By forming the coating layer with a thickness within the above range, the desired effects can be fully achieved. The coating layer may be formed over the entire surface of the hydrophilic resin, or may be formed on only a portion of the surface of the hydrophilic resin. Specifically, the coating layer is preferably formed so as to occupy at least 50% of the total surface area of ​​the hydrophilic resin.

[0180] Specifically, the low-melting-point resin used in the coating layer is preferably a resin in which the polar component is 50% by mass or less of the total components, and more preferably a polyolefin-based resin. Resins with polar components within the above range have an appropriate difference in SP value with the rubber component (A) and a melting point that is appropriately lower than the maximum vulcanization temperature. This allows for easy melting during vulcanization and promotes foaming of the vulcanized rubber while ensuring sufficient affinity with the rubber component (A). This allows for more reliably improved dispersion of the hydrophilic resin fiber in the rubber composition and reliable formation of cavities within the composite fiber.

[0181] The polyolefin-based resin may be branched, linear, or the like. It may also be an ionomer resin in which ethylene-methacrylic acid copolymer molecules are crosslinked with metal ions. Specific examples of the polyolefin-based resin include polyethylene, polypropylene, polybutene, polystyrene, ethylene-propylene copolymer, ethylene-methacrylic acid copolymer, ethylene-ethyl acrylate copolymer, ethylene-propylene-diene terpolymer, ethylene-vinyl acetate copolymer, and ionomer resins thereof. These may be used alone or in combination of two or more. Among these, polyethylene-based resins, polypropylene-based resins, polyolefin ionomers, and maleic anhydride-modified α-polyolefins are preferred as the polyolefin-based resin. When polyolefin ionomers or maleic anhydride-modified α-polyolefins are used, they also adhere to the hydroxyl groups of hydrophilic resins, thereby further improving rubber strength.

[0182] To produce a composite fiber made of a hydrophilic resin with a coating layer made of the low-melting-point resin, the resins can be blended using a mixing mill, melt-spun to form an undrawn yarn, and then hot-drawn the undrawn yarn to form a fiber. Alternatively, the resins can be blended using two twin-screw extruders equipped with dies and then similarly shaped into a fiber. In this case, the hydrophilic resin and the low-melting-point resin are simultaneously extruded from the two die outlets, forming an undrawn yarn. The amount of resins added to the mixing mill or hopper varies depending on the length and diameter of the resulting composite (fiber), but is preferably 5 to 300 parts by mass, more preferably 10 to 150 parts by mass, of the low-melting-point resin per 100 parts by mass of the hydrophilic resin. Adding these resins in amounts within the above ranges effectively forms a coating layer that can exert the desired effects on the surface of the hydrophilic resin composite (fiber) obtained after the drawing process.

[0183] The average length of the resulting composite fiber (D) is preferably 0.1 to 500 mm, more preferably 0.1 to 7 mm, and the average diameter is preferably 0.001 to 2 mm, more preferably 0.005 to 0.5 mm. When the average length and average diameter are within the above ranges, there is no risk of the composite fibers becoming entangled more than necessary, and there is no risk of impairing good dispersibility. The aspect ratio is preferably 10 to 4,000, more preferably 50 to 2,000. The aspect ratio refers to the ratio of the major axis to the minor axis of the composite fiber.

[0184] Furthermore, with regard to the resulting composite fiber (D), the ratio (A / B) of the length A of the cross section in the major axis direction in a cross section perpendicular to the major axis direction to the length B of the cross section in the minor axis direction perpendicular to the major axis direction is preferably greater than 1, more preferably 1.5 or more, even more preferably 1.8 or more, and particularly preferably 2.0 or more. Furthermore, the ratio A / B is preferably 20 or less, even more preferably 15 or less, and particularly preferably 10 or less. By keeping it within the above range, the performance on ice is further improved. Note that, as long as A / B is greater than 1, the cross-sectional shape is not particularly limited and may be any of elliptical, rectangular, polygonal, irregular, etc.

[0185] The blending amount of the hydrophilic resin composite fiber (D) having the coating layer formed thereon is preferably 0.1 to 100 parts by mass, more preferably 0.3 to 30 parts by mass, even more preferably 0.5 to 10 parts by mass, and even more preferably 1 to 6 parts by mass, per 100 parts by mass of the rubber component (A). When the blending amount of the hydrophilic resin composite fiber having the coating layer formed thereon is within the above range, cavities are formed inside the composite fiber, thereby exhibiting good drainage properties and maintaining sufficient durability. Furthermore, the content ratio of the composite fiber (D) to the void-introducing agent (C) is not particularly limited, but from the viewpoint of achieving and improving both abrasion resistance and performance on ice, the mass ratio of the composite fiber to the void-introducing agent (void-introducing agent / composite fiber) is preferably 0.5 to 10, more preferably 1 to 8, even more preferably 1.5 to 7, and particularly preferably 2 to 6.

[0186] (Resin) The rubber composition for a tire of the present embodiment may contain a resin. Examples of the resin include terpene-based resins, rosin-based resins, C５ based resin, C ５ -C ９ based resin, C ９ Examples of suitable resins include cyclopentadiene-based resins, aromatic resins, coumarone resins, indene resins, coumarone-indene-based resins, olefin-based resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, 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 -C ９ 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.

[0187] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). Furthermore, the resin 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.

[0188] 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.

[0189] 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.

[0190] 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.

[0191] Said C ５ -C ９ The C-based resin is ５ -C９ 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.

[0192] Said C ９ The C-based resin is ９ 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.

[0193] 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 ３The 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.).

[0194] 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.

[0195] The softening point of the resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, more preferably 80 ° C. or higher, more preferably higher than 110 ° C., more preferably 116 ° C. or higher, more preferably 120 ° C. or higher, more preferably 123 ° C. or higher, and even more preferably 127 ° C. or higher. From the viewpoint of processability, the softening point of the resin is preferably 160 ° C. or lower, more preferably 150 ° C. or lower, more preferably 145 ° C. or lower, more preferably 141 ° C. or lower, and even more preferably 136 ° C. or lower. In this specification, the softening point of the resin is the temperature at which the ball drops when the softening point as defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0196] Commercially available resins can be used, and examples of commercially available resins include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Kraton Corporation, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Polymers, Inc., Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0197] The content of the resin is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the resin is preferably in the range of 5 to 100 parts by mass, more preferably in the range of 10 to 60 parts by mass, per 100 parts by mass of the rubber component (A).

[0198] (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.

[0199] 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.

[0200] 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 even more preferably 8 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the plant-derived silica (B1) (or the total amount of silica).

[0201] (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.

[0202] 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.

[0203] 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.

[0204] 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.

[0205] 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.

[0206] 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).

[0207] (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.

[0208] 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.

[0209] 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.

[0210] 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).

[0211] (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.

[0212] 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).

[0213] (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.

[0214] 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).

[0215] (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.

[0216] The content of stearic acid is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber component (A) is applied, the tire component, the target performance, etc. For example, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 1 part 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).

[0217] (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.

[0218] 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).

[0219] (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.

[0220] 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).

[0221] (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.

[0222] 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 0.4 parts by mass or more, more preferably 0.8 parts by mass or more, and even more preferably 1.2 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 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0223] (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.

[0224] 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.

[0225] 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).

[0226] (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.

[0227] 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).

[0228] (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).

[0229] (Method for Producing Rubber Composition) The method for producing the rubber composition for tires of the present embodiment is not particularly limited, but for example, the tire rubber composition can be produced by blending the plant-derived silica (B1), the void-introducing agent (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.

[0230] 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.

[0231] 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.

[0232] 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.

[0233] 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.

[0234] (Uses) The rubber composition for a tire of this embodiment can be applied to various constituent members of a tire, such as a tread (cap tread, base tread, undertread), cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, insulation, chafer, inner liner, etc., and can also be used for a side reinforcing layer of a run-flat tire, etc. In addition to tires, the rubber composition of this embodiment can also be applied to rubber crawlers, seismic isolation rubber, etc. Among these, the rubber composition for a tire of this embodiment is suitable for use in a tire tread because it does not impair performance on ice.

[0235] <Vulcanized rubber for tires> The vulcanized rubber for tires of this embodiment is characterized by being obtained by vulcanizing the rubber composition for tires of this embodiment described above. Because the vulcanized rubber for tires of this embodiment is obtained by vulcanizing the rubber composition for tires of this embodiment described above, by applying the vulcanized rubber for tires of this embodiment, it is possible to increase the proportion of sustainable materials in the tire.

[0236] The vulcanized rubber for tires of this embodiment preferably has voids. Vulcanized rubber for tires having voids can improve the tire's performance on ice. The void ratio of the vulcanized rubber is preferably 1 to 50%, and more preferably 5 to 40%. By having a void ratio within this range, when applied to a tire, the voids on the tire surface do not become too large, ensuring a sufficient contact area, and maintaining an appropriate amount of air bubbles while ensuring the formation of voids that function effectively as drainage channels, so there is no risk of impairing durability. Here, the void ratio of the vulcanized rubber means the average void ratio Vs, and specifically means the value calculated by the following formula (1): Vs = (ρ ０ / ρ １ -1)×100(%) (1) In formula (1), ρ １ is the density of the vulcanized rubber (g / cm ３ ) and ρ ０ is the density of the solid phase in the vulcanized rubber (g / cm ３ The density of the vulcanized rubber and the density of the solid phase of the vulcanized rubber are calculated by measuring the mass in ethanol and the mass in air.

[0237] <Tread Rubber> The tread rubber of this embodiment is characterized by being made from the rubber composition for a tire or the vulcanized rubber for a tire of this embodiment described above. Since the tread rubber of this embodiment is made from the rubber composition for a tire or the vulcanized rubber for a tire of this embodiment described above, by applying it to a tire, it is possible to increase the proportion of sustainable materials in the tire. Note that the tread rubber of this embodiment may be applied to new tires or retread tires.

[0238] <Tire> The tire of this embodiment is characterized by including the above-mentioned tread rubber. Because the tire of this embodiment includes the above-mentioned tread rubber, the proportion of sustainable materials is increased and performance is not compromised. Here, the tire of this embodiment is suitable as a studless tire because performance on ice is not compromised.

[0239] Next, an embodiment of a tire of the present invention will be described in detail with reference to the drawings. Fig. 3 is a cross-sectional view of an embodiment of a tire of the present invention. The tire 1 of this embodiment shown in Fig. 3 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 the crown portion of the carcass 5.

[0240] The carcass 5 of the tire 1 shown in FIG. 3 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.

[0241] 3 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 comprise 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.

[0242] 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.

[0243] 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. 3, 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.

[0244] 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.

[0245] 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.

[0246] <Preparation and Evaluation of Rubber Compositions> Rubber compositions of Examples and Comparative Examples were prepared according to the formulations shown in Table 1. The total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) was calculated for each rubber composition to calculate the sustainable material ratio. The sustainable material ratio was expressed as an integer. The evaluation results are shown in Table 1.

[0247]

[0248] *1 NR: Natural rubber, TSR20 *2 BR: Butadiene rubber, manufactured by Ube Industries, Ltd., product name "UBEPOL BR150L" *3 SBR: Modified styrene-butadiene rubber (modified SBR) produced by the following method

[0249] <Method for Synthesizing Modified SBR> A cyclohexane solution of 1,3-butadiene and a cyclohexane solution of styrene were added to a dried, nitrogen-purged 800 mL pressure-resistant glass vessel so that the total weight of the 1,3-butadiene and styrene was 67.5 g and 7.5 g, respectively, and 0.6 mmol of 2,2-ditetrahydrofurylpropane and 0.8 mmol of n-butyllithium were added, followed by polymerization at 50°C for 1.5 hours. To the polymerization reaction system, which had reached a polymerization conversion rate of nearly 100%, 0.72 mmol of N,N-bis(trimethylsilyl)-3-[diethoxy(methyl)silyl]propylamine was added as a modifier, and the modification reaction was carried out at 50°C for 30 minutes. Subsequently, 2 mL of a 5% by mass solution of 2,6-di-t-butyl-p-cresol (BHT) in isopropanol was added to terminate the reaction, and the mixture was dried in a conventional manner to obtain modified SBR. The microstructure of the resulting modified SBR was measured, and it was found that the bound styrene content was 10% by mass and the vinyl bond content in the butadiene moiety was 40%.

[0250] *4 Carbon black: N134 equivalent grade *5 Mineral-derived silica: Tosoh Silica Corporation, cetyltrimethylammonium bromide (CTAB) adsorption specific surface area = 155 m ２ / g *6 Plant-derived silica: rice husk silica *7 Foaming agent: Nizitrosopentamethylenetetramine *8 Oil: Softener, manufactured by Idemitsu Kosan Co., Ltd., product name "Diana Process Oil NS-28"

[0251] * 9 Composite fiber: Short fiber resin having an elliptical cross section, Resin 4 (flat resin) used in Example 4 of WO 2018 / 207472, ethylene-vinyl alcohol copolymer (manufactured by Kuraray Co., Ltd., trade name "Eval F104B"), on the surface of a hydrophilic fiber made of polyethylene (manufactured by Japan Polyethylene Co., Ltd., trade name "Novatec HJ360") Short fiber on which a coating layer made of polyethylene (manufactured by Japan Polyethylene Co., Ltd., trade name "Novatec HJ360") is formed, the ratio A / B of the length A of the cross section in the major axis direction in a cross section perpendicular to the major axis direction to the length B of the cross section in the minor axis direction perpendicular to the major axis direction is controlled between 2.01 and 10, the average value of length A = 0.05 mm, the average area of ​​the cross section perpendicular to the major axis direction = 0.0007 mm ２ , average value of the length C in the long axis direction = 3 mm

[0252] *10 Silane coupling agent: Shin-Etsu Chemical Co., Ltd., trade name "ABC-856" *11 Resin: Mitsui Petrochemical Co., Ltd., trade name "Hi-Rets G-100X" *12 Stearic acid: New Japan Chemical Co., Ltd., trade name "50S" *13 Zinc oxide: Hakusui Tech Co., Ltd., trade name "Zinc oxide type 2", powder *14 Vulcanization accelerator: Total amount including Ouchi Shinko Chemical Industry Co., Ltd., trade name "Nocceler CZ-G" *15 Vulcanizing agent: Tsurumi Chemical Industry Co., Ltd., trade name "Sulfax 5" *16 Antiaging agent: Sumitomo Chemical Co., Ltd., trade name "Antigen"

[0253] 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.

[0254] A: Pores with a roughly cylindrical shape B: Pores with an ink bottle shape M ａ , M ｂ : diameter of opening on the outer surface of the particle R ａ , R ｂ : Pore diameter (inner diameter) inside the particle C: Mercury intrusion curve D: Mercury discharge curve 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 void-introducing agent (C), wherein the filler (B) comprises plant-derived silica (B1).

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

3. The rubber composition for tires according to claim 2, wherein the rubber component (A) further comprises at least one rubber selected from the group consisting of butadiene rubber and styrene-butadiene rubber.

4. The rubber composition for tires according to claim 1, wherein the content of the filler (B) is 50 to 90 parts by mass per 100 parts by mass of the rubber component (A).

5. The rubber composition for tires according to claim 1, further comprising a foaming agent (C1) as the void-introducing agent (C).

6. The rubber composition for tires according to claim 1, further comprising composite fibers (D).

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

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

9. A vulcanized rubber for tires, which is obtained by vulcanizing the rubber composition for tires according to claim 1.

10. The tire vulcanizate according to claim 9, which has voids.

11. A tread rubber comprising the rubber composition for tires according to claim 1 or the vulcanized rubber for tires according to claim 9.

12. A tire comprising a tread rubber according to claim 11.

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