Bead filler and tire

Abstract

To provide a bead filler capable of increasing a proportion of a sustainable material of a tire, and a tire with a proportion of a sustainable material increased.SOLUTION: A tire 1 includes: a bead filler 8 including a rubber composition containing a rubber constituent (A) and a regenerated carbon black (B); a pair of bead parts 2; a pair of side wall parts 3; a tread part 4 connected to both of the side wall part 3; and a carcass 6 toroidally extended between bead cores 5 respectively embedded in the bead parts 2. In the tire 1, the bead filler 8 is arranged outside in the tire radius direction of the bead core 5.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a bead filler and a tire. [Background technology]

[0002] In general, in the bead portion of a tire, a bead filler is disposed on the outer side of the bead core in the tire radial direction in order to improve the rigidity of the bead portion. The bead filler usually uses a rubber composition in which carbon black, sulfur, etc. are blended with the rubber component.

[0003] On the other hand, in recent years, from the viewpoint of social sustainability, there has been a demand for increasing the ratio of so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, for various components used in tires. For example, Patent Document 1 below refers to the use of a rubber composition containing recycled rubber for tires. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2007-126518 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the use of sustainable materials for the bead fillers of the above-mentioned tires has not been considered until now.

[0006] Therefore, an object of the present invention is to provide a bead filler that can increase the proportion of sustainable materials in tires. Another object of the present invention is to provide a tire with an improved proportion of sustainable materials. [Means for solving the problem]

[0007] The main configurations of the bead filler and tire of the present invention that solve the above problems are as follows.

[0008] [1] A bead filler comprising a rubber composition containing a rubber component (A) and recycled carbon black (B). The bead filler of the present invention described in [1] above can increase the proportion of sustainable materials in tires.

[0009] [2] The bead filler according to [1], wherein the recycled carbon black (B) is obtained by thermal decomposition of a vulcanized rubber product containing carbon black. For the bead filler described in [2] above, recycled carbon black (B) is readily available.

[0010] [3] The bead filler according to [1] or [2], wherein the recycled carbon black (B) has an ash content of 20 mass% or less. The bead filler described in [3] above has improved physical properties.

[0011] [4] A tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, a carcass extending in a toroidal shape between bead cores embedded in the bead portions, and a bead filler disposed radially outward of the bead cores, A tire, characterized in that the bead filler is the bead filler described in any one of [1] to [3]. The tire of the present invention described in [4] above has an improved proportion of sustainable materials. Effect of the Invention

[0012] According to the present invention, it is possible to provide a bead filler that can increase the proportion of sustainable materials in a tire. Furthermore, according to the present invention, it is possible to provide a tire with an improved proportion of sustainable materials. [Brief description of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view of one embodiment of a tire of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The bead filler and tire of the present invention will be described in detail below with reference to examples based on embodiments thereof.

[0015] <Definition> The compounds described herein may be derived in whole or in part from fossil sources, from biological sources such as plant sources, from recycled sources such as used tires, or from a mixture of two or more of fossil sources, biological sources, and / or renewable sources.

[0016] In this specification, the "proportion of sustainable materials" refers to the total mass ratio of materials derived from biological resources (biomass resources) and materials derived from renewable resources (recycled resources) in the target bead filler and tire.

[0017] In this specification, the biological resources (biomass resources) refer to carbon-neutral organic resources derived from living organisms, and include, for example, those stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and are resources other than fossil resources (petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but are preferably non-edible from the viewpoint of not competing with food and of effective resource utilization.

[0018] Specific examples of the biological resources include cellulosic crops (pulp, kenaf, wheat straw, rice straw, waste paper, papermaking residues, etc.), wood, charcoal, compost, food waste, vegetable oil residues, fishery residues, livestock waste, food waste, wastewater sludge, natural rubber, cotton, oils and fats (palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive ... Examples of the biological resources include crops (corn, wheat, rice, rice husks, rice bran, old rice, potatoes, buckwheat, cassava, sago palm, sugarcane, etc.), bagasse (i.e., the residue after squeezing juice from sugarcane), soybeans, soybean pulp, essential oils (pine oil, orange oil, eucalyptus oil, etc.), pulp black liquor, algae, etc. The biological resources may be processed (i.e., biological resource-derived substances). Examples of the processing methods include biological processing methods that utilize the functions of microorganisms, plants, animals, and tissue cultures thereof; chemical processing methods that utilize acids, alkalis, catalysts, thermal energy, light energy, etc.; physical processing methods such as micronization, compression, microwave processing, and electromagnetic wave processing; and the like. The biological resources may also be extracted and refined from the biological resources or biological resources that have been processed (i.e., biological resource-derived substances). For example, sugars, proteins, amino acids, fatty acids, fatty acid esters, etc., purified from the biological resources can be used. Examples of the sugars include sucrose, glucose, trehalose, fructose, lactose, galactose, xylose, allose, talose, gulose, altrose, mannose, idose, arabinose, apiose, maltose, cellulose, starch, chitin, etc., derived from biological resources. Examples of the proteins include compounds derived from biological resources and formed by linking amino acids (preferably L-amino acids), including oligopeptides such as dipeptides. Examples of the amino acids include valine, leucine, isoleucine, arginine, lysine, asparagine, glutamine, phenylalanine, etc., derived from biological resources, and among these, valine, leucine, isoleucine, arginine, and phenylalanine are preferred.The amino acid may be either an L-amino acid or a D-amino acid, but L-amino acids are preferred from the viewpoints of abundance in nature and ease of availability. The fatty acids include butyric acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, etc., which are derived from biological resources. The fatty acid esters include modified products of vegetable oils, animal oils, and fats and oils derived from biological resources. These biological resources may be contaminated with various materials and impurities.

[0019] 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.

[0020] <Bead filler> The bead filler of the present embodiment is characterized by being made of a rubber composition containing a rubber component (A) and recycled carbon black (B).

[0021] In the bead filler of this embodiment, the recycled carbon black (B) is a material derived from a recycled resource (recycled resource), so the bead filler of this embodiment has a high ratio of sustainable materials. Therefore, by applying the bead filler of this embodiment to a tire, it is possible to increase the ratio of sustainable materials in the tire.

[0022] In general, recycled carbon black (B) has a high ash content and therefore has a lower reinforcing property than normal (unused) carbon black. Therefore, a rubber composition containing recycled carbon black (B) is likely to have reduced abrasion resistance, and when applied to a member constituting the surface of a tire, such as a tread, tire performance is likely to be reduced. On the other hand, a bead filler is one of the internal members of a tire and does not require high abrasion resistance. Therefore, the bead filler of this embodiment can maintain tire performance even when applied to a tire. Therefore, by applying the bead filler of this embodiment to a tire, it is possible to improve the ratio of sustainable materials in the tire while maintaining tire performance.

[0023] (Rubber component (A)) The rubber composition constituting the bead filler of this embodiment contains a rubber component (A), and the rubber component (A) provides rubber elasticity to the composition and the bead filler. The rubber component (A) preferably has a sustainability rate of 30 mass% or more, more preferably 40 mass% or more, more preferably 50 mass% or more, more preferably 60 mass% or more, more preferably 70 mass% or more, even more preferably 80 mass% or more, even more preferably 90 mass% or more, and particularly preferably 100 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).

[0024] As the rubber component (A), the rubber derived from biological resources and the rubber derived from recycled resources are preferred. Here, the proportion of the monomer components derived from biological resources in 100 mol% of the monomer components constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. The proportion of monomer components derived from recycled resources in 100 mol% of monomer components constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, still more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0025] The rubber component (A) is a component that contributes to crosslinking, and usually 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, for example, by converting the weight average molecular weight (Mw) into standard polystyrene based on a measurement value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0026] The rubber component (A) is preferably a diene rubber, and the diene rubber is preferably an isoprene rubber or a butadiene rubber, where the isoprene rubber refers to a rubber containing a unit derived from isoprene as a monomer unit, and the butadiene rubber refers to a rubber containing a unit derived from butadiene as a monomer unit.

[0027] Examples of the isoprene-based rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). Examples of the natural rubber (NR) that can be used include those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20). The origin of the natural rubber (NR) is not particularly limited, and examples of the natural rubber include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of the synthetic isoprene rubber (IR) are not particularly limited, and examples of the synthetic isoprene rubber that can be used include those commonly used in the tire industry, such as IR2200. Examples of the modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of the modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. The modified IR includes epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, grafted synthetic isoprene rubber, etc. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0028] The isoprene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to set the sustainability rate of the isoprene-based rubber within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from renewable resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from renewable resources, a copolymer of a monomer derived from biological resources and a monomer derived from renewable resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from renewable resources and a monomer derived from a fossil resource (petroleum, etc.).

[0029] Examples of the butadiene rubber include butadiene rubber (BR), aromatic vinyl compound-butadiene copolymer rubber (for example, styrene-butadiene rubber (SBR)), etc. Here, butadiene, which is a raw material for butadiene rubber, is preferably derived from biological resources or recycled resources.

[0030] Examples of the butadiene rubber (BR) include high cis content butadiene rubber, low cis content butadiene rubber, and butadiene rubber containing syndiotactic polybutadiene crystals. Commercially available products can be used as the butadiene rubber (BR), and examples of commercially available butadiene rubbers include products from UBE Elastomers Co., Ltd., ENEOS Materials Corporation, Asahi Kasei Co., Ltd., and Zeon Corporation. These butadiene rubbers may be used alone or in combination of two or more.

[0031] Examples of the aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR) include emulsion-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., emulsion-polymerized styrene-butadiene rubber (E-SBR)), solution-polymerized aromatic vinyl compound-butadiene copolymer rubber (e.g., solution-polymerized styrene-butadiene rubber (S-SBR)), and the like. In the aromatic vinyl compound-butadiene copolymer rubber, examples of the aromatic vinyl compound (aromatic vinyl monomer) include styrene, vinylnaphthalene, divinylnaphthalene, and the like. These aromatic vinyl compounds may be used alone or in combination of two or more. Among these, styrene is preferred, and styrene derived from biological resources and styrene derived from recycled resources are particularly preferred. That is, the aromatic vinyl compound-butadiene copolymer rubber is preferably SBR. The styrene may have a substituent. As the aromatic vinyl compound-butadiene copolymer rubber, commercially available products can be used, and examples of the commercially available products include products from Asahi Kasei Corporation, ENEOS Materials Corporation, Nippon Zeon Corporation, Sumitomo Chemical Co., Ltd., and the like. These aromatic vinyl compound-butadiene copolymer rubbers may be used alone or in combination of two or more.

[0032] The butadiene-based rubber has a sustainability rate of preferably 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, still more preferably 60% by mass or more, still more preferably 70% by mass or more, even more preferably 80% by mass or more, still more preferably 90% by mass or more, and particularly preferably 100% by mass. In order to make the sustainability rate of the butadiene-based rubber fall within the above range, for example, a polymer synthesized using butadiene derived from biological resources, butadiene derived from renewable resources, aromatic vinyl compounds derived from biological resources (e.g., styrene derived from biological resources), and aromatic vinyl compounds derived from renewable resources (e.g., styrene derived from renewable resources) as monomer components may be used. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from renewable resources, a copolymer of a monomer derived from biological resources and a monomer derived from renewable resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from renewable resources and a monomer derived from a fossil resource (petroleum, etc.). In addition, the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (e.g., styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene, etc. according to a conventional method, but also rubber obtained by reactions or enzyme reactions caused by microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.").

[0033] 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 monomer components derived from biological resources or monomer components derived from recycled resources as monomer components.

[0034] Generally, materials for rubber compositions for tires (rubber and its monomers, fillers, resins, etc.) require large-scale manufacturing equipment for their production, and are therefore usually produced in large factories in specific regions, and a lot of energy is required for the storage and transportation of raw materials and products. In contrast, materials derived from biological resources (biomass resources) are derived from agricultural products, forests, etc. in each region, and can be produced on a small scale by fermentation of microorganisms and catalytic reactions, so by utilizing products and waste from each region, the energy required for the transportation and storage of raw materials can be reduced, and further the energy required for the transportation and storage of the produced materials to tire factories can also be reduced, which is environmentally friendly. In addition, materials derived from regenerated resources (recycled resources) can be obtained, for example, by dismantling and pyrolyzing used tires to extract materials that constitute tires, such as rubber, fillers, and steel cords. In addition, sulfur can be obtained from biological resources or processed products of biological resources by a method including a desulfurization step of desulfurizing biological resources or processed products of biological resources to remove sulfur-containing substances from the biological resources or processed products of biological resources, a recovery step of recovering sulfur from the desulfurization residue generated in the desulfurization step, and a processing step of processing the recovered sulfur into sulfur for vulcanization (for example, the method described in Japanese Patent Application No. 2022-140390), and materials for rubber compositions for tires can be obtained from various wastes and used items. In this way, by using sustainable materials (materials derived from biological resources or materials derived from recycled resources), it is possible to reduce the overall environmental load in tire manufacturing, such as reducing carbon dioxide emissions (LCCO2) over the entire life cycle, reducing energy consumption (LCE) over the entire life cycle, reducing costs (LCC) incurred over the entire life cycle, and reducing the amount of fossil resources used.

[0035] In addition, when producing the rubber composition, the ratio of the monomer components derived from biological resources, the monomer components derived from renewable resources, and the monomer components derived from fossil resources can be appropriately selected according to the supply situation of biological resources, recycled resources, and fossil resources (e.g., monomer components derived from fossil resources) and / or market demand (e.g., demand for biological resources as food), and the monomer components derived from biological resources, the monomer components derived from renewable resources, and the monomer components derived from fossil resources can be polymerized to obtain rubber derived from sustainable materials (materials derived from biological resources or materials derived from renewable resources) having performance equivalent to that of conventional synthetic rubber. When using monomer components derived from renewable resources, it may be difficult to separate them from monomer components derived from fossil resources due to the manufacturing process of the monomer. In that case, the impact on the environment can be evaluated by adopting the concept of mass balance.

[0036] The ratio of each monomer unit (e.g., unit derived from isoprene, unit derived from butadiene, unit derived from aromatic vinyl compound) in the entire rubber component (A) can be adjusted appropriately. 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. In addition, the ratio of cis-bond units in the unit derived from butadiene can also be adjusted appropriately. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "unit derived from isoprene" refers to a structural unit in a polymer constituted based on the monomer isoprene (including the isoprene unit in natural rubber), the term "unit derived from butadiene" refers to a structural unit in a polymer constituted based on the monomer butadiene, and the term "unit derived from an aromatic vinyl compound" refers to a structural unit in a polymer constituted based on the monomer aromatic vinyl compound. In this specification, the ratio of each monomer unit is measured by NMR.

[0037] 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.

[0038] The rubber component (A) may be modified to introduce a functional group that interacts with a filler such as carbon black or silica. Examples of the functional group include amino, amide, isocyanate, imino, imidazole, urea, ammonium, imide, hydrazo, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxy, epoxy, ether, carbonyl, oxycarbonyl, silyl, alkoxysilyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, and thiocarbonyl groups, and these functional groups may have a substituent. These functional groups may be introduced into the rubber component alone or in combination of two or more. Among these, an amino group, an alkoxy group, and an alkoxysilyl group are preferred, and a substituted amino group in which a hydrogen atom of an amino group is substituted with an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, and an alkoxysilyl group having 1 to 6 carbon atoms are more preferred.

[0039] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component. The functional group is a modified functional group having an interactive property with a filler such as silica or carbon black, and examples thereof include a nitrogen-containing functional group, a silicon-containing functional group, and an oxygen-containing functional group. Examples of compounds (modifiers) having a nitrogen-containing functional group include amino group-containing compounds, and examples of compounds (modifiers) having a silicon-containing functional group include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having an oxygen-containing functional group include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples of the compounds include those described in International Publication No. 2016 / 194316 and International Publication No. 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0040] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from renewable resources) can be produced in the same manner as conventional synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from renewable resources, and, if necessary, monomer components derived from fossil resources. The rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions with microorganisms or enzyme reactions.

[0041] Regarding the method for preparing rubber derived from biological resources from the above-mentioned biological resources, for example, the method described in JP 2022-179158 A can be used. For example, by using butadiene obtained from biological resources as a monomer component, it is possible to obtain butadiene rubber (B-BR) derived from biological resources (biomass resources), and by using styrene obtained from biological resources and butadiene obtained from biological resources as monomer components, it is possible to obtain styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources). Here, methods for obtaining B-BR and B-SBR from biological resources include, in addition to artificial polymerization methods, methods of polymerization in vivo, and methods of polymerization with biological enzymes. The molecular weight, branching, microstructure, etc. of the obtained B-BR and B-SBR can be appropriately adjusted by changing the polymerization conditions according to known methods according to the target tire performance.

[0042] As the butadiene obtained from the biological resources, butadiene derived from alkyl alcohols (preferably ethanol and butanol, more preferably butanol), butadiene derived from alkenes (preferably ethylene), and butadiene derived from unsaturated carboxylic acids (preferably tiglic acid) can be suitably used. Two or more of these butadienes may be used in combination. As the styrene obtained from the biological resources, styrene obtained from a plant (preferably a plant belonging to the family Hamamelidaceae, Styraxaceae, or Apocynaceae, more preferably a plant belonging to the genera Liquidamus, Styrax, or Catharanthus, and even more preferably Sweetgum, Styrax rosa, or Catharanthus roseus) or a microorganism (preferably a microorganism belonging to the genera Penicillium or Escherichia, more preferably P. citrinum or transformed E. coli) can be suitably used. Two or more of these styrenes may be used in combination.

[0043] Recently, biomass combinat mainly using bioethanol, bioethylene, etc. are planned, but bioethanol and bioethylene are mainly produced using sugars and / or cellulose as biological resources, and other biological resources such as proteins, lipids, and amino acids cannot be effectively utilized. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, it is preferable to use multiple types of monomer components derived from biological resources as the monomer components derived from the biological resources, or to use monomer components derived from biological resources, monomer components derived from renewable resources, and monomer components derived from fossil resources in combination, and further to appropriately adjust the ratio of these monomer components. This makes it possible to effectively utilize a wide range of biological resources and renewable resources such as sugars, proteins, and lipids without relying on one type of biological resource, and to stably supply rubber derived from sustainable materials, and further to consider the environment depending on the situation at the time of production. In addition, when using multiple types of monomer components derived from biological resources, it is preferable to use monomer components derived from different biological resources, i.e., monomer components obtained from different biological resources. Specifically, it is preferable to use a mixture of butadiene derived from multiple types of biological resources with different origins as the butadiene derived from biological resources, and / or to use a mixture of styrene derived from multiple types of biological resources with different origins as the styrene derived from biological resources. This allows multiple types of biological resources to be effectively utilized.

[0044] The rubber component (A) is not particularly limited, but preferably contains a modified conjugated diene polymer obtained by modifying a conjugated diene polymer, and more preferably contains an amine-modified conjugated diene polymer obtained by amine modification. The rubber component (A) may contain such a modified conjugated diene polymer in a proportion of 30% by mass or more, preferably 50% by mass or more. When the rubber component (A) contains 30% by mass or more of the modified conjugated diene polymer, the obtained rubber has low heat generation and can reduce rolling resistance without impairing running durability.

[0045] The modified conjugated diene polymer preferably contains at least one of a tin atom, a nitrogen atom, and a silicon atom as a modifying functional group in the molecule. Preferred examples of the compound containing at least one tin atom in the molecule include tin tetrachloride, tributyltin chloride, dioctyltin dichloride, dibutyltin dichloride, and triphenyltin chloride. Examples of the compound containing at least one nitrogen atom in the molecule include isocyanate compounds, aminobenzophenone compounds, urea derivatives, 4-dimethylaminobenzylideneaniline, dimethylimidazolidinone, and N-methylpyrrolidone. Examples of the functional group containing a silicon atom include a silane group formed by bonding a hydrocarbyloxy group and / or a hydroxy group to a silicon atom. Such a modifying functional group may be present at any one of the polymerization initiation terminal, the side chain, and the polymerization active terminal of the conjugated diene polymer, but preferably at the polymerization terminal, more preferably at the same polymerization active terminal, it has a protic amino group and / or an amino group protected by a leaving group, and a silicon atom to which a hydrocarbyloxy group and / or a hydroxy group is bonded, and particularly preferably a silicon atom to which one or two hydrocarbyloxy groups and / or hydroxy groups are bonded.

[0046] The modified conjugated diene polymer is preferably an amine-modified conjugated diene polymer, and preferably has an amine-based functional group, which is a protic amino group and / or an amino group protected by a removable group, introduced into the molecule as a modifying functional group, and more preferably has a functional group containing a silicon atom introduced into the molecule. The protic amino group may be at least one selected from a primary amino group, a secondary amino group, and salts thereof. On the other hand, examples of amino groups protected by a removable group include N,N-bis(trihydrocarbylsilyl)amino and N-(trihydrocarbylsilyl)imino groups, preferably trialkylsilyl groups in which the hydrocarbyl group is an alkyl group having 1 to 10 carbon atoms, and particularly preferably trimethylsilyl groups. An example of a primary amino group protected by a removable group (also called a protected primary amino group) is N,N-bis(trimethylsilyl)amino, and an example of a secondary amino group protected by a removable group is N-(trimethylsilyl)imino. The N-(trimethylsilyl)imino group-containing group may be either a noncyclic imine residue or a cyclic imine residue.

[0047] Of the amine-modified conjugated diene polymers, the primary amine-modified conjugated diene polymer modified with a primary amino group is preferably a primary amine-modified conjugated diene polymer modified with a protected primary amino group obtained by reacting an active terminal of a conjugated diene polymer with a protected primary amine compound.

[0048] The conjugated diene polymer used for modification may be a homopolymer of a conjugated diene compound, or a copolymer of a conjugated diene compound and an aromatic vinyl compound. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-phenyl-1,3-butadiene, 1,3-hexadiene, etc. These may be used alone or in combination of two or more, with 1,3-butadiene being particularly preferred. Examples of aromatic vinyl compounds used for copolymerization with a conjugated diene compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc. These may be used alone or in combination of two or more, with styrene being particularly preferred. The conjugated diene polymer is preferably polybutadiene or a styrene-butadiene copolymer, and particularly preferably polybutadiene.

[0049] The modified conjugated diene polymer thus obtained had a Mooney viscosity (ML 1+4 ,100°C) is preferably 10 to 150, more preferably 15 to 100. If the Mooney viscosity is less than 10, sufficient rubber properties such as fracture resistance cannot be obtained, and if it exceeds 150, workability is poor and kneading with compounding ingredients is difficult. In addition, the Mooney viscosity (ML 1+4 , 130° C.) is preferably 10 to 150, more preferably 30 to 100. The modified conjugated diene polymer preferably has a ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn), i.e., a molecular weight distribution (Mw / Mn) of 1 to 3, more preferably 1.1 to 2.7. By controlling the molecular weight distribution (Mw / Mn) of the modified conjugated diene polymer within the above range, the workability of the rubber composition is not deteriorated even when the modified conjugated diene polymer is blended into the rubber composition, and the rubber composition can be easily kneaded and the physical properties of the rubber composition can be sufficiently improved.

[0050] The modified conjugated diene polymer preferably has a number average molecular weight (Mn) of 100,000 to 500,000, more preferably 150,000 to 300,000. By setting the number average molecular weight of the modified conjugated diene polymer within the above range, a decrease in elastic modulus of the vulcanizate and an increase in hysteresis loss are suppressed to obtain excellent fracture resistance, and a rubber composition containing the modified conjugated diene polymer has excellent kneading workability. The modified conjugated diene polymers may be used alone or in combination of two or more.

[0051] (Recycled Carbon Black (B)) The rubber composition constituting the bead filler of this embodiment contains recycled carbon black (B). Since the recycled carbon black (B) is a material derived from a renewable resource (recycled resource), by blending the recycled carbon black (B) into the rubber composition, the ratio of sustainable materials in the bead filler to which the rubber composition is applied can be increased.

[0052] In this specification, "recycled carbon black" refers to carbon black obtained by recovering from raw materials that are waste materials that have been subjected to recycling. Examples of the waste materials that have been subjected to recycling include rubber products (particularly vulcanized rubber products) that contain carbon black, such as used rubber and used tires, and waste oil. "Recycled carbon black" is different from carbon black that is produced directly from raw materials such as hydrocarbons, such as petroleum and natural gas, that is, carbon black that is not recycled. Note that "used" here includes not only carbon black that has been actually used and then discarded, but also carbon black that has been produced but discarded without actually being used.

[0053] In addition, the recycled carbon black (B) is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. The recycled carbon black obtained by pyrolysis of a vulcanized rubber product containing carbon black is easily available because there are a large number of vulcanized rubber products containing carbon black and it is easily obtained by pyrolysis. Furthermore, the recycled carbon black (B) is preferably obtained from a solid residue generated by 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 the recycled carbon black can be recovered from either of them. However, it is preferable that the recycled carbon black (B) does not include carbon black recovered from oil.

[0054] The solid residue obtained by pyrolysis of wastes such as used rubber and used tires contains ash in addition to carbon black. The ash is derived from non-volatile components contained in rubber and tires. Therefore, the recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, in consideration of the various physical properties required for tires manufactured using the recycled carbon black, the higher the carbon content in the recycled carbon black, the better. In the recycled carbon black (B), the carbon content is preferably 80% by mass or more, more preferably 85% by mass or more, more preferably 87% by mass or more, and even more preferably 89% by mass or more. The carbon content in the recycled carbon black (B) is preferably 97% by mass or less. The carbon content is a value that does not include adsorbed moisture.

[0055] Specific examples of ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, magnesium oxide, and the like. In the case of recycled carbon black produced from 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 (B) is allowed to contain ash. The lower limit of the ash content of the recycled carbon black (B) may be 0.5% by mass. On the other hand, in consideration of the various physical properties required for tires and the quality of the recycled carbon black, the ash content of the recycled carbon black (B) is preferably 20% by mass or less, more preferably 15% by mass or less, and even more preferably 5.0% by mass or less. When the ash content of the recycled carbon black (B) is 20% by mass or less, the various physical properties of the bead filler to which the rubber composition is applied can be improved. In this specification, the ash content of carbon black is calculated from the mass of unburned components (ash content) obtained by burning carbon black at 550° C.±25° C. to convert it to incineration.

[0056] The recycled carbon black (B) can also be obtained from a pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3427975, referring to "Rubber Chemistry and Technology", Vol. 85, No. 3, pp. 408-449 (2012), in particular pp. 438, 440, and 442, describes that the recycled carbon black (B) can be obtained by pyrolysis of organic materials at 550-800°C with the exclusion of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

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

[0057] The regenerated carbon black (B) may lack a functional group on its surface, or may be treated to include a functional group on its surface. The treatment to include a functional group on the surface of the regenerated carbon black can be carried out by a conventional method. For example, in European Patent Application Publication No. 3173251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black having hydroxyl and / or carboxyl groups on its surface. In Japanese Patent No. 6856781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol group or disulfide group to obtain a carbon black with an activated surface. The regenerated carbon black according to the present embodiment also includes carbon black that has been treated to include a functional group on its surface.

[0058] Moreover, examples of the thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0059] The regenerated carbon black (B) used in this embodiment has a nitrogen adsorption specific surface area (N 2 SA) is 15 to 80m 2 / g. Recycled carbon black is obtained by recycling tire cases, and is therefore in a state where multiple carbon blacks are mixed together, so there is a low loss even if the nitrogen adsorption area is the same as that of conventional carbon black. The nitrogen adsorption specific surface area of ​​the regenerated carbon black (B) is 80m 2 / g or less, the heat generation caused by the recycled carbon black (B) can be suppressed, and the heat generation of the vulcanized rubber can be suppressed. 2 / g or more, the reinforcing properties of the vulcanized rubber can be improved. From the viewpoint of improving low heat generation properties and durability and extending the life of the tire, the nitrogen adsorption specific surface area of ​​the recycled carbon black (B) is 30 to 75 m 2 / g is more preferable, and 40 to 70m 2 It is more preferable that the molecular weight is / g. In this specification, the nitrogen adsorption specific surface area (N 2 SA) is calculated according to JIS K 6217-2:2017 (ISO 4652:2012).

[0060] The recycled carbon black (B) used in this embodiment preferably has a DBP oil absorption of 70 to 120 mL / 100 g. The DBP oil absorption is used as an index of the degree of development of the aggregate structure of carbon black (sometimes referred to as "structure"). The larger the DBP oil absorption, the larger the aggregates tend to be. When the DBP oil absorption of the recycled carbon black (B) is 70 mL / 100 g or more, the tensile strength and compression resistance of the vulcanized rubber are improved and the high-temperature softening resistance of the tire can be improved, and when the DBP oil absorption is 120 mL / 100 g or less, heat generation can be suppressed and the high-temperature softening resistance can be improved. From the same viewpoint, the DBP oil absorption of the recycled carbon black is more preferably 75 to 110 mL / 100 g, and even more preferably 75 to 105 mL / 100 g. In this specification, the DBP oil absorption of carbon black is determined in accordance with JIS K 6217-4:2017.

[0061] Furthermore, the recycled carbon black (B) preferably contains carbon black with a large particle size and high structure. Generally, the larger the particle size of carbon black, the lower the structure. However, by using recycled carbon black with a large particle size but high structure, heat generation can be further suppressed and tensile strength and compressive strength can be further improved, so that the softening resistance of the tire at high temperatures can be further improved. Specifically, the nitrogen adsorption specific surface area of ​​the regenerated carbon black (B) is 15 to 80 m 2 / g and the DBP oil absorption is preferably 70 to 120 mL / 100 g.

[0062] In addition, as the recycled carbon black in the present embodiment, a commercially available product can be used. For example, a commercially available product under the trade name "PB365" manufactured by Enrestec can be used. PB365 is a recycled carbon black produced by pyrolysis of used tires, and has a high N 2 SA is 73.6m 2 / g. PB365 also contains about 17% by mass of ash.

[0063] The content of the recycled carbon black (B) is preferably 55 to 110 parts by mass, and more preferably 60 to 100 parts by mass, per 100 parts by mass of the rubber component (A). When the content of the recycled carbon black (B) is 60 parts by mass or more per 100 parts by mass of the rubber component (A), the effect of improving the ratio of sustainable materials in the bead filler is large, and when it is 120 parts by mass or less, the strength of the bead filler can be sufficiently ensured.

[0064] (resin) The rubber composition constituting the bead filler of the present embodiment may contain a resin. Examples of the resin include terpene-based resin, rosin-based resin, C 5 Resin, C 5 -C 9 Resin, C 9Examples of the resins include cyclopentadiene resins, aromatic resins, coumarone resins, indene resins, coumarone-indene resins, olefin resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene resins, rosin resins, C 5 based resin, C 5 -C 9 based resin, C 9 Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins and aromatic resins, and particularly preferred are terpene-based resins and rosin-based resins. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins, and therefore can reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry road surfaces, wet road surfaces, snowy road surfaces, and frozen road surfaces. 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 well-balanced manner, while the aromatic resin can improve grip performance, abrasion resistance and rubber strength in a well-balanced manner.

[0065] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). In addition, the resin may be modified to introduce a functional group that interacts with a filler such as carbon black or silica. Examples of the functional group include an amino group, an amide group, an isocyanate group, an imino group, an imidazole group, a urea group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, an ether group, a carbonyl group, an oxycarbonyl group, a silyl group, an alkoxysilyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, and a thiocarbonyl group.

[0066] The terpene resin is a solid resin obtained by blending turpentine obtained at the same time when rosin is obtained from pine trees, or a polymerization component separated therefrom, and polymerizing it using a Friedel-Crafts catalyst, and examples of the terpene resin include β-pinene resin and α-pinene resin. The terpene resin also includes terpene-aromatic compound resin, and representative examples of the terpene-aromatic compound resin include terpene-phenol resin and styrene-terpene resin. The terpene-phenol resin can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing with formalin. The styrene-terpene resin can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes as the raw material are not particularly limited, and are preferably monoterpene hydrocarbons such as α-pinene and limonene, more preferably those containing α-pinene, and particularly preferably α-pinene.

[0067] Examples of the rosin-based resin include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil. Examples of modified rosin, rosin derivatives, and modified rosin derivatives include polymerized rosin, partially hydrogenated rosin thereof, glycerin ester rosin, partially hydrogenated rosin thereof, and fully hydrogenated rosin thereof, pentaerythritol ester rosin, partially hydrogenated rosin thereof, and polymerized rosin, etc.

[0068] Said C 5 As for the resin, C is obtained by thermal cracking of naphtha in the petrochemical industry. 5 Examples include aliphatic petroleum resins obtained by (co)polymerizing the fraction. 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, and the like.

[0069] Said C 5 -C9 The resin is C 5 -C 9 C refers to synthetic petroleum resin. 5 -C 9 As a type of resin, for example, petroleum-derived C 5 -C 11 The fraction was dissolved in AlCl 3 , B.F. 3 More specifically, copolymers mainly composed of styrene, vinyl toluene, α-methyl styrene, indene, etc., can be mentioned. 5 -C 9 As for the resin, 9 Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. 9 "Less than 100% of the total resin content" means that 9 This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0070] Said C 9 The resin is C 9 This refers to synthetic petroleum resins, such as AlCl 3 Or BF 3 Using Friedel-Crafts type catalysts such as C 9 It refers to the solid polymer obtained by polymerizing the fraction. 9 Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, or the like as a main component.

[0071] The cyclopentadiene resin refers to a resin containing a unit derived from a cyclopentadiene monomer as a monomer unit. Examples of the cyclopentadiene resin include a homopolymer of a cyclopentadiene monomer, a copolymer of two or more cyclopentadiene monomers, and a copolymer of a cyclopentadiene monomer and another monomer. Examples of the cyclopentadiene monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred, that is, the cyclopentadiene resin is preferably a dicyclopentadiene resin. The dicyclopentadiene resin is, for example, AlCl 3 Or BF 3 It refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as . Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, and copolymers of dicyclopentadiene and C 9 Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0072] The aromatic resin refers to a resin containing a unit derived from an aromatic monomer as a monomer unit. Examples of the aromatic resin include a homopolymer of an aromatic monomer, a copolymer of two or more aromatic monomers, and a copolymer of an aromatic monomer and another monomer. Examples of the aromatic monomer include styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenolic monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0073] The softening point of the resin is preferably 30° C. or higher, more preferably 60° C. or higher, more preferably 80° C. or higher, more preferably higher than 110° C., more preferably 116° C. or higher, more preferably 120° C. or higher, more preferably 123° C. or higher, and even more preferably 127° C. or higher. From the viewpoint of processability, the softening point of the resin is preferably 160° C. or lower, more preferably 150° C. or lower, more preferably 145° C. or lower, more preferably 141° C. or lower, and even more preferably 136° C. or lower. In this specification, the softening point of the resin is the temperature at which the ball drops when the softening point defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0074] As the resin, commercially available products can be used, and examples of commercially available resin products that can be used include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Clayton, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Clayton Polymers, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0075] 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 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, based on 100 parts by mass of the rubber component (A).

[0076] (silica) The rubber composition constituting the bead filler of this embodiment may contain silica. Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, etc., and among these, wet silica is preferred because it has a large number of silanol groups. These silicas may be used alone or in combination of two or more. As the silica, commercially available products may be used, and examples of the commercially available silica products include products from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, Tokuyama Corporation, etc.

[0077] As the silica, silica derived from silicic acid plants is preferred from the viewpoint of reducing environmental load. The silicic acid plants are present, for example, in mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. Among these plants, Gramineae plants are preferred. In addition, the Gramineae plants include rice, bamboo grass, sugarcane, and the like, among which rice is preferred. Since rice is widely cultivated for food, it can be procured locally in a wide area, and since rice husks are generated in large quantities as industrial waste, it is easy to secure the amount. Therefore, from the viewpoint of easy availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. By using the rice husk silica, rice husks that become industrial waste can be effectively utilized, and since the raw material can be procured locally near the tire manufacturing plant, the energy and cost of transportation and storage can be reduced, which is environmentally preferable from various viewpoints. The rice husk silica may be a powder of rice husk charcoal obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet method using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali and extracting the rice husk ash with an alkali silicate aqueous solution. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husks can be pyrolyzed by steaming them in a kiln to obtain rice husk charcoal. The rice husk charcoal thus obtained is pulverized using a known pulverizer (for example, a ball mill), and then sorted and classified into a predetermined particle size range to obtain rice husk charcoal powder. The rice husk-derived precipitated silica can be produced by the method described in JP 2019-38728 A. 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 the raw material for semiconductors, glass bottles, etc., and recycling the extracted silica for use in the production.

[0078] The silica has a nitrogen adsorption specific surface area (N 2 SA) is 50m 2 / g or more, and 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and2 / g or less, and 2 / g or less is more preferable, 2 / g or less is more preferable, 2 It is even more preferable that the molecular weight is not more than 1 / g. In this specification, the nitrogen adsorption specific surface area (N 2 SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0079] The content of the silica can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the target performance, etc. For example, the content of the silica is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, more preferably 30 parts by mass or more, more preferably 50 parts by mass or more, more preferably 70 parts by mass or more, even more preferably 80 parts by mass or more, still more preferably 100 parts by mass or more, particularly preferably 110 parts by mass or more, and 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).

[0080] (Silane coupling agent) When the rubber composition constituting the bead filler of this embodiment contains silica, it is preferable that the rubber composition contains a silane coupling agent in order to improve the effect of the silica. The silane coupling agent is bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, Examples of the silane coupling agent include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide, etc. As the silane coupling agent, a commercially available product can be used, and examples of the commercially available silane coupling agent include products from Evonik, Momentive, Shin-Etsu Silicone Co., Ltd., Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used alone or in combination of two or more.

[0081] Bioethanol can also be used as a raw material for the silane coupling agent. Bioethanol is produced mainly using sugars and / or cellulose as biological resources, and other biological resources such as proteins, lipids, and amino acids cannot be effectively utilized. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, it is preferable to use multiple types of ethanol (bioethanol) derived from biological resources as the raw material for the silane coupling agent, or to use ethanol (bioethanol) derived from biological resources, ethanol derived from renewable resources, and ethanol derived from fossil resources in combination, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (for example, the demand for biomass resources as food). This makes it possible to effectively utilize a wide range of biological resources and renewable resources such as sugars, proteins, and lipids without relying on one type of biological resource, and also to consider the environment depending on the situation at the time of production.

[0082] The content of the silane coupling agent can be appropriately adjusted depending on, for example, the tire category to which it is applied, the target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the silica.

[0083] (Other carbon blacks) The rubber composition constituting the bead filler of this embodiment may contain carbon black other than the above-mentioned recycled carbon black (B). As the other carbon black, carbon black derived from plants is particularly preferable. Examples of carbon black derived from plants include those derived from castor oil and rosin oil. The grade of the other carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. As the other carbon black, commercially available products can be used, and examples of the other carbon black commercially available products include products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Co., Ltd., Nippon Steel Carbon Co., Ltd., Birla Carbon Co., Ltd., and the like. These other carbon blacks may be used alone or in combination of two or more.

[0084] The nitrogen adsorption specific surface area (N 2 SA) is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the target performance, etc. For example, the nitrogen adsorption specific surface area (N 2 SA) is 20m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 70m 2 / g or more is more preferable, and 90m 2 / g or more is more preferable, and 200m 2 / g or less is preferable, and 150m 2 / g or less is more preferable, and 130m 2 / g or less is more preferable.

[0085] The content of the other carbon black is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the target performance, etc. For example, the content of the other carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component (A).

[0086] (rubber powder) The rubber composition constituting the bead filler of this embodiment may contain rubber powder. The rubber powder may be obtained by crushing used rubber products such as used tires, and removing reinforcing materials such as steel materials and fibers, dust, glass, sand, stones, etc., as desired, or by preparing a new vulcanized rubber composition to produce rubber powder and crushing it. For example, rubber powder can be obtained from vulcanized rubber by the method described in "Rubber Chemistry And Technology". In the process of crushing vulcanized rubber to obtain rubber powder, mechanical treatment or low-temperature treatment may be used. For example, in the mechanical treatment, various crushing devices such as a cracker mill and a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In the low-temperature treatment, the finely chopped vulcanized rubber is frozen at a very low temperature and then crushed into fine particles. In addition, a magnetic separator or the like can be used to remove steel materials, and an air separator or the like can be used to remove fibers. As the rubber powder, a commercially available product can be used, and examples of the commercially available rubber powder include products from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental load, it is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more kinds.

[0087] The composition of the rubber powder is not particularly limited, and depends on the composition of vulcanized rubber such as used rubber products (used tires) that serve as a raw material. In one embodiment, the rubber powder contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber powder may be the same as or different from the rubber component, carbon black, silica, etc. that may be contained in the rubber composition constituting the bead filler of the present embodiment described above.

[0088] The rubber powder has a volume average particle size of preferably 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. The smaller the volume average particle size of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle size is measured by a laser diffraction particle size distribution measuring device, for example, "CAPA500" manufactured by Horiba, Ltd.

[0089] The rubber powder has a 60 mesh sieve residue of preferably less than 1 mass%, more preferably 0.5 mass% or less, and even more preferably 0.1 mass% or less, with no particular lower limit. Also, the rubber powder has an 80 mesh sieve residue of preferably less than 10 mass%, more preferably 1 mass% or less, and even more preferably 0.5 mass% or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0090] The rubber powder has an acetone extractable content of preferably 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractables in the rubber powder refer to the acetone extractables (%) determined by the acetone extraction method in accordance with JIS K6350.

[0091] The content of the rubber powder 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 target performance, etc. For example, the content of the rubber powder is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0092] (liquid softener) The rubber composition constituting the bead filler 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, among which oil is preferable. These liquid softeners may be used alone or in combination of two or more.

[0093] The oil is a general term for the extender oil contained in the rubber component and the liquid oil added as a compounding agent of the rubber composition, and examples thereof include vegetable oil, process oil, oil obtained by recycling vegetable oil or process oil, or a mixture thereof. From the viewpoint of reducing the environmental load, the oil is preferably vegetable oil or oil obtained by recycling. Examples of the vegetable oil include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, peanut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, coconut oil, etc. Examples of the process oil include paraffin-based process oil, aromatic process oil, naphthene-based process oil, etc. The oil may be a commercially available product, and examples of the commercially available oil include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0094] The liquid polymer is preferably a liquid diene polymer. Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or the terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0095] The content of the liquid softener is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the softener is applied, the target performance, etc. For example, the content of the liquid softener is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 50 parts by mass or less, and even more preferably 30 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0096] (Anti-aging agent) The rubber composition constituting the bead filler of this embodiment may contain an antioxidant, such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. As the antiaging agent, commercially available products can be used, and examples of the commercially available antiaging agent include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis Co., Ltd., etc. These antiaging agents may be used alone or in combination of two or more.

[0097] The content of the antiaging agent is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the antiaging agent is applied, the target performance, etc. For example, the content of the antiaging agent is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0098] (wax) The rubber composition constituting the bead filler of this embodiment may contain a wax. Examples of the wax include natural waxes such as vegetable wax and animal wax; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available products can be used as the wax, and examples of the commercially available wax products include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0099] 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 composition is applied, 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, relative to 100 parts by mass of the rubber component (A).

[0100] (Stearic acid) The rubber composition constituting the bead filler of the present embodiment may contain stearic acid. Commercially available stearic acid may be used, and examples of the commercially available stearic acid include products from NOF Corp., Kao Corp., Fujifilm Wako Pure Chemical Corp., Chiba Fatty Acid Corp., etc. These commercially available stearic acid products may be used alone or in combination of two or more.

[0101] The content of the stearic acid is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the target performance, etc. For example, the content of the stearic acid is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0102] (Zinc Oxide) The rubber composition constituting the bead filler of this embodiment may contain zinc oxide (zinc white). The zinc oxide is preferably obtained not only from zinc ingot but also from recycled zinc or zinc dross (i.e., obtained by recycling). Commercially available products can be used as the zinc oxide, and examples of the commercially available zinc oxide include products from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., and the like. These commercially available zinc oxide products may be used alone or in combination of two or more.

[0103] 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 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).

[0104] (sulfur) The rubber composition constituting the bead filler of this embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or materials derived from biological resources. From the viewpoint of reducing the environmental load, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of a method for obtaining sulfur from waste derived from biological resources include the method described in the above-mentioned Japanese Patent Application No. 2022-140390. In addition, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are generally used as crosslinking agents in the rubber industry. As the sulfur, commercially available products can be used, and examples of commercially available sulfur products include products from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Co., Ltd., etc. These sulfurs may be used alone or in combination of two or more types.

[0105] The sulfur content is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, 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, and more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0106] (Vulcanization accelerator) The rubber composition constituting the bead filler of the present embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, recycled resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing environmental load. The vulcanization accelerator derived from biological resources can be obtained by the method disclosed in, for example, JP-A-2005-139239. Examples of the vulcanization accelerator include sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; 1,3-diphenylguanidine (DPG), 1,3-diphenylguanidine (DPG), and 1,3-diphenylguanidine (DPG). Examples of the vulcanization accelerator include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available products can be used as the vulcanization accelerator, and examples of the commercially available vulcanization accelerators include products from Ouchi Shinko Chemical Industry Co., Ltd. and Sumitomo Chemical Co., Ltd. These vulcanization accelerators may be used alone or in combination of two or more.

[0107] The content of the vulcanization accelerator is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the target performance, etc. For example, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5.5 parts by mass or less, relative to 100 parts by mass of the rubber component (A).

[0108] (Cellulose nanofiber) The rubber composition constituting the bead filler of this embodiment may contain cellulose nanofibers (CNF). The cellulose nanofibers can reinforce the rubber composition by blending them with the rubber composition. The cellulose nanofibers are preferably modified cellulose nanofibers, which are fine fibers made from modified cellulose. The fiber diameter of the cellulose nanofibers is not particularly limited, but is about 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofibers can be obtained by averaging the fiber diameters and fiber lengths obtained from the results of observing each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofibers can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment and defibration treatment.

[0109] 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.

[0110] The content of the cellulose nanofibers is not particularly limited, and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the target performance, etc. For example, the content of the cellulose nanofibers is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 70 parts by weight, and even more preferably in the range of 10 to 40 parts by mass, relative to 100 parts by mass of the rubber component (A).

[0111] (others) In addition to the above-mentioned components, the rubber composition constituting the bead filler of the present embodiment may further contain various additives commonly used in the tire industry, such as fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica; organic peroxides; etc. The content of these additives is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber is applied, the target performance, etc., and is preferably in the range of 0.1 to 200 parts by mass with respect to 100 parts by mass of the rubber component (A).

[0112] (Method of manufacturing rubber composition) The method for producing the rubber composition constituting the bead filler of this embodiment is not particularly limited, but for example, the rubber component (A) can be produced by blending recycled carbon black (B) and various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a bead filler (vulcanized rubber).

[0113] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0114] The conditions of the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, heat-in device, etc. can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roller machine usually used for heat-in of a rubber composition.

[0115] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder that is usually used for extruding a rubber composition. The extrusion temperature can be appropriately determined.

[0116] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected according to the purpose. As the vulcanization apparatus, a molding vulcanizer using a mold used for vulcanizing a rubber composition can be mentioned. As the vulcanization condition, the temperature is, for example, about 100 to 190°C.

[0117] <Tires> The tire of the present embodiment includes a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, a carcass extending in a toroidal shape between bead cores embedded in the bead portions, and a bead filler disposed radially outward of the bead cores. The tire of the present embodiment is characterized in that the bead filler is the bead filler of the present embodiment described above. The tire of this embodiment includes the bead filler of this embodiment described above, and therefore has an increased proportion of sustainable materials.

[0118] Next, one embodiment of the tire of the present invention will be described in detail with reference to the drawings. Fig. 1 is a cross-sectional view of one embodiment of a tire of the present invention. The tire 1 of this embodiment shown in Fig. 1 includes a pair of bead portions 2, a pair of sidewall portions 3, a tread portion 4 connected to both sidewall portions 3, a carcass 6 extending in a toroidal shape between bead cores 5 embedded in the bead portions 2, a belt 7 consisting of two belt layers arranged on the radially outer side of the crown portion of the carcass 6, and a bead filler 8 arranged on the radially outer side of the bead cores 5.

[0119] 1 is composed of one carcass ply, and also of a main body extending in a toroidal shape between a pair of bead cores 5 each embedded in the bead portion 2, and a turn-up portion wound up radially outward from the inside to the outside in the tire width direction around each bead core 5, but the number and structure of the plies of the carcass 6 in the tire of the present invention are not limited to this. Also, the bead filler 8 is disposed between the main body and the turn-up portion of the carcass on the outside of the bead core 5 in the tire radial direction.

[0120] 1 is made up of two belt layers, each of which is usually made up of a rubberized layer of cords extending at an angle to the tire equatorial plane, preferably a rubberized layer of steel cords, and further, the two belt layers are laminated such that the cords constituting the belt layers cross each other with the tire equatorial plane in between to constitute the belt 7. Note that, although the belt 7 in the figure is made up of two belt layers, the number of belt layers constituting the belt 7 in the tire of the present invention is not limited to this.

[0121] Various modifications can be made to the tire of the present invention. For example, a side reinforcing rubber may be disposed on the inner side in the tire width direction of the carcass 6 of the sidewall portion 3, or a belt reinforcing layer may be disposed on the outer side in the tire radial direction of the belt 7.

[0122] In the tire 1 of the present embodiment, the bead filler of the present embodiment described above is used for the bead filler 8. Therefore, the tire 1 of the present embodiment has an improved ratio of sustainable materials.

[0123] The tire of this embodiment can be manufactured by a normal method using the above-mentioned bead filler. For example, 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, depending on the type of tire to be applied. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium. EXAMPLES

[0124] 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.

[0125] <Method of measuring physical properties of modified conjugated diene polymer> (1) Microstructure analysis method The vinyl bond content (mass%) of the butadiene portion is measured by an infrared method (Morello method).

[0126] (2) Measurement of number average molecular weight (Mn), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) The measurements were performed using a GPC (Tosoh Corporation, HLC-8020) with a refractometer as a detector, and the values ​​are expressed in terms of polystyrene, with monodisperse polystyrene as the standard. The column was a GMHXL (Tosoh Corporation), and the eluent was tetrahydrofuran.

[0127] (3) Measurement of primary amino group content (mmol / kg) First, the polymer is dissolved in toluene, and then precipitated in a large amount of methanol to separate the amino group-containing compounds not bound to the polymer from the rubber, and then dried. The polymer that has been subjected to this treatment is used as a sample to quantify the total amino group content by the "Total Amine Value Test Method" described in JIS K7237. Next, the contents of secondary amino groups and tertiary amino groups are quantified by the "Acetylacetone Blocked Method" using the polymer that has been subjected to the above treatment as a sample. o-Nitrotoluene is used as the solvent for dissolving the sample, acetylacetone is added, and potentiometric titration is performed with a perchloric acid solution. The contents of secondary amino groups and tertiary amino groups are subtracted from the total amino group content to determine the primary amino group content (mmol), and the primary amino group content bound to the polymer (mmol / kg) is calculated by dividing the result by the mass of the polymer used in the analysis.

[0128] <Preparation and Evaluation of Rubber Composition for Bead Filler> Rubber compositions of the examples and comparative examples are prepared according to the compounding recipes shown in Table 1. The total mass ratio of materials derived from biological resources (biomass resources) and materials derived from recycled resources (recycled resources) is calculated for each rubber composition to calculate the sustainable material ratio. The evaluation results are shown in Table 1.

[0129] [Table 1]

[0130] *1 Natural rubber: RSS#1 *2 Modified conjugated diene polymer: Modified conjugated diene polymer synthesized by the following method.

[0131] (Method of producing modified conjugated diene polymer) (1) Production of unmodified polybutadiene In a nitrogen-purged 5L autoclave, 1.4 kg of cyclohexane, 250 g of 1,3-butadiene, and 0.0285 mmol of 2,2-ditetrahydrofurylpropane were poured as a cyclohexane solution under nitrogen, and 2.85 mmol of n-butyllithium (BuLi) was added to the solution, followed by polymerization for 4.5 hours in a 50°C warm water bath equipped with a stirrer. The reaction conversion rate of 1,3-butadiene was nearly 100%. A portion of the polymer solution was withdrawn into a methanol solution containing 1.3 g of 2,6-di-tert-butyl-p-cresol to terminate the polymerization, after which the solvent was removed by steam stripping and the solution was dried on a roll at 110°C to obtain unmodified polybutadiene. The microstructure (vinyl bond content), weight average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the obtained unmodified polybutadiene were measured to find that the vinyl bond content was 14 mass%, Mw was 150,000 and Mw / Mn was 1.1.

[0132] (2) Manufacture of primary amine modified polybutadiene The polymer solution obtained in (1) above is kept at a temperature of 50°C without deactivating the polymerization catalyst, and 1129 mg (3.364 mmol) of N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane with protected primary amino groups is added to perform a modification reaction for 15 minutes. Finally, 2,6-di-tert-butyl-p-cresol is added to the polymer solution after the reaction. Next, the solvent is removed by steam stripping and the protected primary amino groups are deprotected, and the rubber is dried by a heated roll adjusted to 110°C to obtain a primary amine-modified polybutadiene. The microstructure (vinyl bond amount), weight average molecular weight (Mw), molecular weight distribution (Mw / Mn) and primary amino group content of the obtained modified polybutadiene are measured, and the vinyl bond amount is 14 mass%, Mw is 150,000, Mw / Mn is 1.2, and the primary amino group content is 4.0 mmol / kg.

[0133] *3 Recycled carbon black: Obtained by thermal decomposition of vulcanized rubber products containing carbon black, ash content = 15-18% by mass *4 Carbon black: N550, manufactured by Asahi Carbon Co., Ltd., product name "Asahi #60", ash content = 0.1% by mass *5 Cashew modified phenolic resin: Sumitomo Bakelite Co., Ltd., product name "SUMILITE RESIN PR-BSN-21" *6 Hexamethylenetetramine: manufactured by Wako Pure Chemical Industries, Ltd. *7 Thiuram vulcanization accelerator TOT: Tetrakis(2-ethylhexyl)thiuram disulfide, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Noccela TOT-N" *8 Sulfenamide vulcanization accelerator NS: N-(tert-butyl)-2-benzothiazolylsulfenamide, manufactured by Sanshin Chemical Industry Co., Ltd., product name "Suncerer NS-G" *9 Antioxidant 6C: N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, manufactured by Ouchi Shinko Chemical Industry Co., Ltd., product name "Nocrac 6C"

[0134] From Table 1, it can be seen that the bead filler made of a rubber composition containing recycled carbon black (B) has a high ratio of sustainable materials, and the use of this bead filler can increase the ratio of sustainable materials in tires.

[0135] [Contribution to the United Nations-led Sustainable Development Goals (SDGs)] The SDGs have been proposed to realize a sustainable society. One embodiment of the present invention is considered to be a technology that can contribute to "No. 12_Responsible Consumption and Production" and "No. 13_Concrete measures against climate change." [Explanation of symbols]

[0136] 1: Tires 2: Bead section 3: Sidewall 4: Tread section 5: Bead core 6: Carcass 7: Belt 8: Bead filler

Claims

1. A bead filler comprising a rubber composition containing a rubber component (A) and recycled carbon black (B).

2. 2. The bead filler according to claim 1, wherein the recycled carbon black (B) is obtained by pyrolysis of a vulcanized rubber product containing carbon black.

3. The bead filler according to claim 1 , wherein the recycled carbon black (B) has an ash content of 20 mass% or less.

4. A tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, a carcass extending in a toroidal shape between bead cores respectively embedded in the bead portions, and a bead filler disposed radially outward of the bead cores, A tire, characterized in that the bead filler is the bead filler according to claim 1 .

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