Rubber composition and tire

Abstract

Provided is a rubber composition that is capable of inhibiting occurrence of rubber surface roughening during mold vulcanization, and that can contribute to the improvement of sustainability. This rubber composition comprises a rubber component and carbon black including recycled carbon black, and is characterized in that the recycled carbon black forms a plurality of aggregates in the rubber composition, and, in the carbon black, the proportion of carbon black having a diameter of at least 5.0 μm in a particle size distribution A of carbon black having a diameter of 1.0 μm or more is at least 1%.

Description

Rubber composition and tire

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

[0002] During the vulcanization process in tire manufacturing, air may not be sufficiently removed between the mold and the rubber surface in contact with the mold, resulting in air entrapment. When this air entrapment occurs, roughness may develop on the rubber surface after vulcanization. This problem of rubber surface roughness is often seen in tire bead sections and other areas molded into complex outer shapes, and can be a factor in poor tire appearance.

[0003] To address the above-mentioned problems, for example, Patent Document 1 discloses that by placing a urethane film on the inner surface of the mold or the outer surface of the tire prior to the vulcanization process, the urethane film acts as a protective film that is effective in suppressing the occurrence of air trapping and, ultimately, in suppressing the occurrence of roughness on the rubber surface.

[0004] Japanese Patent Application Laid-Open No. 2017-094853

[0005] The technology described in Patent Document 1 requires an additional member and process, namely, the formation of a urethane film. In contrast, there is a demand for optimizing the rubber material itself that comes into contact with the mold to address the above-mentioned problems.

[0006] Furthermore, in recent years, from the perspective of social sustainability, there has been a demand for businesses and products to use so-called sustainable materials, such as materials derived from biological resources (biomass resources) and materials derived from recycled resources, and there is also a demand for an increase in the rate of sustainable material use (hereinafter sometimes referred to as the "sustainability rate") for the various components used in tires.

[0007] Therefore, an object of the present invention is to provide a rubber composition that can suppress the occurrence of rubber surface roughening during mold vulcanization and contribute to improving sustainability.Another object of the present invention is to provide a tire that suppresses rubber surface roughening and contributes to improving sustainability.

[0008] That is, the rubber composition and tire of the present invention that solve the above problems are outlined below.

[0009] [1] A rubber composition containing a rubber component and carbon black including recycled carbon black, wherein the recycled carbon black forms a plurality of agglomerates in the rubber composition, and the proportion of the carbon black having a diameter of 5.0 μm or more is 1% or more in particle size distribution A for carbon black having a diameter of 1.0 μm or more.

[0010] [2] The rubber composition according to [1], wherein the recycled carbon black is obtained by thermal decomposition of a vulcanized rubber product containing carbon black.

[0011] [3] The rubber composition according to [1] or [2], wherein the recycled carbon black has an ash content of 20% by mass or less.

[0012] [4] The rubber composition according to any one of [1] to [3], wherein in the particle size distribution A, the proportion of particles having a diameter of 5.0 μm or more is 10% or more.

[0013] [5] The rubber composition according to any one of [1] to [4], further containing at least one of rubber powder and reclaimed rubber.

[0014] [6] A tire characterized by using the rubber composition according to any one of [1] to [5].

[0015] [7] A tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass consisting of at least one carcass ply extending in a toroidal shape across the pair of bead portions, wherein the tire further comprises a side rubber on the outer side of the carcass in the tire width direction in the sidewall portions, and the rubber composition is used for the side rubber. [6] The tire according to [6].

[0016] [8] A tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass consisting of at least one carcass ply extending in a toroidal shape across the pair of bead portions, wherein the tire further comprises a gum chafer arranged in at least a part of the contact portion between the bead portion and the rim, and the rubber composition is used for the gum chafer. [6] The tire according to [7] or [8].

[0017] According to the present invention, it is possible to provide a rubber composition that can suppress the occurrence of rubber surface roughening during mold vulcanization and that can contribute to improving sustainability. Also, according to the present invention, it is possible to provide a tire that suppresses rubber surface roughening and that can contribute to improving sustainability.

[0018] The rubber composition and tire of the present invention will be described in detail below with reference to examples based on embodiments thereof.

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

[0020] In this specification, the term "sustainability rate" refers to the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) in a target material.

[0021] In this specification, the term "biological resources (biomass resources)" refers to carbon-neutral organic resources derived from living organisms, and includes, for example, materials stored in the form of starch or cellulose, the bodies of animals that grow by eating plants, and products obtained by processing plants or animals, and is a resource excluding fossil resources (petroleum, coal, natural gas, etc.). The biological resources may be edible or non-edible, but are preferably non-edible in order not to compete with food and from the viewpoint of effective resource utilization.

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

[0023] In this specification, the term "recycled resources" refers to resources obtained by regenerating (recycling) products that have been used once, or that have been collected without being used, or that have been discarded. For example, recycled resources include resources obtained by regenerating (recycling) used rubber products such as used tires.

[0024] <Rubber Composition> A rubber composition according to one embodiment of the present invention (hereinafter sometimes referred to as the "rubber composition of the present embodiment") contains a rubber component and carbon black, including recycled carbon black. This embodiment is characterized in that the recycled carbon black forms a plurality of agglomerates in the rubber composition, and in a particle size distribution (particle size distribution A) of carbon black with a diameter of 1.0 μm or more, the proportion of particles with a diameter of 5.0 μm or more is 1% or more.

[0025] As used herein, "agglomeration" refers to a single recycled carbon black particle entangled with itself or two or more recycled carbon black particles entangled with each other to form a single mass, and "agglomerate" refers to a mass having a structure in which a single recycled carbon black particle entangles with itself or two or more recycled carbon black particles entangled with each other. This "agglomerate" is composed substantially only of recycled carbon black.

[0026] In this specification, "carbon black having a diameter of 1.0 μm or more" includes carbon black having a primary particle diameter of 1.0 μm or more and carbon black having an aggregate diameter (secondary particle diameter) of 1.0 μm or more.

[0027] In this specification, "particle size distribution A of carbon black having a diameter of 1.0 μm or more" can be obtained by first measuring the volumetric particle size distribution of all carbon black using a laser diffraction particle size analyzer, and then normalizing the particle size distribution by excluding data with diameters of less than 1.0 μm. Such particle size distribution A is, for example, a cumulative distribution.

[0028] The rubber composition of this embodiment contains dispersed agglomerates of recycled carbon black, and in the particle size distribution A, the proportion of particles with diameters of 5.0 μm or greater is 1% or greater. That is, in the rubber composition of this embodiment, the size of the carbon black, including the recycled carbon black agglomerates, is optimized. Furthermore, when this rubber composition is vulcanized in a mold, appropriate irregularities are formed on the rubber surface, and the presence of these irregularities facilitates air flow. As a result, the rubber composition of this embodiment can significantly suppress the occurrence of roughness on the rubber surface. Furthermore, since the rubber composition of this embodiment uses recycled carbon black, it can contribute to improving sustainability.

[0029] In particle size distribution A, the proportion of particles having a diameter of 5.0 μm or more is preferably 10% or more. In this case, roughening of the rubber surface can be further suppressed. From the same viewpoint, the proportion is more preferably 15% or more, and even more preferably 40% or more. On the other hand, from the viewpoint of the fracture properties of the rubber, the proportion is preferably 80% or less, and more preferably 70% or less.

[0030] The "proportion of particles having a diameter of 5.0 μm or more in particle diameter distribution A" can be adjusted by, for example, appropriately controlling the type of recycled carbon black used, the blending amount, the kneading method, etc. Furthermore, recycled carbon black that already contains a predetermined amount of "aggregates having a diameter of 5.0 μm or more" can also be used as the recycled carbon black to be blended into the rubber component.

[0031] The rubber composition of the present embodiment may contain recycled carbon black that does not form agglomerates, as long as it contains a plurality of agglomerates formed of recycled carbon black.

[0032] Next, various materials that may be contained in the rubber composition of the present embodiment will be described.

[0033] (Rubber Component) The rubber composition of the present embodiment contains a rubber component, which provides rubber elasticity to the composition. The rubber component 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.

[0034] The rubber component is preferably the rubber derived from biological resources and the rubber derived from recycled resources. Here, the proportion of the monomer component derived from biological resources in 100 mol% of the monomer components constituting the rubber derived from biological resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%. Furthermore, the proportion of the monomer component derived from recycled resources in 100 mol% of the monomer components constituting the rubber derived from recycled resources is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, even more preferably 90 mol% or more, particularly preferably 95 mol% or more, and may be 100 mol%.

[0035] The rubber component is a component that contributes to crosslinking, and typically has a weight average molecular weight (Mw) of 10,000 or more, preferably 50,000 or more, more preferably 150,000 or more, and even more preferably 200,000 or more, and preferably 5,000,000 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 can be determined in terms of standard polystyrene based on measurements obtained using, for example, a gel permeation chromatograph (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation).

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

[0037] Examples of the isoprene-based rubber include natural rubber (NR), synthetic isoprene rubber (IR), modified natural rubber (modified NR), modified natural rubber (modified NR), and modified synthetic isoprene rubber (modified IR). Examples of natural rubber (NR) that can be used include those commonly used in the tire industry, such as RSS#3 and TSR20 (e.g., SIR20 and STR20). The origin of the natural rubber (NR) is not particularly limited, and examples include those derived from Hevea brasiliensis, guayule, and Russian dandelion. Examples of synthetic isoprene rubber (IR) are not particularly limited, and examples include those commonly used in the tire industry, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized synthetic isoprene rubber, hydrogenated synthetic isoprene rubber, and grafted synthetic isoprene rubber. These isoprene-based rubbers may be used alone or in combination of two or more. Among these, NR is preferred as the isoprene-based rubber.

[0038] The isoprene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve a sustainability rate within the above range, it is preferable to use natural rubber (NR) or a polymer synthesized using isoprene derived from biological resources or isoprene derived from recycled resources as a monomer component. In this case, the synthesized polymer may be a homopolymer of a monomer derived from biological resources, a homopolymer of a monomer derived from recycled resources, a copolymer of a monomer derived from biological resources and a monomer derived from recycled resources, or a copolymer of a monomer derived from biological resources and / or a monomer derived from recycled resources and a monomer derived from fossil resources (petroleum, etc.).

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

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

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

[0042] The butadiene-based rubber preferably has a sustainability rate of 30% by mass or more, more preferably 40% by mass or more, more preferably 50% by mass or more, more preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 100% by mass. To achieve a sustainability rate within the above range, for example, a polymer synthesized using a bioresource-derived butadiene, a recycled resource-derived butadiene, a bioresource-derived aromatic vinyl compound (e.g., bioresource-derived styrene), or a recycled resource-derived aromatic vinyl compound (e.g., recycled resource-derived styrene) as a monomer component may be used. In this case, the synthesized polymer may be a homopolymer of a bioresource-derived monomer, a homopolymer of a recycled resource-derived monomer, a copolymer of a bioresource-derived monomer and a recycled resource-derived monomer, or a copolymer of a bioresource-derived monomer and / or a recycled resource-derived monomer and a fossil resource (e.g., petroleum)-derived monomer. Note that the butadiene rubber (B-BR) derived from biological resources (biomass resources) and aromatic vinyl compound-butadiene copolymer rubber derived from biological resources (for example, styrene-butadiene rubber (B-SBR) derived from biological resources (biomass resources)) include not only rubber obtained by polymerizing butadiene or the like according to conventional methods, but also rubber obtained by reactions involving microorganisms, plants, animals, and tissue cultures thereof (hereinafter also referred to as "microorganisms, etc.") or enzymatic reactions.

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

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

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

[0046] The ratio of each monomer unit (e.g., isoprene-derived units, butadiene-derived units, and aromatic vinyl compound-derived units) in the entire rubber component can be adjusted appropriately depending on the components to which the rubber is applied. The ratio of each monomer unit in the entire rubber component can be adjusted, for example, by appropriately combining the above-mentioned isoprene-based rubber and butadiene-based rubber. The ratio of cis-bond units in the butadiene-derived units can also be adjusted appropriately depending on the components to which the rubber is applied. In this specification, the term "monomer unit" refers to a structural unit of a polymer, the term "isoprene-derived unit" refers to a structural unit in a polymer based on the isoprene monomer (including isoprene units in natural rubber), the term "butadiene-derived unit" refers to a structural unit in a polymer based on the butadiene monomer, and the term "aromatic vinyl compound-derived unit" refers to a structural unit in a polymer based on the aromatic vinyl compound monomer. In this specification, the ratio of each monomer unit is measured by NMR.

[0047] The rubber component may contain diene rubbers such as acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), styrene-isoprene-butadiene copolymer rubber (SIBR), etc., in addition to the above-mentioned isoprene-based rubber, butadiene rubber (BR), and aromatic vinyl compound-butadiene copolymer rubber (e.g., SBR). These rubber components may be used alone or in combination of two or more.

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

[0049] The functional group can be introduced, for example, by reacting a compound (modifier) ​​having the functional group with the rubber component. The functional group is a modified functional group that has interactivity with fillers such as silica and carbon black, and examples thereof include nitrogen-containing functional groups, silicon-containing functional groups, and oxygen-containing functional groups. Examples of compounds (modifiers) having nitrogen-containing functional groups include amino group-containing compounds, and examples of compounds (modifiers) having silicon-containing functional groups include silicon halides and hydrocarbyloxysilane compounds. Examples of compounds (modifiers) having oxygen-containing functional groups include alkoxy group-containing compounds, alkylene oxide group-containing compounds, and trialkylsilyloxy group-containing compounds. More specifically, examples of the compounds described in WO 2016 / 194316 and WO 2019 / 117256 include the compounds described in WO 2016 / 194316 and WO 2019 / 117256. These modifiers may be used alone or in combination of two or more.

[0050] The rubber derived from sustainable materials (materials derived from biological resources or materials derived from recycled resources) can be produced in the same manner as conventional methods for producing synthetic rubber derived from fossil resources, for example, by using monomer components derived from biological resources or monomer components derived from recycled resources, and, if necessary, monomer components derived from fossil resources. Furthermore, the rubber derived from sustainable materials (particularly rubber derived from biological resources) can also be obtained by reactions using microorganisms or enzyme reactions.

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

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

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

[0054] (Recycled Carbon Black) The rubber composition of this embodiment contains recycled carbon black, which forms a plurality of agglomerates in the rubber composition.

[0055] As used herein, "recycled carbon black" refers to carbon black recovered from recycled waste materials. Examples of such waste include waste rubber, used tires, and waste oil. Waste rubber refers to all discarded rubber, including not only waste generated from rubber products but also unwanted scraps generated during the production or repair of rubber products. Examples of scraps include buffing powder and peeled rubber. Buffing powder is fine rubber generated during the buffing process of scraping the tread portion remaining on the base tire during tire retreading, for example. Peeled rubber is a long piece of rubber, e.g., 1 to 2 cm wide, peeled from the surface of a rubber product such as a tire. Peeled rubber is generated by scraping the surface of a rubber product such as a tire using a U- or V-shaped knife like a peeler. Furthermore, waste rubber is not limited to crosslinked rubber but also includes unvulcanized rubber. Rubber products include, for example, final products such as tires and rubber hoses, as well as rubber parts or components during the manufacturing process of final products. Used tires may be tires to be retreaded, or may be tires discarded for some reason, such as tires generated during tire replacement or scrapping, or ELTs (End-of-Life Tires) that have reached the end of their service life. Waste oils are not limited to those generated during the decomposition of plastics and rubber, but also include used oils discharged from industry, such as animal and vegetable oils, lubricating oils, insulating oils, and cutting oils. Among these, waste oils that contain no non-organic components, such as those derived from silicone rubber or polyvinyl chloride, are desirable. Furthermore, waste oils containing carbon black or rubber containing carbon black are desirable. "Recycled carbon black" differs from carbon black produced directly from hydrocarbons such as petroleum, natural gas, and coal, i.e., non-recycled carbon black. Note that "used" here refers not only to waste oils discarded after actual use, but also to waste oils that were produced but discarded without actually being used.

[0056] The recycled carbon black used in this embodiment is preferably obtained by pyrolysis of a vulcanized rubber product containing carbon black. The recycled carbon black obtained by pyrolysis tends to have a high proportion of agglomerates with a diameter of 5.0 μm or more. Therefore, the use of such recycled carbon black makes it easier to obtain the rubber composition of this embodiment. Furthermore, the recycled carbon black used in this embodiment is preferably obtained from the solid residue produced by the pyrolysis of the vulcanized rubber product containing carbon black. When a rubber product containing carbon black is pyrolyzed, a solid residue and a volatile component (oil) are obtained, and recycled carbon black can be recovered from either. When recovering carbon black from the volatile component, the oil with a specific gravity suitable for producing carbon black can be recovered and used to produce carbon black using existing carbon black production methods (e.g., JP 2015-520259 A). Unlike carbon black recovered from solid residues, this method offers advantages such as no impurities and no mixing of different grades. In addition, in the production of environmentally friendly carbon black, various options are available, including oils obtained by recovering volatile components from rubber pyrolysis, as described above, as well as vegetable oils and oils derived from waste plastics. However, edible resources such as vegetable oils are needed for other uses, such as food, and there are challenges in securing sufficient quantities, as well as the environmental impact of expanding cultivated land. Furthermore, oils derived from waste plastics are also used for other purposes, such as horizontal plastic recycling, so supply issues are also a concern. On the other hand, using volatile components (oils) produced by the pyrolysis of vulcanized rubber products, particularly tires, allows for the continued use of existing materials due to the tire industry's ongoing system of using existing materials, thereby reducing the consumption of new materials in new tire production and contributing to a reduction in the industry's environmental impact. The grade of carbon black is not particularly limited, and examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762.

[0057] Solid residues obtained by pyrolysis of waste materials such as used rubber and used tires contain ash in addition to carbon black. The ash is derived from non-volatile components contained in rubber and tires. Therefore, recycled carbon black obtained from the solid residue has a relatively low carbon black content. On the other hand, considering the various physical properties required for tires manufactured using recycled carbon black, the higher the carbon content in the recycled carbon black, the better. The carbon content of the recycled carbon black used in this embodiment is preferably 75% by mass or more, more preferably 80% by mass or more, even more preferably 87% by mass or more, and even more preferably 89% by mass or more. The carbon content of the recycled carbon black used in this embodiment is preferably 97% by mass or less. Note that the carbon content does not include adsorbed moisture.

[0058] Specific examples of the ash include zinc oxide, zinc sulfide, silica, iron compounds (iron oxide), calcium oxide, aluminum oxide, and magnesium oxide. In the case of recycled carbon black produced from solid residues obtained by pyrolysis of waste, a certain amount of ash remains even after various processes for removing the ash. In this embodiment, the recycled carbon black is allowed to contain ash. The lower limit of the ash content of the recycled carbon black used in this embodiment may be 0.5% by mass. Meanwhile, considering the various physical properties required for tires and the quality of the recycled carbon black, the ash content of the recycled carbon black is preferably 25% by mass or less, more preferably 15% by mass or less, and even more preferably 5.0% by mass or less. Herein, the ash content of carbon black is determined in accordance with ASTM D8474 and D1506.

[0059] Recycled carbon black can also be obtained from the pyrolysis process of used pneumatic tires. For example, European Patent Application Publication No. 3,427,975, citing "Rubber Chemistry and Technology," Vol. 85, No. 3, pp. 408-449 (2012), particularly pp. 438, 440, and 442, describes that recycled carbon black can be obtained by pyrolysis of organic materials at 550-800°C in the absence of oxygen, or by vacuum pyrolysis at relatively low temperatures (

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

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

[0060] Recycled carbon black may lack functional groups on its surface, or may be treated to include functional groups on its surface. The treatment to include functional groups on the surface of recycled carbon black can be carried out by conventional methods. For example, in European Patent Application Publication No. 3,173,251, carbon black obtained from a pyrolysis process is treated with potassium permanganate under acidic conditions to obtain carbon black containing hydroxyl and / or carboxyl groups on its surface. Furthermore, in Japanese Patent No. 6,856,781, carbon black obtained from a pyrolysis process is treated with an amino acid compound containing at least one thiol or disulfide group to obtain surface-activated carbon black. The recycled carbon black according to this embodiment also includes carbon blacks that have been treated to include functional groups on their surfaces.

[0061] Furthermore, examples of thermal decomposition of crosslinked rubber products (vulcanized rubber products) such as used tires include thermal decomposition methods at temperatures of 650° C. or higher.

[0062] The crosslinked rubber products to be decomposed may be grouped by the type of rubber component previously compounded, and then the decomposition process may be carried out for each group. Alternatively, the crosslinked rubber products may be grouped by the type of filler previously compounded (e.g., the type of carbon black, the type of silica, the mixing ratio of carbon black and silica, etc.), and then the decomposition process may be carried out for each group. Furthermore, the crosslinked rubber products may be grouped by both the type of rubber component and the type of filler, and then the decomposition process may be carried out for each group. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and when the recycled carbon black is compounded again into a rubber component, a rubber composition with better performance can be obtained.

[0063] Furthermore, when the crosslinked rubber product to be decomposed is derived from tires, the tires may be grouped in advance by type (e.g., for passenger cars, for trucks and buses, for large vehicles such as off-road vehicles, for aircraft, for agricultural vehicles, etc.), and then the decomposition process may be carried out for each group. Alternatively, the tires may be grouped in advance by tire component (e.g., tread rubber, sidewall rubber, bead rubber, steel cord-coated rubber, organic fiber-coated rubber, pad rubber, cushion rubber, etc.), and then the decomposition process may be carried out for each group. Furthermore, the tires may be grouped both by type and by tire component, and then the decomposition process may be carried out for each group. When the decomposition process is carried out for each group in this way, recycled carbon black with more uniform physical properties can be obtained, and therefore, when the recycled carbon black is blended again into a rubber component, a rubber composition with better performance can be obtained.

[0064] The recycled carbon black used in this embodiment has a nitrogen adsorption specific surface area (N ２ SA) is 40 to 100m ２ / g, and 50 to 90m ２ / g, and more preferably 55 to 75m ２ / g is particularly preferred. In addition, the DBP oil absorption is preferably 70 to 120 mL / 100 g, more preferably 75 to 110 mL / 100 g, and particularly preferably 80 to 100 mL / 100 g. Note that, as the recycled carbon black in this embodiment, a commercially available product can be used, and an example of such a commercially available product is "PB365" manufactured by Enrestec. PB365 is recycled carbon black produced through the thermal decomposition of used tires, and has an N ２ SA is 73.6m ２ / g. PB365 contains about 17% by mass of ash. In this specification, the nitrogen adsorption specific surface area (N ２ SA) is the statistical thickness specific surface area (STSA) and is determined in accordance with ASTM D6556. In addition, in this specification, the DBP oil absorption of carbon black is determined in accordance with ASTM D2414.

[0065] The pH of the recycled carbon black is preferably 4 to 12, more preferably 5 to 11, and particularly preferably 6 to 10. In this specification, the pH of the recycled carbon black is determined in accordance with ASTM D1512.

[0066] The recycled carbon black preferably has a toluene color transmittance of 60% or more, more preferably 70% or more, and particularly preferably 80% or more. Herein, the toluene color transmittance of recycled carbon black is determined in accordance with ASTM D1618.

[0067] The recycled carbon black preferably has a heat loss of 3% by mass or less, more preferably 2.5% by mass or less, and particularly preferably 2% by mass or less at 125°C. Herein, the heat loss of recycled carbon black at 125°C is determined in accordance with ASTM D1509.

[0068] The recycled carbon black preferably has a sulfur content of 5% by mass or less, more preferably 3.5% by mass or less, and particularly preferably 3% by mass or less.

[0069] The recycled carbon black preferably has a 35 mesh sieve residue of 20 mass ppm or less, more preferably 15 mass ppm or less, and particularly preferably 10 mass ppm or less. Herein, the 35 mesh sieve residue of recycled carbon black is determined in accordance with ASTM D1514.

[0070] The recycled carbon black preferably has a 325 mesh (44 μm) sieve residue of 1000 mass ppm or less, more preferably 700 mass ppm or less, and particularly preferably 300 mass ppm or less. Herein, the 325 mesh (44 μm) sieve residue of the recycled carbon black is determined in accordance with ASTM D1514.

[0071] The recycled carbon black preferably has a pellet hardness of 100 cN or less, more preferably 90 cN or less, and particularly preferably 80 cN or less. Herein, the pellet hardness of recycled carbon black is determined in accordance with ASTM D5230.

[0072] The recycled carbon black preferably has a pellet fine powder content of 10% by mass or less, more preferably 7% by mass or less, and particularly preferably 5% by mass or less. Herein, the pellet fine powder content of recycled carbon black is determined in accordance with ASTM D1508.

[0073] The particle size (D97) of the recycled carbon black is preferably 25 μm or less, more preferably 15 μm or less, and particularly preferably 10 μm or less. Here, in this specification, the particle size (D97) of the recycled carbon black is determined using a laser diffraction particle size distribution analyzer, assuming a refractive index of 1.33 for water and a refractive index of 1.75 for the filler.

[0074] The recycled carbon black preferably contains particles of 5 μm or less in a proportion of 50% by volume or more, more preferably 70% by volume or more, and particularly preferably 80% by volume or more.

[0075] The recycled carbon black preferably has a compressed dibutyl phthalate (24M4DBP) absorption capacity of 50 to 110 mL / 100 g, more preferably 60 to 100 mL / 100 g, and particularly preferably 70 to 90 mL / 100 g. Herein, the 24M4DBP absorption capacity of the recycled carbon black is determined in accordance with ASTM D3493.

[0076] The content of the recycled carbon black in the rubber composition of this embodiment is not particularly limited, but is preferably 2 parts by mass or more and preferably 100 parts by mass or less per 100 parts by mass of the rubber component. A recycled carbon black content of 2 parts by mass or more can more reliably suppress the occurrence of rubber surface roughness and further contribute to improving sustainability. Furthermore, a recycled carbon black content of 100 parts by mass or less can fully exhibit the various properties inherent to the rubber component, such as elastomer properties and durability. From the same viewpoint, the content of recycled carbon black per 100 parts by mass of the rubber component is more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and more preferably 80 parts by mass or less, even more preferably 50 parts by mass or less.

[0077] (Carbon Black Other Than Recycled Carbon Black) The rubber composition of the present embodiment may further contain, in addition to the recycled carbon black described above, carbon black other than recycled carbon black (virgin carbon black). Examples of carbon black other than recycled carbon black include plant-derived carbon black, such as those derived from castor oil and pine oil.

[0078] The grade of the carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks can be used, and examples of commercially available carbon blacks include those manufactured by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Birla Carbon Co., Ltd. These carbon blacks may be used alone or in combination of two or more.

[0079] The nitrogen adsorption specific surface area (N ２ The nitrogen adsorption specific surface area (N SA) of carbon black is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. ２ SA) is 20m ２ / g or more is preferable, and 50m ２ / g or more is more preferable, and 70m ２ / g or more is more preferable, ２ / g or more is more preferable, and ２ / g or less is preferable, and 150m ２ / g or less is more preferable, and 130m ２ / g or less is more preferable.

[0080] The carbon black content is not particularly limited and can be adjusted as appropriate depending on, for example, the tire category, tire components, target performance, etc. However, from the viewpoint of forming agglomerates of recycled carbon black as desired, the rubber composition of this embodiment preferably does not contain any carbon black other than recycled carbon black. This is because, in general, the primary particle size of virgin carbon black, or the size of agglomerates that can be formed from virgin carbon black, tends to be relatively small.

[0081] (Silica) The rubber composition of this embodiment may contain silica. Examples of the silica include wet silica (hydrated silicic acid), dry silica (anhydrous silicic acid), calcium silicate, and aluminum silicate. Among these, wet silica is preferred because it contains a large number of silanol groups. These silicas may be used alone or in combination of two or more. Commercially available silicas can be used, and examples of commercially available silicas include products from Tosoh Silica Corporation, Evonik, Solvay, Solvay Japan, and Tokuyama Corporation.

[0082] From the viewpoint of reducing environmental impact, silica derived from siliceous plants is preferred as the silica. Examples of siliceous plants include mosses, ferns, horsetails, Cucurbitaceae, Urticaceae, and Gramineae plants. Among these plants, grasses are preferred. Examples of grasses include rice, bamboo, and sugarcane, with rice being preferred. Rice is widely cultivated for food and therefore can be procured locally over a wide area. Furthermore, rice husks are generated in large quantities as industrial waste, making it easy to secure a sufficient supply. Therefore, from the viewpoint of availability, silica derived from rice husks (hereinafter also referred to as "rice husk silica") is particularly preferred as silica. The use of rice husk silica allows for the effective use of rice husks, which are industrial waste, and also allows for the local procurement of raw materials near tire manufacturing plants, thereby reducing the energy and costs involved in transportation and storage, which is environmentally preferable from various viewpoints. The rice husk silica may be rice husk charcoal powder obtained by carbonizing rice husks by heating, or may be precipitated silica produced by a wet process using an alkali silicate aqueous solution, which is prepared by extracting rice husk ash generated when rice husks are burned as fuel in a biomass boiler with an alkali. The method for producing the rice husk charcoal is not particularly limited, and various known methods can be used. For example, rice husk charcoal can be obtained by pyrolyzing the rice husks by steaming them in a kiln. The rice husk charcoal obtained in this manner is pulverized using a known pulverizer (e.g., a ball mill), and then sorted and classified into a predetermined particle size range to obtain rice husk charcoal powder. Furthermore, the rice husk-derived precipitated silica can be produced by the method described in JP 2019-38728 A. Further examples of the silica include silica produced by recycling silicon components from silicon wafer scraps, glass bottles, and the like, which are used as raw materials for semiconductors.

[0083] 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, and ２ / g or less, and ２ / g or less is more preferable, and 230m ２ / g or less is more preferable, and 200m ２ / g or less. In this specification, the nitrogen adsorption specific surface area (N ２ SA) is a value measured by the BET method in accordance with ASTM D3037-93.

[0084] The content of the silica can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of silica is, relative to 100 parts by mass of the rubber component, 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, still more preferably 180 parts by mass or less, and particularly preferably 150 parts by mass or less.

[0085] The proportion of silica in the total content of silica and carbon black is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, in the case of tread rubber for passenger car tires, the proportion of silica in the total content of silica and carbon black is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, even more preferably 90% by mass or more, and particularly preferably 95% by mass or more. Furthermore, the proportion of silica in the total content of silica and carbon black may be 100% by mass, but is preferably 98% by mass or less.

[0086] (Silane Coupling Agent) When the rubber composition of this embodiment contains silica, in order to improve the effect of the silica, the rubber composition preferably contains a silane coupling agent. Examples of the silane coupling agent include bis(3-triethoxysilylpropyl)tetrasulfide, bis(3-triethoxysilylpropyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N,N-dimethylthiocarbamoyltetrasulfide, Examples of such tetrasulfides include N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-trimethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl benzothiazolyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide, 3-trimethoxysilylpropyl methacrylate monosulfide, bis(3-diethoxymethylsilylpropyl)tetrasulfide, 3-mercaptopropyldimethoxymethylsilane, dimethoxymethylsilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, and dimethoxymethylsilylpropyl benzothiazolyl tetrasulfide. As the silane coupling agent, commercially available products can be used, and examples of commercially available silane coupling agents that can be used include products from Evonik, Momentive, Shin-Etsu Silicones Co., Ltd., Dow Corning Toray Co., Ltd., Tokyo Chemical Industry Co., Ltd., and Azumax Co., Ltd. These silane coupling agents may be used alone or in combination of two or more.

[0087] The content of the silane coupling agent can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire component, the target performance, etc. For example, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 6 parts by mass or more, and even more preferably 8 parts by mass or more, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, relative to 100 parts by mass of the silica.

[0088] Bioethanol can also be used as a raw material for silane coupling agents. Bioethanol is produced primarily using sugars and / or cellulose as biological resources, and does not effectively utilize other biological resources such as proteins, lipids, and amino acids. Furthermore, sugars compete with food, and excessive use of cellulose leads to deforestation. Therefore, depending on the supply status of various biological resources, the supply status of renewable resources, the supply status of fossil resources, and market demands (e.g., demand for biomass resources as food), it is preferable to use multiple types of monomer components derived from biological resources as the biological resource-derived monomer component, or to use a combination of a monomer component derived from a biological resource, a monomer component derived from a renewable resource, and a monomer component derived from a fossil resource. This allows for the effective use of a wide range of biological resources and renewable resources, such as sugars, proteins, and lipids, without relying on a single type of biological resource, and also allows for environmental considerations depending on the production conditions.

[0089] (Rubber crumb) The rubber composition of the present embodiment preferably contains rubber crumb. In this case, the occurrence of roughness on the rubber surface can be further suppressed. In this specification, rubber crumb is not included in the above-mentioned "rubber component" by definition.

[0090] The rubber crumb may be obtained by crushing used rubber products such as used tires and, if desired, removing reinforcing materials such as steel and fibers, dust, glass, sand, stones, etc., or by preparing a new vulcanized rubber composition for producing the rubber crumb and crushing the resulting product. For example, rubber crumb can be obtained from vulcanized rubber by the method described in "Rubber Chemistry and Technology." The process of crushing vulcanized rubber to obtain rubber crumb may involve mechanical treatment or low-temperature treatment. For example, in mechanical treatment, various crushing devices such as a cracker mill or a granulator can be used to mechanically crush the vulcanized rubber into fine particles. In low-temperature treatment, the finely chopped vulcanized rubber is frozen at a cryogenic temperature and then crushed into fine particles. A magnetic separator or the like can be used to remove steel, and an air separator or the like can be used to remove fibers. The rubber powder may be a commercially available product, such as those from Global Corporation or Nantong Huili Rubber Corporation. From the viewpoint of reducing the environmental impact, it is preferable to use rubber powder obtained by crushing used rubber products such as used tires. The rubber powder may be used alone or in combination of two or more types.

[0091] The composition of the rubber crumb is not particularly limited and depends on the composition of the vulcanized rubber from used rubber products (used tires) or the like that serve as the raw material. In one embodiment, the rubber crumb contains a rubber component, carbon black, silica, etc. The rubber component, carbon black, silica, etc. contained in the rubber crumb may be the same as or different from the rubber component, carbon black, silica, etc. contained in the rubber composition of this embodiment described above.

[0092] The rubber powder preferably has a volume average particle diameter of 1000 μm or less, more preferably 500 μm or less, even more preferably 200 μm or less, and even more preferably 100 μm or less. The smaller the volume average particle diameter of the rubber powder, the better, and there is no particular lower limit. In this specification, the volume average particle diameter is measured with a laser diffraction particle size distribution analyzer, for example, a "CAPA500" manufactured by Horiba, Ltd.

[0093] The rubber powder preferably has a 60-mesh sieve residue of less than 1% by mass, more preferably 0.5% by mass or less, and even more preferably 0.1% by mass or less, with no particular lower limit. The rubber powder preferably has an 80-mesh sieve residue of less than 10% by mass, more preferably 1% by mass or less, and even more preferably 0.5% by mass or less, with no particular lower limit. In this specification, the sieve residue is measured in accordance with ASTM D5644-01.

[0094] The rubber crumb has an acetone extractable content of preferably 12% by mass or less, more preferably 11% by mass or less, and even more preferably 10% by mass or less, and preferably 1% by mass or more, more preferably 2% by mass or more, and even more preferably 3% by mass or more. In this specification, the acetone extractable content in the rubber crumb refers to the acetone extractable content (%) determined by the acetone extraction method in accordance with JIS K6350.

[0095] The content of the rubber crumb is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of the rubber crumb is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 200 parts by mass or less, more preferably 150 parts by mass or less, more preferably 100 parts by mass or less, more preferably 50 parts by mass or less, more preferably 30 parts by mass or less, still more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0096] (Reclaimed Rubber) The rubber composition of this embodiment preferably contains reclaimed rubber (also referred to as "reclaimed rubber"). In this case, the occurrence of rubber surface roughness can be further suppressed. In this specification, reclaimed rubber is, by definition, not included in the above-mentioned "rubber component." Furthermore, reclaimed rubber is typically reclaimed rubber that has been subjected to a devulcanization treatment, and is, by definition, not included in the above-mentioned "rubber crumb."

[0097] Commercially available reclaimed rubber can be used as reclaimed rubber. Reclaimed rubber refers to recycled rubber from used rubber such as automobile tires, tubes, and other rubber products as specified in JIS K6313-2012, as well as rubber with equivalent properties, excluding powdered rubber.

[0098] The type of reclaimed rubber may be selected from tube reclaimed rubber, tire reclaimed rubber, and other reclaimed rubber, or a combination of multiple types may be used. Among these, tire reclaimed rubber is preferred. The method for producing reclaimed rubber is not particularly limited, and known methods such as the oil pan method and the reclamation method may be used.

[0099] The content of the reclaimed rubber is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the tire is applied, the tire components, the target performance, etc. For example, the content of the reclaimed rubber 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 100 parts by mass or less, more preferably 75 parts by mass or less, more preferably 50 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0100] (Resin) The rubber composition of the present embodiment may contain a resin. Examples of the resin include terpene-based resins, rosin-based resins, C ５ based resin, C ５ -C ９ based resin, C ９Examples of suitable resins include cyclopentadiene-based resins, aromatic resins, coumarone resins, indene resins, coumarone-indene-based resins, olefin-based resins, polyurethane resins, and acrylic resins. These resins may be used alone or in combination of two or more. Among these resins, terpene-based resins, rosin-based resins, and C ５ based resin, C ５ -C ９ based resin, C ９ Preferred are cyclopentadiene-based resins, cyclopentadiene-based resins, and aromatic resins, with terpene-based resins and rosin-based resins being particularly preferred. Terpene-based resins and rosin-based resins are naturally derived, sustainable resins that can further reduce the environmental impact and can further improve tire performance, such as grip performance on various road surface conditions, including dry roads, wet roads, snow-covered roads, and frozen roads. ５ based resin, C ９ based resin, C ５ -C ９ The cyclopentadiene-based resin and the cyclopentadiene-based resin can improve abrasion resistance and fuel economy in a balanced manner, while the aromatic resin can improve grip performance, abrasion resistance, and rubber strength in a balanced manner.

[0101] The resin may be hydrogenated, i.e., may be a hydrogenated resin (hydrogenated resin). Furthermore, the resin may be modified to introduce a functional group that interacts with fillers such as carbon black and silica. Examples of such functional groups include amino groups, amide groups, isocyanate groups, imino groups, imidazole groups, urea groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, ether groups, carbonyl groups, oxycarbonyl groups, silyl groups, alkoxysilyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, and thiocarbonyl groups.

[0102] The terpene resin is a solid resin obtained by blending turpentine, which is obtained simultaneously with the extraction of rosin from pine trees, or a polymerization component separated therefrom, and polymerizing the blend using a Friedel-Crafts catalyst. Examples of such resins include β-pinene resin and α-pinene resin. Terpene resins also include terpene-aromatic compound resins, representative examples of which include terpene-phenol resin and styrene-terpene resin. Terpene-phenol resins can be obtained by reacting terpenes with various phenols using a Friedel-Crafts catalyst, or by further condensing the terpene with formalin. The styrene-terpene resin can be obtained by reacting styrene with terpenes using a Friedel-Crafts catalyst. The terpenes used as raw materials are not particularly limited; monoterpene hydrocarbons such as α-pinene and limonene are preferred, with those containing α-pinene being more preferred, and α-pinene being particularly preferred.

[0103] Examples of the rosin-based resin include natural resin rosins such as gum rosin, tall oil rosin, and wood rosin contained in raw pine resin and tall oil, and examples of modified rosins, rosin derivatives, and modified rosin derivatives include polymerized rosin and partially hydrogenated rosin thereof; glycerin ester rosin and partially hydrogenated rosin thereof and fully hydrogenated rosin thereof; pentaerythritol ester rosin and partially hydrogenated rosin thereof and polymerized rosin; and the like.

[0104] Said C ５ As a resin based on C, there is C obtained by thermal decomposition of naphtha in the petrochemical industry. ５ and aliphatic petroleum resins obtained by (co)polymerizing the distillate. ５ The fraction usually contains olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene, 1,2-pentadiene, 1,3-pentadiene, and 3-methyl-1,2-butadiene.

[0105] Said C ５ -C ９ The C-based resin is ５ -C９ It refers to synthetic petroleum resin, ５ -C ９ Examples of the resin include petroleum-derived C ５ -C １１ The fraction was treated with AlCl ３ , B.F. ３ More specifically, copolymers containing styrene, vinyltoluene, α-methylstyrene, indene, etc. as the main component may be mentioned. ５ -C ９ As the resin, ９ Resins containing less of the above components are preferred from the viewpoint of compatibility with the rubber component. ９ "Low amount of the above components" means that the C ９ This means that the content of the above components is less than 50% by mass, preferably 40% by mass or less.

[0106] Said C ９ The C-based resin is ９ This refers to synthetic petroleum resins, such as AlCl ３ or BF ３ Using a Friedel-Crafts type catalyst such as C ９ It refers to a solid polymer obtained by polymerizing the fraction. ９ Examples of the resin include copolymers containing indene, α-methylstyrene, vinyltoluene, etc. as main components.

[0107] The cyclopentadiene-based resin refers to a resin containing a unit derived from a cyclopentadiene-based monomer as a monomer unit. Examples of the cyclopentadiene-based resin include a homopolymer of a cyclopentadiene-based monomer, a copolymer of two or more cyclopentadiene-based monomers, and a copolymer of a cyclopentadiene-based monomer and another monomer. Here, examples of the cyclopentadiene-based monomer include cyclopentadiene, dicyclopentadiene, and tricyclopentadiene. Among these, dicyclopentadiene is preferred. That is, the cyclopentadiene-based resin is preferably a dicyclopentadiene-based resin. The dicyclopentadiene-based resin is, for example, a copolymer of AlCl ３ or BF ３The term "dicyclopentadiene-based resin" refers to a resin obtained by polymerizing dicyclopentadiene using a Friedel-Crafts catalyst such as Benzene, etc. Dicyclopentadiene-based resins include homopolymers of dicyclopentadiene, copolymers of dicyclopentadiene and aromatic monomers, copolymers of dicyclopentadiene and C ９ Examples include copolymers with distillates (vinyl toluene, indene, etc.).

[0108] The aromatic resin refers to a resin containing units derived from aromatic monomers as monomer units. Examples of the aromatic resin include homopolymers of aromatic monomers, copolymers of two or more aromatic monomers, and copolymers of aromatic monomers with other monomers. Examples of the aromatic monomer include styrene-based monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, and p-phenylstyrene; phenol-based monomers such as phenol, alkylphenol, and alkoxyphenol; and naphthol-based monomers such as naphthol, alkylnaphthol, and alkoxynaphthol.

[0109] The softening point of the resin is preferably 30 ° C. or higher, more preferably 60 ° C. or higher, more preferably 80 ° C. or higher, more preferably higher than 110 ° C., more preferably 116 ° C. or higher, more preferably 120 ° C. or higher, more preferably 123 ° C. or higher, and even more preferably 127 ° C. or higher. From the viewpoint of processability, the softening point of the resin is preferably 160 ° C. or lower, more preferably 150 ° C. or lower, more preferably 145 ° C. or lower, more preferably 141 ° C. or lower, and even more preferably 136 ° C. or lower. In this specification, the softening point of the resin is the temperature at which the ball drops when the softening point as defined in JIS K 6220-1:2015 (ISO 28641:2010) is measured using a ring and ball softening point tester.

[0110] Commercially available resins can be used, and examples of commercially available resins include products from ENEOS Corporation, Arakawa Chemical Industries, Ltd., ExxonMobil Corporation, Kraton Corporation, Yasuhara Chemical Co., Ltd., Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton Polymers, Inc., Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., and Taoka Chemical Co., Ltd.

[0111] The content of the resin is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the resin is preferably in the range of 5 to 100 parts by mass, and more preferably in the range of 10 to 60 parts by mass, per 100 parts by mass of the rubber component.

[0112] (Liquid Softener) The rubber composition 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 preferred. These liquid softeners may be used alone or in combination of two or more.

[0113] The oil is a general term for extender oils contained in rubber components and liquid oils added as compounding agents to rubber compositions. Examples include vegetable oils, process oils, oils obtained by recycling vegetable oils or process oils, and mixtures thereof. From the perspective of reducing environmental impact, vegetable oils and recycled oils are preferred. Examples of vegetable oils include palm oil, castor oil, cottonseed oil, soybean oil, linseed oil, rapeseed oil, coconut oil, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, and coconut oil. Examples of process oils include paraffin-based process oils, aromatic process oils, and naphthenic process oils. As the oil, commercially available products can be used, and examples of commercially available oils that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., and Nisshin Oillio Group Co., Ltd. These oils may be used alone or in combination of two or more.

[0114] The liquid polymer is preferably a liquid diene-based polymer. Examples of the liquid diene-based polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid polybutadiene (liquid BR), liquid polyisoprene (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer), liquid polyfarnesene, and liquid farnesene-butadiene copolymer. These liquid polymers may be hydrogenated, or their terminals or main chains may be modified with functional groups (polar groups). These liquid polymers may be used alone or in combination of two or more.

[0115] The content of the liquid softener is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which it is applied, the tire components, the target performance, etc. For example, the content of the liquid softener is preferably 5 parts by mass or more, and more preferably 10 parts by mass or more, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, still more preferably 50 parts by mass or less, and still more preferably 30 parts by mass or less, per 100 parts by mass of the rubber component.

[0116] (Antiaging Agent) The rubber composition of the present embodiment may contain an antioxidant. Examples of the antioxidant include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, 2,2,4-trimethyl-1,2-dihydroquinoline polymer (TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline (AW), and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. Commercially available products can be used as the antioxidant, and examples of commercially available antioxidants that can be used include products from Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., Seiko Chemical Co., Ltd., Flexis Co., Ltd., etc. These antioxidants may be used alone or in combination of two or more.

[0117] The content of the antioxidant is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the antioxidant is applied, the tire components, the target performance, etc. For example, the content of the antioxidant is preferably 1 part by mass or more, more preferably 1.5 parts by mass or more, and even more preferably 2 parts by mass or more, and is preferably 12 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component.

[0118] (Wax) The rubber composition of this embodiment may contain a wax. Examples of the wax include natural waxes such as plant waxes and animal waxes; petroleum waxes such as paraffin wax and microcrystalline wax; and synthetic waxes such as ethylene polymers and propylene polymers. Commercially available waxes can be used, and examples of commercially available waxes include products from Seiko Chemical Co., Ltd., Nippon Seiro Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and the like. These waxes may be used alone or in combination of two or more.

[0119] The content of the wax is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the wax is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0120] (Stearic Acid) The rubber composition of the present embodiment may contain stearic acid. Commercially available stearic acid products are available, including those from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Chiba Fatty Acid Co., Ltd., and the like. These commercially available stearic acid products may be used alone or in combination of two or more.

[0121] The content of stearic acid is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of stearic acid is preferably 1 part by mass or more, 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.

[0122] (Zinc Oxide) The rubber composition of the present embodiment may contain zinc oxide (zinc white). The zinc oxide is preferably zinc oxide obtained by recycling. Commercially available zinc oxide can be used, and examples of commercially available zinc oxide include products from Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., Mitsui Mining & Smelting Co., Ltd., and Toho Zinc Co., Ltd. These commercially available zinc oxide products may be used alone or in combination of two or more. The zinc used for the zinc oxide may be not only zinc ores, but also zinc obtained from recycled zinc or zinc dross.

[0123] The content of the zinc oxide is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the zinc oxide is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component.

[0124] (Sulfur) The rubber composition of this embodiment preferably contains sulfur. The sulfur may be derived from fossil resources, recycled resources, or sulfur obtained by processing biological resource-derived materials. From the perspective of reducing environmental impact, it is particularly preferable to use sulfur obtained from waste derived from biological resources. Examples of methods for obtaining sulfur from waste derived from biological resources include the method described in the aforementioned Japanese Patent Application No. 2022-140390. Furthermore, the sulfur may be powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, or the like, which are commonly used as crosslinking agents in the rubber industry. Commercially available sulfur products can be used, including those from Tsurumi Chemical Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., and Flexis Corporation. These sulfurs may be used alone or in combination of two or more.

[0125] 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 tire components, the target performance, etc. For example, the sulfur content is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and even more preferably 0.8 parts by mass or more, and is preferably 8 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0126] (Vulcanization Accelerator) The rubber composition of this embodiment preferably contains a vulcanization accelerator. The vulcanization accelerator may be derived from fossil resources, renewable resources, or biological resources, but is preferably derived from biological resources from the viewpoint of reducing the environmental impact. Vulcanization accelerators derived from biological resources can be obtained, for example, by the method disclosed in JP 2005-139239 A. Examples of the vulcanization accelerator include sulfenamide vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolsulfenamide, and N,N'-diisopropyl-2-benzothiazolsulfenamide; 1,3-diphenylguanidine (DPG), 1,3-dibenzothiazolylsulfenamide, and the like. Examples of suitable vulcanization accelerators include guanidine-based vulcanization accelerators such as o-tolylguanidine and o-tolylbiguanidine; thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole (M) and di-2-benzothiazolyl disulfide (MBTS, DM); and thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrastearylthiuram disulfide, tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N). Commercially available vulcanization accelerators can be used, including those manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Sumitomo Chemical Co., Ltd., and the like. These vulcanization accelerators may be used alone or in combination of two or more.

[0127] The content of the vulcanization accelerator is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the vulcanization accelerator is applied, the tire components, the target performance, etc. For example, the content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, and is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and even more preferably 5.5 parts by mass or less, per 100 parts by mass of the rubber component.

[0128] (Cellulose Nanofiber) The rubber composition of this embodiment may contain cellulose nanofiber (CNF). The cellulose nanofiber can be blended into the rubber composition to reinforce the rubber composition. The cellulose nanofiber is preferably a modified cellulose nanofiber, which is a fine fiber made from modified cellulose. The fiber diameter of the cellulose nanofiber is not particularly limited, but is approximately 3 to 500 nm. The average fiber diameter and average fiber length of the cellulose nanofiber can be obtained by averaging the fiber diameters and fiber lengths obtained from the observation of each fiber using a scanning electron microscope (SEM), an atomic force microscope (AFM), or a transmission electron microscope (TEM). The cellulose nanofiber can be obtained by defibrating cellulose. The average fiber length and average fiber diameter of the fine fibers can be adjusted by oxidation treatment or defibration treatment.

[0129] 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.

[0130] The content of the cellulose nanofibers is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the cellulose nanofibers is preferably in the range of 1 to 100 parts by mass, more preferably in the range of 5 to 70 parts by mass, and even more preferably in the range of 10 to 40 parts by mass, per 100 parts by mass of the rubber component.

[0131] (Porous Cellulose Particles) The rubber composition of this embodiment may contain porous cellulose particles. The porous cellulose particles are preferably cellulose particles having a porous structure with a porosity of 75 to 95%, and by incorporating them into the rubber composition, performance on ice can be improved. When the porosity of the porous cellulose particles is 75% or more, the effect of improving performance on ice is excellent, and when the porosity is 95% or less, the strength of the particles can be increased. The porosity is more preferably 80 to 90%. The porosity of the porous cellulose particles can be calculated by measuring the volume of a certain mass of sample (i.e., porous cellulose particles) with a measuring cylinder, determining the bulk specific gravity, and using the following formula: Porosity (%) = {1 - [bulk specific gravity of sample (g / mL)] / [true specific gravity of sample (g / mL)]} × 100, where the true specific gravity of cellulose is 1.5.

[0132] The particle size of the porous cellulose particles is not particularly limited, but from the viewpoint of abrasion resistance, an average particle size of 1000 μm or less is preferred. The lower limit of the average particle size is not particularly limited, but it is preferably 5 μm or more. The average particle size is more preferably 100 to 800 μm, and even more preferably 200 to 800 μm. The porous cellulose particles are preferably spherical particles with a major axis / minor axis ratio of 1 to 2. The use of particles with such a spherical structure improves dispersibility in the rubber composition, contributing to improved performance on ice and the maintenance of abrasion resistance. The major axis / minor axis ratio is more preferably 1.0 to 1.5. The average particle size and major axis / minor axis ratio of the porous cellulose particles can be determined as follows. That is, porous cellulose particles are observed under a microscope to obtain an image, and this image is used to measure the long and short diameters of the particles (if the long and short diameters are the same, the length in a certain axis direction and the length in an axis direction perpendicular to it) for 100 particles, and the average particle size is obtained by calculating the average value, and the long diameter / short diameter ratio is obtained by averaging the values ​​obtained by dividing the long diameter by the short diameter.

[0133] The porous cellulose particles are commercially available from Rengo Co., Ltd. under the name "Viscopal" and are also described in JP-A Nos. 2001-323095 and 2004-115284, and can be suitably used.

[0134] The content of the porous cellulose particles is not particularly limited and can be appropriately adjusted depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the porous cellulose particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by mass, and even more preferably in the range of 3 to 15 parts by mass, per 100 parts by mass of the rubber component.

[0135] (Solid Particles) The rubber composition of this embodiment may contain solid particles. Blending the solid particles into the rubber composition can improve performance on ice. The solid particles preferably have an average particle diameter of 1 μm or more, preferably 1000 μm or less, and more preferably 300 μm or less. Examples of the solid particles include plant-derived powders obtained from plants, such as rice husks, walnut flour, and walnut shells; animal-derived powders obtained from animals, such as eggshells (eggshell powder) and bone powder; powders derived from natural minerals, such as whitebait; inorganic particles, such as graphite and zinc oxide whiskers; water-soluble metal salt particles, such as magnesium sulfate and metal salts of lignosulfonic acid; and non-metallic fibers, such as glass fibers. Of these, rice husks, walnut shells, eggshells, and whitebait are preferred.

[0136] The content of the solid fine particles is not particularly limited and can be adjusted appropriately depending on, for example, the tire category to which the rubber composition is applied, the tire components, the target performance, etc. For example, the content of the solid fine particles is preferably in the range of 0.3 to 20 parts by mass, more preferably in the range of 1 to 15 parts by mass, and even more preferably in the range of 3 to 15 parts by mass, per 100 parts by mass of the rubber component.

[0137] (Others) In addition to the above-mentioned components, the rubber composition 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 adjusted appropriately depending on, for example, the tire category to which they are applied, the tire components, the target performance, etc., and is preferably, for example, in the range of 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0138] (Method for Producing Rubber Composition) The method for producing the rubber composition of the present embodiment is not particularly limited, but the rubber composition can be produced, for example, by blending the rubber component with recycled carbon black and various components appropriately selected as necessary, and kneading, heating, extruding, etc. The obtained rubber composition can be vulcanized to produce a vulcanized rubber.

[0139] The conditions for the kneading are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of kneading device, etc. can be appropriately selected depending on the purpose. Examples of the kneading device include a Banbury mixer, an intermix, a kneader, a roll, etc. that are usually used for kneading rubber compositions.

[0140] The conditions for the heat-in are not particularly limited, and various conditions such as the heat-in temperature, heat-in time, and heat-in device can be appropriately selected depending on the purpose. Examples of the heat-in device include a heat-in roll mill typically used for heat-in of rubber compositions.

[0141] The extrusion conditions are not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion device, and extrusion temperature can be appropriately selected depending on the purpose. Examples of the extrusion device include an extruder typically used for extruding rubber compositions. The extrusion temperature can be appropriately determined.

[0142] The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected depending on the purpose. Examples of apparatuses for vulcanization include molding vulcanizers using molds used for vulcanizing rubber compositions. The vulcanization temperature is, for example, about 100 to 190°C.

[0143] (Uses) The rubber composition of the present embodiment can be applied to various constituent members of a tire, for example, tread (cap tread, base tread, undertread), cushion rubber, shoulder, sidewall, clinch, bead filler, carcass coating rubber, insulation, chafer, inner liner, etc. It can also be used for side reinforcing layers of run-flat tires, etc. In addition to tires, the rubber composition of the present embodiment can also be applied to rubber crawlers, seismic isolation rubber, hoses, etc.

[0144] <Tire> The tire of the present invention is characterized by using the rubber composition of the present embodiment described above. In other words, the tire of the present embodiment is characterized by including the rubber composition of the present embodiment. By using the rubber composition of the present embodiment, the tire obtained can suppress rubber surface roughening and contribute to improving sustainability.

[0145] A tire according to another embodiment of the present invention includes a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass formed of at least one carcass ply extending in a toroidal shape across the pair of bead portions, and further includes side rubbers on the outer sides of the carcass in the tire width direction in the sidewall portions, the side rubbers using the rubber composition according to the present embodiment. In this case, surface roughness of the tire side rubbers is suppressed.

[0146] A tire according to one embodiment of the present invention includes a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass consisting of at least one carcass ply extending toroidally between the pair of bead portions. The tire further includes a gum chafer disposed in at least a portion of the contact portion between the bead portion and the rim, and the rubber composition according to this embodiment is used for the gum chafer. In this case, the rubber surface roughening of the gum chafer of the tire is suppressed. The gum chafer is typically a rubber component disposed to accommodate high contact pressure with the applicable rim.

[0147] The tire of this embodiment can be manufactured by a conventional method using the above-mentioned rubber composition. For example, depending on the type of tire to be applied, the tire of this embodiment may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, or by molding a semi-vulcanized rubber that has been subjected to a pre-vulcanization process or the like and then further vulcanizing it. The tire of this embodiment is preferably a pneumatic tire, and the gas to be filled into the pneumatic tire may be normal air or air with an adjusted oxygen partial pressure, or an inert gas such as nitrogen, argon, or helium.

[0148] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples and can be modified as appropriate within the scope of the present invention.

[0149] Two types of rubber compositions were prepared with the formulations shown in Table 1. It was confirmed that the recycled carbon black constituted multiple agglomerates in the rubber composition of Example 1. For each rubber composition, the total mass ratio of components derived from biological resources (biomass resources) and components derived from recycled resources (recycled resources) was calculated, and the sustainable material ratio was calculated as an integer. The results are shown in Table 1.

[0150] Furthermore, the volumetric particle size distribution of the carbon black (virgin carbon black, recycled carbon black) blended in each example was measured using a laser diffraction particle size analyzer (Shimadzu Corporation). Next, data with diameters of less than 1.0 μm were excluded from the particle size distribution and normalized to obtain "particle size distribution A for carbon black with diameters of 1.0 μm or greater." The proportion of particles with diameters of 5.0 μm or greater was then determined from the particle size distribution A. The results are shown in Table 1.

[0151] Furthermore, for each rubber composition, three 2 mm unvulcanized rubber sheets were prepared. These three unvulcanized rubber sheets were stacked, and holes of 1 mm and 2 mm depth were drilled only in the topmost rubber sheet. The three stacked unvulcanized rubber sheets were then vulcanized. After vulcanization, the degree of blockage of the holes was visually confirmed. If the holes were blocked, it was evaluated as A, and if the holes were not blocked, it was evaluated as B. If the holes were blocked, it was determined that the occurrence of roughness on the rubber surface could be suppressed. The results are shown in Table 1.

[0152]

[0153] Butadiene rubber: UBE Elastomers, trade name "BR150L" Virgin carbon black: Asahi Carbon, N550 Recycled carbon black: Enrestec, trade name "PB365", ash content = 17 mass% Antioxidant 1: Ouchi Shinko Chemical Industry, trade name "Nocrac 6C" Antioxidant 2: Ouchi Shinko Chemical Industry, trade name "Nocrac 224" Oil: ENEOS, trade name "A / Omix" Fatty acid: Miyoshi Oil & Fats, trade name "MXST" Other chemicals: total of sulfur, vulcanization accelerator, and resin (these compositions are constant)

[0154] According to the present invention, it is possible to provide a rubber composition that can suppress the occurrence of rubber surface roughening during mold vulcanization and that can contribute to improving sustainability. Also, according to the present invention, it is possible to provide a tire that suppresses rubber surface roughening and that can contribute to improving sustainability.

Claims

1. A rubber composition containing a rubber component and carbon black including recycled carbon black, wherein the recycled carbon black forms a plurality of agglomerates in the rubber composition, and in particle size distribution A targeting carbon black with a diameter of 1.0 μm or more among the carbon black, the proportion of carbon black with a diameter of 5.0 μm or more is 1% or more.

2. The rubber composition according to claim 1, wherein the recycled carbon black is obtained by pyrolysis of a vulcanized rubber product containing carbon black.

3. A rubber composition according to claim 1 or 2, wherein the recycled carbon black has an ash content of 20 mass% or less.

4. The rubber composition according to claim 1 or 2, wherein in said particle size distribution A, the proportion of particles having a diameter of 5.0 μm or more is 10% or more.

5. The rubber composition according to claim 1 or 2, further comprising at least one of rubber powder and reclaimed rubber.

6. A tire characterized by using the rubber composition according to claim 1 or 2.

7. A tire according to claim 6, comprising a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass consisting of at least one carcass ply extending in a toroidal shape spanning the pair of bead portions, said tire further comprising a side rubber on the outer side of said carcass in the tire width direction in said sidewall portions, said rubber composition being used for said side rubber.

8. A tire comprising a pair of bead portions, a pair of sidewall portions, a tread portion connected to both sidewall portions, and a carcass consisting of at least one carcass ply extending in a toroidal shape between the pair of bead portions, said tire further comprising a gum chafer disposed in at least a portion of the contact portion between the bead portion and the rim, said rubber composition being used for said gum chafer, as described in claim 6.

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