tire

Abstract

We provide tires with excellent fuel efficiency. [Solution] The present invention relates to a tire having a sidewall made of a rubber composition comprising a rubber component, microcellulose, and a coupling agent, wherein the average fiber diameter of the microcellulose is 20 μm or more, and the ratio ((A × C) / T) of the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent per 100 parts by mass of the rubber component to the thickness T (mm) of the sidewall is greater than 1.5.

Description

[Technical Field]

[0001] This invention relates to tires. [Background technology]

[0002] Tires are required to have various performance characteristics, including low fuel consumption (see Patent Document 1). [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2019-65240 [Overview of the project] [Problems that the invention aims to solve]

[0004] The present invention aims to solve the aforementioned problems and provide a tire with excellent fuel efficiency. [Means for solving the problem]

[0005] The present invention relates to a tire having a sidewall made of a rubber composition comprising a rubber component, microcellulose, and a coupling agent, The average fiber diameter of the microcellulose is 20 μm or more. The present invention relates to a tire characterized in that the ratio ((A × C) / T) of the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent per 100 parts by mass of the rubber component, to the thickness T (mm) of the sidewall, exceeds 1.5. [Effects of the Invention]

[0006] The present invention relates to a tire having a sidewall composed of a rubber composition containing a rubber component, microcellulose, and a coupling agent, wherein the average fiber diameter of the microcellulose is 20 μm or more, and the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent with respect to 100 parts by mass of the rubber component, and the ratio ((A × C) / T) of the thickness T (mm) of the sidewall exceeds 1.5. Therefore, a tire excellent in low fuel consumption can be provided.

Brief Description of the Drawings

[0007] [Figure 1] It is a cross-sectional view showing a part of a pneumatic tire. [Figure 2] It is an enlarged cross-sectional view showing the vicinity of the tread of the tire of FIG. 1.

Embodiments for Carrying Out the Invention

[0008] The above tire includes a sidewall composed of a rubber composition containing a rubber component, microcellulose, and a coupling agent, the average fiber diameter of the microcellulose is 20 μm or more, and the ratio ((A × C) / T) of the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent with respect to 100 parts by mass of the rubber component, and the thickness T (mm) of the sidewall exceeds 1.5.

[0009] The reason why the above-described operational effects are obtained by the above tire is not necessarily clear, but it is presumed as follows. Since nanosized cellulose materials (nanocellulose) tend to aggregate in the rubber matrix, there was room for improvement in terms of dispersibility. On the other hand, microcellulose with an average fiber diameter of 20 μm or more is less likely to aggregate compared to nanocellulose, and is highly dispersed by reaction with a coupling agent, and the interface with the rubber is reinforced. When applying a rubber composition containing microcellulose to the sidewall of a tire, it is necessary to consider the impact on fuel efficiency. However, microcellulose is advantageous for fuel efficiency because of its high dispersibility and interfacial reinforcement properties with rubber. Furthermore, by adjusting the average fiber diameter of the microcellulose and the content of the coupling agent according to the thickness of the sidewall, it is believed that the dispersibility of the microcellulose in the sidewall rubber and the interfacial reinforcement with the rubber can be improved, thereby improving fuel efficiency. Based on the above, it is presumed that a tire containing rubber components, microcellulose with an average fiber diameter of 20 μm or more, and a coupling agent, and satisfying the above (A × C) / T > 1.5, can be made to have excellent fuel efficiency.

[0010] Thus, the above-mentioned tire, having a sidewall composed of a rubber composition containing rubber components, microcellulose with an average fiber diameter of 20 μm or more, and a coupling agent, solves the problem (objective) of improving fuel efficiency by satisfying the relationship "(A×C) / T>1.5". In other words, the parameter "(A×C) / T>1.5" does not define the problem (objective); the problem of this application is to improve fuel efficiency, and the configuration that satisfies this parameter is a means of solving that problem.

[0011] The above tire has a sidewall made of the above rubber composition.

[0012] In this specification, the sidewall is a member arranged on the outside of the case from the shoulder portion to the bead portion, and specifically refers to the member shown in Figure 1 of Japanese Patent Publication No. 2005-280612, Figure 1 of Japanese Patent Publication No. 2000-185529, etc.

[0013] Regarding the above-mentioned tire, first, we will explain the rubber composition that makes up the sidewall.

[0014] The above rubber composition contains rubber components. In this specification, the above-mentioned rubber component is a component that contributes to crosslinking, and generally, a polymer with a weight-average molecular weight (Mw) of 10,000 or more that is not extracted by acetone is considered a rubber component. The above-mentioned rubber component is in a solid state at 25°C.

[0015] The weight-average molecular weight of the above rubber component is preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, particularly preferably 270,000 or more, and also preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. When it is within the above range, the effect tends to be better obtained.

[0016] In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) can be determined by converting the measured values ​​obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalents.

[0017] The above rubber component may be either unmodified rubber or modified rubber. Examples of modified rubbers include rubbers having functional groups that interact with fillers such as silica. For example, end-modified rubber (end-modified rubber having the functional group at the end) is obtained by modifying at least one end of the rubber with a compound (modifier) ​​having the functional group; main-chain modified rubber having the functional group in the main chain; main-chain end-modified rubber having the functional group in both the main chain and the end (for example, main-chain end-modified rubber having the functional group in the main chain and at least one end modified with the modifier); and end-modified rubber that has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule, and into which hydroxyl groups or epoxy groups have been introduced.

[0018] Examples of the above functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl 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, and the like. These functional groups may have substituents. Among these, amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), alkoxy groups (preferably alkoxy groups having C1-C6), and alkoxysilyl groups (preferably alkoxysilyl groups having C1-C6) are preferred.

[0019] Examples of the above rubber components include isoprene rubber, butadiene rubber (BR), styrene-butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR). Butyl rubber and fluororubber are also examples. These may be used individually or in combination of two or more types. In particular, from the viewpoint of obtaining better effects, it is preferable to include at least one of isoprene rubber, butadiene rubber, and styrene-butadiene rubber; more preferably to include at least one of isoprene rubber and butadiene rubber; even more preferably to include isoprene rubber and butadiene rubber; and even more preferably to include isoprene rubber, butadiene rubber, and styrene-butadiene rubber.

[0020] The above rubber components may be modified or hydrogenated, and stretched rubber, which has been stretched with oil, resin, liquid rubber components, etc., may also be used.

[0021] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, common types used in the rubber industry can be used, such as SIR20, RSS#3, and TSR20. For IR, there are no particular limitations; common types used in the rubber industry can be used, such as IR2200. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity natural rubber. Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used individually or in combination of two or more types.

[0022] BR is not particularly limited, and for example, high-cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, and BR synthesized using a rare-earth catalyst (rare-earth BR) can be used. These may be used individually or in combination of two or more. In particular, it is preferable that the BR contains high-cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more, and even more preferably 97% by mass or more. The cis content can be measured by infrared absorption spectroscopy.

[0023] The cis amount of BR refers to the cis amount of a single type of BR, and the average cis amount if there are multiple types of BR. The average cis content of BR can be calculated using the formula {Σ(content of each BR × cis content of each BR)} / total BR content. For example, if 20% of BR has a cis content of 90% and 10% has a cis content of 40% out of 100% of rubber components, the average cis content of BR is 73.3% (=(20 × 90 + 10 × 40) / (20 + 10)).

[0024] Both unmodified and modified BR can be used. Modified BR includes BR with functional groups similar to those introduced in modified rubber. Hydrogenated butadiene polymers (hydrogenated BR) can also be used.

[0025] For example, products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation can be used as BRs.

[0026] The SBR is not particularly limited; for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc., can be used. These may be used individually or in combination of two or more types.

[0027] The styrene content of SBR is preferably 5% by mass or more, more preferably 7% by mass or more, and even more preferably 9% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. When the content is within the above range, a better effect tends to be obtained. In this specification, the amount of styrene is a value calculated by methods such as NMR measurement, pyrolysis gas chromatography, and infrared absorption spectroscopy.

[0028] The styrene content of SBR refers to the styrene content of a single type of SBR if it is one type, and to the average styrene content if it is one of multiple types. The average styrene content of SBR can be calculated using the formula {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBR. For example, if 85% of the rubber component is SBR with 40% styrene content and 5% is SBR with 25% styrene content, the average styrene content of the SBR is 39.2% (=(85 × 40 + 5 × 25) / (85 + 5)).

[0029] The vinyl content of SBR is preferably 3% by mass or more, more preferably 10% by mass or more, and even more preferably 17% by mass or more. When the vinyl content is within the above range, preferably 60% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less, the effect tends to be better. In this specification, the vinyl content (amount of 1,2-bonded butadiene units) is a value calculated by methods such as NMR measurement, pyrolysis gas chromatography, and infrared absorption spectroscopy.

[0030] The vinyl content of SBR (amount of 1,2-bonded butadiene units) is the ratio of vinyl bonds to the total mass of the butadiene portion in the SBR, with the total mass being 100 (unit: mass%). The formula is: vinyl content [mass%] + cis content [mass%] + trans content [mass%] = 100 [mass%]. If there is only one type of SBR, it refers to the vinyl content of that SBR; if there are multiple types, it refers to the average vinyl content. The average vinyl content of SBR can be calculated using the formula: Σ{Content of each SBR × (100 [mass%] - Styrene content of each SBR [mass%]) × Vinyl content of each SBR [mass%]} / Σ{Content of each SBR × (100 [mass%] - Styrene content of each SBR [mass%])}. For example, if 100 parts by mass of rubber component, 75 parts by mass of SBR contain 40% by mass of styrene and 30% by mass of vinyl, and 25% by mass of vinyl, If 15 parts by mass of SBR have a 20% vinyl content and the remaining 10 parts by mass are other than SBR, the average vinyl content of the SBR is 28% by mass (= {75 × (100 [mass%] - 40 [mass%]) × 30 [mass%] + 15 × (100 [mass%] - 25 [mass%]) × 20 [mass%])} / {75 × (100 [mass%] - 40 [mass%]) + 15 × (100 [mass%] - 25 [mass%])}.

[0031] Both unmodified and modified SBR can be used. Modified SBR includes SBR with functional groups similar to those introduced in modified rubber. Hydrogenated styrene-butadiene copolymer (hydrogenated SBR) can also be used as SBR.

[0032] In the case of hydrogenated SBR, there are no particular limitations on the method of hydrogenation or reaction conditions; hydrogenation can be carried out using known methods and conditions. Typically, this is done at 20-150°C, under a hydrogen pressure of 0.1-10 MPa, and in the presence of a hydrogenation catalyst. Other manufacturing methods and conditions are also not particularly limited; for example, the contents described in International Publication No. 2016 / 039005 can be applied. Furthermore, hydrogenated SBR has the same structure as a copolymer of ethylene, butadiene, and styrene as a result of hydrogen being added to the butadiene portion of SBR. Therefore, in this specification, hydrogenated SBR includes not only hydrogenated butadiene-styrene copolymers (SBR) but also copolymers of ethylene, butadiene, and styrene.

[0033] The hydrogenation rate of hydrogenated SBR is preferably 65 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, with the total butadiene units before hydrogenation being 100 mol%, and also preferably 95 mol% or less, more preferably 92 mol% or less, and even more preferably 90 mol% or less. Within the above range, better effects tend to be obtained. The hydrogenation rate is calculated using methods such as NMR measurement, pyrolysis gas chromatography, and infrared absorption spectroscopy.

[0034] The glass transition temperature (Tg) of hydrogenated SBR is preferably -90°C or higher, more preferably -80°C or higher, even more preferably -75°C or higher, and also preferably -15°C or lower, more preferably -30°C or lower, even more preferably -40°C or lower, and even more preferably -60°C or lower. A better effect tends to be obtained when the temperature is within the above range. The glass transition temperature is determined according to ISO 22768:2006 by recording the DSC curve while increasing the temperature within a specified range, finding the peak top (inflection point) of the DSC differential curve, and defining the temperature of this peak top as the glass transition temperature.

[0035] The weight-average molecular weight (Mw) of hydrogenated SBR is preferably 200,000 or more, more preferably 300,000 or more, even more preferably 350,000 or more, and also preferably 2,000,000 or less, more preferably 1,000,000 or less, even more preferably 700,000 or less, and particularly preferably 480,000 or less. Within this range, better effects tend to be obtained. The weight-average molecular weight of hydrogenated SBR can be controlled within the above numerical range by adjusting various polymerization conditions such as the amount of monomer added, polymerization time, polymerization temperature, and polymerization pressure during the polymerization process.

[0036] For example, SBR manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Co., Ltd. can be used. Alternatively, SBR synthesized by known methods can also be used.

[0037] The raw materials (monomers) for synthetic rubbers such as IR, SBR, and BR may be derived from underground resources such as petroleum and natural gas, or they may be recycled from rubber products such as tires or non-rubber products such as polystyrene. The monomers obtained by recycling (recycled monomers) are not particularly limited, but examples include recycled polyisoprene, recycled butadiene, and recycled aromatic vinyl. Examples of butadiene include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl include styrene, but are not particularly limited. In particular, it is preferable to use recycled polyisoprene (recycled isoprene), recycled butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0038] The method for producing recycled monomer is not particularly limited, and for example, it can be synthesized from recycled naphtha obtained by decomposing rubber products such as tires. Furthermore, the method for producing recycled naphtha is not particularly limited, and for example, rubber products such as tires may be decomposed under high temperature and pressure, decomposed by microwaves, or extracted after mechanical grinding.

[0039] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. In this specification, biomass refers to substances derived from natural resources such as plants. Biomass is not particularly limited, but examples include agricultural, forestry, and fishery products, sugars, wood chips, plant residues after obtaining useful components, plant-derived ethanol, and biomass naphtha.

[0040] The biomass-derived monomer (biomass monomer) is not particularly limited and includes biomass-derived butadiene and biomass-derived aromatic vinyl. The butadiene is 1,2-butadiene and 1,3-butadiene. The aromatic vinyl is not particularly limited and includes styrene. Furthermore, the method for producing the biomass monomer is not particularly limited and includes, for example, biological and / or chemical and / or physical conversion of plants and animals. A typical biological conversion is fermentation by microorganisms, while chemical and / or physical conversions include those by catalysts, high heat, high pressure, electromagnetic waves, critical liquids, and combinations thereof.

[0041] The polymer synthesized from biomass monomer components (biomass polymer) is not particularly limited, and examples include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0042] Whether the raw materials for a polymer are biomass-derived can be determined by measuring pMC (percent Modern Carbon) in accordance with ASTMD6866-10.

[0043] pMC stands for Modern Standard Reference Carbon. 14 Sample relative to C concentration14 It is the ratio of C concentration and is a value used as an index indicating the biomass ratio of a compound. The significance of this value is described below.

[0044] In one mole (6.02×10 23 pieces) of carbon atoms, there are approximately 6.02×10 11 pieces, which is about one trillionth of ordinary carbon atoms. 14 14C exists. 14 14C is called a radioactive isotope, and its half-life is 5730 years and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, after carbon dioxide in the atmosphere and the like are taken up and fixed by plants and the like, in fossil fuels such as coal, oil, and natural gas where more than 226,000 years are considered to have passed, all of the 14 14C elements have decayed. Therefore, at present in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain 14 14C elements at all. Therefore, chemical substances produced from these fossil fuels also do not contain 14 14C elements at all.

[0045] On the other hand, 14 14C is constantly generated by nuclear reactions of cosmic rays in the atmosphere, and the decrease due to radioactive decay is balanced. In the earth's atmospheric environment, the amount of 14 14C is a certain amount. Therefore, the 14 14C concentration of substances derived from biomass resources that are circulating in the current environment is about 1×10 -12 mol% with respect to the total C atoms as described above. Therefore, the biomass ratio of a certain compound can be calculated using the difference between these values.

[0046] This 14 14C is generally measured as follows. Using accelerator mass spectrometry based on a tandem accelerator, 13 14C concentration ( 13 14C / 12 12C), 14 13C concentration ( 14 13C / 12 12C) are measured. In the measurement,14 As a modern standard reference for the concentration of C, the amount of cyclic carbon in nature as of 1950 14 The C concentration will be used. The specific standard material will be the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific radioactivity of carbon in this oxalic acid (per gram of carbon) will be used. 14 The radioactivity intensity of C is separated by carbon isotope, 13 The standard value is obtained by correcting C to a constant value and applying decay correction from 1950 AD to the measurement date. 14 This value is used as the C concentration value (100%). The ratio of this value to the value of the sample actually measured is the pMC value.

[0047] Therefore, if rubber is made from 100% biomass-derived materials, although there are regional differences, under normal conditions it will often not reach 100, and will show a value of approximately 110 pMC. On the other hand, regarding chemical substances derived from fossil fuels such as petroleum, 14 When the C concentration is measured, it will show a value of approximately 0 pMC (for example, 0.3 pMC). This value corresponds to a biomass ratio of 0% as mentioned above.

[0048] For the reasons stated above, using materials such as rubber with a high pMC value, that is, materials such as rubber with a high biomass ratio, in rubber compositions is preferable from an environmental protection standpoint.

[0049] When the above rubber composition contains isoprene-based rubber, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more, and also preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. When the content is within the above range, the effect tends to be better obtained.

[0050] When the above rubber composition contains BR, the BR content in 100% by mass of the rubber component is preferably 20% by mass or more, more preferably 30% by mass or more, even more preferably 40% by mass or more, and even more preferably 50% by mass or more, and also preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. When the content is within the above range, the effect tends to be better obtained.

[0051] When the above rubber composition contains SBR, the SBR content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and also preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less. When the content is within the above range, the effect tends to be better obtained.

[0052] The above rubber composition contains microcellulose.

[0053] The above-mentioned microcellulose is not particularly limited and includes, for example, resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf, as well as waste biomass such as pulp, paper, cloth, agricultural residues, food waste, and sewage sludge obtained from these raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, and cellulose produced by sea squirts, acetic acid bacteria, etc. The above-mentioned microcellulose may be used individually or in combination of two or more types.

[0054] In this specification, microcellulose typically refers to cellulose fibers with an average fiber diameter in the range of 20 μm to 1 mm, and more typically, cellulose fibers with an average fiber diameter of 20 to 500 μm, which are formed by aggregates of cellulose molecules and have a larger average fiber diameter than cellulose microfibrils (nanocellulose), which typically have an average fiber diameter of 10 μm or less. Typical microcellulose is formed, for example, as an aggregate of cellulose fibers having the average fiber diameters described above.

[0055] The above-mentioned method for producing microcellulose is not particularly limited, but examples include chemically treating the microcellulose raw material with an alkali such as sodium hydroxide as needed, and then mechanically grinding or beating it using a refiner, twin-screw kneader (twin-screw extruder), twin-screw kneading extruder, high-pressure homogenizer, media stirring mill, millstone, grinder, vibratory mill, sand grinder, etc. In these methods, lignin is separated from the raw material by chemical treatment, so a microcellulose that is substantially free of lignin is obtained. In addition, other methods include treating the microcellulose raw material under ultra-high pressure.

[0056] The above-mentioned microcellulose can include not only unmodified microcellulose obtained by the above-mentioned manufacturing method, but also microcellulose that has undergone oxidation treatment or various chemical modification treatments, or natural materials that can be used as the source of microcellulose (for example, wood, pulp, bamboo, hemp, jute, kenaf, agricultural waste, cloth, paper, sea squirt cellulose, etc.) that have been subjected to oxidation treatment or various chemical modification treatments, and then defibration treatment as necessary. For example, oxidized microcellulose can be suitably used.

[0057] Examples of the chemical modification of the microcellulose described above include esterification, etherification, and acetalization. Specifically, preferred examples include acylation such as acetylation, cyanoethylation, amination, sulfone esterification, phosphate esterification, alkyl esterification, alkyl etherification, complex esterification, β-ketoesterification, alkylation such as butylation, and chlorination. Furthermore, alkylcarbamate and arylcarbamate can also be exemplified. All of these chemical modification treatments make the microcellulose hydrophobic, and using microcellulose that has undergone such chemical modification treatments tends to improve the dispersibility of the microcellulose.

[0058] The average fiber diameter A of the above microcellulose is 20 μm or more, preferably 30 μm or more, more preferably 40 μm or more, and also preferably 1 mm or less, more preferably 500 μm or less, even more preferably 300 μm or less, and particularly preferably 200 μm or less. When it is within the above range, the effect tends to be better obtained. Furthermore, from the viewpoint of preventing fracture nuclei in the rubber, 40 μm or less is preferred, and 30 μm or less is more preferred.

[0059] The average fiber length of the above microcellulose is preferably 60 μm or more, more preferably 80 μm or more, even more preferably 200 μm or more, even more preferably 500 μm or more, even more preferably 900 μm or more, and particularly preferably 2 mm or more. The upper limit of the average fiber length is not particularly limited, but is preferably 5 mm or less, more preferably 4 mm or less, and even more preferably 3 mm or less. Within the above range, the effect tends to be better obtained. Also, from the viewpoint of the degree of orientation, such as when you do not want to orient the fibers too much, 2 mm or less is preferred, 900 μm or less is more preferred, 500 μm or less is even more preferred, 200 μm or less is even more preferred, 80 μm or less is even more preferred, and 60 μm or less is even more preferred. On the other hand, 10 μm or more is preferred, 20 μm or more is more preferred, and 30 μm or more is even more preferred.

[0060] Although the mechanism by which using microcellulose with an average fiber length above a certain level yields greater effectiveness is not clear, it is thought that the larger the average fiber length of the microcellulose, the more effectively the dispersion effect of the microcellulose is obtained, thereby resulting in good fuel efficiency.

[0061] In this specification, the average fiber diameter and average fiber length of microcellulose can be measured by scanning electron microscopy, transmission electron microscopy, atomic force microscopy, X-ray scattering data analysis, pore electrical resistance method (Coulter principle method), etc. In this specification, the average fiber diameter and average fiber length of microcellulose (cellulose fiber) typically refer to the average fiber diameter and average fiber length of an aggregate of cellulose fibers formed by the aggregation of cellulose molecules.

[0062] Furthermore, if the above microcellulose consists of a combination of two or more types, the average fiber diameter and average fiber length are calculated as the average of the entire microcellulose.

[0063] In the above rubber composition, the content of the microcellulose per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 5 parts by mass or more. Also, it is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, even more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. When it is within the above range, the effect tends to be better obtained. Furthermore, from the viewpoint of the rubber reinforcing effect, 5 parts by mass or less is preferred, more preferably 2 parts by mass or less, even more preferably 1 part by mass or less, on the other hand, 0.1 parts by mass or more is preferred, and even more preferably 0.5 parts by mass or more.

[0064] The above rubber composition may also contain a reinforcing filler. In this specification, reinforcing fillers refer to carbon black and silica.

[0065] The carbon blacks that can be used are not particularly limited, but include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. The raw materials for the carbon black may be biomass materials such as lignin and vegetable oil. The manufacturing method of the carbon black may be by combustion such as the furnace process, by hydrothermal carbonization (HTC), or by thermal decomposition of methane such as the thermal black process. Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Corporation. These may be used individually or in combination of two or more types.

[0066] The nitrogen adsorption specific surface area (N2SA) of carbon black is 20 m². 2 Preferably 30m / g or more. 2 More preferably 40m 2 A value of 1 / g or more is even more preferable. Furthermore, the above N2SA is 150m 2 Preferably less than / g, 130m 2 / g or less is more preferable, 120m 2 A value of less than / g is even more preferable. Within the above range, there is a tendency to obtain better effects. Furthermore, the N2SA rating for carbon black is determined in accordance with JIS K6217-2:2001.

[0067] When the above rubber composition contains carbon black, the carbon black content is preferably 5 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 50 parts by mass or more, and also preferably 150 parts by mass or less, more preferably 100 parts by mass or less, and even more preferably 90 parts by mass or less, per 100 parts by mass of the rubber component. Within the above range, the effect tends to be better obtained. Furthermore, from the viewpoint of the reinforcing effect of the rubber, 50 parts by mass or less is preferred, 30 parts by mass or less is more preferred, 5 parts by mass or less is even more preferred, on the other hand, 1 part by mass or more is preferred, and 3 parts by mass or more is even more preferred.

[0068] The silica that can be used is not particularly limited, and common types used in the tire industry can be used, such as silica prepared by the dry method (anhydrous silica) or silica prepared by the wet method (hydrated silica). The raw material for silica is not particularly limited, and may be a mineral-derived raw material such as quartz, or a biological-derived raw material such as rice husks (for example, silica made from biomass materials such as rice husks), or silica recycled from silica-containing products may be used. Among these, hydrated silica prepared by the wet method is preferred because it has a high silanol group content. These silicas may be used individually or in combination of two or more types.

[0069] Silica derived from biomass materials can be obtained, for example, by extracting silicates from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then using these silicates to react with sulfuric acid in the same way as conventional wet silica, the precipitate of silicon dioxide is filtered, washed with water, dried, and pulverized.

[0070] The silica recycled from silica-containing products can be, for example, silica recovered from products containing silica such as semiconductors and other electronic components, tires, desiccants, and diatomaceous earth and other filter materials. The recovery method is not particularly limited and can include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from semiconductors and other electronic components or tires is preferred.

[0071] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and combustion time, the crystallization of silica in rice husk ash can be suppressed (see Japanese Patent Publication No. 2009-2594, Akita Prefectural University Web Journal B / 2019, vol.6, pp.216-222, etc.).

[0072] Amorphous silica extracted from rice husks can be commercially available from companies such as Wilmar.

[0073] The nitrogen adsorption specific surface area (N2SA) of silica is preferably 50 m².2 / g or more, comfortably 100m 2 / g or more, more preferably 150m 2 It is 1 / g or more. Furthermore, the upper limit of N2SA in silica is not particularly limited, but preferably 350m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 It is less than or equal to / g. Within the above range, there is a tendency for better results to be obtained. Note that the N2SA value of silica is measured by the BET method in accordance with ASTM D3037-93.

[0074] When the above rubber composition contains silica, the silica content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 50 parts by mass or less. When the silica content is within the above range, the effect tends to be better obtained.

[0075] The above rubber composition may also contain fillers in addition to microcellulose and reinforcing fillers. The above-mentioned fillers are not particularly limited, and materials known in the rubber field can be used, such as inorganic fillers such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, aluminum oxide, and mica, as well as biochar (BIO CHAR); and poorly dispersible fillers. These may be used individually or in combination of two or more.

[0076] Examples of the poorly dispersible fillers mentioned above include microfibrillated plant fibers, short fibrous cellulose, and gel-like compounds. Among these, microfibrillated plant fibers are preferred.

[0077] As the above-mentioned microfibrillated plant fiber, cellulose microfibrils are preferred in that they provide good reinforcing properties. The cellulose microfibrils are not particularly limited as long as they are derived from natural products, and examples include resource biomass such as fruits, grains, and root vegetables; wood, bamboo, hemp, jute, and kenaf, as well as waste biomass such as pulp, paper, cloth, agricultural residues, food waste, and sewage sludge obtained from these raw materials, unused biomass such as rice straw, wheat straw, and thinned wood, and cellulose produced by sea squirts, acetic acid bacteria, etc. One type of these microfibrillated plant fiber may be used, or two or more types may be used in combination.

[0078] In this specification, cellulose microfibrils typically refer to cellulose fibers having an average fiber diameter of 10 μm or less, and more typically, cellulose fibers having a microstructure with an average fiber diameter of 500 nm or less, formed by an aggregate of cellulose molecules. Typical cellulose microfibrils are formed, for example, as aggregates of cellulose fibers having the average fiber diameter described above.

[0079] When the above rubber composition contains a poorly dispersible filler, the content of the poorly dispersible filler is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When the content is within the above range, the effect tends to be better obtained.

[0080] The above rubber composition contains a coupling agent. In this specification, a coupling agent is a compound that can interact with both rubber components and microcellulose. The coupling agent is not particularly limited and any known in the rubber field can be used, for example, bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl) trisulfide, bis(4-trimethoxysilylbutyl) trisulfide, bis(3-triethoxysilylpropyl) disulfide, bis(2-triethoxysilylethyl) disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N- Examples include sulfide-based compounds such as dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z from Momentive; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based and amino-based compounds are preferred, with amino-based compounds being particularly preferred. Commercially available products from companies such as Evonik, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. can be used. These can be used individually or in combination of two or more types.

[0081] Although the mechanism by which the inclusion of an amino-based coupling agent yields better results is not clear, it is believed that the amino-based coupling agent effectively disperses the microcellulose, thereby resulting in good fuel efficiency.

[0082] In the above rubber composition, the content of the coupling agent is preferably 0.1 parts by mass or more, more preferably 0.5 parts by mass or more, even more preferably 1.0 part by mass or more, and particularly preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit of the content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 5.0 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0083] The above rubber composition may contain a plasticizer. In this specification, "plasticizer" refers to a material that imparts plasticity to rubber components, and is a concept that includes both liquid plasticizers at 25°C and solid plasticizers at 25°C. Examples of plasticizers include resin components, oils, liquid polymers, and ester-based plasticizers. These plasticizers may be derived from mineral resources such as petroleum and natural gas, from biomass, or from naphtha recycled from rubber or non-rubber products. In addition, low molecular weight hydrocarbon components obtained by thermal decomposition and extraction of used tires or products containing various components may be used as plasticizers. These plasticizers may be used individually or in combination of two or more types.

[0084] Examples of the plasticizers mentioned above include oils, liquid polymers, and resins. These may be used individually or in combination of two or more.

[0085] Examples of oils include mineral oil, vegetable oil, and animal oil. From a life cycle assessment perspective, waste oil used in rubber mixers and engines, or refined waste cooking oil used in restaurants, may also be used.

[0086] In this specification, mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oils (mineral oil), naphthenic oils, and aromatic oils. Specific examples of mineral oil include MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract). Furthermore, for environmental reasons, oils with a low content of polycyclic aromatic compounds (PCA) can be used. Examples of such low-PCA oils include MES, TDAE, and heavy naphthenic oils.

[0087] In this specification, vegetable oils include, for example, linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and wood wax. Furthermore, vegetable oils may also include refined oils obtained by refining the above oils (such as salad oil), transesterified oils obtained by transesterifying the above oils, hydrogenated oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidized polymerized oils obtained by oxidizing the above oils, and waste cooking oils recovered from use as edible oils. Note that vegetable oils may be liquid or solid at 25°C. These vegetable oils may be used individually or in combination of two or more types.

[0088] The vegetable oil according to this embodiment preferably contains acylglycerol, and more preferably contains triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin and a fatty acid are ester-bonded. The acylglycerol is not particularly limited and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer of three or more. Note that acylglycerols of two or more forms can be obtained by thermal polymerization, oxidative polymerization, etc. Also, the acylglycerol may be a liquid or a solid at 25°C.

[0089] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, 1 This can be confirmed by 1H-NMR measurement. For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at 25°C for 24 hours, and after removing the rubber composition, it is measured at room temperature. 1 When 1H-NMR was measured and the tetramethylsilane (TMS) signal was set to 0.00 ppm, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm. These signals are presumed to originate from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atom of the ester group. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0090] The aforementioned fatty acids are not particularly limited and may be either unsaturated or saturated fatty acids. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0091] In particular, it is desirable that the fatty acid contains fatty acids with few double bonds, i.e., saturated fatty acids or monounsaturated fatty acids, and oleic acid is preferred. As a vegetable oil containing such fatty acids, for example, a vegetable oil containing saturated fatty acids or monounsaturated fatty acids may be used, or a vegetable oil that has been modified by transesterification or other means may be used. Furthermore, in order to produce a vegetable oil containing such fatty acids, plants may be improved by breeding, genetic modification, genome editing, etc.

[0092] As for the oil, commercially available products from companies such as Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Fuji Kosan Co., Ltd., and Nisshin Oillio Group Ltd. can be used.

[0093] Examples of the above-mentioned liquid polymers (polymers that are liquid at 25°C) include liquid diene polymers (liquid rubber) and liquid farnesene polymers that are liquid at 25°C. Examples of liquid rubbers include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), liquid styrene-isoprene copolymer (liquid SIR), liquid styrene-butadiene-styrene block copolymer (liquid SBS block polymer), and liquid styrene-isoprene-styrene block copolymer (liquid SIS block polymer). These polymers may have polar groups modified at the ends or main chain. Hydrogenated versions of these polymers can also be used. In particular, from the viewpoint of obtaining better effects, it is preferable to include a liquid diene polymer that is liquid at 25°C.

[0094] The above liquid diene polymer has a weight-average molecular weight (Mw) on a polystyrene basis, measured by gel permeation chromatography (GPC), of 1.0 × 10⁻⁶. 3 ~5.0×10 4 Preferably, 3.0 × 10 3 ~1.5×10 4 It is more preferable that this is the case. Furthermore, the lower or upper limit of Mw for the liquid diene polymer may be 4500 or 8500. In this specification, the Mw of liquid diene polymers is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0095] Examples of liquid diene polymers that can be used include products from companies such as Clay Valley, Sartomer, and Kuraray Co., Ltd.

[0096] The above-mentioned resins can be those commonly used in tire compounding, and may be liquid or solid at 25°C. Examples include aromatic vinyl polymers, coumarone indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, and acrylic resins. The resin may also be a hydrogenated resin. These may be used individually or in combination of two or more. The resin itself may also be a copolymer of monomer components of multiple origins. Among these, aromatic vinyl polymers, petroleum resins, terpene resins, and their hydrogenated resins are particularly desirable.

[0097] When using a resin that is solid at 25°C, the softening point of the above-mentioned resin is preferably 50°C or higher, more preferably 55°C or higher, even more preferably 60°C or higher, and particularly preferably 85°C or higher. Furthermore, it is preferably 160°C or lower, more preferably 150°C or lower, even more preferably 140°C or lower, and particularly preferably 100°C or lower. Within the above range, the effect tends to be better obtained. When the resin is liquid at 25°C, the softening point is preferably 20°C or lower, preferably 10°C or lower, and preferably 0°C or lower. In the case of hydrogenated resins, it is desirable that the softening point be the same as described above. The softening point of the above resin is determined by measuring the softening point specified in JIS K6220-1:2001 using a ring-type softening point measuring device, and the temperature at which the sphere descends is the softening point.

[0098] The above-mentioned aromatic vinyl polymer is a polymer containing aromatic vinyl monomers as constituent units. Examples include resins obtained by polymerizing α-methylstyrene and / or styrene, specifically, homopolymers of styrene (styrene resin), homopolymers of α-methylstyrene (α-methylstyrene resin), copolymers of α-methylstyrene and styrene, copolymers of styrene and other monomers.

[0099] The above-mentioned coumarone-indene resin is a resin that contains coumarone and indene as the main monomer components that constitute the resin's backbone (main chain). Other monomer components that may be included in the backbone besides coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0100] The coumarone resin described above is a resin that contains coumarone as the main monomer component that constitutes the resin's backbone (main chain).

[0101] The above-mentioned indene resin is a resin that contains indene as the main monomer component that constitutes the resin's backbone (main chain).

[0102] As the phenolic resin mentioned above, known polymers such as those obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or alkali catalyst can be used. Among these, those obtained by reaction with an acid catalyst (such as novolac-type phenolic resins) are preferred.

[0103] Examples of the rosin resins mentioned above include natural rosin, polymerized rosin, modified rosin, their ester compounds, and rosin-based resins represented by their hydrogenated products.

[0104] Examples of the above petroleum resins include C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, C9 / DCPD resins, and hydrogenated versions thereof. Among these, DCPD resins, hydrogenated DCPD resins, C9 / DCPD resins, and C9 / hydrogenated DCPD resins are preferred.

[0105] The above-mentioned terpene resins are polymers containing terpenes as constituent units. Examples include polyterpene resins obtained by polymerizing terpene compounds, and aromatically modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. As aromatically modified terpene resins, terpene-phenol resins made from terpene compounds and phenolic compounds, terpene-styrene resins made from terpene compounds and styrene compounds, and terpene-phenol-styrene resins made from terpene compounds, phenolic compounds, and styrene compounds can also be used. Examples of terpene compounds include α-pinene and β-pinene, examples of phenolic compounds include phenol and bisphenol A, and examples of aromatic compounds include styrene compounds (styrene, α-methylstyrene, etc.). Among these, aromatically modified terpene resins are preferred.

[0106] The above-mentioned acrylic resin is a polymer containing acrylic monomers as constituent units. Examples include styrene-acrylic resins such as styrene-acrylic resin, which have carboxyl groups and are obtained by copolymerizing an aromatic vinyl monomer component with an acrylic monomer component. Among these, solvent-free carboxyl group-containing styrene-acrylic resins can be suitably used.

[0107] Examples of resins that can be used include those from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, ExxonMobil, Kraton, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Industries, Ltd., and others.

[0108] From a sustainability perspective, it is desirable to use plant-derived plasticizers such as the aforementioned plant-derived oils and farnesene polymers as plasticizers.

[0109] Farnesene polymers are polymers obtained by polymerizing farnesene and have constituent units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene), but (E)-β-farnesene, which has the following structure, is preferred. [ka]

[0110] The farnesene polymer may be a farnesene homopolymer (farnesene homopolymer) or a farnesene-vinyl monomer copolymer (farnesene-vinyl monomer copolymer). These may be used individually or in combination of two or more. Among these, the farnesene-vinyl monomer copolymer is preferred.

[0111] Examples of vinyl monomers include aromatic vinyl compounds such as styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-t-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl)dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-t-butylstyrene, 3-t-butylstyrene, 4-t-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, and tertiary amino group-containing diphenylethylene, as well as conjugated diene compounds such as butadiene and isoprene. These may be used individually or in combination of two or more. Among these, butadiene is preferred. In other words, a copolymer of farnesene and butadiene (farnesene-butadiene copolymer) is preferred as the farnesene-vinyl monomer copolymer.

[0112] In farnesene-vinyl monomer copolymers, the mass-based copolymerization ratio (farnesene / vinyl monomer) of farnesene to vinyl monomer is preferably 40 / 60 to 90 / 10.

[0113] Farnesene polymers with a weight-average molecular weight (Mw) of 3,000 to 300,000 are preferably used. The Mw of the farnesene polymer is preferably 8,000 or more, more preferably 10,000 or more, and also preferably 100,000 or less, more preferably 60,000 or less, and even more preferably 50,000 or less. Within the above range, the effect tends to be more favorably obtained.

[0114] The farnesene polymer may be in either a liquid or solid state at 25°C. However, a liquid farnesene polymer at 25°C is preferred.

[0115] In the above rubber composition, the plasticizer content (total amount of plasticizer) is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. When the content is within the above range, a better effect tends to be obtained. Furthermore, the plasticizer content includes the amount of oil and resin contained in oil-extracted rubber and resin-extracted rubber.

[0116] In the above rubber composition, the content of the solid plasticizer, which is solid at 25°C, is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component, and may be 0 parts by mass. When the content is within the above range, a better effect tends to be obtained.

[0117] In the above rubber composition, the content of the resin in a solid state at 25°C is preferably 30 parts by mass or less, more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component, and may be 0 parts by mass. When the content is within the above range, a better effect tends to be obtained.

[0118] In the above rubber composition, the content of liquid plasticizer, which is in a liquid state at 25°C, is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained. The above liquid plasticizer content also includes the amount of oil contained in the oil-stretched rubber and the amount of liquid resin in the resin-stretched rubber that has been stretched with liquid resin.

[0119] In the above rubber composition, the oil content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. When the oil content is within the above range, a better effect tends to be obtained. Note that the oil content also includes the amount of oil contained in the oil-applied rubber.

[0120] The above rubber composition may further contain vulcanized rubber particles. Vulcanized rubber particles are particles made of vulcanized rubber, and specifically, rubber powder as specified in JIS K 6316:2017 can be used. From the viewpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used individually or in combination of two or more types.

[0121] The vulcanized rubber particles are not particularly limited and may be either unmodified or modified vulcanized rubber particles.

[0122] Commercially available vulcanized rubber particles can be used, for example, products from Lehigh, Muraoka Rubber Industries, Ltd., and others.

[0123] In the above rubber composition, the content of vulcanized rubber particles is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, even more preferably 10 parts by mass or more, and preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0124] The above rubber composition preferably contains an anti-aging agent from the viewpoint of crack resistance, ozone resistance, etc.

[0125] While not particularly limited, examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditril-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as methyl amine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, with polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline being more preferred. Commercially available products include those from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis.

[0126] In the above rubber composition, the content of the anti-aging agent is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, and even more preferably 3.0 parts by mass or more, per 100 parts by mass of the rubber component. The content is preferably 10.0 parts by mass or less, and more preferably 6.0 parts by mass or less.

[0127] The above rubber composition preferably contains stearic acid. In the above-mentioned rubber composition for side members, the stearic acid content is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the rubber component.

[0128] In addition, conventionally known stearic acid can be used, such as products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Corporation, Chiba Fatty Acid Co., Ltd.

[0129] The above rubber composition preferably contains zinc oxide. In the above rubber composition, the zinc oxide content is preferably 0.5 parts by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and preferably 6.0 parts by mass or less, and more preferably 4.0 parts by mass or less, per 100 parts by mass of the rubber component.

[0130] In addition, conventionally known zinc oxides can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd.

[0131] The above rubber composition may contain wax. In the above rubber composition, the wax content is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and preferably 8.0 parts by mass or less, more preferably 5.0 parts by mass or less, per 100 parts by mass of the rubber component.

[0132] The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to waxes derived from natural resources such as plants. Among these, mineral waxes are preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. The wax can be commercially available from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. These waxes may be used individually or in combination of two or more types.

[0133] In the above rubber composition, it is preferable to incorporate sulfur as a crosslinking agent, as this forms appropriate crosslinked chains in the polymer chains and imparts good performance.

[0134] In the above rubber composition, the sulfur content is 1.0 part by mass or more, preferably 1.5 parts by mass or more, and more preferably 1.8 parts by mass or more, per 100 parts by mass of the rubber component. The sulfur content is preferably 7.0 parts by mass or less, more preferably 5.0 parts by mass or less, and even more preferably 4.0 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0135] Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercially available products include those from Tsurumi Chemical Industries, Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industry Co., Ltd. These can be used individually or in combination of two or more types.

[0136] The above rubber composition preferably contains a vulcanization accelerator. In the above rubber composition, there are no particular restrictions on the content of the vulcanization accelerator, and it can be freely determined according to the desired vulcanization rate and crosslinking density. However, it is preferably 0.5 parts by mass or more, more preferably 0.8 parts by mass or more, even more preferably 1.0 part by mass or more, even more preferably 1.5 parts by mass or more, and even more preferably 2.0 parts by mass or more, per 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 6.0 parts by mass or less, and even more preferably 5.0 parts by mass or less.

[0137] There are no particular restrictions on the type of vulcanization accelerator; commonly used ones can be used. Examples of vulcanization accelerators include benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiadylsulfenamide; thiram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolesulfenamide, Nt-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolesulfenamide, and N,N'-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, diortotrilguanidine, and orthotrilbiguanidine. These may be used individually or in combination of two or more. Among them, sulfenamide, guanidine, and benzothiazole vulcanization accelerators are preferred, sulfenamide and guanidine vulcanization accelerators are more preferred, it is even more preferable to include at least a guanidine vulcanization accelerator, and it is even more preferable to use a combination of a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator.

[0138] Although the mechanism by which including at least a guanidine-based vulcanization accelerator yields better results is not clear, it is thought that the guanidine-based vulcanization accelerator effectively disperses microcellulose, thereby resulting in good fuel efficiency.

[0139] In addition to the above components, the above rubber composition may also contain other compounding agents commonly used in the tire industry, such as mold release agents.

[0140] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. As a method for obtaining the above formulations from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0141] The above rubber composition is obtained by kneading each of the above components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing it.

[0142] Regarding the mixing conditions, in the base mixing step in which additives other than the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is preferably 50°C or higher, more preferably 80°C or higher, and also preferably 200°C or lower, more preferably 190°C or lower. The mixing time is preferably 30 seconds or more, more preferably 1 minute or more, and also preferably 30 minutes or lower. In the finish mixing step in which the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is preferably 10°C or higher, also preferably 100°C or lower, more preferably 80°C or lower. The composition mixed with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is preferably 120°C or higher, more preferably 140°C or higher, also preferably 200°C or lower, more preferably 180°C or lower.

[0143] The above rubber composition is used for sidewalls.

[0144] The above-mentioned tire is manufactured by conventional methods using the above-mentioned rubber composition. Specifically, the composition, which may contain various additives as needed, is extruded to match the shape of the sidewall at the unvulcanized stage, molded in conventional methods on a tire molding machine, bonded together with other tire components to form an unvulcanized tire, and then heated and pressurized in a vulcanizing machine to manufacture the tire.

[0145] The above-mentioned tires are not particularly limited and include, for example, pneumatic tires, solid tires, and airless tires. Among these, pneumatic tires are preferred.

[0146] The above-mentioned tires are suitably used as passenger car tires, large passenger car tires, large SUV tires, truck and bus tires, motorcycle tires, racing tires, winter tires (studless tires, snow tires, studded tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc.

[0147] The above-mentioned tire has a sidewall made of a rubber composition containing the above-mentioned rubber component, the above-mentioned microcellulose, and the above-mentioned coupling agent, wherein the average fiber diameter of the microcellulose is 20 μm or more, and the ratio ((A × C) / T) of the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent per 100 parts by mass of the rubber component to the thickness T (mm) of the sidewall is greater than 1.5. The above (A×C) / T is preferably greater than 1.9, more preferably greater than 5.0, even more preferably greater than 10.0, even more preferably greater than 15.0, even more preferably greater than 20.0, and even more preferably greater than 25.0. The upper limit of the above (A×C) / T is not particularly limited, but is preferably less than 200, more preferably less than 175, even more preferably less than 150, and even more preferably less than 100. When it is within the above range, the effect tends to be better obtained.

[0148] The lower limit of the sidewall thickness T (mm) is preferably 1.0 mm or more, more preferably 2.0 mm or more, and even more preferably 3.0 mm or more. The upper limit is preferably 10.0 mm or less, more preferably 9.0 mm or less, even more preferably 8.0 mm or less, and particularly preferably 7.0 mm or less. Within the above range, the effect tends to be more favorably obtained.

[0149] In this specification, the sidewall thickness T is the distance (mm) from the sidewall surface to the carcass cord surface, measured along the normal L of the tire's maximum width position PW. "Tire's maximum width position PW" refers to the position of maximum width within the tire's widthwise cross-section as measured under normal conditions.

[0150] In this specification, dimensions such as thickness are values ​​measured under normal conditions. "Normal conditions" refers to a state in which the tire is mounted on a normal rim, filled to the normal internal pressure, and under no load. Here, "normal rim" refers to the rim specified for each tire in the standards system, including the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA YEAR BOOK," for ETRTO (The European Tyre and Rim Technical Organisation), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and for TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of tires not specified in the standards, it refers to the rim with the smallest diameter and the narrowest rim width among rims that can be mounted on and can maintain internal pressure, i.e., rims that do not cause air leakage from between the rim and tire. Furthermore, "standard internal pressure" refers to the air pressure specified for each tire in the standards system, including the standard on which the tire is based. For example, it refers to the "maximum air pressure" for JATMA, "INFLATION PRESSURE" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. Refer to JATMA, ETRTO, and TRA in that order, and if an applicable size is available at the time of reference, follow that standard. In the case of tires not specified in the standards, it refers to the standard internal pressure (but at least 250 kPa) of another tire size (specified in the standards) that uses the standard rim as the standard rim. If multiple standard internal pressures of 250 kPa or higher are listed, refer to the lowest value among them.

[0151] The aspect ratio of the above-mentioned tire is not particularly limited, but is preferably 60% or less, more preferably 55% or less, even more preferably 50% or less, and even more preferably 45% or less. Also, is preferably 25% or more, more preferably 30% or more, even more preferably 35% or more, and even more preferably 40% or more. When it is within the above range, the effect tends to be better obtained.

[0152] By setting the aspect ratio of the tire to a predetermined level or lower, the handling stability of the tire can be improved. At the same time, by making the sidewall out of the above-mentioned rubber composition, the decrease in fuel efficiency can be suppressed. Therefore, it is believed that even low-aspect-ratio tires can have good fuel efficiency.

[0153] In this specification, the "aspect ratio" of a tire is the ratio of the tire's cross-sectional height Ht (mm) to its cross-sectional width Wt (mm), expressed as a percentage, and can be calculated by Ht / Wt × 100.

[0154] The tire's "section width Wt (mm)" is the maximum width between the outer surfaces of the sidewalls in a normal state, excluding any patterns or letters on the tire's sidewall.

[0155] The "outer diameter Dt (mm)" of a tire refers to the outer diameter of the tire in its normal state.

[0156] The "section height Ht (mm)" of a tire refers to the height in the radial direction of the tire's radial cross-section. When the tire's rim diameter is R (mm), it corresponds to half the difference between the tire's outer diameter Dt and its rim diameter R. In other words, the section height Ht can be calculated using (Dt-R) / 2.

[0157] The following diagram illustrates an example of a tire, but the tire is not limited to this form.

[0158] In Figure 1, the vertical direction is the radial direction of tire 2, the horizontal direction is the axial direction of tire 2, and the direction perpendicular to the plane of the paper is the circumferential direction of tire 2. Tire 2 is symmetrical. Tread 4 is a single-layer tread structure.

[0159] Although Figure 1 shows an example of a single-layer tread 4, a two-layer tread consisting of a cap tread and a base tread, or a tread with three or more layers, may also be used.

[0160] In tire 2, each sidewall 6 extends radially inward from the edge of the tread 4. The radially outer portion of this sidewall 6 is joined to the tread 4. The radially inner portion of this sidewall 6 is joined to the clinch 10. This sidewall 6 can prevent damage to the carcass 14.

[0161] In the tire 2 shown in Figure 1, the sidewall 6 is made of the above-mentioned rubber composition. Specifically, the sidewall 6 is made of a rubber composition that includes a rubber component, microcellulose with an average fiber diameter of 20 μm or more, and a coupling agent.

[0162] Each wing 8 in Figure 1 is located between the tread 4 and the sidewall 6. The wing 8 is joined to both the tread 4 and the sidewall 6, respectively.

[0163] Each clinch 10 is located approximately radially inward of the sidewall 6 and has at least one portion that contacts the rim.

[0164] The carcass 14 is provided with a carcass ply 36. In this tire 2, the carcass 14 consists of one carcass ply 36, but it may be composed of two or more.

[0165] In this tire 2, the carcass ply 36 spans between the bead cores 32 on both sides and runs along the tread 4 and sidewall 6. The carcass ply 36 is folded back axially from the inside to the outside around each bead core 32. This folding gives the carcass ply 36 a main portion 36a and a pair of folded portions 36b. In other words, the carcass ply 36 comprises a main portion 36a and a pair of folded portions 36b.

[0166] Each bead core 32 is provided with a bead apex 34 extending radially outward from the bead core 32. The bead core 32 is preferably ring-shaped and contains a wound, non-stretchable wire. The bead apex 34 tapers radially outward.

[0167] Although not shown in the diagram, the carcass ply 36 preferably consists of a number of parallel cords and a topping rubber. The absolute value of the angle that each cord makes with respect to the equatorial plane CL is preferably between 75° and 90°. In other words, it is preferable that the carcass 14 has a radial structure.

[0168] The belt layer 16 in Figure 1 is located radially inward of the tread 4. The belt layer 16 is laminated with the carcass 14. The belt layer 16 reinforces the carcass 14. In the tire 2 of Figure 1, the belt layer 16 consists of an inner layer 38 and an outer layer 40. As is clear from Figure 1, it is desirable that the width of the inner layer 38 is slightly larger than the width of the outer layer 40 in the axial direction. In this tire 2, the axial width of the belt layer 16 is preferably 0.6 times or more, and preferably 0.9 times or less, the cross-sectional width of the tire 2.

[0169] Preferably, each of the inner layer 38 and the outer layer 40 consists of a number of parallel single-strand steel cords (steel monofilaments) and a topping rubber (coating rubber). In other words, the belt layer 16 contains a number of parallel steel monofilaments.

[0170] In Figure 1, band 18 is located radially outside the belt layer 16. In the axial direction, band 18 has a width equal to the width of the belt layer 16. Band 18 may have a width greater than the width of the belt layer 16.

[0171] Although not shown in the diagram, the band 18 preferably consists of a cord and a topping rubber. The cord is wound in a spiral shape. This band 18 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The angle of the cord with respect to the circumferential direction is preferably 5° or less, and more preferably 2° or less. Since the belt layer 16 is restrained by this cord, lifting of the belt layer 16 is suppressed.

[0172] The belt layer 16 and band 18 in Figure 1 constitute the reinforcing layer. The reinforcing layer may also be composed of only the belt layer 16.

[0173] In tire 2 of Figure 1, the thickness T of the sidewall 6 is the distance (mm) from the sidewall surface to the carcass cord surface, measured along the normal L of the tire's maximum width position PW on the sidewall, and is denoted as T in the example in Figure 1. Tire 2 satisfies the relationship that the ratio ((A × C) / T) between the product of the average fiber diameter A (μm) of microcellulose with an average fiber diameter of 20 μm or more contained in the rubber composition constituting the sidewall 6 and the content C (parts by mass) of the coupling agent per 100 parts by mass of rubber component, and the thickness T (mm), is greater than 1.5.

[0174] Figure 2 is a magnified view of the area around tread 4 in Figure 1. The tire in Figure 2 is a tire 2 having grooves 26 on the tire's equatorial plane (on the CL).

[0175] The inner liner 20 is located inside the carcass 14. The inner liner 20 is bonded to the inner surface of the carcass 14. Typical base rubbers for the inner liner 20 are butyl rubber or halogenated butyl rubber. The inner liner 20 maintains the internal pressure of the tire 2.

[0176] Each chafer 22 is located near the bead 12. In this embodiment, it is preferable that the chafer 22 consists of cloth and rubber impregnated into the cloth. The chafer 22 may be integrated with the clinch 10.

[0177] In this tire 2, the tread 4 is provided with main grooves 42 as grooves 26. As shown in Figure 1, this tread 4 has multiple main grooves 42, specifically three. These main grooves 42 are spaced apart in the axial direction. The three main grooves 42 in this tread 4 form four ribs 44 that extend in the circumferential direction. In other words, the space between the ribs 44 is the main groove 42.

[0178] Each main groove 42 extends in the circumferential direction. The main grooves 42 are continuous and uninterrupted in the circumferential direction. The main grooves 42 promote the drainage of water present between the road surface and the tire 2, for example, in rainy weather. As a result, the tire 2 can maintain sufficient contact with the road surface even when it is wet.

[0179] In tire 2, it is desirable that the average fiber diameter A (μm) of microcellulose containing an average fiber diameter of 20 μm or more in the rubber composition constituting the sidewall 6, the content C (parts by mass) of the coupling agent per 100 parts by mass of the rubber component in the rubber composition, and the thickness T (mm) of the sidewall are within the aforementioned ranges, and that (A × C) / T is within the aforementioned ranges. [Examples]

[0180] The following examples (implementations) are considered preferable for implementation, but the scope of the present invention is not limited to these examples.

[0181] The following is a summary of the various chemicals used in tire manufacturing. Note that these chemicals are purified according to standard procedures as needed. NR:TSR20 SBR: Hydrogenated SBR produced in the following manufacturing example 1 (hydrogenation rate: 80 mol%, styrene content: 35% by mass, Mw: 480,000, Tg: -60℃) BR: Ubepol BR150B manufactured by Ube Industries, Ltd. (Cis content: 97% by mass) Carbon Black: N550 (N2SA: 41m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silica: Evonik UltraSil VN3 (N2SA: 175m 2 / g) Microcellulose 1: Wood-P manufactured by Rettenmeyer (average fiber diameter: 40 μm, average fiber length: 80 μm) Microcellulose 2: B800 manufactured by Rettenmeyer (average fiber diameter: 20 μm, average fiber length: 60 μm) Microcellulose 3: BWW40 manufactured by Rettenmeyer (average fiber diameter: 20 μm, average fiber length: 200 μm) Microcellulose 4: B400 manufactured by Rettenmeyer (average fiber diameter: 20 μm, average fiber length: 900 μm) Microcellulose 5: FIF400 manufactured by Rettenmeyer (average fiber diameter: 20 μm, average fiber length: 2000 μm) Coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik. Coupling agent 2: KBE-903 (3-aminopropyltriethoxysilane) manufactured by Shin-Etsu Silicone Co., Ltd. Oil: VIVATEC500 (aromatherapy process oil) by H&R. Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Anti-aging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Beads of stearic acid manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (5% oil-containing powdered sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noxellar CZ-G (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0182] (Manufacturing Example 1: Manufacturing of Hydrogenated SBR) In a thoroughly nitrogen-purged heat-resistant reaction vessel, 2000 mL of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of THF, and 0.45 mmol of n-butyllithium are added, and the mixture is stirred at 50°C for 5 hours to carry out the polymerization reaction. Next, hydrogen gas is supplied at a pressure of 0.4 MPa-Gauge while stirring for 20 minutes to react with unreacted lithium at the polymer ends to form lithium hydride. The hydrogen gas supply pressure is set to 0.7 MPa-Gauge and the reaction temperature to 90°C, and hydrogenation is carried out using a catalyst mainly composed of titanocene dichloride. When the cumulative amount of hydrogen absorption reaches the desired hydrogenation rate, the reaction temperature is reduced to room temperature, the hydrogen pressure is returned to atmospheric pressure, and the mixture is withdrawn from the reaction vessel. The reaction solution is then stirred into water and the solvent is removed by steam stripping to obtain hydrogenated SBR.

[0183] (Examples and Comparative Examples) <Preparation of test tire 1> According to the formulation shown in Table 1, the materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Sulfur and a vulcanization accelerator are added to the mixture, and the mixture is kneaded using an open roll at 80°C for 5 minutes to obtain an uncrosslinked rubber composition. The uncrosslinked rubber composition is molded into the shape of a sidewall, bonded together with other tire components on a tire molding machine to form an unvulcanized tire, and vulcanized at 170°C for 10 minutes to produce test tire 1 (size 205 / 55R17, passenger car tire).

[0184] <Preparation of test tire 2> According to the formulation shown in Table 2, the materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Sulfur and a vulcanization accelerator are added to the mixture, and the mixture is kneaded using an open roll at 80°C for 5 minutes to obtain an uncrosslinked rubber composition. The uncrosslinked rubber composition is molded into the shape of a sidewall, bonded together with other tire components on a tire molding machine to form an unvulcanized tire, and vulcanized at 170°C for 10 minutes to produce test tire 2 (size 225 / 45R17, passenger car tire).

[0185] Tables 1 and 2 show the results calculated based on the evaluation method below, assuming test tires 1 and 2 obtained from compositions whose formulations and specifications were changed according to Tables 1 and 2. The reference comparison examples are as follows: Table 1: Comparative Example 1-1 Table 2: Comparative Example 2-1

[0186] <Fuel efficiency> Using a rolling resistance tester, a test tire is mounted on a rim (rim size: 17 x 6.5J), an internal pressure (210 kPa) is applied, and a load of 4.82 kN is applied. Then, the rolling resistance is measured while the vehicle is driven at 80 km / h and expressed as an index with the reference comparison set to 100. A higher index indicates better fuel efficiency.

[0187] In Tables 1 and 2, "(A × C) / T" represents the ratio of the product of the average fiber diameter A (μm) of microcellulose and the content C (parts by mass) of the coupling agent per 100 parts by mass of rubber component to the sidewall thickness T (mm).

[0188] [Table 1]

[0189] [Table 2]

[0190] The present invention (1) relates to a tire having a sidewall made of a rubber composition comprising a rubber component, microcellulose, and a coupling agent, wherein the average fiber diameter of the microcellulose is 20 μm or more, and the ratio ((A × C) / T) of the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent per 100 parts by mass of the rubber component to the thickness T (mm) of the sidewall is greater than 1.5.

[0191] Invention (2) is the tire described in Invention (1) wherein (A × C) / T is greater than 5.0.

[0192] The present invention (3) is the tire according to the present invention (1) in which (A × C) / T exceeds 10.0.

[0193] The present invention (4) is the tire according to the present invention (1) wherein (A × C) / T exceeds 25.0.

[0194] The present invention (5) is a tire in which the rubber composition is any combination of any of the present inventions (1) to (4) containing an amino coupling agent.

[0195] The present invention (6) is a tire in any combination of the rubber composition with any of the present inventions (1) to (5), wherein the rubber composition contains at least a guanidine-based vulcanization accelerator.

[0196] The present invention (7) is a tire in any combination of the present invention (1) to (6), wherein the average fiber diameter of the microcellulose is 40 μm or more.

[0197] The present invention (8) is a tire in any combination of the present invention (1) to (7) wherein the average fiber length of the microcellulose is 60 μm or more.

[0198] The present invention (9) is a tire in any combination with any of the present inventions (1) to (8), wherein the aspect ratio of the tire is 50% or less. [Explanation of Symbols]

[0199] 2 tires 4 tread 6 Sidewall 8 Wing 10. Clinch 12 beads 14 Carcass 16 Belt Layer 18 bands 20 Inner Liner 22 Chafer 24 Tread surface 26 Groove 32 Bead Core 34 Bead Apex 36 Carcass ply 36a Main section 36b Folded section 38 Inner layer 40 outer layer 42 Main groove 44 Ribs CL tire equatorial plane T Sidewall thickness

Claims

1. A tire having a sidewall made of a rubber composition containing a rubber component, microcellulose, and a coupling agent, The average fiber diameter of the microcellulose is 20 μm or more. A tire characterized in that the ratio ((A × C) / T) between the product of the average fiber diameter A (μm) of the microcellulose and the content C (parts by mass) of the coupling agent per 100 parts by mass of the rubber component and the thickness T (mm) of the sidewall exceeds 1.

5.

2. The tire according to claim 1, wherein (A × C) / T exceeds 5.

0.

3. The tire according to claim 1, wherein (A × C) / T exceeds 10.

0.

4. The tire according to claim 1, wherein the (A × C) / T is greater than 25.

0.

5. The tire according to any one of claims 1 to 4, wherein the rubber composition comprises an amino-based coupling agent.

6. The tire according to any one of claims 1 to 4, wherein the rubber composition comprises at least a guanidine-based vulcanization accelerator.

7. The tire according to any one of claims 1 to 4, wherein the average fiber diameter of the microcellulose is 40 μm or more.

8. The tire according to any one of claims 1 to 4, wherein the average fiber length of the microcellulose is 60 μm or more.

9. The tire according to any one of claims 1 to 4, wherein the aspect ratio of the tire is 50% or less.

Images