tire

Abstract

To provide a tire capable of improving durability and a riding comfort performance after high speed traveling.SOLUTION: A tire 1 includes a tread part 2. The tread part 2 has tread rubber 2A forming a ground surface 2a, and a band layer 8 arranged inside in a tire radial direction of the tread rubber 2A. The band layer 8 includes at least one band ply 8A where band cords 8a composed of polyester fibers are arranged. The band cord 8a has stress σ1 in 2.5% elongation of 0.05 N / tex or more and 0.18 N / tex or less, and stress σ2 in 5.0% elongation of 0.09 N / tex or more and 0.33 N / tex or less. The tread rubber 2A contains styrene. The tread rubber 2A is composed of a rubber composition having a glass transition point Tg of -20°C or higher. A styrene content S in 100 pts.mass of the rubber component in the tread rubber 2A is 25 pts.mass or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to a tire having a tread portion. [Background technology]

[0002] Conventionally, tires have been known that have a tread portion having a tread rubber that forms a contact surface with the ground and a band layer disposed radially inward of the tread rubber. For example, Patent Document 1 below proposes a tire that has a jointless band in which cords made of organic fiber are arranged. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-178294 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in recent years, with improvements in vehicle performance and the development of infrastructure such as expressways, there is still room for further improvement in the durability and ride comfort performance after high-speed driving even in the tire of Patent Document 1.

[0005] The present disclosure has been devised in view of the above circumstances, and has as its main object to provide a tire that can improve durability and ride comfort performance after high-speed driving. [Means for solving the problem]

[0006] The present disclosure relates to a tire having a tread portion, the tread portion having tread rubber that forms a contact surface with the tire, and a band layer arranged radially inward of the tread rubber, the band layer including at least one band ply in which band cords containing polyester fibers are arranged, the band cords having a stress of 0.05 N / tex or more and 0.18 N / tex or less at 2.5% elongation and a stress of 0.09 N / tex or more and 0.33 N / tex or less at 5.0% elongation, the tread rubber including styrene and made of a rubber composition having a glass transition point of -20°C or higher, and the styrene content in 100 parts by mass of the rubber component of the tread rubber is 25 parts by mass or less. [Effects of the Invention]

[0007] The tire of the present disclosure has such a tread rubber and band layer, and thus can improve durability and ride comfort performance after high-speed running. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view of a tire according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view of a band layer according to the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described in detail with reference to the drawings. 1 shows a tire meridian cross section including the rotation axis of a tire 1 of this embodiment in a normal state. Here, the "normal state" refers to a state in which, if the tire 1 is a pneumatic tire, the tire 1 is mounted on a normal rim, the tire pressure is adjusted to a normal level, and no load is applied. Unless otherwise specified below, the dimensions of each part of the tire 1 are values measured in this normal state.

[0010] If there is a standard system that includes the standard on which tire 1 is based, a "genuine rim" is a rim that is determined for each tire by that standard, for example, a "standard rim" for JATMA, a "design rim" for TRA, or a "measuring rim" for ETRTO. If there is no standard system that includes the standard on which tire 1 is based, a "genuine rim" is a rim that can be mounted on a rim and does not cause air leakage, and that has the smallest rim diameter and narrowest rim width among those rims.

[0011] "Normal internal pressure" is the air pressure set for each tire by a standard system that includes the standard on which tire 1 is based, if there is such a system; for JATMA, it is the "maximum air pressure," for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES," and for ETRTO, it is the "INFLATION PRESSURE." If there is no standard system that includes the standard on which tire 1 is based, the "normal internal pressure" is 250 kPa for passenger car tires.

[0012] The tire 1 of this embodiment is suitable for use as a passenger car tire. In this specification, a passenger car tire refers to a pneumatic tire designed to be mounted on a four-wheeled vehicle and having a normal load of 1000 kg or less.

[0013] As for passenger car tires, there are no particular limitations as long as the normal load is 1000 kg or less, but from the viewpoint of suppressing excessive deformation in the tread portion 2, it is preferable that the normal load be 900 kg, more preferably 750 kg, and even more preferably 700 kg.

[0014] "Normal load" is the load specified for each tire by each standard in the standard system, including the standard on which tire 1 is based, and is the "maximum load capacity" in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and the "LOAD CAPACITY" in the case of ETRTO.

[0015] The tire 1 is not limited to a passenger vehicle tire, but can be applied to various types of tires 1, such as pneumatic tires such as heavy-duty tires, motorcycle tires, and racing tires, and non-pneumatic tires that are not filled with pressurized air inside.

[0016] 1, the tire 1 of this embodiment includes a tread portion 2 extending annularly, a pair of sidewall portions 3 extending on both sides of the tread portion 2, and a pair of bead portions 4 extending continuous to the sidewall portions 3. The tire 1 has, for example, a toroidal carcass 6 extending across between bead cores 5 of the pair of bead portions 4, and a belt layer 7 disposed radially outward of the carcass 6 and radially inward of the tread portion 2, and has the following features.

[0017] The tread portion 2 of this embodiment has a tread rubber 2A that forms a contact surface 2a, and a band layer 8 that is disposed inside the tread rubber 2A in the tire radial direction.

[0018] The tread rubber 2A of this embodiment is made of a rubber composition containing at least styrene. The styrene content S in 100 parts by mass of the rubber component of the tread rubber 2A is preferably 25 parts by mass or less. The glass transition temperature Tg of the rubber composition of the tread rubber 2A of this embodiment is -20°C or higher.

[0019] Fig. 2 is a perspective view of the band layer 8 of this embodiment. As shown in Fig. 1 and Fig. 2, the band layer 8 of this embodiment includes at least one band ply 8A in which band cords 8a containing polyester fibers are arranged. The band cords 8a preferably have a stress σ1 at 2.5% elongation of 0.05 N / tex or more and 0.18 N / tex or less, and a stress σ2 at 5.0% elongation of 0.09 N / tex or more and 0.33 N / tex or less.

[0020] By providing these characteristics, the tire 1 of the present embodiment can improve durability and ride comfort after high-speed driving, and the mechanism behind this is presumed to be as follows: However, the effects of the present embodiment are not limited to the following theory.

[0021] The tread rubber 2A of this embodiment contains 25 parts by mass or less of styrene in the rubber component, which generates domains due to the styrene portion in the rubber component, which is thought to enable the tire 1 to more easily absorb impacts during running in the tread rubber 2A.

[0022] At the same time, by limiting the amount of styrene in the tread rubber 2A to one-fourth or less of the rubber component, excessive softening of the rubber component due to heat generated during high-speed driving is suppressed, which is thought to prevent the tire 1 from generating flat spots on the surface of the tread portion 2 due to re-agglomeration of the styrene portion when cooled.

[0023] Furthermore, by making the glass transition temperature of the tread rubber 2A -20°C or higher, it is possible to make it easier for the rubber elasticity to be exhibited at room temperature and at high temperatures during high-speed driving, and to make it easier for the impact transmitted to the tread portion 2 to be absorbed.

[0024] Furthermore, the band layer 8 of this embodiment contains polyester fiber. Since polyester fiber is a material with a higher glass transition temperature than conventionally used fibers such as nylon, the band layer 8 of this embodiment is prevented from softening due to heat during high-speed driving.

[0025] As a result, even when centrifugal force is applied to the tire 1 during high-speed driving, the band layer 8 exerts a restraining force, suppressing heat setting when the tire is cooled after high-speed driving and suppressing the occurrence of flat spots on the contact surface 2a of the tread portion 2.

[0026] At the same time, by setting the stress σ1 of the band cord 8a at 2.5% elongation to a range of 0.05 N / tex or more and 0.18 N / tex or less, tension can be generated in the cord when normal internal pressure is applied. Also, by setting the stress of the band cord 8a at 5.0% elongation to a range of 0.09 N / tex or more and 0.33 N / tex or less, the restraining force during high-speed driving can be increased and the band layer 8 can be made less likely to elongate due to centrifugal force.

[0027] As a result, deformation of the tread portion 2 of the tire 1 is suppressed, heat generation is reduced, and the occurrence of heat setting and flat spots can be suppressed.

[0028] As a result of the above, impacts are easily absorbed within the tread rubber 2A, and both the tread rubber 2A and the band layer 8 are less likely to develop flat spots after high-speed driving, so the roundness of the tire 1 can be maintained even after high-speed driving, and deformation when the tire is driven again is uniform, which is thought to make it possible to improve the overall performance of durability and ride comfort.

[0029] The tread rubber 2A of this embodiment will be described in detail below.

[0030] As described above, the tread rubber 2A of this embodiment contains styrene in the rubber component, such as styrene-butadiene rubber (SBR), styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), and styrene-ethylene-butadiene copolymer.

[0031] Other rubber components used in the tread rubber 2A include, for example, isoprene-based rubbers such as natural rubber (NR) and isoprene rubber (IR), and diene-based rubbers such as butadiene rubber (BR), chloroprene rubber (CR), acrylonitrile butadiene rubber (NBR), and butyl rubber (IIR).

[0032] The other rubber component may be used alone, or two or more different rubber components may be used in combination. As the other rubber component, it is preferable to use at least one of an isoprene-based rubber and BR, from the viewpoint of forming a phase-separated structure in the rubber component and obtaining styrene domains. Therefore, the tread rubber 2A preferably uses a rubber component consisting of a combination of an isoprene-based rubber and SBR, a combination of SBR and BR, or a combination of an isoprene-based rubber, SBR, and BR.

[0033] It is preferable to use SBR for the tread rubber 2 A. For the tread rubber 2 A, one type of SBR may be used alone, or two or more different types of SBR may be used in combination.

[0034] As described above, the styrene content S in 100 parts by mass of the rubber component of the tread rubber 2A is preferably 25 parts by mass or less. Such a tread rubber 2A can reduce bonding due to aggregation of the styrene component and can suppress the occurrence of flat spots in the tread portion 2. From this perspective, the styrene content S in 100 parts by mass of the rubber component of the tread rubber 2A is more preferably 20 parts by mass or less.

[0035] The styrene content S in the rubber component of the tread rubber 2 A is preferably 5 parts by mass or more from the viewpoint of facilitating absorption of impact during rolling in the tread rubber 2 A. The styrene content S in the rubber component refers to the parts by mass of styrene in the rubber component of the tread rubber 2 A, and does not include styrene derived from components that can be extracted from the rubber composition with acetone, such as resin components.

[0036] For example, if a rubber composition contains 50 parts by mass of SBR1 (styrene content 25%) and 10 parts by mass of SBR2 (styrene content 35%), the styrene content S is calculated as 16 parts by mass using the following formula (1). {(25×50)+(35×10)} / 100 = 16 … (1)

[0037] As can be seen from formula (1), the styrene content S in the rubber component can be adjusted appropriately by the content of rubber components having styrene units and the styrene content contained in each rubber component having styrene units.

[0038] The content of SBR in 100 parts by mass of the rubber component used in the tread rubber 2A is, for example, preferably more than 5 parts by mass, more preferably more than 50 parts by mass, and even more preferably 55 parts by mass or more. On the other hand, the upper limit of the content of SBR is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, even more preferably 65 parts by mass or less, and most preferably 60 parts by mass or less. By keeping the content within such a range, the effects of this embodiment can be more easily obtained.

[0039] The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. The styrene content of SBR is preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 15% by mass. On the other hand, from the viewpoints of heat buildup and durability, the upper limit of the styrene content of SBR is preferably less than 50% by mass, more preferably less than 40% by mass, and even more preferably less than 35% by mass.

[0040] The vinyl bond content (amount of 1,2-bonded butadiene units) of SBR is, for example, more than 5 mass% and less than 70 mass%. The structure of SBR (measurement of styrene content and vinyl bond content) can be performed using, for example, a JNM-ECA series instrument manufactured by JEOL Ltd.

[0041] There are no particular limitations on the SBR, and examples that can be used include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. The SBR may be either unmodified SBR or modified SBR, or may be hydrogenated SBR in which the double bonds in the butadiene moiety are hydrogenated.

[0042] The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR (terminal-modified SBR having a functional group at the terminal) in which at least one terminal of SBR has been modified with a compound having a functional group (modifying agent), main-chain-modified SBR having a functional group in the main chain, main-chain terminal-modified SBR having functional groups in the main chain and at the terminals (for example, main-chain terminal-modified SBR having a functional group in the main chain and at least one terminal modified with a modifier), and terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

[0043] Examples of such 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, and epoxy groups. These functional groups may have a substituent.

[0044] As the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following chemical formula 1 can be used. [ka]

[0045] In Chemical Formula 1, R1, R2, and R3 may be the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. R4 and R5 may be the same or different and represent a hydrogen atom or an alkyl group. R4 and R5 may be bonded to form a ring structure together with the nitrogen atom. n represents an integer.

[0046] As the modified SBR modified with a compound (modifier) represented by this chemical formula, SBR in which the polymerization terminals (active terminals) of solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by this chemical formula can be used.

[0047] R1, R2, and R3 are preferably alkoxy groups (preferably alkoxy groups having 1 to 8 carbon atoms, more preferably 1 to 4 carbon atoms). R4 and R5 are preferably alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. When R4 and R5 combine to form a ring structure together with the nitrogen atom, it is preferably a 4- to 8-membered ring. Incidentally, alkoxy groups also include cycloalkoxy groups (cyclohexyloxy group, etc.) and aryloxy groups (phenoxy group, benzyloxy group, etc.).

[0048] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0049] Modified SBR may also be modified with the following compounds (modifiers): Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups, such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)amidopropyltrimethoxysilane, alkoxysilanes such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, N,N,N',N'-bis-(tetraethylamino)benzophenone, and other (thio)benzophenone compounds having an amino group and / or a substituted amino group; 4-N,N benzaldehyde compounds having an amino group and / or a substituted amino group, such as dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; and N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with this compound (modifying agent) can be carried out by a known method.

[0050] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used.

[0051] The rubber composition used for the tread rubber 2A may further contain an isoprene-based rubber, if necessary. In this case, the content (total content) of the isoprene-based rubber per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, from the viewpoint of obtaining good low heat buildup and durability during high-speed driving.

[0052] On the other hand, the upper limit of the content of isoprene-based rubber is not particularly limited, but from the viewpoint of obtaining good ride comfort performance, it is preferably 95 parts by mass or less, more preferably 80 parts by mass or less, even more preferably 50 parts by mass or less, and most preferably 35 parts by mass or less. Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR.

[0053] As the NR, for example, SIR20, RSS#3, TSR20, and other commonly used rubbers in the tire industry can be used. As the IR, there are no particular limitations, and for example, IR2200, and other commonly used rubbers in the tire industry can be used. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0054] The rubber composition used for the tread rubber 2A may further contain BR as necessary. In this case, the content of BR in 100 parts by mass of the rubber component is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, from the viewpoint of, for example, abrasion resistance. On the other hand, the upper limit of the BR content is not particularly limited, but is preferably 95 parts by mass or less, more preferably less than 40 parts by mass, even more preferably 30 parts by mass or less, and most preferably 20 parts by mass or less.

[0055] The weight-average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl bond content of the BR is, for example, more than 1% by mass and less than 30% by mass. The cis content of the BR is, for example, more than 1% by mass and less than 98% by mass. The trans content of the BR is, for example, more than 1% by mass and less than 60% by mass.

[0056] The BR is not particularly limited, and can be a BR with a high cis content (cis content of 90% or more), a BR with a low cis content, or a BR containing syndiotactic polybutadiene crystals. The BR can be either unmodified or modified, and examples of modified BR include modified BRs into which the above-mentioned functional groups have been introduced. These can be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0057] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0058] The rubber composition of the tread rubber 2A may also contain, as other rubber components, rubber (polymer) that is generally used in the manufacture of tires 1, such as nitrile rubber (NBR).

[0059] In this embodiment, the rubber composition of the tread rubber 2A preferably contains a filler. Specific examples of the filler include silica, carbon black, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Among these, silica and carbon black are preferably used as reinforcing agents. When silica is used, it is preferable to use it in combination with a silane coupling agent.

[0060] The rubber composition of the tread rubber 2A preferably contains silica. The BET specific surface area of the silica is preferably greater than 140 m2 / g, more preferably greater than 160 m2 / g, from the viewpoint of obtaining good durability. On the other hand, from the viewpoint of obtaining good rolling resistance, it is preferably less than 250 m2 / g, more preferably less than 220 m2 / g. Note that this BET specific surface area is the N2SA value measured by the BET method in accordance with ASTM D3037-93.

[0061] From the viewpoint of obtaining good reinforcement and improving durability, the average primary particle diameter of silica is preferably 22 nm or less, more preferably 18 nm or less. On the other hand, the lower limit is not particularly limited, but is preferably 10 nm or more. The average primary particle diameter of silica can be calculated by calculating the area of each primary particle image of silica observed by a transmission electron microscope (TEM) or the like in the rubber composition, and then averaging the values that approximate the diameters of circles having the same area.

[0062] When silica is used as a filler reinforcing agent, the content of silica per 100 parts by mass of the rubber component is preferably more than 35 parts by mass, more preferably more than 40 parts by mass, from the viewpoint of obtaining good durability. On the other hand, the upper limit of the silica content is not particularly limited, but is preferably less than 200 parts by mass, more preferably less than 150 parts by mass, more preferably less than 70 parts by mass, more preferably less than 65 parts by mass, and even more preferably less than 60 parts by mass.

[0063] Examples of silica include dry process silica (anhydrous silica) and wet process silica (hydrated silica). Of these, wet process silica is preferred because it contains a large number of silanol groups. In addition to silica made from these hydrated silicas, silica made from biomass materials such as rice husks may also be used.

[0064] As silica, for example, products from Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0065] The rubber composition of the tread rubber 2A preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include 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-dimethyl Examples of suitable silanes include sulfide-based silanes such as thiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These silanes may be used alone or in combination of two or more.

[0066] As the silane coupling agent, for example, products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used.

[0067] The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0068] The rubber composition of the tread rubber 2A preferably contains carbon black. The content of carbon black is, for example, more than 1 part by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0069] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon blacks) such as FT and MT; channel blacks (channel carbon blacks) such as EPC, MPC, and CC; and graphite. These may be used alone or in combination of two or more.

[0070] The nitrogen adsorption specific surface area (N2SA) of the carbon black is, for example, more than 30 m2 / g and less than 250 m2 / g. The dibutyl phthalate (DBP) absorption of the carbon black is, for example, more than 50 ml / 100 g and less than 250 ml / 100 g. The nitrogen adsorption specific surface area of the carbon black is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93.

[0071] Specific carbon blacks are not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks include those manufactured by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These may be used alone or in combination of two or more.

[0072] The rubber composition of the tread rubber 2A may further contain, in addition to carbon black and silica, fillers commonly used in the tire industry, such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these fillers is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0073] The rubber composition of the tread rubber 2A may contain oil (including extender oil) or liquid rubber as a softener. The total content of these is preferably more than 5 parts by mass per 100 parts by mass of the rubber component. The upper limit of the total content is preferably less than 70 parts by mass, more preferably less than 50 parts by mass, and even more preferably less than 30 parts by mass. The oil content includes the amount of oil contained in the rubber (oil-extended rubber).

[0074] Examples of oils include mineral oils (commonly referred to as process oils), vegetable oils, and mixtures thereof. Examples of mineral oils (process oils) that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. From the perspective of life cycle assessment, the oil may be, for example, machine oil or waste cooking oil used as a lubricant in a blender or automobile engine, as appropriate. These may be used alone or in combination of two or more.

[0075] Specific examples of process oils (mineral oils) that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and the like.

[0076] The liquid rubbers mentioned as softeners are polymers that are in a liquid state at room temperature (25°C) and contain the same monomers as solid rubbers. Examples of liquid rubbers include farnesene-based polymers, liquid diene-based polymers, and hydrogenated products thereof.

[0077] Examples of liquid diene polymers include liquid styrene butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene isoprene copolymer (liquid SIR).

[0078] The liquid diene polymer has a weight average molecular weight (Mw) measured by gel permeation chromatography (GPC) in terms of polystyrene of, for example, more than 1.0 × 10 and less than 2.0 × 10. In this specification, the Mw of the liquid diene polymer is a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

[0079] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0080] Furthermore, the rubber composition of the tread rubber 2A preferably contains a resin component as needed. The resin component may be solid or liquid at room temperature, and specific examples of the resin component include styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more of these may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, and more preferably less than 30 parts by mass, per 100 parts by mass of the rubber component.

[0081] Styrenic resins are polymers that use styrene monomers as constituent monomers, and examples thereof include polymers obtained by polymerizing styrene monomers as the main component (50% by mass or more). Specific examples of styrene resins include homopolymers obtained by polymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of styrene monomers and other monomers that can be copolymerized therewith.

[0082] Examples of other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids such as maleic anhydride or acid anhydrides thereof, and the like.

[0083] As the coumarone-based resin, a coumarone-indene resin is preferably used. The coumarone-indene resin is a resin containing coumarone and indene as monomer components constituting the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0084] The amount of the coumarone-indene resin per 100 parts by mass of the rubber component is, for example, more than 1.0 part by mass and less than 50.0 parts by mass.

[0085] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide, expressed in milligrams, required to neutralize acetic acid bonded to hydroxyl groups when acetylating 1 g of the resin, and is a value measured by potentiometric titration (JIS-K0070:1992).

[0086] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS-K6220-1:2001 is measured using a ring and ball softening point tester.

[0087] Examples of terpene resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are hydrocarbons represented by the formula (C5H8)n and their oxygen-containing derivatives, and are compounds with a basic skeleton of a terpene classified as monoterpene (C10H16), sesquiterpene (C15H24), diterpene (C20H32), etc. Examples include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0088] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds as raw materials, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins.

[0089] Examples of terpene phenols include resins obtained by copolymerizing a terpene compound with a phenolic compound, and resins obtained by hydrogenating such resins.Specific examples of terpene phenols include resins obtained by condensing a terpene compound, a phenolic compound, and formalin.

[0090] Examples of phenolic compounds include phenol, bisphenol A, cresol, xylenol, etc. Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by subjecting such resins to hydrogenation treatment.

[0091] The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

[0092] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 or 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as a C5 petroleum resin.

[0093] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified C9 resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples that are suitable for use include coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resin.

[0094] As the aromatic vinyl resin, a homopolymer of α-methylstyrene or styrene, or a copolymer of α-methylstyrene and styrene is preferred, and a copolymer of α-methylstyrene and styrene is more preferred, because they are economical, easy to process, and have excellent heat generation properties. As the aromatic vinyl resin, for example, commercially available products from Kraton Corporation, Eastman Chemical Company, etc. can be used.

[0095] "C5C9 resin" refers to a resin obtained by copolymerizing a C5 fraction and a C9 fraction, and may be a hydrogenated or modified resin. Examples of C5 fractions and C9 fractions include the petroleum fractions mentioned above. As the C5C9 resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used.

[0096] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0097] Examples of solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) with minimal use of secondary raw materials such as polymerization initiators, chain transfer agents, organic solvents, etc. In this specification, (meth)acrylic means methacrylic and acrylic.

[0098] Examples of monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0099] In addition, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative as a monomer component constituting the acrylic resin.

[0100] The acrylic resin may be a resin composed only of (meth)acrylic components, or a resin containing components other than (meth)acrylic components as constituent elements. The acrylic resin may also contain hydroxyl groups, carboxyl groups, silanol groups, etc.

[0101] As the resin component, for example, products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nitto Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Nippon Energy Corporation, Arakawa Chemical Industries, Ltd., Taoka Chemical Co., Ltd., etc. can be used.

[0102] The rubber composition of the tread rubber 2A preferably contains an antioxidant. The content of the antioxidant is, for example, more than 1 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component.

[0103] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants 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, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of such antioxidants include p-phenylenediamine antioxidants such as quinolone; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more.

[0104] As the antioxidant, for example, products from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis Co., Ltd., etc. can be used.

[0105] The rubber composition of the tread rubber 2A may contain stearic acid. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component. As the stearic acid, conventionally known stearic acids can be used, such as products from NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0106] The rubber composition of the tread rubber 2A may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 10 parts by mass per 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known one can be used, and for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0107] The rubber composition of the tread rubber 2A preferably contains wax. The content of the wax per 100 parts by mass of the rubber component is, for example, 0.5 parts by mass or more, preferably 1.0 parts by mass or more, and more preferably 1.5 parts by mass or more. The upper limit of the content of the wax per 100 parts by mass of the rubber component is, for example, 20 parts by mass or less, preferably 15 parts by mass or less, and more preferably 10 parts by mass or less.

[0108] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax; natural waxes such as plant wax and animal wax; and synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more.

[0109] As the wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0110] The rubber composition of the tread rubber 2A preferably contains a crosslinking agent such as sulfur, etc. The content of the crosslinking agent is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0111] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0112] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0113] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylenedithiosulfate dihydrate) manufactured by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by Lanxess, as well as organic peroxides such as dicumyl peroxide.

[0114] The rubber composition of the tread rubber 2A preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0115] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-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-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more.

[0116] In addition to these components, the rubber composition of the tread rubber 2A may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylic acid metal salts, organic peroxides, etc. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0117] The rubber composition of the tread rubber 2A preferably has a glass transition temperature Tg of −20° C. or higher. Such tread rubber 2A can exhibit rubber elasticity at any temperature, from room temperature to high temperatures. Therefore, the tire 1 of this embodiment can mitigate deformation of the tread portion 2 after high-speed running, making it easier to restore the original state, and can suppress the occurrence of flat spots in the tread portion 2.

[0118] Furthermore, such tread rubber 2A is likely to provide damping properties during rolling at room temperature or higher, and can improve the ride comfort performance of the tire 1 after high-speed running. Therefore, the tire 1 of this embodiment can improve durability and ride comfort performance after high-speed running.

[0119] Here, the glass transition temperature Tg of the rubber composition was determined as follows. First, a temperature distribution curve of tan δ was measured using an Iplexer series manufactured by GABO under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, a heating rate of 2°C / min, and an extension mode. The tan δ peak temperature corresponding to the largest tan δ value in the measured temperature distribution curve was determined as the glass transition temperature Tg. The rubber sample used to measure the glass transition temperature Tg was taken from the vulcanized tire 1, and was taken so that the longitudinal direction of the sample coincided with the circumferential direction of the tire 1.

[0120] The glass transition temperature Tg of the rubber composition can be adjusted appropriately by changing the glass transition temperature Tg of the rubber component contained in the rubber composition and the type and amount of plasticizer. Specifically, the glass transition temperature Tg of the rubber composition can be increased by reducing the amount of rubber components with low glass transition temperatures Tg, such as NR and BR, contained in the rubber component, and increasing the amount of rubber components with high glass transition temperatures Tg, such as SBR, or by increasing the glass transition temperature Tg of the plasticizer and increasing its blending amount. On the other hand, when lowering the glass transition temperature Tg of the rubber composition, this can be adjusted by reversing these steps.

[0121] The loss tangent tanδ of the tread rubber 2A at 30° C. is preferably 0.15 or less, more preferably 0.13 or less, and even more preferably 0.11 or less. Such a tread rubber 2A suppresses heat generation and helps improve the durability and ride comfort of the tread portion 2.

[0122] On the other hand, if the heat buildup of the tread rubber 2A is too low, there is a risk that the grip performance will not be sufficiently exhibited. From this viewpoint, the loss tangent tanδ of the tread rubber 2A at 30°C is preferably 0.06 or more, more preferably 0.07 or more, and even more preferably 0.08 or more.

[0123] The complex modulus E* of the tread rubber 2A at 30° C. is preferably 4.5 MPa or more, and more preferably 5.3 MPa or more. On the other hand, the upper limit of the complex modulus E* of the tread rubber 2A at 30° C. is preferably 10.0 MPa or less, and more preferably 7.6 MPa. Such a tread rubber 2A can improve steering stability and ride comfort in a well-balanced manner.

[0124] Here, the loss tangent tanδ and complex modulus E* of the tread rubber 2A at 30°C are values measured using a dynamic viscoelasticity measuring device (Iplexer series) manufactured by GABO under the following conditions in accordance with the provisions of JIS-K6394. The rubber sample used to measure the loss tangent tanδ and complex modulus E* was taken from the vulcanized tire 1, and was taken so that the longitudinal direction of the sample coincided with the circumferential direction of the tire 1. Initial strain: 5% Dynamic strain amplitude: ±1% Frequency: 10Hz Deformation mode: tension Measurement temperature: 30℃

[0125] The loss tangent tanδ and complex modulus E* at 30°C can be adjusted as appropriate by changing the glass transition temperature Tg of the tread rubber 2A and the types and amounts of various compounding agents. Specifically, the loss tangent tanδ can be increased by increasing the glass transition temperature Tg of the rubber composition, decreasing the average particle size of reinforcing agents such as carbon and silica, increasing the amount of reinforcing agents, decreasing the amount of vulcanizing agents such as sulfur and accelerators, etc. The complex modulus E* can also be increased by increasing the glass transition temperature Tg of the rubber composition, decreasing the average particle size of reinforcing agents such as carbon and silica, increasing the amount of reinforcing agents, decreasing the total amount of plasticizers, increasing the amount of vulcanizing agents such as sulfur and accelerators, etc.

[0126] Next, the band layer 8 of this embodiment will be described in detail.

[0127] The band layer 8 is preferably disposed radially outward of the belt layer 7. As described above, the band layer 8 of this embodiment includes at least one band ply 8A in which band cords 8a containing polyester fibers are arranged. In such a band layer 8, the band cords 8a have a high glass transition temperature Tg1, so that heat setting of the band cords 8a can be suppressed even when heat is generated during high-speed running.

[0128] Here, polyester fiber is polyester formed into a fibrous form. Polyester refers to a polycondensate synthesized by dehydration condensation of a polycarboxylic acid (dicarboxylic acid) and a polyalcohol (diol) to form an ester bond.

[0129] Examples of polyester fibers for the band cord 8a include polyethylene terephthalate (PET), polyethylene naphthalate (PEN), etc. Such band cord 8a is useful for improving the durability and ride comfort of the tire 1 after high-speed running.

[0130] The band ply 8A is composed of band cords 8a arranged at an angle of 5° or less with respect to the tire circumferential direction, for example. The band ply 8A is preferably configured as a so-called jointless band in which one band cord 8a is wound spirally in the tire circumferential direction.

[0131] As described above, the stress σ1 of the band cord 8a at 2.5% elongation is preferably 0.05 N / tex or more and 0.18 N / tex or less. When the stress σ1 of the band cord 8a at 2.5% elongation is 0.05 N / tex or more, if the tire 1 is a pneumatic tire, tension is more likely to be generated when a normal load is applied to the tire 1 in a normal state, and the durability of the tire 1 after high-speed driving can be improved.

[0132] By setting the stress σ1 of the band cord 8a at 2.5% elongation to 0.18 N / tex or less, excessive restraining force can be suppressed, and the ride comfort performance of the tire 1 after high-speed running can be improved. From this perspective, the stress σ1 of the band cord 8a at 2.5% elongation is more preferably 0.07 N / tex or more, and the upper limit is more preferably 0.15 N / tex or less.

[0133] As described above, the stress σ2 of the band cord 8a at 5.0% elongation is preferably 0.09 N / tex or more and 0.33 N / tex or less. Such a band cord 8a can increase the binding force of the tire 1, is less likely to elongate even during high-speed running, and is useful for improving the durability and ride comfort of the tire 1 after high-speed running. From this perspective, the stress σ2 of the band cord 8a at 5.0% elongation is more preferably 0.11 N / tex or more, and even more preferably 0.14 N / tex or more. On the other hand, the upper limit of the stress σ2 of the band cord 8a at 5.0% elongation is more preferably 0.28 N / tex or less, and even more preferably 0.21 N / tex or less.

[0134] Here, the stress σ1 at 2.5% elongation and the stress σ2 at 5.0% elongation of the band cord 8a are values obtained by dividing the forces at 2.5% and 5.0% elongation of the cord taken out of the tire 1 by the total fineness. The test method for these stresses σ1 and σ2 complies with JIS-L1017, Test Method for Chemical Fiber Tire Cords, 8.6, Test Method for Load at Constant Elongation. The total fineness of the cord used in this test is calculated for the cord taken out of the tire 1 by a method conforming to JIS-L1017, 8.3, Correct Fineness b).

[0135] The values of these stresses σ1 and σ2 can be adjusted by the temperature and / or tension in the DIP treatment process during cord production. Specifically, the values of stresses σ1 and σ2 can be increased by increasing the temperature in the DIP treatment process or the tension applied to the cord.

[0136] The stress σ2 of the band cord 8a at 5.0% elongation is preferably 1.5 times or more the stress σ1 at 2.5% elongation. Also, the stress σ2 of the band cord 8a at 5.0% elongation is preferably 2.5 times or less the stress σ1 at 2.5% elongation. Such a band cord 8a helps to improve the durability of the tire 1 after high-speed running.

[0137] 1 and 2, the product (σ2 × S) of the stress σ2 (N / tex) at 5.0% elongation of the band cord 8a of this embodiment and the styrene content S (parts by mass) in 100 parts by mass of the rubber component of the tread rubber 2A is 2.7 to 8.0. Generally, if the styrene content of the tread rubber 2A is low, heat generation during high-speed running is suppressed, and the band cord 8a tends to have a hard time exhibiting its hoop effect.

[0138] In the tread portion 2 of this embodiment, by specifying the product (σ2 × S) of the stress σ2 at 5.0% elongation of the band cord 8a and the styrene content S of the tread rubber 2A, the elongation of the band cord 8a is suppressed when the heat generation of the tread rubber 2A is low, thereby achieving a good balance between low heat generation and durability of the tire 1 during high-speed driving.

[0139] In this embodiment, the product (σ1 × tanδ) of the stress σ1 (N / tex) at 2.5% elongation of the band cord 8a and the loss tangent tanδ of the tread rubber 2A at 30° C. is 0.02 or less. Such a tread portion 2 can prevent heat from being transferred from the tread rubber 2A to the band cord while maintaining good ride comfort, and can improve the durability of the tire 1 after high-speed running.

[0140] From this viewpoint, the product (σ1 × tanδ) of the stress σ1 (N / tex) at 2.5% elongation of the band cord 8a and the loss tangent tanδ of the tread rubber 2A at 30°C is preferably 0.017 or less, more preferably 0.015 or less, and even more preferably 0.013 or less.

[0141] The band cord 8a of the present embodiment has a heat shrinkage stress σ3 of 0.01 N / tex or more at 100° C. Such a band cord 8a can prevent the high-temperature band cord 8a from becoming elongated after high-speed running, and can prevent the occurrence of flat spots in the tread portion 2.

[0142] Here, the thermal shrinkage stress σ3 of the band cord 8a is a value measured for two minutes at a temperature of 100°C based on the test method of ASTM D5591, after the band cord 8a to be measured is fixed at a length of 25 cm with an initial load of 20 g / cord, for the cord removed from the tire 1.

[0143] The thermal contraction stress σ3 of the band cord 8a can be adjusted by the temperature and / or tension in the DIP treatment process during cord production. Specifically, the thermal contraction stress σ3 can be increased by increasing the temperature in the DIP treatment process or the tension applied to the cord.

[0144] The value (S / σ3) obtained by dividing the styrene content S (parts by mass) in 100 parts by mass of the rubber component of the tread rubber 2A of this embodiment by the thermal shrinkage stress σ3 (N / tex) of the band cord 8a at 100°C is not more than 1000. Such a tread portion 2 increases the thermal shrinkage stress σ3 of the band cord 8a when heat generation in the tread rubber 2A is low, thereby achieving a good balance between low heat generation and durability of the tire 1 during high-speed running.

[0145] 2, the band ply 8A preferably includes a topping rubber 8b that covers the band cord 8a. Examples of the rubber component of the topping rubber 8b include isoprene-based rubber, butadiene-based rubber, styrene-butadiene rubber, nitrile rubber, and butyl rubber.

[0146] The total thickness of the band layer 8 in which the band cord 8a is covered with the topping rubber 8b is preferably 0.60 mm or more and 0.80 mm or less.

[0147] The total fineness D of the band cord 8a is preferably 1500 dtex or more and 3500 dtex or less. Such a band cord 8a helps to improve the durability and ride comfort performance of the tire 1 after high-speed running. From this viewpoint, the total fineness D of the band cord 8a is more preferably 2000 dtex or more and 3000 dtex or less.

[0148] The band cord 8a is, for example, a twisted wire formed by twisting together a plurality of filament yarns 8c. The filament yarns 8c may be, for example, monofilament yarns made of a single fiber, or multifilament yarns made of a plurality of thin fibers. The band cord 8a of this embodiment is formed by twisting together two multifilament yarns made of polyester fibers.

[0149] The band cord 8a of this embodiment is made only of polyester fiber. Here, "the cord is made only of polyester fiber" means that the substance that performs the function of the cord is made only of polyester fiber and does not contain other fibers, and does not exclude the inclusion of incidental components (for example, adhesives, etc.).

[0150] The band cord 8a may be a so-called hybrid cord in which a first filament yarn made of polyester fiber and a second filament yarn made of another fiber, such as nylon fiber, are twisted together. In this case, the first filament yarn and the second filament yarn may each be a monofilament yarn or a multifilament yarn.

[0151] In this case, it is desirable that the fineness D1 of the first filament yarn is larger than the fineness D2 of the second filament yarn. The fineness D1 of the first filament yarn is, for example, 101% or more and 105% or less of the fineness D2 of the second filament yarn. Such a band cord 8a is expected to have an excellent cost reduction effect.

[0152] The number of twists N1 per 100 mm of the band cord 8a is preferably 20 or more and 60 or less. Such a band cord 8a helps to improve the durability and ride comfort of the tire 1 after high-speed running. From this perspective, the number of twists N1 per 100 mm of the band cord 8a is more preferably 30 or more and 50 or less.

[0153] The band cord 8a of the present embodiment has a twist coefficient Nd, which is the value obtained by multiplying the number of twists N2 (turns) per 10 mm of the cord of the band cord 8a by the square root of the total fineness D (dtex), of equal to or greater than 200. Such a band cord 8a is subject to a smaller stress when stretched, so that the occurrence of flat spots can be more reliably suppressed and the durability of the tire 1 after high-speed running can be improved.

[0154] The band ply 8A preferably has an ends count, which is the number of cords per 5 cm of ply width in a cross section perpendicular to the longitudinal direction of the band cord 8a, of 40 to 60. Such a band ply 8A helps to improve the durability and ride comfort of the tire 1 after high-speed running.

[0155] As shown in Fig. 1, the carcass 6 is composed of, for example, one carcass ply 6A. The carcass ply 6A includes carcass cords and a topping rubber covering the carcass cords. The carcass cords are arranged at an angle of, for example, 75° or more and 90° or less with respect to the tire circumferential direction. Organic fiber cords such as nylon, polyester, or rayon are preferably used for the carcass cords.

[0156] The carcass ply 6A has, for example, a main body portion 6a and a turned-up portion 6b. The main body portion 6a desirably extends from the tread portion 2 through the sidewall portion 3 to the bead core 5 of the bead portion 4. The turned-up portion 6b, for example, is continuous with the main body portion 6a and is turned back around the bead core 5 from the axially inner side to the outer side, extending radially outward in the tire. For example, the carcass ply 6A may have a so-called ultra-high turn-up structure in which the end of the turned-up portion 6b reaches between the main body portion 6a and the belt layer 7.

[0157] The belt layer 7 includes, for example, two belt plies 7A and 7B. Each of the belt plies 7A and 7B includes, for example, belt cords arranged at an angle to the tire circumferential direction and a topping rubber covering the belt cords. Each belt cord is preferably inclined at an angle of 10° to 45° to the tire circumferential direction.

[0158] Although particularly preferred embodiments of the present disclosure have been described in detail above, the present disclosure is not limited to the above-described embodiments and can be modified and implemented in various forms. [Example]

[0159] Based on formulations 1 to 10 shown in Tables 3 and 4, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes at 140°C using a Banbury mixer to obtain a kneaded product. Sulfur and vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition.

[0160] The unvulcanized rubber composition thus obtained was used to form tread rubber, which was then arranged together with other tire components and vulcanized to form prototype tires having the basic structure shown in Figures 1 and 2, based on the specifications in Tables 1 and 2. The prototype tires were tested for durability and ride comfort after high-speed driving. The common specifications and test methods are as follows:

[0161] <Common specifications> Tire size: 215 / 60R16 Rim size: 16 x 6.5J Air pressure: 210kPa

[0162] <Durability after high-speed driving> The prototype tires were mounted on all wheels of a domestically produced front-wheel drive vehicle (2L engine displacement), and the vehicle was driven at 100 km / h for one hour. After leaving the vehicle stationary for at least 24 hours, the tires were mounted on a drum testing machine, and the speed was increased in steps of 10 km / h from 180 km / h under a vertical load of 5.88 N, and the time until the tire was damaged was measured. The results were expressed as an index, with Comparative Example 1 being set at 100, and the higher the index, the longer the time until damage and the better the durability after high-speed driving.

[0163] <Ride comfort after high-speed driving> The prototype tires were mounted on all wheels of a domestically produced front-wheel drive vehicle (2L engine displacement), and the vehicle was driven at 100 km / h for one hour. After leaving the vehicle stationary for at least 24 hours, the vehicle was driven at 100 km / h on a paved test course that included straight driving, cornering, and meandering turns. The test driver then evaluated the ride comfort performance of the vehicle on a scale of 1 to 5 based on his sense of touch. Similar tests were conducted by 20 test drivers, and the total score was calculated. The results were expressed as an index, with the total score of Comparative Example 1 being 100, and a higher index value indicates better ride comfort performance at high speeds.

[0164] The test results are shown in Tables 1 and 2. [Table 1]

[0165] [Table 2]

[0166] Here, tread rubber compounds 1 to 10 shown in Tables 1 and 2 are as shown in Tables 3 and 4 below.

[0167] [Table 3]

[0168] [Table 4]

[0169] As a result of the test, the tires of the examples were superior to the comparative examples in terms of ride comfort and durability after high-speed driving, and the overall performance, which is determined by the sum of the individual performance values, was also good, confirming that it was possible to achieve both ride comfort and durability after high-speed driving.

[0170] [Note] The present disclosure includes the following aspects.

[0171] [Disclosure 1] A tire having a tread portion, the tread portion having tread rubber forming a contact surface with the tire, and a band layer arranged radially inward of the tread rubber, the band layer including at least one band ply in which band cords made of polyester fibers are arranged, the band cords having a stress of 0.05 N / tex or more and 0.18 N / tex or less at 2.5% elongation and a stress of 0.09 N / tex or more and 0.33 N / tex or less at 5.0% elongation, the tread rubber being made of a rubber composition containing styrene and having a glass transition point of -20°C or higher, and the styrene content in 100 parts by mass of the rubber component of the tread rubber being 25 parts by mass or less.

[0172] [Disclosure 2] The tire according to Disclosure 1, wherein the styrene content in 100 parts by mass of the rubber component of the tread rubber is 20 parts by mass or less.

[0173] [Disclosure 3] The tire according to Disclosure 1 or 2, wherein the stress of the band cord at 5.0% elongation is 0.11 N / tex or more and 0.28 N / tex or less.

[0174] [Disclosure 4] The tire according to any one of Disclosures 1 to 3, wherein the product of the stress (N / tex) of the band cord at 5.0% elongation and the styrene content (parts by mass) in 100 parts by mass of the rubber component of the tread rubber is 2.7 or more and 8.0 or less.

[0175] [Disclosure 5] The tire according to any one of Disclosures 1 to 4, wherein the band cord has a twist coefficient, which is the value obtained by multiplying the number of twists (turns) per 10 mm of the band cord by the square root of the total fineness (dtex), of 200 or more.

[0176] [Disclosure 6] The tire according to any one of Disclosures 1 to 5, wherein the band cord has a heat shrinkage stress at 100°C of 0.01 N / tex or more.

[0177] [Disclosure 7] The tire according to any one of Disclosures 1 to 6, wherein the value obtained by dividing the styrene content (parts by mass) in 100 parts by mass of the rubber component of the tread rubber by the thermal shrinkage stress (N / tex) of the band cord at 100°C is 1000 or less. [Explanation of symbols]

[0178] 1 tire 2 Tread section 2A Tread rubber 2a Ground plane 8 Band Layer 8A Band Ply 8a band cord

Claims

1. A tire having a tread portion, The tread portion has a tread rubber that forms a contact surface with the ground and a band layer that is disposed on the inner side of the tread rubber in the tire radial direction, The band layer includes at least one band ply in which band cords made of polyester fibers are arranged, The band cord has a stress of 0.05 N / tex or more and 0.18 N / tex or less at 2.5% elongation, and a stress of 0.09 N / tex or more and 0.33 N / tex or less at 5.0% elongation, the tread rubber is made of a rubber composition containing styrene and having a glass transition point of −20° C. or higher; The styrene content in 100 parts by mass of the rubber component of the tread rubber is 25 parts by mass or less, The band cord has a twist coefficient, which is the value obtained by multiplying the number of twists (turns) per 10 mm of the band cord by the square root of the total fineness (dtex), of 200 or more. tire.

2. A tire having a tread portion, The tread portion has a tread rubber that forms a contact surface with the ground and a band layer that is disposed on the inner side of the tread rubber in the tire radial direction, The band layer includes at least one band ply in which band cords made of polyester fibers are arranged, The band cord has a stress of 0.05 N / tex or more and 0.18 N / tex or less at 2.5% elongation, and a stress of 0.09 N / tex or more and 0.33 N / tex or less at 5.0% elongation, the tread rubber is made of a rubber composition containing styrene and having a glass transition point of −20° C. or higher; The styrene content in 100 parts by mass of the rubber component of the tread rubber is 25 parts by mass or less, The band cord has a heat shrinkage stress of 0.01 N / tex or more at 100°C. tire.

3. A tire having a tread portion, The tread portion has a tread rubber that forms a contact surface with the ground and a band layer that is disposed on the inner side of the tread rubber in the tire radial direction, The band layer includes at least one band ply in which band cords made of polyester fibers are arranged, The band cord has a stress of 0.05 N / tex or more and 0.18 N / tex or less at 2.5% elongation, and a stress of 0.09 N / tex or more and 0.33 N / tex or less at 5.0% elongation, the tread rubber is made of a rubber composition containing styrene and having a glass transition point of −20° C. or higher; The styrene content in 100 parts by mass of the rubber component of the tread rubber is 25 parts by mass or less, a value obtained by dividing the styrene content (parts by mass) in 100 parts by mass of the rubber component of the tread rubber by the heat shrinkage stress (N / tex) of the band cord at 100°C is 1,000 or less; tire.

4. The tire according to claim 1 , wherein the styrene content in 100 parts by mass of the rubber component of the tread rubber is 20 parts by mass or less.

5. The tire according to any one of claims 1 to 4, wherein the stress of the band cord at 5.0% elongation is 0.11 N / tex or more and 0.28 N / tex or less.

6. 6. The tire according to claim 1, wherein a product of a stress (N / tex) of the band cord at 5.0% elongation and the styrene content (parts by mass) in 100 parts by mass of a rubber component of the tread rubber is 2.7 or more and 8.0 or less.

Images