Tire

Abstract

The present invention addresses the problem of providing a tire in which the persistence of wet grip performance after the elapse of time is improved. A tire provided with: a tread surface in which the content of a polymer having an ethylene unit in 100% by mass of a rubber component is 50% by mass or more; the resin content Rc (parts by mass) and the oil content Oc (parts by mass) per 100 parts by mass of the rubber component in the tread surface, and the oil content Ob (parts by mass) per 100 parts by mass of the rubber component in the tread base portion satisfy the following formula (1). (1) Rcgt; oc > = Ob.

Description

Technical Field

[0001] The present invention relates to tires. Background Art

[0002] Tires have been required to have various properties such as wet grip performance. Recently, from the perspective of environmental concerns, it is desired to maintain wet grip performance for a long period of time. Summary of the invention [Problems to be solved by the invention]

[0003] An object of the present invention is to solve the above-mentioned problems and to provide a tire having improved sustainability of wet-grip performance over time.

Methods for solving the problem

[0004] The present invention is a tire having a tread cap and a tread base. In the cap tread, the content of the polymer having ethylene units in 100% by mass of the rubber component is 50% by mass or more, The resin content Rc (parts by mass) and the oil content Oc (parts by mass) in the cap tread relative to 100 parts by mass of the rubber component and the oil content Ob (parts by mass) in the base tread relative to 100 parts by mass of the rubber component satisfy the following formula (1). (1)Rc>Oc≥Ob [Effects of the Invention]

[0005] The present invention is a tire having a tread surface and a base tread, wherein the content of a polymer having ethylene units in the tread surface is 50% by mass or more in 100% by mass of the rubber component and satisfies the above formula (1), thereby improving the sustainability of wet grip performance over time. BRIEF DESCRIPTION OF THE DRAWINGS

[0006]

Figure 1

Figure 2

[0007] The above-mentioned tire comprises a tread running surface and a tread base portion, and the content of polymers having ethylene units in 100% by mass of the rubber component in the tread running surface is 50% by mass or more, and the resin content Rc (parts by mass) and oil content Oc (parts by mass) in the tread running surface relative to 100 parts by mass of the rubber component and the oil content Ob (parts by mass) in the tread base portion relative to 100 parts by mass of the rubber component satisfy the formula (1) "Rc>Oc≥Ob".

[0008] The reason why the above-mentioned effects are obtained by the tire is not necessarily clear, but is presumed as follows. The polymer having ethylene units has fewer double bonds than styrene butadiene rubber, butadiene rubber, and the like, and has good physical properties after heat aging. Therefore, in a cap tread containing a polymer having such ethylene units at or above a certain level, by making the blended resin content (Rc) larger than the oil content (Oc), the change with time in the hardness Hs due to oil penetration becomes smaller. Furthermore, by making the content of oil in the cap tread (Oc) larger than the content of oil in the base tread (Ob), the change in hardness Hs over time due to oil penetration can be further suppressed. Based on the above mechanism, it is estimated that the sustainability of the wet grip performance of the rear tire is improved over time.

[0009] The tire has a cap tread and a base tread. The cap tread is composed of a rubber composition for a cap tread, and the base tread is composed of a rubber composition for a base tread.

[0010] Chemical substances that can be commonly used in the rubber composition for cap treads and the rubber composition for base treads are described below.

[0011] The rubber composition for a cap tread and the rubber composition for a base tread contain a rubber component. Here, the rubber component is a component that contributes to crosslinking, and generally, a polymer component that cannot be extracted by acetone among polymers having a weight average molecular weight (Mw) of 10,000 or more corresponds to the rubber component. The rubber component is in a solid state at room temperature (25°C).

[0012] The weight average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, further preferably 200,000 or more, particularly preferably 270,000 or more, and preferably 2,000,000 or less, more preferably 1,500,000 or less, further preferably 1,000,000 or less. Within the above range, there is a tendency to obtain better effects.

[0013] In this specification, the weight average molecular weight (Mw) can be determined by converting to standard polystyrene based on the measured value using gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, chromatographic column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation).

[0014] The rubber component that can be used for the rubber composition for cap treads and the rubber composition for base treads may be either an unmodified rubber or a modified rubber. Examples of modified rubbers include rubbers having functional groups that interact with fillers such as silica, etc. For example, examples include terminal-modified rubbers in which at least one terminal of the rubber is modified by a compound (modifier) ​​having the above functional group (terminal-modified rubber having the above functional group at the terminal), main chain-modified rubbers having the above functional group on the main chain, main chain-terminal-modified rubbers having the above functional group on the main chain and the terminal (for example, main chain-terminal-modified rubbers having the above functional group on the main chain and at least one terminal modified by the above modifier), and terminal-modified rubbers modified (coupled) by a multifunctional compound having two or more epoxy groups in the molecule and into which a hydroxyl group or epoxy group is introduced.

[0015] As the functional group, for example, amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazole, urea, ether, carbonyl, oxycarbonyl, mercapto, sulfide, disulfide, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imido, hydrazine, azo, diazo, carboxyl, nitrile, pyridyl, cycloalkyloxy, hydroxyl, oxy, epoxy, etc. can be mentioned. In addition, these functional groups may also have a substituent. Among them, amino (preferably an amino group in which the hydrogen atom of the amino group is substituted by an alkyl group having 1 to 6 carbon atoms), alkoxy (preferably an alkoxy group having 1 to 6 carbon atoms), alkoxysilyl (preferably an alkoxysilyl group having 1 to 6 carbon atoms) are preferred.

[0016] Examples of the rubber component include diene rubber.

[0017] As diene rubber, isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene-isoprene-butadiene rubber (SIBR), ethylene-propylene rubber (EPDM), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR) etc. can be cited. In addition, as rubber component, butyl rubber, fluororubber etc. can also be cited. These can be used alone or in combination of two or more. In addition, these rubber components can be modified, hydrogenated, or can use expanded rubber that has been expanded by oil, resin, liquid rubber component etc. Among diene rubber, isoprene rubber, BR, SBR are preferred. Among them, the cap tread preferably contains at least isoprene-based rubber. The base tread preferably contains at least one of isoprene-based rubber and butadiene rubber, and more preferably contains isoprene-based rubber and butadiene rubber.

[0018] As isoprene-based rubber, natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, modified IR, etc. can be listed. As NR, for example, SIR20, RSS#3, TSR20, etc., which are commonly used in the tire industry, can be used. As IR, there is no particular limitation, and for example, IR2200, etc., which are commonly used in the tire industry, can be used. As modified NR, deproteinized natural rubber (DPNR), high-purity natural rubber, etc. can be listed, as modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. can be listed, as modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. can be listed. These can be used alone or in combination of two or more.

[0019] BR is not particularly limited, and for example, high cis BR with a high cis content, BR containing syndiotactic polybutadiene crystals, BR synthesized using a rare earth catalyst (rare earth BR), etc. can be used. These can be used alone or in combination of two or more. Among them, BR preferably contains a high cis BR with a cis content of 90% by mass or more. The cis content is more preferably 95% by mass or more. In addition, the cis content can be measured by infrared absorption spectrometry.

[0020] When there is one type of BR, the cis content of BR refers to the cis content of the BR, and when there are multiple types of BR, the cis content of BR refers to the average cis content. The average cis content of BR can be calculated by {Σ(content of each BR×cis content of each BR)} / total content of all BRs. For example, when BR with a cis content of 90% by mass is 20% by mass and BR with a cis content of 40% by mass is 10% by mass in 100% by mass of the rubber component, the average cis content of BR is 73.3% by mass (=(20×90+10×40) / (20+10)).

[0021] In addition, BR may be either unmodified BR or modified BR. As the modified BR, there may be mentioned a modified BR into which the same functional group as the modified rubber is introduced. In addition, a hydrogenated butadiene polymer (hydrogenated BR) may be used as the BR.

[0022] The SBR is not particularly limited, and for example, emulsion polymerized styrene butadiene rubber (E-SBR), solution polymerized styrene butadiene rubber (S-SBR), etc. can be used. These can be used alone or in combination of two or more.

[0023] The styrene content of SBR is preferably 5% by mass or more, more preferably 20% by mass or more, and further preferably 25% by mass or more. The styrene content is preferably 60% by mass or less, more preferably 40% by mass or less, and further preferably 35% by mass or less. Within the above range, there is a tendency to obtain better effects. In addition, in this specification, the styrene content can be 1 The measurement was carried out by H-NMR measurement.

[0024] When there is one type of SBR, the styrene content of the SBR refers to the styrene content of the SBR, and when there are multiple types of SBR, the styrene content of the SBR refers to the average styrene content. The average styrene content of SBR can be calculated by {Σ(content of each SBR×styrene content of each SBR)} / total content of all SBRs. For example, when SBR with a styrene content of 40% by mass is 85% by mass and SBR with a styrene content of 25% by mass is 5% by mass in 100% by mass of the rubber component, the average styrene content of SBR is 39.2% by mass (=(85×40+5×25) / (85+5)).

[0025] The vinyl bonding amount of SBR is preferably 3% by mass or more, more preferably 5% by mass or more, and further preferably 7% by mass or more. The vinyl bonding amount is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less. Within the above range, there is a tendency to obtain better effects. In addition, in this specification, the vinyl bond amount (1,2-bonded butadiene unit amount) can be measured by infrared absorption spectroscopic analysis.

[0026] The vinyl content (1,2-bonded butadiene unit amount) of SBR is the ratio of vinyl bonds (unit: mass %) when the total mass of the butadiene part in SBR is set to 100, and the vinyl content [mass %] + cis mass [mass %] + trans mass [mass %] = 100 [mass %]. When there is one type of SBR, it indicates the vinyl content of the SBR, and when there are multiple types, it indicates the average vinyl content. The average vinyl content of SBR can be calculated by 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, in 100 parts by mass of the rubber component, SBR with a styrene content of 40% by mass and a vinyl content of 30% by mass is 75 parts by mass, and SBR with a styrene content of 25% by mass is 75 parts by mass. When the amount of SBR containing 10 parts by mass of SBR and 20 parts by mass of SBR having a vinyl content of 20% is 15 parts by mass, and the remaining 10 parts by mass of non-SBR, the average vinyl content of 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%])}).

[0027] The SBR may be either unmodified SBR or modified SBR. Examples of the modified SBR include modified SBRs into which the same functional groups as those of the modified rubber are introduced.

[0028] Examples of the rubber component include a rubber having an ethylene unit (a structural unit composed of ethylene: -CH 2 -CH 2 -) polymers. In this patent, the polymer having ethylene units used for the tread is a polymer having high molecular weight ethylene units, which is a component that cannot be extracted from the rubber composition after vulcanization by organic solvents such as acetone, and is used as a rubber component. In addition, the polymer having high molecular weight ethylene units preferably has a weight average molecular weight of the above-mentioned rubber component.

[0029] The polymer having ethylene units is not particularly limited as long as it is a polymer having ethylene units, but a multi-component copolymer containing ethylene units, conjugated diene units, and aromatic vinyl units is preferred from the viewpoint of obtaining good effects.

[0030] In the above multi-component copolymer, the conjugated diene unit is a structural unit derived from a conjugated diene compound. Examples of the conjugated diene compound include 1,3-butadiene, isoprene, 1,3-pentadiene, 2,3-dimethylbutadiene, 2-phenyl-1,3-butadiene, and 1,3-hexadiene. These may be used alone or in combination of two or more, preferably 1,3-butadiene and isoprene, and more preferably 1,3-butadiene.

[0031] In the above multi-component copolymer, the aromatic vinyl unit is a structural unit derived from an aromatic vinyl compound. Examples of the aromatic vinyl compound include styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, vinylethylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc. These may be used alone or in combination of two or more, preferably styrene and α-methylstyrene, and more preferably styrene.

[0032] The above-mentioned multi-polymer can be prepared by, for example, a method for copolymerizing ethylene, a conjugated diene compound and an aromatic vinyl compound, or by converting a portion of the conjugated diene units into non-conjugated olefin units by hydrogenation after copolymerizing a conjugated diene compound and an aromatic vinyl compound, or a copolymer of a conjugated diene compound and an aromatic vinyl compound, or a hydride (hydrogenated copolymer) of a copolymer of ethylene, a conjugated diene compound and an aromatic vinyl compound. These can be used alone or in combination with more than two kinds. Wherein, based on the viewpoint that the effect can be obtained better, the hydride of the copolymer of a conjugated diene compound and an aromatic vinyl compound is preferably a hydrogenated styrene-butadiene copolymer.

[0033] When preparing the above multi-component copolymer, the polymerization method is not particularly limited, and it may be random polymerization or block polymerization, and random polymerization is preferred.

[0034] When the multi-polymer is a hydrogenated copolymer, the method and reaction conditions of hydrogenation are not particularly limited, as long as the hydrogenation is carried out by a known method and under known conditions. It is usually carried out at 20 to 150°C, 0.1 to 10 MPa of hydrogen pressure, and in the presence of a hydrogenation catalyst. Other methods and conditions related to the preparation are not particularly limited, and for example, the contents described in International Publication No. 2016 / 039005 can be applied.

[0035] In the rubber composition for tread, the content of the polymer having the above-mentioned ethylene unit in 100% by mass of the rubber component is 50% by mass or more, preferably 60% by mass or more, more preferably 65% ​​by mass or more, and further preferably 70% by mass or more. The upper limit is not particularly limited, and can be 100% by mass, preferably 95% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less. Within the above range, there is a tendency to obtain a good effect.

[0036] In the rubber composition for cap tread, the content of isoprene-based rubber in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 15% by mass or more, and further preferably 20% by mass or more, and is preferably 50% by mass or less, more preferably 40% by mass or less, and further preferably 30% by mass or less. Within the above range, there is a tendency to obtain good effects.

[0037] In the rubber composition for a base tread, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 60% by mass or more, more preferably 65% ​​by mass or more, and further preferably 75% by mass or more, and is preferably 95% by mass or less, more preferably 90% by mass or less, and further preferably 85% by mass or less. Within the above range, there is a tendency that the effect is well obtained.

[0038] In the rubber composition for a base tread, the content of BR in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and further preferably 15% by mass or more, and is preferably 40% by mass or less, more preferably 30% by mass or less, and further preferably 25% by mass or less. Within the above range, there is a tendency to obtain good effects.

[0039] The rubber composition for cap treads and the rubber composition for base treads preferably contain a plasticizer. In the present specification, a plasticizer is a material that imparts plasticity to a rubber component, and may be liquid or solid at room temperature (25° C.) These may be used alone or in combination of two or more.

[0040] Examples of the plasticizer include oils, liquid polymers, and resins, etc. These may be used alone or in combination of two or more.

[0041] As the above-mentioned oil, there is no particular limitation, and conventionally known oils such as paraffinic process oil, aromatic process oil, naphthenic process oil, low PCA (polycyclic aromatic) process oils such as TDAE and MES, oils of plant origin, and mixtures thereof can be used. These can be used alone or in combination of two or more. In addition, based on the viewpoint of life cycle assessment (Life Cycle Assessment), lubricating oils used in rubber mixers, automobile engines, etc., and discarded edible oils can also be appropriately used.

[0042] Examples of the plant-derived oils (also referred to as 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 oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia oil, and tung oil.

[0043] As the above oil, for example, products of Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Manufacturing Co., Ltd., Showa Shell Sekiyu Co., Ltd., Fuji Kosan Co., Ltd., Nissin OilliO Group Co., Ltd., etc. can be used.

[0044] As the above-mentioned liquid polymer, for example, liquid diene polymers (liquid rubber) and liquid farnesene polymers at 25° C. can be cited. As liquid rubber, liquid styrene butadiene copolymers (liquid SBR), liquid butadiene polymers (liquid BR), liquid isoprene polymers (liquid IR), liquid styrene isoprene copolymers (liquid SIR), liquid styrene butadiene styrene block copolymers (liquid SBS block polymers), liquid styrene isoprene styrene block copolymers (liquid SIS block polymers) can be cited. Even if their ends and main chains are modified on polar groups, it is also possible to use their hydrides.

[0045] The weight average molecular weight (Mw) of the liquid diene polymer measured by gel permeation chromatography (GPC) in terms of polystyrene is preferably 1.0×10 3 ~5.0×10 4 , more preferably 3.0×10 3 ~1.5×10 4 The lower limit or upper limit of the Mw of the liquid diene polymer may be 4500 or 8500. In the present specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0046] As the liquid diene polymer, for example, products produced by Sartomer Co., Ltd. and Kuraray Co., Ltd. can be used.

[0047] As the above-mentioned resin, a resin commonly used as a tire mixture can be used, which can be liquid or solid at room temperature (25°C). For example, aromatic vinyl polymers, coumarone-indene resins, coumarone resins, indene resins, phenolic resins, rosin resins, petroleum resins, terpene resins, acrylic (ester) resins, etc. can be mentioned. These can be used alone or in combination of two or more. In addition, the resin itself can also be copolymerized from monomer components of multiple sources. Among them, hydrogenated resins are preferred from the viewpoint of being able to obtain good effects. In addition, aromatic vinyl polymers, petroleum resins, terpene resins and their hydrogenated resins are also preferred.

[0048] The mechanism by which the effect is better obtained when a hydrogenated resin is used is not clear, but it is speculated that the compatibility with the polymer having the ethylene unit is increased, oil bleeding is suppressed, and the change in hardness Hs after heat aging is suppressed, thereby improving the performance sustainability of wet grip performance.

[0049] When a resin that is solid at room temperature is used, the softening point of the resin is preferably 50° C. or higher, more preferably 55° C. or higher, further preferably 60° C. or higher, and particularly preferably 85° C. or higher. In addition, it is preferably 160° C. or lower, more preferably 150° C. or lower, further preferably 140° C. or lower, further preferably 120° C. or lower, and particularly preferably 100° C. or lower. Within the above range, there is a tendency for better effects to be obtained. When the resin is liquid at room temperature, the softening point is preferably 20° C. or lower, preferably 10° C. or lower, and preferably 0° C. or lower. The softening point of the hydrogenated resin is also preferably the same as above. The softening point of the resin is a softening point specified in JIS K6220-1:2001 measured by a softening point measuring device, and is a temperature at which a ball falls.

[0050] The aromatic vinyl polymer is a polymer containing an aromatic vinyl monomer as a structural unit, and examples thereof include resins obtained by polymerizing α-methylstyrene and / or styrene, and specifically include homopolymers of styrene (styrene resins), homopolymers of α-methylstyrene (α-methylstyrene resins), copolymers of α-methylstyrene and styrene, and copolymers of styrene and other monomers.

[0051] The coumarone-indene resin is a resin containing coumarone and indene as the main monomer components constituting the backbone (main chain) of the resin. In addition to coumarone and indene, monomer components contained in the backbone include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0052] The coumarone resin is a resin containing coumarone as a main monomer component constituting the skeleton (main chain) of the resin.

[0053] The indene resin is a resin containing indene as a main monomer component constituting the skeleton (main chain) of the resin.

[0054] As the phenolic resin, for example, known polymers obtained by reacting phenol with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or base catalyst can be used. Among them, those obtained by reacting with an acid catalyst (such as novolac-type phenolic resin) are preferred.

[0055] Examples of the rosin resin include rosin-based resins represented by natural rosin, polymerized rosin, modified rosin, ester compounds thereof, and hydrogenated products thereof.

[0056] Examples of the petroleum resin include C5 resins, C9 resins, C5 / C9 resins, dicyclopentadiene (DCPD) resins, C9 / DCPD resins, and hydrogenates thereof, among which DCPD resins, hydrogenated DCPD resins, C9 / DCPD resins, and C9 / hydrogenated DCPD resins are preferred.

[0057] The terpene resin is a polymer containing terpene as a structural unit. For example, polyterpene resins obtained by polymerization of terpene compounds, aromatic modified terpene resins obtained by polymerization of terpene compounds and aromatic compounds, etc. can be cited. As the aromatic modified terpene resin, terpene phenol resins using the terpene compounds and phenolic compounds as raw materials, terpene styrene resins using the terpene compounds and styrene compounds as raw materials, and terpene phenol styrene resins using terpene compounds, phenolic compounds and styrene compounds as raw materials can be cited. In addition, as terpene compounds, α-pinene, β-pinene, etc. can be cited, as phenolic compounds, phenol, bisphenol A, etc. can be cited, and as aromatic compounds, styrene compounds (styrene, α-methylstyrene, etc.) can be cited. Among them, aromatic modified terpene resins are preferred.

[0058] The acrylic resin is a polymer containing an acrylic monomer as a structural unit. Examples thereof include styrene acrylic resins such as styrene acrylic resins obtained by copolymerizing a carboxyl group, an aromatic vinyl monomer component and an acrylic monomer component. Among them, solvent-free carboxyl-containing styrene acrylic resins are preferably used.

[0059] As the resin, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical, ExxonMobil, KRATON, Nippon Paint Chemicals Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used.

[0060] As the plasticizer, from the viewpoint of sustainability, it is preferred to use a plant-derived plasticizer such as the above-mentioned plant-derived oil and farnesene-based polymer.

[0061] Farnesene polymers refer to polymers obtained by polymerizing farnesene, and have structural 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), and (E)-β-farnesene having the following structure is preferred.

Chemical formula 1

[0062] Farnesene polymers can be homopolymers of farnesene (farnesene homopolymers), or copolymers of farnesene and vinyl monomers (farnesene-vinyl monomer copolymers). These can be used alone or in combination of two or more. Among them, copolymers of farnesene and vinyl monomers are preferred.

[0063] As the vinyl monomer, styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, 4-tert-butylstyrene, 5-tert-butyl-2-methylstyrene, vinylethylbenzene, divinylbenzene, trivinylbenzene, divinylnaphthalene, tert-butylstyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N,N-dimethylaminoethylstyrene, N,N-dimethylaminomethylstyrene, 2-ethylstyrene, 3-ethylstyrene, 4-ethylstyrene, 2-tert-butylstyrene, 3-tert-butylstyrene, 4-tert-butylstyrene, vinylxylene, vinylnaphthalene, vinyltoluene, vinylpyridine, diphenylethylene, aromatic vinyl compounds such as diphenylethylene containing tertiary amino groups, and conjugated diene compounds such as butadiene and isoprene can be listed. These can be used alone or in combination of two or more. Among them, butadiene is preferred. That is, as the farnesene-vinyl monomer copolymer, a copolymer of farnesene and butadiene (farnesene-butadiene copolymer) is preferred.

[0064] In the farnesene-vinyl monomer copolymer, the mass standard copolymerization ratio of farnesene to vinyl monomer (farnesene / vinyl monomer) is preferably 40 / 60 to 90 / 10.

[0065] The farnesene polymer preferably has a weight average molecular weight (Mw) of 3000 or more and 300,000 or less. The Mw of the farnesene polymer is preferably 8000 or more, more preferably 10000 or more, and preferably 100,000 or less, more preferably 60,000 or less, and further preferably 50,000 or less. Within the above range, there is a tendency to obtain better effects.

[0066] The farnesene polymer may be in a liquid state or a solid state at room temperature (25° C.), and among them, a liquid farnesene polymer that is in a liquid state at room temperature (25° C.) is preferred.

[0067] In the rubber composition for cap tread, the content Pc (total amount of plasticizer) of the plasticizer is preferably 40 parts by mass or more, more preferably 45 parts by mass or more, further preferably 50 parts by mass or more, further preferably 60 parts by mass or more, and preferably 100 parts by mass or less, more preferably 80 parts by mass or less, further preferably 75 parts by mass or less, relative to 100 parts by mass of the rubber component. The lower limit is not particularly limited, and within the above range, there is a tendency to obtain better effects. It should be noted that the content of the plasticizer also includes the amount of oil and resin contained in the oil-extended rubber and the resin-extended rubber.

[0068] In the rubber composition for cap tread, the content of the solid plasticizer in a solid state at room temperature (25° C.) is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 35 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and further preferably 50 parts by mass or less. Within the above range, there is a tendency to obtain better effects.

[0069] In the rubber composition for tread, the content of the liquid plasticizer in a liquid state at room temperature (25°C) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 25 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, further preferably 35 parts by mass or less, relative to 100 parts by mass of the rubber component. If it is within the above range, there is a tendency to be able to obtain better effects. In addition, the content of the liquid plasticizer also includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin of the resin-extended rubber that has been expanded with the liquid resin.

[0070] In the rubber composition for tread, the content Rc (total amount of the resin) of the above resin is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and further preferably 35 parts by mass or more, and is preferably 80 parts by mass or less, more preferably 60 parts by mass or less, and further preferably 50 parts by mass or less, relative to 100 parts by mass of the rubber component. If it is within the above range, there is a tendency to obtain better effects.

[0071] In the rubber composition for cap tread, the oil content Oc (total amount of oil) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, further preferably 20 parts by mass or more, particularly preferably 25 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, further preferably 35 parts by mass or less, relative to 100 parts by mass of the rubber component. Within the above range, there is a tendency to obtain better effects. In addition, the oil content also includes the amount of oil contained in the oil-extended rubber.

[0072] In the rubber composition for base tread, the content Pb of the plasticizer (total amount of the plasticizer) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and further preferably 10 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less. Within the above range, there is a tendency that the effect can be better obtained. The content of the plasticizer also includes the amount of oil or resin contained in the oil-extended rubber or the resin-extended rubber.

[0073] In the rubber composition for base tread, the content of the solid plasticizer in a solid state at room temperature (25° C.) is preferably 20 parts by mass or less, more preferably 10 parts by mass or less, further preferably 5 parts by mass or less, and may be 0 parts by mass or less, relative to 100 parts by mass of the rubber component. Within the above range, there is a tendency to obtain better effects.

[0074] In the rubber composition for base tread, the content of the liquid plasticizer in a liquid state at room temperature (25° C.) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and further preferably 10 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less. Within the above range, there is a tendency that the effect can be better obtained. In addition, the content of the liquid plasticizer also includes the amount of oil contained in the oil-extended rubber and the amount of liquid resin in the resin-extended rubber that has been extended with the liquid resin.

[0075] In the rubber composition for base tread, the oil content Ob (total amount of oil) is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and further preferably 10 parts by mass or more, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 20 parts by mass or less, relative to 100 parts by mass of the rubber component. Within the above range, there is a tendency that the effect can be better obtained. It should be noted that the oil content also includes the amount of oil contained in the oil-extended rubber.

[0076] In the above-mentioned tire, the resin content Rc (mass parts) in the rubber composition for the tread relative to 100 mass parts of the rubber component, the oil content Oc (mass parts) in the rubber composition for the tread relative to 100 mass parts of the rubber component, and the oil content Ob (mass parts) in the rubber composition for the base tread relative to 100 mass parts of the rubber component satisfy the following formula (1). (1)Rc>Oc≥Ob

[0077] Rc / Oc is preferably 1.1 or more, more preferably 1.2 or more, further preferably 1.3 or more, and further preferably 1.4 or more. The upper limit of Rc / Oc is not particularly limited, but is preferably 3.0 or less, more preferably 2.0 or less, further preferably 1.7 or less, and further preferably 1.5 or less. Within the above range, there is a tendency to obtain better effects.

[0078] Oc / Ob is preferably 1.0 or more, more preferably 1.5 or more, further preferably 2.0 or more, and further preferably 2.5 or more. The upper limit of Oc / Ob is not particularly limited, but is preferably 4.0 or less, more preferably 3.5 or less, and further preferably 3.0 or less. Within the above range, there is a tendency to obtain better effects.

[0079] Rc / Ob is preferably 2.5 or more, more preferably 3.0 or more, further preferably 3.3 or more, and further preferably 3.5 or more. The upper limit of Rc / Ob is not particularly limited, but is preferably 8.0 or less, more preferably 7.5 or less, further preferably 7.0 or less, and further preferably 5.0 or less. Within the above range, there is a tendency to obtain better effects.

[0080] In the above-mentioned tire, based on the viewpoint of being able to obtain better effects, it is preferred that the plasticizer content Pc (parts by mass) in the rubber composition for the tread surface relative to 100 parts by mass of the rubber component is greater than the plasticizer content Pb (parts by mass) in the rubber composition for the base tread relative to 100 parts by mass of the rubber component.

[0081] The ratio of Pc to Pb (Pc / Pb) is preferably 4.0 or more, more preferably 4.5 or more, further preferably 5.0 or more, further preferably 5.5 or more, further preferably 6.0 or more, and preferably 10.0 or less, more preferably 8.0 or less, further preferably 7.5 or less. Within the above range, there is a tendency to obtain better effects.

[0082] Although the mechanism of the effect of adjusting Pc>Pb, especially adjusting Pc / Pb to 5.0 or more, is not clear, it is believed that by making the plasticizer content (Pc) of the tread surface greater than the plasticizer content (Pb) of the tread base, the change in hardness Hs over time due to the penetration of the plasticizer can be further suppressed. Therefore, it is speculated that the durability of the tire is improved.

[0083] The rubber composition for cap treads and the rubber composition for base treads preferably contain a filler. The filler is not particularly limited, and materials known in the rubber field can be used, such as inorganic fillers such as carbon black, silica, calcium carbonate, talc, alumina, clay, aluminum hydroxide, alumina, and mica; biochar (BIO CHAR), etc.; poorly dispersible fillers, etc. Among them, carbon source fillers such as carbon black (carbon-containing fillers) and silica are preferred from the viewpoint of being able to obtain better effects.

[0084] In the rubber composition for the tread surface and the rubber composition for the base tread, the carbon black that can be used is not particularly limited, and N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. can be listed. As commercial products, products of Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin Nichia Carbon Co., Ltd., Columbia Carbon Black Co., Ltd., etc. can be used. These can be used alone or in combination of two or more. In addition, in addition to the existing carbon black made from mineral oil and the like, carbon black made from biomass materials such as lignin can also be used. In addition, regenerated carbon black obtained by decomposing rubber products, plastic products, etc. containing carbon black such as tires can also be used, and the above-mentioned carbon black can be appropriately replaced in equal amounts for use.

[0085] Nitrogen adsorption specific surface area of ​​carbon black (N 2 SA) is preferably 5m 2 / g or more, more preferably 10m 2 / g or more, more preferably 15m 2 / g or more. In addition, the above N 2 SA is preferably 150m 2 / g or less, more preferably 130m2 / g or less, more preferably 120m 2 / g or less, and more preferably 111m 2 Within the above range, there is a tendency that the effect can be better obtained. The nitrogen adsorption specific surface area of ​​carbon black is determined in accordance with JIS K6217-2:2001.

[0086] The dibutyl phthalate oil absorption (DBP) of carbon black is preferably 40 ml / 100 g or more, more preferably 60 ml / 100 g or more, and even more preferably 70 ml / 100 g or more. In addition, the DBP is preferably 200 ml / 100 g or less, more preferably 150 ml / 100 g or less, and even more preferably 100 ml / 100 g or less. Within the above range, there is a tendency that a better effect can be obtained. In addition, the DBP of carbon black can be determined by the measurement method of JIS K6217-4:2001.

[0087] In the rubber composition for the tread surface and the rubber composition for the base tread, as the silica that can be used, dry-process silica (anhydrous silica), wet-process silica (hydrous silica) and the like can be cited. Among them, based on the reason that there are more silanol groups, wet-process silica is preferred. As commercially available products, products of Degussa, Rhodia, Tosoh Silicon Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Co., Ltd. and the like can be used. These can be used alone or in combination of two or more.

[0088] As the silicon dioxide, plant-derived silicon dioxide can also be preferably used. As plant-derived silica, plant-derived silica containing silica components and the like can be cited. Plants containing silica components include rice, corn, sugar cane, buckwheat, wheat, barley, rye, coix seed, millet, foxtail millet, Miscanthus, erianthus, etc. In addition, saccharification residues of plants containing the silica components can also be used. Among them, rice husks and straws with a high silica content are preferred, and rice husks are more preferred. In addition, plants containing silica components can be turned into ash by burning or carbonized.

[0089] The nitrogen adsorption specific surface area of ​​silicon dioxide (N 2 SA) is preferably 50m 2 / g or more, more preferably 100m 2 / g or more, more preferably 150m 2 / g or more, more preferably 175m 2 / g or more. In addition, N 2The upper limit of SA is not particularly limited, but is preferably 350 m 2 / g or less, more preferably 300m 2 / g or less, more preferably 250m 2 Within the above range, there is a tendency that the effect can be better obtained. It should be noted that the N 2 SA is a value measured by the BET method according to ASTM D3037-93.

[0090] Examples of poorly dispersible fillers include microfibrillated plant fibers, short-fiber cellulose, and gel compounds, among which microfibrillated plant fibers are preferred.

[0091] As the microfibrillated plant fiber, cellulose microfibrils are preferred based on the viewpoint that good reinforcing properties can be obtained. As cellulose microfibrils, as long as they are from natural products, there are no particular restrictions, and examples thereof include resource biomass from fruits, grains, root vegetables, etc., wood, bamboo, hemp, jute, kenaf, and waste biomass such as pulp, paper, cloth, crop waste, food waste or wastewater sludge obtained from these as raw materials, unused biomass such as straw, wheat straw, thinning materials, and cellulose microfibrils made from cellulose such as sea squirts and acetic acid bacteria. These microfibrillated plant fibers can be used in one kind, or in combination of two or more kinds.

[0092] It should be noted that in this specification, the so-called cellulose microfibrils typically refer to cellulose fibers with an average fiber diameter of 10 μm or less, and more typically refer to cellulose fibers having a microstructure with an average fiber diameter of 500 nm or less formed by an aggregation of cellulose molecules. Typical cellulose microfibrils are formed by, for example, an aggregation of cellulose fibers having the above average fiber diameter.

[0093] In the rubber composition for tread, the content Fc of the filler (the total amount of fillers such as silica and carbon black) is preferably 70 parts by mass or more, more preferably 75 parts by mass or more, further preferably 85 parts by mass or more, further preferably 105 parts by mass or more, and preferably 200 parts by mass or less, more preferably 150 parts by mass or less, further preferably 130 parts by mass or less, relative to 100 parts by mass of the rubber component. If it is within the above range, there is a tendency to obtain better effects.

[0094] Although the mechanism by which the effect is better obtained when the filler content is adjusted to 75 parts by mass or more is not clear, it is believed that by increasing the amount of filler, the polymer ratio is reduced, thereby suppressing the change in physical properties after heat aging. Therefore, it is speculated that the performance sustainability of wet grip performance is improved.

[0095] In the rubber composition for tread, the content of carbon black is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and further preferably 5 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and further preferably 10 parts by mass or less. Within the above range, there is a tendency to obtain better effects.

[0096] In the rubber composition for cap tread, the content of silica is preferably 65 parts by mass or more, more preferably 70 parts by mass or more, further preferably 80 parts by mass or more, further preferably 100 parts by mass or more, and is preferably 150 parts by mass or less, more preferably 130 parts by mass or less, further preferably 120 parts by mass or less, relative to 100 parts by mass of the rubber component. Within the above range, there is a tendency that the effect can be better obtained.

[0097] When the rubber composition for tread 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 further preferably 5 parts by mass or more, relative to 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, further preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, there is a tendency to obtain a better effect.

[0098] In the rubber composition for base tread, the filler content Fb (total amount of fillers such as silica and carbon black) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 30 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, further preferably 50 parts by mass or less, and further preferably 40 parts by mass or less. Within the above range, there is a tendency that the effect can be better obtained.

[0099] In the rubber composition for base tread, the content of carbon black is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and further preferably 30 parts by mass or more, relative to 100 parts by mass of the rubber component, and is preferably 100 parts by mass or less, more preferably 70 parts by mass or less, further preferably 50 parts by mass or less, and further preferably 40 parts by mass or less. Within the above range, there is a tendency that the effect can be better obtained.

[0100] In the rubber composition for base tread, the content of silica is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, further preferably 5 parts by mass or less, and may be 0 parts by mass, relative to 100 parts by mass of the rubber component. Within the above range, there is a tendency that the effect can be better obtained.

[0101] When the rubber composition for the base tread 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 further preferably 5 parts by mass or more, relative to 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, further preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, there is a tendency to obtain better effects.

[0102] The ratio of the filler content Fc in the rubber composition for the cap tread relative to 100 parts by mass of the rubber component to the filler content Fb in the rubber composition for the base tread relative to 100 parts by mass of the rubber component (Fc / Fb) is preferably 1.7 or more, more preferably 2.3 or more, further preferably 2.8 or more, further preferably 3.2 or more, and particularly preferably 3.5 or more. The upper limit of Fc / Fb is not particularly limited, but is preferably 5.0 or less, more preferably 4.5 or less, and further preferably 4.0 or less. Within the above range, there is a tendency to obtain better effects.

[0103] Although the mechanism by which the effect is better obtained when Fc / Fb is adjusted to a certain value or more, especially to 3.2 or more, is not clear, it is believed that by making the filler content (Fc) of the cap tread greater than the filler content (Fb) of the base tread by a certain amount, the polymer ratio of the cap tread can be reduced, thereby suppressing the change in physical properties after heat aging. Therefore, it is speculated that the performance sustainability of wet grip performance is improved.

[0104] The ratio of the carbon black content Cc in the rubber composition for the cap tread relative to 100 parts by mass of the rubber component to the carbon black content Cb in the rubber composition for the base tread relative to 100 parts by mass of the rubber component (Cc / Cb) is preferably 0.10 or more, more preferably 0.15 or more, and further preferably 0.17 or more. The upper limit of Cc / Cb is not particularly limited, but is preferably 0.30 or less, more preferably 0.23 or less, and further preferably 0.20 or less. Within the above range, there is a tendency to obtain better effects.

[0105] Although the mechanism of the trend that the effect is better obtained when Cc / Cb is adjusted to a certain value or more, especially to 0.15 or more, is not clear, it is believed that by making the carbon black content (Cc) of the tread surface greater than the carbon black content (Cb) of the base tread by a certain amount, the polymer ratio of the tread surface can be reduced, thereby suppressing the change in physical properties after heat aging. Therefore, it is speculated that the performance sustainability of wet grip performance is improved.

[0106] When the rubber composition for a cap tread or the rubber composition for a base tread contains silica, it is preferred that the rubber composition further contains a silane coupling agent. The silane coupling agent is not particularly limited, and those known in the rubber field can be used, 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)tetrasulfide, and bis(4-triethoxysilylbutyl)tetrasulfide. sulfide, 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-trimethoxysilyl Sulfide-based silyl groups such as 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silane groups such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyltriethoxysilane , vinyl trimethoxysilane, etc.; amino-based silanes such as 3-aminopropyl triethoxysilane and 3-aminopropyl trimethoxysilane; glycidyloxy-based silanes such as γ-glycidyloxypropyl triethoxysilane and γ-glycidyloxypropyl trimethoxysilane; nitro-based silanes such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; chlorine-based silanes such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. As commercially available products, products of Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZmax Co., Ltd., Dow Corning Toray Co., Ltd., etc. can be used. These can be used alone or in combination of two or more.

[0107] In the rubber composition for the tread cap and the rubber composition for the base tread, the content of the silane coupling agent is preferably 0.1 parts by mass or more, more preferably 3 parts by mass or more, further preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more relative to 100 parts by mass of silica. The upper limit of the content is preferably 50 parts by mass or less, more preferably 20 parts by mass or less, further preferably 15 parts by mass or less, and particularly preferably 10 parts by mass or less. Within the above range, there is a tendency to obtain a better effect.

[0108] The rubber composition for cap treads and the rubber composition for base treads preferably contain an antioxidant from the viewpoint of crack resistance, ozone resistance, and the like.

[0109] The antioxidant is not particularly limited, and examples thereof include naphthylamine antioxidants such as phenyl-α-naphthylamine; diphenylamine antioxidants such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; p-phenylenediamine antioxidants such as N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and N,N′-di-2-naphthyl-p-phenylenediamine; quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; bisphenol, trisphenol and polyphenol antioxidants such as tetrakis[methylene-3-(3′,5′-di-tert-butyl-4′-hydroxyphenol) propionate]methane; and the like. Among them, p-phenylenediamine antioxidants and quinoline antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexis Co., Ltd., etc. can be used.

[0110] In the rubber composition for cap treads and the rubber composition for base treads, the content of the antioxidant is preferably 0.2 parts by mass or more, more preferably 2.0 parts by mass or more, and further preferably 2.5 parts by mass or more, relative to 100 parts by mass of the rubber component. The content is preferably 7.0 parts by mass or less, and more preferably 3.5 parts by mass or less.

[0111] The rubber composition for a cap tread and the rubber composition for a base tread preferably contain stearic acid. In the rubber composition for cap treads and the rubber composition for base treads, the content of stearic acid is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0112] As stearic acid, conventionally known stearic acid may be used, and for example, products of NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., and the like may be used.

[0113] The rubber composition for a cap tread and the rubber composition for a base tread preferably contain zinc oxide. In the rubber composition for cap treads and the rubber composition for base treads, the content of zinc oxide is preferably 0.5 parts by mass or more, more preferably 2.0 parts by mass or more, and is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, relative to 100 parts by mass of the rubber component.

[0114] As zinc oxide, conventionally known zinc oxide may be used, and for example, products of Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Shiroshui Chemical Co., Ltd., Shodo Chemical Co., Ltd., Sakai Chemical Co., Ltd., and the like may be used.

[0115] The rubber composition for cap treads and the rubber composition for base treads may also contain wax. In the rubber composition for cap treads and the rubber composition for base treads, the wax content is preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, and is preferably 10.0 parts by mass or less, more preferably 2.0 parts by mass or less, per 100 parts by mass of the rubber component.

[0116] The wax is not particularly limited, and petroleum wax, natural wax, etc. may be mentioned. In addition, synthetic wax obtained by refining or chemically treating a plurality of waxes may also be used. These waxes may be used alone or in combination of two or more.

[0117] Examples of petroleum waxes include paraffin wax and microcrystalline wax. Examples of natural waxes include plant waxes such as candelilla wax, carnauba wax, wood wax, rice wax, and jojoba wax; animal waxes such as beeswax, lanolin, and spermaceti; mineral waxes such as ozokerite, ceresin, and petrolatum; and refined products thereof. Examples of commercially available products include products of Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd.

[0118] In the rubber composition for cap treads and the rubber composition for base treads, sulfur is preferably blended from the viewpoint of forming appropriate crosslinking chains on polymer chains and imparting good performance.

[0119] In the rubber composition for cap treads, the sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 1.5 parts by mass or more, relative to 100 parts by mass of the rubber component. The sulfur content is preferably 5.0 parts by mass or less, more preferably 3.0 parts by mass or less, and further preferably 2.0 parts by mass or less.

[0120] In the rubber composition for a base tread, the sulfur content is preferably 1.0 parts by mass or more, more preferably 2.0 parts by mass or more, and further preferably 2.5 parts by mass or more, relative to 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 further preferably 4.0 parts by mass or less.

[0121] As sulfur, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc. commonly used in the rubber industry can be cited. As commercially available products, products of Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Co., Ltd., Nippon Dry Ryu Industry Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used. These can be used alone or in combination of two or more.

[0122] The rubber composition for a cap tread and the rubber composition for a base tread preferably contain a vulcanization accelerator.

[0123] In the rubber composition for cap tread, the content of the vulcanization accelerator is not particularly limited and can be freely determined according to the desired vulcanization speed or crosslinking density. It is preferably 3.0 parts by mass or more, more preferably 5.0 parts by mass or more, and further preferably 5.3 parts by mass or more relative to 100 parts by mass of the rubber component. The upper limit is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and further preferably 6.0 parts by mass or less.

[0124] In the rubber composition for base tread, the content of the vulcanization accelerator is not particularly limited and can be freely determined according to the desired vulcanization speed or crosslinking density. It is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and further preferably 1.5 parts by mass or more relative to 100 parts by mass of the rubber component. The upper limit is preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, and further preferably 2.0 parts by mass or less.

[0125] There is no particular limitation on the type of vulcanization accelerator, and commonly used ones can be used. As the vulcanization accelerator, benzothiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide can be listed; 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, N-tert-butyl-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolyldiguanidine can be used alone or in combination of two or more. Among them, sulfenamide-based, guanidine-based, and benzothiazole-based vulcanization accelerators are preferred.

[0126] In addition to the above-mentioned components, compounding agents commonly used in the tire industry, such as materials such as mold release agents, may be appropriately compounded into the rubber composition for cap treads and the rubber composition for base treads.

[0127] The rubber composition for cap treads and the rubber composition for base treads can be produced by, for example, kneading the above-mentioned components using a rubber kneading apparatus such as an open roll mill or a Banbury mixer, followed by vulcanization.

[0128] As the mixing conditions, in the basic kneading process of mixing additives other than the crosslinking agent (vulcanizing agent) and the vulcanization accelerator, the mixing temperature is preferably 100°C or more, more preferably 120°C or more, and preferably 180°C or less, and more preferably 170°C or less. In the refining process of mixing the vulcanizing agent and the vulcanization accelerator, the mixing temperature is preferably 80°C or more, and preferably 120°C or less, and more preferably 110°C or less. In addition, the composition obtained by mixing the vulcanizing agent and the vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. As the vulcanization temperature, it is preferably 140°C or more, more preferably 150°C or more, and preferably 190°C or less, and more preferably 185°C or less.

[0129] The rubber composition for a cap tread and the rubber composition for a base tread are used for a cap tread and a base tread, respectively, of tire components.

[0130] It should be noted that, in the present specification, the tread running surface refers to the rubber layer that forms the radial outermost layer of the tire among the rubber layers that constitute the tread. In the case of a two-layer structure tread of the tread running surface and the tread base, it is equivalent to the rubber layer that forms the surface layer. In the case of a tread having a structure with more than three layers, it is equivalent to the rubber layer that forms the outermost layer.

[0131] In the present specification, the tread base refers to, among the rubber layers constituting the tread of a multi-layer structure, a rubber layer that is arranged on the radially inner side of the tread running surface forming the radially outermost layer of the tire; in the case of a tread with a two-layer structure of a tread running surface and a tread base, it is equivalent to the rubber layer forming the radially inner side of the tire; in the case of a tread having a structure having more than three layers, it is equivalent to one or more layers of the rubber layer that is arranged on the radially inner side of the tread running surface.

[0132] The tire is manufactured by a conventional method using the rubber composition for cap tread and the rubber composition for base tread. That is, the composition mixed with various additives as needed is extruded in the shape of cap tread and base tread in an unvulcanized stage, molded in a tire molding machine by a conventional method, bonded together with other tire components to form an unvulcanized tire, and then heated and pressurized in a vulcanizer to manufacture the tire.

[0133] The tire is not particularly limited, and examples thereof include pneumatic tires, solid tires, airless tires, etc. Among them, pneumatic tires are preferred.

[0134] The above tires can be suitable for use as passenger car tires, large passenger car tires, large SUV tires, truck / bus tires, two-wheeled vehicle tires, racing tires, winter tires (studless anti-skid tires, snow tires, studded anti-skid tires), all-season tires, run-flat tires, aircraft tires, mining tires, etc.

[0135] In the above tire, the thickness Tc (mm) of the tread running surface is preferably 12 mm or less, more preferably 11 mm or less, further preferably 10 mm or less, and further preferably 9 mm or less. The lower limit is preferably 5 mm or more, more preferably 6 mm or more, further preferably 7 mm or more, and further preferably 8 mm or more. Within the above range, there is a tendency to obtain good effects.

[0136] In the above tire, the thickness Tb (mm) of the tread base is preferably 4 mm or less, more preferably 3 mm or less, and further preferably 2 mm or less. The lower limit is preferably 0.5 mm or more, and more preferably 1 mm or more. Within the above range, there is a tendency to obtain good effects.

[0137] Tc / Tb is preferably 1.5 or more, more preferably 2.1 or more, further preferably 2.4 or more, further preferably 3.0 or more, further preferably 3.5 or more, further preferably 4.0 or more, further preferably 4.5 or more. The upper limit is preferably 9.2 or less, more preferably 7.0 or less, further preferably 5.5 or less, further preferably 5.0 or less. Within the above range, there is a tendency to obtain good effects.

[0138] Although the mechanism by which the effect is better obtained when Tc / Tb is adjusted to a predetermined range is not clear, it is considered that the change in hardness Hs over time due to the penetration of the plasticizer can be further suppressed. Therefore, it is estimated that the sustainability of wet grip performance over time is improved.

[0139] In the above tire, the ratio (Rc / Tc) of the resin content Rc (parts by mass) in the rubber composition for the tread surface relative to 100 parts by mass of the rubber component to the thickness Tc (mm) of the tread surface is preferably 2.3 or more, more preferably 3.0 or more, further preferably 3.5 or more, further preferably 3.8 or more, further preferably 3.9 or more, further preferably 4.0 or more. The upper limit is preferably 8.0 or less, more preferably 6.0 or less, further preferably 5.0 or less, further preferably 4.3 or less, further preferably 4.2 or less. If it is within the above range, there is a tendency to obtain a good effect.

[0140] Although the mechanism by which the effect is better obtained when Rc / Tc is adjusted to a certain value or more is not clear, it is believed that by adding a larger amount of resin per unit thickness, the change in hardness Hs over time due to oil penetration can be further suppressed. Therefore, it is estimated that the sustainability of wet grip performance over time is improved.

[0141] In addition, in this specification, the thickness Tc of the tread running surface (running surface layer) refers to the thickness of the tread running surface on the tire equatorial plane in the radial section of the tire, which is the straight-line distance from the tread surface (the surface of the tread running surface) to the radial inner side of the tread running surface in the radial section of the tire.

[0142] The thickness Tb of the base tread (base layer) refers to the thickness of the base tread on the tire equatorial plane in the tire radial cross section, and is the straight-line distance from the tire radial outer surface to the tire radial inner surface of the base tread in the tire radial cross section.

[0143] The thickness of the cap tread and the base tread on the tire equatorial plane are values ​​measured from the outermost surface of the cap tread and the outermost surface of the base tread along the tire equatorial plane. When a conducting member or the like exists on the tire equatorial plane, the value is measured along the tire equatorial plane from a straight line connecting the ends of the interface shielded by the conducting member. When there are grooves on the tire equatorial plane, the thickness is measured at the center of the tire width direction of the land portion closest to the tire equatorial plane, and the thickness is measured in the normal direction of the radially outer surface of the tread running surface and the radially outer surface of the tread base.

[0144] In addition, in this specification, the thickness and other dimensions are measured in a state where the bead portion of the tire is consistent with the width of the regular rim. When measuring, the tire is cut along the tire radial direction, and the bead ends on both sides of the sample are fixed in a state consistent with the width of the regular rim.

[0145] In this specification, unless otherwise specified, the dimensions of each part of the tire are values ​​measured under normal conditions. In this specification, the "normal state" means a state in which the tire is mounted on a normal rim (not shown), is filled with a normal internal pressure, and is unloaded.

[0146] If the measurement cannot be performed with the tire mounted on a regular rim, the dimensions and angles of each part in the meridian cross-section of the tire can be measured by making the distance between the left and right beads consistent with the distance between the beads in a tire mounted on a regular rim in the tire cross-section obtained by cutting the tire along a plane including the rotation axis.

[0147] "Regular rim" means a rim specified for each tire in a specification system including the specification to which the tire is based, for example, JATMA (Japan Automobile Tire Association) refers to the "standard rim" in the applicable size listed in the "JATMA YEAR BOOK", ETRTO (The European Tyre and Rim Technical Organisation) refers to the "measuring rim" listed in the "STANDARDS MANUAL", and TRA (The Tire and Rim Association, Inc.) refers to the "design rim" listed in the "YEAR BOOK". JATMA, ETRTO, and TRA are referenced in that order, and if there is an applicable size, that specification is followed. In addition, in the case of a tire not specified in the specification, it refers to a tire with the smallest rim diameter and the narrowest rim width among the rims that can be assembled and can maintain the internal pressure, that is, the rims that do not cause air leakage from the rim / tire.

[0148] "Normal internal pressure" refers to the air pressure specified for each tire in the specification system including the specification to which the tire is based. In JATMA, it refers to the "maximum air pressure", in ETRTO, it refers to the "INFLATION PRESSURE", and in TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". Like the "regular rim", it is referenced in the order of JATMA, ETRTO, and TRA, according to its specifications. In addition, in the case of a tire not specified in the specification, it refers to the regular internal pressure (but above 250KPa) of other tire sizes (specified in the specification) that record the regular rim as a standard rim. In addition, in the case of multiple regular internal pressures above 250KPa, it refers to the minimum value among them.

[0149] In addition, in this specification, "normal load" refers to the load specified for each tire in the specification system including the specification to which the tire is based. In JATMA, it refers to the maximum load capacity, in ETRTO, it refers to "LOADCAPACITY (load capacity)", and in TRA, it refers to the maximum value recorded in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATIONPRESSURES (tire load limit at various cold inflation pressures)". Like the above-mentioned "normal rim" and "normal internal pressure", it is referenced in the order of JATMA, ETRTO, and TRA, and the specifications are used. In addition, in the case of a tire not specified in the specification, the normal load W is calculated by the following calculation: L . V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt W L =0.000011×V+175 W L :Normal load(kg) V: Virtual volume of the tire (mm 3 ) Dt: Tire outer diameter (mm) Ht: Tire section height (mm) Wt: tire section width (mm)

[0150] The "cross-sectional width Wt (mm)" of a tire is the maximum width between the outer surfaces of the sidewalls excluding patterns or characters when there are patterns or characters on the side of the tire in a normal state.

[0151] The "outer diameter Dt (mm)" of a tire refers to the outer diameter of the tire in a normal state.

[0152] The "cross-section height Ht (mm)" of a tire refers to the height of the tire radial direction in the radial cross section of the tire, and when the rim diameter of the tire is set to R (mm), it is equivalent to half of the difference between the outer diameter Dt of the tire and the rim diameter R. In other words, the cross-section height Ht can be calculated by (Dt-R) / 2.

[0153] Hereinafter, an example of the above-mentioned tire will be described with reference to the drawings, but the present invention is not limited to this embodiment.

[0154] exist Figure 1 In the figure, the up-down direction is the radial direction of the tire 2, the left-right direction is the axial direction of the tire 2, and the direction perpendicular to the paper surface is the circumferential direction of the tire 2. The tire 2 is bilaterally symmetrical. The tread portion 4 includes a running surface layer 30 (tread running surface) and a base layer 28 (tread base).

[0155] in addition, Figure 1 Although the example of the tread portion 4 having a two-layer structure composed of the cap layer 30 and the base layer 28 is shown, a tread having a structure of three or more layers may also be used.

[0156] exist Figure 1 In the tire 2, the running surface layer 30 is composed of the above-mentioned rubber composition for the running surface, the base layer 28 is composed of the rubber composition for the base tread, and the content of the polymer having ethylene units in 100% by mass of the rubber component of the running surface layer 30 is 50% by mass or more. In addition, the resin content Rc (parts by mass) and the oil content Oc (parts by mass) in the running surface layer 30 relative to 100 parts by mass of the rubber component, and the oil content Ob (parts by mass) in the base layer 28 relative to 100 parts by mass of the rubber component satisfy the formula (1) "Rc>Oc≥Ob".

[0157] In the tire 2, each sidewall 6 extends radially inwardly from the end of the tread portion 4. The radially outer portion of the sidewall 6 is joined to the tread portion 4. The radially inner portion of the sidewall 6 is joined to the clinch portion 10. The sidewall 6 can prevent damage to the carcass 14.

[0158] Figure 1 Each tread wing 8 is located between the tread portion 4 and the sidewall 6. The tread wing 8 is joined to the tread portion 4 and the sidewall 6, respectively.

[0159] Each clinch portion 10 is located substantially on the inner side of the sidewall 6 in the radial direction, and has at least one portion that contacts the rim.

[0160] The carcass 14 includes a carcass ply 36. In the tire 2, the carcass 14 is composed of a single carcass ply 36, but may be composed of two or more carcass ply.

[0161] In the tire 2, the carcass ply 36 is laid between the bead cores 32 on both sides, along the tread portion 4 and the sidewall 6. The carcass ply 36 is folded from the axial inside to the outside around the respective bead cores 32. By the folding, a main portion 36a and a pair of folded portions 36b are formed on the carcass ply 36. That is, the carcass ply 36 includes the main portion 36a and the pair of folded portions 36b.

[0162] Each bead core 32 includes a bead apex 34 extending radially outward from the bead core 32. The bead core 32 is annular and preferably includes a wound inelastic wire. The bead apex 34 tapers radially outward.

[0163] Although not shown, the carcass ply 36 is preferably composed of a plurality of parallel cords and a topper. The absolute value of the angle formed by each cord with respect to the equatorial plane CL is preferably 75° to 90°. In other words, the carcass 14 preferably has a meridian structure.

[0164] Figure 1 The belt layer 16 is located radially inside the tread portion 4. The belt layer 16 is stacked with the carcass 14. The belt layer 16 reinforces the carcass 14. Figure 1 In the tire 2, the belt layer 16 is composed of an inner layer 38 and an outer layer 40. Figure 1 As is clear, the width of the inner layer 38 in the axial direction is preferably slightly greater than that of the outer layer 40. In the 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.

[0165] Each of the inner layer 38 and the outer layer 40 is preferably composed of a plurality of parallel single-line steel cords (steel monofilaments) and a topping rubber (covering rubber). In other words, the belt layer 16 includes a plurality of parallel steel monofilaments.

[0166] Figure 1 The belt 18 is located radially outside the belt layer 16. In the axial direction, the belt 18 has a width equal to the width of the belt layer 16. The belt 18 may have a greater width than the width of the belt layer 16.

[0167] Although not shown, the belt 18 is preferably composed of a cord and a top rubber. The cord is wound in a spiral shape. The belt 18 has a so-called jointless structure. The cord substantially extends in the circumferential direction. The angle of the cord relative to the circumferential direction is preferably 5° or less, more preferably 2° or less. Since the belt layer 16 is constrained by the cord, the warping of the belt layer 16 is suppressed.

[0168] Figure 1 The belt layer 16 and the belt 18 constitute a reinforcing layer. The reinforcing layer may also be constituted by the belt layer 16 alone.

[0169] Figure 2 yes Figure 1 An enlarged view of the vicinity of the tread portion 4 . Figure 2 The tire in FIG. 1 is a tire 2 having grooves 26 on the tire equatorial plane (on CL). In this case, the thickness of the tread running surface (Tc) is the thickness measured at the center portion in the tire width direction of the land portion of the groove 26 on the tire equatorial plane in the radial cross section of the tire, and is the thickness measured in the normal direction of the surface of the running surface layer 30 (tread running surface). More specifically, it refers to the straight-line distance in the normal direction from the radial outer surface of the running surface layer 30 to the interface on the outermost side of the tire of the base layer 28. In addition, the thickness of the tread base (Tb) is the thickness measured at the center portion in the tire width direction of the land portion of the groove 26 on the tire equatorial plane in the radial cross-section of the tire, and is the thickness measured in the normal direction of the radial outer surface of the base layer 28 (tread base). More specifically, it refers to the straight-line distance in the normal direction from the outer surface of the base layer 28 to the interface on the outermost side of the tire of the belt 18.

[0170] The inner liner 20 is located inside the carcass 14. The inner liner 20 is bonded to the inner surface of the carcass 14. A typical base rubber of the inner liner 20 is butyl rubber or halogenated butyl rubber. The inner liner 20 maintains the internal pressure of the tire 2.

[0171] Each chafer 22 is located near the bead 12. In this embodiment, the chafer 22 is preferably composed of cloth and rubber impregnated in the cloth. The chafer 22 may be formed integrally with the clinch 10.

[0172] In the tire 2, the tread portion 4 includes a main groove 42 as the groove 26. Figure 1 As shown, a plurality of, specifically three, main grooves 42 are engraved on the tread portion 4. These main grooves 42 are arranged at intervals in the axial direction. By engraving three main grooves 42 on the tread surface 4, four ribs 44 extending in the circumferential direction are formed. That is, the main grooves 42 are between the ribs 44 and the ribs 44.

[0173] Each main groove 42 extends in the circumferential direction. The main groove 42 is continuous and uninterrupted in the circumferential direction. The main groove 42 promotes the drainage of water between the road surface and the tire 2, for example, on rainy days. Therefore, even if the road surface is slippery, the tire 2 can fully contact the road surface.

[0174] In the tire 2, the resin content Rc (parts by mass) and the oil content Oc (parts by mass) in the cap layer 30 relative to 100 parts by mass of the rubber component, the oil content Ob (parts by mass) in the base layer 28 relative to 100 parts by mass of the rubber component, the plasticizer content Pc (parts by mass) in the cap layer 30 relative to 100 parts by mass of the rubber component, the plasticizer content Pb (parts by mass) in the base layer 28 relative to 100 parts by mass of the rubber component, the filler content Fc (parts by mass) in the cap layer 30 relative to 100 parts by mass of the rubber component, The filler content Fb (parts by mass) in the base layer 28 relative to 100 parts by mass of the rubber component, the carbon black content Cc (parts by mass) in the driving surface layer 30 relative to 100 parts by mass of the rubber component, the carbon black content Cb (parts by mass) in the base layer 28 relative to 100 parts by mass of the rubber component, the thickness Tc (mm) of the driving surface layer 30, the thickness Tb (mm) of the base layer 28, preferably Rc / Oc, Oc / Ob, Rc / Ob, Pc / Pb, Fc / Fb, Cc / Cb, Tc / Tb and Rc / Tc are within the above-mentioned ranges. [Example]

[0175] Examples (embodiments) considered to be preferable when implementing the present invention are shown below, but the scope of the present invention is not limited to the examples.

[0176] The following is a summary of various chemicals used in synthesis and polymerization. In addition, the chemicals are purified according to prescribed methods as needed. n-Hexane: Made by Kanto Chemical Co., Ltd. Styrene: Made by Kanto Chemical Co., Ltd. Butadiene: 1,3-Butadiene manufactured by Tokyo Chemical Industry Co., Ltd. TMEDA: N,N,N',N'-Tetramethylethylenediamine manufactured by Kanto Chemical Co., Ltd. n-Butyl lithium solution: 1.6 M n-Butyl lithium hexane solution manufactured by Kanto Chemical Co., Ltd. Ethanol: Manufactured by Kanto Chemical Co., Ltd. 2,6-Di-tert-butyl-p-cresol: NOCRAC 200 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0177] In addition, the evaluation methods of the copolymers are summarized and described below.

[0178] (Measurement of Hydrogenation Rate of Conjugated Diene Moiety of Copolymer) A 15 mass % solution was prepared using carbon tetrachloride as a solvent and the 1 The spectral reduction rate of the unsaturated bond part of H-NMR was calculated.

[0179] (Determination of Styrene Content) Measured at 25°C using a JEOL JNM-A 400 NMR instrument 1 The styrene content was determined by the ratio of phenyl protons based on styrene units (6.5 to 7.2 ppm) to ethylene protons based on butadiene units (4.9 to 5.4 ppm) obtained from the H-NMR spectrum.

[0180] (Measurement of weight average molecular weight (Mw)) The weight average molecular weight (Mw) of the copolymer was determined by conversion to standard polystyrene from the value measured by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0181] (Production Example 1: Synthesis of hydrogenated styrene-butadiene copolymer 1: hydrogenation rate 95 mol%) Into a heat-resistant reaction vessel fully replaced with nitrogen, 2000 ml of n-hexane, 60 g of styrene, 140 g of butadiene, 0.93 g of TMEDA, and 0.45 mmol of n-butyl lithium were added, and the mixture was stirred at 50°C for 5 hours to carry out polymerization reaction. Then, hydrogen was supplied at a pressure of 0.4 MPa-Gauge, and stirred for 20 minutes to react with unreacted polymer terminal lithium to form lithium hydride. The hydrogen supply pressure was 0.7 MPa-Gauge, the reaction temperature was 90°C, and hydrogenation was carried out using a catalyst based on dichlorodipentadiene titanocene. When the absorption of hydrogen reached the cumulative amount of the target hydrogenation rate, the reaction temperature was set to room temperature, the hydrogen pressure was restored to normal pressure, and it was extracted from the reaction vessel, the reaction solution was stirred and put into water, and the solvent was removed by steam stripping to obtain hydrogenated styrene-butadiene copolymer 1 (hydrogenation rate 95 mol%, weight average molecular weight (Mw) 450,000, styrene content 30 mass%, butadiene content 70 mass%).

[0182] (Production Example 2: Synthesis of hydrogenated styrene-butadiene copolymer 2: hydrogenation rate 80 mol %) In order to achieve the target hydrogenation rate, the same formulation as that of hydrogenated styrene-butadiene copolymer 1 was used except that the absorbed cumulative amount of hydrogen was adjusted to obtain hydrogenated styrene-butadiene copolymer 2 (hydrogenation rate 80 mol%, weight average molecular weight (Mw) 480,000, styrene content 30 mass%).

[0183] The following is a summary of various chemicals used to manufacture cap treads and base treads. In addition, the chemicals are purified according to a prescribed method as needed. (Tread surface) Hydrogenated styrene-butadiene copolymers 1 and 2: the above-mentioned Production Examples 1 and 2 (polymers having ethylene units) NR:TSR20 Carbon black: SHOBLACK N220 (N 2 SA: 111m 2 / g) Silicon dioxide: ULTRASIL VN3 (N 2 SA: 175m 2 / g) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Degussa Wax: OZOACE 0355 manufactured by Nippon Seiro Co., Ltd. Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Oil: Vivatec 500 manufactured by H&R (TDAE, aromatic process oil) Resin 1: Sylvatraxx 4401 manufactured by Arizona Chemical (styrene α-methylstyrene resin (copolymer of styrene and α-methylstyrene)) Resin 2: PR120 manufactured by ExxonMobil (hydrogenated dicyclopentadiene resin, softening point 120°C) Stearic acid: "Tsubaki" manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining and Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator CZ: NOCCELER CZ-G (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator DPG: NOCCELER D (N,N'-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator TBzTD: Sanshin Chemical Industry Co., Ltd. (Tetrabenzylthiuram disulfide)

[0184] (Tread base) NR:SIR20 BR: BR150B manufactured by Ube Industries, Ltd. Carbon black: SHOBLACK N220 (N 2 SA: 111m 2 / g) Oil: Aroma oil manufactured by ENEOS Co., Ltd. Stearic acid: "Tsubaki" manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining and Smelting Co., Ltd. Antioxidant: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Wax: OZOACE 0355 manufactured by Nippon Seiro Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator TBBS: NOCCELER NS (N-tert-butyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0185] (Production of rubber composition for cap tread) According to the compounding contents shown in Table 1, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Sulfur and a vulcanization accelerator were added to the kneaded product, and kneaded for 5 minutes at 80° C. using an open roll mill to obtain an unvulcanized rubber composition.

[0186] (Preparation of rubber composition for base tread) According to the compounding contents shown in Table 2, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a 1.7 L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a kneaded product. Sulfur and a vulcanization accelerator were added to the kneaded product, and kneaded for 5 minutes at 80° C. using an open roll mill to obtain an unvulcanized rubber composition.

[0187] <Method for preparing test tire> According to the specifications of Table 1, the above-mentioned unvulcanized rubber composition for tread was molded into a tread, and the above-mentioned unvulcanized rubber composition for base tread was molded into the shape of a base tread, and 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 manufacture a test tire (size 205 / 70R15, passenger car tire).

[0188] Table 1 shows the results of test tires obtained by changing the composition and specifications according to Table 1 and calculated by the following evaluation method.

[0189] <Hardness> (new product) A test piece was cut from the tread surface of each test tire (new product), and the JIS-A hardness (new product) at room temperature (25°C) was measured using a type A durometer in accordance with JIS K6253-3 (2012) "Rubber, vulcanized and thermoplastic rubber - Methods for determining hardness - Part 3: Durometer hardness". (After heat aging) After the hardness (new product) was measured, the test piece was heat treated at 80° C. for 168 hours under the condition of an oxygen concentration of 20%. The JIS-A hardness at room temperature (after heat aging) was measured in the same manner.

[0190] <Sustainability of wet grip performance over time> (new product) Each test tire was mounted on a domestically produced 2000cc FF vehicle and the vehicle was driven on a wet 25°C road surface. The locking brake was depressed at a speed of 150 km / h and the stopping distance (initial) required to stop was measured. (Wet grip performance after time) After the actual vehicle has traveled 20,000 km, the stopping distance (after time) required to stop is measured in the same manner. The wet grip performance maintenance rate (%) was calculated based on the stopping distances of each test tire when it was new and after aging. A greater wet-grip performance maintenance rate indicates better sustainability of the wet-grip performance.

[0191]

Table 1

[0192]

Table 2

[0193] The present invention (1) is a tire having a cap tread and a base tread. In the cap tread, the content of the polymer having ethylene units in 100% by mass of the rubber component is 50% by mass or more, The resin content Rc (parts by mass) and the oil content Oc (parts by mass) in the cap tread relative to 100 parts by mass of the rubber component and the oil content Ob (parts by mass) in the base tread relative to 100 parts by mass of the rubber component satisfy the following formula (1). (1)Rc>Oc≥Ob

[0194] The present invention (2) is the tire according to the present invention (1), wherein the resin contains a hydrogenated resin.

[0195] The present invention (3) is the tire according to the present invention (1) or (2), wherein the content of the filler in the cap tread is 75 parts by mass or more per 100 parts by mass of the rubber component.

[0196] The present invention (4) is a tire according to any combination of any one of the present inventions (1) to (3), wherein Rc / Oc is 1.5 or less.

[0197] The present invention (5) is a tire according to any combination of any one of the present inventions (1) to (4), wherein Oc / Ob is 2.5 or more.

[0198] The present invention (6) is a tire according to any combination of any one of the present inventions (1) to (5), wherein Rc / Ob is 3.3 or more.

[0199] The present invention (7) is a tire according to any combination of any one of the present inventions (1) to (6), wherein the plasticizer content Pc (parts by mass) in the tread running surface relative to 100 parts by mass of the rubber component is greater than the plasticizer content Pb (parts by mass) in the tread base relative to 100 parts by mass of the rubber component.

[0200] The present invention (8) is the tire according to the present invention (7), wherein Pc / Pb is 5.0 or more.

[0201] The present invention (9) is a tire according to any combination of any one of the present inventions (1) to (8), wherein the cap tread contains isoprene rubber, the base tread contains isoprene rubber and butadiene rubber, In the cap tread, the content of the isoprene-based rubber in 100% by mass of the rubber component is 5 to 40% by mass.

[0202] The present invention (10) is a tire according to any combination of any one of the present inventions (1) to (9), wherein the ratio (Fc / Fb) of the filler content Fc in the tread running surface relative to 100 parts by mass of the rubber component to the filler content Fb in the tread base relative to 100 parts by mass of the rubber component is 3.2 or more.

[0203] The present invention (11) is a tire according to any combination of any one of the present inventions (1) to (10), wherein the ratio (Cc / Cb) of the carbon black content Cc in the tread running surface relative to 100 parts by mass of the rubber component to the carbon black content Cb in the tread base relative to 100 parts by mass of the rubber component is greater than 0.15.

[0204] The present invention (12) is a tire according to any combination of any one of the present inventions (1) to (11), wherein the ratio (Tc / Tb) of the thickness Tc (mm) of the tread running surface to the thickness Tb (mm) of the tread base is 2.1 to 9.2.

[0205] The present invention (13) is a tire according to any combination of any one of the present inventions (1) to (12), wherein the ratio (Rc / Tc) of the resin content Rc (parts by mass) in the tread surface relative to 100 parts by mass of the rubber component to the thickness Tc (mm) of the tread surface is 3.0 or more.

Claims

1. A tire, characterized in that: It has a tread surface and a tread base. In the cap tread, the content of the polymer having ethylene units in 100% by mass of the rubber component is 50% by mass or more, The resin content Rc and the oil content Oc in the cap tread relative to 100 parts by mass of the rubber component, and the oil content Ob in the base tread relative to 100 parts by mass of the rubber component satisfy the following formula (1), wherein the units of the resin content Rc, the oil content Oc in the cap tread, and the oil content Ob in the base tread are parts by mass, (1)Rc>Oc≥Ob.

2. The tire according to claim 1, wherein: The resin contains a hydrogenated resin.

3. The tire according to claim 1 or 2, wherein: In the cap tread, the content of the filler is 75 parts by mass or more based on 100 parts by mass of the rubber component.

4. The tire according to any one of claims 1 to 3, wherein Rc / Oc is 1.5 or less.

5. The tire according to any one of claims 1 to 4, wherein: Oc / Ob is 2.5 or more.

6. The tire according to any one of claims 1 to 5, wherein: Rc / Ob is 3.3 or more.

7. The tire according to any one of claims 1 to 6, wherein The plasticizer content Pc in the cap tread relative to 100 parts by mass of the rubber component is greater than the plasticizer content Pb in the base tread relative to 100 parts by mass of the rubber component, and the units of the plasticizer content Pc in the cap tread and the plasticizer content Pb in the base tread are parts by mass.

8. The tire according to claim 7, wherein: Pc / Pb is 5.0 or more.

9. The tire according to any one of claims 1 to 8, wherein The tread surface contains isoprene rubber, and the base tread contains isoprene rubber and butadiene rubber. In the cap tread, the content of the isoprene-based rubber in 100% by mass of the rubber component is 5 to 40% by mass.

10. The tire according to any one of claims 1 to 9, wherein The ratio Fc / Fb of the filler content Fc in the cap tread relative to 100 parts by mass of the rubber component to the filler content Fb in the base tread relative to 100 parts by mass of the rubber component is 3.2 or more.

11. The tire according to any one of claims 1 to 10, wherein The ratio Cc / Cb of the carbon black content Cc in the cap tread relative to 100 parts by mass of the rubber component to the carbon black content Cb in the base tread relative to 100 parts by mass of the rubber component is 0.15 or more.

12. The tire according to any one of claims 1 to 11, wherein A ratio (Tc / Tb) of a cap tread thickness Tc to a base tread thickness Tb is 2.1 to 9.2, and the cap tread thickness Tc and the base tread thickness Tb are expressed in mm.

13. The tire according to any one of claims 1 to 12, wherein: The ratio Rc / Tc of the resin content Rc in the cap tread relative to 100 parts by mass of the rubber component to the thickness Tc of the cap tread is 3.0 or more, wherein the unit of the resin content Rc in the cap tread is part by mass and the unit of the thickness Tc of the cap tread is mm.

Images