Pneumatic tire

Abstract

Provided is a pneumatic tire having a favorable balance of wear resistance and slip resistance, and in particular, having a high degree of compatibility between wear resistance and slip resistance when traveling in rainy weather. The pneumatic tire comprises at least one rubber layer that forms a tread with a rubber composition containing styrene-butadiene rubber and isoprene-based rubber as a rubber component, and satisfies the following Expressions (1) to (4), where R1 (parts by mass) is the quantity of styrene-butadiene rubber and R2 (parts by mass) is the quantity of isoprene-based rubber per 100 parts by mass of the rubber component, and Wt (mm) is the width of the contact patch and Dt (mm) is the diameter of the tire when mounted on a standard rim and inflated to an internal pressure of 250 kPa.　(1): R1 + R2 ≥ 60 (2): 35 ≤ R2 ≤ 80 (3): 1963.4 ≤ (Dt2 × π / 4) / Wt ≤ 2827.4 (4): |R2 - R1| × Wt ≥ 3500

Description

pneumatic tires

[0001] The present disclosure relates to pneumatic tires.

[0002] In recent years, there has been a growing demand for automobiles to have lower fuel consumption due to growing concerns about environmental issues and economic considerations, and improvements in fuel economy are also being sought for pneumatic tires (hereinafter simply referred to as "tires") mounted on automobiles.

[0003] Conventionally, a specific means for improving the fuel economy of tires has generally been to apply a terminal-modified polymer to synthetic rubber and form the tread portion using a tire compound containing modified synthetic rubber in which the polymer molecular weight is reduced and the number of terminals is increased in order to improve the modification effect.

[0004] However, in such tire compounds, the molecular weight of the polymers contained in the compound is low, which may result in reduced breaking strength and abrasion resistance of the finished tire.

[0005] Therefore, it has been proposed to compound isoprene-based rubber, which has excellent breaking strength, together with styrene-butadiene rubber (SBR: synthetic rubber) (for example, Patent Documents 1 to 4).

[0006] JP 2014-213836 A JP 2017-52329 A JP 2018-154181 A JP 2019-85445 A

[0007] However, even if a small amount of isoprene-based rubber is added to SBR, the reinforcing filler (e.g., silica) is unevenly distributed in the isoprene-based rubber phase, which may result in insufficient reinforcement of the SBR phase and lead to deterioration of abrasion resistance.

[0008] Furthermore, simply adding isoprene-based rubber reduces the SBR ratio in the rubber component, which may result in a decrease in the tire's grip on the road surface and a decrease in slip resistance.

[0009] As such, conventional compounding methods leave room for improvement in wear resistance and slip resistance, and there is a strong demand for tires that combine good wear resistance and slip resistance, especially when driving in the rain.

[0010] Therefore, an object of the present disclosure is to provide a pneumatic tire that has a well-balanced improvement in both wear resistance and slip resistance, and in particular, that achieves a high level of both wear resistance and slip resistance when driving in the rain.

[0011] The present inventors have conducted extensive research into solving the above problems, and have found that the above problems can be solved by the disclosure described below, leading to the completion of the present disclosure.

[0012] The present disclosure relates to a pneumatic tire, characterized in that at least one rubber layer forming a tread portion is formed from a rubber composition containing styrene-butadiene rubber and isoprene-based rubber as rubber components, and the amount of the styrene-butadiene rubber in 100 parts by mass of the rubber component is R1 (parts by mass) and the amount of the isoprene-based rubber is R2 (parts by mass), and when the tire is mounted on a regular rim and the internal pressure is set to 250 kPa, the tire has a contact width Wt (mm) and a diameter Dt (mm), and the following (Equations 1) to (4) are satisfied: R1+R2≧60 (Equation 1) 35≦R2≦80 (Equation 2) 1963.4≦(Dt ２ ×π / 4) / Wt≦2827.4 (Formula 3) |R2-R1|×Wt≧3500 (Formula 4)

[0013] According to the present disclosure, it is possible to provide a pneumatic tire in which both wear resistance and slip resistance are improved in a balanced manner, and in particular, which achieves a high level of both wear resistance and slip resistance when driving in the rain.

[0014] Hereinafter, the present disclosure will be specifically described based on embodiments.

[0015] [1] Characteristics of the Tire According to the Present Disclosure First, the characteristics of the tire according to the present disclosure will be described.

[0016] The present inventors believed that in order to solve the problem of the present disclosure, which is to provide a pneumatic tire that has a well-balanced improvement in both abrasion resistance and slip resistance, and in particular, that achieves a high degree of both abrasion resistance and slip resistance when driving in the rain, the conventional technology of simply controlling the rubber properties by compounding is insufficient, and that it is necessary to also consider the tire shape. As a result of various experiments and considerations, the present disclosure has been completed.

[0017] Specifically, in the tire according to the present disclosure, at least one rubber layer forming the tread portion is formed from a rubber composition containing styrene butadiene rubber (SBR rubber) and isoprene-based rubber as rubber components.

[0018] When the amount of SBR rubber in 100 parts by mass of the rubber component is R1 (parts by mass) and the amount of isoprene-based rubber is R2 (parts by mass), the following (Equation 1) and (Equation 2) are satisfied: R1+R2≧60 (Equation 1) 35≦R2≦80 (Equation 2)

[0019] Furthermore, the tire according to the present disclosure satisfies the following (Equation 3) and (Equation 4) when the tire contact width is Wt (mm) and the diameter is Dt (mm) when mounted on a regular rim and the internal pressure is set to 250 kPa. ２ ×π / 4) / Wt≦2827.4 ・(Formula 3) |R2-R1|×Wt≧3500 ・・・・・・・・・・・・(Formula 4)

[0020] By providing the above-mentioned features, it is possible to provide a tire that achieves a good balance between wear resistance and slip resistance, and that achieves a high level of both wear resistance and slip resistance, particularly when driving in the rain.

[0021] When the tread portion is formed of multiple rubber layers, such as a cap rubber layer forming the outermost surface of the tread portion and a base rubber layer forming the inner side of the tread portion, this rubber composition is preferably used for the cap rubber layer. Also, an additional rubber layer may be provided between the cap rubber layer and the base rubber layer, making the tread portion three or more layers.

[0022] The mechanism by which the tire according to the present disclosure achieves both high levels of wear resistance and slip resistance when running in the rain is presumed to be as follows.

[0023] As mentioned above, isoprene-based rubber has excellent breaking strength, and therefore, when used as the rubber component of the rubber composition that forms the tread portion, it is considered to be effective in improving the wear resistance of the tire.

[0024] However, when the tread portion is formed from a rubber composition containing only isoprene-based rubber, sufficient grip on wet road surfaces cannot be ensured, and therefore, when turning left or right in the rain, if the accelerator is depressed with the steering wheel turned, tire slippage may occur, resulting in the vehicle body slipping. Furthermore, this slippage may lead to a deterioration in wear resistance.

[0025] Therefore, in the present disclosure, SBR rubber, which has higher heat buildup and superior gripping power than isoprene-based rubber, is used as a rubber component together with the isoprene-based rubber, and the total amount of the isoprene-based rubber and SBR rubber per 100 parts by mass of the rubber component is set to 60 parts by mass or more (Equation 1), and the amount of the isoprene-based rubber is set to 35 parts by mass or more and 80 parts by mass or less (Equation 2).

[0026] This makes it possible to improve abrasion resistance and slip resistance in a balanced manner, and also makes it possible to enhance heat generation while preventing the rubber from losing its conformability due to uneven distribution of the reinforcing filler, thereby achieving a high level of both abrasion resistance and slip resistance when driving on wet roads in the rain.

[0027] The total amount of the isoprene-based rubber and SBR rubber is more preferably 75 parts by mass or more and 85 parts by mass or less, and the amount of the isoprene-based rubber is more preferably 55 parts by mass or more and 65 parts by mass or less.

[0028] Furthermore, when driving in the rain, slippage occurs between the tread portion and the road surface, which increases the frequency of deformation applied to the tread rubber, making it more likely to lose its ability to follow the road surface.

[0029] Therefore, in the present disclosure, when a tire is mounted on a regular rim and the internal pressure is set to 250 kPa, the contact width Wt (mm) and diameter Dt (mm) are set to 1963.4≦(Dt ２ ×π / 4) / Wt≦2827.4 (Equation 3) is satisfied.

[0030] In addition, in (Equation 3), (Dt ２ ×π / 4) / Wt is more preferably 1963.5 or more, even more preferably 2018 or more, even more preferably 2137 or more, even more preferably 2143 or more, even more preferably 2153 or more, even more preferably 2155 or more, even more preferably 2174 or more, even more preferably 2187 or more, even more preferably 2467 or more, even more preferably 2474 or more, even more preferably 2483 or more, even more preferably 2485 or more, even more preferably 2492 or more, and even more preferably 2501 or more.

[0031] The above formula (3) is the area of ​​the tire from the lateral direction [(Dt / 2) ２ ×π) = (Dt ２ ×π / 4)] is larger than in conventional tires, which means that the frequency of deformation applied to the tread rubber can be made lower than in conventional tires, making it easier for the tread rubber to follow the road surface, and also allowing the heat generation in the SBR rubber phase to be effectively utilized as gripping power with the road surface, reducing the frequency of contact with the road surface even during normal driving. This makes it possible to prevent slipping when driving in the rain and improve wear resistance.

[0032] In the above description, a "regular rim" refers to a rim that is determined for each tire by a standard system that includes the standard on which the tire is based, such as the standard rim for the applicable size listed in the "JATMA YEAR BOOK" for the Japan Automobile Tire Manufacturers Association (JATMA), the "Measuring Rim" listed in the "STANDARDS MANUAL" for the European Tire and Rim Technical Organization (ETRTO), or the "Design Rim" listed in the "YEAR BOOK" for the Tire and Rim Association, Inc. (TRA). In the case of tires not specified by the standard, it refers to the rim that can be mounted on a rim and can maintain internal pressure, i.e., the rim with the smallest rim diameter and the next narrowest rim width, among rims that do not cause air leakage between the rim and tire.

[0033] In the above description, "contact width Wt" refers to the maximum linear distance in the axial direction of the tire at the contact surface with the flat plate when the tire is mounted on a "regular rim," inflated to an air pressure of 250 kPa, and the tire is placed stationary in a vertical position on a flat plate and a "regular load" is applied.

[0034] Here, the ground contact width Wt (mm) is preferably 153 mm or more, more preferably 154 mm or more, even more preferably 155 mm or more, even more preferably 156 mm or more, and even more preferably 173 mm or more. On the other hand, although there is no particular upper limit, it is preferably 275 mm or less, more preferably 245 mm or less, and even more preferably 215 mm or less.

[0035] Furthermore, the diameter Dt (mm) is preferably 691 mm or more, more preferably 692 mm or more, even more preferably 693 mm or more, even more preferably 694 mm or more, even more preferably 695 mm or more, even more preferably 698 mm or more, even more preferably 699 mm or more, even more preferably 700 mm or more, and even more preferably 701 mm or more.

[0036] The "normal load" is a load determined for each tire by each standard in the standard system, including the standard on which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, this is the maximum load capacity, in the case of TRA, this is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, this is the "LOAD CAPACITY".

[0037] Furthermore, in a rubber component containing isoprene rubber and SBR rubber, if the difference in the compounding amounts of the isoprene rubber and the SBR rubber becomes small, the isoprene rubber phase and the SBR rubber phase form a co-continuous phase, which is thought to easily hinder the movement of each phase. In particular, in tires with a small total width (small contact width), the grip force decreases when a steering angle is applied, so by increasing the difference in the compounding amounts of the isoprene rubber and the SBR rubber to form a sea-island structure, maneuverability can be improved, and it is thought that slippage in rainy weather can be prevented and wear resistance can be improved.

[0038] Based on this idea, experiments and studies were conducted and it was found that the "difference in the compounding amount of isoprene-based rubber and SBR rubber" and the "contact width" need only satisfy (Equation 4) |R2-R1| x Wt≧3500.

[0039] The above-mentioned |R2-R1|×Wt is more preferably 6120 or more, even more preferably 6160 or more, even more preferably 6200 or more, even more preferably 6240 or more, even more preferably 6920 or more, even more preferably 6960 or more, even more preferably 7000 or more, even more preferably 7040 or more, and even more preferably 7080 or more. There is no particular upper limit, but it is preferably 10000 or less.

[0040] Further experiments and studies revealed that if the complex modulus E* (MPa) of a rubber composition measured under conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, and the contact width Wt (mm) satisfy the following formula, slip prevention in rainy weather and wear resistance can be further improved. E* x Wt≦2000

[0041] The E* is measured on rubber cut out from at least a portion radially outward of the groove bottom of the tire, preferably from a portion radially outward of half the depth of the deepest circumferential groove. Specifically, the measurement can be performed using a viscoelasticity measuring device, for example, an "IPLEXER (registered trademark)" manufactured by GABO Corporation.

[0042] Here, E* (MPa) is preferably 7.5 MPa or more, more preferably 8.0 MPa or more, even more preferably 8.5 MPa or more, and even more preferably 9.0 MPa or more. The upper limit is not particularly limited, but is preferably 15.0 MPa or less. Furthermore, E* x Wt is preferably 1575 or less, more preferably 1557 or less, even more preferably 1479 or less, even more preferably 1416 or less, even more preferably 1404 or less, even more preferably 1386 or less, even more preferably 1326 or less, even more preferably 1320 or less, and even more preferably 1300.5 or less. On the other hand, the lower limit is not particularly limited, but is preferably 1000 or more. [2] Embodiments of the Present Disclosure Hereinafter, the present disclosure will be specifically described based on embodiments.

[0043] 1. Rubber Composition Forming the Tread Portion In the present embodiment, the rubber composition of the rubber layer forming at least one layer of the tread portion (hereinafter also simply referred to as "rubber composition") can be obtained from the rubber components and other compounding materials described below.

[0044] (a) Rubber Component In this embodiment, as shown in (Formula 1), styrene-butadiene rubber and isoprene-based rubber are contained in an amount of 60 parts by mass or more, preferably 75 parts by mass or more and 85 parts by mass or less, per 100 parts by mass of the rubber component, and as shown in (Formula 2), the isoprene-based rubber is contained in an amount of 35 parts by mass or more and 80 parts by mass or less, preferably 55 parts by mass or more and 65 parts by mass or less.

[0045] (a) Isoprene-based rubber Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Of these, NR is preferably used.

[0046] Specific examples of NR include SIR20, RSS#3, TSR20, and other commonly used NRs in the tire industry. IR is not particularly limited, and examples of IR include IR2200 and other commonly used NRs in the tire industry. Modified NR includes deproteinized natural rubber (DPNR), high-purity natural rubber (UPNR), and other modified NRs, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, and other modified IRs, including epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0047] (b) Styrene-butadiene rubber (SBR) As the styrene-butadiene rubber, SBR having a weight-average molecular weight of, for example, 100,000 or more and 2,000,000 or less is preferably used. This can improve the strength of the SBR phase against strain and stress, and can further improve the breaking strength of the tire.

[0048] The styrene content in the SBR used in this embodiment (hereinafter also referred to as "styrene amount") is preferably 5% by mass or more and 25% by mass or less. The styrene content in the rubber composition is preferably 1% by mass or more and 5% by mass or less. This makes it possible to suppress aggregation of styrene units in the rubber composition, thereby improving tread conformability. The amount of vinyl bonds (amount of 1,2-bonded butadiene units) in the butadiene portion of the SBR is preferably 40% by mass or less. The structure of the SBR (measurement of the styrene amount and vinyl bond amount) can be performed using, for example, a JNM-ECA series instrument manufactured by JEOL Ltd.

[0049] The SBR is not particularly limited, and examples thereof include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. The SBR may be either unmodified SBR or modified SBR, but modified S-SBR is preferred because it is expected to improve dispersibility and further improve abrasion resistance and slip resistance.

[0050] The modified SBR may be any SBR having a functional group that interacts with a filler such as silica, and examples thereof include terminal-modified SBR in which at least one terminal of the SBR has been modified with a compound (modifying agent) having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain-terminal-modified SBR in which the main chain and the above functional group have been modified with the above modifier, and main-chain-terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier, and terminal-modified SBR in which the SBR has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and into which a hydroxyl group or an epoxy group has been introduced.

[0051] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0052] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifier) ​​represented by the following formula can be used.

[0053]

[0054] In the formula, R １ , R ２ and R ３ are the same or different and represent an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (—COOH), a mercapto group (—SH), or a derivative thereof. ４ and R ５ are the same or different and represent a hydrogen atom or an alkyl group. ４ and R ５ may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0055] As the modified SBR modified with the compound (modifying agent) represented by the above formula, SBR in which the polymerization terminals (active terminals) of solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with the compound represented by the above formula (such as the modified SBR described in JP 2010-111753 A).

[0056] R １ , R ２ and R ３ is preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). ４ and R ５is preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. ４ and R ５ When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (e.g., a cyclohexyloxy group) and an aryloxy group (e.g., a phenoxy group, a benzyloxy group).

[0057] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0058] Furthermore, modified SBR modified with the following compounds (modifiers) can also be used as the modified SBR. Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidylamino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, Alkoxysilanes such as thyltriethoxysilane; (thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; Benzaldehyde compounds having an amino group and / or a substituted amino group, such as dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde, and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-t-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam, as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-triones , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

[0059] Examples of SBR that can be used include SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, Versalis, etc. SBR may be used alone or in combination of two or more types. When two or more types of SBR are used in combination, the weight average of each SBR is used for the above-mentioned styrene amount, vinyl bond amount, etc.

[0060] (C) Butadiene Rubber The rubber composition may further contain butadiene rubber (BR) as a rubber component. When BR is contained, the amount of BR per 100 parts by mass of the rubber component is, for example, 40 parts by mass or less, preferably 20 parts by mass or less. The weight average molecular weight of the BR is, for example, 100,000 or more and 2,000,000 or less. The vinyl bond amount of the BR is, for example, 1% by mass or more and 30% by mass or less. The cis content of the BR is, for example, 1% by mass or more and 98% by mass or less. The trans content of the BR is, for example, 1% by mass or more and 60% by mass or less.

[0061] The BR is not particularly limited, and can be, for example, a BR with a high cis content (cis content of 90% or more), a BR with a low cis content, or a BR containing syndiotactic polybutadiene crystals. The BR can be either unmodified or modified, and examples of modified BR include modified BR with the aforementioned functional groups introduced therein. These can be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy.

[0062] As the BR, for example, products of Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0063] (d) Other Rubber Components The other rubber components may include rubbers (polymers) that are generally used in the manufacture of tires, such as nitrile rubber (NBR).

[0064] (b) Compounding Materials Other Than Rubber Component (a) Silica The rubber composition preferably contains silica as a reinforcing filler. The content per 100 parts by mass of the rubber component is preferably 60 parts by mass or more, more preferably 80 parts by mass or more. The upper limit is not particularly limited as long as the rubber composition can be kneaded, but is preferably, for example, about 200 parts by mass. This allows the silica to be dispersed throughout the rubber system without being unevenly distributed in either NR or SBR, thereby further improving wear resistance and slip resistance.

[0065] As silica, the BET specific surface area is 180m ２ / g or more, 300m ２ / g or less of silica can be preferably used. This further enhances the reinforcing properties of silica, thereby improving wear resistance in particular. The BET specific surface area is the nitrogen adsorption specific surface area (N ２ SA).

[0066] Specific examples of silica include dry process silica (anhydrous silica), wet process silica (hydrated silica), etc. Among these, wet process silica is preferred because it has a large number of silanol groups, and products available from, for example, Evonik, Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan, Tokuyama Corporation, etc. can be used.

[0067] (ii) Silane Coupling Agent The rubber composition preferably contains a silane coupling agent together with silica. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocalcium nitrate, Examples include sulfide-based compounds such as bamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These compounds may be used alone or in combination of two or more.

[0068] The content of the silane coupling agent is preferably, for example, 10 mass% or more and 15 mass% or less, more preferably 11 mass% or more, relative to 100 mass parts of silica.Specific silane coupling agents that can be used include products from Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., AZMAX Co., Ltd., and Dow Corning Toray Co., Ltd.

[0069] (C) Carbon Black The rubber composition preferably contains carbon black. The amount of carbon black per 100 parts by mass of the rubber component is, for example, 1 part by mass or more and 200 parts by mass or less, and more preferably 5 parts by mass or more.

[0070] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon blacks) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon blacks) such as FT and MT; and channel blacks (channel carbon blacks) such as EPC, MPC, and CC. These may be used alone or in combination of two or more.

[0071] The nitrogen adsorption specific surface area of ​​carbon black (N ２ SA) is, for example, 30 m ２ / g or more, 250m ２ The dibutyl phthalate (DBP) absorption of carbon black is, for example, 50 ml / 100 g or more and 250 ml / 100 g or less. The nitrogen adsorption specific surface area of ​​carbon black is measured in accordance with ASTM D4820-93, and the DBP absorption is measured in accordance with ASTM D2414-93.

[0072] Specific carbon blacks are not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available carbon blacks include those manufactured by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nichika Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These may be used alone or in combination of two or more.

[0073] (D) Plasticizer Component The rubber composition may contain a plasticizer component such as oil or a thermoplastic resin. The content of the plasticizer component is preferably, for example, 5 parts by mass or more and 40 parts by mass or less, more preferably 8 parts by mass or more and 35 parts by mass or less, and even more preferably 15 parts by mass or more and 25 parts by mass or less, per 100 parts by mass of the rubber component. This weakens the cohesive force between silica particles during kneading of the rubber composition and improves dispersibility, thereby improving the tread's ability to follow the road surface and further improving wear resistance and slip resistance. The oil content also includes the amount of oil contained in the rubber (oil-extended rubber).

[0074] Examples of oils include process oils, vegetable oils, and mixtures thereof. Examples of process oils that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice bran oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more.

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

[0076] Examples of plasticizer components of thermoplastic resins (resins) include C5 resins, C5-C9 resins, C9 resins, terpene resins, terpene-aromatic compound resins, rosin resins, dicyclopentadiene resins (DCPD resins), and alkylphenol resins.

[0077] "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as the C5 petroleum resin.

[0078] "C9 petroleum resin" (aromatic petroleum resin) refers to a resin obtained by polymerizing a C9 fraction, and may be hydrogenated or modified. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. Preferred aromatic vinyl resins are homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene, with copolymers of α-methylstyrene and styrene being more preferred, due to their economical efficiency, ease of processing, and excellent heat generation. Examples of aromatic vinyl resins that can be used include those commercially available from Kraton, Eastman Chemical, and the like.

[0079] "C5-C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of the C5 fraction and the C9 fraction include the petroleum fractions described above. As the C5-C9 petroleum resin, for example, commercially available products from Tosoh Corporation, LUHUA Corporation, etc. can be used.

[0080] Examples of terpene resins and terpene-aromatic compound resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C ５ H ８ ) ｎ Monoterpenes (C １０ H １６ ), sesquiterpenes (C １５ H ２４ ), diterpenes (C ２０ H ３２ ), and examples thereof include α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, and γ-terpineol.

[0081] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are made from the above-mentioned terpene compounds, as well as hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins. Specific examples include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

[0082] As commercially available terpene resins, for example, products from Yasuhara Chemical Co., Ltd. can be used, and they may be used alone or in combination of two or more kinds.

[0083] The rosin-based resin is not particularly limited, but examples thereof include natural resin rosin and rosin-modified resins obtained by modifying rosin by hydrogenation, disproportionation, dimerization, esterification, etc.

[0084] The alkylphenol resin is not particularly limited, but examples thereof include alkylphenol formaldehyde resin, alkylphenol acetylene resin, and oil-modified phenol formaldehyde resin.

[0085] (e) Antiaging Agent The rubber composition preferably contains an antioxidant. The content of the antioxidant per 100 parts by mass of the rubber component is, for example, 1 part by mass or more and 10 parts by mass or less, and more preferably 2.5 parts by mass or more.

[0086] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. p-phenylenediamine-based antioxidants such as quinolone; quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more.

[0087] As the antioxidant, for example, products available from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0088] (F) Stearic Acid The rubber composition may contain stearic acid. The content of stearic acid is, for example, 0.5 parts by mass or more and 10.0 parts by mass or less, and more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component. As the stearic acid, a conventionally known stearic acid can be used, for example, products from NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc.

[0089] (G) Zinc Oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, 0.5 parts by mass or more and 10 parts by mass or less, and more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known product can be used, and for example, products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc. can be used.

[0090] (H) Crosslinking Agent and Vulcanization Accelerator The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, 0.1 parts by mass or more and 10.0 parts by mass or less, and more preferably 2 parts by mass or more, per 100 parts by mass of the rubber component.

[0091] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, soluble sulfur, etc., which are commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0092] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0093] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms such as TACKIROL V200 manufactured by Taoka Chemical Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylene-dithiosulfate dihydrate) manufactured by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane) manufactured by LANXESS, as well as organic peroxides such as dicumyl peroxide.

[0094] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, 0.3 parts by mass or more and 10.0 parts by mass or less, and more preferably 1 part by mass or more, per 100 parts by mass of the rubber component.

[0095] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, N-t-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more.

[0096] (i) Others In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides, and fillers such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. The content of these additives is, for example, 0.1 part by mass or more and 200 parts by mass or less per 100 parts by mass of the rubber component.

[0097] 2. Preparation of Tread Rubber Composition The rubber composition is prepared by a general method, for example, a production method including a base kneading step of kneading a rubber component with a filler such as silica or carbon black, and a finish kneading step of kneading the kneaded product obtained in the base kneading step with a crosslinking agent.

[0098] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0099] The kneading temperature in the base kneading step is, for example, 50° C. or higher and 200° C. or lower, and the kneading time is, for example, 30 seconds or higher and 30 minutes or lower. In the base kneading step, in addition to the above components, compounding agents conventionally used in the rubber industry, for example, softeners such as oil, stearic acid, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as needed.

[0100] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, room temperature or higher and 80°C or lower, and the kneading time is, for example, 1 minute or longer and 15 minutes or shorter. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

[0101] 3. Tire Manufacturing The tire of the present disclosure is manufactured by a conventional method using the unvulcanized rubber composition obtained through the above-described finishing mixing step. That is, the unvulcanized rubber composition is extruded to match the shape of each tire component of the tread, and then molded together with other tire components in a tire building machine by a conventional method to first produce an unvulcanized tire.

[0102] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component for withstanding the load, impact, and inflation pressure to which the tire is subjected, and a belt as a component for tightly fastening the carcass and increasing the rigidity of the tread are wound around a forming drum, and both ends of the carcass are fixed to both side edges, and bead portions as components for fixing the tire to the rim are arranged. After forming into a toroidal shape, a tread is attached to the center of the outer periphery, and sidewall portions as components for protecting the carcass and withstanding bending are attached to the radially outer side, thereby producing an unvulcanized tire.

[0103] In this embodiment, it is preferable to provide an inclined belt layer that extends at an angle of 55° or more and 75° or less with respect to the tire circumferential direction as the belt, thereby ensuring the durability of the tire and sufficiently maintaining the rigidity of the tread.

[0104] The unvulcanized tire is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization process can be carried out by using a known vulcanization method. The vulcanization temperature is, for example, 120°C or higher and 200°C or lower, and the vulcanization time is, for example, 5 minutes or higher and 15 minutes or lower.

[0105] At this time, the tire is molded into a shape that satisfies the above-mentioned (Equation 3) and (Equation 4).

[0106] Specific tires that can satisfy the above (Equation 3) and (Equation 4) include tires with size notations such as 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, and 195 / 55R20.

[0107] In the present embodiment, among the tires that can satisfy (Equation 1) to (Equation 4), it is preferable to apply the present invention to pneumatic tires for passenger cars. By satisfying these equations, both the wear resistance and the slip resistance are improved in a balanced manner, and in particular, this can more suitably contribute to solving the problem in the present disclosure of achieving a high level of both wear resistance and slip resistance when driving in the rain.

[0108] The pneumatic tires for passenger cars referred to here are tires mounted on automobiles with four wheels and have a maximum load capacity of 1000 kg or less.

[0109] The maximum load capacity is not particularly limited as long as it is 1000 kg or less, but generally, as the maximum load capacity increases, the tire weight tends to increase, and accordingly the braking distance becomes longer due to inertia. Therefore, it is preferably 900 kg or less, more preferably 800 kg or less, and even more preferably 700 kg or less.

[0110] From the viewpoint of the braking distance due to inertia described above, the tire weight is preferably 20 kg or less, more preferably 15 kg or less, and even more preferably 12 kg or less, 10 kg or less, or 8 kg or less. Note that the tire of the present disclosure may be equipped with electronic components. In this case, the tire weight referred to here includes the weight of the electronic components and the electronic component mounting members. Furthermore, if a sealant, sponge, or the like is provided in the inner cavity, the tire weight also includes these.

[0111] Hereinafter, the present disclosure will be described more specifically with reference to examples.

[0112] 1. Production of Rubber Composition for Tread First, a rubber composition for a tread was produced.

[0113] (1) Mixed Materials First, the following mixed materials were prepared.

[0114] (a) Rubber component (a) NR: TSR20 (b-1) SBR-A: T3830 (Tufden 3830) manufactured by Asahi Kasei Corporation (styrene content: 35% by mass) (b-2) SBR-B: Nipol NS616 manufactured by Nippon Zeon Co., Ltd. (modified S-SBR, styrene content: 20% by mass) (c) BR: BR150 manufactured by Ube Industries, Ltd.

[0115] (b) Compounding materials other than rubber components (a) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation (b-1) Silica-A: Ultrasil VN3 manufactured by Evonik (BET specific surface area: 140 m ２ / g) (B-2) Silica-B: Ultrasil 9000Gr manufactured by Evonik (BET specific surface area: 210 m ２ / g) (c) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Degussa Corporation (d) Oil: Process X-140 manufactured by Japan Energy Corporation (e-1) Resin-A: Petrotack 100V (C5 resin) manufactured by Tosoh Corporation (e-2) Resin-B: YS Polystar U130 (terpene-aromatic compound resin) manufactured by Yasuhara Chemical Co., Ltd. (f) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (g) Stearic acid: Camellia stearic acid manufactured by NOF Corporation (h) Antiaging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. (i) Crosslinking agent and vulcanization accelerator Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0116] (2) Production of Rubber Compositions According to the formulations A-1 to A-6 and B-1 to B-9 shown in Table 1, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes under the condition of 150°C using a Banbury mixer to obtain kneaded materials. The amounts of each compound are in parts by mass.

[0117]

[0118] 2. Tire Manufacturing Next, sulfur and a vulcanization accelerator were added to the resulting kneaded mixture, and the mixture was kneaded using an open roll at 80°C for 5 minutes to obtain a tread rubber composition. A tread was molded using the resulting tread rubber composition, and the resulting tread was laminated together with other tire components to form an unvulcanized tire. The tire was then press-vulcanized for 10 minutes at 170°C to produce test tires of sizes 155 (Table 2) and 175 (Table 3). Tables 2 and 3 also show the contact width Wt (mm) and diameter Dt (mm) of each test tire, as well as the complex modulus E* (MPa) of each tread composition, measured using a GABO "Eplexer" under conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%.

[0119] 3. Performance Evaluation Test (1) Slip Resistance Each test tire was mounted on all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000 cc) and inflated to 250 kPa. The vehicle was then driven around a test course on a wet road surface while gradually increasing its speed in a steady circular motion, and the maximum speed at which the driver felt the vehicle begin to slip was measured. Evaluation was performed by calculating the average of the measurement results from five drivers for each test tire and then indexing the average against the reference test tire. A higher value indicates better slip resistance when driving in the rain. The results are also shown in Tables 2 and 3.

[0120] (2) Abrasion Resistance Each test tire was mounted on all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000 cc) and inflated with air at 250 kPa. After driving 8000 km at a speed of 80 km / h on a test course on a wet road surface, the groove depth near the equator of the tire was measured and the reduction rate compared to the depth before the test was calculated. Evaluation was performed by indexing the ratio of the result for the standard test tire to the result for each test tire using the following formula. A larger value indicates better abrasion resistance. The results are also shown in Tables 2 and 3. Abrasion resistance = [(reduction rate of standard test tire / reduction rate of test tire)] x 100

[0121] (3) Evaluation Results Table 2 shows the evaluation results for the size 155 type, and Table 3 shows the evaluation results for the size 175 type. Note that the test tire used as the reference tire is the test tire of Example 1-1 in Table 2, and the test tire of Example 2-1 in Table 3. The balance between slip resistance and wear resistance can be evaluated by averaging the evaluation results of (1) slip resistance and (2) wear resistance.

[0122]

[0123]

[0124] Tables 2 and 3 show that, for both size 155 and size 175 tires, if all of the above-described (Equations 1) to (Equations 4) are satisfied, a tire can be provided that exhibits high levels of both wear resistance and slip resistance when running in the rain.

[0125] Furthermore, it is clear that by satisfying the requirements defined in claim 2 and subsequent claims, it is possible to provide a tire that achieves both high levels of wear resistance and slip resistance when running in the rain.

[0126] On the other hand, if any of (Equation 1) to (Equation 4) is not satisfied, it cannot be said that a high level of both wear resistance and slip resistance when driving in the rain is achieved.

[0127] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above embodiments. Various modifications can be made to the above embodiments within the scope of the same or equivalent to the present disclosure.

[0128] The present disclosure (1) is a pneumatic tire characterized in that at least one rubber layer forming a tread portion is formed from a rubber composition containing styrene-butadiene rubber and isoprene-based rubber as rubber components, and the amount of the styrene-butadiene rubber in 100 parts by mass of the rubber component is R1 (parts by mass) and the amount of the isoprene-based rubber is R2 (parts by mass), and when the tire is mounted on a regular rim and the internal pressure is set to 250 kPa, the tire has a contact width Wt (mm) and a diameter Dt (mm), and the following (formulas 1) to (formula 4) are satisfied: R1+R2≧60 (formula 1) 35≦R2≦80 (formula 2) 1963.4≦(Dt ２ ×π / 4) / Wt≦2827.4 (Formula 3) |R2-R1|×Wt≧3500 (Formula 4)

[0129] The present disclosure (2) is the pneumatic tire according to the present disclosure (1), characterized in that the weight average molecular weight of the styrene-butadiene rubber is 100,000 or more and 2,000,000 or less.

[0130] The present disclosure (3) is the pneumatic tire according to the present disclosure (1) or (2), characterized in that the styrene-butadiene rubber is a modified solution-polymerized styrene-butadiene rubber.

[0131] The present disclosure (4) is a pneumatic tire characterized in that the styrene content in the styrene-butadiene rubber is 5% by mass or more and 25% by mass or less, and is any combination with any of the present disclosures (1) to (3).

[0132] The present disclosure (5) is a pneumatic tire characterized in that the styrene content in the rubber composition is 1 mass % or more and 5 mass % or less, and is any combination with any of the present disclosures (1) to (4).

[0133] The present disclosure (6) is a pneumatic tire characterized in that the rubber composition further contains 40 parts by mass or less of butadiene rubber per 100 parts by mass of the rubber component, and is any combination with any of the present disclosures (1) to (5).

[0134] The present disclosure (7) is a pneumatic tire characterized in that the rubber composition contains 5 parts by mass or more and 40 parts by mass or less of a plasticizer component per 100 parts by mass of the rubber component, and is any combination with any of the present disclosures (1) to (6).

[0135] The present disclosure (8) is the pneumatic tire according to the present disclosure (7), characterized in that the plasticizer component contains a thermoplastic resin.

[0136] The present disclosure (9) is the pneumatic tire according to the present disclosure (8), characterized in that the thermoplastic resin is a thermoplastic resin selected from the group consisting of C5-based resins, C5-C9-based resins, C9-based resins, terpene-based resins, terpene-aromatic compound-based resins, rosin-based resins, dicyclopentadiene resins, and alkylphenol-based resins.

[0137] The present disclosure (10) is a pneumatic tire characterized in that the rubber composition contains 60 parts by mass or more of silica per 100 parts by mass of the rubber component, and is any combination with any of the present disclosures (1) to (9).

[0138] The present disclosure (11) is characterized in that the BET specific surface area of ​​the silica is 180 m ２ / g or more, 300m ２ / g or less, and is a pneumatic tire according to the present disclosure (10).

[0139] The present disclosure (12) is the pneumatic tire according to the present disclosure (10) or (11), characterized in that a silane coupling agent is contained in an amount of 10 mass % or more and 15 mass % or less relative to 100 mass parts of the silica.

[0140] The present disclosure (13) is a pneumatic tire in any combination with any of the present disclosures (1) to (12), characterized in that when the complex modulus of elasticity of the rubber composition measured under conditions of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is defined as E* (MPa), the following formula is satisfied: E*×Wt≦2000

[0141] The present disclosure (14) is a pneumatic tire characterized in that the tread portion is formed from a plurality of rubber layers, and the rubber composition is used in a cap rubber layer of the tread, and is any combination with any of the present disclosures (1) to (13).

[0142] The present disclosure (15) is characterized by being a pneumatic tire for passenger cars, and is a pneumatic tire in any combination with any of the present disclosures (1) to (14).

Claims

1. A pneumatic tire, in which at least one rubber layer forming a tread portion is formed from a rubber composition containing styrene-butadiene rubber and isoprene-based rubber as rubber components, and the amount of the styrene-butadiene rubber in 100 parts by mass of the rubber component is R1 (parts by mass) and the amount of the isoprene-based rubber is R2 (parts by mass), and when the tire is mounted on a regular rim and the internal pressure is set to 250 kPa, the tire has a contact width Wt (mm) and a diameter Dt (mm), and the following (formula 1) to (formula 4) are satisfied. R1+R2≧60 (Formula 1) 35≦R2≦80 (Formula 2) 1963.4≦(Dt ２ ×π / 4) / Wt≦2827.4 (Formula 3) |R2-R1|×Wt≧3500 (Formula 4) 2. The pneumatic tire according to claim 1, wherein the weight average molecular weight of the styrene-butadiene rubber is 100,000 or more and 2,000,000 or less.

3. The pneumatic tire according to claim 1 or 2, characterized in that the styrene-butadiene rubber is a modified solution-polymerized styrene-butadiene rubber.

4. A pneumatic tire according to any one of claims 1 to 3, characterized in that the styrene butadiene rubber has a styrene content of 5 mass % or more and 25 mass % or less.

5. A pneumatic tire according to any one of claims 1 to 4, characterized in that the styrene content in the rubber composition is 1 mass % or more and 5 mass % or less.

6. A pneumatic tire according to any one of claims 1 to 5, characterized in that the rubber composition further contains 40 parts by mass or less of butadiene rubber per 100 parts by mass of the rubber component.

7. A pneumatic tire according to any one of claims 1 to 6, characterized in that the rubber composition contains 5 parts by mass or more and 40 parts by mass or less of a plasticizer component per 100 parts by mass of the rubber component.

8. The pneumatic tire according to claim 7, characterized in that the plasticizer component contains a thermoplastic resin.

9. The pneumatic tire according to claim 8, wherein the thermoplastic resin is a thermoplastic resin selected from the group consisting of C5 resins, C5-C9 resins, C9 resins, terpene resins, terpene-aromatic compound resins, rosin resins, dicyclopentadiene resins, and alkylphenol resins.

10. A pneumatic tire according to any one of claims 1 to 9, characterized in that the rubber composition contains 60 parts by mass or more of silica per 100 parts by mass of the rubber component.

11. The BET specific surface area of ​​the silica is 180 m ２ / g or more, 300m ２ The pneumatic tire according to claim 10, characterized in that the tensile strength is 1 / g or less.

12. A pneumatic tire as described in claim 10 or 11, characterized in that a silane coupling agent is contained in an amount of 10 mass % or more and 15 mass % or less relative to 100 mass parts of the silica.

13. The pneumatic tire according to any one of claims 1 to 12, characterized in that the following formula is satisfied when the complex modulus of elasticity of the rubber composition measured under conditions of 30°C, a frequency of 10 Hz, an initial strain of 5% and a dynamic strain rate of 1% is defined as E* (MPa): E*×Wt≦2000 14. A pneumatic tire as claimed in any one of claims 1 to 13, characterized in that the tread portion is formed from a plurality of rubber layers, and the rubber composition is used in a cap rubber layer of the tread.

15. A pneumatic tire according to any one of claims 1 to 14, which is a pneumatic tire for passenger cars.