Pneumatic tire

Abstract

A pneumatic tire is provided that has a beneficial balance of wear resistance and anti-skid properties, particularly with high compatibility of wear resistance and anti-skid properties when driving in rainy conditions. The pneumatic tire includes at least one rubber layer forming the tread, the tread being formed of a rubber composition comprising styrene-butadiene rubber and isoprene rubber as rubber components and satisfying the following formulas (1) to (4), where R1 (parts by mass) is the amount of styrene-butadiene rubber relative to 100 parts by mass of the rubber component, R2 (parts by mass) is the amount of isoprene rubber relative to 100 parts by mass of the rubber component, Wt (mm) is the ground contact width when mounted on a standard rim and inflated to an internal pressure of 250 kPa, and Dt (mm) is the tire diameter 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 ≤ (Dt) 2 ×π / 4) / Wt≦2827.4; (4): |R2‑R1|×Wt≧3500.

Description

Technical Field

[0001] This disclosure relates to an inflatable tire. Background Technology

[0002] In recent years, due to increasing concerns about environmental issues and economic benefits, the requirements for automobile fuel efficiency have been growing, and there is a need to improve the fuel efficiency of pneumatic tires (hereinafter referred to as "tires") installed on automobiles.

[0003] Traditionally, as a specific means of improving tire fuel efficiency, tire treads are typically formed using tire compounding containing modified synthetic rubber (terminal modified polymers are applied to synthetic rubber, and the number of ends is increased by reducing the molecular weight of the polymer to improve the modification effect).

[0004] However, in this type of tire compound, the polymer contained in the compound has a low molecular weight, which may reduce the breaking strength and wear resistance of the tire product.

[0005] Therefore, it has been proposed to blend isoprene rubber (which has excellent fracture strength) with styrene-butadiene rubber (SBR: synthetic rubber) (e.g., Patent Documents 1 to 4).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: JP 2014-213836 A

[0009] Patent Document 2: JP 2017-52329 A

[0010] Patent Document 3: JP 2018-154181 A

[0011] Patent Document 4: JP 2019-85445 A Summary of the Invention

[0012] The problem to be solved by the present invention

[0013] However, even if a small amount of isoprene rubber is added to SBR, the wear resistance will still deteriorate because the reinforcing filler (such as silica) is not evenly distributed in the isoprene rubber phase, resulting in insufficient reinforcement of the SBR phase.

[0014] Furthermore, simply adding isoprene-based rubber will reduce the SBR ratio in the rubber composition, which may lead to a decrease in tire grip and anti-skid performance on the road surface.

[0015] As mentioned above, there is still room for improvement in wear resistance and anti-skid properties in traditional compound design methods, especially for tires that are required to have both anti-skid and wear resistance when driving in the rain.

[0016] Therefore, this disclosure provides a pneumatic tire in which wear resistance and anti-skid properties are improved in a good balance, especially when driving in the rain, wear resistance and anti-skid properties are highly compatible.

[0017] Problem-solving methods

[0018] The authors of this disclosure have diligently researched solutions to the above-mentioned problems and found that these problems can be solved by the following disclosure, thereby completing this disclosure.

[0019] This disclosure pertains to an inflatable tire, wherein:

[0020] At least one of the rubber layers forming the tread area is formed of a rubber composition comprising styrene-butadiene rubber and isoprene rubber as rubber components;

[0021] When the amount of styrene-butadiene rubber in 100 parts by mass of rubber component is R1 (parts by mass) and the amount of isoprene rubber is R2 (parts by mass), and when the tire is mounted on a standardized rim with an internal pressure of 250 kPa and the tire's contact patch width is Wt (mm) and diameter is Dt (mm), the following equations (1) to (4) are satisfied:

[0022] R1+R2≧60 (Equation 1)

[0023] 35≦R²≦80 (Equation 2)

[0024] 1963.4≦(Dt 2 ×π / 4) / Wt≦2827.4(Equation 3)

[0025] |R2-R1|×Wt≧3500(Equation 4)

[0026] Effects of the present invention

[0027] According to this disclosure, a pneumatic tire in which wear resistance and anti-skid properties are improved in a good balance, especially when driving in the rain, can be provided. Detailed Implementation

[0028] The present disclosure will now be described in detail based on the embodiments.

[0029] [1] Features of the tires disclosed in this disclosure

[0030] First, the characteristics of the tire according to this disclosure will be described.

[0031] To address the aforementioned problems, namely, to provide a pneumatic tire that achieves a good balance between wear resistance and anti-skid properties, particularly exhibiting a high degree of compatibility between these two properties when driving in the rain, the present discloses that conventional techniques for controlling the physical properties of rubber through compounding are insufficient, and that the shape of the tire must be studied. Through various experiments and studies, the present discloses this invention.

[0032] Specifically, in the tire according to this disclosure, at least one of the rubber layers forming the tread is formed of a rubber composition comprising styrene-butadiene rubber (SBR rubber) and isoprene rubber as rubber components.

[0033] When the amount of SBR rubber is R1 (parts by mass) and the amount of isoprene rubber is R2 (parts by mass), the following equations (1) and (2) are satisfied:

[0034] R1+R2≧60 (Equation 1)

[0035] 35≦R²≦80 (Equation 2)

[0036] When the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the tire's contact patch width is Wt (mm) and its diameter is Dt (mm). The tire according to this disclosure further satisfies the following (Equation 3) and (Equation 4):

[0037] 1963.4≦(Dt 2 ×π / 4) / Wt≦2827.4(Equation 3)

[0038] |R2-R1|×Wt≧3500(Equation 4)

[0039] By possessing the above characteristics, wear resistance and anti-skid properties are improved in a good balance, and in particular, a tire with a high degree of compatibility between wear resistance and anti-skid properties can be provided when driving in the rain.

[0040] When the tread portion is formed of multiple rubber layers (e.g., a tread rubber layer forming the outermost surface of the tread portion and a base rubber layer forming the interior of the tread portion), this rubber composition is preferably used for the tread rubber layer. Furthermore, additional rubber layers may be provided between the tread rubber layer and the base rubber layer to form a tread portion with more than three layers.

[0041] In the tires according to this disclosure, the mechanism by which wear resistance and anti-skid properties are highly compatible when driving in the rain is presumed as follows.

[0042] As mentioned above, isoprene rubbers have excellent tensile strength. Therefore, when isoprene rubbers are used as rubber components in rubber compositions forming the tread, they are considered to effectively improve tire wear resistance.

[0043] However, when the tread is formed from a rubber composition containing only isoprene-based rubber as a rubber component, sufficient grip on wet surfaces cannot be guaranteed. This can lead to tire slippage and vehicle skidding if the throttle is turned while making a left or right turn in rainy weather. Furthermore, such slippage can result in decreased wear resistance.

[0044] Therefore, in this disclosure, SBR rubber (which has higher thermal properties than isoprene rubber and excellent grip) is used together with isoprene rubber as a rubber component; in 100 parts by mass of the rubber component, the total amount of isoprene rubber and SBR rubber is 60 parts by mass or more (Formula 1), and the amount of isoprene rubber is 35 parts by mass or more and 80 parts by mass or less (Formula 2).

[0045] Therefore, a good balance between wear resistance and anti-slip properties can be achieved, and heat generation can be increased while preventing the rubber from losing its traction due to uneven distribution of reinforcing fillers. Thus, a high degree of compatibility between wear resistance and anti-slip properties can be achieved when driving on wet roads in rainy weather.

[0046] The total amount of the aforementioned 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 isoprene-based rubber is more preferably 55 parts by mass or more and 65 parts by mass or less.

[0047] In addition, when driving in the rain, slippage occurs between the tread and the road surface, which increases the frequency of deformation applied to the tread rubber and reduces the vehicle's ability to follow the road surface.

[0048] Therefore, in this disclosure, when the tire is mounted on a standardized rim and the internal pressure is 250 kPa, the ground contact width Wt (mm) and diameter Dt (mm) satisfy 1963.4 ≦ (Dt) 2 ×π / 4) / Wt≦2827.4 (Equation 3).

[0049] In equation (3), (Dt) 2 The value of ×π / 4) / Wt is more preferably 1963.5 or more, further preferably 2018 or more, further preferably 2137 or more, further preferably 2143 or more, further preferably 2153 or more, further preferably 2155 or more, further preferably 2174 or more, further preferably 2187 or more, further preferably 2467 or more, further preferably 2474 or more, further preferably 2485 or more, further preferably 2492 or more, and further preferably 2501 or more.

[0050] Equation 3 above shows that the lateral area from the tire [(Dt / 2)] is relative to the tire's contact patch width Wt. 2 ×π) =(Dt2 [×π / 4] is larger than that of conventional tires. Therefore, the deformation frequency applied to the tread rubber can be lower than before, and the tread rubber can follow the road surface more easily. Moreover, since the heat generation in the SBR rubber phase effectively plays a role as a gripping force with the road surface, the frequency of contact with the road surface can be reduced even during normal driving, thus preventing slippage when driving in the rain and improving wear resistance.

[0051] In the above description, "standardized rim" refers to the rim defined for each tire within a standards system, including the standards upon which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Association), it is the standard rim of applicable dimensions described in the "JATMA Yearbook"; in the case of ETRTO (European Tyre and Rim Technology Organization), it is the "measuring rim" described in the "Standards Manual"; and in the case of TRA (Tire and Rim Association), it is the "design rim" described in the "Yearbook". In the case of tires not specified in the standards, it refers to a rim that can be assembled and maintain internal pressure, i.e., a rim that does not cause air leakage between the rim and the tire and has the minimum rim diameter and the narrowest rim width.

[0052] In the above description, "grounding width Wt" refers to the maximum straight-line distance between the tire and the contact surface of the flat plate in the axial direction when the tire is mounted on a "standardized rim", inflated with 250 kPa air pressure, placed statically on a vertical flat plate, and subjected to a "standardized load".

[0053] In this document, the grounding 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, there is no particular upper limit, but it is preferably 275 mm or less, more preferably 245 mm or less, and even more preferably 215 mm or less.

[0054] 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, even more preferably 701 mm or more.

[0055] In this article, "standardized load" refers to the load defined for each tire within a standard system, including the standard on which the tire is based, and refers to the maximum mass that the tire can bear. In the case of JATMA, it is the maximum load capacity; in the case of TRA, it is the maximum value described in the table "Tire Load Limits at Different Cold Inflation Pressures"; and in the case of ETRTO, it is the "load capacity".

[0056] Furthermore, in rubber components containing isoprene rubber and SBR rubber, when the difference in the blending amounts of isoprene rubber and SBR rubber decreases, the isoprene rubber phase and the SBR rubber phase form a co-continuous phase, which is thought to easily hinder the mutual movement of these phases. In particular, for tires with a small overall width (small ground contact width), grip decreases when the steering angle is set. Therefore, by further increasing the difference in the blending amounts of isoprene rubber and SBR rubber to form a sea-island structure, it is believed that flowability can be improved, thus preventing slippage in rainy weather and improving wear resistance.

[0057] Based on this idea, experiments and research were conducted, and it was found that the difference between the mixing amounts of isoprene rubber and SBR rubber and the grounding width should satisfy |R2-R1|×Wt≧3500 (Equation 4).

[0058] The aforementioned |R2-R1|×Wt is more preferably 6120 or more, further preferably 6160 or more, further preferably 6200 or more, further preferably 6240 or more, further preferably 6920 or more, further preferably 6960 or more, further preferably 7000 or more, further preferably 7040 or more, and further preferably 7080 or more. There is no particular upper limit, but it is preferably 10000 or less.

[0059] Further experiments and research revealed that when the complex elastic modulus E* (MPa) and ground contact width Wt (mm) of the rubber composition, measured under conditions of 30℃, 10Hz frequency, 5% initial strain, and 1% dynamic strain ratio, satisfy the following formula, it can further contribute to improved slip resistance and abrasion resistance in rainy weather:

[0060] E*×Wt≦2000

[0061] The measurement of E* is performed on the rubber cut radially outward from at least the bottom of the tire grooves, preferably radially outward from half the depth of the deepest circumferential groove. Specifically, it can be measured using a viscoelasticity measuring device such as the "Eplexor (registered trademark)" manufactured by GABO.

[0062] In this document, 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. There is no particular limitation on the upper limit, but it is preferably 15.0 MPa or less. Furthermore, E*×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, there is no particular limitation on the lower limit, but it is preferably 1000 or more.

[0063] [2] The SBR disclosed herein

[0064] The present disclosure will now be described in detail based on implementation methods.

[0065] 1. A rubber composition forming the tread area

[0066] In this embodiment, the rubber composition (hereinafter also referred to as the "rubber composition") forming at least one rubber layer of the tread can be obtained from the following rubber components and other compounding materials.

[0067] (a) Rubber components

[0068] In this embodiment, as shown in Formula 1, in 100 parts by mass of the rubber component, the content of styrene-butadiene rubber and isoprene-based rubber is 60 parts by mass or more, preferably 75 parts by mass or more and 85 parts by mass or less. As shown in Formula 2, the content of isoprene-based rubber is 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.

[0069] (a-1) Isoprene-based rubber

[0070] Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. Among these, NR is preferred.

[0071] Specific types of natural rubber (NR) can include, for example, SIR20, RSS#3, and TSR20, commonly used in the tire industry. There are no particular restrictions on IR; for example, IR 2200, commonly used in the tire industry, can be used. Modified NRs include deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR), while modified NRs include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IRs include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These can be used individually or in combination of two or more.

[0072] (a-2) Styrene-butadiene rubber (SBR)

[0073] As a styrene-butadiene rubber, SBR with a weight-average molecular weight of, for example, 100,000 or more and 2 million or less is preferred. Therefore, the resistance of the SBR phase to strain and stress can be improved, thereby further improving the breaking strength of the tire.

[0074] The styrene content (hereinafter also referred to as "styrene amount") in the SBR used in this embodiment 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. Therefore, the aggregation of styrene in the rubber composition can be suppressed, thereby improving the tread's following ability. The amount of vinyl bonds (the amount of 1,2-bonded butadiene units) in the butadiene portion of the SBR is preferably 40% by mass or less. Then, the structure of the SBR can be identified (by measuring the amount of styrene and the amount of vinyl bonds) using an instrument such as the JNM-ECA series manufactured by Nippon Egis Corporation.

[0075] There are no particular limitations on SBR; for example, emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR) can be used. SBR can be unmodified or modified, but when modified S-SBR is used, dispersibility is improved, potentially leading to further improvements in abrasion resistance and anti-slip properties. Therefore, modified S-SBR is preferred.

[0076] Modified SBRs can be any SBR with functional groups that interact with fillers such as silica. Examples include:

[0077] Terminal modified SBR (terminal modified SBR having the above-mentioned functional groups at the end), wherein at least one end of the SBR is modified with a compound (modifier) ​​having the above-mentioned functional groups.

[0078] Main chain modified SBR with functional groups on the main chain;

[0079] Main-chain end-modified SBR with functional groups on both the main chain and the ends (e.g., a main-chain end-modified SBR with the aforementioned functional groups on the main chain and at least one end modified with the aforementioned modifier); and

[0080] SBR is modified by using a polyfunctional compound with two or more epoxy groups in the molecule for modification (coupling) and introducing epoxy or hydroxyl groups to the terminal of the compound.

[0081] Examples of functional groups include: amino, amide, silyl, alkoxysilyl, isocyanate, imino, imidazo, urea, ether, carbonyl, oxycarbonyl, mercapto, thioether, dithioether, sulfonyl, sulfinyl, thiocarbonyl, ammonium, imide, hydrazine, azo, diazo, carboxyl, nitrile, pyridyl, alkoxy, hydroxyl, oxygen, and epoxy. Furthermore, these functional groups may have substituents.

[0082] In addition, as a modified SBR, an SBR modified with, for example, a compound (modifier) ​​represented by the following formula can be used.

[0083] [Chemical Formula 1]

[0084]

[0085] In the formula, R 1 R 2 and R 3 Same or different, and indicating alkyl, alkoxy, silyloxy, acetal, carboxyl (-COOH), mercapto (-SH) or their derivatives. R 4 and R 5 Same or different, and indicates a hydrogen atom or an alkyl group. R 4 and R 5 They can be combined to form a ring structure containing nitrogen atoms. n represents an integer.

[0086] As a modified SBR modified by the compound (modifier) ​​represented by the above formula, an SBR in which the polymerization end (active end) of a solution-polymerized styrene-butadiene rubber (S-SBR) is modified by the compound represented by the above formula (e.g., the modified SBR described in JP-A-2010-111753).

[0087] As R 1 R 2 and R 3 Alkoxy groups (preferably alkoxy groups having 1 to 8 carbon atoms, more preferably alkoxy groups having 1 to 4 carbon atoms) are suitable. As R 4 and R 5 Alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms) are suitable. n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. Further, when R... 4 and R 5 When combined with nitrogen atoms to form a cyclic structure, 4- to 8-membered rings are preferred. Alkoxy groups also include cycloalkoxy groups (such as cyclohexyloxy) and aryloxy groups (such as phenoxy and benzyloxy).

[0088] Specific examples of the aforementioned modifiers include: 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These can be used alone or in combination of two or more.

[0089] In addition, modified SBRs can also be used as modified SBRs by the following compounds (modifiers). Examples of modifiers include:

[0090] Polyhydric alcohol polyglycidyl ethers, such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether and trimethylolpropane triglycidyl ether;

[0091] Polyglycidyl ethers of aromatic compounds having two or more phenolic groups, such as diglycidylated bisphenol A;

[0092] Polyepoxides, such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene and polyepoxide liquid polybutadiene;

[0093] Tertiary amines containing epoxy groups, such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine;

[0094] Diglycidylamino compounds, such as diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidyl-m-xylyldiamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, and tetraglycidyl-1,3-diaminomethylcyclohexane;

[0095] Amino-containing acyl chlorides, such as bis-(1-methylpropyl)carbamoyl chloride, 4-morpholine carbamoyl chloride, 1-pyrrolidine carbamoyl chloride, N,N-dimethylcarbamoyl chloride and N,N-diethylcarbamoyl chloride;

[0096] Silane compounds containing epoxy groups, such as 1,3-bis-(glycidoxypropyl)-tetramethyldisiloxane and (3-glycidoxypropyl)-pentamethyldisiloxane;

[0097] Silane compounds containing thioether groups, such as (trimethylsilyl)[3-(trimethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl] sulfide, and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide;

[0098] N-substituted aziridine compounds, such as ethyleneimine and propyleneimine;

[0099] Alkoxysilanes, such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;

[0100] (Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-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;

[0101] Benzaldehyde compounds having an amino group and / or substituted amino groups, such as 4-N,N-dimethylaminobenzaldehyde, 4-N,N-diphenylaminobenzaldehyde and 4-N,N-divinylaminobenzaldehyde;

[0102] N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone and N-methyl-5-methyl-2-pyrrolidone;

[0103] N-substituted piperidinones, such as N-methyl-2-piperidinone, N-vinyl-2-piperidinone and N-phenyl-2-piperidinone;

[0104] N-substituted lactams, such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-lauryl lactam, N-vinyl-ω-lauryl lactam, N-methyl-β-propiolactam and N-phenyl-β-propiolactam;

[0105] N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethylurea, 1,3-divinylethylurea, 1,3-diethyl-2-imidazolinone, 1-methyl-3-ethyl-2-imidazolinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, and 1,7-bis(methylethylamino)-4-heptanone.

[0106] Modification using the above-mentioned compounds (modifiers) can be carried out by known methods.

[0107] As SBRs, SBRs manufactured and sold by companies such as Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, and Versalis Co., Ltd. can be used. SBRs can be used alone or in combination of two or more. When two or more SBRs are used in combination, the weight average of each SBR is used for the styrene content, vinyl bond content, etc. mentioned above.

[0108] (a-3) Butadiene rubber

[0109] The rubber composition may also contain butadiene rubber (BR) as a rubber component. When BR is present, the content of BR in 100 parts by weight of the rubber component is, for example, 40 parts by weight or less, preferably 20 parts by weight or less. The weight-average molecular weight of BR is, for example, 100,000 or more and 2 million or less. The vinyl bonding content of BR is, for example, 1% by weight or more and 30% by weight or less. The cis content of BR is, for example, 1% by weight or more and 98% by weight or less. The trans content of BR is, for example, 1% by weight or more and 60% by weight or less.

[0110] There are no particular limitations on BR (brane ester), and BRs with high cis content (cis content above 90%), low cis content, or containing isotactic polybutadiene crystals can be used. BRs can be unmodified or modified; examples of modified BRs include those with the aforementioned functional groups introduced. These can be used alone or in combination of two or more. The cis content can be measured by infrared absorption spectroscopy analysis.

[0111] As a BR (Brandinger), products from companies such as Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Zeon Corporation can be used.

[0112] (a-4) Other rubber components

[0113] In addition, as another rubber component, it may contain rubber (polymer) commonly used in the production of tires, such as nitrile rubber (NBR).

[0114] (b) Compounds other than rubber components

[0115] (b-1) Silicon dioxide

[0116] The rubber composition preferably contains silica as a reinforcing filler. The silica content is preferably 60 parts by mass or more, more preferably 80 parts by mass or more, relative to 100 parts by mass of the rubber component. There is no particular upper limit (as long as the rubber composition can be kneaded), but it is preferably, for example, about 200 parts by mass. Therefore, the silica is dispersed throughout the rubber system without being unevenly distributed in the NR or SBR, allowing for further improvement in abrasion resistance and anti-slip properties.

[0117] As silicon dioxide, a BET specific surface area of ​​180 m² is preferred. 2 / g or more and 300m 2 The silica content is below / g. Therefore, the reinforcing properties of silica can be further improved, especially the wear resistance. The BET specific surface area is the value of nitrogen adsorption specific surface area (N2SA) measured by the BET method according to ASTM D3037-93.

[0118] Specific examples of silica include dry-process silica (anhydrous silica) and wet-process silica (hydrated silica). Of these, wet-process silica is preferred because it contains a large number of silanol groups. Products from companies such as Evonik, Degussa, Rhodia, Tosoh Silicon Co., Ltd., Solvay Ltd., and Tokuyama Corporation can be used.

[0119] (b-2) Silane coupling agent

[0120] The rubber composition preferably contains both a silane coupling agent and silica. There are no particular limitations on the silane coupling agent. Examples of silane coupling agents include:

[0121] Sulfide-based silane coupling agents, such as 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)tetrasulfide, and bis(2-triethoxysilylethyl)tetrasulfide. 3-Trimethoxysilylpropyl disulfide, bis(4-triethoxysilylbutyl) disulfide, bis(3-trimethoxysilylpropyl) disulfide, bis(2-trimethoxysilylethyl) disulfide, bis(4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide;

[0122] Mercaptosilane coupling agents, such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, NXT and NXT-Z (both are available from Momentive).

[0123] Vinyl silane coupling agents, such as vinyltriethoxysilane and vinyltrimethoxysilane; amino silane coupling agents, such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane;

[0124] Epoxypropoxysilane coupling agents, such as γ-epoxypropoxypropyltriethoxysilane and γ-epoxypropoxypropyltrimethoxysilane;

[0125] Nitrosilane coupling agents, such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and

[0126] Chlorinated silane coupling agents, such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane.

[0127] These can be used individually or in combination of two or more.

[0128] For example, the content of the silane coupling agent is preferably 10% by mass or more and 15% by mass or less, more preferably 11 parts by mass or more (relative to 100 parts by mass of silicon dioxide). As specific silane coupling agents, products from companies such as Degussa, Momentive, Shin-Etsu Silicones, Tokyo Chemical Industry Co., Ltd., Azumax Corporation, and Toray Dow Corning Co., Ltd. can be used.

[0129] (b-3) Carbon black

[0130] The rubber composition preferably contains carbon black. The carbon black content is, for example, more than 1 part by mass and less than 200 parts by mass relative to 100 parts by mass of the rubber component.

[0131] There are no particular limitations on carbon black, and examples include: furnace black (furnace carbon black), such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal black (thermal cracking carbon black), such as FT and MT; and channel black (channel carbon black), such as EPC, MPC, and CC. These can be used alone or in combination of two or more.

[0132] For example, the nitrogen adsorption specific surface area (N2SA) of carbon black is 30 m². 2 / g or more and 250m 2 / g or less. For example, carbon black absorbs more than 50 mL / 100g and less than 250 mL / 100g of dibutyl phthalate (DBP). The nitrogen adsorption specific surface area of ​​carbon black is measured according to ASTM D4820-93, and the amount of DBP absorbed is measured according to ASTM D2414-93.

[0133] There are no specific restrictions on the type of carbon black used; examples include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. Commercially available products include those from companies such as Asahi Carbon Co., Ltd., Cabot Japan Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Co., Ltd., Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., and Columbia Carbon Co., Ltd. These can be used alone or in combination of two or more.

[0134] (b-4) Plasticizer components

[0135] The rubber composition may contain a plasticizer component, such as oil or a thermoplastic resin (resin). The content of the plasticizer component relative to 100 parts by weight of the rubber composition is preferably, for example, 5 parts by weight or more and 40 parts by weight or less, more preferably 8 parts by weight or more and 35 parts by weight or less, and even more preferably 15 parts by weight or more and 25 parts by weight or less. Therefore, when the rubber composition is kneaded, the tread's road surface following is improved due to the weakening of the cohesive forces between silica particles and the improvement of dispersibility, and wear resistance and anti-skid properties can be further improved. The oil content also includes the amount of oil contained in the rubber (oil-extended rubber).

[0136] Examples of oils include processing oils, vegetable oils, and mixtures thereof. Processing oils may include, for example, paraffinic processing oils, aromatic processing oils, naphthenic processing oils, etc. 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 oil, and tung oil. These can be used alone or in combination of two or more.

[0137] As specific examples of oils, products from Idemitsu Kosan Co., Ltd., Sankyo Oil & Chemical Co., Ltd., Nippon Oil Energy Co., Ltd., Orison Ltd., H&R, Toyokuni Oil Co., Ltd., Showa Shell Oil Co., Ltd., and Fuji Kosan Co., Ltd. can be used.

[0138] Examples of plasticizer components in 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.

[0139] "C5 series petroleum resin" refers to resin obtained by polymerizing C5 fractions. 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 a C5 series petroleum resin.

[0140] "C9-based petroleum resins" (aromatic petroleum resins) refer to resins obtained by polymerizing C9 fractions, which can 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, for example, coumarone-indene resin, coumarone resin, indene resin, and aromatic vinyl resins. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene, are preferred because they are economical, easy to process, and have excellent exothermic properties. Copolymers of α-methylstyrene and styrene are more preferred. As aromatic vinyl resins, those available from companies such as Clayton and Eastman Chemical can be used.

[0141] "C5-C9 series petroleum resin" refers to a resin obtained by copolymerizing C5 and C9 fractions, which can be hydrogenated or modified. Examples of C5 and C9 fractions include the aforementioned petroleum fractions. C5-C9 petroleum resins can be those purchased from, for example, Tosoh Corporation, LUHUA, etc.

[0142] Examples of terpene-based resins and terpene aromatic compound-based resins include polyterpenes, terpene phenols, and aromatically modified terpene resins. Polyterpenes include resins obtained by polymerizing terpene compounds and their hydrogenation additives. Terpene compounds include those with (C5H8) n Hydrocarbons and their oxygen-containing derivatives are composed of terpenes. Terpenes are compounds with terpenes as their basic skeleton, including α-pinene, β-pinene, dipentene, limonene, myrcene, allociperene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc.

[0143] Examples of polyterpenes include terpene resins made from the aforementioned terpene compounds, such as α-pinene resins, β-pinene resins, limonene resins, dipentene resins, and β-pinene / limonene resins, as well as hydrogenated terpene resins obtained by hydrogenating terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the aforementioned terpene compounds and phenolic compounds, as well as resins obtained by hydrogenating such resins. Specifically, resins obtained by condensing the aforementioned terpene compounds, phenolic compounds, and formalin may be mentioned. Examples of phenolic compounds include phenol, bisphenol A, cresol, xylene, etc. Examples of aromatic-modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, as well as resins obtained by hydrogenating such resins. There are no particular restrictions on aromatic compounds (as long as they have an aromatic ring), and examples include: phenolic compounds, such as phenol, alkylphenol, alkoxyphenol and phenol containing an unsaturated hydrocarbon group; naphthol compounds, such as naphthol, alkylnaphthol, alkoxynaphthol and naphthol containing an unsaturated hydrocarbon group; styrene derivatives, such as styrene, alkylstyrene, alkoxystyrene and styrene containing an unsaturated hydrocarbon group; coumarone, indene, etc.

[0144] As a commercially available terpene resin, products such as those from Yasuhara Chemical Co., Ltd. can be used. It can be used alone or in combination of two or more.

[0145] There are no particular limitations on rosin-based resins. Examples include natural rosin resins and rosin-modified resins obtained through hydrogenation, disproportionation, dimerization, esterification, etc.

[0146] There are no particular limitations on alkylphenol-formaldehyde resins; examples include alkylphenol-formaldehyde resins, alkylphenol-acetylene resins, and oil-modified phenol-formaldehyde resins.

[0147] (b-5) Anti-aging agents

[0148] The rubber composition preferably contains an anti-aging agent. The content of the anti-aging agent relative to 100 parts by weight of the rubber component is, for example, 1 part by weight or more and 10 parts by weight or less, more preferably 2.5 parts by weight or more.

[0149] Examples of anti-aging agents include: naphthylamine-based anti-aging agents, such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents, such as octyl diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; p-phenylenediamine-based anti-aging agents, 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-based anti-aging agents, such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol-based anti-aging agents, such as 2,6-di-tert-butyl-4-methylphenol and styrylphenol; and bisphenol-based, triphenol-based, or polyphenol-based anti-aging agents, such as tetra[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. These can be used alone or in combination of two or more.

[0150] As an anti-aging agent, products from companies such as Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinsei Chemical Co., Ltd., and Flextronics Co., Ltd. can be used.

[0151] (b-6) Stearic acid

[0152] The rubber composition may contain stearic acid. The stearic acid content, relative to 100 parts by weight of the rubber component, is, for example, 0.5 parts by weight or more and 10.0 parts by weight or less, more preferably 2 parts by weight or more. Conventionally known stearic acids can be used, such as those from Nippon Oil Co., Ltd., NOF Co., Ltd., Kao Corporation, Fujifilm, and Koh Geny Pharmaceutical Co., Ltd., and Chiba Fatty Acid Co., Ltd.

[0153] (b-7) Zinc oxide

[0154] The rubber composition may contain zinc oxide. The zinc oxide content, relative to 100 parts by weight of the rubber component, is, for example, 0.5 parts by weight or more and 10 parts by weight or less, more preferably 1.5 parts by weight or more. Conventionally known zinc oxides may be used, such as products from Mitsui Metal Mining Co., Ltd., Toho Co., Ltd., Hakusui Technology Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Co., Ltd.

[0155] (b-8) Crosslinking agents and vulcanization accelerators

[0156] The rubber composition preferably contains a crosslinking agent (e.g., 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, more preferably 2 parts by mass or more, relative to 100 parts by mass of the rubber component.

[0157] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and soluble sulfur, all of which are commonly used in the rubber industry. These can be used alone or in combination of two or more.

[0158] As sulfur, products from companies such as Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flex Industries, Nippon Inkyu Corporation, and Hosoi Chemical Industry Co., Ltd. can be used.

[0159] Examples of crosslinking agents other than sulfur include: sulfur-containing vulcanizing agents, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylene dithiosulfate dihydrate) manufactured by Flex, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyl dithiohexane)) manufactured by Lanxess; and organic peroxides, such as dicumyl peroxide.

[0160] 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, more preferably 1 part by mass or more, relative to 100 parts by mass of the rubber component.

[0161] Examples of vulcanization accelerators include:

[0162] Thiazole-based sulfidation accelerators, such as 2-mercaptobenzothiazole, di-2-benzothiazole disulfide, and N-cyclohexyl-2-benzothiazole sulfenamide;

[0163] Thiuram-based vulcanization accelerators, such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetra(2-ethylhexyl)thiuram disulfide (TOT-N).

[0164] Sulphamides are vulcanization accelerators, such as N-cyclohexyl-2-benzothiazole sulfenamide, N-tert-butyl-2-benzothiazole sulfenamide, N-ethoxy-2-benzothiazole sulfenamide, N-ethoxy-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and

[0165] Guanidine-based sulfurization accelerators, such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanidine.

[0166] These can be used individually or in combination of two or more.

[0167] (b-9) Other

[0168] In addition to the components described above, the rubber composition may also contain additives commonly used in the tire industry, such as fillers, organic peroxides, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. The content of these additives relative to 100 parts by weight of the rubber component is, for example, 0.1 parts by weight or more and 200 parts by weight or less.

[0169] 2. Production of tread rubber composition

[0170] The rubber composition is produced by conventional methods, such as production methods that include a basic kneading step (kneading the rubber components and fillers such as silica or carbon black) and a final kneading step (kneading the kneaded product obtained from the basic kneading step and the crosslinking agent).

[0171] Kneading can be performed using known (sealed) kneading machines (such as Banbury internal mixers, kneaders, or open rolling mills).

[0172] The kneading temperature for the basic kneading step is, for example, above 50°C and below 200°C, and the kneading time is, for example, above 30 seconds and below 30 minutes. In addition to the components mentioned above, commonly used compounding agents in the rubber industry, such as softeners (e.g., oils), stearic acid, zinc oxide, anti-aging agents, waxes, and vulcanization accelerators, may be added as needed during the basic kneading process.

[0173] In the final kneading step, the kneading product obtained in the basic kneading step and the crosslinking agent are kneaded together. The kneading temperature in the final kneading step is, for example, above room temperature and below 80°C, and the kneading time is, for example, above 1 minute and below 15 minutes. In addition to the above components, in the final kneading step, vulcanization accelerators, zinc oxide, etc., may be added as needed, and kneading is then performed.

[0174] 3. Tire manufacturing

[0175] The tire disclosed herein is manufactured using conventional methods with an uncured rubber composition obtained through a final kneading step. In other words, the uncured rubber composition is extruded according to the shape of each tire component of the tread and formed together with other tire components on a tire forming machine using conventional methods to produce an uncured tire.

[0176] Specifically, on a forming roller, the inner liner (as a component ensuring tire airtightness), the carcass (as a component that bears the load, impact, and inflation pressure received by the tire), and the belt (as a component that strongly tightens the carcass to increase tread rigidity) are wound. The two ends of the carcass are fixed to the side edges, and the bead portion (as a component that fixes the tire to the rim) is arranged and shaped into a ring. Then, the tread is glued to the center of the outer periphery, and the sidewall portion (as a component that protects the carcass and withstands bending) is glued to the radially outer side, thereby producing an uncured tire.

[0177] In this embodiment, it is preferable to provide an inclined belt layer extending at an angle of 55° or more and 75° or less relative to the tire circumference as the belt. Therefore, tire durability is ensured while maintaining sufficient tread rigidity.

[0178] The manufactured uncured tires are then heated and pressurized in a vulcanizing machine to obtain the tire. The vulcanization step can be carried out using known vulcanization methods. The vulcanization temperature is, for example, above 120°C and below 200°C, and the vulcanization time is, for example, above 5 minutes and below 15 minutes.

[0179] At this point, the tire is shaped to satisfy the above (Equation 3) and (Equation 4).

[0180] The specific tires that can meet the requirements of Formula 3 and Formula 4 above include 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.

[0181] In this embodiment, the tires that satisfy the above formulas (1) to (4) are preferably used in passenger car pneumatic tires; by satisfying the above formulas, it can better help to solve the problems in this disclosure, that is, to provide a tire in which wear resistance and anti-skid properties are improved in a good balance, especially when driving in the rain, wear resistance and anti-skid properties are highly compatible.

[0182] The pneumatic tires for passenger cars referred to here are tires installed on vehicles with four wheels and a maximum load capacity of less than 1000 kg.

[0183] There is no particular limitation on the maximum load capacity, as long as it is below 1000 kg. However, as the maximum load capacity increases, the tire weight tends to increase; due to inertia, the braking distance also increases accordingly. Therefore, the maximum load capacity is preferably below 900 kg, more preferably below 800 kg, and even more preferably below 700 kg.

[0184] From the perspective of braking distance due to the aforementioned inertia, the tire weight is preferably 20 kg or less, more preferably 15 kg or less, even more preferably 12 kg or less, 10 kg or less, and 8 kg or less. The tire of this disclosure may contain electronic components; in this case, the tire weight referred to herein includes the weight of the electronic components and their mounting components. If sealant, sponge, etc., are provided in the cavity, the tire weight includes them.

[0185] Example

[0186] The present disclosure will now be described in more detail with reference to embodiments.

[0187] 1. Manufacturing of rubber compositions for tire treads

[0188] First, produce the rubber composition for tire tread.

[0189] (1) Compounding materials

[0190] First, each of the following compound materials is prepared.

[0191] (a) Rubber components

[0192] (a-1) NR: TSR20

[0193] (a-2-1) SBR-A: T3830 (Toughden 3830) manufactured by Asahi Kasei Corporation; (amount of styrene: 35% by mass)

[0194] (a-2-2) SBR-B: Nipol NS616 (modified S-SBR, styrene content: 20% by mass) manufactured by Zeon Corporation, Japan.

[0195] (a-3) BR: BR150 manufactured by Ube Industries, Ltd.

[0196] (b) Compounds other than rubber components

[0197] (b-1) Carbon black: Diablack N220 manufactured by Mitsubishi Chemical Corporation

[0198] (b-2-1) Silica A: Ultrasil VN3 manufactured by Evonik Industries (BET specific surface area: 140 m²) 2 / g)

[0199] (b-2-2) Silica B: Ultrasil 9000 Gr manufactured by Evonik Industries (BET specific surface area: 210 m²) 2 / g)

[0200] (b-3) Silane coupling agent: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Degussa

[0201] (b-4) Oil: Process X-140 manufactured by Nippon Energy Corporation

[0202] (b-5-1) Resin A: Petrotac 100V (C5 resin) manufactured by Tosoh Corporation.

[0203] (b-5-2) Resin B: YS Polystar U130 (terpene-aromatic compound resin) manufactured by Yasuhara Chemical Co., Ltd.

[0204] (b-6) Zinc oxide: Zinc oxide white No. 1 manufactured by Mitsui Metals Mining Co., Ltd.

[0205] (b-7) Stearic acid: TSUBAKI stearic acid manufactured by Nippon Oil Co., Ltd.

[0206] (b-8) Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd.

[0207] (b-9) Crosslinking agents and vulcanization accelerators

[0208] Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.

[0209] Vulcanization accelerator: Nocceler CZ (N-cyclohexyl-2-benzothiazole sulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.

[0210] (2) Production of rubber compositions

[0211] Based on the blending contents of A-1 to A-6 and B-1 to B-9 shown in Table 1, the materials, excluding sulfur and vulcanization accelerator, were kneaded for 5 minutes in a Banbury internal mixer at 150°C to obtain the kneaded product. Each blending amount is in parts by mass.

[0212] [Table 1]

[0213]

[0214] 2. Tire manufacturing

[0215] Next, sulfur and a vulcanization accelerator were added to the resulting kneaded product, and the mixture was kneaded at 80°C for 5 minutes using an open-roll mill to obtain a tread rubber composition. The resulting tread rubber composition was used to form a tread, which was then bonded to other tire components to form an unvulcanized tire. This tire was then vulcanized at 170°C for 10 minutes to produce test tires of sizes 155 (Table 2) or 175 (Table 3). For each test tire, Tables 2 and 3 show the ground contact width Wt (mm), diameter Dt (mm), and complex modulus of elasticity E* (MPa) measured using a GABO-manufactured "Eplexor" at 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%.

[0216] 3. Performance Evaluation Test

[0217] (1) Anti-slip properties

[0218] Each test tire was installed on all wheels of a Japanese-made front-wheel-drive vehicle (2000cc engine) and inflated with 250 kPa air. The vehicle was then driven in a stable circular turning pattern on a wet test track, with the speed gradually increased until the driver felt the vehicle slipping at the highest speed. Evaluation was conducted as follows: For each test tire, the average of the measurements from five drivers was calculated, and this average was then expressed as an index relative to a reference test tire. A higher index indicates better anti-skid performance in rainy conditions. The results are shown in Tables 2 and 3.

[0219] (2) Abrasion resistance

[0220] Each test tire was mounted on all wheels of a Japanese-made front-wheel-drive vehicle (2000cc engine) and inflated with 250 kPa air. After driving 8000 km at 80 km / h on a wet test track, the groove depth near the equator was measured to determine the reduction rate relative to the depth before the test. The ratio of the results from the reference test tire to the results from each test tire was used for evaluation by indexing using the following formula. A higher value indicates better wear resistance. The results are shown in Tables 2 and 3.

[0221] Abrasion resistance = [(Reduction rate of reference test tire / Reduction rate of test tire)] × 100

[0222] (3) Evaluation results

[0223] Table 2 shows the evaluation results for size 155, and Table 3 shows the evaluation results for size 175. As reference test tires, the test tires of Example 1-1 were used in Table 2, and the test tires of Example 2-1 were used in Table 3. The balance between anti-skid properties and abrasion resistance can be evaluated by averaging the evaluation results of anti-skid properties (1) and abrasion resistance (2).

[0224] [Table 2]

[0225]

[0226] [Table 3]

[0227]

[0228] As can be seen from Tables 2 and 3, for any size tire (155 and 175), if all of the above (Equations 1) to (Equations 4) are satisfied, a tire with a high degree of compatibility between wear resistance and anti-skid performance when driving in the rain can be provided.

[0229] Then it can be seen that by meeting the specified requirements, a tire with a higher degree of compatibility between wear resistance and anti-skid performance when driving in the rain can be provided.

[0230] On the other hand, when any of the terms (Equation 1) to (Equation 4) are not satisfied, it can be seen that a high degree of compatibility between wear resistance and anti-slip properties cannot be achieved when driving in rainy weather.

[0231] Although this disclosure has been described above based on embodiments, this disclosure is not limited to the embodiments described above. Various modifications can be made to the embodiments described above within the same and equivalent scope as this disclosure.

[0232] This disclosure (1) is a pneumatic tire, wherein,

[0233] At least one of the rubber layers forming the tread area is formed of a rubber composition comprising styrene-butadiene rubber and isoprene rubber as rubber components;

[0234] When the amount of styrene-butadiene rubber in 100 parts by mass of rubber component is R1 (parts by mass) and the amount of isoprene rubber is R2 (parts by mass), and when the tire is mounted on a standardized rim with an internal pressure of 250 kPa and the tire's contact patch width is Wt (mm) and diameter is Dt (mm), the following equations (1) to (4) are satisfied:

[0235] R1+R2≧60 (Equation 1)

[0236] 35≦R²≦80 (Equation 2)

[0237] 1963.4≦(Dt 2 ×π / 4) / Wt≦2827.4(Equation 3)

[0238] |R2-R1|×Wt≧3500(Equation 4).

[0239] This disclosure (2) is a pneumatic tire according to this disclosure (1), wherein the weight-average molecular weight of the styrene-butadiene rubber is 100,000 or more and 2 million or less.

[0240] This disclosure (3) is an inflatable tire according to this disclosure (1) or (2), wherein the styrene-butadiene rubber is a modified solution polymerized styrene-butadiene rubber.

[0241] This disclosure (4) is a pneumatic tire of any combination of this disclosure (1) to (3), wherein the styrene content in the styrene-butadiene rubber is more than 5% by mass and less than 25% by mass.

[0242] This disclosure (5) is a pneumatic tire of any combination of the present disclosures (1) to (4), wherein the styrene content in the rubber composition is more than 1% by mass and less than 5% by mass.

[0243] This disclosure (6) is an inflatable tire of any combination of this disclosure (1) to (5), wherein the rubber composition further comprises less than 40 parts by mass of butadiene rubber in 100 parts by mass of the rubber component.

[0244] This disclosure (7) is a pneumatic tire of any combination of this disclosure (1) to (6), wherein the rubber composition contains more than 5 parts by mass and less than 40 parts by mass of plasticizer component relative to 100 parts by mass of rubber component.

[0245] This disclosure (8) is a pneumatic tire according to this disclosure (7), wherein a thermoplastic resin is included as the plasticizer component.

[0246] This disclosure (9) is an inflatable tire according to this disclosure (8), wherein the thermoplastic resin is selected from: C5 resin, C5-C9 resin, C9 resin, terpene resin, terpene-aromatic compound resin, rosin resin, dicyclopentadiene resin and alkylphenol resin.

[0247] This disclosure (10) is a pneumatic tire of any combination of the present disclosures (1) to (9), wherein the rubber composition contains more than 60 parts by mass of silica relative to 100 parts by mass of the rubber component.

[0248] This disclosure (11) is a pneumatic tire according to this disclosure (10), wherein the BET specific surface area of ​​the silica is 180 m². 2 / g or more and 300m 2 / g or less.

[0249] This disclosure (12) is a pneumatic tire according to this disclosure (10) or (11), wherein the pneumatic tire contains 10% by mass and less than 15% by mass of silane coupling agent relative to 100 parts by mass of silica.

[0250] This disclosure (13) is a pneumatic tire of any combination of disclosures (1) to (12), wherein the complex elastic modulus of the rubber composition, measured at 30°C, 10Hz, 5% initial strain, and 1% dynamic strain rate, is E* (MPa), and satisfies the following formula:

[0251] E*×Wt≦2000.

[0252] This disclosure (14) is a pneumatic tire of any combination of disclosures (1) to (13), wherein the tread is formed of a plurality of rubber layers, the rubber composition being used for the tread running rubber layer.

[0253] This disclosure (15) is any combination of the pneumatic tires of disclosures (1) to (14), wherein the pneumatic tires are pneumatic tires for passenger cars.

Claims

1. A pneumatic tire, wherein, At least one of the rubber layers forming the tread area is formed of a rubber composition comprising styrene-butadiene rubber and isoprene rubber as rubber components; When the complex elastic modulus of a rubber composition is E* (MPa) measured under conditions of 30℃, 10Hz frequency, 5% initial strain, and 1% dynamic strain rate, it satisfies the following formula: E*×Wt≦2000, When the amount of styrene-butadiene rubber in 100 parts by mass of rubber component is R1 (parts by mass) and the amount of isoprene rubber is R2 (parts by mass), and when the tire is mounted on a standardized rim with an internal pressure of 250 kPa and the tire's contact patch width is Wt (mm) and diameter is Dt (mm), the following equations (1) to (4) are satisfied: R1+R2≧60 (Equation 1) 35≦R²≦65 (Equation 2) 1963.4≦(Dt 2 ×π / 4) / Wt≦2827.4(Equation 3) 3500≦|R2-R1|×Wt≦10000(Equation 4), The diameter Dt is 691 or more. The grounding width Wt is 153mm or more and 215mm or less.

2. The pneumatic tire according to claim 1, wherein, The weight-average molecular weight of the styrene-butadiene rubber is above 100,000 and below 2 million.

3. The pneumatic tire according to claim 1, wherein, The condition is satisfied that |R2-R1|×Wt≧6120.

4. The pneumatic tire according to claim 1 or 2, wherein, The styrene-butadiene rubber is a modified solution-polymerized styrene-butadiene rubber.

5. The pneumatic tire according to claim 1 or 2, wherein, The styrene content in the styrene-butadiene rubber is more than 5% by mass and less than 25% by mass.

6. The pneumatic tire according to claim 1 or 2, wherein, The styrene content in the rubber composition is more than 1% by mass and less than 5% by mass.

7. The pneumatic tire according to claim 1 or 2, wherein, The rubber composition further includes less than 40 parts by mass of butadiene rubber in 100 parts by mass of the rubber component.

8. The pneumatic tire according to claim 1 or 2, wherein, The rubber composition contains 5 or more but less than 40 parts by mass of a plasticizer component relative to 100 parts by mass of the rubber component.

9. The pneumatic tire according to claim 8, wherein, Thermoplastic resin is included as the plasticizer component.

10. The pneumatic tire according to claim 9, wherein, The thermoplastic resin is selected from: C5 resin, C5-C9 resin, C9 resin, terpene resin, terpene-aromatic compound resin, rosin resin, dicyclopentadiene resin and alkylphenol resin.

11. The pneumatic tire according to claim 1 or 2, wherein, The rubber composition contains 60 or more parts by mass of silica relative to 100 parts by mass of the rubber component.

12. The pneumatic tire according to claim 11, wherein, The BET specific surface area of ​​the silica is 180 m². 2 / g or more and 300m 2 / g or less.

13. The pneumatic tire according to claim 11, wherein, The pneumatic tire contains 10% to 15% by mass of silane coupling agent relative to 100 parts by mass of silica.

14. The pneumatic tire according to claim 1 or 2, wherein, The tread portion is formed of multiple rubber layers, and the rubber composition is used in the tread driving surface rubber layer.

15. The pneumatic tire according to claim 1 or 2, wherein, The pneumatic tire is a passenger car pneumatic tire.

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