Pneumatic tires

Abstract

To provide a pneumatic tire which is excellent in durability, and can sufficiently achieve improvement of low fuel consumption and reduction in road noise.SOLUTION: A pneumatic tire includes a tread part having a tread rubber forming an outer surface, and a side wall part having a side wall rubber forming the outer surface, in which the tread rubber has a cap rubber in which a plurality of circumferential groove parts and a plurality of circumferential land parts are formed on the outer surface part and a contact surface is formed, and a base rubber arranged inside in a tire radial direction of the cap rubber so as to extend to the side wall part, and in the contact surface, an area formed by the circumferential groove parts is 15-30% with respect to the total contact area, and a loss tangent (tanδb) of the base rubber and a loss tangent (tanδs) of the side wall rubber measured under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of 1%, and a deformation mode of tension satisfy (tanδb / tanδs)<1.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a pneumatic tire. [Background technology]

[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 from the standpoint of economic efficiency, and there is also a strong demand for improved fuel efficiency in pneumatic tires (hereinafter simply referred to as "tires") that are fitted to automobiles.

[0003] On the other hand, from the viewpoint of passenger stability within an automobile, there is an increasing demand for a reduction in noise (road noise) caused by unevenness of the road surface.

[0004] However, it is not easy to simultaneously improve fuel economy and reduce road noise.

[0005] Therefore, in order to achieve both improved fuel economy and reduced road noise, various techniques have been proposed (for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] WO2015 / 159538 publication [Patent Document 2] JP 2018-103931 A [Patent Document 3] JP 2019-084961 A [Patent Document 4] JP 2020-066394 A Summary of the Invention [Problem to be solved by the invention]

[0007] However, in tires manufactured based on the above-mentioned conventional techniques, it cannot be said that both improvement in fuel economy and reduction in road noise are sufficiently achieved at the same time, and further improvement is required. Also, further improvement in durability is required.

[0008] Therefore, an object of the present invention is to provide a pneumatic tire which is excellent in durability and which satisfactorily achieves both improved fuel economy and reduced road noise. [Means for solving the problem]

[0009] The present inventors have conducted extensive research into solving the above problems, and have found that the above problems can be solved by the invention described below, thereby completing the present invention.

[0010] The invention described in claim 1 is A pneumatic tire having a tread portion having a tread rubber forming an outer surface, and a sidewall portion having a sidewall rubber forming an outer surface, The tread rubber is a cap rubber having a ground contact surface formed on an outer surface thereof by a plurality of circumferential grooves and a plurality of circumferential land portions; a base rubber disposed on the radially inner side of the cap rubber and extending to the sidewall portion, In the ground contact surface, an area formed by the circumferential groove portion is 15 to 30% of the total ground contact area, A total cross-sectional area of ​​the plurality of circumferential groove portions is 10% or more and less than 30% of a cross-sectional area of ​​the tread portion, a groove portion other than the circumferential groove portion is provided on a surface portion of the tread portion, In the ground contact surface, an area occupied by grooves other than the circumferential groove portion is smaller than an area occupied by the circumferential groove portion, When the ground contact surface is equally divided into four regions in the tire width direction, an area ratio occupied by the circumferential groove portion in the two inner regions is smaller than an area ratio occupied by the circumferential groove portion in the two outer regions, The pneumatic tire is characterized in that the loss tangent (tan δb) of the base rubber and the loss tangent (tan δs) of the sidewall rubber measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: tension satisfy the following (Equation 1). (tanδb / tanδs)<1 (Formula 1)

[0012] Claim 2 The invention according to The loss tangent (tanδc) of the cap rubber and the loss tangent (tanδb) of the base rubber, measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: tension, satisfy the following (Formula 2), and the claim 1 to is a pneumatic tire as described. 1.3 ≦ (tanδc / tanδb) < 3.0 ····· (Formula 2)

[0013] Claim 3 The invention according to The loss tangent (tanδc) of the cap rubber, the loss tangent (tanδb) of the base rubber, and the loss tangent (tanδs) of the sidewall rubber, measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: tension, satisfy the following (Formula 3), and Claim 1 or Claim 2 is a pneumatic tire as described. tanδb < tanδs < tanδc ····· (Formula 3)

[0014] Claim 4 The invention according to The complex elastic modulus Eb of the base rubber and the complex elastic modulus Ec of the cap rubber, measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: extension * and * satisfy the following (Formula 4), and the pneumatic tire according to any one of Claims 1 to 3 is as described. Eb * / Ec * < 1 ····· (Formula 4)

[0016] Claim 5 The invention according to 2. The tire according to claim 1, wherein when the contact patch is divided equally into four regions in the tire width direction, the total area of ​​the two inner regions excluding the grooves is 30 to 60% of the total area of ​​the contact patch excluding the grooves. 4 13. The pneumatic tire according to claim 12,

[0017] Claim 6 The invention described in A sipe is formed in the circumferential land portion in a region closest to the tire equator, the sipe connecting both side portions of the circumferential land portion, 10. The tire according to claim 1, wherein the straight line connecting both ends of the sipe is inclined at an angle of 15 to 25 degrees with respect to the width direction. 5 13. The pneumatic tire according to claim 12,

[0019] Claim 7 The invention described in 2. The tire according to claim 1, wherein the tread rubber is formed using a rubber composition containing styrene-butadiene rubber and / or butadiene rubber as a rubber component. 6 13. The pneumatic tire according to claim 12,

[0020] Claim 8 The invention described in The tread rubber is formed using a rubber composition containing 50 parts by mass or more of silica per 100 parts by mass of a rubber component. 7 The pneumatic tire is as described above.

[0021] Claim 9 The invention described in 2. The tire according to claim 1, wherein the sidewall rubber is formed using a rubber composition containing an isoprene-based rubber and a butadiene rubber as rubber components. 8 13. The pneumatic tire according to claim 12,

[0022] Claim 10 The invention described in The sidewall rubber is formed using a rubber composition containing 50 parts by mass or more of carbon black per 100 parts by mass of a rubber component. 9 The pneumatic tire is as described above.

[0023] Claim 11 The invention described in Claims 1 to 5 are pneumatic tires for passenger cars. 10 13. The pneumatic tire according to claim 12, Effect of the Invention

[0024] According to the present invention, it is possible to provide a pneumatic tire that is excellent in durability and satisfactorily achieves both improved fuel economy and reduced road noise. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] The present invention will be described below based on embodiments.

[0026] [1] Characteristics of the tire according to the present invention First, the features of the tire according to the present invention will be described.

[0027] 1. Overview The tire of the present invention is a pneumatic tire having a tread portion having tread rubber forming an outer surface, and a sidewall portion having sidewall rubber forming the outer surface, characterized in that the tread rubber has a cap rubber having a contact surface formed on the outer surface by a plurality of circumferential groove portions and a plurality of circumferential land portions, and a base rubber arranged radially inward of the cap rubber and extending to the sidewall portion.

[0028] The tire is characterized in that the area of ​​the ground contact surface of the tread portion that is formed by the circumferential groove portion is 15 to 30% of the total ground contact surface area.

[0029] Furthermore, the tire according to the present invention is characterized in that the loss tangent (tan δb) of the base rubber and the loss tangent (tan δs) of the sidewall rubber measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of 1%, and a deformation mode of tension satisfy (tan δb / tan δs)<1 (Equation 1).

[0030] According to the present invention, by having the above-mentioned structural and configuration features and material features, it is possible to provide a pneumatic tire that has excellent durability and satisfactorily achieves both improved fuel efficiency and reduced road noise, as will be described later.

[0031] In the above description, the "contact surface" refers to the outer peripheral surface of the tire that comes into contact with the road surface when the tire is mounted on a standard rim, inflated to standard internal pressure, and in a standard, unloaded condition, and rolled under a standard load.

[0032] The contact area can be determined, for example, by mounting a tire on a standard rim, applying standard internal pressure, and leaving it at 25°C for 24 hours. Then, ink is applied to the surface of the tread, and the tire is pressed against cardboard under a standard load to transfer the ink to the paper. The sum of the areas of the blackened land areas and the whitened groove areas is the "total contact area."

[0033] Here, "genuine rim" refers to a rim that is specified 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 JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" listed in the "STANDARDS MANUAL" for ETRTO (The European Tire and Rim Technical Organisation), and the "Design Rim" listed in the "YEAR BOOK" for TRA (The Tire and Rim Association, Inc.). In the case of a tire not specified by a standard, it refers to a rim that can be assembled to a rim and can hold internal pressure, that is, a rim that does not leak air from between the rim and tire, and has the smallest rim diameter and the next narrowest rim width.

[0034] "Normal internal pressure" refers to the air pressure specified for each tire by the above-mentioned standard; in the case of JATMA, it refers to the maximum air pressure; in the case of TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES"; and in the case of ETRTO, it refers to "INFLATION PRESSURE."

[0035] In addition, "normal load" refers to the load specified for each tire by each of the above standards, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, it is the maximum load capacity, in the case of TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and in the case of ETRTO, it is the "LOAD CAPACITY".

[0036] 2. Mechanism of effect manifestation in the tire according to the present invention The mechanism by which the tire according to the present invention exerts its effects, that is, the mechanism by which excellent durability, improved fuel economy and reduced road noise are sufficiently achieved at the same time, is presumed to be as follows.

[0037] As described above, in the tire according to the present invention, the tread rubber has a cap rubber having a contact surface formed on an outer surface thereof by a plurality of circumferential groove portions and a plurality of circumferential land portions, and a base rubber arranged radially inward of the cap rubber, the base rubber is arranged extending to the sidewall portion, and the loss tangent (tan δb) of the base rubber measured under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of 1%, and a deformation mode of tension is smaller than the loss tangent (tan δs) of the sidewall rubber ((tan δb / tan δs)<1).

[0038] Loss tangent tanδ is a parameter that indicates the energy absorption performance, and the larger the value, the more energy can be absorbed and the more impacts can be absorbed during driving. As described above, by making the loss tangent (tanδb) of the base rubber smaller than the loss tangent (tanδs) of the sidewall rubber and extending it to the sidewall, it is believed that the impacts received by the tread from the road surface can be transmitted to the sidewall in a sufficiently absorbed state. As a result, even if the thickness of the sidewall rubber is thin, the impacts from the road surface can be sufficiently absorbed, so that the weight of the tire can be reduced, sufficient low rolling resistance can be exhibited, and the generation of road noise can be sufficiently reduced, and it is believed that both improved fuel efficiency and reduced road noise can be achieved. In addition, durability can be improved.

[0039] The above-mentioned tan δ can be measured, for example, by using a viscoelasticity measuring device such as "IPLEXER (registered trademark)" manufactured by GABO.

[0040] In addition, in the ground contact surface of the tread portion of the tire according to the present invention, the area formed by the circumferential groove portion is set to 15 to 30% of the total ground contact area.

[0041] By setting it to 30% or less, uneven wear can be suppressed and durability can be improved. By setting it to 27% or less, it is more preferable, and by setting it to 24% or less, it is even more preferable. On the other hand, by setting it to 15% or more, low rolling resistance can be improved. By setting it to 18% or more, it is more preferable, and by setting it to 21% or more, it is even more preferable.

[0042] [2] More preferred embodiments of the tire according to the present invention The tire according to the present invention can achieve even greater effects by adopting the following aspects.

[0043] 1. Circumferential grooves formed in the tread In the tire according to the present invention, the total cross-sectional area of ​​the plurality of circumferential groove portions is preferably 10% or more and less than 30% of the cross-sectional area of ​​the tread portion.

[0044] By making it less than 30%, uneven wear can be suppressed and durability can be improved. It is more preferable that it is 26% or less, and even more preferable that it is 22% or less. On the other hand, by making it 10% or more, low rolling resistance can be improved. It is more preferable that it is 14% or more, and even more preferable that it is 18% or more.

[0045] 2.Loss tangent (tanδ) In the tire according to the present invention, it is preferable that the loss tangent (tan δc) of the cap rubber and the loss tangent (tan δb) of the base rubber measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of 1%, and a deformation mode of tension satisfy 1.3≦(tan δc / tan δb)<3.0 (Equation 2).

[0046] As described above, the loss tangent tan δ is a parameter that indicates the energy absorption performance, and it is considered that the larger the value, the more energy can be absorbed and the more shocks during driving can be alleviated.

[0047] Therefore, when tanδc is made larger than tanδb to satisfy the above relationship, the tread rubber forming the outer surface of the tread portion can relieve the impact received from the road surface and transmit it to the inner base rubber, thereby reducing road noise and improving durability.

[0048] In addition, as the lower limit value of (tanδc / tanδb) described above, it is more preferably 1.6 or more, and further preferably 1.9 or more. On the other hand, as the upper limit value, it is more preferably 2.7 or less, and further preferably 2.4 or less.

[0049] Note that the loss tangent (tanδc) of the cap rubber measured under the same conditions is larger than the loss tangent (tanδb) of the base rubber and the loss tangent (tanδs) of the sidewall rubber. That is, it is preferably satisfied that tanδb < tanδs < tanδc (Equation 3), whereby further improvement in durability, and further compatibility between improvement in low fuel consumption and reduction in road noise can be achieved.

[0050] 3. Complex elastic modulus In the tire according to the present invention, the complex elastic modulus Eb of the base rubber measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain rate of 1%, and a deformation mode: extension * , and the complex elastic modulus Ec of the cap rubber * preferably satisfy Eb * / Ec * < 1 (Equation 4). In this way, by making the complex elastic modulus Eb of the base rubber * smaller than the complex elastic modulus Ec of the cap rubber * , the strain generated in the base rubber becomes larger than the strain generated in the cap rubber during free rolling of the tire, so that further improvement in low rolling resistance can be achieved and sufficient low fuel consumption can be exhibited. Note that it is more preferably 0.8 or less, and further preferably 0.6 or less.

[0051] In addition, these complex elastic moduli E *can be measured, for example, using a viscoelasticity measuring device "IPLEXER (registered trademark)" manufactured by GABO.

[0052] 4. Grooves other than circumferential grooves In the tire according to the present invention, a groove portion other than the circumferential groove portion is provided in the surface portion of the tread portion, and it is preferable that the area occupied by the groove portion other than the circumferential groove portion in the ground contact surface is smaller than the area occupied by the circumferential groove portion. Specifically, the area occupied by the groove portion other than the circumferential groove portion is, for example, preferably 90% or less, more preferably 85% or less, and even more preferably 80% or less, of the area occupied by the circumferential groove portion.

[0053] In this way, by providing grooves other than the circumferential groove portion having an area smaller than the area occupied by the circumferential groove portion, sufficient drainage can be ensured and sufficient grip on the road surface can be ensured, thereby further achieving both improved fuel efficiency and reduced road noise.

[0054] 5. Ground plane In the tire according to the present invention, when the ground contact patch is divided equally into four regions in the tire width direction, the total area of ​​the two inner regions excluding the grooves is preferably 30 to 60% of the total area of ​​the ground contact patch excluding the grooves. This allows the contact pressure on the ground contact patch to be uniform, thereby further reducing the rolling resistance and further improving the low rolling resistance. It is more preferable that the total area is 40 to 55%, and even more preferably 45 to 50%.

[0055] When the ground contact surface is divided into four equal regions in the tire width direction, it is preferable that a sipe is formed in the circumferential land portion of the region closest to the tire equator, connecting both sides of the circumferential land portion, and the straight line connecting both ends of the sipe is inclined at an angle of 15° or more and 25° or less with respect to the width direction. This can further improve the drainage in the tread portion, thereby improving the driving stability and durability. Note that the "sipe" refers to a narrow groove formed on the outer surface of the tread portion with a groove width of 1.5 mm or less. The inclination angle is more preferably 17° or more, and even more preferably 19° or more. On the other hand, it is more preferably 23° or less, and even more preferably 21° or less.

[0056] In addition, when the ground contact patch is divided equally into four regions in the tire width direction, it is preferable that the area ratio of the circumferential groove portion in the two inner regions is smaller than the area ratio of the circumferential groove portion in the two outer regions. This ensures sufficient rigidity in the two inner regions of the ground contact patch, improving steering stability and durability. This also includes the case where the circumferential groove portion is not provided in the two inner regions.

[0057] [3] Specific embodiments of the present invention Hereinafter, the present invention will be described in detail based on the embodiments.

[0058] 1. Rubber composition In this embodiment, the tread rubber (cap rubber and base rubber) and the sidewall rubber can be any of the various compounding materials shown below, and can be obtained by appropriately adjusting the compounding amount according to the desired physical properties of the tread rubber or sidewall rubber.

[0059] (1) Compounding materials (a) Rubber component In this embodiment, the rubber component may be a rubber (polymer) that is generally used in tire manufacturing, such as butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene-based rubber, nitrile rubber (NBR), etc. It is preferable to use SBR and / or BR for the tread rubber (cap rubber and base rubber), and it is preferable to use isoprene-based rubber and BR for the sidewall rubber.

[0060] (a) BR The amount of BR in 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 55 parts by mass or more, while it is preferably 80 parts by mass or less, more preferably 75 parts by mass or less, and even more preferably 70 parts by mass or less.

[0061] The weight average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl bond amount of the BR is, for example, more than 1 mass% and less than 30 mass%. The cis content of the BR is, for example, more than 1 mass% and 98 mass% or less. The trans content of the BR is, for example, more than 1 mass% and less than 60 mass%. The cis content can be measured by infrared absorption spectroscopy.

[0062] The BR is not particularly limited, and can be BR with a high cis content (cis content of 90% or more), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, etc. The BR can be either unmodified BR or modified BR, and the modified BR can be, for example, BR modified with a compound (modifier) ​​represented by the following formula:

[0063] [ka]

[0064] In the formula, R1, R2, and R3 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. R4 and R5 are the same or different and represent a hydrogen atom or an alkyl group. R4 and R5 may be bonded to form a ring structure together with the nitrogen atom. n represents an integer.

[0065] The modified BR modified with a compound (modifying agent) represented by the above formula includes BR whose polymerization terminal (active terminal) has been modified with a compound represented by the above formula.

[0066] R1, R2, and R3 are preferably alkoxy groups (preferably alkoxy groups having 1 to 8 carbon atoms, more preferably alkoxy groups having 1 to 4 carbon atoms). R4 and R5 are preferably alkyl groups (preferably alkyl groups having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. In addition, when R4 and R5 combine to form a ring structure together with the nitrogen atom, it is preferably a 4- to 8-membered ring. The alkoxy group also includes cycloalkoxy groups (cyclohexyloxy group, etc.) and aryloxy groups (phenoxy group, benzyloxy group, etc.).

[0067] 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.

[0068] The modified BR may be modified with the following compounds (modifiers): polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline, Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(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 amino groups and / or substituted amino groups, 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, 4-N,N-divinylaminobenzaldehyde, etc.; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, N-methyl-5-methyl-2-pyrrolidone, etc.; N-substituted piperidones, such as N-methyl-2-piperidone, N-vinyl-2-piperidone, N-phenyl-2-piperidone, etc.;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione. , N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophene, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. The modification with the above-mentioned compound (modifying agent) can be carried out by a known method. These modified BRs may be used alone or in combination of two or more kinds.;

[0069] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used.

[0070] (b) Isoprene rubber The content (total content) of the isoprene-based rubber in 100 parts by mass of the rubber component is preferably 25 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 35 parts by mass or more, while it is preferably 55 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 45 parts by mass or less.

[0071] Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR, with NR being preferred from the standpoint of excellent strength.

[0072] As the NR, for example, SIR20, RSS♯3, TSR20, etc., which are common in the tire industry, can be used. As the IR, there is no particular limitation, and for example, IR2200 manufactured by Zeon Corporation, etc., which are common in the tire industry, can be used. As the modified NR, deproteinized natural rubber (DPNR), highly purified natural rubber (UPNR), etc. can be used. As the modified NR, epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), grafted natural rubber, etc. can be used. As the modified IR, epoxidized isoprene rubber, hydrogenated isoprene rubber, grafted isoprene rubber, etc. can be used. These may be used alone or in combination of two or more kinds.

[0073] (C) SBR The rubber component may contain SBR as necessary. In this case, the content of SBR in 100 parts by mass of the rubber component is, for example, 1 part by mass or more and less than 100 parts by mass. It is more preferably more than 5 parts by mass, even more preferably more than 15 parts by mass, and particularly preferably more than 25 parts by mass. On the other hand, it is preferably less than 65 parts by mass, more preferably less than 55 parts by mass, even more preferably less than 45 parts by mass, and particularly preferably less than 35 parts by mass.

[0074] The weight average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. The styrene content of SBR is, for example, preferably more than 5% by mass and less than 50% by mass, more preferably more than 10% by mass and less than 40% by mass, and even more preferably more than 20% by mass and less than 35% by mass. The vinyl bond amount (amount of 1,2-bonded butadiene units) of SBR is, for example, more than 5% by mass and less than 70% by mass. The structure of SBR (measurement of styrene content and vinyl bond amount) can be performed using, for example, a JNM-ECA series device manufactured by JEOL Ltd.

[0075] There are no particular limitations on the SBR, and examples of the SBR that can be used include emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), etc. The SBR may be either unmodified SBR or modified SBR, which may be used alone or in combination of two or more kinds.

[0076] 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 end of SBR has been modified with a compound (modifying agent) having the above-mentioned functional group (terminal-modified SBR having the above-mentioned functional group at the end), main-chain-modified SBR in which the main chain has the above-mentioned functional group, main-chain-terminal-modified SBR in which the main chain and at least one end are modified with the above-mentioned modifier, and terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or epoxy group introduced therein.

[0077] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. may be used. The SBR may be used alone or in combination of two or more kinds.

[0078] (D) Other rubber components Furthermore, as other rubber components, rubbers (polymers) that are generally used in the manufacture of tires, such as nitrile rubber (NBR), may be included.

[0079] (b) Compounding materials other than rubber components (a) Filler In the present embodiment, the rubber composition preferably contains a reinforcing agent such as carbon black or silica as a filler. In addition to the above-mentioned carbon black and silica, examples of the filler include calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. In addition, when silica is used, it is preferable to use it in combination with a silane coupling agent.

[0080] (i) Carbon black The carbon black content is, for example, preferably 10 parts by mass or more, more preferably 30 parts by mass or more, even more preferably 35 parts by mass or more, and particularly preferably 50 parts by mass or more, relative to 100 parts by mass of the rubber component. On the other hand, it is preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less. This can improve the crack growth resistance, durability, ultraviolet degradation resistance, etc. of the tire.

[0081] The nitrogen adsorption specific surface area of ​​carbon black (N 2 SA) is, for example, 30m 2 / g over 250m 2 The carbon black has a dibutyl phthalate (DBP) absorption of, for example, more than 50 ml / 100 g and less than 250 ml / 100 g. The nitrogen adsorption specific surface area of ​​the carbon black is measured according to ASTM D4820-93, and the DBP absorption is measured according to ASTM D2414-93.

[0082] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon black) such as FT and MT; channel blacks (channel carbon black) such as EPC, MPC, and CC; graphite, and the like.

[0083] Examples of commercially available products that can be used include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shinnikka Carbon Co., Ltd., Columbia Carbon Co., etc., and these may be used alone or in combination of two or more types.

[0084] (ii) Silica The rubber composition may further contain silica, if necessary. The BET specific surface area of ​​the silica is 140 m from the viewpoint of obtaining good durability.2 / g or more is preferable, and 160m 2 On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed driving, a tire having a rolling resistance of 250 m 2 / g or less is preferable, and 220m 2 / g or less. From the viewpoint of obtaining good durability, the content of the silica relative to 100 parts by mass of the rubber component is preferably more than 35 parts by mass, more preferably more than 40 parts by mass, even more preferably more than 45 parts by mass, and particularly preferably 50 parts by mass or more. On the other hand, from the viewpoint of obtaining good rolling resistance during high-speed running, the content is preferably less than 70 parts by mass, more preferably less than 65 parts by mass, and even more preferably less than 60 parts by mass. The BET specific surface area is N 2 This is the SA value.

[0085] 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.

[0086] As the silica, for example, products manufactured by Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0087] (iii) Silane coupling agent When silica is used as the filler, it is preferable to contain a silane coupling agent together with silica, as described above. 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-dimethylthiocarbamoyl silane, and the like. Examples of the silane include sulfide-based silanes such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide, mercapto-based silanes such as 3-mercaptopropyl trimethoxysilane, 2-mercaptoethyl triethoxysilane, and NXT and NXT-Z manufactured by Momentive, vinyl-based silanes such as vinyl triethoxysilane and vinyl trimethoxysilane, amino-based silanes such as 3-aminopropyl triethoxysilane and 3-aminopropyl trimethoxysilane, glycidoxy-based silanes such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane, nitro-based silanes such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane, and chloro-based silanes such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. These may be used alone or in combination of two or more.

[0088] As the silane coupling agent, for example, products available from Degussa, Momentive, Shin-Etsu Silicones, Tokyo Chemical Industry, Azumax, Dow Corning Toray, etc. can be used.

[0089] The content of the silane coupling agent is, for example, more than 3 parts by mass and less than 25 parts by mass relative to 100 parts by mass of silica.

[0090] (iv) Other fillers In addition to the above-mentioned carbon black and silica, the rubber composition may further contain fillers commonly used in the tire industry, such as calcium carbonate, talc, alumina, clay, aluminum hydroxide, mica, etc. The content of these fillers is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0091] (b) Softener The rubber composition may contain oil (including extender oil) or liquid rubber as a softener. The total content of these is, for example, preferably more than 5 parts by mass, more preferably more than 10 parts by mass, and even more preferably more than 12 parts by mass, per 100 parts by mass of the rubber component. Also, it is preferably less than 30 parts by mass, more preferably less than 20 parts by mass, and even more preferably less than 17 parts by mass. The oil content includes the amount of oil contained in the rubber (oil-extended rubber).

[0092] Examples of the oil include mineral oils, vegetable oils, or mixtures thereof, which are generally called process oils. Examples of the process oils (mineral oils) that can be used include paraffin-based process oils, aromatic process oils, and naphthenic process oils. Examples of the vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, and tung oil. These may be used alone or in combination of two or more.

[0093] Examples of process oils (mineral oils) that can be used include products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., Japan Energy Co., Ltd., Orisoi Co., Ltd., H&R Co., Ltd., Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., and the like.

[0094] The liquid rubbers mentioned as softeners are polymers that are in a liquid state at room temperature (25° C.) and contain the same monomers as solid rubbers. Examples of liquid rubbers include farnesene-based polymers, liquid diene-based polymers, and hydrogenated products thereof.

[0095] Farnesene polymers are polymers obtained by polymerizing farnesene and contain structural units based on farnesene. Farnesene has isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0096] The farnesene-based polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0097] Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene-isoprene copolymer (liquid SIR).

[0098] The liquid diene polymer has a weight average molecular weight (Mw) of, for example, 1.0×10 3 Super, 2.0×10 5 In this specification, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0099] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0100] (C) Resin component The rubber composition preferably contains a resin component as necessary. The resin component may be solid or liquid at room temperature, and specific examples of the resin component include styrene resin, coumarone resin, terpene resin, C5 resin, C9 resin, C5C9 resin, and acrylic resin, and two or more of them may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, more preferably less than 30 parts by mass, based on 100 parts by mass of the rubber component.

[0101] The styrene resin is a polymer using a styrene monomer as a constituent monomer, and examples thereof include polymers polymerized with a styrene monomer as the main component (50% by mass or more).Specific examples thereof include homopolymers obtained by polymerizing each of the styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more kinds of styrene monomers, and copolymers of a styrene monomer and another monomer that can be copolymerized therewith.

[0102] Examples of the other monomer include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylics and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene and butadiene-isoprene, olefins such as 1-butene and 1-pentene, α,β-unsaturated carboxylic acids such as maleic anhydride, or acid anhydrides thereof.

[0103] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins that contain coumarone and indene as monomer components that constitute the resin skeleton (main chain). Other monomer components contained in the skeleton besides coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

[0104] The amount of the coumarone-indene resin per 100 parts by mass of the rubber component is, for example, more than 1.0 part by mass and less than 50.0 parts by mass.

[0105] The hydroxyl value (OH value) of the coumarone-indene resin is, for example, more than 15 mgKOH / g and less than 150 mgKOH / g. The OH value is the amount of potassium hydroxide required to neutralize acetic acid bonded to hydroxyl groups when acetylating 1 g of the resin, expressed in milligrams, and is a value measured by potentiometric titration (JIS K 0070:1992).

[0106] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0107] Terpene resins include polyterpene, terpene phenol, 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 The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: 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.

[0108] 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, and specifically include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. Examples of phenolic compounds include, for example, 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, alkylphenols, alkoxyphenols, and phenols containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthols, alkoxynaphthols, and naphthols containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrenes, alkoxystyrenes, and styrenes containing an unsaturated hydrocarbon group; coumarone, indene, and the like.

[0109] "C5 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. As a C5 petroleum resin, dicyclopentadiene resin (DCPD resin) is preferably used.

[0110] The term "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a resin obtained by hydrogenating or modifying the resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of suitable resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, because they are economical, easy to process, and have excellent heat generation properties. As aromatic vinyl resins, for example, those commercially available from Kraton, Eastman Chemical, etc. can be used.

[0111] The term "C5C9 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. As the C5C9 resin, for example, those commercially available from Tosoh Corporation, LUHUA, etc. can be used.

[0112] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0113] Examples of the solvent-free acrylic resin include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A-59-6207, JP-B-5-58005, JP-A-1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyuu Nenpo TREND 2000 Vol. 3, p. 42-45, etc.) using as little secondary raw material as possible, such as polymerization initiators, chain transfer agents, and organic solvents. In the present invention, (meth)acrylic means methacryl and acrylic.

[0114] Examples of monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0115] In addition, aromatic vinyls such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative as a monomer component constituting the acrylic resin.

[0116] The acrylic resin may be a resin composed only of a (meth)acrylic component, or a resin containing components other than the (meth)acrylic component as constituent elements. The acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0117] Examples of the resin component that can be used include products from Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JX Energy Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Co., Ltd.

[0118] (D) Anti-aging agents The rubber composition preferably contains an antioxidant. The content of the antioxidant is, for example, more than 1 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component.

[0119] Examples of the antioxidant include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, and N,N'-di-2-naphthyl-p-phenylenediamine. Examples of such antioxidants include p-phenylenediamine antioxidants such as quinolinone, quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline, monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol, and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. These antioxidants may be used alone or in combination of two or more.

[0120] 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.

[0121] (e) Stearic acid The rubber composition may contain stearic acid. The content of stearic acid is, for example, more than 0.5 parts by mass and less than 10.0 parts by mass with respect to 100 parts by mass of the rubber component. As the stearic acid, a conventionally known product can be used, for example, a product from NOF Corporation, NOF Corporation, Kao Corporation, FUJIFILM Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. can be used.

[0122] (F) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 10 parts by mass with respect to 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known product can be used, for example, a product of 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.

[0123] (G) Wax The rubber composition preferably contains wax. The content of the wax per 100 parts by mass of the rubber component is, for example, 0.5 to 20 parts by mass, preferably 1.0 to 15 parts by mass, and more preferably 1.5 to 10 parts by mass.

[0124] The wax is not particularly limited, and examples thereof include petroleum waxes such as paraffin wax and microcrystalline wax, natural waxes such as vegetable wax and animal wax, synthetic waxes such as polymers of ethylene, propylene, etc. These may be used alone or in combination of two or more kinds.

[0125] As the wax, for example, products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0126] (H) Crosslinking agents and vulcanization accelerators The rubber composition preferably contains a crosslinking agent such as sulfur, etc. The content of the crosslinking agent is, for example, more than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0127] 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 kinds.

[0128] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanritsu Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0129] Examples of crosslinking agents other than sulfur include vulcanizing agents containing sulfur atoms, such as TACKIROL V200 manufactured by Taoka Chemical Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylenedithiosulfate dihydrate) manufactured by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane: hybrid crosslinking agent) manufactured by LANXESS, as well as organic peroxides such as dicumyl peroxide.

[0130] The rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, more than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0131] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazyl sulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more kinds.

[0132] (R) Other In addition to the above components, the rubber composition may further contain additives commonly used in the tire industry, such as fatty acid metal salts, carboxylate metal salts, organic peroxides, etc. The content of these additives is, for example, more than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0133] (2) Preparation of rubber composition The tread rubber composition and the sidewall rubber composition are produced by a general method, for example, a manufacturing method including a base kneading step of kneading a rubber component with a filler such as carbon black, and a finish kneading step of kneading the kneaded product obtained in the base kneading step with a crosslinking agent.

[0134] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0135] The kneading temperature in the base kneading step is, for example, more than 50° C. and less than 200° C., and the kneading time is, for example, more than 30 seconds and less than 30 minutes. In the base kneading step, in addition to the above-mentioned 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 necessary.

[0136] 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, higher than room temperature and lower than 80° C., and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. 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.

[0137] 2. Tire manufacturing The tire according to the present embodiment is manufactured by a normal method using each unvulcanized rubber composition obtained through the above-mentioned finish mixing process. That is, each unvulcanized rubber composition is extruded using a tread rubber composition (cap tread composition and base tread composition) and a sidewall rubber composition according to the respective shapes of the cap rubber, base rubber and sidewall rubber, and molded together with other tire components by a normal method on a tire building machine to first produce an unvulcanized tire.

[0138] Specifically, an inner liner as a member for ensuring the airtightness of the tire, a carcass as a member that withstands the load, impact, and filled air pressure received by the tire, and a belt as a member that tightly fastens the carcass and increases the rigidity of the tread are wound around a molding drum, and both ends of the carcass are fixed to both side edges, and bead portions as members for fixing the tire to the rim are arranged. After molding into a toroidal shape, the tread is attached to the center of the outer periphery, and the side portions (sidewalls and clinch portions) as members that protect the carcass and withstand bending are attached to the radially outside, to produce an unvulcanized tire.

[0139] In this embodiment, it is preferable to provide an inclined belt layer extending at an angle of 15° to 30° with respect to the tire circumferential direction as the belt, which ensures the durability of the tire and can sufficiently maintain the rigidity of the tread. In addition, since the tire can be restrained in the circumferential direction, it is easy to suppress the growth of the outer diameter.

[0140] The unvulcanized tire thus produced is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization step can be carried out by applying a known vulcanization method. The vulcanization temperature is, for example, more than 120°C and less than 200°C, and the vulcanization time is, for example, more than 5 minutes and less than 15 minutes.

[0141] The tire according to the present embodiment is particularly preferably applied to pneumatic tires for passenger cars in the summer, and can more suitably contribute to solving the problem of the present invention, which is to provide a pneumatic tire that is excellent in durability and satisfactorily achieves both improved fuel efficiency and reduced road noise. EXAMPLES

[0142] The present invention will now be described more specifically with reference to examples.

[0143] [1] Manufacturing of rubber composition 1. Tread rubber composition First, a tread rubber composition was produced.

[0144] (1) Compounding materials First, the following blended materials were prepared.

[0145] (a) Rubber component (a) NR:TSR20 (b) BR-1: UBEPOL-BR150B manufactured by Ube Industries, Ltd. (Cis content: 97% by mass) (c) BR-2: Nipol-BR1250H manufactured by Nippon Zeon Co., Ltd. (Tin-terminated BR, cis content: 40% by mass) (d) BR-3: UBEPOL VCR617 manufactured by Ube Industries, Ltd. (Cis content: 98% by mass) (E) SBR: Europrene SOL R C2525 manufactured by Versalis (styrene content: 26% by mass, vinyl bond content: 24% by mass)

[0146] (b) Compounding materials other than rubber components (a) Carbon black: Show Black N330T manufactured by Cabot Japan Co., Ltd. (DOP oil absorption: 104ml / 100g) (b) Silica: Ultrasil VN3 manufactured by Evonik (c) Silane coupling agent: Degussa Si363 (d) Resin component: PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (Cashew oil modified phenolic resin) (e) Hardener: Sumikanol 507 manufactured by Taoka Chemical Co., Ltd. (F) Oil: Process X-140 manufactured by Japan Energy Co., Ltd. (g) Stearic acid: NOF Corp.'s "Tsubaki" stearic acid (H) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (i) Wax: Sunnock wax manufactured by Ouchi Shinko Chemical Co., Ltd. (J) Anti-aging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (k) Anti-aging agent-2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline) (l) Crosslinking agents and vulcanization accelerators Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator-1: Noccela NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-tert-butyl-2-benzothiazolylsulfenamide) Vulcanization accelerator-2: Noccela CZ-G (CZ) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazolyl sulfenamide) Vulcanization accelerator-3: Noccela D (DPG) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (1,3-Diphenylguanidine)

[0147] (2) Production of Rubber Composition The cap rubber composition was prepared according to the formulation shown in Table 1, and the base rubber composition was prepared according to the formulation shown in Table 2. Using a Banbury mixer, materials other than sulfur and vulcanization accelerator were kneaded for 5 minutes under the condition of 150°C to obtain a kneaded mixture, after which sulfur and vulcanization accelerator were added, and the mixture was kneaded for 5 minutes under the condition of 80°C using an open roll to obtain a cap rubber composition and a base rubber composition. The respective amounts are in parts by mass.

[0148] [Table 1]

[0149] [Table 2]

[0150] 2. Preparation of Sidewall Rubber Composition Next, a sidewall rubber composition was produced.

[0151] (1) Compounding materials First, the following blended materials were prepared.

[0152] (a) Rubber component (a) NR:TSR20 (b) BR-1: UBEPOL-BR150B manufactured by Ube Industries, Ltd. (Cis content: 97% by mass) (c) BR-2: Nipol-BR1250H manufactured by Nippon Zeon Co., Ltd. (Tin-terminated BR, cis content: 40% by mass) (d) BR-3: UBEPOL VCR617 manufactured by Ube Industries, Ltd. (Cis content: 98% by mass)

[0153] (b) Compounding materials other than rubber components (a) Carbon black-1: Show Black N550 manufactured by Cabot Japan Co., Ltd. (DOP oil absorption: 115ml / 100g) (b) Carbon black-2: Show Black N330T manufactured by Cabot Japan Co., Ltd. (DOP oil absorption: 104ml / 100g) (c) Oil: Process X-140 manufactured by Japan Energy Co., Ltd. (d) Stearic acid: NOF Corp.'s "Tsubaki" stearic acid (e) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (F) Wax: Sunnock wax manufactured by Ouchi Shinko Chemical Co., Ltd. (G) Anti-aging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (H) Anti-aging agent-2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline) (i) Crosslinking agents and vulcanization accelerators Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. Vulcanization accelerator: Noccela NS manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-tert-butyl-2-benzothiazolylsulfenamide)

[0154] (2) Preparation of sidewall rubber composition According to the composition shown in Table 3, materials other than sulfur and the vulcanization accelerator were kneaded for 5 minutes at 150° C. using a Banbury mixer to obtain a kneaded product. The amounts of each ingredient are in parts by mass.

[0155] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded mixture, and the mixture was kneaded for 5 minutes under the condition of 80°C using an open roll to obtain sidewall rubber compositions of four types of blends A to D shown in Table 3.

[0156] [Table 3]

[0157] [2] Tire manufacturing (1) Tire manufacturing Using the cap rubber composition and base rubber composition obtained above, a two-layered tread rubber was prepared in a predetermined shape, and using the sidewall rubber composition, a sidewall rubber in a predetermined shape was prepared, which was then laminated together with other tire components in the combinations shown in Tables 4 and 5 to form an unvulcanized tire, which was press-vulcanized for 10 minutes under a condition of 170°C to produce each test tire of size 195 / 40R20. Note that each test tire had sipes connecting both sides of the circumferential land portion provided at an angle of 20° with respect to the width direction, and the area occupied by grooves other than the circumferential grooves on the ground contact surface was 80% of the area occupied by the circumferential grooves, which is smaller than the area occupied by the circumferential grooves.

[0158] (2) Calculation of parameters Then, the circumferential groove area ratio (%) of each test tire (the ratio of the area formed by the circumferential groove to the total ground contact area) was determined. In addition, rubber test pieces for viscoelasticity measurement were prepared by cutting out pieces of 20 mm length x 4 mm width x 2 mm thickness from the tread portion (cap rubber, base rubber) and sidewall portion of each test tire so that the long side was in the tire circumferential direction, and each rubber test piece was measured for tan δ in the deformation mode: tension and for E in the deformation mode: extension using an Iplexer series manufactured by GABO Corporation under the conditions of temperature 30°C, frequency 10 Hz, initial strain 5%, and dynamic strain 1%. * (Eb * , Ec * ) and from the measurement results, tanδb / tanδs and Eb * / Ec * The thickness direction of the sample was the radial direction of the tire. The results are shown in Tables 4 and 5.

[0159] (3) Performance evaluation test (a) Evaluation of rolling resistance (high speed driving) Each test tire was fitted to all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000cc) and filled with air to an internal pressure of 250kPa. The vehicle was then driven around a test course on a dry surface for 10km at a speed of 100km / h, after which the accelerator was released and the distance from when the accelerator was turned off until the vehicle came to a stop was measured as the rolling resistance.

[0160] Next, the rolling resistance was relatively evaluated by indexing it according to the following formula, with the result of Comparative Example 1 set as 100. The larger the value, the longer the distance from when the accelerator was released until the vehicle stopped, the smaller the rolling resistance in the steady state, and the more excellent the fuel economy. Rolling resistance = [(measurement result of test tire) / (measurement result of Comparative Example 1)] x 100

[0161] (b) Evaluation of durability Each test tire was fitted to all wheels of a vehicle (domestic FF vehicle, 2000cc displacement) and filled with air to an internal pressure of 250kPa. The vehicle was then overloaded and driven around a test course on a dry road surface at a speed of 50km / h for 10 laps, and then repeatedly driven over uneven surfaces at a speed of 80km / h. The vehicle then went around again at a speed of 50km / h, and the speed was gradually increased, and the speed at which the driver felt something was wrong was measured.

[0162] Next, the result of Comparative Example 1 was set as 100, and the durability was relatively evaluated by indexing it according to the following formula. A larger value indicates better durability. Durability performance=[(measurement result of test tire) / (measurement result of Comparative Example 1)]×100

[0163] (c) Road noise evaluation Each test tire was fitted to all wheels of a vehicle (a domestically produced FF vehicle with an engine displacement of 2000cc) and air was inflated so that the internal pressure in the front wheels was 230kPa and the internal pressure in the rear wheels was 220kPa. The vehicle was then driven on a test course with a dry surface at a speed of 60km / h while the driver sat by the window and performed a sensory test on noise on a 5-point scale.

[0164] The evaluation was carried out by adding up the scores of the 20 drivers, indexing the total score of Comparative Example 1 to 100, and using the reciprocal of this index to evaluate the tire. A larger index value indicates better road noise reduction. Road noise=[(Evaluation score of Comparative Example 1) / (Evaluation score of test tire)]×100

[0165] (d) Overall evaluation The results of the above evaluations (1) to (3) were summed up to give an overall evaluation.

[0166] (4) Evaluation results The results of each evaluation are shown in Tables 4 and 5.

[0167] [Table 4]

[0168] [Table 5]

[0169] From Tables 4 and 5, it can be seen that when the circumferential groove area ratio is 15 to 30% and tan δb / tan δs<1 is satisfied, excellent durability is achieved, and both improved fuel economy and reduced road noise are sufficiently achieved.

[0170] Also, when 1.3≦(tan δc / tan δb)<3.0 is satisfied, it is understood that excellent durability is achieved, and both improved fuel economy and reduced road noise are sufficiently achieved.

[0171] Also, Eb * / Ec * When the ratio <1 is satisfied, it is understood that the tire has excellent durability, and both improved fuel economy and reduced road noise are sufficiently achieved.

[0172] In addition, it is found that when the circumferential groove cross-sectional area ratio is 10% or more and less than 30%, excellent durability is achieved, and both improved fuel economy and reduced road noise are sufficiently achieved. In addition, it is found that better performance is achieved when the land area ratio is 30 to 60%.

[0173] Although the present invention has been described above based on the embodiment, the present invention is not limited to the above embodiment. Various modifications can be made to the above embodiment within the same and equivalent scope of the present invention.

Claims

1. A pneumatic tire having a tread portion having a tread rubber forming an outer surface, and a sidewall portion having a sidewall rubber forming an outer surface, The tread rubber is a cap rubber having a ground contact surface formed on an outer surface thereof by a plurality of circumferential grooves and a plurality of circumferential land portions; a base rubber disposed on the radially inner side of the cap rubber and extending to the sidewall portion, In the ground contact surface, an area formed by the circumferential groove portion is 15 to 30% of the total ground contact area, a total cross-sectional area of ​​the plurality of circumferential groove portions is 10% or more and less than 30% of a cross-sectional area of ​​the tread portion; a groove portion other than the circumferential groove portion is provided on a surface portion of the tread portion, In the ground contact surface, an area occupied by grooves other than the circumferential groove portion is smaller than an area occupied by the circumferential groove portion, When the ground contact surface is equally divided into four regions in the tire width direction, an area ratio occupied by the circumferential groove portion in the two inner regions is smaller than an area ratio occupied by the circumferential groove portion in the two outer regions, A pneumatic tire characterized in that the loss tangent (tan δb) of the base rubber and the loss tangent (tan δs) of the sidewall rubber measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: tension satisfy the following (Equation 1): (tanδb / tanδs)<1 (Formula 1)

2. The pneumatic tire according to claim 1, characterized in that the loss tangent (tan δc) of the cap rubber and the loss tangent (tan δb) of the base rubber measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: tension satisfy the following (Equation 2). 1.3≦(tanδc / tanδb)<3.0 (Formula 2)

3. The pneumatic tire according to claim 1 or 2, characterized in that the loss tangent (tan δc) of the cap rubber, the loss tangent (tan δb) of the base rubber, and the loss tangent (tan δs) of the sidewall rubber measured under the conditions of temperature: 30°C, frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: tension satisfy the following (Equation 3). tanδb<tanδs<tanδc (Formula 3)

4. The complex elastic modulus Eb of the base rubber measured under the conditions of temperature: 30° C., frequency: 10 Hz, initial strain: 5%, dynamic strain: 1%, and deformation mode: extension ＊ , and the complex elastic modulus Ec of the cap rubber ＊ The pneumatic tire according to any one of claims 1 to 3, characterized in that the following (Formula 4) is satisfied: Eb ＊ / Ec ＊ <1・・・・・(Formula 4)

5. 5. The pneumatic tire according to claim 1, characterized in that, when the contact patch is divided equally into four regions in the tire width direction, the total area excluding the grooves in the two inner regions is 30 to 60% of the area of ​​the entire contact patch excluding the grooves.

6. A sipe is formed in the circumferential land portion in a region closest to the tire equator, the sipe connecting both side portions of the circumferential land portion, 6. The pneumatic tire according to claim 1, wherein a straight line connecting both ends of the sipe is inclined at an angle of 15 to 25 degrees with respect to the width direction.

7. 7. The pneumatic tire according to claim 1, wherein the tread rubber is formed using a rubber composition containing a styrene-butadiene rubber and / or a butadiene rubber as a rubber component.

8. 8. The pneumatic tire according to claim 7, wherein the tread rubber is formed using a rubber composition containing 50 parts by mass or more of silica per 100 parts by mass of a rubber component.

9. 9. The pneumatic tire according to claim 1, wherein the sidewall rubber is formed using a rubber composition containing an isoprene-based rubber and a butadiene rubber as rubber components.

10. 10. The pneumatic tire according to claim 9, wherein the sidewall rubber is formed using a rubber composition containing 50 parts by mass or more of carbon black per 100 parts by mass of a rubber component.

11. The pneumatic tire according to any one of claims 1 to 10, which is a pneumatic tire for a passenger vehicle.

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