Pneumatic tires

Abstract

To provide a pneumatic tire which achieves both reduction in rolling resistance and improvement of uneven abrasion resistance performance.SOLUTION: A pneumatic tire includes a tread part having at least two or more rubber layers including a surface layer and an inner layer in a central region having a width of 50% of a ground width of a ground surface with a tire equator line as a center, and a side wall part, in which the tread part has a circumferential groove in continuous communication in a circumferential direction, and a plurality of land parts partitioned by the circumferential groove and a ground contact end; an outside part of the side wall part overlaps the outside of an end in a tire width direction of the tread part; an end in a width direction of the inner layer enters into a part of an interface between the surface layer and the side wall part; complex elastic modulus E*1 (MPa) of the surface layer and complex elastic modulus E*2 (MPa) of the inner layer satisfy (E*2 / E*1)<1.0; and a groove area ratio CR (%) in the central region and a groove area ratio SR (%) in a region excluding the central region from the ground surface satisfy |CR-SR|≤15.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] The fuel efficiency of a tire can be evaluated by its rolling resistance, and it is known that the smaller the rolling resistance, the more fuel efficient the tire.

[0004] Therefore, it has been proposed to reduce the rolling resistance and improve fuel economy by devising a compounding scheme for the rubber composition constituting the tire tread portion (for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2018-178034 A [Patent Document 2] JP 2019-089911 A [Patent Document 3] WO2018 / 186367 publication [Patent Document 4] JP 2019-206643 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, even in tires manufactured by the above-mentioned conventional techniques, the reduction in rolling resistance is still insufficient, and further improvement is desired. In addition, since these tires are prone to uneven wear in the tread portion during running, improvement in uneven wear resistance is desired.

[0007] Therefore, an object of the present invention is to provide a pneumatic tire that achieves both reduced rolling resistance and improved resistance to uneven wear. [Means for solving the problem]

[0008] 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.

[0009] The invention described in claim 1 is A pneumatic tire having a tread portion having at least two or more rubber layers including a surface layer and an inner layer in a central region having a width that is 50% of the contact width of the contact surface centered on the tire equator line, and a sidewall portion having a sidewall rubber that forms an outer surface, The tread portion has a circumferential groove communicating in a circumferential direction, and includes a plurality of land portions separated by the circumferential groove and a ground contact edge portion, The tread portion and the sidewall portion are such that an outer portion of the sidewall portion is overlapped with an outer side of an end portion in the tire width direction of the tread portion, a width direction end portion of the inner layer of the tread portion intrudes into a part of an interface between a surface layer of the tread portion and the sidewall portion, The complex elastic modulus of the surface layer of the tread portion at 30 ° C. is E * 1 (MPa), the complex modulus of elasticity of the inner layer of the tread portion at 30°C is E * 2 (MPa), the following (Equation 1) is satisfied, Furthermore, when the groove area ratio in the central region is CR (%) and the groove area ratio in the region excluding the central region from the contact patch is SR (%), the pneumatic tire is characterized in that it satisfies the following (Equation 2). (E* 2 / E * 1)<1.0 (Formula 1) |CR-SR|≦15 (Formula 2)

[0010] The invention described in claim 2 is The pneumatic tire according to claim 1, characterized in that the following (Formula 3) is satisfied: (E * 2 / E * 1)<0.9 (Formula 3)

[0011] The invention described in claim 3 is The pneumatic tire according to claim 2, characterized in that the following (Formula 4) is satisfied: (E * 2 / E * 1)<0.8 (Equation 4)

[0012] The invention described in claim 4 is The pneumatic tire according to any one of claims 1 to 3, characterized in that the following (Formula 5) is satisfied. E * 2×|CR-SR|≦100 (Formula 5)

[0013] The invention described in claim 5 is The pneumatic tire according to claim 4, characterized in that the following (Formula 6) is satisfied: E * 2×|CR-SR|≦75 (Formula 6)

[0014] The invention described in claim 6 is The pneumatic tire according to any one of claims 1 to 5, wherein when a loss tangent of the inner layer of the tread portion at 30°C is taken as tan δ2, the following formula (7) is satisfied: tanδ2×|CR-SR|≦3.75 (Formula 7)

[0015] The invention described in claim 7 is A belt reinforcing layer is provided on the radially inner side of the tread portion, In the central region of the tread portion, A height Ht (mm) from the outer peripheral surface of the belt reinforcing layer to a surface of the circumferential land portion is 30 mm or less, and a height Hg (mm) from the outer peripheral surface of the belt reinforcing layer to a bottom surface of the main groove is 5 mm or less, The pneumatic tire according to any one of claims 1 to 6 is further characterized in that the height h (mm) from the outer peripheral surface of the belt reinforcing layer at the widthwise center position of the circumferential land portion to the interface between the surface layer and the inner layer of the tread portion is 0.5 mm or more, and h>Hg.

[0016] The invention described in claim 8 is Sipes are formed in a center land portion and a shoulder land portion partitioned by two or more circumferential main grooves provided in the tread portion, The pneumatic tire according to any one of claims 1 to 7, characterized in that the directions of the sipes in adjacent land portions with respect to the circumferential direction of the tire are opposite to each other.

[0017] The invention described in claim 9 is 9. The pneumatic tire according to claim 1, wherein a ratio of a total groove area to a total area within the contact width of the tread portion is 20 to 40%. Effect of the Invention

[0018] According to the present invention, it is possible to provide a pneumatic tire that achieves both reduced rolling resistance and improved uneven wear resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will be described below based on embodiments.

[0020] [1] Characteristics of the tire according to the present invention First, the features of the tire according to the present invention will be described.

[0021] 1. Overview The tire of the present invention is a pneumatic tire having a tread portion having at least two rubber layers including a surface layer and an inner layer in a central region having a width that is 50% of the contact width of the contact surface centered on the tire equator line, and a sidewall portion having sidewall rubber that forms the outer surface.

[0022] In terms of structure, the tread portion has circumferential grooves that communicate in the circumferential direction and is provided with a plurality of land portions separated by the circumferential grooves and the ground contact edges, and the outer portions of the sidewall portions are overlapped on the outsides of the tire width direction edges of the tread portion, and the width direction edges of the inner layer of the tread portion penetrate into part of the interface between the surface layer of the tread portion and the sidewall portions.

[0023] On the other hand, in terms of physical properties, the complex modulus of elasticity of the surface layer of the tread at 30°C is E * 1 (MPa), and the complex modulus of elasticity of the inner layer of the tread at 30°C is E * 2 (MPa), E * 2 / E * 1)<1.0 (Equation 1).

[0024] Furthermore, when the groove area ratio in the central region is CR (%) and the groove area ratio in the area excluding the central region is SR (%), it is characterized by satisfying |CR-SR|≦15 (Equation 2).

[0025] According to the present invention, by having the above-mentioned structural and physical property features, it is possible to provide a pneumatic tire that achieves both reduced rolling resistance and improved uneven wear resistance, as will be described later.

[0026] In the above description, the "contact patch" refers to the outer peripheral surface of the tire that comes into contact with the road surface when the tire is mounted on a regular rim, inflated to the regular internal pressure, and rolled under a regular load. Specifically, for example, the tire is mounted on a regular rim, inflated to the regular internal pressure, and left to stand at 25°C for 24 hours, after which the surface of the tread is painted with ink, and the tire is pressed against cardboard under a regular load to transfer the ink to the paper. The total area of ​​the blackened land areas and the whitened groove areas is the "total contact area." Furthermore, the "contact width" refers to the maximum width in the tire width direction within the contact patch.

[0027] 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.

[0028] The "normal internal pressure" is the air pressure specified for each tire by the standard, which is the maximum air pressure for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "INFLATION PRESSURE" for ETRTO. For tires not specified by the standard, it is 250 kPa.

[0029] The "normal load" is the load specified for each tire by the standard, and refers to the maximum mass that can be loaded on the tire, which is the maximum load capacity for JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA, and "LOAD CAPACITY" for ETRTO. For tires not specified in the standard, the value can be calculated using the following formula. Normal load (kg) = 0.000011 x V + 175 V={Dt 2 -(Dt-Ht1) 2}×Wt

[0030] where V is the virtual volume occupied by the tire (mm 3 ), Dt is the outer diameter of the tire (mm), Ht1 is the tire section height (mm), and Wt is the tire section width (mm), all of which are values ​​measured under normal conditions.

[0031] In addition, the tire section width Wt indicates the linear distance of the maximum width of the tire in a normal state, and does not include surface irregularities such as letters. The tire section height can be calculated by subtracting the rim diameter (mm) from the outer diameter Dt.

[0032] 2. Mechanism of effect manifestation in the tire according to the present invention The mechanism by which the effect of the tire according to the present invention is realized, that is, the mechanism by which both the reduction in rolling resistance and the improvement in uneven wear resistance are achieved, is presumed to be as follows.

[0033] As described above, the tire according to the present invention has at least two rubber layers including a surface layer and an inner layer in a central region having a width of 50% of the contact width of the contact surface centered on the tire equator line, and the complex modulus of elasticity of the surface layer at 30° C. is E * 1 (MPa), the complex modulus of elasticity of the inner layer at 30°C is E * 2 (MPa), (E * 2 / E * 1) < 1.0 (Equation 1) is satisfied.

[0034] Complex modulus E * is a parameter indicating stiffness, and as mentioned above, the complex elastic modulus E of the inner layer * 2 is the complex elastic modulus of the surface layer, E * By making it smaller than 1, the entire tread part is able to deform from the inside during driving and come into contact with the road surface, which is believed to suppress uneven deformation and stress concentration in the tread part, and therefore suppress the occurrence of rolling resistance and uneven wear. In addition, it is believed that the edge of the surface layer is less susceptible to force when it comes into contact with the ground, making it more likely to slip.

[0035] Therefore, by covering the edge of the surface layer with an inner layer that is less rigid than the surface layer, it is possible for the ground contact edge to follow the road surface even with a slight force, which is believed to reduce uneven wear due to slippage at the surface layer edge and heat generation due to friction. As a result, a uniform ground contact surface can be obtained in the center of the tread, and sufficient followability can be obtained even at the width direction edge of the surface layer, which is believed to suppress rolling resistance and uneven wear. In addition, (E * 2 / E * 1) is more preferably less than 0.9, and even more preferably less than 0.8.

[0036] In addition, E in the above description * 1 and E * 2 is a value 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 of extension, and can be measured using a viscoelasticity measuring device such as GABO's "IPLEXER (registered trademark)".

[0037] The complex elastic modulus E at 30°C of the surface layer of the tread portion * The value of 1 is not particularly limited, but is preferably 5 MPa or more, more preferably 8 MPa or more, and even more preferably 9.5 MPa or more. On the other hand, the upper limit is also not particularly limited, but is preferably 15 MPa or less, and more preferably 12 MPa or less.

[0038] The complex elastic modulus E of the inner layer of the tread portion at 30°C * The value of 2 is not particularly limited, but is preferably 3.0 MPa or more, more preferably 3.5 MPa or more, and even more preferably 4 MPa or more. On the other hand, the upper limit is also not particularly limited, but is preferably 10 MPa or less, more preferably 7 MPa or less, and even more preferably 6 MPa or less.

[0039] Furthermore, in the present invention, when the groove area ratio in the central region is CR (%) and the groove area ratio in the region excluding the central region is SR (%), the following is satisfied: |CR-SR|≦15 (Equation 2).

[0040] In this way, by keeping the groove area ratio CR in the central region and the groove area ratio SR in the region other than the central region within a predetermined range so that they do not differ significantly, it is possible to equalize the distribution of rigidity in the width direction of the tread portion and ensure a stable ground contact state even if the tread portion deforms during running, which is believed to suppress the occurrence of uneven wear and reduce rolling resistance. Note that |CR-SR| is preferably 13 or less, and more preferably 10 or less.

[0041] The groove area ratio CR (%) in the central region is preferably 5% or more, more preferably 7% or more, and even more preferably 10% or more. By setting the groove area ratio CR (%) in the above range, it is believed that the rigidity of the entire tread in the central region can be appropriately reduced, and the tread portion can be made to contact the ground uniformly.

[0042] On the other hand, the groove area ratio CR (%) in the central region is preferably 40% or less, more preferably 35% or less, and even more preferably 30% or less. If it exceeds 40%, the amount of deformation in the central region increases, and it is considered that the effect of improving fuel efficiency is reduced.

[0043] The groove area ratio SR (%) in the region excluding the central region is preferably 7% or more, more preferably 10% or more, and even more preferably 12% or more. By setting the groove area ratio SR (%) in the above range, it is believed that good ground contact can be obtained even in the tread shoulder portion, and that the tread portion can be easily brought into uniform contact with the ground.

[0044] On the other hand, the groove area ratio SR (%) in the region excluding the central region is preferably 45% or less, more preferably 40% or less, and even more preferably 35% or less. If it exceeds 45%, the ground contact in the shoulder portion becomes too high, and it is considered that it becomes difficult to obtain the effect of suppressing uneven wear.

[0045] The "groove area ratio" refers to the ratio (%) of the total area of ​​the circumferential grooves to the total area including the circumferential grooves and the circumferential land portions of each region on the contact surface of the tread portion.

[0046] [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.

[0047] 1. Relationship between the complex elastic modulus of the base rubber and the groove area ratio As mentioned above, it is believed that the distribution of stiffness in the tread portion can be made uniform by keeping the difference between CR and SR within a predetermined range. However, when the difference between CR and SR is large, E * By reducing 2, the inner layer of the tread part deforms, which makes the ground pressure distribution on the entire tread surface uniform and suppresses uneven deformation. * By reducing both of these factors, it is possible to suppress the occurrence of uneven deformation in the tread portion, thereby making it possible to further reduce rolling resistance and improve resistance to uneven wear.

[0048] Therefore, the inventor of the present invention * Experiments and studies were conducted to determine the favorable relationship between E 2 and |CR-SR|.* 2×|CR-SR|≦100 (Equation 5) is sufficient. * It has been found that it is even more preferable to satisfy 2×|CR−SR|≦75 (equation 6).

[0049] 2. Relationship between loss tangent of base rubber and each groove area ratio The loss tangent tan δ is a parameter that indicates the heat generation property of a tire, and it is considered that the smaller the value, the more the heat generation property in the tread portion during running can be reduced and the more the temperature rise of the tire can be suppressed.

[0050] In particular, when the difference between CR and SR is large, the amount of deformation near the interface between the central portion and the portion excluding the central portion becomes large, and it is believed that by reducing the heat generation of the inner layer at that portion, the rolling resistance can be sufficiently reduced.

[0051] In addition, by simultaneously reducing the difference between CR and SR and tan δ, it is also possible to suppress heat generation due to deformation in the inner layer of the tread portion, and it is believed that the rolling resistance can be sufficiently reduced.

[0052] The inventors conducted experiments and studies on tan δ and found that, when the loss tangent of the inner layer of the tread portion at 30° C. is tan δ2, if tan δ2×|CR−SR|≦3.75 (Formula 7) is satisfied, the rolling resistance can be further reduced and the uneven wear resistance can be further improved. It is more preferable that tan δ2×|CR−SR| is 3.50 or less, and even more preferable that it is 3.25 or less.

[0053] In addition, tan δ2 is the above-mentioned E * In the same manner as in the measurement of (1), a viscoelasticity measuring device such as "IPLEXER (registered trademark)" manufactured by GABO may be used, and the measurement may be performed under the same conditions except that the deformation mode is set to tension.

[0054] The tan δ of the inner layer of the tread portion at 30° C. is preferably 0.25 or less, more preferably 0.20 or less, even more preferably 0.15 or less, and even more preferably 0.10 or less. On the other hand, although there is no particular lower limit, it is preferably 0.02 or more, and more preferably 0.03 or more.

[0055] 3.Belt reinforcement layer In the tire according to the present invention, it is preferable to include a belt reinforcing layer on the radially inner side of the tread portion.

[0056] By providing a belt reinforcing layer radially inside the tread portion, it is possible to suppress deformation of the tread portion due to internal pressure, which is believed to stably reduce rolling resistance and improve resistance to uneven wear.

[0057] Therefore, the inventors conducted experiments and studies on the belt reinforcement layer and found that if, in the central region of the tread portion, the height Ht from the outer peripheral surface of the belt reinforcement layer to the surface of the circumferential land portion is set to 30 mm or less, while the height Hg from the outer peripheral surface of the belt reinforcement layer to the bottom surface of the circumferential groove is set to 5 mm or less, the thickness of the entire tread portion can be appropriately secured, thereby sufficiently reducing rolling resistance.

[0058] The circumferential land portion referred to here is any land portion in the central region, and it is particularly preferable that the land portion closest to the tread equatorial plane satisfies the above relationship. Also, the circumferential groove refers to the deepest circumferential groove among the circumferential land portions adjacent to the circumferential land portion.

[0059] The height Ht from the outer circumferential surface of the belt reinforcing layer to the surface of the circumferential land portion is preferably 15 mm or less, more preferably 10 mm or less, while Ht is preferably 5 mm or more, more preferably 7 mm or more.

[0060] The height Hg from the outer circumferential surface of the belt reinforcing layer to the bottom surface of the circumferential groove is preferably 4 mm or less, more preferably 2 mm or less, while Hg is preferably 0.5 mm or more, more preferably 1 mm or more.

[0061] In addition, if the height h from the outer peripheral surface of the belt reinforcing layer at the widthwise center position of the circumferential land portion to the boundary between the surface layer and the inner layer is 0.5 mm or more, the inner layer can be reliably arranged below the land portion to suppress deterioration of heat generation, and further, by making h>Hg, it is possible to easily deform the entire tread portion from the bottom surface of the land portion, and it is believed that the pressure at the time of contact with the ground can be made uniform. As a result, it was found that it is possible to further reduce the rolling resistance and further improve the uneven wear resistance.

[0062] The belt reinforcing layer is preferably provided so as to extend at an angle of ±5° or less with respect to the tire circumferential direction, which is believed to prevent the tire from being deformed by internal pressure and to enable a uniform distribution of ground contact pressure, thereby reducing rolling resistance and improving uneven wear resistance.

[0063] 4. Sipe In the tire according to the present invention, sipes are formed in two or more land portions partitioned by two or more circumferential main grooves provided in the tread portion, and it is preferable that the orientation of the sipes in adjacent land portions relative to the tire circumferential direction is opposite.

[0064] By providing such sipes, it is believed that the ground contact of the tread land surface can be improved and the movement of the tread land can be minimized, which further reduces the rolling resistance. At the same time, since the directions of adjacent sipes are different, the forces acting perpendicular to the sipe direction cancel each other out in the width direction, and the forces are limited to the circumferential component, which is believed to facilitate uniform wear of the land portion.

[0065] The sipes referred to here refer to narrow grooves with a groove width of less than 2 mm, and may or may not be open to the circumferential groove.

[0066] 5. Proportion of groove area within the tread width In the tire according to the present invention, the ratio of the total groove area to the total area within the contact width of the tread portion is preferably 20 to 40%.

[0067] In this way, by setting the ratio of the total groove area to the total area within the contact width of the tread portion to be 20% or more and 40% or less, it is possible to ensure sufficient heat dissipation from the grooves and to properly ensure the rigidity of the entire tread portion, which is believed to reduce rolling resistance and improve resistance to uneven wear.

[0068] The "total groove area" refers to the sum of the areas of circumferential grooves and widthwise grooves such as sipes, and the sum of this and all land areas equals the "total area."

[0069] The ratio of the total groove area is more preferably 25% or more, and even more preferably 27% or more, while the upper limit is more preferably 38% or less, and even more preferably 35% or less.

[0070] [3] Specific embodiments of the present invention Hereinafter, the present invention will be described in detail based on the embodiments.

[0071] 1. Rubber composition In this embodiment, the tread rubber having a surface layer and an inner layer can use 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 surface layer and the inner layer.

[0072] (1) Compounding materials (a) Rubber component In the present embodiment, the rubber component may be a rubber (polymer) that is generally used in the manufacture of tires, such as butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber, nitrile rubber (NBR), etc. These may be used alone or in combination of two or more kinds.

[0073] The tread rubber preferably contains an isoprene-based rubber, BR, or SBR, and more preferably uses any of an isoprene-based rubber and BR, BR and SBR, or SBR and an isoprene-based rubber in combination. An isoprene-based rubber, BR, and SBR may also be used in combination.

[0074] (a) BR The amount of BR in 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more, while it is preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less.

[0075] 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.

[0076] 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:

[0077] [ka]

[0078] 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.

[0079] 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.

[0080] 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.).

[0081] 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.

[0082] 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.;

[0083] As the BR, for example, products from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used.

[0084] (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.

[0085] 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.

[0086] 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.

[0087] (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, 20 parts by mass or more and 100 parts by mass or less. It is more preferable that it is more than 25 parts by mass, and even more preferable that it is more than 30 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.

[0088] 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.

[0089] 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.

[0090] 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.

[0091] As the SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, etc. can be used. The SBR may be used alone or in combination of two or more kinds.

[0092] (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.

[0093] (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.

[0094] (i) Carbon black The carbon black content is, for example, preferably 2 parts by mass or more, more preferably 3 parts by mass or more, even more preferably 8 parts by mass or more, and particularly preferably 10 parts by mass or more, per 100 parts by mass of the rubber component. On the other hand, it is preferably 100 parts by mass or less, more preferably 50 parts by mass or less, and even more preferably 40 parts by mass or less. This makes it possible to maintain the wear resistance and suppress uneven wear while reducing the rolling resistance of the tire.

[0095] The nitrogen adsorption specific surface area (N2SA) of carbon black 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.

[0096] 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.

[0097] 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.

[0098] (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. From the viewpoint of obtaining good rolling resistance, the content is preferably less than 150 parts by mass, more preferably less than 100 parts by mass, and even more preferably less than 70 parts by mass. The BET specific surface area mentioned above is the value of N2SA measured by the BET method according to ASTM D3037-93.

[0099] 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.

[0100] As the silica, for example, products manufactured by Degussa, Rhodia, Tosoh Silica Co., Ltd., Solvay Japan Co., Ltd., Tokuyama Corporation, etc. can be used.

[0101] (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.

[0102] 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.

[0103] 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.

[0104] (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.

[0105] (b) Softener The rubber composition may contain oil (including extender oil), liquid rubber, resin components, etc. as softeners. 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 50 parts by mass, more preferably less than 35 parts by mass, and even more preferably less than 20 parts by mass. The oil content includes the amount of oil contained in the rubber (oil-extended rubber).

[0106] (i) Oil 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.

[0107] 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.

[0108] (ii) Liquid rubber 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.

[0109] 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).

[0110] 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).

[0111] 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).

[0112] 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).

[0113] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Co., Ltd., etc. can be used.

[0114] (iii) Resin component In addition, it is preferable to contain, as a resin component, a resin such as a styrene-based resin, a coumarone-based resin, a terpene-based resin, a C5 resin, a C9 resin, a C5C9 resin, or an acrylic resin, as necessary. These resin components may be solid or liquid at room temperature, and two or more types may be used in combination. The content of the resin component is preferably more than 2 parts by mass and less than 45 parts by mass, and more preferably less than 30 parts by mass, based on 100 parts by mass of the rubber component.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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).

[0120] 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.

[0121] 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 (C5H8) 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.

[0122] 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.

[0123] "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.

[0124] 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.

[0125] 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.

[0126] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0127] 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.

[0128] 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.

[0129] 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.

[0130] 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.

[0131] 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.

[0132] (C) Hardening resin component The rubber composition preferably contains a curable resin component as necessary. The content of the curable resin component is, for example, preferably 4 parts by mass or more, more preferably 6 parts by mass or more, based on 100 parts by mass of the rubber component. On the other hand, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less.

[0133] Examples of the curable resin component include modified resorcinol resin and modified phenol resin. Specific examples of modified resorcinol resin include Sumikanol 620 (modified resorcinol resin) manufactured by Taoka Chemical Co., Ltd., and examples of modified phenol resin include PR12686 (cashew oil modified phenol resin) manufactured by Sumitomo Bakelite Co., Ltd.

[0134] When using the modified resorcinol resin, it is preferable to contain a methylene donor as a curing agent as necessary. Examples of the methylene donor include hexamethylenetetramine (HMT), hexamethoxymethylolmelamine (HMMM), and hexamethylolmelamine pentamethylether (HMMPME), and the like, and the methylene donor is preferably contained in an amount of, for example, 5 parts by mass or more and 15 parts by mass or less per 100 parts by mass of the curable resin component.

[0135] As a specific example of the methylene donor, Sumikanol 507 manufactured by Taoka Chemical Co., Ltd. can be used.

[0136] (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.

[0137] 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.

[0138] 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.

[0139] (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.

[0140] (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.

[0141] (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.

[0142] 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.

[0143] As the wax, for example, products available from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Seiko Chemical Co., Ltd., etc. can be used.

[0144] (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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148] 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.

[0149] 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.

[0150] (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.

[0151] (2) Preparation of rubber composition The rubber composition constituting the tread rubber is 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.

[0152] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0153] 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.

[0154] 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.

[0155] 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 according to the shape of the tread rubber including the surface layer and the inner layer, and molded together with other tire components by a normal method on a tire building machine to produce an unvulcanized tire.

[0156] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component that withstands the load, impact, and filled air pressure received by the tire, and a belt as a component 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 components for fixing the tire to the rim are arranged. After molding into a toroidal shape, tread rubber is attached to the center of the outer periphery, and side portions (sidewalls and clinch portions) as components that protect the carcass and withstand bending are attached to the radially outside, to produce an unvulcanized tire.

[0157] 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.

[0158] The tire according to the present embodiment is particularly preferably applied to pneumatic tires for passenger cars, and can more suitably contribute to solving the problem of the present invention, which is to provide a pneumatic tire that achieves both reduced rolling resistance and improved resistance to uneven wear. EXAMPLES

[0159] The present invention will be described more specifically below with reference to examples. In the following, a tread rubber having a two-layer structure of a surface layer and an inner layer was used as the tread rubber.

[0160] 1. Production of rubber composition for tread production Prior to the production of tires, first, rubber compositions for preparing a surface layer and an inner layer, that is, a first rubber composition for preparing a surface layer and a second rubber composition for preparing an inner layer, were produced.

[0161] (1) Compounding materials First, the following blended materials were prepared.

[0162] (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)

[0163] (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-1: Terpene styrene resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (Aromatic modified terpene resin) (E) Resin component-2: PR12686 manufactured by Sumitomo Bakelite Co., Ltd. (Cashew oil modified phenolic resin) (F) Hardener: Sumikanol 507 manufactured by Taoka Chemical Co., Ltd. (g) Oil: Process X-140 manufactured by Japan Energy Co., Ltd. (H) Stearic acid: "Tsubaki" stearic acid manufactured by NOF Corporation (i) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (J) Wax: Sunnock wax manufactured by Ouchi Shinko Chemical Co., Ltd. (K) Anti-aging agent-1: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (L) Anti-aging agent-2: Antage RD manufactured by Kawaguchi Chemical Industry Co., Ltd. (2,2,4-trimethyl-1,2-dihydroquinoline) (W) 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)

[0164] (2) Production of Rubber Composition The first rubber composition was prepared according to the formulation shown in Table 1, and the second 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 product, and then 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 the first rubber composition and the second rubber composition. The respective compounding amounts are parts by mass.

[0165] [Table 1]

[0166] [Table 2]

[0167] 2. Tire manufacturing A tread portion consisting of a two-layer tread rubber was produced in the combinations shown in Tables 3 and 4, with the first rubber composition obtained above used as a surface layer and the second rubber composition used as an inner layer. The tread portion was then laminated together with other tire components to form an unvulcanized tire, which was then press-vulcanized for 10 minutes under a condition of 170°C to produce each test tire (Examples 1 to 7 and Comparative Examples 1 to 6) having a size of 175 / 55R20.

[0168] In manufacturing each test tire, the tread portion and the sidewall portion were positioned so that the outer portion of the sidewall portion was overlapped on the outside of the tire width direction end portion of the tread portion, and the width direction end portion of the inner layer of the tread portion penetrated into part of the interface between the surface layer of the tread portion and the sidewall portion.

[0169] In each test tire, a belt reinforcing layer was disposed on the radially inner side of the tread portion. Specifically, the gauges of the surface layer and the inner layer were adjusted so that in the central region of the tread portion, the height Ht from the outer peripheral surface of the belt reinforcing layer to the surface of the circumferential land portion was 8.5 mm, and the height h from the outer peripheral surface of the belt reinforcing layer at the widthwise center position of the circumferential land portion to the boundary between the outermost surface rubber of the tread portion and the rubber penetrating into the interface was 3 mm.

[0170] Each test tire had three circumferential grooves. The groove depth was adjusted so that the height Hg from the outer peripheral surface of the belt reinforcing layer to the bottom surface of the main groove was 1.5 mm. The groove width was changed for each test tire to adjust the groove area ratio CR in the central region and the groove area ratio SR in the region excluding the central region. The center position and depth of the grooves were made the same. In addition, sipes were formed so that the directions of adjacent land portions of the center land portion and the shoulder land portion partitioned by the circumferential grooves were opposite to each other with respect to the tire circumferential direction.

[0171] The ratio of the total groove area to the total area within the contact width of the tread was set to 30%.

[0172] 3. Calculation of parameters Then, rubber test pieces for viscoelasticity measurement were prepared by cutting out the surface layer and inner layer of the tread of each test tire with a length of 20 mm, width of 4 mm, and thickness of 2 mm so that the long side was in the tire circumferential direction. For each rubber test piece, the complex elastic modulus E of the surface layer and inner layer was measured in the deformation mode: extension using a GABO Iplexer series under the conditions of temperature 30°C, frequency 10 Hz, initial strain 5%, dynamic strain 1%. * 1 (MPa) and E * 2 (MPa), (E * 2 / E * 1) was obtained, and the loss tangent tanδ2 of the inner layer was measured in the deformation mode: tension.

[0173] And the above |CR-SR|, E * 2×|CR-SR| and tan δ2×|CR-SR| were calculated. The results are shown in Tables 3 and 4.

[0174] 4.Performance evaluation test (1) Rolling resistance evaluation 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 80km / h, after which the accelerator was released and the distance from when the accelerator was turned off until the vehicle came to a halt was measured as the rolling resistance.

[0175] Next, the rolling resistance was relatively evaluated by indexing it according to the following formula, with the result of Comparative Example 5 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 better the fuel economy. Rolling resistance = [(measurement result of test tire) / (measurement result of Comparative Example 5)] x 100

[0176] (2) Evaluation of resistance to uneven wear 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 driven 10,000km on a test course with a dry road surface, and the amount of wear in the tread center and shoulders after the drive was measured, and the ratio between the two was calculated. The closer the ratio is to 1, the less uneven wear has occurred.

[0177] Next, the calculation result in Comparative Example 5 was set to 100, and the uneven wear resistance was relatively evaluated by indexing it according to the following formula. A larger value indicates that uneven wear has not occurred and that uneven wear resistance is excellent. Uneven wear resistance=[(calculation result of Comparative Example 5) / (calculation result of test tire)]×100

[0178] (3) Overall evaluation The results of the evaluations (1) and (2) above were summed up to determine the overall evaluation.

[0179] (4) Evaluation results The results of each evaluation are shown in Tables 3 and 4.

[0180] [Table 3]

[0181] [Table 4]

[0182] From Tables 3 and 4, it can be seen that the outer side of the sidewall is overlapped with the outer side of the tread end in the tire width direction, and the end of the inner layer in the width direction penetrates into a part of the interface between the surface layer and the sidewall. * 2 / E * It can be seen that by satisfying |CR-SR|≦1.0 (Equation 1) and |CR-SR|≦15 (Equation 2), it is possible to provide a pneumatic tire that achieves both reduced rolling resistance and improved resistance to uneven wear.

[0183] It is also understood that when the above formulas (3) to (7) are satisfied, or when a belt reinforcing layer is appropriately provided, it is possible to reduce rolling resistance and further improve uneven wear resistance.

[0184] 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 comprising a tread portion having at least two or more rubber layers including a surface layer and an inner layer in a central region having a width that is 50% of the contact width of the contact surface centered on the tire equator line, and a sidewall portion having a sidewall rubber that forms an outer surface, The tread portion has a circumferential groove communicating in a circumferential direction, and includes a plurality of land portions separated by the circumferential groove and a ground contact edge portion, The tread portion and the sidewall portion are such that an outer portion of the sidewall portion is overlapped with an outer side of an end portion in the tire width direction of the tread portion, a width direction end portion of the inner layer of the tread portion intrudes into a part of an interface between a surface layer of the tread portion and the sidewall portion, The complex elastic modulus of the surface layer of the tread portion at 30 ° C. is E * １ (MPa), the complex elastic modulus of the inner layer of the tread portion at 30 ° C. is E * ２ (MPa), the following (Equation 1) is satisfied, Furthermore, when a groove area ratio in the central region is CR (%) and a groove area ratio in the region excluding the central region is SR (%), the pneumatic tire is characterized in that it satisfies the following (Equation 2): (E * ２ / E * １ )<1.0...(Formula 1) |CR-SR|≦15...(Formula 2)

2. 2. The pneumatic tire according to claim 1, wherein the following formula (3) is satisfied: (E * ２ / E * １ )<0.9...(Formula 3)

3. 3. The pneumatic tire according to claim 2, wherein the following formula 4 is satisfied: (E * ２ / E * １ )<0.8...(Formula 4)

4. 4. The pneumatic tire according to claim 1, wherein the following formula 5 is satisfied: E * ２ ×|CR - SR| ≤ 100 ·····(Equation 5)

5. 5. The pneumatic tire according to claim 4, wherein the following formula (6) is satisfied: E * ２ ×|CR - SR| ≤ 75 ······ (Equation 6)

6. The loss tangent of the inner layer of the tread portion at 30° C. is tan δ ２ 6. The pneumatic tire according to claim 1, wherein the following formula (7) is satisfied: tanδ ２ ×|CR - SR| ≤ 3.75 ····· (Equation 7)

7. A belt reinforcing layer is provided on the radially inner side of the tread portion, In the central region of the tread portion, A height Ht (mm) from an outer peripheral surface of the belt reinforcing layer to a surface of the circumferential land portion is 30 mm or less, and a height Hg (mm) from the outer peripheral surface of the belt reinforcing layer to a bottom surface of a main groove is 5 mm or less, The pneumatic tire according to any one of claims 1 to 6, characterized in that a height h (mm) from an outer peripheral surface of the belt reinforcing layer at a widthwise center position of the circumferential land portion to an interface between the surface layer and the inner layer of the tread portion is 0.5 mm or more, and h>Hg.

8. Sipes are formed in a center land portion and a shoulder land portion partitioned by two or more circumferential main grooves provided in the tread portion, 8. The pneumatic tire according to claim 1, wherein the sipes of adjacent land portions are oriented in opposite directions relative to the circumferential direction of the tire.

9. 9. The pneumatic tire according to claim 1, wherein a ratio of a total groove area to a total area within the contact width of the tread portion is 20 to 40%.

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