tire

Abstract

To provide a tire in which a tread part is formed of two or more rubber layers including isoprene rubber, and steering stability at the time of high-speed traveling is maintained.SOLUTION: A tire comprises a tread part which comprises at least a first rubber layer forming a tread surface and a second rubber layer adjacent to the inner side of the first rubber layer in a tire radial direction. The first rubber layer is formed of a rubber composition comprising a rubber component including isoprene rubber and has an acetone extraction content of 25 mass% or less. The second rubber layer is formed of a rubber composition comprising a rubber component including isoprene rubber and has an amine amount B of 10.00 mass% or more in an acetone extraction content. When an amine amount (mass%) in the acetone extraction content of the first rubber layer is defined as A, the A and the B satisfy B>A. A rate of change E in complex elastic modulus E* of the rubber composition forming the first rubber layer between before and after an ozone deterioration test for the tire is 30% or less.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to tires. [Background technology]

[0002] In recent years, with the growing concern about the environment, there has been a strong demand for reducing the rolling resistance of tires. To reduce the rolling resistance, a technique is known in which isoprene-based rubber is used in the tread portion of a tire (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-25006 Summary of the Invention [Problem to be solved by the invention]

[0004] However, isoprene rubber is easily degraded by heat and ozone, and is particularly susceptible to self-heating during high-speed driving, so the rubber that constitutes the tread is more likely to harden than the rubber on the inner side, which creates a difference in rigidity between the rubber that constitutes the tread and the rubber on the inner side, resulting in problems such as impaired steering stability during high-speed driving.

[0005] An object of the present disclosure is to maintain steering stability during high-speed driving in a tire having a tread portion composed of two or more rubber layers containing an isoprene-based rubber. [Means for solving the problem]

[0006] The present inventors have conducted intensive studies in light of the above-mentioned problems, and as a result, have found that in a tire having a tread portion including at least a first rubber layer constituting a tread surface, and a second rubber layer adjacent to the first rubber layer on the radially inner side of the tire, when both the first rubber layer and the second rubber layer contain isoprene-based rubber, the acetone extractable content of the first rubber layer is 25 mass% or less, the amine amount B in the acetone extractable content of the second rubber layer is 10.00 mass% or more, and the amine amount (mass%) in the acetone extractable content of the first rubber layer is A, where A and B satisfy B>A, and the rate of change E of the complex modulus E* of the first rubber layer before and after an ozone degradation test is 30% or less. After further studies, the present inventors have completed the present disclosure.

[0007] That is, the present disclosure relates to the following tires. A tire having a tread portion including at least a first rubber layer constituting a tread surface and a second rubber layer adjacent to the first rubber layer on the radially inner side of the tire, the first rubber layer is made of a rubber composition including a rubber component including an isoprene-based rubber, and has an acetone extractable content of 25 mass% or less; the second rubber layer is made of a rubber composition including a rubber component including an isoprene-based rubber, and an amine amount B in an acetone extract is 10.00 mass% or more; When the amount of amine (mass%) in the acetone extract of the first rubber layer is A, A and B satisfy B>A, The tire has a rate of change E of a complex modulus E* of a rubber composition constituting the first rubber layer before and after an ozone degradation test of the tire of 30% or less. Effect of the Invention

[0008] According to the present disclosure, in a tire having a tread portion constituted by two or more rubber layers containing an isoprene-based rubber, it is possible to maintain steering stability during high-speed running. [Brief description of the drawings]

[0009] [Figure 1] 1 is an example of a tread pattern for a tire of the present disclosure. [Diagram 2] 1 is an example of a tread pattern for a tire of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The present disclosure relates to a tire having a tread portion including at least a first rubber layer constituting a tread surface and a second rubber layer adjacent to the first rubber layer on the radially inner side thereof, wherein the first rubber layer is made of a rubber composition containing a rubber component including an isoprene-based rubber and has an acetone extractable content of 25% by mass or less, the second rubber layer is made of a rubber composition containing a rubber component including an isoprene-based rubber and has an amine content B of 10.00% by mass or more in the acetone extractable content, and when the amine content (mass%) in the acetone extractable content of the first rubber layer is A, A and B satisfy B>A, and a rate of change E of the complex modulus E* of the rubber composition constituting the first rubber layer before and after an ozone degradation test of the tire is 30% or less.

[0011] Although it is not intended to be bound by theory, the mechanism by which steering stability at high speeds is maintained in the tire of the present disclosure is thought to be as follows. That is, the acetone extract is a component that can move between the first rubber layer and the second rubber layer, and the amine contained therein can also move between the first rubber layer and the second rubber layer, but by making the amine concentration in the acetone extract in the second rubber layer higher than that in the first rubber layer, the migration of amines from the first rubber layer to the second rubber layer is suppressed, and further, it is expected that amines will be supplied from the second rubber layer to the first rubber layer. In this way, if the amine concentration in the acetone extract in the first rubber layer is maintained, the hardening of the first rubber layer, which is in contact with the road surface all the time and is prone to hardening due to excessive heat hardening, is suppressed, and as a result, the rigidity difference between the first rubber layer and the second rubber layer is also suppressed. It is believed that this makes it difficult for deterioration in steering stability at high speeds to occur and maintains it.

[0012] The rubber component of the second rubber layer preferably contains 45% by mass or more of isoprene-based rubber, because blending a large amount of isoprene-based rubber having low polarity in the second rubber layer is expected to have the effect of promoting migration of amines in the second rubber layer to the first rubber layer.

[0013] The rubber component of the first rubber layer preferably contains 12.5 mass % or more of isoprene-based rubber. Since isoprene-based rubber is easily deteriorated by heat or ozone, the effect of the present disclosure is more easily exhibited by including a large amount of isoprene-based rubber in the first rubber layer.

[0014] When the rubber composition constituting the first rubber layer contains an antioxidant and the content (mass%) of the antioxidant in the rubber composition is C, and the rubber composition constituting the second rubber layer contains an antioxidant and the content (mass%) of the antioxidant in the rubber composition is D, it is preferable that D≧C is satisfied. This is because it is expected that the antioxidant can be transferred from the second rubber layer to the first rubber layer, and the same effect as that of the present disclosure can be expected.

[0015] The aforementioned E is preferably 25% or less, since this is an aspect in which the effects of the present disclosure can be more strongly exhibited.

[0016] It is preferable that A and B satisfy BA≧5.00, because the effects of the present disclosure are more easily exhibited.

[0017] It is preferable that C and D satisfy DC≧0.50, because the effects of the present disclosure are more easily exhibited.

[0018] At the position of the tire centerline of the tread portion, the ratio F of the thickness of the second rubber layer to the thickness of the entire tread is preferably 10 to 50%. This is because when the ratio of the thickness of the second rubber layer is a predetermined value or more in the entire tread, it is advantageous in terms of supplying amine to the first rubber layer, while when the ratio is a predetermined value or less, steering stability is improved.

[0019] It is preferable that the above A, B, and F satisfy (B - A)×F ≥ 30. By restricting each other so that the values of (B - A) and F do not become less than the respective predetermined values, the suppression of the rigidity difference between the first rubber layer and the second rubber layer and the contribution to the handling stability by suppressing the thickness of the second rubber layer cooperate with each other, making it easier to obtain the effects of the present disclosure.

[0020] The rubber component of the first rubber layer preferably includes styrene-butadiene rubber. This is because styrene-butadiene rubber can be expected to improve the grip performance.

[0021] The rubber component of the second rubber layer preferably includes butadiene rubber. This is because butadiene rubber can be expected to improve the abrasion resistance.

[0022] The tread pattern of the tread surface has a circumferential main groove and the circumferential main groove is provided in at least one of the two half-tread regions divided by the tire center line, and is an outer circumferential main groove that is on the outer side when the tire is mounted on a vehicle, and an inner circumferential main groove provided inside thereof, and at least includes the outer circumferential main groove When the groove width (mm) of the outer circumferential main is G and the groove width (mm) of the inner circumferential main groove is H, it is preferable that G and H satisfy H < G. When the tire contacts a wet road surface, the water on the road surface tends to flow from the tire center line to the outer side in the tire width direction. Therefore, by widening the groove width of the outer circumferential main groove that contributes to drainage, the wet performance can be improved and it can contribute to maintaining the handling stability.

[0023] It is preferable that G, H, and E satisfy (H / G)×E ≤ 25. By restricting each other so that the values of H / G and E do not become greater than the respective predetermined values, the contribution to the handling stability due to the improvement of the wet performance and the contribution to the handling stability due to the suppression of the rigidity difference cooperate with each other, making it easier to obtain the effects of the present disclosure.

[0024] In the tread pattern of the tread surface, when a region having a width equivalent to 50% of the tread ground contact width centered on the tire centerline is defined as a center region, a plurality of sipes are formed in the land portion included in the center region, and it is preferable that the angle I between the longitudinal direction of the sipe and the tire width direction is 8° or more and less than 45°. By setting the sipe angle within the above range, the pattern rigidity of the tire can be increased and the uneven wear resistance in the center region can be improved, which can contribute to maintaining steering stability.

[0025] It is preferable that A, B, and I satisfy (BA) / I≧0.20. By regulating the values ​​of (BA) and I so that they are not equal to or less than a predetermined value, the rigidity difference between the first rubber layer and the second rubber layer is suppressed, and uneven wear resistance in the center region is improved, which cooperates to easily obtain the effects of the present disclosure.

[0026] In the present disclosure, the upper and lower limit values ​​of "more than", "less than", and "to" in the description of a numerical range are values ​​that can be arbitrarily combined, and in addition, the numerical values ​​in the examples can be combined with the upper and lower limits. In addition, when a numerical range is specified by "to", it means that both ends of the range are included unless otherwise specified. Furthermore, in the present disclosure, a numerical range that is indicated as including the end values ​​is understood to simultaneously indicate a numerical range that does not include the end values, unless it is contrary to the spirit of the present disclosure.

[0027] <Definition> A "genuine rim" is a rim that is determined for each tire by the standard system that includes the standards on which the tire is based. In the case of JATMA, it is called a "standard rim," in the case of TRA, it is called a "Design Rim," and in the case of ETRTO, it is called a "Measuring Rim."

[0028] "Normal internal pressure" is the air pressure set for each tire by each standard in the standard system on which the tire is based. For JATMA, it is the "maximum air pressure." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "INFLATION PRESSURE."

[0029] "Normal condition" refers to a state in which a tire is mounted on a normal rim, inflated to normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions and angles of each part of the tire are measured in the normal condition. If there are patterns or letters on the side of the tire, the measurements are made assuming that the patterns or letters are not present.

[0030] "Normal load" is the load that each standard specifies for each tire in the system of standards on which the tire is based. For JATMA, it is the "maximum load capacity." For TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." For ETRTO, it is the "LOAD CAPACITY."

[0031] The "tread contact edge" refers to the outermost contact point in the tire width direction when a normal tire is loaded with a normal load and touches the ground on a flat surface with a camber angle of 0 degrees. When the tire is mounted on a vehicle, there is an outer contact edge (To) that is on the outside, and an inner contact edge (Ti) that is on the inside.

[0032] The term "circumferential groove" refers to a groove that extends continuously in the circumferential direction of the tire and has a width of 3.0 mm or more on the tread surface.

[0033] "Sipe" means a lateral groove having a width of less than 2.0 mm on the tread surface and an edge component in the tire width direction larger than the edge component in the tire circumferential direction.

[0034] "Overall tread thickness" means the total thickness of the rubber layers constituting the tread portion, and refers to the shortest distance from the tread surface to the belt layer at the tire centerline in a meridian cross section of the tire. line In the case where there is a groove on the upper tread surface, the groove is considered not to exist. The same applies to the "thickness of the first rubber layer" and the "thickness of the second rubber layer" that constitute the tread portion.

[0035] <Measurement method> (Amount of acetone extract (AE amount)) The amount of acetone extractables (acetone extractable amount) is determined in accordance with JIS K 6229 by immersing each vulcanized rubber test piece in acetone for 72 hours to extract the soluble components, measuring the mass of each test piece before and after extraction, and then calculating using the following formula. Acetone extractable amount (%) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction) / (mass of rubber test piece before extraction)} x 100

[0036] (Amine amount) The amount of amines (%) in the acetone extract is measured in accordance with JIS K 6220-3:2001, "8. Method for measuring purity by high performance liquid chromatography (HPLC)". In this case, the reversed phase HPLC used is a chromatograph instead of an ultraviolet absorption detector. Differential A refractometer is provided, and the amount of amine is calculated using the following formula. Amount of amine in acetone extract (%) = (peak area of ​​peak detected at detection time of 6PPD) / (peak area of ​​all peaks detected) × 100 (Here, 6PPD is N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, and the detection time of 6PPD is the detection time at which the maximum peak is detected when 6PPD with a purity of 95% or more is previously measured under the same conditions as the measurement of the acetone extract.)

[0037] (Ozone Degradation Test) In accordance with JIS K 6259, a dynamic ozone degradation test is performed by reciprocating a test piece of a specified size for 48 hours under the following conditions: reciprocating frequency 0.5±0.025Hz, ozone concentration 50±5pphm, test temperature 40°C, and tensile strain 20±2%.

[0038] (Complex Modulus of Elasticity) A viscoelasticity measurement sample of 20 mm in length, 4 mm in width, and 1 mm in thickness is taken from inside the first rubber layer of the tread portion of each test tire so that the long side is in the tire circumferential direction, and the complex modulus E* is measured using an Iplexer series manufactured by GABO under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an elongation mode. The thickness direction of the sample is the tire radial direction.

[0039] "Styrene content" is 1 This is a value calculated by H-NMR measurement and is applied to rubber components having repeating units derived from styrene, such as SBR.

[0040] "Vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and applies to rubber components having repeating units derived from butadiene, such as SBR and BR.

[0041] "Cis content (cis-1,4-bond content)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and applies to rubber components having repeating units derived from butadiene, such as BR.

[0042] The "weight average molecular weight (Mw)" can be determined by converting the measured value obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) into standard polystyrene equivalent. For example, this applies to SBR, BR, etc.

[0043] "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0044] "DBP oil absorption of carbon black" is measured in accordance with JIS K 6217-4:2017.

[0045] "N2SA of Silica" is measured by the BET method in accordance with ASTM D3037-93.

[0046] <Tires> The tire of the present disclosure has a tread portion including at least a first rubber layer constituting a tread surface and a second rubber layer adjacent to the first rubber layer on the radially inner side of the tire. The tread portion may include a rubber layer other than the first rubber layer and the second rubber layer. That is, the tread portion is made up of at least two layers, but may be made up of three layers by having an additional rubber layer on the inner side of the second rubber layer, or may be made up of more than two layers.

[0047] (First rubber layer) The first rubber layer is made of a rubber composition containing a rubber component containing an isoprene-based rubber, and has an acetone extractable content of 25.0% by mass or less. If the acetone extractable content exceeds 25% by mass, the amount of components that can move between the rubber layers becomes too large, which is not preferable. The amount of acetone extractable content of the first rubber layer is preferably 20.0% by mass or less, more preferably 15.0% by mass or less. The lower limit of the amount of the acetone extractable content is not particularly limited, and may be, for example, about 5.0% by mass.

[0048] When the amount of amines (mass%) in the acetone extract is A, the amount of amines A is preferably 30.00 mass% or less. The amount of amines A is preferably 25.00 mass% or less, more preferably 20.00 mass% or less, even more preferably 15.00 mass% or less, even more preferably 13.00 mass% or less, even more preferably 11.00 mass% or less, and even more preferably 10.00 mass% or less. The lower limit of the amount of amines A is not particularly limited, but may be, for example, about 5.00 mass%.

[0049] (Second rubber layer) The second rubber layer is made of a rubber composition containing a rubber component containing an isoprene-based rubber, and the amine amount B in the acetone extract is 10.00 mass% or more. If the amine amount B in the acetone extract is less than 10.00 mass%, the amount of amine supplied to the first rubber layer is reduced, which is not preferable. The amine amount B is preferably 12.00 mass% or more, and more preferably 15.00 mass% or more. The amine amount B The upper limit is not particularly limited, but may be, for example, about 30.00 mass %.

[0050] (Amine amount) The amine amount A and the amine amount B satisfy B>A. That is, the amine amount B in the second rubber layer is greater than the amine amount A in the first rubber layer. This suppresses the migration of amine from the first rubber layer to the second rubber layer, and is also expected to supply amine from the second rubber layer to the first rubber layer. If the amine concentration in the acetone extract in the first rubber layer is maintained, hardening of the first rubber layer, which is in constant contact with the road surface and is prone to hardening due to excessive heat hardening, is suppressed, and as a result, the rigidity difference between the first rubber layer and the second rubber layer is also suppressed.

[0051] The value of B / A is preferably 1.10 or more, more preferably 1.50 or more, and further preferably 2.00 or more. The upper limit of the value of B / A is not particularly limited, and may be, for example, about 5.00.

[0052] In the present disclosure, the term "amine" relating to the amine amount refers to a compound that is quantified by the above-mentioned method for measuring the amine amount.

[0053] (Complex Modulus of Elasticity E*) The complex modulus E* of the rubber composition constituting the first rubber layer has a change rate E of 30% or less before and after the ozone degradation test. If the change rate E exceeds 30%, the effect of the first rubber layer tends to progress, which is not preferable. The change rate E is preferably 28% or less, more preferably 26% or less, even more preferably 25% or less, and even more preferably 22% or less. The lower the change rate E, the better, but it is acceptable for it to be about 15% to 20%. The change rate preferably means the rate of increase before and after the ozone degradation test.

[0054] (Anti-aging agent content) In one embodiment, the rubber composition constituting the first rubber layer and the rubber composition constituting the second rubber layer contain an antioxidant, and when the content (mass%) of the antioxidant in the rubber composition constituting the first rubber layer is C and the content (mass%) of the antioxidant in the rubber composition constituting the second rubber layer is D, D≧C is satisfied. This suppresses migration of the antioxidant from the first rubber layer to the second rubber layer, and is also expected to supply the antioxidant from the second rubber layer to the first rubber layer. The antioxidant is preferably an amine-based antioxidant.

[0055] The D / C value is preferably 1.50 or more, more preferably 2.00 or more, and even more preferably 2.40 or more. There is no particular upper limit to the D / C value, and it may be, for example, about 5.00.

[0056] (BA) In one embodiment, from the viewpoint of suppressing hardening of the first rubber layer, it is preferable that A and B satisfy BA≧5.00. The BA value is more preferably 7.00 or more, further preferably 10.00 or more, further preferably 11.00 or more, and further preferably 13.00 or more. The upper limit of the BA value is not particularly limited, and may be, for example, about 20.00.

[0057] (DC) In one embodiment, from the viewpoint of maintaining the content of the antioxidant in the first rubber layer, it is preferable that C and D satisfy DC≧0.50. The value of DC is more preferably 0.80 or more, further preferably 1.10 or more, further preferably 1.30 or more, and further preferably 1.50 or more. The upper limit of the value of DC is not particularly limited, and may be, for example, about 5.00.

[0058] (Thickness of the second rubber layer) In one embodiment, the ratio F of the thickness of the second rubber layer to the entire thickness of the tread at the tire centerline of the tread portion is preferably 10 to 50%. The value of F is more preferably 15% or more, and further preferably 20% or more. On the other hand, the value of F is more preferably 40% or less, and further preferably 30% or less.

[0059] ((BA)×F) In one embodiment, it is preferable that A, B, and F satisfy (BA)×F≧30. The value of (BA)×F is preferably 40 or more, more preferably 50 or more, and further preferably 60 or more. There is no particular restriction on the upper limit of the value of (BA)×F, and it may be, for example, about 350 to 400.

[0060] (Circumferential main groove width) In one embodiment, the tread pattern of the tread surface has a circumferential main groove The circumferential direction main grooveIt is provided in at least one of two half-tread regions divided by the tire center line, and is the outer circumferential main when the tire is mounted on a vehicle. groove And the inner circumferential main provided inside thereof groove It includes at least, and the outer circumferential main groove Let G be the groove width (mm) of, and H be the groove width (mm) of the inner circumferential main groove When, from the viewpoint of improving wet performance, it is preferable that H <G. Here, the circumferential main groove Refers to those having a groove width of 3 mm or more in the tire width direction. The groove width when the groove width changes in the tire circumferential direction means the average value of the groove widths measured at a plurality of locations including the maximum value and the minimum value.

[0061] FIG. 1 shows an example of the tread pattern. In FIG. 1, among the two half-tread regions divided by the tire center line CL, an outer circumferential groove 11 and an inner circumferential groove 12 are provided in the half-tread region that becomes the outer side when the tire is mounted on a vehicle. Further, an outer circumferential groove 13 and an inner circumferential groove 14 are provided in the half-tread region that becomes the inner side when the tire is mounted on a vehicle. And the outer circumferential groove 11 has a wider groove width than the inner circumferential groove 12, and the outer circumferential groove 13 has a wider groove width than the inner circumferential groove 14.

[0062] The value of H / G is preferably 0.99 or less, more preferably 0.80 or less, and still more preferably 0.70 or less. The value of H / G is preferably 0.30 or more, more preferably 0.40 or more, and still more preferably 0.50 or more.

[0063] ((H / G)×E) In one embodiment, it is preferable that G, H, and E satisfy (H / G)×E≦25. The value of (H / G)×E is preferably 24 or less, more preferably 23 or less, and still more preferably 22 or less. (H / G)×E There is no particular limitation on the lower limit of the value, and for example, it may be about 1 to 3.

[0064] (Angle formed by the sipes) In one embodiment, in the tread pattern of the tread surface, when a region having a width equivalent to 50% of the tread contact width centered on the tire centerline is defined as a center region, a plurality of sipes are formed in the land portion included in the center region, and it is preferable that an angle I between the longitudinal direction of the sipe and the tire width direction is 8° or more and less than 45°.

[0065] Fig. 2 shows an example of the tread pattern. In Fig. 2, an area having a width equivalent to 50% of the tread contact width W centered on the tire center line CL is shown as a center area CA. In the center area CA, a sipe 21 is formed on the To side, and a sipe 22 is formed on the Ti side. Here, the angle I between the longitudinal direction of the sipe and the tire width direction refers to the angle (°) between a straight line connecting both ends of the sipe in the longitudinal direction and the tire width direction.

[0066] The sipes may be curved or bent. In Fig. 2, the sipes are curved. In addition, it is preferable that at least one end of the sipes is connected to the circumferential main groove. This is because it is expected to further contribute to the steering stability on wet road surfaces.

[0067] The value of the angle I is preferably 10° or more, more preferably 15° or more, and even more preferably 20° or more. The value of the angle I is preferably 43° or less, more preferably 41° or less, and even more preferably 40° or less.

[0068] ((BA) / I) In one embodiment, it is preferable that A, B, and I satisfy (BA) / I≧0.20. The value of (BA) / I is preferably 0.21 or more, more preferably 0.22 or more, and even more preferably 0.30 or more. There is no particular restriction on the lower limit of the value of (BA) / I, and it may be, for example, about 1.00 to 0.80.

[0069] <Rubber composition for first rubber layer> (Rubber component) The rubber component used in the rubber composition for the first rubber layer includes an isoprene-based rubber. As other rubber components, diene-based rubbers such as styrene butadiene rubber (SBR), butadiene rubber (BR), and acrylonitrile butadiene rubber (NBR) can be used, as well as non-diene-based rubbers such as butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber can be used. These rubber components may be used alone or in combination of two or more. As other rubber components, SBR or BR is preferred, and SBR is more preferred, or SBR and BR can be used in combination.

[0070] <Isoprene rubber> As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more. The NR is not particularly limited, and may be a common one in the tire industry, such as SIR20, RSS#3, and TSR20.

[0071] There are no particular limitations on the NR, and any NR commonly used in the tire industry, such as SIR20, RSS#3, or TSR20, can be used.

[0072] From the viewpoint of the present disclosure, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 12.5% ​​by mass or more, more preferably 15.0% by mass or more, and even more preferably 20.0% by mass or more. The content is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less.

[0073] <Styrene butadiene rubber> The SBR is not particularly limited, and examples thereof include emulsion-polymerized SBR (E-SBR) and solution-polymerized SBR (S-SBR). SBRs modified with a modifier (modified SBR) and hydrogenated SBRs (hydrogenated SBR) can also be used. SBRs may be used alone or in combination of two or more.

[0074] The styrene content of the SBR is preferably 18% by mass or more, more preferably 20% by mass or more, and even more preferably 23% by mass or more, from the viewpoint of grip performance. From the viewpoint of the effects of the present disclosure, the styrene content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 42% by mass or less. The styrene content is 1 This value is calculated by H-NMR measurement.

[0075] The vinyl bond content of the SBR is preferably 10 mol% or more, more preferably 13 mol% or more, and even more preferably 15 mol% or more from the viewpoint of rubber strength and abrasion resistance. From the viewpoint of the effects of the present disclosure, the vinyl bond content is preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 58 mol% or less. The vinyl content is a value calculated by infrared absorption spectrum analysis according to JIS K 6239-2:2017.

[0076] The weight average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 300,000 or more. The Mw is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. The Mw of SBR can be calculated based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) in terms of standard polystyrene.

[0077] The modified SBR may have its main chain and / or terminals modified with a modifying agent, or may have a partially branched structure modified with a polyfunctional modifying agent such as tin tetrachloride or silicon tetrachloride. Of these, it is particularly preferred that the main chain and / or terminals of the SBR are modified with a modifying agent having a functional group that interacts with silica. Examples of such modifying agents include alkoxysilanes.

[0078] Examples of SBR include those manufactured and sold by JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and the like.

[0079] When SBR is contained, the content in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more from the viewpoint of wet grip performance, and is preferably 90% by mass or less, more preferably 88% by mass or less, and even more preferably 85% by mass or less from the viewpoint of abrasion resistance and rolling resistance performance.

[0080] <Butadiene rubber> The BR is not particularly limited, and may be, for example, a BR having a cis 1,4 bond content of less than 50% (low cis BR), a BR having a cis 1,4 bond content of 90% or more (high cis BR), a rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, a BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high cis modified BR, low cis modified BR), or the like, which are common in the tire industry. The BR may be used alone or in combination of two or more kinds. Among them, it is more preferable to use high cis BR from the viewpoint of wear resistance.

[0081] The weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more, from the viewpoint of abrasion resistance and grip performance. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. Mw can be determined by standard polystyrene conversion based on the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0082] Examples of high cis BR include high cis BR manufactured and sold by JSR Corporation, Zeon Corporation, Ube Industries, Ltd., etc. Among high cis BR, those having a cis 1,4-bond content of 95% or more are preferred, more preferably 97% or more, and even more preferably 98% or more. The cis content (cis-1,4-bond content) is a value calculated by infrared absorption spectrum analysis according to JIS K 6239-2:2017.

[0083] When BR is contained, the content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more from the viewpoints of abrasion resistance and rolling resistance performance, and the content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less from the viewpoint of wet grip performance.

[0084] (Filler) Examples of the filler include silica and carbon black. In addition, calcium carbonate, alumina, clay, talc, and other fillers that are conventionally used in rubber compositions for tires can be blended. Among these, silica and / or carbon black are preferred. One or more fillers can be used.

[0085] <Silica> Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it has many silanol groups and many reaction sites with silane coupling agents. Silica may be used alone or in combination of two or more. Examples of silica include silica manufactured and sold by Evonik Degussa, Solvay, Tosoh Silica, Tokuyama, etc.

[0086] From the standpoint of wear resistance, the N2SA (BET specific surface area) of silica is 130m 2 / g or more is preferable, and 150m 2 / g or more, more preferably 170m 2 From the viewpoint of processability, the BET specific surface area is 500 m 2 / g or less is preferable, and 300m 2 / g or less, more preferably 270m 2 / g or less, and more preferably 250m 2 / g or less. The N2SA of silica is measured by the BET method according to ASTM D3037-93.

[0087] The content of silica per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, from the viewpoint of reinforcement. The content is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less, from the viewpoint of processability.

[0088] <Silane coupling agent> When silica is contained, it is preferable to use a silane coupling agent. Examples of silane coupling agents include sulfide-based agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide, mercapto-based agents such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane, thioether-based agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane and 3-octanoylthio-1-propyltrimethoxysilane, vinyl-based agents such as vinyltriethoxysilane, amino-based agents such as 3-aminopropyltriethoxysilane, glycidoxy-based agents such as γ-glycidoxypropyltriethoxysilane, nitro-based agents such as 3-nitropropyltrimethoxysilane, and chloro-based agents such as 3-chloropropyltrimethoxysilane. These agents may be used alone or in combination of two or more. Among these, sulfide-based coupling agents, particularly bis(3-triethoxysilylpropyl) disulfide, are preferred from the standpoint of ease of temperature control in the reaction with silica and the effect of improving the reinforcement of the rubber composition.

[0089] When the silane coupling agent is contained, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, based on 100 parts by mass of silica from the viewpoint of processability.The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on the viewpoint of blending effect commensurate with cost.

[0090] Carbon black The carbon black is not particularly limited, and GPF, FEF, HAF, ISAF, SAF, and other carbon blacks commonly used in the tire industry can be used. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N351H, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be preferably used, and in addition, products synthesized in-house can also be preferably used. Carbon black may be used alone or in combination of two or more types.

[0091] Examples of carbon black include carbon black manufactured and sold by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shinnikka Carbon Co., Ltd., Columbia Carbon Company, and the like.

[0092] The nitrogen adsorption specific surface area (N2SA) of carbon black is 80m 2 / g or more is preferable, and 100m 2 / g or more is more preferable, and 110m 2 / g or more is more preferable. 2 / g or less is preferable, and 250m 2 / g or less is more preferable. "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0093] From the viewpoint of wear resistance, the DBP oil absorption of carbon black is preferably 50mL / 100g or more, more preferably 80mL / 100g or more, even more preferably 100mL / 100g or more, and particularly preferably 110mL / 100g or more. From the viewpoint of grip performance, the DBP oil absorption is preferably 250mL / 100g or less, more preferably 200mL / 100g or less, and even more preferably 135mL / 100g or less. The DBP oil absorption of carbon black is measured in accordance with JIS K 6217-4:2017.

[0094] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 5 parts by mass or more, and on the other hand, is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, and more preferably 10 parts by mass or less, from the viewpoint of good fuel economy and weather resistance.

[0095] (Other compounding agents) In addition to the above-mentioned components, the rubber composition for the first rubber layer may appropriately contain compounding agents conventionally commonly used in the tire industry, such as a softener, a tackifier resin, an antioxidant, wax, zinc oxide, stearic acid, a vulcanizing agent, and a vulcanization accelerator, as necessary.

[0096] <Softener> The softener may be oil. Examples of the oil include process oils such as paraffin-based, aromatic-based, and naphthenic process oils. When the oil is contained, the content is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. The content of the oil is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 55 parts by mass or less, based on 100 parts by mass of the rubber component. When the content of the oil is within the above range, the effect of containing the oil can be sufficiently obtained, and good wear resistance can be obtained. In this specification, the content of the oil includes the amount of oil contained in the oil-extended rubber.

[0097] Other examples of the softener include liquid polymers and low-temperature plasticizers. Examples of the liquid polymer include liquid SBR, liquid BR, liquid IR, and liquid SIR. Of these, it is preferable to use liquid SBR, since it can improve durability and grip performance in a well-balanced manner. Examples of the low-temperature plasticizer include liquid components such as dioctyl phthalate (DOP), dibutyl phthalate (DBP), tris(2-ethylhexyl) phosphate (TOP), and bis(2-ethylhexyl) sebacate (DOS). One or more types of softeners can be used.

[0098] <Tackifying resin> Examples of tackifying resins include cyclopentadiene resins, coumarone resins, petroleum resins (aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, etc.), phenolic resins, rosin derivatives, etc. The tackifying resins may be used alone or in combination of two or more.

[0099] Examples of aromatic petroleum resins include aromatic vinyl resins and C9 petroleum resins other than aromatic vinyl resins. In aromatic vinyl resins, for example, styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc. are used as aromatic vinyl monomers (units), and they may be either homopolymers of each monomer or copolymers of two or more monomers. They may also be modified.

[0100] When a tackifier resin is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, from the viewpoints of wet grip performance and dry grip performance. When a tackifier resin, particularly an aromatic vinyl resin, is contained, the content per 100 parts by mass of the rubber component is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, from the viewpoints of abrasion resistance, fuel economy, and embrittlement fracture at low temperatures.

[0101] <Anti-aging agent> The antiaging agent is not particularly limited, and may be appropriately selected and blended from, for example, amine-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts. These antiaging agents may be used alone or in combination of two or more. Among them, amine-based antiaging agents are preferred due to their high antiaging effect, and examples thereof include N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, and N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. p-phenylenediamine-based antioxidants such as nylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, and phenyloctyl-p-phenylenediamine are more preferred, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine is particularly preferred.

[0102] The antioxidant may be a so-called reactive antioxidant, such as N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine.

[0103] In the case where an antioxidant is contained, the content thereof based on 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of the effects of the present disclosure. The content is preferably 5 parts by mass or less, more preferably 4 parts by mass or less, and further preferably 3 parts by mass or less.

[0104] <Wax, zinc oxide, stearic acid> Any material conventionally used in the tire industry can be used.

[0105] Examples of the wax include petroleum wax, mineral wax, synthetic wax, etc. When the wax is contained, the content per 100 parts by mass of the rubber component is preferably 0.3 parts by mass or more, more preferably 0.7 parts by mass or more, and even more preferably 0.8 parts by mass or more, from the viewpoint of the effects of the present disclosure. The content is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0106] When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of abrasion resistance.

[0107] When stearic acid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of vulcanization speed.

[0108] <Vulcanizing agent> The rubber composition may contain a vulcanizing agent. As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent may be used. As the organic peroxide, for example, benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, or 1,3-bis(t-butylperoxypropyl)benzene may be used. As the sulfur-based vulcanizing agent, for example, sulfur, morpholine disulfide, etc. may be used. The vulcanizing agent may be used alone or in combination of two or more kinds. Among these, sulfur is preferred.

[0109] When a vulcanizing agent is contained, the content thereof per 100 parts by mass of the rubber component is 0.5 parts by mass or more, preferably 1 part by mass or more, from the viewpoint of abrasion resistance, and the content is 5 parts by mass or less, preferably 3 parts by mass or less.

[0110] <Vulcanization accelerator> The vulcanization accelerator is not particularly limited, but examples thereof include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. Among these, sulfenamide-based and guanidine-based vulcanization accelerators are preferred because they allow the effects of the present disclosure to be more suitably obtained.

[0111] Examples of sulfenamide vulcanization accelerators include CBS (N-cyclohexyl-2-benzothiazolyl sulfenamide), TBBS (Nt-butyl-2-benzothiazolyl sulfenamide), N-oxyethylene-2-benzothiazolyl sulfenamide, N,N'-diisopropyl-2-benzothiazolyl sulfenamide, and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide. Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazolyl disulfide. Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide (TBzTD). Examples of guanidine vulcanization accelerators include diphenylguanidine (DPG), di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Of these, it is preferable to use CBS and DPG in combination, as this allows the effects of the present disclosure to be more suitably obtained.

[0112] When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of abrasion resistance, and the content is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less.

[0113] <Rubber composition for second rubber layer> (Rubber component) No. twoThe rubber component used in the rubber composition for the rubber layer includes an isoprene-based rubber. As other rubber components, diene-based rubbers such as styrene butadiene rubber (SBR), butadiene rubber (BR), and acrylonitrile butadiene rubber (NBR) can be used, as well as non-diene-based rubbers such as butyl rubber (IIR), hydrogenated nitrile rubber (HNBR), ethylene propylene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber can be used. These rubber components may be used alone or in combination of two or more. As other rubber components, SBR or BR is preferred, BR is more preferred, or SBR and BR can be used in combination.

[0114] <Isoprene rubber> As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more. The NR is not particularly limited, and may be a common one in the tire industry, such as SIR20, RSS#3, and TSR20.

[0115] There are no particular limitations on the NR, and any NR commonly used in the tire industry, such as SIR20, RSS#3, or TSR20, can be used.

[0116] From the viewpoint of the present disclosure, the content of the isoprene-based rubber in 100% by mass of the rubber component is preferably 45% by mass or more, more preferably 50% by mass or more, and even more preferably 55% by mass or more. The content is preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less.

[0117] <Styrene butadiene rubber> The SBR is not particularly limited, and examples thereof include emulsion-polymerized SBR (E-SBR) and solution-polymerized SBR (S-SBR). SBRs modified with a modifier (modified SBR) and hydrogenated SBRs (hydrogenated SBR) can also be used. SBRs may be used alone or in combination of two or more.

[0118] From the viewpoint of the effects of the present disclosure, the styrene content of the SBR is preferably 18% by mass or more, more preferably 20% by mass or more, and even more preferably 23% by mass or more. From the viewpoint of the effects of the present disclosure, the styrene content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 42% by mass or less. The styrene content is 1 This value is calculated by H-NMR measurement.

[0119] From the viewpoint of the effects of the present disclosure, the vinyl bond content of the SBR is preferably 10 mol% or more, more preferably 13 mol% or more, and even more preferably 15 mol% or more. From the viewpoint of the effects of the present disclosure, the vinyl bond content is preferably 65 mol% or less, more preferably 60 mol% or less, and even more preferably 58 mol% or less. The vinyl content is a value calculated by infrared absorption spectrum analysis according to JIS K 6239-2:2017.

[0120] The weight average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 300,000 or more. The Mw is preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. The Mw of SBR can be calculated based on the measured value by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation) in terms of standard polystyrene.

[0121] The modified SBR may have its main chain and / or terminals modified with a modifying agent, or may have a partially branched structure modified with a polyfunctional modifying agent such as tin tetrachloride or silicon tetrachloride. Of these, it is particularly preferred that the main chain and / or terminals of the SBR are modified with a modifying agent having a functional group that interacts with silica. Examples of such modifying agents include alkoxysilanes.

[0122] Examples of SBR include those manufactured and sold by JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and the like.

[0123] When SBR is contained, the content in 100% by mass of the rubber component is preferably 40% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more from the viewpoint of wet grip performance, and is preferably 90% by mass or less, more preferably 88% by mass or less, and even more preferably 85% by mass or less from the viewpoint of abrasion resistance and rolling resistance performance.

[0124] <Butadiene rubber> The BR is not particularly limited, and may be, for example, a BR having a cis 1,4 bond content of less than 50% (low cis BR), a BR having a cis 1,4 bond content of 90% or more (high cis BR), a rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, a BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high cis modified BR, low cis modified BR), or the like, which are common in the tire industry. The BR may be used alone or in combination of two or more kinds. Among them, it is more preferable to use high cis BR from the viewpoint of wear resistance.

[0125] Examples of high cis BR include high cis BR manufactured and sold by JSR Corporation, Zeon Corporation, Ube Industries, Ltd., etc. Among high cis BR, those having a cis 1,4-bond content of 95% or more are preferred, more preferably 97% or more, and even more preferably 98% or more. The cis content (cis-1,4-bond content) is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017,

[0126] The weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more, from the viewpoint of abrasion resistance and grip performance. From the viewpoint of crosslinking uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. Mw can be determined by standard polystyrene conversion based on the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation).

[0127] When BR is contained, the content in 100% by mass of the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more from the viewpoints of abrasion resistance and rolling resistance performance, and the content is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less from the viewpoint of wet grip performance.

[0128] (Filler) Examples of the filler include silica and carbon black. In addition, calcium carbonate, alumina, clay, talc, and other fillers that are conventionally used in rubber compositions for tires can be blended. Among these, silica and / or carbon black are preferred. One or more fillers can be used.

[0129] <Silica> Examples of silica include dry silica (anhydrous silicic acid) and wet silica (hydrated silicic acid), but wet silica is preferred because it has many silanol groups and many reaction sites with silane coupling agents. Silica may be used alone or in combination of two or more. Examples of silica include silica manufactured and sold by Evonik Degussa, Solvay, Tosoh Silica, Tokuyama, etc.

[0130] From the standpoint of wear resistance, the N2SA (BET specific surface area) of silica is 130m 2 / g or more is preferable, and 150m 2 / g or more, more preferably 170m 2 From the viewpoint of processability, the BET specific surface area is 500 m 2 / g or less is preferable, and 300m 2 / g or less, more preferably 270m 2 / g or less, and more preferably 250m 2 / g or less. The N2SA of silica is measured by the BET method according to ASTM D3037-93.

[0131] When silica is contained, the content per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 30 parts by mass or more, and even more preferably 40 parts by mass or more, from the viewpoint of reinforcement. The content is preferably 120 parts by mass or less, more preferably 110 parts by mass or less, and even more preferably 100 parts by mass or less, from the viewpoint of processability.

[0132] <Silane coupling agent> When silica is contained, it is preferable to use a silane coupling agent. Examples of silane coupling agents include sulfide-based agents such as bis(3-triethoxysilylpropyl) disulfide and bis(3-triethoxysilylpropyl) tetrasulfide, mercapto-based agents such as 3-mercaptopropyltrimethoxysilane and 3-mercaptopropyltriethoxysilane, thioether-based agents such as 3-octanoylthio-1-propyltriethoxysilane, 3-hexanoylthio-1-propyltriethoxysilane and 3-octanoylthio-1-propyltrimethoxysilane, vinyl-based agents such as vinyltriethoxysilane, amino-based agents such as 3-aminopropyltriethoxysilane, glycidoxy-based agents such as γ-glycidoxypropyltriethoxysilane, nitro-based agents such as 3-nitropropyltrimethoxysilane, and chloro-based agents such as 3-chloropropyltrimethoxysilane. These agents may be used alone or in combination of two or more. Among these, sulfide-based coupling agents, particularly bis(3-triethoxysilylpropyl) disulfide, are preferred from the standpoint of ease of temperature control in the reaction with silica and the effect of improving the reinforcement of the rubber composition.

[0133] When the silane coupling agent is contained, the content of the silane coupling agent is preferably 1 part by mass or more, more preferably 2 parts by mass or more, based on 100 parts by mass of silica from the viewpoint of processability.The content is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, based on the viewpoint of blending effect commensurate with cost.

[0134] Carbon black The carbon black is not particularly limited, and GPF, FEF, HAF, ISAF, SAF, and other carbon blacks commonly used in the tire industry can be used. Specifically, N110, N115, N120, N125, N134, N135, N219, N220, N231, N234, N293, N299, N326, N330, N339, N343, N347, N351, N351H, N356, N358, N375, N539, N550, N582, N630, N642, N650, N660, N683, N754, N762, N765, N772, N774, N787, N907, N908, N990, N991, etc. can be preferably used, and in addition, products synthesized in-house can also be preferably used. Carbon black may be used alone or in combination of two or more types.

[0135] Examples of carbon black include carbon black manufactured and sold by Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shinnikka Carbon Co., Ltd., Columbia Carbon Company, and the like.

[0136] The nitrogen adsorption specific surface area (N2SA) of carbon black is 40m 2 / g or more is preferable, and 50m 2 / g or more is more preferable, and 60m 2 / g or more is more preferable. 2 / g or less is preferable, and 80m 2 / g or less is more preferable. "N2SA of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0137] From the viewpoint of wear resistance, the DBP oil absorption of carbon black is preferably 50mL / 100g or more, more preferably 80mL / 100g or more, even more preferably 100mL / 100g or more, and particularly preferably 110mL / 100g or more. From the viewpoint of grip performance, the DBP oil absorption is preferably 250mL / 100g or less, more preferably 200mL / 100g or less, and even more preferably 135mL / 100g or less. The DBP oil absorption of carbon black is measured according to JIS K 6217-4:2017.

[0138] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, and more preferably 5 parts by mass or more, from the viewpoint of good fuel economy and weather resistance, and is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and more preferably 60 parts by mass or less.

[0139] (Other compounding agents) In addition to the above-mentioned components, the rubber composition for the first rubber layer may appropriately contain compounding agents conventionally commonly used in the tire industry, such as a softener, a tackifier resin, an antioxidant, wax, zinc oxide, stearic acid, a vulcanizing agent, and a vulcanization accelerator, as necessary.

[0140] <Softener> The softener may be oil. Examples of the oil include process oils such as paraffin-based, aromatic-based, and naphthenic process oils. When the oil is contained, the content is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more, based on 100 parts by mass of the rubber component. The content of the oil is preferably 60 parts by mass or less, more preferably 55 parts by mass or less, and even more preferably 55 parts by mass or less, based on 100 parts by mass of the rubber component. When the content of the oil is within the above range, the effect of containing the oil can be sufficiently obtained, and good wear resistance can be obtained. In this specification, the content of the oil includes the amount of oil contained in the oil-extended rubber.

[0141] Other examples of the softener include liquid polymers and low-temperature plasticizers. Examples of the liquid polymer include liquid SBR, liquid BR, liquid IR, and liquid SIR. Of these, it is preferable to use liquid SBR, since it can improve durability and grip performance in a well-balanced manner. Examples of the low-temperature plasticizer include liquid components such as dioctyl phthalate (DOP), dibutyl phthalate (DBP), tris(2-ethylhexyl) phosphate (TOP), and bis(2-ethylhexyl) sebacate (DOS). One or more types of softeners can be used.

[0142] <Tackifying resin> Examples of tackifying resins include cyclopentadiene resins, coumarone resins, petroleum resins (aliphatic petroleum resins, aromatic petroleum resins, alicyclic petroleum resins, etc.), phenolic resins, rosin derivatives, etc. The tackifying resins may be used alone or in combination of two or more.

[0143] Examples of aromatic petroleum resins include aromatic vinyl resins and C9 petroleum resins other than aromatic vinyl resins. In aromatic vinyl resins, for example, styrene, α-methylstyrene, 1-vinylnaphthalene, 3-vinyltoluene, ethylvinylbenzene, divinylbenzene, 4-cyclohexylstyrene, 2,4,6-trimethylstyrene, etc. are used as aromatic vinyl monomers (units), and they may be either homopolymers of each monomer or copolymers of two or more monomers. They may also be modified.

[0144] When a tackifier resin is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and even more preferably 3 parts by mass or more, from the viewpoints of wet grip performance and dry grip performance. When a tackifier resin, particularly an aromatic vinyl resin, is contained, the content per 100 parts by mass of the rubber component is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, from the viewpoints of abrasion resistance, fuel economy, and embrittlement fracture at low temperatures.

[0145] <Anti-aging agent> The antiaging agent is not particularly limited, and may be appropriately selected and blended from, for example, amine-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts. These antiaging agents may be used alone or in combination of two or more. Among them, amine-based antiaging agents are preferred due to their high antiaging effect, and examples thereof include N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N,N'-bis(1-methylheptyl)-p-phenylenediamine, and N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine. p-phenylenediamine-based antioxidants such as nylenediamine, N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N-4-methyl-2-pentyl-N'-phenyl-p-phenylenediamine, N,N'-diaryl-p-phenylenediamine, hindered diaryl-p-phenylenediamine, phenylhexyl-p-phenylenediamine, and phenyloctyl-p-phenylenediamine are more preferred, and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine is particularly preferred.

[0146] In the case where an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, and more preferably 1 part by mass or more, from the viewpoint of the effects of the present disclosure. The content is preferably 8 parts by mass or less, more preferably 6 parts by mass or less, and further preferably 5 parts by mass or less.

[0147] <Wax, zinc oxide, stearic acid> Any material conventionally used in the tire industry can be used.

[0148] Examples of the wax include petroleum wax, mineral wax, synthetic wax, etc. When the wax is contained, the content per 100 parts by mass of the rubber component is preferably 0.3 parts by mass or more, more preferably 0.7 parts by mass or more, and even more preferably 0.8 parts by mass or more, from the viewpoint of the effects of the present disclosure. The content is preferably 3.0 parts by mass or less, more preferably 2.5 parts by mass or less, and even more preferably 2.0 parts by mass or less.

[0149] When zinc oxide is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of abrasion resistance.

[0150] When stearic acid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of vulcanization speed.

[0151] <Vulcanizing agent> The rubber composition may contain a vulcanizing agent. As the vulcanizing agent, an organic peroxide or a sulfur-based vulcanizing agent may be used. As the organic peroxide, for example, benzoyl peroxide, dicumyl peroxide, di-t-butyl peroxide, t-butylcumyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)hexyne-3, or 1,3-bis(t-butylperoxypropyl)benzene may be used. As the sulfur-based vulcanizing agent, for example, sulfur, morpholine disulfide, etc. may be used. The vulcanizing agent may be used alone or in combination of two or more kinds. Among these, sulfur is preferred.

[0152] When a vulcanizing agent is contained, the content thereof per 100 parts by mass of the rubber component is 0.5 parts by mass or more, preferably 1 part by mass or more, from the viewpoint of abrasion resistance, and the content is 5 parts by mass or less, preferably 3 parts by mass or less.

[0153] <Vulcanization accelerator> The vulcanization accelerator is not particularly limited, but examples thereof include sulfenamide-based, thiazole-based, thiuram-based, thiourea-based, guanidine-based, dithiocarbamic acid-based, aldehyde-amine-based or aldehyde-ammonia-based, imidazoline-based, and xanthate-based vulcanization accelerators. Among these, sulfenamide-based and guanidine-based vulcanization accelerators are preferred because they allow the effects of the present disclosure to be more suitably obtained.

[0154] Examples of sulfenamide vulcanization accelerators include CBS (N-cyclohexyl-2-benzothiazolyl sulfenamide), TBBS (Nt-butyl-2-benzothiazolyl sulfenamide), N-oxyethylene-2-benzothiazolyl sulfenamide, N,N'-diisopropyl-2-benzothiazolyl sulfenamide, and N,N-dicyclohexyl-2-benzothiazolyl sulfenamide. Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole and dibenzothiazolyl disulfide. Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, and tetrabenzylthiuram disulfide (TBzTD). Examples of guanidine vulcanization accelerators include diphenylguanidine (DPG), di-orthotolylguanidine, and orthotolylbiguanidine. These may be used alone or in combination of two or more. Among these, CBS, DPG, and combinations thereof are preferred since the effects of the present disclosure can be more suitably obtained.

[0155] When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more, from the viewpoint of abrasion resistance, and the content is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less.

[0156] <Method for producing rubber composition for first rubber layer and rubber composition for second rubber layer> The rubber composition for the first rubber layer and the rubber composition for the second rubber layer can both be produced by a general method, for example, by kneading the above-mentioned components other than the vulcanizing agent and vulcanization accelerator in a known kneading machine generally used in the tire industry, such as a Banbury mixer, a kneader, or an open roll (base kneading process), then adding the vulcanizing agent and the vulcanization accelerator and further kneading (finish kneading process), and vulcanizing the resulting unvulcanized rubber composition.

[0157] The kneading conditions are not particularly limited, but in the case of the rubber composition for the first rubber layer, it is preferable to knead for 1 to 5 minutes at a discharge temperature of 140 to 160° C. in the base kneading step, and knead for 1 to 5 minutes until the temperature reaches 75 to 100° C. in the finish kneading step. In the case of the rubber composition for the second rubber layer, it is preferable to knead for 1 to 5 minutes at a discharge temperature of 140 to 160° C. in the base kneading step, and knead for 1 to 5 minutes until the temperature reaches 75 to 100° C. in the finish kneading step. As for the vulcanization conditions, it is preferable to vulcanize both the rubber composition for the first rubber layer and the rubber composition for the second rubber layer at 140 to 180° C. for 3 to 20 minutes, for example.

[0158] <Tire manufacturing method> The tire of the present disclosure can be manufactured by extruding the above-mentioned unvulcanized rubber composition for the first rubber layer and the unvulcanized rubber composition for the second rubber layer into a predetermined tread shape, laminating them with other tire components on a tire building machine to form an unvulcanized tire, and heating and pressurizing the unvulcanized tire in a vulcanizer. The tread can also be formed by extruding the unvulcanized rubber composition for the first rubber layer and the unvulcanized rubber composition for the second rubber layer into a predetermined shape, and then laminating them together. The heating and pressurizing conditions are, for example, 140 to 180°C for 3 to 20 minutes.

[0159] <Tires> The tire of the present disclosure can be suitably used as a passenger car tire, a truck / bus tire, a motorcycle tire, or a racing tire, and is preferably used as a passenger car tire. Note that a passenger car tire is a tire that is intended to be mounted on a four-wheeled vehicle and has a normal load of 1000 kg or less. The tire of the present disclosure is preferably a pneumatic tire. EXAMPLES

[0160] Hereinafter, the present disclosure will be described based on examples, but the present disclosure is not limited to these examples.

[0161] The various chemicals used during synthesis and polymerization are described below. The chemicals were purified by conventional methods as necessary. n-Hexane: Kanto Chemical Co., Ltd. Styrene: Kanto Chemical Co., Ltd. Butadiene: 1,3-butadiene manufactured by Tokyo Chemical Industry Co., Ltd. TMEDA: N,N,N',N'-Tetramethylethylenediamine manufactured by Kanto Chemical Co., Ltd. n-Butyllithium solution: 1.6M n-butyllithium hexane solution manufactured by Kanto Chemical Co., Ltd. 2,6-Di-tert-butyl-p-cresol: Nocrac 200 manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Alcohol: Ethanol manufactured by Kanto Chemical Co., Ltd. Amine-based modifier: N,N-bis(trimethylsilyl)aminopropylmethyldiethoxysilane

[0162] Synthesis Example 1 (Synthesis of hydrogenated SBR, hydrogenation rate 95 mol%) 2000mL of n-hexane, 60g of styrene, 140g of 1,3-butadiene, 0.9g of TMEDA, and 0.45mmol of n-butyllithium were added to a heat-resistant reaction vessel that had been fully substituted with nitrogen, and the mixture was stirred at 50°C for 5 hours to carry out a polymerization reaction. Next, the mixture was stirred for 20 minutes while supplying hydrogen gas at a pressure of 0.4MPa-Gauge, and reacted with the unreacted lithium at the polymer end to produce lithium hydride. The hydrogen gas supply pressure was set to 0.7MPa-Gauge, the reaction temperature was set to 90°C, and hydrogenation was carried out using a catalyst mainly composed of titanocene dichloride. When the absorption of hydrogen reached the cumulative amount that would result in the desired hydrogenation rate, the reaction temperature was set to room temperature, the hydrogen pressure was returned to normal pressure, and the mixture was removed from the reaction vessel, the reaction solution was stirred and poured into water, and the solvent was removed by steam stripping to obtain hydrogenated SBR.

[0163] <Evaluation of the obtained copolymer> (Measurement of hydrogenation rate) A 15% solution was prepared using carbon tetrachloride as a solvent and was operated at 100 MHz. 1 It was calculated from the spectral reduction rate of the unsaturated bond in H-NMR.

[0164] (Measurement of styrene content) At 25°C, using a JEOL JNM-A 400 NMR instrument 1 H-NMR was measured, and the phenyl protons based on the styrene unit at 6.5 to 7.2 ppm were determined from the spectrum. 4 Styrene content was determined from the ratio of vinyl protons based on butadiene units from .9 to 5.4 ppm.

[0165] (Measurement of weight average molecular weight (Mw)) Mw was determined based on the measured value obtained by gel permeation chromatography (GPC) (GPC-8000 series, manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M, manufactured by Tosoh Corporation) and converted into standard polystyrene.

[0166] The hydrogenation rate of the obtained hydrogenated SBR was 95 mol %, the styrene content was 30 mass %, and the weight average molecular weight (Mw) was 450,000.

[0167] The various chemicals used in the examples and comparative examples are listed below. ·NR:RSS#3 SBR1: HPR355 manufactured by JSR Corporation (S-SBR modified with alkoxysilane, styrene content: 28% by mass, vinyl bond content: 56% by mole, Mw: 400,000) SBR2: Synthesized according to Synthesis Example 1 above (hydrogenated S-SBR, hydrogenation rate: 95%, styrene content: 30% by mass, Mw: 450,000) SBR3: JSR1502 manufactured by JSR Corporation (E-SBR, styrene content: 24% by mass, vinyl bond content: 16%, Mw: approx. 600,000) BR: UBEPOL-BR360B manufactured by Ube Industries, Ltd. (high cis BR, cis 1,4-bond content: 98%, Mw: 570,000) Carbon black 1: Show Black N220 (N2SA: 114m) manufactured by Cabot Japan Co., Ltd. 2 / g, DBP oil absorption: 114mL / 100g) Carbon black 2: Show Black N351H (N2SA:69m) manufactured by Cabot Japan Co., Ltd. 2 / g, DBP oil absorption: 128mL / 100g) Silica: ULTRASIL® VN3 manufactured by Evonik Degussa (BET specific surface area: 175 m 2 / g) Silane coupling agent: Evonik Degussa Si266 (bis(3-triethoxysilylpropyl) disulfide) Oil: Diana Process NH-70S (aromatic process oil) manufactured by Idemitsu Kosan Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corp. Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Anti-aging agent 1: Antigen 6C (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Antioxidant 2 (reactive antioxidant): Nocrac G-1 (N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator 1: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0168] (Preparation of Unvulcanized Rubber Composition for First Rubber Layer) According to the compounding recipe shown in Table 1, chemicals other than sulfur and vulcanization accelerator were added using a 16L Banbury mixer manufactured by Kobe Steel, Ltd., and kneaded for 5 minutes so that the discharge temperature became 160° C. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture in the compounding amounts shown in Table 1, and then kneaded for 5 minutes until the temperature reached 80° C. using a 16L Banbury mixer manufactured by Kobe Steel, Ltd., to obtain unvulcanized rubber compositions A to E for the first rubber layer corresponding to the first rubber layer compounds A to E, respectively.

[0169] [Table 1]

[0170] (Preparation of Rubber Composition for Second Rubber Layer) According to the compounding recipe shown in Table 2, chemicals other than sulfur and vulcanization accelerator were added using a 16L Banbury mixer manufactured by Kobe Steel, Ltd., and kneaded for 3 minutes so that the discharge temperature became 160° C. Next, sulfur and vulcanization accelerator were added to the obtained kneaded mixture in the compounding amounts shown in Table 2, and then kneaded for 5 minutes until the temperature reached 80° C. using a 16L Banbury mixer manufactured by Kobe Steel, Ltd., to obtain unvulcanized rubber compositions a to e for the second rubber layer corresponding to the second rubber layer compounds a to e.

[0171] [Table 2]

[0172] (Preparation of tires of Examples 1 to 6 and Comparative Examples 1 to 5) Using the unvulcanized rubber compositions A to E for the first rubber layer and the unvulcanized rubber compositions a to e for the second rubber layer, the first rubber layer and the second rubber layer were combined according to Table 3, and the ratio (F) of the thickness of the second rubber layer to the thickness of the entire tread (first rubber layer and second rubber layer) was adjusted, and the resultant was extrusion-molded into a tread shape, bonded to other members, and vulcanized at 170°C for 12 minutes to obtain pneumatic tires (size 195 / 65R15) of Examples 1 to 6 and Comparative Examples 1 to 5. Note that, as for the tread pattern, as shown in FIG. 1, in each of two half tread regions divided by the tire centerline, an outer circumferential direction main groove and the inner circumferential direction groove The specimens having the following characteristics were used.

[0173] (Preparation of tires of Examples 7 to 12 and Comparative Examples 6 to 10) Using the unvulcanized rubber compositions A to E for the first rubber layer and the unvulcanized rubber compositions a to e for the second rubber layer, the first rubber layer and the second rubber layer were combined according to Table 4, and the ratio (F) of the thickness of the second rubber layer to the thickness of the entire tread (the first rubber layer and the second rubber layer) was adjusted, and the resultant was extruded into a tread shape, bonded to other members, and vulcanized at 170°C for 12 minutes to obtain pneumatic tires (size 195 / 65R15) of Examples 7 to 12 and Comparative Examples 6 to 10. As the tread pattern, as shown in FIG. 2, a land portion included in a center region having a width equivalent to 50% of the tread ground contact width with the tire center line as the center was formed so that a plurality of sipes were formed so that the angle between the longitudinal direction and the tire width direction was I°.

[0174] The pneumatic tires obtained in each of the Examples and Comparative Examples were measured by the methods described below, and desired values ​​were calculated from the measured values. The results are shown in Tables 3 and 4.

[0175] <Measurement> (Acetone extractable amount (AE amount)) The amount of acetone extractable was calculated according to the following formula by immersing each vulcanized rubber test piece in acetone for 72 hours to extract the soluble components, measuring the mass of each test piece before and after extraction, and then calculating the amount of acetone extractable according to the following formula. Acetone extractable amount (%) = {(mass of rubber test piece before extraction - mass of rubber test piece after extraction) / (mass of rubber test piece before extraction)} x 100

[0176] (Amine amount) The amine amount of the extract obtained by the above acetone extraction was measured according to the method for measuring the amine amount (%) in the acetone extract. The amine amount of the first rubber layer is A (mass%), and the amine amount of the second rubber layer is B (mass%).

[0177] (Change in complex modulus of elasticity E* before and after ozone degradation test (E)) <Complex modulus of elasticity E* before ozone degradation test> A viscoelasticity measurement sample of 20 mm in length, 4 mm in width, and 1 mm in thickness was taken from inside the first rubber layer of the tread portion of each test tire so that the long side was in the tire circumferential direction, and the complex modulus E* was measured using an Iplexer series manufactured by GABO under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an elongation mode. The thickness direction of the sample was the tire radial direction.

[0178] <Complex modulus of elasticity E* after ozone degradation test> For each viscoelasticity measurement sample collected in the same manner as above, a dynamic ozone degradation test was performed in accordance with JIS K 6259, in which the samples were subjected to reciprocating motion for 48 hours under the conditions of a reciprocating motion frequency of 0.5±0.025Hz, an ozone concentration of 50±5pphm, a test temperature of 40°C, and a tensile strain of 20±2%.

[0179] The complex modulus E* of each sample after the ozone degradation test was measured using an Iplexer series manufactured by GABO under the conditions of a temperature of 30° C., an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode.

[0180] <Change rate before and after ozone degradation test (E)> From the complex elastic modulus E* before the ozone degradation test and the complex elastic modulus E* after the ozone degradation test measured above, the rate of change E (%) of the complex elastic modulus E* before and after the ozone degradation test was calculated according to the following formula. E(%)={(E* after ozone test deterioration - E* before ozone test deterioration) / E* before ozone test deterioration}×100

[0181] <Evaluation> (Stability during high speed driving) Each test tire was fitted to all wheels of a domestically produced FF vehicle with an engine displacement of 660cc, and the vehicle was driven on a test course with a dry asphalt surface at temperatures between 20°C and 30°C. The test drivers evaluated the driving stability based on the feeling they had when driving straight, changing lanes, and accelerating and decelerating while driving at 120km / h. The evaluation was done on a scale of 10 points, with a higher score indicating better driving stability, and the total score of the 20 test drivers was calculated based on this. The total score of the reference comparative example was set as the reference value (100), and the total score of each test tire was indexed. The target index value is 127 or more.

[0182] [Table 3]

[0183] [Table 4]

[0184] From the results in Tables 3 and 4, it can be seen that the tires according to the present disclosure according to the examples exhibit superior high-speed steering stability compared to the tires of the comparative examples.

[0185] <Embodiment> Examples of embodiments of the present disclosure are provided below.

[0186] [1] A tire having a tread portion including at least a first rubber layer constituting a tread surface and a second rubber layer adjacent to the first rubber layer on the radially inner side of the tire, the first rubber layer is made of a rubber composition including a rubber component including an isoprene-based rubber, and has an acetone extractable content of 25% by mass or less, preferably 20% by mass or less, and more preferably 15% by mass or less; The second rubber layer is made of a rubber composition containing a rubber component containing an isoprene-based rubber, and the amine amount B in the acetone extract is 10.00 mass% or more, preferably 12.00 mass% or more. .00 % by mass or more, more preferably 15 .00 % by mass or more, When the amount of amine (mass%) in the acetone extract of the first rubber layer is A, the relationship between A and B is preferably B>A, more preferably B / A≧1.1, more preferably B / A≧1.5, and further preferably B / A≧2.0; a rate of change E of a complex modulus E* of a rubber composition constituting the first rubber layer before and after an ozone degradation test of the tire is 30% or less, preferably 28% or less, and more preferably 26% or less; [2] The tire according to the above [1], wherein the rubber component of the second rubber layer contains 45% by mass or more, preferably 50% by mass or more, and more preferably 55% by mass or more of an isoprene-based rubber. [3] The tire according to the above [1] or [2], wherein the rubber component of the first rubber layer contains an isoprene-based rubber in an amount of 12.5% ​​by mass or more, preferably 15.0% by mass or more, and more preferably 20.0% by mass or more. [4] The tire according to any one of the above [1] to [3], wherein the rubber composition constituting the first rubber layer contains an antioxidant, the content (mass%) of the antioxidant in the rubber composition is C, and the rubber composition constituting the second rubber layer contains an antioxidant, the content (mass%) of the antioxidant in the rubber composition is D, and D≧C is satisfied. [5] The tire according to any one of the above [1] to [4], wherein the E is 25% or less, preferably 22% or less. [6] The tire according to any one of the above [1] to [5], wherein A and B satisfy BA≧5.00, preferably BA≧7.00, more preferably BA≧10.00, even more preferably BA≧11.00, and still more preferably BA≧13.00. [7] The tire according to any one of the above [1] to [6], wherein C and D satisfy DC≧0.50, preferably DC≧0.80, more preferably DC≧1.10, even more preferably DC≧1.30, and still more preferably DC≧1.50. [8] The tire according to any one of the above [1] to [7], wherein a ratio F of a thickness of the second rubber layer to a thickness of the entire tread at a position of a tire center line of the tread portion is 10 to 50%, preferably 15 to 40%, and more preferably 20 to 30%. [9] The tire according to [8] above, wherein A, B, and F satisfy (B - A) × F ≥ 30, preferably (B - A) × F ≥ 40, more preferably (B - A) × F ≥ 50, and even more preferably (B - A) × F ≥ 60.

[10] The tire according to any one of [1] to [9] above, wherein the rubber component of the first rubber layer contains styrene-butadiene rubber.

[11] The tire according to any one of [1] to

[10] above, wherein the rubber component of the second rubber layer contains butadiene rubber.

[12] The tread pattern of the tread surface has a circumferential main groove and the circumferential main groove is provided in at least one of two half-tread regions divided by the tire center line, and is an outer circumferential main provided on the outer side when the tire is mounted on a vehicle. groove and an inner circumferential main provided inside thereof. groove The tire according to any one of [1] to

[11] above, which includes at least the outer circumferential main groove Let the groove width (mm) of the outer circumferential main be G, and the groove width (mm) of the inner circumferential main be H. When G and H satisfy H < G. groove

[13] The tire according to

[12] above, wherein G, H, and E satisfy (H / G) × E ≤ 25, preferably (H / G) × E ≤ 24, more preferably (H / G) × E ≤ 23, and even more preferably (H / G) × E ≤ 22.

[14] In the tread pattern of the tread surface, when a region having a width corresponding to 50% of the tread contact width centered on the tire center line is defined as the center region, a plurality of sipes are formed on the land portion included in the center region, and the angle I formed by the longitudinal direction of the sipes and the tire width direction is 8° or more and less than 45°, preferably 10° or more and 43° or less, more preferably 15° or more and 41° or less, and even more preferably 20° or more and 40° or less. The tire according to any one of [1] to

[13] above.

[15] The tire according to the above

[14] , wherein A, B, and I satisfy (BA) / I≧0.20, preferably (BA) / I≧0.21, more preferably (BA) / I≧0.22, and further preferably (BA) / I≧0.30. [Explanation of symbols]

[0187] CL Tire centerline Ti inner grounding end To outer ground end 11 Outer circumferential groove 12 Inner circumferential groove 13 Outer circumferential groove 14 Inner circumferential groove W Tread width CA Center Area 21 Sipe 22 Sipe I Angle between the longitudinal direction of the sipe and the width direction of the tire

Claims

1. A tire having a tread portion including at least a first rubber layer constituting a tread surface and a second rubber layer adjacent to the first rubber layer on the radially inner side of the tire, the first rubber layer is made of a rubber composition including a rubber component including an isoprene-based rubber, and has an acetone extractable content of 25 mass% or less; the second rubber layer is made of a rubber composition including a rubber component including an isoprene-based rubber, and an amine amount B in an acetone extract is 10.00 mass% or more; When the amount of amine (mass%) in the acetone extract of the first rubber layer is A, A and B satisfy B>A, The tire has a rate of change E of a complex modulus E* of the rubber composition constituting the first rubber layer before and after an ozone degradation test of the tire of 30% or less.

2. The tire according to claim 1 , wherein the rubber component of the second rubber layer contains 45% by mass or more of an isoprene-based rubber.

3. The tire according to claim 1 or 2, wherein the rubber component of the first rubber layer contains 12.5 mass % or more of an isoprene-based rubber.

4. The tire according to any one of claims 1 to 3, wherein a rubber composition constituting the first rubber layer contains an antioxidant, a content (mass%) of the antioxidant in the rubber composition is C, and a rubber composition constituting the second rubber layer contains an antioxidant, a content (mass%) of the antioxidant in the rubber composition is D, where D≧C is satisfied.

5. The tire according to any one of claims 1 to 4, wherein E is 25% or less.

6. The tire according to any one of claims 1 to 5, wherein the A and the B satisfy B-A≧5.

00.

7. The tire according to any one of claims 1 to 6, wherein the C and the D satisfy DC≧0.

50.

8. The tire according to any one of claims 1 to 7, wherein a ratio F of a thickness of the second rubber layer to a thickness of the entire tread at a position of a tire center line of the tread portion is 10 to 50%.

9. The tire according to claim 8, wherein A, B, and F satisfy (B-A) x F ≥ 30.

10. The tire according to any one of claims 1 to 9, wherein a rubber component of the first rubber layer contains a styrene-butadiene rubber.

11. The tire according to any one of claims 1 to 10, wherein a rubber component of the second rubber layer contains a butadiene rubber.

12. The tire according to any one of claims 1 to 11, wherein a tread pattern of the tread surface is provided with a circumferential main groove, the circumferential main groove being provided in at least one of two half tread regions divided by a tire center line, the outer circumferential main groove being on the outer side when the tire is mounted on a vehicle, and an inner circumferential main groove being provided on the inner side of the outer circumferential main groove, and wherein, when a groove width (mm) of the outer circumferential main groove is G and a groove width (mm) of the inner circumferential main groove is H, the G and the H satisfy H<G.

13. The tire according to claim 12, wherein the G, the H, and the E satisfy (H / G)×E≦25.

14. The tire according to any one of claims 1 to 13, wherein in a tread pattern of the tread surface, when an area having a width equivalent to 50% of the tread ground contact width centered on the tire center line is defined as a center area, a plurality of sipes are formed in the land portion included in the center area, and an angle I between the longitudinal direction of the sipe and the tire width direction is 8° or more and less than 45°.

15. The tire according to claim 14, wherein the A, the B, and the I satisfy (B-A) / I≧0.20.

Images