tire

Abstract

To provide a tire improved in chipping resistance.SOLUTION: The tire comprises a tread constituted of n-rubber layers (n represents integers of three or more). Neutron scattering measurement is performed by emitting neutron rays to a rubber sample including a boundary surface between the rubber layer on the K-th from a tread surface (k represents integers of one or more and n-2 or less) and the rubber layer on the k+1-th from the tread surface; scattering intensity at the time when a scattering vector determined from an obtained scattering intensity curve is 0.12nm-1 is set to Xk (cm-1); neutron scattering measurement is performed by emitting neutron rays to a rubber sample including a boundary surface between the rubber layer on the K+1-th from the tread surface and the rubber layer on the k+2-th from the tread surface, which are cut out from the tread; and scattering intensity at the time when the scattering vector determined from the obtained scattering intensity curve is 0.12nm-1 is set to Xk+1(cm-1), where |Xk-Xk+1| is 0.10 cm-1 or less for at least one k.SELECTED DRAWING: None

Description

[Technical Field]

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

[0002] In polymeric materials such as rubber, energy loss, chipping resistance, and abrasion resistance are important physical quantities that affect various product characteristics. For example, in tires, which are rubber products, energy loss is closely related to fuel economy and grip performance, while chipping resistance and abrasion resistance are closely related to the tire's lifespan.

[0003] Patent Document 1 describes that abrasion resistance can be further improved by making the crosslinking state of the rubber composition uniform and reducing voids during elongation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2018-28100 A Summary of the Invention [Problem to be solved by the invention]

[0005] When a tread is made up of multiple rubber layers, the thickness of each layer becomes thinner if the overall thickness of the tread remains the same, making chipping more likely to occur. It was found that chipping is particularly likely to occur when the crosslink density between adjacent rubber layers differs significantly.

[0006] The present disclosure aims to provide a tire with improved chipping resistance. [Means for solving the problem]

[0007] As a result of extensive research, it was found that the scattering intensity for a specific scattering vector when a rubber sample is irradiated with neutrons is strongly correlated with the non-uniformity of crosslinking of the rubber component. It was also found that chipping resistance can be improved by setting the difference in scattering intensity between adjacent rubber layers that make up the tread within a predetermined range.

[0008] That is, the present disclosure relates to a tire having a tread made up of n rubber layers (n represents an integer of 3 or more), and a rubber sample cut out from the tread, the rubber sample including the interface between the kth rubber layer (k represents an integer of 1 or more and n-2 or less) and the k+1th rubber layer counting from the tread surface, is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector calculated from the obtained scattering intensity curve is 0.12 nm. -1 The scattering intensity at k (cm -1 ) and a rubber sample cut out from the tread, including the boundary surface of the (k+1)th rubber layer and the (k+2)th rubber layer counting from the tread surface, is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector obtained from the obtained scattering intensity curve is 0.12 nm -1 The scattering intensity at k+1 (cm -1 ), then for at least one k, |X k -X k+1 | is 0.10cm -1 The present invention relates to a tire that is: [Effects of the Invention]

[0009] According to the present disclosure, a tire is provided with improved chipping resistance. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is an enlarged cross-sectional view of a portion of a tread of a tire according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] A tire according to one embodiment of the present disclosure is a tire having a tread made up of n rubber layers (n represents an integer of 3 or more), and is characterized in that a rubber sample cut out from the tread and including the interface between the kth rubber layer (k represents an integer of 1 or more and n-2 or less) and the k+1th rubber layer counting from the tread surface is irradiated with neutrons to perform neutron scattering measurement, and a scattering vector calculated from the obtained scattering intensity curve is 0.12 nm -1 The scattering intensity at k (cm -1 ) and a rubber sample cut out from the tread, including the boundary surface of the (k+1)th rubber layer and the (k+2)th rubber layer counting from the tread surface, is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector obtained from the obtained scattering intensity curve is 0.12 nm -1 The scattering intensity at k+1 (cm -1 ), then for at least one k, |X k -X k+1 | is 0.10cm -1 Less than (preferably 0.09 cm -1 Less than 0.08cm, preferably 0.08cm -1 Less than 0.07cm, more preferably -1 Below 0.06 cm, particularly preferably -1 (See below) It is a tire with |X k -X k+1 There is no particular restriction on the lower limit of |, but for example, 0 cm -1 Super, 0.001cm -1 More than 0.01cm -1 It can be more than that.

[0012] A rubber sample cut out from the tread, including the boundary surface of adjacent rubber layers, was irradiated with neutrons and subjected to neutron scattering measurement. The scattering vector determined from the obtained scattering intensity curve was 0.12 nm. -1 It has been found that the scattering intensity at this time is strongly correlated with the non-uniformity of crosslinking of the rubber component. The tire of the present disclosure can improve chipping resistance by setting the difference in scattering intensity between adjacent rubber layers constituting the tread within a predetermined range.

[0013] The n is preferably 3, 4, 5, or 6, more preferably 3, 4, or 5, even more preferably 3 or 4, and particularly preferably 3.

[0014] In other embodiments of the present disclosure, for two or more k, |X k -X k+1 | is 0.10cm -1 Less than (preferably 0.09 cm -1 Less than 0.08cm, preferably 0.08cm -1 Less than 0.07cm, more preferably -1 Below 0.06 cm, particularly preferably -1 (See below).

[0015] In another embodiment of the present disclosure, for all k, |X k -X k+1 | is 0.10cm -1 Less than (preferably 0.09 cm -1 Less than 0.08cm, preferably 0.08cm -1 Less than 0.07cm, more preferably -1 Below 0.06 cm, particularly preferably -1 (See below).

[0016] In another embodiment of the present disclosure, at least when k is 1, |X k -X k+1 | is 0.10cm -1 Less than (preferably 0.09 cm -1 Less than 0.08cm, preferably 0.08cm -1 Less than 0.07cm, more preferably -1 Below 0.06 cm, particularly preferably -1 (See below).

[0017] The tire of the present disclosure has an X1 of 1.00 cm -1 Preferably, it is less than 0.90 cm -1 More preferably, it is 0.70 cm or less. -1 More preferably, it is equal to or less than 0.50 cm -1 It is particularly preferred that:

[0018] In the tire of the present disclosure, X1 and X2 are both 1.00 cm -1 Preferably, it is less than 0.90 cm -1 More preferably, it is 0.70 cm or less. -1 More preferably, it is equal to or less than 0.50 cm -1 It is particularly preferred that:

[0019] The tire of the present disclosure has X k and X k+1 All are 1.00cm -1 Preferably, it is less than 0.90 cm -1 More preferably, it is 0.70 cm or less. -1 More preferably, it is equal to or less than 0.50 cm -1 It is particularly preferred that:

[0020] In addition, the tire |X of the present disclosure k -X k+1 can be appropriately adjusted by controlling the crosslinking state of the rubber composition by the method described below. k -X k+1 can be adjusted appropriately by changing the types and amounts of the rubber component, filler, plasticizer, etc., which will be described later.

[0021] The tread preferably has circumferential grooves extending continuously in the circumferential direction of the tire, and is formed so that the deepest part of the groove bottom of at least one of the circumferential grooves is located radially inward of the outermost part of the second rubber layer counting from the tread surface.

[0022] The tread of the present disclosure has three or more rubber layers. The configuration of the rubber layers is not particularly limited, but includes at least a first layer (the first rubber layer counting from the tread surface) whose outer surface forms the tread surface, a second layer (the second rubber layer counting from the tread surface) adjacent to the radially inner side of the first layer, and a third layer (the third rubber layer counting from the tread surface) adjacent to the radially inner side of the second layer. The first layer typically corresponds to a cap tread. The second and third layers typically correspond to a base tread or undertread. Furthermore, as long as the object of the present disclosure is achieved, one or more additional rubber layers may be present between the third layer and the outer layer of the belt.

[0023] 1 is an enlarged cross-sectional view schematically showing a portion of a tire tread. In FIG. 1, the vertical direction is the tire radial direction, the horizontal direction is the tire width direction, and the direction perpendicular to the paper surface is the tire circumferential direction.

[0024] The tread of the present disclosure has circumferential grooves 1 that extend continuously in the circumferential direction of the tire. The circumferential grooves 1 may extend linearly along the circumferential direction, or may extend in a zigzag pattern along the circumferential direction.

[0025] The groove depth H of the circumferential groove 1 is determined by the distance between the extension line 4 of the land portion 2 and the extension line 5 of the deepest part of the groove bottom of the circumferential groove 1. Note that, for example, when there are multiple circumferential grooves 1, the groove depth H can be the distance between the extension line 4 of the land portion 2 and the extension line 5 of the deepest part of the groove bottom of the circumferential groove 1 having the deepest groove depth among the multiple circumferential grooves 1 (the circumferential groove 1 on the left side in FIG. 1 ).

[0026] In the present disclosure, as shown in FIG. 1 , the tread includes a first layer 6 whose outer surface constitutes a tread surface 3, a second layer 7 adjacent to the radially inner side of the first layer 6, and a third layer 8 adjacent to the radially inner side of the second layer 7. One circumferential groove 1 shown on the left side of FIG. 1 is formed so that the deepest portion of the groove bottom of the circumferential groove 1 is located radially inward of the outermost part of the second layer 7. Specifically, the second layer 7 has a recess recessed radially inward of the outer surface of the tire, and a portion of the first layer 6 is formed with a predetermined thickness within the recess of the second layer 7. The circumferential groove 1 is formed so as to extend beyond the outer surface of the second layer 7 and into the inside of the recess of the second layer 7. Note that the circumferential groove 1 may be formed with a groove depth that does not reach the outermost part of the second layer 7, as in the circumferential groove 1 shown on the right side of FIG. 1 .

[0027] In Figure 1, the double arrow t1 indicates the thickness of the first layer 6, the double arrow t2 indicates the thickness of the second layer 7, and the double arrow t3 indicates the thickness of the third layer 8. In Figure 1, the midpoint of the land portion 2 in the tire width direction is indicated by the symbol P. The line indicated by the symbol N is a line (normal line) that passes through point P and is perpendicular to the tangent plane at point P. In this specification, the thicknesses t1, t2, and t3 are measured along the normal line N drawn from point P on the tread surface at a position where no grooves exist in the cross section of Figure 1.

[0028] In the present disclosure, the total thickness of the tread is not particularly limited, but is preferably 30 mm or less, more preferably 25 mm or less, even more preferably 20 mm or less, and particularly preferably 15 mm or less. The total thickness of the tread is more preferably 3.0 mm or more, more preferably 5.0 mm or more, and even more preferably 7.0 mm or more.

[0029] In the present disclosure, the thickness of each layer of the tread is not particularly limited, but is preferably 0.5 mm or more, more preferably 1.0 mm or more, even more preferably 1.5 mm or more, and particularly preferably 2.0 mm or more. The thickness of each layer of the tread is preferably 10.0 mm or less, more preferably 9.0 mm or less, and even more preferably 8.0 mm or less.

[0030] From the viewpoint of the effects of the present disclosure, the ratio t1 / H of the thickness t1 (mm) of the first layer 6 to the groove depth H (mm) of the circumferential groove is preferably less than 2.00, more preferably less than 1.50, even more preferably less than 1.00, still more preferably less than 0.95, even more preferably less than 0.90, still more preferably less than 0.85, and particularly preferably less than 0.80. Moreover, t1 / H is preferably greater than 0.20, more preferably greater than 0.30, even more preferably greater than 0.40, and particularly preferably greater than 0.50.

[0031] From the viewpoint of the effects of the present disclosure, the ratio |X1-X2| / (t1 / H) of |X1-X2| to t1 / H is preferably 0.40 or less, more preferably 0.30 or less, even more preferably 0.25 or less, still more preferably 0.20 or less, and particularly preferably 0.15 or less. The lower limit of |X1-X2| / (t1 / H) is not particularly limited, but can be, for example, more than 0, 0.001 or more, or 0.01 or more.

[0032] In this disclosure, the groove depth H of the circumferential groove and the thickness of each rubber layer constituting the tread are values ​​measured by dividing the tire in half along a plane including the tire meridian and assembling one half onto a regular rim. The total thickness of the tread is calculated by the shortest distance between the tread surface and the outer layer of the belt.

[0033] The neutron scattering measurement according to the present disclosure is preferably small-angle neutron scattering (SANS) (scattering angle: usually 10 degrees or less), in which a target rubber sample is irradiated with neutrons and the scattering intensity is measured. In small-angle neutron scattering, a substance is irradiated with neutrons and the neutrons scattered with small scattering angles are measured to obtain structural information about the substance, allowing analysis of ordered structures at the level of several nanometers, such as the microphase separation structure of polymer materials.

[0034] SANS measurements can be performed using known methods based on magnetic structures or deuteration. When using the deuteration method, for example, a polymeric material is swollen in a deuterated solvent, and the polymeric material in equilibrium in the deuterated solvent is irradiated with neutrons to measure the scattering intensity. Examples of deuterated solvents that can be used to swell polymeric materials include deuterated water, deuterated hexane, deuterated toluene, deuterated chloroform, deuterated methanol, deuterated DMSO ((DC)S=O), deuterated tetrahydrofuran, deuterated acetonitrile, deuterated dichloromethane, deuterated benzene, and deuterated N,N-dimethylformamide.

[0035] The neutron beam used for the neutron scattering measurement is obtained using the beamline SANS-J of the JRR-3 research reactor owned by the Japan Atomic Energy Agency.

[0036] The neutron flux intensity (neutrons / cm) of the above neutron beam is chosen because it provides a neutron scattering profile with a high S / N ratio. 2 / s) is preferably 10 3 More than 10, preferably 4 Although there is no particular upper limit, it is preferable to use a neutron flux intensity that is not greater than the level at which radiation damage occurs.

[0037] In SANS measurement, scattered neutrons are detected by a neutron detector, and neutron detection data from the detector is used to generate an image by an image processor, etc. As the neutron detector, a known two-dimensional or one-dimensional detector can be used, and as the image processor, a known device capable of generating a neutron scattering image can be used, and they can be selected appropriately.

[0038] The rubber sample to be subjected to neutron scattering measurement according to the present disclosure is cut from inside the rubber layer of the tread portion of the tire so that the long sides are in the tire circumferential direction, for example, 20 mm long x 20 mm wide x 20 mm thick, and so as to include the boundary surfaces of the rubber layers. It is preferable that the thicknesses of adjacent rubber layers in each rubber sample are the same.

[0039] In the present disclosure, "0°C tan δ" refers to the loss tangent tan δ under conditions of a temperature of 0°C, a frequency of 10 Hz, and an elongation strain of 2.5%. From the viewpoint of the effects of the present disclosure, the 0°C tan δ of the rubber composition constituting the first rubber layer (first layer) counting from the tread surface is preferably 0.40 or more, more preferably 0.45 or more, even more preferably 0.50 or more, and particularly preferably 0.55 or more. Furthermore, the 0°C tan δ of the rubber composition constituting the second rubber layer (second layer) counting from the tread surface is preferably 0.30 or more, more preferably 0.35 or more, even more preferably 0.40 or more, and particularly preferably 0.45 or more. Meanwhile, from the viewpoint of fuel economy, the 0°C tan δ of the rubber compositions constituting each layer of the tread is preferably 2.00 or less, more preferably 1.50 or less, even more preferably 1.20 or less, and particularly preferably 0.90 or less. The 0°C tan δ value of the rubber composition constituting the first layer is preferably greater than the 0°C tan δ value of the rubber composition constituting the second layer. The difference between the 0°C tan δ of the rubber composition constituting the first layer and the 0°C tan δ of the rubber composition constituting the second layer is preferably 0.02 or more, more preferably 0.04 or more, even more preferably 0.06 or more, and particularly preferably 0.08 or more.

[0040] In the present disclosure, "30°C tan δ" refers to the loss tangent tan δ under conditions of a temperature of 30°C, a frequency of 10 Hz, and an elongation strain of 2.5%. The 30°C tan δ of the rubber composition constituting the first layer is preferably 0.10 or more, more preferably 0.12 or more, even more preferably 0.14 or more, even more preferably 0.16 or more, and particularly preferably 0.18 or more. By setting the 30°C tan δ of the rubber composition constituting the first layer within the above range, grip performance can be obtained. Furthermore, the 30°C tan δ of the rubber composition constituting the second layer is preferably 0.08 or more, more preferably 0.10 or more, even more preferably 0.12 or more, and particularly preferably 0.14 or more. On the other hand, from the viewpoint of fuel economy, the 30°C tan δ of the rubber composition constituting each layer of the tread is preferably 0.75 or less, more preferably 0.70 or less, even more preferably 0.65 or less, and particularly preferably 0.60 or less. The 30°C tan δ value of the rubber composition constituting the first layer is preferably greater than the 30°C tan δ value of the rubber composition constituting the second layer. The difference between the 30°C tan δ of the rubber composition constituting the first layer and the 30°C tan δ of the rubber composition constituting the second layer is preferably 0.01 or more, more preferably 0.02 or more, even more preferably 0.03 or more, and particularly preferably 0.04 or more.

[0041] In this disclosure, EB refers to the elongation at break (elongation at break) measured in accordance with JIS K 6251:2017 at a tensile speed of 3.3 mm / sec in an atmosphere of 23°C. From the viewpoint of maintaining surface smoothness, the EB of the rubber composition constituting the first layer is preferably 460% or more, more preferably 470% or more, even more preferably 480% or more, and particularly preferably 490% or more. The EB of the rubber composition constituting the second layer is preferably 410% or more, more preferably 420% or more, even more preferably 430% or more, and particularly preferably 440% or more. There is no particular upper limit on the EB of the rubber composition constituting each layer of the tread.

[0042] In the present disclosure, "0°C E*" refers to the complex modulus E* under conditions of a temperature of 0°C, a frequency of 10 Hz, and an elongation strain of 2.5%. From the viewpoint of anchor friction, the 0°C E* of the rubber composition constituting the first layer is preferably 3.0 MPa or more, more preferably 3.5 MPa or more, even more preferably 4.0 MPa or more, and particularly preferably 4.5 MPa or more. From the viewpoint of anchor friction, the 0°C E* of the rubber composition constituting the second layer is preferably 2.0 MPa or more, more preferably 2.5 MPa or more, even more preferably 3.0 MPa or more, and particularly preferably 3.5 MPa or more. Meanwhile, from the viewpoint of road surface following performance, the 0°C E* of the rubber compositions constituting each layer of the tread is preferably 20 MPa or less, more preferably 15 MPa or less, and even more preferably 10 MPa or less. The 0°C E* value of the rubber composition constituting the first layer is preferably greater than the 0°C E* value of the rubber composition constituting the second layer. The difference between the 0°C E* of the rubber composition constituting the first layer and the 0°C E* of the rubber composition constituting the second layer is preferably 0.2 MPa or more, more preferably 0.4 MPa or more, even more preferably 0.6 MPa or more, and particularly preferably 0.8 MPa or more.

[0043] The 0°C tan δ, 30°C tan δ, EB, and 0°C E* of the rubber composition of the present disclosure can be adjusted appropriately by the types and amounts of the rubber components, fillers, plasticizers, etc. described below.

[0044] The glass transition temperature (Tg) in this disclosure refers to the tan δ peak temperature measured by the following method. Specifically, a rubber test specimen (e.g., 20 mm long x 4 mm wide x 1 mm thick) was cut from the rubber layer in the tread portion of each test tire, with the long side aligned in the tire circumferential direction. A temperature distribution curve of tan δ was measured using a dynamic viscoelasticity evaluation device (GABO's Iplexer series) under conditions of a frequency of 10 Hz and an elongation strain of 2.5%, and the temperature corresponding to the largest tan δ value in the obtained temperature distribution curve (tan δ peak temperature) was defined as the glass transition temperature (Tg) in this disclosure. The Tg of the rubber composition constituting the first layer is preferably −25°C or higher, more preferably −24°C or higher, even more preferably −23°C or higher, even more preferably −22°C or higher, and particularly preferably −21°C or higher. A Tg of −25°C or higher tends to result in a higher loss tangent tan δ in the temperature range above Tg compared to a Tg below −25°C, thereby improving wet grip performance. The Tg of the rubber composition constituting the second layer is preferably −40° C. or higher, more preferably −35° C. or higher, and even more preferably −32° C. or higher. The upper limit of the Tg of the rubber composition constituting each layer of the tread is not particularly limited, but is preferably 20° C. or lower, more preferably 15° C. or lower, and even more preferably 10° C. or lower. The Tg of each rubber layer can be adjusted appropriately by the types and amounts of the rubber components, fillers, plasticizers, etc.

[0045] In this disclosure, unless otherwise specified, the dimensions and angles of each component of a tire are measured when the tire is mounted on a standard rim and inflated to the standard internal pressure. No load is applied to the tire during measurement. Note that, in this specification, a "standard rim" refers to the rim specified for each tire by the standard system that includes the standard on which the tire is based. For example, in the case of JATMA, it refers to the standard rim, in the case of TRA, it refers to the "Design Rim," and in the case of ETRTO, it refers to the "Measuring Rim." In this specification, the "standard internal pressure" refers to the air pressure specified for each tire by the standard, which refers to the maximum air pressure in the case of JATMA, the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" in the case of TRA, and it refers to the "INFLATION PRESSURE" in the case of ETRTO.

[0046] A manufacturing procedure for a tire according to one embodiment of the present disclosure will be described in detail below. However, the following description is an example for explaining the present disclosure and is not intended to limit the technical scope of the present disclosure to the described range. In this specification, when a numerical range is indicated using "to" it is intended to include both ends of the numerical range.

[0047] <Rubber component> The rubber composition constituting each layer of the tread according to the present disclosure preferably contains, as a rubber component, at least one selected from the group consisting of isoprene-based rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR). The rubber components constituting the first and second layers preferably contain SBR, more preferably contain SBR and BR, and may be rubber components consisting only of SBR and BR. The rubber component constituting the third layer preferably contains isoprene-based rubber, more preferably contain isoprene-based rubber and BR, and may be rubber components consisting only of isoprene-based rubber and BR.

[0048] (Isoprene rubber) Examples of isoprene-based rubbers that can be used include those commonly used in the tire industry, such as isoprene rubber (IR) and natural rubber. Natural rubber includes unmodified natural rubber (NR) as well as modified natural rubbers such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), highly purified natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0049] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0050] When the rubber component constituting the first and second layers contains an isoprene-based rubber (preferably natural rubber, more preferably unmodified natural rubber (NR)), the content in the rubber component is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, and particularly preferably 20% by mass or less. The lower limit of the content of the isoprene-based rubber when it is contained is not particularly limited, but may be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more. When the rubber component constituting the rubber layer radially inward of the third layer contains an isoprene-based rubber, the content in the rubber component is not particularly limited, but may be, for example, 10% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, or 60% by mass or more.

[0051] (SBR) The SBR is not particularly limited, and examples thereof include unmodified solution-polymerized SBR (S-SBR) and emulsion-polymerized SBR (E-SBR), as well as modified SBRs (modified S-SBR, modified E-SBR). Modified SBRs include SBRs whose ends and / or main chains are modified, and modified SBRs (condensates, those having a branched structure, etc.) coupled with tin or silicon compounds. Of these, E-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR) can also be used. These SBRs may be used alone or in combination of two or more.

[0052] The SBR may be either oil-extended or non-oil-extended. When oil-extended SBR is used, the amount of oil extension of the SBR, i.e., the content of the oil-extending oil contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of the rubber solids content of the SBR.

[0053] As the S-SBR that can be used in the present disclosure, commercially available products from JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and the like can be used.

[0054] The modified SBR may be one whose main chain and / or terminals have been modified with a modifying agent, or one whose main chain and / or terminals have been modified with a polyfunctional modifying agent such as tin tetrachloride or silicon tetrachloride to have a partially branched structure, but SBR whose main chain and / or terminals have been modified with a modifying agent having a functional group that interacts with silica (silica-modified BR) is preferred. In particular, it is preferred that the first layer and / or second layer contain the modified SBR.

[0055] The functional group that interacts with silica can be exemplified by, for example, amino group, amide group, alkoxysilyl group, isocyanate group, imino group, imidazole group, urea group, ether group, carbonyl group, oxycarbonyl group, sulfide group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazo group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydrocarbon group, hydroxyl group, oxy group, epoxy group, etc.It should be noted that these functional groups can have a substituent.Among them, from the viewpoint of improving the dispersibility of silica, amino group, epoxy group, hydroxyl group, alkoxy group, and alkoxysilyl group are preferred, and amino group and alkoxysilyl group are more preferred.

[0056] From the viewpoints of wet grip performance and abrasion resistance, the styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, and even more preferably 20% by mass or more. From the viewpoints of temperature dependency of grip performance and blow resistance, the styrene content is preferably 60% by mass or less, more preferably 55% by mass or less, and even more preferably 50% by mass or less. In this specification, the styrene content of SBR is 1 It is calculated by H-NMR measurement.

[0057] The vinyl content of SBR is preferably 10 mol% or more, more preferably 15 mol% or more, and even more preferably 20 mol% or more, from the viewpoints of ensuring reactivity with silica, wet grip performance, rubber strength, and abrasion resistance. Furthermore, the vinyl content of SBR is preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less, from the viewpoints of preventing an increase in temperature dependency, elongation at break, and abrasion resistance. In this specification, the vinyl content of SBR (amount of 1,2-bonded butadiene units) is measured by infrared absorption spectroscopy.

[0058] From the viewpoint of wet grip performance, the weight-average molecular weight (Mw) of SBR is preferably 200,000 or more, more preferably 250,000 or more, and even more preferably 300,000 or more. From the viewpoint of crosslinking uniformity, the weight-average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. In this specification, the weight-average molecular weight of SBR can be determined in terms of standard polystyrene based on measurements 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).

[0059] When the rubber components constituting the first and second layers contain SBR, the content of SBR in the rubber components is preferably 20% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and particularly preferably 35% by mass or more, from the viewpoint of chipping resistance. Furthermore, from the viewpoint of abrasion resistance, 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. When the rubber component constituting the rubber layer radially inward of the third layer contains SBR, the content of SBR in the rubber component is not particularly limited.

[0060] (BR) The BR is not particularly limited, and can be one commonly used in the tire industry, such as BR with a cis content of less than 50% by mass (low-cis BR), BR with a cis content of 90% by mass or more (high-cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high-cis modified BR, low-cis modified BR), etc. These BRs may be used alone or in combination of two or more.

[0061] As the high-cis BR, for example, commercially available products from Zeon Corporation, Ube Industries, Ltd., JSR Corporation, etc. can be used. The inclusion of high-cis BR can improve low-temperature properties and wear resistance. The cis content is preferably 95% by mass or more, more preferably 96% by mass or more, even more preferably 97% by mass or more, and particularly preferably 98% by mass or more. In this specification, the cis content (amount of cis-1,4-bonded butadiene units) is a value calculated by infrared absorption spectroscopy.

[0062] The rare earth BR is synthesized using a rare earth catalyst and has a vinyl content of preferably 1.8 mol % or less, more preferably 1.0 mol % or less, and even more preferably 0.8 mol % or less, and a cis content of preferably 95 mass % or more, more preferably 96 mass % or more, even more preferably 97 mass % or more, and particularly preferably 98 mass % or more. Commercially available rare earth BRs available from, for example, Lanxess K.K. can be used.

[0063] The SPB-containing BR is not one in which 1,2-syndiotactic polybutadiene crystals are simply dispersed in the BR, but one in which the 1,2-syndiotactic polybutadiene crystals are dispersed after being chemically bonded to the BR. As such SPB-containing BR, commercially available products from Ube Industries, Ltd. and the like can be used.

[0064] Examples of modified BR include those obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, with the terminals of the modified BR molecule being bonded with tin-carbon bonds (tin-modified BR), and butadiene rubber in which the main chain and / or terminals of the butadiene rubber have been modified with a modifier having a functional group that interacts with silica (silica-modified BR).Modified BR may be either non-hydrogenated or hydrogenated.

[0065] From the viewpoint of abrasion resistance, the weight-average molecular weight (Mw) of the 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 crosslinking uniformity, it is preferably 2,000,000 or less, more preferably 1,000,000 or less. The weight-average molecular weight of the BR can be determined in terms of standard polystyrene based on measurements obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTPORE HZ-M manufactured by Tosoh Corporation).

[0066] When the rubber component constituting each layer of the tread contains BR, the content in the rubber component is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, and particularly preferably 35% by mass or less, from the viewpoint of chipping resistance. Furthermore, when BR is contained, the lower limit of the content is not particularly limited, but can be, for example, 1% by mass or more, 3% by mass or more, 5% by mass or more, 10% by mass or more, or 15% by mass or more.

[0067] (Other rubber components) The rubber component according to the present disclosure may contain rubber components other than the isoprene-based rubber, SBR, and BR. Examples of other rubber components include crosslinkable rubber components commonly used in the tire industry, such as isoprene-based rubbers such as styrene-isoprene rubber (SIR), styrene-isoprene-butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile-butadiene rubber (NBR); diene-based rubbers other than SBR and BR; and non-diene-based rubbers such as butyl rubber (IIR), halogenated butyl rubber, ethylene-propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. These other rubber components may be used alone or in combination of two or more. The rubber component according to the present disclosure preferably contains 80% by mass or more of diene-based rubber, more preferably 90% by mass or more, even more preferably 95% by mass or more, and particularly preferably 98% by mass or more. The rubber component may consist solely of diene-based rubber. In addition to the rubber component, the composition may or may not contain a known thermoplastic elastomer.

[0068] <Filler> The rubber composition constituting each layer of the tread according to the present disclosure preferably uses a filler containing carbon black and / or silica. The rubber compositions constituting the first and second layers preferably contain silica as a filler, more preferably carbon black and silica. The rubber composition constituting the rubber layer radially inward of the third layer preferably contains carbon black as a filler.

[0069] (carbon black) As the carbon black, any carbon black commonly used in the tire industry can be used as appropriate, such as GPF, FEF, HAF, ISAF, SAF, etc. These carbon blacks may be used alone or in combination of two or more.

[0070] The nitrogen adsorption specific surface area (N2SA) of carbon black is 20m from the viewpoint of reinforcement.2 / g or more is preferable, and 40m 2 / g or more is more preferable, and 60m 2 / g or more is more preferable, and 80m 2 / g or more is particularly preferable. From the viewpoint of fuel economy and processability, 200m 2 / g or less is preferable, and 170m 2 / g or less is more preferable, and 140m 2 The N2SA of carbon black is a value measured in accordance with JIS K 6217-2 "Fundamental properties of carbon black for rubber - Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0071] When the rubber composition constituting the first and second layers contains carbon black, the content thereof per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, from the viewpoints of abrasion resistance and wet grip performance. Furthermore, from the viewpoint of fuel economy, the content thereof is preferably 50 parts by mass or less, more preferably 35 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less. When the rubber composition constituting the rubber layer radially inward of the third layer contains carbon black, the content thereof per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and even more preferably 30 parts by mass or more, from the viewpoint of abrasion resistance. Furthermore, from the viewpoint of fuel economy, the content thereof is preferably 80 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 60 parts by mass or less.

[0072] (silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica) or silica prepared by a wet method (hydrated silica), which are commonly used in the tire industry. Among them, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. These silicas can be used alone or in combination of two or more.

[0073] The nitrogen adsorption specific surface area (N2SA) of silica is 120m from the viewpoint of chipping resistance. 2 / g or more is preferable, and 140m 2 / g or more is more preferable, and 160m 2 / g or more is more preferable. From the viewpoint of fuel efficiency and processability, 2 / g or less is preferable, and 300m 2 / g or less is more preferable, and 250m 2 / g or less is more preferable. In this specification, the N2SA of silica is a value measured by the BET method in accordance with ASTM D3037-93.

[0074] When the rubber compositions constituting the first and second layers contain silica, the content of silica per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, even more preferably 50 parts by mass or more, and particularly preferably 60 parts by mass or more, from the viewpoint of wet grip performance. Furthermore, from the viewpoint of abrasion resistance, the content is preferably 130 parts by mass or less, more preferably 120 parts by mass or less, and even more preferably 110 parts by mass or less. When the rubber composition constituting the rubber layer radially inward of the third layer contains silica, the content of silica in the rubber component is not particularly limited.

[0075] The total content of silica and carbon black per 100 parts by mass of the rubber component is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more from the viewpoint of chipping resistance, and is preferably 160 parts by mass or less, more preferably 140 parts by mass or less, even more preferably 120 parts by mass or less, and particularly preferably 110 parts by mass or less from the viewpoint of fuel economy and elongation at break.

[0076] The proportion of silica to the total content of silica and carbon black in the rubber composition constituting the first and second layers is preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 85% by mass or more, from the viewpoint of a balance between fuel economy, wet grip performance, and chipping resistance. The proportions of silica and carbon black in the rubber composition constituting the rubber layer radially inward of the third layer are not particularly limited, but the proportion of carbon black to the total content of silica and carbon black can be, for example, 50% by mass or more, 70% by mass or more, 90% by mass or more, or 100% by mass.

[0077] (Silane coupling agent) Silica is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and any silane coupling agent conventionally used in combination with silica in the tire industry can be used. Examples thereof include the following mercapto-based silane coupling agents; sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silane coupling agents such as 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane and 3-(2-aminoethyl)aminopropyltriethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. Among these, sulfide-based silane coupling agents and / or mercapto-based silane coupling agents are preferred, and mercapto-based silane coupling agents are more preferred. These silane coupling agents may be used alone or in combination of two or more.

[0078] The mercapto-based silane coupling agent is preferably a compound represented by the following formula (1) and / or a compound containing a bonding unit A represented by the following formula (2) and a bonding unit B represented by the following formula (3). [ka] (In the formula, R 101 , R 102 , and R 103 are each independently an alkyl having 1 to 12 carbon atoms, an alkoxy having 1 to 12 carbon atoms, or -O-(R 111 -O) z -R 112 (z R 111 each independently represents a divalent hydrocarbon group having 1 to 30 carbon atoms; R 112 represents an alkyl having 1 to 30 carbon atoms, an alkenyl having 2 to 30 carbon atoms, an aryl having 6 to 30 carbon atoms, or an aralkyl having 7 to 30 carbon atoms; z represents an integer of 1 to 30; 104 represents an alkylene having 1 to 6 carbon atoms. [ka] [ka] (wherein x represents an integer of 0 or more; y represents an integer of 1 or more; R 201 represents a hydrogen atom, an alkyl having 1 to 30 carbon atoms, an alkenyl having 2 to 30 carbon atoms, or an alkynyl having 2 to 30 carbon atoms (the alkyl, alkenyl, and alkynyl may be substituted with a halogen atom, a hydroxyl, or a carboxyl); R 202 represents an alkylene having 1 to 30 carbon atoms, an alkenylene having 2 to 30 carbon atoms, or an alkynylene having 2 to 30 carbon atoms; 201 and R 202 may form a ring structure with

[0079] Examples of the compound represented by formula (1) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following formula (4) (Si363 manufactured by Evonik Degussa GmbH), and the compound represented by the following formula (4) can be preferably used. These may be used alone or in combination of two or more. [ka]

[0080] Examples of compounds containing a bonding unit A represented by formula (2) and a bonding unit B represented by formula (3) include those manufactured and sold by Momentive, Inc. These may be used alone or in combination of two or more.

[0081] The content of the silane coupling agent per 100 parts by mass of the rubber component (the total amount when multiple silane coupling agents are used in combination) is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, even more preferably 2.0 parts by mass or more, and particularly preferably 4.0 parts by mass or more, from the viewpoint of improving the dispersibility of silica. Also, from the viewpoint of preventing a decrease in abrasion resistance, it is preferably 20 parts by mass or less, more preferably 12 parts by mass or less, even more preferably 10 parts by mass or less, and particularly preferably 9.0 parts by mass or less.

[0082] The content of the silane coupling agent relative to 100 parts by mass of silica (when multiple silane coupling agents are used in combination, the total amount of all) is preferably 1.0 parts by mass or more, more preferably 3.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, from the viewpoint of improving the dispersibility of silica.Furthermore, from the viewpoint of cost and processability, it is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 12 parts by mass or less.

[0083] As the filler, in addition to carbon black and silica, other fillers may also be used. Such fillers are not particularly limited, and any fillers commonly used in this field, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, etc., may be used. These fillers may be used alone or in combination of two or more.

[0084] <Other compounding agents> The rubber composition constituting each layer of the tread according to the present disclosure may contain, in addition to the above-mentioned components, compounding agents conventionally commonly used in the tire industry, such as plasticizers, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, vulcanization accelerators, etc., as appropriate.

[0085] The rubber composition constituting each layer of the tread according to the present disclosure preferably contains a plasticizer, such as a resin component, oil, liquid rubber, or an ester-based plasticizer.

[0086] The resin component is not particularly limited, but examples thereof include petroleum resins, terpene resins, rosin resins, phenolic resins, etc. These resin components may be used alone or in combination of two or more.

[0087] As used herein, "C5 petroleum resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is preferably used as the C5 petroleum resin.

[0088] As used herein, "aromatic petroleum resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified version of the resin. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of aromatic petroleum resins that are suitable for use include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. Preferred aromatic vinyl resins are homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene, with copolymers of α-methylstyrene and styrene being more preferred, due to their economical efficiency, ease of processing, and excellent heat generation properties. Examples of aromatic vinyl resins that can be used include commercially available products from Kraton, Eastman Chemical Company, and the like.

[0089] As used herein, the term "C5C9 petroleum resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of the C5 fraction and the C9 fraction include the petroleum fractions described above. As the C5C9 petroleum resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used.

[0090] Examples of terpene resins include polyterpene resins made of at least one terpene compound selected from α-pinene, β-pinene, limonene, dipentene, and the like; aromatic modified terpene resins made from the terpene compound and an aromatic compound; terpene phenolic resins made from a terpene compound and a phenolic compound; and those obtained by subjecting these terpene resins to hydrogenation treatment (hydrogenated terpene resins). Examples of aromatic compounds used as raw materials for aromatic modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds used as raw materials for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol.

[0091] The rosin-based resin is not particularly limited, but examples thereof include natural resin rosins such as tall rosin, gum rosin, and wood rosin, and rosin-modified resins obtained by modifying natural rosins by hydrogenation, disproportionation, dimerization, esterification, etc.

[0092] The phenolic resin is not particularly limited, but examples thereof include phenol formaldehyde resin, alkylphenol formaldehyde resin, alkylphenol acetylene resin, and oil-modified phenol formaldehyde resin.

[0093] From the viewpoint of wet grip performance, the softening point of the resin component is preferably 60°C or higher, more preferably 65°C or higher, and even more preferably 70°C or higher. From the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower. In this specification, the softening point may be defined as the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0094] When the rubber composition constituting each layer (particularly the first layer and / or second layer) of the tread according to the present disclosure contains a resin component, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and particularly preferably 12 parts by mass or more, from the viewpoint of chipping resistance. Also, from the viewpoint of suppressing heat buildup, the content is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and particularly preferably 30 parts by mass or less.

[0095] Examples of oils include process oil, vegetable oils, and animal fats. Examples of the process oil include paraffinic process oil, naphthenic process oil, and aromatic process oil. Furthermore, as an environmental measure, process oil with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of the low-PCA process oil include mild extract solvates (MES), treated distillate aromatic extracts (TDAE), and heavy naphthenic oil.

[0096] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more, from the viewpoint of processability. Furthermore, from the viewpoint of abrasion resistance, the content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 80 parts by mass or less, and particularly preferably 60 parts by mass or less. In this specification, the oil content includes the amount of oil contained in the oil-extended rubber.

[0097] The liquid rubber is not particularly limited as long as it is a polymer that is in a liquid state at room temperature (25°C), and examples thereof include liquid butadiene rubber (liquid BR), liquid styrene butadiene rubber (liquid SBR), liquid isoprene rubber (liquid IR), liquid styrene isoprene rubber (liquid SIR), liquid farnesene rubber, etc. These liquid rubbers may be used alone or in combination of two or more.

[0098] When a liquid rubber is contained, the content thereof per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 7 parts by mass or more. The content of the liquid rubber is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 20 parts by mass or less.

[0099] Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). These ester-based plasticizers may be used alone or in combination of two or more.

[0100] When the rubber composition constituting each layer (particularly the first layer and / or second layer) of the tread according to the present disclosure contains a plasticizer, the content (total amount when multiple plasticizers are used) per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more from the viewpoint of wet grip performance. Also, from the viewpoint of processability, the content is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less.

[0101] When the wax 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 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of weather resistance of the rubber, and is preferably 10.0 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of preventing whitening of the tire due to bloom.

[0102] Examples of processing aids include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, and mixtures of fatty acid metal salts and fatty acid amides. These processing aids may be used alone or in combination of two or more. Examples of processing aids that can be used include those commercially available from Schill + Seilacher, Performance Additives, etc.

[0103] When a processing aid 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 improving processability, and is preferably 10 parts by mass or less, more preferably 8 parts by mass or less, from the viewpoint of abrasion resistance and breaking strength.

[0104] The antioxidant is not particularly limited, but examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, as well as metal carbamates. Preferred are phenylenediamine-based antioxidants such as N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine, N-isopropyl-N'-phenyl-p-phenylenediamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-2-naphthyl-p-phenylenediamine, and N-cyclohexyl-N'-phenyl-p-phenylenediamine, and quinoline-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline. These antioxidants may be used alone or in combination of two or more.

[0105] When an antioxidant 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 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of ozone crack resistance of the rubber, 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 and wet grip performance.

[0106] When stearic acid 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 vulcanization rate.

[0107] 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 part 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.

[0108] As the vulcanizing agent, sulfur is preferably used, and examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0109] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably 0.1 parts by mass or more, more preferably 0.3 parts by mass or more, and even more preferably 0.5 parts by mass or more, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, the content is preferably 5.0 parts by mass or less, more preferably 4.0 parts by mass or less, and even more preferably 3.0 parts by mass or less. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0110] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensate, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. These vulcanizing agents other than sulfur can be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, etc.

[0111] Examples of vulcanization accelerators 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. These vulcanization accelerators may be used alone or in combination of two or more. Among them, one or more vulcanization accelerators selected from the group consisting of sulfenamide-based, guanidine-based, and thiazole-based vulcanization accelerators are preferred, and sulfenamide-based vulcanization accelerators are more preferred.

[0112] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among these, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0113] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Among these, 1,3-diphenylguanidine (DPG) is preferred.

[0114] Examples of the thiazole vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0115] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the rubber component is preferably 1.0 part by mass or more, more preferably 1.5 parts by mass or more. The content thereof per 100 parts by mass of the rubber component is preferably 8.0 parts by mass or less, more preferably 7.0 parts by mass or less, and even more preferably 6.0 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

[0116] The rubber composition constituting each layer of the tread according to the present disclosure can be produced, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll, an internal kneader (Banbury mixer, kneader, etc.), etc. As a method for producing the rubber composition constituting each layer of the tread according to the present disclosure, a production method that can make the crosslinked state of the rubber composition uniform can be adopted, as described below.

[0117] A preferred method for making the crosslinked state of the rubber composition uniform is, for example, a production method including a step of starting kneading of the rubber component with the sulfur atom-containing vulcanization accelerator before kneading the rubber component with the filler, and then adding the filler to the obtained kneaded mixture and kneading the mixture.

[0118] The sulfur atom-containing vulcanization accelerator refers to a vulcanization accelerator containing a sulfur atom bonded to another molecule by a single bond. Among the sulfur atom-containing vulcanization accelerators, there are those that release active sulfur and those that do not, but from the viewpoint of suppressing the progress of the crosslinking reaction during kneading, a sulfur atom-containing vulcanization accelerator that does not release active sulfur is preferred.

[0119] It is believed that by starting the kneading of the rubber component and the sulfur atom-containing vulcanization accelerator before the kneading of the rubber component and the filler, it is possible to prevent the sulfur atom-containing vulcanization accelerator from being adsorbed by the filler, thereby efficiently dispersing the sulfur atom-containing vulcanization accelerator in the rubber component and making the crosslinked state of the rubber composition uniform.

[0120] This production method is characterized in that the kneading of the rubber component and the sulfur-containing vulcanization accelerator is initiated before the filler is added, and that after the filler is added, the kneading is preferably carried out at a kneading temperature of 120°C or higher. Any of the materials may be added at any step as long as these requirements are met. For example, when the kneading process is a two-step process consisting of step X and step F, kneading of the rubber component and the sulfur-containing vulcanization accelerator may be initiated at the beginning of step X, the filler may be added during step X, and the kneading may be carried out at a kneading temperature of 120°C or higher, and then step F may be carried out. Furthermore, when the kneading process is a three-step process consisting of step X, step Y, and step F, kneading of the rubber component and the sulfur-containing vulcanization accelerator may be initiated in step X, the filler may be added in the subsequent step Y, and the kneading may be carried out at a kneading temperature of 120°C or higher, and then step F may be carried out. In another example of the three-step process, kneading of the rubber component and the sulfur-containing vulcanization accelerator may be started at the beginning of step X, a filler may be added during step X, and kneading may be continued at a kneading temperature of 120°C or higher, followed by steps Y and F. Alternatively, kneading of the rubber component and the sulfur-containing vulcanization accelerator may be started at the beginning of step X, a filler may be added during step X, and further filler may be added in step Y, and kneading may be continued at a kneading temperature of 120°C or higher, followed by step F. Remilling may be performed between each step.

[0121] The kneading temperature for mixing the rubber component and the sulfur atom-containing vulcanization accelerator is not particularly limited, but is preferably less than 160°C, more preferably 150°C or less, from the viewpoint of suppressing the progress of the crosslinking reaction caused by the sulfur atom-containing vulcanization accelerator.

[0122] The time for kneading the rubber component and the sulfur atom-containing vulcanization accelerator before adding the filler to the rubber component is not particularly limited, but is, for example, 10 seconds or more from the viewpoint of improving dispersibility.

[0123] The kneading temperature after adding the filler is preferably 170° C. or lower in order to prevent the crosslinking reaction from proceeding too far.

[0124] Furthermore, the kneading time after the filler is added to the rubber component and the kneading temperature reaches 120°C is not particularly limited, but is, for example, 2 minutes or more from the viewpoint of improving dispersibility. Note that the kneading time referred to here is the time from the point at which the filler is added to the rubber component and the kneading temperature reaches 120°C to the point at which all steps in the kneading process are completed, i.e., when the filler is added to the rubber component in step X and the kneading temperature reaches 120°C, it is the time from that point to the point at which step F is completed.

[0125] In addition to the above methods, other methods for making the crosslinking state of a rubber composition uniform include (a) using a silica-modified styrene butadiene rubber and / or a silica-modified butadiene rubber, (b) using a sulfur-containing oligomer as sulfur (vulcanizing agent), (c) using a resin with good dispersibility (aromatic modified terpene resin, coumarone-indene resin, etc.) as a resin, (d) using a rosin-based resin that can make the sulfur crosslinking uniform, and (e) using a filler that is mainly silica and increasing the amount of filler (for example, a silica amount of 95 parts by mass or more, and a filler content of 37 mass% or more in 100 mass% of the total rubber composition), either alone or in combination as appropriate.

[0126] The reason why the crosslinked state of the rubber composition can be made uniform by the methods (a) to (e) is presumed to be as follows.

[0127] (a) When a silica-modified styrene-butadiene rubber and / or a silica-modified butadiene rubber is used, the polymer bonds with the OH groups on the silica surface during kneading, improving the dispersion of the silica and integrating the polymer and silica, which is thought to result in a uniform crosslinking state of the rubber composition.

[0128] (b) When a sulfur-containing oligomer is used, the oligomer has a high affinity with the polymer and a molecular weight close to that of the polymer, so it is uniformly incorporated into the polymer, forming elemental sulfur and further a sulfur-accelerator-zinc-fatty acid complex, which allows for the formation of uniform interpolymer crosslinks, and therefore it is believed that the crosslinked state of the rubber composition is made uniform.

[0129] (c) When a resin with good dispersibility is used, the resin does not block the diene bond sites of the polymer, and the sulfur element can approach the diene bond sites, which is thought to result in a uniform crosslinking state of the rubber composition.

[0130] (d) When using rosin-based resins, the carboxyl groups (-COOH) of the rosin adsorb sulfur and distribute the sulfur element uniformly inside the polymer, which is thought to result in a uniform crosslinking state of the rubber composition.

[0131] (e) When the filler is mainly composed of silica and the amount of filler is increased, the filler has the effect of breaking up polymer clumps, reducing self-aggregation of polymers and making the volume ratio of polymer to filler closer, which is thought to result in a more uniform crosslinked state of the rubber composition.

[0132] In the methods (a) to (e), the kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into multiple steps as desired.

[0133] The kneading conditions are not particularly limited, but examples include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and a method in which the final kneading step involves kneading for 1 to 5 minutes at 70 to 110°C. The vulcanization conditions are not particularly limited, but examples include a method in which vulcanization is carried out for 10 to 30 minutes at 150 to 200°C.

[0134] [tire] The tire according to the present disclosure has a tread consisting of n rubber layers (n is an integer of 3 or more), and may be a pneumatic tire or a non-pneumatic tire. Examples of pneumatic tires include passenger car tires, truck and bus tires, motorcycle tires, and high-performance tires, and the tire is particularly suitable for use as a passenger car tire. In this specification, a passenger car tire refers to a tire designed to be mounted on a four-wheeled vehicle and having a maximum load capacity of 1000 kg or less. A high-performance tire refers to a tire with particularly excellent grip performance, and is a concept that also includes racing tires used on racing vehicles.

[0135] A tire having a tread consisting of n rubber layers (n is an integer of 3 or more) can be manufactured by a conventional method using the above rubber composition. That is, an unvulcanized rubber composition obtained by blending the above components with the rubber component as needed is extruded to match the shape of each rubber layer using an extruder equipped with a die of a predetermined shape, and the extruded composition is bonded together with other tire components on a tire building machine and molded by a conventional method to form an unvulcanized tire. The unvulcanized tire can then be heated and pressurized in a vulcanizer to manufacture the tire. [Example]

[0136] The present disclosure will be described based on examples, but the present disclosure is not limited to only the examples.

[0137] The various chemicals used in the examples and comparative examples are listed below. NR:TSR20 SBR1: SBR1502 manufactured by JSR Corporation (unmodified E-SBR, styrene content: 23.5% by mass, vinyl content: 18% by mole, Mw: 500,000) SBR2: Silica-modified SBR produced in Production Example 1 below (styrene content: 27% by mass, vinyl content: 53% by mole, Mw: 400,000) BR: BR150B manufactured by Ube Industries, Ltd. (unmodified BR, cis content: 97% by mass, Mw: 440,000) Silica: Ultrasil VN3 (N2SA: 175 ml) manufactured by Evonik Degussa 2 / g) Carbon black: N220 (N2SA: 114m) manufactured by Cabot Japan Co., Ltd. 2 / g) Silane coupling agent: Momentive NXT (mercapto silane coupling agent) Antioxidant 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antioxidant 2: Nocrac RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Co., Ltd. Wax: Sunnock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Oil: Diana Process Oil PA32 manufactured by Idemitsu Kosan Co., Ltd. Resin component 1: YS Resin TO-125 (aromatic modified terpene resin, softening point: 125°C) manufactured by Yasuhara Chemical Co., Ltd. Resin component 2: Hariestar P (rosin-modified pentaerythritol ester, softening point 102°C) manufactured by Harima Chemical Co., Ltd. Stearic acid: Camellia stearic acid beads manufactured by NOF Corporation Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Karuizawa Sulfur Co., Ltd. Vulcanization accelerator: Noccela CZ (N-cyclohexyl-2-benzothiazolyl sulfenamide (CBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0138] (Production Example 1) Under a nitrogen atmosphere, 20.8 g of 3-(N,N-dimethylamino)propyltrimethoxysilane (manufactured by Azmax Co., Ltd.) was placed in a 250 mL volumetric flask, and further anhydrous hexane (manufactured by Kanto Chemical Co., Inc.) was added to make the total volume 250 mL to prepare a terminal modifier. Next, into a nitrogen-substituted 30 L pressure-resistant container, 18 L of n-hexane, 540 g of styrene (manufactured by Kanto Chemical Co., Inc.), 1460 g of butadiene, and 17 mmol of tetramethylethylenediamine were added, the temperature was raised to 40 °C, and 3.5 mL of a 0.4 mol / L silicon tetrachloride / hexane solution was added thereto, followed by stirring for 30 minutes. Thereafter, 10.5 mL of butyllithium was added, the temperature was raised to 50 °C, and stirring was carried out for 3 hours. Thereafter, 30 mL of the above terminal modifier was added and stirring was carried out for 30 minutes. After adding 2 mL of methanol (manufactured by Kanto Chemical Co., Inc.) in which 0.2 g of 2,6-tert-butyl-p-cresol (manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.) was dissolved to the reaction solution, the reaction solution was placed in a stainless steel container containing 18 L of methanol to recover the aggregate. The obtained aggregate was dried under reduced pressure for 24 hours to obtain SBR2.

[0139] (Examples and Comparative Examples) According to the formulation contents shown in Table 1, various chemicals shown in Step X were kneaded in a 1.7 L Banbury mixer at a discharge temperature of 100 °C for 5.0 minutes (Step X). Next, the kneaded product of Step X and various chemicals shown in Step Y were kneaded in a 1.7 L Banbury mixer at 140 °C or higher for 30 seconds and further kneaded at a discharge temperature of 150 °C for 3 minutes (Step Y). Then, the kneaded product of Step Y and various chemicals shown in Step F were kneaded using an open roll at about 80 °C according to the kneading time shown in Table 1 (Step F) to obtain an unvulcanized rubber composition. Using the obtained unvulcanized rubber composition, it was molded into the shapes of the first layer (thickness: 3.0 mm), second layer (thickness: 2.0 mm), third layer (thickness: 2.0 mm), and fourth layer (thickness: 0.5 mm) of the tread, and bonded together with other tire members to produce an unvulcanized tire, which was vulcanized at 170 °C to obtain each test tire (size: 205 / 65R15, rim: 15×6JJ, internal pressure: 230 kPa) described in Table 2. The groove depth (deepest part) of the circumferential groove was 4.0 mm.

[0140] <SANS Measurement> From the rubber layer of the tread of each test tire, rubber samples were cut out, measuring 20 mm in length, 20 mm in width, and 1 mm in thickness, with the long axis aligned in the tire circumferential direction. These samples included the interface between the first and second layers, the interface between the second and third layers, and the interface between the third and fourth layers. The thickness of each adjacent rubber layer in each rubber sample was 0.5 mm. Each rubber sample was swollen in deuterated toluene for 12 hours. The equilibrium-swollen rubber sample was then mounted on a sample holder and irradiated with neutrons at room temperature. Scattering intensity curves were obtained from measurements at distances of 2.5 m and 10 m from the sample to the detector. To obtain information on the small-angle side, a scattering intensity curve was also obtained from measurements using a focusing lens at a distance of 10 m from the sample to the detector. The three scattering intensity curves were then combined using the least-squares method. The three scattering intensity curves were combined by fixing the scattering intensity curve obtained from the measurement at a distance of 2.5 m from the sample to the detector, and then shifting the scattering intensity curve obtained from the measurement at a distance of 10 m from the sample to the detector and the scattering intensity curve obtained from the focusing lens measurement, to obtain the scattering intensity curve by SANS measurement. From the scattering intensity curve obtained by SANS measurement, it was found that the scattering vector was 0.12 nm. -1 The scattering intensity was calculated when the scattering vector was 0.12 nm when a neutron beam was irradiated onto a rubber sample including the interface between the first and second layers. -1 The scattering intensity at this time is X1 (cm -1 ), the scattering vector when neutrons were irradiated onto a rubber sample including the interface between the second and third layers was 0.12 nm. -1 The scattering intensity at this time is X2 (cm -1 ), the scattering vector when neutrons were irradiated onto a rubber sample including the interface between the third and fourth layers was 0.12 nm. -1 The scattering intensity at this time is X3(cm -1 ) was decided.

[0141] (SANS device) SANS: SANS measurement equipment attached to the beamline SANS-J of the JRR-3 research reactor owned by the Japan Atomic Energy Agency (Measurement conditions) Neutron wavelength: 6.5Å Neutron flux intensity of neutron beam: 9.9×10 7 neutrons / cm 2 / s Distance from sample to detector: 2.5m, 10m (detector) 2D detector ( 3 He 2D detector and 2D photomultiplier + ZnS / 6 LiF detector)

[0142] <Loss tangent tanδ and complex modulus of elasticity E* measurement> Each rubber test specimen was cut from the rubber layer of the tread portion of each test tire, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, with the long side aligned in the tire circumferential direction. The loss tangent (tanδ) of each specimen was measured using an Iplexer (registered trademark) series dynamic viscoelasticity measuring device manufactured by GABO under conditions of temperatures of 0°C and 30°C, a frequency of 10 Hz, and an elongation strain of 2.5%. The complex modulus (E*) of each rubber test specimen was also measured under conditions of temperatures of 0°C, a frequency of 10 Hz, and an elongation strain of 2.5%. The thickness direction of the sample was the radial direction of the tire.

[0143] <Measurement of glass transition temperature (Tg)> Each rubber test specimen was cut from the rubber layer of the tread portion of each test tire to a length of 20 mm, width of 4 mm, and thickness of 1 mm, with the long side aligned in the tire circumferential direction. A temperature distribution curve of the loss tangent (tanδ) was measured using an Iplexer series manufactured by GABO under conditions of a frequency of 10 Hz and an elongation strain of 2.5%, and the temperature corresponding to the largest tanδ value in the obtained temperature distribution curve (tanδ peak temperature) was taken as the glass transition temperature (Tg). The thickness direction of the sample was the radial direction of the tire.

[0144] <Tensile test> A 1 mm thick dumbbell-shaped No. 7 test piece was cut from inside the rubber layer of the tread portion of each test tire so that the tensile direction was the tire circumferential direction, and a tensile test was carried out in accordance with JIS K 6251:2017 at a temperature of 23°C and a tensile speed of 3.3 mm / sec to measure the elongation at break EB (%). The thickness direction of the sample was the tire radial direction.

[0145] <Chipping resistance> Each test tire was mounted on a standard rim and inflated to the standard internal pressure. The tire was then mounted on a vehicle and driven over rough terrain at a speed of 50 km / h for 4 hours. After the run, the circumferential length of any cracks that had developed on the tire surface was measured, and the maximum circumferential length was determined for each tire. The results were expressed as an index using the following formula, with Comparative Example 1 being set at 100. A larger index indicates smaller cracks and better chipping resistance. (Chipping resistance performance index) = (Circumferential length of the crack in the tire of Comparative Example 3) / (Circumferential length of the crack in each test tire)×100

[0146] [Table 1]

[0147] [Table 2]

[0148] The results in Tables 1 and 2 show that the tires of the present disclosure, in which the difference in neutron beam scattering intensity between adjacent rubber layers constituting the tread is set within a predetermined range, have improved chipping resistance.

[0149] <Embodiment> Examples of embodiments of the present disclosure are provided below.

[0150] [1] A tire having a tread consisting of n rubber layers (n represents an integer of 3 or more), wherein a rubber sample cut out from the tread and including the interface between the kth rubber layer (k represents an integer of 1 or more and n-2 or less) and the k+1th rubber layer counting from the tread surface is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector obtained from the obtained scattering intensity curve is 0.12 nm -1 The scattering intensity at k (cm -1 ) and a rubber sample cut out from the tread, including the boundary surface of the (k+1)th rubber layer and the (k+2)th rubber layer counting from the tread surface, is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector obtained from the obtained scattering intensity curve is 0.12 nm -1 The scattering intensity at k+1 (cm -1 ), then for at least one k, |X k -X k+1 | is 0.10cm -1 Less than (preferably 0.09 cm -1 Less than 0.08cm, preferably 0.08cm -1 Less than 0.07cm, more preferably -1 Below 0.06 cm, particularly preferably -1 (See below) tires. [2] For all k, X k and X k+1 All are 1.00cm -1 Less than 0.90cm (preferably -1 Less than 0.70cm, preferably -1 Less than 0.50 cm, more preferably -1 The tire according to the above [1], wherein [3] A tire according to [1] or [2] above, wherein the tread has circumferential grooves extending continuously in the tire circumferential direction, and the deepest part of the groove bottom of at least one of the circumferential grooves is formed so as to be located radially inward of the outermost part of the second rubber layer counting from the tread surface. [4] The tire according to any one of the above [1] to [3], wherein the total thickness of the tread is 30 mm or less (preferably 25 mm or less, more preferably 20 mm or less, and even more preferably 15 mm or less). [5] The tire according to any one of the above [1] to [4], wherein the tan δ at 0°C of the rubber composition constituting the first rubber layer counted from the tread surface is 0.40 or more (preferably 0.45 or more, more preferably 0.50 or more, and even more preferably 0.55 or more). [6] A tire according to any one of [1] to [5] above, wherein the elongation at break of the rubber composition constituting the first rubber layer counted from the tread surface, as measured in accordance with JIS K 6251:2017, is 460% or more (preferably 470% or more, more preferably 480% or more, and even more preferably 490% or more). [7] A tire according to any one of the above [1] to [6], wherein the complex modulus at 0°C (0°C E*) of the rubber composition constituting the first rubber layer counted from the tread surface is 3.0 MPa or more (preferably 3.5 MPa or more, more preferably 4.0 MPa or more, and even more preferably 4.5 MPa or more). [8] The tire according to any one of the above [1] to [7], wherein the glass transition temperature of the rubber composition constituting the first rubber layer counted from the tread surface is −25°C or higher (preferably −24°C or higher, more preferably −23°C or higher, even more preferably −22°C or higher, and particularly preferably −21°C or higher). [9] The tire according to any one of the above [1] to [8], wherein the tan δ at 30°C of the rubber composition constituting the first rubber layer counted from the tread surface is 0.10 or more (preferably 0.12 or more, more preferably 0.14 or more, even more preferably 0.16 or more, and particularly preferably 0.18 or more).

[10] The tire according to any one of the above [1] to [9], wherein the tan δ at 0°C of the rubber composition constituting the second rubber layer counting from the tread surface is 0.30 or more (preferably 0.35 or more, more preferably 0.40 or more, and even more preferably 0.45 or more).

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

[10] above, wherein the elongation at break of the rubber composition constituting the second rubber layer counting from the tread surface, measured in accordance with JIS K 6251:2017, is 410% or more (preferably 420% or more, more preferably 430% or more, and even more preferably 440% or more).

[12] A tire according to any one of the above [1] to

[11] , wherein the complex modulus at 0°C (0°C E*) of the rubber composition constituting the second rubber layer counting from the tread surface is 2.0 MPa or more (preferably 2.5 MPa or more, more preferably 3.0 MPa or more, and even more preferably 3.5 MPa or more).

[13] A tire according to any one of [1] to

[12] above, wherein the tread has circumferential grooves extending continuously in the tire circumferential direction, and |X1-X2| / (t1 / H) is 0.40 or less, where t1 (mm) is the thickness of a first rubber layer counted from the tread surface, and H (mm) is the groove depth of the circumferential groove. [Explanation of symbols]

[0151] 1...Circumferential groove 2... land department 3. Tread surface 4. Extension of land area 5. Extension line of the deepest part of the bottom of the circumferential groove 6...First layer 7...Second layer 8...Third layer 9. Extension of the outer surface of the second layer

Claims

1. A tire having a tread made of n rubber layers (n represents an integer of 3 or more), A rubber sample cut out from the tread and including the boundary surface of the kth rubber layer (k is an integer of 1 to n-2) and the k+1th rubber layer counting from the tread surface is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector obtained from the obtained scattering intensity curve is 0.12 nm. -1 The scattering intensity at this time is X k (cm -1 )year, A rubber sample cut out from the tread and including the boundary surface of the (k+1)th rubber layer and the (k+2)th rubber layer counted from the tread surface is irradiated with neutrons to perform neutron scattering measurement, and the scattering vector obtained from the obtained scattering intensity curve is 0.12 nm. -1 The scattering intensity at this time is X k+1 (cm -1 ), then for at least one k, |X k -X k+1 | is 0.10 cm -1 The tires are as follows:

2. For all k, X k and X k+1 Both are 1.00 cm -1 2. The tire of claim 1, wherein:

3. The tread has a circumferential groove that extends continuously in the tire circumferential direction, The tire according to claim 1 or 2, wherein the deepest portion of the groove bottom of at least one of the circumferential grooves is formed so as to be located radially inward of an outermost portion of a second rubber layer counting from the tread surface.

4. The tire according to any one of claims 1 to 3, wherein the total thickness of the tread is 30 mm or less.

5. The tire according to any one of claims 1 to 4, wherein a rubber composition constituting the first rubber layer counted from the tread surface has a tan δ at 0°C of 0.40 or more.

6. The tire according to any one of claims 1 to 5, wherein a rubber composition constituting a first rubber layer counted from the tread surface has an elongation at break measured in accordance with JIS K 6251:2017 of 460% or more.

7. The tire according to any one of claims 1 to 6, wherein a complex modulus of elasticity at 0°C (0°C E*) of a rubber composition constituting a first rubber layer counted from the tread surface is 3.0 MPa or more.

8. The tire according to any one of claims 1 to 7, wherein the glass transition temperature of a rubber composition constituting the first rubber layer counted from the tread surface is -25°C or higher.

9. The tire according to any one of claims 1 to 8, wherein a rubber composition constituting a first rubber layer counted from the tread surface has a tan δ at 30°C of 0.10 or more.

10. The tire according to any one of claims 1 to 9, wherein a rubber composition constituting the second rubber layer counting from the tread surface has a tan δ at 0°C of 0.30 or more.

11. The tire according to any one of claims 1 to 10, wherein a rubber composition constituting a second rubber layer counting from the tread surface has an elongation at break measured in accordance with JIS K 6251:2017 of 410% or more.

12. The tire according to any one of claims 1 to 11, wherein a complex modulus at 0°C (0°C E*) of a rubber composition constituting a second rubber layer counting from the tread surface is 2.0 MPa or more.

13. The tread has a circumferential groove that extends continuously in the tire circumferential direction, When the thickness of the first rubber layer counted from the tread surface is t1 (mm) and the groove depth of the circumferential groove is H (mm), |X 1 -X 2 The tire according to any one of claims 1 to 12, wherein | / (t1 / H) is 0.40 or less.

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