tire

Abstract

To provide a tire of which operation stability on a snow road surface is improved even when reducing a tire weight for maximum load capacity.SOLUTION: In a tire, a tread part has a tread end To that is an outer side of a vehicle and a tread end Ti that is an inner side of the vehicle when being attached to the vehicle, and one or more circumferential grooves 11, 12 continuously extending in a tire circumferential direction, and two or more land parts 40, 41 partitioned by the circumferential groove are provided between the tread end and the tread end. The land part has a plurality of lateral grooves 20, 21 extending a tire width direction, the tread part contains a rubber composition having a glass-transition temperature (Tg) of -40°C to -15°C, and the rubber composition contains a rubber component in which a total styrene amount (S) is less than 20.0% by mass. A lateral groove area ratio (R) of at least one of the land parts satisfies a condition (1) of 10%≤R≤40%, and a weight (WT)(kg) and a maximum load capacity (WL)(kg) of the tire satisfy a condition (2) of WT / WL≤0.015.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] In recent years, as environmental regulations have become stricter, there has been an increasing demand for tires with excellent fuel efficiency. One method proposed for reducing fuel consumption is to reduce the thickness of the rubber to reduce the tire weight (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2014-4844 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, tires with relatively thin rubber have a problem in that the rubber surface is easily cooled in low temperature environments, and when the rubber surface cools, its ability to follow the road surface decreases, raising concerns about reduced steering stability on snowy roads.

[0005] An object of the present invention is to improve driving stability on snowy road surfaces even in a tire in which the thickness of the rubber is relatively thin. [Means for solving the problem]

[0006] As a result of intensive research by the present inventors to solve the above-mentioned problems, it has been found that a tire with improved steering stability on snowy road surfaces can be obtained by providing a tire in which the ratio of tire weight to maximum load capacity is a predetermined value or less, in a tread portion thereof, one or more circumferential grooves and land portions separated by the circumferential grooves and having a plurality of lateral grooves, and by controlling the glass transition temperature (Tg) of the rubber composition constituting the tread portion within a predetermined range, controlling the total styrene amount in the rubber component constituting the rubber composition to be equal to or less than a predetermined value, and further controlling the lateral groove area ratio of at least one land portion within a predetermined range. After further research, the present inventors have completed the present invention.

[0007] That is, the present invention provides [1] A tire having a tread portion, the tread portion has a tread end To which is on the outer side of a vehicle when the tread portion is mounted on a vehicle, and a tread end Ti which is on the inner side of the vehicle, and between the tread end To and the tread end Ti, one or more circumferential grooves which extend continuously in the tire circumferential direction and two or more land portions which are partitioned by the circumferential grooves, the land portions having a plurality of lateral grooves which extend in the tire width direction, The tread portion includes a rubber composition having a glass transition temperature (Tg) of −40° C. to −15° C., The rubber composition includes a rubber component having a total styrene content (S) of less than 20.0 mass%, Among the land portions, a lateral groove area ratio (R) of at least one land portion satisfies the following condition (1), The weight (WT) (kg) and maximum load capacity (W L ) (kg) refers to tires that meet the following condition (2): (1) 10%≦R≦40% (2)WT / W L ≦0.015 [2] The tire according to the above [1], wherein the change in Tg of the rubber composition before and after immersion in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components is 15°C or more; [3] The tire according to the above [1] or [2], wherein the total styrene content (S) and the tire weight (WT) satisfy the following condition (3): (3) S / WT≦3.0 [4] The tire according to any one of the above [1] to [3], wherein the rubber composition satisfies the following condition (4): (4) 0℃ tan δ / 30℃ tan δ > 2.0 (0℃ tan δ represents the loss tangent measured under the conditions of temperature 0℃, frequency 10Hz, initial strain 10%, and dynamic strain 2.5%, and 30℃ tan δ represents the loss tangent measured under the conditions of temperature 30℃, frequency 10Hz, initial strain 5%, and dynamic strain 1%.) [5] The tire according to any one of the above [1] to [4], wherein the difference between the rubber hardness of the rubber composition at -10°C and the rubber hardness at 25°C is 3 to 18. [6] The tire according to any one of the above [1] to [5], wherein the rubber component contains a modified styrene-butadiene rubber. [7] The tire according to any one of the above [1] to [6], wherein the rubber composition contains an aromatic ring-containing resin, and the content of the aromatic ring-containing resin is 5 parts by mass or more per 100 parts by mass of the rubber component. [8] The tire according to any one of the above [1] to [7], wherein the rubber composition contains vulcanized rubber particles. [9] A tire according to any one of the above [1] to [8], wherein the number of the circumferential grooves is three or more, and the tread portion has a pair of shoulder land portions separated by a pair of outermost peripheral grooves located at the outermost end in the tire width direction, and two or more center land portions located between the pair of shoulder land portions.

[10] The tire according to [9] above, wherein a groove width of at least one of the pair of outermost circumferential grooves is narrower than a groove width of at least one of the pair of circumferential grooves that is not the outermost circumferential groove.

[11] The tire according to the above [9] or

[10] , wherein one end of a lateral groove of at least one of the pair of shoulder land portions reaches the tread ground edge, and the other end does not reach the outermost circumferential groove and remains within the land portion.

[12] A tire according to any one of the above [9] to

[11] , wherein one end of a lateral groove of at least one of the two or more central land portions is connected to one of the two circumferential grooves defining the central land portion, and the other end of the lateral groove does not reach the other circumferential groove and remains within the land portion.

[13] The tire according to

[12] above, wherein the two circumferential grooves defining the central land portion are composed of a circumferential groove having a larger distance from the tire center line and a circumferential groove having a smaller distance from the tire center line, and the circumferential groove to which the lateral grooves are connected is the circumferential groove having the larger distance from the tire center line. Regarding. Effect of the Invention

[0008] According to the present invention, it is possible to provide a tire that has improved driving stability on snowy roads even when the tire weight relative to the maximum load capacity is reduced. [Brief description of the drawings]

[0009] [Figure 1] 1 is a development view of a tread portion showing one embodiment of the present disclosure. FIG. [Diagram 2] 1 is a development view of a tread portion showing one embodiment of the present disclosure. FIG. [Diagram 3] 1 is a development view of a tread portion showing one embodiment of the present disclosure. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The tire disclosed herein is a tire having a tread portion, the tread portion having a tread end To that is on the outer side of a vehicle when mounted on a vehicle and a tread end Ti that is on the inner side of the vehicle, and having one or more circumferential grooves that extend continuously in the tire circumferential direction and two or more land portions separated by the circumferential grooves between the tread end To and the tread end Ti, the land portions having a plurality of lateral grooves that extend in the tire width direction, the tread portion containing a rubber composition having a glass transition temperature (Tg) of −40° C. to −15° C., the rubber composition containing a rubber component having a total styrene amount (S) of less than 20.0 mass %, a lateral groove area ratio (R) of at least one of the land portions satisfying the following condition (1), and the weight (WT) (kg) and maximum load capacity (W L ) (kg) refers to tires that satisfy the following condition (2). (1) 10%≦R≦40% (2)WT / W L ≦0.015

[0011] Although not intending to be bound by theory, the mechanism by which the tire disclosed herein improves steering stability on snowy road surfaces while being a tire with reduced tire weight relative to the maximum load capacity is as follows. That is, in a tire with reduced tire weight in this way, the rubber surface is easily cooled in a low-temperature environment due to the relatively thin rubber thickness, and when the rubber surface cools, the road surface tracking ability decreases, so there is concern about a decrease in steering stability on snowy road surfaces. However, the tire disclosed herein has the following characteristics: (1) the total styrene content (S) in the rubber component is less than 20.0 mass%, so aggregation by the styrene part in the rubber matrix is ​​suppressed, and it is easy to obtain road surface tracking ability; (2) the Tg of the rubber composition constituting the tread part is -40°C to -15°C, so heat generation is high even in a low-temperature environment; (3) the aggregation of the styrene part is further suppressed by the increase in the rubber surface temperature; and (4) the lateral groove area ratio in the land part is 10 to 40%, so the land part surface is easily deformed even in a low-temperature environment. These features work together to improve the tire's ability to follow the road surface, which is thought to be a remarkable effect of improving handling stability on snowy roads, even with a tire that has a reduced tire weight relative to its maximum load capacity.

[0012] It is preferable that the tire has a change in Tg of the rubber composition of 15° C. or more before and after immersion in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components.

[0013] It is believed that by increasing the Tg of the rubber composition by components such as plasticizers extracted with acetone, it is possible to improve heat generation without impairing conformability even in low-temperature environments. While the change in hardness of rubber with temperature change is thought to be strongly influenced by the rubber matrix, low-molecular-weight plasticizers and resins are in a dissolved state in the rubber, and therefore do not affect the hardness of the rubber surface as much as the rubber matrix does, even in low-temperature environments.

[0014] It is preferable that the total styrene amount (S) and the tire weight (WT) of the tire satisfy the following condition (3). (3) S / WT≦3.0

[0015] It is believed that by reducing the amount of styrene as a result of the reduction in tire weight, it becomes easier to improve steering stability in low-temperature environments. The lighter the tire, the weaker the force pressing the land portion against the road surface, so it is believed that even a small amount of styrene aggregation will have a greater impact on the tread surface as the tire becomes lighter.

[0016] In the tire, it is preferable that the rubber composition satisfies the following condition (4). (4) 0℃ tan δ / 30℃ tan δ > 2.0 (0℃ tan δ represents the loss tangent measured under the conditions of temperature 0℃, frequency 10Hz, initial strain 10%, and dynamic strain 2.5%, and 30℃ tan δ represents the loss tangent measured under the conditions of temperature 30℃, frequency 10Hz, initial strain 5%, and dynamic strain 1%.)

[0017] By making the heat generation rate at low temperatures more than twice that at room temperature, it is believed that sufficient heat generation can be ensured even at low temperatures, and conformance to the road surface can be obtained.

[0018] In the tire, the difference between the rubber hardness of the rubber composition at -10°C and the rubber hardness at 25°C is preferably 3-18.

[0019] It is believed that by reducing the temperature dependency of the hardness of the rubber composition, deterioration of the steering stability in a low-temperature environment can be suppressed.

[0020] In the tire, the rubber component preferably contains a modified styrene-butadiene rubber.

[0021] It is believed that the effect of the functional groups of the modified styrene-butadiene rubber is to improve the dispersion of the filler, thereby preventing the aggregation of the filler and improving the conformability of the rubber composition.

[0022] It is preferable that, in the tire, the rubber composition contains an aromatic ring-containing resin, and the content of the aromatic ring-containing resin is 5 parts by mass or more per 100 parts by mass of the rubber component.

[0023] It is believed that the aromatic ring-containing resin exhibits compatibility with rubber containing a styrene portion in the rubber component (such as styrene-butadiene rubber), and can facilitate improvement of heat build-up without impairing conformability.

[0024] In the tire, the rubber composition preferably contains vulcanized rubber particles.

[0025] Vulcanized rubber particles are particles that have the same hardness as a rubber matrix that has already formed domains, so by incorporating them, fine irregularities are formed on the rubber surface, which is expected to provide an even greater scratching effect on the tread surface, which is already in a highly conformable state.

[0026] It is preferable that the tire has three or more circumferential grooves, and the tread portion has a pair of shoulder land portions separated by a pair of outermost circumferential grooves located at the outermost end in the tire width direction, and two or more center land portions located between the pair of shoulder land portions.

[0027] By dividing the tread into four or more parts widthwise, the load transmitted to each land section is increased, making it possible to increase the pressure with which the rubber surface is pressed against the road surface, which is believed to further improve steering stability on snowy roads.

[0028] In the tire, it is preferable that the groove width of at least one of the pair of outermost grooves is narrower than the groove width of at least one of the circumferential grooves other than the pair of outermost grooves. Moreover, the at least one outermost groove having a groove width narrower than the at least one of the circumferential grooves other than the pair of outermost grooves is preferably the outermost groove on the tread edge To side of the pair of outermost grooves, and more preferably a pair of outermost grooves on both the tread edge To side and the tread edge Ti side.

[0029] When cornering, the pressure in the tread portion of the tire inevitably tends to be higher on the outer side in the tire width direction, and this tendency tends to be greater on the tread end To side than on the tread end Ti side. Therefore, by narrowing the groove width as described above, it is possible to increase the reaction force in the shoulder land portion, which is thought to make it easier to improve steering stability on snowy roads.

[0030] It is preferable that in the tire, a lateral groove of at least one of the pair of shoulder land portions has one end reaching a tread ground contact edge and the other end remaining within the land portion without reaching an outermost circumferential groove.

[0031] Because one end of the lateral groove reaches the tread contact edge, shear deformation at the contact edge is easily achieved, and because the other end of the lateral groove remains within the land portion, a reaction force is also easily obtained, which is thought to make it easier to achieve steering stability on snowy roads.

[0032] It is preferable that, in the tire, one end of a lateral groove in at least one of the two or more center land portions is connected to one of the two circumferential grooves that define the center land portion, and the other end remains within the land portion without reaching the other circumferential groove.

[0033] This is because such a configuration can increase the pattern rigidity of the center land portion.

[0034] It is preferable that the two circumferential grooves defining the center land portion of the tire consist of a circumferential groove having a large distance from the tire center line and a circumferential groove having a small distance from the tire center line, and that the circumferential groove to which the lateral grooves are connected is the circumferential groove having the large distance from the tire center line.

[0035] It is considered that a reaction force from the center of the tire contacting the ground is more easily generated when the lateral groove is connected to a circumferential groove that is distant from the tire center line.

[0036] <Definition> "Tire weight" is expressed in WT (kg). Note that WT is the weight of the tire alone, not including the weight of the rim.

[0037] "Genuine rim" refers to a rim that is specified for each tire by a standard system that includes the standard on which the tire is based, such as the standard rim for the applicable size listed in the "JATMA YEAR BOOK" for JATMA (Japan Automobile Tire Manufacturers Association), the "Measuring Rim" listed in the "STANDARDS MANUAL" for ETRTO (The European Tyre and Rim Technical Organisation), and the "Design Rim" listed in the "YEAR BOOK" for TRA (The Tire and Rim Association, Inc.). In the case of a tire not specified by a standard, it refers to a rim that can be assembled to a rim and can hold internal pressure, that is, the rim with the smallest rim diameter and the next narrowest rim width among rims that do not leak air from between the rim and tire.

[0038] "Normal internal pressure" is the pressure set for each tire by each standard, including the standard on which the tire is based. For JATMA, it is the "maximum pressure", for TRA, it is the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES", and for ETRTO, it is the "INFLATION PRESSURE". For tires not specified in the standard, the normal internal pressure is 250kPa.

[0039] "Normal condition" means a condition in which the tire is mounted on a normal rim, inflated to normal internal pressure, and no load is applied. In this specification, unless otherwise specified, the dimensions of each part of the tire (such as the tire section width Lt) are measured in the normal condition.

[0040] "Maximum load capacity (W L ) (kg)" is determined by the following formulas (1) and (2) where Lt (mm) is the tire section width, Ht (mm) is the tire section height, and Dt (mm) is the tire outer diameter measured under normal conditions. The tire section width Lt is the maximum width between the outer sidewall surfaces under normal conditions, excluding any patterns or letters on the sidewalls. The tire section height Ht is the distance from the bottom surface of the bead to the outermost surface of the tread, and is half the difference between the tire outer diameter and the nominal rim diameter. V = {(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Lt (1) W L =0.000011×V+100 (2)

[0041] "Tread ends Ti, To" refer to the outermost contact points when a tire in a normal state is loaded with the maximum load capacity and contacts a flat surface with a camber angle of 0 degrees. The tread end Ti refers to the tread end that is on the inside of the vehicle when the tire is mounted on the vehicle, and the tread end To refers to the tread end that is on the outside of the vehicle.

[0042] "Tread width TW" is the distance between tread ends To and Ti in the tire width direction W (the left-right direction in Figs. 1 to 3).

[0043] The "land portion" refers to an area in the tread portion that is partitioned by circumferential grooves that extend continuously in the tire circumferential direction between the tread end To and the tread end Ti. For example, when there are two circumferential grooves, the land portion is divided into a pair of shoulder land portions and a center land portion sandwiched between them, and when there are three circumferential grooves, the center land portion is further divided into a land portion that is on the inside of the vehicle when the tire is mounted on the vehicle and a land portion that is on the outside of the vehicle.

[0044] The "lateral groove area ratio (R) (%) of land portion" can be determined from the contact shape of a tire obtained by mounting the tire on a regular rim, maintaining the regular internal pressure (maximum internal pressure), applying ink to the tread portion, applying a load of the maximum load capacity, pressing the tire vertically against paper or the like, and transferring the ink applied to the tread portion. In other words, the proportion (%) of the lateral groove area in a given land portion to the area (area including the lateral groove portion) obtained from the outline of the land portion in the contact shape is the lateral groove area ratio (R) of the land portion. The above method of determining the lateral groove area ratio (R) can be applied in the same way whether the target land portion is one or multiple.

[0045] "Acetone extraction (AE)" refers to immersing a rubber composition in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components. The sample subjected to AE is a vulcanized rubber composition. When the sample is prepared by cutting it out from a tire, it is cut out from the tread portion of the tire.

[0046] "Total styrene content in the rubber component (S)" refers to the total content (mass%) of styrene moieties contained in 100% by mass of the rubber component, and is calculated by Σ(styrene content (mass%) of each styrene-containing rubber × content (mass%) of each styrene-containing rubber in the rubber component / 100). For example, when the rubber component is composed of 30% by mass of a first SBR (styrene content 25% by mass), 60% by mass of a second SBR (styrene content 27.5% by mass), and 10% by mass of BR, the total styrene content (S) in 100% by mass of the rubber component is 24.0% by mass (=25×30 / 100+27.5×60 / 100). The styrene content of the styrene-containing rubber is 1 It is calculated by H-NMR measurement.

[0047] The term "vulcanized rubber particles" refers to a rubber composition obtained by a process different from that of the rubber matrix constituting the rubber composition of the present disclosure, and forms a domain that is distinguished from the rubber matrix constituting the rubber composition of the present disclosure by image analysis such as SEM. Generally, it is reclaimed rubber and powdered rubber, which will be described later, but it is not limited to this, and a rubber composition different from the rubber composition of the present disclosure may be prepared and crushed according to the application. Here, "reclaimed rubber" refers to recycled rubber from used rubber of automobile tires, tubes, and other rubber products as specified in JIS K 6313:2012, and rubber having properties equivalent thereto. Powdered rubber is excluded. In addition, the reclaimed rubber is subjected to devulcanization treatment. "Powdered rubber" refers to vulcanized powdered rubber recycled from waste rubber products. As the raw material for powdered rubber, it is preferable to use crushed tread rubber from used tires, spew and burrs from harvesting, etc. (crushed waste tires) from the viewpoint of environmental consideration and cost.

[0048] "SP value of aromatic ring-containing resin" means the solubility parameter calculated by the Hoy method based on the structure of the compound, and the smaller the difference in SP value between two components, the better the compatibility. The Hoy method is a calculation method described, for example, in KL Hoy "Table of Solubility Parameters", Solvent and Coatings Materials Research and Development Department, Union Carbites Corp. (1985).

[0049] "Oil content" includes the amount of oil contained in oil-extended rubber.

[0050] In this specification, when a numerical range is indicated using "to", the numerical range is intended to include both ends of the range unless otherwise specified.

[0051] <Measurement method> The "Tg of the rubber composition" is determined by measuring a temperature distribution curve of tan δ under the conditions of a frequency of 10 Hz, an initial strain of 10%, an amplitude of ±0.5%, and a heating rate of 2°C / min using an Iplexer series manufactured by GABO Corporation, and determining the temperature (tan δ peak temperature) corresponding to the largest tan δ value in the obtained temperature distribution curve. The sample for Tg measurement is a vulcanized rubber composition having a length of 20 mm, a width of 4 mm, and a thickness of 1 mm. When cutting out from a tire, the sample is cut out from the tread portion of the tire, and the length direction is the tire circumferential direction.

[0052] "0°C tan δ" is the loss tangent measured under the conditions of temperature 0°C, frequency 10Hz, initial strain 10%, dynamic strain 2.5%, and elongation mode. The sample for measuring the loss tangent is a vulcanized rubber composition having a length of 20mm, a width of 4mm, and a thickness of 1mm. When cutting out from a tire, the sample is cut out from the tread portion of the tire.

[0053] "30°C tan δ" is the loss tangent measured under the conditions of temperature 30°C, frequency 10Hz, initial strain 5%, dynamic strain 1%, and elongation mode. The sample for measuring the loss tangent is prepared in the same manner as for 0°C tan δ.

[0054] "Rubber hardness" is the hardness measured at a specified temperature (-10°C or 25°C) using a type A durometer in accordance with JIS K 6253. Samples for measuring rubber hardness are prepared by cutting out a sample from the tread portion that forms the tire's contact surface so that the tire's radial direction is the thickness direction. The measurement is performed by pressing a measuring tool against the sample from the contact surface side of the hardness measurement sample.

[0055] "Styrene content" is 1 It is calculated by H-NMR measurement. For example, it is applied to styrene-containing rubbers such as SBR.

[0056] "Vinyl content (amount of 1,2-bonded butadiene units)" is measured by infrared absorption spectroscopy. For example, it is applied to SBR.

[0057] The "cis 1,4-bond content" is a value calculated by infrared absorption spectrum analysis. For example, it is applied to BR.

[0058] The "weight average molecular weight" can be determined by converting the measured value into a standard polystyrene equivalent value using gel permeation chromatography (GPC) (e.g., GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMALTIPORE HZ-M manufactured by Tosoh Corporation). For example, this applies to SBR, BR, aromatic ring-containing resins, etc.

[0059] "N2SA of carbon black" is measured in accordance with JIS K 6217-2 "Basic properties of carbon black for rubber - Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0060] "N2SA of Silica" is measured by the BET method in accordance with ASTM D3037-93.

[0061] The "ratio of natural rubber in the rubber component" is a value determined by pyrolysis gas chromatography (PyGC). For example, it applies to reclaimed rubber, rubber powder, etc.

[0062] The "average particle size of powdered rubber" is the average particle size on a mass basis calculated from the particle size distribution measured in accordance with JIS Z 8815:1994.

[0063] The "softening point" is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point measuring apparatus.

[0064] <Tires> The tire of the present disclosure will be described below.

[0065] (Tread area) The tread portion has a tread end To that is on the outer side of the vehicle when mounted on the vehicle, and a tread end Ti that is on the inner side of the vehicle, and between the tread end To and the tread end Ti, one or more circumferential grooves that extend continuously in the tire circumferential direction and two or more land portions separated by the circumferential grooves, and the land portions have a plurality of lateral grooves that extend in the tire width direction.

[0066] ≪Circumferential groove, land section≫ The circumferential groove may extend linearly or zigzag. The number of circumferential grooves may be one or more, but if there are two or more circumferential grooves, the land portion is divided into at least a pair of shoulder land portions and a center land portion sandwiched between them, and if there are three or more circumferential grooves, the center land portion is further divided into a land portion that is on the inside of the vehicle when mounted on the vehicle and a land portion that is on the outside of the vehicle. This makes it possible to make the tread patterns of the respective land portions different, which is preferable because it improves the degree of freedom in designing the tread pattern. When the number of circumferential grooves is three or more, a pair of circumferential grooves located on the outermost sides in the tire width direction are called the outermost peripheral grooves. The number of circumferential grooves may be four or more, or may be five or more.

[0067] When the number of circumferential grooves is three or more, a pair of circumferential grooves located at the outermost ends in the tire width direction are referred to as outermost circumferential grooves, and the circumferential grooves other than the outermost circumferential grooves are referred to as central circumferential grooves. As described above, it is preferable that the groove width of at least one of the pair of outermost circumferential grooves is narrower than the groove width of at least one of the central circumferential grooves. It is more preferable that both of the groove widths of the pair of outermost circumferential grooves are narrower than the groove width of the central circumferential groove.

[0068] When the number of circumferential grooves is five or more, it is preferable that the groove width of the central circumferential groove among the three or more central circumferential grooves is wider than the groove width of the pair of central circumferential grooves on both sides. By adopting such a configuration, since the pressure on the outer side in the tire width direction in the tread part of the tire inevitably tends to be high during cornering, by adjusting the groove width as described above, it is possible to increase the reaction force in the shoulder land part, which tends to improve the steering stability on snowy road surfaces.

[0069] <<Yokomizo in the land area>> The land portion has a plurality of lateral grooves extending in the tire width direction. The width of the lateral grooves is not particularly limited, but is usually 8 mm or less. Among the lateral grooves, those with a width of 2 mm or less are particularly called sipes. The direction of the lateral grooves may have a predetermined angle (θ) with respect to the tire width direction W. The range of θ is, for example, 0° to ±80°. For one lateral groove, θ may be constant at any position in the tire width direction, or θ may change depending on the position displacement in the tire width direction.

[0070] From the viewpoint of increasing the pattern rigidity, it is preferable that the lateral groove has one end that does not communicate with the circumferential groove. For example, in at least one of the pair of shoulder land portions, preferably in both shoulder land portions, it is preferable that one end of the lateral groove reaches the tread ground edge, and the other end does not reach the outermost peripheral groove and remains within the land portion. In addition, it is preferable that in at least one center land portion, one end of the lateral groove communicates with one of the two circumferential grooves that define the center land portion, and the other end does not reach the other circumferential groove and remains within the land portion. In addition, when the two circumferential grooves that define the center land portion are composed of a circumferential groove that is far from the tire center line and a circumferential groove that is far from the tire center line, it is preferable that the circumferential groove to which the lateral groove communicates is the circumferential groove that is far from the tire center line.

[0071] Although all of the lateral grooves may be connected to all of the adjacent circumferential grooves, it is preferable that some of the lateral grooves have one end that does not communicate with the adjacent circumferential grooves, and it is more preferable that all of the lateral grooves have one end that does not communicate with the adjacent circumferential grooves.

[0072] <Ratio of land area to horizontal grooves (Condition (1))> In the present disclosure, the groove area ratio (R) is 10% to 40% in at least one land portion. If R is less than 10%, sufficient steering stability on snow cannot be obtained. On the other hand, if R exceeds 40%, the tread pattern rigidity decreases, and steering stability on dry road surfaces decreases.

[0073] The land portion having R in the above range may be at least one of the land portions of the tire of the present disclosure, but it is preferable from the viewpoint of the effect of the present disclosure that it is a land portion closer to the tire center line. The land portion having R in the above range may be a plurality of land portions, or may be all land portions. For example, in the case of three circumferential grooves, it is preferable that R is in the above range in the center land portion rather than the shoulder land portion, and among the center land portions, it is preferable that R is in the above range in the center land portion closer to the tire center line. The land portion having R in the above range may be a shoulder land portion.

[0074] From the viewpoint of the effects of the present disclosure, the range of R is preferably 12% or more, more preferably 14% or more, and even more preferably 15% or more, while it is preferably 37% or less, more preferably 33% or less, and even more preferably 30% or less.

[0075] The lateral groove area ratio can be adjusted by appropriate adjustment in a conventional manner, for example, by appropriately adjusting the shape, width, length, direction, number, etc. of the lateral grooves.

[0076] <Tread pattern> The tread pattern of the tire of the present disclosure is not particularly limited as long as it follows the above description. Hereinafter, the tread pattern of the tire of the present disclosure will be described with reference to the drawings, but the drawings are merely for the purpose of explaining the embodiment, and the contents of the present disclosure are in no way limited by these drawings.

[0077] FIG. 1 is a development view of a tread portion showing an embodiment of the present disclosure. W represents the tire width direction. TW represents the distance in the tire width direction W between the inner tread edge Ti and the outer tread edge To. The tread portion has five linear circumferential grooves 10 (three central circumferential grooves 11 and two outermost grooves 12). The widest central circumferential groove 11 passes over the tire center line CL, a pair of slightly narrower central circumferential grooves 11 pass outside of it, and a pair of narrower outermost grooves 12 pass outside of it. In the shoulder land portion 30, the lateral groove 20 reaches the tread ground contact edge Ti or To at one end, and the other end reaches the outermost groove. In a pair of center land portions 40 that are in contact with the central circumferential groove 11 that passes through the tire center line CL, the lateral grooves (sipes) 21 are connected at both ends to the two central circumferential grooves 11 that define the center land portion. A pair of center land portions 41 located further outboard of the center land portion have no lateral grooves.

[0078] Fig. 2 is a development view of a tread portion showing one embodiment of the present disclosure. Fig. 2 differs from Fig. 1 in that, in a pair of shoulder land portions 30, one end of the lateral grooves 20 reaches the tread edge, but the other end does not reach the outermost circumferential groove.

[0079] Fig. 3 is a development view of a tread portion showing an embodiment of the present disclosure. Fig. 3 differs from Fig. 1 in that, in a pair of shoulder land portions 30, one end of the lateral grooves 20 reaches the tread ground contact edge, but the other end does not reach the outermost peripheral groove, and further, in a pair of center land portions 40 separated by a central circumferential groove 11, one end of the lateral groove (sipe) 21 reaches the central circumferential groove 11 that is farther from the tire center line CL than the two central circumferential grooves 11 that define each center land portion, but the other end does not reach the central circumferential groove 11 that passes through the tire center line and remains within the land portion.

[0080] <Glass transition temperature> The rubber composition constituting the tread portion has a glass transition temperature (Tg) in the range of -40°C to -15°C. If the Tg is less than -40°C or more than -15°C, the heat build-up cannot be sufficiently increased in a low-temperature environment. The Tg is preferably -38°C or higher, and more preferably -35°C or higher. On the other hand, the Tg is preferably -17°C or lower, and more preferably -20°C or lower. The Tg of the rubber composition is measured by the above-mentioned measurement method.

[0081] The Tg of the rubber composition can be adjusted by a common method in the tire industry, specifically, by changing the type and amount of chemicals (e.g., rubber components, fillers, softeners, sulfur, vulcanization accelerators, silane coupling agents, etc.) blended in the rubber composition. For example, the Tg can be increased by increasing the content of resins such as aromatic ring-containing resins, and conversely, the Tg can be decreased by decreasing the content. Therefore, a person skilled in the art can adjust the Tg as appropriate.

[0082] <Total amount of styrene> In the rubber composition constituting the tread portion, the total styrene content (S) in the rubber component is less than 20.0% by mass. If S exceeds 20.0% by mass, the aggregation due to the styrene portion in the rubber matrix (sulfur-crosslinked rubber component) cannot be suppressed, and it becomes difficult to obtain conformability to the road surface. The value of S is preferably 19.5% by mass or less, more preferably 19.0% by mass or less, and even more preferably 18.5% by mass or less. There is no particular restriction on the lower limit of S, and the lower the better from the viewpoint of suppressing aggregation due to the styrene portion, but it is usually preferably 13% by mass or more, more preferably 14% by mass or more, and even more preferably 15% by mass or more.

[0083] (Tire weight and maximum load capacity (Condition (2))) In the tire disclosed herein, the tire weight (WT) (kg) and maximum load capacity (W L ) (kg) satisfies the following condition (2). (2)WT / W L ≦0.015

[0084] That is, the tire of the present disclosure has a maximum load capacity (W L The weight (WT) of the tire relative to the maximum load capacity is equal to or less than a predetermined value. Generally, as the maximum load capacity increases, the weight of the rubber and other components increases, so the tire weight tends to increase. However, the tire disclosed in the present disclosure has a lower tire weight relative to the maximum load capacity than conventional tires. Therefore, it has excellent fuel efficiency. WT / W L is preferably 0.014 or less, more preferably 0.013 or less. L From the viewpoint of fuel economy, there is no particular lower limit for , but it may be, for example, 0.010 or more.

[0085] (Change in Tg of rubber composition before and after acetone extraction) In the tire of the present disclosure, the change in Tg of the rubber composition before and after immersion in acetone for 72 hours in accordance with JIS K 6229 to extract the soluble components is preferably 15°C or more. This is because, as described above, it is believed that by doing so, heat generation can be improved without impairing the tracking ability even in a low-temperature environment. The change in Tg is preferably 16°C or more, more preferably 17°C or more, and even more preferably 18°C ​​or more. The upper limit of the change in Tg is not particularly limited, but may be, for example, 25°C or less, or 23°C or less. The acetone extraction is performed by the above-mentioned method.

[0086] (Total styrene content and tire weight (condition (3))) In the tire of the present disclosure, it is preferable that the total styrene amount (S) and the tire weight (WT) satisfy the following condition (3). (3) S / WT≦3.0

[0087] This is because, as described above, it is believed that even if the tire weight is reduced, it is easier to improve the steering stability in a low-temperature environment. S / WT is preferably 2.9 or less, more preferably 2.8 or less, and even more preferably 2.7 or less. On the other hand, there is no particular lower limit for S / WT from the viewpoint of steering stability, but it is usually 1.8 or more, preferably 1.9 or more, and more preferably 2.0 or more.

[0088] (0℃ tan δ and 30℃ tan δ (Condition (4))) In the tire of the present disclosure, it is preferable that the rubber composition constituting the tread portion satisfies the following condition (4). (4) 0℃ tan δ / 30℃ tan δ > 2.0 (0℃ tan δ represents the loss tangent measured under the conditions of temperature 0℃, frequency 10Hz, initial strain 10%, and dynamic strain 2.5%, and 30℃ tan δ represents the loss tangent measured under the conditions of temperature 30℃, frequency 10Hz, initial strain 5%, and dynamic strain 1%.)

[0089] By doing so, as described above, it is believed that sufficient heat generation can be ensured even at low temperatures, and that road surface conformity can be obtained. 0°C tan δ / 30°C tan δ is preferably 2.1 or more, more preferably 2.2 or more, and even more preferably 2.3 or more. On the other hand, from the viewpoint of heat generation, there is no particular upper limit for 0°C tan δ / 30°C tan δ, but it is usually 2.7 or less, preferably 2.5 or less, and even more preferably 2.4 or less.

[0090] The 0°C tan δ value and the 30°C tan δ value can be adjusted by a common method in the tire industry, specifically, by changing the type and amount of chemicals (e.g., rubber components, fillers, softeners, sulfur, vulcanization accelerators, silane coupling agents, etc.) blended into the rubber composition. For example, the 0°C tan δ value and the 30°C tan δ value can be reduced by reducing the content of silica or aromatic ring-containing resin, and conversely, the 0°C tan δ value and the 30°C tan δ value can be increased by increasing the content. Therefore, a person skilled in the art can appropriately adjust the 0°C tan δ value and the 30°C tan δ value according to the target 0°C tan δ / 30°C tan δ.

[0091] (Rubber hardness at -10℃ and 25℃) In the tire of the present disclosure, the difference between the rubber hardness at -10°C and the rubber hardness at 25°C of the rubber composition constituting the tread portion is preferably 3 to 18. By doing so, it is believed that the deterioration of the steering stability in a low temperature environment can be suppressed as described above. The hardness difference is preferably 4 or more, more preferably 5 or more, and even more preferably 6 or more. On the other hand, the hardness difference is preferably 17 or less, more preferably 16 or less, and even more preferably 15 or less. The rubber hardness is measured by the above-mentioned measurement method.

[0092] The rubber hardness of the rubber composition can be adjusted by a common method in the tire industry, specifically, by changing the type and amount of chemicals (e.g., rubber components, fillers, softeners, sulfur, vulcanization accelerators, silane coupling agents, etc.) blended in the rubber composition. For example, the rubber hardness can be lowered by increasing the oil content, and conversely, the rubber hardness can be increased by decreasing the oil content. Therefore, a person skilled in the art can adjust the rubber hardness as appropriate.

[0093] <Rubber composition> Regarding the rubber composition constituting the tread portion of the tire of the present disclosure, the components blended into the rubber composition will be described below.

[0094] (Rubber component) The rubber component preferably contains at least one selected from the group consisting of isoprene-based rubber, styrene-butadiene rubber (SBR), and butadiene rubber (BR), more preferably contains SBR, and even more preferably contains SBR and BR. The rubber component may consist of only SBR and BR.

[0095] ≪SBR≫ There is no particular limitation on the SBR, and examples thereof include solution-polymerized SBR (S-SBR), emulsion-polymerized SBR (E-SBR), and modified SBRs thereof (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, silicon compounds, etc. Among these, S-SBR and modified SBR are preferred. Furthermore, hydrogenated products of these SBRs (hydrogenated SBR), etc. can also be used. These SBRs may be used alone or in combination of two or more.

[0096] Examples of S-SBR that can be used in the present disclosure include S-SBR manufactured and sold by JSR Corporation, Sumitomo Chemical Co., Ltd., Ube Industries, Ltd., Asahi Kasei Corporation, ZS Elastomers Co., Ltd., and the like.

[0097] 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 wet grip performance and abrasion resistance. Also, from the viewpoints of temperature dependency of grip performance and blow resistance, it is preferably 60% by mass or less, and from the viewpoint of the effects of the present disclosure, it is preferably 35% by mass or less, and more preferably 30% by mass or less. The styrene content of SBR is measured by the above-mentioned measurement method.

[0098] 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. Also, 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, breaking elongation, and abrasion resistance. The vinyl content of SBR is measured by the above-mentioned measurement method.

[0099] 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. 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. The Mw of SBR is measured by the above-mentioned measurement method.

[0100] In the case where SBR is contained, the content in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 50% by mass or more, and even more preferably 60% by mass or more, from the viewpoint of the effects of the present disclosure. The content of SBR may be 100% by mass, or is preferably 95% by mass or less, more preferably 90% by mass or less, and even more preferably 80% by mass or less.

[0101] The BR is not particularly limited, and may be, for example, a BR having a cis 1,4 bond content (cis content) of less than 50% (low cis BR), a BR having a cis 1,4 bond content of 90% or more (high cis BR), a rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, a BR containing syndiotactic polybutadiene crystals (SPB-containing BR), modified BR (high cis modified BR, low cis modified BR), or the like, which are common in the tire industry. These BRs may be used alone or in combination of two or more. The cis 1,4 bond content of BR is measured by the above-mentioned measurement method.

[0102] The modified BR is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and includes those in which the terminals of the modified BR molecule are bonded with tin-carbon bonds (tin-modified BR), butadiene rubber having a condensed alkoxysilane compound at the active terminal of the butadiene rubber (silica-modified BR), etc. Examples of such modified BR include tin-modified BR and silica-modified BR manufactured and sold by ZS Elastomer Co., Ltd.

[0103] From the viewpoint of abrasion resistance, the weight average molecular weight (Mw) of BR is preferably 300,000 or more, more preferably 350,000 or more, and even more preferably 400,000 or more. From the viewpoint of crosslink uniformity, it is preferably 2,000,000 or less, and more preferably 1,000,000 or less. The Mw of BR is measured by the above-mentioned measurement method.

[0104] When BR is contained, the content in 100% by mass of the rubber component is preferably 3% by mass or more, more preferably 5% by mass or more, and even more preferably 10% by mass or more, from the viewpoint of the effects of the present disclosure. The content of BR is preferably 40% by mass or less, more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0105] <Isoprene rubber> As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are common in the tire industry, can be used. In addition to unmodified natural rubber (NR), natural rubber also includes modified natural rubber such as epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), deproteinized natural rubber (DPNR), high-purity natural rubber, and grafted natural rubber. These isoprene-based rubbers may be used alone or in combination of two or more.

[0106] The NR is not particularly limited, and any NR commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0107] When an isoprene-based rubber is contained, the content thereof in 100% by mass of the rubber component is preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less, from the viewpoint of the present disclosure. In addition, when an isoprene-based rubber is contained, the lower limit of the content is not particularly limited, and may be 0% by mass.

[0108] <Other rubber components> The rubber component according to the present disclosure may contain rubber components other than the isoprene-based rubber, SBR, and BR. As the other rubber components, crosslinkable rubber components generally used in the tire industry can be used, such as styrene-isoprene-butadiene copolymer rubber (SIBR), styrene-isobutylene-styrene block copolymer (SIBS), chloroprene rubber (CR), acrylonitrile-butadiene rubber (NBR), hydrogenated nitrile rubber (HNBR), butyl rubber (IIR), ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), hydrin rubber, and the like. These other rubber components may be used alone or in combination of two or more. The content of the other rubber in the rubber component may be 0% by mass.

[0109] (Filler) The rubber composition according to the present disclosure preferably contains silica as a filler, more preferably contains carbon black and silica, or is preferably composed of carbon black and silica.

[0110] <Carbon black, silica> As the carbon black, any carbon black commonly used in the tire industry can be appropriately used, such as N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. These carbon blacks may be used alone or in combination of two or more kinds.

[0111] From the perspective of reinforcement, the nitrogen adsorption specific surface area (N2SA) of carbon black is 80m 2 / g or more is preferable, and 90m 2 / g or more is more preferable, and 100m 2 From the viewpoints of fuel economy and processability, N2SA is more preferably 200m 2 / g or less is preferable, and 170m 2 / g or less is more preferable, and 155m 2 The N2SA of carbon black is measured by the above-mentioned measuring method.

[0112] When carbon black 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, and even more preferably 5 parts by mass or more from the viewpoint of abrasion resistance and wet grip performance, and is preferably 50 parts by mass or less, more preferably 30 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 10 parts by mass or less from the viewpoint of fuel efficiency.

[0113] The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica), silica prepared by a wet method (hydrated silica), or other silica 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.

[0114] The nitrogen adsorption specific surface area (N2SA) of silica is set at 140m from the viewpoints of fuel efficiency and wear resistance. 2 / g or more is preferable, and 170m 2 From the viewpoints of fuel efficiency and processability, it is more preferable that the tensile strength is 350 m 2 / g or less is preferable, and 300m 2 / g or less is more preferable, and 250m 2 The N2SA of silica is measured by the above-mentioned measuring method.

[0115] When silica is contained, the content per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 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, and is preferably 180 parts by mass or less, more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less from the viewpoint of abrasion resistance.

[0116] 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 abrasion resistance performance, and is preferably 200 parts by mass or less, more preferably 170 parts by mass or less, even more preferably 150 parts by mass or less, and even more preferably 120 parts by mass or less from the viewpoints of fuel economy performance and elongation at break.

[0117] The proportion of silica to the total content of silica and carbon black is preferably 60 mass % or more, more preferably 70 mass % or more, further preferably 80 mass % or more, and particularly preferably 85 mass % or more.

[0118] Other fillers Fillers other than silica and carbon black may include aluminum hydroxide, calcium carbonate, alumina, clay, talc, and other fillers that have been commonly used in the tire industry. In addition, in the present disclosure, vulcanized rubber particles may be blended. Examples of vulcanized rubber particles include reclaimed rubber and rubber powder. One or more types of vulcanized rubber particles may be used.

[0119] <Recycled rubber, rubber powder> Rubber compositions containing recycled rubber or rubber powder usually have the problem of easily deteriorating breaking elongation, but in the present disclosure, when the rubber component contains a rubber containing a styrene portion (such as styrene butadiene rubber) and an aromatic ring resin, the rubber containing a styrene portion is compatible with the aromatic ring-containing resin, and therefore, due to the effect of the compatibility between the rubber containing a styrene portion and the aromatic ring-containing resin, it is considered that even when recycled rubber or rubber powder is compounded, the problem of deterioration in breaking elongation, etc. is unlikely to occur. At least one selected from recycled rubber and rubber powder may be only recycled rubber, may be only rubber powder, or may be a combination of recycled rubber and rubber powder, but it is preferable to use only recycled rubber.

[0120] The type of reclaimed rubber may be any of reclaimed rubber from tubes, reclaimed rubber from tires, and other reclaimed rubbers, and a combination of a plurality of types may also be used. Among these, reclaimed rubber from tires is preferred.

[0121] The reclaimed rubber may be obtained by a known manufacturing method. For example, the most common pan method (oil method), as well as a method using a Banbury mixer / two-screw reactive extruder, a method using microwaves, a method using ultrasonic waves, and a method using electron beam irradiation have been developed, and any method may be used. Commercially available reclaimed rubber may also be used. One specific example of a method for producing reclaimed rubber is a method in which vulcanized rubber powder is put into an internal mixer or extruder, heated to 100 to 250°C, and treated for 5 to 50 minutes while applying mechanical shearing force to devulcanize and regenerate the rubber. Commercially available products include those manufactured and sold by Muraoka Rubber Co., Ltd., Asahi Reclaimed Rubber Co., Ltd., and the like.

[0122] The rubber component in the reclaimed rubber preferably has a natural rubber content of 40% by mass or more, more preferably 50% by mass or more, and even more preferably 70% by mass or more. When the natural rubber content is within the above range, excellent elongation at break tends to be obtained. The natural rubber content is measured by the above-mentioned measurement method.

[0123] Reclaimed rubber can be used alone or in combination of two or more types.

[0124] When reclaimed rubber is contained, the content per 100 parts by mass of the diene rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more from the viewpoint of environmental consideration. Also, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less from the viewpoint of easily exerting the effects of the present disclosure.

[0125] Rubber powder is vulcanized rubber powder made by recycling waste rubber products, and the raw material for rubber powder is not particularly limited to the type of waste rubber, and examples include diene rubbers such as NR, SBR, BR, and IR. Rubber powder that can be used includes 30 mesh pass or 40 mesh pass products in Tyler mesh. Rubber powder can be used alone or in combination of two or more types.

[0126] The average particle size of the powdered rubber is preferably 70 μm or more, more preferably 100 μm or more. The average particle size is preferably 1 mm or less, more preferably 750 μm or less. The average particle size of the powdered rubber is measured by the above-mentioned measuring method.

[0127] The rubber powder contains preferably 40% by mass or more of natural rubber, more preferably 50% by mass or more, and even more preferably 60% by mass or more of natural rubber. When the natural rubber content is within the above range, excellent elongation at break tends to be obtained. The natural rubber content is measured by the above-mentioned measuring method.

[0128] Examples of the rubber powder that can be used include those manufactured and sold by Muraoka Rubber Industries Co., Ltd., Asahi Reclaimed Rubber Co., Ltd., Lehigh Technologies Inc., etc. One type of rubber powder can be used, or two or more types can be used in combination.

[0129] When the powdered rubber is contained, the content per 100 parts by mass of the diene rubber component is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more from the viewpoint of environmental consideration. Also, the content is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 15 parts by mass or less, from the viewpoint of easily exerting the effects of the present disclosure.

[0130] From the viewpoint of environmental consideration, the content of the vulcanized rubber particles 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, based on 100 parts by mass of the diene rubber component. Also, from the viewpoint of easily exerting the effects of the present disclosure, the content is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0131] (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 of the silane coupling agent 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 vinyl triethoxysilane and vinyl trimethoxysilane; amino-based silane coupling agents such as 3-aminopropyl triethoxysilane, 3-aminopropyl trimethoxysilane and 3-(2-aminoethyl) aminopropyl triethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyl triethoxysilane and γ-glycidoxypropyl trimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyl trimethoxysilane and 3-nitropropyl triethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyl trimethoxysilane and 3-chloropropyl triethoxysilane. Among these, sulfide-based silane coupling agents and mercapto-based silane coupling agents are preferred. These silane coupling agents may be used alone or in combination of two or more.

[0132] The mercapto-based silane coupling agent is preferably a compound represented by the following formula (7) and / or a compound containing a bonding unit A represented by the following formula (8) and a bonding unit B represented by the following formula (9). [ka] (In the formula, R 101 , R 102 , and R 103 are each independently an alkyl group having 1 to 12 carbon atoms, an alkoxy group 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 112represents an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, an aryl group having 6 to 30 carbon atoms, or an aralkyl group 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, a halogen atom, an alkyl group having 1 to 30 carbon atoms, an alkenyl group having 2 to 30 carbon atoms, or an alkynyl group having 2 to 30 carbon atoms, which may be substituted by a hydroxyl or carboxyl group; 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.)

[0133] Examples of the compound represented by formula (7) include 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and the compound represented by the following formula (10) (Si363 manufactured by Evonik Degussa), and the compound represented by the following formula (10) can be preferably used. These may be used alone or in combination of two or more kinds. [ka]

[0134] Examples of compounds containing a bond unit A represented by formula (8) and a bond unit B represented by formula (9) include those manufactured and sold by Momentive, Inc. These may be used alone or in combination of two or more.

[0135] The content of silane coupling agent with respect to 100 parts by mass of silica (when multiple silane coupling agents are used, the total amount of all of them) 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 increasing 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.

[0136] As the filler, in addition to carbon black and silica, other fillers may be used. Such fillers are not particularly limited, and any fillers generally 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.

[0137] (Aromatic ring-containing resin) In the present disclosure, the term "aromatic ring-containing resin" means a resin containing an aromatic ring in its structure. Specifically, the aromatic ring-containing resin is a homopolymer or copolymer of a monomer containing an aromatic ring-containing monomer, and the aromatic ring-containing monomer is preferably an aromatic ring-containing resin having at least one hydroxyl group. The aromatic ring-containing resin is not particularly limited as long as it is a resin used in this field and contains an aromatic ring. Examples of such resins include C9 petroleum resins, C5C9 petroleum resins, alkylphenol resins, coumarone resins, aromatic modified terpene resins, terpene phenol resins, and the like. Among them, it is preferable to include at least one of C9 petroleum resins and terpene phenol resins, and at least one of C9 petroleum resins and terpene phenol resins is more preferable, because it has better compatibility with SBR. The aromatic ring-containing resin may be only C9 petroleum resins, or may be only terpene phenol resins. In addition, the resin in which the aromatic ring-containing monomer has at least one hydroxyl group is preferably at least one of an alkylphenol resin and a terpene phenol resin, and more preferably a terpene phenol resin. The aromatic ring-containing resin may be used alone or in combination of two or more kinds.

[0138] <C9 petroleum resin> Examples of C9 petroleum resins include resins obtained by cationic polymerization of monomers such as styrene, vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fractions) having 8 to 10 carbon atoms. For example, C9 petroleum resins manufactured and sold by ENEOS Corporation and the like can be used. Specific examples of C9 petroleum resins include styrene resins. Although the styrene resins are not particularly limited, α-methylstyrene resins (AMS) are preferably used. Examples of α-methylstyrene resins include homopolymers of α-methylstyrene (poly-α-methylstyrene) and copolymers of α-methylstyrene with other compounds including aromatic compounds and phenolic compounds. Examples of other compounds that can constitute this copolymer include styrene, methylstyrene, methoxystyrene, and divinylbenzene, and examples of this copolymer include copolymers of α-methylstyrene and styrene. Examples of α-methylstyrene resins that are preferably used include those manufactured by Kraton.

[0139] <C5C9 petroleum resin> C5C9 petroleum resin is a resin obtained by copolymerizing a C5 fraction and a C9 fraction, and is also called an aliphatic / aromatic copolymerized petroleum resin. The above petroleum resin may be hydrogenated. The C5 fraction may be obtained by thermal cracking of naphtha, and the components contained in the C5 fraction may be olefinic hydrocarbons such as 1-pentene, 2-pentene, 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene, and diolefinic hydrocarbons such as 2-methyl-1,3-butadiene (isoprene), 1,2-pentadiene, 1,3-pentadiene (piperylene), and 3-methyl-1,2-butadiene. The C9 fraction is the same as the C9 fraction for the above-mentioned C9 petroleum resin. Examples of C5C9 petroleum resins include copolymers mainly composed of indene, styrene, vinyltoluene, isoprene and piperylene, copolymers mainly composed of indene, styrene, vinyltoluene and piperylene, etc. Examples of C5C9 petroleum resins that can be used include those manufactured and sold by LUHUA, Qilong, Tosoh Corporation, etc.

[0140] <Alkylphenol resin> Examples of the alkylphenol resin include alkylphenol-aldehyde condensation resins obtained by reacting alkylphenol with aldehydes such as formaldehyde, acetaldehyde, and furfural using an acid or alkali catalyst; alkylphenol-alkyne condensation resins obtained by reacting alkylphenol with alkynes such as acetylene; and modified alkylphenol resins obtained by modifying these resins with compounds such as cashew nut oil, tall oil, linseed oil, various animal and vegetable oils, unsaturated fatty acids, rosin, alkylbenzene resins, aniline, and melamine. Examples of the alkylphenols constituting the alkylphenol resin include cresol, xylenol, tert-butylphenol, octylphenol, and nonylphenol. Examples of the alkylphenol resin that can be used include those manufactured and sold by Taoka Chemical Co., Ltd., etc.

[0141] <Coumarone resin> The coumarone resin is a resin containing coumarone as a main component, and examples thereof include coumarone resin, coumarone-indene resin, copolymer resin containing coumarone, indene, and styrene as main components, etc. As the coumarone resin, for example, those manufactured and sold by Nippon Paint Chemical Co., Ltd. can be used.

[0142] <Aromatic modified terpene resin> Aromatic modified terpene resin is a resin obtained by copolymerizing a terpene compound as a monomer with an aromatic compound. A terpene compound is a polymer of isoprene (C5H8), and is a monoterpene (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) and other compounds having a basic skeleton of terpene, which is classified as one of the following: α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, camphene, tricyclene, sabinene, paramentadienes, and carenes. Examples of aromatic compounds include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of aromatic modified terpene resins that can be used include those manufactured and sold by Yasuhara Chemical Co., Ltd. and the like.

[0143] <Terpene phenol resin> The terpene phenol resin is a resin obtained by copolymerizing a terpene compound and a phenolic compound as monomers. The terpene phenol resin may be hydrogenated or may not be hydrogenated. The terpene compound is the same as the terpene compound for the aromatic modified terpene resin described above. Examples of the phenolic compound include phenol, bisphenol A, cresol, and xylenol, and phenol is preferred. The terpene phenol resin may be, for example, one manufactured and sold by Yasuhara Chemical Co., Ltd.

[0144] <Mw of aromatic ring-containing resin> The weight average molecular weight (Mw) of the aromatic ring-containing resin is preferably 300 or more, more preferably 400 or more, and even more preferably 500 or more, from the viewpoint of being less volatile and having good grip performance. Moreover, the Mw is preferably 10,000 or less, more preferably 2,500 or less, more preferably 1,500 or less, and even more preferably 1,200 or less. The Mw of the aromatic ring-containing resin is measured by the above-mentioned measurement method.

[0145] <Softening point of aromatic ring-containing resin> The softening point of the aromatic ring-containing resin is preferably 160° C. or less, more preferably 145° C. or less, and even more preferably 130° C. or less. The softening point is preferably 20° C. or more, more preferably 35° C. or more, and even more preferably 50° C. or more. When the softening point of the aromatic ring-containing resin is within the above range, the effects of the present disclosure tend to be more favorably exhibited. The softening point of the aromatic ring-containing resin is measured by the above-mentioned measurement method.

[0146] <SP value of aromatic ring-containing resin> The SP value of the aromatic ring-containing resin is preferably 8.00 or more, more preferably 8.50 or more, and even more preferably 8.80 or more. The SP value is preferably 11.00 or less, more preferably 10.00 or less, and even more preferably 9.50 or less. When the SP value of the aromatic ring-containing resin is within the above range, the compatibility with SBR is improved, and the "pseudo-connection of SBR-aromatic ring-containing resin-carbon black" is easily effectively expressed, and the effect of the present disclosure tends to be better exhibited. The SP value of the aromatic ring-containing resin is measured by the above-mentioned measurement method.

[0147] <Content of aromatic ring-containing resin> The content of the aromatic ring-containing resin relative to 100 parts by mass of the diene rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, more preferably 1.5 parts by mass or more, even more preferably 2.0 parts by mass or more, and even more preferably 5.0 parts by mass or more, because the "pseudo-connection of SBR-aromatic ring-containing resin-carbon black" is easily effectively expressed. The content is preferably 30.0 parts by mass or less, more preferably 20.0 parts by mass or less, and even more preferably 10.0 parts by mass or less. When the content of the aromatic ring-containing resin is within the above range, the effect of the present disclosure tends to be better exhibited.

[0148] (Other compounding agents) In addition to the above-mentioned components, the rubber composition according to the present disclosure may appropriately contain compounding agents commonly used in the tire industry, such as softeners, waxes, processing aids, stearic acid, zinc oxide, antioxidants, vulcanizing agents, and vulcanization accelerators.

[0149] <Softener> The rubber composition according to the present disclosure preferably contains a softener. Examples of the softener include oil, liquid rubber, ester plasticizer, and resin other than the aromatic ring-containing resin. The softener may be used alone or in combination of two or more.

[0150] Examples of the oil include process oil, vegetable oil, and animal oil. Examples of the process oil include paraffin-based process oil, naphthenic process oil, and aromatic process oil. In addition, as an environmental measure, process oil with a low content of polycyclic aromatic compound (PCA) compounds can be used. Examples of the low PCA content process oil include light extract solvate (MES), treated distillate aromatic extract (TDAE), and heavy naphthenic oil. One type of oil may be used alone, or two or more types may be used in combination.

[0151] When oil is contained, the content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 7 parts by mass or more, and even more preferably 10 parts by mass or more from the viewpoint of processability, and is preferably 40 parts by mass or less, more preferably 30 parts by mass or less, and even more preferably 20 parts by mass or less from the viewpoint of abrasion resistance.

[0152] 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 kinds.

[0153] When the liquid rubber is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. The content of the liquid rubber is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

[0154] 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), trixylenyl phosphate (TXP), etc. These ester-based plasticizers may be used alone or in combination of two or more.

[0155] When an ester plasticizer is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more, even more preferably 3 parts by mass or more, and particularly preferably 5 parts by mass or more. The content of the ester plasticizer is preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less.

[0156] The resin other than the aromatic ring-containing resin is not particularly limited, and examples thereof include terpene-based resins, rosin-based resins, etc., which are commonly used in the tire industry. Among these resins, one type may be used alone, or two or more types may be used in combination.

[0157] The content of the softener per 100 parts by mass of the rubber component (the total amount when multiple softeners are used in combination) 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, and is preferably 120 parts by mass or less, more preferably 100 parts by mass or less, even more preferably 50 parts by mass or less, even more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less from the viewpoint of processability.

[0158] <Wax> 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, and more preferably 1 part by mass or more, from the viewpoint of weather resistance of the rubber, and is preferably 10 parts by mass or less, and more preferably 5 parts by mass or less, from the viewpoint of preventing whitening of the tire due to bloom.

[0159] <Processing aids> Examples of the processing aid include fatty acid metal salts, fatty acid amides, amide esters, silica surfactants, fatty acid esters, mixtures of fatty acid metal salts and amide esters, mixtures of fatty acid metal salts and fatty acid amides, etc. These processing aids may be used alone or in combination of two or more. Examples of the processing aids that can be used include those commercially available from Schill+Seilacher, Performance Additives, etc.

[0160] 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 viewpoints of abrasion resistance and breaking strength.

[0161] <Anti-aging agent> The antiaging agent is not particularly limited, but examples thereof include amine-based, quinoline-based, quinone-based, phenol-based, and imidazole-based compounds, and carbamic acid metal salts, and the like. Phenylenediamine-based antiaging agents 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 antiaging agents such as 2,2,4-trimethyl-1,2-dihydroquinoline polymer and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline are preferred. These antiaging agents may be used alone or in combination of two or more.

[0162] 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 part by mass or more, from the viewpoint of ozone crack resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance and wet grip performance.

[0163] <Stearic acid> When stearic acid is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of vulcanization speed.

[0164] <Zinc oxide> 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 part by mass or more, from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5 parts by mass or less, from the viewpoint of abrasion resistance.

[0165] <Vulcanizing agent> As the vulcanizing agent, sulfur is preferably used, and examples of the sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.

[0166] 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 sufficient vulcanization reaction. Also, 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. Note that, when oil-containing sulfur is used as a vulcanizing agent, the content of the vulcanizing agent is the total content of the pure sulfur contained in the oil-containing sulfur.

[0167] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensates, sodium 1,6-hexamethylene-dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. As these vulcanizing agents other than sulfur, commercially available products from Taoka Chemical Co., Ltd., Lanxess Co., Ltd., Flexis, etc. can be used.

[0168] <Vulcanization accelerator> Examples of the vulcanization accelerator 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.

[0169] 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 them, N-cyclohexyl-2-benzothiazolylsulfenamide (CBS) is preferred.

[0170] Examples of the guanidine vulcanization accelerator 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 them, 1,3-diphenylguanidine (DPG) is preferable.

[0171] Examples of the thiazole-based vulcanization accelerator include 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, etc. Among these, 2-mercaptobenzothiazole is preferred.

[0172] When a vulcanization accelerator is contained, the content per 100 parts by mass of the rubber component is preferably 1 part by mass or more, more preferably 2 parts by mass or more. The content per 100 parts by mass of the rubber component is preferably 8 parts by mass or less, more preferably 7 parts by mass or less, and even more preferably 6 parts by mass or less. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be secured.

[0173] <Manufacturing> The rubber composition according to the present disclosure can be produced by a known method, for example, by kneading the above-mentioned components using a rubber kneading device such as an open roll or an internal kneader (such as a Banbury mixer or kneader).

[0174] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and the vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and the 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 a plurality of steps as desired.

[0175] The kneading conditions are not particularly limited, but examples thereof include a method in which in the base kneading step, kneading is performed for 3 to 10 minutes at a discharge temperature of 150 to 170° C., and in the final kneading step, kneading is performed for 1 to 5 minutes at 70 to 110° C. The vulcanization conditions are not particularly limited, but examples thereof include a method in which vulcanization is performed for 10 to 30 minutes at 150 to 200° C.

[0176] The tire of the present disclosure, which is made of the rubber composition, can be manufactured by a normal method using the rubber composition. That is, an unvulcanized rubber composition, in which the above-mentioned components are mixed with the rubber component as necessary, is extruded into a tread shape, laminated together with other tire components on a tire building machine, and molded by a normal method to form an unvulcanized tire, and the unvulcanized tire is heated and pressurized in a vulcanizer to manufacture a tire. Note that the above tread refers to the outermost layer of the tread when the tread portion is made of multiple layers.

[0177] <Application> The tire of the present disclosure can be suitably used as a passenger car tire, a truck / bus tire, a motorcycle tire, or a racing tire, and is preferably used as a passenger car tire. Note that a passenger car tire is a tire that is intended to be mounted on a four-wheeled vehicle and has a maximum load capacity of 1000 kg or less. The tire of the present disclosure can be used as an all-season tire, a summer tire, or a winter tire such as a studless tire, and is preferably used as a winter tire. EXAMPLES

[0178] The present disclosure will be specifically described below based on examples, but the present disclosure is not limited to these examples.

[0179] <Various chemicals> The various chemicals used in the examples and comparative examples are listed below. SBR1: Terminally modified S-SBR produced in Production Example 1 described later (styrene content: 25% by mass, vinyl content: 25% by mole, Mw: 250,000, non-oil extended product) SBR2: HPR850 manufactured by JSR Corporation (styrene content: 27.5% by mass, vinyl content: 59.0% by mass, non-oil extended product) BR: UBEPOL BR (registered trademark) 150B manufactured by Ube Industries, Ltd. (cis content: 97%, Mw: 440,000) Vulcanized rubber particle 1: Reclaimed rubber containing 73% natural rubber by mass (available from Muraoka Rubber Industry Co., Ltd.) Vulcanized rubber particles 2: Rubber powder W2-A (available from Asahi Reclaimed Rubber Co., Ltd.) Carbon black: Diablack N220 (N2SA: 115m) manufactured by Mitsubishi Chemical Corporation 2 / g) Silica: ULTRASIL® VN3 (N2SA: 175 ml) manufactured by Evonik Degussa 2 / g) Silane coupling agent: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Evonik Degussa Oil: H&R VIVATEC 500 (TDAE oil) Aromatic ring-containing resin: Sylvares SA85 manufactured by Kraton (copolymer of α-methylstyrene and styrene, softening point: 85°C) Wax: Sannock N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Stearic acid: Beads of stearic acid camellia manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: HK-200-5 (5% oil sulfur) manufactured by Hosoi Chemical Industry Co., Ltd. Vulcanization accelerator 1: Noccela NS (TBBS, N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccelaer D (DPG, 1,3-diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0180] (Production of SBR1) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-substituted autoclave reactor. The temperature of the reactor contents was adjusted to 20°C, and n-butyllithium was added to initiate polymerization. Polymerization was carried out under adiabatic conditions, with the maximum temperature reaching 85°C. When the polymerization conversion rate reached 99%, 1,3-butadiene was added, and polymerization was continued for another 5 minutes, after which N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane was added as a modifier to modify the polymer. After the polymerization reaction was completed, 2,6-di-tert-butyl-p-cresol was added. Next, the solvent was removed by steam stripping, and the mixture was dried with a heated roll adjusted to 110°C to obtain SBR1.

[0181] <Production of Unvulcanized Rubber Composition> According to the composition shown in Table 1, the chemicals other than sulfur and the vulcanization accelerator were kneaded for 4 minutes at a discharge temperature of 160°C using a 1.7 L closed Banbury mixer to obtain a kneaded product. Next, using an open roll, sulfur and the vulcanization accelerator were added to the kneaded product obtained, and the mixture was kneaded for 4 minutes to obtain an unvulcanized rubber composition.

[0182] <Production of test tires> Each of the obtained unvulcanized rubber compositions was extruded to form a tread shape having the tread pattern shown in Fig. 1, and this was laminated together with other components to produce a raw tire. Next, in the vulcanization process, the tire was press molded at 170°C for 20 minutes to produce each of the test tires shown in Tables 2 and 3.

[0183] In the same manner, the test tires shown in Table 4 were manufactured using the tread pattern of FIG. 2, and the test tires shown in Table 5 were manufactured using the tread pattern of FIG.

[0184] <Evaluation> The measurement and evaluation methods are shown below.

[0185] (Tg of rubber composition) For each test sample (length 20 mm x width 4 mm x thickness 1 mm) taken from inside the rubber layer of the tread of the test tire with the long side in the tire circumferential direction, a temperature distribution curve of tan δ was measured using an Iplexer series manufactured by GABO under the conditions of a frequency of 10 Hz, an initial strain of 10%, a dynamic strain of 0.5%, and a heating rate of 2°C / min. The tan δ peak temperature corresponding to the largest tan δ value in the measured temperature distribution curve was taken as the glass transition point (Tg).

[0186] (Change in Tg of rubber composition before and after acetone extraction (AE)) The Tg obtained above was taken as the Tg of the rubber composition before AE.

[0187] Next, each test sample whose Tg had been measured was extracted with acetone. The acetone extraction was performed by immersing each test piece of the vulcanized rubber sheet in acetone for 72 hours to extract the soluble components in accordance with JIS K 6229. For each test piece after extraction, the Tg of the rubber composition was measured according to the above method, and this was taken as the Tg of the rubber composition after AE.

[0188] The difference between the Tg of the rubber composition before AE and the Tg of the rubber composition after AE was determined as the change in Tg of the rubber composition before and after AE.

[0189] (0℃ tanδ / 30℃ tanδ) The 0°C tan δ was determined by measuring the loss tangent of each test sample (length 20 mm × width 4 mm × thickness 1 mm) prepared in the same manner as above, using an Iplexer series manufactured by GABO, under the conditions of a temperature of 0°C, an initial strain of 10%, a dynamic strain of 2.5%, a frequency of 10 Hz, and an extension mode.

[0190] The 30°C tan δ was determined by measuring the loss tangent of each test sample (length 20 mm × width 4 mm × thickness 1 mm) prepared in the same manner as above using an Iplexer series manufactured by GABO under the conditions of a temperature of 30°C, an initial strain of 5%, a dynamic strain of 1%, a frequency of 10 Hz, and an extension mode.

[0191] From the 0°C tan δ and 30°C tan δ thus obtained, 0°C tan δ / 30°C tan δ was calculated.

[0192] (Difference in rubber hardness between -10℃ and 25℃) For hardness measurement samples cut out from the tread portion forming the contact surface of each test tire such that the tire radial direction was the thickness direction, a type A durometer was pressed against the sample from the contact surface side to measure the rubber hardness at -10°C in accordance with JIS K 6253.

[0193] The rubber hardness at 25°C was measured in the same manner as above, except that the temperature was set to 25°C.

[0194] From each rubber hardness value obtained above, the difference between the rubber hardness at -10°C and the rubber hardness at 25°C was calculated.

[0195] (Steering stability on snowy roads) A test vehicle fitted with each test tire was driven on a test course on a snowy road surface, and 20 drivers sensorily evaluated the steering stability performance at that time using a 5-point scale from 1 to 5. The scores thus obtained were added up and indexed according to the following formula, with the standard comparative example being 100. A higher index indicates better steering stability performance. Steering stability index = [(total score for test tire) / (total score for reference comparative example)] x 100

[0196] [Table 1]

[0197] [Table 2]

[0198] [Table 3]

[0199] [Table 4]

[0200] [Table 5]

[0201] From the results in Tables 2 to 5, it is evident that the tires of the examples exhibit superior steering stability indexes compared to the tires of the comparative examples, and have improved steering stability on snowy road surfaces. [Explanation of symbols]

[0202] 10 Circumferential groove 11 Center circumferential groove 12 Outermost groove 20 Yokomizo 21 Sipe 30 Shoulder Land Section 40 Center Land Section 41 Center Land Section CL Tire centerline Ti inner tread edge To outer tread edge TW tread width W Tire width direction

Claims

1. A tire having a tread portion, the tread portion has a tread end To which is on the outer side of a vehicle when the tread portion is mounted on a vehicle, and a tread end Ti which is on the inner side of the vehicle, and between the tread end To and the tread end Ti, one or more circumferential grooves which extend continuously in the tire circumferential direction and two or more land portions which are partitioned by the circumferential grooves, the land portions having a plurality of lateral grooves which extend in the tire width direction, The tread portion includes a rubber composition having a glass transition temperature (Tg) of −40° C. to −15° C., The rubber composition includes a rubber component having a total styrene amount (S) of less than 20.0 mass% in the rubber component, the change in Tg of the rubber composition before and after immersion in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components is 15° C. or more; Among the land portions, a lateral groove area ratio (R) of at least one land portion satisfies the following condition (1), The weight (WT) (kg) and maximum load capacity (W L ) (kg) refers to a tire that satisfies the following condition (2). (1) 10%≦R≦40% (2)WT / W L ≦0.015

2. A tire having a tread portion, the tread portion has a tread end To which is on the outer side of a vehicle when the tread portion is mounted on a vehicle, and a tread end Ti which is on the inner side of the vehicle, and between the tread end To and the tread end Ti, one or more circumferential grooves which extend continuously in the tire circumferential direction and two or more land portions which are partitioned by the circumferential grooves, the land portions having a plurality of lateral grooves which extend in the tire width direction, The tread portion includes a rubber composition having a glass transition temperature (Tg) of −40° C. to −15° C., The rubber composition includes a rubber component having a total styrene amount (S) of less than 20.0 mass% in the rubber component, The difference between the rubber hardness of the rubber composition at −10° C. and the rubber hardness of the rubber composition at 25° C. is 3 to 18; Among the land portions, a lateral groove area ratio (R) of at least one land portion satisfies the following condition (1), A tire, the weight (WT) (kg) and the maximum load capacity (WL) (kg) of which satisfy the following condition (2): (1) 10%≦R≦40% (2) WT / W L ≦0.015

3. 2. The tire according to claim 1, wherein the change in Tg of the rubber composition before and after immersion in acetone for 72 hours in accordance with JIS K 6229 to extract soluble components is 16° C. or more.

4. The tire according to any one of claims 1 to 3, wherein the total styrene amount (S) and the tire weight (WT) satisfy the following condition (3): (3) S / WT≦3.0

5. The tire according to any one of claims 1 to 4, wherein the rubber composition satisfies the following condition (4): (4) 0℃tanδ / 30℃tanδ>2.0 (0°C tan δ represents the loss tangent measured under the conditions of a temperature of 0°C, a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 2.5%, and 30°C tan δ represents the loss tangent measured under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%.)

6. The tire according to any one of claims 1 to 5, wherein the rubber component contains a modified styrene-butadiene rubber.

7. The tire according to any one of claims 1 to 6, wherein the rubber composition contains an aromatic ring-containing resin, and a content of the aromatic ring-containing resin is 5 parts by mass or more per 100 parts by mass of the rubber component.

8. The tire according to any one of claims 1 to 7, wherein the rubber composition comprises vulcanized rubber particles.

9. The tire according to any one of claims 1 to 8, wherein the number of the circumferential grooves is three or more, and the tread portion has a pair of shoulder land portions separated by a pair of outermost peripheral grooves located at the outermost end in the tire width direction, and two or more center land portions located between the pair of shoulder land portions.

10. 10. The tire of claim 9, wherein a groove width of at least one of the pair of outermost circumferential grooves is narrower than a groove width of at least one of the pair of circumferential grooves that is not the outermost circumferential groove.

11. The tire according to claim 9 or 10, wherein one end of a lateral groove of at least one of the pair of shoulder land portions reaches a tread ground-contact edge and the other end does not reach an outermost circumferential groove and remains within the land portion.

12. The tire according to any one of claims 9 to 11, wherein one end of a lateral groove of at least one of the two or more central land portions is connected to one of the two circumferential grooves that define the central land portion, and the other end of the lateral groove does not reach the other circumferential groove and remains within the land portion.

13. The tire according to claim 12, wherein the two circumferential grooves defining the central land portion are composed of a circumferential groove having a larger distance from the tire center line and a circumferential groove having a smaller distance from the tire center line, and the circumferential groove to which the lateral grooves are connected is the circumferential groove having the larger distance from the tire center line.

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