tire

Abstract

This tire is provided with a tread part that includes a water absorptive rubber layer comprising a water absorptive rubber composite, and a rubber layer that is disposed at the inner side in the radial direction of the tire as compared to the tread part and has embedded therein a metal cord. A non-water absorptive rubber layer comprising a non-water absorptive rubber composite exists between an end of the water absorptive rubber layer and the metal cord. As regards a sample that is cut out from the water absorptive rubber layer and has a rectangular parallelepiped shape of 30 mm long, 20 mm wide, and 2 mm thick, a water absorption velocity VWAB from a dry state is equal to or more than 0.020 g / day, an evaporation velocity VWEV from a water-saturated state is equal to or more than 0.030 g / day, and the ratio tanδSAT / tanδDRY of the loss tangent of the water absorptive rubber composite in the water-saturated state at 30°C with respect to the loss tangent in the dry state at 30°C is equal to or more than 1.05. The thickness D (mm) of the non-water absorptive rubber layer and the VWEV satisfy formula (1). The purpose of the present invention is to enhance total performance of grip performance and durability performance on a road surface which is in a mixture of a dry state and a wet state. (1): VWEV×D>0.10

Description

tire

[0001] The present invention relates to a tire.

[0002] BACKGROUND ART A technique is known in which zinc oxide particles having a relatively small average particle size are used in rubber compositions for tire treads to improve grip performance (for example, see Patent Document 1).

[0003] Japanese Patent Application Laid-Open No. 2008-285524

[0004] However, there remains a significant technical challenge for tires, namely how to deal with changes in grip performance when the road surface changes from dry to wet, or from wet to dry. There is also a need to maintain and improve durability.

[0005] An object of the present invention is to provide a tire that has improved overall performance in terms of grip performance and durability on road surfaces where dry and wet conditions coexist.

[0006] The present invention relates to the following tire: A tire comprising a tread portion and a rubber layer in which metal cords are embedded, the rubber layer being disposed radially inward of the tread portion, wherein the tread portion includes a water-absorbent rubber layer made of a water-absorbent rubber composition, and a non-water-absorbent rubber layer made of a non-water-absorbent rubber composition is present between an end of the water-absorbent rubber layer and the metal cord in the tire radial direction, and a rectangular sample having a length of 30 mm, a width of 20 mm, and a thickness of 2 mm cut out from the water-absorbent rubber layer has a water absorption rate V from a dry state of 1000 sq.m. WAB is 0.020 g / day or more, and the evaporation rate V from the water saturated state WEV is 0.030 g / day or more, and tanδ, which is the loss tangent of the water-absorbing rubber composition in a dry state at 30°C, DRY tanδ, which is the loss tangent at water saturation and 30 ° C. SAT The ratio tan δ SAT / tanδ DRY is 1.05 or more, and when the thickness (mm) of the non-water-absorbent rubber layer is D, D and V WEV A tire that satisfies the following formula (1): WEV ×D>0.10

[0007] According to the present invention, a tire is provided that exhibits improved overall performance in terms of grip performance and durability on road surfaces where dry and wet conditions coexist.

[0008] The reason why the tire according to the present invention has improved overall performance in terms of grip performance and durability on road surfaces where dry and wet conditions coexist is thought to be as follows, without intending to be bound by theory: (1) The water-absorbing rubber composition constituting the tread rubber layer of the tire according to the present invention has a loss tangent tanδ in a dry state at 30°C. DRY tanδ, which is the loss tangent at water saturation and 30 ° C. SAT The ratio tan δ SAT / tanδ DRY Therefore, when wetted with water, the loss tangent becomes larger than that when dry, which contributes to improving wet grip performance. WAB and the evaporation rate from the saturated water state V WEV and are each equal to or greater than a predetermined value. This allows the rubber's physical properties to change in response to environmental changes from dry to wet conditions and from wet to dry conditions, contributing to improved dry grip performance and wet grip performance. Furthermore, (3) in the tire according to the present invention, a non-water-absorbent rubber layer is present between the tread rubber layer made of a water-absorbent rubber composition and the rubber layer in which the metal cords are embedded, and the thickness of this rubber layer is adjusted in response to the drying speed of the water-absorbent rubber layer. This contributes to the suppression of rusting of the metal cords. Furthermore, it is believed that the cooperation of (1) to (3) improves the overall performance of grip performance and durability on road surfaces where dry and wet conditions coexist.

[0009] 1 is a cross-sectional view of a tire according to an embodiment of the present invention taken along a plane including a tire rotation axis.

[0010] A tire according to one embodiment of the present invention is the following tire: The tire comprises a tread portion and a rubber layer in which metal cords are embedded, the rubber layer being disposed radially inward of the tread portion, the tread portion including a water-absorbent rubber layer made of a water-absorbent rubber composition, a non-water-absorbent rubber layer made of a non-water-absorbent rubber composition existing between an end of the water-absorbent rubber layer and the metal cord in the tire radial direction, and a rectangular sample having a length of 30 mm, a width of 20 mm, and a thickness of 2 mm cut out from the water-absorbent rubber layer has a water absorption rate V from a dry state of WAB is 0.020 g / day or more, and the evaporation rate V from the water saturated state WEV is 0.030 g / day or more, and tanδ, which is the loss tangent of the water-absorbing rubber composition in a dry state at 30°C, DRY tanδ, which is the loss tangent at water saturation and 30 ° C. SAT The ratio tan δ SAT / tanδ DRY is 1.05 or more, and when the thickness (mm) of the non-water-absorbent rubber layer is D, D and V WEV A tire that satisfies the following formula (1): WEV ×D>0.10

[0011] The water-absorbing rubber composition preferably contains an ion-binding material.

[0012] Without intending to be bound by theory, when a water-absorbing rubber composition contains an ionic bonding material, the ionic bonds are reversibly broken after the rubber composition absorbs water. This is thought to result in a relaxation of the bonding strength within the rubber composition, resulting in an increase in tan δ. On the other hand, since ionic bonds are the strongest of all non-covalent bonds, it is thought that the restored ionic bonds can maintain the bonding strength when the rubber is dry. This is thought to result in excellent grip performance even on road surfaces that are both dry and wet.

[0013] The evaporation rate V WEV to the water absorption rate V WAB The value obtained by subtracting is preferably greater than 0, and more preferably greater than 0.010.

[0014] Evaporation rate V WEV The water absorption rate is V WAB It is believed that a larger value than the above will enable a quicker response when the environment changes from wet to dry, thereby further improving safety.

[0015] The rubber component in the water-absorbing rubber composition preferably contains at least one of styrene-butadiene rubber and butadiene rubber.

[0016] It is believed that the use of synthetic rubber improves reactivity and dispersibility with silica, thereby improving rolling resistance and grip performance.

[0017] The total content of the styrene-butadiene rubber and the butadiene rubber in the rubber component is preferably 50% by mass or more.

[0018] The water-absorbing rubber composition preferably contains 50 parts by mass or more of silica per 100 parts by mass of the rubber component.

[0019] It is believed that silica contributes to improved wet grip performance.

[0020] The water-absorbing rubber composition preferably contains a resin.

[0021] It is believed that the resin increases the flexibility of the rubber, contributing to improved grip performance.

[0022] The water-absorbing rubber composition preferably contains 3.0 parts by mass or less of sulfur per 100 parts by mass of the rubber component.

[0023] It is thought that reducing the cross-linked structure increases the flexibility of the rubber, contributing to improved grip performance.

[0024] The land ratio R of the tread surface of the tread portion is preferably 0.70 or more.

[0025] Generally, a high land ratio improves grip performance on dry roads, but there is concern that wet grip performance on wet roads may decrease due to poor drainage. However, since the tread made of the above rubber composition can exhibit high grip performance even on wet roads, it is believed that it is possible to achieve both grip performance on dry roads and wet grip performance on wet roads even with a relatively high land ratio.

[0026] The evaporation rate V WEV and the land ratio R is preferably greater than 0.030.

[0027] When rubber has a high evaporation rate and a large land ratio, i.e., a large amount of rubber, it responds quickly to changes from a wet environment to a dry environment, which is thought to eliminate safety concerns in dry environments.

[0028] <Definition> The term "water absorbing agent" refers to a substance that, when compounded into a rubber composition containing a rubber component mainly composed of diene rubber, increases the water absorption rate V of the rubber composition. WAB is 0.020 g / day or more, and the evaporation rate V WEV The term "mainly composed of diene rubber" means that the content of diene rubber in the rubber component is 90% by mass or more, and the term "rubber composition" means a mixture in which the content of the rubber component in the rubber composition is 10% by mass or more and 90% by mass or less.

[0029] The "water-absorbing rubber composition" is a rubber composition whose physical properties change reversibly between a water-absorbing state and a dry state, and has a tan δ at 30°C. SAT / tanδ DRYThe term "non-water-absorbing rubber composition" refers to a rubber composition having a water-saturated state and a loss tangent of 1.05 or more. Here, "reversibly changing" means that the physical properties of the rubber composition change reversibly in the presence of water. For example, the physical properties may change reversibly when the rubber composition changes from dry to wet to dry. The physical properties do not necessarily have to be the same in the first dry state and the second dry state. The term "non-water-absorbing rubber composition" refers to a rubber composition that is not a water-absorbing rubber composition, i.e., a rubber composition that satisfies one or more of the following: (1) a rectangular parallelepiped sample measuring 30 mm in length, 20 mm in width, and 2 mm in thickness has a water absorption rate from a dry state of less than 0.020 g / day; (2) the evaporation rate of the sample from a water-saturated state is less than 0.030 g / day; and (3) the ratio of the loss tangent in a water-saturated state at 30°C to the loss tangent in a dry state at 30°C is less than 1.05. The water absorption rate of the non-water-absorbent rubber composition is preferably less than 0.010 g / day, more preferably less than 0.0050 g / day, and even more preferably less than 0.0025 g / day. If it is difficult to directly cut out the rectangular parallelepiped sample, multiple cut pieces may be gathered together to form a single sample. In this case, the number of pieces is preferably three or less.

[0030] "Normal condition" refers to a condition in which the tire is mounted on a normal rim and filled with air at normal internal pressure, with no load applied.

[0031] Unless otherwise specified, the "dimensions of each part of the tire" are values ​​that are specified when the tire appears on the outer surface and is in its normal state, while the "dimensions of each part of the tire" are values ​​that are specified when the tire is cut along a plane that includes the tire rotation axis and the cut piece of tire is maintained within the rim width of a normal rim and is in its normal state when it appears on the outer surface and is in its normal state when it appears on the inner surface of the tire and is in its normal state when it appears on the outer surface of the tire ...

[0032] "Genuine rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, in the case of JATMA (Japan Automobile Tire Manufacturers Association), it refers to the "standard rim" for the applicable size listed in the "Jatma Year Book," in the case of ETRTO (The European Tyre and Rim Technical Organization), it refers to the "Measuring Rim" listed in the "STANDARDS MANUAL," and in the case of TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "YEAR BOOK." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. In the case of a tire not specified in the above standards, it refers to the narrowest rim among the smallest diameter rims that can be mounted on the tire and can maintain internal pressure (i.e., do not leak air between the rim and tire).

[0033] "Normal internal pressure" refers to the air pressure specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA, it refers to "Maximum Air Pressure," for ETRTO, it refers to "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." As with regular rims, refer to JATMA, ETRTO, and TRA in that order, and follow the standard if there is an applicable size at the time of reference. Note that in the case of tires not specified in the above standards, it refers to the normal internal pressure (250 kPa or more) of another tire size (defined in the standard) that is specified using the regular rim as the standard rim. If multiple normal internal pressures of 250 kPa or more are listed, it refers to the smallest value among them.

[0034] "Normal load" is the load specified for each tire in the standard system including the standard on which the tire is based, for example, "Maximum Load Capacity" for JATMA, "Load Capacity" for ETRTO, and the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES" for TRA. As with normal rims and normal internal pressures, JATMA, ETRTO, and TRA should be referenced in that order, and if there is an applicable size at the time of reference, that standard should be followed. In addition, for tires not specified in the above standards, the maximum load capacity W calculated separately should be used. L is the normal load.

[0035] "Maximum load capacity W L " is calculated by the following formula: "V" is the virtual volume of the tire (mm 3 ), "Dt" is the outer diameter (mm) of the tire in a normal state, "Ht" is the tire's cross-sectional height (mm) in the tire radial direction in a cross section of the tire taken along a plane including the tire rotation axis, and "Wt" is the tire's cross-sectional width (mm) in a normal state. Ht can be calculated by (Dt - R) / 2, where R is the tire rim diameter. Wt is the value obtained by excluding any patterns or letters on the tire sidewall. Note that in this specification, the maximum load capacity is the same value as the normal load.

[0036]

[0037] The "tread portion" is the portion of the tire that forms the contact surface of the tire. When the tire includes components that form the tire frame from steel or textile materials, such as a belt layer, a belt reinforcing layer, and a carcass layer, the "tread portion" is the component that is radially outward of these components in the tire radial cross section. The tread portion includes a water-absorbent rubber layer made of a water-absorbent rubber composition. The water-absorbent rubber layer preferably forms the tread surface. The tread portion may consist of only the water-absorbent rubber layer, or may also include a non-water-absorbent rubber layer made of a non-water-absorbent rubber composition.

[0038] The "rubber layer with embedded metal cords" refers to a rubber layer constituting a tire component that forms or reinforces the tire frame, and specifically includes a belt layer, a carcass layer, etc. The metal cord is not particularly limited as long as it is a metal cord that is normally used in tires, and a typical example is a steel cord.

[0039] The "thickness of the non-water-absorbent rubber layer" is the thickness (mm) measured on the center line of the tire in a cross section passing through the tire rotation axis. For example, this corresponds to D in Figure 1.

[0040] The "contact area" is the area of ​​the tread obtained from the outline of the tire when pressed against the ground. The tire is mounted on a standard rim, inflated to the standard internal pressure, and left to stand at 25°C for 24 hours. After that, ink is applied to the tire tread surface, and the tire is pressed vertically against cardboard under a standard load (camber angle 0°) to transfer the ink. The area of ​​the contact area is called the total contact area. The total contact area can be calculated by rotating the tire 72 degrees each time and performing the above transfer process at a total of five locations, and then averaging the five areas obtained.

[0041] The "effective contact area" is the area of ​​the tread that makes contact with the ground when the tire is pressed against the ground. It is obtained by assembling the tire on a standard rim, inflating it to the standard internal pressure, leaving it at 25°C for 24 hours, then applying ink to the tire tread surface, and pressing the tire vertically against cardboard (camber angle 0°) under a standard load to transfer the ink. The area of ​​the effective contact area is called the effective contact area. The effective contact area can be calculated by rotating the tire 72 degrees each time, performing the above transfer process at a total of five locations, and averaging the five areas obtained.

[0042] The "land ratio R" is calculated from the total contact area of ​​the contact patch and the effective contact area of ​​the effective contact patch by the following formula: (land ratio) = (effective contact area / total contact area).

[0043] A "softener" is a material that imparts plasticity to a rubber component. For example, it is extracted from a rubber composition using acetone. Softeners include softeners that are liquid (fluid) at 25°C and softeners that are solid at 25°C. However, this does not include waxes and stearic acid that are commonly used in the tire industry.

[0044] The "softener content" includes the amount of softener contained in an extended rubber component that has been previously extended with a softener such as oil, resin, liquid polymer, ester-based plasticizer, etc. The same applies to the oil content, resin content, liquid polymer content, and ester-based plasticizer content. For example, if the extended component is oil, the extended oil is included in the oil content.

[0045] <Measurement method> “Water absorption rate V WAB " is the water absorption rate (g / day) of a rectangular rubber composition measuring 30 mm long x 20 mm wide x 2 mm thick. First, a rectangular rubber composition measuring 30 mm long x 20 mm wide x 2 mm thick is prepared as a measurement sample, and its mass is measured. Next, the measurement sample is left to stand under an environment of 25°C, 50% relative humidity, and 1 atm until it reaches constant weight, and the mass at that point is taken as the dry mass (g). Here, constant weight refers to a state in which the mass change has become sufficiently small. Specifically, when the mass measurement of the measurement sample is repeated every two hours, the difference between the mass of the measurement result and the mass of the immediately preceding measurement result is within 0.05 μg. However, if constant weight is not reached after 7 days, it is considered to have been reached after 7 days have passed. The measurement sample is then immersed in a water tank filled with ion-exchanged water (set at a water temperature of 40°C) in an amount sufficient to completely immerse the sample under an environment of 1 atm. The measurement sample is removed every two hours and its mass is measured. The mass at which a constant mass is reached is taken as the water absorption mass (g), and the time required for immersion up to that point is taken as the immersion time. Here, the constant mass has the same meaning as the constant mass in the measurement of the dry mass. The water absorption rate (g / day) is calculated from the dry mass (g), the water absorption mass (g), and the immersion time (hours) using the following formula, and the water absorption rate V WABHowever, if the weight is considered to have reached a constant value after 7 days of soaking, calculate by replacing "soaking time / 24" with "7". Water absorption rate = (absorbed mass - dry mass) / (soaking time / 24)

[0046] "Evaporation rate V WEV " is the water evaporation rate (g / day) of a rectangular rubber composition measuring 30 mm long x 20 mm wide x 2 mm thick. First, a rectangular rubber composition measuring 30 mm long x 20 mm wide x 2 mm thick is prepared as a measurement sample. Next, the measurement sample is immersed in a water tank filled with ion-exchanged water (set at 40°C) in an amount sufficient to completely immerse the sample, under an environment of 1 atm, for 7 days. After immersion, the measurement sample is removed and its mass is measured. This mass is defined as the saturated mass (g). The measurement sample is then left to dry under an environment of 40°C, 50% relative humidity, and 1 atm, and its mass is measured every two hours. The mass at which a constant mass is reached is defined as the dry mass (g), and the time required for drying up to that point is defined as the drying time. Here, "constant mass" refers to when, when the mass of the measurement sample is measured every two hours, the difference between the mass of the measurement result and the mass of the immediately preceding measurement is within 0.05 μg. However, if the weight does not reach a constant value after 7 days, it is considered to have reached a constant weight after 7 days. The evaporation rate (g / day) is calculated from the saturated mass (g), the dry mass (g), and the drying time (hours) using the following formula. WEV However, if the weight is considered to be constant after 7 days of drying, calculate by replacing "drying time / 24" with "7". Evaporation rate = (saturated mass - dry mass) / (drying time / 24)

[0047] The water absorption rate of the non-water-absorbing rubber composition is the water absorption rate V WAB is measured in the same manner as

[0048] "Tan δ" is the loss tangent measured using a dynamic viscoelasticity measuring device (for example, the Iplexer series manufactured by GABO) under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an extension mode. The measurement sample 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 the sample from the tread portion of the tire, the sample is cut out from the tread portion of the tire so that the long side is in the tire circumferential direction and the thickness direction is in the tire radial direction. "Tan δ" SAT " is measured by immersing the measurement sample in ion-exchanged water at 25°C for 12 hours to make it saturated with water. DRY " is measured on a dry sample saturated with water, which is dried under reduced pressure at 80°C and 1 kPa or less until it reaches a constant weight.

[0049] "Styrene content" is 1 This is a value calculated by H-NMR measurement, and is applied to rubber components having repeating units derived from styrene, such as SBR.

[0050] The "vinyl content (amount of 1,2-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and applies to rubber components having repeating units derived from butadiene, such as SBR and BR.

[0051] The "cis content (amount of cis-1,4-bonded butadiene units)" is a value calculated by infrared absorption spectroscopy in accordance with JIS K 6239-2:2017, and is applied to a rubber component having a repeating unit derived from butadiene, such as BR.

[0052] The "weight average molecular weight (Mw)" can be determined by standard polystyrene conversion based on measurements obtained by gel permeation chromatography (GPC) (for example, GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKgel SuperMultipore HZ-M manufactured by Tosoh Corporation). For example, this applies to SBR, BR, softeners, etc.

[0053] The "nitrogen adsorption specific surface area (N2SA) of carbon black" is measured in accordance with JIS K 6217-2:2017.

[0054] The "nitrogen adsorption specific surface area (N2SA) of silica" is measured by the BET method in accordance with ASTM D3037-93.

[0055] The "average primary particle size" is determined by photographing particles with a transmission or scanning electron microscope and calculating the arithmetic mean of the particle sizes of 400 particles. When the particle shape is nearly circular, the diameter of the circle is used as the particle size; when the particle shape is needle-like or rod-like, the minor axis is used as the particle size; in other cases, the equivalent circle diameter is calculated from the electron microscope image. The equivalent circle diameter is determined as the positive square root of (4 x (particle area) / π). The average primary particle size is applied to silica, carbon black, etc.

[0056] The "softening point of the resin" is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2015 7.7 is measured using a ring and ball softening point tester.

[0057] Each embodiment will be described in detail below. However, the following description is merely an example for explaining the present invention, and the present invention is not limited thereto. Furthermore, although the description will be made using drawings as appropriate, the drawings are merely examples.

[0058] [Tire] The tire according to the present embodiment includes a tread portion and a rubber layer in which metal cords are embedded, the tread portion being positioned radially inward of the tread portion. The tread portion includes a water-absorbent rubber layer made of a water-absorbent rubber composition. Furthermore, a non-water-absorbent rubber layer is disposed radially between the end of the water-absorbent rubber layer and the metal cords, the thickness of which satisfies a predetermined relationship with the evaporation rate of the water-absorbent rubber. For example, consider a tire in which, from the contact surface side, a cap tread, a base tread, a band ply, and a belt ply are layered. In the tire, the cap tread is the water-absorbent rubber layer, and the belt ply is a component including metal cords. The base tread, the covering rubber in the band ply, and the portion of the covering rubber in the belt ply up to the metal cord constitute the non-water-absorbent rubber layer disposed between the end of the water-absorbent rubber layer and the metal cords. Furthermore, in the assumed tire, when the base tread is a water-absorbent rubber layer and the band ply is a component including a metal cord, the portion of the covering rubber in the band ply up to the metal cord becomes a non-water-absorbent rubber layer that is arranged between the end of the water-absorbent rubber layer and the metal cord.

[0059] In Figure 1, a tire 1 has a tread portion 2. The tread portion 2 is composed of a cap rubber layer 4a and a base rubber layer 4b that form a tread surface 3, and the cap rubber layer 4a is composed of a water-absorbent rubber composition. Radially inward from the tread portion 2, the tire has band plies 5 and 6 in which organic fiber cords are embedded, belt plies 7 and 8 in which steel cords are embedded, and a carcass ply 9. The rubber present between the radially inner end of the cap rubber layer 4a and the steel cords (not shown) embedded in the belt ply 7 is all composed of a non-water-absorbent rubber composition. Therefore, the thickness of the non-water-absorbent rubber layer present in the radial direction of the tire from the end of the water-absorbent rubber layer to the metal cords is the sum of the thickness of the base rubber layer 4b, the thickness of the band ply 5, and the thickness from the radially outer end of the belt ply 7 to the steel cords, and this thickness is indicated by D.

[0060] 1, the tread portion 2 is composed of two layers, a cap rubber layer 4a and a base rubber layer 4b, which form the tread surface 3, but the tread portion may be composed of three or more rubber layers. When the tread portion is composed of three or more rubber layers, the water-absorbing rubber layer may be at least one of those rubber layers, but it is preferably the rubber layer that forms the tread surface.

[0061] (Rubber Layer with Embedded Metal Cords) Examples of the rubber layer with embedded metal cords include band plies, belt plies, carcass plies, etc., each of which is made up of metal cords and a coating rubber that covers the cords.

[0062] In Figure 1, belt plies 7 and 8 are rubber layers in which metal cords are embedded and are located radially inward of the tread portion 2. In this case, the metal cords used when measuring the thickness D of the non-water-absorbent rubber layer are, as described above, steel cords embedded in the belt ply 7 located at the outermost side in the tire radial direction. Although steel cords are used as the metal cords in the belt plies 7 and 8, metal cords commonly used in the tire industry can also be used as the metal cords. Also, in Figure 1, the number of belt plies and the number of carcass plies are two and one, respectively, but a different number of plies can be used for each ply. For example, the number of belt plies may be more or less than that shown in Figure 1.

[0063] (Non-Water-Absorbent Rubber Layer) The non-water-absorbent rubber layer is made of a non-water-absorbent rubber composition, and any layer can be used as long as its thickness satisfies the relationship of formula (1). In the tire industry, rubber compositions used for treads, bands, belts, carcasses, etc. are usually non-water-absorbent rubber compositions, and therefore these can be suitably used.

[0064] (Equation (1)) When the thickness (mm) of the non-water-absorbent rubber layer is D, D and the evaporation rate V of the water-absorbent rubber composition are WEV satisfies the following formula (1): (1) V WEV ×D>0.10

[0065] In the above formula (1), when the non-water-absorbent rubber layer is made up of a single rubber layer, the thickness of the rubber layer is D. On the other hand, when the non-water-absorbent rubber layer is made up of multiple rubber layers, D in the above formula (1) is the total value of the thicknesses of the individual rubber layers.

[0066] The value of the right side of formula (1) is preferably 0.11, more preferably 0.13, even more preferably 0.15, even more preferably 0.17, even more preferably 0.20, even more preferably 0.23, even more preferably 0.26, even more preferably 0.30, even more preferably 0.40, even more preferably 0.50, even more preferably 0.60. On the other hand, there is no particular upper limit to the value of the right side of formula (1), but it is about 1.0.

[0067] The preparation of the non-water-absorbing rubber layer is the same as the preparation of rubber compositions commonly used in the tire industry, and the non-water-absorbing rubber can be prepared, for example, by not blending a water-absorbing agent or an ionic bonding material, which will be described later. The water absorption rate of the non-water-absorbing rubber layer can be decreased by reducing the amount of hydrophilic material (such as silica) or increasing the amount of lipophilic material (such as oil), and conversely, can be increased by increasing the amount of hydrophilic material (such as silica) or decreasing the amount of lipophilic material (such as oil).

[0068] Those skilled in the art can adjust the value of formula (1) by appropriately adjusting the thickness of the non-water-absorbent rubber layer and the evaporation rate of the water-absorbent rubber layer.

[0069] (Land Ratio R) In a tire having the above rubber composition applied to the tread portion, the land ratio R of the tread surface of the tread portion is preferably 0.70 or more. From the viewpoint of ensuring drainage and suppressing the occurrence of hydroplaning, the land ratio R is preferably less than 0.85, more preferably less than 0.80, and even more preferably less than 0.75. The land ratio R can be varied in a conventional manner; that is, it can be increased by reducing the groove area of ​​the tread surface, or conversely, it can be decreased by reducing the groove area of ​​the tread surface.

[0070] (evaporation rate V WEVand the land ratio R) In a tire in which the rubber composition is applied to a tread portion, the evaporation rate V WEV and the land ratio R is preferably greater than 0.030. The value of this product is preferably greater than 0.030, more preferably greater than 0.040, even more preferably greater than 0.050, even more preferably greater than 0.055, even more preferably 0.056 or greater, even more preferably greater than 0.060, and even more preferably 0.063 or greater.

[0071] [Water-absorbent rubber composition] <Water absorption rate V WAB , evaporation rate V WEV The water-absorbing rubber composition according to the present embodiment (hereinafter also simply referred to as "rubber composition") has a water absorption rate V WAB is 0.020 g / day or more, and the evaporation rate V from the water saturated state WEV is 0.030 g / day or more.

[0072] The water absorption rate is preferably 0.025 g / day or more, more preferably 0.030 g / day or more, even more preferably 0.035 g / day or more, even more preferably 0.040 g / day or more, even more preferably 0.045 g / day or more, and even more preferably 0.050 g / day or more.

[0073] The evaporation rate is preferably 0.036 g / day or more, more preferably 0.041 g / day or more, even more preferably 0.046 g / day or more, even more preferably 0.051 g / day or more, even more preferably 0.056 g / day or more, even more preferably 0.061 g / day or more, even more preferably 0.070 g / day or more, even more preferably 0.080 g / day or more, and even more preferably 0.090 g / day or more.

[0074] V is the value obtained by subtracting the water absorption rate from the evaporation rate WEV -V WAB is preferably greater than 0, more preferably greater than 0.010, even more preferably greater than 0.020, even more preferably greater than 0.030, even more preferably 0.040 or greater, and even more preferably 0.050 or greater.

[0075] The water absorption rate can be adjusted by appropriately setting the content and type of water absorbing agent in the rubber composition. For example, the water absorption rate can be increased by increasing the amount of water absorbing agent, and by using a water absorbing agent with excellent water absorption properties. On the other hand, the water absorption rate can be decreased by reducing the amount of water absorbing agent or by using a water absorbing agent with lower water absorption properties.

[0076] The evaporation rate can be adjusted by appropriately selecting the type of water-absorbing agent in the rubber composition. For example, resins such as those used in diapers have high water-retaining properties, but the evaporation rate can be increased by using a water-absorbing agent that does not retain water.

[0077] <tan δ SAT / tanδ DRY The rubber composition has a loss tangent tanδ in a dry state at 30°C. DRY tanδ, which is the loss tangent at water saturation and 30 ° C. SAT The ratio tan δ SAT / tanδ DRY is 1.05 or more. SAT and tan δ DRY are measured by the above-mentioned measurement methods.

[0078] The tan δ SAT / tanδ DRY is preferably greater than 1.05, more preferably 1.06 or greater, even more preferably greater than 1.06, and even more preferably 1.07 or greater.

[0079] Without intending to be bound by theory, the mechanism by which the tan δ value of the water-absorbing rubber composition according to this embodiment reversibly changes depending on the presence or absence of water is believed to be as follows. That is, the water-absorbing rubber composition according to this embodiment has a cross-linked polymer structure, and at least a portion of the cross-links are formed by electrostatic interactions such as ionic bonds. It is believed that such electrostatic interaction bonds are present in a sufficient amount to change the tan δ value by a predetermined value or more. When the rubber composition contains electrostatic interaction bonds, these bonds can be reversibly separated when the rubber composition is wetted by water absorption, which is believed to increase tan δ. Furthermore, since the electrostatic interaction bonds are restored when water is no longer present, it is believed that tan δ increases again when the rubber composition is dried. In particular, among the bonds formed by electrostatic interactions, ionic bonds are the strongest non-covalent bonds, and therefore are believed to be able to increase the difference in tan δ between wet and dry states. Note that ionic bonds are a typical example of the electrostatic interaction, but other examples include hydrogen bonds.

[0080] The method for introducing bonds due to electrostatic interaction into the crosslinked structure in the rubber composition is not particularly limited, but may include, for example, a rubber component containing a rubber component into which a hydrophilic functional group has been introduced, or silica, a silane coupling agent, a resin, etc. may contain a hydrophilic functional group. Here, examples of the hydrophilic functional group include functional groups containing at least one element selected from the group consisting of nitrogen, oxygen, silicon, and sulfur, and preferably at least one selected from the group consisting of a carboxyl group, an amino group, and a hydroxyl group.

[0081] tan δ SAT / tanδ DRY The value of tan δ can be adjusted by the type and amount of functional groups introduced into the rubber component, silica, silane coupling agent, resin, etc., and the content of the rubber component, silica, silane coupling agent, resin, etc. into which the functional group has been introduced. For example, by increasing the content of the rubber component, silica, silane coupling agent, resin, etc. into which the functional group has been introduced, the value of tan δ SAT / tanδ DRYThe value of tends to increase, and conversely, decreases.

[0082] tan δ SAT The value of tan δ SAT / tanδ DRY is not particularly limited as long as it is within the above range, but is usually preferably 1.00 or more, more preferably 1.02 or more, even more preferably 1.05 or more, and is preferably 2.00 or less, more preferably 1.80 or less, even more preferably 1.50 or less. DRY The value of tan δ SAT / tanδ DRY is not particularly limited as long as it is within the above range, but is usually preferably 0.10 or more, more preferably 0.15 or more, even more preferably 0.20 or more, and is preferably 0.80 or less, more preferably 0.50 or less, even more preferably 0.30 or less.

[0083] The value of tan δ of the rubber composition itself can be adjusted appropriately by the types and amounts of rubber components, resins, oils, etc., which will be described later.

[0084] (Ionic Bonding Material) A material capable of introducing ionic bonds into a rubber composition is called an ionic bonding material. For example, ionic bonds can be introduced between rubbers, between rubbers and fillers, or between fillers. Examples of ionic bonding materials include ionically bond-modified rubbers, ionically bond-modified silica, ionically bond-modified silane coupling agents, and ionically bond-modified softeners, which have been modified to form ionic bonds. Examples of ionically bond-modified softeners include ionically bond-modified resins and ionically bond-modified liquid polymers. Specific examples of these ionic bonding materials are described in the sections on rubber components, silica, silane coupling agents, and softeners, respectively. The ionic bonding material is preferably one or more selected from ionically bond-modified rubbers, ionically bond-modified silane coupling agents, and ionically bond-modified liquid polymers. It is more preferable that the ionic bonding material include an ionically bond-modified silane coupling agent and / or an ionically bond-modified liquid polymer. One or more ionic bonding materials may be used alone, or two or more may be used in combination.

[0085] <Rubber Component> The rubber composition preferably uses a diene rubber as the rubber component. Examples of diene rubbers include isoprene rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene rubber (SIR), styrene isoprene butadiene rubber (SIBR), chloroprene rubber (CR), and acrylonitrile butadiene rubber (NBR). These diene rubbers may be modified rubbers treated with modifying groups capable of interacting with fillers such as carbon black and silica, or may be hydrogenated rubbers in which some of the unsaturated bonds have been hydrogenated. Among the modified rubbers, modified rubbers into which the hydrophilic functional groups have been introduced can be preferably used as ionically bonded modified rubbers. As the diene rubber, an extended rubber that has been previously extended using a softener described below may be used. One type of diene rubber may be used alone, or two or more types may be used in combination.

[0086] As the diene rubber component, at least one selected from the group consisting of isoprene rubber, styrene butadiene rubber (SBR), and butadiene rubber (BR) is preferably used. The rubber component preferably contains at least one of SBR and BR, more preferably contains isoprene rubber, SBR, and BR, and may be a rubber component consisting only of isoprene rubber, SBR, and BR.

[0087] Here, the diene rubber is the main component in the rubber component. Here, "main component" means that the content of the diene rubber in the rubber component is 90% by mass or more. The content is preferably more than 90% by mass, more preferably 95% by mass or more. Furthermore, the rubber component may be a rubber component consisting solely of the diene rubber.

[0088] (Isoprene-based rubber) As the isoprene-based rubber, for example, isoprene rubber (IR) and natural rubber, which are commonly used in the tire industry, can be used. Natural rubber includes unmodified natural rubber (NR), as well as 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. One type of isoprene-based rubber may be used alone, or two or more types may be used in combination.

[0089] The NR is not particularly limited, and those commonly used in the tire industry can be used, such as SIR20, RSS#3, and TSR20.

[0090] From the viewpoint of the effects of the present invention, the content of the isoprene-based rubber in the rubber component is preferably less than 70% by mass, more preferably less than 65% by mass, even more preferably less than 60% by mass, even more preferably less than 55% by mass, and still more preferably less than 50% by mass. Also, from the viewpoint of the effects of the present invention, the content is preferably more than 20% by mass, more preferably more than 25% by mass, even more preferably more than 30% by mass, even more preferably more than 35% by mass, and still more preferably more than 40% by mass.

[0091] (SBR) SBR is not particularly limited, and examples thereof include unmodified solution-polymerized SBR (S-SBR) and emulsion-polymerized SBR (E-SBR), as well as modified SBRs thereof (modified S-SBR, modified E-SBR). Examples of modified SBR include SBR whose ends and / or main chains have been 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 two or more types may be used in combination.

[0092] Among the modified SBRs, SBR whose terminals and / or main chains are modified with a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, silicon, and sulfur can be suitably used as the ionically bond-modified SBR. Examples of the functional group include an amino group (preferably an amino group in which a hydrogen atom of the amino group is substituted with an alkyl group having 1 to 6 carbon atoms), an amide group, a silyl group, an alkoxysilyl group (preferably an alkoxysilyl group having 1 to 6 carbon atoms), an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imido group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group (preferably an alkoxy group having 1 to 6 carbon atoms), a hydroxyl group, an oxy group, and an epoxy group. One or more functional groups selected from the group consisting of an amino group, a carboxyl group, and an alkoxysilyl group are preferred. These functional groups may have a substituent. Examples of the substituent include functional groups such as an amino group, an amide group, an alkoxysilyl group, a carboxyl group, and a hydroxyl group. The modified SBR may be hydrogenated, epoxidized, or tin-modified.

[0093] As the SBR, either extended or unextended SBR can be used. When extended SBR is used, the amount of extension of the SBR, i.e., the content of the extension softener contained in the SBR, is preferably 10 to 50 parts by mass per 100 parts by mass of the rubber solid content of the SBR.

[0094] The SBRs listed above may be used alone or in combination of two or more thereof. As the SBRs listed above, for example, commercially available products from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, Zeon Corporation, ZS Elastomers Co., Ltd., etc. can be used.

[0095] The styrene content of SBR is preferably less than 40% by mass, more preferably less than 37% by mass, even more preferably less than 34% by mass, and particularly preferably less than 30% by mass. The styrene content of SBR is preferably more than 5% by mass, more preferably more than 7% by mass, even more preferably more than 10% by mass, and particularly preferably more than 12% by mass. The styrene content of SBR is measured by the above-mentioned measurement method.

[0096] The vinyl content of SBR is preferably more than 10 mol%, more preferably more than 20 mol%, and even more preferably more than 40 mol%, from the viewpoints of ensuring reactivity with silica and abrasion resistance. Furthermore, the vinyl content of SBR is preferably less than 75 mol%, more preferably less than 70 mol%, and even more preferably less than 65 mol%, from the viewpoints of breaking elongation and abrasion resistance. The vinyl content of SBR is measured by the above-mentioned measurement method.

[0097] From the viewpoint of the effects of the present invention, the weight average molecular weight (Mw) of SBR is preferably 100,000 or more, more preferably 200,000 or more, and even more preferably 300,000 or more. From the viewpoint of crosslinking uniformity, the weight average molecular weight is preferably 2,000,000 or less, more preferably 1,800,000 or less, and even more preferably 1,500,000 or less. The weight average molecular weight of SBR is measured by the above-mentioned measurement method.

[0098] From the viewpoint of the effects of the present invention, the content of SBR in the rubber component is preferably more than 15% by mass, more preferably more than 20% by mass, even more preferably more than 25% by mass, even more preferably more than 30% by mass, and still more preferably 35% by mass or more. Also, from the viewpoint of the effects of the present invention, the content is preferably less than 65% by mass, more preferably less than 6% by mass, even more preferably less than 55% by mass, even more preferably less than 50% by mass, and still more preferably less than 45% by mass.

[0099] (BR) The BR is not particularly limited, and can be, for example, a BR commonly used in the tire industry, such as BR having a cis content of less than 50 mol% (low cis BR), BR having a cis content of 90 mol% or more (high cis BR), rare earth butadiene rubber (rare earth BR) synthesized using a rare earth catalyst, BR containing syndiotactic polybutadiene crystals (SPB-containing BR), or modified BR (high cis modified BR, low cis modified BR). One type of BR may be used alone, or two or more types may be used in combination.

[0100] As the high-cis BR, for example, commercially available products from Zeon Corporation, UBE Corporation, JSR Corporation, etc. can be used. The inclusion of high-cis BR can improve abrasion resistance. The cis content of the high-cis BR is preferably 95 mol% or more, more preferably 96 mol% or more, and even more preferably 97 mol% or more. The cis content of BR is measured by the above-mentioned measurement method.

[0101] Among modified BRs, BR whose terminals and / or main chains are modified with a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, silicon, and sulfur can be suitably used as the ionically bond-forming modified BR. Examples of the functional group include those exemplified for the modified SBR.

[0102] Other examples of modified BR include tin-modified BR, which is obtained by polymerizing 1,3-butadiene with a lithium initiator and then adding a tin compound, and in which the terminals of the modified BR molecule are further bonded with a tin-carbon bond (tin-modified BR). The modified BR may be either non-hydrogenated or hydrogenated.

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

[0104] From the viewpoint of the effects of the present invention, the content of BR in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, and even more preferably 15% by mass or more. Also, from the viewpoint of the effects of the present invention, the content is preferably 35% by mass or less, more preferably 30% by mass or less, even more preferably 25% by mass or less, even more preferably 20% by mass or less, and even more preferably 15% by mass or less.

[0105] The total content of SBR and BR in the rubber component is preferably 50% by mass or more, more preferably more than 50% by mass, and even more preferably 55% by mass or more.

[0106] (Rubber component synthesized from recycled / biomass-derived raw materials) The raw materials (monomers) of synthetic rubbers such as SBR and BR may be derived from petroleum or may be recycled from rubber products such as tires or non-rubber products such as polystyrene. Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples thereof include recycled-derived butadiene and recycled-derived aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not particularly limited to, styrene. In particular, it is preferable to use recycled-derived butadiene (recycled butadiene) and / or recycled-derived styrene (recycled styrene) as raw materials.

[0107] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0108] Furthermore, the raw materials (monomers) for synthetic rubbers such as SBR and BR may be derived from biomass. Examples of biomass-derived monomers (biomass monomers) include, but are not limited to, biomass-derived butadiene and biomass-derived aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyl include, but are not limited to, styrene. Furthermore, methods for producing biomass monomers are not particularly limited, and include, for example, biological and / or chemical and / or physical conversion of animals and plants. A typical example of biological conversion is fermentation by microorganisms, while examples of chemical and / or physical conversion include catalytic, high-temperature, high-pressure, electromagnetic, critical fluid, and combinations thereof. Biomass sources for these monomers include sugar, wood, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha.

[0109] The polymer synthesized from a biomass monomer component (biomass polymer) is not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymer synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl. Examples of the aromatic vinyl / butadiene copolymer include styrene-butadiene rubber synthesized from biomass-derived butadiene and / or biomass-derived styrene.

[0110] Whether the raw material of a polymer is derived from biomass can be determined by the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0111] pMC is the modern standard reference carbon 14 of sample with respect to C concentration 14 This value is used as an index showing the biomass ratio of the compound (rubber). The significance of this value will be described below.

[0112] 1 mole of carbon atoms (6.02 x 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14 The half-life of C is 5,730 years and it decreases regularly. It takes 226,000 years for all of it to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms more than 226,000 years ago, C was also included in these when it was first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemical substances produced using these fossil fuels as raw materials also contain no C element. 14 The element C is not contained at all.

[0113] on the other hand, 14 C is produced continuously by nuclear reactions in the atmosphere caused by cosmic rays, and this balances with the decrease due to radioactive decay. In the Earth's atmospheric environment, 14 Therefore, the amount of C in the biomass resources currently circulating in the environment is 14 As mentioned above, the C concentration is about 1 × 10 -12 Therefore, by utilizing the difference between these values, it is possible to calculate the ratio (biomass ratio) of compounds derived from natural resources (compounds derived from biomass resources) in a certain compound (rubber).

[0114] this 14 C is typically measured as follows: using accelerator mass spectrometry based on a tandem accelerator; 13 C concentration ( 13 C / 12 C), 14 C concentration ( 14 C / 12 C) is measured. 14 The modern standard reference for C concentration is the carbon circulating in nature as of 1950. 14The specific standard substance used is an oxalic acid standard provided by the National Institute of Standards and Technology (NIST). The specific radioactivity of carbon in this oxalic acid (per gram of carbon) is 14 C radioactivity intensity) for each carbon isotope, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 The ratio of this value to the value of the actually measured sample is the pMC value.

[0115] Therefore, if rubber is made from 100% biomass (natural) derived materials, it will show a value of approximately 110 pMC, although there may be regional differences (currently, under normal conditions, it is often not 100). On the other hand, for chemical substances derived from fossil fuels such as petroleum, 14 When the C concentration is measured, it will be approximately 0 pMC (for example, 0.3 pMC), which corresponds to the biomass ratio of 0% mentioned above.

[0116] From the above, it is preferable in terms of environmental protection to use a material such as rubber having a high pMC value, that is, a material such as rubber having a high biomass ratio, in a rubber composition.

[0117] (Other Rubber Components) The rubber component may contain other rubber components besides diene rubbers, as long as the effects of the present invention are not affected. Examples of other rubber components besides diene rubbers include crosslinkable rubber components commonly used in the tire industry, such as butyl rubber (IIR), halogenated butyl rubber, ethylene propylene rubber, polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber, fluororubber (FKM), acrylic rubber (ACM), and hydrin rubber. In addition to the above rubber components, a known thermoplastic elastomer may or may not be contained. The other rubber components may be used alone, or two or more may be used in combination.

[0118] (Three-component system) When the rubber component consists of only two selected from the group consisting of isoprene-based rubber, SBR, and BR, if the range of the content of one of the rubber components is defined based on the above explanation, the range of the content of the remaining rubber components will naturally be determined accordingly. Also, when the rubber component consists of only isoprene-based rubber, SBR, and BR, if the ranges of the content of any two of these rubber components are defined based on the above explanation, the range of the content of the remaining rubber components will naturally be determined accordingly.

[0119] <Water absorbing agent> The rubber composition may contain a water absorbing agent. The water absorbing agent is a water absorbing agent that, when blended into a rubber composition containing a rubber component mainly composed of a diene rubber, increases the water absorption rate V WAB is 0.020 g / day or more, and the evaporation rate V WEV The water-absorbing agent is a single additive material or a combination of multiple additive materials such that the water-absorbing capacity is 0.030 g / day or more. Here, "containing a diene rubber as a main component" means that the content of the diene rubber in the rubber component is 90 mass % or more, and "rubber composition" means a mixture in which the content of the rubber component in the rubber composition is 10 mass % or more and 90 mass % or less. In this specification, any water-absorbing agent can be used as long as it exhibits the above characteristics.

[0120] Examples of the single additive material include water-absorbent resins and water-absorbent polymers. The water-absorbent resins and water-absorbent polymers are water-insoluble hydrophilic substances obtained by introducing intermolecular crosslinks into water-soluble polymers having hydrophilic groups such as carboxyl groups, hydroxyl groups, or salts thereof, or copolymers with derivatives thereof. More specific examples generally known are the following 1) to 13). The water-absorbing agents may be used alone or in combination of two or more. 1) A copolymer of a polymerizable vinyl compound such as methyl vinyl ether, vinyl acetate or styrene with maleic anhydride or a derivative thereof, or a crosslinked product of its alkali-neutralized product. 2) A copolymer of an α-olefin such as ethylene, propylene, butene-1-isobutylene or diisobutylene, preferably an α-olefin having 2 to 12 carbon atoms, with maleic anhydride or a derivative thereof, or a crosslinked product of its alkali-neutralized product. 3) A polymer of acrylic acid or methacrylic acid, a copolymer mainly composed of these, or a crosslinked product of the alkali-neutralized copolymer. 4) A self-crosslinking alkali metal acrylate polymer obtained from an alkali metal acrylate or an alkali metal methacrylate. 5) A saponified copolymer of a vinyl ester and a (meth)acrylic ester. 6) A product obtained by graft polymerizing (meth)acrylonitrile onto starch, or a crosslinked product of the alkali-neutralized product. 7) A product obtained by graft polymerizing acrylic acid, methacrylic acid or maleic anhydride onto starch, or a crosslinked product of the alkali-neutralized product. 8) Starch carboxymethylated with monochloroacetic acid or the like and crosslinked with formalin or the like. 9) Cellulose graft polymerized with (meth)acrylonitrile, or a crosslinked product of its alkali neutralization. 10) Polyoxyethylene crosslinked by radiation or the like. 11) Crosslinked product of cellulose carboxymethylated with monochloroacetic acid or the like. I2) Polyvinyl alcohol crosslinked by dialdehyde or radiation or the like. 13) Crosslinked polyvinyl alcohol modified with maleic anhydride, itaconic acid or crotonic acid.

[0121] Among these, polymers of acrylic acid or methacrylic acid, copolymers mainly containing them, or crosslinked products of alkali-neutralized copolymers thereof are preferred. As the water-absorbing agent, for example, commercially available products from Toagosei Co., Ltd. can be used.

[0122] The content of the water absorbing agent 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 9 parts by mass or more, from the viewpoint of the effects of the present invention, while 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, from the viewpoint of the effects of the present invention.

[0123] The rubber composition according to the present embodiment may contain fillers, silane coupling agents, and other compounding agents in addition to the rubber component and the water absorbing agent.

[0124] <Filler> The filler preferably contains silica, more preferably contains carbon black and silica, and may be a filler consisting of only carbon black and silica.

[0125] (Silica) The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica) or silica prepared by a wet method, which are commonly used in the tire industry. The raw material for silica is not particularly limited, and can be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from biomass materials such as rice husk), or silica recycled from silica-containing products. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number of silanol groups. The silica may be surface-modified with hydrophilic functional groups such as carboxyl groups, amino groups, or hydroxyl groups. Such modified silica can be suitably used as ion-bonded modified silica. These silicas can be used alone or in combination of two or more types.

[0126] Silica made from biomass materials can be obtained, for example, by extracting silicate from rice husk ash obtained by burning rice husks using a sodium hydroxide solution, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

[0127] Silica recycled from silica-containing products can be, for example, silica recovered from products containing silica, such as electronic components such as semiconductors, tires, desiccants, and filtering materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and decomposition by electromagnetic waves. Among these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0128] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0129] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Inc., etc.

[0130] The nitrogen adsorption specific surface area (N2SA) of silica is 110 m from the viewpoints of reinforcement, fracture strength, and abrasion resistance. 2 / g or more is preferable, and 130m 2 / g or more is more preferable, and 150m 2 / g or more is more preferable, and 170m 2 From the viewpoint of heat buildup and processability, it is particularly preferable that the viscosity is 350 m / g or more. 2 / g or less is preferable, and 300m 2 / g or less is more preferable, and 250m 2 / g or less is more preferable. The N2SA of silica is measured by the above-mentioned measurement method.

[0131] The average primary particle size of silica is preferably 20 nm or less, more preferably 19 nm or less, even more preferably 18 nm or less, and particularly preferably 17 nm or less, from the viewpoint of increasing the specific surface area of ​​silica, increasing the interaction with the rubber component, suppressing the movement of molecular chains, and thereby suppressing heat generation. The lower limit of the average primary particle size is not particularly limited, but from the viewpoint of the dispersibility of silica, it is preferably 1 nm or more, more preferably 3 nm or more, and even more preferably 5 nm or more. The average primary particle size of silica is measured by the above-mentioned measurement method.

[0132] From the viewpoint of reinforcement, the content of silica per 100 parts by mass of the rubber component is preferably more than 20 parts by mass, more preferably more than 30 parts by mass, even more preferably more than 40 parts by mass, even more preferably more than 50 parts by mass, even more preferably more than 60 parts by mass, and still more preferably 70 parts by mass or more. Also, from the viewpoint of processability and weight reduction of the rubber, the content is preferably less than 200 parts by mass, more preferably less than 160 parts by mass, even more preferably less than 120 parts by mass, and particularly preferably less than 100 parts by mass.

[0133] (Carbon Black) Carbon black is not particularly limited, and examples thereof include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. The raw material for carbon black may be a biomass material such as lignin or vegetable oil, or pyrolysis oil obtained by pyrolysis of waste tires. Carbon black may be produced by combustion, such as in a furnace process, by hydrothermal carbonization (HTC), or by pyrolysis of methane, such as in a thermal black process. Commercially available carbon blacks include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., and Columbia Carbon Co., Ltd. Carbon black may be used alone or in combination of two or more types.

[0134] The nitrogen adsorption specific surface area (N2SA) of carbon black is 50m from the viewpoint of weather resistance and reinforcement. 2 / g or more, and 80m 2 / g or more is more preferable, and 100m 2From the viewpoints of dispersibility, fuel efficiency, breaking characteristics and durability, it is more preferable that the pore size is more than 250 m / g. 2 / g or less is preferred, 2 / g is more preferable, and 190m 2 The N2SA of carbon black is measured by the above-mentioned measurement method.

[0135] The average primary particle size of carbon black is preferably 32 nm or less, more preferably 28 nm or less, even more preferably 26 nm or less, and particularly preferably 22 nm or less. The average primary particle size is preferably 8 nm or more, more preferably 10 nm or more, even more preferably 12 nm or more, and particularly preferably 14 nm or more. The average primary particle size of carbon black is measured by the above-mentioned measurement method.

[0136] When carbon black is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 3 parts by mass, and even more preferably more than 5 parts by mass from the viewpoints of weather resistance and reinforcement, and is preferably less than 30 parts by mass, more preferably less than 25 parts by mass, even more preferably less than 20 parts by mass, and particularly preferably less than 15 parts by mass from the viewpoint of fuel economy.

[0137] The ratio of the carbon black content to the silica content is preferably 0.40 or less, more preferably 0.33 or less, even more preferably 0.25 or less, even more preferably 0.20 or less, and even more preferably 0.15 or less. By setting the ratio of the carbon black content to the silica content within the above range, fuel economy performance can be further improved. On the other hand, the lower limit of the ratio of the carbon black content to the silica content is not particularly limited and can be, for example, 0.01 or more, 0.02 or more, or 0.05 or more, and the filler may not contain carbon black.

[0138] (Other Fillers) Fillers other than silica and carbon black are not particularly limited, and may include those that have been commonly used in the tire industry, such as aluminum hydroxide, alumina (aluminum oxide), calcium carbonate, magnesium sulfate, talc, clay, biochar, etc. The other fillers may be used alone or in combination of two or more.

[0139] The total amount of fillers per 100 parts by mass of the rubber component is more than 45 parts by mass, preferably more than 55 parts by mass, more preferably more than 65 parts by mass, and even more preferably more than 70 parts by mass from the viewpoint of ensuring reinforcing properties in a dry state. Also, from the viewpoints of fuel economy and processability, the amount is preferably less than 200 parts by mass, more preferably less than 160 parts by mass, even more preferably less than 120 parts by mass, and particularly preferably less than 100 parts by mass.

[0140] <Silane Coupling Agent> When silica is used, it is preferable to use a silane coupling agent in combination. The silane coupling agent is not particularly limited, but examples thereof include sulfide-based silane coupling agents such as bis(3-triethoxysilylpropyl)disulfide and bis(3-triethoxysilylpropyl)tetrasulfide; mercapto-based silane coupling agents such as 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; vinyl-based silane coupling agents such as vinyltriethoxysilane and vinyltrimethoxysilane; 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane and N-2-(aminoethyl)-3-aminopropyltrimethoxysilane Examples of suitable silane coupling agents include amino-based silane coupling agents such as N-2-(aminoethyl)-3-aminopropyltriethoxysilane and N-phenyl-3-aminopropyltrimethoxysilane; glycidoxy-based silane coupling agents such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silane coupling agents such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based silane coupling agents such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane, as well as quaternary ammonium salt-based silane coupling agents such as aqueous silane coupling agents having a quaternary ammonium salt in the organic functional group. Of these, amino-based silane coupling agents, glycidoxy-based silane coupling agents, and quaternary ammonium salt-based silane coupling agents can be suitably used as ionically bond-modified silane coupling agents. As the silane coupling agent, for example, those commercially available from Evonik Industries, Momentive, Shin-Etsu Chemical Co., Ltd., Topco Technologies Corporation, etc. can be used. The silane coupling agent may be used alone or in combination of two or more.

[0141] The content of the silane coupling agent relative to 100 parts by mass of silica is preferably more than 1.0 parts by mass, more preferably more than 3.0 parts by mass, even more preferably more than 5.0 parts by mass, and even more preferably more than 7.0 parts by mass, from the viewpoint of improving the dispersibility of silica.In addition, from the viewpoint of cost and processability, it is preferably less than 20 parts by mass, more preferably less than 15 parts by mass, and even more preferably less than 12 parts by mass.

[0142] <Other Compounding Agents> The rubber composition according to the present embodiment may further contain other compounding agents that are commonly used in the tire industry. Examples of such other compounding agents include softeners, waxes, stearic acid, zinc oxide, antioxidants, rubber powder, vulcanizing agents, vulcanization accelerators, etc.

[0143] (Softener) A softener is a material that imparts plasticity to a rubber component. The term "softener" encompasses both softeners that are liquid (fluid) at room temperature (25°C) and softeners that are solid at room temperature (25°C). Examples of softeners include resins, oils, liquid polymers, and ester-based plasticizers. These softeners may be derived from petroleum, biomass, or naphtha recycled from rubber or non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as softeners. Among these softeners, those modified with a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, silicon, and sulfur can be suitably used as ionically modified softeners. These softeners may be used alone or in combination.

[0144] <<Resin>> The rubber composition according to this embodiment may contain a resin in combination. Resins that can be used in this embodiment are not particularly limited, but resins commonly used in the tire industry can be used, such as C9 resins, C5 resins, C5C9 resins, dicyclopentadiene resins, aromatic vinyl resins, coumarone resins, indene resins, terpene resins, rosin resins, and phenolic resins. These resins may be used alone or in combination of two or more. Each resin may also be used alone or in combination of two or more.

[0145] C9 Resin: "C9 resin" refers to a resin obtained by polymerizing a C9 fraction. It may be a polymer obtained by polymerizing a C9 fraction alone, or a copolymer obtained by copolymerizing a C9 fraction with other components. For example, a resin obtained by copolymerizing dicyclopentadiene (DCPD) with a C9 fraction is called a DCPD / C9 resin. The C9 resin may also be a hydrogenated or modified version of the above. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, coumarone, indene, methylindene, and dicyclopentadiene. Examples of C9 resins that can be used include commercially available C9 resins from BASF, Zeon Corporation, ENEOS Corporation, and others.

[0146] C5 Resin "C5 resin" refers to a resin obtained by polymerizing a C5 fraction, and may be a hydrogenated or modified version of the C5 fraction. Examples of C5 fractions other than dicyclopentadiene include petroleum fractions having 4 to 5 carbon atoms, such as cyclopentadiene, isoprene, piperylene, 2-methyl-1-butene, 2-methyl-2-butene, and 1-pentene. As the C5 resin, for example, commercially available products from Struktol Corporation, Zeon Corporation, ENEOS Corporation, etc. can be used.

[0147] C5C9 Resin: The term "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5C9 petroleum resins that can be used include those commercially available from Tosoh Corporation, LUHUA Corporation, etc.

[0148] Dicyclopentadiene-Based Resin "Dicyclopentadiene-based resin" refers to a resin containing cyclopentadiene (CPD) and / or dicyclopentadiene (DCPD) as the monomer component with the highest content, and may be a hydrogenated or modified version of these. Preferred examples of dicyclopentadiene-based resins include polymers obtained by polymerizing only dicyclopentadiene as a monomer, and copolymers obtained by copolymerizing dicyclopentadiene with the C9 fraction (DCPD / C9 resin). Examples of dicyclopentadiene-based resins that can be used include commercially available products from ExxonMobil Corporation, ENEOS Corporation, Zeon Corporation, Maruzen Petrochemical Co., Ltd., and the like.

[0149] Aromatic vinyl resins: "Aromatic vinyl resins" refer to resins containing aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, and p-chlorostyrene as the monomer component with the highest content, and may be hydrogenated or modified versions of these. As aromatic vinyl resins, homopolymers of α-methylstyrene or styrene, or copolymers of α-methylstyrene and styrene are preferred, and copolymers of α-methylstyrene and styrene are more preferred, because they are economical, easy to process, and have excellent heat generation properties. As aromatic vinyl resins, commercially available products from Kraton, Eastman Chemical Company, Mitsui Chemicals, Inc., and the like can be used.

[0150] Coumarone Resin: "Cumarone resin" refers to a resin containing coumarone as a monomer component, and may be a hydrogenated or modified version of the coumarone resin. Examples of coumarone resins include coumarone resins, which are polymers containing only coumarone as a monomer component; coumarone-indene resins, which are copolymers containing coumarone and indene as monomer components; and coumarone-indene-styrene resins, which are copolymers containing coumarone, indene, and styrene as monomer components. Examples of coumarone resins that can be used include those commercially available from Rutgers, Nippon Paint Chemicals, Mitsui Chemicals, and others.

[0151] Indene-based resins: "Indene-based resins" refer to resins containing indene as a monomer component, and may be hydrogenated or modified versions of these. Examples of preferred indene-based resins include coumarone-indene resins, which are copolymers containing coumarone and indene as monomer components, and coumarone-indene-styrene resins, which are copolymers containing coumarone, indene, and styrene as monomer components. Examples of indene-based resins that can be used include those commercially available from Rutgers, Nippon Paint Chemicals, Mitsui Chemicals, and others.

[0152] Terpene Resins: "Terpene resins" refer to resins containing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene as monomer components, and may be hydrogenated or modified. Examples of terpene resins include polyterpene resins, which are polymers containing only one or more of the terpene compounds as monomer components; aromatic-modified terpene resins, which are copolymers containing the terpene compound and an aromatic compound as monomer components; and terpene phenolic resins, which are copolymers containing the terpene compound and a phenolic compound as monomer components. Examples of aromatic compounds that serve as monomer components for aromatic-modified terpene resins include styrene, α-methylstyrene, vinyltoluene, and divinyltoluene. Examples of phenolic compounds that serve as monomer components for terpene phenolic resins include phenol, bisphenol A, cresol, and xylenol. Examples of terpene resins that can be used include commercially available terpene resins from Yasuhara Chemical Co., Ltd., Arakawa Chemical Industries, Ltd., and Japan Terpene Chemical Co., Ltd.

[0153] Rosin-based resins "Rosin-based resins" refer to resins containing rosin acid compounds such as abietic acid, neoabietic acid, palustric acid, and isopimaric acid, and may be hydrogenated or modified. Examples of rosin-based resins include, but are not limited to, natural rosin resins and rosin-modified resins obtained by modifying the natural rosin resins by hydrogenation, disproportionation, dimerization, esterification, and the like. Rosin-based resins that can be used include those commercially available from Harima Chemicals Co., Ltd., Arakawa Chemical Industries, Ltd., and Airec Co., Ltd.

[0154] Phenolic Resin The term "phenolic resin" refers to a resin containing a phenolic compound such as phenol or cresol as a monomer component, and may be a hydrogenated or modified version of such a resin. Examples of phenolic resins include, but are not limited to, phenol-formaldehyde resin, alkylphenol-formaldehyde resin, alkylphenol-acetylene resin, oil-modified phenol-formaldehyde resin, and terpene-phenol resin. Examples of phenolic resins that can be used include commercially available resins from Sumitomo Bakelite Co., Ltd., DIC Corporation, Asahi Organic Materials Co., Ltd., and the like.

[0155] From the viewpoint of grip performance, the softening point of the resin is preferably 60° C. or higher, more preferably 70° C. or higher, and even more preferably 80° C. or higher. From the viewpoint of processability and improving the dispersibility of the rubber component and the filler, the softening point is preferably 150° C. or lower, more preferably 140° C. or lower, and even more preferably 130° C. or lower. The softening point of the resin is measured by the above-mentioned measurement method.

[0156] When a resin is contained, the content per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 5 parts by mass, even more preferably more than 10 parts by mass, and still more preferably more than 12 parts by mass. From the viewpoint of suppressing heat buildup, the content is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably less than 30 parts by mass.

[0157] <Oil> Examples of oils include process oil, vegetable oil, and animal oil. Examples of process oils include paraffinic process oil (mineral oil), naphthenic process oil, and aromatic process oil. Specific examples of process oils include mild extracted solvate (MES), distillate aromatic extract (DAE), treated distillate aromatic extract (TDAE), treated residual aromatic extract (TRAE), and residual aromatic extract (RAE). Furthermore, as an environmental measure, process oils with a low content of polycyclic aromatic compounds (PCA) can also be used. Examples of low PCA process oils include MES, TDAE, and heavy naphthenic oil. Furthermore, from the perspective of life cycle assessment, refined waste oil from rubber mixers and engines, or waste cooking oil from restaurants, may also be used.

[0158] Examples of vegetable oils include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar oil, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and Japan wax. Further examples of vegetable oils include refined oils (such as salad oil) obtained by refining the above oils, interesterified oils obtained by interesterifying the above oils, hardened oils obtained by hydrogenating the above oils, thermally polymerized oils obtained by thermally polymerizing the above oils, oxidatively polymerized oils obtained by oxidizing the above oils, and waste edible oils recovered from edible oils. Vegetable oils may be liquid or solid at room temperature (25°C). One vegetable oil may be used alone, or two or more may be used in combination.

[0159] The vegetable oil preferably contains acylglycerol, and more preferably triacylglycerol. In this specification, acylglycerol refers to a compound in which a hydroxyl group of glycerin is esterified with a fatty acid. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, the acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. Furthermore, the acylglycerol may be liquid or solid at room temperature (25°C).

[0160] The method for confirming whether the rubber composition contains the acylglycerol is not particularly limited, but may be 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room temperature (25°C) for 24 hours, and after removing the rubber composition, the rubber composition is immersed in deuterated chloroform at room temperature. 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm, assuming that the signal of tetramethylsilane (TMS) was 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester groups. In this paragraph, "around" refers to a range of ±0.10 ppm.

[0161] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid, and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0162] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., saturated fatty acid or monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing saturated fatty acid or monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

[0163] As the vegetable oil, for example, commercially available oils from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Orisoi Corporation, H&R Corporation, Toyokuni Oil Mills Co., Ltd., Fuji Kosan Co., Ltd., Nisshin Oillio Group Co., Ltd., etc. can be used.

[0164] The content of oil per 100 parts by mass of the rubber component (when multiple oils are used in combination, the total amount of all oils) is preferably more than 1 part by mass, more preferably more than 5 parts by mass, and even more preferably more than 8 parts by mass from the viewpoint of processability, and is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably less than 30 parts by mass from the viewpoint of rubber hardness.

[0165] Liquid Polymers The liquid polymer is not particularly limited as long as it is a polymer that is liquid at room temperature (25°C). Examples include liquid butadiene polymer (liquid BR), liquid isoprene rubber polymer (liquid IR), liquid styrene butadiene copolymer (liquid SBR), liquid styrene isoprene rubber copolymer (liquid SIR), and polymers containing myrcene or farnesene. Among these liquid polymers, those whose terminals and / or main chains are modified with a functional group containing at least one element selected from the group consisting of nitrogen, oxygen, silicon, and sulfur can be suitably used as ionically bonded modified liquid polymers. Examples of the functional group include those exemplified for the modified SBR. Examples of liquid polymers that can be used include those manufactured by Kuraray Co., Ltd. One type of liquid polymer may be used alone, or two or more types may be used in combination.

[0166] When a liquid polymer is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 1 part by mass, more preferably more than 5 parts by mass, even more preferably more than 10 parts by mass, and still more preferably more than 12 parts by mass. The content of the liquid polymer is preferably less than 50 parts by mass, more preferably less than 40 parts by mass, and even more preferably less than 30 parts by mass.

[0167] When any one or more of the rubber component, silica, resin, and liquid polymer are modified with a carboxyl group, various metal salts may be blended to form ionic bonds in the rubber composition. Examples of these metal salts include metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, rubidium carbonate, cesium carbonate, beryllium carbonate, magnesium carbonate, calcium carbonate, strontium carbonate, barium carbonate, and lithium acetate; metal acetates such as sodium acetate, potassium acetate, rubidium acetate, cesium acetate, beryllium acetate, magnesium acetate, calcium acetate, strontium acetate, and barium acetate; and metal phenoxides such as lithium phenoxide, sodium phenoxide, potassium phenoxide, rubidium phenoxide, cesium phenoxide, beryllium diphenoxide, magnesium diphenoxide, calcium diphenoxide, strontium diphenoxide, and barium diphenoxide.

[0168] Ester-Based Plasticizers Examples of ester-based plasticizers include dibutyl adipate (DBA), diisobutyl adipate (DIBA), dioctyl adipate (DOA), di-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), diisononyl adipate (DINA), diethyl phthalate (DEP), dioctyl phthalate (DOP), diundecyl phthalate (DUP), dibutyl phthalate (DBP), dioctyl sebacate (DOS), tributyl phosphate (TBP), trioctyl phosphate (TOP), triethyl phosphate (TEP), trimethyl phosphate (TMP), thymidine triphosphate (TTP), tricresyl phosphate (TCP), and trixylenyl phosphate (TXP). These ester-based plasticizers may be used alone or in combination of two or more.

[0169] The amount of the softener per 100 parts by mass of the rubber component (the total amount when multiple softeners are used in combination) is preferably more than 5 parts by mass, more preferably more than 10 parts by mass, even more preferably more than 15 parts by mass, and still more preferably more than 20 parts by mass. The amount is also preferably less than 100 parts by mass, more preferably less than 80 parts by mass, and even more preferably less than 60 parts by mass.

[0170] (Wax) The wax is not particularly limited, and any wax commonly used in the tire industry can be suitably used. Examples include petroleum-based waxes, mineral waxes, synthetic waxes, and plant-derived waxes. Of these, petroleum-based waxes and plant-derived waxes are preferred, and petroleum-based waxes are more preferred. Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of petroleum-based waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. The wax according to this embodiment does not contain stearic acid. Waxes that can be used include those commercially available from, for example, Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Paramelt Co., Ltd. One type of wax may be used alone, or two or more types may be used in combination.

[0171] When the wax is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of weather resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of preventing whitening of the tire due to bloom.

[0172] (Antiaging Agent) The antiaging agent is not particularly limited, and examples thereof include naphthylamine-based antiaging agents such as phenyl-α-naphthylamine; diphenylamine-based antiaging agents such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine-based antioxidants such as N-isopropyl-N'-phenyl-p-phenylenediamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline-based antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and a polymer of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline is more preferred. Commercially available products that can be used include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, and the like. One type of antioxidant may be used alone, or two or more types may be used in combination.

[0173] When an antioxidant is contained, the content per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of ozone crack resistance of the rubber, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of abrasion resistance.

[0174] (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 1.0 parts by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of vulcanization rate.

[0175] (Zinc Oxide) When zinc oxide is contained, the content thereof per 100 parts by mass of the rubber component is preferably 0.5 parts by mass or more, more preferably 1.0 part by mass or more, and even more preferably 1.5 parts by mass or more from the viewpoint of processability, and is preferably 10 parts by mass or less, more preferably 5.0 parts by mass or less from the viewpoint of abrasion resistance.

[0176] (Rubber crumb) The rubber crumb is particles made of vulcanized rubber, and specifically, rubber crumb specified in JIS K 6316:2017 or the like can be used. From the viewpoint of environmental considerations and cost, recycled rubber crumb produced from crushed waste tires or the like is preferred. One type of rubber crumb may be used alone, or two or more types may be used in combination.

[0177] The rubber powder is not particularly limited, and may be either unmodified vulcanized rubber particles or modified vulcanized rubber particles. Commercially available rubber powder products include those from Lehigh Co., Ltd. and Muraoka Rubber Industries Co., Ltd.

[0178] The content of the vulcanized rubber particles 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, per 100 parts by mass of the rubber component, and is preferably 20 parts by mass or less, more preferably 15 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above ranges, the effects of the present invention tend to be more favorably obtained.

[0179] (Vulcanizing Agent) Sulfur is preferably used as the vulcanizing agent. Examples of sulfur that can be used include powdered sulfur, oil-treated sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The vulcanizing agent may be used alone or in combination of two or more.

[0180] When sulfur is contained as a vulcanizing agent, the content per 100 parts by mass of the rubber component is preferably more than 0.1 parts by mass, more preferably more than 0.5 parts by mass, and even more preferably more than 1.0 part by mass, from the viewpoint of ensuring a sufficient vulcanization reaction. Furthermore, from the viewpoint of preventing deterioration, the content is preferably less than 5.0 parts by mass, more preferably less than 4.0 parts by mass, and even more preferably less than 3.5 parts by mass. Furthermore, from the viewpoint of the effects of the present invention, the content of the vulcanizing agent is preferably 3.0 parts by mass or less, more preferably less than 2.5 parts by mass, even more preferably less than 2.0 parts by mass, and even more preferably 1.5 parts by mass or less, in order to reduce the density of sulfur crosslinks. When oil-containing sulfur is used as the vulcanizing agent, the content of the vulcanizing agent is the total content of pure sulfur contained in the oil-containing sulfur.

[0181] Examples of vulcanizing agents other than sulfur include alkylphenol-sulfur chloride condensate, 1,6-hexamethylene-sodium dithiosulfate dihydrate, 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane, etc. These vulcanizing agents other than sulfur may be commercially available from Taoka Chemical Co., Ltd., Lanxess K.K., Flexis, etc. One type of vulcanizing agent other than sulfur may be used alone, or two or more types may be used in combination.

[0182] (Vulcanization accelerator) Examples of vulcanization accelerators include sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, guanidine vulcanization accelerators, thiuram vulcanization accelerators, dithiocarbamate vulcanization accelerators, caprolactam disulfide, etc. Among them, in order to more suitably obtain the desired effect, one or more vulcanization accelerators selected from the group consisting of sulfenamide vulcanization accelerators, thiazole vulcanization accelerators, and guanidine vulcanization accelerators are preferred, and it is more preferred to use a sulfenamide vulcanization accelerator and a guanidine vulcanization accelerator in combination. One vulcanization accelerator may be used alone, or two or more may be used in combination.

[0183] Examples of sulfenamide vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N,N-dicyclohexyl-2-benzothiazolylsulfenamide (DCBS), etc. Among these, TBBS and CBS are preferred.

[0184] Examples of thiazole vulcanization accelerators include 2-mercaptobenzothiazole (MBT) or its salts, di-2-benzothiazolyl disulfide (MBTS), 2-(2,4-dinitrophenyl)mercaptobenzothiazole, 2-(2,6-diethyl-4-morpholinothio)benzothiazole, etc. Among these, MBTS and MBT are preferred, and MBTS is more preferred.

[0185] Examples of guanidine vulcanization accelerators include 1,3-diphenylguanidine (DPG), 1,3-di-o-tolylguanidine, 1-o-tolylbiguanide, di-o-tolylguanidine salt of dicatechol borate, 1,3-di-o-cumenylguanidine, 1,3-di-o-biphenylguanidine, 1,3-di-o-cumenyl-2-propionylguanidine, etc. Of these, DPG is preferred.

[0186] When a vulcanization accelerator is contained, the content thereof per 100 parts by mass of the rubber component is preferably more than 0.5 parts by mass, more preferably more than 1.0 part by mass, and even more preferably more than 1.5 parts by mass. The content of the vulcanization accelerator per 100 parts by mass of the rubber component is preferably less than 8.0 parts by mass, more preferably less than 6.0 parts by mass, and even more preferably less than 5.0 parts by mass. By setting the content of the vulcanization accelerator within the above range, breaking strength and elongation tend to be ensured.

[0187] In this specification, various materials containing carbon atoms (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from atmospheric carbon dioxide. The various materials may be obtained from carbon dioxide by directly converting carbon dioxide or by converting methane obtained through a methanation process in which methane is synthesized from carbon dioxide.

[0188] [Production of Rubber Composition and Tire] The water-absorbing rubber composition 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 (e.g., a Banbury mixer or a kneader).

[0189] The kneading step includes, for example, a base kneading step in which compounding ingredients and additives other than the vulcanizing agent and vulcanization accelerator are kneaded, and a final kneading (F kneading) step in which the vulcanizing agent and vulcanization accelerator are added to the kneaded product obtained in the base kneading step and kneaded. Furthermore, the base kneading step can be divided into a plurality of steps as desired.

[0190] The kneading conditions are not particularly limited, but examples thereof include a method in which the base kneading step involves kneading for 3 to 10 minutes at a discharge temperature of 150 to 170°C, and a method in which the final kneading step involves kneading for 1 to 5 minutes at 70 to 110°C. The vulcanization conditions are not particularly limited, but examples thereof include a method in which vulcanization is carried out for 10 to 30 minutes at 150 to 200°C.

[0191] A tire according to the present embodiment, which includes a tread portion including a water-absorbent rubber layer made of the water-absorbent rubber composition, can be manufactured by a conventional method. For example, an unvulcanized rubber composition obtained by blending the above-described components with a rubber component as needed is extruded to match the shape of the water-absorbent rubber layer that constitutes the tread portion, and the resulting composition is arranged so that a non-water-absorbent rubber layer is located on the tire radially inner side of the tread portion, and a rubber layer with embedded metal cords is located further inside that. The resulting composition is then bonded together with other tire components in a tire building machine and molded by a conventional method to form an unvulcanized tire. This unvulcanized tire can then be heated and pressurized in a vulcanizer to produce a tire. Vulcanization conditions are not particularly limited, and examples include vulcanization at 150 to 200°C for 10 to 30 minutes.

[0192] [Use of Tire] The tire according to the present embodiment can be suitably used as a passenger car tire, a truck / bus tire, a motorcycle tire, or a racing tire, and is particularly 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.

[0193] Examples (working examples) that are considered preferable for carrying out the present invention are shown below, but the scope of the present invention is not limited to these examples. Tires having a first layer of a tread portion obtained according to the formulations in Table 1 were examined using the various chemicals shown below, and the results calculated based on the evaluation method described below are shown at the bottom of Table 1.

[0194] The various chemicals used in the examples and comparative examples are summarized below. IR rubber: natural rubber (TSR20) SBR: Nipol NS616 (S-SBR, styrene content: 21 mass%, vinyl content: 61 mol%, Mw: 510,000, non-oil extended) manufactured by ZS Elastomers Co., Ltd. BR: Nipol BR1220 (BR synthesized using a cobalt-based catalyst, cis content: 96 mol%, Mw: 460,000) manufactured by Nippon Zeon Co., Ltd. Carbon black: Seast N220 (N2SA: 114m) manufactured by Tokai Carbon Co., Ltd. 2 / g, average primary particle size: 22 nm) Silica: ULTRASIL (registered trademark) VN3 (NSA: 175 m) manufactured by Evonik Industries 2 / g, average primary particle size: 17 nm) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik Industries. Silane coupling agent 2 (ionically bonded modified silane coupling agent): KBE603 (N-2-(aminoethyl)-3-aminopropyltriethoxysilane, amino-based silane coupling agent) manufactured by Topco Technologies Corporation. Silane coupling agent 3 (ionically bonded modified silane coupling agent): X-12-1126 (quaternary ammonium salt-based silane coupling agent) manufactured by Shin-Etsu Chemical Co., Ltd. Liquid polymer (ionically bonded modified liquid polymer): Kurapren LIR410 manufactured by Kuraray Co., Ltd. (modified liquid polyisoprene having approximately 10 carboxyl groups per molecule and a number average molecular weight of 25,000). Water absorbent: Junron PW-120 manufactured by Toagosei Co., Ltd. (crosslinked polyacrylic acid, loss on drying: 5% or less, viscosity (aqueous solution concentration, temperature): 8,000 to 20,000 mPa·s / 25°C (0.2% neutralization, 25°C), pH: 2.5 to 4.0 (0.2% aqueous solution concentration), bulk density: 0.3 to 0.5 g / L) Oil: Process X-140 manufactured by ENEOS Corporation Resin: Petrotack 90 manufactured by Tosoh Corporation (C5C9 petroleum resin, Mw 1600, softening point 95°C) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: Camellia stearate beads manufactured by NOF Corporation Wax: Sunnock N (paraffin wax) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Antiaging agent: Antigen 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Sumitomo Chemical Co., Ltd. Sulfur: powdered sulfur manufactured by Karuizawa Iso Co., Ltd. Vulcanization accelerator 1: Noccela D (1,3-diphenylguanidine (DPG)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noccela NS-G (N-tert-butyl-2-benzothiazolylsulfenamide (TBBS)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0195] [Examples and Comparative Examples] According to the formulations shown in Tables 1 and 2, chemicals other than sulfur and a vulcanization accelerator were kneaded using a closed-type Banbury mixer to obtain a kneaded mixture. Next, sulfur and a vulcanization accelerator were added to the kneaded mixture using a two-screw open roll, and the mixture was kneaded to obtain an unvulcanized rubber composition. The unvulcanized rubber composition was extruded to fit the shape of a cap tread using an extruder equipped with a predetermined die. A base tread made of a non-water-absorbing rubber composition, a band ply having nylon cords embedded therein and covered with a non-water-absorbing rubber composition, and a belt ply having steel cords embedded therein and covered with a non-water-absorbing rubber layer were arranged in this order on the tire radially inward side of the tire centerline of the cap tread, and these were then laminated together with other tire components to produce an unvulcanized tire. The test tires (size: 195 / 65R15) shown in Tables 1 and 2 were then produced by press-vulcanizing.

[0196] <Water absorption rate V of water-absorbing rubber composition WAB (g / day)> A rectangular rubber test piece measuring 30 mm in length, 20 mm in width, and 2 mm in thickness was cut from the inside of the cap tread of each test tire, and its mass was measured. Each rubber test piece thus obtained was left to stand in an environment of 25°C, 50% relative humidity, and 1 atm until it reached constant weight, and the mass at that point was taken as the dry mass (g). Here, constant weight means that when the mass measurement of each rubber test piece was repeated every two hours, the difference between the mass of the measurement result and the mass of the immediately preceding measurement result was within 0.05 μg. However, if constant weight was not reached after 7 days, it was deemed to have been reached after 7 days had passed. Thereafter, each rubber test piece was immersed in a water tank filled with ion-exchanged water (set at a water temperature of 40°C) in an amount sufficient to completely immerse the rubber test piece, under an environment of 1 atm. Every two hours, each rubber test piece was removed and its mass was measured. The mass at which a constant weight was reached was taken as the water-absorbed mass (g), and the time required for immersion up to that point was taken as the immersion time. Here, the term "constant weight" has the same meaning as the constant weight in the measurement of the dry mass. The water absorption rate (g / day) was calculated from the dry mass (g), the water-absorbed mass (g), and the immersion time (hours) using the following formula, and the water absorption rate V WABHowever, if the weight is considered to have reached a constant value after 7 days of soaking, calculate by replacing "soaking time / 24" with "7". Water absorption rate = (absorbed mass - dry mass) / (soaking time / 24)

[0197] <Evaporation rate V of water-absorbing rubber composition WEV (g / day)> Each rubber test piece was cut from the inside of the cap tread of each test tire into a rectangular parallelepiped shape measuring 30 mm in length, 20 mm in width, and 2 mm in thickness. Each rubber test piece thus obtained was immersed in a water tank containing ion-exchanged water (set at 40°C) in an amount sufficient to completely immerse each rubber test piece, under an environment of 1 atm, for 7 days. After immersion, each rubber test piece was removed and its mass was measured. This mass was taken as the saturated mass (g). Each rubber test piece was then allowed to dry statically under an environment of 40°C, 50% relative humidity, and 1 atm, with the mass measured every two hours. The mass at which a constant mass was reached was taken as the dry mass (g), and the time required for drying up to that point was taken as the drying time. Here, "constant mass" refers to a situation in which, when the mass of each rubber test piece was repeatedly measured every two hours, the difference between the mass of the measurement result and the mass of the immediately preceding measurement was within 0.05 μg. However, if the weight does not reach a constant value after 7 days, it is considered to have reached a constant weight after 7 days. The evaporation rate (g / day) is calculated from the saturated mass (g), the dry mass (g), and the drying time (hours) using the following formula. WEV However, if the weight is considered to be constant after 7 days of drying, calculate by replacing "drying time / 24" with "7". Evaporation rate = (saturated mass - dry mass) / (drying time / 24)

[0198] <Thickness D of Non-Water-Absorbing Rubber Composition> For each test tire, the thickness of the base tread on the tire centerline, the thickness of the band ply, and the thickness from the band ply to the steel cord in the belt ply adjacent to the band ply were summed to obtain the thickness D of the non-water-absorbent rubber layer.

[0199] Viscoelasticity measurement (tan δ SAT , tanδ DRYEach vulcanized rubber test piece was cut from the inside of the cap tread of each test tire, measuring 20 mm in length, 4 mm in width, and 1 mm in thickness, with the long side aligned in the tire circumferential direction and the thickness direction aligned in the tire radial direction. The test piece was then immersed in ion-exchanged water at 25°C for 12 hours to obtain a water-wetted vulcanized rubber composition. Tan δ of the water-wetted vulcanized rubber composition was measured using a dynamic viscoelasticity measuring device (GABO's Iplexer series) under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an extension mode. SAT Next, the vulcanized rubber composition after wetting with water is dried under reduced pressure at 80°C and 1 kPa or less until it reaches a constant weight, thereby obtaining a dried vulcanized rubber composition. This dried vulcanized rubber composition is measured for tanδ using a dynamic viscoelasticity measuring device (GABO Iplexer series) under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, a dynamic strain of ±1%, and an extension mode. DRY Measure.

[0200] <Grip Performance> Each test tire was manufactured according to the above manufacturing example, and each test tire was mounted on all wheels of a vehicle (domestic FF 2000cc). The time required to complete one lap around a circuit course (2 km per lap) on an asphalt road surface with a mixture of wet and dry road surfaces was measured. The time saved by the tire of each example was measured using the time saved by the tire of the reference example (the tire of Comparative Example 1 in which the rubber component was changed to 100% IR rubber). The higher the index shown below, the better the grip performance. (Grip performance index) = (time saved by tire of each example) / (time saved by tire of Comparative Example 1) × 100

[0201] <Durability Performance> Each test tire is immersed in water at room temperature and normal pressure for 30 days, and then dried at high temperature. This tire is mounted on a regular rim and inflated with air to an internal pressure of 250 kPa. This tire is mounted on a drum-type running test machine and run under conditions of a load of 7.33 kN and a speed of 100 km / h without replenishing the air pressure, and the running distance until damage occurs is measured. The running distance is expressed as an index, with the reference comparative example being set at 100. A higher value indicates higher durability.

[0202] <Overall Performance> Overall performance is indicated by the sum of the grip performance index and the durability performance index.

[0203]

[0204]

[0205] <Embodiments> Examples of embodiments of the present invention are shown below.

[0206] [1] A tire comprising a tread portion and a rubber layer in which metal cords are embedded, the rubber layer being disposed radially inward of the tread portion, wherein the tread portion includes a water-absorbent rubber layer made of a water-absorbent rubber composition, and a non-water-absorbent rubber layer made of a non-water-absorbent rubber composition is present between an end of the water-absorbent rubber layer and the metal cord in the tire radial direction, and the water absorption rate V from a dry state of a rectangular parallelepiped sample having a length of 30 mm, a width of 20 mm, and a thickness of 2 mm cut out from the water-absorbent rubber layer is WAB is 0.020 g / day or more, and the evaporation rate V from the water saturated state WEV is 0.030 g / day or more, and tanδ, which is the loss tangent of the water-absorbing rubber composition in a dry state at 30°C, DRY tanδ, which is the loss tangent at water saturation and 30 ° C. SAT The ratio tan δ SAT / tanδ DRY is 1.05 or more, and when the thickness (mm) of the non-water-absorbent rubber layer is D, D and V WEV A tire that satisfies the following formula (1): WEV [2] The tire according to the above [1], wherein the water-absorbing rubber composition contains an ionic bonding material. [3] The evaporation rate V WEV to the water absorption rate V WAB The tire according to the above [1] or [2], wherein the evaporation rate V is greater than 0. WEV to the water absorption rate V WAB[1] The tire according to the above [1] or [2], wherein the value obtained by subtracting the above is greater than 0.010. [5] The tire according to any one of the above [1] to [4], wherein the rubber component in the water-absorbing rubber composition contains at least one of styrene-butadiene rubber and butadiene rubber. [6] The tire according to the above [5], wherein the total content of the styrene-butadiene rubber and butadiene rubber in the rubber component is 50% by mass or more. [7] The tire according to any one of the above [1] to [6], wherein the water-absorbing rubber composition contains 50 parts by mass or more of silica per 100 parts by mass of the rubber component. [8] The tire according to any one of the above [1] to [7], wherein the water-absorbing rubber composition contains a resin. [9] The tire according to any one of the above [1] to [8], wherein the water-absorbing rubber composition contains 3.0 parts by mass or less of sulfur per 100 parts by mass of the rubber component.

[10] The tire according to any one of the above [1] to [9], wherein the land ratio R of the tread surface of the tread portion is 0.70 or more.

[11] The evaporation rate V WEV and the land ratio R is greater than 0.030.

[0207] 1 Tire 2 Tread portion 3 Tread surface 4 Tread rubber layer 5 Band ply 6 Band ply 7 Belt ply 8 Belt ply 9 Carcass ply D Thickness of non-water-absorbent rubber layer CL Tire center line

Claims

1. A tire having a tread portion and a rubber layer in which metal cords are embedded, the rubber layer being disposed radially inward of the tread portion, the tread portion including a water-absorbent rubber layer made of a water-absorbent rubber composition, a non-water-absorbent rubber layer made of a non-water-absorbent rubber composition existing between an end of the water-absorbent rubber layer and the metal cord in the tire radial direction, and a rectangular sample of 30 mm in length x 20 mm in width x 2 mm in thickness cut out from the water-absorbent rubber layer, the water absorption speed V from a dry state of WAB is 0.020 g / day or more, and the evaporation rate V from the water saturated state WEV is 0.030 g / day or more, and the loss tangent tanδ of the water-absorbing rubber composition in a dry state at 30° C. is DRY tan δ, which is the loss tangent at 30° C. and in a water saturated state SAT Ratio tan δ SAT / tan δ DRY is 1.05 or more, and when the thickness (mm) of the non-water-absorbent rubber layer is D, D and V WEV A tire that satisfies the following formula (1). WEV ×D>0.10 2. The tire according to claim 1, wherein said water-absorbing rubber composition contains an ionic bonding material.

3. The evaporation rate V WEV from the water absorption rate V WAB The tire according to claim 1 or 2, wherein the value obtained by subtracting 4. The evaporation rate V WEV from the water absorption rate V WAB The tire according to claim 1 or 2, wherein the value obtained by subtracting 5. The tire according to any one of claims 1 to 4, wherein the rubber component in the water-absorbing rubber composition contains at least one of a styrene-butadiene rubber and a butadiene rubber.

6. The tire according to claim 5, wherein the total content of the styrene-butadiene rubber and the butadiene rubber in the rubber component is 50 mass % or more.

7. The tire according to any one of claims 1 to 6, wherein the water-absorbing rubber composition contains 50 parts by mass or more of silica per 100 parts by mass of the rubber component.

8. The tire according to any one of claims 1 to 7, wherein the water-absorbing rubber composition contains a resin.

9. The tire according to any one of claims 1 to 8, wherein the water-absorbing rubber composition contains 3.0 parts by mass or less of sulfur per 100 parts by mass of the rubber component.

10. The tire according to any one of claims 1 to 9, wherein the land ratio R of the tread surface of the tread portion is 0.70 or greater.

11. The evaporation rate V WEV and said land ratio R is greater than 0.030.

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