Tire

Abstract

Provided is a tire capable of sufficiently improving wet grip performance during high-speed rotation even when a sustainable material is used. A tire in which a plurality of land portions and groove portions are provided on the surface of a tread portion, in which the tread portion is formed by laminating a tread tread and a tread base portion from the ground contact surface side, the depression ratio Nr (%) within the width of the ground contact surface is less than 20%, and both the tread tread and the tread base portion are configured from a rubber composition containing a vulcanized rubber powder, when the area ratio of the vulcanized rubber powder in the tread running surface is Srout (%) and the area ratio of the vulcanized rubber powder in the tread base part is Srin (%), Nr, Srout, and Srin satisfy the following formula (1): 3 > = (Srout + Srin) / Nr (formula (1)).

Description

Technical Field

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

[0002] As a technique for improving the wet grip performance of a tire, various proposals have been made regarding tire shape, rubber composition formulation, and the like (for example, Patent Documents 1 to 3).

Prior art literature

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-043709 [Patent Document 2] Japanese Patent Application Publication No. 2018-135436 [Patent Document 3] Japanese Patent No. 2021-167401 Summary of the Invention [Problems to be Solved by the Invention]

[0004] However, in recent years, with the improvement of expressways and vehicle performance, high-speed driving has become common, and there is an increasing demand for improved grip performance during high-speed cornering on slippery roads (wet grip performance during high-speed cornering).

[0005] Furthermore, with the increasing momentum of environmental protection in recent years, there is a growing demand for tires that use sustainable materials and reduce their environmental impact. However, the indiscriminate use of sustainable materials, while reducing environmental impact, can lead to reduced tire performance. For example, vulcanized rubber powder, a recycled material obtained by pulverizing vulcanized rubber, has recently attracted attention as a sustainable material, and attempts have been made to incorporate it into rubber compositions used to form tires, but this can lead to reduced tire performance.

[0006] In view of the above problems, the present invention aims to provide a tire that can sufficiently improve wet grip performance during high-speed cornering even when vulcanized rubber powder made of a sustainable material is used. [Means for solving the problem]

[0007] The present invention is a tire characterized by: A tire having a plurality of land portions and groove portions on the surface of the tread portion. The tread portion is formed by laminating a cap tread and a base tread from the contact surface side, and a concavity rate Nr (%) within the contact surface width is less than 20%. The cap tread and the base tread are both composed of a rubber composition containing vulcanized rubber powder. The area ratio of the vulcanized rubber powder in the cap tread is Sr out(%), the area ratio of the vulcanized rubber powder in the base tread is Sr in (%), the Nr, Sr out and Sr in Satisfies the following (Formula 1), 3≥(Sr out +Sr in ) / Nr(Formula 1). [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a tire capable of sufficiently improving wet grip performance in high-speed cornering even when using sustainable materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0009]

Figure 1

[0010] [1] Features of the tire of the present invention First, the features of the tire of the present invention will be described.

[0011] 1. Summary The tire of the present invention is a tire having a plurality of land portions and groove portions on the surface of a tread portion, wherein the tread portion is formed by laminating a cap tread and a base tread from the contact surface side, and wherein the concavity rate Nr (%) within the width of the contact surface is less than 20%, and both the cap tread and the base tread are composed of a rubber composition containing vulcanized rubber powder. Furthermore, when the area ratio of the vulcanized rubber powder in the cap tread is Sr out(%), the area ratio of the vulcanized rubber powder in the base tread is Sr in (%), Nr, Sr out and Sr in The following (Formula 1) is satisfied. 3≥(Sr out +Sr in ) / Nr (Formula 1)

[0012] By having these features, as will be described later, it is possible to provide a tire that can sufficiently improve wet grip performance in high-speed cornering even when using sustainable materials.

[0013] 2. Mechanism of the Effects of the Tire of the Present Invention The mechanism by which the tire of the present invention exhibits the above-mentioned effects is considered to be as follows.

[0014] (1) Concave rate In the tire of the present invention, the tread portion is formed so that the concavity ratio Nr (%) within the width of the contact patch is less than 20%.

[0015] It is believed that by suppressing the sag ratio Nr within the contact patch width to less than 20%, a large contact area between the tire and the road surface is maintained. This allows the tire to firmly grip the road surface and follow the road surface even during high-speed cornering on slippery and wet roads, significantly improving wet grip performance during high-speed cornering. This ratio is more preferably 15% or less, and even more preferably 10% or less.

[0016] In the above description, the sag ratio Nr (%) within the contact patch width refers to the ratio (%) of the total open area of the multiple grooves to the virtual contact area of the tread portion with the multiple grooves completely filled (the total contact area of the entire circumference of the tire, when the tread portion of the tire with the multiple grooves completely filled is pressed against a flat surface at a camber angle of 0°, with the tire in a normal state, under normal internal pressure and normal load). It should be noted that the virtual contact area and the groove area can be calculated by calculating the groove area of the contact patch over the entire circumference of the tire. More simply, this can be measured by applying ink, etc., to the tire surface and transferring the ink.

[0017] Specifically, the ground contact shape can be obtained by assembling the tire on a regular rim, applying a regular internal pressure, and then standing at 25°C for 24 hours. Then, ink is applied to the tire surface, a regular load is applied, and the tire is pressed on thick paper (camber angle is 0°), and then transferred to the paper. The tire is rotated in the circumferential direction at intervals of 72° and transferred at 5 positions. That is, the ground contact shape is obtained by 5 times. For the 5 ground contact shapes, the average value of the maximum length in the axial direction of the tire is L, and the average value of the length in the direction perpendicular to the axial direction is W. The concave rate (%) is calculated by [1-{average area of 5 ground contact shapes (ink parts) transferred on thick paper / (L×W)}]×100(%). Here, the average value of the length and area is a simple average of the 5 values, and L×W in the formula refers to the area of the imaginary surface obtained by connecting the blank parts of the main groove and the transverse groove when the ground contact shape is obtained.

[0018] Here, the "normal state" refers to an unloaded state in which the rim is assembled on a normal rim and filled with a normal internal pressure.

[0019] It should be noted that "regular rims" are rims specified for each tire in a specification system that includes the specifications on which the tire is based. For example, in JATMA (Japan Automobile Tire Association), they refer to standard rims in applicable sizes listed in the "JATMA Yearbook (JATMAYEAR BOOK)", in ETRTO (The European Tyre and Rim Technical Organisation), they refer to "Measuring Rim" listed in the "Standards MANUAL", and in TRA (The Tire and Rim Association, Inc.), they refer to "Design Rim" listed in the "Yearbook (YEAR BOOK)". Reference should be made to JATMA, ETRTO, and TRA in that order. If there is an applicable size when referring, then that specification should be followed. Furthermore, in the case of tires not specified in the specifications, the rim refers to the rim with the smallest rim diameter and the narrowest rim width among the rims that can be assembled and maintain internal pressure, that is, the rim that does not cause air leakage from the rim / tire.

[0020] Then, "regular internal pressure" refers to the air pressure specified for each tire in each specification system that includes the specifications on which the tire is based. In JATMA, it refers to the "maximum air pressure", in ETRTO, it refers to the "inflation pressure (INFLATION PRESSURE)", and in TRA, it refers to the maximum value recorded in the table "Tire load limits at various cold inflation pressures (TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES)". Similar to regular rims, reference is made to JATMA, ETRTO, and TRA in that order. If there is an applicable size when referencing, that specification is followed. In addition, in the case of tires not specified in the specifications, it refers to the regular internal pressure (of which 250 kPa or more) of other tire sizes (tire sizes specified in the specifications) recorded using the regular rim as the standard rim. It should be noted that when there are multiple regular internal pressures of 250 kPa or more, the minimum value is referred to.

[0021] In addition, "normal load" refers to the load of each tire specified in the specification system including the specifications on which the tire is based, and the maximum mass allowed to be loaded on the tire. The maximum value stated in the "maximum load capacity" in the JATMA specification, the "load capacity (LOAD CAPACITY)" in the ETRTO specification, and the "tire load limits at various cold inflation pressures (TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES)" in the TRA specification is the "normal load". Like the normal rim and normal internal pressure, reference is made in the order of JATMA, ETRTO, and TRA. If there is an applicable size when referencing, then that specification shall be followed. In addition, in the case of tires not specified in the specifications, the normal load W is obtained by the following calculation: L (kg). V={(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt W L =0.000011×V+175 W L :Regular load (kg) V: imaginary volume of the tire (mm 3 ) Dt: Tire outer diameter Dt (mm) Ht: Tire section height (mm) Wt: tire section width (mm)

[0022] (2) Tread running surface and tread base In the tire of the present invention, the tread portion includes a cap tread and a base tread laminated from the ground contact surface side, and both the cap tread and the base tread are composed of a rubber composition containing vulcanized rubber powder.

[0023] By mixing vulcanized rubber powder in both the tread running surface and the tread base at a specific area ratio or more, the contact area between the tread running surface and the tread base can be increased, thereby firmly strengthening the interface between the tread running surface and the tread base, making it easier to apply force between the tread running surface and the tread base, and thus making it easier for the tread portion as a whole to follow the road surface.

[0024] Then, as described above, it is believed that by suppressing the sag rate to a small level, a large contact area between the tire and the road surface can be ensured. Due to the synergy of these, even when turning at high speed on a slippery road surface, the tire can firmly grip the road surface and follow the movement of the road surface, thereby fully improving the wet grip performance in high-speed turning.

[0025] However, if the content of the vulcanized rubber powder is too high, the area ratio of the vulcanized rubber powder becomes too large, which may lead to a reduction in the reinforcing effect in the tread portion, and is therefore not preferable.

[0026] That is, in order to improve the wet grip performance during high-speed cornering, it is necessary to appropriately suppress the area ratio and the concavity ratio Nr of the vulcanized rubber powder.

[0027] Specifically, it can be considered that the area ratio of the vulcanized rubber powder in the tread cap is Sr out (%), the area ratio of the vulcanized rubber powder in the base tread is Sr in (%), if [(Sr out +Sr in ) / Nr] is 3 or less (3≥(Sr out +Sr in ) / Nr), through the synergistic effect of the above effects, the interface between the vulcanized rubber powder tread running surface and the tread base is firmly strengthened. Even when turning at high speed on a wet road, the tire can firmly grip the road surface and follow the changes in the road surface, fully improving the wet grip performance during high-speed turning. out +Sr in ) / Nr] is more preferably 1.5 or less, further preferably 1.0 or less, and further preferably 0.5 or less.

[0028] The above-mentioned "area ratio occupied by vulcanized rubber powder" can be determined by cutting a sample produced by cutting the tread portion with a plane parallel to the tread surface as a cross-section for observation, capturing an image using a scanning electron microscope, and determining the ratio of the area of the region occupied by the vulcanized rubber powder in the images of the obtained cross-sections of the cap tread and base tread to the area of the entire cross-section.

[0029] [2] A more preferred embodiment of the tire of the present invention The tire of the present invention can achieve further significant effects by adopting the following aspects.

[0030] 1. Average particle size of vulcanized rubber powder In the present invention, the average particle size of the vulcanized rubber powder is preferably 550 μm or less. It is believed that since the specific surface area of the vulcanized rubber powder with a small particle size is large, the iodine value increases and the surface reactivity is improved, a large structure can be formed. As a result, due to the increase in physical bonding force with the polymer in the rubber composition, the tread rubber is more strongly reinforced and the rigidity increases, and the wet grip performance during high-speed steering is further improved. It is more preferably 350 μm or less, further preferably 300 μm or less, and particularly preferably 250 μm or less. The lower limit is not particularly limited, but is preferably 50 μm or more, more preferably 80 μm or more, further preferably 100 μm or more, and particularly preferably 150 μm or more.

[0031] As described above, from the perspective of particle size, the particle size of the vulcanized rubber powder in the present invention is preferably finer than a 15-mesh sieve, more preferably finer than a 20-mesh sieve, and even more preferably finer than a 30-mesh sieve, as measured through a test sieve specified in JIS Z8801. Furthermore, although not particularly limited, the particle size is preferably coarser than a 200-mesh sieve, more preferably coarser than a 100-mesh sieve, and even more preferably coarser than a 50-mesh sieve.

[0032] 2. Loss tangent In the present invention, the loss tangent (tan δ at 30°C) of the cap tread, measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%, is preferably 0.22 or less. It is more preferably 0.20 or less, further preferably 0.18 or less, and particularly preferably 0.17 or less. While not particularly limited, the lower limit is preferably 0.10 or greater, more preferably 0.12 or greater, further preferably 0.14 or greater, and particularly preferably 0.16 or greater.

[0033] On the other hand, the 30°C tanδ of the base tread is preferably 0.08 or less, more preferably 0.07 or less, and even more preferably 0.06 or less. The lower limit is not particularly limited, but is preferably 0.03 or more, more preferably 0.04 or more, and even more preferably 0.05 or more.

[0034] The ratio of the tanδ at 30°C of the cap tread to the tanδ at 30°C of the base tread is preferably 2.50 or greater, more preferably 2.75 or greater, even more preferably 2.80 or greater, and particularly preferably 2.85 or greater. The upper limit is, for example, preferably 3.15 or less, more preferably 3.10 or less, even more preferably 3.05 or less, and particularly preferably 3.00 or less.

[0035] The loss tangent tanδ is a viscoelastic parameter that indicates energy absorption performance. By controlling the 30° tanδ of the tread and base tread to such an appropriate value, the input-response phase difference between the tread and base tread is reduced, and the transmission of force from the tread on the contact surface to the inner base tread is accelerated, ensuring good responsiveness even during cornering, further improving wet grip performance during high-speed cornering.

[0036] In addition, the tread portion, which bends due to contact with the road during cornering, easily returns to its original shape when leaving the road, and easily bends again when re-contacting. This further improves wet grip performance during high-speed cornering.

[0037] Among the above, the loss tangent (tan δ) can be measured using a viscoelasticity measuring device such as "EPLEXOR (registered trademark)" manufactured by GABO Corporation.

[0038] 3. Elongation at break In the present invention, the elongation at break (EB) of the cap tread, as measured in accordance with JIS K6251:2017, is preferably 550% or greater, more preferably 580% or greater, and even more preferably 600% or greater. The upper limit is not particularly limited, but is preferably 650% or less, more preferably 630% or less, and even more preferably 610% or less.

[0039] On the other hand, the elongation at break (EB) of the base tread is preferably 420% or greater, more preferably 440% or greater, and even more preferably 460% or greater. The upper limit is not particularly limited, but is preferably 520% or less, more preferably 500% or less, and even more preferably 480% or less.

[0040] The ratio of the EB of the cap tread to the EB of the base tread is preferably 1.20 or greater, more preferably 1.25 or greater, and even more preferably 1.27 or greater. The upper limit is preferably 1.40 or less, more preferably 1.35 or less, and even more preferably 1.32 or less.

[0041] The elongation at break (EB) is an indicator of how well the rubber follows the deformation caused by the force applied to the rubber. By controlling the EB of the tread running surface and the tread base to such appropriate values, it is possible to easily follow the deformation and ensure good responsiveness even during high-speed cornering, thereby further improving the wet grip performance during high-speed cornering.

[0042] 4. Contact area ratio in the shoulder area of the tread In the present invention, the contact patch ratio of the shoulder region, located outside the tread contact patch, is preferably less than 3%. By reducing the contact patch ratio in the shoulder region, even tires with minimal sag within the contact patch width can effectively drain water from the shoulder region, further improving wet grip performance during high-speed cornering. A ratio of less than 2% is more preferred. While the lower limit is not particularly limited, it is preferably greater than 0%, and more preferably greater than 1%.

[0043] The ground contact area ratio mentioned above refers to the ratio (in %) of the actual ground contact area when grooves are formed to the imaginary ground contact area of the tread portion, and is measured in the same manner as the determination of the depression rate, and is calculated by {the average area of 5 ground contact shapes (ink parts) transferred from thick paper / L×W)}×100(%).

[0044] [3] Implementation Hereinafter, the present invention will be described in detail based on the embodiments.

[0045] 1. Tire structure Figure 1 This is a schematic cross-sectional view showing the structure of a tire according to one embodiment of the present invention. Figure 1 , the vertical direction is the radial direction of the tire, the left-right direction is the axial direction, and the direction perpendicular to the paper is the circumferential direction.

[0046] like Figure 1 As shown, the tire 1 includes a tread portion 4, a sidewall 6, a clinch 8, a bead 10, a carcass 12, a belt 14, a band 16, an inner liner 18, and a chafer 20. The bead 10 includes a bead core 30 and a bead apex 32. It should be noted that 2 and 3 respectively denote the tire's axial contact patch area and the shoulder area.

[0047] The tread 4 has a plurality of grooves 22 and a plurality of land portions 23 formed in the surface thereof to form a tread pattern. The tread 4 is formed by laminating a base tread 24 and a cap tread 26, and is formed so that the concavity ratio within the width of the contact patch is less than 20%.

[0048] The carcass 12 is composed of a plurality of carcass plies ( Figure 1The cord is preferably a cord made of organic fibers, for example, polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

[0049] The belt layer 14 is composed of multiple layers of rubber covered with topping rubber on parallel cords ( Figure 1 The carcass 12 is composed of an inner layer 50 and an outer layer 52 in the middle to reinforce the carcass 12. The cords of each layer are inclined relative to the equatorial plane, and the inner layer 50 and the outer layer 52 are inclined in opposite directions. As the cord, a steel cord is preferably used, but an organic fiber cord can also be used.

[0050] The band layer 16 is located radially outward from the belt layer 14. The band layer 16 is composed of cords and topping rubber. The cords are wound in a spiral shape. The band layer 16 has a so-called seamless structure. The cords substantially extend in the circumferential direction. Since the belt layer 14 is restrained by the cords, the lifting of the belt layer 14 is suppressed. The cords are preferably made of organic fibers, for example, nylon fibers, polyester fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

[0051] With such a configuration, by appropriately controlling the settings of the aforementioned parameters, a tire having sufficiently improved wet grip performance during high-speed cornering can be obtained.

[0052] 2. Rubber composition In the present invention, the rubber composition constituting the cap tread (rubber composition for cap tread) and the rubber composition constituting the base tread (rubber composition for base tread) can be obtained from the rubber components described below and other compounding materials.

[0053] (1) Compounding materials (a) Rubber component The rubber component is not particularly limited, and can include isoprene rubbers such as natural rubber (NR), diene rubbers such as butadiene rubber (BR), styrene-butadiene rubber (SBR), and acrylonitrile-butadiene rubber (NBR), and butyl rubbers such as butyl rubber. Any rubber (polymer) commonly used in tire manufacturing can be used. These polymers can be used alone or in combination. A combination of NR and BR, or NR and SBR, is preferred, and a combination of NR, SBR, and BR is more preferred.

[0054] (I) Isoprene rubber Examples of the isoprene-based rubber include natural rubber (NR), foreign diene rubber (IR), modified NR, modified NR, and modified IR. NR is preferred because of its excellent strength.

[0055] Examples of NR include SVR-L, SIR20, RSS#3, and TSR20, which are commonly used in the tire industry. IR is not particularly limited, and examples of IR, which are commonly used in the tire industry, include IR2200 manufactured by Zeon Corporation of Japan. Modified NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (UPNR). Modified NR includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Modified IR includes epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These materials may be used alone or in combination of two or more.

[0056] In the rubber composition for cap treads and the rubber composition for base treads, the content of the isoprene-based rubber per 100 parts by mass of the rubber component is preferably 55 parts by mass or more, more preferably 60 parts by mass or more, and even more preferably 65 parts by mass or more. The upper limit is, for example, preferably 85 parts by mass or less, more preferably 80 parts by mass or less, and even more preferably 75 parts by mass or less.

[0057] (II)SBR The weight average molecular weight of SBR is, for example, greater than 100,000 and less than 2,000,000. The styrene content of SBR is, for example, preferably greater than 5 mass %, more preferably greater than 10 mass %, more preferably greater than 15 mass %. On the other hand, it is preferably less than 40 mass %, more preferably less than 35 mass %, more preferably less than 30 mass %. The vinyl content (1,2-bonded butadiene unit amount) of SBR is, for example, preferably greater than 5 mass %, more preferably greater than 10 mass %, more preferably greater than 15 mass %. On the other hand, it is preferably less than 70 mass %, more preferably less than 40 mass %, more preferably less than 30 mass %. It should be noted that the structural identification of SBR (styrene content, determination of vinyl content) can be carried out by using the device of JNM-ECA series made by, for example, JEOL Ltd.

[0058] As SBR, there is no particular limitation, for example, emulsion polymerization styrene butadiene rubber (E-SBR), solution polymerization styrene butadiene rubber (S-SBR) etc. can be used. SBR can be any of non-modified SBR and modified SBR. In addition, hydrogenated SBR with hydrogenation of the butadiene part in SBR can be used, and hydrogenated SBR can be obtained by hydrogenating the BR part in SBR, or by copolymerizing styrene, ethylene and butadiene to obtain the same structure.

[0059] As the modified SBR, it is preferably SBR having functional groups that interact with fillers such as silica. For example, there can be mentioned terminal-modified SBR (terminal-modified SBR having the above functional groups at the terminal) modified with a compound (modifier) having the above functional groups at at least one end of SBR, main-chain modified SBR having the above functional groups on the main chain, main-chain terminal-modified SBR having the above functional groups on the main chain and at the terminal (for example, main-chain terminal-modified SBR having the above functional groups on the main chain and at least one end modified with the above modifier), terminal-modified SBR modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and having a hydroxyl group or an epoxy group introduced therein, etc.

[0060] As the above functional groups, for example, there can be mentioned amino group, amide group, silyl group, alkoxysilyl group, isocyanate group, imino group, imidazole group, ureido group, ether group, carbonyl group, oxycarbonyl group, mercapto group, thioether group, disulfide group, sulfonyl group, sulfinyl group, thiocarbonyl group, ammonium group, imide group, hydrazino group, azo group, diazo group, carboxyl group, nitrile group, pyridyl group, alkoxy group, hydroxyl group, oxy group, epoxy group, etc. It should be noted that these functional groups can have substituents.

[0061] In addition, as the modified SBR, for example, SBR modified with a compound (modifier) represented by the following formula can be used.

[0062]

Chemical formula 1

[0063] It should be noted that in the formula, R 1 、R 2 and R 3 may be the same or different and represent an alkyl group, an alkoxy group, a silanyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH) or a derivative thereof. R 4 and R 5 may be the same or different and represent a hydrogen atom or an alkyl group. R 4 and R 5 can be bonded to form a cyclic structure together with the nitrogen atom. n represents an integer.

[0064] As the modified SBR modified with the compound (modifier) represented by the above formula, SBR obtained by modifying the polymerization terminal (active terminal) of solution-polymerized styrene-butadiene rubber (S-SBR) with the compound represented by the above formula (modified SBR described in Japanese Patent Laid-Open No. 2010-111753, etc.) can be used.

[0065] As R 1 、R 2 and R 3, preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 , preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. 4 and R 5 When the bond forms a cyclic structure together with a nitrogen atom, it is preferably a 4- to 8-membered ring. In addition, the alkoxy group also includes cycloalkoxy groups (cyclohexyloxy and the like) and aryloxy groups (phenoxy, benzyloxy and the like).

[0066] Specific examples of the above-mentioned modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These modifiers may be used alone or in combination of two or more.

[0067] In addition, as modified SBR, modified SBR modified with the following compounds (modifiers) can also be used. Examples of the modifier include: polyglycidyl ethers of polyols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as diglycidyl bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; tertiary amines containing epoxy groups such as 4,4'-diglycidyldiphenylmethylamine and 4,4'-diglycidyldibenzylmethylamine; diglycidylaniline, N,N'- Diglycidylamino compounds such as diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidyl-m-phenylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamoyl chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylformyl chloride, N,N-diethylformyl chloride; 1,3-bis-(glycidyloxypropyl)tetramethyldisiloxane, (3-glycidyl) Silane compounds containing epoxy groups, such as (trimethylsilyl)[3-(trimethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl] sulfide, (trimethylsilyl)[3-(tripropoxysilyl)propyl] sulfide Silane compounds containing a sulfide group, such as [3-(methyldipropoxysilyl)propyl]sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide; N-substituted aziridine compounds, such as ethyleneimine and propyleneimine; alkoxysilanes, such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;(Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; and 4-N,N-dimethylaminobenzaldehyde Benzaldehyde compounds having an amino group and / or a substituted amino group, such as 4-N,N-diphenylaminobenzaldehyde and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone; -substituted piperidones; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam, N-phenyl-β-propiolactam and other N-substituted lactams; and N,N-bis-(2,3-epoxypropyloxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine -2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. It should be noted that modification using the above-mentioned compounds (modifiers) can be carried out by known methods.

[0068] As SBR, for example, SBR manufactured and sold by Sumitomo Chemical Co., Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Corporation, Nippon Zeon Co., Ltd., etc. can be used. SBR can be used alone or in combination of two or more.

[0069] In the rubber composition for cap treads and the rubber composition for base treads, the SBR content per 100 parts by mass of the rubber component is preferably 20 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 30 parts by mass or more, and particularly preferably 35 parts by mass or more. The upper limit is, for example, preferably 80 parts by mass or less, more preferably 55 parts by mass or less, even more preferably 50 parts by mass or less, and particularly preferably 45 parts by mass or less.

[0070] (III)BR The weight-average molecular weight of BR is, for example, greater than 100,000 and less than 2,000,000. The vinyl content of BR is, for example, greater than 1% by mass and less than 30% by mass. The cis content of BR is, for example, greater than 1% by mass and less than 98% by mass. The trans content of BR is, for example, greater than 1% by mass and less than 60% by mass. The cis content can be measured by infrared absorption spectroscopy.

[0071] BR is not particularly limited, and BR with a high cis content (a cis content of 90% or greater), BR with a low cis content, BR containing syndiotactic polybutadiene crystals, and the like can be used. BR may be either unmodified or modified. As modified BR, for example, BR modified with a compound (modifier) represented by the following formula can be used.

[0072]

[0073] It should be noted that, in the formula, R 1 、R 2 and R 3 R may be the same or different and represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group (-COOH), a mercapto group (-SH), or a derivative thereof. 4 and R 5 R may be the same or different and represents a hydrogen atom or an alkyl group. 4 and R 5 It can bond with the nitrogen atom to form a ring structure. n represents an integer.

[0074] Examples of the modified BR modified with the compound (modifying agent) represented by the above formula include BR in which the polymerization terminal (active terminal) is modified with the compound represented by the above formula.

[0075] As R 1 、R 2 and R 3 , preferably an alkoxy group (preferably an alkoxy group having 1 to 8 carbon atoms, more preferably an alkoxy group having 1 to 4 carbon atoms). 4 and R 5 , preferably an alkyl group (preferably an alkyl group having 1 to 3 carbon atoms). n is preferably 1 to 5, more preferably 2 to 4, and even more preferably 3. 4 and R 5 When the alkoxy group forms a ring structure together with a nitrogen atom, the ring is preferably a 4- to 8-membered ring.

[0076] Specific examples of the above-mentioned modifier include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane. These modifiers may be used alone or in combination of two or more.

[0077] In addition, as modified BR, modified BR modified with the following compounds (modifiers) can also be used. Examples of the modifier include: polyglycidyl ethers of polyols such as ethylene glycol diglycidyl ether, glycerol triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenolic groups such as diglycidyl bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; tertiary amines containing epoxy groups such as 4,4'-diglycidyldiphenylmethylamine and 4,4'-diglycidyldibenzylmethylamine; diglycidylaniline, N,N'- Diglycidylamino compounds such as diglycidyl-4-glycidyloxyaniline, diglycidyl-o-toluidine, tetraglycidyl-m-phenylenediamine, tetraglycidylaminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidylaminomethylcyclohexane, tetraglycidyl-1,3-bisaminomethylcyclohexane; acyl chlorides containing amino groups such as bis-(1-methylpropyl)carbamoyl chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylformyl chloride, N,N-diethylformyl chloride; 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane, (3-glycidyl) Silane compounds containing epoxy groups, such as (trimethylsilyl) [3-(trimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(triethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tripropoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tributoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldimethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(methyldiethoxysilyl) propyl] sulfide, (trimethylsilyl) [3-(tripropoxysilyl) propyl] sulfide Silane compounds containing a sulfide group, such as [3-(methyldipropoxysilyl)propyl]sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl]sulfide; N-substituted aziridine compounds, such as ethyleneimine and propyleneimine; alkoxysilanes, such as methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane and N,N-bis(trimethylsilyl)aminoethyltriethoxysilane;(Thio)benzophenone compounds having an amino group and / or a substituted amino group, such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-tert-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, and N,N,N',N'-bis-(tetraethylamino)benzophenone; and 4-N,N-dimethylaminobenzaldehyde Benzaldehyde compounds having an amino group and / or a substituted amino group, such as 4-N,N-diphenylaminobenzaldehyde and 4-N,N-divinylaminobenzaldehyde; N-substituted pyrrolidones such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, N-tert-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone; -substituted piperidones; N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurolactam, N-vinyl-ω-laurolactam, N-methyl-β-propiolactam, N-phenyl-β-propiolactam and other N-substituted lactams; and N,N-bis-(2,3-epoxypropyloxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), tris-(2,3-epoxypropyl)-1,3,5-triazine -2,4,6-triones, N,N-diethylacetamide, N-methylmaleimide, N,N-diethylurea, 1,3-dimethylethyleneurea, 1,3-divinylethyleneurea, 1,3-diethyl-2-imidazolidinone, 1-methyl-3-ethyl-2-imidazolidinone, 4-N,N-dimethylaminoacetophenone, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. It should be noted that the modification using the above-mentioned compounds (modifiers) can be carried out by a known method. In addition, these modified BRs can be used alone or in combination of two or more. ;

[0078] As BR, for example, products of Ube Industries, Ltd., ENEOS Materials Co., Ltd., Asahi Kasei Corporation, Nippon Zeon Corporation, etc. can be used.

[0079] In the rubber composition for cap treads and the rubber composition for base treads, the BR content per 100 parts by mass of the rubber component is preferably 10 parts by mass or more, more preferably 25 parts by mass or more, and even more preferably 30 parts by mass or more. On the other hand, it is preferably 80 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less.

[0080] (IV) Other rubber components The rubber composition may contain, as other rubber components, a rubber (polymer) generally used in the production of tires, such as nitrile rubber (NBR), as necessary.

[0081] It should be noted that the raw materials (monomers) of synthetic rubbers such as SBR and BR mentioned above can come from underground resources such as petroleum and natural gas, or can be recycled from rubber products such as tires and non-rubber products such as polystyrene.

[0082] The monomer obtained by recycling (recovered monomer) is not particularly limited, and examples thereof include recycled isoprene, recycled butadiene, and recycled aromatic vinyl compounds. Examples of the butadiene include 1,2-butadiene and 1,3-butadiene. Examples of the aromatic vinyl compound are not particularly limited, and examples thereof include styrene. Among them, it is preferred to use recycled isoprene (recovered isoprene), butadiene (recovered butadiene), and / or recycled styrene (recovered styrene) as raw materials.

[0083] The method for producing the recovered monomer is not particularly limited, and an example thereof includes synthesis from recycled naphtha obtained by decomposing rubber products such as tires. Furthermore, the method for producing the recovered naphtha is not particularly limited, and an example thereof includes decomposing rubber products such as tires under high temperature and high pressure, decomposing them using microwaves, or mechanically pulverizing them followed by extraction.

[0084] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR can be derived from biomass. Here, biomass refers to substances derived from natural resources such as plants. As biomass, there is no particular limitation, and examples include agricultural, forestry, and aquatic products, sugar, wood, plant residues after extraction of useful components, plant ethanol, biomass naphtha, etc. As monomers derived from biomass (biomass monomers), there is no particular limitation, and examples include butadiene from biomass, aromatic vinyl compounds from biomass, etc. As the butadiene, 1,2-butadiene and 1,3-butadiene can be given. As the aromatic vinyl compound, there is no particular limitation, and examples include styrene, etc. In addition, the method for producing biomass monomers is not particularly limited, and for example, examples include biological and / or chemical and / or physical transformations of animals and plants. As biological transformations, microbial fermentation is a representative example, and as chemical and / or physical transformations, examples include catalysts, high heat, high pressure, electromagnetic waves, supercritical fluids, and combinations thereof.

[0085] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited, and examples thereof include polybutadiene rubber synthesized from biomass-derived butadiene, and aromatic vinyl / butadiene copolymers 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.

[0086] Whether the raw material of a polymer is derived from biomass can be determined by measuring pMC (percent Modern Carbon) according to ASTM D6866-10.

[0087] pMC refers to the sample 14 C concentration relative to standard modern carbon (modern standard reference material: modern standard reference) 14 The ratio of C concentration is used as an indicator of the biomass ratio of the compound (rubber). The meaning of this value is as follows.

[0088] 1 mole of carbon atoms (6.02×10 23 There are about one trillionth of the normal carbon atoms, that is, about 6.02×10 11 individual 14 C. 14 C is called a radioactive isotope, and its half-life is 5730 years, and it decreases regularly. It takes 226,000 years for all of these to decay. Therefore, in fossil fuels such as coal, oil, and natural gas (which are believed to be produced by plants taking up and fixing atmospheric carbon dioxide over a period of more than 226,000 years), the carbon dioxide that was originally fixed and contained in these fossil fuels is 14 The C element has completely decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas do not contain any 14 Therefore, the chemical products produced from these fossil fuels do not contain any 14 Element C.

[0089] On the other hand, cosmic rays undergo nuclear reactions in the atmosphere, continuously generating 14 C, due to radioactive decay 14 The reduction phase equilibrium of C, in the Earth's atmosphere, 14 The amount of C is constant. Therefore, as mentioned above, the amount of substances from biomass resources that are circulating in the current environment is 14 The C concentration relative to all C atoms is about 1×10 -12 Therefore, the difference between these values can be used to calculate the biomass ratio in a certain compound.

[0090] Should 14 C is usually determined as follows. Using tandem accelerator-based accelerator mass spectrometry, 13 C concentration ( 13 C / 12 C) 14 C concentration ( 14 C / 12 C) determination. In the determination, as a 14 The standard modern carbon used as the benchmark for C concentration is the natural circulating carbon in 1950. 14 C concentration. As a specific standard substance, oxalic acid standard provided by NIST (National Institute of Standards and Technology: National Institute of Standards and Technology, USA) was used. The specific radioactivity of carbon in the oxalic acid (per 1g of carbon) was calculated. 14 The radioactivity intensity of C) is distinguished by each carbon isotope. 13 C is corrected to a constant value, and the value after decay correction from 1950 AD to the date of measurement is used as the standard 14 The ratio of the actual measured sample value to this value is the pMC value.

[0091] Therefore, if rubber is made from 100% biomass (natural), it will show a value of about 110 pMC, although there are 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, when measuring this value, 14 When the concentration of C is about 0 pMC (for example, 0.3 pMC), this value corresponds to the above-mentioned biomass ratio of 0%.

[0092] In summary, it is preferable to use a rubber or other material having a high pMC value, that is, a rubber or other material having a high biomass ratio, in a rubber composition from the viewpoint of environmental protection (sustainability).

[0093] (b) Compounding materials other than rubber components (I) Vulcanized rubber powder As described above, the rubber composition for cap treads and the rubber composition for base treads in the present invention contain vulcanized rubber powder.

[0094] Vulcanized rubber powder is particles made of vulcanized rubber. Specifically, rubber powders specified in JIS K 6316:2017 can be used. Recycled rubber powders produced from crushed waste tires, etc., are preferred due to environmental and cost considerations. These can be used alone or in combination of two or more.

[0095] The vulcanized rubber powder is not particularly limited and may be either unmodified vulcanized rubber powder or modified vulcanized rubber powder.

[0096] Vulcanized rubber powder is produced by pulverizing used tires using a roller press, a grinder, or the like. Examples of pulverization methods include mechanical pulverization using a mill, freeze pulverization in which flakes are frozen in liquid nitrogen and then mechanically pulverized, and hydraulic pulverization in which flakes are pulverized using a high-pressure water jet. Among these, hydraulic pulverization is preferred because vulcanized rubber powder produced by hydraulic pulverization exhibits superior tensile strength and wear resistance compared to mechanically pulverized or freeze pulverized products of the same particle size.

[0097] Specifically, because freeze-milling and mechanical pulverization involve mechanical pulverization, they are non-selective in the cutting area and physically break chemical bonds. In contrast, hydraulic pulverization uses water, so chemical bonds are not physically broken. As a result, the vulcanized rubber powder obtained by hydraulic pulverization has more surface irregularities than the vulcanized rubber powder obtained by mechanical pulverization and freeze-milling, increasing its specific surface area and creating traction with the matrix rubber, thereby enhancing its reinforcing properties during deformation. Furthermore, this increased specific surface area exposes more reactive double bonds on the surface, increasing the iodine value and surface reactivity, allowing the vulcanized rubber powder to chemically bond with the matrix rubber.

[0098] Furthermore, since vulcanized rubber powder can reduce the consumption of petroleum-derived materials, it is preferred as a sustainable material that is suitable for the growing momentum for environmental protection in recent years.

[0099] The content of the vulcanized rubber powder per 100 parts by mass of the rubber component is, for example, preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, and particularly preferably 10 parts by mass or more. The upper limit is, for example, preferably 70 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less.

[0100] As commercially available vulcanized rubber particles, for example, products from Lehigh Corporation, Muraoka Rubber Industries, Ltd., and the like can be used.

[0101] (II) Filler The rubber composition of the present invention preferably contains a filler. Specific examples of fillers include carbon black, silica, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Carbon black is preferred, and silica may be further included as needed. When silica is used, it is preferably used in combination with a silane coupling agent.

[0102] The amount of the filler compounded is preferably 40 parts by mass or more, more preferably 50 parts by mass or more, and even more preferably 60 parts by mass or more per 100 parts by mass of the rubber component. The upper limit is, for example, preferably 100 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less.

[0103] (i) Carbon black Preferably, carbon black is used for the purpose of improving the crack growth resistance, durability, resistance to ultraviolet degradation, and the like of the tire.

[0104] The nitrogen adsorption specific surface area (N2SA) of carbon black is preferably 30 m2, for example, from the viewpoint of reinforcing properties for rubber. 2 / g or more, more preferably 50m 2 / g or more, more preferably 60m 2 / g or more. On the other hand, from the viewpoint of heat generation, 250m 2 / g or less, more preferably 150m 2 / g or less, more preferably 120m 2 The nitrogen adsorption specific surface area of carbon black is measured in accordance with ASTM D4820-93.

[0105] The dibutyl phthalate (DBP) absorption of carbon black is preferably 50 ml / 100 g or greater, more preferably 100 ml / 100 g or greater, from the perspective of rubber rigidity. On the other hand, from the perspective of rubber deformation compliance, it is preferably 250 ml / 100 g or less, more preferably 150 ml / 100 g or less. The DBP absorption of carbon black is measured in accordance with ASTM D2414-93.

[0106] Carbon black is not particularly limited, but includes furnace blacks such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black; thermal blacks such as FT and MT; and channel blacks such as EPC, MPC, and CC. Product numbers include N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, and N762. These may be used alone or in combination of two or more.

[0107] The raw materials of carbon black can be biomass materials such as lignin and vegetable oil in addition to mineral oil, or pyrolysis oil (regenerated carbon black) obtained by pyrolysis of rubber products containing carbon black such as waste tires.

[0108] Furthermore, carbon black can be produced by combustion such as a furnace method, hydrothermal carbonization (HTC), or thermal decomposition of methane such as a thermal black method.

[0109] As commercially available products, there can be used products of Asahi Carbon Co., Ltd., Cabot Japan KK, Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Corporation, etc. These carbon blacks may be used alone or in combination of two or more.

[0110] The carbon black content is preferably 30 parts by mass or more, more preferably 40 parts by mass or more, and even more preferably 50 parts by mass or more relative to 100 parts by mass of the rubber component. The upper limit is not particularly limited, but is, for example, preferably 75 parts by mass or less, more preferably 70 parts by mass or less, and even more preferably 65 parts by mass or less.

[0111] (ii) Silicon dioxide The rubber composition of the present invention preferably contains silica as needed. From the viewpoint of obtaining good durability, the BET specific surface area of silica is preferably greater than 100 m 2 / g, more preferably greater than 130m 2 / g. On the other hand, it is preferably less than 250m 2 / g, more preferably less than 200m 2 It should be noted that the above-mentioned BET specific surface area is the N2SA value measured by the BET method according to ASTM D3037-93.

[0112] Silica is not particularly limited. For example, dry-process silica (anhydrous silica) and wet-process silica (hydrous silica) commonly used in the tire industry can be used. Commercially available silica includes products from Evonik Degussa GmbH, Rhodia Japan Ltd., Tosoh Silica Corporation, Solvay Japan, Ltd., and Tokuyama Corporation.

[0113] The raw material for silica is not particularly limited, and examples thereof include mineral raw materials such as quartz, biological raw materials such as rice husks (e.g., silica produced from biomass materials such as rice husks), and silica recovered from silica-containing products. Among these, hydrous silica produced by a wet process is preferred due to its high content of silanol groups.

[0114] 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, reacting the silicate with sulfuric acid in the same manner as conventional wet silica, and filtering the resulting silica precipitate, washing with water, drying, and pulverizing it.

[0115] Silica recovered from products containing silica can be, for example, silica recovered from electronic components such as semiconductors, tires, desiccants, and filter materials such as diatomaceous earth. The recovery method is not particularly limited, and examples include thermal decomposition and electromagnetic wave decomposition. Of these, silica recovered from electronic components such as semiconductors or tires is preferred.

[0116] If silica crystallizes, it becomes insoluble in water, making its silicic acid component unusable. By controlling the combustion temperature and duration, the crystallization of silica in rice husk ash can be suppressed (see, for example, Japanese Patent Laid-Open No. 2009-2594, Akita Prefectural University Online Journal B / 2019, vol. 6, pp. 216-222).

[0117] As the amorphous silica extracted from rice husks, commercially available products such as those from Wilmar Corporation can be used.

[0118] It should be noted that these silicas may be used alone or in combination of two or more. From the viewpoint of environmental protection (sustainability), it is preferred to use biomass silica and recycled silica.

[0119] The silica content per 100 parts by mass of the rubber component is preferably 5 parts by mass or more, more preferably 25 parts by mass or more, and even more preferably 45 parts by mass or more. The upper limit is not particularly limited, but is preferably 115 parts by mass or less, more preferably 85 parts by mass or less, and even more preferably 65 parts by mass or less.

[0120] (iii) Silane coupling agent When silica is used, it is preferably used in combination with a silane coupling agent. The silane coupling agent is not particularly limited, and examples thereof include bis(3-triethoxysilylpropyl)tetrasulfide, bis(2-triethoxysilylethyl)tetrasulfide, bis(4-triethoxysilylbutyl)tetrasulfide, bis(3-trimethoxysilylpropyl)tetrasulfide, bis(2-trimethoxysilylethyl)tetrasulfide, bis(2-triethoxysilylethyl)trisulfide, bis(4-trimethoxysilylbutyl)trisulfide, bis(3-triethoxysilylpropyl)disulfide, bis(2-triethoxysilylethyl)disulfide, bis(4-triethoxysilylbutyl)disulfide, bis(3-trimethoxysilylpropyl)disulfide, bis(2-trimethoxysilylethyl)disulfide, bis(4-trimethoxysilylbutyl)disulfide, 3-trimethoxysilylpropyl-N, Sulfide-based silanes such as N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyltetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based silanes such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and NXT and NXT-Z manufactured by Momentive; vinyl-based silanes such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based silanes such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based silanes such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based silanes such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chlorine-based silanes such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These silanes can be used alone or in combination of two or more.

[0121] As the silane coupling agent, for example, products of Evonik Industries, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azmax Co., Ltd., Dow Corning Toray Industries, Ltd., and the like can be used.

[0122] The content of the silane coupling agent relative to 100 parts by mass of silica is, for example, greater than 3 parts by mass and less than 15 parts by mass.

[0123] (iv) Other fillers The rubber composition may contain, as necessary, fillers commonly used in the tire industry, such as graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica, in addition to the aforementioned carbon black and silica. The content of these fillers is, for example, greater than 0.1 parts by mass and less than 200 parts by mass per 100 parts by mass of the rubber component.

[0124] (III) Softener ingredient In the rubber composition, a softener component is preferably used as needed to ensure proper dispersion of the powdered material during kneading. The term "softener / plasticizer component" herein refers to a material that imparts plasticity to the rubber component, and includes both softeners that are liquid at 25°C and softeners that are solid at 25°C.

[0125] Examples of softeners include resin components, oils, liquid polymers, and ester plasticizers. These softeners can be derived from mineral resources such as petroleum and natural gas, biomass, or naphtha recycled from rubber and non-rubber products. Low-molecular-weight hydrocarbon components extracted through thermal decomposition of products including used tires and various components can also be used as softeners. Among these, softeners derived from biomass or recycled materials are preferred as sustainable softeners.

[0126] It should be noted that these softeners may be used alone or in combination of two or more. The amount of the plasticizer component relative to 100 parts by mass of the rubber component is preferably 50 parts by mass or less, more preferably 25 parts by mass or less, even more preferably 20 parts by mass or less, and particularly preferably 15 parts by mass or less. As a lower limit, for example, it is preferably 1 part by mass or more, more preferably 3 parts by mass or more, even more preferably 7 parts by mass or more, and particularly preferably 10 parts by mass or more. It should be noted that the amount of the plasticizer component also includes the amount of oil contained in the rubber (oil-extended rubber), etc.

[0127] (i)Oil Examples of the oil include mineral oil, vegetable oil, and animal oil. Furthermore, from the perspective of life cycle assessment, oils refined from waste oil used in rubber mixers and engines, or waste cooking oil from restaurants, etc., may also be used.

[0128] (i-1) Mineral oil Mineral oil refers to oil derived from mineral resources such as petroleum and natural gas. Examples of mineral oil include paraffinic oil (mineral oil), naphthenic oil, and aromatic oil.

[0129] Specific examples of mineral oil include MES (Mild Extract Solvated), DAE (Distillate Aromatic Extract), TDAE (Treated Distillate Aromatic Extract), TRAE (Treated Residual Aromatic Extract), and RAE (Residual Aromatic Extract).

[0130] In addition, due to environmental policy, oils with low polycyclic aromatic compound (PCA) content may also be used. Examples of such low PCA content oils include MES, TDAE, and heavy naphthenic oils.

[0131] Examples of commercially available mineral oils include paraffinic, aromatic, and naphthenic oils, and products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Manufacturing Co., Ltd., Showa Shell Sekiyu Co., Ltd., and Fuji Kosan Co., Ltd. can be used alone or in combination of two or more.

[0132] (i-2) Vegetable oil Examples of the vegetable oil include linseed oil, rapeseed oil, safflower oil, soybean oil, corn oil, cottonseed oil, rice bran oil, tall oil, sesame oil, perilla oil, castor oil, tung oil, pine oil, pine tar, sunflower oil, coconut oil, palm oil, palm kernel oil, olive oil, camellia oil, jojoba oil, macadamia nut oil, peanut oil, grapeseed oil, and wood wax.

[0133] Further examples of vegetable oils include refined oils (such as salad oils) obtained by refining the above-mentioned oils, transesterified oils obtained through transesterification, hardened oils obtained through hydrogenation, thermally polymerized oils obtained through thermal polymerization, oxidatively polymerized oils obtained through oxidation, and waste edible oils recovered after use as edible oils. It should be noted that vegetable oils can be either liquid or solid at room temperature (25°C). These can be used alone or in combination of two or more.

[0134] As a vegetable oil, it is preferred to contain acylglycerol, and more preferably triacylglycerol. It should be noted that acylglycerol refers to a compound in which the hydroxyl group of glycerol forms an ester bond with a fatty acid. There are no particular limitations on the acylglycerol, and it can be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. In addition, acylglycerol can be a monomer, a dimer, or a polymer of a trimer or higher. It should be noted that acylglycerols of dimers or higher can be obtained by thermal polymerization or oxidative polymerization. In addition, acylglycerol can be liquid or solid at room temperature (25°C).

[0135] The method for confirming whether or not the rubber composition contains acylglycerols is not particularly limited, and the method can be performed by 1 For example, a rubber composition mixed with triacylglycerol is immersed in deuterated chloroform at room temperature (25°C) for 24 hours, and after removing the rubber composition, the rubber composition is measured at room temperature. 1 H-NMR, with the tetramethylsilane (TMS) signal set at 0.00 ppm, observed signals near 5.26 ppm, 4.28 ppm, and 4.15 ppm. These signals are presumed to originate from hydrogen atoms bonded to carbon atoms adjacent to the oxygen atoms of the ester groups, confirming the presence of acylglycerols. Note that "nearby" here refers to a range of ±0.10 ppm.

[0136] It should be noted that, as fatty acid, there is no particular limitation, and it can be an unsaturated fatty acid or a saturated fatty acid. As unsaturated fatty acid, monounsaturated fatty acids such as oleic acid and polyunsaturated fatty acids such as linoleic acid and linolenic acid can be enumerated. In addition, as saturated fatty acid, butyric acid, lauric acid etc. can be enumerated.

[0137] Among these, the fatty acids are preferably fatty acids with few double bonds, that is, preferably saturated fatty acids or monounsaturated fatty acids, with oleic acid being preferred. Vegetable oils containing such fatty acids include, for example, those containing saturated fatty acids or monounsaturated fatty acids, or those modified by transesterification or the like. Furthermore, to produce vegetable oils containing such fatty acids, plants can be modified through breeding, genetic recombination, genome editing, and the like.

[0138] As the vegetable oil, for example, commercially available products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Co., Ltd., Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Manufacturing Co., Ltd., Fuji Kosan Co., Ltd., Nissin Oillio Group Co., Ltd., etc. can be used.

[0139] (ii) Liquid rubber Liquid rubber refers to a polymer that is liquid at room temperature (25° C.) and is a rubber component that can be extracted from a vulcanized tire by acetone extraction. Examples of liquid rubber include farnesene polymers, liquid diene polymers, and hydrogenated products thereof.

[0140] Farnesene polymers are polymers obtained by polymerizing farnesene and have structural units based on farnesene. Farnesene exists in isomers such as α-farnesene ((3E,7E)-3,7,11-trimethyl-1,3,6,10-dodecatetraene) and β-farnesene (7,11-dimethyl-3-methylene-1,6,10-dodecatriene).

[0141] The farnesene polymer may be a homopolymer of farnesene (farnesene homopolymer) or a copolymer of farnesene and a vinyl monomer (farnesene-vinyl monomer copolymer).

[0142] Examples of the liquid diene polymer include liquid styrene-butadiene copolymer (liquid SBR), liquid butadiene polymer (liquid BR), liquid isoprene polymer (liquid IR), and liquid styrene-isoprene copolymer (liquid SIR).

[0143] The weight average molecular weight (Mw) of the liquid diene polymer in terms of polystyrene measured by gel permeation chromatography (GPC) is, for example, greater than 1.0×10 3 , less than 2.0×10 5 Here, the Mw of the liquid diene polymer is a polystyrene-equivalent value measured by gel permeation chromatography (GPC).

[0144] As the liquid rubber, for example, products of Kuraray Co., Ltd., Cray Valley Corporation, etc. can be used.

[0145] (iii) Resin component The resin component also plays a role as a component that imparts adhesiveness. It can be solid or liquid at room temperature. Specific examples of the resin component include rosin-based resins, styrene-based resins, coumarone-based resins, terpene-based resins, C5 resins, C9 resins, C5C9 resins, acrylic resins, and the like. Two or more types may be used in combination. It should be noted that these resin components may also be provided with a modifying group that reacts with silica or the like, as needed.

[0146] Rosin-based resins are resins obtained by processing rosin and having rosin acid as the main component. Rosin-based resins (rosins) can be classified according to whether they are modified or not, and can be classified into unmodified rosin (unmodified rosin) and rosin modifications (rosin derivatives). Examples of unmodified rosin include tall oil rosin (also known as tall oil rosin), gumrosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and rosin with other chemical modifications. Modified rosin is a modified form of unmodified rosin, and examples include rosin esters, unsaturated carboxylic acid-modified rosins, unsaturated carboxylic acid-modified rosin esters, amide compounds of rosin, and amine salts of rosin.

[0147] Styrene resins are polymers using styrene monomers as constituent monomers, and examples thereof include polymers obtained by polymerization of styrene monomers as the largest constituent monomer. Specifically, examples include homopolymers obtained by homopolymerizing styrene monomers (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.), copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of styrene monomers and other monomers copolymerizable therewith.

[0148] Examples of the other monomers include acrylonitriles such as acrylonitrile and methacrylonitrile, unsaturated carboxylic acids such as acrylic acid and methacrylic acid, unsaturated carboxylic acid esters such as methyl acrylate and methyl methacrylate, dienes such as chloroprene, butadiene, and isoprene, olefins such as 1-butene and 1-pentene, and α,β-unsaturated carboxylic acids such as maleic anhydride or their anhydrides.

[0149] Among coumarone resins, coumarone indene resins are preferred. Coumarone indene resins are resins containing coumarone and indene as monomer components constituting the backbone (main chain) of the resin. Examples of monomer components contained in the backbone other than coumarone and indene include styrene, α-methylstyrene, methylindene, and vinyltoluene.

[0150] The hydroxyl value (OH value) of the coumarone indene resin is, for example, greater than 15 mgKOH / g and less than 150 mgKOH / g. The OH value refers to the amount of potassium hydroxide (in milligrams) required to neutralize acetic acid bound to the hydroxyl groups when 1 g of the resin is acetylated, and is measured by potentiometric titration (JIS K 0070:1992).

[0151] The softening point of the coumarone indene resin is, for example, higher than 30° C. and lower than 160° C. The softening point is the softening point specified in JIS K 6220-1:2001, measured using a ring and ball softening point measuring apparatus, and is the temperature at which the ball falls.

[0152] Examples of terpene resins include polyterpene, terpene phenol, and aromatic modified terpene resins. Polyterpene is a resin obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are composed of (C5H8) n The hydrocarbons and their oxygenated derivatives are classified as monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H 32 ) and the like, which are compounds with terpenes as the basic skeleton, include, for example, α-pinene, β-pinene, dipentene, limonene, myrcene, alloocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, and the like.

[0153] Examples of polyterpenes include terpene resins such as α-pinene resin, β-pinene resin, limonene resin, dipentene resin, and β-pinene / limonene resin, which are derived from the above-mentioned terpene compounds. Examples of polyterpenes include hydrogenated terpene resins obtained by hydrogenating the terpene resins. Examples of terpene phenols include resins obtained by copolymerizing the above-mentioned terpene compounds with phenolic compounds, and resins obtained by hydrogenating the above-mentioned resins. Specifically, examples include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. It should be noted that examples of phenolic compounds include phenol, bisphenol A, cresol, and xylenol. Examples of aromatic modified terpene resins include resins obtained by modifying terpene resins with aromatic compounds, and resins obtained by hydrogenating the above-mentioned resins. It should be noted that the aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenol compounds such as phenol, alkylphenol, alkoxyphenol, and phenol containing an unsaturated hydrocarbon group; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and naphthol containing an unsaturated hydrocarbon group; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and styrene containing an unsaturated hydrocarbon group; benzofuran, indene, etc.

[0154] "C5 resin" refers to a resin obtained by polymerizing a C5 fraction. Examples of C5 fractions include petroleum fractions with 4 to 5 carbon atoms, such as cyclopentadiene, pentene, pentadiene, and isoprene. Dicyclopentadiene resin (DCPD resin) is a suitable C5 petroleum resin.

[0155] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may also be a product after hydrogenation or modification. Examples of the C9 fraction include petroleum fractions corresponding to 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples include coumarone indene resins, coumarone resins, indene resins, and aromatic vinyl resins. As aromatic vinyl resins, based on the reasons of economy, ease of processing, and good heat generation, α-methylstyrene (AMS resin) or a homopolymer of styrene, or a copolymer of α-methylstyrene and styrene, more preferably a copolymer of α-methylstyrene and styrene. As aromatic vinyl resins, commercially available products such as KRATON and Eastman Chemical can be used.

[0156] "C5C9 resin" refers to a resin obtained by copolymerizing the aforementioned C5 fraction and the aforementioned C9 fraction, and may also be a product of hydrogenation or modification thereof. Examples of the C5 and C9 fractions include the aforementioned petroleum fractions. Commercially available C5C9 resins, such as those from Tosoh Corporation and Luhua, can be used.

[0157] The acrylic resin is not particularly limited, and for example, a solvent-free acrylic resin can be used.

[0158] Examples of solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by a high-temperature continuous polymerization method (high-temperature continuous bulk polymerization method) (described in, for example, U.S. Patent No. 4,414,370, Japanese Patent Unexamined Publication No. 59-6207, Japanese Patent Unexamined Publication No. 5-58005, Japanese Patent Unexamined Publication No. 1-313522, U.S. Patent No. 5,010,166, and Toa Synthesis Research Annual Report TREND 2000, No. 3, pp. 42-45) without using auxiliary materials such as polymerization initiators, chain transfer agents, and organic solvents. It should be noted that, in the present invention, "(meth)acrylic acid" refers to both methacrylic acid and acrylic acid.

[0159] Examples of the monomer components constituting the acrylic resin include (meth)acrylic acid, (meth)acrylic acid esters (alkyl esters, aryl esters, aralkyl esters, etc.), (meth)acrylamide, and (meth)acrylic acid derivatives such as (meth)acrylamide derivatives.

[0160] As monomer components constituting the acrylic resin, aromatic vinyl groups such as styrene, α-methylstyrene, vinyltoluene, vinylnaphthalene, divinylbenzene, trivinylbenzene, and divinylnaphthalene may be used together with (meth)acrylic acid or a (meth)acrylic acid derivative.

[0161] The acrylic resin may be composed solely of a (meth)acrylic acid component or may contain components other than the (meth)acrylic acid component as constituent elements. The acrylic resin may have a hydroxyl group, a carboxyl group, a silanol group, or the like.

[0162] As the resin component, for example, products of Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Kraton, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., ENEOS Co., Ltd., Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used.

[0163] (IV) Wax The rubber composition may contain wax. The wax content is, for example, preferably 0.7 to 20 parts by mass, more preferably 1.0 to 15 parts by mass, and even more preferably 1.3 to 10 parts by mass, relative to 100 parts by mass of the rubber component.

[0164] The wax is not particularly limited, and any wax commonly used in the tire industry can be used as appropriate. Examples include mineral waxes and plant-derived waxes. Mineral waxes are waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes are waxes derived from natural resources such as plants. Among these, mineral waxes are preferred.

[0165] Examples of plant-derived waxes include rice wax, carnauba wax, and candelilla wax. Examples of mineral waxes include paraffin wax, microcrystalline wax, and selected special waxes thereof, with paraffin wax being preferred. It should be noted that the waxes in the present invention do not include stearic acid.

[0166] As the wax, for example, commercially available products from Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., Paramelt Co., Ltd., etc. These waxes may be used alone or in combination of two or more.

[0167] (V) Antioxidant The rubber composition may contain an antioxidant, and the content of the antioxidant relative to 100 parts by mass of the rubber component is, for example, greater than 1 part by mass and less than 10 parts by mass.

[0168] As antioxidant, there are no particular restrictions, and examples thereof include naphthylamine antioxidants such as phenyl-α-naphthylamine; diphenylamine antioxidants such as octylated diphenylamine and 4,4'-bis(α,α'-dimethylbenzyl)diphenylamine; N-isopropyl-N'-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (77PD), N,N'-diphenyl-p-phenylenediamine (DPPD), N,N'-ditolyl-p-phenylenediamine Paraphenylenediamine antioxidants such as diamine (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as polymers of 2,2,4-trimethyl-1,2-dihydroquinoline; monophenol antioxidants such as 2,6-di-tert-butyl-4-methylphenol and styrenated phenol; and bisphenol-, trisphenol-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate]methane. Among these, paraphenylenediamine antioxidants and quinoline antioxidants are preferred, with polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline being more preferred. These antioxidants can be used alone or in combination of two or more.

[0169] As commercially available products, for example, products of Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., Flexsys Corporation, and the like can be used.

[0170] (VI) Lubricant (stearic acid) The rubber composition may contain a lubricant. A lubricant based on a fatty acid derivative, such as stearic acid, is preferably used as the lubricant. Conventionally known stearic acids can be used, and specifically, products from NOF Corporation, Kao Corporation, Fujifilm Corporation, Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., and the like can be used. Alternatively, Struktol WB16 manufactured by Struktol Corporation may be used.

[0171] The content of stearic acid relative to 100 parts by mass of the rubber component is preferably, for example, greater than 0.5 parts by mass and less than 10.0 parts by mass.

[0172] (VII) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, greater than 0.5 parts by mass and less than 10 parts by mass per 100 parts by mass of the rubber component. Conventionally known zinc oxides can be used, such as those produced by Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Shodo Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd.

[0173] (VIII) Crosslinking agent and vulcanization accelerator The rubber composition preferably contains a crosslinking agent such as sulfur. The crosslinking agent content is, for example, greater than 0.1 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component. The sulfur content is pure sulfur; when insoluble sulfur is used, it is the amount excluding oil components.

[0174] Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur commonly used in the rubber industry. These may be used alone or in combination of two or more.

[0175] As sulfur, for example, products of Tsurumi Chemical Co., Ltd., Karuizawa Sulfur Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexsys Co., Ltd., Nippon Senryu Industry Co., Ltd., Hosoi Chemical Co., Ltd., and the like can be used.

[0176] Cross-linking agents other than sulfur can be used. Specifically, for example, sulfur-containing vulcanizing agents such as Tackirol V200 manufactured by Taoka Chemical Industry Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylenedithiosulfate dihydrate) manufactured by Flexsys, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldisulfide)hexane: mixed cross-linking agent) manufactured by Lanxess, and organic peroxides such as dicumyl peroxide can be used.

[0177] Furthermore, each rubber composition preferably contains a vulcanization accelerator. The content of the vulcanization accelerator is, for example, greater than 0.3 parts by mass and less than 10.0 parts by mass per 100 parts by mass of the rubber component.

[0178] Examples of the vulcanization accelerator include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, and N-cyclohexyl-2-benzothiazolylsulfenamide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD), tetrabenzylthiuram disulfide (TBzTD), and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiazolylsulfenamide, N-tert-butyl-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolylsulfenamide, N-oxyethylene-2-benzothiazolylsulfenamide, and N,N'-diisopropyl-2-benzothiazolylsulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, di-o-tolylguanidine, and o-tolylbiguanide. These may be used alone or in combination of two or more.

[0179] (IX) Others In addition to the above components, the rubber composition may also contain additives commonly used in the tire industry, such as organic fillers such as cellulose fibers, organic peroxides, etc., as needed. The content of these additives is, for example, greater than 0.1 parts by mass and less than 50 parts by mass per 100 parts by mass of the rubber component.

[0180] It should be noted that among the various materials described above, the various carbon-containing materials (e.g., rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) of the present invention may be carbon dioxide derived from the atmosphere. The compound of the present invention may be obtained from carbon dioxide by direct conversion of carbon dioxide or by conversion of methane obtained through a methanation process to methane from carbon dioxide.

[0181] (2) Preparation of rubber composition The rubber composition for the tread surface and the rubber composition for the tread base can be produced by a conventional method, for example, a manufacturing method comprising a basic mixing step of mixing the rubber component with a filler (filler) such as carbon black and a final mixing step of mixing the mixture obtained in the above basic mixing step with a cross-linking agent.

[0182] Kneading can be performed using a known (closed type) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0183] The mixing temperature in the basic mixing step is, for example, greater than 50°C and less than 200°C, and the mixing time is, for example, greater than 30 seconds and less than 30 minutes. In the basic mixing step, in addition to the above-mentioned ingredients, compounding agents conventionally used in the rubber industry, such as softeners such as oil, stearic acid, zinc oxide, antioxidants, waxes, and vulcanization accelerators, may be appropriately added as needed and mixed.

[0184] In the final kneading step, the kneaded product obtained in the basic kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, above room temperature and below 80°C, and the kneading time is, for example, above 1 minute and below 15 minutes. In addition to the above-mentioned ingredients, a vulcanization accelerator, zinc oxide, etc. may be added as needed during kneading in the final kneading step.

[0185] The rubber composition for a cap tread and the rubber composition for a base tread obtained above can then be laminated and extruded into a specific shape to form a tread.

[0186] 3. Tire manufacturing The tire of this embodiment can be manufactured using conventional methods. First, the cap tread rubber composition and base tread rubber composition obtained above are molded into a specific shape to produce a tread. This is then combined with other rubber components on a tire building machine to produce an unvulcanized tire.

[0187] Specifically, an inner liner (a component for ensuring the airtightness of the tire), a carcass (a component for withstanding the load, impact, and filling air pressure borne by the tire), a belt layer component (a component for strongly fastening the carcass and improving the rigidity of the tread), a band layer, etc. are wound on a forming drum, and bead portions (a component for fixing the two ends of the carcass and fixing the tire on the rim at the same time) are arranged on the edge portions on both sides. After being formed into a ring shape, the tread is adhered to the central portion of the outer periphery, and the sidewall is adhered to the radial outside to form a sidewall portion, thereby producing an unvulcanized tire.

[0188] The unvulcanized tire prepared above is then heated and pressurized in a vulcanizer to produce a tire. The vulcanization step can be carried out using known vulcanization methods. The vulcanization temperature is, for example, greater than 120°C and less than 200°C, and the vulcanization time is, for example, greater than 5 minutes and less than 15 minutes.

[0189] As described above, the tire obtained above can achieve sufficiently improved wet grip performance during high-speed cornering even when using sustainable materials. The tire of the present invention is particularly preferably used as a tire for light trucks. [Example]

[0190] Hereinafter, examples (embodiments) which are considered to be preferable in practice will be described, but the scope of the present invention is not limited to these examples.

[0191] By Figure 1Wet grip performance during high-speed cornering was evaluated on test tires (tire size: 205 / 80R17.5 120 / 118L) fabricated with the structure shown. The evaluation results are shown in Tables 1 and 2. The contact patch ratio in the shoulder region of the tread of the test tires was 2%.

[0192] [1] Production of test tires 1. Manufacturing of tread (1) Production of rubber composition for tread First, a rubber composition for a cap tread and a rubber composition for a base tread were produced using the following compounding materials.

[0193] (a) Compounding materials (a-1) Rubber component (I)NR:TSR20 (II) SBR: SBR1502 manufactured by ENEOS Materials (III) BR: BR730 manufactured by ENEOS Materials

[0194] (a-2) Compounding materials other than rubber components (I) Vulcanized rubber powder: TyreXol TW50 manufactured by Tyre Recycling Solutions (hydraulic crushed rubber powder, particle size: 50 mesh, average particle size: 192 μm) (II) Carbon black-1: SHOBLACK N220 manufactured by Cabot Japan Co., Ltd. (CTAB specific surface area: 111 m 2 / g) (III) Carbon black-2: SHOBLACK N351H (N2SA: 69m 2 / g) (IV) Oil: Diana Process NH-70S (aromatic processing oil) manufactured by Idemitsu Kosan Co., Ltd. (V) Wax: OZOACE-0355 manufactured by Nippon Seiro Co., Ltd. (VI) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (VII) Stearic acid: "Tsubaki" stearic acid manufactured by NOF Corporation (VIII) Antioxidant: Nocrac 6C (N-(1,3-dimethyl) butyl)-N'-phenyl-p-phenylenediamine) (IX) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. (X) Vulcanization accelerator: Nocceler CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0195] (b) Production of rubber composition for cap tread and rubber composition for base tread According to the compounding contents shown in Table 1, materials other than sulfur and the vulcanization accelerator were kneaded at 150° C. for 5 minutes using a Banbury mixer to obtain a kneaded product.

[0196] Then, zinc oxide, sulfur, and a vulcanization accelerator were added to the obtained kneaded products, and the mixtures were kneaded at 80° C. for 5 minutes using an open roll mill to obtain a rubber composition for a cap tread (cap) and a rubber composition for a base tread (base).

[0197] (2) Tread forming The rubber compositions obtained above were stacked and extruded into a specific shape to obtain a tread.

[0198] 2. Manufacturing of test tires The tread obtained above and other tire components prepared separately were laminated together to form an unvulcanized tire, which was then press-vulcanized at 170° C. for 10 minutes to produce test tires of Examples 1 to 5 and Comparative Examples 1 to 6.

[0199] 3. Parameter calculation Then, the following parameters were obtained for each test tire.

[0200] (1) Concave rate (Nr) Based on the above-mentioned method for calculating the concave ratio, the concave ratio Nr (%) was calculated.

[0201] (2) Area ratio of vulcanized rubber powder (Sr out and Sr. in ) First, samples for observation were cut out from the cap tread and base tread of each test tire, with the plane parallel to the tread surface serving as a cross section for observation.

[0202] Then, the cross section of each sample for observation was photographed using a scanning electron microscope (Teneo manufactured by Thermo Fisher) at an accelerating voltage of 15 kV to obtain an electron microscope image with a magnification of 50 times.

[0203] Then, within the 2.54 mm x 1.69 mm area of the obtained electron microscope image, the area of the region belonging to the vulcanized rubber powder was calculated, and the ratio of this area to the entire cross-sectional area was calculated. Thus, three fields of view were observed for each sample, and the average value was used as the area ratio occupied by the vulcanized rubber powder.

[0204] (3)(Sr out +Sr in ) / Nr Based on the above-mentioned Nr, Sr out 、Sr in , calculate (Sr out +Sr in The results are shown in Tables 1 and 2.

[0205] (4) Loss tangent (tanδ at 30°C) Rubber test specimens measuring 20 mm long, 4 mm wide, and 1 mm thick were cut from the cap tread and base tread of each test tire, with the longer side in the tire circumferential direction. The loss tangent (tan δ at 30°C) of each rubber test specimen was measured using an EPLEXOR series instrument manufactured by GABO Corporation in the tensile deformation mode at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%.

[0206] (5) Determination of elongation at break (EB) The elongation at break (EB) was measured on the cap tread and base tread of each test tire in accordance with the test method of JIS K6251:2017 (No. 3 dumbbell test piece).

[0207] 4. Performance evaluation (wet grip performance evaluation during high-speed cornering) Each test tire was mounted on all wheels of a vehicle (a domestic light truck), inflated to the specified internal pressure, and driven at 100 km / h on a wet test track. The drivers evaluated cornering performance using a five-point sensory evaluation system (higher values indicate better performance) for each test tire. The total sensory evaluation score of the 20 drivers was then calculated.

[0208] The wet grip performance during high-speed steering was evaluated by indexing based on the following formula, with the result of Comparative Example 2 being 100. A larger numerical value indicates better wet grip performance during high-speed steering. Wet grip performance during high-speed cornering =[(results of the test tire) / (results of Comparative Example 2)]×100

[0209]

Table 1

[0210]

Table 2

[0211] The above description is based on the embodiment of the present invention, but the present invention is not limited to the above embodiment. Various modifications can be made to the above embodiment within the same and equivalent scope as the present disclosure.

[0212] The present invention (1) is a tire characterized by: A tire with multiple land portions and grooves on the surface of the tread. The tread portion is formed by laminating a cap tread and a base tread from the contact surface side, and a concavity rate Nr (%) within the contact surface width is less than 20%. The cap tread and the base tread are both composed of a rubber composition containing vulcanized rubber powder. The area ratio of the vulcanized rubber powder in the cap tread is Sr out (%), the area ratio of the vulcanized rubber powder in the base tread is Sr in (%), the Nr, Sr out and Sr in Satisfies the following (Formula 1), 3≥(Sr out +Sr in ) / Nr (Formula 1)

[0213] The present invention (2) is a tire according to the present invention (1), characterized in that: The [(Sr out +Sr in ) / Nr] is less than 1.5.

[0214] The present invention (3), according to the tire described in the present invention (2), is characterized in that: The [(Sr out +Sr in ) / Nr] is less than 1.0

[0215] The present invention (4) is a tire according to any one of the present inventions (1) to (3), characterized in that: The concave rate is 15% or less.

[0216] The present invention (5) is a tire according to the present invention (4), characterized in that: The concave rate is 10% or less.

[0217] The present invention (6) is a tire according to any one of the present inventions (1) to (5), characterized in that: The average particle size of the vulcanized rubber powder is 350 μm or less.

[0218] The present invention (7) is a tire according to any one of the present inventions (1) to (6), characterized in that: The loss tangent (30°C tanδ) of the cap tread measured in a tensile deformation mode at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% is 0.20 or less.

[0219] The present invention (8), according to the tire of the present invention (7), is characterized in that: The loss tangent (30°C tan δ) of the cap tread is 0.18 or less.

[0220] The present invention (9) is a tire according to any one of the present inventions (1) to (8), characterized in that: The loss tangent (30°C tan δ) of the base tread measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% is 0.08 or less.

[0221] The present invention (10), according to the tire of the present invention (9), is characterized in that: The loss tangent (tan δ at 30°C) of the base tread is 0.07 or less.

[0222] The present invention (11) is a tire according to any one of the present inventions (1) to (10), characterized in that: The loss tangent (30°C tanδ) of the tread running surface measured in a tensile deformation mode at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% is greater than 2.75 relative to the loss tangent (30°C tanδ) of the tread base measured in a tensile deformation mode at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%.

[0223] The present invention (12), according to the tire of the present invention (11), is characterized in that: A ratio of tan δ at 30° C. of the cap tread to tan δ at 30° C. of the base tread is 2.80 or greater.

[0224] The present invention (13) is a tire according to any one of the present inventions (1) to (12), characterized in that: The breaking elongation of the cap tread measured in accordance with JIS K6251:2017 is 550% or more.

[0225] The present invention (14) is a tire according to any one of the present inventions (1) to (13), characterized in that: The elongation at break of the base tread measured in accordance with JIS K6251:2017 is 420% or more.

[0226] The present invention (15), according to the tire of the present invention (14), is characterized in that: The elongation at break of the base tread is greater than 440%.

[0227] The present invention (16) is a tire according to any one of the present inventions (1) to (15), characterized in that: A ratio of the elongation at break of the cap tread measured in accordance with JIS K6251:2017 to the elongation at break of the base tread measured in accordance with JIS K6251:2017 is 1.20 or more.

[0228] The present invention (17) is a tire according to the present invention (16), characterized in that: A ratio of the elongation at break of the cap tread to the elongation at break of the base tread is 1.25 or greater.

[0229] The present invention (18) is a tire according to any one of the present inventions (1) to (17), characterized in that: A contact patch ratio in a shoulder region of the tread portion is less than 3%.

[0230] The present invention (19) is a tire according to any one of the present inventions (1) to (18), characterized in that: The vulcanized rubber powder is produced by hydraulic pulverization.

[0231] The present invention (20) is a tire according to any one of the present inventions (1) to (19), characterized in that: It is a tire for light trucks.

Claims

1. A tire, characterized in that: A tire having a plurality of land portions and groove portions on the surface of the tread portion. The tread portion is formed by laminating a cap tread and a base tread from the contact surface side, and a concavity rate Nr within the contact surface width is less than 20%. The cap tread and the base tread are both composed of a rubber composition containing vulcanized rubber powder. The area ratio of the vulcanized rubber powder in the cap tread is Sr out The area ratio of the vulcanized rubber powder in the base tread is Sr in When the Nr and Sr out and Sr in Satisfies the following formula 1, 3≥(Sr out +Sr in ) / Nr (Equation 1) Nr、Sr out , and Sr in The unit is %.

2. The tire according to claim 1, wherein: The [(Sr out +Sr in ) / Nr] is less than 1.

5.

3. The tire according to claim 2, characterized in that The [(Sr out +Sr in ) / Nr] is less than 1.

0.

4. The tire according to any one of claims 1 to 3, characterized in that The concave rate is 15% or less.

5. The tire according to claim 4, characterized in that The concave rate is 10% or less.

6. The tire according to any one of claims 1 to 3, characterized in that The average particle size of the vulcanized rubber powder is 350 μm or less.

7. The tire according to any one of claims 1 to 3, characterized in that The loss tangent 30°C tan δ of the cap tread measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% is 0.20 or less.

8. The tire according to claim 7, characterized in that The loss tangent 30°C tanδ of the cap tread is 0.18 or less.

9. The tire according to any one of claims 1 to 3, characterized in that The loss tangent 30°C tan δ of the base tread measured in a tensile deformation mode under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% is 0.08 or less.

10. The tire according to claim 9, characterized in that The base tread has a loss tangent 30°C (tan δ) of 0.07 or less.

11. The tire according to any one of claims 1 to 3, characterized in that The loss tangent 30°C tanδ of the tread running surface measured in a tensile deformation mode at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1% is greater than 2.75 relative to the loss tangent 30°C tanδ of the tread base measured in a tensile deformation mode at a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain of 1%.

12. The tire according to claim 11, characterized in that A ratio of tan δ at 30° C. of the cap tread to tan δ at 30° C. of the base tread is 2.80 or greater.

13. The tire according to any one of claims 1 to 3, characterized in that The breaking elongation of the cap tread measured in accordance with JIS K6251:2017 is 550% or more.

14. The tire according to any one of claims 1 to 3, characterized in that The elongation at break of the base tread measured in accordance with JIS K6251:2017 is 420% or more.

15. The tire according to claim 14, characterized in that The elongation at break of the base tread is greater than 440%.

16. The tire according to any one of claims 1 to 3, characterized in that A ratio of the elongation at break of the cap tread measured in accordance with JIS K6251:2017 to the elongation at break of the base tread measured in accordance with JIS K6251:2017 is 1.20 or more.

17. The tire according to claim 16, characterized in that A ratio of the elongation at break of the cap tread to the elongation at break of the base tread is 1.25 or greater.

18. The tire according to any one of claims 1 to 3, characterized in that A contact patch ratio in a shoulder region of the tread portion is less than 3%.

19. The tire according to any one of claims 1 to 3, characterized in that The vulcanized rubber powder is produced by hydraulic pulverization.

20. The tire according to any one of claims 1 to 3, characterized in that It is a tire for light trucks.

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