Tire

Abstract

To provide a tire having sufficiently enhanced wet grip performance during high speed turning even while using sustainable material.SOLUTION: In a tire which is provided with a plurality of land parts and groove parts on a surface of a tread part, the tread part is laminated with a cap tread and a base tread from a ground side and is formed so that negative rate Nr (%) within the contact area width is less than 20%. Each of the cap tread and the base tread is composed of a rubber composition which contains vulcanization rubber powder. When area ratio at which the vulcanization rubber powder occupies in the cap tread is Srout(%) and area ratio at which the vulcanization rubber powder occupies in the base tread is Srin(%), Nr, Srout and Srin are satisfied with below equation 1. 3≥(Srout+Srin) / Nr (1)SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] As techniques for improving the wet grip performance of tires, various proposals have been made regarding tire shapes, rubber composition blends, and the like (for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-043709 [Patent Document 2] Japanese Patent Application Publication No. 2018-135436 [Patent Document 3] Patent No. 2021-167401 Summary of the Invention [Problem to be solved by the invention]

[0004] However, with the construction of expressways and improvements in vehicle performance in recent years, it is not uncommon to drive at high speeds, and there is an increasing demand for improved grip performance when turning at high speeds on wet roads (wet grip performance during high-speed turning).

[0005] Furthermore, in recent years, there has been an increasing trend toward environmental protection, and there is a growing demand for tires that use sustainable materials and have a reduced environmental impact. However, if sustainable materials are used too easily, although the environmental impact can be reduced, there is a risk of reducing the performance of the tire. For example, vulcanized rubber powder, which is a recycled material obtained by pulverizing vulcanized rubber, has been attracting attention in recent years as a sustainable material, and attempts have been made to incorporate it into rubber compositions that form tires, but there is a risk of reducing the performance of the tire.

[0006] In view of the above-mentioned problems, an object of the present invention is to provide a tire that uses vulcanized rubber powder, which is a sustainable material, and yet has sufficiently improved wet grip performance during high-speed cornering. [Means for solving the problem]

[0007] The present invention provides A tire having a plurality of land portions and groove portions on the surface of a tread portion, The tread portion is formed by laminating a cap tread and a base tread from the ground contact side, and has a negative ratio Nr (%) within the ground contact width of less than 20%, The cap tread and the base tread are both made of a rubber composition containing vulcanized rubber powder, The area ratio of the vulcanized rubber powder in the cap tread is Sr out (%), and the area ratio of the vulcanized rubber powder in the base tread is Sr in (%), the above Nr and Sr out , and Sr in The tire is characterized by satisfying the following formula (1): 3≧(Sr out +Sr in ) / Nr (1 set) [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a tire that uses sustainable materials and yet has sufficiently improved wet grip performance during high-speed cornering. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic cross-sectional view showing the configuration of a tire according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

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

[0011] 1. Overview The tire according to the present invention is a tire having a plurality of land portions and groove portions on the surface of the tread portion, and the tread portion is formed by laminating a cap tread and a base tread from the contact surface side, and the negative ratio Nr (%) within the contact surface width is less than 20%, and both the cap tread and the base tread are made of a rubber composition containing vulcanized rubber powder. Furthermore, the area ratio occupied by the vulcanized rubber powder in the cap tread is set to Sr out (%), and the area ratio of vulcanized rubber powder in the base tread is Sr in (%), Nr, Sr out , and Sr in However, the following equation (1) is satisfied. 3≧(Sr out +Sr in ) / Nr (1 set)

[0012] These features make it possible to provide a tire that uses sustainable materials and yet has sufficiently improved wet grip performance during high-speed cornering, as will be described later.

[0013] 2. Mechanism of effect manifestation in the tire according to the present invention The mechanism by which the above-described effects of the tire according to the present invention are exhibited is believed to be as follows.

[0014] (1) Negative rate In the tire according to the present invention, the negative ratio Nr (%) within the contact patch width of the tread portion is set to less than 20%.

[0015] By controlling the negative ratio Nr within the contact patch width to less than 20%, a large contact area between the tire and the road surface is ensured, and the tire can firmly grip the road surface and move in accordance with the road surface even when turning at high speed on a wet road surface, which is thought to sufficiently improve wet grip performance during high-speed turning. A ratio of 15% or less is more preferable, and 10% or less is even more preferable.

[0016] In the above, the negative rate 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 all multiple grooves filled (the total contact area over the entire circumference of the tire that comes into contact with the ground when a tire having a tread portion with all multiple grooves filled is in its normal state, under normal internal pressure and normal load conditions, and the tread portion is pressed against a flat surface at a camber angle of 0°). Note that the virtual contact area and groove area can be calculated by determining the area of ​​the grooves in the contact patch around the entire circumference of the tire, and can be measured simply by applying ink or the like to the tire surface and transferring it.

[0017] Specifically, the contact patch was obtained by mounting the tire on a standard rim, applying standard internal pressure, and leaving it at 25°C for 24 hours. After that, ink was applied to the tire surface, and the tire was pressed against cardboard under a standard load (camber angle 0°) and transferred to the paper. The tire was rotated 72° in circumferential directions, and the transfer was performed at five locations. In other words, five contact patch patterns were obtained. The average maximum axial length of the five contact patch patterns was defined as L, and the average length perpendicular to the axial direction was defined as W. The negativity (%) was calculated as [1 - {average area of ​​the five contact patch patterns (inked portions) transferred to the cardboard / (L × W)}] × 100 (%). Here, the average length and area were calculated by simply averaging the five values, and L × W in the formula refers to the area of ​​the imaginary surface obtained by joining the gaps created by the main and lateral grooves when the contact patch was obtained.

[0018] Here, "normal condition" refers to a state in which the tire is mounted on a normal rim, is inflated to a normal internal pressure, and is not under load.

[0019] "Genuine rim" refers to the rim specified for each tire in the standard system that includes the standard on which the tire is based. For example, for JATMA (Japan Automobile Tire Manufacturers Association), it refers to the standard rim for the applicable size listed in the "JATMA Year Book." For ETRTO (The European Tire and Rim Technical Organization), it refers to the "Measuring Rim" listed in the "Standards Manual." For TRA (The Tire and Rim Association, Inc.), it refers to the "Design Rim" listed in the "Year Book." JATMA, ETRTO, and TRA are referenced in that order, and if an applicable size is available at the time of reference, that standard is followed. For tires not specified in the standard, it refers to the rim that can be mounted on the rim and can maintain internal pressure, i.e., the rim with the smallest rim diameter and the next narrowest rim width, among rims that do not leak air between the rim and tire.

[0020] "Normal internal pressure" refers to the air pressure specified for each tire by each standard in the standard system, including the standard on which the tire is based. For JATMA, it refers to "Maximum Air Pressure," for ETRTO, it refers to "INFLATION PRESSURE," and for TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES." Refer to JATMA, ETRTO, and TRA in that order, and follow the standard if there is an applicable size at the time of reference. In the case of a tire not specified in the standard, it refers to the normal internal pressure (250 kPa or more) of another tire size (specified in the standard) that is specified using the normal rim as the standard rim. Note that if multiple normal internal pressures of 250 kPa or more are listed, it refers to the smallest value among them.

[0021] Furthermore, "normal load" refers to the load determined for each tire by each standard in the standard system, including the standard on which the tire is based, and refers to the maximum mass that can be loaded on the tire. In the case of JATMA, it refers to the maximum load capacity, in the case of ETRTO, it refers to the "LOAD CAPACITY", and in the case of TRA, it refers to the maximum value listed in the table "TIRE LOAD LIMITS AT VARIOUS COLD INFLATION PRESSURES". As with the above-mentioned "normal rim" and "normal internal pressure", JATMA, ETRTO, and TRA are referenced in that order and their standards are followed. In the case of tires not specified in the standard, the normal load W is calculated as follows: L Ask for. V={(Dt / 2) 2 -(Dt / 2-Ht) 2}×π×Wt W L =0.000011×V+175 W L :Normal load (kg) V: Virtual volume of the tire (mm 3 ) Dt: Tire outer diameter Dt (mm) Ht: tire section height (mm) Wt: tire cross-sectional width (mm)

[0022] (2) Cap tread and base tread In the tire according to the present invention, the tread portion is formed by laminating a cap tread and a base tread from the ground contact side, and both the cap tread and the base tread are made of a rubber composition containing vulcanized rubber powder.

[0023] By compounding vulcanized rubber powder into both the cap tread and the base tread so that the amount is equal to or greater than a predetermined area ratio, the contact area between the cap tread and the base tread can be increased, and the interface between the cap tread and the base tread can be strongly reinforced. This makes it easier for force to be applied between the cap tread and the base tread, making it easier for the entire tread to follow the road surface.

[0024] Furthermore, as mentioned above, by controlling the negative rate to a small value, a large contact area between the tire and the road surface can be ensured. These factors work together to enable the tire to firmly grip the road surface and move in accordance with the road surface, even when turning at high speed on a wet road surface, and it is believed that wet grip performance during high-speed turning is significantly improved.

[0025] However, if the content of vulcanized rubber powder is too high, the area ratio of the vulcanized rubber powder becomes too large, which may reduce the reinforcing effect in the tread portion, which is undesirable.

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

[0027] Specifically, the area ratio of vulcanized rubber powder in the cap tread is Sr out (%), and the area ratio of vulcanized rubber powder in the base tread is Sr in (%), [(Sr out +Sr in ) / Nr] is 3 or less (3≧(Sr out +Sr in ) / Nr), the above-mentioned effects work together, and the vulcanized rubber powder can strongly reinforce the interface between the cap tread and the base tread. This allows the tire to firmly grip the road surface and move in accordance with the road surface even when cornering at high speed on a wet road surface, and is thought to result in a sufficient improvement in wet grip performance during high-speed cornering. out +Sr in ) / Nr] is more preferably 1.5 or less, even more preferably 1.0 or less, and even more preferably 0.5 or less.

[0028] The above-mentioned "area ratio occupied by vulcanized rubber powder" can be obtained by cutting the tread portion to prepare a sample so that a plane parallel to the tread surface becomes the cross section for observation, photographing the sample with a scanning electron microscope, determining the area of ​​the region occupied by vulcanized rubber powder in the images of the cut surfaces of the cap tread and base tread obtained, and calculating the ratio of this area to the area of ​​the entire cut surface.

[0029] [2] More preferred embodiments of the tire according to the present invention The tire according to the present invention can achieve even greater 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. Since vulcanized rubber powder with such a small particle size has a large specific surface area, it is believed that the iodine value increases, improving surface reactivity and allowing the formation of a large structure. As a result, the physical bonding strength with the polymer in the rubber composition increases, which is believed to further reinforce the tread rubber, increasing rigidity and further improving wet grip performance during high-speed cornering. It is more preferably 350 μm or less, even more 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, even more preferably 100 μm or more, and particularly preferably 150 μm or more.

[0031] In terms of particle size, the particle size of the vulcanized rubber powder in the present invention is preferably finer than 15 mesh pass, more preferably finer than 20 mesh pass, and even more preferably finer than 30 mesh pass, as measured using a test sieve specified in JIS Z8801. Although not particularly limited, it is preferably coarser than 200 mesh pass, more preferably coarser than 100 mesh pass, and even more preferably coarser than 50 mesh pass.

[0032] 2.Loss tangent In the present invention, the loss tangent (30°C tanδ) of the cap tread measured in a tensile deformation mode under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is preferably 0.22 or less, more preferably 0.20 or less, even more preferably 0.18 or less, and particularly preferably 0.17 or less. There is no particular restriction on the lower limit, but it is preferably 0.10 or more, more preferably 0.12 or more, even more preferably 0.14 or more, and particularly preferably 0.16 or more.

[0033] On the other hand, the 30°C tan δ of the base tread is preferably 0.08 or less, more preferably 0.07 or less, and even more preferably 0.06 or less. There is no particular lower limit, but it 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 30°C tan δ of the cap tread to the 30°C tan δ of the base tread is preferably 2.50 or more, more preferably 2.75 or more, even more preferably 2.80 or more, and particularly preferably 2.85 or more. 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, and by appropriately controlling the 30°C tanδ of the cap tread and base tread to these values, the input-response phase difference between the cap tread and the base tread becomes smaller, which speeds up the transmission of force from the cap tread, which is the contact surface, to the inner base tread. This ensures good responsiveness even during cornering, and is thought to further improve wet grip performance during high-speed cornering.

[0036] Furthermore, the tread portion that flexes when it comes into contact with the road surface during rolling can easily return to its original shape when it leaves the road surface, and can easily flex again when it comes back into contact with the ground. This is also thought to further improve wet grip performance during high-speed cornering.

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

[0038] 3. Elongation at break In the present invention, the elongation at break (EB) of the cap tread measured in accordance with JIS K6251;2017 is preferably 550% or more, more preferably 580% or more, and even more preferably 600% or more. 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 more, more preferably 440% or more, and even more preferably 460% or more. There is no particular upper limit, but it 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 more, more preferably 1.25 or more, and even more preferably 1.27 or more, while 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 breaking elongation EB is an index that shows how well the rubber can follow deformation that occurs as a result of the force applied to it. By appropriately controlling the EB of the cap tread and base tread to these values, it is possible to easily follow deformation during high-speed cornering and ensure good responsiveness, which is thought to further improve wet grip performance during high-speed cornering.

[0042] 4. Land ratio in the shoulder area of ​​the tread In the present invention, the land ratio of the shoulder region located on the outer side of the tread contact patch is preferably less than 3%. By reducing the land ratio of the shoulder region in this way, even in a tire in which the negative ratio within the contact patch width is controlled to be small, sufficient water can be drained from the shoulder region, which is thought to further improve wet grip performance during high-speed cornering. It is more preferably less than 2%. There is no particular lower limit, but it is preferably more than 0%, and more preferably more than 1%.

[0043] In the above, the land ratio refers to the ratio (%) of the actual contact area when the grooves are formed to the virtual contact area of ​​the tread portion, and can be measured in the same manner as the measurement of the negative rate described above, and is calculated as {average area of ​​five contact shapes (ink parts) transferred onto cardboard / L × W} × 100 (%).

[0044] [3] Implementation form The present invention will be specifically described below based on embodiments.

[0045] 1. Tire configuration Fig. 1 is a schematic cross-sectional view showing the configuration of a tire according to one embodiment of the present invention. In Fig. 1, the up-down direction is the radial direction of the tire, the left-right direction is the axial direction, and the direction perpendicular to the paper surface is the circumferential direction. Note that the dashed-dotted line CL represents the equatorial plane of the tire 1.

[0046] As shown in Fig. 1, a 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. Note that 2 and 3 respectively indicate the contact patch region and shoulder region in the tire axial direction.

[0047] A tread pattern is formed on the surface of the tread portion 4 by forming a plurality of grooves 22 and a plurality of land portions 23. The tread 4 is formed by laminating a base tread 24 and a cap tread 26, and has a negative ratio of less than 20% within the contact patch width.

[0048] The carcass 12 is made up of a plurality of carcass plies (first to third in FIG. 1) in which parallel cords are covered with topping rubber. The cords are preferably made of organic fibers, such as polyester fibers, nylon fibers, rayon fibers, polyethylene naphthalate fibers, and aramid fibers.

[0049] The belt 14 is composed of multiple layers (inner layer 50 and outer layer 52 in FIG. 1) in which parallel cords are coated with topping rubber, and reinforces the carcass 12. In each layer, the cords are inclined with respect to the equator plane, and the inner layer 50 and the outer layer 52 are inclined in opposite directions to each other. Steel cords are preferred as the cords, but organic fiber cords may also be used.

[0050] The band 16 is located radially outward of the belt 14. The band 16 is made of a cord and a topping rubber. The cord is wound spirally. The band 16 has a so-called jointless structure. The cord extends substantially in the circumferential direction. The belt 14 is restrained by the cord, thereby suppressing lifting of the belt 14. The cord is preferably made of an organic fiber, such as nylon fiber, polyester fiber, rayon fiber, polyethylene naphthalate fiber, or aramid fiber.

[0051] By configuring in this way and appropriately controlling the settings of the above-mentioned parameters, it is possible to obtain a tire with sufficiently improved wet grip performance during high-speed cornering.

[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 and other compounding materials described below.

[0053] (1) Compounding materials (a) Rubber component The rubber component is not particularly limited, and rubbers (polymers) generally used in tire production can be used, such as isoprene-based rubbers such as natural rubber (NR), diene-based rubbers such as butadiene rubber (BR), styrene butadiene rubber (SBR), and nitrile rubber (NBR), and butyl-based rubbers such as butyl rubber. These polymers may be used alone or in combination, and among them, it is preferable to use NR and BR, or NR and SBR in combination, and it is more preferable to use three types of NR, SBR, and BR.

[0054] (a) Isoprene rubber Examples of isoprene-based rubber include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR, with NR being preferred due to its excellent strength.

[0055] Examples of NR that can be used include those commonly used in the tire industry, such as SVR-L, SIR20, RSS#3, and TSR20. IR is not particularly limited, and examples of IR that can be used include those commonly used in the tire industry, such as IR2200 manufactured by Zeon Corporation. Examples of modified NR include deproteinized natural rubber (DPNR) and highly purified natural rubber (UPNR). Examples of modified NR include epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Examples of modified IR include epoxidized isoprene rubber, hydrogenated isoprene rubber, and grafted isoprene rubber. These may be used alone or in combination of two or more.

[0056] In the rubber composition for cap tread and the rubber composition for base tread, the content of the isoprene-based rubber in 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] (b) SBR The weight-average molecular weight of SBR is, for example, more than 100,000 and less than 2,000,000. The styrene content of SBR is, for example, preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 15% by mass. On the other hand, it is preferably less than 40% by mass, more preferably less than 35% by mass, and even more preferably less than 30% by mass. The vinyl content (amount of 1,2-bonded butadiene units) of SBR is, for example, preferably more than 5% by mass, more preferably more than 10% by mass, and even more preferably more than 15% by mass. On the other hand, it is preferably less than 70% by mass, more preferably less than 40% by mass, and even more preferably less than 30% by mass. SBR structural identification (measurement of styrene content and vinyl content) can be performed using, for example, a JNM-ECA series instrument manufactured by JEOL Ltd.

[0058] The SBR is not particularly limited, and examples that can be used include emulsion-polymerized styrene-butadiene rubber (E-SBR) and solution-polymerized styrene-butadiene rubber (S-SBR). SBR may be either unmodified or modified. Hydrogenated SBR, in which the butadiene portion of SBR is hydrogenated, may also be used. Hydrogenated SBR may be obtained by subsequently hydrogenating the BR portion of SBR, or a similar structure may be obtained by copolymerizing styrene, ethylene, and butadiene.

[0059] The modified SBR is preferably an SBR having a functional group that interacts with a filler such as silica. Examples include terminal-modified SBR in which at least one terminal of the SBR has been modified with a compound (modifier) ​​having the above functional group (terminal-modified SBR having the above functional group at the terminal), main-chain-modified SBR in which the main chain has the above functional group, main-chain terminal-modified SBR in which the main chain and the terminals have the above functional group (for example, main-chain terminal-modified SBR in which the main chain has the above functional group and at least one terminal has been modified with the above modifier), and terminal-modified SBR in which the SBR has been modified (coupled) with a polyfunctional compound having two or more epoxy groups in the molecule and in which a hydroxyl group or epoxy group has been introduced.

[0060] Examples of the functional group include an amino group, an amide group, a silyl group, an alkoxysilyl group, an isocyanate group, an imino group, an imidazole group, a urea group, an ether group, a carbonyl group, an oxycarbonyl group, a mercapto group, a sulfide group, a disulfide group, a sulfonyl group, a sulfinyl group, a thiocarbonyl group, an ammonium group, an imide group, a hydrazo group, an azo group, a diazo group, a carboxyl group, a nitrile group, a pyridyl group, an alkoxy group, a hydroxyl group, an oxy group, an epoxy group, etc. These functional groups may have a substituent.

[0061] Furthermore, as the modified SBR, for example, SBR modified with a compound (modifying agent) represented by the following formula can be used.

[0062] [ka]

[0063] In the formula, R 1 , R 2 and R 3 R may be the same or different and represent 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 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0064] The modified SBR modified with a compound (modifier) ​​represented by the above formula can be an SBR in which the polymerization terminals (active terminals) of a solution-polymerized styrene-butadiene rubber (S-SBR) have been modified with a compound represented by the above formula (such as the modified SBR described in JP 2010-111753 A).

[0065] R 1 , R 2 and R 3 R is 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 is 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. In addition, R 4 and R 5 When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0066] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0067] Modified SBR may also be modified with the following compounds (modifiers): Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups, such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxy sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyl alkoxysilanes such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-butylaminobenzophenone, 4-N,N-diphenylaminobenzophenone, 4,4'-bis(dimethylamino)benzophenone, 4,4'-bis(diethylamino)benzophenone, 4,4'-bis(diphenylamino)benzophenone, N,N,N',N'-bis-(tetraethylamino)benzophenone, and other (thio)benzophenone compounds having an amino group and / or a substituted amino group; 4-N,N-di Benzaldehyde compounds having an amino group and / or a substituted amino group, such as methylaminobenzaldehyde, 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, Nt-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; and N-substituted piperidones such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione , 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-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods.

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

[0069] In the rubber composition for cap treads and the rubber composition for base treads, the content of SBR in 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] (C)BR The weight-average molecular weight of the BR is, for example, more than 100,000 and less than 2,000,000. The vinyl content of the BR is, for example, more than 1% by mass and less than 30% by mass. The cis content of the BR is, for example, more than 1% by mass and not more than 98% by mass. The trans content of the BR is, for example, more than 1% by mass and less than 60% by mass. The cis content can be measured by infrared absorption spectroscopy.

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

[0072] [ka]

[0073] In the formula, R 1 , R 2 and R 3 R may be the same or different and represent 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 are the same or different and represent a hydrogen atom or an alkyl group. 4 and R 5 may bond to form a ring structure together with the nitrogen atom, and n represents an integer.

[0074] The modified BR modified with the compound (modifying agent) represented by the above formula includes BR whose polymerization terminal (active terminal) has been modified with the compound represented by the above formula.

[0075] R 1 , R 2 and R 3 R is 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 R5 is 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. In addition, R 4 and R 5 When the groups bond to form a ring structure together with the nitrogen atom, the ring is preferably a 4- to 8-membered ring. The alkoxy group also includes a cycloalkoxy group (such as a cyclohexyloxy group) and an aryloxy group (such as a phenoxy group or a benzyloxy group).

[0076] Specific examples of the modifying agent include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, 3-diethylaminopropyltriethoxysilane, etc. These may be used alone or in combination of two or more.

[0077] The modified BR may also be modified with the following compounds (modifiers): Examples of the modifier include polyglycidyl ethers of polyhydric alcohols such as ethylene glycol diglycidyl ether, glycerin triglycidyl ether, trimethylolethane triglycidyl ether, and trimethylolpropane triglycidyl ether; polyglycidyl ethers of aromatic compounds having two or more phenol groups, such as diglycidylated bisphenol A; polyepoxy compounds such as 1,4-diglycidylbenzene, 1,3,5-triglycidylbenzene, and polyepoxidized liquid polybutadiene; epoxy group-containing tertiary amines such as 4,4'-diglycidyl-diphenylmethylamine and 4,4'-diglycidyl-dibenzylmethylamine; diglycidylaniline, N,N'-diglycidyl-4-glycidyloxyaniline; Diglycidyl amino compounds such as diglycidyl orthotoluidine, tetraglycidyl meta-xylenediamine, tetraglycidyl aminodiphenylmethane, tetraglycidyl-p-phenylenediamine, diglycidyl aminomethylcyclohexane, and tetraglycidyl-1,3-bisaminomethylcyclohexane; amino group-containing acid chlorides such as bis-(1-methylpropyl)carbamic acid chloride, 4-morpholinecarbonyl chloride, 1-pyrrolidinecarbonyl chloride, N,N-dimethylcarbamic acid chloride, and N,N-diethylcarbamic acid chloride; epoxy group-containing silane compounds such as 1,3-bis-(glycidyloxypropyl)-tetramethyldisiloxane and (3-glycidyloxypropyl)-pentamethyldisiloxane;(Trimethylsilyl)[3-(trimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(triethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(trippropoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(tributoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldimethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldiethoxysilyl)propyl]sulfide, (trimethylsilyl)[3-(methyldipropoxysilyl)propyl]sulfide sulfide group-containing silane compounds such as (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide and (trimethylsilyl)[3-(methyldibutoxysilyl)propyl] sulfide; N-substituted aziridine compounds such as ethyleneimine and propyleneimine; methyltriethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltrimethoxysilane, N,N-bis(trimethylsilyl)-3-aminopropyltriethoxysilane, N,N-bis(trimethylsilyl)aminoethyltrimethoxysilane, N,N-bis(trimethylsilyl)aminoethyl Alkoxysilanes such as triethoxysilane; (thio)benzophenone compounds having an amino group and / or a substituted amino group such as 4-N,N-dimethylaminobenzophenone, 4-N,N-di-t-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; benzaldehyde compounds having an amino group and / or a substituted amino group, such as 4-N,N-diphenylaminobenzaldehyde, 4-N,N-divinylaminobenzaldehyde, etc.; N-substituted pyrrolidones, such as N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-phenyl-2-pyrrolidone, Nt-butyl-2-pyrrolidone, and N-methyl-5-methyl-2-pyrrolidone; N-substituted piperidones, such as N-methyl-2-piperidone, N-vinyl-2-piperidone, and N-phenyl-2-piperidone;N-substituted lactams such as N-methyl-ε-caprolactam, N-phenyl-ε-caprolactam, N-methyl-ω-laurylolactam, N-vinyl-ω-laurylolactam, N-methyl-β-propiolactam, and N-phenyl-β-propiolactam; as well as N,N-bis-(2,3-epoxypropoxy)-aniline, 4,4-methylene-bis-(N,N-glycidylaniline), and tris-(2,3-epoxypropyl)-1,3,5-triazine-2,4,6-trione , 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-dimethylaminoacetophen, 4-N,N-diethylaminoacetophenone, 1,3-bis(diphenylamino)-2-propanone, 1,7-bis(methylethylamino)-4-heptanone, etc. Modification with the above compounds (modifiers) can be carried out by known methods. These modified BRs may be used alone or in combination of two or more.

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

[0079] In the rubber composition for cap tread and the rubber composition for base tread, the content of BR in 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, while 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] (d) Other rubber components The rubber composition may contain, as other rubber components, rubbers (polymers) that are generally used in the production of tires, such as nitrile rubber (NBR), as necessary.

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

[0082] Monomers obtained by recycling (recycled monomers) are not particularly limited, and examples thereof include recycled isoprene, recycled butadiene, and recycled aromatic vinyl. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not particularly limited to, styrene. Among these, it is preferable to use recycled isoprene (recycled isoprene), butadiene (recycled butadiene), and / or recycled styrene (recycled styrene) as raw materials.

[0083] The method for producing the recycled monomer is not particularly limited, and examples thereof include synthesis from recycled naphtha obtained by decomposing rubber products such as tires. The method for producing recycled naphtha is also not particularly limited, and examples thereof include decomposing rubber products such as tires under high temperature and pressure, decomposing with microwaves, or mechanically crushing and then extracting.

[0084] Furthermore, the raw materials (monomers) of synthetic rubbers such as IR, SBR, and BR may be derived from biomass. Here, biomass refers to materials derived from natural resources such as plants. Examples of biomass include, but are not limited to, agricultural, forestry, and fishery products, sugar, wood, plant residues after useful components have been extracted, plant-derived ethanol, and biomass naphtha. Examples of biomass-derived monomers (biomass monomers) include, but are not limited to, biomass-derived butadiene and biomass-derived aromatic vinyls. Examples of butadienes include 1,2-butadiene and 1,3-butadiene. Examples of aromatic vinyls include, but are not limited to, styrene. Methods for producing biomass monomers are also not limited, and include, for example, biological and / or chemical and / or physical conversion of plants and animals. Typical biological conversions include microbial fermentation, while examples of chemical and / or physical conversions include catalytic, high-temperature, high-pressure, electromagnetic, and critical fluid conversions, as well as combinations thereof.

[0085] Polymers synthesized from biomass monomer components (biomass polymers) are not particularly limited and include polybutadiene rubber synthesized from biomass-derived butadiene, aromatic vinyl / butadiene copolymers synthesized from biomass-derived butadiene and / or biomass-derived aromatic vinyl, etc. Examples of the aromatic vinyl / butadiene copolymers 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 the pMC (percent modern carbon) measured in accordance with ASTM D6866-10.

[0087] pMC is the modern standard reference 14 of sample against C concentration 14This is the ratio of the carbon concentration, and this value is used as an index showing the biomass ratio of the compound (rubber). The significance of this value is explained below.

[0088] 1 mole of carbon atoms (6.02 × 10 23 ) contains approximately 6.02 × 10 atoms, which is about one trillionth of the number of ordinary carbon atoms. 11 pieces 14 C exists. 14 C is called a radioactive isotope, and its half-life is 5,730 years, and it decreases regularly. It takes 226,000 years for all of it to decay. Therefore, in fossil fuels such as coal, oil, and natural gas, which are thought to have been absorbed and fixed by plants and other organisms for more than 226,000 years, C was also included in these when they were first fixed. 14 All C elements have decayed. Therefore, in the 21st century, fossil fuels such as coal, oil, and natural gas contain 14 Therefore, chemicals produced from these fossil fuels do not contain any C element. 14 It does not contain any C elements.

[0089] on the other hand, 14 C is produced continuously by nuclear reactions in the atmosphere caused by cosmic rays, and in the Earth's atmospheric environment, the amount of C is balanced by the decrease caused by radioactive decay. 14 Therefore, the amount of carbon derived from biomass resources currently circulating in the environment is constant. 14 As mentioned above, the C concentration is approximately 1 × 10 -12 The value is approximately mol %. Therefore, the biomass ratio in a compound can be calculated by using the difference between these values.

[0090] this 14 C is typically measured using accelerator mass spectrometry based on a tandem accelerator. 13 C concentration ( 13 C / 12 C). 14 C concentration ( 14 C / 12 C) is measured.14 The modern standard reference for the C concentration is the carbon circulating in nature as of 1950. 14 The specific standard substance used is the oxalic acid standard provided by NIST (National Institute of Standards and Technology). The specific activity of carbon in this oxalic acid (per gram of carbon) is 14 The radioactivity of C is separated into carbon isotopes, 13 The standard value is the value corrected for decay from 1950 to the measurement date. 14 This is used as the C concentration value (100%). The ratio of this value to the value of the actually measured sample is the pMC value.

[0091] Therefore, if rubber is made from 100% biomass (natural) derived materials, although there are regional differences, under normal circumstances it will usually not reach 100, and will show a value of approximately 110 pMC. On the other hand, when measuring the 14C concentration of chemicals derived from fossil fuels such as petroleum, it will show a value of around 0 pMC (for example, 0.3 pMC). This value corresponds to the 0% biomass ratio mentioned above.

[0092] For these reasons, it is preferable from the standpoint of environmental protection (sustainability) to use a material such as rubber with a high pMC value, that is, a material such as rubber with a high biomass ratio, in a rubber composition.

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

[0094] Vulcanized rubber powder is particles made of vulcanized rubber, and specifically, rubber powder specified in JIS K 6316:2017 can be used. From the standpoint of environmental considerations and cost, recycled rubber powder produced from crushed waste tires is preferred. These may be used alone or in combination of two or more types.

[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 mill, grinder, etc. Pulverization methods include mechanical pulverization using a mill, freeze pulverization in which chips are frozen with liquid nitrogen and then mechanically pulverized, and hydraulic pulverization in which chips are pulverized using high-pressure water (water jet).Of these, vulcanized rubber powder produced by hydraulic pulverization is preferred because it has superior tensile strength and abrasion resistance compared to mechanically pulverized or freeze-pulverized products of the same particle size.

[0097] In other words, freeze-pulverization and mechanical pulverization involve mechanical pulverization, which does not select the cutting site and physically breaks chemical bonds, whereas hydraulic pulverization uses water to pulverize, so chemical bonds are not physically broken. As a result, the vulcanized rubber powder obtained by hydraulic pulverization has more surface irregularities and a larger specific surface area than vulcanized rubber powder obtained by mechanical pulverization or freeze-pulverization, which is thought to cause the vulcanized rubber powder to catch on the matrix rubber and improve reinforcement during deformation. Furthermore, the increased specific surface area exposes many reactive double bonds on the surface, increasing the iodine value and increasing surface reactivity, which is thought to chemically bond the vulcanized rubber powder and matrix rubber.

[0098] Furthermore, vulcanized rubber powder can reduce the consumption of petroleum-derived materials, making it a desirable sustainable material that can adapt to the growing trend toward environmental protection in recent years.

[0099] The content of the vulcanized rubber powder relative to 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 Co., Ltd., etc. can be used.

[0101] (b) Filler In the present invention, the rubber composition preferably contains a filler. Specific examples of the filler include carbon black, silica, graphite, calcium carbonate, talc, alumina, clay, aluminum hydroxide, and mica. Among these, carbon black is preferred, and silica may also be contained as needed. When silica is used, it is preferred to use it in combination with a silane coupling agent.

[0102] The amount of the filler mixed 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 Carbon black is preferably used for the purpose of improving the crack growth resistance, durability, resistance to ultraviolet degradation, etc. of the tire.

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

[0105] From the viewpoint of rubber rigidity, the dibutyl phthalate (DBP) absorption of carbon black is preferably, for example, 50 ml / 100 g or more, and more preferably 100 ml / 100 g or more. On the other hand, from the viewpoint of rubber deformation compliance, it is preferably 250 ml / 100 g or less, and more preferably 150 ml / 100 g or less. The DBP absorption of carbon black is measured according to ASTM D2414-93.

[0106] The carbon black is not particularly limited, and examples thereof include furnace blacks (furnace carbon black) such as SAF, ISAF, HAF, MAF, FEF, SRF, GPF, APF, FF, CF, SCF, and ECF; acetylene black (acetylene carbon black); thermal blacks (thermal carbon black) such as FT and MT; and channel blacks (channel carbon black) such as EPC, MPC, and CC, and examples of 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] In addition to mineral oil, the raw material for carbon black may be biomass materials such as lignin and vegetable oil, or it may be pyrolysis oil obtained by pyrolyzing rubber products containing carbon black, such as waste tires (recycled carbon black).

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

[0109] Commercially available products include those from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Nippon Steel Carbon Co., Ltd., Columbia Carbon Co., Ltd., etc. These may be used alone or in combination of two or more.

[0110] The amount of carbon black per 100 parts by mass of the rubber component 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. 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) Silica In the present invention, the rubber composition preferably contains silica as needed. From the viewpoint of obtaining good durability, the BET specific surface area of ​​the silica is 100 m 2 / g, and preferably greater than 130m 2 / g. On the other hand, it is more preferable that the 2 / g, and preferably less than 200m 2 / g or less. The BET specific surface area is the N2SA value measured by the BET method in accordance with ASTM D3037-93.

[0112] The silica is not particularly limited, and can be, for example, silica prepared by a dry method (anhydrous silica) or silica prepared by a wet method (hydrated silica), which is commonly used in the tire industry. Commercially available products include those from Evonik Industries, Rhodia, Tosoh Silica Corporation, Solvay Japan, and Tokuyama Corporation.

[0113] The raw material for silica is not particularly limited, and may be, for example, a mineral-derived raw material such as quartz, a biological raw material such as rice husk (for example, silica made from a biomass material such as rice husk), or silica recycled from a product containing silica. Among these, hydrated silica prepared by a wet method is preferred because it contains a large number 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, and then reacting the silicate with sulfuric acid in the same manner as conventional wet-process silica to produce a silicon dioxide precipitate, which is then filtered, washed with water, dried, and pulverized.

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

[0116] When silica crystallizes, it becomes insoluble in water, and its component, silicic acid, cannot be utilized. By controlling the combustion temperature and duration, it is possible to suppress the crystallization of silica in rice husk ash (see, for example, JP 2009-2594 A and Akita Prefectural University Web Journal B / 2019, vol. 6, pp. 216-222).

[0117] Amorphous silica extracted from rice husks may be commercially available from Wilmar Co., Ltd., for example.

[0118] These silicas may be used alone or in combination of two or more. The use of biomass silica or recycled silica is preferable from the viewpoint of environmental protection (sustainability).

[0119] The amount of silica 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 preferable to use a silane coupling agent in combination. 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,N-dimethylthiocathanide, Examples of such compounds include sulfide-based compounds such as rubamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, and Momentive's NXT and NXT-Z; vinyl-based compounds such as vinyltriethoxysilane and vinyltrimethoxysilane; amino-based compounds such as 3-aminopropyltriethoxysilane and 3-aminopropyltrimethoxysilane; glycidoxy-based compounds such as γ-glycidoxypropyltriethoxysilane and γ-glycidoxypropyltrimethoxysilane; nitro-based compounds such as 3-nitropropyltrimethoxysilane and 3-nitropropyltriethoxysilane; and chloro-based compounds such as 3-chloropropyltrimethoxysilane and 3-chloropropyltriethoxysilane. These compounds may be used alone or in combination of two or more.

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

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

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

[0124] (c) Softener ingredients In consideration of proper dispersion of powder materials during kneading, it is preferable to use a softener component in the rubber composition as needed. Note that the term "softener / plasticizer component" as used herein refers to a material that imparts plasticity to the rubber component, and is a concept that 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-based plasticizers. These softeners may be derived from mineral resources such as petroleum and natural gas, biomass-derived, or naphtha recycled from rubber or non-rubber products. Low-molecular-weight hydrocarbon components obtained by pyrolysis and extraction of used tires or products containing various components may also be used as softeners. Among these, biomass-derived and recycled softeners are preferred as sustainable softeners.

[0126] These softeners may be used alone or in combination of two or more. The content of the plasticizer component per 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. The lower limit is, for example, 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. The content of the plasticizer component also includes the amount of oil contained in the rubber (oil-extended rubber) etc.

[0127] (i) Oil Examples of oils include mineral oil, vegetable oil, animal oil, etc. From the viewpoint of life cycle assessment, waste oils used in rubber mixers or engines, or refined waste cooking oils used in restaurants 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 oils 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] Additionally, to address environmental concerns, oils with low polycyclic aromatic compound (PCA) content can be used, such as MES, TDAE, and heavy naphthenic oils.

[0131] Examples of commercially available mineral oils include paraffinic, aromatic, and naphthenic oils, and usable products include those from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., ENEOS Corporation, Oriso Co., Ltd., H&R Corporation, Toyokuni Oil Mills Co., Ltd., Showa Shell Sekiyu K.K., and Fuji Kosan Co., Ltd. These may be used alone or in combination of two or more.

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

[0133] Further examples of vegetable oils include refined oils (such as salad oils) obtained by refining the above oils, interesterified oils, hydrogenated hardened oils, thermally polymerized oils, oxidatively polymerized oils, and waste edible oils recovered from edible oils. Vegetable oils may be liquid or solid at room temperature (25°C). These may be used alone or in combination of two or more.

[0134] The vegetable oil preferably contains acylglycerol, and more preferably triacylglycerol. Acylglycerol refers to a compound in which a hydroxyl group of glycerin is ester-bonded to a fatty acid. The acylglycerol is not particularly limited, and may be 1-monoacylglycerol, 2-monoacylglycerol, 1,2-diacylglycerol, 1,3-diacylglycerol, or triacylglycerol. Furthermore, acylglycerol may be a monomer, a dimer, or a polymer (trimer or higher). Dimer or higher acylglycerols can be obtained by thermal polymerization, oxidative polymerization, or the like. Acylglycerol may be liquid or solid at room temperature (25°C).

[0135] The method for confirming whether or not acylglycerol is contained in the rubber composition is not particularly limited, but may be 1 For example, a rubber composition containing triacylglycerol is immersed in deuterated chloroform at room temperature (25°C) for 24 hours, and after removing the rubber composition, the rubber composition is immersed in deuterated chloroform at room temperature. 1 When H-NMR was measured, signals were observed around 5.26 ppm, 4.28 ppm, and 4.15 ppm when the signal of tetramethylsilane (TMS) was set at 0.00 ppm. These signals are presumed to be signals derived from hydrogen atoms bonded to the carbon atoms adjacent to the oxygen atoms of the ester groups, and therefore the presence of acylglycerol can be confirmed. Here, "around" refers to a range of ±0.10 ppm.

[0136] The fatty acid is not particularly limited and may be either an unsaturated fatty acid or a saturated fatty acid. Examples of unsaturated fatty acids include monounsaturated fatty acids such as oleic acid and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Examples of saturated fatty acids include butyric acid and lauric acid.

[0137] Among these, it is desirable that the fatty acid contains a fatty acid with few double bonds, i.e., saturated fatty acid or monounsaturated fatty acid, and oleic acid is preferred. As a vegetable oil containing such a fatty acid, for example, vegetable oil containing saturated fatty acid or monounsaturated fatty acid may be used, or vegetable oil modified by ester exchange or the like may be used. Furthermore, in order to produce vegetable oil containing such a fatty acid, plants may be improved by breeding, genetic modification, genome editing, or the like.

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

[0139] (ii) Liquid rubber Liquid rubber is a polymer that is in a liquid state at room temperature (25°C) and is a rubber component that can be extracted from vulcanized tires by acetone extraction. Examples of liquid rubber include farnesene polymers, liquid diene polymers, and hydrogenated versions of these polymers.

[0140] Farnesene polymers are polymers obtained by polymerizing farnesene, which has structural units based on farnesene. Farnesene has 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-based 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 liquid diene polymers 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 liquid diene polymer has a weight average molecular weight (Mw) of, for example, 1.0 × 10 in terms of polystyrene measured by gel permeation chromatography (GPC). 3 Super, 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 Co., Ltd., etc. can be used.

[0145] (iii) Resin component The resin component also functions as a tackifier and may be solid or liquid at room temperature. Specific examples of the resin component include rosin resins, styrene resins, coumarone resins, terpene resins, C5 resins, C9 resins, C5C9 resins, and acrylic resins, and two or more of these may be used in combination. These resin components may be provided with a modifying group capable of reacting with silica, etc., as needed.

[0146] Rosin-based resins are resins whose main component is rosin acid, which is obtained by processing pine resin. These rosin-based resins (rosins) can be classified based on whether they are modified or not, and can be divided into unmodified rosin (unmodified rosin) and modified rosin (rosin derivatives). Examples of unmodified rosins include tall rosin (also known as tall oil rosin), gum rosin, wood rosin, disproportionated rosin, polymerized rosin, hydrogenated rosin, and other chemically modified rosins. Modified rosin is a modification of unmodified rosin, and examples include rosin esters, unsaturated carboxylic acid-modified rosin esters, unsaturated carboxylic acid-modified rosin esters, rosin amide compounds, and rosin amine salts.

[0147] Styrenic resins are polymers that use styrene monomers as constituent monomers, and examples thereof include polymers polymerized with styrene monomers as the most abundant constituent monomer. Specific examples include homopolymers obtained by polymerizing each styrene monomer (styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, etc.) alone, copolymers obtained by copolymerizing two or more styrene monomers, and copolymers of a styrene monomer and another monomer that can be copolymerized with it.

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

[0149] Among the coumarone resins, coumarone-indene resins are preferred. Coumarone-indene resins are resins containing coumarone and indene as monomer components that constitute the resin skeleton (main chain). Monomer components contained in the skeleton other than coumarone and indene include styrene, α-methylstyrene, methylindene, vinyltoluene, etc.

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

[0151] The softening point of the coumarone-indene resin is, for example, more than 30° C. and less than 160° C. The softening point is the temperature at which the ball drops when the softening point specified in JIS K 6220-1:2001 is measured using a ring and ball softening point tester.

[0152] Terpene resins include polyterpenes, terpene phenols, and aromatic modified terpene resins. Polyterpenes are resins obtained by polymerizing terpene compounds and their hydrogenated products. Terpene compounds are (C5H8) n The hydrocarbons and their oxygen-containing derivatives are represented by the following composition: monoterpenes (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpenes (C 20 H32 ), and examples thereof include 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, and γ-terpineol.

[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 made from the above-mentioned terpene compounds, as well as 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. Specific examples include resins obtained by condensing the above-mentioned terpene compounds, phenolic compounds, and formalin. 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. The aromatic compound is not particularly limited as long as it is a compound having an aromatic ring, and examples thereof include phenolic compounds such as phenol, alkylphenol, alkoxyphenol, and unsaturated hydrocarbon group-containing phenol; naphthol compounds such as naphthol, alkylnaphthol, alkoxynaphthol, and unsaturated hydrocarbon group-containing naphthol; styrene derivatives such as styrene, alkylstyrene, alkoxystyrene, and unsaturated hydrocarbon group-containing styrene; coumarone, indene, and the like.

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

[0155] "C9 resin" refers to a resin obtained by polymerizing a C9 fraction, and may be a hydrogenated or modified version. Examples of C9 fractions include petroleum fractions having 8 to 10 carbon atoms, such as vinyltoluene, alkylstyrene, indene, and methylindene. Specific examples of suitable aromatic vinyl resins include coumarone-indene resins, coumarone resins, indene resins, and aromatic vinyl resins. Preferred aromatic vinyl resins are α-methylstyrene (AMS resin), styrene homopolymers, and copolymers of α-methylstyrene and styrene, with copolymers of α-methylstyrene and styrene being more preferred, due to their economical efficiency, ease of processing, and excellent heat generation. Examples of aromatic vinyl resins that can be used include those commercially available from Kraton, Eastman Chemical, and the like.

[0156] "C5C9 resin" refers to a resin obtained by copolymerizing the C5 fraction and the C9 fraction, and may be a hydrogenated or modified resin. Examples of C5 fractions and C9 fractions include the petroleum fractions mentioned above. As the C5C9 resin, for example, commercially available products from Tosoh Corporation, LUHUA, etc. can be used.

[0157] The acrylic resin is not particularly limited, but for example, a solventless acrylic resin can be used.

[0158] Examples of solvent-free acrylic resins include (meth)acrylic resins (polymers) synthesized by high-temperature continuous polymerization (high-temperature continuous bulk polymerization) (methods described in U.S. Pat. No. 4,414,370, JP-A Nos. 59-6207, JP-B Nos. 5-58005, 1-313522, U.S. Pat. No. 5,010,166, and Toa Gosei Kenkyusho Annual Report TREND 2000, Vol. 3, pp. 42-45, etc.), with minimal use of secondary raw materials such as polymerization initiators, chain transfer agents, and organic solvents. In the present invention, (meth)acrylic refers to both methacrylic and acrylic.

[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] Furthermore, aromatic vinyls 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 as a monomer component constituting the acrylic resin.

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

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

[0163] (D) Wax The rubber composition may contain wax. The content of the wax 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, per 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 suitably used. Examples include mineral waxes and plant-derived waxes. Mineral waxes refer to waxes derived from mineral resources such as oil and natural gas. Plant-derived waxes refer to 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. In the present invention, the wax does not contain stearic acid.

[0166] The wax that can be used may be commercially available waxes from, for example, 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] (e) Antiaging agents The rubber composition may contain an antioxidant. The content of the antioxidant is, for example, more than 1 part by mass and less than 10 parts by mass per 100 parts by mass of the rubber component.

[0168] The antioxidant is not particularly limited, but examples thereof include naphthylamine-based antioxidants such as phenyl-α-naphthylamine; diphenylamine-based 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), and N,N'-ditolyl-p-phenylenediamine. p-phenylenediamine antioxidants such as diphenyl ether (DTPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), and N,N'-di-2-naphthyl-p-phenylenediamine (DNPD); quinoline antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers; monophenol antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol antioxidants such as tetrakis-[methylene-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane. Among these, p-phenylenediamine-based antioxidants and quinoline-based antioxidants are preferred, and polymers of N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine and 2,2,4-trimethyl-1,2-dihydroquinoline are more preferred. These may be used alone or in combination of two or more.

[0169] As commercially available products, for example, products from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., Flexis, etc. can be used.

[0170] (f) Lubricant (stearic acid) The rubber composition may contain a lubricant. Fatty acid derivative-based lubricants such as stearic acid are preferably used as the lubricant. Conventionally known stearic acids can be used, specifically, products from NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries, Ltd., Chiba Fatty Acid Co., Ltd., etc. Alternatively, Struktol WB16 manufactured by Struktol Co., Ltd. can also be used.

[0171] The amount of stearic acid per 100 parts by mass of the rubber component is, for example, preferably more than 0.5 parts by mass and less than 10.0 parts by mass.

[0172] (g) Zinc oxide The rubber composition may contain zinc oxide. The content of zinc oxide is, for example, more than 0.5 parts by mass and less than 10 parts by mass per 100 parts by mass of the rubber component. As the zinc oxide, a conventionally known product can be used, such as products from Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., Sakai Chemical Industry Co., Ltd., etc.

[0173] (H) Crosslinking agents and vulcanization accelerators The rubber composition preferably contains a crosslinking agent such as sulfur. The content of the crosslinking agent is, for example, more 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 the pure sulfur content, and when insoluble sulfur is used, it is the content excluding oil content.

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

[0175] As sulfur, for example, products from Tsurumi Chemical Industry Co., Ltd., Karuizawa Iso Co., Ltd., Shikoku Chemical Industry Co., Ltd., Flexis Corporation, Nippon Kanzuri Kogyo Co., Ltd., Hosoi Chemical Industry Co., Ltd., etc. can be used.

[0176] Crosslinking agents other than sulfur may also be used. Specific examples include vulcanizing agents containing sulfur atoms, such as Tackirol V200 manufactured by Taoka Chemical Co., Ltd., DURALINK HTS (sodium 1,6-hexamethylenedithiosulfate dihydrate) manufactured by Flexis, and KA9188 (1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane: hybrid crosslinking agent) manufactured by Lanxess, as well as organic peroxides such as dicumyl peroxide.

[0177] The rubber composition preferably contains a vulcanization accelerator in an amount of, for example, more 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-benzothiazyl sulfenamide; 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-benzothiazole sulfenamide, Nt-butyl-2-benzothiazolyl sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, N-oxyethylene-2-benzothiazole sulfenamide, and N,N'-diisopropyl-2-benzothiazole sulfenamide; and guanidine-based vulcanization accelerators such as diphenyl guanidine, di-orthotolyl guanidine, and orthotolyl biguanidine. These may be used alone or in combination of two or more.

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

[0180] In the present invention, among the above-mentioned materials, various materials containing carbon atoms (for example, rubber, oil, resin, vulcanization accelerator, antioxidant, surfactant, etc.) may be derived from carbon dioxide in the atmosphere. As a method for obtaining the compound of the present invention from carbon dioxide, carbon dioxide may be directly converted, or methane obtained through a methanation process in which methane is synthesized from carbon dioxide may be converted.

[0181] (2) Preparation of rubber composition The rubber composition for the cap tread and the rubber composition for the base tread can be produced by a general method, for example, a manufacturing method including a base kneading step in which a rubber component and a filler (filling agent) such as carbon black are kneaded together, and a finish kneading step in which the kneaded product obtained in the base kneading step is kneaded together with a crosslinking agent.

[0182] The kneading can be carried out using a known (internal) kneading machine such as a Banbury mixer, a kneader, or an open roll.

[0183] The kneading temperature in the base kneading step is, for example, higher than 50° C. and lower than 200° C., and the kneading time is, for example, higher than 30 seconds and lower than 30 minutes. In the base kneading step, in addition to the above components, compounding agents conventionally used in the rubber industry, for example, softeners such as oil, stearic acid, zinc oxide, antioxidants, waxes, vulcanization accelerators, etc., may be appropriately added and kneaded as needed.

[0184] In the final kneading step, the kneaded product obtained in the base kneading step is kneaded with a crosslinking agent. The kneading temperature in the final kneading step is, for example, higher than room temperature and lower than 80°C, and the kneading time is, for example, longer than 1 minute and shorter than 15 minutes. In the final kneading step, in addition to the above components, a vulcanization accelerator, zinc oxide, etc. may be appropriately added and kneaded as necessary.

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

[0186] 3. Tire manufacturing The tire according to the present embodiment can be manufactured by a conventional method. First, the rubber composition for a cap tread and the rubber composition for a base tread obtained as described above are molded into a predetermined shape to manufacture a tread. Next, the resulting tread is combined with other rubber components on a tire building machine to manufacture an unvulcanized tire.

[0187] Specifically, an inner liner as a component for ensuring the airtightness of the tire, a carcass as a component for withstanding the load, impact, and inflation pressure to which the tire is subjected, and a belt component, band, etc. as a component for tightly fastening the carcass and increasing the rigidity of the tread are wound around a forming drum, and both ends of the carcass are fixed to both side edges, and bead portions as components for fixing the tire to the rim are arranged. After forming into a toroidal shape, a tread is attached to the center of the outer periphery and sidewalls are attached to the radially outer side to form the side portions, thereby producing an unvulcanized tire.

[0188] The unvulcanized tire thus prepared is then heated and pressurized in a vulcanizer to obtain a tire. The vulcanization process can be carried out by using a known vulcanization method. 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 as described above can be a tire that uses sustainable materials and yet has sufficiently improved wet grip performance during high-speed cornering. The tire according to the present invention is particularly preferably a tire for light trucks. [Example]

[0190] Examples (embodiments) that are considered preferable for carrying out the present invention will be shown below, but the scope of the present invention is not limited to these examples.

[0191] We evaluated the wet grip performance during high-speed cornering using a test tire (tire size: 205 / 80R17.5 120 / 118L) manufactured with the configuration shown in Figure 1. The evaluation results are shown in Tables 1 and 2. In the test tire, the land ratio in the shoulder region of the tread was 2%.

[0192] [1] Preparation of test tires 1. Tread manufacturing (1) Manufacturing of rubber composition for tread First, a rubber composition for a cap tread and a rubber composition for a base tread are produced using the various compounding materials shown below.

[0193] (a) Compound materials (a-1) Rubber component (a) NR:TSR20 (b) SBR: SBR1502 manufactured by ENEOS Materials Co., Ltd. (c) BR: BR730 manufactured by ENEOS Materials Co., Ltd.

[0194] (a-2) Compounding materials other than rubber components (a) Vulcanized rubber powder: TyreXol TW50 manufactured by Tyre Recycling Solutions (hydraulic crushed rubber powder, particle size: 50 mesh pass, average particle size: 192 μm) (b) Carbon black-1: Show Black N220 manufactured by Cabot Japan Co., Ltd. (CTAB specific surface area: 111m 2 / g) (c) Carbon black-2: Show Black N351H manufactured by Cabot Japan Co., Ltd. (N2SA:69m 2 / g) (d) Oil: Idemitsu Kosan Diana Process Oil NH-70S (Aromatic processed oil) (E) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. (f) Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. (g) Stearic acid: NOF Corporation's "Tsubaki" stearic acid (H) Anti-aging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine) (i) Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. (J) Vulcanization accelerator: Noccela CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazolylsulfenamide)

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

[0196] Next, zinc oxide, sulfur, and a vulcanization accelerator are added to each of the obtained kneaded products, and the mixture is kneaded for 5 minutes at 80°C using an open roll to obtain a rubber composition for a cap tread (cap) and a rubber composition for a base tread (base).

[0197] (2) Tread molding Each of the rubber compositions obtained above is laminated into a predetermined shape and extruded to obtain a tread.

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

[0199] 3. Calculation of parameters Next, the following parameters are determined for each test tire.

[0200] (1) Negative rate (Nr) The negative rate Nr (%) is calculated based on the above-mentioned method for calculating the negative rate.

[0201] (2) Area ratio of vulcanized rubber powder (Sr out and Sr in ) First, a sample for observation is cut out from the cap tread and base tread of each test tire so that a plane parallel to the tread surface becomes the cross section for observation.

[0202] Next, the cross section for observation of each sample is photographed using a scanning electron microscope (Teneo manufactured by ThermoFisher) at an acceleration voltage of 15 kV to obtain an electron microscope image at a magnification of 50 times.

[0203] Next, within the 2.54mm x 1.69mm range of the obtained electron microscope image, the area of ​​the region corresponding to the vulcanized rubber powder is calculated, and the ratio of this area to the area of ​​the entire cross section is calculated. This is done for three fields of view per sample, and the average value is taken as the area ratio occupied by the vulcanized rubber powder.

[0204] (3)(Sr out +Sr in ) / Nr Nr and Sr obtained above out , Sr in Based on (Sr out +Sr in ) / Nr is calculated. The results are shown in Tables 1 and 2.

[0205] (4) Loss tangent (30℃tanδ) Rubber test specimens for measurement were prepared by cutting out 20 mm long x 4 mm wide x 1 mm thick pieces from each of the cap tread and base tread of each test tire, with the long sides aligned in the tire circumferential direction. The loss tangent (30°C tanδ) of each rubber test specimen was measured using a GABO Iplexer series under the conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1%, in a deformation mode of tension.

[0206] (5) Measurement of elongation at break (EB) The elongation at break (EB) of each of the cap tread and base tread of each test tire is measured using a test method (No. 3 dumbbell test piece) in accordance with JIS K6251;2017.

[0207] 4. Performance evaluation (evaluation of wet grip performance during high-speed cornering) Each test tire was fitted to all wheels of a vehicle (a domestic light truck) and inflated to the correct internal pressure. The vehicle was then driven at 100km / h on a wet test course, and the drivers were given a sensory evaluation of the cornering performance when entering a corner on a 5-point scale (the higher the number, the better). The total score of the sensory evaluations by the 20 drivers was then calculated.

[0208] Next, the result of Comparative Example 2 was set to 100 and indexed according to the following formula to evaluate wet grip performance during high-speed cornering. A larger value indicates better wet grip performance during high-speed cornering. Wet grip performance during high-speed cornering = [(Test tire results) / (Comparative example 2 results)] × 100

[0209] [Table 1]

[0210] [Table 2]

[0211] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments. Various modifications can be made to the above-described embodiments within the scope of the same or equivalent to the present invention.

[0212] The present invention (1) is A tire having a plurality of land portions and groove portions on the surface of a tread portion, The tread portion is formed by laminating a cap tread and a base tread from the ground contact side, and has a negative ratio Nr (%) within the ground contact width of less than 20%, The cap tread and the base tread are both made of a rubber composition containing vulcanized rubber powder, The area ratio of the vulcanized rubber powder in the cap tread is Sr out (%), and the area ratio of the vulcanized rubber powder in the base tread is Sr in (%), the above Nr and Sr out , and Sr in The tire is characterized by satisfying the following formula (1): 3≧(Sr out +Sr in ) / Nr (1 set)

[0213] The present invention (2) is The aforementioned [(Sr out +Sr in ) / Nr] is 1.5 or less, and is a tire according to the present invention (1).

[0214] The present invention (3) is The aforementioned [(Sr out +Sr in ) / Nr] is 1.0 or less, and is a tire according to the present invention (2).

[0215] The present invention (4) is The tire is characterized in that the negative rate is 15% or less, and is an optional combination with any of the present inventions (1) to (3).

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

[0217] The present invention (6) is The tire is characterized in that the average particle size of the vulcanized rubber powder is 350 μm or less, and is an optional combination with any of the present inventions (1) to (5).

[0218] The present invention (7) is The loss tangent (30°C tanδ) 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 rate of 1% is 0.20 or less, and the tire is an optional combination with any of the present inventions (1) to (6).

[0219] The present invention (8) is The tire according to 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 The tire is characterized in that the loss tangent (30°C tanδ) 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 rate of 1% is 0.08 or less, and is an optional combination with any of present inventions (1) to (8).

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

[0222] The present invention (11) is The ratio of the loss tangent (30°C tanδ) 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 rate of 1% to the loss tangent (30°C tanδ) 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 rate of 1%, is 2.75 or more, and the tire is any combination with any of the present inventions (1) to (10).

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

[0224] The present invention (13) is The tire is characterized in that the elongation at break of the cap tread measured in accordance with JIS K6251;2017 is 550% or more, and is an optional combination with any of the present inventions (1) to (12).

[0225] The present invention (14) is The tire is characterized in that the base tread has an elongation at break of 420% or more as measured in accordance with JIS K6251;2017, and is an optional combination with any of the present inventions (1) to (13).

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

[0227] The present invention (16) is The tire is characterized in that the 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, and is an optional combination with any of the present inventions (1) to (15).

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

[0229] The present invention (18) is The tire is characterized in that the land ratio in the shoulder region of the tread portion is less than 3%, and is an optional combination with any of the present inventions (1) to (17).

[0230] The present invention (19) is The tire is characterized in that the vulcanized rubber powder is vulcanized rubber powder produced by hydraulic crushing, and is an optional combination with any of the present inventions (1) to (18).

[0231] The present invention (20) is The tire is characterized by being a tire for a light truck, and is a tire in any combination with any of the present inventions (1) to (19). [Explanation of symbols]

[0232] 1 tire 2. Contact area 3 Shoulder area 4 Tread section 6 Sidewall 8 Clinch 10 beads 12 Carcass 14 Belt 16 bands 18 Inner liner 20 Chafer 22 Groove 23 Land 24 base tread 26 Cap Tread 30 bead core 32 Bead Apex 50 inner layer 52 Outer layer

Claims

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

2. The [(Sr ｏｕｔ + Sr ｉｎ 2. The tire according to claim 1, wherein the ratio of [Nr / Nr] to [Nr] is 1.5 or less.

3. The [(Sr ｏｕｔ + Sr ｉｎ 3. The tire according to claim 2, wherein the ratio of [Nr / Nr] to [Nr / Nr] is 1.0 or less.

4. 4. The tire according to claim 1, wherein the negative rate is 15% or less.

5. 5. The tire according to claim 4, wherein the negative rate is 10% or less.

6. 4. The tire according to claim 1, wherein the vulcanized rubber powder has an average particle size of 350 μm or less.

7. 4. The tire according to claim 1, wherein the loss tangent (30°C tanδ) of the cap tread measured in a tensile deformation mode under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 0.20 or less.

8. 8. The tire according to claim 7, wherein the loss tangent (30° C. tan δ) of the cap tread is 0.18 or less.

9. 4. The tire according to claim 1, wherein the loss tangent (30°C tanδ) measured in a tensile deformation mode under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% for the base tread is 0.08 or less.

10. The tire according to claim 9, wherein the loss tangent (30° C. tan δ) of the base tread is 0.07 or less.

11. 4. The tire according to claim 1, wherein the ratio of the loss tangent (30°C tan δ) of the cap tread measured in a tensile deformation mode under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% to the loss tangent (30°C tan δ) of the base tread measured in a tensile deformation mode under conditions of a temperature of 30°C, a frequency of 10 Hz, an initial strain of 5%, and a dynamic strain rate of 1% is 2.75 or more.

12. 12. The tire of claim 11, wherein the ratio of 30° C. tan δ of the cap tread to 30° C. tan δ of the base tread is 2.80 or greater.

13. The tire according to any one of claims 1 to 3, wherein the cap tread has an elongation at break measured in accordance with JIS K6251;2017 of 550% or more.

14. The tire according to any one of claims 1 to 3, wherein the base tread has an elongation at break measured in accordance with JIS K6251;2017 of 420% or more.

15. 15. The tire of claim 14, wherein the base tread has an elongation at break of 440% or greater.

16. 4. The tire according to claim 1, wherein a ratio of an elongation at break of the cap tread measured in accordance with JIS K6251;2017 to an elongation at break of the base tread measured in accordance with JIS K6251;2017 is 1.20 or more.

17. 17. The tire of claim 16, wherein the 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. 4. The tire according to claim 1, wherein a land ratio in a shoulder region of the tread portion is less than 3%.

19. 4. The tire according to claim 1, wherein the vulcanized rubber powder is produced by hydraulic crushing.

20. 4. The tire according to claim 1, which is a tire for a light truck.

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