Rubber composition for tires and tires

Abstract

To provide a rubber composition for tires and a tire which are capable of improving overall performance of fuel economy and wet grip performance.SOLUTION: The present invention relates to the rubber composition for tires which contains a rubber component containing a styrene-butadiene rubber and an isoprene rubber, silica, a resin component, and a calcium compound. The following relations are satisfied: (the amount of acetone extraction)>(the content of the isoprene rubber); (the content of the isoprene rubber)>(the content of the resin component); and (the content of the resin component)>(the content of the calcium compound in terms of calcium element).SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for tires and a tire.

Background Art

[0002] Conventionally, various methods for improving low fuel consumption and grip performance have been studied (see, for example, Patent Documents 1 and 2). However, in recent years, further improvement of these performances has been demanded.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] An object of the present invention is to provide a rubber composition for tires and a tire that solve the above problems and can improve the overall performance of low fuel consumption and wet grip performance.

Means for Solving the Problems

[0005] The present invention relates to a rubber composition for tires containing a rubber component including styrene-butadiene rubber and isoprene rubber, silica, a resin component, and a calcium compound, wherein the acetone extraction amount > the content of the isoprene rubber, the content of the isoprene rubber > the content of the resin component, and the content of the resin component > the calcium element equivalent content of the calcium compound.

[0006] It is preferable that the calcium compound is a fatty acid salt.

[0007] It is preferable that the average particle diameter of the silica is 18 nm or less.

[0008] The rubber composition preferably contains a mercapto-based silane coupling agent.

[0009] In 100% by mass of the rubber component, the content of the isoprene-based rubber is preferably 20 to 50% by mass.

[0010] In 100% by mass of the acetone extract, the content of the resin component is preferably 50% by mass or more.

[0011] The resin component preferably contains a terpene resin.

[0012] The rubber composition preferably contains a dibenzylamine compound.

[0013] The present invention also relates to a tire using the rubber composition.

Advantages of the Invention

[0014] The present invention provides a rubber composition for a tire, which contains a rubber component including styrene-butadiene rubber and isoprene-based rubber, silica, a resin component, and a calcium compound, and in which the acetone extract amount > the content of the isoprene-based rubber, the content of the isoprene-based rubber > the content of the resin component, and the content of the resin component > the calcium element conversion content of the calcium compound. Therefore, the overall performance of low fuel consumption and wet grip performance is good.

Modes for Carrying Out the Invention

[0015] [[ID=三十八]]The rubber composition for a tire of the present invention contains a rubber component including styrene-butadiene rubber and isoprene-based rubber, silica, a resin component, and a calcium compound, and in which the acetone extract amount > the content of the isoprene-based rubber, the content of the isoprene-based rubber > the content of the resin component, and the content of the resin component > the calcium element conversion content of the calcium compound.

[0016] The reason why the above rubber composition produces the aforementioned effects is presumed to be as follows. In the above rubber composition, by setting the amount of acetone extracted > isoprene rubber content > resin component content, the high molecular weight isoprene rubber is sufficiently plasticized, and the resin component is more easily incorporated into the isoprene rubber phase, which is thought to increase tackiness and improve wet grip performance. Furthermore, in the above rubber composition, by satisfying the relationship that the content of the resin component is greater than the calcium element content of the calcium compound, it is possible to suppress the resin component from adhering to the rolls, etc., during kneading, thereby providing sufficient mechanical shear to the kneaded material. These effects promote uniform mixing of the polymer (rubber component) phase and dispersion of silica and resin within the polymer phase, resulting in improved silica-polymer interaction and tackiness. As a result, overall performance in fuel efficiency and wet grip is expected to be significantly improved.

[0017] The above rubber composition contains rubber components. Here, the rubber component is a component that contributes to crosslinking, and generally has a weight-average molecular weight (Mw) of 10,000 or more.

[0018] The weight-average molecular weight of the rubber component is preferably 50,000 or more, more preferably 150,000 or more, even more preferably 200,000 or more, and also preferably 2,000,000 or less, more preferably 1,500,000 or less, and even more preferably 1,000,000 or less. Within this range, a better effect tends to be obtained.

[0019] In this specification, the weight-average molecular weight (Mw) can be determined by converting the measured values ​​obtained by gel permeation chromatography (GPC) (GPC-8000 series manufactured by Tosoh Corporation, detector: differential refractometer, column: TSKGEL SUPERMULTIPORE HZ-M manufactured by Tosoh Corporation) to standard polystyrene equivalents.

[0020] From the viewpoint of overall performance such as fuel efficiency and wet grip performance, it is preferable that in the above rubber composition, the total amount of styrene in the rubber component is less than the total amount of vinyl in the rubber component.

[0021] The ratio of the total vinyl content in the rubber component to the total styrene content in the rubber component is preferably 1.5 or more, more preferably 2.0 or more, even more preferably 2.4 or more, and also preferably 4.5 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. Within this range, a better effect tends to be obtained.

[0022] The total styrene content in the rubber component is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 12% by mass or more, and also preferably 35% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. Within the above range, a better effect tends to be obtained.

[0023] Here, the total amount of styrene in the rubber component is the total amount of styrene contained in the entire rubber component (unit: mass%), and can be calculated using the formula Σ(content of each rubber component × amount of styrene in each rubber component / 100). For example, if 85 mass% of SBR with a styrene content of 40 mass% is out of 100 mass% of the rubber component, 5 mass% of SBR with a styrene content of 25 mass% is out of 5 mass%, and 10 mass% of BR with a styrene content of 0 mass%, then the total amount of styrene in the rubber component is 35.25 mass% (= 85 × 40 / 100 + 5 × 25 / 100 + 10 × 0 / 100).

[0024] The total vinyl content in the rubber component is preferably 15% by mass or more, more preferably 25% by mass or more, even more preferably 30% by mass or more, and also preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 35% by mass or less. Within the above range, a better effect tends to be obtained.

[0025] Here, the total amount of vinyl in the rubber component is the total amount of vinyl contained in the entire rubber component (unit: mass%), and can be calculated using the formula Σ(content of each rubber component × amount of vinyl in each rubber component / 100). For example, if 85 mass% of 100 mass% of rubber component is SBR with a vinyl content of 30 mass%, 5 mass% is SBR with a vinyl content of 20 mass%, and 10 mass% is BR with a vinyl content of 10 mass%, then the total amount of vinyl in the rubber component is 27.5 mass% (= 85 × 30 / 100 + 5 × 20 / 100 + 10 × 10 / 100).

[0026] The amounts of styrene and vinyl in each rubber component can be measured by nuclear magnetic resonance (NMR) spectroscopy. Furthermore, while the total amount of styrene and vinyl in the rubber component is calculated in accordance with the above-described formula in the examples of this specification, it may also be analyzed from the tire using, for example, a pyrolysis gas chromatograph-mass spectrometer (Py-GC / MS).

[0027] The above rubber composition contains styrene-butadiene rubber (SBR) as a rubber component. SBR is not particularly limited; for example, emulsion polymerized styrene-butadiene rubber (E-SBR) and solution polymerized styrene-butadiene rubber (S-SBR) can be used. Commercially available products include those from Sumitomo Chemical Co., Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation.

[0028] The styrene content of SBR is preferably 10% by mass or more, more preferably 15% by mass or more, even more preferably 20% by mass or more, and also preferably 45% by mass or less, more preferably 35% by mass or less, and even more preferably 30% by mass or less. Within the above range, a better effect tends to be obtained.

[0029] The vinyl content of SBR is preferably 35% by mass or more, more preferably 45% by mass or more, even more preferably 55% by mass or more, and also preferably 75% by mass or less, more preferably 70% by mass or less, and even more preferably 65% ​​by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0030] The styrene and vinyl content of SBRs mentioned above refer to the styrene and vinyl content of a single type of SBR if that type is used, and to the average styrene and vinyl content if there are multiple types of SBRs. The average styrene content of SBR can be calculated using the formula {Σ(content of each SBR × styrene content of each SBR)} / total content of all SBR. For example, if 85% of the rubber component is SBR with a styrene content of 40% by mass and 5% is SBR with a styrene content of 25% by mass, the average styrene content of the SBR is 39.2% by mass (=(85 × 40 + 5 × 25) / (85 + 5)). Similarly, the average vinyl content of SBR can be calculated as {Σ(content of each SBR × vinyl content of each SBR)} / total content of all SBR. For example, if 85% of the rubber component is SBR with a vinyl content of 30% by mass and 5% is SBR with a vinyl content of 20% by mass, the average vinyl content of the SBR is 29.4% by mass (=(85 × 30 + 5 × 20) / (85 + 5)).

[0031] The SBR content in 100% by mass of the rubber component is preferably 30% by mass or more, more preferably 40% by mass or more, even more preferably 50% by mass or more, and also preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0032] The above rubber composition contains isoprene-based rubber as a rubber component. Examples of isoprene-based rubbers include natural rubber (NR), isoprene rubber (IR), modified NR, modified NR, and modified IR. For NR, examples include SIR20, RSS#3, TSR20, etc., which are commonly used in the tire industry. For IR, there are no particular limitations; examples include IR2200, etc., which are commonly used in the tire industry. Examples of modified NR include deproteinized natural rubber (DPNR) and high-purity 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 individually or in combination of two or more. Among these, NR is preferred.

[0033] The isoprene-based rubber content in 100% by mass of the rubber component is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, and also preferably 60% by mass or less, more preferably 50% by mass or less, and even more preferably 45% by mass or less. Within the above range, a better effect tends to be obtained.

[0034] Other rubber components that can be used besides SBR and isoprene-based rubbers include diene-based rubbers such as butadiene rubber (BR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (IIR), and styrene-isoprene-butadiene copolymer rubber (SIBR). These may be used individually or in combination of two or more. Among these, BR is preferred.

[0035] The BR is not particularly limited, and high-cis-content BR, low-cis-content BR, BR containing syndiotactic polybutadiene crystals, etc., can be used. Commercial products include those from Ube Industries, Ltd., JSR Corporation, Asahi Kasei Corporation, and Nippon Zeon Corporation.

[0036] The cis content of BR is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and also preferably 99% by mass or less, more preferably 98% by mass or less, and even more preferably 97% by mass or less. When it is within the above range, the effect tends to be better obtained. The cis amount of BR can be measured by infrared absorption spectroscopy.

[0037] The cis amount of BR mentioned above refers to the cis amount of a single type of BR if there is only one type, and to the average cis amount if there are multiple types. The average cis content of BR can be calculated using the formula {Σ(content of each BR × cis content of each BR)} / total BR content. For example, if 20% of BR has a cis content of 90% and 10% has a cis content of 40% out of 100% of rubber components, the average cis content of BR is 73.3% (=(20 × 90 + 10 × 40) / (20 + 10)).

[0038] The BR content in 100% by mass of the rubber component is preferably 1% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, and also preferably 30% by mass or less, more preferably 20% by mass or less, and even more preferably 10% by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0039] The rubber component may have functional groups that interact with fillers such as silica introduced through modification. Examples of the above functional groups include amino groups, amide groups, silyl groups, alkoxysilyl groups, isocyanate groups, imino groups, imidazole groups, urea groups, ether groups, carbonyl groups, oxycarbonyl groups, mercapto groups, sulfide groups, disulfide groups, sulfonyl groups, sulfinyl groups, thiocarbonyl groups, ammonium groups, imide groups, hydrazo groups, azo groups, diazo groups, carboxyl groups, nitrile groups, pyridyl groups, alkoxy groups, hydroxyl groups, oxy groups, epoxy groups, and the like. These functional groups may have substituents. Among these, amino groups (preferably amino groups in which the hydrogen atoms of the amino group are substituted with C1-C6 alkyl groups), alkoxy groups (preferably alkoxy groups having C1-C6), and alkoxysilyl groups (preferably alkoxysilyl groups having C1-C6) are preferred.

[0040] Specific examples of compounds (modifiers) having the above-mentioned functional groups include 2-dimethylaminoethyltrimethoxysilane, 3-dimethylaminopropyltrimethoxysilane, 2-dimethylaminoethyltriethoxysilane, 3-dimethylaminopropyltriethoxysilane, 2-diethylaminoethyltrimethoxysilane, 3-diethylaminopropyltrimethoxysilane, 2-diethylaminoethyltriethoxysilane, and 3-diethylaminopropyltriethoxysilane.

[0041] The above rubber composition contains silica. Examples of silica include dry-process silica (anhydrous silicic acid) and wet-process silica (hydrated silicic acid), but wet-process silica is preferred because it contains a large number of silanol groups. Commercially available products include those from EVONIK, Tosoh Silica Co., Ltd., Solvay Japan Ltd., and Tokuyama Corporation. These may be used individually or in combination of two or more types.

[0042] The average particle size of silica is preferably 24 nm or less, more preferably 17 nm or less, even more preferably 15 nm or less, and also preferably 6 nm or more, more preferably 9 nm or more, and even more preferably 12 nm or more. Within this range, a better effect tends to be obtained.

[0043] In this specification, the method for measuring the average particle size of silica is transmission electron microscopy (TEM) observation. Specifically, silica particles are photographed with a transmission electron microscope, and if the particle shape is spherical, the diameter of the sphere is defined as the particle size; if it is needle-shaped or rod-shaped, the shorter axis is defined as the particle size; if it is irregularly shaped, the average particle size from the center is defined as the particle size; and the average value of the particle sizes of 100 fine particles is defined as the average particle size.

[0044] The silica content is preferably 50 parts by mass or more, more preferably 65 parts by mass or more, and even more preferably 75 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 120 parts by mass or less, more preferably 90 parts by mass or less, and even more preferably 80 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0045] The above rubber composition preferably contains a silane coupling agent. The silane coupling agent is not particularly limited and includes, for example, 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 Examples include sulfide-based compounds such as ropyl-N,N-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, and 3-triethoxysilylpropyl methacrylate monosulfide; mercapto-based compounds such as 3-mercaptopropyltrimethoxysilane and 2-mercaptoethyltriethoxysilane; 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. Commercially available products include those from companies such as Degussa, Momentive, Shin-Etsu Silicone Co., Ltd., Tokyo Chemical Industry Co., Ltd., Azumax Co., Ltd., and Toray Dow Corning Co., Ltd. These can be used individually or in combination of two or more types. Mercapto-based products are particularly preferred.

[0046] In addition, as the mercapto-based silane coupling agent, in addition to the compound having a mercapto group, a compound having a structure in which the mercapto group is protected by a protecting group (for example, the compound represented by the following formula (S1)) can also be used.

[0047] Particularly preferred mercapto-based silane coupling agents include the silane coupling agent represented by the following formula (S1), and the silane coupling agent containing the bonding unit A represented by the following formula (I) and the bonding unit B represented by the following formula (II).

Chemical formula

Chemical formula

Chemical formula

[0048] In equation (S1), R 1005 , R 1006 , R 1007 and R 1008 Each of these is preferably independently selected from the group consisting of linear, cyclic, or branched alkyl groups, alkenyl groups, aryl groups, and aralkyl groups having 1 to 18 carbon atoms. 1002 If is a monovalent hydrocarbon group having 1 to 18 carbon atoms, it is preferably a group selected from the group consisting of linear, cyclic, or branched alkyl groups, alkenyl groups, aryl groups, and aralkyl groups. 1009 The alkylene group is preferably linear, cyclic, or branched, and is particularly preferred to be linear. 1004 Examples of these include alkylene groups having 1 to 18 carbon atoms, alkenylene groups having 2 to 18 carbon atoms, cycloalkylene groups having 5 to 18 carbon atoms, cycloalkylalkylene groups having 6 to 18 carbon atoms, arylene groups having 6 to 18 carbon atoms, and aralkylene groups having 7 to 18 carbon atoms. The alkylene groups and alkenylene groups may be linear or branched, and the cycloalkylene groups, cycloalkylalkylene groups, arylene groups, and aralkylene groups may have functional groups such as lower alkyl groups on their rings. 1004Preferably, the alkylene group has 1 to 6 carbon atoms, and in particular, linear alkylene groups such as methylene, ethylene, trimethylene, tetramethylene, pentamethylene, and hexamethylene groups are preferred.

[0049] R in equation (S1) 1002 , R 1005 , R 1006 , R 1007 and R 1008 Specific examples include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, pentyl group, hexyl group, octyl group, decyl group, dodecyl group, cyclopentyl group, cyclohexyl group, vinyl group, propenyl group, allyl group, hexenyl group, octenyl group, cyclopentenyl group, cyclohexenyl group, phenyl group, tolyl group, xylyl group, naphthyl group, benzyl group, phenethyl group, naphthylmethyl group, and the like. R in equation (S1) 1009 Examples of linear alkylene groups include methylene, ethylene, n-propylene, n-butylene, and hexylene groups, while examples of branched alkylene groups include isopropylene, isobutylene, and 2-methylpropylene groups.

[0050] Specific examples of silane coupling agents represented by formula (S1) include 3-hexanoylthiopropyltriethoxysilane, 3-octanoylthiopropyltriethoxysilane, 3-decanoylthiopropyltriethoxysilane, 3-lauroylthiopropyltriethoxysilane, 2-hexanoylthioethyltriethoxysilane, 2-octanoylthioethyltriethoxysilane, 2-decanoylthioethyltriethoxysilane, 2-lauroylthioethyltriethoxysilane, 3-hexanoylthiopropyltrimethoxysilane, 3-octanoylthiopropyltrimethoxysilane, 3-decanoylthiopropyltrimethoxysilane, 3-lauroylthiopropyltrimethoxysilane, 2-hexanoylthioethyltrimethoxysilane, 2-octanoylthioethyltrimethoxysilane, 2-decanoylthioethyltrimethoxysilane, and 2-lauroylthioethyltrimethoxysilane. These may be used individually or in combination of two or more. Among them, 3-octanoylthiopropyltriethoxysilane is particularly preferred.

[0051] In a silane coupling agent containing a bonding unit A represented by formula (I) and a bonding unit B represented by formula (II), the content of bonding unit A is preferably 30 mol% or more, more preferably 50 mol% or more, preferably 99 mol% or less, and more preferably 90 mol% or less. The content of bonding unit B is preferably 1 mol% or more, more preferably 5 mol% or more, even more preferably 10 mol% or more, preferably 70 mol% or less, more preferably 65 mol% or less, and even more preferably 55 mol% or less. The total content of bonding units A and B is preferably 95 mol% or more, more preferably 98 mol% or more, and particularly preferably 100 mol%. The content of bonding units A and B includes the amount when bonding units A and B are located at the ends of the silane coupling agent. The form of bonding units A and B when they are located at the ends of the silane coupling agent is not particularly limited, as long as they form units corresponding to formulas (I) and (II) that represent bonding units A and B.

[0052] R in equations (I) and (II)11 Examples of halogens include chlorine, bromine, and fluorine. Examples of branched or unbranched alkyl groups with 1 to 30 carbon atoms include methyl and ethyl groups. Examples of branched or unbranched alkenyl groups with 2 to 30 carbon atoms include vinyl and 1-propenyl groups. Examples of branched or unbranched alkynyl groups with 2 to 30 carbon atoms include ethynyl and propynyl groups.

[0053] R in equations (I) and (II) 12 Regarding branched or unbranched alkylene groups with 1 to 30 carbon atoms, examples include ethylene and propylene groups. Regarding branched or unbranched alkenylene groups with 2 to 30 carbon atoms, examples include vinylene and 1-propenylene groups. Regarding branched or unbranched alkylene groups with 2 to 30 carbon atoms, examples include ethynylene and propynylene groups.

[0054] In a silane coupling agent containing a bonding unit A represented by formula (I) and a bonding unit B represented by formula (II), the sum of the number of repeats of bonding unit A (v) and the number of repeats of bonding unit B (w), (v+w), is preferably in the range of 3 to 300.

[0055] The content of the silane coupling agent is preferably 3 parts by mass or more, more preferably 6 parts by mass or more, even more preferably 8 parts by mass or more, and preferably 15 parts by mass or less, more preferably 12 parts by mass or less, and even more preferably 10 parts by mass or less, per 100 parts by mass of silica. Within the above range, a better effect tends to be obtained.

[0056] The above rubber composition contains a resin component. The resin component is not particularly limited, but aromatic resins and terpene resins can be suitably used. These may be used individually or in combination of two or more. Among these, terpene resins are preferred.

[0057] Aromatic resins are polymers that contain aromatic monomers as constituent monomers. Examples include homopolymers obtained by polymerizing one type of aromatic monomer alone, copolymers obtained by copolymerizing two or more types of aromatic monomers, and copolymers of aromatic monomers with other monomers that can copolymerize with them.

[0058] Examples of aromatic monomers include styrene monomers such as styrene, o-methylstyrene, m-methylstyrene, p-methylstyrene, α-methylstyrene, p-methoxystyrene, p-tert-butylstyrene, p-phenylstyrene, o-chlorostyrene, m-chlorostyrene, and p-chlorostyrene; phenol monomers such as phenol, alkylphenol, and alkoxyphenol; naphthol monomers such as naphthol, alkylnaphthol, and alkoxynaphthol; and coumarone and indene. These may be used individually or in combination of two or more. Among these, styrene monomers are preferred, and styrene and α-methylstyrene are more preferred.

[0059] From the viewpoint of overall performance such as fuel efficiency and wet grip performance, aromatic resins are preferably α-methylstyrene resins (α-methylstyrene homopolymers, copolymers of α-methylstyrene and styrene, etc.), and copolymers of α-methylstyrene and styrene are more preferred.

[0060] The aromatic resin content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0061] Terpene resins are polymers that contain terpene compounds (terpene monomers) as constituent monomers. Examples include homopolymers obtained by polymerizing one type of terpene compound alone, copolymers obtained by copolymerizing two or more types of terpene compounds, and copolymers of a terpene compound and other monomers that can copolymerize it.

[0062] Terpene compounds are (C5H8) n A hydrocarbon and its oxygen-containing derivative represented by the following composition, monoterpene (C 10 H 16 ), sesquiterpenes (C 15 H 24 ), diterpene (C 20 H 32 These are compounds with a terpene as their basic skeleton, classified as such, and examples include α-pinene, β-pinene, dipentene, limonene, myrcene, allocimene, ocimene, α-phellandrene, α-terpinene, γ-terpinene, terpinolene, 1,8-cineole, 1,4-cineole, α-terpineol, β-terpineol, γ-terpineol, etc. These may be used individually or in combination of two or more.

[0063] From the viewpoint of overall performance such as fuel efficiency and wet grip performance, terpene resins are preferably copolymers of terpene compounds and aromatic monomers (aromatically modified terpene resins), and more preferably copolymers of terpene compounds and styrene (terpene styrene resins). In this specification, polymers containing terpene compounds and aromatic monomers as constituent monomers, such as terpene styrene resins, are treated as terpene resins, not aromatic resins.

[0064] The terpene resin content is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 20 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 40 parts by mass or less, more preferably 35 parts by mass or less, and even more preferably 30 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0065] Commercially available resins from companies such as Maruzen Petrochemical Co., Ltd., Sumitomo Bakelite Co., Ltd., Yasuhara Chemical Co., Ltd., Tosoh Corporation, Rutgers Chemicals, BASF, Arizona Chemical Company, Nippon Paint Chemical Co., Ltd., Nippon Shokubai Co., Ltd., JXTG Energy Corporation, Arakawa Chemical Industries, Ltd., and Taoka Chemical Industries, Ltd. can be used.

[0066] The resin component content (total content when multiple types of resins are used in combination) is preferably 10 parts by mass or more, more preferably 15 parts by mass or more, even more preferably 25 parts by mass or more, and particularly preferably 30 parts by mass or more, per 100 parts by mass of rubber component. It is also preferably 50 parts by mass or less, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0067] In the above rubber composition, the content of isoprene-based rubber is greater than the content of resin components.

[0068] The isoprene rubber content / resin component content is preferably 1.5 or more, more preferably 1.8 or more, even more preferably 2.0 or more, particularly preferably 2.2 or more, and also preferably 4.5 or less, more preferably 3.5 or less, and even more preferably 3.0 or less. Within the above range, a better effect tends to be obtained.

[0069] In these relationships, the isoprene rubber content is the content in 100% by mass of the rubber component (unit: mass%), and the resin component content is the content per 100 parts by mass of the rubber component (unit: parts by mass).

[0070] In the above rubber composition, the ratio of resin component content to silica content is preferably 0.05 or more, more preferably 0.10 or more, even more preferably 0.20 or more, and also preferably 0.80 or less, more preferably 0.60 or less, even more preferably 0.40 or less, and particularly preferably 0.30 or less. When the ratio is within the above range, a better effect tends to be obtained. In this relationship, the resin content and silica content are expressed as the content per 100 parts by mass of rubber component (unit: parts by mass).

[0071] The above rubber composition contains a calcium compound. Calcium compounds are compounds containing calcium, such as inorganic salts like calcium oxide, calcium hydroxide, and calcium carbide; and oxo salts like calcium carbonate, calcium nitrate, and calcium sulfate. Oxo salts also include fatty acid salts such as calcium acetate and calcium stearate. Other examples of substances containing calcium compounds include eggshells (main component: calcium carbonate) and WB16 manufactured by Structol (a mixture of calcium fatty acid, fatty acid amide, and fatty acid amide ester). These may be used individually or in combination of two or more. Among these, oxo salts are preferred, and fatty acid salts (calcium fatty acid) are more preferred.

[0072] In the above rubber composition, the calcium compound content is preferably 0.01 parts by mass or more, more preferably 0.03 parts by mass or more, even more preferably 0.05 parts by mass or more, and preferably 0.40 parts by mass or less, more preferably 0.25 parts by mass or less, and even more preferably 0.15 parts by mass or less, when converted to elemental calcium, per 100 parts by mass of the rubber component. When the content is within the above range, the effect tends to be better obtained.

[0073] In the above rubber composition, the content of the resin component is greater than the content of the calcium compound in terms of calcium element.

[0074] The ratio of the resin component content to the calcium compound content (calcium element equivalent) is preferably 10 or more, more preferably 100 or more, even more preferably 200 or more, particularly preferably 300 or more, and also preferably 600 or less, more preferably 500 or less, and even more preferably 400 or less. Within the above range, a better effect tends to be obtained.

[0075] In these relationships, the content of resin components and the calcium element content of calcium compounds are expressed as content per 100 parts by mass of rubber components (unit: parts by mass).

[0076] The above rubber composition preferably contains a dibenzylamine compound. Dibenzylamine compounds are compounds that have at least one group represented by the following formula (a dibenzylamine group). [ka]

[0077] Specific examples of dibenzylamine compounds include dibenzylamine, tetrabenzylthiuram disulfide (TBzTD), zinc dibenzyldithiocarbamate, and 1,6-bis(N,N'-dibenzylthiocarbamoyldithio)hexane. Commercially available products include those from Sanshin Chemical Industry Co., Ltd., Ouchi Shinko Chemical Industry Co., Ltd., and Lanxess. These may be used individually or in combination of two or more. Among these, compounds having two dibenzylamine groups are preferred, and tetrabenzylthiuram disulfide is more preferred.

[0078] The content of the dibenzylamine compound is preferably 0.1 parts by mass or more, preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, and preferably 4 parts by mass or less, more preferably 2 parts by mass or less, and even more preferably 1 part by mass or less, per 100 parts by mass of the rubber component. When the content is within the above range, a better effect tends to be obtained.

[0079] The above rubber composition preferably contains carbon black. The carbon black used is not particularly limited and includes N134, N110, N220, N234, N219, N339, N330, N326, N351, N550, N762, etc. Commercially available products from Asahi Carbon Co., Ltd., Cabot Japan Co., Ltd., Tokai Carbon Co., Ltd., Mitsubishi Chemical Corporation, Lion Corporation, Shin-Nippon Chemical Carbon Co., Ltd., Columbia Carbon, etc. can be used. These may be used individually or in combination of two or more types.

[0080] The specific surface area of ​​cetyltrimethylammonium bromide (CTAB) in carbon black is preferably 110 m². 2 / g or more, more preferably 120m 2 / g or more, more preferably 130m 2 It is 1 / g or more, and preferably 200m 2 / g or less, more preferably 160m 2 / g or less, more preferably 140m 2 It is less than or equal to / g. Within the above range, there is a tendency for better results to be obtained. The CTAB specific surface area of ​​carbon black is measured according to JIS K6217-3:2001.

[0081] The carbon black content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0082] The above rubber composition may contain oil. Examples of oils include process oils, vegetable oils, or mixtures thereof. Examples of process oils include paraffinic process oils, aromatic process oils, naphthenic process oils, etc. Examples of vegetable oils include castor oil, cottonseed oil, linseed oil, rapeseed oil, soybean oil, palm oil, coconut oil, peanut oil, rosin, pine oil, pine tar, tall oil, corn oil, rice oil, safflower oil, sesame oil, olive oil, sunflower oil, palm kernel oil, camellia oil, jojoba oil, macadamia nut oil, tung oil, etc. Commercial products from Idemitsu Kosan Co., Ltd., Sankyo Yuka Kogyo Co., Ltd., JXTG Energy Corporation, Orisoy Co., Ltd., H&R Co., Ltd., Toyokuni Oil Co., Ltd., Showa Shell Sekiyu K.K., Fuji Kosan Co., Ltd., etc. may be used. These may be used individually or in combination of two or more types.

[0083] The oil content is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 5 parts by mass or more, per 100 parts by mass of rubber component, and also preferably 30 parts by mass or less, more preferably 20 parts by mass or less, and even more preferably 10 parts by mass or less. Within the above range, a better effect tends to be obtained.

[0084] The above rubber composition may contain an anti-aging agent. Examples of anti-aging agents include naphthylamine-based anti-aging agents such as phenyl-α-naphthylamine; diphenylamine-based anti-aging agents such as octylated diphenylamine and 4,4′-bis(α,α′-dimethylbenzyl)diphenylamine; N-isopropyl-N′-phenyl-p-phenylenediamine, N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine, and N,N′-di-2-naphthyl-p-phenylenediamine. Examples include p-phenylenediamine-based antioxidants such as 2,2,4-trimethyl-1,2-dihydroquinoline polymers and other quinoline-based antioxidants; monophenol-based antioxidants such as 2,6-di-t-butyl-4-methylphenol and styrenated phenol; and bis-, tris-, and polyphenol-based antioxidants such as tetrakis-[methylene-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane. Commercially available products include those from Seiko Chemical Co., Ltd., Sumitomo Chemical Co., Ltd., Ouchi Shinko Chemical Co., Ltd., and Flexis Co., Ltd. These may be used individually or in combination of two or more.

[0085] The amount of the antioxidant is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less. When the amount is within the above range, a better effect tends to be obtained.

[0086] The above rubber composition may contain wax. The wax is not particularly limited and can be any petroleum-based wax such as paraffin wax or microcrystalline wax; a natural wax such as plant-based wax or animal-based wax; or a synthetic wax such as polymers of ethylene or propylene. Commercially available products from companies such as Ouchi Shinko Chemical Industry Co., Ltd., Nippon Seiro Co., Ltd., and Seiko Chemical Co., Ltd. can be used. These can be used individually or in combination of two or more types.

[0087] The wax content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of rubber component. Within this range, a better effect tends to be obtained.

[0088] The above rubber composition may contain stearic acid. Conventional known stearic acid can be used, and commercially available products from companies such as NOF Corporation, Kao Corporation, Fujifilm Wako Pure Chemical Industries Ltd., and Chiba Fatty Acid Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0089] The stearic acid content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within this range, a better effect tends to be obtained.

[0090] The above rubber composition may contain zinc oxide. Conventional known zinc oxides can be used, and commercially available products from companies such as Mitsui Mining & Smelting Co., Ltd., Toho Zinc Co., Ltd., Hakusui Tech Co., Ltd., Seido Chemical Industry Co., Ltd., and Sakai Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0091] The zinc oxide content is preferably 1 part by mass or more, more preferably 2 parts by mass or more, and preferably 10 parts by mass or less, and more preferably 6 parts by mass or less, per 100 parts by mass of the rubber component. Within this range, a better effect tends to be obtained.

[0092] The above rubber composition may contain sulfur. Examples of sulfur commonly used in the rubber industry include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersible sulfur, and soluble sulfur. Commercially available products from companies such as Tsurumi Chemical Industries, Karuizawa Sulfur Co., Ltd., Shikoku Chemicals Co., Ltd., Flexis Co., Ltd., Nippon Dry Distillation Co., Ltd., and Hosoi Chemical Industry Co., Ltd. can be used. These may be used individually or in combination of two or more types.

[0093] The sulfur content is preferably 0.8 parts by mass or more, more preferably 1.2 parts by mass or more, and even more preferably 1.5 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 6 parts by mass or less, more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0094] The above rubber composition may contain a vulcanization accelerator. Examples of vulcanization accelerators include thiazole-based vulcanization accelerators such as 2-mercaptobenzothiazole and di-2-benzothiazolyl disulfide; thiuram-based vulcanization accelerators such as tetramethylthiuram disulfide (TMTD) and tetrakis(2-ethylhexyl)thiuram disulfide (TOT-N); sulfenamide-based vulcanization accelerators such as N-cyclohexyl-2-benzothiadylsulfenamide (CBS), N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-oxyethylene-2-benzothiazolesulfenamide, and N,N′-diisopropyl-2-benzothiazolesulfenamide; and guanidine-based vulcanization accelerators such as diphenylguanidine, dioltotolylguanidine, and orthotolylbiguanidine. Commercially available products include those from Sumitomo Chemical Co., Ltd. and Ouchi Shinko Chemical Co., Ltd. These may be used individually or in combination of two or more.

[0095] The content of the vulcanization accelerator is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of the rubber component, and also preferably 10 parts by mass or less, more preferably 8 parts by mass or less, and even more preferably 6 parts by mass or less. When the content is within the above range, a better effect tends to be obtained.

[0096] In addition to the above components, the above rubber composition may further contain additives commonly used in the tire industry, such as organic peroxides; fillers such as talc, alumina, clay, aluminum hydroxide, and mica. The content of these additives is preferably 0.1 to 200 parts by mass per 100 parts by mass of the rubber component.

[0097] In the above rubber composition, the amount of acetone extract is preferably 60 parts by mass or less, more preferably 50 parts by mass or less, even more preferably 45 parts by mass or less, per 100 parts by mass of the rubber component, and also preferably 10 parts by mass or more, more preferably 25 parts by mass or more, even more preferably 35 parts by mass or more, and particularly preferably 40 parts by mass or more. When the amount is within the above range, a better effect tends to be obtained. The amount of acetone extracted (phr (parts by mass)) can be calculated using the following formula, based on the value (mass%) measured by extracting the above-mentioned rubber composition after vulcanization with acetone for 24 hours in accordance with JIS K 6229:2015, and the amount of rubber components (mass%) obtained by acetone extractive thermogravimetric analysis (TGA), etc. Acetone extraction amount (phr) = Acetone extraction amount (mass%) / Amount of rubber component (mass%) × 100

[0098] In 100% by mass of acetone extract, the resin component content is preferably 10% by mass or more, more preferably 25% by mass or more, even more preferably 40% by mass or more, particularly preferably 50% by mass or more, and also preferably 80% by mass or less, more preferably 70% by mass or less, and even more preferably 60% by mass or less. Within the above range, a better effect tends to be obtained. The resin component content in 100% by mass of acetone extract can be calculated from the analysis results of the acetone extract and the amount of resin component blended. Furthermore, if the resin type (terpene-based, styrene-based, etc.) is known, it is also possible to estimate the resin content using a reference sample created by varying the amount of the same type of resin.

[0099] In the above rubber composition, the amount extracted with acetone is greater than the amount of isoprene-based rubber.

[0100] The acetone extraction amount / isoprene rubber content is preferably 1.1 or more, more preferably 4.0 or less, more preferably 2.0 or less, and even more preferably 1.5 or less. Within this range, better results tend to be obtained.

[0101] In these relationships, the amount of acetone extracted is the amount per 100 parts by mass of the rubber component (unit: parts by mass), and the isoprene rubber content is the content in 100% by mass of the rubber component (unit: mass%).

[0102] The above rubber composition can be produced, for example, by kneading each of the above components using a rubber kneading device such as an open roll or Banbury mixer, and then vulcanizing it.

[0103] Regarding the mixing conditions, in the base mixing step where additives other than the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 100 to 180°C, preferably 120 to 170°C. In the finish mixing step where the vulcanizing agent and vulcanization accelerator are mixed, the mixing temperature is usually 120°C or lower, preferably 85 to 110°C. Furthermore, the composition mixed with the vulcanizing agent and vulcanization accelerator is usually subjected to a vulcanization treatment such as press vulcanization. The vulcanization temperature is usually 140 to 190°C, preferably 150 to 185°C. The vulcanization time is usually 5 to 15 minutes.

[0104] The above rubber composition can be used (as a tire rubber composition) in tire components such as the tread (cap tread), sidewall, base tread, under tread, shoulder, clinch, bead apex, breaker cushion rubber, carcass cord covering rubber, insulation, chafer, inner liner, etc., as well as the side reinforcement layer of run-flat tires. It is particularly suitable for use in treads.

[0105] The tire of the present invention is manufactured by conventional methods using the above-mentioned rubber composition. Specifically, the rubber composition is extruded to match the shape of a tread or the like at the unvulcanized stage, and then molded together with other tire components in a conventional manner on a tire molding machine to form an unvulcanized tire. This unvulcanized tire is then heated and pressurized in a vulcanizing machine to obtain a tire.

[0106] The above-mentioned tires (pneumatic tires, etc.) can be used for passenger car tires; truck and bus tires; motorcycle tires; high-performance tires; winter tires such as studless tires; run-flat tires with side reinforcement layers; tires with sound-absorbing materials such as sponges inside the tire cavity; tires with sealing materials that can be sealed in the event of a puncture inside the tire or tire cavity; and tires with electronic components that have electronic components such as sensors and wireless tags inside the tire or tire cavity, and are particularly suitable for passenger car tires.

[0107] The tire sizes mentioned above are not particularly limited; for example, tire widths can be selected within the range of 100-400mm, aspect ratios within the range of 25-85%, and rim diameters within the range of 10-25 inches, as appropriate. Specific examples include 105 / 50R16, 115 / 50R17, 125 / 55R20, 135 / 45R21, 145 / 45R21, 155 / 45R18, 165 / 45R22, 175 / 45R23, 185 / 60R20, 195 / 55R14, 205 / 40R16, 215 / 40R16, 225 / 40R17, 235 / 40R17, 245 / 40R16, 255 / 40R17, 265 / 40R17, 275 / 35R18, 285 / 30R19, 295 / 45R20, etc.

[0108] The above-mentioned tire preferably satisfies the following relationship between the tire outer diameter Dt and the tire section width Wt.

number

[0109] Examples of tires that can satisfy the above formula include 145 / 60R18, 145 / 60R19, 155 / 55R18, 155 / 55R19, 155 / 70R17, 155 / 70R19, 165 / 55R20, 165 / 55R21, 165 / 60R19, 165 / 65R19, 165 / 70R18, 175 / 55R19, 175 / 55R20, 175 / 55R22, 175 / 60R18, 185 / 55R19, 185 / 60R20, 195 / 50R20, 195 / 55R20, etc.

[0110] Tires that satisfy the above formula are preferably applied to pneumatic tires for passenger cars. This is because pneumatic tires for passenger cars that satisfy the above formula tend to be more suitable for solving the problems of this invention. [Examples]

[0111] The present invention will be specifically described based on the examples provided, but the present invention is not limited to these examples.

[0112] The various chemicals used in the examples and comparative examples are described below.

[0113] (Rubber component) Natural rubber: TSR20 SBR1: LANXESS Buna VSL 5228-2 (styrene content: 28% by mass, vinyl content: 52% by mass, oil content: 37.5 parts by mass per 100 parts by mass of rubber solids) SBR2: JSR1502 manufactured by JSR Corporation (styrene content: 24% by mass, vinyl content: 16% by mass) SBR3: Modified SBR synthesized in Manufacturing Example 1 below (styrene content: 25% by mass, vinyl content: 60% by mass, Mw: 150,000) SBR4: Modified SBR synthesized in Manufacturing Example 2 below (styrene content: 10% by mass, vinyl content: 40% by mass, Mw: 200,000) BR: BR150B manufactured by Ube Industries, Ltd. (Cystic content: 97% by mass, Vinyl content: 1% by mass)

[0114] (Chemicals other than rubber components) Carbon Black: N134 (CTAB: 135m) 2 / g) Silica 1: ZEOSIL 1115MP manufactured by Rhodia Corporation (average particle size: 24nm) Silica 2: UltraSil VN3 manufactured by Evonik DeGussa (average particle size: 17nm) Silica 3: Evonik DeGussa's UltraSil 9100GR (average particle size: 15nm) Silane coupling agent 1: Si266 (bis(3-triethoxysilylpropyl) disulfide) manufactured by Evonik DeGussa. Silane coupling agent 2: NXT (3-octanoylthiopropyltriethoxysilane) manufactured by Momentive Oil: H&R VIVATEC500 (TDAE oil) Resin 1: Sylvatraxx 4401 (α-methylstyrene-based resin (polymer of α-methylstyrene and styrene)) manufactured by Arizona Chemical Corporation. Resin 2: YS Resin TO125 manufactured by Yasuhara Chemical Co., Ltd. (Terpene styrene resin (polymer of terpene compound and styrene)) Wax: Ozoace 0355 manufactured by Nippon Seiro Co., Ltd. Anti-aging agent 1: Nocrack 6C (N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Anti-aging agent 2: Nocrack RD (poly(2,2,4-trimethyl-1,2-dihydroquinoline)) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Calcium compound 1: Tancal #200 manufactured by Takehara Chemical Industry Co., Ltd. (calcium carbonate, calcium element content: approximately 40% by mass) Calcium compound 2: WB16 manufactured by Structol (a mixture of calcium fatty acid, fatty acid amide, and fatty acid amide ester; calcium element content: approximately 5% by mass) Stearic acid: Stearic acid "Tsubaki" manufactured by NOF Corporation Zinc oxide: Zinc oxide No. 1 manufactured by Mitsui Mining & Smelting Co., Ltd. Sulfur: Powdered sulfur manufactured by Tsurumi Chemical Industries Co., Ltd. Vulcanization accelerator 1: Noxellar NS (N-tert-butyl-2-benzothiazolyl sulfenamide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Noxellar D (diphenylguanidine) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Dibenzylamine compound: Sunceller TBzTD (tetrabenzyl thiuram disulfide) manufactured by Sanshin Chemical Industry Co., Ltd.

[0115] (Manufacturing Example 1) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization proceeded under adiabatic conditions, reaching a maximum temperature of 85°C. When the polymerization conversion rate reached 99%, butadiene was added, and polymerization was continued for another 5 minutes. Then, 3-diethylaminopropyltrimethoxysilane was added as a modifier, and the reaction was carried out for 15 minutes. After the polymerization reaction was complete, 2,6-di-tert-butyl-p-cresol was added. Subsequently, the solvent was removed by steam stripping, and the mixture was dried on a heated roller at 110°C to obtain SBR3.

[0116] (Manufacturing example 2) Cyclohexane, tetrahydrofuran, styrene, and 1,3-butadiene were charged into a nitrogen-purged autoclave reactor. After adjusting the temperature of the reactor contents to 20°C, n-butyllithium was added to initiate polymerization. Polymerization proceeded under adiabatic conditions, reaching a maximum temperature of 85°C. When the polymerization conversion rate reached 99%, butadiene was added, and polymerization was continued for another 5 minutes. Then, 3-dimethylaminopropyltriethoxysilane was added as a modifier, and the reaction was carried out for 15 minutes. After the polymerization reaction was complete, 2,6-di-tert-butyl-p-cresol was added. Subsequently, the solvent was removed by steam stripping, and the mixture was dried on a heated roller at 110°C to obtain SBR4.

[0117] (Examples and Comparative Examples) According to the formulation shown in Table 1, all materials except the dibenzylamine compound, sulfur, and vulcanization accelerator were mixed for 5 minutes at 150°C using a 1.7L Banbury mixer manufactured by Kobe Steel, Ltd. to obtain a mixture. Next, the dibenzylamine compound, sulfur, and vulcanization accelerator were added to the mixture and mixed for 5 minutes at 80°C using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was molded into a tread shape and bonded together with other tire components to form an unvulcanized tire. The tire was then press-vulcanized for 12 minutes at 150°C to produce a test tire (size: 175 / 60R18). The obtained test tire was evaluated as follows, and the results are shown in Table 1. In Table 1, the rubber content in the oil-applied rubber is listed in the "rubber" column, and the oil content in the oil-applied rubber is added to the "oil" column.

[0118] (Amount of acetone extracted) A sample (vulcanized rubber composition) was taken from the tread of the above-mentioned test tire, and the amount of acetone extracted was measured by acetone extraction for 24 hours in accordance with JIS K 6229:2015. Then, using the obtained amount of acetone extracted (mass%) and the amount of rubber component in the sample (mass%) determined by TGA, the amount of acetone extracted per 100 parts by mass of rubber component (phr(parts by mass)) was calculated.

[0119] (Fuel efficiency) Using a rolling resistance tester, the rolling resistance of each test tire was measured while running at a speed of 80 km / h, and the results were expressed as an index with Comparative Example 1 set to 100. A higher index indicates lower rolling resistance and better fuel efficiency.

[0120] (Wet grip performance) Each test tire was mounted on a vehicle, and the braking distance from an initial speed of 80 km / h on a wet asphalt surface was measured and expressed as an index with Comparative Example 1 set to 100. A higher index indicates a shorter braking distance and better wet grip performance.

[0121] [Table 1]

[0122] Table 1 shows that the example demonstrated superior overall performance (sum of all indices) in terms of fuel efficiency and wet grip performance compared to the comparative example.

Claims

1. It contains rubber components including styrene-butadiene rubber and isoprene-based rubber, silica, resin components, and calcium compounds. The amount extracted with acetone / the content of the isoprene-based rubber is greater than or equal to 40 / 35. The content of the isoprene-based rubber / the content of the resin component is greater than or equal to 35 / 20. The content of the aforementioned resin component is greater than the calcium element content of the aforementioned calcium compound. A rubber composition for tires in which the content of the resin component and the content of the silica are 0.20 or more and 0.80 or less.

2. The tire rubber composition according to claim 1, wherein the calcium compound is a fatty acid salt.

3. The tire rubber composition according to claim 1 or 2, wherein the average particle size of the silica is 18 nm or less.

4. A tire rubber composition according to any one of claims 1 to 3, comprising a mercapto-silane coupling agent.

5. The tire rubber composition according to any one of claims 1 to 4, wherein the content of the isoprene-based rubber is 20 to 50% by mass in 100% by mass of the rubber component.

6. The tire rubber composition according to any one of claims 1 to 5, wherein the content of the resin component is 50% by mass or more in 100% by mass of the acetone extract.

7. The rubber composition for tires according to any one of claims 1 to 6, wherein the resin component comprises a terpene resin.

8. A tire using the rubber composition described in any one of claims 1 to 7.