Rubber composition for tire tread and tire

Abstract

To improve a balance between WET performance and rolling resistance performance.SOLUTION: A rubber composition for a tire tread contains a diene-based rubber component, a thermoplastic elastomer, a resin, and silica. The diene-based rubber component has a total styrene amount of less than 10 mass%. The thermoplastic elastomer is obtained by hydrogenation of a block copolymer of a styrene-based monomer and a diene-based monomer, and the content of a butylene unit is 25 mass% or less with respect to the total mass of an ethylene unit and a butylene unit. The resin is at least one kind selected from the group consisting of a terpene-based resin, an unhydrogenated petroleum resin, a hydrogenated petroleum resin having a softening point of 115°C or higher, a rosin-based resin, and a coumarone-indene-based resin. The amount of the thermoplastic elastomer is 1 to 20 pts.mass with respect to 100 pts.mass of the diene-based rubber component.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a rubber composition for a tire tread and a tire using the same.

Background Art

[0002] Generally, tires are used in various driving environments, and for example, it is required to improve the WET performance, which is the grip performance on a wet road surface in the rain.

[0003] As a technique for improving the WET performance, for example, Patent Document 1 describes that a specific amount of silica and a resin such as a C5-based resin are blended with a rubber component containing butadiene rubber, and by defining the polymer amount / acetone extraction amount, the wet grip performance and handling stability after aging can be improved. Patent Document 1 also describes that a styrene-based thermoplastic elastomer may be further blended.

[0004] Patent Document 2 describes that a C5-based resin and / or a C5-C9-based resin and an aromatic vinyl-based polymer such as an aromatic vinyl-based thermoplastic elastomer are blended with a rubber component containing isoprene rubber and styrene-butadiene rubber, and thereby the wet grip performance during high-speed driving is improved.

[0005] Patent Document 3 describes that a thermoplastic elastomer having a tanδ peak value in the range of -20 to 20°C and a peak value of 1 or more is blended with a rubber component containing a specific amount of solution-polymerized styrene-butadiene rubber, and thereby the WET performance, fatigue resistance, and tear resistance are improved in a well-balanced manner. Patent Document 3 also describes that a tackifying resin having a softening point of 90 to 160°C may be further blended.

[0006] Patent Document 4 describes that a styrene·alkylene block copolymer having a total styrene unit content of 30% by mass or more and a CTAB adsorption specific surface area of 110 m 2Compounding a filler of less than / g and thereby highly balancing the low loss property, wet performance, and dry handling property of the tire are described. In Patent Document 4, a styrene-alkylene block copolymer having a butylene unit content of 41% by mass or more based on the total mass of the butylene unit and the ethylene unit is used.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0008] When formulating a rubber composition for the purpose of improving wet performance, there is a problem that the rolling resistance of the tire increases, that is, the rolling resistance performance deteriorates. Thus, the wet performance and the rolling resistance performance are in an antinomic relationship.

[0009] In view of the above points, an embodiment of the present invention aims to provide a rubber composition for a tire tread that can improve the antinomy between wet performance and rolling resistance performance, that is, improve the balance between both performances, and a tire using the same.

[0010] Although Patent Documents 1 to 3 describe that a rubber component containing styrene-butadiene rubber is blended with silica, a thermoplastic elastomer, and a resin, it is not described that the wet performance and the rolling resistance performance are compatible in a blend in which the total styrene amount of the rubber component is less than 10% by mass. Further, Patent Document 4 only discloses a styrene-alkylene block copolymer which is a thermoplastic elastomer having a large content of butylene units, and does not disclose using one having a butylene unit content of 25% by mass or less.

Means for Solving the Problems

[0011] The present invention includes the embodiments shown below. [1] A diene rubber component having a total styrene amount of less than 10% by mass, A thermoplastic elastomer obtained by hydrogenating a block copolymer of a styrene monomer and a diene monomer, wherein the content of butylene units represented by -[CH2-CH(C2H5)]- is 25% by mass or less based on the total mass of ethylene units represented by -(CH2-CH2)- and the butylene units, a thermoplastic elastomer, At least one resin selected from the group consisting of terpene resins, unhydrogenated petroleum resins, hydrogenated petroleum resins having a softening point of 115°C or higher, rosin resins, and coumarone-indene resins, and, Silica, is included, A rubber composition for a tire tread, wherein the amount of the thermoplastic elastomer with respect to 100 parts by mass of the diene rubber component is 1 to 20 parts by mass.

[0012] [2] The rubber composition for a tire tread according to [1], wherein the diene rubber component contains styrene-butadiene rubber. [3] In the temperature curve of tanδ obtained by a dynamic viscoelasticity test of a tensile method with a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% in accordance with JIS K6394:2007 for the vulcanized rubber composition, the peak temperature of the diene rubber component is less than -20°C, the rubber composition for a tire tread according to [1] or [2]. [4] In the temperature curve of tanδ obtained by a dynamic viscoelasticity test with a tensile method of a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% in accordance with JIS K6394:2007 for the vulcanized rubber composition, the peak temperature of the thermoplastic elastomer is -20°C or higher and 20°C or lower, the rubber composition for a tire tread according to any one of [1] to [3]. [5] The amount of the resin is 20 to 50 parts by mass with respect to 100 parts by mass of the diene rubber component, the rubber composition for a tire tread according to any one of [1] to [4]. [6] The content ratio (resin / thermoplastic elastomer) of the resin and the thermoplastic elastomer is 1.5 or more by mass ratio, the rubber composition for a tire tread according to any one of [1] to [5]. [7] A tire including a tread produced from the rubber composition according to any one of [1] to [6]. [Advantages of the Invention]

[0013] According to the rubber composition for a tire tread according to the embodiment of the present invention, the balance between the WET performance and the rolling resistance performance can be improved. [Brief Description of the Drawings]

[0014]

Figure 1

[0015] The rubber composition for a tire tread according to the embodiment of the present invention (hereinafter, also simply referred to as "rubber composition") contains (A) a diene rubber component, (B) a thermoplastic elastomer, (C) a resin, and (D) silica.

[0016] [(A) Diene Rubber Component] In this embodiment, the total styrene content of the diene rubber component is less than 10% by mass. That is, one diene rubber or a combination of a plurality of diene rubbers is combined so that the total styrene content in the diene rubber component is less than 10% by mass to constitute the diene rubber component. By the total styrene content of the diene rubber component being less than 10% by mass, the glass transition temperature of the diene rubber component can be lowered. In this embodiment, on the premise of using such a diene rubber component, by combining with a specific thermoplastic elastomer and resin, the balance between the WET performance and the rolling resistance performance can be improved while maintaining the low temperature performance to a certain extent. The total styrene content in the diene rubber component may be 0% by mass, but is preferably greater than 0% by mass, more preferably 1.0 to 9.5% by mass, still more preferably 2.5 to 9.5% by mass, and still more preferably 5.0 to 9.5% by mass. Here, the diene rubber refers to a rubber having a repeating unit corresponding to a diene monomer having a conjugated double bond, and has a double bond in the polymer main chain.

[0017] Here, the total styrene content in the diene rubber component is the total content (% by mass) of styrene units contained in the total amount of the diene rubber component, and is calculated by Σ (content of each diene rubber (% by mass) × styrene content in each rubber (% by mass) / 100). The content (% by mass) of each diene rubber is the mass ratio of the diene rubber in 100% by mass of the diene rubber component. The styrene content (% by mass) in each diene rubber is 1 determined by 1H-NMR.

[0018] The diene rubber component preferably contains styrene butadiene rubber (SBR). Examples of SBR include solution-polymerized styrene butadiene rubber (SSBR) and emulsion-polymerized styrene butadiene rubber (ESBR). As SBR, modified styrene butadiene rubber (modified SBR) with modified terminals, main chains, etc. may be used, unmodified styrene butadiene rubber (unmodified SBR) without modification may also be used, or modified SBR and unmodified SBR may be used in combination. Preferably, SBR contains modified solution-polymerized styrene butadiene rubber (modified SSBR), and modified SSBR and unmodified SSBR may be used in combination. In this case, it is preferable that the modified SBR (preferably modified SSBR) accounts for 50% by mass or more, more preferably 60% by mass or more, in 100% by mass of SBR.

[0019] As the modified SBR (preferably modified SSBR), SBR modified by a functional group introduced into the terminal and / or main chain that interacts with silica is used. As the functional group, those containing an oxygen atom and / or a nitrogen atom are preferable, and examples include at least one selected from the group consisting of an amino group, a hydroxy group, an amide group, an alkoxy group, a silyl group, an alkoxysilyl group, an epoxy group, and a carboxy group. By using such modified SBR, the dispersibility of silica can be improved.

[0020] The diene rubber component may be composed of only SBR, or may contain other diene rubbers. Preferably, in order to make the total styrene amount less than 10% by mass, a diene rubber containing no styrene unit is used in combination with other diene rubbers. Examples of other diene rubbers include natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), nitrile rubber (NBR), chloroprene rubber (CR), styrene-isoprene copolymer rubber, butadiene-isoprene copolymer rubber, etc. Among these, it is preferable to use at least one selected from the group consisting of NR, IR, and BR, and more preferably BR.

[0021] In one embodiment, 100 parts by mass of the diene rubber component may include 20 to 90 parts by mass of SBR, 10 to 80 parts by mass of BR, and 0 to 30 parts by mass of NR and / or IR, may include 30 to 85 parts by mass of SBR, 15 to 70 parts by mass of BR, and 0 to 25 parts by mass of NR and / or IR, may include 40 to 80 parts by mass of SBR, 20 to 50 parts by mass of BR, and 0 to 20 parts by mass of NR and / or IR, may include 50 to 80 parts by mass of SBR, 20 to 40 parts by mass of BR, and 0 to 15 parts by mass of NR and / or IR, may include 60 to 80 parts by mass of SBR, 20 to 30 parts by mass of BR, and 0 to 15 parts by mass of NR and / or IR. Here, the amount of NR and / or IR may be 0 parts by mass or may be 5 parts by mass or more.

[0022] [(B) Thermoplastic elastomer] A thermoplastic elastomer is compounded in the rubber composition according to this embodiment. By compounding the thermoplastic elastomer, it becomes easier to improve the rolling resistance performance.

[0023] As the thermoplastic elastomer, a hydrogenated styrene-based thermoplastic elastomer obtained by hydrogenating a block copolymer of a styrene-based monomer and a diene-based monomer is used. The hydrogenated styrene-based thermoplastic elastomer is a block copolymer having a block derived from a styrene-based monomer as a hard segment and a block derived from a diene-based monomer as a soft segment, and the diene part is hydrogenated. The thermoplastic elastomer is usually solid at normal temperature (25°C), that is, it does not have fluidity. In this specification, (B) the thermoplastic elastomer is not included in (A) the diene rubber component and (C) the resin.

[0024] Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, etc., and styrene is preferred. Examples of the diene-based monomer include butadiene (that is, 1,3-butadiene), isoprene, etc. Any one of these may be used alone, or two or more thereof may be used in combination.

[0025] Specific examples of the thermoplastic elastomer include hydrogenated products of styrene-butadiene-styrene triblock copolymers (SBS) (SEBS), hydrogenated products of styrene-isoprene-styrene triblock copolymers (SIS) (SEPS, SEEPS), hydrogenated products of styrene-isoprene-butadiene-styrene triblock copolymers, hydrogenated products of styrene-butadiene diblock copolymers, hydrogenated products of styrene-isoprene diblock copolymers, etc. Any one of these may be used alone or two or more of them may be used in combination. The microstructure of the block derived from the diene monomer may be 1,4-bond, 1,2-bond, or may contain both. Therefore, for example, the hydrogenated product of SBS also includes the hydrogenated product of styrene-vinylbutadiene-styrene triblock copolymer, the hydrogenated product of SIS also includes the hydrogenated product of styrene-vinylisoprene-styrene triblock copolymer, and the hydrogenated product of styrene-isoprene-butadiene-styrene triblock copolymer also includes the hydrogenated product of styrene-vinylisoprene-vinylbutadiene-styrene triblock copolymer.

[0026] The hydrogenated styrenic thermoplastic elastomer has, as its structural unit, a styrene unit derived from a styrenic monomer and may contain an ethylene unit and / or a butylene unit derived from butadiene, an ethylene unit derived from isoprene, a propylene unit and / or an isopropylethylene (hydrogenated vinylisoprene) unit.

[0027] In this embodiment, as the thermoplastic elastomer, one in which the content of butylene units represented by -[CH2-CH(C2H5)]- is 25% by mass or less based on the total mass of ethylene units represented by -(CH2-CH2)- and the butylene units is used. By the content of butylene units being 25% by mass or less, the balance between WET performance and rolling resistance performance can be improved. The content of butylene units may be 0% by mass. For example, when butadiene is not included as the diene monomer, the content of butylene units is 0% by mass, that is, no butylene units are included. The content of butylene units is preferably 0 to 22% by mass, more preferably 0 to 15% by mass, and still more preferably 0 to 10% by mass.

[0028] The content of styrene units in the thermoplastic elastomer is not particularly limited. For example, it may be 5 to 50% by mass, may be 8 to 45% by mass, or may be 10 to 40% by mass.

[0029] The contents of butylene units, ethylene units, and styrene units in the thermoplastic elastomer 1 are determined by the integration ratio of 1H-NMR.

[0030] As the thermoplastic elastomer, it is preferable that the glass transition temperature (Tg) is -35°C or higher and 0°C or lower. Thereby, it becomes easier to adjust the peak temperature of the thermoplastic elastomer in the temperature curve of tanδ for the rubber composition described later to the range of -20°C to +20°C. The Tg of the thermoplastic elastomer is more preferably -34°C to -5°C, and still more preferably -33°C to -10°C.

[0031] In this specification, the glass transition temperature (Tg) is a value measured by the differential scanning calorimetry (DSC) method in accordance with JIS K7121:2012 at a heating rate of 20°C / min (measurement temperature range: -150°C to 50°C).

[0032] The content of the thermoplastic elastomer is 1 to 20 parts by mass, more preferably 3 to 18 parts by mass, and still more preferably 5 to 15 parts by mass with respect to 100 parts by mass of the diene rubber component. When it is within the above range, the effects according to the present embodiment tend to be obtained more favorably.

[0033] [(C) Resin] In the rubber composition according to the present embodiment, a resin is blended in order to improve the balance between the WET performance and the rolling resistance performance. As such a resin, in the present embodiment, at least one selected from the group consisting of terpene resins, unhydrogenated petroleum resins, hydrogenated petroleum resins having a softening point of 115° C. or higher, rosin resins, and coumarone-indene resins is used. By using these resins, it becomes easy to adjust the peak temperature of the thermoplastic elastomer in the temperature curve of tan δ for the rubber composition described later to the range of -20° C. to +20° C., and it becomes easy to improve the balance between the WET performance and the rolling resistance performance. Note that these resins may be solid or liquid at normal temperature (25° C.).

[0034] The terpene resin is a resin obtained by polymerizing terpene compounds such as α-pinene, β-pinene, limonene, and dipentene, and has units derived from the terpene compounds. The terpene resin may be a polyterpene resin obtained by polymerizing only terpene monomers, or a modified terpene resin obtained by polymerizing terpene compounds and monomers other than terpenes. Examples of the modified terpene resin include aromatic modified terpene resins obtained by polymerizing terpene compounds and aromatic compounds. As the terpene resin, a pinene resin containing α-pinene and / or β-pinene as constituent monomers is preferable, and poly-pinene obtained by polymerizing only α-pinene and / or β-pinene may also be used.

[0035] The unhydrogenated petroleum resin is a petroleum resin that has not been hydrogenated. The hydrogenated petroleum resin is a hydrogenated petroleum resin, and includes those that are partially hydrogenated. Examples of the petroleum resin include aliphatic petroleum resins (C5-based petroleum resins), aromatic petroleum resins (C9-based petroleum resins), and aliphatic / aromatic copolymer-based petroleum resins (C5 / C9-based petroleum resins).

[0036] C5 petroleum resin is a resin obtained by cationic polymerization of unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions (C5 fraction) corresponding to 4 to 5 carbon atoms. C9 petroleum resin is a resin obtained by cationic polymerization of monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions (C9 fraction) corresponding to 8 to 10 carbon atoms. C5 / C9 petroleum resin is a resin obtained by copolymerizing a C5 fraction and a C9 fraction by cationic polymerization.

[0037] In this embodiment, for the hydrogenated petroleum resin, those with a softening point of 115 °C or higher are used. When the petroleum resin is hydrogenated, its compatibility with diene rubber components becomes relatively high, and the rolling resistance performance is improved. At this time, if the softening point is high, the peak temperature of the thermoplastic elastomer in the temperature curve of tanδ for the rubber composition can be shifted to the high-temperature side and broadened, so that the WET performance can be made relatively high. The softening point of the hydrogenated petroleum resin is preferably 115 °C to 160 °C, more preferably 120 °C to 150 °C. Here, the softening point is measured using a ring and ball softening point measuring device in accordance with JIS K6220-1:2001.

[0038] Examples of rosin-based resins include natural resin rosin, and rosin-modified resins obtained by modifying it by hydrogenation, disproportionation, dimerization, esterification, etc. (for example, hydrogenated rosin ester, rosin-modified maleic acid resin).

[0039] Coumarone-indene resin is a resin containing coumarone and indene as constituent monomers. For example, in addition to copolymers of coumarone and indene, copolymers of coumarone and indene with other monomers copolymerizable therewith are included.

[0040] Any one of the above resins may be used alone, or two or more of them may be used in combination. In addition, except for the hydrogenated petroleum resin, the softening point is not particularly limited, and it may be liquid at room temperature as described above. For example, the softening point may be 160°C or lower, or may be 50°C to 150°C.

[0041] The content of the resin is preferably 20 to 50 parts by mass, more preferably 25 to 46 parts by mass, and still more preferably 28 to 45 parts by mass with respect to 100 parts by mass of the diene rubber component. When it is within the above range, the effects according to this embodiment tend to be obtained more favorably.

[0042] (C) The content ratio of the resin to (B) the thermoplastic elastomer (resin / thermoplastic elastomer) is preferably 1.5 or more by mass ratio. When the resin / thermoplastic elastomer is 1.5 or more, it becomes easier to improve the balance between the WET performance and the rolling resistance performance. The resin / thermoplastic elastomer is more preferably 2 to 10, and still more preferably 3 to 7.

[0043] [(D) Silica] In the rubber composition according to this embodiment, silica is used as a reinforcing filler. The silica is not particularly limited, and for example, wet silica such as wet precipitation method silica or wet gel method silica may be used.

[0044] The nitrogen adsorption specific surface area of the silica is not particularly limited, and for example, it may be 100 to 300 m 2 / g. Preferably it is 120 to 270 m 2 / g, more preferably 150 to 250 m 2 / g, and still more preferably 160 to 240 m 2 / g. Here, the nitrogen adsorption specific surface area of the silica is the BET specific surface area measured according to the BET method described in JIS K6430:2008.

[0045] The silica content is preferably 100 to 180 parts by mass, more preferably 105 to 150 parts by mass, and still more preferably 120 to 140 parts by mass with respect to 100 parts by mass of the diene rubber component. When it is within the above range, the effects according to this embodiment tend to be obtained more favorably.

[0046] The rubber composition according to this embodiment preferably contains a silane coupling agent. Examples of the silane coupling agent 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-dimethylthiocarbamoyl tetrasulfide, 2-triethoxysilylethyl-N,N-dimethylthiocarbamoyl tetrasulfide, 3-triethoxysilylpropyl methacrylate monosulfide and other sulfide-based silane coupling agents, 3-mercaptopropyltrimethoxysilane, 2-mercaptoethyltriethoxysilane, "NXT" (3-octanoylthio-1-propyltriethoxysilane) manufactured by Momentive, "NXT Z45" manufactured by Momentive, "VP Si363" formula: HS-(CH2)3-Si(OC2H5) m (O(C2H4O) k -C 13 H 27 ) nExamples of mercapto-based silane coupling agents include those such as (where m = average 1, n = average 2, k = average 5). Any one of these may be used alone or two or more of them may be used in combination. Among these, a thioester group-containing silane coupling agent having a thioester bond (-S-CO-) in which the mercapto group (-SH) is blocked, for example, 3-octanoylthio-1-propyltriethoxysilane, is preferable for enhancing the effects according to the present embodiment.

[0047] When containing a silane coupling agent, its content is preferably 3 to 20% by mass, more preferably 5 to 15% by mass, based on the content of silica.

[0048] [Other Components] In addition to the above components, the rubber composition according to the present embodiment may be blended with various additives generally used in rubber compositions, such as fillers other than silica, oils, zinc oxide, stearic acid, waxes, processing aids, anti-aging agents, vulcanizing agents, vulcanization accelerators, etc.

[0049] Examples of fillers other than silica include carbon black. The carbon black is not particularly limited, and various known varieties can be used. The content of carbon black is not particularly limited. For example, when used for coloring or the like, it may be 10 parts by mass or less, or 1 to 10 parts by mass, based on 100 parts by mass of the diene rubber component.

[0050] The content of the oil is not particularly limited. For example, it may be 0 to 40 parts by mass, 5 to 40 parts by mass, or 10 to 35 parts by mass, based on 100 parts by mass of the diene rubber component. In addition, when an oil-extended rubber is used as the diene rubber, the amount of oil contained in the oil-extended rubber is also included in the content of the oil.

[0051] The content of zinc oxide is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass, based on 100 parts by mass of the diene rubber component.

[0052] The content of stearic acid is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass with respect to 100 parts by mass of the diene rubber component.

[0053] The content of wax is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass with respect to 100 parts by mass of the diene rubber component.

[0054] The content of the processing aid is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass with respect to 100 parts by mass of the diene rubber component.

[0055] Examples of the anti-aging agent include various anti-aging agents such as amine-ketone type, aromatic secondary amine type, monophenol type, bisphenol type, and benzimidazole type, and any one kind or a combination of two or more kinds can be used. The content of the anti-aging agent is not particularly limited. For example, it may be 0 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 4 parts by mass with respect to 100 parts by mass of the diene rubber component.

[0056] As the vulcanizing agent, sulfur is preferably used. The content of the vulcanizing agent is not particularly limited and may be 0.1 to 10 parts by mass, 0.5 to 5 parts by mass, or 1 to 3 parts by mass with respect to 100 parts by mass of the diene rubber component.

[0057] Examples of the vulcanization accelerator include various vulcanization accelerators such as sulfenamide type, guanidine type, thiuram type, and thiazole type, and any one kind alone or a combination of two or more kinds can be used. The content of the vulcanization accelerator is not particularly limited and may be 0.1 to 10 parts by mass, 1 to 7 parts by mass, or 2 to 5 parts by mass with respect to 100 parts by mass of the diene rubber component.

[0058] [Rubber composition for tire tread] The rubber composition according to this embodiment preferably has a peak temperature of the diene rubber component below -20°C in the temperature curve of tanδ obtained by a dynamic viscoelasticity test with a tensile method of a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% in accordance with JIS K6394:2007 for the vulcanized rubber composition. When the peak temperature of the diene rubber component is below -20°C, it becomes easier to maintain low-temperature performance suitable for applications such as winter tires and all-season tires. The peak temperature of the diene rubber component is more preferably -50°C to -23°C, still more preferably -45°C to -25°C, and still more preferably -40°C to -30°C. Note that the peak temperature of the diene rubber component in the temperature curve of tanδ can be adjusted mainly by the composition of the diene rubber component.

[0059] The rubber composition according to this embodiment preferably has a peak temperature of the thermoplastic elastomer of -20°C or higher and 20°C or lower in the temperature curve of tanδ obtained by a dynamic viscoelasticity test with a tensile method of a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% in accordance with JIS K6394:2007 for the vulcanized rubber composition. When the peak temperature of the thermoplastic elastomer is -20°C to 20°C, it becomes easier to further improve the balance between WET performance and rolling resistance performance. The peak temperature of the thermoplastic elastomer is more preferably -15°C to 18°C, and still more preferably -12°C to 16°C. Note that the peak temperature of the thermoplastic elastomer in the temperature curve of tanδ can be adjusted mainly by the type and amount of the thermoplastic elastomer and the combination with the resin.

[0060] The rubber composition according to this embodiment can be prepared by kneading in accordance with a conventional method using a mixer such as a commonly used Banbury mixer, kneader, roll, etc. That is, for example, in the first mixing stage, other additives excluding the vulcanizing agent and vulcanization accelerator are added and mixed to the diene rubber component, and then the vulcanizing agent and vulcanization accelerator are added and mixed to the obtained mixture in the final mixing stage to prepare the rubber composition.

[0061] The rubber composition thus obtained can be used for the tread of a tire. Examples of the tire include pneumatic tires for various applications and various sizes, such as passenger car tires, large tires for trucks and buses. Preferably, it is used for the tread of winter tires or all-season tires.

[0062] The tire according to one embodiment includes a tread produced using the above rubber composition. That is, the tire according to one embodiment includes a tread rubber made of the above rubber composition. The tread rubber of the tire has a two-layer structure consisting of a cap rubber and a base rubber, and a single-layer structure in which both are integrated. In the case of the single-layer structure, the tread rubber may be formed of the above rubber composition. In the case of the two-layer structure, it is preferable that the outer cap rubber in contact with the road surface is formed of the above rubber composition, but the base rubber disposed inside the cap rubber may be formed of the above rubber composition, or both the cap rubber and the base rubber may be formed of the above rubber composition.

[0063] The manufacturing method of the tire is not particularly limited. For example, the above rubber composition is formed into a predetermined shape by extrusion according to a conventional method to obtain an unvulcanized tread rubber member. By combining the tread rubber member with other tire members, an unvulcanized tire (green tire) is produced. Then, for example, the tire can be manufactured by vulcanization molding at 140°C to 180°C.

Examples

[0064] Examples of the present invention are shown below, but the present invention is not limited to these examples.

[0065] Each component used in the examples and comparative examples is as follows. ·SBR-1: Terminally modified SSBR, styrene content = 10% by mass, "HPR840" manufactured by ENEOS MATERIALS Co., Ltd. ·SBR-2: Unmodified SSBR, styrene content = 17% by mass, "Tufdene 1834" manufactured by Asahi Kasei Corporation, 37.5 parts by mass of oil product per 100 parts by mass of rubber content · SBR-3: Terminally modified SSBR, styrene content = 27.5 mass%, "HPR850" manufactured by ENEOS MATERIALS Co., Ltd. · BR: Nd-BR, "Buna CB22" manufactured by Lanxess Co., Ltd. · NR: RSS#3

[0066] · Carbon black: HAF-HS, "Seast KH" manufactured by Tokai Carbon Co., Ltd. · Silica-1: Nitrogen adsorption specific surface area = 125 m 2 / g, "Ultrasil VN2" manufactured by Evonik · Silica-2: Nitrogen adsorption specific surface area = 180 m 2 / g, "Ultrasil VN3" manufactured by Evonik · Silica-3: Nitrogen adsorption specific surface area = 230 m 2 / g, "9100GR" manufactured by Evonik

[0067] · Coupling agent-1: Sulfide-based, "Si69" manufactured by Evonik · Coupling agent-2: Mercapto-based, "NXT" manufactured by Momentive · Oil: "Process NC140" manufactured by ENEOS Co., Ltd.

[0068] · Resin-1: α-pinene-based liquid resin, "Dercolyte LTG" manufactured by DRT · Resin-2: α-pinene / β-pinene mixed resin, softening point = 115 °C, "SYLVATRAXX4150" manufactured by Clayton · Resin-3: Hydrogenated rosin ester, softening point = 95 °C, "Pentalyn H-E" manufactured by Synthomer · Resin-4: Unhydrogenated C5-based petroleum resin, softening point = 100 °C, "HHC-1100" manufactured by Henghe Materials& Science Technology Co., Ltd. · Resin-5: Unhydrogenated C5-based petroleum resin, softening point = 70 °C, "Quintone B170" manufactured by Nippon Zeon Co., Ltd. · Resin-6: Unhydrogenated C5-based petroleum resin, softening point = 96 °C, "Quintone R100" manufactured by Nippon Zeon Co., Ltd. · Resin - 7: Unhydrogenated C5 / C9 petroleum resin, softening point = 100°C, "Petrotac 90" manufactured by Tosoh Corporation · Resin - 8: Partially hydrogenated C9 petroleum resin, softening point = 120°C, "HM - 1200" manufactured by Henghe Materials & Science Technology Co., Ltd. · Resin - 9: Partially hydrogenated C9 petroleum resin, softening point = 140°C, "HM - 1400" manufactured by Henghe Materials & Science Technology Co., Ltd.

[0069] · Resin - 10: Styrene resin: softening point = 85°C, "SYLVATRAXX 4401" manufactured by Crayton · Resin - 11: Hydrogenated C5 / C9 petroleum resin, softening point = 110°C, "Oppera PR - 383" manufactured by Exxon Mobil · Resin - 12: Partially hydrogenated C9 petroleum resin, softening point = 100°C, "HM - 1000" manufactured by Henghe Materials & Science Technology Co., Ltd.

[0070] · TPE - 1: Hydrogenated product of styrene - butadiene - styrene triblock copolymer (SEBS), content of styrene units = 40% by mass, content of butylene units relative to the total mass of butylene units and ethylene units = 4% by mass, Tg = - 24°C, "S.O.E. S1606" manufactured by Asahi Kasei Corporation

[0071] · TPE - 2: Hydrogenated product of styrene - vinyl isoprene - styrene triblock copolymer, content of styrene units = 20% by mass, content of butylene units = 0% by mass, Tg = - 15°C, "Hybrar 7125F" manufactured by Kuraray Co., Ltd.

[0072] · TPE - 3: Hydrogenated product of styrene - vinyl isoprene·vinyl butadiene - styrene triblock copolymer, content of styrene units = 12% by mass, content of butylene units relative to the total mass of butylene units and ethylene units = 20% by mass, Tg = - 32°C, "Hybrar 7311F" manufactured by Kuraray Co., Ltd.

[0073] · TPE-4: Styrene-vinyl isoprene-styrene triblock copolymer (unhydrogenated), styrene unit content = 20% by mass, butylene unit content = 0% by mass, Tg = 8°C, "Hybrar 5127" manufactured by Kuraray Co., Ltd.

[0074] · TPE-5: Hydrogenated product of styrene-butadiene-styrene triblock copolymer (SEBS), styrene unit content = 28% by mass, butylene unit content = 39% by mass, Tg = -47°C, "SEPTON 8004" manufactured by Kuraray Co., Ltd.

[0075] · Zinc oxide: "Zinc Oxide Type 2" manufactured by Mitsui Kinzoku Kogyo Co., Ltd. · Stearic acid: "Bead Stearic Acid" manufactured by NOF Corporation. · Wax: "OZOACE0355" manufactured by Nippon Seiro Co., Ltd. · Processing aid: "Actiplast PP" manufactured by Rancess Co., Ltd. · Antioxidant: "No Crack 6C" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0076] · Vulcanization accelerator - 1: "Nocceler D" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. · Vulcanization accelerator - 2: "Nocceler CZ-G (CZ)" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd. · Sulfur: "Powdered Sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.

[0077] Using a Banbury mixer, according to the formulations (parts by mass) shown in Tables 1 to 4 below, first, in the first mixing stage, compounding agents excluding sulfur and vulcanization accelerators were added to the diene rubber component and kneaded (discharge temperature = 155°C). Then, sulfur and vulcanization accelerators were added to the obtained kneaded product in the final mixing stage and kneaded (discharge temperature = 90°C) to prepare a rubber composition. Note that the amount in parentheses for SBR-2 in the table is the amount as the rubber content. The styrene amount in the table is the total styrene amount in the diene rubber component.

[0078] For each of the obtained rubber compositions, the 300% tensile stress (S300) was measured, and the peak temperatures of the diene rubber component and the thermoplastic elastomer were determined, and the WET performance and the rolling resistance performance were evaluated. The measurement methods and evaluation methods are as follows.

[0079] [S300] A tensile test conforming to JIS K6251:2017 was conducted. Specifically, the rubber composition was vulcanized at 170 °C for 15 minutes to prepare dumbbell-shaped No. 3 test pieces, and the stress (S300) at 300% elongation when a tensile test was carried out using the test pieces was measured, and an index with the value of Comparative Example 1 taken as 100 was determined. The larger the index, the larger the S300.

[0080] [Peak temperatures of diene rubber component and thermoplastic elastomer] A dynamic viscoelasticity test conforming to JIS K6394:2007 was conducted. Specifically, the rubber composition was vulcanized at 170 °C for 15 minutes to prepare test pieces with a width of 5 mm, a thickness of 2 mm, and a length of 30 mm, and a dynamic viscoelasticity test with a tensile method at a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% was carried out with a grip interval of 20 mm. From the obtained temperature curve of tanδ, the peak temperature (temperature at the peak top) of the diene rubber component and the peak temperature (temperature at the peak top) of the thermoplastic elastomer were determined. In the table, the peak temperature of the diene rubber component is shown as "tanδ (rubber)" and the peak temperature of the thermoplastic elastomer is shown as "tanδ (TPE)".

[0081] As an example, FIG. 1 is a temperature curve of tanδ for the rubber composition of Example 3. From the temperature curve shown in FIG. 1, it can be read that the peak temperature of the diene rubber component is -35 °C and the peak temperature of the thermoplastic elastomer is 0 °C.

[0082] [WET performance] A test radial tire (tire size: 215 / 45ZR17) was manufactured by using the rubber composition for the tread rubber and vulcanizing and molding it according to a conventional method. Four of the obtained tires were mounted on a vehicle, and the vehicle was driven on a road surface sprinkled with water to a depth of 2 - 3 mm under the condition of an air temperature of 25°C, and the frictional resistance was measured at a speed of 100 km / h to evaluate the wet grip performance. The frictional resistance value of Comparative Example 1 was expressed as an index with 100 as the reference. The larger the index, the greater the frictional resistance, indicating excellent WET performance.

[0083] [Rolling Resistance Performance (RR Performance)] Regarding the above test radial tire, under the conditions of an air pressure of 230 kPa, a load of 450 kgf (4.4 kN), 23°C, and 80 km / h, the rolling resistance was measured by a rolling resistance measurement drum, and the reciprocal of the rolling resistance was expressed as an index with the value of Comparative Example 1 as 100. The larger the index, the smaller the rolling resistance, indicating excellent rolling resistance performance.

[0084] [Table 1]

[0085] [Table 2]

[0086] [Table 3]

[0087] [Table 4]

[0088] The results are as shown in Tables 1 to 4. Comparative Example 1 is a control formulation with 105 parts by mass of silica, using a sulfide-based silane coupling agent and not containing a thermoplastic elastomer. In Comparative Example 2, where the amount of silica was increased and a mercapto-based silane coupling agent was used, the WET performance improved, but the rolling resistance performance decreased slightly compared to Comparative Example 1.

[0089] In Comparative Example 3, although a thermoplastic elastomer was compounded, an off-specification styrene-based resin was used as the resin. As a result, although the rolling resistance performance improved significantly, the WET performance deteriorated. In Comparative Examples 4 and 5, although a thermoplastic elastomer was compounded, an off-specification hydrogenated petroleum resin with a low softening point was used as the resin. As a result, although the rolling resistance performance improved significantly, the WET performance deteriorated.

[0090] In Comparative Example 6, since a non-hydrogenated thermoplastic elastomer was used, the WET performance improved, but the rolling resistance performance deteriorated. In Comparative Example 7, since a hydrogenated thermoplastic elastomer with a high content of butylene units was used, it was excellent in rolling resistance performance, but the WET performance deteriorated. In Comparative Example 8, since the amount of the thermoplastic elastomer was more than the specified amount and no resin was compounded, it was excellent in rolling resistance performance, but the WET performance deteriorated.

[0091] On the other hand, in Examples 1 to 24, at least one of the WET performance or the rolling resistance performance was improved without degrading the other compared to Comparative Example 1, and the antinomy between the WET performance and the rolling resistance performance was improved. That is, the balance between the WET performance and the rolling resistance performance was improved. From the comparison of Examples 3 to 10, it was found that when using a petroleum resin, especially a hydrogenated petroleum resin with a high softening point, the balance between the WET performance and the rolling resistance performance tended to be further improved compared to when using a terpene-based resin as the resin.

[0092] In addition, for the various numerical ranges described in the specification, their upper limit values and lower limit values can be arbitrarily combined with each other, and all such combinations are considered to be described in this specification as preferred numerical ranges. Also, the description of the numerical range "X to Y" means X or more and Y or less.

Claims

1. A diene rubber component having a total styrene content of less than 10% by mass, A thermoplastic elastomer obtained by hydrogenating a block copolymer of a styrene-based monomer and a diene-based monomer, wherein the content of butylene units represented by -[CH ２ -CH(C ２ H ５ )- is 25% by mass or less based on the total mass of ethylene units represented by -(CH ２ -CH ２ )- and the butylene units, a thermoplastic elastomer, at least one resin selected from the group consisting of terpene resins, unhydrogenated petroleum resins, hydrogenated petroleum resins having a softening point of 115°C or higher, rosin resins, and coumarone-indene resins, and silica, A rubber composition for a tire tread, wherein the amount of the thermoplastic elastomer is 1 to 20 parts by mass with respect to 100 parts by mass of the diene rubber component.

2. The rubber composition for a tire tread according to Claim 1, wherein the diene rubber component contains styrene-butadiene rubber.

3. The rubber composition for a tire tread according to Claim 1, wherein in the temperature curve of tan δ obtained by a dynamic viscoelasticity test of a tensile method with a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% in accordance with JIS K6394:2007 for the vulcanized rubber composition, the peak temperature of the diene rubber component is less than -20°C.

4. The rubber composition for a tire tread according to Claim 1, wherein in the temperature curve of tan δ obtained by a dynamic viscoelasticity test of a tensile method with a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% in accordance with JIS K6394:2007 for the vulcanized rubber composition, the peak temperature of the thermoplastic elastomer is -20°C or higher and 20°C or lower.

5. The rubber composition for a tire tread according to Claim 1, wherein the amount of the resin is 20 to 50 parts by mass with respect to 100 parts by mass of the diene rubber component.

6. The rubber composition for a tire tread according to Claim 1, wherein the content ratio (resin / thermoplastic elastomer) of the resin and the thermoplastic elastomer is 1.5 or more by mass ratio.

7. A tire comprising a tread produced from the rubber composition according to any one of Claims 1 to 6.

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