Rubber composition for tire tread and tire

Abstract

To improve a balance among WET performance, rolling resistance performance and snow 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 at least one kind of thermoplastic elastomer selected from the group consisting of a block copolymer of a styrene-based monomer and a diene-based monomer and a hydrogenated product thereof, and the content of a butylene unit is 25 mass% or less with respect to the total mass of an ethylene unit and the butylene unit. The resin is at least one kind selected from the group consisting of a styrene-based resin and a hydrogenated petroleum resin. The amount of the thermoplastic elastomer is 1 to 10 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] In recent years, from the viewpoint of low fuel consumption during vehicle driving, it is required to reduce the rolling resistance of tires, that is, to improve the rolling resistance performance. Also, from the viewpoint of safety, improvement of WET performance, which is the driving performance on a wet road surface at normal temperature, is required. Further, in winter tires and all-season tires, in addition to these performances, improvement of snow performance, which is the driving performance on a snowy road, is also required.

[0003] As a technique for improving WET performance, for example, Patent Document 1 describes that by blending a specific amount of silica and a resin such as a C5-based resin with a rubber component containing a butadiene rubber and regulating 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 blending 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 with a rubber component containing an isoprene-based rubber and a styrene-butadiene-based rubber, and thereby improving the wet grip performance during high-speed driving.

[0005] Patent Document 3 describes blending a thermoplastic elastomer that exhibits a tanδ peak value in the range of -20 to 20°C and has a peak value of 1 or more with respect to a rubber component containing a specific amount of solution-polymerized styrene-butadiene rubber, and thereby improving the WET performance, fatigue resistance, and tear resistance 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 compounding a rubber component with a styrene-alkylene block copolymer having a total styrene unit content of 30% by mass or more and a filler having a CTAB adsorption specific surface area of 110 m 2 / g or less, and thereby highly balancing the low loss property, wet performance, and dry handling property of the tire. In Patent Document 4, the styrene-alkylene block copolymer used has a butylene unit content of 41% by mass or more based on the total mass of the butylene unit and the ethylene unit.

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] Among the above rolling resistance performance, WET performance, and snow performance, the rolling resistance performance and snow performance can be improved by compounding a diene rubber having a low glass transition temperature into the rubber component constituting the tread of the tire. However, when a compounding design is carried out using a diene rubber having a low glass transition temperature, it becomes difficult to sufficiently ensure the WET performance. Therefore, there is a problem that it is difficult to achieve both of these performances in a well-balanced manner.

[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 antagonism between WET performance, rolling resistance performance, and snow performance, that is, improve the balance of these performances, and a tire using the same.

[0010] In Patent Documents 1 to 3, it is described that silica, a thermoplastic elastomer, and a resin are blended with a rubber component containing styrene-butadiene rubber. However, in a blend where the total styrene amount in the rubber component is less than 10% by mass, improving the balance among WET performance, rolling resistance performance, and snow performance is not described. 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 a material 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, At least one thermoplastic elastomer selected from the group consisting of a block copolymer of a styrene-based monomer and a diene-based monomer and a hydrogenated product thereof, wherein the content of butylene units represented by -[CH2-CH(C2H5)]- is 25% by mass or less with respect to 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 a styrene-based resin and a hydrogenated petroleum resin, and, Silica, 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 10 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 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 diene rubber component is -20°C or lower, the rubber composition for a tire tread according to [1] or [2]. [4] The glass transition temperature of the thermoplastic elastomer is -35°C or higher and 10°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 15 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]. [Effect of the Invention]

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

[0014]

Figure 1

[0015] The rubber composition for a tire tread according to an 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 the present 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. When the total styrene content of the diene rubber component is less than 10% by mass, the glass transition temperature of the diene rubber component becomes lower. In the present embodiment, on the premise of using such a diene rubber component, by combining with a specific thermoplastic elastomer and resin, the balance among the snow performance, WET performance, and rolling resistance performance can be improved. 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. The diene rubber refers to a rubber having a repeating unit corresponding to a diene monomer having a conjugated double bond and having 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 entire diene rubber component, and is calculated by Σ (content (% by mass) of each diene rubber × styrene content (% by mass) in each rubber / 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, or unmodified styrene-butadiene rubber (unmodified SBR) without modification may 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) is contained in an amount of 50% by mass or more, more preferably 60% by mass or more, based on 100% by mass of SBR.

[0019] As the modified SBR (preferably modified SSBR), SBR modified by a functional group introduced at 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 only of SBR, or may contain other diene rubbers. Preferably, in order to make the total styrene content 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, and the like. 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 contain 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 contain 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 contain 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 contain 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 contain 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 a thermoplastic elastomer, it becomes easier to improve the rolling resistance performance.

[0023] As the thermoplastic elastomer, at least one styrenic thermoplastic elastomer selected from the group consisting of block copolymers of styrenic monomers and diene monomers and hydrogenated products thereof is used. The styrenic thermoplastic elastomer is a block copolymer having a block derived from a styrenic monomer as a hard segment and a block derived from a diene monomer as a soft segment, and may be a hydrogenated product in which the diene part is hydrogenated or an unhydrogenated product that has not been 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 styrenic monomer include styrene, α-methylstyrene, p-methylstyrene, etc., and styrene is preferred. Examples of the diene 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 styrene-butadiene-styrene triblock copolymer (SBS) and its hydrogenated product (SEBS), styrene-isoprene-styrene triblock copolymer (SIS) and its hydrogenated product (SEPS, SEEPS), styrene-isoprene-butadiene-styrene triblock copolymer and its hydrogenated product, styrene-butadiene diblock copolymer and its hydrogenated product, and styrene-isoprene diblock copolymer and its hydrogenated product. 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 a 1,4-bond, a 1,2-bond, or may include both. Therefore, for example, the above-mentioned SBS and its hydrogenated product include styrene-vinylbutadiene-styrene triblock copolymer and its hydrogenated product, SIS and its hydrogenated product include styrene-vinylisoprene-styrene triblock copolymer and its hydrogenated product, and styrene-isoprene-butadiene-styrene triblock copolymer and its hydrogenated product include styrene-vinylisoprene-vinylbutadiene-styrene triblock copolymer and its hydrogenated product.

[0026] The styrenic thermoplastic elastomer has, as its constituent units, (a) styrene units derived from a styrenic monomer, and (b1) at least one selected from the group consisting of unsaturated 1,2-bond units and 1,4-bond units, and saturated ethylene units and butylene units derived from butadiene, and / or (b2) at least one selected from the group consisting of unsaturated 1,2-bond units, 3,4-bond units and 1,4-bond units, and saturated ethylene units, propylene units and isopropylethylene (hydrogenated vinylisoprene) units derived from isoprene. It may contain.

[0027] In this embodiment, as the thermoplastic elastomer, one having a content of butylene units represented by -[CH2-CH(C2H5)]- of 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 the butylene units being 25% by mass or less, the balance among the WET performance, the rolling resistance performance, and the snow performance can be improved. The content of the butylene units may be 0% by mass. For example, when butadiene is not included as the diene monomer, the content of the butylene units is 0% by mass, that is, no butylene units are included. Further, even when butadiene is included as the diene monomer, in the unhydrogenated product, since its constituent units are unsaturated 1,2-bond units and / or 1,4-bond units, no butylene units are included. The content of the 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 the 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 the butylene units, ethylene units, and styrene units in the thermoplastic elastomer are 1 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 10°C or lower. Thereby, it is easy to maintain the WET performance. The Tg of the thermoplastic elastomer is more preferably -35°C to 0°C, 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 a 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 10 parts by mass, more preferably 3 to 9 parts by mass, and even more preferably 4 to 8 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] The rubber composition according to the present embodiment is blended with at least one resin selected from the group consisting of a styrene resin and a hydrogenated petroleum resin. These are resins having high compatibility with the diene rubber component, and although they tend to reduce the WET performance, they improve the rolling resistance performance and the snow performance. On the other hand, although the above (B) thermoplastic elastomer tends to reduce the snow performance, it improves the WET performance and the rolling resistance performance. Therefore, by combining the above (B) thermoplastic elastomer with a resin having high compatibility, the balance of the WET performance, the rolling resistance performance, and the snow performance can be improved.

[0034] The styrene resin is a resin obtained by polymerizing a styrene-based monomer as a constituent monomer, and is a general term for resins composed of a polymer of a styrene-based monomer and a copolymer having a styrene-based monomer as a main component (50% by mass or more). The styrene resin may be a homopolymer obtained by polymerizing one type of styrene-based monomer alone, a copolymer obtained by copolymerizing two or more types of styrene-based monomers, or a copolymer of a styrene-based monomer and another monomer copolymerizable therewith. Examples of the styrene-based monomer include styrene, α-methylstyrene, p-methylstyrene, and the like.

[0035] Specific examples of styrene resins include polystyrene, α-methylstyrene homopolymer, styrene / α-methylstyrene copolymer, styrene monomer / aliphatic monomer copolymer, α-methylstyrene / aliphatic monomer copolymer, styrene monomer / α-methylstyrene / aliphatic monomer copolymer, etc. Any one of these may be used alone or two or more of them may be used in combination. Among these, polystyrene, α-methylstyrene homopolymer, and styrene / α-methylstyrene copolymer are preferred.

[0036] Hydrogenated petroleum resin is a hydrogenated petroleum resin and includes those that are partially hydrogenated. Examples of petroleum resins 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). Any one of these may be used alone or two or more of them may be used in combination.

[0037] C5-based petroleum resin is a resin obtained by cationically polymerizing unsaturated monomers such as isoprene and cyclopentadiene, which are petroleum fractions corresponding to 4 to 5 carbon atoms (C5 fraction). C9-based petroleum resin is a resin obtained by cationically polymerizing monomers such as vinyltoluene, alkylstyrene, and indene, which are petroleum fractions corresponding to 8 to 10 carbon atoms (C9 fraction). C5 / C9-based petroleum resin is a resin obtained by copolymerizing the C5 fraction and the C9 fraction by cationic polymerization.

[0038] The softening point of the styrene resin and the hydrogenated petroleum resin is not particularly limited. For example, it is preferably 50°C to 160°C, more preferably 70°C to 150°C, and still more preferably 80°C to 140°C. Here, the softening point is measured using a ring and ball softening point measuring device in accordance with JIS K6220-1:2001.

[0039] The resin content is preferably 15 to 50 parts by mass, more preferably 25 to 45 parts by mass, and still more preferably 28 to 40 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.

[0040] (C) The content ratio of the resin to the (B) thermoplastic elastomer (resin / thermoplastic elastomer) is preferably 1.5 or more in terms of mass ratio. When the resin / thermoplastic elastomer is 1.5 or more, it becomes easier to further improve the balance of the WET performance, the rolling resistance performance, and the snow performance. The resin / thermoplastic elastomer is more preferably 2 to 15, still more preferably 3 to 10, and even more preferably 3.5 to 8.

[0041] [(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.

[0042] 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.

[0043] The content of the silica 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.

[0044] 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" manufactured by Evonik Degussa, formula: HS-(CH2)3-Si(OC2H5) m (O(C2H4O) k -C 13 H 27 ) n (wherein m = average 1, n = average 2, k = average 5), and other mercapto-based silane coupling agents. 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 a mercapto group (-SH) is blocked, for example, 3-octanoylthio-1-propyltriethoxysilane, is preferable for enhancing the effects according to this embodiment.

[0045] 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.

[0046] [Other components] In the rubber composition according to this embodiment, in addition to the above components, 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, and vulcanization accelerators, can be blended.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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, based on 100 parts by mass of the diene rubber component.

[0051] 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, based on 100 parts by mass of the diene rubber component.

[0052] 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.

[0053] Examples of the antioxidant include various antioxidants 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 antioxidant 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] Sulfur is preferably used as the vulcanizing agent. The content of the vulcanizing agent is not particularly limited. It 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.

[0055] 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. It 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.

[0056] [Rubber Composition for Tire Tread] Regarding the rubber composition according to this embodiment, in the temperature curve of tanδ obtained by the dynamic viscoelasticity test of the 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, it is preferable that the peak temperature of the diene rubber component is -20°C or lower. By having the peak temperature of the diene rubber component be -20°C or lower, it is possible to impart snow 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.

[0057] 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 except for the vulcanizing agent and vulcanization accelerator are added and mixed to the diene rubber component, and then, to the obtained mixture, the vulcanizing agent and vulcanization accelerator are added and mixed in the final mixing stage to prepare the rubber composition.

[0058] The rubber composition thus obtained can be used for the tread of a tire. Examples of the tire include pneumatic tires of various applications and various sizes such as passenger car tires, large tires for trucks and buses. Preferably, because of its excellent snow performance, it is used for the treads of winter tires and all-season tires.

[0059] 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 may have a two-layer structure consisting of a cap rubber and a base rubber, or 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.

[0060] 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. Thereafter, the tire can be manufactured by vulcanization molding at, for example, 140°C to 180°C.

Examples

[0061] Examples of the present invention are shown below, but the present invention is not limited to these examples.

[0062] 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% by mass, "HPR850" manufactured by ENEOS MATERIALS Co., Ltd. ·BR: Nd-BR, "Buna CB22" manufactured by LANXESS Co., Ltd. ·NR: RSS#3

[0063] · 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

[0064] · 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.

[0065] · Resin-1: Terpene resin, softening point = 115 °C, "SYLVATRAXX4150" manufactured by Clayton · Resin-2: Unhydrogenated C5-based petroleum resin, softening point = 100 °C, "HHC-1100" manufactured by Henghe Materials& Science Technology Co., Ltd. · Resin-3: Styrene-based resin: softening point = 85 °C, "SYLVATRAXX 4401" manufactured by Clayton · Resin-4: Hydrogenated C5 / C9-based petroleum resin, softening point = 110 °C, "Oppera PR-383" manufactured by Exxon Mobil · Resin-5: Partially hydrogenated C9-based petroleum resin, softening point = 90 °C, "HM-900" manufactured by Henghe Materials& Science Technology Co., Ltd. · Resin-6: Partially hydrogenated C9-based petroleum resin, softening point = 100 °C, "HM-1000" manufactured by HengheMaterials & Science Technology Co., Ltd. · Resin-7: Partially hydrogenated C9-based petroleum resin, softening point = 140 °C, "HM-1400" manufactured by HengheMaterials & Science Technology Co., Ltd. · Resin - 8: Hydrogenated C5 petroleum resin, softening point = 100°C, "H5 - 1002" manufactured by Henghe Materials & Science Technology Co., Ltd. · Resin - 9: Partially hydrogenated C5 petroleum resin, softening point = 100°C, "H5 - 1000W" manufactured by Henghe Materials & Science Technology Co., Ltd.

[0066] · 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

[0067] · 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.

[0068] · 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.

[0069] · TPE - 4: Styrene - vinyl isoprene - styrene triblock copolymer (unhydrogenated), content of styrene units = 20% by mass, content of butylene units = 0% by mass, Tg = 8°C, "Hybrar 5127" manufactured by Kuraray Co., Ltd.

[0070] · TPE - 5: Hydrogenated product of styrene - butadiene - styrene triblock copolymer (SEBS), content of styrene units = 28% by mass, content of butylene units = 39% by mass, Tg = - 47°C, "SEPTON 8004" manufactured by Kuraray Co., Ltd.

[0071] · Zinc Oxide: "Two Types of Zinc Oxide" 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: "Nocrack 6C" manufactured by Ouchi Shinko Chemical Industry Co., Ltd.

[0072] · Vulcanization Accelerator - 1: "Nocceler D" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. · Vulcanization Accelerator - 2: "Nocceler CZ - G (CZ)" manufactured by Ouchi Shinko Chemical Industry Co., Ltd. · Sulfur: "Powder Sulfur" manufactured by Tsurumi Chemical Industry Co., Ltd.

[0073] Using a Banbury mixer, according to the formulations (parts by mass) shown in Tables 1 to 3 below, first, in the first mixing stage, compounding agents excluding sulfur and vulcanization accelerators were added to the diene - based rubber component and kneaded (discharge temperature = 155°C). Then, in the final mixing stage, sulfur and vulcanization accelerators were added to the obtained kneaded product 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 rubber content. The styrene amount in the table is the total styrene amount in the diene - based rubber component.

[0074] For each of the obtained rubber compositions, the peak temperature of the diene - based rubber component was determined, and the snow performance, rolling resistance performance, and WET performance were evaluated. Their measurement methods and evaluation methods are as follows.

[0075] [Peak Temperature of Diene - based Rubber Component] A dynamic viscoelasticity test in accordance with 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. With a gripping tool interval of 20 mm, a dynamic viscoelasticity test in the tensile method with a frequency of 10 Hz, a static strain of 10%, and a strain amplitude of 0.2% was carried out. From the obtained temperature curve of tanδ, the peak temperature (the temperature at the peak top) of the diene - based rubber component was determined. In the table, the peak temperature of the diene - based rubber component is shown as "tanδ (rubber)".

[0076] As an example, FIG. 1 is a temperature curve of tan δ 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.

[0077] [Snow performance] Using the rubber composition as tread rubber, a test radial tire (tire size: 215 / 45ZR17) was produced by vulcanization molding according to a conventional method. Four of the obtained tires were mounted on a vehicle, and the braking distance was measured when the ABS was activated from a state of traveling on a snow road at a speed of 60 km / h and decelerated to 20 km / h under the condition of an air temperature of -10°C. The reciprocal of the measured value was calculated and shown as an index with the calculated value of Comparative Example 1 being 100. The larger the index, the shorter the braking distance, indicating excellent snow braking performance.

[0078] [Rolling resistance performance (RR performance)] For the above test radial tire, the rolling resistance was measured with a rolling resistance measurement drum 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 reciprocal of the rolling resistance was shown as an index with the value of Comparative Example 1 being 100. The larger the index, the smaller the rolling resistance, indicating excellent rolling resistance performance. [WET performance] Four of the above test radial 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. It was shown as an index with the frictional resistance value of Comparative Example 1 being 100. The larger the index, the greater the frictional resistance, indicating excellent WET performance.

[0079] [Table 1]

[0080] [Table 2]

[0081]

Table 3

[0082] The results are as shown in Tables 1 to 3. Comparative Example 1 is a control formulation in which the amount of silica is 105 parts by mass, a sulfide-based silane coupling agent is used, a terpene resin excellent in WET performance is blended, and no thermoplastic elastomer is blended. In Comparative Example 2, in which the amount of silica was increased, a mercapto-based silane coupling agent was used, and a thermoplastic elastomer was blended, the rolling resistance performance was improved, but since the resin was a terpene resin, the snow performance deteriorated significantly. In Comparative Example 3, the resin was changed from a terpene resin to an unhydrogenated petroleum resin in Comparative Example 2. However, as in Comparative Example 2, although the rolling resistance performance was improved, the snow performance deteriorated.

[0083] In Comparative Example 4, although a hydrogenated petroleum resin was used as the resin, since the amount of the thermoplastic elastomer was more than the specified amount, the rolling resistance performance was improved, but the snow performance deteriorated. In Comparative Example 5, instead of not blending the thermoplastic elastomer with respect to Comparative Example 4, the amount of the resin was increased. Although the snow performance was improved, the rolling resistance performance deteriorated. In Comparative Example 6, since a thermoplastic elastomer having a high content of butylene units was used, it was excellent in rolling resistance performance, but the snow performance deteriorated.

[0084] On the other hand, in Examples 1 to 20, while maintaining the excellent WET performance with respect to Comparative Example 1, both the snow performance and the rolling resistance performance were improved, and the trade-off between the WET performance, the snow performance, and the rolling resistance performance was improved. That is, the balance among the WET performance, the snow performance, and the rolling resistance performance was improved.

[0085] In addition, the various numerical ranges described in the specification can arbitrarily combine their upper limit values and lower limit values, and all of these combinations are described in the specification as preferred numerical ranges. Also, the description of the numerical range of "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, At least one thermoplastic elastomer selected from the group consisting of a block copolymer of a styrene-based monomer and a diene-based monomer and a hydrogenated product thereof, 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 a styrene resin and a hydrogenated petroleum resin, and silica, wherein the amount of the thermoplastic elastomer relative to 100 parts by mass of the diene rubber component is 1 to 10 parts by mass, a rubber composition for a tire tread.

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

3. 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 -20°C or lower, the rubber composition for a tire tread according to Claim 1.

4. The rubber composition for a tire tread according to Claim 1, wherein the glass transition temperature of the thermoplastic elastomer is -35°C or higher and 10°C or lower.

5. The rubber composition for a tire tread according to Claim 1, wherein the amount of the resin is 15 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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