Rubber composition for tires, and tire

Abstract

The present invention discloses a rubber composition for tires, characterized by comprising 100 parts by mass of a diene-based rubber consisting of a styrene / butadiene copolymer rubber and, mixed therewith, 5-120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less.

Description

Rubber composition for tires and tires

[0001] The present invention relates to a rubber composition for a tire and a tire using the same, more particularly to a rubber composition for a tire that can maintain or improve abrasion resistance and improve wet grip performance, and a tire using the same. The present invention also relates to a rubber composition for a tire that can maintain or improve steering stability and improve both dry grip performance and warm-up performance, and a tire using the same.

[0002] Generally, racing pneumatic tires are available in two types: tires for dry roads and tires for wet roads, with the optimal tire selected depending on the weather and road conditions. For racing tires designed for wet roads, techniques such as incorporating large amounts of high-specific-surface-area fillers or resins have been used to improve wet grip performance, but these techniques have had the drawback of reducing wear resistance. For racing tires designed for dry roads, techniques such as incorporating large amounts of small-particle carbon black or resins have been known to improve grip performance on dry roads (dry grip performance). However, these compounding techniques have the drawback of requiring a long time for dry grip performance to be achieved and reducing warm-up performance. Meanwhile, the incorporation of softeners such as low-softening-point resins or oils has also been investigated, but neither technique is able to achieve both dry grip performance and handling stability.

[0003] While the techniques for blending a rosin-based resin into a rubber composition for tires are found in Patent Documents 1 to 3 listed below, there is no disclosure or suggestion whatsoever of a technique for blending a specific amount of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less with a diene-based rubber consisting solely of a styrene-butadiene copolymer rubber, which will be described below.

[0004] Japanese Patent Application Publication No. 2018-193444 Japanese Patent Application Publication No. 7151083 Japanese Patent Application Publication No. 2021-95465

[0005] Therefore, an object of the present invention is to provide a rubber composition for a tire that can maintain or improve abrasion resistance and improve wet grip performance, and a tire using the same. Another object of the present invention is to provide a rubber composition for a tire that can maintain or improve steering stability and improve both dry grip performance and warm-up performance, and a tire using the same.

[0006] As a result of extensive research, the present inventors have found that the above-mentioned problems can be solved by blending a specific amount of a hydrogenated rosin ester resin having an acid value within a specific range with a diene rubber consisting solely of a styrene-butadiene copolymer rubber, and have thereby been able to complete the present invention.

[0007] That is, the present invention provides a rubber composition for tires, characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and a nitrogen adsorption specific surface area (N ２ SA) is 100 to 500m ２ The present invention provides a rubber composition for tires, which is characterized by compounding 50 to 200 parts by mass of carbon black having a molecular weight of 1 / g.

[0008] The rubber composition for a tire of the present invention is characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of a diene rubber consisting solely of a styrene-butadiene copolymer rubber, and therefore it is possible to provide a rubber composition for a tire that can maintain or improve abrasion resistance and improve wet grip performance, and a tire using the same. Also, the rubber composition for a tire of the present invention is characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and a nitrogen adsorption specific surface area (N ２SA) is 100 to 500m ２ The rubber composition is characterized by blending 50 to 200 parts by mass of carbon black having a molecular weight of 1 / g or more, and therefore it is possible to provide a rubber composition for tires that can maintain or improve steering stability and improve both dry grip performance and warm-up performance, and a tire using the same.

[0009] The rosin ester resin used in the present invention has an acid value of 30 mgKOH / g or less, which enhances compatibility with styrene-butadiene copolymer rubber compared to resins with higher acid values. Furthermore, the rosin ester resin does not exhibit excessive reactivity when a vulcanization accelerator is used, thereby suppressing decreases in break strength and hardness. Furthermore, the hydrogenation of the rosin ester resin enhances compatibility with styrene-butadiene copolymer rubber. This is believed to provide a rubber composition for tires that can maintain or improve abrasion resistance and improve wet grip performance. Furthermore, because the rosin ester resin possesses the above properties, when blended with carbon black, it can maintain or improve steering stability and simultaneously enhance dry grip performance and warm-up performance.

[0010] The present invention will be described in further detail below. A rubber composition for tires characterized by blending 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less with 100 parts by mass of a diene rubber consisting solely of a styrene-butadiene copolymer rubber may be referred to as embodiment (1) of the present invention. Also, a rubber composition for tires characterized by blending 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less with 100 parts by mass of a diene rubber consisting solely of a styrene-butadiene copolymer rubber and a nitrogen adsorption specific surface area (N ２ SA) is 100 to 500m ２ A rubber composition for a tire characterized by compounding 50 to 200 parts by mass of carbon black having a molecular weight of 1 / g or more is sometimes referred to as embodiment (2) of the present invention.

[0011] (Diene-Based Rubber) In the above-described embodiments (1) and (2) of the present invention, the diene-based rubber used in the present invention consists solely of styrene-butadiene copolymer rubber (SBR). The molecular weight and microstructure of the SBR are not particularly limited, and it may be terminally modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl, or the like, or may be epoxidized. The weight-average molecular weight (Mw) of the SBR is not particularly limited, but for reasons such as the superior effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight-average molecular weight (Mw) and number-average molecular weight (Mn) are values ​​calculated in terms of standard polystyrene obtained by gel permeation chromatography (GPC) measurement. In the embodiment (2) of the present invention, the SBR used in the present invention preferably has a styrene content of less than 35% by mass, more preferably 30% by mass or less. By setting the styrene content within the above range, the polarity of the SBR is reduced, and compatibility with the rosin ester resin can be further improved.

[0012] (Rosin Ester Resin) In the above-described embodiments (1) and (2) of the present invention, the rosin ester resin used in the present invention can be obtained by reacting a raw material rosin ester, such as gum rosin, tall oil rosin, or wood rosin, with an alcohol and polymerizing the resulting mixture in the presence of a catalyst. The esterification and polymerization reactions may be carried out under known conditions. The resulting rosin ester resin may be purified as needed, and the color of the purified rosin ester resin typically has a Gardner color scale of 10 or less. The rosin ester resin used in the present invention has an acid value of 30 mgKOH / g or less. Having an acid value of 30 mgKOH / g or less enhances compatibility with SBR, thereby achieving the effects described above. In the present invention, an acid value of 20 mgKOH / g or less is even more preferable. Furthermore, the rosin ester resin used in the present invention is hydrogenated. Hydrogenation enhances compatibility with styrene-butadiene copolymer rubber, thereby improving breaking strength. The hydrogenation is preferably carried out until the Hazen color number (JIS K0071-1) of the rosin ester resin is 200 or less. From the viewpoint of improving the effects of the present invention, the hydroxyl value of the rosin ester resin used in the present invention is preferably 50 mgKOH / g or less, more preferably 30 mgKOH / g or less. Having a hydroxyl value of 50 mgKOH / g or less enhances compatibility with SBR, further improving wet grip performance and dry grip performance. From the viewpoint of improving the effects of the present invention, the weight-average molecular weight of the rosin ester resin used in the present invention is preferably 200 to 1800, more preferably 300 to 1500, the glass transition temperature is preferably 20 to 100°C, more preferably 30 to 90°C, and the softening point (JIS K6220-1) is preferably 60 to 150°C, more preferably 70 to 140°C.The rosin ester resin used in the present invention may be a commercially available product, and examples thereof include KE-359 (hydrogenated rosin ester resin, acid value = 13 mgKOH / g, hydroxyl value = 45 mgKOH / g), KE-100 (hydrogenated rosin ester resin, acid value = 6 mgKOH / g, hydroxyl value = 0 mgKOH / g), and KE-311 (hydrogenated rosin ester resin, acid value = 7 mgKOH / g, hydroxyl value = 0 mgKOH / g), all manufactured by Arakawa Chemical Industries, Ltd.

[0013] (Bulking ratio) In the form (1) of the present invention, the rubber composition of the present invention is characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of a diene rubber consisting solely of a styrene-butadiene copolymer rubber. If the blending amount of the rosin ester resin is less than 5 parts by mass, the blending amount is too small to achieve the effects of the present invention. Conversely, if it exceeds 120 parts by mass, the breaking strength decreases. The blending amount of the rosin ester resin is preferably 15 to 110 parts by mass, more preferably 25 to 100 parts by mass, based on 100 parts by mass of the diene rubber. In the form (2) of the present invention, the rubber composition of the present invention is characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and a nitrogen adsorption specific surface area (N ２ SA) is 100 to 500m ２The rubber composition is characterized in that 50 to 200 parts by mass of carbon black having a molecular weight of 1 / g is blended. If the blending amount of the rosin ester resin is less than 5 parts by mass, the blending amount is too small to achieve the effects of the present invention. Conversely, if it exceeds 120 parts by mass, the hardness (100°C) decreases. The blending amount of the rosin ester resin is preferably 5 to 120 parts by mass, more preferably 15 to 110 parts by mass, and particularly preferably 25 to 100 parts by mass, per 100 parts by mass of diene rubber. Furthermore, if the blending amount of the carbon black is less than 50 parts by mass, the hardness (100°C) decreases, and conversely, if it exceeds 200 parts by mass, the hardness (20°C) decreases. The blending amount of the carbon black is preferably 50 to 200 parts by mass, more preferably 70 to 180 parts by mass, per 100 parts by mass of diene rubber. The nitrogen adsorption specific surface area (N ２ The nitrogen adsorption specific surface area (N SA) range is an effective range for achieving the effects of the present invention, and the more preferable range is ２ SA) Range is 120-400m ２ / g. The nitrogen adsorption specific surface area (N ２ SA) is a value determined in accordance with JIS K6217-2.

[0014] In the embodiment (1) of the present invention, the rubber composition for a tire of the present invention has a nitrogen adsorption specific surface area (N ２ SA) is 100 to 300 m ２ It is preferable to blend silica having a nitrogen adsorption specific surface area (N ２ SA) is 120-260m ２ The compounding amount of silica is preferably 50 to 250 parts by mass, more preferably 70 to 200 parts by mass, per 100 parts by mass of the diene rubber. The nitrogen adsorption specific surface area (N ２ SA) is a value determined in accordance with JIS K6217-2. In the present invention, silica made from a biomass material such as rice husk may also be used.

[0015] In the embodiment (1) of the present invention, the rubber composition for a tire of the present invention preferably contains aluminum hydroxide, from the viewpoint of further improving the effects of the present invention. The amount of aluminum hydroxide added is preferably 10 parts by mass or more, more preferably 15 to 60 parts by mass, per 100 parts by mass of the diene rubber.

[0016] In the embodiment (1) of the present invention, the rubber composition for a tire of the present invention can be blended with a silane coupling agent. As the silane coupling agent, a silane coupling agent having a mercapto group is preferred due to its high reactivity. The blending amount of the silane coupling agent is preferably 2.5 to 30 mass % relative to the silica, and more preferably 5 to 12 mass %.

[0017] (Liquid Aromatic Vinyl-Conjugated Diene Rubber) In the embodiment (2) of the present invention, the rubber composition for a tire of the present invention preferably contains a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40°C or higher. By incorporating such a liquid aromatic vinyl-conjugated diene rubber, the glass transition temperature (Tg) of the rubber composition is increased, thereby improving dry grip performance. Furthermore, the liquid aromatic vinyl-conjugated diene rubber is compatible with SBR and enhances the dispersibility of the rosin ester resin used in the present invention, thereby enhancing the effects of the present invention. A liquid aromatic vinyl-conjugated diene rubber is preferably a liquid styrene-butadiene copolymer (liquid SBR). The liquid SBR has a weight-average molecular weight of 2,000 to 40,000, preferably 3,000 to 20,000. The glass transition temperature of the liquid SBR is -40°C or higher, as described above, and is more preferably -20°C to -5°C. Commercially available liquid SBRs can be used, such as RICON 100 manufactured by Cray Valley and L-SBR 820 manufactured by Kuraray Co., Ltd. The Tg used in the present invention is the midpoint temperature of the transition region measured by differential scanning calorimetry (DSC) at a heating rate of 20°C / min. The liquid aromatic vinyl-conjugated diene rubber used in the present invention is a liquid at 23°C. Therefore, it is distinguished from the diene rubber, which is solid at this temperature. The amount of the liquid aromatic vinyl-conjugated diene rubber compounded is preferably 5 to 50 parts by mass, more preferably 10 to 45 parts by mass, per 100 parts by mass of the diene rubber.

[0018] (Other Components) In addition to the above-mentioned components, the rubber composition for a tire of the present invention may contain various additives that are generally compounded in rubber compositions, such as vulcanization or crosslinking agents; vulcanization or crosslinking accelerators; zinc oxide; various fillers such as clay, talc, and calcium carbonate; antioxidants; and plasticizers. These additives can be kneaded by a general method to form a composition, which can then be used for vulcanization or crosslinking. The amounts of these additives that can be compounded may be conventional amounts, as long as they do not deviate from the object of the present invention.

[0019] In the above-described embodiment (1) of the present invention, the rubber composition for a tire of the present invention can maintain or improve abrasion resistance and improve wet grip performance, and therefore can be suitably used in tire treads, particularly capped treads, preferably racing tire treads, and particularly capped treads. The tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, and other gases. In the above-described embodiment (2) of the present invention, the rubber composition for a tire of the present invention can maintain or improve steering stability and improve both dry grip performance and warm-up performance, and therefore can be suitably used in tire treads, particularly capped treads, preferably racing tire treads, and particularly capped treads. The tire of the present invention is preferably a pneumatic tire, and can be filled with air, an inert gas such as nitrogen, and other gases.

[0020] The present invention will be further explained below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0021] Standard Example 1, Examples 1-7, and Comparative Examples 1-4 Sample Preparation: In the formulation (parts by mass) shown in Table 1, the components excluding the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.7-liter internal Banbury mixer, and the rubber was discharged from the mixer and cooled to room temperature. The rubber was then placed back into the mixer, and the vulcanization accelerator and sulfur were added and further kneaded to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a specified mold at 160°C for 20 minutes to obtain vulcanized rubber test pieces, and the physical properties of the vulcanized rubber test pieces were measured using the test methods shown below.

[0022] Breaking strength: According to JIS K6251, No. 3 dumbbell-shaped sample pieces were punched out from the vulcanized rubber test pieces and subjected to a tensile test at a tensile speed of 500 mm / min to measure the breaking elongation (%). The results were expressed as an index, with the value of Standard Example 1 being 100. A larger index indicates better breaking strength and abrasion resistance. Wet grip performance: According to JIS K6394, tan δ (0°C) was measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under conditions of initial strain = 10%, amplitude = ±2%, and frequency = 20 Hz, and this value was used to evaluate wet grip performance. The results were expressed as an index, with Standard Example 1 being 100. A larger index indicates better wet grip performance. The results are also shown in Table 1.

[0023]

[0024] The annotations in Table 1 are as follows: *1: SBR (Nipol NS522 manufactured by ZS Elastomers Co., Ltd., oil extension amount = 37.5 parts by mass per 100 parts by mass of SBR) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *3: Silica-1 (Ultrasil 7000GR(N2SA 171m manufactured by Evonik) 2 / g) *4: Silica-2 (Solvay Zeosil 1085GR (N2SA 86m 2 / g) *5: Carbon black (Seast 9 manufactured by Tokai Carbon Co., Ltd.) *6: Aluminum hydroxide (BF013 manufactured by Nippon Light Metal Co., Ltd.) *7: Resin-1 (Gum Rosin WW manufactured by Arakawa Chemical Industries, Ltd., unhydrogenated rosin resin, acid value 170 mgKOH / g, hydroxyl value 0 mgKOH / g) *8: Resin-2 (Alcon P-90 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated petroleum resin, acid value 0 mgKOH / g, hydroxyl value 0 mgKOH / g) *9: Resin-3 (Ester Gum 105 manufactured by Arakawa Chemical Industries, Ltd., unhydrogenated rosin ester resin, acid value 14 mgKOH / g, hydroxyl value 0 mgKOH / g) *10: Resin-4 (KR-140 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin resin, acid value 147 mgKOH / g, hydroxyl value 0 mgKOH / g) *11: Resin-5 (KE-359 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 13 mg KOH / g, hydroxyl value 45 mg KOH / g) *12: Resin-6 (KE-100 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 6 mg KOH / g, hydroxyl value 0 mg KOH / g) *13: Resin-7 (KE-311 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 7 mg KOH / g, hydroxyl value 0 mg KOH / g) *14: Silane coupling agent-1 (Si69 manufactured by Evonik, bis(3-triethoxysilylpropyl) tetrasulfide) *15: Silane coupling agent-2: NXT-Z45 manufactured by Momentive, silane coupling agent having a mercapto group) *16: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu K.K.) *17: Stearic acid (Beads Stearic Acid YR manufactured by NOF Corporation) *18: Zinc oxide (Zinc oxide 3 types manufactured by Seido Chemical Industry Co., Ltd.) *19: Antioxidant (6PPD manufactured by Flexis) *20: Vulcanization accelerator-1 (Suncerer D-G manufactured by Sanshin Chemical Industry Co., Ltd.) *21: Vulcanization accelerator-2 (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *22: Sulfur (Kinka-jirushi oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0025] The results in Table 1 show that the rubber compositions for tires in the Examples contain 100 parts by mass of diene rubber consisting solely of styrene-butadiene copolymer rubber and 5 to 120 parts by mass of hydrogenated rosin ester resin with an acid value of 30 mgKOH / g or less. Therefore, compared to Reference Example 1, the abrasion resistance is maintained or improved, and wet grip performance is improved. In contrast, Comparative Example 1 uses a hydrogenated petroleum resin, resulting in decreased breaking strength and worsened abrasion resistance. Comparative Example 2 uses a non-hydrogenated rosin ester resin, resulting in decreased abrasion resistance and wet grip performance. Comparative Example 3 uses a rosin ester resin with an acid value exceeding the upper limit specified in the present invention, resulting in decreased wet grip performance. Comparative Example 4 uses a butadiene rubber (BR), resulting in decreased wet grip performance.

[0026] Standard Example 2, Examples 8-13, and Comparative Examples 5-9: Sample Preparation: In the formulation (parts by mass) shown in Table 2, the components excluding the vulcanization accelerator and sulfur were kneaded for 5 minutes in a 1.7-liter internal Banbury mixer, and the rubber was discharged from the mixer and cooled to room temperature. The rubber was then re-charged into the same mixer, and the vulcanization accelerator and sulfur were added and further kneaded to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a specified mold at 160°C for 20 minutes to obtain vulcanized rubber test pieces, and the physical properties of the vulcanized rubber test pieces were measured using the test methods shown below.

[0027] Warm-up performance: Hardness was measured at 20°C in accordance with JIS K6253, and dry grip performance was evaluated using this value. The results were expressed as an index, with the value for Standard Example 2 being 100. A smaller index indicates better warm-up performance. Steering stability: Hardness was measured at 100°C in accordance with JIS K6253, and steering stability was evaluated using this value. The results were expressed as an index, with the value for Standard Example 2 being 100. A larger index indicates higher hardness at 100°C and better steering stability. Dry grip performance: In accordance with JIS K6394, tan δ (100°C) was measured using a viscoelasticity spectrometer manufactured by Toyo Seiki Seisakusho, Ltd. under conditions of initial strain = 10%, amplitude = ±2%, and frequency = 20 Hz, and dry grip performance was evaluated using this value. The results were expressed as an index, with the value for Standard Example 2 being 100. A larger index indicates better dry grip performance. The results are also shown in Table 2.

[0028]

[0029] The annotations in Table 2 are as follows: *1: SBR-1 (Nipol 1739 manufactured by Nippon Zeon Co., Ltd., styrene content = 40 mass%, oil extension amount = 37.5 mass parts per 100 mass parts of SBR) *2: SBR-2 (Nipol 1723 manufactured by Nippon Zeon Co., Ltd., styrene content = 23.5 mass%, oil extension amount = 37.5 mass parts per 100 mass parts of SBR) *3: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd.) *4: Carbon black-1 (Seaste 9 (N2SA 142m manufactured by Tokai Carbon Co., Ltd.) 2 / g) *5: Carbon black-2 (Cabot Japan Co., Ltd. Show Black N339 (N2SA 94m 2 / g)) *6: Resin-1 (Arakawa Chemical Industries, Ltd. Gum Rosin WW, unhydrogenated rosin resin, acid value 170 mg KOH / g, hydroxyl value 0 mg KOH / g) *7: Resin-2 (Arakawa Chemical Industries, Ltd. Alcon P-90, hydrogenated petroleum resin, acid value 0 mg KOH / g, hydroxyl value 0 mg KOH / g) *8: Resin-3 (Arakawa Chemical Industries, Ltd. Ester Gum 105, unhydrogenated rosin ester resin, acid value 14 mg KOH / g, hydroxyl value 0 mg KOH / g) *9: Resin-4 (Arakawa Chemical Industries, Ltd. KR-140, hydrogenated rosin resin, acid value 147 mg KOH / g, hydroxyl value 0 mg KOH / g) *10: Resin-5 (Arakawa Chemical Industries, Ltd. KE-359, hydrogenated rosin ester resin, acid value 13 mg KOH / g, hydroxyl value 45mgKOH / g) *11: Resin-6 (KE-100 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 6mg KOH / g, hydroxyl value 0mgKOH / g) *12: Resin-7 (KE-311 manufactured by Arakawa Chemical Industries, Ltd., hydrogenated rosin ester resin, acid value 7mg KOH / g, hydroxyl value 0mgKOH / g) *13: Liquid SBR (RICON 100 manufactured by Cray Valley, weight average molecular weight = 6400, Tg = -15°C) *14: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.) *15: Stearic acid (Beads Stearic Acid YR manufactured by NOF Corporation) *16: Zinc oxide (Zinc oxide type 3 manufactured by Seido Chemical Industry Co., Ltd.) *17: Antioxidant (6PPD manufactured by Flexis) *18: Vulcanization accelerator (Noccela CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) * 19: Sulfur (Kinka-in oil-filled fine sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.)

[0030] From the results in Table 2, the rubber compositions for tires of the examples contain 100 parts by mass of diene rubber consisting of only styrene-butadiene copolymer rubber, 5 to 120 parts by mass of hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less, and a nitrogen adsorption specific surface area (N ２ SA) is 100 to 500m ２It can be seen that, compared to Reference Example 2, handling stability was maintained or improved, and dry grip performance and warm-up performance were simultaneously improved, since 50 to 200 parts by mass of carbon black with a carbon black content of 1 / g were blended. In contrast, Comparative Example 5 is an example in which a hydrogenated petroleum resin was used, and therefore handling stability and dry grip performance were deteriorated. Comparative Example 6 is an example in which a non-hydrogenated rosin ester resin was used, and therefore warm-up performance was deteriorated. Comparative Example 7 is an example in which a rosin ester resin with an acid value exceeding the upper limit specified in the present invention was used, and therefore warm-up performance was deteriorated. Comparative Example 8 is an example in which the nitrogen adsorption specific surface area (N ２ Since the SA) was outside the range of the present invention, the handling stability and dry grip performance were deteriorated. Comparative Example 9 is an example in which butadiene rubber (BR) was compounded, so the handling stability and dry grip performance were deteriorated.

[0031] The present disclosure includes the following embodiments. Embodiment 1: A rubber composition for a tire, characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of a diene rubber consisting solely of a styrene-butadiene copolymer rubber. Embodiment 2: The rubber composition for a tire according to Embodiment 1, characterized in that the rosin ester resin has a hydroxyl value of 50 mgKOH / g or less. Embodiment 3: A rubber composition for a tire, characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less is blended with 100 parts by mass of the diene rubber. ２ SA) is 100 to 300 m ２The rubber composition for a tire according to embodiment 1 or 2, characterized in that 50 to 250 parts by mass of silica having an acid value of 30 mgKOH / g or less and 50 to 250 parts by mass of silica having an acid value of 30 mgKOH / g / g are blended. Embodiment 4: The rubber composition for a tire according to any one of embodiments 1 to 3, characterized in that 10 parts by mass or more of aluminum hydroxide are further blended with 100 parts by mass of the diene rubber. Embodiment 5: The rubber composition for a tire according to embodiment 3, characterized in that 2.5 to 30% by mass of a silane coupling agent having a mercapto group is further blended with 100 parts by mass of the diene rubber. Embodiment 6: The rubber composition for a tire according to embodiment 6, characterized in that 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and 50 to 250 parts by mass of silica having an acid value of 30 mgKOH / g / g are blended with 100 parts by mass of the diene rubber. ２ SA) is 100 to 500m ２ A rubber composition for a tire, characterized in that 50 to 200 parts by mass of carbon black having a molecular weight of 1 / g is blended therein. Embodiment 7: The rubber composition for a tire according to embodiment 6, characterized in that the styrene-butadiene copolymer rubber has a styrene content of less than 35% by mass. Embodiment 8: The rubber composition for a tire according to embodiment 6 or 7, characterized in that the rubber composition further contains 5 to 50 parts by mass of a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40°C or higher per 100 parts by mass of the diene rubber. Embodiment 9: A tire using the rubber composition for a tire according to any one of embodiments 1 to 8 in a cap tread.

Claims

1. A rubber composition for tires, comprising 100 parts by mass of a diene rubber consisting solely of a styrene-butadiene copolymer rubber, and 5 to 120 parts by mass of a hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less.

2. The rubber composition for tires according to claim 1, wherein the hydroxyl value of the rosin ester resin is 50 mgKOH / g or less.

3. For 100 parts by mass of the diene rubber, a nitrogen adsorption specific surface area (N ２ SA) is 100 to 300 m ２ 2. The rubber composition for tires according to claim 1, further comprising 50 to 250 parts by mass of silica having a molecular weight of 1 / g.

4. The rubber composition for tires according to claim 1, further comprising 10 parts by mass or more of aluminum hydroxide per 100 parts by mass of the diene rubber.

5. The rubber composition for tires according to claim 3, further comprising 2.5 to 30 mass % of a silane coupling agent having a mercapto group blended with respect to the silica.

6. For 100 parts by mass of diene rubber consisting only of styrene-butadiene copolymer rubber, 5 to 120 parts by mass of hydrogenated rosin ester resin having an acid value of 30 mgKOH / g or less and a nitrogen adsorption specific surface area (N ２ SA) is 100 to 500m ２ 2. A rubber composition for tires, comprising 50 to 200 parts by mass of carbon black having a molecular weight of 1.0 to 1.0 g / g.

7. The rubber composition for tires according to claim 6, characterized in that the styrene-butadiene copolymer rubber has a styrene content of less than 35 mass %.

8. The rubber composition for tires according to claim 6, further comprising 5 to 50 parts by mass of a liquid aromatic vinyl-conjugated diene rubber having a glass transition temperature (Tg) of -40°C or higher, per 100 parts by mass of the diene rubber.

9. A tire using the rubber composition for tires according to claim 1 in the cap tread.

Images