TIRE

Abstract

An object of the present invention is to improve propulsion performance on a snow-covered road surface, and provided is a tire with a tread portion having a groove, wherein the cap rubber layer forming the tread portion contains 40 parts by mass or more and 80 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of its rubber component, and 60 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and is formed from a rubber composition having a loss tangent 10 C. tan measured under the conditions of temperature of 10 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% and in deformation mode; tensile of less than 0.28, and a glass transition temperature Tg ( C.) of 40 C. or lower; and the glass transition temperature Tg ( C.) and the depth G(mm) of the groove satisfy Tg0.5G35.

Claims

1. A tire with a tread portion having a groove, wherein the cap rubber layer forming the tread portion contains 40 parts by mass or more and 80 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of its rubber component, and 60 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and is formed from a rubber composition having a loss tangent 10 C. tan measured under the conditions of temperature of 10 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% and in deformation mode; tensile of less than 0.28, and a glass transition temperature Tg ( C.) of 40 C. or lower; and the glass transition temperature Tg ( C.) and the depth G(mm) of the groove satisfy the following (formula 1).
Tg0.5G35(formula 1)

2. The tire according to claim 1, wherein the styrene-butadiene rubber (SBR) has a styrene content of 20% by mass or less.

3. The tire according to claim 2, wherein the styrene-butadiene rubber (SBR) has a styrene content of 15% by mass or less.

4. The tire according to claim 1, wherein content of the filler is 80 parts by mass or more with respect to 100 parts by mass of the rubber component.

5. The tire according to claim 1, wherein the 10 C. tan is 0.25 or less.

6. The tire according to claim 1, wherein the loss tangent 0 C. tan of the cap rubber layer measured under the conditions of temperature of 0 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, and in deformation mode: tensile, is 0.30 or less.

7. The tire according to claim 1, wherein the 0 C. tan is 0.28 or less.

8. The tire according to claim 1, wherein the loss tangent 30 C. tan of the cap rubber layer measured under the conditions of temperature of 30 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, and in deformation mode: tensile, is 0.26 or less.

9. The tire according to claim 1, wherein the following (formula 2) is satisfied.
Tg0.5G42(Formula 2)

10. The tire according to claim 1, wherein the ratio of the 10 C. tan to the groove depth G (mm) (10 C. tan /G) is 0.025 or less.

11. The tire according to claim 1, wherein the thickness of the cap rubber layer is 10% or more of the entire tread portion.

12. The tire according to claim 1, wherein the land ratio in the tread portion is 40% or more, and the product of the content (parts by mass) of the styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component and the land ratio (%) in the tread portion (SBR contentland ratio) is 6700 or less.

13. The tire according to claim 1, wherein the aspect ratio is 80% or less, the cap layer contains silica, and the product of the silica content (parts by mass) with respect to 100 parts by mass of the rubber component and the aspect ratio (silica contentaspect ratio) is 9000 or less.

Description

EXAMPLE

[0206] Examples considered to be preferable when implementing the present invention are shown below, but the scope of the present invention is not limited to these examples. In the examples, a pneumatic tire (tire size: LT275/70R18, aspect ratio: 70%, land ratio: 63%) made from a composition obtained by using various chemicals mentioned below and changing the formulation according to each Table were evaluated. The results calculated based on the following evaluation methods are shown in Tables 2 to 4.

1. Rubber Composition Forming Cap Rubber Layer

(1) Compounding Material

(a) Rubber Component

[0207] (a-1) SBR-1: Modified S-SBR obtained by the method shown in the next paragraph (Styrene content: 25% by mass, vinyl content: 25% by mass) [0208] (a-2) SBR-2: HPR840 (S-SBR) manufactured by ENEOS Materials Co., Ltd. (Styrene content: 10% by mass, vinyl content: 42% by mass) [0209] (a-3) NR: TSR20 [0210] (a-4) BR: Ubepol BR150B (Hi-cis BR) manufactured by Ube Industries, Ltd. (cis content 97% by mass, trans content 2% by mass, vinyl content 1% by mass)

(Manufacture of SBR-1)

[0211] The above SBR-1 is produced according to the following procedure. First, two autoclaves having an internal volume of 10 L, having an inlet at the bottom and an outlet at the top, equipped with a stirrer and a jacket, were connected in series as reactors. Butadiene, styrene, and cyclohexane were each mixed in a predetermined ratio. This mixed solution is passed through a dehydration column filled with activated alumina, mixed with n-butyllithium in a static mixer to remove impurities. Then, it is continuously supplied from the bottom of the first reactor, further 2,2-bis(2-oxolanyl)propane as a polar substance and n-butyllithium as a polymerization initiator are continuously supplied at a predetermined rate from the bottom of the first reactor, and the internal temperature of the reactor is kept at 95 C. The polymer solution is continuously withdrawn from the top of the first reactor and supplied to the second reactor. The temperature of the second reactor is kept at 95 C., and a mixture of tetraglycidyl-1,3-bisaminomethylcyclohexane (monomer) as a modifier and an oligomer component is continuously added, as a 1000-fold dilution of cyclohexane, at a predetermined rate to carry out the denaturation reaction. This polymer solution is continuously withdrawn from the reactor, an antioxidant is added continuously by a static mixer, and the solvent is removed to obtain the desired modified diene polymer (SBR-1).

[0212] The vinyl content (unit: mass %) of the SBR-1 is determined by infrared spectroscopy from the absorption intensity near 910 cm.sup.1, which is the absorption peak of the vinyl group. Also, the styrene content (unit: % by mass) is determined from the refractive index according to JIS K6383:1995.

(b) Compounding Materials Other than Rubber Components [0213] (b-1) Carbon black: Show Black N134 manufactured by Cabot Japan Co., Ltd. (CTAB specific surface area: 135 m.sup.2/g) [0214] (b-2) Silica: Ultrasil VN3 manufactured by Evonik Industries Co., Ltd. (N.sub.2SA: 175 m.sup.2/g, 18 nm) [0215] (b-3) Silane coupling agent: Si266 manufactured by Evonik Industries (bis(3-triethoxysilylpropyl) disulfide) [0216] (b-4) Resin: Petrotac 90 (C5/C9 copolymer petroleum resin) manufactured by Tosoh Corporation [0217] (b-5) Oil: Diana Process AH-24 (aroma oil) manufactured by Idemitsu Kosan Co., Ltd. [0218] (b-6) Wax: Sannok N manufactured by Ouchi Shinko Chemical Industry Co., Ltd. [0219] (b-7) Anti-aging agent-1: Antigen 6C manufactured by Sumitomo Chemical Co., Ltd. (N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine) [0220] (b-8) Anti-aging agent-2: Antigen RD manufactured by Sumitomo Chemical Co., Ltd. (Polymer of 2,2,4-trimethyl-1,2-dihydroquinoline) [0221] (b-9) Stearic acid: bead stearic acid Tsubaki manufactured by NOF Corporation [0222] (b-10) Zinc oxide: Two types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. [0223] (b-11) Processing aid: EF44 (saturated fatty acid zinc salt) manufactured by Structol Co., Ltd. [0224] (b-12) Sulfur: powdered sulfur (containing 5% oil) manufactured by Tsurumi Chemical Industry Co., Ltd. [0225] (b-13) Vulcanization accelerator: Nocceler CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazylsulfenamide (CBS))

(2) Rubber Composition Forming Cap Rubber Layer

[0226] Using a Banbury mixer, materials other than sulfur and a vulcanization accelerator are kneaded at 150 C. for 5 minutes according to the formulations shown in Tables 2 to 4 to obtain a kneaded product. Note that, each compounding amount is a mass part.

[0227] Next, sulfur and a vulcanization accelerator are added to the kneaded product, and kneaded at 80 C. for 5 minutes using an open roll to obtain a rubber composition forming a cap rubber layer.

2. Rubber Composition Forming Base Rubber Layer

[0228] In parallel, a rubber composition for forming the base rubber layer is obtained based on the formulation shown in Table 1 in the same manner as the rubber composition for forming the cap rubber layer.

TABLE-US-00001 TABLE 1 Compounding amount Compounding material (part by mass) NR (TSR20) 70 BR (UBEPOL-BR150B manufactured by 30 Ube Industries, Ltd.) Carbon black (Show Black N330T 35 manufactured by Cabot Japan Co., Ltd.) Stearic acid 2 (Tsubaki stearic acid manufactured by NOF Corporation) Zinc oxide (Zinc white No.1 manufactured by 4 Mitsui Mining & Smelting Co., Ltd.) Wax (Sannok wax manufactured by Ouchi 2 Shinko Chemical Co., Ltd.) Antiaging agent (Nocrac 6C manufactured by 3 Ouchi Shinko Chemical Industry Co., Ltd) Antiaging agent (Antage RD manufactured 1 by Kawaguchi Chemical Industry Co., Ltd.) Sulfur (powder sulfur manufactured by 1.7 Tsurumi Chemical Industry Co., Ltd.) Vulcanization accelerator (Nocceler CZ-G 1.2 manufactured by Ouchi Shinko Chemical Industry Co., Ltd.)

3. Cap Rubber and Pneumatic Tire

[0229] Each rubber composition is extruded into a predetermined shape with a total thickness of 17.5 mm so that (thickness of cap rubber layer/thickness of base rubber layer)=90/10, and a tread portion is produced.

[0230] After that, it is pasted together with other tire members to form an unvulcanized tire, and press-vulcanized for 10 minutes at 170 C. to produce each pneumatic tire (test tire) of Examples 1 to 17 and Comparative Examples 1 to 5.

4. Calculation of Parameters

[0231] The following parameters are then determined for each test tire.

(1) tan

[0232] From the cap rubber layer of the tread portion of each test tire, a rubber test piece for viscoelasticity measurement is prepared by cutting a size of 20 mm in length4 mm in width2 mm in thickness so that the tire circumferential direction is the long side. For each rubber test piece, tan is measured using Eplexor series manufactured by GABO under the conditions of frequency of 10 Hz, initial strain of 5%, dynamic strain of 1%, and deformation mode: tensile at a temperature of 0 C., 10 C., and 30 C. to obtain 0 C. tan , 10 C. tan and 30 C. tan . The 30 C. tan of the base rubber layer is 0.07.

(2) Tg

[0233] Regarding each measurement sample prepared by cutting out from the cap rubber layer of the tread portion of each test tire with a size of 20 mm in length4 mm in width1 mm in thickness, so that the tire circumferential direction was the long side, tan is measured using Eplexor (registered trademark) series manufactured by GABO under the conditions of frequency of 10 Hz, initial strain of 2%, amplitude of 1%, and a heating rate of 2 C./min, with changing the temperature from 80 C. to 40 C., and the temperature corresponding to the largest tan value in the obtained temperature distribution curve is determined as Tg ( C.).

(3) AE

[0234] Using a vulcanized rubber test piece prepared by cutting out from the cap rubber layer of the tread portion of each test tire, AE (% by mass) is determined according to JIS K 6229:2015.

(4) Groove Depth

[0235] Each test tire is placed in a standardized state, and the height from the groove bottom to the opening of the groove is measured under no load, and the maximum value is determined as the groove depth G (mm).

[0236] After that, using the obtained groove depth G (mm), [0.5G35] and [0.5G42] are calculated. Also, [10 C. tan /G (mm)] is calculated from 10 C. tan and the groove depth G (mm).

(5) Other Parameters

[0237] Then, the amount of silica/the amount of carbon black (silica/CB) in each test tire is obtained. (SBR contentland ratio) and (silica contentaspect ratio) are calculated based on the specifications and compounding contents of each test tire.

5. Performance Evaluation (Propulsion Performance on Snow-Covered Road Surface)

[0238] Each test tire is installed on all wheels of a test vehicle (displacement 2400 cc, four-wheel drive vehicle), filled with air to the standardized internal pressure, and then run on a snow-covered road surface. Each of the 20 drivers sensorily evaluated the propulsion performance in 5 stages (the higher the number, the better). Then, the total points of the evaluations by the 20 drivers are calculated.

[0239] Next, with the result in Comparative Example 2 set to 100, the measured result is indexed based on the following formula to evaluate propulsion performance on a snow-covered road surface. A larger value indicates better propulsion performance on a snow-covered road surface.

Propulsion performance on a snow-covered road surface=[(Result of test tire)/(Result of Comparative Example 2)]100

TABLE-US-00002 TABLE 2 EXAMPLE 1 2 3 4 5 6 7 8 Formulation of cap rubber layer SBR-1 40 60 60 60 60 60 60 SBR-2 60 NR 20 BR 40 40 40 40 40 40 40 40 Carbon black (CB) 25 25 50 25 25 25 50 30 Silica 75 75 40 75 75 75 40 55 Coupling agent 6 6 3.2 6 6 6 3.2 4.4 Resin 7 7 7 3 7 10 Oil 33 33 25 36 33 33 33 27 Wax 2 2 2 2 2 2 2 2 Anti-aging agent-1 2 2 2 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 1 1 1 Stearic acid 2 2 2 2 2 2 2 2 Zinc oxide 2 2 2 2 2 2 2 2 Processing aid 2 2 2 2 2 2 2 2 Sulfur 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Vulcanization accelerator 2 2 2 2 2 2 2 2 Parameter AE (% by mass) 15.5 15.5 13.5 15.2 15.5 16.5 13.8 11.8 Filler amount 100 100 90 100 100 100 90 85 (part by mass) Groove depth G (mm) 14 14 14 14 10 10 14 14 0.5 G 35 42 42 42 42 40 40 42 42 0.5 G 42 49 49 49 49 47 47 49 49 Tg ( C.) 42 47 47 48 47 48 48 48 10 C. tan 0.27 0.27 0.27 0.26 0.27 0.27 0.24 0.23 0 C. tan 0.32 0.31 0.31 0.28 0.31 0.29 0.27 0.26 30 C. tan 0.27 0.26 0.26 0.25 0.26 0.25 0.23 0.21 10 C. tan /G (mm) 0.0193 0.0193 0.0193 0.0186 0.0270 0.0270 0.0171 0.0164 Silica amount/ 3 3 0.8 3 3 3 0.8 1.8 CB amount SBR amount 2520 3780 3780 3780 3780 3780 3780 3780 land ratio (%) Amount of silica 5250 5250 2800 5250 5250 5250 2800 3850 aspect ratio (%) Performance evaluation Propulsion performance 102 106 113 115 109 114 124 127 on snowy roads

TABLE-US-00003 TABLE 3 EXAMPLE 9 10 11 12 13 14 15 Formulation of cap rubber layer SBR-1 60 60 60 60 60 80 SBR-2 60 NR BR 40 40 40 40 40 40 20 Carbon black (CB) 30 50 50 30 50 50 25 Silica 55 40 40 55 30 30 75 Coupling agent 4.4 3.2 3.2 4.4 2.4 2.4 6 Resin 2 7 7 Oil 27 25 33 27 25 25 33 Wax 2 2 2 2 2 2 2 Antiaging agent-1 2 2 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 1 1 Stearic acid 2 2 2 2 2 2 2 Zinc oxide 2 2 2 2 2 2 2 Processing aid 2 2 2 2 2 2 2 Sulfur 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Vulcanization accelerator 2 2 2 2 2 2 2 Parameter AE (% by mass) 12.4 13.5 13.8 11.8 11.4 11.4 15.5 Filler amount 85 90 90 85 80 80 100 (part by mass) Groove depth G (mm) 14 9 12 12 14 12 10 0.5 G 35 42 40 41 41 42 41 40 0.5 G 42 49 47 48 48 49 48 47 Tg ( C.) 50 47 48 48 48 48 40 10 C. tan 0.23 0.27 0.24 0.23 0.23 0.23 0.27 0 C. tan 0.24 0.31 0.27 0.26 0.27 0.27 0.33 30 C. tan 0.20 0.26 0.23 0.21 0.21 0.21 0.24 10 C. tan /G (mm) 0.0164 0.0300 0.0200 0.0192 0.0164 0.0192 0.0270 Silica amount/ 1.8 0.8 0.8 1.8 0.6 0.6 3 CB amount SBR amount 3780 3780 3780 3780 3780 3780 5040 land ratio (%) Amount of silica 3850 2800 2800 3850 2100 2100 5250 aspect ratio (%) Performance evaluation Propulsion performance 135 120 135 138 139 144 104 on snowy roads

TABLE-US-00004 TABLE 4 EXAMPLE COMPARATIVE EXAMPLE 16 17 1 2 3 4 5 Formulation of cap rubber layer SBR-1 60 60 30 40 60 60 60 SBR-2 NR 30 20 40 BR 40 40 40 40 40 40 Carbon black (CB) 25 25 25 25 25 30 25 Silica 35 55 75 30 75 40 50 Coupling agent 2.8 6 6 2.4 6 3.2 6 Resin 15 7 12 17 7 20 Oil 10 18 33 23 18 5 Wax 2 2 2 2 2 2 2 Anti-aging agent-1 2 2 2 2 2 2 2 Anti-aging agent-2 1 1 1 1 1 1 1 Stearic acid 2 2 2 2 2 2 2 Zinc oxide 2 2 2 2 2 2 2 Processing aid 2 2 2 2 2 2 2 Sulfur 1.4 1.4 1.4 1.4 1.4 1.4 1.4 Vulcanization accelerator 2 2 2 2 2 2 2 Parameter AE (% by mass) 15.5 15.5 13.1 6.6 15.5 11.9 11.4 Filler amount 100 100 100 55 100 70 75 (part by mass) Groove depth G (mm) 10 10 10 10 10 5 14 0.5 G 35 40 40 40 40 40 38 42 0.5 G 42 47 47 47 47 47 45 49 Tg ( C.) 42 47 43 42 41 38 40 tan at 10 C. 0.21 0.24 0.27 0.22 0.32 0.27 0.27 0 C. tan 0.33 0.29 0.31 0.31 0.37 0.39 0.37 30 C. tan 0.18 0.21 0.25 0.18 0.29 0.23 0.23 10 C. tan /G (mm) 0.021 0.024 0.0270 0.0220 0.0320 0.0540 0.0193 Silica amount/ 1.4 2.2 3 1.2 3 1.3 2 CB amount SBR amount 3120 3120 1890 2520 3780 3780 3780 land ratio (%) Amount of silica 2450 3850 5250 2100 5250 2800 3500 aspect ratio (%) Performance evaluation Propulsion performance 105 113 96 100 88 82 98 on snowy roads

[0240] Although the present invention has been described above based on the embodiments, the present invention is not limited to the above embodiments. Various modifications can be made to the above embodiment within the same and equivalent scope of the present invention.

[0241] The present invention (1) is [0242] a tire with a tread portion having a groove, wherein [0243] the cap rubber layer forming the tread portion contains 40 parts by mass or more and 80 parts by mass or less of styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of its rubber component, and 60 parts by mass or more of a filler with respect to 100 parts by mass of the rubber component, and is formed from a rubber composition having a loss tangent 10 C. tan measured under the conditions of temperature of 10 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1% and in deformation mode; tensile of less than 0.28, and a glass transition temperature Tg ( C.) of 40 C. or lower; and [0244] the glass transition temperature Tg ( C.) and the depth G(mm) of the groove satisfy the following (formula 1).

Tg0.5G35(formula 1)

[0245] The present invention (2) is [0246] the tire according to the present invention (1), wherein the styrene-butadiene rubber (SBR) has a styrene content of 20% by mass or less.

[0247] The present invention (3) is [0248] the tire according to the present invention (2), wherein the styrene-butadiene rubber (SBR) has a styrene content of 15% by mass or less.

[0249] The present invention (4) is [0250] the tire of any combination of the present inventions (1) to (3), wherein content of the filler is 80 parts by mass or more with respect to 100 parts by mass of the rubber component.

[0251] The present invention (5) is [0252] the tire of any combination of the present inventions (1) to (4), wherein the 10 C. tan is 0.25 or less.

[0253] The present invention (6) is [0254] the tire of any combination of the present inventions (1) to (5), wherein the loss tangent 0 C. tan of the cap rubber layer measured under the conditions of temperature of 0 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, and in deformation mode: tensile, is 0.30 or less.

[0255] The present invention (7) is [0256] the tire of any combination of the present inventions (1) to (6), wherein the 0 C. tan is 0.28 or less.

[0257] The present invention (8) is [0258] the tire of any combination of the present inventions (1) to (7), wherein the loss tangent 30 C. tan of the cap rubber layer measured under the conditions of temperature of 30 C., frequency of 10 Hz, initial strain of 5%, and dynamic strain rate of 1%, and in deformation mode: tensile, is 0.26 or less.

[0259] The present invention (9) is [0260] the tire of any combination of the present inventions (1) to (8), wherein the following (formula 2) is satisfied.

Tg0.5G42(Formula 2)

[0261] The present invention (10) is [0262] the tire of any combination of the present inventions (1) to (9), wherein the ratio of the 10 C. tan to the groove depth G (mm) (10 C. tan /G) is 0.025 or less.

[0263] The present invention (11) is [0264] the tire of any combination of the present inventions (1) to (10), wherein the thickness of the cap rubber layer is 10% or more of the entire tread portion.

[0265] The present invention (12) is [0266] the tire of any combination of the present inventions (1) to (11), wherein the land ratio in the tread portion is 40% or more, and the product of the content (parts by mass) of the styrene-butadiene rubber (SBR) having a styrene content of 25% by mass or less in 100 parts by mass of the rubber component and the land ratio (%) in the tread portion (SBR contentland ratio) is 6700 or less.

[0267] The present invention (13) is [0268] the tire of any combination of the present inventions (1) to (12), wherein the aspect ratio is 80% or less, the cap layer contains silica, and the product of the silica content (parts by mass) with respect to 100 parts by mass of the rubber component and the aspect ratio (silica contentaspect ratio) is 9000 or less.