PNEUMATIC TIRE

Abstract

Provided is a pneumatic tire that ensures sufficient steering stability even when a vehicle runs on a wet road surface at a high speed. The pneumatic tire has a tread portion formed of a rubber composition containing: a rubber component of styrene-butadiene rubber and isoprene-based rubber; and a resin component, wherein when Q (parts by mass) is the content of the resin component with respect to 100 parts by mass of the rubber component, the tire is installed on a standardized rim, the internal pressure is 250 kPa, Wt (mm) is the cross-sectional width of the tire, and Dt (mm) is the outer diameter, the content Q (parts by mass) of the resin component with respect to 100 parts by mass of the rubber component exceeds 25 parts by mass, and (formula 1) and (formula 2) are satisfied.

1600≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)

Q/Wt>0.1  (formula 2)

Claims

1. A pneumatic tire, in which the tread portion is formed of a rubber composition containing styrene-butadiene rubber and isoprene-based rubber as rubber components and a resin component, the content Q (parts by mass) of the resin component is more than 25 parts by mass with respect to 100 parts by mass of the rubber component, and the following (formula 1) and (formula 2) are satisfied:
1600≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)
Q/Wt>0.1  (formula 2), where the content of the resin component with respect to 100 parts by mass of the rubber component is Q (parts by mass), and the cross-sectional width of the tire is Wt (mm) and the outer diameter of the tire is Dt (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

2. The pneumatic tire according to claim 1, wherein, when the amount of styrene-butadiene rubber is R.sup.1 (parts by mass) and the amount of isoprene-based rubber is R.sup.2 (parts by mass), in 100 parts by mass of the rubber component, the following (formula 3) and (formula 4) are satisfied:
R1+R2≥60  (formula 3)
50<R1≤80  (formula 4)

3. The pneumatic tire according to claim 1, wherein the following formula is satisfied:
1865≤(Dt.sup.2×π/4)/Wt.

4. The pneumatic tire according to claim 1, wherein the content Q (parts by mass) of the resin component with respect to 100 parts by mass of the rubber component is more than 30 parts by mass.

5. The pneumatic tire according to claim 1, wherein the following (formula 5) is satisfied:
Q/Wt>0.15  (formula 5),

6. The pneumatic tire according to claim 1, wherein the following (formula 5) is satisfied:
Q/Wt<0.35  (formula 6),

7. The pneumatic tire according to claim 1, wherein the styrene-butadiene rubber has a weight-average molecular weight of 100,000 or more and 2,000,000 or less.

8. The pneumatic tire according to claim 1, wherein the styrene-butadiene rubber is a modified solution-polymerized styrene-butadiene rubber.

9. The pneumatic tire according to claim 1, wherein the styrene content in the styrene-butadiene rubber is 5% by mass or more and 25% by mass or less.

10. The pneumatic tire according to claim 1, wherein the styrene content in the rubber composition is 1% by mass or more and 5% by mass or less.

11. The pneumatic tire according to claim 1, wherein the rubber composition further contains 40 parts by mass or less of butadiene rubber in 100 parts by mass of the rubber component.

12. The pneumatic tire according to claim 1, wherein the resin component is selected from the group consisting of C5-based resins, C5-C9-based resins, C9-based resins, terpene-based resins, terpene-aromatic compound-based resins, rosin-based resins, dicyclopentadiene resins, and alkylphenol-based resins.

13. The pneumatic tire according to claim 1, wherein the rubber composition contains 40 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

14. The pneumatic tire according claim 13, wherein the silica has a BET specific surface area of 180 m.sup.2/g or more and 300 m.sup.2/g or less.

15. The pneumatic tire according to claim 13, wherein more than 3 parts by mass and less than 15 parts by mass of a silane coupling agent is contained with respect to 100 parts by mass of the silica.

16. The pneumatic tire according to claim 1, which has an aspect ratio of 40% or more.

17. The pneumatic tire according to claim 1, wherein the outer diameter Dt is less than 685 (mm).

18. The pneumatic tire according to claim 1, wherein the cross-sectional width Wt (mm) is less than 305 mm.

19. The pneumatic tire according to claim 1, wherein (Dt−2×Ht) is 430 (mm) or more, where the outer diameter of the tire is Dt (mm) and the cross-sectional height of tire is Ht (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

20. The pneumatic tire according to claim 1, wherein, when the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the cross-sectional height is Ht (mm), when the tire is installed on a standardized rim and the internal pressure is 250 kPa, the virtual volume V (mm.sup.3) of the tire, the space occupied by the tire, and the Wt satisfy the following formula:
[(V+1.5×10.sup.7)/Wt]≤4.02×10.sub.5.

21. The pneumatic tire according to claim 20, wherein the following formula is satisfied:
[(V+2.0×10.sup.7)/Wt]≤4.02×10.sup.5.

22. The pneumatic tire according to claim 21, wherein the following formula is satisfied:
[(V+2.5×10.sup.7)/Wt]≤4.02×10.sup.5.

23. The pneumatic tire according to claim 1, which is a pneumatic tire for a passenger car.

Description

EXAMPLES

[0167] Hereinafter, the present disclosure will be described in more detail with reference to examples.

1. Manufacture of Rubber Compositions for Treads

[0168] First, a rubber composition for tread was produced.

(1) Compounding Material

[0169] First, each compounding material shown below was prepared. [0170] (a) Rubber component [0171] (a-1) NR: RSS #3 [0172] (a-2) SBR: NS116 manufactured by JSR Corporation (Styrene content: 20% by mass) [0173] (a-3) BR: UBEPOL BR150B manufactured by Ube Industries, Ltd. [0174] (b) Compounding materials other than rubber components [0175] (b-1) Carbon black: Show Black N220 manufactured by Cabot Japan Co., Ltd. (N2SA: 111 m.sup.2/g, DBP: 115 ml/100 g) [0176] (b-2) Silica: Ultrasil VN3 manufactured by Degussa (N.sub.2SA: 175 m.sup.2/g) [0177] (b-3) Silane coupling agent: Si69 manufactured by Degussa (Bis 3-triethoxysilylpropyl)tetrasulfide) [0178] (b-4) Process oil: Process X-140 (aroma oil) manufactured by Japan Energy Co., Ltd. [0179] (b-5) Resin component: Sylvatraxx 4401 manufactured by Kraton (Copolymer of α-methylstyrene and styrene) [0180] (b-6) Zinc white: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. [0181] (b-7) Stearic acid: stearic acid “Tsubaki” manufactured by NOF Corporation [0182] (b-8) Anti-aging agent: Nocrac 6C manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-1,3-dimethylbutyl-N′-phenyl-p-phenylenediamine) [0183] (b-9) Wax: Sannok wax manufactured by Ouchi Shinko Chemical Industry Co., Ltd. [0184] (b-10) Cross-linking agent and vulcanization accelerator [0185] Sulfur: powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd. [0186] Vulcanization accelerator 1: Nocceler CZ manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N-cyclohexyl-2-benzothiazolylsulfenamide) [0187] Vulcanization accelerator-2: Nocceler D manufactured by Ouchi Shinko Chemical Industry Co., Ltd. (N, N′-diphenylguanidine)

(2) Manufacture of Rubber Composition

[0188] Table 1 shows the amount (parts by mass) of each compounding material excluding the resin component. The compounding amount (parts by mass) of the resin component was the amount shown in Tables 2 to 4.

TABLE-US-00001 TABLE 1 Compounding material Compounding amount NR 20 SBR 60 BR 20 Carbon black 10 Silica 60 Silane coupling agent 5 Oil 3 Zinc white 2.5 Stearic acid 2 Anti-aging agent 1.5 Wax 1 Sulfur 1.5 Vulcanization accelerator-1 1 Vulcanization accelerator-2 1

[0189] Among the compounding materials shown in Table 1, each compounding material excluding sulfur, vulcanization accelerator 1 and vulcanization accelerator-2, and the resin component were kneaded for 5 minutes at 150° C. to obtain a kneaded product.

2. Tire Manufacturing

[0190] Next, sulfur and a vulcanization accelerator were added to the obtained kneaded product, and the mixture was kneaded at 80° C. for 5 minutes using an open roll to obtain a tread rubber composition. A tread is formed using the obtained tread rubber composition, bonded together with other tire members to form an unvulcanized tire, which is then vulcanized for 10 minutes under the condition of 170° C. to produce each test tire having the size of 155 type (Table 2), 205 type (Table 3), or 245 type (Table 4).

[0191] Then, the cross-sectional width Wt (mm), the outer diameter Dt (mm), the cross-sectional height Ht (mm), and the aspect ratio (%) of each test tire were determined, and the virtual volume V (mm 3) was calculated.

[0192] Then, (Dt−2×Ht), (V+1.5×10.sup.7)/Wt, (V+2.0×10.sup.7)/Wt, (V+2.5×10.sup.7)/Wt, and Q/Wt were calculated. The results are shown in Tables 2-4.

3. Evaluation of Steering Stability

(1) Test Method

[0193] Each test tire is installed on all wheels of a vehicle (domestic FF vehicle, displacement 2000 cc). After filling air so that the internal pressure is 250 kPa, it is run on a wet test course at 40 km/h and 120 km/h, and the change in handling performance due to changes in running speed was evaluated sensorily by the driver on a 5-point scale from 1 (feeling a large change) to 5 (feeling almost no change). Then, the total points of the evaluations by the 20 drivers were calculated.

[0194] Then, the result of the tire used as the evaluation reference (Comparative Example 1-2 in Table 2, Comparative Example 2-2 in Table 3, and Comparative Example 3-3 in Table 4) was set to 100, and, the calculated results were indexed as wet steering stability index, based on the following formula. The higher the value, the better the steering stability during high-speed running on wet roads.

Wet steering stability index=[(result of test tire)/result of evaluation reference tire)]×100

(2) Evaluation Results

[0195] Table 2 shows the evaluation results for the size 155 type, Table 3 shows the evaluation results for the size 205 type, and Table 4 shows the evaluation results for the size 245 type.

TABLE-US-00002 TABLE 2 Example No. Comparative example No. 1-1 1-2 1-1 1-2 SIZE 155/70R19 155/70R19 155/70R19 155/70R19 Content of Resin component 26 40 10 15 (Q: Part by mass) Wt (mm) 155 155 155 155 Dt (mm) 699.6 699.6 699.6 699.6 Ht(mm) 109 109 109 109 V (mm.sup.3) 31230020 31230020 31230020 31230020 Aspect ratio (%) 70 70 70 70 Dt-2 × Ht(mm) 483 483 483 483 (Dt.sup.2 × π/4)/Wt 2480 2480 2480 2480 (V + 1.5 × 10.sup.7)/Wt 298258 298258 298258 298258 (V + 2.0 × 10.sup.7)/Wt 330516 330516 330516 330516 (V + 2.5 × 10.sup.7)/Wt 362774 362774 362774 362774 Q/Wt 0.17 0.26 0.06 0.10 Wet steering stability index 105 120 85 100

TABLE-US-00003 TABLE 3 Example No. Comparative example No. 2-1 2-2 2-1 2-2 SIZE 205/70R17 205/70R17 205/70R17 205/70R17 Content of Resin component 30 50 10 20 (Q: Part by mass) Wt (mm) 205 205 205 205 Dt (mm) 718.8 718.8 718.8 718.8 Ht(mm) 144 144 144 144 V (mm.sup.3) 53167961 53167961 53167961 53167961 Aspect ratio (%) 70 70 70 70 Dt-2 × Ht(mm) 432 432 432 432 (Dt.sup.2 × π/4)/Wt 1979 1979 1979 1979 (V + 1.5 × 10.sup.7)/Wt 332527 332527 332527 332527 (V + 2.0 × 10.sup.7)/Wt 356917 356917 356917 356917 (V + 2.5 × 10.sup.7)/Wt 381307 381307 381307 381307 Q/Wt 0.15 0.24 0.05 0.10 Wet steering stability index 110 130 90 100

TABLE-US-00004 TABLE 4 Example No. Comparative example No. 3-1 3-2 3-1 3-2 3-3 SIZE 245/60R20 245/60R20 245/60R20 245/60R20 245/60R20 Content of Resin component 30 50 15 25 26 (Q: Part by mass) Wt (mm) 255 255 255 255 255 Dt (mm) 802 802 802 802 802 Ht(mm) 147 147 147 147 147 V (mm.sup.3) 77134503 77134503 77134503 77134503 77134503 Aspect ratio (%) 58 58 58 58 58 Dt-2 × Ht(mm) 508 508 508 508 508 (Dt.sup.2 × π/4)/Wt 1981 1981 1981 1981 1981 (V + 1.5 × 10.sup.7)/Wt 361312 361312 361312 361312 361312 (V + 2.0 × 10.sup.7)/Wt 380920 380920 380920 380920 380920 (V + 2.5 × 10.sup.7)/Wt 400527 400527 400527 400527 400527 Q/Wt 0.12 0.20 0.06 0.10 0.10 Wet steering stability index 115 135 85 95 100

[0196] It is shown from Tables 2 to 4 that, in tires of any size, 155 size, 205 size, or 245 size, when the resin component amount Q is ¼ of the rubber component amount, that is, 25 parts by mass per 100 parts by mass of the rubber component, and the above-mentioned (formula 1) and (formula 2) are satisfied, the wet steering stability index exceeds 100, and a pneumatic tire with sufficiently improved steering stability when running on a wet road surface at high speed can be provided.

[0197] Further, it is understood that, by satisfying the requirements specified in the present disclosure (2) and later, the wet steering stability index can be further increased, and a pneumatic tire with further improved steering stability when running on wet roads at high speed can be provided.

[0198] On the other hand, when the resin component amount Q is ¼ or less of the rubber component amount (25 parts by mass or less with respect to 100 parts by mass of the rubber component), or when either (formula 1) or (formula 2) was not satisfied, the wet steering stability index is 100 or less, and it cannot be said that the steering stability is sufficiently improved when running on wet roads at high speed.

[0199] Although the present disclosure has been described above based on the embodiments, the present disclosure is not limited to the above embodiments. Various modifications can be made to the above embodiment within the same and equivalent range as the present disclosure.

[0200] The present disclosure (1) is; [0201] a pneumatic tire in which [0202] the tread portion is formed of a rubber composition containing styrene-butadiene rubber and isoprene-based rubber as rubber components and a resin component, [0203] the content Q (parts by mass) of the resin component is more than 25 parts by mass with respect to 100 parts by mass of the rubber component, and [0204] the following (formula 1) and (formula 2) are satisfied:

1600≤(Dt.sup.2×π/4)/Wt≤2827.4  (formula 1)

Q/Wt>0.1  (formula 2),

where the content of the resin component with respect to 100 parts by mass of the rubber component is Q (parts by mass), and the cross-sectional width of the tire is Wt (mm) and the outer diameter of the tire is Dt (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

[0205] The present disclosure (2) is the pneumatic tire according to the present disclosure (1), wherein, when the amount of styrene-butadiene rubber is R.sup.1 (parts by mass) and the amount of isoprene-based rubber is R.sup.2 (parts by mass), in 100 parts by mass of the rubber component, the following (formula 3) and (formula 4) are satisfied.

R1+R2≥60  (formula 3)

50<R1≤80  (formula 4)

[0206] The present disclosure (3) is the pneumatic tire according to the present disclosure (1) or (2), wherein the following formula is satisfied.

1865≤(Dt.sup.2×π/4)/Wt

[0207] The present disclosure (4) is the pneumatic tire of any combination of the present disclosures (1) to (3), wherein the content Q (parts by mass) of the resin component with respect to 100 parts by mass of the rubber component is more than 30 parts by mass.

[0208] The present disclosure (5) is the pneumatic tire of any combination of the present disclosures (1) to (4), wherein the following (formula 5) is satisfied.

Q/Wt>0.15  (formula 5)

[0209] The present disclosure (6) is the pneumatic tire of any combination of the present disclosures (1) to (5), wherein the following (formula 5) is satisfied.

Q/Wt<0.35  (formula 6)

[0210] The present disclosure (7) is the pneumatic tire of any combination of the present disclosures (1) to (6), wherein the styrene-butadiene rubber has a weight-average molecular weight of 100,000 or more and 2,000,000 or less.

[0211] The present disclosure (8) is the pneumatic tire of any combination of the present disclosures (1) to (7), wherein the styrene-butadiene rubber is a modified solution-polymerized styrene-butadiene rubber.

[0212] The present disclosure (9) is the pneumatic tire of any combination of the present disclosures (1) to (8), wherein the styrene content in the styrene-butadiene rubber is 5% by mass or more and 25% by mass or less.

[0213] The present disclosure (10) is the pneumatic tire of any combination of the present disclosures (1) to (9), wherein the styrene content in the rubber composition is 1% by mass or more and 5% by mass or less.

[0214] The present disclosure (11) is the pneumatic tire of any combination of the present disclosures (1) to (10), wherein the rubber composition further contains 40 parts by mass or less of butadiene rubber in 100 parts by mass of the rubber component.

[0215] The present disclosure (12) is the pneumatic tire of any combination of the present disclosures (1) to (11), wherein the resin component is selected from the group consisting of C5-based resins, C5-C9-based resins, C9-based resins, terpene-based resins, terpene-aromatic compound-based resins, rosin-based resins, dicyclopentadiene resins, and alkylphenol-based resins.

[0216] The present disclosure (13) is the pneumatic tire of any combination of the present disclosures (1) to (12), wherein the rubber composition contains parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

[0217] The present disclosure (14) is the pneumatic tire according to the present disclosure (13), wherein the silica has a BET specific surface area of 180 m.sup.2/g or more and 300 m.sup.2/g or less.

[0218] The present disclosure (15) is the pneumatic tire according to the present disclosure (13) or (15), wherein more than 3 parts by mass and less than 15 parts by mass of a silane coupling agent is contained with respect to 100 parts by mass of the silica.

[0219] The present disclosure (16) is the pneumatic tire of any combination of the present disclosures (1) to (15), which has an aspect ratio of 40% or more.

[0220] The present disclosure (17) is the pneumatic tire of any combination of the present disclosures (1) to (16), wherein the outer diameter Dt is less than 685 (mm).

[0221] The present disclosure (18) is the pneumatic tire of any combination of the present disclosures (1) to (17), wherein the cross-sectional width Wt (mm) is less than 305 mm.

[0222] The present disclosure (19) is the pneumatic tire of any combination of the present disclosures (1) to (18), wherein (Dt−2×Ht) is 430 (mm) or more, where the outer diameter of the tire is Dt (mm) and the cross-sectional height of tire is Ht (mm) when the tire is installed on a standardized rim and the internal pressure is 250 kPa.

[0223] The present disclosure (20) is the pneumatic tire of any combination of the present disclosures (1) to (19), wherein, when the cross-sectional width of the tire is Wt (mm), the outer diameter is Dt (mm), and the cross-sectional height is Ht (mm), when the tire is installed on a standardized rim and the internal pressure is 250 kPa, the virtual volume V (mm.sup.3) of the tire, the space occupied by the tire, and the Wt satisfy the following formula.

[(V+1.5×10.sup.7)/Wt]≤4.02×10.sup.5

[0224] The present disclosure (21) is the pneumatic tire according to the present disclosure (20), wherein the following formula is satisfied.

[(V+2.0×10.sup.7)/Wt]≤4.02×10.sup.5

[0225] The present disclosure (22) is the pneumatic tire according to the present disclosure (21), wherein the following formula is satisfied.

[(V+2.5×10.sup.7)/Wt]≤4.02×10.sup.5

[0226] The present disclosure (23) is the pneumatic tire of any combination of the present disclosures (1) to (22), which is a pneumatic tire for a passenger car.