RUBBER COMPOSITION AND TIRE

Abstract

A rubber composition comprising silica that has a BET specific surface area of not more than 130 m.sup.2/g and hardness of granulated particles as measured based on JIS K6221-1982 6.3.3 of not less than 23.5 cN can provide a rubber composition which is excellent in rubber physical properties while maintaining energy efficiency. A tire comprising a component consisted of the rubber composition can be also provided.

Claims

1-12. (canceled)

13. A rubber composition comprising silica that has a BET specific surface area of not more than 130 m.sup.2/g and a hardness of granulated particles as measured based on JIS K6221-1982 6.3.3 of not less than 23.5 cN.

14. The rubber composition of claim 13, wherein a DBP oil absorption amount of the silica is not more than 180 ml/100 g.

15. The rubber composition of claim 13, wherein a pore volume in pores with a pore diameter of 10 to 100 nm in the silica is not more than 1.7 ml/g.

16. A tire comprising a component consisted of the rubber composition of claim 13.

17. A tire comprising a component consisted of the rubber composition of claim 14.

18. A tire comprising a component consisted of the rubber composition of claim 15.

19. A tire comprising a base tread consisted of the rubber composition of claim 13.

20. A tire comprising a clinch apex consisted of the rubber composition of claim 13.

21. A tire for truck and bus comprising a tread consisted of the rubber composition of claim 13.

22. A tire comprising a bead apex consisted of the rubber composition of claim 13.

23. A tire comprising an inner liner consisted of the rubber composition of claim 13.

24. A winter tire comprising a tread consisted of the rubber composition of claim 13.

25. A tire comprising a side wall consisted of the rubber composition of claim 13.

26. A tire comprising an under tread consisted of the rubber composition of claim 13.

Description

EXAMPLE

[0055] Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited thereto only.

[0056] A variety of chemicals used in Examples and Comparative Examples will be described below. [0057] SBR 1: Buna VSL 2525-0 (S-SBR, styrene content: 25% by mass, vinyl content: 25% by mass) manufactured by LANXESS AG [0058] SBR 2: Nipol1502 (E-SBR, styrene content: 23.5% by mass, vinyl content: 18% by mass) manufactured by ZEON Corporation [0059] BR: BR150B (cis content: 97%, MLi+.sub.4 (100° C.): 40, Mw/Mn: 3.3) manufactured by Ube Industries, Ltd. [0060] VCR: VCR617 (SPB-containing BR, content of SPB: 17% by mass, melting point of SPB: 200° C.) manufactured by Ube Industries, Ltd. [0061] NR 1: TSR20 [0062] NR 2: RSS#3 [0063] ENR: ENR25 (epoxidation rate: 25%) manufactured by Kumpulan Guthrie Berhad [0064] Carbon black 1: DIABLACK I (ISAF carbon, N2SA: 114 m.sup.2/g, DBP oil absorption amount: 114 ml/ 100 g) manufactured by Mitsubishi Chemical Corporation [0065] Carbon black 2: ShoBlack N351H (N.sub.2SA: 64 m.sup.2/g, DBP oil absorption amount: 136 m1/100 g) manufactured by Cabot Japan K. K. [0066] Carbon black 3: SEAST N (N330, N2SA: 74 m.sup.2/g, DBP oil absorption amount: 102 ml/ 100 g) manufactured by Tokai Carbon Co., Ltd. [0067] Carbon black 4: SEAST V (N660, N.sub.2SA: 27 m.sup.2/g, DBP oil absorption amount: 26 ml/ 100 g) manufactured by Tokai Carbon Co., Ltd. [0068] Carbon black 5: ShoBlack N330 (HAF, N2SA: 75 m.sup.2/g, DBP oil absorption amount: 102 ml/ 100 g) manufactured by Cabot Japan K. K. [0069] Carbon black 6: ShoBlack N550 (FEF, N.sub.2SA: 42 m.sup.2/g, DBP oil absorption amount: 115 m1/100 g) manufactured by Cabot Japan K. K. [0070] Silica 1: granulated silica as prepared by a production method shown below [0071] Silica 2: granulated silica as prepared by a production method shown below [0072] Silica 3: ZEOSIL115GR manufactured by Rhodia Co., Ltd. [0073] Silica 4: 5000GR manufactured by Evonik Degussa GmbH [0074] Silica 5: Ultrasil U360 manufactured by Degussa GmbH [0075] Silane coupling agent 1: Si69 (bis(3-triethoxysilylpropyl)tetrasulfide) manufactured by Degussa GmbH [0076] Silane coupling agent 2: Si266 (bis(3-triethoxysilylpropyl)disulfide) manufactured by Degussa GmbH [0077] Oil 1: TDAE oil manufactured by Japan Energy Corporation [0078] Oil 2: process oil manufactured by JX Nippon Oil & Energy Corporation [0079] Oil 3: mineral oil PW-380 manufactured by Idemitsu Kosan Co., Ltd. [0080] Wax: OZOACE 0355 manufactured by Nippon Seiro Co., Ltd. [0081] Zinc oxide: Zinc oxide II manufactured by Mitsui Mining & Smelting Co., Ltd. [0082] Stearic acid: stearic acid beads “Tsubaki” manufactured by NOF Corporation [0083] Anti-aging agent 1: Nocrac 6C (N-(1,3-dimethylbutyl)-N-phenyl-p-phenylenediamine, 6PPD) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD. [0084] Anti-aging agent 2: Nocrac 224 (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD. [0085] Anti-aging agent 3: Antage RD (2,2,4-trimethyl-1,2-dihydroquinoline polymer) manufactured by Kawaguchi Chemical Industry Co., Ltd. [0086] Sulfur 1: sulfur powder manufactured by TSURUMI CHEMICAL INDUSTRY CO., LTD. [0087] Sulfur 2: Mu-cron OT20 (insoluble sulfur) manufactured by SHIKOKU CHEMICALS CORPORATION [0088] Vulcanization accelerator 1: Nocceler NS (N-tert-butyl-2-benzothiazolylsulfeneamide) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD. [0089] Vulcanization accelerator 2: Nocceler D (1,3-Diphenylguanidine) manufactured by OUCHI SHINKO CHEMICAL INDUSTRIAL CO., LTD.

Production of Granulated Silica

[0090] The above silica 1 and silica 2 were prepared based on a normal production method of wet processed silica except that pressures of a granulation compactor were changed.

[0091] The hardness of granulated particles, BET specific surface area, DBP oil absorption amount and pore volume of silica 1 to 5 were measured. The results are shown in Table 1.

TABLE-US-00001 TABLE 1 Hardness of DBP oil granulated BET specific absorption particles surface area amount Pore volume (cN) (g) (m.sup.2/g) (ml/100 g) (ml/g) Silica 1 30.4 31 115 170 1.50 Silica 2 34.3 35 113 169 1.52 Silica 3 22.6 23 110 180 1.63 Silica 4 21.6 22 114 180 1.71 Silica 5 17.7 18 50 220 1.18

Examples 1 and 2 and Comparative Examples 1 to 3

[0092] According to formulations shown in Table 2, all of the chemicals (other than sulfur and vulcanization accelerators) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerators were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the following evaluations were conducted. The evaluations were conducted regarding Comparative Example 1 as a standard Comparative Example. The results are shown in Table 2.

<Index of Processability>

[0093] According to a measuring method of a Mooney viscosity in accordance with JIS K6300-1 “Rubber, unvulcanized—Physical property—Part 1: Determination of Mooney viscosity and scorch time with Mooney viscometer”, a Mooney viscosity (ML.sub.1+4) of each unvulcanized rubber composition was measured under a temperature condition of 130° C. The results are shown with indices in accordance with the following calculation formula, regarding the ML.sub.1+4 of the standard Comparative Example as 100. The larger the index of processability is, the smaller the ML.sub.1+4 is and the more excellent the processability is.

(Index of processability)=(ML.sub.1+4 of standard Comparative Example)/(ML.sub.1+4 of each composition)×100

<Index of Rolling Resistance>

[0094] A loss tangent (tans) of each vulcanized rubber composition was measured under a condition of a temperature of 70° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho K. K. The results are shown with indices in accordance with the following calculation formula, regarding the tan δ of the standard Comparative Example as 100. The larger the index of rolling resistance is, the more excellent the energy efficiency is.

(Index of rolling resistance)=(tan δ of standard Comparative Example)/(tan δ of each composition)×100

<Index of Rubber Strength>

[0095] According to JIS K6251 “Vulcanized rubber and thermoplastic rubber—calculation of tensile characteristics”, a tensile test was conducted under an atmosphere of 23° C. using a No.3 dumbbell type test piece comprising each of the vulcanized rubber compositions, and an elongation at break (EB) (%) and a tensile strength at break (TB) (MPa) were measured. The results are shown with indices in accordance with the following calculation formula, regarding the EB×TB of the standard Comparative Example as 100. The larger the index of rubber strength is, the more excellent the breaking resistance is.

(Index of rubber strength)=(EB×TB of each composition)/(EB×TB of standard Comparative Example)×100

<Index of Abrasion Resistance>

[0096] An abrasion amount of each of the vulcanized rubber compositions was measured under a condition of room temperature, a weight load of 1.0 kg and a slipping rate of 30% using a Lambourn abrasion testing machine. The results are shown with indices in accordance with the following calculation formula, regarding the abrasion amount of the standard Comparative Example as 100. The larger the index is, the more excellent the abrasion resistance is.

(Index of abrasion resistance)=(abrasion amount of standard Comparative Example)/(abrasion amount of each composition)×100

<Index of Steering Stability>

[0097] A complex modulus (E*) of each of the vulcanized rubber compositions was measured under a condition of a temperature of 70° C., an initial strain of 10%, a dynamic strain of 2%, and a frequency of 10 Hz using a viscoelastic spectrometer VES manufactured by Iwamoto Seisakusho K. K. The results are shown with indices in accordance with the following calculation formula, regarding the E* of the standard Comparative Example as 100. The larger the index of steering stability is, the more excellent the steering stability is.

(Index of steering stability)=(E* of each composition)/(E* of standard Comparative Example)×100

TABLE-US-00002 TABLE 2 Example Comparative Example 1 2 1 2 3 Compounded amount (part by mass) SBR 1 60 60 60 60 60 BR 40 40 40 40 40 Carbon black 1 5 5 5 5 5 Silica 1 100 — — — — Silica 2 — 100 — — — Silica 3 — — 100 — — Silica 4 — — — 100 — Silica 5 — — — — 100 Silane coupling agent 1 8 8 8 8 8 Oil 1 20 20 20 20 20 Wax 2 2 2 2 2 Zinc oxide 2 2 2 2 2 Stearic acid 2 2 2 2 2 Anti-aging agent 1 2.5 2.5 2.5 2.5 2.5 Sulfur 1 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator 1 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator 2 1.5 1.5 1.5 1.5 1.5 Evaluation Index of processability 100 98 100 98 103 Index of rolling resistance 105 103 100 102 105 Index of rubber strength 120 125 100 108 90 Index of abrasion resistance 110 115 100 95 89 Index of steering stability 108 110 100 103 95

[0098] From the results of Table 2, it can be seen that the rubber composition comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in abrasion resistance, rubber strength and rubber elasticity while maintaining energy efficiency.

Examples 3 and 4 and Comparative Examples 4 and 5 (Rubber Composition for Base Tread)

[0099] According to formulations shown in Table 3, all of the chemicals (other than sulfur and vulcanization accelerators) were kneaded for five minutes with a 1.7L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerators were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability and index of rolling resistance were evaluated and the following evaluations were conducted. The evaluations were conducted regarding Comparative Example 4 as a standard Comparative Example. The results are shown in Table 3.

<Index of Bending Resistance>

[0100] In accordance with JIS K 6260 “Rubber, vulcanized or thermoplastic—Determination of flex cracking resistance and flex crack growth resistance (De Mattia type)”, flex crack growth resistance of each of the vulcanized rubber compositions was measured. The results are shown with indices in accordance with the following calculation formula, regarding the crack growth rate of the standard Comparative Example as 100. The smaller the index of crack growth resistance is, the more excellent the bending resistance is.

(Index of bending resistance)=(crack growth rate of each composition)/(crack growth rate of standard Comparative Example)×100

TABLE-US-00003 TABLE 3 Example Comparative Example 3 4 4 5 Compounded amount (part by mass) NR 1 60 60 60 60 BR 20 20 20 20 VCR 20 20 20 20 Carbon black 2 5 5 5 5 Silica 1 50 — — — Silica 2 — 50 — — Silica 3 — — 50 — Silica 4 — — — 50 Silane coupling agent 2 4 4 4 4 Oil 2 4 4 4 4 Wax 2 2 2 2 Zinc oxide 2 2 2 2 Stearic acid 2 2 2 2 Anti-aging agent 1 2 2 2 2 Anti-aging agent 2 1 1 1 1 Sulfur 2 2.5 2.5 2.5 2.5 Vulcanization accelerator 1 1.8 1.8 1.8 1.8 Vulcanization accelerator 2 0.5 0.5 0.5 0.5 Evaluation Index of processability 98 99 100 98 Index of rolling resistance 104 103 100 101 Index of bending resistance 80 75 100 95

[0101] From the results of Table 3, it can be seen that the rubber composition for base tread comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in bending resistance while maintaining energy efficiency.

Examples 5 and 6 and Comparative Examples 6 and 7 (Rubber Composition for Clinch Apex)

[0102] According to formulations shown in Table 4, all of the chemicals (other than sulfur and vulcanization accelerator) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerator were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance, index of rubber strength and index of steering stability were evaluated. The evaluations were conducted regarding Comparative Example 6 as a standard Comparative Example. The results are shown in Table 4.

TABLE-US-00004 TABLE 4 Example Comparative Example 5 6 6 7 Compounded amount (part by mass) NR 1 50 50 50 50 BR 50 50 50 50 Carbon black 1 20 20 20 20 Silica 1 40 — — — Silica 2 — 40 — — Silica 3 — — 40 — Silica 4 — — — 40 Silane coupling agent 1 3 3 3 3 Oil 1 8 8 8 8 Wax 1 1 1 1 Zinc oxide 4 4 4 4 Stearic acid 1 1 1 1 Anti-aging agent 1 1 1 1 1 Sulfur 1 1.5 1.5 1.5 1.5 Vulcanization accelerator 1 1.5 1.5 1.5 1.5 Evaluation Index of processability 100 97 100 98 Index of rolling resistance 105 103 100 102 Index of rubber strength 120 125 100 107 Index of steering stability 107 110 100 102

[0103] From the results of Table 4, it can be seen that the rubber composition for clinch apex comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in rubber strength and steering stability while maintaining energy efficiency.

Examples 7 to 9 and Comparative Examples 8 and 9 (Rubber Composition for Tread of a Tire for Truck and Bus)

[0104] According to formulations shown in Table 5, all of the chemicals (other than sulfur and vulcanization accelerators) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerators were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance, index of rubber strength, index of abrasion resistance and index of steering stability were evaluated. The evaluations were conducted regarding Comparative Example 8 as a standard Comparative Example. The results are shown in Table 5.

TABLE-US-00005 TABLE 5 Example Comparative Example 7 8 9 8 9 Compounded amount (part by mass) NR 1 80 80 80 80 80 BR 20 20 20 20 20 Carbon black 1 40 40 32 40 40 Silica 1 20 — — — — Silica 2 — 20 30 — — Silica 3 — — — 20 — Silica 4 — — — — 20 Silane coupling agent 1 2 2 3 2.5 2 Oil 1 5 5 5 5 5 Zinc oxide 3 3 3 3 3 Anti-aging agent 1 3 3 3 3 3 Sulfur 1 1.5 1.5 1.5 1.5 1.5 Vulcanization accelerator 1 1 1 1 1 1 Vulcanization accelerator 2 0.5 0.5 0.7 0.5 0.5 Evaluation Index of processability 100 99 98 100 98 Index of rolling resistance 104 102 104 100 101 Index of rubber strength 115 120 126 100 104 Index of abrasion resistance 110 113 112 100 97 Index of steering stability 106 108 106 100 102

[0105] From the results of Table 5, it can be seen that the rubber composition for tread of a tire for truck and bus comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in rubber strength, abrasion resistance and steering stability while maintaining energy efficiency.

Examples 10 to 13 and Comparative Examples 10 to 13 (Rubber Composition for Bead Apex)

[0106] According to formulations shown in Tables 6 and 7, all of the chemicals (other than sulfur and vulcanization accelerator) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerator were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance, index of rubber strength, index of abrasion resistance and index of steering stability were evaluated. The evaluations were conducted regarding Comparative Example 10 as a standard Comparative Example for Table 6, and regarding Comparative Example 12 as a standard Comparative Example for Table 7. The results are shown in Tables 6 and 7.

TABLE-US-00006 TABLE 6 Example Comparative Example 10 11 10 11 Compounded amount (part by mass) NR 2 70 70 70 70 SBR 2 30 30 30 30 Silica 1 50 — — — Silica 2 — 50 — — Silica 3 — — 50 — Silica 4 — — — 50 Silane coupling agent 1 4 4 4 4 Zinc oxide 4 4 4 4 Stearic acid 2 2 2 2 Anti-aging agent 3 1 1 1 1 Sulfur 1 1 1 1 1 Vulcanization accelerator 1 1 1 1 1 Evaluation Index of processability 100 98 100 98 Index of rolling resistance 105 103 100 102 Index of rubber strength 120 125 100 108

TABLE-US-00007 TABLE 7 Example Comparative Example 12 13 12 13 Compounded amount (part by mass) NR 2 70 70 70 70 SBR 2 30 30 30 30 Carbon black 3 20 20 20 20 Silica 1 40 — — — Silica 2 — 40 — — Silica 3 — — 40 — Silica 4 — — — 40 Silane coupling agent 1 3.2 3.2 3.2 3.2 Zinc oxide 4 4 4 4 Stearic acid 2 2 2 2 Anti-aging agent 3 1 1 1 1 Sulfur 1 1 1 1 1 Vulcanization accelerator 1 1 1 1 1 Evaluation Index of processability 100 100 100 96 Index of rolling resistance 106 105 100 101 Index of rubber strength 118 117 100 105

[0107] From the results of Tables 6 and 7, it can be seen that the rubber composition for bead apex comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in rubber strength while maintaining energy efficiency.

Examples 14 and 15 and Comparative Examples 14 and 15 (Rubber Composition for Inner Liner)

[0108] According to formulations shown in Table 8, all of the chemicals (other than sulfur and vulcanization accelerator) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerator were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance and index of rubber strength were evaluated and the following evaluation was conducted. The evaluations were conducted regarding Comparative Example 14 as a standard Comparative Example. The results are shown in Table 8.

<Index of Air Permeation Resistance>

[0109] Rubber test pieces (diameter: 90 mm, thickness: 1 mm) respectively comprising each of vulcanized rubber compositions were prepared and air permeation coefficient (cc.Math.cm/cm.sup.2.Math.sec/cmHg) of each rubber test piece was calculated in accordance with ASTM D 1434-75M. The results are shown with indices in accordance with the following calculation formula, regarding the air permeation coefficient of the standard Comparative Example as 100. The larger the index of air permeation resistance is, the harder the air transmits and the more excellent the air permeation resistance is.

(Index of air permeation resistance)=(Air permeation coefficient of standard Comparative Example)/(Air permeability coefficient of each composition)×100

TABLE-US-00008 TABLE 8 Example Comparative Example 14 15 14 15 Compounded amount (part by mass) NR 2 50 50 50 50 ENR 50 50 50 50 Carbon black 4 8 8 8 8 Silica 1 50 — — — Silica 2 — 50 — — Silica 3 — — 50 — Silica 4 — — — 50 Silane coupling agent 1 1 1 1 1 Zinc oxide 4 4 4 4 Stearic acid 2 2 2 2 Anti-aging agent 3 1 1 1 1 Sulfur 1 1 1 1 1 Vulcanization accelerator 1 1 1 1 1 Evaluation Index of processability 103 101 100 99 Index of rolling resistance 103 100 100 98 Index of rubber strength 104 101 100 97 Index of air permeation resistance 103 99 100 98

[0110] From the results of Table 8, it can be seen that the rubber composition for inner liner comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in rubber strength and air permeation resistance while maintaining energy efficiency.

Examples 16 and 17 and Comparative Examples 16 and 17 (Rubber Composition for Tread of Winter Tire)

[0111] According to formulations shown in Table 9, all of the chemicals (other than sulfur and vulcanization accelerator) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerator were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance, index of rubber strength, index of abrasion resistance and index of steering stability were evaluated. Further, the obtained each unvulcanized rubber composition was molded into the shape of a tread, laminated with other components of the tire in a tire building machine to form an unvulcanized tire and the unvulcanized tire was press-vulcanized for 12 minutes at 170° C. to obtain winter tires for test. With respect to these winter tires for test, the following evaluation was conducted. The evaluation was conducted regarding Comparative Example 16 as a standard Comparative Example. The results are shown in Table 9.

<Index of Performance on Ice>

[0112] Each test tire was mounted on a test car (Japanese-made FR car, displacement: 2000 cc) and at Hokkaido Nayoro test course (temperature: −6 to −1° C.), a distance (stoppage distance) from the place where the brake of the test car running at a speed of 30 km/h was locked to the place where the test car stopped was measured. The results are shown with indices according to the following formula, regarding the stoppage distance of the standard Comparative Example as 100. The larger the index of performance on ice is, the more excellent the braking performance on ice is. The experimental results are shown in Table 9.

(Index of braking performance on ice)=(Stoppage distance of standard Comparative Example)/(Stoppage distance of each test tire)×100

TABLE-US-00009 TABLE 9 Example Comparative Example 16 17 16 17 Compounded amount (part by mass) NR 2 40 40 40 40 BR 60 60 60 60 Carbon black 5 5 5 5 5 Silica 1 45 — — — Silica 2 — 45 — — Silica 3 — — 45 — Silica 4 — — — 45 Silane coupling agent 1 3 3 3 3 Oil 3 25 25 25 25 Wax 1 1 1 1 Zinc oxide 1.5 1.5 1.5 1.5 Stearic acid 1 1 1 1 Anti-aging agent 1 2 2 2 2 Sulfur 1 1 1 1 1 Vulcanization accelerator 1 2 2 2 2 Evaluation Index of processability 100 99 100 102 Index of rolling resistance 104 103 100 101 Index of rubber strength 118 122 100 107 Index of abrasion resistance 109 114 100 96 Index of steering stability 107 109 100 102 Index of performance on ice 106 109 100 99

[0113] From the results of Table 9, it can be seen that the rubber composition for tread of a winter tire comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in rubber strength, abrasion resistance, steering stability and performance on ice while maintaining energy efficiency.

Examples 18 and 19 and Comparative Examples 18 and 19 (Rubber Composition for Side Wall)

[0114] According to formulations shown in Table 8, all of the chemicals (other than sulfur and vulcanization accelerators) were kneaded for five minutes with a 1.7 L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerators were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance and index of bending resistance were evaluated. The evaluations were conducted regarding Comparative Example 18 as a standard Comparative Example. The results are shown in Table 10.

TABLE-US-00010 TABLE 10 Example Comparative Example 18 19 18 19 Compounded amount (part by mass) NR 1 40 40 40 40 BR 60 60 60 60 Carbon black 6 5 5 5 5 Silica 1 50 — — — Silica 2 — 50 — — Silica 3 — — 50 — Silica 4 — — — 50 Silane coupling agent 2 4 4 4 4 Oil 2 5 5 5 5 Wax 1 1 1 1 Zinc oxide 2 2 2 2 Stearic acid 2 2 2 2 Anti-aging agent 1 2 2 2 2 Anti-aging agent 2 1 1 1 1 Sulfur 1 2 2 2 2 Vulcanization accelerator 1 1 1 1 1 Vulcanization accelerator 2 0.5 0.5 0.5 0.5 Evaluation Index of processability 100 100 100 99 Index of rolling resistance 104 103 100 101 Index of bending resistance 75 70 100 95

[0115] From the results of Table 10, it can be seen that the rubber composition for side wall comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in bending resistance while maintaining energy efficiency.

Examples 20 and 21 and Comparative Examples 20 and 21 (Rubber Composition for Under Tread)

[0116] According to formulations shown in Table 11, all of the chemicals (other than sulfur and vulcanization accelerators) were kneaded for five minutes with a 1.7L Banbury mixer at the compound temperature at the time of discharge from mixer of 150° C. to obtain a kneaded product. Then, sulfur and the vulcanization accelerators were added to the obtained kneaded product and the mixture was kneaded for four minutes at the compound temperature at the time of discharge from mixer of 105° C. to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press-vulcanized in a mold having a thickness of 1 mm for 30 minutes at 150° C. to obtain a vulcanized rubber composition. With respect to the obtained unvulcanized rubber composition and vulcanized rubber composition, the above-mentioned index of procesability, index of rolling resistance, index of rubber strength and index of steering stability were evaluated. The evaluations were conducted regarding Comparative Example 20 as a standard Comparative Example. The results are shown in Table 11.

TABLE-US-00011 TABLE 11 Example Comparative Example 20 21 20 21 Compounded amount (part by mass) NR 1 100 100 100 100 Carbon black 1 10 10 10 10 Silica 1 45 — — — Silica 2 — 45 — — Silica 3 — — 45 — Silica 4 — — — 45 Silane coupling agent 1 3.6 3.6 3.6 3.6 Oil 1 5 5 5 5 Zinc oxide 2 2 2 2 Anti-aging agent 1 1.5 1.5 1.5 1.5 Sulfur 1 1.5 1.5 1.5 1.5 Vulcanization accelerator 1 1 1 1 1 Vulcanization accelerator 2 0.5 0.5 0.5 0.5 Evaluation Index of processability 100 98 100 98 Index of rolling resistance 105 103 100 102 Index of rubber strength 120 125 100 108 Index of steering stability 108 110 100 103

[0117] From the results of Table 11, it can be seen that the rubber composition for under tread comprising silica that has a BET specific surface area and a hardness of granulated particles as measured in accordance with a predetermined method within a predetermined range is excellent in rubber strength and steering stability while maintaining energy efficiency.