Rubber composition and heavy load tire using same

Abstract

The present invention discloses a rubber composition that includes 50-80 parts by mass of carbon black and 1-15 parts by mass of a resin per 100 parts by mass of a rubber component including 70% or more of a styrene-butadiene copolymer rubber, and that satisfies expressions (1) and (2). (1): –5°C≤T1–T0≤7°C (where T1 is the peak temperature of a tanδ curve of the rubber composition, and T0 is the peak temperature of a tanδ curve of the rubber composition when the resin has not been included). (2): 0.20≤P1–P100≤0.30 (where P1 is the peak tanδ value of the tanδ curve of the rubber composition, and P100 is the tanδ value of the rubber composition at 100°C).

Description

Rubber composition and heavy-duty tire using the same

[0001] The present invention relates to a rubber composition and a heavy-duty tire using the same, and more specifically, to a rubber composition that can improve abrasion resistance, chipping resistance, and cut resistance while maintaining low heat generation, and a heavy-duty tire using the same.

[0002] Heavy-duty tires, such as those used on construction vehicles operating in quarries and large-scale construction sites, operate for extended periods under heavy loads. These large tires require features that suppress heat generation and prevent overheating. Furthermore, heavy-duty tires operate on both paved and unpaved surfaces, and particularly on unpaved surfaces, they demand a high level of balance between off-wear resistance (known as off-wear), cut resistance, and chipping resistance. One method to improve cut resistance is increasing hardness. While methods such as increasing the amount of carbon black or crosslinking agent are employed to increase hardness, this comes at the cost of reduced elongation at break. This reduction in elongation at break raises concerns about a deterioration in chipping resistance.

[0003] Furthermore, Patent Document 1 discloses a rubber composition for the cap tread of a heavy-duty tire, for the purpose of improving fuel efficiency, comprising 100 parts by mass of a rubber component containing at least one selected from the group consisting of isoprene rubber, butadiene rubber, and styrene-butadiene rubber, 50 to 89 parts by mass of carbon black, and 5 to 30 parts by mass of C5C9 petroleum resin, wherein the rubber component contains isoprene rubber, the content of isoprene rubber in the rubber component is 50% by mass or more, and the C5C9 petroleum resin is a resin obtained by copolymerizing C5 fraction and C9 fraction, with a copolymerization ratio of C9 fraction of 70% or more. Furthermore, Patent Document 2 discloses a tire having a tread portion with at least one rubber layer for the purpose of improving chipping resistance, wherein the rubber layer constitutes the tread surface, and the rubber composition constituting the rubber layer comprises a rubber component, a filler, and a resin component, wherein the rubber component contains 20% by mass or more of styrene-butadiene rubber and isoprene-based rubber, and the filler contains carbon black, and when the glass transition temperature (°C) of the styrene-butadiene rubber is T and the thickness (mm) of the rubber layer is G, T and G satisfy 2G - T ≥ 70 (where T is less than -50). Furthermore, Patent Document 3 discloses a tire for the purpose of improving heat resistance, abrasion resistance, etc., in which the nitrogen adsorption specific surface area (N) is calculated for 100 parts by weight of a rubber component made of natural rubber and / or diene-based synthetic rubber. ２ SA) is 80m ２ A heavy-duty pneumatic tire is disclosed, characterized in that the tire tread portion uses a rubber composition comprising 30 to 60 parts by weight of carbon black having a concentration of 1 / g or more and a dibutyl phthalate oil absorption capacity (24M4DBP) of 95 ml / 100g or more, and 1 to 40 parts by weight of a thermoplastic resin having a melting point of 80 to 160°C.

[0004] Patent No. 7484174 JP 2024-41050 JP 11-80430

[0005] The object of the present invention is to provide a rubber composition that can improve abrasion resistance, chipping resistance, and cut resistance while maintaining low heat generation, and a heavy-duty tire using the same.

[0006] As a result of intensive research, the inventors of the present invention have found that the above problems can be solved by blending carbon black and a resin in specific amounts with respect to a diene rubber having a specific composition and providing a specific tan δ curve to the rubber composition, thereby completing the present invention.

[0007] That is, the present invention provides the following rubber composition. With respect to 100 parts by mass of a rubber component containing 70 parts by mass or more of a styrene-butadiene copolymer rubber, 50 to 80 parts by mass of carbon black, 1 to 15 parts by mass of a resin are blended, and the following formulae (1) and (2) are satisfied. -5°C ≤ T １ - T ０ ≤ 7°C (1) 0.20 ≤ P １ - P １００ ≤ 0.30 (2) In formula (1), T １ is the peak temperature of the tan δ curve of the rubber composition, and T ０ is the peak temperature of the tan δ curve of the rubber composition when the resin is removed from the rubber composition. In formula (2), P １ is the tan δ value at the peak of the tan δ curve of the rubber composition, and P １００ is the tan δ value at 100°C of the rubber composition.

[0008] Further, the present invention provides a heavy load tire using the above rubber composition.

[0009] The rubber composition of the present invention is characterized in that, with respect to 100 parts by mass of a rubber component containing 70 parts by mass or more of a styrene-butadiene copolymer rubber, 50 to 80 parts by mass of carbon black, 1 to 15 parts by mass of a resin are blended, and the following formulae (1) and (2) are satisfied. -5°C ≤ T １ - T ０ ≤ 7°C (1) 0.20 ≤ P １ - P １００ ≤ 0.30 (2) In formula (1), T １ is the peak temperature of the tan δ curve of the rubber composition, and T ０ is the peak temperature of the tan δ curve of the rubber composition when the resin is removed from the rubber composition. In formula (2), P１ This is the tanδ value at the peak of the tanδ curve of the rubber composition, and P １００ This is the tanδ value of the rubber composition at 100°C. The rubber composition of the present invention can improve abrasion resistance, chipping resistance, and cut resistance while maintaining low heat generation.

[0010] The present invention relates to a rubber composition containing a resin, characterized in that the tanδ curve of the rubber composition, with or without the resin, satisfies formulas (1) and (2). The rubber composition of the present invention that satisfies formulas (1) and (2) simultaneously exhibits incompatibility between the rubber component, in which styrene-butadiene copolymer rubber accounts for 70% by mass or more, and the resin, thereby improving abrasion resistance, chipping resistance, and cut resistance while maintaining low heat generation.

[0011] This is a diagram illustrating the tanδ curve in the present invention. This is a cross-sectional view including the meridional plane illustrating one embodiment of the heavy-duty tire of the present invention.

[0012] The present invention will be described in more detail below.

[0013] The rubber component used in this invention contains styrene-butadiene copolymer rubber as an essential component. The amount of styrene-butadiene copolymer rubber is 70 parts by mass or more, preferably 90 to 100 parts by mass, when the total rubber is 100 parts by mass. In this invention, for example, natural rubber (NR), synthetic isoprene rubber (IR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), etc. can also be used as the rubber component. These may be used alone or in combination of two or more. Furthermore, their molecular weight and microstructure are not particularly limited, and they may be end-modified with amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl groups, etc., or epoxidized. The weight-average molecular weight (Mw) of the rubber component is not particularly limited, but 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, for reasons that result in superior effects of the present invention. In this specification, the weight-average molecular weight (Mw) is the standard polystyrene equivalent value obtained by gel permeation chromatography (GPC) measurement. Furthermore, the styrene-butadiene copolymer rubber preferably has a glass transition temperature (Tg) of -40°C or lower. In this invention, the glass transition temperature (Tg) refers to the temperature at the midpoint of the transition region when a thermogram is measured by differential scanning calorimetry (DSC) under a heating rate condition of 20°C / min. A more preferable Tg is -50°C or lower. Furthermore, the styrene-butadiene copolymer rubber used in this invention is preferably emulsion polymerized styrene-butadiene copolymer rubber (E-SBR). By using E-SBR, wear resistance, chipping resistance, and cut resistance can be further enhanced.

[0014] (Carbon Black) Specifically, examples of carbon black used in the present invention include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF, and these may be used individually or in combination of two or more. Furthermore, from the viewpoint of improving the effects of the present invention, the specific surface area of ​​the carbon black with nitrogen adsorption (N) may be used.２ The specific surface area (SA) is preferably 60 to 150 m ２ / g, more preferably 80 to 155 m ２ / g, and particularly preferably 95 to 155 m ２ / g. The nitrogen adsorption specific surface area (N ２ SA) is a value measured in accordance with JIS K6217-2:2001 "Part 2: Method for determining specific surface area - Nitrogen adsorption method - Single point method".

[0015] (Resin) The resin used in the present invention can be a resin usually blended in a rubber composition, particularly a tire for heavy loads, and is not particularly limited as long as it can satisfy the following formulas (1) and (2). Specifically, terpene resins, rosin resins, petroleum resins, phenolic resins, xylene resins, styrene resins, dicyclopentadiene resins (DCPD), hydrogenated resins (hydrogenated styrene resins, hydrogenated DCPD, etc.) and the like can be mentioned.

[0016] In the present invention, from the viewpoint of providing a tanδ curve that satisfies the following formulas (1) and (2), it is preferable that the resin has one or more of the following conditions (A) to (C). (A) The weight average molecular weight (MW) of the resin is preferably 300 to 5000, more preferably 1000 to 4000, and particularly preferably 1000 to 3000. (B) The glass transition temperature of the resin is preferably 30 to 110°C, more preferably 40 to 100°C, and particularly preferably 60 to 100°C. (C) The resin is a thermoplastic resin, composed of aliphatic monomers and aromatic monomers, and preferably has an aromatic proton content of 1 to 65%, more preferably 1 to 35%. The content of aromatic protons is the ratio of the content of aromatic protons to the total content of aromatic protons and aliphatic protons contained in the thermoplastic resin, １ and can be determined from the measurement results of the H-NMR spectrum. The tanδ curve can be measured by a conventional method. For example, using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., it can be measured under the conditions of an initial strain of 10%, an amplitude of ±2%, and a frequency of 20 Hz.

[0017] (Blending Ratio of Rubber Composition) The rubber composition of the present invention is prepared by blending 50 to 80 parts by mass of carbon black and 1 to 15 parts by mass of resin with respect to 100 parts by mass of the rubber component. When the blending amount of the carbon black is less than 50 parts by mass, the abrasion resistance and cut resistance deteriorate. Conversely, when it exceeds 80 parts by mass, the heat generation property, abrasion resistance, and chipping resistance deteriorate. When the blending amount of the resin is less than 1 part by mass, the blending amount is too small to achieve the effects of the present invention. Conversely, when it exceeds 15 parts by mass, the heat generation property deteriorates.

[0018] From the perspective of improving the effects of the present invention, it is preferable that the blending amounts of the respective raw materials satisfy one or more of the following conditions (D) to (E). (D) With respect to 100 parts by mass of the rubber component, the blending amount of the carbon black is preferably 50 to 80 parts by mass. (E) With respect to 100 parts by mass of the rubber component, the blending amount of the resin is preferably 3 to 10 parts by mass.

[0019] From the perspective of enhancing the dispersibility of each raw material and further improving the heat generation property, the rubber composition of the present invention preferably contains 0.1 to 10 parts by mass of a processing aid with respect to 100 parts by mass of the rubber component. Examples of the processing aid include higher fatty acids such as stearic acid, higher fatty acid amides such as stearic acid amide, aliphatic higher amines such as stearylamine, aliphatic higher alcohols such as stearyl alcohol, partial esters of fatty acids and polyhydric alcohols such as glycerin fatty acid esters, and fatty acid metal salts such as zinc stearate. Among them, glycerin fatty acid esters are preferred. Examples of the fatty acid in the glycerin fatty acid ester include fatty acids having 6 to 24 carbon atoms. Examples of commercially available glycerin fatty acid esters include DS100A (diglycerin monostearate), DO100V (diglycerin monooleate), S71D (diglycerin stearate), Poem J-4081V (tetraglycerin stearate), J-0021 (decaglycerin laurate), J-0081HV (decaglycerin stearate), J-0381V (decaglycerin oleate), etc. manufactured by Riken Vitamin Co., Ltd.

[0020] (Other Components) In addition to the components mentioned above, the rubber composition of the present invention may contain various additives commonly used in rubber compositions, such as vulcanizing or crosslinking agents; vulcanizing or crosslinking accelerators; zinc oxide; various fillers; antioxidants; and plasticizers. These additives can be mixed in a conventional manner to form a composition which can then be used for vulcanization or crosslinking. The amounts of these additives can also be the conventional amounts, as long as they do not contradict the purpose of the present invention.

[0021] The rubber composition of the present invention is characterized by satisfying the following formulas (1) and (2): -5℃ ≤ T １ -T ０ ≤7℃ (1) 0.20 ≤P １ -P １００ ≤0.30 (2) Figure 1 is a diagram illustrating the tanδ curve in the present invention. In Figure 1, the tanδ value is plotted against temperature (°C) and a tanδ curve is formed. In Figure 1, T １ This is the peak temperature of the tanδ curve of the rubber composition of the present invention containing resin, and T ０ This is the peak temperature of the tanδ curve of the rubber composition without resin. Figure 1 shows T １ -T ０ This illustrates the case where is positive. In the present invention, as shown in formula (1) above, T １ and T ０ The difference is -5 to 7°C, preferably 0 to 5°C. On the other hand, in the tanδ curve of Figure 1, P １ This is the peak tanδ value of the rubber composition of the present invention containing resin, and P １００ This is the tanδ value at 100°C of the rubber composition of the present invention containing the resin. In the present invention, as shown in formula (2) above, P １ and P １００The difference is 0.20 to 0.30, preferably 0.25 to 0.30. As described above, when formulas (1) and (2) are satisfied, the styrene-butadiene copolymer rubber exhibits incompatibility between the rubber component, which accounts for 70% or more by mass, and the resin, and the desired effects of the present invention are well achieved. On the other hand, if formula (1) is satisfied but formula (2) is not, it leads to a decrease in heat resistance, abrasion resistance, and cut resistance, which is undesirable. Conversely, if formula (2) is satisfied but formula (1) is not, it leads to a decrease in heat resistance, abrasion resistance, and cut resistance, which is undesirable. In order to satisfy formulas (1) and (2), one means of selecting a resin that satisfies one or more of the above conditions (A) to (C) is mentioned, and preferably, the formulation design is made to satisfy one or more of the above conditions (D) to (E).

[0022] Furthermore, since the rubber composition of the present invention can improve abrasion resistance, chipping resistance, and cut resistance while maintaining low heat generation, it is particularly preferable to use it in the cap treads of truck and bus tires and construction vehicle tires. The tire of the present invention is preferably a pneumatic tire and can be filled with air, nitrogen or other inert gases, and other gases. Construction vehicles refer to vehicles used for construction work such as roads and buildings. The rubber composition of the present invention can also be used to manufacture pneumatic tires according to conventional tire manufacturing methods, such as those for pneumatic tires.

[0023] Figure 2 is a cross-sectional view including a meridional plane illustrating one embodiment of the heavy-duty tire of the present invention. As shown in Figure 2, this pneumatic tire 1 is configured to be substantially symmetrical with respect to the equatorial plane 50 of the tire. Here, the equatorial plane 50 is a plane that is perpendicular to the axis of rotation and passes through the center of the width of the pneumatic tire 1. Since this pneumatic tire 1 is configured to be substantially symmetrical with respect to the equatorial plane 50, only one side is shown in Figure 2 with respect to the equatorial plane 50. The tire width direction refers to the direction parallel to the axis of rotation of the pneumatic tire, the tire diameter direction refers to the direction perpendicular to the axis of rotation, and the tire circumferential direction refers to the direction of rotation with the axis of rotation as the center of rotation. The outermost part in the tire width direction refers to the part furthest from the equatorial plane 50 in the tire width direction.

[0024] As shown in Figure 2, the pneumatic tire 1 is a composite material in which a carcass, reinforcing belts, etc., are covered with a rubber material, and the tread surface 2 makes contact with the ground. The pneumatic tire 1 has an undertread 4 between the inner liner 3 and the tread surface 2, and a cap tread 5 between the tread surface 2 and the undertread 4. In the explanation of Figure 2, the rubber material that constitutes the cap tread 5 is called the tread rubber, and the tread surface 2 is located on the radial outer surface of the cap tread 5 formed by this tread rubber. The tread surface 2 has a plurality of circumferential main grooves 6 that extend in the circumferential direction of the tire, and land rows 8 partitioned by the circumferential main grooves 6, and the tread pattern is formed by a plurality of land rows 8, preferably at least three land rows 8.

[0025] The pneumatic tire 1 is composed of a tread portion 15 having the tread surface 2 on its surface, left and right shoulder portions 16 continuous on both sides thereof, a sidewall portion 17, and a bead portion 18. The carcass, which forms the skeleton of the pneumatic tire 1, extends from both sides of the tread portion 15, through the left and right shoulder portions 16 and sidewall portions 17, to the bead portion 18, with the equatorial plane 50 as the center. This carcass is a strength member that acts as a pressure vessel when the pneumatic tire 1 is filled with air, and has a structure that supports the load with its internal pressure and can withstand the dynamic load during driving.

[0026] In the heavy-duty tire of the present invention, when the tire tread width is W and the width of the outermost tread section in the tire width direction is Wsh (the maximum width of the shoulder section 16 in Figure 1), it is preferable that the following formula (4) is satisfied: 0.15 ≤ Wsh / W ≤ 0.27 (4) Here, the tire tread width refers to the length along the profile of the meridional section of the tread section 15 between the outer ends in the tire width direction when the tire is mounted on a specified rim, has a specified air pressure, and is in an unloaded state without any load applied to the pneumatic tire 1. Furthermore, in the heavy-duty tire of the present invention, when the maximum tread thickness of the tread center section provided in the center in the tire width direction (tread gauge), that is, the maximum tread thickness at the equatorial plane 50 of the tire is Gcc, it is preferable that the following formula (5) is satisfied: 12.0 mm ≤ Gcc ≤ 30.0 mm (5)

[0027] The present invention will be further described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0028] <Synthesis of Resin A> 660 g of Chinese gum rosin (manufactured by Arakawa Chemical Co., Ltd.) and 165 g of maleic anhydride were charged into a reaction vessel and reacted at 220°C for 4 hours while stirring under a nitrogen stream. Then, the volatile components were removed under reduced pressure to obtain the addition reaction product. 200 g of the obtained addition reaction product and 2.0 g of 5% palladium carbon (water content 50%) were charged into a 1 liter shaking autoclave. After removing oxygen from the system, the system was pressurized to 10 MPa with hydrogen and heated to 220°C, and the hydrogenation reaction was carried out for 3 hours to obtain resin A. The weight-average molecular weight (MW) of the obtained resin A was 1600, the glass transition temperature was 59°C, and the aromatic proton content was 15%.

[0029] <Synthesis of Resin B> 900 g of gum rosin was placed in a four-necked flask equipped with a stirrer, reflux condenser with water divider, and thermometer, and heated to 180°C while stirring to melt it. Next, 83 g of pentaerythritol and 4 g of calcium hydroxide were added, and the mixture was heated to 280°C while stirring to react. After cooling to 220°C, 100 g of Neopolymer 160 (manufactured by ENEOS Material Co., Ltd., maleic acid-modified petroleum resin) was charged, and 857 g of a 70% xylene solution of resol-type p-nonylphenol (600 g solids) was added dropwise over 5 hours while maintaining the temperature. After the addition was complete, volatile components were removed by reducing the pressure to 160 mmHg for 10 minutes, and after cooling, resin B was obtained. The weight-average molecular weight (MW) of the obtained resin B was 1100, the glass transition temperature was 91°C, and the aromatic proton content was 9.3%.

[0030] <Synthesis of Resin C> In a 2-liter four-necked flask equipped with a thermometer, stirrer, dropping funnel, and condenser, add 560 g of toluene, 0.02 g of water, and 4.2 g of AlCl as a catalyst. ３ The mixture was added and stirred while maintaining a temperature of 60°C. A mixture of 160 g of α-pinene and 373 g of β-pinene was added dropwise over 2 hours, and then stirred for 1 hour to allow the reaction to proceed. After the reaction, the mixture was washed with water to remove the catalyst, and volatile components were removed by distillation under reduced pressure of 10 mmHg at a maximum temperature of 200°C to obtain 500 g of a pale yellow resinous substance called resin C. The weight-average molecular weight (MW) of the obtained resin C was 20,000, the glass transition temperature was 120°C, and the aromatic proton content was 20%.

[0031] <Synthesis of Resin D> 500 g of para-tert-butylphenol (PTBP) and 250 g of toluene were placed in a reactor and heated to 100°C to dissolve the PTBP. Next, triethylamine was added as a catalyst. Then, 320 g of aqueous formaldehyde (37%) solution was added dropwise under reflux conditions over 20 minutes. 50 g of morpholine and 50 g of rosin were added to the mixture, and reflux was continued for another 2 hours. Finally, the reaction mixture was dehydrated first under atmospheric pressure, then under 200°C and 40 mmHg vacuum conditions to remove volatile substances and obtain resin D. The weight-average molecular weight (MW) of the obtained resin D was 1300, the glass transition temperature was 45°C, and the aromatic proton content was 8%.

[0032] Reference example, Examples 1-8, and Comparative Examples 1-6: In the formulations (parts by mass) shown in Sample Preparation Tables 1 and 2, the components excluding the vulcanization accelerator and sulfur were kneaded in a 1.7-liter sealed Banbury mixer for 5 minutes, and the rubber was released from the mixer and allowed to cool to room temperature. The rubber was then put back into the mixer, the vulcanization accelerator and sulfur were added, and the mixture was kneaded further to obtain a rubber composition. The obtained rubber composition was then press-vulcanized in a predetermined 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 method described below.

[0033] Heat generation (tanδ 60°C): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tanδ (60°C) was measured under the conditions of initial strain 10%, amplitude ±2%, frequency 20Hz, and temperature 60°C. The results were expressed as an index by calculating the reciprocal of the measured value and setting the value of the reference example to 100. A larger value indicates lower heat generation. An index of 96 or higher indicates sufficient low heat generation for practical use and good heat resistance. Abrasion resistance: Abrasion was measured using a pico abrasion tester in accordance with ASTM-D2228. The results were expressed as an index by calculating the reciprocal of the measured value and setting the value of Reference Example 1 to 100. A larger value indicates superior abrasion resistance. An index of 105 or higher indicates excellent abrasion resistance as off-wear. Chipping resistance: Elongation at break was measured at 100°C in accordance with JIS K6251. The results were expressed as an index by setting the value of the reference example to 100. A higher index indicates greater elongation at high temperatures and superior chipping resistance; an index of 105 or higher indicates excellent chipping resistance. Cut resistance (guillotine cut): A sample measuring 50 mm (length) x 100 mm (width) x 20 mm (height) was prepared from the vulcanized rubber test piece. At room temperature, a sharp blade weighing 5.4 kg was dropped onto the sample from 25 cm above, and the depth of the resulting crack [mm] was measured. The result was calculated by taking the reciprocal of the measured value and expressing it as an index with the reference example value set to 100. A higher value indicates superior cut resistance. An index of 105 or higher indicates excellent cut resistance. The results are shown in Tables 1 and 2.

[0034]

[0035]

[0036] *1: NR (SIR20, Tg = -60°C) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd., Tg = -106°C) *3: E-SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd., emulsion polymerized styrene-butadiene copolymer rubber, Tg = -50°C) *4: S-SBR (Nipol NS616 manufactured by Nippon Zeon Co., Ltd., solution polymerized styrene-butadiene copolymer rubber, Tg = -30°C) *5: Silica (Zeosil 1085GR manufactured by Solvay Japan, nitrogen adsorption specific surface area (N) ２ SA) = 90m ２ / g, CTAB specific surface area = 80m ２ / g) *6: Carbon black CB (S118 carbon black manufactured by Cabot Japan, nitrogen adsorption specific surface area (N ２ SA) = 148m ２ / g) *7: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl) tetrasulfide) *8: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu K.K.) *9: Glycerin fatty acid ester (STRUKTOL HT207 manufactured by Struktol, glycerin fatty acid ester) *10: Stearic acid (Bead Stearic Acid YR manufactured by NOF Corporation) *11: Anti-aging agent (SANTOFLEX 6PPD manufactured by Flexis) *12: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *13: Vulcanization accelerator CZ (Noxellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *14: Vulcanization accelerator NS (Sunceller NS-G manufactured by Sanshin Chemical Industry Co., Ltd.) *15: Sulfur (Oil-treated sulfur manufactured by Karuizawa Smelting Plant) *Resins A-D: Resins A-D synthesized as described above.

[0037] From the results in Tables 1 and 2, it can be seen that the rubber compositions of each example contain 100 parts by mass of rubber component containing 70 parts by mass or more of styrene-butadiene copolymer rubber, 50 to 80 parts by mass of carbon black, and 1 to 15 parts by mass of resin, and satisfy formulas (1) and (2) above. Therefore, compared to the reference example, abrasion resistance, chipping resistance, and cut resistance are improved while maintaining low heat generation. In contrast, Comparative Example 1 had a worsened heat generation because the proportion of resin exceeded the upper limit specified in the present invention. Comparative Example 2 is represented by T (1)１ -T ０ and P represented by equation (2) １ -P １００ Since it is below the lower limit defined in the present invention, the heat generation, wear resistance, and chipping resistance deteriorated. Comparative Example 3 is a T represented by formula (1) １ -T ０ and P represented by equation (2) １ -P １００ In Comparative Example 4, the amount of carbon black was less than the lower limit specified in the present invention, resulting in reduced abrasion resistance and cut resistance. In Comparative Example 5, the amount of carbon black was less than the lower limit specified in the present invention, resulting in reduced abrasion resistance and cut resistance. In Comparative Example 6, the amount of carbon black was more than the upper limit specified in the present invention, resulting in worsened heat generation, abrasion resistance, and chipping resistance.

[0038] The present invention encompasses the following embodiments. Embodiment 1: A rubber composition characterized by comprising 100 parts by mass of a rubber component containing 70 parts by mass or more of styrene-butadiene copolymer rubber, 50 to 80 parts by mass of carbon black, and 1 to 15 parts by mass of resin, and satisfying the following formulas (1) and (2). -5℃≦T １ -T ０ ≤7℃ (1) 0.20 ≤P １ -P １００ ≦0.30 (2) In formula (1), T １ This is the peak temperature of the tanδ curve of the rubber composition, and T ０ P is the peak temperature of the tanδ curve of the rubber composition when the resin is removed from the rubber composition. In formula (2), P １ This is the tanδ value at the peak of the tanδ curve of the rubber composition, and P １００is the tanδ value of the rubber composition at 100°C. Embodiment 2: The rubber composition according to Embodiment 1, characterized in that the glass transition temperature of the styrene-butadiene copolymer rubber is -40°C or lower. Embodiment 3: The rubber composition according to Embodiment 1 or 2, characterized in that the styrene-butadiene copolymer rubber is an emulsion polymerized styrene-butadiene copolymer rubber. Embodiment 4: The rubber composition according to any one of Embodiments 1 to 3, characterized in that the resin is selected from terpene resins, rosin resins, petroleum resins, phenolic resins, xylene resins, styrene resins, dicyclopentadiene resins, hydrogenated styrene resins, and hydrogenated dicyclopentadiene resins. Embodiment 5: The rubber composition according to any one of Embodiments 1 to 4, characterized in that the weight-average molecular weight (MW) of the resin is 300 to 5000. Embodiment 6: The rubber composition according to any one of Embodiments 1 to 5, characterized in that 0.1 to 10 parts by mass of a processing aid is further added to 100 parts by mass of the rubber component. Embodiment 7: A heavy-duty tire using the rubber composition described in any of Embodiments 1 to 6.

[0039] 1. Pneumatic tire 2. Tread surface 3. Inner liner 4. Undertread 5. Cap tread 6. Circumferential main groove 8. Land groove 15. Tread section 16. Shoulder section 17. Sidewall section 18. Bead section

Claims

1. A rubber composition characterized by comprising 100 parts by mass of a rubber component containing 70 parts by mass or more of styrene-butadiene copolymer rubber, 50 to 80 parts by mass of carbon black, and 1 to 15 parts by mass of resin, and satisfying the following formulas (1) and (2). -5℃≦T １ -T ０ ≤7℃ (1) 0.20 ≤P １ -P １００ ≦0.30 (2) In formula (1), T １ This is the peak temperature of the tanδ curve of the rubber composition, and T ０ P is the peak temperature of the tanδ curve of the rubber composition when the resin is removed from the rubber composition. In formula (2), P １ This is the tanδ value at the peak of the tanδ curve of the rubber composition, and P １００ This is the tanδ value of the rubber composition at 100°C.

2. The rubber composition according to claim 1, characterized in that the glass transition temperature of the styrene-butadiene copolymer rubber is -40°C or lower.

3. The rubber composition according to claim 1, characterized in that the styrene-butadiene copolymer rubber is an emulsion polymerized styrene-butadiene copolymer rubber.

4. The rubber composition according to claim 1, characterized in that the resin is selected from terpene resins, rosin resins, petroleum resins, phenolic resins, xylene resins, styrene resins, dicyclopentadiene resins, hydrogenated styrene resins, and hydrogenated dicyclopentadiene resins.

5. The rubber composition according to claim 1, characterized in that the weight-average molecular weight (MW) of the resin is 300 to 5000.

6. The rubber composition according to claim 1, characterized in that 0.1 to 10 parts by mass of a processing aid is further added to 100 parts by mass of the rubber component.

7. A heavy-duty tire using the rubber composition described in claim 1.

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