Rubber composition and heavy-duty tire using the same

Abstract

Construction vehicles operate for long periods under heavy loads, so they require a balance of heat generation suppression, wear resistance, chipping resistance, and cut resistance. [Solution] A rubber composition satisfying formulas (1) and (2) is obtained by blending 50 to 80 parts by mass of carbon black and 1 to 15 parts by mass of resin with 100 parts by mass of a rubber component containing 70% or more of styrene-butadiene copolymer rubber. -5℃≦T1-T0≦7℃ (1) (T1 is the peak temperature of the tanδ curve of the rubber composition, T0 is the peak temperature of the tanδ curve of the rubber composition without resin), 0.20≦P1-P 100 ≤0.30 (2) (P1 is the peak tanδ value of the tanδ curve of the rubber composition, P 100 (This refers to the tanδ value of the rubber composition at 100°C.)

Description

[Technical Field]

[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. [Background technology]

[0002] Heavy-duty tires, such as those on construction vehicles operating in quarries and large construction sites, operate for extended periods under heavy loads. Large tires fitted to such construction vehicles require features that suppress heat generation and prevent overheating. Furthermore, heavy-duty tires are used on both paved and unpaved surfaces, and are particularly required to have a high level of balance between off-wear resistance (known as off-wear), cut resistance, and chipping resistance when driving on unpaved surfaces. One method to improve cut resistance is to increase hardness. Methods such as increasing the amount of carbon black or crosslinking agent are employed to increase hardness, but this has the drawback of reducing the 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 describes a method for improving heat resistance, abrasion resistance, etc., in which 100 parts by weight of a rubber component made of natural rubber and / or diene-based synthetic rubber has a nitrogen adsorption specific surface area (N2SA) of 80 m². 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. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 7484174 [Patent Document 2] Japanese Patent Publication No. 2024-41050 [Patent Document 3] Japanese Patent Application Publication No. 11-80430 [Overview of the Initiative] [Problems that the invention aims to solve]

[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. [Means for solving the problem]

[0006] As a result of diligent research, the inventors discovered that the above problems can be solved by blending specific amounts of carbon black and resin into a diene rubber of a specific composition, thereby giving the rubber composition a specific tanδ curve, and thus completed the present invention.

[0007] In other words, the present invention provides the following rubber composition. For every 100 parts by mass of a rubber component containing 70 parts by mass or more of styrene-butadiene copolymer rubber, 50-80 parts by mass of carbon black, The resin is blended in 1 to 15 parts by mass, and A rubber composition characterized by satisfying the following formulas (1) and (2). -5℃≦T1-T0≦7℃ (1) 0.20 ≤ P1 - P 100 ≤0.30 (2) In formula (1), T1 is the peak temperature of the tanδ curve of the rubber composition, and T0 is the peak temperature of the tanδ curve of the rubber composition when the resin is removed from the rubber composition. In equation (2), P1 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.

[0008] Furthermore, the present invention provides a heavy-duty tire using the aforementioned rubber composition. [Effects of the Invention]

[0009] The rubber composition of the present invention is 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℃≦T1-T0≦7℃ (1) 0.20 ≤ P1 - P 100 ≤0.30 (2) In formula (1), T1 is the peak temperature of the tanδ curve of the rubber composition, and T0 is the peak temperature of the tanδ curve of the rubber composition when the resin is removed from the rubber composition. In formula (2), P1 is the tanδ value at the peak of the tanδ curve of the rubber composition, and P 100 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 is a rubber composition containing a resin, and is characterized in that the tanδ curves of the rubber composition with or without the resin satisfy the above formulas (1) and (2). The rubber composition of the present invention that simultaneously satisfies the above formulas (1) and (2) shows incompatibility between the rubber component in which the styrene-butadiene copolymer rubber accounts for 70% by mass or more and the resin, thereby maintaining low heat generation while improving abrasion resistance, chipping resistance and cut resistance.

Brief Description of the Drawings

[0011] [Figure 1] It is a diagram for explaining the tanδ curve in the present invention. [Figure 2] It is a cross-sectional view including a meridian plane for explaining an embodiment of the heavy-duty tire of the present invention.

Embodiments for Carrying out the Invention

[0012] Hereinafter, the present invention will be described in more detail.

[0013] The rubber component used in the present invention contains a styrene-butadiene copolymer rubber as an essential component. The blending amount of the 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. Furthermore, in this invention, 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 individually or in combination of two or more. In addition, 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 for reasons that the effects of the present invention are superior, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000. In this specification, the weight-average molecular weight (Mw) is a 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, measured by differential scanning calorimetry (DSC) under a heating rate of 20°C / min. A more preferable Tg is -50°C or lower. Furthermore, the styrene-butadiene copolymer rubber used in the present invention is preferably emulsion polymerized styrene-butadiene copolymer rubber (E-SBR). By using E-SBR, abrasion resistance, chipping resistance, and cut resistance can be further enhanced.

[0014] (Carbon Black) Examples of carbon blacks used in the present invention include furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF, which may be used individually or in combination of two or more. Furthermore, from the viewpoint of improving the effects of the present invention, carbon black should have a nitrogen adsorption specific surface area (N2SA) of 60 to 150 m². 2 It is preferable that the amount is / g, and 80-155m2 It is even more preferable that it be / g. The nitrogen adsorption specific surface area (N2SA) was measured according to JIS K 6217-2:2001 "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 commonly used in rubber compositions, particularly heavy-duty tires, and is not particularly limited as long as it satisfies formulas (1) and (2) described below. Specifically, examples include terpene resins, rosin resins, petroleum resins, phenolic resins, xylene resins, styrene resins, DCPD resins, and hydrogenated resins (hydrogenated styrene resins, hydrogenated DCPD resins, etc.).

[0016] In this invention, from the viewpoint of having a tanδ curve that satisfies equations (1) and (2) described below, it is preferable that the resin meets 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, and more preferably 1000 to 4000. (B) The glass transition temperature of the resin is preferably 30 to 110°C, and more preferably 40 to 100°C. (C) The resin is preferably a thermoplastic resin composed of aliphatic monomers and aromatic monomers, with an aromatic proton content of 1 to 65%. The aromatic proton content is the ratio of the aromatic proton content to the total content of aromatic protons and aliphatic protons contained in the thermoplastic resin. 1 This can be determined from the measurement results of the H-NMR spectrum. The tanδ curve can be measured using conventional methods. For example, it can be measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., under conditions of initial strain of 10%, amplitude of ±2%, and frequency of 20 Hz.

[0017] (Ratio of rubber composition) The rubber composition of the present invention is obtained by blending 50 to 80 parts by mass of carbon black and 1 to 15 parts by mass of resin with 100 parts by mass of the rubber component. If the amount of carbon black added is less than 50 parts by mass, the wear resistance and cut resistance deteriorate, while if it exceeds 80 parts by mass, the heat generation, wear resistance, and chipping resistance deteriorate. If the amount of the aforementioned resin is less than 1 part by mass, the amount is too small to achieve the effects of the present invention, and conversely, if it exceeds 15 parts by mass, the heat generation deteriorates.

[0018] From the viewpoint of improving the effects of the present invention, it is preferable that the amount of each of the above raw materials satisfies one or more of the following conditions (D) to (E). (D) The amount of carbon black added is preferably 50 to 80 parts by mass per 100 parts by mass of the rubber component. (E) The amount of resin added is preferably 3 to 10 parts by mass per 100 parts by mass of the rubber component.

[0019] From the viewpoint of improving the dispersibility of each raw material and further enhancing the heat generation properties, it is preferable that the rubber composition of the present invention contains an additional 0.1 to 10 parts by mass of a processing aid per 100 parts by mass of the rubber component. Examples of processing aids 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 these, glycerin fatty acid esters are preferred.

[0020] (Other ingredients) 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 that can then be used for vulcanization or crosslinking. The amounts of these additives can also be 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°C ≤ T1 - T0 ≤ 7°C (1) 0.20 ≤ P1 - P 100 ≤ 0.30 (2) FIG. 1 is a diagram for explaining the tanδ curve in the present invention. In FIG. 1, the tanδ value is plotted against the temperature (°C), and a tanδ curve is formed. In FIG. 1, T1 is the peak temperature of the tanδ curve of the rubber composition of the present invention containing a resin, and T0 is the peak temperature of the tanδ curve of the rubber composition without the resin. Note that FIG. 1 illustrates the case where T1 - T0 is positive (plus). In the present invention, as shown by the above formula (1), the difference between T1 and T0 is -5 to 7°C, preferably 0 to 5°C. On the other hand, in the tanδ curve of FIG. 1, P1 is the tanδ value at the peak of the rubber composition of the present invention containing a resin, and P 100 is the tanδ value at 100°C of the rubber composition of the present invention containing a resin. In the present invention, as shown by the above formula (2), the difference between P1 and P 100 is 0.20 to 0.30, preferably 0.25 to 0.30. As described above, when the above formulas (1) and (2) are satisfied, the styrene-butadiene copolymer rubber shows immiscibility between the rubber component and the resin occupying 70% by mass or more, and the desired effects of the present invention are achieved well. On the other hand, when the above formula (1) is satisfied but the above formula (2) is not satisfied, it leads to a decrease in heat generation durability, abrasion resistance, and cut resistance, which is not preferable. Conversely, when the above formula (2) is satisfied but the above formula (1) is not satisfied, it leads to a decrease in heat generation durability, abrasion resistance, and cut resistance, which is not preferable. In addition, in order to satisfy the above formulas (1) and (2), there is a means of selecting a resin so as to satisfy one or more of the above conditions (A) to (C), and preferably, a formulation design is performed so as 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. Furthermore, the rubber composition of the present invention can 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, this 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 makes up the cap tread 5 is called the tread rubber, and the tread surface 2 is located on the outer peripheral surface of the cap tread 5 in the radial direction of the tire, which is formed by this tread rubber. This 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 3 land rows 8.

[0025] The pneumatic tire 1 consists 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, centered on the equatorial plane 50, through the left and right shoulder portions 16 and sidewall portions 17 to the bead portion 18. This carcass is a structural member that acts as a pressure vessel when the pneumatic tire 1 is filled with air, and it 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 land 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 meridional profile of the tread portion 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 (tread gauge) of the tread center portion located in the center in the tire width direction, that is, the maximum tread thickness at the equatorial plane 50 of the tire, is denoted as Gcc, it is preferable that the following formula (5) is satisfied. 12.0mm ≤ Gcc ≤ 30.0mm (5) [Examples]

[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> 660g of Chinese-made gum rosin (manufactured by Arakawa Chemical Co., Ltd.) and 165g of maleic anhydride were charged into a reaction vessel, and the reaction was carried out at 220°C for 4 hours while stirring under a nitrogen stream. Subsequently, 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 (50% water content) were placed in a 1 liter shaking autoclave. After removing the 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 obtained resin A had a weight-average molecular weight (MW) of 1600, a glass transition temperature of 59°C, and an aromatic proton content of 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 (600 g solids) of a 70% xylene solution of resol-type p-nonylphenol 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 obtained resin B had a weight-average molecular weight (MW) of 1100, a glass transition temperature of 91°C, and an aromatic proton content of 9.3%.

[0030] <Synthesis of resin C> In a 2-liter four-necked flask equipped with a thermometer, stirrer, dropping funnel, and condenser, 560 g of toluene, 0.02 g of water, and 4.2 g of AlCl3 as a catalyst were added. The mixture was stirred while maintaining a temperature of 60°C, and a mixture of 160 g of α-pinene and 373 g of β-pinene was added dropwise over 2 hours. The mixture was 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 the 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 obtained resin C had a weight-average molecular weight (MW) of 20,000, a glass transition temperature of 120°C, and an aromatic proton content of 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, and then under 200°C and a vacuum of 40 mmHg to remove volatile substances and obtain resin D. The obtained resin D had a weight-average molecular weight (MW) of 1300, a glass transition temperature of 45°C, and an aromatic proton content of 8%.

[0032] Reference example, Examples 1-7, and Comparative Examples 1-6 Sample preparation In the formulations (parts by mass) shown in Table 1, 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. Next, the rubber was 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 (tanδ60℃): Using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., tanδ(60℃) was measured under the conditions of initial strain 10%, amplitude ±2%, frequency 20Hz, and temperature 60℃. The results were calculated by taking the reciprocal of the measured value and expressing it as an exponent with the reference example value set to 100. A larger value indicates lower heat generation. If the exponent is 96 or higher, it can be judged that it has sufficient low heat generation for practical use and possesses sufficient heat resistance. Abrasion Resistance: Abrasion was measured using a pico abrasion tester in accordance with ASTM-D2228. The results were expressed as an index, with the value of Reference Example 1 set to 100, by calculating the reciprocal of the measured value. A higher value indicates superior abrasion resistance. An index of 105 or higher indicates excellent abrasion resistance as an off-wear material. Chipping resistance: The elongation at break was measured at 100°C in accordance with JIS K6251. The results are expressed as an index, with the value of the reference example set to 100. A higher index indicates a higher elongation at high temperatures and superior chipping resistance; a value 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 results were expressed as an index by calculating the reciprocal of the measured value, 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 Table 1.

[0034] [Table 1]

[0035] *1: NR (SIR20, Tg=-60℃) *2: BR (Nipol BR 1220 manufactured by Nippon Zeon Corporation, Tg=-106℃) *3: E-SBR (Nipol 1502 manufactured by Zeon Corporation, emulsion polymerized styrene-butadiene copolymer rubber, Tg=-50℃) *4: S-SBR (Nipol NS616 manufactured by Zeon Corporation, solution polymerized styrene-butadiene copolymer rubber, Tg=-30℃) *5: Silica (Zeosil 1085GR manufactured by Solvay Japan, nitrogen adsorption specific surface area (N2SA) = 90m²) 2 / g, CTAB specific surface area=80m 2 / g) *6: Carbon Black CB (S118, manufactured by Cabot Japan, Nitrogen Adsorption Specific Surface Area (N2SA) = 148m²) 2 / g) *7: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl)tetrasulfide) *8: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.) *9: Glycerin fatty acid ester (STRUKTOL HT207, manufactured by Struktol) *10: Stearic acid (YR bead stearic acid 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 (Noxeller 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 (Sulfur processed by Karuizawa Refinery Co., Ltd.) *Resins A-D: Resins A-D synthesized as described above.

[0036] From the results in Table 1, it can be seen that the rubber compositions of each example contain 70 parts by mass or more of styrene-butadiene copolymer rubber in a rubber component of 100 parts by mass, 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 standard example, abrasion resistance, chipping resistance, and cut resistance are improved while maintaining low heat generation. In contrast, Comparative Example 1 showed poor heat generation because the proportion of resin exceeded the upper limit specified in the present invention. Comparative Example 2 is T1-T0 represented by formula (1) and P1-P represented by formula (2). 100 Since this value is below the lower limit specified in the present invention, the heat generation, wear resistance, and chipping resistance deteriorated. Comparative Example 3 is T1-T0 represented by formula (1) and P1-P represented by formula (2). 100 Since this exceeds the upper limit defined in the present invention, the wear resistance and cut resistance have decreased. In Comparative Example 4, natural rubber accounted for 70 parts by mass out of 100 parts by mass of rubber components, resulting in reduced abrasion resistance and cut resistance. Comparative Example 5 had a carbon black content below the lower limit specified in the present invention, resulting in reduced abrasion resistance and cut resistance. Comparative Example 6 showed deterioration in heat generation, wear resistance, and chipping resistance because the amount of carbon black used exceeded the upper limit specified in the present invention.

[0037] The present invention encompasses the following embodiments. Embodiment 1: For every 100 parts by mass of a rubber component containing 70 parts by mass or more of styrene-butadiene copolymer rubber, 50-80 parts by mass of carbon black, The resin is blended in 1 to 15 parts by mass, and A rubber composition characterized by satisfying the following formulas (1) and (2). -5℃≦T1-T0≦7℃ (1) 0.20 ≤ P1 - P 100 ≤0.30 (2) In formula (1), T1 is the peak temperature of the tanδ curve of the rubber composition, and T0 is the peak temperature of the tanδ curve of the rubber composition when the resin is removed from the rubber composition. In equation (2), P1 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. 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 weight-average molecular weight (MW) of the resin is 300 to 5000. Embodiment 5: The rubber composition according to any one of Embodiments 1 to 4, 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 6: A heavy-duty tire using the rubber composition described in any of Embodiments 1 to 5. [Explanation of Symbols]

[0038] 1. Pneumatic tire 2 Tread surface 3 Inner liner 4 Undertread 5 Cap Tread 6 Circumferential main groove 8 Rikubu row 15 Tread section 16 Shoulder section 17 Sidewall section 18 Bead section

Claims

1. A rubber component containing 70 parts by mass or more of styrene-butadiene copolymer rubber is used in 100 parts by mass. 50 to 80 parts by mass of carbon black, The resin is blended in 1 to 15 parts by mass, and A rubber composition 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) In formula (1), T １ This is the peak temperature of the tanδ curve of the rubber composition, and T ０ This 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 weight-average molecular weight (MW) of the resin is 300 to 5000.

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

6. A heavy-duty tire comprising the rubber composition described in claim 1.

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