Rubber composition and heavy-duty tire using same

Abstract

The present invention discloses a rubber composition which is obtained by blending 40-60 parts by mass of carbon black and 1-15 parts by mass of a resin with 100 parts by mass of a rubber component containing 50% or more of an isoprene-based rubber. The resin / carbon black mass ratio is 0.05-0.20. The rubber composition satisfies formulae (1) and (2). Formula (1): 2.0ºC≤T1-T0≤7.0ºC. (T1 is a peak temperature on a tanδ curve of the rubber composition, and T0 is a peak temperature on a tanδ curve of the rubber composition containing no resin). Formula (2): 0.60≤P1-P100≤0.90. (P1 is a peak tanδ value on a tanδ curve of the rubber composition, and P100 is a 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 and uneven abrasion resistance while maintaining low heat generation, and a heavy-duty tire using the same.

[0002] Large construction vehicles, such as dump trucks, operating in quarries and large-scale construction sites operate for long periods under heavy loads. The large tires fitted to these construction vehicles are required to suppress heat generation and prevent overheating. Meanwhile, the strengthening of international standards in the United Nations Economic Commission for Europe (UN / ECE) R-117 and the stricter greenhouse gas (GHG) regulations by the U.S. Environmental Protection Agency (EPA) have led to a demand for tires with low rolling resistance. Furthermore, in recent years, with the advancement of road infrastructure, vehicles are traveling at higher speeds and over longer distances, increasing the demand for resistance to uneven wear in addition to the wear resistance that has traditionally been considered the most important performance characteristic.

[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 and uneven abrasion 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, and thus have completed 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 50 parts by mass or more of an isoprene rubber, 40 to 60 parts by mass of carbon black, 1 to 15 parts by mass of a resin are blended, the ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and the rubber composition is characterized by satisfying the following formulas (1) and (2). 2.0 °C ≤ T １ -T ０ ≤ 7.0 °C (1) 0.60 ≤ P １ -P １００ ≤ 0.90 (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 of the rubber composition at 100 °C.

[0008] The present invention also provides a heavy-duty tire using the rubber composition for a tire tread.

[0009] The rubber composition of the present invention is characterized in that, with respect to 100 parts by mass of a rubber component containing 50 parts by mass or more of an isoprene rubber, 40 to 60 parts by mass of carbon black, 1 to 15 parts by mass of a resin are blended, the ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and the following formulas (1) and (2) are satisfied. 2.0 °C ≤ T １ -T ０ ≤ 7.0 °C (1) 0.60 ≤ P １ -P １００ ≤ 0.90 (2) In formula (1), T１ is the peak temperature of the tanδ curve of the rubber composition, and T ０ 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 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 and uneven abrasion resistance while maintaining low heat generation.

[0010] The present invention is a rubber composition containing a resin, 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) exhibits high compatibility between the rubber component in which the isoprene-based rubber accounts for 50% by mass or more and the resin, and thereby can improve abrasion resistance and uneven abrasion resistance while maintaining low heat generation.

[0011] It is a diagram for explaining the tanδ curve in the present invention. It is a cross-sectional view including a meridian plane for explaining one embodiment of the heavy load tire of the present invention.

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

[0013] The rubber component used in this invention contains isoprene rubber as an essential component. Examples of isoprene rubber include natural rubber (NR) and / or synthetic isoprene rubber (IR). The amount of isoprene rubber blended is 50 parts by mass or more, preferably 60 to 100 parts by mass, when the total rubber is 100 parts by mass. In this invention, for example, styrene-butadiene copolymer rubber (SBR), 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 rubber component preferably has a glass transition temperature (Tg) of -55°C or lower. When multiple types of rubber components are included, Tg as used herein is the value calculated based on the weight average, i.e., the sum of the weight fractions of each component is assumed to be 1.0. In this invention, the glass transition temperature (Tg) is defined as 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 -60°C or lower.

[0014] (Carbon Black) As the carbon black used in the present invention, specifically, for example, furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, SRF, etc. can be mentioned. These may be used alone or in combination of two or more. Further, from the viewpoint of improving the effects of the present invention, the carbon black preferably has a nitrogen adsorption specific surface area (N ２ SA) of 60 to 160 m ２ / g, more preferably 65 to 155 m ２ / g, and particularly preferably 90 to 150 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 that is 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), the resin preferably has one or more of the following conditions (A) to (D). (A) The weight average molecular weight (MW) of the resin is preferably 300 to 2000, more preferably 400 to 1800, and particularly preferably 400 to 1700. (B) It is preferable to satisfy the following formula (3). (P ０ -P １００ )×MW≤25 (3) In formula (3), P １００ is the tanδ value of the rubber composition at 100°C, and P ０(1) is the tanδ value at 100°C of the rubber composition when the resin is removed from the rubber composition, and MW is the weight-average molecular weight of the resin. The value of formula (3) is more preferably 20 or less, and particularly preferably 19 or less. (C) The glass transition temperature of the resin is preferably 40 to 130°C, more preferably 50 to 120°C, and particularly preferably 55 to 110°C. (D) The resin is a thermoplastic resin composed of aliphatic monomers and aromatic monomers, and preferably has an aromatic proton content of 0 to 15%, and more preferably 3 to 12%. 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 by conventional methods; for example, it can be measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd. under the 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 formulated by blending 40 to 60 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, wherein the ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio). If the amount of carbon black is less than 40 parts by mass, the abrasion resistance deteriorates, and conversely, if it exceeds 60 parts by mass, the heat generation deteriorates. If the amount of 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. If the ratio of the resin to the carbon black is less than 0.05 as the resin / carbon black (mass ratio), the effects of the present invention cannot be achieved, and conversely, if it exceeds 0.20, the heat generation deteriorates.

[0018] From the viewpoint of improving the effects of the present invention, it is preferable that the amount of each raw material blended satisfies one or more of the following conditions (E) to (G): (E) The amount of carbon black blended is preferably 45 to 60 parts by mass per 100 parts by mass of the rubber component. (F) The amount of resin blended is preferably 3 to 10 parts by mass per 100 parts by mass of the rubber component. (G) The ratio of the resin to the carbon black is preferably 0.05 to 0.15 as the resin / carbon black (mass ratio), and more preferably 0.07 to 0.12.

[0019] From the viewpoint of improving the dispersibility of each raw material and further enhancing the heat generation properties, the rubber composition of the present invention preferably 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. Examples of fatty acids in the glycerol fatty acid ester include fatty acids having 6 to 24 carbon atoms. Examples of commercially available glycerol fatty acid esters include DS100A (diglycerol monostearate), DO100V (diglycerol monooleate), S71D (diglycerol stearate), Poem J-4081V (tetraglycerol stearate), J-0021 (decaglycerol laurate), J-0081HV (decaglycerol stearate), and J-0381V (decaglycerol oleate), all 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): 2.0℃ ≤ T １ -T ０ ≤7.0℃ (1) 0.60 ≤P １ -P １００ ≤0.90 (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. In the present invention, as shown in formula (1) above, T １ and T ０ The difference is 2.0 to 7.0°C, preferably 3.0 to 7.0°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 １００ The difference is 0.60 to 0.90, preferably 0.60 to 0.80. ０ This is the tanδ value at 100°C for a rubber composition without resin. As described above, when formulas (1) and (2) are satisfied, the rubber component, in which isoprene rubber accounts for 50% by mass or more, exhibits high compatibility with 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, the heat generation is poor, which is undesirable. Conversely, if formula (2) is satisfied but formula (1) is not, the chipping resistance is poor, 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 (D) is mentioned, and preferably, the formulation design is carried out so that one or more of the above conditions (E) to (G) are satisfied.

[0022] Furthermore, since the rubber composition of the present invention can improve abrasion resistance and uneven wear 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 in 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> 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. ３The 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 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. The obtained resin A had a glass transition temperature (Tg) of 70°C, a number-average weight molecular weight of 900, a weight-average molecular weight of 2300, and an aromatic hydrocarbon-derived proton content of 0%.

[0029] <Synthesis of Resin B> 750 g of dicyclopentadiene and 750 g of piperine, dissolved separately in 1500 g of xylene, were continuously supplied to a stirred-tank reactor and reacted with stirring for 1 hour under conditions of 260°C and 2.5 MPa. Next, polymerization was carried out for 1 hour under conditions of 270°C and 2.5 MPa. The obtained product was reduced under reduced pressure at 200°C for 30 minutes to obtain a resinous product. Hydrogenation was carried out twice using 0.5 wt% palladium catalyst and 4 L / min of hydrogen relative to the total weight of the obtained resinous product under conditions of 260°C and 10 MPa. The obtained resin B had a Tg (glass transition temperature) of 58°C, a number-average weight molecular weight of 500, a weight-average molecular weight of 900, and an aromatic hydrocarbon-derived proton content of 10%.

[0030] <Synthesis of Resin C> 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 the resin product. The obtained resin C had a glass transition temperature (Tg) of 45°C, a number-average weight molecular weight of 780, a weight-average molecular weight of 1300, and an aromatic hydrocarbon-derived proton content of 8%.

[0031] <Synthesis of Resin D> 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 with stirring under a nitrogen stream. Then, the volatile components were removed under reduced pressure to obtain an 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 a hydrogenation reaction was carried out for 3 hours to obtain a colorless rosin derivative. The obtained resin D had a Tg (glass transition temperature) of 59°C, a number-average weight molecular weight of 1100, a weight-average molecular weight of 1600, and an aromatic hydrocarbon-derived proton content of 11%.

[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] Abrasion Resistance: The Lambourn abrasion index was measured using a Lambourn abrasion tester (manufactured by Iwamoto Seisakusho Co., Ltd.) under the conditions of a load of 5 kg (= 49 N), a slip ratio of 25%, a time of 4 minutes, and room temperature. The results were expressed as an index with the reference example value set to 100. A higher index indicates better abrasion resistance. An index of 105 or higher indicates good abrasion resistance. Uneven Abrasion Resistance: An 11R22.5 test tire with a tread made of the vulcanized rubber obtained above was mounted on a rim and mounted on a truck with a gross vehicle weight of 20 tons under the condition of an air pressure of 700 kPa. After driving 20,000 km on a dry road surface, the amount of uneven abrasion (block step difference) due to heel-and-toe abrasion that occurred on the blocks was measured. The results were calculated by taking the reciprocal of the measured value and expressed as an index with the reference example value set to 100. A higher index indicates better uneven abrasion resistance. An index of 105 or higher indicates good uneven abrasion resistance. 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 20 Hz, and temperature 60°C. 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. An exponent of 95 or higher indicates sufficient low heat generation. The results are shown in Tables 1 and 2.

[0034]

[0035]

[0036] *1: NR (STR20, Tg = -61°C) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd., Tg = -105°C) *3: E-SBR (Nipol 1502 manufactured by Nippon Zeon Co., Ltd., emulsion polymerized styrene-butadiene copolymer rubber) *4: 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) *5: Carbon black CB (S118 carbon black manufactured by Cabot Japan, nitrogen adsorption specific surface area (N ２ SA) = 148m２ / g) *6: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl) tetrasulfide) *7: Oil (Extract No. 4 S manufactured by Showa Shell Sekiyu K.K.) *8: Stearic acid (Bead Stearic Acid YR manufactured by NOF Corporation) *8-1: Glycerin fatty acid ester (Product name HT207 manufactured by Structol, glycerin fatty acid ester) *9: Anti-aging agent (SANTOFLEX 6PPD manufactured by Flexis) *10: Zinc oxide (3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd.) *11: Vulcanization accelerator CZ (Noxellar CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *12: Vulcanization accelerator NS (Sancellar NS-G manufactured by Sanshin Chemical Industry Co., Ltd.) *13: Sulfur (Sulfur treated with oil from Karuizawa Smelting Plant) *Resins A to D: Resins A to D synthesized as described above

[0037] From the results in Tables 1 and 2, it can be seen that the rubber composition of each example contains 100 parts by mass of rubber component containing 50 parts by mass or more of isoprene rubber, 40 to 60 parts by mass of carbon black, and 1 to 15 parts by mass of resin, and the ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and satisfies formulas (1) and (2), so compared to the reference example, it can be seen that abrasion resistance and uneven abrasion resistance are improved while maintaining low heat generation. In contrast, Comparative Example 1 has 60 parts by mass of butadiene rubber in 100 parts by mass of rubber component, so uneven abrasion resistance is reduced. Comparative Example 2 has a carbon black content below the lower limit specified in the present invention, so abrasion resistance is reduced. Comparative Example 3 has a carbon black content exceeding the upper limit specified in the present invention, so heat generation is worsened. Comparative Example 4 has a resin content exceeding the upper limit specified in the present invention, so heat generation is worsened. Comparative Example 5 is represented by formula (1) T １ -T ０ Since it is below the lower limit defined in the present invention, the heat generation deteriorated. Comparative Example 6 is a T represented by formula (1) １ -T ０ The value is less than the lower limit defined in this invention, and P is represented by formula (2). １ -P １００Since this is below the lower limit defined in this invention, the heat generation has deteriorated.

[0038] The present invention encompasses the following embodiments. Embodiment 1: A rubber composition comprising 100 parts by mass of a rubber component containing 50 parts by mass or more of isoprene rubber, 40 to 60 parts by mass of carbon black, and 1 to 15 parts by mass of resin, wherein the ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and the following formulas (1) and (2) are satisfied. 2.0℃≦T １ -T ０ ≤7.0℃ (1) 0.60 ≤P １ -P １００ ≦0.90 (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 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 rubber component is -55°C or lower. Embodiment 3: The rubber composition according to Embodiment 1 or 2, characterized in that it satisfies the following formula (3). (P ０ -P １００ )×MW≦25 (3) In formula (3), P １００ P is the tanδ value of the rubber composition at 100°C, and ０is the tanδ value at 100°C of the rubber composition when the resin is removed from the rubber composition, and MW is the weight-average molecular weight of the resin. Embodiment 4: The rubber composition according to any one of Embodiments 1 to 3, 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 5: The rubber composition according to any one of Embodiments 1 to 4, 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 6: The rubber composition according to any one of Embodiments 1 to 5, characterized in that the weight-average molecular weight (MW) of the resin is 300 to 2000. Embodiment 7: A heavy-duty tire using the rubber composition according to any one of Embodiments 1 to 6 in the tire tread. Embodiment 8: A heavy-duty tire according to Embodiment 7, characterized in that it has a plurality of circumferential main grooves extending in the circumferential direction of the tire, and at least three rows of land sections partitioned by the circumferential main grooves, and satisfies the following formula (4) when the tire tread width is W and the width of the outermost row of land sections in the tire width direction is Wsh: 0.15 ≤ Wsh / W ≤ 0.27 (4) Embodiment 9: A heavy-duty tire according to Embodiment 7 or 8, characterized in that it satisfies the following formula (5) when the tread gauge at the tread center portion provided in the center in the tire width direction is Gcc: 12.0 mm ≤ Gcc ≤ 30.0 mm (5)

[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 50 parts by mass or more of isoprene rubber, 40 to 60 parts by mass of carbon black, and 1 to 15 parts by mass of resin, wherein the ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and satisfying the following formulas (1) and (2). 2.0℃≦T １ -T ０ ≤7.0℃ (1) 0.60 ≤P １ -P １００ ≦0.90 (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 rubber component is -55°C or lower.

3. The rubber composition according to claim 1, characterized by satisfying the following formula (3). (P ０ -P １００ ) × MW ≤ 25 (3) In formula (3), P １００ is the tan δ value of the rubber composition at 100 °C, and P ０ is the tan δ value of the rubber composition at 100 °C when the resin is removed from the rubber composition, and MW is the weight average molecular weight of the resin.

4. 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.

5. 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.

6. The rubber composition according to claim 1, characterized in that the weight-average molecular weight (MW) of the resin is 300 to 2000.

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

8. A heavy-duty tire according to claim 5, having a plurality of circumferential main grooves extending in the circumferential direction of the tire, and at least three rows of land sections partitioned by the circumferential main grooves, wherein the tire tread width is W and the width of the outermost row of land sections in the tire width direction is Wsh, and the following formula (4) is satisfied: 0.15 ≤ Wsh / W ≤ 0.27 (4) 9. The heavy-duty tire according to claim 5, characterized in that when the tread gauge at the tread center portion located in the center of the tire width direction is Gcc, the following formula (5) is satisfied: 12.0 mm ≤ Gcc ≤ 30.0 mm (5)

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