Rubber composition and heavy-duty tire using the same

Abstract

Construction vehicles operate for long periods under heavy loads, so they require features that suppress heat generation, improve uneven wear resistance, and enhance overall wear resistance. [Solution] A rubber composition comprising 100 parts by mass of a rubber component containing 50% or more isoprene-based rubber, 40 to 60 parts by mass of carbon black, and 1 to 15 parts by mass of resin, wherein the mass ratio of the resin to the carbon black is 0.05 to 0.20, and satisfying formulas (1) and (2). 2.0℃≦T1-T0≦7.0℃ (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), 0.60≦P1-P 100 ≤0.90 (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 and uneven abrasion resistance while maintaining low heat generation, and a heavy-duty tire using the same. [Background technology]

[0002] Construction vehicles such as large dump trucks operating in quarries and large-scale construction sites operate for long periods of time under heavy loads. The large tires fitted to such 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 tightening of greenhouse gas (GHG) regulations by the U.S. Environmental Protection Agency (EPA) have led to a demand for tires with lower rolling resistance. In addition, with the recent advancement of road infrastructure, vehicles are traveling at higher speeds and longer distances, and in addition to wear resistance, which has traditionally been considered the most important performance characteristic, there is an even stronger demand for resistance to uneven wear.

[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, the rubber composition constituting the rubber layer comprises a rubber component, a filler, and a resin component, the rubber component contains 20% by mass or more of styrene-butadiene rubber and isoprene-based rubber, 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 project] [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 and uneven abrasion 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 rubber component containing 50 parts by mass or more of isoprene-based rubber, Carbon black, 40-60 parts by mass, The resin is blended in 1 to 15 parts by mass, The ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and A rubber composition characterized by satisfying the following formulas (1) and (2). 2.0℃≦T1-T0≦7.0℃ (1) 0.60 ≤ P1 - P 100 ≤0.90 (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 in the tire tread. [Effects of the Invention]

[0009] The rubber composition of the present invention contains 50 parts by mass or more of isoprene rubber per 100 parts by mass of a rubber component, and 40 to 60 parts by mass of carbon black and 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 it is characterized by satisfying the following formulas (1) and (2). 2.0 °C ≤ T1 - T0 ≤ 7.0 °C (1) 0.60 ≤ P1 - P 100 ≤ 0.90 (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 and eccentric abrasion 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 high compatibility between the rubber component in which isoprene rubber occupies 50% by mass or more and the resin, and thereby can improve abrasion resistance and eccentric abrasion resistance while maintaining low heat generation.

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 one embodiment of the heavy-duty tire of the present invention.

Embodiments for Carrying Out the Invention

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

[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. Furthermore, in this invention, for example, styrene-butadiene copolymer rubber (SBR), butadiene rubber (BR), acrylonitrile-butadiene copolymer rubber (NBR), etc., can 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, it is preferable that the rubber component has a glass transition temperature (Tg) of -55°C or lower. In cases where multiple types of rubber components are included, the Tg as used herein is calculated based on the weighted average, which is the sum of the products obtained by multiplying the glass transition temperature of each rubber by the weight fraction of each rubber. For calculation purposes, the sum of the weight fractions of each component is assumed to be 1.0. 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) at a heating rate of 20°C / min using a thermogram. A more preferable Tg is -60°C or lower.

[0014] (Carbon Black) Specific examples of the carbon black used in the present invention include, for example, furnace carbon blacks such as SAF, ISAF, HAF, FEF, GPE, and SRF. These may be used alone or in combination of two or more. In addition, from the viewpoint of improving the effects of the present invention, the carbon black preferably has a nitrogen adsorption specific surface area (N2SA) of 60 to 160 m 2 / g, more preferably 65 to 155 m 2 / g. The nitrogen adsorption specific surface area (N2SA) is a value measured in accordance with 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 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, DCPD resins, hydrogenated resins (hydrogenated styrene resins, hydrogenated DCPD resins, etc.) and the like can be mentioned.

[0016] In the present invention, from the viewpoint of having a tanδ curve that satisfies the following formulas (1) and (2) described below, it is preferable that the resin 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 500 to 1500. (B) It is preferable to satisfy the following formula (3). (P0 - P 100 ) × MW ≤ 25 (3) In formula (3), P 100 is the tanδ value of the rubber composition at 100°C, P0 is the tanδ 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. The value of formula (3) is more preferably ≤ 20. (C) The glass transition temperature of the resin is preferably 40 to 130°C, and more preferably 50 to 120°C. (D) The resin is preferably a thermoplastic resin composed of aliphatic monomers and aromatic monomers, with an aromatic proton content of 0 to 15%. 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 comprises 100 parts by mass of the rubber component, 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). If the amount of carbon black used is less than 40 parts by mass, the wear resistance deteriorates, while if it exceeds 60 parts by mass, the heat generation deteriorates. 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. If the ratio of the resin to the carbon black is less than 0.05 (mass ratio of the resin to the carbon black), 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 of the above raw materials satisfies one or more of the following conditions (E) to (G). (E) The amount of carbon black added is preferably 45 to 60 parts by mass per 100 parts by mass of the rubber component. (F) The amount of resin added 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 mass ratio of the resin to the carbon black.

[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 glycerol fatty acid esters, and fatty acid metal salts such as zinc stearate. Among these, glycerol 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). 2.0℃≦T1-T0≦7.0℃ (1) 0.60 ≤ P1 - 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), forming a tanδ curve. In Figure 1, T1 is the peak temperature of the tanδ curve of the rubber composition of the present invention with resin added, and T0 is the peak temperature of the tanδ curve of the rubber composition without resin added. In the present invention, as shown by formula (1) above, the difference between T1 and T0 is 2.0 to 7.0°C, preferably 3.0 to 7.0°C. On the other hand, in the tanδ curve in Figure 1, P1 is the peak tanδ value of the rubber composition of the present invention containing the 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, P1 and P 100 The difference is 0.60 to 0.90, preferably 0.60 to 0.80. P0 is the tanδ value at 100°C for the rubber composition without resin. As described above, when formulas (1) and (2) are satisfied, the isoprene-based rubber component, which accounts for 50% or more by mass, 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 becomes poor, which is undesirable. Conversely, if formula (2) is satisfied but formula (1) is not satisfied, the chipping resistance becomes poor, which is undesirable. In order to satisfy the above formulas (1) and (2), one means of selecting a resin that satisfies one or more of the above conditions (A) to (D) is used, 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. Note that "construction vehicle" refers to a vehicle 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> 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 placed 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 the mixture was 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. 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> In a stirred-tank reactor, 750 g of dicyclopentadiene and 750 g of piperine, dissolved separately in 1500 g of xylene, were continuously supplied and reacted with stirring for 1 hour under conditions of 260°C and 2.5 MPa. Polymerization was then carried out for 1 hour under conditions of 270°C and 2.5 MPa. The resulting 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 resinous product, under conditions of 260°C and 10 MPa. The resulting resin B had a glass transition temperature (Tg) of 58°C, a number-average weight molecular weight (GPC) 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 resulting 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> 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 atmosphere. 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 (50% water content) were placed in a 1 liter shaking autoclave. After removing oxygen from the system, the system was pressurized with hydrogen to 10 MPa and heated to 220°C, and the hydrogenation reaction was carried out for 3 hours to obtain a colorless rosin derivative. The obtained resin D had a glass transition temperature (Tg) of 59°C, a number-average weight molecular weight of 1100 and a weight-average molecular weight of 1600 as determined by GPC, and an aromatic hydrocarbon-derived proton content of 11%.

[0032] Reference example, Examples 1-5, 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] Abrasion Resistance: The Lamborn abrasion index was measured using a Lamborn 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 are expressed as an index with the value of the standard example set to 100. A higher index indicates better abrasion resistance. An index of 105 or higher indicates good abrasion resistance. Uneven Wear Resistance: A test tire with a tread made of the vulcanized rubber obtained above, measuring 11R22.5, was mounted on a rim and fitted to a truck with a gross vehicle weight of 20 tons under an air pressure of 700 kPa. After driving 20,000 km on a dry road surface, the amount of uneven wear (block step difference) caused by heel-and-toe wear on the blocks was measured. The results were 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 index indicates better uneven wear resistance. An index of 105 or higher indicates good uneven wear resistance. Generating properties (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 generating properties. An exponent of 95 or higher indicates sufficiently low generating properties. The results are shown in Table 1.

[0034] [Table 1]

[0035] *1: NR (STR20, Tg=-61℃) *2: BR (Nipol BR1220 manufactured by Nippon Zeon Co., Ltd., Tg=-105℃) *3: E-SBR (Nipol 1502 manufactured by Zeon Corporation, emulsion polymerized styrene-butadiene copolymer rubber) *4: Silica (Zeosil 1085GR manufactured by Solvay Japan, nitrogen adsorption specific surface area (N2SA) = 90m²) 2 / g, CTAB specific surface area=80m 2 / g) *5: Carbon black CB (S118, manufactured by Cabot Japan, Nitrogen adsorption specific surface area (N2SA) = 148m²) 2 / g) *6: Silane coupling agent (Si69 manufactured by Evonik Degussa, bis(3-triethoxysilylpropyl)tetrasulfide) *7: Oil (Extract No. 4S manufactured by Showa Shell Sekiyu K.K.) *8: Stearic acid (YR bead stearic acid manufactured by NOF Corporation) *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 (Noxeller CZ-G manufactured by Ouchi Shinko Chemical Industry Co., Ltd.) *12: Vulcanization accelerator NS (Sunceller NS-G, manufactured by Sanshin Chemical Industry Co., Ltd.) *13: 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 composition of each example contains 100 parts by mass of rubber component containing 50 parts by mass or more of isoprene-based rubber, 40 to 60 parts by mass of carbon black, and 1 to 15 parts by mass of resin, with the ratio of the resin to the carbon black being 0.05 to 0.20 in terms of resin / carbon black (mass ratio), and satisfies formulas (1) and (2). Therefore, 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 had a reduced resistance to uneven wear because, out of 100 parts by mass of rubber components, butadiene rubber accounted for 60 parts by mass. Comparative Example 2 showed reduced wear resistance because the amount of carbon black used was below the lower limit specified in the present invention. In Comparative Example 3, the amount of carbon black used exceeded the upper limit specified in the present invention, resulting in poor heat generation. In Comparative Example 4, the ratio of resin to carbon black exceeded the upper limit specified in the present invention, resulting in poor heat generation. In Comparative Example 5, the heat generation was poor because T1-T0, represented by formula (1), was below the lower limit specified in the present invention. Comparative Example 6 has a T1-T0 represented by formula (1) that is less than the lower limit defined in the present invention, and P1-P represented by formula (2) 100 Since this is below the lower limit defined in this invention, the heat generation has deteriorated.

[0037] The present invention encompasses the following embodiments. Embodiment 1: For every 100 parts by mass of rubber component containing 50 parts by mass or more of isoprene-based rubber, Carbon black, 40-60 parts by mass, The resin is blended in 1 to 15 parts by mass, The ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and A rubber composition characterized by satisfying the following formulas (1) and (2). 2.0℃≦T1-T0≦7.0℃ (1) 0.60 ≤ P1 - P 100 ≤0.90 (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 rubber component is -55°C or lower. Embodiment 3: A rubber composition according to Embodiment 1 or 2, characterized in that it satisfies the following formula (3). (P0-P 100 ) × MW ≤ 25 (3) In formula (3), P 100P0 is the tanδ value of the rubber composition at 100°C, P0 is the tanδ 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. 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: A heavy-duty tire comprising a rubber composition according to any one of Embodiments 1 to 4 used in the tire tread. Embodiment 6: A heavy-duty tire according to Embodiment 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) Embodiment 7: A heavy-duty tire according to embodiment 5 or 6, characterized in that when the tread gauge at the tread center portion located in the center in the tire width direction is Gcc, the following formula (5) is satisfied. 12.0mm ≤ Gcc ≤ 30.0mm (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. For every 100 parts by mass of rubber component containing 50 parts by mass or more of isoprene-based rubber, 40 to 60 parts by mass of carbon black, The resin is blended in 1 to 15 parts by mass, The ratio of the resin to the carbon black is 0.05 to 0.20 as the resin / carbon black (mass ratio), and A rubber composition 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) 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 rubber component is -55°C or lower.

3. The rubber composition according to claim 1, 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 ０ is the tanδ value at 100°C of the rubber composition after the resin has been 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 are further added to 100 parts by mass of the rubber component.

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

6. The 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)

7. The heavy-duty tire according to claim 5, characterized in that when the tread gauge at the tread center portion located in the center in the tire width direction is Gcc, the following formula (5) is satisfied. 12.0mm≦Gcc≦30.0mm (5)

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