tire

Abstract

We provide tires with low rolling resistance, low electrical resistance, excellent durability, and superior handling stability. [Solution] The system includes a rim cushion rubber 30 provided on the bead portion 3 and in contact with the rim on which the tire is mounted, and a tie rubber 10 positioned on the inside of the tire relative to the carcass and extending along the carcass between the bead cores. The specific surface area of ​​CTAB adsorption of carbon black contained in the rim cushion rubber [m 2 The specific surface area × mass fraction (RC) is the product of the carbon black [ / g] and the mass fraction in the rubber composition, and the specific surface area [m²] of the carbon black adsorbed by CTAB in the rubber. 2 With respect to the specific surface area × mass fraction (TR), which is the product of [ / g] and the mass fraction in the carbon black rubber composition, 30

Description

[Technical Field]

[0001] The present invention relates to a tire in which a rim cushion rubber is provided in the bead portion. [Background technology]

[0002] To reduce environmental impact, there is a demand for improved vehicle fuel efficiency. Therefore, tires are required to generate less heat during rolling and have low rolling resistance. To reduce tire heat generation, for example, reducing the amount of carbon black in the rubber composition of each part of the tire is effective. In recent years, research has been conducted to further improve fuel efficiency by suppressing heat generation in all parts of the tire except for the tread rubber that contacts the road surface.

[0003] On the other hand, as tire heat generation decreases, the amount of carbon black used in the compound decreases, which leads to the problem of increased electrical resistance in the tire. High electrical resistance in tires makes it difficult for static electricity accumulated in the vehicle to discharge to the road surface, which can cause problems such as noise in the car's radio (see, for example, Patent Document 1). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2013-237337 [Overview of the project] [Problems that the invention aims to solve]

[0005] Furthermore, depending on the part of the tire where the amount of carbon black is adjusted, heat generation may lead to a decrease in tire durability or a reduction in handling stability.

[0006] The present invention aims to provide a tire that has low rolling resistance, low electrical resistance, excellent durability, and excellent handling stability. [Means for solving the problem]

[0007] This disclosure includes the following aspects: Appearance [1] It is a tire, A pair of annular bead cores provided in the bead portion of the tire, A carcass is stretched between the bead cores in a toroidal shape, A rim cushion rubber is provided on the bead portion and contacts the rim on which the tire is mounted, The tire comprises a tie rubber positioned on the inside of the carcass and extending along the carcass between the bead cores, The rim cushion rubber and the tie rubber each consist of a rubber composition containing carbon black. The specific surface area of ​​CTAB adsorption of the carbon black contained in the rim cushion rubber [m² 2 The specific surface area × mass fraction (RC) is the product of the carbon black [ / g] and the mass fraction of the carbon black in the rubber composition, and the CTAB adsorption specific surface area [m²] of the carbon black contained in the rubber, and 2 With respect to the specific surface area × mass fraction (TR), which is the product of [ / g] and the mass fraction of the carbon black in the rubber composition, 30 < specific surface area × mass fraction (RC) + specific surface area × mass fraction (TR) < 57, A tire characterized by the condition that 20 < specific surface area × mass fraction (TR) < 40.

[0008] Appearance [2] A tire according to embodiment [1], satisfying 10 < specific surface area × mass fraction (RC) < 24.

[0009] Appearance [3] The tire according to embodiment [1] or [2], wherein the tie rubber contains 65 to 95 parts by mass of isoprene-based rubber in 100 parts by mass of the rubber component contained in the tie rubber.

[0010] Appearance [4] The tire according to any one of aspects [1] to [3], wherein the rim cushion rubber contains 52 to 67 parts by mass of the carbon black with respect to 100 parts by mass of the rubber component contained in the rim cushion rubber.

[0011] Aspect [5] The tire rubber contains, as the carbon black, 5 to 40 parts by mass of carbon black (A) having a CTAB adsorption specific surface area of 25 to 50 m 2 / g and 20 to 80 parts by mass of carbon black (B) having a CTAB adsorption specific surface area of 70 to 130 m 2 / g, and The tire according to any one of aspects [1] to [4], wherein the total content of the carbon black (A) and the carbon black (B) is 35 parts by mass or more with respect to 100 parts by mass of the rubber component contained in the tire rubber.

Advantages of the Invention

[0012] According to the tire of the above aspect, the rolling resistance is small, the electrical resistance is small, the durability is excellent, and the handling stability is excellent.

Brief Description of the Drawings

[0013] [Figure 1] It is a view showing a meridian cross section of a tire of one embodiment.

Modes for Carrying Out the Invention

[0014] Hereinafter, the tire of the embodiment will be described in detail. The tire of the present invention is preferably a tire for filling internal pressure such as a pneumatic tire. The tire of the present embodiment is a pneumatic tire. A cavity region surrounded by a rim and a tire for filling internal pressure mounted on the rim can be filled with air, an inert gas such as nitrogen, or other gases.

[0015] Figure 1 shows a meridian cross-section of the tire of this embodiment. The tire of this embodiment comprises a tread portion 1 that extends in the circumferential direction of the tire and forms an annular shape, a pair of sidewall portions 2 arranged on both sides of the tread portion 1 in the tire width direction, and a pair of bead portions 3 arranged on the radial side of the sidewall portions 2. In Figure 1, CL indicates the tire center line.

[0016] Each of the bead sections 3 has an annular bead core 5, which for example is made by winding a rubber-coated steel wire multiple times in the circumferential direction of the tire.

[0017] The carcass 4 is stretched across a pair of bead cores 5 in a toroidal shape, extending between the bead cores 5 and folded back around the bead cores 5 from the inside to the outside in the tire width direction. The carcass 4 is made of multiple reinforcing cords that are aligned to extend in the tire diameter direction and covered with rubber. The reinforcing cords are made of organic fibers such as PET fibers.

[0018] A bead filler 6 is positioned on the radially outer side of the bead core 5. The bead filler 6 is encased in a portion of the carcass 4 that is folded back around the bead core 5.

[0019] In the tread section 1, multiple layers (two layers in the example shown in Figure 1) of belts 7 are embedded on the radially outer side of the carcass 4. Each belt 7 includes multiple reinforcing cords (e.g., steel cords) that are inclined with respect to the circumferential direction of the tire, and the inclination directions of the reinforcing cords with respect to the circumferential direction of the tire are arranged to intersect with each other between layers. The inclination angle of the reinforcing cords of each belt 7 with respect to the circumferential direction of the tire is, for example, 10° to 40°.

[0020] A belt cover 8 is provided on the outer side of the upper layer (outer side in the tire radial direction) belt 7 in the tire radial direction. In the example shown in Figure 1, multiple layers of belt covers 8 are provided, consisting of a lower layer (inner side in the tire radial direction) belt cover 8 that covers the entire area of ​​the belt 7 in the tire width direction, and a pair of upper layers of belt covers 8 that cover both ends of the lower layer belt cover 8 in the tire width direction. The belt cover 8 includes organic fiber cords oriented in the tire circumferential direction. The inclination angle of the organic fiber cords of the belt cover 8 with respect to the tire circumferential direction is, for example, 0° to 5°.

[0021] An inner liner 9 is provided on the surface of the tire facing the side of the cavity region between the tire and the rim (the inner side of the tire). The inner liner 9 is positioned on the inner side of the tire relative to the carcass 4 and is a rubber that extends along the carcass 4 between a pair of bead cores 5. The inner liner 9 is composed of a rubber composition mainly of butyl rubber (IIR). The end of the inner liner 9 on the bead core 5 side is preferably in contact with the rim cushion rubber 30, which will be described later, as shown in Figure 1.

[0022] A tie rubber 10 is positioned between the carcass 4 and the inner liner 9. The tie rubber 10 is a rubber that is sandwiched between the carcass 4 and the inner liner 9 and extends along the carcass 4 between the pair of bead cores 5. When conductive rubber, described later, is provided on the tread portion 1, it is preferable that the tie rubber 10 extends at least from the bead core 5 side to a position beyond a straight line that extends in the tire radial direction, passing through the inner end of the conductive rubber in the tire radial direction. With a tie rubber 10 of this form, a path for electricity to flow between the rim and the road surface is easily secured. It is preferable that both ends of the tie rubber 10 on the bead core 5 side are in contact with the rim cushion rubber 30. In the example shown in Figure 1, the ends of the inner liner 9 and tie rubber 10 on the bead core 5 side are sandwiched between the carcass 4 and the rim cushion rubber 30 on the inner side of the bead core 5 in the tire radial direction.

[0023] The tread portion 1 has tread rubber 11 positioned radially outward of the carcass 4. The tread rubber 11 in the example shown in Figure 1 has a cap tread rubber 12 that has a contact surface that contacts the road surface, and an under tread rubber 13 positioned radially inward of the cap tread rubber 12. The under tread rubber 13 is in contact with the cap tread rubber 12 and the belt cover 8.

[0024] Preferably, the tread rubber 11 has a conductive rubber (also called earth tread rubber) embedded in it, which is not shown. The conductive rubber is in contact with the belt 7, or in the example shown in Figure 1, with the belt cover 8, and penetrates the tread rubber 11 in the tire radial direction to be exposed on the contact surface. The conductive rubber, for example, runs around the tire circumferentially along the tire center line CL, and its length in the tire width direction is, for example, 1 to 5 mm. The conductive rubber is made of a rubber composition containing carbon black, with the carbon black being, for example, 40 to 80 parts by mass per 100 parts by mass of the rubber components contained in the rubber composition.

[0025] In the sidewall section 2, the side rubber 20 is positioned on the outer side in the tire width direction of the carcass 4.

[0026] The bead portion 3 has a rim cushion rubber 30 arranged around the carcass 4 so as to be in contact with the rim.

[0027] The rim cushion rubber 30 and the tie rubber 10 each consist of a rubber composition containing carbon black. Such rim cushion rubber 30 and tie rubber 10 function as a series path for electricity to flow between the rim and the road surface, contributing to reducing the electrical resistance of the tire.

[0028] The specific surface area [m²] of carbon black adsorbed by CTAB (n-hexadecyltrimethylammonium bromide) contained in rim cushion rubber 30. 2 The specific surface area × mass fraction (RC) [m²] is the product of the mass fraction [parts / parts] of carbon black in the rubber composition of the rim cushion rubber 30 and the mass fraction [m²] of carbon black. 2[g], and the specific surface area of ​​carbon black adsorption [m²] of the CTAB contained in the rubber 10. 2 The specific surface area × mass fraction (TR) [m²] is the product of the mass fraction [parts / parts] of carbon black in the rubber composition of Thai Rubber 10. 2 Regarding / g], the tire of this embodiment is given by the following formula (1): 30<specific surface area x mass fraction (RC)+specific surface area x mass fraction (TR)<57...(1) Satisfying the conditions, The following equation (2): 20<specific surface area x mass fraction (TR)<40...(2) The following conditions are met. In this specification, the CTAB adsorption specific surface area of ​​carbon black is a value measured in accordance with JIS K6217-3.

[0029] According to the inventors' research, the ease with which various parts of a tire generate heat and the magnitude of its electrical resistance are strongly correlated with the magnitude of the product between the specific surface area of ​​CTAB adsorption of carbon black contained in each part of the tire and the mass fraction of carbon black in the rubber composition. It was found that a larger product value leads to easier heat generation, while a smaller product value leads to increased electrical resistance. Based on this finding, even if the amount of carbon black in each part of the tire is small, if the particle size of the carbon black is too small, the above product value will be large, and heat generation cannot be sufficiently suppressed. Conversely, even if the amount of carbon black in each part of the tire is large, if the particle size of the carbon black is too large, the above product value will be small, and electrical resistance cannot be sufficiently reduced. It is thought that when the particle size of carbon black is large, the spacing between particles becomes wider compared to when the particle size of carbon black is small, even if the above product value is the same, resulting in increased electrical resistance.

[0030] Since the tie rubber 10 forms a long conductive path between the rim and the contact surface, the electrical resistance of the tire can be efficiently reduced when the value of specific surface area × mass fraction (TR) exceeds 20, as shown in equation (2). However, if the value of specific surface area × mass fraction (TR) is too large, the tie rubber 10 is prone to overheating, increasing the rolling resistance of the tire. Therefore, the value of specific surface area × mass fraction (TR) is limited to less than 40, as shown in equation (2). On the other hand, if the heat generation of the tire around the bead core 5 cannot be suppressed, the durability of the tire may decrease. Therefore, in order to suppress the heat generation of the rim cushion rubber 30 and tie rubber 10 located around the bead core 5, the value of specific surface area × mass fraction (RC) + specific surface area × mass fraction (TR) is limited to less than 57, as shown in equation (1). On the other hand, if the value of specific surface area × mass fraction (RC) + specific surface area × mass fraction (TR) is too small, the rigidity of the part around the tire bead filler 6 will be insufficient, and the handling stability will decrease. Therefore, as shown in equation (1), the value of specific surface area × mass fraction (RC) + specific surface area × mass fraction (TR) is limited to exceeding 30.

[0031] Therefore, the tire of this embodiment satisfies equations (1) and (2), resulting in low electrical resistance, low rolling resistance, excellent durability, and excellent handling stability. With such a tire, the amount of carbon black in each part of the tire, excluding the cap tread rubber, is small, and even in a tire with low rolling resistance, electrical resistance can be effectively reduced.

[0032] For equation (1), the value of specific surface area × mass fraction (RC) + specific surface area × mass fraction (TR) is preferably 36 to 44.

[0033] For equation (2), the value of specific surface area × mass fraction (TR) is preferably 23 to 29.

[0034] According to one embodiment, the thickness of the tie rubber 10 is preferably 0.05 to 0.6 mm.

[0035] The tire of this embodiment is given by the following formula (3): 10<specific surface area x mass fraction (RC)<24...(3) It is preferable that the following conditions are met. When the specific surface area × mass fraction (RC) exceeds 10, the electrical resistance of the tire tends to decrease. Since the rim cushion rubber 30 has a large contact area with the rim, unlike the tire rubber 10, conductivity can be ensured even if the specific surface area × mass fraction (RC) is 20 or less, that is, even if the value of the specific surface area × mass fraction (RC) is smaller than the lower limit of the specific surface area × mass fraction (TR) in equation (2). When the specific surface area × mass fraction (RC) is less than 24, the rim cushion rubber 30 does not generate heat easily, so the rolling resistance of the tire tends to decrease, and the part around the bead core 5 of the tire does not generate heat easily, so durability does not deteriorate easily. The specific surface area × mass fraction (RC) is preferably 12 to 22, and more preferably 12 to 19.

[0036] Of the specific surface area × mass fraction of the rim cushion rubber 30 and the tie rubber 10, the specific surface area × mass fraction (RC) of the rim cushion rubber 30 has a greater influence on the rolling resistance of the tire. On the other hand, of the specific surface area × mass fraction of the rim cushion rubber 30 and the tie rubber 10, the tie rubber 10 has a greater influence on the electrical resistance of the tire. Because the rim cushion rubber 30 has a large contact area with the rim, it does not have as much influence on the electrical resistance of the tire as the specific surface area × mass fraction (TR) of the tie rubber 10. Therefore, according to one embodiment, it is preferable that the specific surface area × mass fraction (TR) is greater than the specific surface area × mass fraction (RC). On the other hand, it is preferable that the difference between the specific surface area × mass fraction (RC) and the specific surface area × mass fraction (TR) is 5 to 15.

[0037] The Thai Rubber 10 preferably contains 65 to 95 parts by mass of isoprene-based rubber per 100 parts by mass of the rubber components in the Thai Rubber 10 rubber composition. When the amount of isoprene-based rubber is 65 parts by mass or more per 100 parts by mass of the rubber components, the break elongation of the Thai Rubber 10 tends to improve, contributing to improved tire durability. Furthermore, when the amount of isoprene-based rubber is 95 parts by mass or less per 100 parts by mass of the rubber components, defects such as holes forming in the unvulcanized rubber sheet of the rolled Thai Rubber 10 tend to be suppressed. The Thai Rubber 10 more preferably contains 75 to 90 parts by mass of isoprene-based rubber per 100 parts by mass of the rubber components, and even more preferably contains 77 to 89 parts by mass. The isoprene-based rubber is, for example, natural rubber (NR). Specifically, the rubber components contained in the rubber composition of the Thai Rubber 10 are diene-based rubbers. Thai Rubber 10 may further contain, in addition to isoprene-based rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), etc., as rubber components.

[0038] The rim cushion rubber 30 preferably contains 40 to 70 parts by mass of isoprene rubber in 100 parts by mass of the rubber components contained in the rubber composition of the rim cushion rubber 30. Specifically, the rubber components contained in the rubber composition of the rim cushion rubber 30 are diene rubbers. Isoprene rubbers are, for example, natural rubber (NR). In addition to isoprene rubber, the rim cushion rubber 30 may also contain butadiene rubber (BR) or the like as rubber components.

[0039] The rim cushion rubber 30 preferably contains 52 to 67 parts by mass of carbon black with respect to 100 parts by mass of the rubber component contained in the rim cushion rubber 30. When the blending amount of carbon black is 52 parts by mass or more with respect to 100 parts by mass of the rubber component, the unvulcanized rubber sheet of the rolled rim cushion rubber 30 is difficult to shrink, and the shrinkage of the tire in the molding process performed after rolling can be suppressed. That is, a decrease in dimensional stability can be suppressed. Further, when the blending amount of carbon black is 67 parts by mass or less with respect to 100 parts by mass of the rubber component, it is possible to suppress an increase in the mixing time of the rubber component and carbon black when producing the rubber composition of the rim cushion rubber 30, and a decrease in productivity can be suppressed. The rim cushion rubber 30 more preferably contains 61 to 66 parts by mass of carbon black with respect to 100 parts by mass of the rubber component contained in the rim cushion rubber 30.

[0040] For the tire rubber 10, as the carbon black, 5 to 40 parts by mass of carbon black (A) having a CTAB adsorption specific surface area of 25 to 50 m 2 / g and carbon black having a CTAB adsorption specific surface area of 70 to 130 m 2The tie rubber 10 contains 20 to 80 parts by mass of carbon black (B) at a concentration of / g, and it is preferable that the total content of carbon black (A) and carbon black (B) is 35 parts by mass or more. By including carbon black (A), which has a larger particle size, in addition to carbon black (B), which has a smaller particle size, in the above-mentioned amounts, the rolling resistance of the tire tends to be lower compared to when only carbon black (B) is included in the above-mentioned amounts. Examples of carbon black (A) include GPF and FEF grades. Examples of carbon black (B) include HAF and ISAF grades. Furthermore, when the total content of carbon black (A) and carbon black (B) is 35 parts by mass or more, the unvulcanized rubber sheet of the rolled tie rubber 10 is less likely to shrink, and the processability of the unvulcanized rubber sheet of the tie rubber 10 is good. If the sheet shrinks, for example, when it is rolled up with the unvulcanized rubber sheet of the inner liner 9, wrinkles will occur in the overlapping sheets, making it difficult to roll them up properly. The total content of carbon black (A) and carbon black (B) is preferably 40 parts by mass or more, and more preferably 65 parts by mass or less, based on 100 parts by mass of rubber components contained in the rubber composition of Thai Rubber 10.

[0041] Furthermore, when a rubber composition contains carbon black with multiple types of CTAB adsorption specific surface area, the specific surface area × mass fraction is calculated as a weighted average value weighted by the mass fraction of each carbon black in the rubber composition.

[0042] The specific surface area of ​​carbon black adsorption (CTAB) in the rubber composition of the rim cushion rubber 30 is preferably 25 to 50 m². 2 The amount is expressed as / g, and for example, grades such as GPF and FEF are used. In addition, the carbon black content in the rubber composition of the rim cushion rubber 30 is preferably 50 to 70 parts by mass per 100 parts by mass of the rubber component.

[0043] The rubber compositions of Thai Rubber 10 and Rim Cushion Rubber 30 preferably contain, in addition to rubber components and carbon black, compounding agents such as oil, antioxidants, stearic acid, zinc oxide, sulfur, and vulcanization accelerators. On the other hand, the rubber composition of Thai Rubber 10 preferably does not contain surfactants such as nonionic surfactants. If surfactants are included, the viscosity of the unvulcanized rubber composition decreases, requiring more time for mixing. Furthermore, the decrease in viscosity may cause the rubber to adhere to the mixing equipment.

[0044] (Examples, Comparative Examples) To verify the effectiveness of the tire of this embodiment, vulcanized test tires with a tire size of 235 / 60R18 and the basic structure shown in Figure 1 were prepared by varying the specifications of the rubber composition of the tie rubber and rim cushion rubber (Comparative Example, Example), and their electrical resistance, rolling resistance, durability, and handling stability were evaluated.

[0045] The specifications for carbon black CB1 to CB4, shown in Tables 4 to 6, are as follows:

[0046] [Table 1]

[0047] The common raw material formulations for the Thai rubber TR1 to TR9 rubber compositions shown in Tables 4 to 6 are as shown in Table 2 below. The values ​​in the table represent parts by mass per 100 parts by mass of rubber component.

[0048] [Table 2]

[0049] The raw material formulations for the rim cushion rubbers RC1 to RC6, shown in Tables 4 to 6, are as shown in Table 3 below. The values ​​in the table represent parts by mass per 100 parts by mass of the rubber component.

[0050] [Table 3]

[0051] Other ingredients listed in the table are as follows: • NR: TSR20 • SBR: Zeon Corporation SBR1502 • BR: Nippon Zeon Co., Ltd. Nipol BR1220 • Oil: Idemitsu Kosan Co., Ltd. Diana Process NH-70S • Anti-aging agent: Nocrack 6C, manufactured by Ouchi Shinko Chemical Co., Ltd. • Stearic acid: Nisshin Rika Co., Ltd. Stearic acid 50S • Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. • Insoluble sulfur: Micron OT-20 manufactured by Shikoku Chemicals, Inc. • Vulcanization accelerator: Sanshin Chemical Industry Co., Ltd. Sunceller NS-G

[0052] The values ​​for raw materials in Tables 4 to 6 represent parts by mass per 100 parts by mass of rubber component. Tables 4 to 6 only show the rubber component and carbon black among the raw materials for the rim cushion rubber and tie rubber rubber compositions. In the tables, "RC" refers to rim cushion rubber and "TR" refers to tie rubber. The specific surface area × mass fraction (total) shown as an index in Tables 4 and 6 represents the sum of specific surface area × mass fraction (RC) and specific surface area × mass fraction (TR). The unit of specific surface area × mass fraction is (m²). 2 It is ( / g)·(parts of mass / parts of mass). The specific surface area × mass fraction of a rubber composition containing two types of carbon black A and B with different specific surface areas is given by the following formula: {(Specific surface area of ​​carbon black A adsorbing CTAB) × (Mass parts of carbon black A)} + (Specific surface area of ​​carbon black B adsorbing CTAB) × (Mass portion of carbon black B) / parts of mass of rubber composition The calculation was performed according to [the formula].

[0053] In each test tire, the tie rubber thickness was set to 0.3 mm. Note that the thickness of the tie rubber after vulcanization during the tire molding process is thinner than before vulcanization. The rubber compositions for each part of the tire, excluding the rim cushion rubber and tie rubber, were those commonly used in fuel-efficient tires. Conductive rubber was provided on the tire center line CL in the tread area.

[0054] In addition to electrical resistance, rolling resistance, durability, and handling stability, the processability of the rolled sheet of unvulcanized Thai rubber, the dimensional stability of the rolled sheet of unvulcanized rim cushion rubber, and the mixing time of the raw materials were evaluated according to the following procedure.

[0055] (Electrical resistance) In an environment with a temperature of 23°C and humidity of 50%, a test tire was mounted on a wheel with a rim size of 18×7J. Under conditions of air pressure of 200kPa and load of 5.26kN, a voltage of 1000V was applied to the wheel, and after 5 minutes, the electrical resistance [Ω] between the tread surface and the rim was measured. Measurements were taken at three points on the circumference of the tire, and the average value was calculated. In the table, the part of the value raised to the power of 10 to the power of n (where n is a natural number) is shown as the electrical resistance [Ω], denoted as "10^n". A smaller n indicates lower electrical resistance, superior discharge performance, and superior anti-static performance of the tire.

[0056] (Rolling resistance) The test tire was mounted on a wheel with a rim size of 18 x 7J, and the rolling resistance was measured using an indoor drum testing machine (drum diameter: 1707.6 mm) in accordance with ISO 28580, under conditions of air pressure of 210 kPa, load of 4.82 kN, and speed of 80 km / h. The measured value was expressed as an index with Comparative Example 1 set to 100. A smaller index value indicates lower rolling resistance and better fuel efficiency for the vehicle. An index value of 103 or less ensures low rolling resistance.

[0057] (durability) The tires were inflated to an air pressure of 120 kPa, mounted on an indoor drum testing machine (drum diameter: 1707.6 mm), subjected to a load of 8.58 kN, and driven at a speed of 81 km / h until tire failure occurred. The driving distance was expressed as an index, with the driving distance of Comparative Example 1 set to 100. A higher index value indicates superior durability. An index value of 98 or higher indicates superior durability.

[0058] (Handling stability) The test tires were mounted on wheels with a rim size of 18 x 7J and fitted to a 2.5L class sedan. The air pressure was set to 250kPa, and a subjective evaluation of handling stability was conducted by a test driver on a test course consisting of dry roads. The evaluation results are shown as an index with Comparative Example 1 set to 100. A higher index value indicates better handling stability. An index value of 98 or higher indicates excellent handling stability.

[0059] Based on the above results, the electrical resistance value in the table is 10 7 A component with a value smaller than Ω, a rolling resistance index of 103 or less, a durability index of 98 or higher, and a handling stability index of 98 or higher was evaluated as having low rolling resistance, low electrical resistance, excellent durability, and excellent handling stability.

[0060] (Processability of rolled sheets) The unvulcanized rubber used as the tie rubber for the test tire was rolled into a sheet and processed into a sheet. The degree of defects within a 100m length of the sheet in the longitudinal direction was investigated. Sheets with through holes of 1mm or more in diameter (maximum length) were evaluated as "defective," sheets without holes of 1mm or more in diameter but with roughness such as unevenness on the sheet surface were evaluated as "acceptable," and sheets that did not fall into any of the above categories were evaluated as "good." The thickness of the unvulcanized rubber sheet was set to 0.5mm.

[0061] (Dimensional stability of rolled sheets) Unvulcanized rubber, which will become the rim cushion rubber, was extruded and wound into a roll. Immediately after extrusion, the sheet was pulled out from the roll, a 70cm length was cut in the longitudinal direction (the direction in which it was pulled out), and the sheet was placed on a table. A 50cm mark was made in the longitudinal direction, and the shrinkage rate was calculated as the ratio of the amount of shrinkage at the mark after 1 hour to the length before shrinkage. A shrinkage rate of 10% or less was considered acceptable, a shrinkage rate of 7% to less than 10% was evaluated as "acceptable", a shrinkage rate of 5% to less than 7% was evaluated as "good", and a shrinkage rate of less than 5% was evaluated as "best".

[0062] (mixing time) The raw materials for the unvulcanized rubber used as rim cushion rubber, excluding sulfur and vulcanization accelerators, were mixed in a 1.8L sealed mixer at a speed of 50 revolutions per minute until the mixture reached 160°C (mixing process). If the Mooney viscosity of the unvulcanized rubber at 100°C, measured using an L-type rotor (hereafter measured under the same conditions), was 60 or less, the mixing process was completed in one pass. If the Mooney viscosity was not 60 or less, the unvulcanized rubber, after being released and cooled, was mixed under the same conditions, and the mixing process was repeated until the Mooney viscosity at the end of mixing was 60 or less. Fewer mixing passes indicated better productivity. Three mixing passes were rated as "acceptable," two as "good," and one as "best."

[0063] [Table 4]

[0064] [Table 5]

[0065] [Table 6]

[0066] From a comparison of the examples and comparative examples, it can be seen that satisfying equations (1) and (2) with respect to specific surface area × mass fraction (RC) and specific surface area × mass fraction (TR) results in low rolling resistance, low electrical resistance, excellent durability, and excellent handling stability.

[0067] From a comparison between Example 2 and Example 1, and between Example 3 and Example 4, it can be seen that by satisfying equation (3) with respect to specific surface area × mass fraction (RC), the effect of reducing electrical resistance while reducing rolling resistance can be obtained. A comparison of Example 5 with Examples 2 and 6 shows that when the isoprene-based rubber in the tie rubber is contained in an amount of 65 to 95 parts by mass per 100 parts by mass of rubber component, the durability of the tire is improved, while the occurrence of defects when the unvulcanized rubber of the tie rubber is processed into a sheet is suppressed. A comparison of Example 7 with Examples 2 and 8 shows that when the carbon black content of the rim cushion rubber is 52 to 67 parts by mass per 100 parts by mass of rubber component, the tire durability is improved, dimensional stability is excellent, and the mixing time of the raw materials for the rubber composition is shortened.

[0068] Although the tire of the present invention has been described in detail above, the tire of the present invention is not limited to the above embodiments or examples, and various improvements and modifications may be made without departing from the spirit of the present invention. [Explanation of Symbols]

[0069] 1. Tread section 2 Sidewall section 3. Bead section 4 Carcass 5 Bead core 6. Bead Filler 7 belts 8 Belt cover 9 Inner Liner 10 Thai rubber 11 Tread Rubber 12 Cap Tread Rubber 13 Undertread Rubber 20 Side rubber 30 Rim cushion rubber

Claims

1. It is a tire, A pair of annular bead cores provided in the bead portion of the tire, A carcass is stretched between the bead cores in a toroidal shape, A rim cushion rubber is provided on the bead portion and contacts the rim on which the tire is mounted, The tire comprises a tie rubber positioned on the inside of the carcass and extending along the carcass between the bead cores, The rim cushion rubber and the tie rubber each consist of a rubber composition containing carbon black. The CTAB adsorption specific surface area [m²] of the carbon black contained in the rim cushion rubber 2 The specific surface area × mass fraction (RC), which is the product of the carbon black / g and the mass fraction of the carbon black in the rubber composition, and the CTAB adsorption specific surface area of ​​the carbon black contained in the rubber [m²]. 2 With respect to the specific surface area × mass fraction (TR), which is the product of [ / g] and the mass fraction of the carbon black in the rubber composition, 30 < specific surface area × mass fraction (RC) + specific surface area × mass fraction (TR) < 57, A tire characterized in that 20 < specific surface area × mass fraction (TR) < 40.

2. The tire according to claim 1, satisfying 10 < specific surface area × mass fraction (RC) < 24.

3. The tire according to claim 1 or 2, wherein the tie rubber contains 65 to 95 parts by mass of isoprene-based rubber in 100 parts by mass of the rubber component contained in the tie rubber.

4. The tire according to claim 1 or 2, wherein the rim cushion rubber contains 52 to 67 parts by mass of carbon black with respect to 100 parts by mass of rubber components contained in the rim cushion rubber.

5. The aforementioned tie rubber has a carbon black content of 25 to 50 m² per 100 parts by mass of the rubber component contained in the tie rubber, with a CTAB adsorption specific surface area of ​​20 to 50 m². 2 5 to 40 parts by mass of carbon black (A) at a concentration of / g, and CTAB adsorption specific surface area of ​​70 to 130 m² 2 It contains 20 to 80 parts by mass of carbon black (B) at a concentration of / g, The tire according to claim 1 or 2, wherein the total content of carbon black (A) and carbon black (B) is 35 parts by mass or more per 100 parts by mass of rubber component contained in the tire rubber.

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