tire

Abstract

To provide a tire with low rolling resistance and electrical resistance, and excellent load-bearing capacity. [Solution] The tire of the embodiment comprises a bead filler rubber and tie rubber extending along the carcass between the bead cores. The tie rubber has a CTAB adsorption specific surface area of ​​25 to 50 m². 2 / g, 70-130m 2 The rubber contains 5 to 40 parts by mass of carbon black (A) and (B) at a concentration of / g, and 20 to 80 parts by mass of carbon black (A) and (B) at a total content of 35 parts by mass or more. The product of the CTAB adsorption specific surface area of ​​the carbon black contained in the rubber and its mass fraction in the rubber composition is 20 to 40. The bead filler rubber has a CTAB adsorption specific surface area of ​​60 to 100 m². 2 The bead filler rubber contains 60 to 85 parts by mass of carbon black at a concentration of / g. The product of the CTAB adsorption specific surface area of ​​the carbon black contained in the bead filler rubber and its mass fraction in the rubber composition is 21 to 27.

Description

[Technical Field]

[0001] The present invention relates to a tire equipped with a bead filler rubber. [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).

[0004] Furthermore, if the amount of carbon black is reduced, the rubber may lack sufficient hardness, and in parts of the tire where the amount of carbon black is adjusted, the load-bearing capacity may decrease. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2013-237337 [Overview of the project] [Problems that the invention aims to solve]

[0006] The present invention aims to provide a tire with low rolling resistance and electrical resistance, and excellent load-bearing capacity. [Means for solving the problem]

[0007] This disclosure includes the following aspects: Appearance [1] It is a tire, A pair of annular bead cores, A carcass is stretched across the pair of bead cores to form a toroidal shape, and folded around the bead cores from the inside to the outside in the tire width direction, A bead filler rubber is positioned on the radially outer side of the bead core and is arranged to be wrapped around the portion of the carcass that is folded back around the bead core. The tire comprises a tie rubber positioned on the inside of the carcass and extending along the carcass between the pair of bead cores, The aforementioned tie rubber has a CTAB adsorption specific surface area of ​​25 to 50 m² per 100 parts by mass of the rubber component contained in the tie rubber. 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 The rubber composition comprises 20 to 80 parts by mass of carbon black (B) at a concentration of / g, 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 the rubber component. The specific surface area of ​​the carbon black (A) with CTAB adsorption [m² 2 The product of [ / g] and the mass fraction of carbon black (A) in the rubber composition, and the CTAB adsorption specific surface area [m²] of carbon black (B) 2 The specific surface area × mass fraction (TR), which is the sum of the product of [ / g] and the mass fraction of carbon black (B) in the rubber composition, is 20 to 40. The bead filler rubber has a CTAB adsorption specific surface area of ​​60 to 100 m² per 100 parts by mass of the rubber component contained in the bead filler rubber. 2 It consists of a rubber composition containing 60 to 85 parts by mass of carbon black at a concentration of / g, The specific surface area of ​​the carbon black adsorption of the carbon black contained in the bead filler rubber [m² 2The ratio surface area × mass fraction (BF), which is the product of the specific surface area of the carbon black in the rubber composition of the tire rubber and the mass fraction of the bead filler rubber, is 21 to 27, a tire characterized by this.

[0008] Aspect [2] On at least one side in the tire width direction with respect to the tire center line of the tire, the range where the tire rubber is located in the height direction of the tire and the range where the bead filler rubber is located in the height direction of the tire overlap by a length of 3% or more of the height of the bead filler rubber. The tire according to Aspect [1].

[0009] Aspect [3] The ratio of the tensile stress M50(BF) [MPa] at 50% elongation of the rubber composition of the bead filler rubber to the tensile stress M50(TR) [MPa] at 50% elongation of the rubber composition of the tire rubber is 2.0 to 5.0. The tire according to Aspect [1] or [2].

[0010] Aspect [4] The rubber composition of the bead filler rubber further contains oil, and the content of the oil is 10 parts by mass or less with respect to 100 parts by mass of the rubber component. The tire according to any one of Aspects [1] to [3].

[0011] Aspect [5] The content of the carbon black (A) in the rubber composition of the tire rubber is equal to or more than the content of the carbon black (B). The tire according to any one of Aspects [1] to [4].

Advantages of the Invention

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

Brief Description of the Drawings

[0013] [Figure 1] It is a figure showing the meridian cross section of the tire of one embodiment. [Modes for carrying out the invention]

[0014] The tires of this embodiment will be described in detail below. The tire of the present invention is preferably a tire for internal pressure filling, such as a pneumatic tire, and the tire of this embodiment is a pneumatic tire. The cavity region surrounded by the rim and the internal pressure filling tire 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 pair of bead cores 5 and folded back around each bead core 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 rubber 6 is positioned on the radially outer side of the bead core 5. The bead filler rubber 6 is encased in a portion of the carcass 4 that is folded over around the bead core 5.

[0019] In the tread section 1, multiple layers (two layers 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 belt 7 in the tire radial direction. In the example shown in Figure 1, two layers of belt covers 8 are provided: a lower layer (inner side in the tire radial direction) belt cover 8 that covers the entire width of the belt 7 in the tire direction, and a pair of upper layers (outer side in the tire radial direction) 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 tire surface facing 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 consisting of butyl rubber (IIR).

[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 the tie rubber 10 is a single piece of rubber that passes through the tire center line CL and has both ends on the bead core 5 side in contact with the rim cushion rubber 30. In the example shown in Figure 1, the inner liner 9 and the bead core 5 side ends of the tie rubber 10 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 Earthtread rubber) embedded in it, which is not shown. The Earthtread rubber is a conductive rubber that is arranged to divide the cap tread rubber 12 and the under tread rubber 13 in the tire width direction by extending in the tire radial direction between the tread surface and the belt 7. The Earthtread rubber is arranged, for example, to go around the tire circumferentially along the tire center line CL. The length (width) of the Earthtread rubber in the tire width direction is, for example, 1 to 20 mm. The Earthtread rubber consists of a rubber composition containing, for example, 40 to 80 parts by mass of carbon black per 100 parts by mass of rubber component in the Earthtread rubber.

[0025] On the sidewall portion 2, a side rubber 20 is disposed on the outer side in the tire width direction of the carcass 4.

[0026] On the bead portion 3, a rim cushion rubber 30 that contacts the rim is disposed around the carcass 4.

[0027] The tread rubber 10 is composed of a rubber composition containing 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, based on 100 parts by mass of the rubber component contained in the tread rubber 10. The rubber component contained in the tread rubber 10 is specifically a diene rubber. In this specification, the CTAB adsorption specific surface area of carbon black is a value measured in accordance with JIS K6217-3.

[0028] When the tread rubber 10 contains carbon black (B) with a small particle size in addition to carbon black (A) with a large particle size in the above content, the electrical resistance of the tire is more likely to be smaller than when only carbon black (A) is contained in the above content. Further, when the tread rubber 10 contains carbon black (A) with a large particle size in addition to carbon black (B) with a small particle size in the above content, the rolling resistance of the tire is more likely to be smaller than when only carbon black (B) is contained in the above content.

[0029] Examples of the carbon black (A) include those of the GPF and FEF grades. The blending amount of the carbon black (A) is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, based on 100 parts by mass of the rubber component. Examples of the carbon black (B) include those of the HAF and ISAF grades. The CTAB adsorption specific surface area of the carbon black (B) is preferably 70 to 125 m 2 / g. The blending amount of the carbon black (B) is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, based on 100 parts by mass of the rubber component.

[0030] From the viewpoint of suppressing heat generation in the tie rubber 10, furnace black, channel black, thermal black, etc., are preferably used for carbon black (A) and carbon black (B). Furthermore, the DBP (dibutyl phthalate) absorption amount of carbon black (A) is preferably 125 mL / 100 g or less, and more preferably 95 mL / 100 g or less. The DBP absorption amount of carbon black (B) is preferably 130 mL / 100 g or less, and more preferably 100 mL / 100 g or less. The DBP absorption amount of carbon black is a value measured in accordance with JIS K6217-4.

[0031] 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. When the total content of carbon black (A) and carbon black (B) is 35 parts by mass or more, the effect of reducing the electrical resistance of the tire is easily obtained, the strength of the tie rubber 10 is ensured, and it contributes to the improvement of load durability. The total content of carbon black (A) and carbon black (B) is preferably 40 parts by mass or more, and more preferably 55 parts by mass or more, per 100 parts by mass of rubber component contained in the rubber composition of the tie rubber 10. On the other hand, if the total content of carbon black (A) and carbon black (B) is too high, the tie rubber 10 may generate heat, and the load durability may actually worsen. The total content of carbon black (A) and carbon black (B) is preferably 85 parts by mass or less, and more preferably 75 parts by mass or more, per 100 parts by mass of rubber component contained in the rubber composition of the tie rubber 10.

[0032] Regarding the rubber composition of Thai Rubber 10, the specific surface area of ​​carbon black (A) adsorbed by CTAB [m² 2 The product of [ / g] and the mass fraction of carbon black (A) in the rubber composition, and the CTAB adsorption specific surface area [m²] of carbon black (B). 2 The specific surface area × mass fraction (TR), which is the sum of the product of [ / g] and the mass fraction of carbon black (B) in the rubber composition, is between 20 and 40.

[0033] In other words, the specific surface area × mass fraction (TR) of the rubber composition of Thai Rubber 10 is given by the following formula: {(CTAB adsorption specific surface area of ​​carbon black (A) [m² 2 / g]) × (Carbon Black (A) content [parts by mass]) +(CTAB adsorption specific surface area [m²] of carbon black (B) 2 / g]) × (Carbon Black (B) content [parts by mass])} Mass [parts by mass] of the rubber composition of Thai Rubber 10 It is calculated according to [the formula].

[0034] 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.

[0035] In this embodiment, the tire's electrical resistance is reduced, heat generation of the rubber 10 is suppressed, and the tire's rolling resistance is reduced because the specific surface area × mass fraction (TR) value is between 20 and 40. In particular, since the rubber 10 forms a long conductive path between the rim and the contact surface, the tire's electrical resistance can be efficiently reduced when the specific surface area × mass fraction (TR) value exceeds 20. Furthermore, a specific surface area × mass fraction (TR) value of 20 to 40 contributes to improving the tire's load durability.

[0036] The value of specific surface area × mass fraction (TR) is preferably 22 to 38, more preferably 24 to 36, and even more preferably 26 to 34.

[0037] The bead filler rubber 6 has a CTAB adsorption specific surface area of ​​60 to 100 m² per 100 parts by mass of the rubber component contained in the bead filler rubber 6. 2 The rubber composition contains 60 to 85 parts by mass of carbon black at a concentration of / g. Specifically, the rubber component contained in the bead filler rubber 6 is a diene-based rubber. The CTAB adsorption specific surface area of ​​the carbon black is 60 m². 2 If the amount is 1 / g or more, the hardness of the bead filler rubber 6 is more easily ensured, contributing to improved load durability. On the other hand, if the CTAB adsorption specific surface area of ​​carbon black is 100m² 2 If the amount is less than / g, the heat generation of the bead filler rubber 6 is easily suppressed, and the rolling resistance of the tire is easily reduced. The specific surface area of ​​carbon black adsorption to CTAB is preferably 65 to 100 m². 2 / g, more preferably 70-95m 2 It is / g.

[0038] When the amount of carbon black added is 60 parts by mass or more, the effect of reducing the electrical resistance of the tire is more easily obtained, and the hardness of the bead filler rubber 6 is more easily ensured, contributing to improved load durability. On the other hand, when the amount of carbon black added is 85 parts by mass or less, the heat generation of the bead filler rubber 6 is more easily suppressed, and the rolling resistance of the tire is more easily reduced. The amount of carbon black added is preferably 65 to 80 parts by mass.

[0039] From the viewpoint of suppressing heat generation in the bead filler rubber 6, furnace black, channel black, thermal black, etc., are preferably used as the carbon black. Furthermore, the DBP absorption amount of the carbon black is preferably 110 mL / 100 g or less.

[0040] CTAB adsorption specific surface area [m²] of carbon black contained in bead filler rubber 6 2The specific surface area × mass fraction (BF), which is the product of the [ / g] and the mass fraction of the bead filler rubber 6 in the rubber composition, is between 21 and 27. When the specific surface area × mass fraction (BF) is 21 or higher, the conductivity of the bead filler rubber 6 improves, and by forming a conductive path together with the tie rubber 10, it contributes to reducing the electrical resistance of the tire. Also, when the specific surface area × mass fraction (BF) is 21 or higher, the strength of the bead filler rubber 6 is ensured, and the load durability of the tire is improved. On the other hand, when the specific surface area × mass fraction (BF) is 27 or lower, heat generation of the bead filler rubber 6 is easily suppressed, and the rolling resistance of the tire is easily reduced. Also, when the specific surface area × mass fraction (BF) is 27 or lower, it is advantageous in improving the load durability of the tire.

[0041] According to the tire of this embodiment described above, rolling resistance and electrical resistance are low, and load-bearing capacity is excellent.

[0042] Since the bead filler rubber 6 forms a conductive path together with the tie rubber 10, it is preferable that the specific surface area × mass fraction (BF) is high. However, from the viewpoint of suppressing heat generation due to the deformation of the bead filler rubber 6 during rolling, it is preferable that the specific surface area × mass fraction (BF) is not too high. Therefore, the value of the specific surface area × mass fraction (BF) is preferably 22 to 26, and more preferably 23 to 25.

[0043] Preferably, on at least one side in the tire width direction with respect to the tire center line CL, the area where the tie rubber 10 is located in the height direction of the tire and the area where the bead filler rubber 6 is located in the height direction of the tire overlap by a length of 3% or more of the height of the bead filler rubber. The height direction of the tire is the direction perpendicular to the rotation axis of the tire in the meridional cross-section of the tire. By overlapping the area where the tie rubber 10 is located and the area where the bead filler rubber 6 is located in this way, the flow of electricity from the rim to the road surface can flow more easily without interruption, and the electrical resistance of the tire is effectively reduced.

[0044] The overlapping length L between the area where the tie rubber 10 is located and the area where the bead filler rubber 6 is located is preferably 25% or more, more preferably 50% or more, and particularly preferably 100% of the height of the bead filler rubber 6. In the example shown in Figure 1, the area where the tie rubber 10 is located includes the area where the bead filler rubber 6 is located, and the above length L is 100% of the height of the bead filler rubber 6. Since the thickness of the tie rubber 10 is usually thin, even if the overlapping length L with the area where the bead filler rubber 6 is located is long, the effect on heat generation is small, and the adverse effect on rolling resistance is small. The height of the bead filler rubber 6 is preferably 15 to 55 mm, and preferably 20 to 50 mm.

[0045] The longer the above length L, the more of the conductive path between the rim and the road surface is secured by the tie rubber 10. Therefore, even if the electrical resistance of each part of the tire around the tie rubber 10 is high, the electrical resistance of the tire can be effectively reduced. Accordingly, by increasing the above length L, it is possible to use a rubber composition with a small amount of carbon black or a large particle size of carbon black as the rubber composition of each part of the tire around the tie rubber 10, thereby obtaining a tire with excellent fuel efficiency while reducing the electrical resistance of the tire. Examples of each part of the tire around the tie rubber 10 include the carcass 4, inner liner 9, side rubber 20, and undertread rubber 13. Furthermore, because the areas where the tie rubber 10 and the bead filler rubber 6 are located overlap, the height of the end of the tie rubber 10 on the bead core 5 side is lower than the height of the end (turn-up height) of the part of the carcass 4 that is folded back outward in the tire width direction and extends outward in the tire diameter direction. This configuration is advantageous when the electrical resistance of the carcass 4 is high. As a rubber composition for the coating rubber that covers the cords of such a carcass 4, for example, a CTAB adsorption specific surface area of ​​25 to 40 m² per 100 parts by mass of rubber component is used. 2 An example of a rubber composition is one containing 30 to 65 parts by mass of carbon black with a DBP absorption rate of 60 to 95 mL / 100 g.

[0046] The ratio of the tensile stress M50(BF)[MPa] of the bead filler rubber 6 at 50% elongation to the tensile stress M50(TR)[MPa] of the Thai rubber composition at 50% elongation is preferably 2.0 to 5.0. The tensile stress M50 is measured in accordance with JIS K6251. If the above ratio exceeds 5.0, the hardness of the bead filler rubber 6 is too hard compared to the hardness of the Thai rubber 10, which can lead to a significant deterioration in load durability and rolling resistance. A ratio of 2.0 or higher is advantageous in terms of achieving both handling stability and load durability. The above ratio is preferably 2.5 to 4.5, and more preferably 3.0 to 4.0.

[0047] The M50(BF) of the bead filler rubber 6 is preferably 5 to 11 MPa, and more preferably 7 to 10 MPa. On the other hand, the M50(TR) of the tie rubber 10 is preferably 1.5 to 5 MPa, and more preferably 2 to 3.5 MPa.

[0048] The content of carbon black (A) in the rubber composition of Thai Rubber 10 is preferably equal to or greater than the content of carbon black (B). This tends to improve at least one of the rolling resistance and load durability. The ratio of the carbon black (A) content to the carbon black (B) content is preferably 1 to 3 and 1.2 to 2.5.

[0049] The bead filler rubber 6 and tie rubber 10 may contain silica as another filler in addition to carbon black. Furthermore, the bead filler rubber 6 and tie rubber 10 may also contain other fillers such as clay, talc, calcium carbonate, mica, aluminum hydroxide, etc.

[0050] The bead filler rubber 6 preferably contains 80 to 100 parts by mass of isoprene rubber and 0 to 20 parts by mass of other diene rubber per 100 parts by mass of the rubber components contained in the bead filler rubber 6. By including isoprene rubber in such proportions, the strength of the bead filler rubber 6 can be ensured and the handling stability of the tire can be ensured. Examples of isoprene rubber include various natural rubbers, epoxidized natural rubbers, and various synthetic polyisoprene rubbers, with natural rubber being particularly suitable. Examples of other diene rubbers include butadiene rubber and styrene-butadiene rubber.

[0051] Preferably, the Tie Rubber 10 contains 50 to 95 parts by mass of isoprene rubber and 5 to 50 parts by mass of styrene-butadiene rubber per 100 parts by mass of the rubber components contained in the Tie Rubber 10. When the amount of isoprene rubber is 50 parts by mass or more per 100 parts by mass of the rubber components, the breaking strength and breaking elongation of the Tie Rubber 10 tend to improve, contributing to improved load durability of the tire. Also, when the amount of isoprene rubber is 95 parts by mass or less per 100 parts by mass of the rubber components, the occurrence of defects such as holes forming in the unvulcanized rubber sheet of the rolled Tie Rubber 10 tends to be suppressed. Examples of isoprene rubber include various natural rubbers, epoxidized natural rubbers, and various synthetic polyisoprene rubbers, and natural rubber can be used particularly suitably. The amount of isoprene rubber is preferably 60 to 90 parts by mass, more preferably 70 to 85 parts by mass, per 100 parts by mass of the rubber components. The amount of styrene-butadiene rubber blended is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass, per 100 parts by mass of the rubber component. In addition to isoprene-based rubber and styrene-butadiene rubber, the rubber composition of Thai Rubber 10 may also include other diene-based rubbers, such as butadiene rubber.

[0052] It is preferable to further incorporate sulfur and a vulcanization accelerator into the bead filler rubber 6 and tie rubber 10. The amount of sulfur contained in the bead filler rubber 6 is preferably 4 to 8 parts by mass, more preferably 5 to 7.5 parts by mass, per 100 parts by mass of the rubber component. The amount of vulcanization accelerator contained in the bead filler rubber 6 is preferably 1.5 to 4 parts by mass, more preferably 2.0 to 3.5 parts by mass, per 100 parts by mass of the rubber component. The amount of sulfur contained in the Thai rubber 10 is preferably 2 to 4 parts by mass, more preferably 2.5 to 3.5 parts by mass, per 100 parts by mass of the rubber component. The amount of vulcanization accelerator contained in the Thai rubber 10 is preferably 0.2 to 1.5 parts by mass, more preferably 0.5 to 1.0 part by mass, per 100 parts by mass of the rubber component.

[0053] The bead filler rubber 6 and tie rubber 10 may contain other compounding agents such as oil, stearic acid, antioxidants, resins, and zinc oxide.

[0054] The amount of oil in the bead filler rubber 6 is preferably 10 parts by mass or less per 100 parts by mass of rubber components. By limiting the amount of oil in the bead filler rubber 6 in this way, it is possible to suppress the migration of oil to various parts of the tire around the bead filler rubber 6 as the tire deteriorates due to dry heat, which can reduce load durability. The oil content in the bead filler rubber 6 is preferably 8 parts by mass or less. On the other hand, the oil content in the bead filler rubber 6 is preferably 4 parts by mass or more, and more preferably 5 parts by mass or more, in order to ensure the processability of the rubber composition. Examples of oils include essential oils.

[0055] The amount of resin in the bead filler rubber 6 is preferably 24 parts by mass or less, and more preferably 22 parts by mass or less, per 100 parts by mass of the rubber component of the bead filler rubber 6, so as to ensure that the M50 (BF) of the bead filler rubber 6 does not become too high and load durability is ensured. Examples of resins contained in the bead filler rubber 6 are phenolic resins, alkylphenolic resins, and phenolic resins modified using cashew oil. Cashew oil is a liquid oil at room temperature obtained from the shell portion of cashew seeds (cashew nuts).

[0056] The amount of the anti-aging agent is preferably 0.1 to 4 parts by mass, and more preferably 0.5 to 3 parts by mass, per 100 parts by mass of the rubber component of the tire rubber 10 or bead filler rubber 6. When the anti-aging agent is included in such amounts, the load durability of the tire tends to improve. The anti-aging agent is preferably an amine-based anti-aging agent, and in the tire rubber 10, preferably 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD) is used as the amine-based anti-aging agent. In the bead filler rubber 6, preferably an aromatic secondary amine-based anti-aging agent such as N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine (6PPD) is used as the amine-based anti-aging agent. The amounts of other compounding agents can be set to standard amounts.

[0057] Furthermore, it is preferable that the rubber composition of Thai Rubber 10 does not contain surfactants such as nonionic surfactants. If surfactants are present, the viscosity of the unvulcanized rubber composition decreases, which increases the time required for mixing. In addition, the decrease in viscosity may cause the rubber to adhere to the mixing equipment.

[0058] The unvulcanized tie rubber 10 is preferably a laminate of unvulcanized rubber, with the lengths of the unvulcanized inner liner 9 being equal to each other in the tire width direction, and the ends in the tire width direction overlapping each other. With this form of tie rubber 10, there is no step in the center of the laminate in the tire width direction, so it is possible to prevent air from entering between adjacent unvulcanized rubbers and remaining inside the tire when manufacturing the unvulcanized tire. In addition, the inner liner 9 can be well adhered to the carcass 4 via this tie rubber 10. Furthermore, with this form of tie rubber 10, it is possible to prevent the rubber of the inner liner 9 from being pressed by the reinforcing cords of the carcass 4 and lifting up on the inner surface of the tire.

[0059] According to one embodiment, the thickness of the tie rubber 10 is preferably 0.05 to 0.6 mm.

[0060] (Examples, Standard Examples, Comparative Examples) To verify the effectiveness of the tire of this embodiment, vulcanized test tires with a tire size of 235 / 45R18 and the basic structure shown in Figure 1 were prepared by varying the specifications of the rubber composition of the tie rubber and bead filler rubber (standard example, comparative example, example), and their electrical resistance, rolling resistance, and load durability after dry heat degradation were evaluated.

[0061] To prepare the rubber compositions, each compound component, excluding the vulcanization accelerator and sulfur, was weighed and kneaded in a 1.8 L sealed Banbury mixer for 5 minutes. The masterbatch was then released and allowed to cool to room temperature. Subsequently, this masterbatch was placed in a 1.8 L sealed Banbury mixer, the vulcanization accelerator and sulfur were added, and the mixture was mixed for 2 minutes to obtain each rubber composition.

[0062] The specifications for carbon blacks CB1 to CB4, shown in Tables 4 and 5, are as follows:

[0063] [Table 1]

[0064] The raw materials and compounding amounts common to the Thai rubber shown in Tables 4 and 5 are as shown in Table 2 below. The values ​​in the table represent parts by mass per 100 parts by mass of rubber component.

[0065] [Table 2]

[0066] The raw materials and compounding amounts for bead filler rubbers A to E shown in Tables 4 and 5 are as shown in Table 3 below. The values ​​in the table represent parts by mass per 100 parts by mass of rubber component.

[0067] [Table 3]

[0068] Other ingredients listed in the table are as follows: • NR: TSR20 • SBR: Zeon Corporation SBR1502 • Aroma oil: Idemitsu Kosan Co., Ltd. Diana Process NH-70S • Stearic acid: Nisshin Rika Co., Ltd. Stearic acid 50S • Zinc oxide: Three types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. • Anti-aging agent 1: N-phenyl-N'-1,3-dimethylbutyl-p-phenylenediamine (6PPD), manufactured by Ouchi Shinko Chemical Co., Ltd., Nocrack 6C • Anti-aging agent 2: 2,2,4-trimethyl-1,2-dihydroquinoline polymer (RD), manufactured by Ouchi Shinko Chemical Co., Ltd., Nocrack 224 • Alkylphenol resin: Hitanol 1502Z, Hitachi Chemical Co., Ltd. • Phenolic resin: Sumitomo Bakelite Co., Ltd. Sumilite Resin PR-NR-1 • Cardanol resin: CD-5L, manufactured by Tohoku Kako Co., Ltd. • Insoluble sulfur: Micron OT-20 manufactured by Shikoku Chemicals, Inc. • Vulcanization accelerator 1: Sanshin Chemical Industry Co., Ltd. Sunceller NS-G • Vulcanization accelerator 2: Sancellar HT-PO manufactured by Sanshin Chemical Industry Co., Ltd.

[0069] The values ​​for raw materials in Tables 4 and 5 represent parts by mass per 100 parts by mass of rubber component. Note that Tables 4 and 5 only show the rubber component and carbon black among the raw materials of Thai rubber's rubber composition. The units for specific surface area × mass fraction shown in Tables 4 and 5 are (m²). 2 It is ( / g)·(parts of mass / parts of mass). In the table, TR stands for tie rubber and BF stands for bead filler rubber. The "overlap with bead filler rubber" of the tie rubber in the table is shown as the percentage (%) of the height of the bead filler rubber, which is the length L in the height direction between the outer edge of the bead filler rubber in the tire radial direction and the inner edge of the tie rubber in the tire radial direction.

[0070] In each test tire, the height of the bead filler rubber was set to 30 mm. The thickness of the rubber tie was kept constant in the tire width direction, at 0.5 mm. The rubber compositions for each part of the tire, excluding the bead filler rubber and tie rubber, employ compositions commonly used in fuel-efficient tires, for example. The carcass has a CTAB adsorption specific surface area of ​​30 m² per 100 parts by mass of rubber component. 2 A coated rubber was used, consisting of a rubber composition containing 50 parts by mass of carbon black with a DBP absorption rate of 87 mL / 100 g, and coated with PET fibers. Conductive rubber is provided on the tire center line CL in the tread area.

[0071] The tensile stress M50 of tie rubber and bead filler rubber at 50% elongation was measured using a No. 3 dumbbell test specimen of vulcanized rubber in accordance with JIS K6251, under conditions of a tensile speed of 500 mm / min and a temperature of 23°C.

[0072] Electrical resistance, rolling resistance, and load durability after dry heat degradation were evaluated according to the following procedure.

[0073] (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.

[0074] (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 the standard example set to 100. A smaller index value indicates lower rolling resistance and better fuel efficiency for the vehicle.

[0075] (Load durability after dry heat degradation) Each test tire was mounted on a wheel with a rim size of 18 x 7J and stored for 7 days at a temperature of 70°C with an internal pressure of 350 kPa and oxygen sealed inside. The pre-treated test tires were then mounted on an indoor drum testing machine (drum diameter: 1707.6 mm) at an internal pressure of 280 kPa, with an ambient temperature of 38 ± 3°C, a load of 100% of the JATMA maximum load, and a speed of 81 km / h, with the load increased by 8% every 2 hours. The distance traveled until tire failure occurred was measured. The evaluation results were expressed as an index using the measured distance traveled, with the standard example set to 100. A higher index value indicates superior durability after dry heat degradation.

[0076] [Table 4]

[0077] [Table 5]

[0078] From a comparison between Example 1 and the standard example, the specific surface area of ​​the tie rubber adsorbing CTAB was 70-130 m². 2 It can be seen that the electrical resistance decreases when carbon black is also included at a concentration of / g. A comparison of Example 1 with Comparative Examples 1 and 2 shows that the CTAB adsorption specific surface area of ​​the tie rubber is 25-50 m². 2 It has been found that including carbon black at a concentration of / g results in lower rolling resistance and superior load durability after dry heat degradation. A comparison of Example 1 with Comparative Examples 3 and 4 shows that when the specific surface area × mass fraction (TR) of the tie rubber is between 20 and 40, the electrical resistance and rolling resistance are low, and the load durability after dry heat degradation is excellent. A comparison of Example 1 with Comparative Examples 5 and 6 shows that when the specific surface area × mass fraction (BF) of the bead filler rubber is between 21 and 27, the electrical resistance and rolling resistance are low, and the load durability after dry heat degradation is excellent.

[0079] 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]

[0080] 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, A carcass is stretched across the pair of bead cores to form a toroidal shape, and folded around the bead cores from the inside to the outside in the tire width direction, A bead filler rubber is positioned on the radially outer side of the bead core and is arranged to be wrapped around the portion of the carcass that is folded back around the bead core. The tire comprises a tie rubber positioned on the inside of the carcass and extending along the carcass between the pair of bead cores, The aforementioned tie rubber has a CTAB adsorption specific surface area of ​​25 to 50 m² per 100 parts by mass of the rubber component contained in the tie rubber. 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 The rubber composition comprises 20 to 80 parts by mass of carbon black (B) at a concentration of / g, 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 the rubber component. The specific surface area of ​​CTAB adsorption of the carbon black (A) [m²] 2 The product of the mass fraction of carbon black (A) in the rubber composition and the CTAB adsorption specific surface area [m²] of carbon black (B) 2 The specific surface area × mass fraction (TR), which is the sum of the product of [ / g] and the mass fraction of carbon black (B) in the rubber composition, is 20 to 40. The bead filler rubber has a CTAB adsorption specific surface area of ​​60 to 100 m² per 100 parts by mass of the rubber component contained in the bead filler rubber. 2 The rubber composition consists of 60 to 85 parts by mass of carbon black at a concentration of / g. The CTAB adsorption specific surface area [m²] of the carbon black contained in the bead filler rubber. 2 A tire characterized in that the specific surface area × mass fraction (BF), which is the product of [ / g] and the mass fraction of carbon black in the rubber composition of the bead filler rubber, is 21 to 27.

2. The tire according to claim 1, wherein, on at least one side in the tire width direction with respect to the tire center line of the tire, the range in which the tie rubber is located in the height direction of the tire and the range in which the bead filler rubber is located in the height direction of the tire overlap by a length of 3% or more of the height of the bead filler rubber.

3. The tire according to claim 1 or 2, wherein the ratio of the tensile stress M50(BF) [MPa] of the bead filler rubber at 50% elongation to the tensile stress M50(TR) [MPa] of the rubber composition of the tie rubber at 50% elongation is 2.0 to 5.

0.

4. The tire according to claim 1 or 2, wherein the rubber composition of the bead filler rubber further contains oil, and the amount of oil is 10 parts by mass or less per 100 parts by mass of the rubber component.

5. The tire according to claim 1 or 2, wherein the content of carbon black (A) in the rubber composition of the tire rubber is equal to or greater than the content of carbon black (B).

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