tire

Abstract

The present invention provides a tire that maintains good side rubber tensile strength and fatigue resistance while improving low heat generation without compromising handling stability and reducing electrical resistance. [Solution] The tire of the embodiment is equipped with a side rubber and a tie rubber. The side rubber has a CTAB adsorption specific surface area of ​​20 to 60 m². 2 It contains 25-50 parts by mass of carbon black per gram. The product of the CTAB adsorption specific surface area and mass fraction of the carbon black in the side rubber is 5-20. The tie rubber has a CTAB adsorption specific surface area of ​​25-50 m². 2 5-40 parts by mass of carbon black (A) per gram, and CTAB adsorption specific surface area of ​​70-130 m². 2 It contains 20 to 80 parts by mass of carbon black (B) at a concentration of / g, and the total content of carbon black (A) and (B) is 35 parts by mass or more. CTAB adsorption specific surface area of ​​carbon black (A) and (B) in Thai rubber [m² 2 The product of [ / g] and mass fraction is between 20 and 40.

Description

[Technical Field]

[0001] The present invention relates to a tire equipped with side rubber in the sidewall portion. [Background technology]

[0002] In pneumatic tires, there is a need to improve fuel efficiency during driving in order to reduce environmental impact. Therefore, efforts are being made to suppress heat generation in the rubber compositions that make up each part of the pneumatic tire. In recent years, to further improve fuel efficiency, for example, efforts are being made to suppress heat generation in the side rubber of pneumatic tires.

[0003] Generally, the tanδ (hereinafter referred to as tanδ(60°C)) at 60°C, measured by dynamic viscoelasticity, is used as an indicator of the heat generation of rubber compositions. The smaller the tanδ(60°C) of the rubber composition, the lower the heat generation. Methods to reduce the tanδ(60°C) of a rubber composition include, for example, reducing the amount of carbon black added. However, with such methods, the required tensile strength for the side rubber may not be sufficient, and the handling stability required for the tire may not be adequately achieved. One way to improve the tensile strength of the side rubber is to adjust the type and composition of the rubber used in the side rubber, but depending on the type and composition of rubber adopted, the fatigue resistance may decrease. Therefore, further measures are needed to improve low heat generation (low tanδ(60°C)) without compromising the handling stability of the tire, while maintaining good tensile strength and fatigue resistance of the side rubber.

[0004] Furthermore, as tire heat generation decreases, the amount of carbon black used in the compound also decreases, which leads to the problem of increased electrical resistance in the tire. High electrical resistance in the tire 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]

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

[0006] The present invention aims to provide a tire that maintains good tensile strength and fatigue resistance of the side rubber, improves low heat generation without impairing handling stability, and reduces electrical resistance. [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 between the bead cores in a toroidal shape, A tie rubber is positioned on the inside of the tire relative to the carcass and extends along the carcass between the bead cores, The tire comprises a side rubber positioned on the outside of the tire relative to the carcass and located on the surface of the tire's sidewall, The aforementioned side rubber has a CTAB adsorption specific surface area of ​​20 to 60 m² per 100 parts by mass of the rubber component contained in the side rubber. 2 It consists of a rubber composition containing 25 to 50 parts by mass of carbon black at a concentration of / g. The CTAB adsorption specific surface area of ​​the carbon black [m²] 2 The specific surface area × mass fraction (SR), which is the product of [ / g] and the mass fraction of carbon black in the rubber composition, is 5 to 20. 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 2It consists of a rubber composition containing 20 to 80 parts by mass of carbon black (B) per g, and 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. The CTAB adsorption specific surface area [m 2 / g] of the carbon black (A) and the product of the mass fraction of the carbon black (A) in the rubber composition of the said rubber, and the CTAB adsorption specific surface area [m 2 / g] of the carbon black (B) and the product of the mass fraction of the carbon black (B) in the rubber composition of the said rubber, and the total of the specific surface area × mass fraction (TR) is 20 to 40. A tire characterized by this.

[0008] Aspect [2] The side rubber contains 30 to 60 parts by mass of isoprene rubber and 40 to 70 parts by mass of butadiene rubber in 100 parts by mass of the rubber component of the side rubber. The tread rubber contains 50 to 95 parts by mass of isoprene rubber and 5 to 50 parts by mass of styrene-butadiene rubber in 100 parts by mass of the rubber component of the tread rubber. The tire according to Aspect [1].

[0009] Aspect [3] The butadiene rubber contained in the side rubber is a butadiene rubber synthesized by a neodymium-based catalyst. The tire according to Aspect [2].

[0010] Aspect [4] The maximum thickness of the side rubber at the tire radial position where the thickness of the side rubber is maximum is 5.0 mm or less. The tire according to any one of Aspects [1] to [3].

[0011] Aspect [5] The ratio T30(SR) / T30(TR) of the 30% vulcanization time [min] T30(SR) of the rubber composition of the side rubber to the 30% vulcanization time [min] T30(TR) of the rubber composition of the tread rubber is 0.5 to 1.7. The tire according to any one of Aspects [1] to [4].

Effect of the Invention

[0012] According to the tire of the above aspect, while maintaining good breaking strength and fatigue resistance characteristics of the side rubber, the low heat generation property is improved without impairing the handling stability, and the electric resistance is reduced.

Brief Description of Drawings

[0013] [Figure 1] It is a figure which shows the meridian cross section of the tire of one Embodiment.

Mode 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] FIG. 1 is a view showing a meridian cross section of the tire of the present embodiment. The tire of the present embodiment includes a tread portion 1 extending in the tire circumferential direction and having an annular shape, a pair of sidewall portions 2 disposed on both sides of the tread portion 1 in the tire width direction, and a pair of bead portions 3 disposed on the inner side in the tire radial direction of the sidewall portion 2. In FIG. 1, CL indicates the tire center line. Hereinafter, the description using FIG. 1 is basically based on the meridian cross-sectional shape, but each part of the tire extends in the tire circumferential direction and has an annular shape.

[0016] Each of the bead portions 3 has, for example, an annular bead core 5 having a structure in which a plurality of steel wires coated with rubber are wound around in the tire circumferential direction.

[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 uppermost belt 7 in the tire radial direction. In the example shown in Figure 1, two layers of belt covers 8 are provided: a lower belt cover 8 (inner side in the tire radial direction) that covers the entire width of the belt 7 in the tire direction, and a pair of upper belt covers 8 (outer side in the tire radial direction) that cover both ends of the lower 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 from the bead core 5 side to a position that exceeds a straight line extending in the tire radial direction, passing at least 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 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 20 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] Each sidewall section 2 is provided with a side rubber 20 positioned on the outer side of the tire (outer side in the tire width direction) relative to the carcass 4, and located on the outer surface of the sidewall section 2. The side rubber 20 is the part of the tire that experiences the greatest bending during driving, and therefore is required to have excellent tensile strength and fatigue resistance.

[0026] In the bead section 3, a rim cushion rubber 30 is arranged around the carcass 4 and in contact with the rim.

[0027] The side rubber 20 has a specific surface area of ​​CTAB adsorption (n-hexadecyltrimethylammonium bromide) of 20-60 m² per 100 parts by mass of the rubber component contained in the side rubber 20. 2 The rubber composition contains 25 to 50 parts by mass of carbon black at a concentration of / g. The specific surface area of ​​CTAB adsorption of carbon black contained in the side rubber 20 [m² 2 The specific surface area × mass fraction (SR) of the side rubber 20, which is the product of the carbon black content ( / g) and the mass fraction of carbon black in the rubber composition, is between 5 and 20. In this specification, the CTAB adsorption specific surface area of ​​carbon black is a value measured in accordance with JIS K6217-3. As described above, if the type or composition of rubber used in the side rubber 20 is adjusted to improve the breaking strength of the side rubber 20, the fatigue resistance of the side rubber 20 may decrease. According to this embodiment, by including large-particle carbon black in the side rubber 20 as described above, it is possible to suppress the deterioration of tanδ (60°C) while maintaining good breaking strength and fatigue resistance of the side rubber 20. In addition, the amount of carbon black blended is set within the above range so as to ensure the breaking strength of the side rubber 20 and so as not to impair the handling stability of the tire. The specific surface area × mass fraction (SR) of the side rubber 20 being between 5 and 20 contributes to improving low heat generation without impairing the handling stability of the tire. When the specific surface area × mass fraction (SR) of the side rubber 20 is 5 or more, the tensile strength of the side rubber 20 is effectively improved. More preferably, the specific surface area × mass fraction (SR) is 5 to 10. Specifically, the rubber component of the side rubber 20 is a diene-based rubber.

[0028] As the carbon black, among the carbon blacks commonly used in rubber compositions for tires, the carbon black having a CTAB adsorption specific surface area of 20 m 2 / g to 60 m 2 / g, preferably 30 m 2 / g to 50 m 2 / g, more preferably 35 m 2 / g to 45 m 2 / g is used. By using such carbon black, it is advantageous for suppressing the deterioration of tanδ(60°C) while maintaining the breaking strength and fatigue resistance characteristics of the side rubber 20 well. If the CTAB adsorption specific surface area of the carbon black is less than 20 m 2 / g, the abrasion resistance decreases. If the CTAB adsorption specific surface area of the carbon black exceeds 60 m 2 / g, the low heat generation property deteriorates. Examples of the carbon black include those of GPF and FEF grades. The side rubber 20 may contain two or more types of carbon blacks having different CTAB adsorption specific surface areas as the carbon black. In this case, the calculation of the specific surface area × mass fraction (SR) of the side rubber 20 is performed using the formula for obtaining the specific surface area × mass fraction (TR) of the tread rubber 10 described later.

[0029] From the viewpoint of not impairing the handling stability of the tire, the blending amount of the carbon black in the side rubber 20 is preferably 30 to 45 parts by mass, more preferably 35 to 40 parts by mass, based on 100 parts by mass of the rubber component contained in the side rubber 20.

[0030] In the tread rubber 10, 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 70 to 130 m of CTAB adsorption specific surface area 2The rubber composition comprises 20 to 80 parts by mass of carbon black (B) at a concentration of / g. 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. When the tie rubber 10 contains large-particle carbon black (A) and small-particle carbon black (B) in the above proportions, it is easier to obtain the effect of suppressing heat generation in the tie rubber 10 while securing a conductive path between the rim and the road surface. In addition, the fact that the proportions of carbon black (A) and carbon black (B) meet the above proportions contributes to improved handling stability. If the proportions of carbon black (A) and carbon black (B) are greater than the above proportions, the 30% vulcanization time T30 (TR) of the tie rubber 10, described later, will be shortened, and as a result, delamination may occur at the interface between the tie rubber 10 and the carcass 9 during driving. Examples of carbon black (A) include GPF and FEF grades. Examples of carbon black (B) include HAF and ISAF grades. 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 the rubber component contained in the rubber composition of Thai Rubber 10. Specifically, the rubber component of Thai Rubber 10 is a diene-based rubber.

[0031] CTAB adsorption specific surface area of ​​carbon black (A) [m²] 2 The product of [ / g] and the mass fraction of carbon black (A) in the rubber composition of Tie Rubber 10, and the CTAB adsorption specific surface area [m²] of carbon black (B). 2 The specific surface area × mass fraction (TR) of Thai rubber 10, which is the sum of the product of [ / g] and the mass fraction of carbon black (B) in the rubber composition of Thai rubber 10, is between 20 and 40.

[0032] 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].

[0033] 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. A larger product value indicates easier heat generation, while a smaller product value indicates 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 will not 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 will not 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. In the tire of this embodiment, the specific surface area × mass fraction (TR) is 20 to 40, which allows the tie rubber 10 to function as a conductive path between the tire and the rim, contributing to a reduction in the tire's electrical resistance. Combined with the above-mentioned effect of improved low heat generation (tanδ(60°C)) due to the side rubber 20, this suppresses heat generation in the tire and prevents deterioration of tanδ(60°C). The specific surface area × mass fraction (TR) is preferably 22 to 38, and more preferably 25 to 35.

[0034] As described above, the tire of this embodiment improves low heat generation without impairing handling stability while maintaining good tensile strength and fatigue resistance of the side rubber 20, and reduces electrical resistance. In particular, in a tire equipped with the side rubber 20 in which the amount of carbon black is limited, it is possible to secure conductive paths and effectively reduce electrical resistance.

[0035] The value of specific surface area × mass fraction (TR) is preferably greater than the value of specific surface area × mass fraction (SR). Among the side rubber 20 and tie rubber 10 that extend in parallel over a long distance between the rim and the road surface, electrical resistance can be effectively reduced by reducing the specific surface area × mass fraction (SR) of the carbon black in the side rubber 20, which is prone to significant bending and heat generation during driving, while increasing the specific surface area × mass fraction (TR) of the tie rubber 10, which extends over a longer distance between the rim and the road surface and is generally thinner than the side rubber. The value of specific surface area × mass fraction (TR) is preferably 1.1 to 2.7 times, and more preferably 1.4 to 1.7 times, the value of specific surface area × mass fraction (SR). Furthermore, the thickness of the tie rubber 10 is preferably thinner than the thickness of the side rubber 20, preferably 0.1 to 2 mm, and more preferably 0.3 to 1.5 mm. Such a thickness of tie rubber 10 contributes to suppressing heat generation in the tie rubber 10 while ensuring a conductive path between the rim and the tire.

[0036] The side rubber 20 preferably contains 30 to 60 parts by mass of isoprene-based rubber and 40 to 70 parts by mass of butadiene rubber per 100 parts by mass of the rubber component of the side rubber 20. A blending amount of isoprene-based rubber of 30 parts by mass or more per 100 parts by mass of the rubber component effectively improves the tensile strength of the side rubber 20, contributing to improved handling stability. On the other hand, a blending amount of isoprene-based rubber of 60 parts by mass or less per 100 parts by mass of the rubber component suppresses a decrease in the fatigue resistance characteristics of the side rubber 20.

[0037] Examples of isoprene-based rubbers included in the side rubber 20 include various natural rubbers, epoxidized natural rubbers, and various synthetic polyisoprene rubbers. Among these isoprene-based rubbers, natural rubber is particularly suitable for use. The amount of isoprene-based rubber blended is preferably 35 to 60 parts by mass, more preferably 40 to 55 parts by mass, per 100 parts by mass of the rubber component (diene-based rubber).

[0038] The amount of butadiene rubber contained in the side rubber 20 is preferably 45 to 65 parts by mass, more preferably 50 to 60 parts by mass, per 100 parts by mass of diene rubber.

[0039] The butadiene rubber contained in the side rubber 20 is preferably butadiene rubber synthesized with a neodymium-based catalyst (hereinafter sometimes referred to as Nd-BR). Using butadiene rubber polymerized with a neodymium-based catalyst contributes to reducing the heat generated by the tire.

[0040] Butadiene rubber polymerized using neodymium-based catalysts (Nd-BR) is a known material, and is butadiene rubber polymerized using neodymium-based catalysts such as elemental neodymium, compounds of neodymium with other metals, and organoneodymium compounds. Butadiene rubber synthesized with these neodymium-based catalysts has the characteristics of high molecular weight and a sharp molecular weight distribution. Commercially available Nd-BR can also be used, such as Buna CB22 and Buna CB24 from Arlanxeo. Polymerizing butadiene rubber using neodymium-based catalysts in this way can improve its low exothermic properties.

[0041] It is preferable that the side rubber 20 contains only one type of butadiene rubber (Nd-BR), and that two or more types of Nd-BR are not used in combination, and that Nd-BR is not used in combination with other types of butadiene rubber.

[0042] The vinyl content in butadiene rubber (Nd-BR) is preferably 0.5% to 1.0% by mass, more preferably 0.5% to 0.8% by mass, and even more preferably 0.6% to 0.7% by mass. Such a low vinyl content is advantageous for improving the heat generation properties. If the vinyl content in butadiene rubber (Nd-BR) is less than 0.5% by mass, the processability decreases. If the vinyl content in butadiene rubber (Nd-BR) exceeds 1.0% by mass, the heat generation properties decrease. The vinyl content of butadiene rubber (Nd-BR) shall be measured by infrared spectroscopy (Hampton method). The increase or decrease in the vinyl content of butadiene rubber can be appropriately adjusted by conventional methods, such as by changing the type of catalyst (specific type of neodymium-based catalyst mentioned above).

[0043] The rubber composition of the side rubber 20 may contain other diene rubbers in addition to isoprene rubber and butadiene rubber. Other diene rubbers that are commonly used in tire rubber compositions can be used. For example, styrene-butadiene rubber can be used. These other diene rubbers can be used alone or in any blend.

[0044] Preferably, the Tyrub 10 contains 50 to 95 parts by mass of isoprene-based rubber and 5 to 50 parts by mass of styrene-butadiene rubber in 100 parts by mass of the rubber component of Tyrub 10. When the amount of isoprene-based rubber is 50 parts by mass or more in 100 parts by mass of the rubber component, the breaking strength and breaking elongation of Tyrub 10 tend to improve, and the durability of the tire tends to improve. Also, when the amount of isoprene-based rubber is 95 parts by mass or less in 100 parts by mass of the rubber component, defects such as holes forming in the unvulcanized rubber sheet of rolled Tyrub 10 tend to be suppressed.

[0045] Examples of isoprene-based rubbers included in Thai Rubber 10 include various natural rubbers, epoxidized natural rubbers, and various synthetic polyisoprene rubbers. Among these isoprene-based rubbers, natural rubber is particularly suitable for use. The amount of isoprene-based rubber blended is preferably 60 to 90 parts by mass, and more preferably 70 to 85 parts by mass, per 100 parts by mass of the rubber component (diene-based rubber).

[0046] The amount of styrene-butadiene rubber contained in Thai rubber 10 is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass, per 100 parts by mass of diene rubber.

[0047] The rubber composition of TyRubber 10 may contain other diene rubbers in addition to isoprene rubber and styrene-butadiene rubber. Other diene rubbers that are commonly used in tire rubber compositions can be used. For example, butadiene rubber can be used. These other diene rubbers can be used alone or in any blend.

[0048] The rubber compositions of the side rubber 20 and the tie rubber 10 may contain fillers other than carbon black. Examples of other fillers include materials commonly used in tire rubber compositions, such as silica, clay, talc, calcium carbonate, mica, and aluminum hydroxide.

[0049] It is preferable to further incorporate sulfur and a vulcanization accelerator into the rubber composition of the side rubber 20. When sulfur and a vulcanization accelerator are incorporated, the total amount is preferably 2.5 parts by mass or more, more preferably 2.5 to 3.0 parts by mass, per 100 parts by mass of the rubber component. By incorporating a sufficient amount of sulfur and a vulcanization accelerator in this way, the low heat generation can be improved. If the total amount of sulfur and a vulcanization accelerator is less than 2.5 parts by mass, the heat generation will decrease. The individual amounts of sulfur and a vulcanization accelerator are not particularly limited, but for sulfur, it is preferably 1.0 to 2.0 parts by mass, more preferably 1.5 to 2.0 parts by mass, and for a vulcanization accelerator, it is preferably 0.5 to 1.5 parts by mass, more preferably 0.5 to 1.0 part by mass.

[0050] The rubber composition of Thai Rubber 10 preferably further contains sulfur and a vulcanization accelerator. Preferably, the amount of sulfur is 2.0 to 3.0 parts by mass, more preferably 2.5 to 3.0 parts by mass, and the amount of vulcanization accelerator is preferably 0.5 to 1.5 parts by mass, more preferably 0.5 to 1.0 part by mass.

[0051] As vulcanization accelerators, those commonly used in tire rubber compositions can be used, for example, sulfenamide-based vulcanization accelerators, guanidine-based vulcanization accelerators, and thiram-based vulcanization accelerators. Examples of sulfenamide-based vulcanization accelerators include N,N-dicyclohexyl-1,3-benzothiazole-2-sulfenamide (DZ), N-cyclohexyl-2-benzothiazolesulfenamide (CZ), N-oxydiethylene-2-benzothiazolesulfenamide (OBS), and N-(tert-butyl)benzothiazole-2-sulfenamide (NS). Examples of guanidine-based vulcanization accelerators include diphenylguanidine and dioltotolylguanidine. Examples of thiram-based vulcanization accelerators include tetramethylthiram monosulfide and tetramethylthiram disulfide.

[0052] Other compounding agents may be added to the rubber compositions of the side rubber 20 and the tie rubber 10. Examples of other compounding agents include vulcanizing or crosslinking agents other than sulfur, waxes, oils, antioxidants, stearic acid, zinc oxide, liquid polymers, and various other compounding agents commonly used in tire rubber compositions. The amounts of these compounding agents can be the conventional amounts, as long as they do not contradict the purpose of the present invention. As for the mixing machine, ordinary rubber mixing machines such as Banbury mixers, kneaders, and rolls can be used. On the other hand, it is preferable that the rubber composition of Thai Rubber 10 does not contain surfactants such as nonionic surfactants. If surfactants are included, 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 stick to the mixing equipment.

[0053] The rubber compositions of the side rubber 20 and tie rubber 10 can be mixed using general methods, but in order to more effectively reduce heat generation, it is preferable to mix isoprene rubber, butadiene rubber or styrene-butadiene rubber and carbon black in the rubber composition of the side rubber 20 before mixing in vulcanizing compounding agents (sulfur, vulcanization accelerator, etc.). In particular, in this process, it is preferable to first mix the entire amount of isoprene rubber and carbon black as the first mixing step, and then add butadiene rubber or styrene-butadiene rubber to the mixture obtained in the first mixing step and mix it as the second mixing step. By mixing in this order, including the first and second mixing steps, the butadiene rubber or styrene-butadiene rubber is added and mixed after the isoprene rubber and carbon black, so it is possible to control the carbon black to be preferentially incorporated into the isoprene rubber that was added first, thereby improving fatigue resistance while achieving reduced heat generation.

[0054] Preferably, the maximum thickness of the side rubber 20 at the tire radial position where the thickness of the side rubber 20 is greatest is 5.0 mm or less. This contributes to reducing the weight of the tire and is advantageous for improving low heat generation. More preferably, the above maximum thickness of the side rubber 20 is 4.5 mm or less. On the other hand, the above maximum thickness of the side rubber 20 is preferably 2.0 mm or more in order to secure an electrical path for the part of the tire other than the tie rubber 10 between the rim and the road surface.

[0055] The ratio T30(SR) / T30(TR) of the 30% vulcanization time T30(SR) [min] of the rubber composition of the side rubber 20 to the 30% vulcanization time T30(TR) [min] of the rubber composition of the tie rubber 10 is preferably 0.5 to 1.7. The 30% vulcanization time T30 refers to the time [min] until the torque reaches {(Fmax-Fmin)×0.3+Fmin}, measured at the maximum (Fmax) and minimum (Fmin) values ​​of the torque in the vulcanization curve of the rubber composition obtained in accordance with JIS K6300-2:2001. In the molding process, the unvulcanized tire is heated from both the outside and inside of the tire. If the temperature difference between the outside and inside of the tire is too large, overvulcanization of the rubber may occur on the side with the higher temperature. Overvulcanized rubber may delaminate at the interface with adjacent rubber during driving. In particular, if the temperature on the inside of the tire is higher, overvulcanization of the tie rubber 10 may occur, and delamination may occur at the interface between the tie rubber 10 and the carcass during driving. By limiting T30(SR) / T30(TR) to the above range, overvulcanization of the side rubber 20 or tie rubber 10 can be suppressed, and the occurrence of delamination at the interface between the side rubber 20 or tie rubber 10 and the adjacent rubber can be suppressed. In other words, delamination resistance is improved. T30(SR) / T30(TR) is preferably 0.7 to 1.5, and more preferably 0.9 to 1.3. A tire in which T30(SR) / T30(TR) satisfies the above range can be obtained by adjusting the composition of the rubber composition so that the T30 of the side rubber 20 and the tie rubber 10 are within a predetermined range.

[0056] (Examples, comparative examples, reference examples) To verify the effectiveness of the tire of this embodiment, rubber compositions were prepared by varying the specifications of the rubber compositions for the side rubber and tie rubber (reference example, comparative example, example), and the tensile strength of the side rubber, fatigue resistance, and tanδ (60°C) of the side rubber and tie rubber were investigated. In addition, the electrical resistance, handling stability, and peel resistance of vulcanized test tires made using each rubber composition were investigated.

[0057] 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.

[0058] The rubber compositions of the side rubbers shown in Tables 3 and 4, excluding the rubber component and carbon black, are all as shown in Table 1 below. The values ​​in the table represent parts by mass per 100 parts by mass of the rubber component.

[0059] [Table 1]

[0060] The raw materials for the side rubber shown in Tables 1, 3, and 4 are as follows: • NR: Natural rubber, NUSIRA • BR1: Butadiene rubber, manufactured by Ube Industries, Ltd. UBEPOL BR150 • BR2: Butadiene rubber synthesized using a neodymium catalyst, manufactured by ARLANXEO, Buna CB22 (cis-1,4-bond content: 98 mol%, glass transition temperature Tg = -106°C, weight-average molecular weight Mw = 7.5) • CB1: Carbon black, manufactured by Nippon Steel Carbon Co., Ltd. CB Nitelon (CTAB adsorption specific surface area: 32m²) 2 / g) • CB2: Carbon black, manufactured by Cabot Japan Co., Ltd. STERLING (CTAB adsorption specific surface area: 45m²) 2 / g) • CB3: Carbon black, manufactured by Cabot Japan, VULCAN MS (CTAB adsorption specific surface area: 90m²) 2 / g) • Wax: OZOACE-0015 manufactured by Nippon Seiro Co., Ltd. • Anti-aging agent: Sumitomo Chemical Antigen 6C • Zinc oxide: ZM Silesia ZINC OXIDE • Stearic acid: Lunac S-25 manufactured by Kao Corporation • Sulfur: MIDAS-105 manufactured by Bigensha • Vulcanization accelerator: Bayer Vulkacit NZ / EG

[0061] The rubber compositions of Thai rubber shown in Tables 3 and 4, excluding the rubber components and fillers, are all as shown in Table 2 below. The values ​​in the table represent parts by mass per 100 parts by mass of the rubber component.

[0062] [Table 2]

[0063] The raw materials for Thai rubber shown in Tables 2 to 4 are as follows: • NR: Natural rubber, TSR20 • SBR: Styrene-butadiene rubber, manufactured by Zeon Corporation, SBR1502 • CB1: Carbon black, OCI Company Ltd. DASHBLAK N660 (CTAB adsorption specific surface area: 32m²) 2 / g) • CB4: Carbon black, manufactured by Nippon Steel Carbon Co., Ltd. Nitelon #300 (CTAB adsorption specific surface area: 115 m²) 2 / g) • Oil: Diana Process NH-70S, manufactured by Idemitsu Kosan Co., Ltd. • Anti-aging agent: Nocrack 6C, manufactured by Ouchi Shinko Chemical Co., Ltd. • Stearic acid: Stearic acid 50S, manufactured by Nisshin Rika Co., Ltd. • Zinc oxide: 3 types of zinc oxide manufactured by Seido Chemical Industry Co., Ltd. • Sulfur: Micron OT-20 manufactured by Shikoku Chemicals Co., Ltd. • Vulcanization accelerator: Sancellar NS-G, manufactured by Sanshin Chemical Industry Co., Ltd.

[0064] The values ​​for raw materials in Tables 3 and 4 represent parts by mass per 100 parts by mass of rubber component. Note that Tables 3 and 4 only show the rubber component and carbon black among the raw materials for the rubber compositions of the side rubber and tie rubber. The specific surface area × mass fraction (SR) of the side rubber containing two types of carbon black with different CTAB adsorption specific surface areas was calculated using the above formula, with the carbon black having the smaller CTAB adsorption specific surface area designated as carbon black (A) and the carbon black having the smaller CTAB adsorption specific surface area designated as carbon black (B). The specific surface area × mass fraction (TR) of the rubber composition of Thai rubber was calculated according to the formula described above.

[0065] In each test tire, the maximum thickness of the side rubber was set to 4 mm, and the thickness of the tie rubber was set to 0.5 mm. The rubber composition of each part of the tire, excluding the side rubber and tie rubber, was a composition commonly used in fuel-efficient tires, for example. Conductive rubber was provided on the tire center line CL in the tread area.

[0066] The rupture strength, fatigue resistance, tanδ (60°C), T30 of the side rubber and tie rubber, electrical resistance, handling stability, and peel resistance of the tire were evaluated according to the following procedure.

[0067] (Breaking strength) Using the rubber composition of each side rubber, vulcanized rubber test specimens were prepared by vulcanizing them at 170°C for 10 minutes using a mold of a predetermined shape. Using these vulcanized rubber test specimens, JIS No. 3 dumbbell-shaped test specimens were cut out in accordance with JIS K6251, and tensile tests were performed at a tensile speed of 500 mm / min at room temperature (20°C). The tensile strength (breaking strength) [MPa] at the time of fracture was measured and is shown in the "Breaking Strength" column of Tables 3 and 4. A higher value indicates greater breaking strength.

[0068] (Fatigue resistance characteristics) Using JIS No. 3 dumbbell-shaped test specimens prepared in accordance with JIS K6251, tensile constant-strain fatigue tests were conducted under the conditions of 20°C, 60% strain, and a test frequency of 6.67 Hz (rotation speed of 400 rpm), referencing JIS-K6270, and the number of cycles until failure was measured. The obtained results are shown in the "Fatigue Resistance Characteristics" column of Tables 3 and 4.

[0069] (tanδ(60℃)) Vulcanized rubber test specimens were prepared by vulcanizing the rubber compositions of each side rubber and tie rubber in a mold of a predetermined shape at 170°C for 10 minutes. For these vulcanized rubber test specimens, the tanδ at 60°C was measured using a viscoelastic spectrometer manufactured by Toyo Seiki Seisakusho Co., Ltd., under the conditions of initial strain of 10%, amplitude of ±2%, frequency of 20Hz, and temperature of 60°C. The measured values ​​are shown in Tables 3 and 4. A smaller value indicates superior low heat generation.

[0070] (30% vulcanization time T30) The vulcanization curves of the rubber compositions obtained in accordance with JIS K6300-2:2001 were measured using a Curlastometer (registered trademark) manufactured by JSR Co., Ltd. For the side rubber, the measurement was taken at 165°C for 15 minutes, and for the tie rubber, the measurement was taken at 170°C for 10 minutes. The maximum (Fmax) and minimum (Fmin) torque values ​​in the vulcanization curve were measured, and the time required to reach a torque of {(Fmax-Fmin)×0.3+Fmin} was defined as the 30% vulcanization time T30 [minutes]. The T30 values ​​for the side rubber and tie rubber are shown in Tables 3 and 4. The T30(SR) / T30(TR) calculated from these T30 values ​​are also shown in Tables 3 and 4.

[0071] (Electrical resistance) In an environment with a temperature of 23°C and humidity of 50%, a test tire was mounted on a 19x8J rim, and under conditions of air pressure of 200kPa and load of 5.26kN, a voltage of 1000V was applied to the wheel. 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. The part of the value raised to the power of 10 to the power of n (where n is a natural number) is shown in the table as the electrical resistance [Ω], represented as "10^n". A smaller n indicates lower electrical resistance, superior discharge performance, and superior anti-static performance of the tire.

[0072] (Handling stability) A test tire (tire size: 245 / 45R19) was manufactured, featuring side rubbers made from different rubber compositions and having the basic structure shown in Figure 1. Each test tire was mounted on a 19-inch rim wheel, inflated to 270 kPa, and fitted to a test vehicle. The vehicle was then driven on a test course, and handling stability was evaluated by the driver's subjective assessment. The results are expressed as an index value with the baseline value set to 100. A higher value indicates superior handling stability.

[0073] (peeling resistance) Each test tire was mounted on a 19x8J rim wheel and placed on a drum testing machine. A 5000km driving test was conducted under conditions of 120kPa air pressure, 6.2kN load, and 80km / h. After the test, the tire was disassembled, and delamination between the carcass and the side rubber and tie rubber was examined. The results were evaluated as "Good" if no delamination was observed, "Acceptable" if slight delamination was observed, and "Unacceptable" if significant surface delamination was observed.

[0074] Based on the above results, the electrical resistance value in the table is 10 11The rubber was evaluated as having a value lower than Ω, a breaking strength of 15 MPa or more, a fatigue resistance of 200,000 cycles or more, a side rubber tanδ (60°C) of 0.110 or less, a tie rubber tanδ (60°C) of 0.20 or less, and a handling stability index of 100 or more, while maintaining good breaking strength and fatigue resistance of the side rubber, improving low heat generation without impairing handling stability, exhibiting excellent dimensional stability of unvulcanized side rubber, and reducing electrical resistance.

[0075] [Table 3]

[0076] [Table 4]

[0077] From a comparison of the embodiment with the reference example and comparative example, it can be seen that the tire of the above embodiment improves low heat generation without impairing handling stability while maintaining good tensile strength and fatigue resistance of the side rubber, and also reduces electrical resistance.

[0078] 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]

[0079] 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 between the bead cores in a toroidal shape, A tie rubber is positioned on the inside of the tire relative to the carcass and extends along the carcass between the bead cores, The tire comprises a side rubber positioned on the outside of the tire relative to the carcass and located on the surface of the tire's sidewall, The aforementioned side rubber has a CTAB adsorption specific surface area of ​​20 to 60 m² per 100 parts by mass of the rubber component contained in the side rubber. 2 The rubber composition consists of 25 to 50 parts by mass of carbon black at a concentration of / g. The CTAB adsorption specific surface area of ​​the carbon black [m²] 2 The specific surface area × mass fraction (SR), which is the product of [ / g] and the mass fraction of carbon black in the rubber composition, is between 5 and 20. 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 A tire characterized in that 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.

2. The side rubber comprises, in 100 parts by mass of the rubber component of the side rubber, 30 to 60 parts by mass of isoprene-based rubber and 40 to 70 parts by mass of butadiene rubber. The tire according to claim 1, wherein the tie rubber comprises 50 to 95 parts by mass of isoprene-based rubber and 5 to 50 parts by mass of styrene-butadiene rubber in 100 parts by mass of the rubber component of the tie rubber.

3. The tire according to claim 2, wherein the butadiene rubber contained in the side rubber is butadiene rubber synthesized with a neodymium-based catalyst.

4. The tire according to claim 1 or 2, wherein the maximum thickness of the side rubber at the tire radial position where the thickness of the side rubber is greatest is 5.0 mm or less.

5. The tire according to claim 1 or 2, wherein the ratio T30(SR) / T30(TR) of the 30% vulcanization time [minutes] T30(SR) of the rubber composition of the side rubber to the 30% vulcanization time [minutes] T30(TR) of the rubber composition of the tie rubber is 0.5 to 1.7.

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