pneumatic tires

Abstract

Pneumatic tire comprising a tread, a sidewall, a bead area with a bead core, a bead reinforcement layer that reinforces the bead, and a carcass that is bonded in layers to a bead core of the bead area, wherein the bead reinforcement layer and adjacent elements to the bead reinforcement layer are each composed of a rubber composition containing an amine-type antioxidant, having a tan δ at 70°C of 0.14 or less and an E* at 70°C of 10 MPa or more, 0.3 to 8 parts by mass of the amine-type antioxidant are contained in the bead reinforcement layer based on 100 parts by mass of the rubber component, the adjacent element that is adjacent to the bead reinforcement layer, and the bead reinforcement layer satisfy the following formula. 3 ≤ B / A ≤ 8 A: Content (weight %) of the amine-type antioxidant in the bead reinforcement layer B: Content (weight %) of the amine-type antioxidant in the adjacent element

Description

[TECHNICAL FIELD]

[0001] The present invention relates to a pneumatic tire, and in particular to a pneumatic tire with a bead reinforcement layer which suppresses the migration of the amine-type antioxidant into the bead reinforcement layer, thereby suppressing a change in the properties of the bead reinforcement layer and the tire. [STATE OF THE ART]

[0002] A pneumatic tire (hereinafter also referred to simply as a "tire") consists of a tread, a sidewall, a bead section, and similar components. The bead section features a bead wedge that extends radially from the bead core. The bead wedge contributes to the tire's stiffness and durability. In recent years, the demand for further improvements in tire stiffness and strength has steadily increased.

[0003] To respond to such a demand, a technology is proposed for improving the stiffness and durability of a tire by suppressing the deformation of the bead wedge by arranging the bead reinforcement layer on the axial outer side of the tire bead wedge (see, for example, patent documents 1 to 3).

[0004] In this technique, sidewalls and clinches are positioned further outside the bead reinforcement layer in the tire's axial direction. Since these adjacent elements are constantly exposed to the elements, it is essential to ensure long-term resistance to cracking and fractures caused by ozone cracking and similar factors. Therefore, these adjacent elements contain a relatively large amount of an amine-type antioxidant with excellent ozone resistance properties. [STATE OF THE ART DOCUMENTS][PATENT DOCUMENTS] [Patent Document 1] JP 2016 078 564 A [Patent Document 2] JP 2016 130 053 A [Patent Document 3] JP 2016 147 567 A [Patent Document 4] JP H07 - 144 516 A [Patent Document 5] JP 2007 - 269 259 A [SUMMARY OF THE INVENTION][PROBLEMS TO BE SOLVED BY THE INVENTION]

[0005] However, the antioxidant content in the conventional bead reinforcement layer was low. Therefore, when the adjacent element and the bead reinforcement layer of the conventional formulation were located close to each other, the antioxidant migrated from the adjacent element with a high content to the bead reinforcement layer with a low content at the interface between them, causing various impairments of properties in the bead reinforcement layer and the tire, such as an increase in heat generation, a decrease in stiffness due to heat generation, a decrease in steering stability, and similar issues.

[0006] Accordingly, an object of the present invention is to provide an air tire in which an adjacent element containing a large amount of amine-type antioxidant is arranged adjacent to the bead reinforcement layer, and the migration of the amine-type antioxidant from the adjacent element to the bead reinforcement layer is suppressed. [Means for solving the problem]

[0007] The inventors of the present invention have conducted intensive studies and found that the aforementioned problems can be solved by the invention described below, and have completed the present invention.

[0008] The first aspect of the present invention (invention 1) is a pneumatic tire comprising a tread, a sidewall, a bead area with a bead core, a bead reinforcement layer that reinforces the bead, and a carcass that is bonded in layers to a bead core of the bead area, wherein The bead reinforcement layer and adjacent elements to the bead reinforcement layer are each composed of a rubber composition containing an amine-type antioxidant, having a tan δ at 70°C of 0.14 or less and an E* at 70°C of 10 MPa or more. 0.3 to 8 parts by mass of the amine-type antioxidant are contained in the bead reinforcement layer based on 100 parts by mass of the rubber component, the adjacent element that is adjacent to the bead reinforcement layer, and the bead reinforcement layer satisfy the following formula. 3≤B / A≤8 A Content (weight %) of the amine-type antioxidant in the bead reinforcement layer B Content (weight %) of the amine-type antioxidant in the adjacent element

[0009] The second aspect of the present invention (invention 2) is the pneumatic tire according to invention 1, wherein the adjacent elements that are adjacent to the bead reinforcement layer, side walls or clamps, and The bead reinforcement layer is provided outside the end section of the carcass layer in the axial direction of the tire.

[0010] The third aspect of the invention (invention 3) is the pneumatic tire according to invention 1 or 2, wherein the rubber composition that forms the bead reinforcement layer has a tan δ at 70°C of 0.09 or less.

[0011] The fourth aspect of the present invention (invention 4) is the pneumatic tire according to one of inventions 1 to 3, wherein the rubber composition that forms the bead reinforcement layer has an E* at 70°C of 50 MPa or more at 70°C.

[0012] The fifth aspect of the present invention (invention 5) is a pneumatic tire according to any one of inventions 1 to 4, wherein The rubber composition that forms the bead reinforcement layer consists of 30 to 60 parts by mass of carbon black with a cetyltrimethylammonium bromide (CTAB) adsorption-specific surface area of ​​30 to 50 m². 2 / g or contains 10 to 25 parts by mass of calcium carbonate based on 100 parts by mass of the rubber component. [Impact of the invention]

[0013] According to the invention, an air tire is provided in which an adjacent element containing a large amount of an amine-type antioxidant is arranged adjacent to the bead reinforcement layer, and the migration of the amine-type antioxidant from the adjacent element to the bead reinforcement layer is suppressed. [BRIEF DESCRIPTION OF THE DRAWINGS] Fig. Figure 1 is a cross-sectional view showing a configuration of a pneumatic tire according to an embodiment of the invention. Fig. Figure 2 is a cross-sectional view showing a configuration of a reinforcement part of a pneumatic tire according to an embodiment of the present invention. Fig. Figure 3 is a cross-sectional view showing a bead part area in a state where a rim of a pneumatic tire is assembled according to an embodiment of the present invention. [FORMS OF EXECUTION FOR THE EXECUTION OF THE INVENTION]

[0014] The present invention is then described on the basis of embodiments. 1. Summary of the invention

[0015] The pneumatic tire according to the invention comprises a tread, a sidewall, a bead area with a bead core, a bead reinforcement layer which reinforces the bead area, and a carcass layer which is attached to a bead core of the bead area, and it has the following properties.

[0016] Adjacent elements, which are adjacent to the bead reinforcement layer and the bead reinforcement layer itself, are each composed of a rubber composition containing an amine-type antioxidant. The bead reinforcement layer contains 0.3 to 8 parts by mass of the amine-type antioxidant based on 100 parts by mass of the rubber component. The adjacent element, which is adjacent to the bead reinforcement layer, and the bead reinforcement layer satisfy the following formula. 3≤B / A≤8 A Content (weight %) of an amine-type antioxidant in the bead reinforcement layer B Content (weight %) of the amine-type antioxidant in the adjacent element

[0017] The inventors of the present invention sought a solution to the aforementioned problems and found that the migration of the amine-type antioxidant from the adjacent element to the bead reinforcement layer (hereinafter also simply referred to as "antioxidant migration") can be suppressed if the content of the amine-type antioxidant relative to 100 parts by mass of the rubber component of the bead reinforcement layer is adjusted to 0.3 to 8 parts by mass, and the ratio (B / A) of the content A (weight %) of the amine-type antioxidant in the bead reinforcement layer and the content B (weight %) of the amine-type antioxidant in the adjacent element is adjusted to 3 to 8.

[0018] By suppressing the migration of the antioxidant in this manner, it was found that various deteriorations in the bead reinforcement layer and the tire itself, caused by this migration, could be mitigated. Furthermore, it was found that this effect is remarkably effective, and therefore, it is preferable to design the tire's bead reinforcement layer to exhibit low heat generation and high stiffness, thereby reducing fuel consumption. 2. Design

[0019] Next, the present invention will be described in detail based on embodiments. (1) Structure of the bulge

[0020] The tire according to the invention is described with reference to the Fig. 1 to 3 described. The Fig.Figure 1 is a sectional view showing a configuration of a bead area of ​​a tire mounted on a rim, and the Fig. Image 2 is an enlarged view of it. Fig. Figure 3 is a cross-sectional view showing the state where the rim is mounted.

[0021] In the Fig. 1 to 3: 1 is a tire, 2 is a bead section, 3 and 31 are sidewalls, 4 is a tread, 5 is a rim, and 22 is a bead wedge. In the tire 1, 23 is a bead reinforcement layer, and a clamping element 24, which is an adjacent element, is arranged adjacent to the bead reinforcement layer 23. Additionally, 21 is a bead core, 25 is a bead strip, and 26 is a strip wedge. Furthermore, 32 is a first carcass ply, 33 is a second carcass ply, and 34 is an inner liner.

[0022] As in the Fig.As shown in Figure 1, the bead reinforcement layer 23 of the present embodiment is located on the outside in the tire axial direction (the right side in the Fig. 1) of the carcass plies 32, 33 arranged. The tire axial direction is a direction parallel to the axis of rotation of the tire, and the outer side in the tire axial direction means that it is the outside in the axial direction when the plane passing through the tire equator (represented by the line CL in Fig. 1) steps, the center is.

[0023] In the Fig. 1. The clamping element 24 is arranged as an adjacent element to the bead reinforcement layer 23. However, in the case of a tire in which the clamping element does not completely cover the outside of the bead reinforcement layer, the adjacent element of the bead reinforcement layer can be a sidewall or a sidewall and a clamping element. (2) Amine-type antioxidants

[0024] As previously described, the bead reinforcement layer of the tire and the adjacent elements of the bead reinforcement layer in the present embodiment contain an amine-type antioxidant with excellent ozone resistance. If the antioxidant content in the bead reinforcement layer is too high, there is a tendency for so-called pre-vulcanization to occur during vulcanization molding. If it is too low, the migration of the antioxidant cannot be suppressed. Therefore, it is necessary to adjust the antioxidant content in the reinforcement layer, taking into account the equilibrium with the content of the amine-type antioxidant in the adjacent element.

[0025] Taking this point into account, in order to suppress the migration of the amine-type antioxidant from the adjacent element to the bead reinforcement layer, the content of the amine-type antioxidant in the bead reinforcement layer is adjusted to 0.3 to 8 parts by mass relative to 100 parts by mass of the rubber component of the bead reinforcement layer, and the ratio (B / A) of the content A (weight %) of the amine-type antioxidant in the bead reinforcement layer and the content B (weight %) of the amine-type antioxidant in the adjacent elements is adjusted to 3 to 8. The content of the amine-type antioxidant in the bead reinforcement layer relative to 100 parts by mass of the rubber component of the bead reinforcement layer is preferably 0.5 to 2.5 parts by mass and more preferably 1 to 1.5 parts by mass. Furthermore, B / A is preferably 3 to 8 and more preferably 4 to 6.

[0026] The antioxidants of the amine type are not particularly limited, and examples include amine derivatives such as those of the diphenylamine, p-phenylenediamine, naphthylamine, and ketoneamine condensate types. These can be used individually or in combination. Examples of diphenylamine derivatives include p-(p-toluenesulfonylamide)-diphenylamine, octylated diphenylamine, 4,4'-bis(α,α'-dimethylbenzyl)-diphenylamine, and similar compounds. Examples of p-phenylenediamine-based derivatives include N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD), N-phenyl-N'-isopropyl-p-phenylenediamine (IPPD), N,N'-di-2-naphthyl-p-phenylenediamine, and similar compounds. Examples of naphthylamine derivatives include phenyl-α-naphthylamine and similar compounds. Of these, those of the phenyldiamine type and the ketoneamine condensate type are preferred.

[0027] Furthermore, the amine-type antioxidant contained in the bead reinforcement layer and the adjacent element may be a combination of the same or similar amine-type antioxidants, or a combination of heterogeneous and different types of amine-type antioxidants. (3) Physical rubber properties of the bead reinforcement layer

[0028] The physical rubber properties of the bead reinforcement layer can be used to exert the following effects in addition to the effect of suppressing the migration of the antioxidant from the adjacent element to the bead reinforcement layer by appropriately adjusting tan δ (loss coefficient) at 70°C and E* (complex modulus of elasticity). (A) tan δ (loss coefficient) at 70°C

[0029] The bead reinforcement layer of the tire of the present embodiment has a tan δ at 70°C (simply referred to as "tan δ") of 0.14 or less. Preferably 0.09 or less.

[0030] Then, for example, while driving on a tire designed for a multi-purpose sports car (SUV) or when driving in cold weather, the deformation stress, i.e., the flat spot in the tire bead wedge, will accumulate during the period until the tire temperature rises when the vehicle is started after being stationary for a certain period, causing a deterioration in fuel economy. However, by adjusting the tan δ to the previous value, the occurrence of flat spots can be suppressed. (B) E* (complex modulus of elasticity)

[0031] The rubber composition forming the bead reinforcement layer has an E* at 70°C of 10 MPa or more. Preferably 50 MPa or more, and more preferably 80 MPa or more.

[0032] Setting E* to the previous value ensures sufficient steering wheel response sensitivity and steering stability.

[0033] The preceding tan δ and E* at 70°C are measured using a viscoelasticity measuring device, for example a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., with a vulcanized rubber composition as the object to be measured at a frequency of 10 Hz, an initial load of 10% and a dynamic load of 5% at 70°C. (4) Rubber composition of the bead reinforcement layer

[0034] The rubber composition used for the production of the bead reinforcement layer of the present embodiment can be obtained by kneading various ingredients, such as a rubber component as a main component, a reinforcing material and additives together with the amine-type antioxidant. (A) Rubber component

[0035] Examples of diene rubbers used as rubber components include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), and butyl rubber (IIR). Of these, NR, IR, BR, and SBR are preferred because they offer satisfactory improvements in steering stability, fuel economy, and extrusion processability. The combined use of NR, BR, and SBR, as well as the combined use of NR, IR, and SBR, is preferred.

[0036] BR is not particularly restricted, and, for example, BR with a high cis content, BR containing a syndiotactic polybutadiene crystal (SPR-containing BR), or similar materials can be used. Of these, SPB-containing BR is preferred from the point of view that the extrusion processability can be greatly improved by the crystal component with its inherent orientation.

[0037] When SPR-containing BR is used, the SPB content in the SPB-containing BR, based on 100 parts by mass of the rubber component, is preferably 15 to 40 parts by mass, more preferably 20 to 30 parts by mass. If the SPB content in SPR-containing BR is within the aforementioned range, extrusion processability can be ensured. Additionally, it is possible to increase the E* of the rubber component. The SPB content in the SPR-containing BR is expressed as the amount of material insoluble in boiling n-hexane.

[0038] The BR content, based on 100 parts by mass of the rubber component, is preferably 70 parts by mass or less, more preferably 50 parts by mass or less. By adjusting the BR content within the aforementioned range, sufficient resistance, extrusion processability, and elongation can be ensured.

[0039] SBR is not particularly limited in its applications, and, for example, emulsion-polymerized styrene-butadiene rubber (E-SBR), solution-polymerized styrene-butadiene rubber (S-SBR), or similar materials can be used. Of these, E-SBR is preferred because carbon black disperses well and it has good processability.

[0040] The styrene content in SBR is preferably 10 to 40 wt%, more preferably 20 to 30 wt%. By adjusting the styrene content to the aforementioned range, sufficient hardness and low fuel consumption can be ensured.

[0041] The SBR content, based on 100 parts by mass of the rubber component, is preferably 15 to 60 parts by mass, more preferably 25 to 40 parts by mass. If the SPR content is within the aforementioned range, sufficient extrusion processability, adequate hardness, and low fuel consumption can be ensured.

[0042] The NR content, based on 100 parts by mass of the rubber component, is preferably 20 to 80 parts by mass, more preferably 40 to 60 parts by mass. By adjusting the NR content within the aforementioned range, sufficient fracture toughness and hardness can be ensured.

[0043] The IR content, based on 100 parts by mass of the rubber component, is preferably 5 to 50 parts by mass, more preferably 15 to 30 parts by mass. If the IR content is within the aforementioned range, processability can be improved and sufficient elongation can be ensured. (B) soot

[0044] It is preferred to mix carbon black as a reinforcing material into the rubber composition of this embodiment. Examples of carbon black include GPF, HAF, ISAF, SAF, FF, FEF, and similar types. One of these can be used alone, or two or more can be used in combination. From the perspective of achieving both extrusion processability and the necessary hardness, it is preferred to use a combination of the soft carbon type FEF and the hard carbon type ISAF, SAF, HAF, and a combination of ISAF and FEF is even more preferred.

[0045] The carbon black content in the rubber composition, based on 100 parts by mass of the rubber composition, is preferably from 30 to 70 parts by mass, more preferably from 45 to 65 parts by mass. By adjusting the amount of carbon black in the rubber composition within the aforementioned range, an excessive increase in E* can be suppressed, and the value of tan δ of the rubber composition can be further reduced.

[0046] From the point of view of extrudability, the carbon black can also preferably be carbon black with a cetyltrimethylammonium bromide adsorption (CTAB) specific surface area of ​​30 to 50 m². 2 / g contained. For example, FEF can be mentioned as a carbon black with a CTAB-specific surface area within the preceding range. As the rubber composition according to the invention, it is particularly preferred that, based on 100 parts by mass of the rubber component, carbon black with a CTAB-specific surface area of ​​30 to 50 m² is used.2 The CATB adsorption-specific surface area can be measured in accordance with JIS K-6217-3:2001. It is contained in a quantity of 30 to 60 parts by mass. (C) Inorganic filler

[0047] The rubber composition of the present embodiment preferably contains an inorganic filler if a combination of soft and hard carbon is not used. Examples of inorganic fillers include calcium carbonate, talc, Hartton, Austin black, fly ash, mica, and similar materials. Of these, calcium carbonate and talc are preferred due to their self-cohesiveness, their resistance to fracture during operation, their good durability, and their significant improvement in extrusion processability (especially the extrusion edge properties). Calcium carbonate is preferred.

[0048] The average particle diameter (mean primary particle diameter) of the inorganic filler is preferably 1 to 100 µm and more preferably 2 to 50 µm. If the average particle diameter of the inorganic filler is within the aforementioned range, the deterioration of strength due to the inorganic filler becoming a fracture core is suppressed. Additionally, sufficient processability at the time of extrusion can be ensured. The average particle diameter of the inorganic filler can be measured, for example, by a laser diffraction / scattering method (Microtrack method).

[0049] The content of the inorganic filler per 100 parts by mass of the rubber component is preferably 10 to 25 parts by mass. Adjusting the amount of inorganic filler within the aforementioned range allows for improved processability without affecting the equilibrium between E* and tan δ. (D) Phenol-type resin

[0050] The rubber composition according to the invention may contain a phenol-type resin. Specific examples of phenol-type resins include phenolic resins, modified phenolic resins, cresol resins, modified cresol resins, and the like. The aforementioned phenolic resin is obtained by reacting phenol with aldehydes, such as formaldehyde, acetaldehyde, furfural, etc., with an acid or alkali catalyst. The aforementioned modified phenolic resin is a phenolic resin modified with a compound such as cashew oil, tall oil, linseed oil, various animal or vegetable oils, an unsaturated fatty acid, rosin, an alkylbenzene resin, aniline, melamine, or the like.

[0051] The phenol-type resin is preferred from the point of view that a hard composite sphere is formed by obtaining sufficient hardness through a curing reaction, or that a large composite sphere is formed; preferably a modified phenolic resin. A cashew oil-modified phenolic resin, or a rosin-modified phenolic resin, is preferred.

[0052] The content of the phenolic resin, based on 100 parts by mass of the rubber component, is preferably 5 to 20 parts by mass, more preferably 10 to 20 parts by mass. If the total content of the phenolic resin is within the aforementioned range, sufficient hardness and low fuel consumption can be ensured. (E) Other

[0053] In the rubber composition according to the invention of the present embodiment, additional materials conventionally used in the rubber industry, such as oil, stearic acid, zinc white, sulfur, vulcanization accelerators, etc., may optionally be added to the aforementioned components. The amount of each added material can be selected appropriately.

[0054] The rubber composition of the present embodiment usually contains sulfur. The sulfur content, based on 100 parts by mass of the rubber component, is preferably 1 to 8 parts by mass, more preferably 2 to 6 parts by mass. By adjusting the sulfur content within the aforementioned range, sufficient steering stability can be ensured, sulfurization and stickiness can be suppressed, and durability can be guaranteed. The sulfur content refers to the pure sulfur content, and if insoluble sulfur is used, it refers to the content excluding the oil content.

[0055] The rubber composition according to the invention usually contains a vulcanization accelerator. The content of the vulcanization accelerator, based on 100 parts by mass of the rubber component, is preferably from 1.5 to 5.0 parts by mass, more preferably from 2 to 4 parts by mass. (5) Manufacturing process of the rubber composition

[0056] The rubber composition can be produced by a known method, for example kneading each of the preceding components using a rubber kneading device, such as an open roller, a Banbury mixer or the like. (6) Tire manufacturing

[0057] The tire of the present embodiment can be manufactured by an ordinary method using the aforementioned rubber composition. That is, the rubber composition is extruded in an unvulcanized state in accordance with the shape of the bead wedge, formed by an ordinary method on a tire molding machine, and bonded together with other tire elements to form an unvulcanized tire. The unvulcanized tire is then heated and pressed in a vulcanizer to produce a tire.

[0058] This makes it possible to provide a pneumatic tire with excellent durability, in which the migration of the amine-type antioxidant from the adjacent element to the bead reinforcement layer is suppressed.

[0059] The application of the tire of the present embodiment is not particularly limited and it can be used for various vehicles, such as passenger cars, heavy goods vehicles, motocross bikes and the like. [EXAMPLES]EXAMPLES

[0060] The present invention will now be described in more detail with reference to examples. In the following examples, side walls are arranged as adjacent elements. The content of the various materials (mixed-in materials, such as rubber and an antioxidant) in the rubber composition is shown in parts by mass per 100 parts by mass of the rubber component. The content A and B of the amine-type antioxidant is given as wt.%. [1] Experiment 11. Preparation of the rubber composition(1) Rubber composition of the sidewall (adjacent element of the bead reinforcement layer)

[0061] Using the following materials, sidewall rubber compositions are prepared with three mixtures of SW 1, SW 2, and SW 3 shown in Table 1. Table 1 shows mass fractions, except for the content B (wt%) of the amine-type antioxidant in the adjacent element. (Rubber component) NR: TSR 20 BR: UBEPOL BR 150 B (manufactured by Ube Industries, Ltd.) (reinforcement material) Soot: FEF, N 550 (manufactured by Showa Cabot Co., Ltd.) (A Softening Agent) Öl: Diana process AH-24 (manufactured by Idemitsu Kosan Co., Ltd.) (amine-type antioxidant) Antioxidant 6C: Nocrac 6 C (antioxidant of the Phen Ltd.)ylenediamine type) (manufactured by Ouchi Shinko Chemical Industrial Co., Antioxidant RD: Nocrac RD (Antioxidant of the Keto Indu (Vulknamine Condensate Type) (manufactured by Ouchi Shinko Chemical Co., Ltd.) oxidizing aid) Stearic acid: Camellia (manufactured by NOF CORPORATION) Zinc oxide: Zinc white (manufactured by Mitsui Mining & Smelting Co., Ltd.) (vulcanizing agent) Sulfur: 5% oil-diluted sulfur (manufactured by Tsurumi Chemical Industry Co., Ltd.) Accelerator: Soxinol CZ (CZ, manufactured by Sumitomo Chemical Co., Ltd.) (Other) Wax: Ltd.)Sannock N (manufactured by Ouchi Shinko Chemical Industrial Co., [Table 1] SW1 SW2 SW3 SW4 NR 40 40 40 40 BR 60 60 60 60 Soot N550 48 48 48 48 Öl 5 5 5 5 wax 1,2 1,2 1,2 1,2 Antioxidant 6C 3 8 0,5 6 Antioxidant RD 1 2 1 1 Stearic acid 2,5 2,5 2,5 2,5 zinc oxide 3 3 3 3 sulfur 1,58 1,58 1,58 1,58 Accelerator CZ 0,90 0,90 0,90 0,90 Total quantity 166,18 172,18 163,68 169,18 Salary B (weight %) 2,4 5,8 0,9 4,1 (2) Rubber composition of the bead reinforcement layer

[0062] Using the following materials, a rubber composition for a bead reinforcement layer was prepared with four mixture formulations AP 1, AP 2, AP 3, and AP 4 shown in Table 2. Table 2 shows the mass parts (wt%) for content A of the amine-type antioxidant in the bead reinforcement layer. The content shown in the bottom part of Table 2 is the mass part (wt%) of the amine-type antioxidant in the rubber composition. (Rubber component) No. 1 TSR 20 SBR: JSR 1502 (Emulsion polymerization SBR (E-SBR)), styrene content 23.5 Weight. -%(Vers(Reinforcement material) Soot: ISAF, N 220 (manufactured by Showa Cabot Co., Ltd.), CTAB- Adsorption-specific surface area 110 m² 2 / G T-NS,N 330 T (manufactured by Showa Cabot Co., Ltd.), CTAB- Adsorption ratio, board area 78 m² 2 / G FEF,N 550 (manufactured by Showa Cabot Co., Ltd.), CTAB- adsorption-specific surface area 42 m² 2 / G (Calcium carbonate) NS # 200 (manufactured by Nitto Denpa Kogyo Co., Ltd.) (Phenolic resin) Sumilit resin PR12686 (Novolak-type phenolic resin) (manufactured (by Sumitomo Bakelite Co., Ltd.) (Vulcanization aid) Stearic acid: Camellia (manufactured by NOF CORPORATION) Zinc oxide: Zinc white (manufactured by Mitsui Mining & Smelting Co., Ltd.) (Antioxidants) Antioxidant 6 C: Nocrac 6 C (antioxidant from Phen) Ltd.)ylenediamine type) (manufactured by Ouchi Shinko Chemical Industrial Co., (A Softening agent) Öl: Process oil A / O MIX (manufactured by Sankyo Yuka Kogyo Co., Ltd.) (vulcanizing agent) Sulfur: M95 M / S (oil-enriched insoluble sulfur, produced by Nippcan Drying Co., Ltd.) Accelerator: HMT, Sansea HT (manufactured by Sanshin Chemical) Industry Co., Ltd.) Ltd.): NS, Sancera NS-G (manufactured by Sanshin Chemical Industry Co., [Table 2] AP1 AP2 AP3 AP4 AP5 NR 60 60 60 60 60 SBR 40 40 40 40 40 Soot N220 10 Carbon black N330T 60 60 45 45 Soot N550 40 Calcium carbonate 15 15 Phenolic resin 5 5 8 13 13 Stearic acid 2 2 2 2 2 zinc oxide 3 3 3 3 3 Antioxidant 6C 1 1 1 1,5 Öl 5 5 5 5 5 sulfur 4 4 4 4 4 HMT accelerator 0,5 0,5 0,8 1,3 1,3 NS 2,35 2,35 2,35 2,35 2,35 Total salary 181,85 182,85 176,15 191,65 192,15 Salary A (weight %) 0 0,52 0,57 0,52 0,78 Salary (bulk portions) 0 1 1 1 1,5 2. Measurements of the physical properties of the rubber

[0063] The tan δ and E* values ​​of the rubber compositions AP 1 to AP 5 of the manufactured bead reinforcement layer were measured at 70°C. The measurement was performed at 70°C under conditions of a frequency of 10 Hz, an initial strain of 10%, and a dynamic strain of 5% using a viscoelasticity device; a viscoelasticity spectrometer manufactured by Iwamoto Seisakusho Co., Ltd., with a vulcanized rubber composition as the measurement. [Table 3] AP 1 AP 2 AP 3 AP 4 AP 5 tan δ (70°C) 0,16 0,16 0,08 0,08 0,08 E* (70°C) 15 15 20 58 58

[0064] The measurement results are shown in Table 3. As shown in Table 3, in AP 1 and AP 2, E* was 10 MPa or more, but tan δ was 0.16. In AP 3, tan δ was 0.09 or less and E* was 10 MPa or more, indicating good results. Furthermore, in the compositions of AP 4 and AP 5, tan δ was 0.09 or less and E* was 50 MPa or more, and particularly good results were achieved. 3. Preparation of a test tire(1) Example 1

[0065] As shown in Table 4, ordinary tires (195 / 65R15) in which sidewalls were arranged with reference to the bead reinforcement layer were manufactured using the rubber compositions SW 1 for the sidewall and AP 3 for the bead reinforcement layer. (2) Examples 2 and 3

[0066] As shown in Table 4, in Example 2, a tire (195 / 65R15) was prepared in the same manner as in Example 1, except that the externally bonded structure, in which the sidewalls adjacent to the bead reinforcement layer were used on the axial outer side of the tire, was used. In Example 3, a test tire was prepared in the same manner as in Example 2, except that AP 4 was used as the rubber composition for the bead reinforcement layer. (3) Examples 4 to 6

[0067] In Examples 4 to 6, a test tire was prepared in the same manner as in Example 2, except that the rubber composition shown in Table 4 was used for each of the sidewall and bead reinforcement layers to form an externally bonded structure. (4) Comparative example 1

[0068] As shown in Table 5, a test tire was prepared in the same way as in Example 1, except that the rubber composition AP 1 was used for the bead reinforcement layer. (5) Comparative examples 2 to 6

[0069] As shown in Table 5, in Comparative Example 2, a test tire was prepared in the same manner as in Example 2, except that rubber composition AP 1 was used for the bead reinforcement layer. In Comparative Examples 3 and 4, test tires were prepared in the same manner as in Comparative Example 2, except that rubber compositions SW 2 and SW 3, respectively, were used for the sidewalls. In Comparative Example 5, a test tire was prepared in the same manner as in Comparative Example 2, except that rubber composition SW 3 was used for the sidewall and rubber composition AP 2 for the bead reinforcement layer. In Comparative Example 6, a test tire was prepared in the same manner as in Comparative Example 2, except that rubber composition SW 2 was used for the sidewall and rubber composition AP 3 for the bead reinforcement layer. (6) Comparative examples 7 to 9

[0070] In comparative examples 7 to 9, a test tire was prepared in the same manner as in comparative example 2, except that the rubber composition shown in Table 4 was used for each of the sidewalls and bead reinforcement layer to form an externally bonded structure. 4. Evaluation procedure(1) Processability

[0071] The rejection rate at the time of intermediate processing was determined based on the following formula, indexed and evaluated with reference to comparison example 1. The higher the value, the better. Processability = [Reject Rate (Comparison Example 1) / Reject Rate (Evaluation Object)] × 100 (2) Steering stability

[0072] The test tire was fitted to all wheels of a vehicle (domestic FF car, 2000 cc displacement) that drove a dry asphalt tire test track at a speed of 80 km / h for 2 hours, and the steering stability (steering response, grip, etc.) was assessed sensorially by the driver. The rating was indexed, based on comparison example 1, according to the following formula. The higher the value, the better. Steering stability = [Steering stability (assessment object) / Steering stability (comparison example 1)] × 100 (3) Crack resistance

[0073] The test tire was exposed to an ozone concentration of 50 ppm and an atmospheric temperature of 40°C for a period of 9 days to check for cracking and determine the defect rate (C-defect rate) due to cracking. The defect rate was indexed and evaluated based on comparative example 1 using the following formula. The higher the value, the better. Crack resistance property = [C−defect rate (comparison example 1) / C−defect rate (object to be evaluated)]×100 (4) Appearance characteristics

[0074] After ten test tires were exposed to the elements for six months each, a visual inspection was performed to assess the condition of the antioxidant precipitation on the sidewall surfaces, and the precipitation-related failure rate (E-defect rate) was determined. Based on comparison example 1, the E-defect rate was indexed and evaluated. The higher the value, the better. Appearance property = [E−Defect rate (comparison example 1) / E−Defect rate (object to be evaluated)]×100 5. Evaluation results

[0075] The evaluation results for examples 1 to 6 are shown in Table 4, and the evaluation results for examples 1 to 9 are shown in Table 5. Tables 4 and 5 show the rubber compositions and the B / A values ​​in the corresponding examples and comparison examples. [Table 4] Examples 1 2 3 4 5 6 Rubber composition (SW) SW 1 SW 1 SW 1 SW 4 SW 4 SW 1 Salary B 2,4 2,4 2,4 4,1 4,1 2,4 Rubber composition (AP) AP 3 AP 3 AP 4 AP 3 AP 4 AP 5 Salary A 0,57 0,57 0,52 0,57 0,52 0,78 B / A 4,2 4,2 4,6 7,2 7,9 3,1 bulge structure Normal Reinforcing layer Reinforcing layer Reinforcing layer Reinforcing layer Reinforcing layer Processability 120 120 130 120 130 128 Steering stability 100 125 150 125 150 150 Crack resistance 100 115 110 115 118 112 Appearance characteristics 100 105 110 110 108 103 [Table 5] Comparative examples 1 2 3 4 5 6 7 8 9 Rubber composition (SW) SW 1 SW 1 SW 2 SW 3 SW 3 SW 2 SW 3 SW 2 SW 3 Salary B 2,4 2,4 5,8 0,9 0,9 5,8 0,9 5,8 0,9 Rubber composition (AP) AP 1 AP 1 AP 1 AP 1 AP 2 AP 3 AP 3 AP 4 AP 4 Salary A 0 0 0 0 0,52 0,57 0,57 0,52 0,52 B / A - - - - 1,7 10,2 1,6 11,2 1,7 bulge structure Normal Reinforcing layer Processability 100 100 100 100 80 120 120 130 130 Steering stability 100 120 120 120 120 135 135 150 150 Crack resistance 100 80 100 50 60 110 60 110 60 Appearance characteristics 100 90 70 90 85 50 85 50 85

[0076] Tables 4 and 5 show that, compared to comparison example 1 with a normal structure, the processability was 120 or higher in all examples, and with regard to comparison examples 2 to 9, the processability was also 100 or higher in all comparison examples except comparison example 5. One result of the test is that good processability can be achieved by using the externally bound structure.

[0077] Steering stability was good in all examples and comparison examples.

[0078] Crack resistance was good in all examples, and particularly good in example 5 at 118. On the other hand, cracks were observed in comparative examples 4, 5, 7 and 9, in which the concentration of the amine-based antioxidant in the sidewall is low, and in comparative example 2, in which the antioxidant is not present.

[0079] The appearance properties were good in all examples, and, particularly in examples 3 and 4, they were extremely good at 110. On the other hand, precipitation of the antioxidant was most frequently observed in comparative examples 6 and 8, in which the concentration of the amine-type antioxidant in the sidewall was highest. Precipitation was also observed in comparative examples 2 to 4, in which the antioxidant was not present in the peak. Additionally, precipitation was also observed in comparative examples 5, 7, and 8.

[0080] Additionally, a deterioration in properties was observed in the tire where the wedge rubber composition did not contain a predetermined amount of the amine-type antioxidant and the B / A ratio was not within the predetermined range. Even in a tire containing an amine-type antioxidant in the wedge (apex) rubber composition, as in Comparative Examples 6 and 8, which are high-B / A comparison examples, deterioration in each of the properties was observed, particularly a deterioration in appearance. In Comparative Examples 5, 7, and 9, which are low-B / A comparison examples, deterioration in each of the properties was observed, particularly a deterioration in crack resistance.On the other hand, in examples 1 to 6, where B / A was in the range of 3 to 8, no deterioration in the tested properties was observed. In particular, improvements in the properties were observed in examples 2 to 6.

[0081] Good test results were also observed on tires using AP 4 and AP 5 with a tan δ at 70°C of 0.09 or less and E* of 50 or more in the bead reinforcement layer. It was suggested that it is preferable to use a rubber composition with a tan δ and E* value within this numerical range for the bead reinforcement layer. [2] Experiment 21. Migration test of the antioxidant

[0082] The tires in Example 3 (B / A = 4.6) and in Comparative Example 8 (BA = 11.2), in which the same rubber composition (AP 4) was used for the bead reinforcement layer, but only the amounts of the amine-type antioxidant in the sidewall differed, and, as a result, the B / A ratio differed, were used. The change and rate of increase of the A content (weight %) of the amine-type antioxidant in the bead reinforcement layer due to migration were investigated. The test period was 180 days, and the A content of the amine-type antioxidant in the bead reinforcement layer at the beginning (0 days) and after 14, 30, and 180 days were measured by liquid chromatography. 2. Evaluation results

[0083] The evaluation results of example 3 and the comparison example 8 are shown in Table 6. [Table 6] Number of days since the start 0 14 30 180 Example 3 Salary A 0,52 0,54 0,58 0,8 Example 3 Rate of increase 0% 4% 16% 60% Comparative example 8 Salary A 0,52 0,8 1,1 1,9 Comparative example 8 Rate of increase 0% 57% 116% 273%

[0084] The test results showed that in comparison example 8, where B / A was 11.2, the content rate after 180 days was 1.9 wt% and the rate of increase was 273%, whereas in example 3, where B / A was 4.6, the content rate after 180 days was 0.8 wt% and the rate of increase was 60%, and a significant suppressive effect of migration was observed.

[0085] Although the present invention has been described based on the embodiments described above, the present invention is not limited to the embodiments described above. Various modifications can be made to the preceding embodiment within the same and equivalent scope as the present invention. [DESCRIPTION OF REFERENCE MARKS] 1. Tires 2. Bead section area 3. Side wall section 4. Running surface 5. Rim 21. Bead core 22. Bead wedge 23. Bead reinforcement layer 24. Embrace 25. Bead band 26. Strip summit 31. Side wall section 32. First carcass layer 33. Second carcass layer 34. Inner lining CL. Tire equator

[0086] A pneumatic tire comprising a tread, a sidewall, a bead area with a bead core, a bead reinforcement layer that reinforces the bead, and a carcass that is bonded in layers to a bead core of the bead area, wherein the bead reinforcement layer and adjacent elements that are adjacent to the bead reinforcement layer are each composed of a rubber composition containing an amine-type antioxidant, 0.3 to 8 parts by mass of the amine-type antioxidant are contained in the bead reinforcement layer based on 100 parts by mass of the rubber component, the adjacent element that is adjacent to the bead reinforcement layer, and the bead reinforcement layer satisfy the following formula. 3≤B / A≤8 A Content (weight %) of the amine-type antioxidant in the bead reinforcement layer B Content (weight %) of the amine-type antioxidant in the adjacent element

Claims

[1] Pneumatic tire comprising a tread, a sidewall, a bead area with a bead core, a bead reinforcement layer which reinforces the bead, and a carcass which is bonded in layers to a bead core of the bead area, wherein the bead reinforcement layer and adjacent elements to the bead reinforcement layer are each composed of a rubber composition containing an amine-type antioxidant, having a tan δ at 70°C of 0.14 or less and an E* at 70°C of 10 MPa or more, 0.3 to 8 parts by mass of the amine-type antioxidant are contained in the bead reinforcement layer based on 100 parts by mass of the rubber component, the adjacent element that is adjacent to the bead reinforcement layer, and the bead reinforcement layer satisfy the following formula. 3≤B / A≤8 A: Content (weight %) of the amine-type antioxidant in the bead reinforcement layer B: Content (weight %) of the amine-type antioxidant in the adjacent element [2] Pneumatic tires according to claim 1, wherein the adjacent elements that are adjacent to the bead reinforcement layer, side walls or clamps, and The bead reinforcement layer is located outside the carcass layer in the axial direction of the tire. [3] Pneumatic tire according to claim 1 or 2, wherein the rubber composition forming the bead reinforcement layer has a tan δ at 70°C of 0.09 or less. [4] Pneumatic tire according to any one of claims 1 to 3, wherein the rubber composition forming the bead reinforcement layer has an E* at 70°C of 50 MPa or more at 70°C. [5] Pneumatic tire according to any one of claims 1 to 4, wherein the rubber composition forming the bead reinforcement layer comprises 30 to 60 parts by mass of carbon black with a cetyltrimethylammonium bromide (CTAB) adsorption-specific surface area of ​​30 to 50 m² 2 / g or contains 10 to 25 parts by mass of calcium carbonate based on 100 parts by mass of the rubber component.

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