Rubber composition for tires and tires

Abstract

To provide a tire rubber composition with which it is possible to improve the puncture resistance of a tire while incorporating a recycled material.SOLUTION: The tire rubber composition comprises a rubber component, a recycled material, and an amine-based antioxidant represented by the general formula (1) in the figure where R1 and R2 are each independently a monovalent saturated hydrocarbon group. The content of the amine-based antioxidant is 0.1-11 pts.mass based on 100 pts.mass of the rubber component.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a rubber composition for tires and a tire. [Background technology]

[0002] In recent years, the use of materials obtained by recycling used products, so-called recycled materials, has been actively researched, and the application of various recycled materials to rubber compositions for tires is also being considered. For example, Patent Document 1 below discloses a method for obtaining carbon black by thermally decomposing waste tires to separate rubber decomposition oil and generating carbon black from the rubber decomposition oil. Furthermore, it discloses a technique for improving the fracture resistance of a rubber composition containing carbon black by adjusting the ash content of the carbon black. In addition, other methods for recycling waste tires include thermal decomposition of the waste tires, crushing the particles obtained from the thermal decomposition to extract carbon black, and then blending the carbon black into a rubber composition; cutting and crushing the waste tires to obtain rubber powder, and then blending the rubber powder into a rubber composition; and cutting and crushing the waste tires, further desulfurizing them to obtain desulfurized rubber (recycled rubber), and then blending the desulfurized rubber into a rubber composition. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2017-8223 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] However, recycled materials generally have a higher content of ash and other components than conventional fillers and rubber components. Therefore, even when such recycled materials are incorporated into rubber compositions, the reinforcing effect is insufficient, making it difficult to ensure sufficient fracture resistance of the rubber composition. Consequently, there has been room for improvement in the fracture resistance of conventional rubber compositions for tires that contain recycled materials.

[0005] Therefore, the object of the present invention is to solve the problems of the above-mentioned prior art and to provide a tire rubber composition that can improve the tire's resistance to damage while containing recycled materials. Furthermore, a further objective of the present invention is to provide a tire that contains recycled materials while exhibiting excellent resistance to fracture. [Means for solving the problem]

[0006] The gist of the present invention, which solves the above problems, is as follows.

[0007] The rubber composition for tires of the present invention is Rubber components, Recycled materials and The following general formula (1): [ka] [In the formula, R 1 and R 2 It comprises an amine-based antioxidant, which is represented by a monovalent saturated hydrocarbon group, and The content of the amine-based antioxidant is characterized in that it is 0.1 to 11 parts by mass per 100 parts by mass of the rubber component. The rubber composition for tires according to the present invention, while containing recycled materials, can improve the tire's fracture resistance (particularly its tensile strength (TB)) when applied to a tire.

[0008] In a preferred example of the rubber composition for a tire of the present invention, the rubber component contains at least one selected from the group consisting of isoprene skeleton rubber, styrene-butadiene rubber, butadiene rubber, and chloroprene rubber. In this case, the rubber elasticity of the rubber composition is excellent, and it becomes a rubber composition more suitable for tire applications.

[0009] In another preferred example of the rubber composition for a tire of the present invention, R in the above general formula (1) 1 and R 2 are each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms. In this case, the ozone resistance and fracture resistance of the rubber composition are further improved.

[0010] Further, the tire of the present invention is characterized by comprising a rubber member made of the above rubber composition for a tire. Such a tire of the present invention includes a recycled material and yet is excellent in fracture resistance (particularly, tensile strength (TB)).

Effects of the Invention

[0011] According to the present invention, it is possible to provide a rubber composition for a tire that can improve the fracture resistance of the tire while containing a recycled material. Further, according to the present invention, it is possible to provide a tire that is excellent in fracture resistance while containing a recycled material.

Modes for Carrying Out the Invention

[0012] Hereinafter, the rubber composition for a tire and the tire of the present invention will be exemplified and described in detail based on their embodiments.

[0013] <Rubber Composition for a Tire> The rubber composition for a tire of the present invention comprises a rubber component, a recycled material, and the following general formula (1):

Chemical Formula

[0014] The tire rubber composition of the present invention contains recycled materials and can contribute to the realization of a sustainable society by promoting the reuse of used products. However, as mentioned above, recycled materials generally have a high ash content, and when recycled materials are blended into a rubber composition, it is difficult to ensure sufficient fracture resistance of the rubber composition. In contrast, the tire rubber composition of the present invention contains 0.1 parts by mass or more of the amine-based antioxidant represented by the above general formula (1) per 100 parts by mass of rubber components, and because the amine-based antioxidant has high basicity, the dispersibility of ash in the recycled material is improved, and the fracture resistance of the rubber composition can be improved. Furthermore, while rubber compositions containing recycled materials generally experience a significant decrease in tensile strength (TB) after exposure to high temperatures, incorporating an amine-based antioxidant represented by the general formula (1) into the rubber composition can suppress the decrease in tensile strength (TB) after exposure to high temperatures. Therefore, the tire rubber composition of the present invention, while containing recycled materials, can improve the tire's fracture resistance (particularly its tensile strength (TB)) when applied to a tire.

[0015] (Rubber component) The rubber composition for tires of the present invention contains a rubber component, which provides the composition with rubber elasticity. The rubber component is preferably a diene rubber, and more preferably isoprene-backed rubber, styrene-butadiene rubber (SBR), butadiene rubber (BR), or chloroprene rubber (CR). Here, isoprene-backed rubber is a rubber whose main backbone is isoprene units, and specifically includes natural rubber (NR), synthetic isoprene rubber (IR), etc. When the rubber component includes at least one selected from the group consisting of isoprene-backed rubber, styrene-butadiene rubber, butadiene rubber, and chloroprene rubber, the rubber elasticity of the rubber composition is excellent, making it a rubber composition more suitable for tire applications. Furthermore, when the rubber component includes at least one selected from the group consisting of isoprene-backed rubber, styrene-butadiene rubber, butadiene rubber, and chloroprene rubber, the effect of improving ozone resistance and suppressing the decrease in tensile strength (TB) after exposure to high temperatures by using an amine-based antioxidant is more readily apparent. The content of diene rubbers such as isoprene skeleton rubber, styrene-butadiene rubber, butadiene rubber, and chloroprene rubber in the rubber component is preferably 80% by mass or more, more preferably 90% by mass or more, and may even be 100% by mass. The rubber component may be a single type or a blend of two or more types.

[0016] (Recycled materials) The rubber composition for tires of the present invention includes recycled material. Here, recycled material refers to material obtained by recycling any used product. In this specification, even if recycled material contains polymers derived from the above-mentioned rubber components, it is treated as separate from the rubber components.

[0017] The content of the recycled material is preferably in the range of 0.1 to 150 parts by mass per 100 parts by mass of the rubber component, and more preferably in the range of 0.1 to 100 parts by mass. When the content of the recycled material is 0.1 parts by mass or more per 100 parts by mass of the rubber component, the fracture resistance of the rubber composition can be sufficiently improved while promoting the reuse of used products, and is more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. On the other hand, when the content of the recycled material is 150 parts by mass or less per 100 parts by mass of the rubber component, the rubber composition can be worked on well without reducing its processability. Furthermore, when the content of the recycled material is 100 parts by mass or less per 100 parts by mass of the rubber component, the processability of the rubber composition becomes particularly good, and is more preferably 80 parts by mass or less, and even more preferably 50 parts by mass or less.

[0018] Examples of the recycled materials include recycled rubber (such as desulfurized rubber) and recycled fillers. These recycled materials are suitable for incorporation into rubber compositions for tires. The method of recycling used products is not particularly limited.

[0019] The desulfurized rubber is obtained by severing (desulfurizing) the sulfur crosslinks between the rubber molecules of vulcanized rubber. For example, desulfurized rubber can be obtained by cutting and crushing used rubber products such as waste tires, kneading them using a roll machine, a closed-type kneader, etc., and severing the sulfur crosslinks with the mechanical shear force and heat generated during this process, or by applying heat from an external source. Alternatively, desulfurized rubber can also be obtained by cutting and crushing used rubber products such as waste tires, adding an oil such as paraffinic process oil and a desulfurizing agent, and heating it under pressure with steam, etc., in an autoclave, etc. Examples of desulfurizing agents include tall oil, pine tar, dipentene, terpene derivatives, coumarone-indene resin, etc.

[0020] The content of the recycled rubber (such as desulfurized rubber) is preferably in the range of 0.1 to 20 parts by mass, and more preferably in the range of 0.1 to 10 parts by mass, per 100 parts by mass of the rubber component. When the recycled rubber content is 0.1 parts by mass or more per 100 parts by mass of the rubber component, the fracture resistance of the rubber composition can be sufficiently improved while promoting the reuse of used products. On the other hand, when the recycled rubber content is 20 parts by mass or less per 100 parts by mass of the rubber component, the fracture resistance of the rubber composition is further improved.

[0021] The recycled filler is not particularly limited as long as it is a filler normally used in rubber products such as tires, and examples include carbon black, silica, powdered rubber, and metal compounds. Examples of the metal compound include zinc compounds, magnesium compounds, and aluminum compounds. Examples of the zinc compound include zinc oxide (zinc oxide) and zinc stearate, examples of the magnesium compound include magnesium hydroxide and magnesium sulfate, and examples of the aluminum compound include aluminum hydroxide. These recycled fillers may be used individually or in combination of two or more types.

[0022] Some of the recycled fillers mentioned above become harder than ordinary fillers, and therefore rubber compositions containing recycled fillers generally have issues with crack resistance. However, by combining the recycled filler with an amine-based antioxidant represented by the general formula (1) above and incorporating it into a rubber composition, sufficient crack resistance of the rubber composition can be ensured.

[0023] The carbon black as the recycled filler is also called recycled carbon black (or recovered carbon black). The recycled carbon black refers to carbon black obtained by a pyrolysis process from used plastics, rubber products, etc. Here, as the manufacturing method of recycled carbon black, mainly two manufacturing methods can be mentioned. The first manufacturing method is a method of obtaining carbon black based on the oil obtained by pyrolyzing used plastics, rubber products, etc. The second manufacturing method is a method of obtaining carbon black based on the ash obtained by pyrolyzing used plastics, rubber products, etc.

[0024] The recycled carbon black preferably has a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area in the range of 80 to 200 m 2 / g, and more preferably 100 to 150 m 2 / g. When the CTAB specific surface area of the recycled carbon black is 80 m 2 / g or more, the fracture resistance of the tire to which the rubber composition containing the recycled carbon black is applied is further improved. Also, when the CTAB specific surface area of the recycled carbon black is 200 m 2 / g or less, the processability of the rubber composition containing the recycled carbon black is good. Also, when the CTAB specific surface area of the recycled carbon black is 100 m 2 / g or more, the fracture resistance is particularly good, and when the CTAB specific surface area of the recycled carbon black is 150 m 2 / g or less, the processability of the rubber composition is particularly good.

[0025] The raw materials for the recycled carbon black can be appropriately collected from rubber products such as waste tires. By appropriately selecting the parts to be recovered from the rubber products, carbon black with a desired CTAB specific surface area can be obtained. Prior to the thermal decomposition of the rubber products, the rubber products to be used as raw materials may be cut, and if the rubber products used contain steel cords, etc., these may be removed before thermal decomposition. The thermal decomposition temperature is preferably in the range of 300 to 600°C, and it is also desirable to carry it out in an oxygen-free gas. An oxygen-free gas is a gas other than oxygen or oxides, and examples include inert gases such as nitrogen, argon, and helium, and flammable gases such as hydrogen, methane, and propane.

[0026] The aforementioned rubber powder can be obtained by cutting and crushing used rubber products such as waste tires. The crushing process may include multiple steps such as a preliminary crushing process and a fine crushing process, and the particle size of the rubber powder to be used may be adjusted by a classification process after the crushing process.

[0027] The content of the recycled filler is preferably in the range of 0.1 to 150 parts by mass per 100 parts by mass of the rubber component, and more preferably in the range of 0.1 to 100 parts by mass. When the recycled filler content is 0.1 parts by mass or more per 100 parts by mass of the rubber component, the fracture resistance of the rubber composition can be sufficiently improved while reusing rubber products such as waste tires, and is more preferably 1 part by mass or more, and even more preferably 3 parts by mass or more. On the other hand, when the recycled filler content is 150 parts by mass or less per 100 parts by mass of the rubber component, the rubber composition can be processed well without reducing its processability. Furthermore, when the recycled filler content is 100 parts by mass or less per 100 parts by mass of the rubber component, the processability of the rubber composition becomes particularly good, and is more preferably 80 parts by mass or less, and even more preferably 50 parts by mass or less.

[0028] As the recycled filler, for example, recycled fillers disclosed in Japanese Patent Publication No. 2017-008223, Japanese Patent Publication No. 2012-001682, Japanese Patent Publication No. 2020-523456, Japanese Patent Publication No. 2017-524065, etc. may be used.

[0029] (Amine-based antioxidant) The tire rubber composition of the present invention contains an amine-based antioxidant represented by the above general formula (1). The amine-based antioxidant represented by general formula (1) contains a phenylenediamine moiety, similar to N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD), which is commonly used as an antioxidant for rubber compositions, but differs from antioxidant 6PPD in that it does not have double bonds other than the phenylenediamine moiety. In addition to improving the ozone resistance of the rubber composition, the amine-based antioxidant represented by general formula (1) has high basicity, improves the dispersibility of ash in recycled materials, and improves the fracture resistance of the rubber composition, particularly by suppressing the decrease in tensile strength (TB) after exposure to high temperatures.

[0030] In the above general formula (1), R 1 and R 2 These are each independently monovalent saturated hydrocarbon groups. 1 and R 2 These may be the same or different, but from a synthesis standpoint, it is preferable that they be the same.

[0031] The number of carbon atoms in the monovalent saturated hydrocarbon group is preferably 1 to 20, more preferably 3 to 10, and particularly preferably 6 and 7. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass increases, resulting in a greater anti-aging effect, higher basicity, and improved ozone resistance and fracture resistance of the rubber composition. In the above general formula (1), R 1 and R 2 From the viewpoint of further improving the ozone resistance and fracture resistance of the rubber composition, it is preferable that each of these be independently a chain or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.

[0032] Examples of the monovalent saturated hydrocarbon group include alkyl groups and cycloalkyl groups. Alkyl groups may be linear or branched, and cycloalkyl groups may have further alkyl groups or the like bonded to them as substituents. Examples of the alkyl groups include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, 1,2-dimethylbutyl group, 1,3-dimethylbutyl group, 2,3-dimethylbutyl group, n-pentyl group, isopentyl group, neopentyl group, 1-methylpentyl group, 2-methylpentyl group, 3-methylpentyl group, 4-methylpentyl group, 1,2-dimethylpentyl group, 1,3-dimethylpentyl group, 1,4-dimethylpentyl group, 2,3-dimethylpentyl group, 2,4-dimethylpentyl group, 3,4-dimethylpentyl group, n-hexyl group, 1-methylhexyl group, 2-methylhexyl group, various octyl groups, various decyl groups, various dodecyl groups, etc., and among these, 1,4-dimethylpentyl group is preferred. Examples of the cycloalkyl group include cyclopentyl group, methylcyclopentyl group, cyclohexyl group, methylcyclohexyl group, cycloheptyl group, and cyclooctyl group, with the cyclohexyl group being preferred among these.

[0033] Specific examples of amine-based antioxidants represented by the above general formula (1) include N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antioxidant 77PD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, and N,N'-dicyclohexyl-p-phenylenediamine (antioxidant CCPD). Among these, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antioxidant 77PD) and N,N'-dicyclohexyl-p-phenylenediamine (CCPD) are preferred, and N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antioxidant 77PD) is particularly preferred. The amine-based antioxidants may be used individually or in combination of two or more.

[0034] The content of the amine-based antioxidant is 0.1 to 11 parts by mass per 100 parts by mass of the rubber component. If the content of the amine-based antioxidant is less than 0.1 parts by mass per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition cannot be sufficiently ensured, and the dispersibility of ash in the recycled material cannot be sufficiently improved, resulting in a decrease in the fracture resistance of the rubber composition, and in particular, the decrease in the tensile strength (TB) of the rubber composition after exposure to high temperatures cannot be sufficiently suppressed. On the other hand, if the content of the amine-based antioxidant exceeds 11 parts by mass per 100 parts by mass of the rubber component, the adverse effects on rubber properties other than ozone resistance and fracture resistance (such as heat generation) become significant, making it unsuitable for tire applications. From the viewpoint of ozone resistance and resistance to destructiveness, the content of the amine-based antioxidant is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, per 100 parts by mass of the rubber component. Furthermore, from the viewpoint of affecting other rubber properties, it is preferably 10 parts by mass or less, and more preferably 8 parts by mass or less, per 100 parts by mass of the rubber component.

[0035] (Quinoline-based anti-aging agent) The rubber composition for tires of the present invention may contain a quinoline-based antioxidant. The quinoline-based antioxidant is an antioxidant having a quinoline portion or a derivative thereof (such as a dihydroquinoline portion). The quinoline-based antioxidant has the effect of improving the ozone resistance of the rubber composition.

[0036] The quinoline-based antioxidant preferably has a dihydroquinoline moiety, and more preferably has a 1,2-dihydroquinoline moiety. Examples of the aforementioned quinoline-based antioxidants include polymers of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ), 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline, and 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline. The quinoline-based antioxidant preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ). A quinoline-based antioxidant containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline has a high effect in improving the ozone resistance of the rubber composition and also has the advantage of being less likely to cause discoloration of the rubber composition. Polymers of 2,2,4-trimethyl-1,2-dihydroquinoline include dimers, trimers, and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline.

[0037] The content of the quinoline-based antioxidant is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. If the content of the quinoline-based antioxidant is 0.1 parts by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition can be further improved. On the other hand, if the content of the quinoline-based antioxidant is 5 parts by mass or less per 100 parts by mass of the rubber component, adverse effects on rubber properties other than ozone resistance (such as heat generation) can be suppressed, making it more suitable for tire applications. From the viewpoint of ozone resistance, the content of the quinoline-based antioxidant is more preferably 0.3 parts by mass or more per 100 parts by mass of the rubber component, and even more preferably 0.5 parts by mass or more. From the viewpoint of affecting other rubber properties, it is more preferably 4 parts by mass or less per 100 parts by mass of the rubber component, and even more preferably 3 parts by mass or less.

[0038] (wax) The rubber composition for tires of the present invention preferably further contains wax. When the rubber composition contains wax, the ozone resistance of the rubber composition is further improved. Examples of the aforementioned waxes include paraffin wax and microcrystalline wax. The amount of wax is preferably 0.1 to 5 parts by mass per 100 parts by mass of the rubber component. If the amount of wax is 0.1 parts by mass or more per 100 parts by mass of the rubber component, the ozone resistance of the rubber composition is further improved. Also, if the amount of wax is 5 parts by mass or less per 100 parts by mass of the rubber component, the effect on rubber properties other than ozone resistance is small. From the viewpoint of ozone resistance, the amount of wax is more preferably 0.5 parts by mass or more per 100 parts by mass of the rubber component, and even more preferably 1 part by mass or more. From the viewpoint of the effect on other rubber properties, it is more preferably 4 parts by mass or less per 100 parts by mass of the rubber component, and even more preferably 3 parts by mass or less.

[0039] (sulfur) The rubber composition for tires of the present invention preferably contains sulfur. The inclusion of sulfur in the rubber composition makes it vulcanizable, which improves the fracture resistance of the rubber composition (particularly its tensile strength (TB)). Various types of sulfur can be used as the aforementioned sulfur, but ordinary sulfur (soluble sulfur (powdered sulfur), etc.) is preferred over insoluble sulfur, and oil-treated sulfur is also preferred. Here, insoluble sulfur is sulfur that is insoluble in carbon disulfide (amorphous polymeric sulfur), and soluble sulfur (powdered sulfur) is sulfur that is soluble in carbon disulfide. The sulfur content is preferably in the range of 0.1 to 10 parts by mass per 100 parts by mass of rubber component, and more preferably in the range of 1 to 5 parts by mass. If the sulfur content is 0.1 parts by mass or more per 100 parts by mass of rubber component, the fracture resistance of the vulcanized rubber can be ensured, and if it is 10 parts by mass or less per 100 parts by mass of rubber component, sufficient rubber elasticity can be ensured.

[0040] (others) In addition to the rubber components, recycled materials, amine-based antioxidants, quinoline-based antioxidants, waxes, and sulfur described above, the rubber composition for tires of the present invention may optionally contain various components commonly used in the rubber industry, such as new fillers other than recycled fillers (silica, carbon black, calcium carbonate, etc.), silane coupling agents, softeners, processing aids, resins, surfactants, organic acids (stearic acid, etc.), zinc oxide (zinc oxide), vulcanization accelerators, vulcanizing agents other than sulfur, etc., selected as appropriate within a range that does not impair the purpose of the present invention. Commercially available products can be suitably used as these compounding agents. The amine-based antioxidant represented by the above general formula (1) may be supported on any carrier. For example, the amine-based antioxidant represented by the above general formula (1) may be supported on recycled fillers or new inorganic fillers such as silica or calcium carbonate. Furthermore, the amine-based antioxidant represented by the general formula (1) above may also be used to form a masterbatch together with a rubber component. The rubber component used when forming the masterbatch is not particularly limited and may be a diene rubber such as natural rubber (NR), or ethylene-propylene-diene rubber (EPDM), etc. Furthermore, the amine-based antioxidant represented by the above general formula (1) may also be in the form of a salt with an organic acid. The organic acid used when forming the salt is not particularly limited, but examples include stearic acid.

[0041] (Method for manufacturing rubber composition) The method for producing the rubber composition is not particularly limited, but for example, it can be produced by mixing the aforementioned rubber components, recycled material, and amine-based antioxidant with various components as needed, and then kneading, heating, extruding, etc. Furthermore, the obtained rubber composition can be vulcanized to produce vulcanized rubber.

[0042] There are no particular restrictions on the mixing conditions, and various conditions such as the input volume of the mixing device, the rotation speed of the rotor, the ram pressure, as well as the mixing temperature, mixing time, and the type of mixing device can be appropriately selected according to the purpose. Examples of mixing devices include Banbury mixers, intermixes, kneaders, and rolls, which are commonly used for mixing rubber compositions.

[0043] There are no particular restrictions on the heat treatment conditions, and various conditions such as heat treatment temperature, heat treatment time, and heat treatment equipment can be appropriately selected according to the purpose. Examples of such heat treatment equipment include heat treatment roll machines commonly used for heat treatment of rubber compositions.

[0044] There are no particular restrictions on the extrusion conditions, and various conditions such as extrusion time, extrusion speed, extrusion equipment, and extrusion temperature can be appropriately selected according to the purpose. Examples of extrusion equipment include extruders typically used for extruding rubber compositions. The extrusion temperature can be determined as appropriate.

[0045] There are no particular restrictions on the apparatus, method, and conditions for performing the vulcanization, and they can be appropriately selected according to the purpose. Typical vulcanization apparatuses include molding vulcanizers using molds, which are commonly used for vulcanizing rubber compositions. The vulcanization temperature is typically around 100-190°C.

[0046] <Tires> The tire of the present invention is characterized by comprising a rubber member made of the above-described tire rubber composition. Because the tire of the present invention comprises a rubber member made of the above-described tire rubber composition, it has excellent fracture resistance (particularly tensile strength (TB)) even while containing recycled materials. Suitable rubber components to which the above tire rubber composition is applied include side rubber, tread rubber, and inner liner, which constitute the tire surface. The rubber components to which the above tire rubber composition is applied may also be rubber components that constitute the inside of the tire. Examples of such rubber components include bead fillers and coating rubber for reinforcing members such as carcasses and belts.

[0047] The tire of the present invention may be obtained by molding an unvulcanized rubber composition and then vulcanizing it, depending on the type of tire to be applied, or by molding a semi-vulcanized rubber that has undergone a pre-vulcanization process, and then further vulcanizing it. The tire of the present invention is preferably a pneumatic tire, and as the gas to be filled into the pneumatic tire, in addition to ordinary air or air with adjusted oxygen partial pressure, an inert gas such as nitrogen, argon, or helium can be used. [Examples]

[0048] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0049] (Preparation and evaluation of rubber compositions) Rubber compositions were manufactured according to the formulations shown in Table 1. The retention rates of elongation at break (EB) and tensile strength (TB) after aging were evaluated for the obtained rubber compositions using the following method. The results are shown in Table 1.

[0050] --Retention rate of elongation at break (EB) and tensile strength (TB) after aging-- Vulcanized rubber test specimens were prepared by vulcanizing the rubber composition. Tensile tests were performed on the test specimens immediately after preparation in accordance with JIS K 6251, and the initial elongation at break (EB) and tensile strength (TB) were measured. Next, vulcanized rubber test pieces were left at 100°C for 24 hours to age. Tensile tests were then performed on the aged test pieces in accordance with JIS K 6251, and the elongation at break (EB) and tensile strength (TB) after aging were measured.

[0051] The maintenance rate of the elongation at break (EB) and tensile strength (TB) after aging was calculated from the initial elongation at break (EB) and tensile strength (TB), as well as the elongation at break (EB) and tensile strength (TB) after aging, according to the following formula. Maintenance rate of rupture elongation (EB) after aging = Relative rupture elongation (EB) after aging / Initial rupture elongation (EB) × 100 (%) Maintenance rate of tensile strength (TB) after aging = Tensile strength after aging (TB) / Initial tensile strength (TB) × 100 (%)

[0052] [Table 1]

[0053] *1 NR: Natural rubber *2 SBR: Total amount (excluding oil content) of styrene-butadiene rubber [amount of bound styrene = 20% by mass, amount of vinyl bound in the butadiene portion = 55% by mass, glass transition temperature (Tg) = -40°C] and styrene-butadiene rubber oil-expandable rubber [amount of bound styrene = 45% by mass, amount of vinyl bound in the butadiene portion = 19% by mass, glass transition temperature (Tg) = -30°C]. *3 Carbon Black: Manufactured by Asahi Carbon Co., Ltd., product name "Asahi #78" *4 Silica: Manufactured by Tosoh Silica Industry Co., Ltd., product name "NipSeal AQ" *5 Anti-aging agent 77PD: R in general formula (1) 1 and R 2 The amine-based antioxidant, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine, manufactured by Eastman, has a saturated hydrocarbon group (1,4-dimethylpentyl group) as its base. Trademark: "Santoflex 77PD" *6 Anti-aging agent 6PPD: R in general formula (1) 1 and R 2 N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, an amine-based antioxidant in which one of the groups is an unsaturated hydrocarbon group (phenyl group), manufactured by Sumitomo Chemical Co., Ltd., trade name "Antigen 6C". *7 Recycled rubber: Recycled material, manufactured by Muraoka Rubber Industry Co., Ltd., wheel tire reclair rubber *8 Silane coupling agent: Bis(triethoxysilylpropyl) polysulfide, manufactured by Shin-Etsu Chemical Co., Ltd., product name "ABC-856" *9 Sulfur: Manufactured by Hosoi Chemical Industry Co., Ltd., product name "HK200-5", 5% oil *10 Accelerator: Total amount of accelerators including at least zinc oxide manufactured by Hakusui Tech Co., Ltd. and the product name "Sunceller CM-G" manufactured by Sanshin Chemical Industry Co., Ltd. *11 Other chemicals: Total amount including at least the oil content of "MS-95" manufactured by Kao Corporation.

[0054] Table 1 shows that, in rubber compositions containing recycled materials, using an amine-based antioxidant represented by the above general formula (1) instead of the antioxidant 6PPD improves the retention rate of elongation at break (EB) and tensile strength (TB) after aging, and improves fracture resistance.

Claims

1. Rubber components, Recycled materials and The following general formula (1): 【Chemistry 1】 [In the formula, R １ and R ２ It comprises an amine-based antioxidant represented by [each being an independently monovalent saturated hydrocarbon group], The aforementioned recycled material is recycled rubber obtained by recycling used rubber products. A rubber composition for tires, characterized in that the content of the amine-based antioxidant is 0.1 to 11 parts by mass per 100 parts by mass of the rubber component.

2. The tire rubber composition according to claim 1, wherein the rubber component comprises at least one selected from the group consisting of isoprene backbone rubber, styrene-butadiene rubber, butadiene rubber, and chloroprene rubber.

3. In the above general formula (1), R １ and R ２ The tire rubber composition according to claim 1 or 2, wherein each is independently a chain or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms.

4. A tire characterized by comprising a rubber member made of the tire rubber composition described in any one of claims 1 to 3.

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