JP2023024192A - Rubber composition for tires and tire - Google Patents

Abstract

To provide a rubber composition for tires which has excellent ozone resistance and high retention rates of elongation at break (EB) and tensile strength (TB) after aging even when an antioxidant 6PPD is not used.SOLUTION: The rubber composition for tires contains a rubber component containing an isoprene skeleton rubber, an amine-based antioxidant represented by general formula (1) [where R1 and R2 each independently represent a monovalent saturated hydrocarbon group], and a quinoline-based antioxidant. The mass ratio of the content of the quinoline-based antioxidant to the content of the amine-based antioxidant (the content of the quinoline-based antioxidant/the content of the amine-based antioxidant) is 0.27-0.7.SELECTED DRAWING: None

Description

TECHNICAL FIELD The present invention relates to a tire rubber composition and a tire.

In general, various rubber members that constitute a tire may deteriorate under the influence of the ambient environment such as the presence of ozone, and as the deterioration progresses, cracks and the like may occur. In order to deal with such problems, rubber compositions containing anti-aging agents are often applied to various rubber members constituting tires.
For example, in Patent Document 1 below, a specific quinoline antioxidant and N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antiaging agent 6PPD) are selected and blended. It is disclosed that cracks and discoloration of the tire surface can be suppressed by applying the resulting rubber composition to the rubber constituting the surface of the tire.

WO2018/056384

However, the N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (anti-aging agent 6PPD) used in Patent Document 1 above may have an impact on the environment, Considering the possibility of regulation by European regulations in the future, it has been desired to use anti-aging agents that have a lower burden on the environment.
Therefore, a technique that does not use anti-aging agent 6PPD in the rubber composition is conceivable. It was found that the ozone resistance of the rubber composition deteriorated, and the durability of the aged rubber composition (in particular, elongation at break (EB) and tensile strength (TB)) deteriorated.

Therefore, the object of the present invention is to solve the above-described problems of the prior art, and to provide excellent ozone resistance, elongation at break (EB) and tensile strength ( An object of the present invention is to provide a tire rubber composition having a high TB) retention ratio.
Furthermore, another object of the present invention is to provide a tire that has excellent ozone resistance and excellent durability after aging.

As a result of studies to solve the above problems, the present inventors have found that, in a rubber composition containing an isoprene skeleton rubber, an amine-based antioxidant having a specific structure and a quinoline-based antioxidant are used in combination. , By optimizing the mass ratio between the content of the amine-based antioxidant and the content of the quinoline-based antioxidant, the ozone resistance of the rubber composition is sufficiently ensured, and the rubber composition after aging It was found that the decrease in elongation at break (EB) and tensile strength (TB) of the product can be suppressed.

［式中、Ｒ^１及びＲ^２は、それぞれ独立して一価の飽和炭化水素基である］で表されるアミン系老化防止剤と、
キノリン系老化防止剤と、を含み、
前記アミン系老化防止剤の含有量に対する前記キノリン系老化防止剤の含有量の質量比（キノリン系老化防止剤の含有量／アミン系老化防止剤の含有量）が、０．２７～０．７であることを特徴とする。
かかる本発明のタイヤ用ゴム組成物は、耐オゾン性に優れ、老化後の切断時伸び（ＥＢ）及び引張強さ（ＴＢ）の維持率が高い。 That is, the rubber composition for tires of the present invention comprises a rubber component containing an isoprene skeleton rubber,
The following general formula (1):

[Wherein, R ¹ and R ² are each independently a monovalent saturated hydrocarbon group];
and a quinoline antioxidant,
The mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant (content of quinoline antioxidant/content of amine antioxidant) is 0.27 to 0.7. It is characterized by
Such a rubber composition for tires of the present invention is excellent in ozone resistance, and has high retention rate of elongation at break (EB) and tensile strength (TB) after aging.

Further, in the rubber composition for tires of the present invention, the quinoline anti-aging agent preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline. In this case, the effect of improving the ozone resistance of the rubber composition is high, and the rubber composition is less likely to discolor.

Furthermore, in the rubber composition for tires of the present invention, R ¹ and R ² in the general formula (1) are each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms. is preferably In this case, the ozone resistance of the rubber composition is further improved.

Furthermore, it is preferable that the rubber composition for tires of the present invention further contains wax, and the content of the wax is 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. In this case, the ozone resistance of the rubber composition is further improved.

The tire of the present invention is characterized by using the rubber composition for tires of the present invention described above.
Such a tire of the present invention has excellent ozone resistance and excellent durability after aging.

ADVANTAGE OF THE INVENTION According to the present invention, a rubber composition for a tire that has excellent ozone resistance and high maintenance rate of elongation at break (EB) and tensile strength (TB) after aging even when anti-aging agent 6PPD is not used. can provide things.
Moreover, according to the present invention, it is possible to provide a tire having excellent ozone resistance and excellent durability after aging.

Hereinafter, the rubber composition for tires and the tire of the present invention will be exemplified in detail based on the embodiments thereof.

［式中、Ｒ^１及びＲ^２は、それぞれ独立して一価の飽和炭化水素基である］で表されるアミン系老化防止剤（以下、単に「アミン系老化防止剤」ということがある。）と、キノリン系老化防止剤と、を含む。 <Rubber composition for tires>
The rubber composition for tires of the present invention comprises a rubber component containing an isoprene skeleton rubber and the following general formula (1):

[In the formula, R ¹ and R ² are each independently a monovalent saturated hydrocarbon group] (hereinafter sometimes simply referred to as "amine antioxidant"). ) and a quinoline antioxidant.

In the rubber composition for tires of the present invention, the mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant (content of quinoline antioxidant / content of amine antioxidant content) is 0.27 to 0.7.
In the presence of an isoprene skeleton rubber, while using both the amine-based antioxidant represented by the general formula (1) and the quinoline-based antioxidant, the quinoline-based aging with respect to the content of the amine-based antioxidant By setting the mass ratio of the content of the inhibitor in the above range (0.27 to 0.7), the ozone resistance of the rubber composition is sufficiently ensured, and the elongation at break (EB ) and a decrease in tensile strength (TB) can be suppressed. In addition, when the mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant is less than 0.27, high ozone resistance can be secured, but elongation at break after aging ( EB) and tensile strength (TB) are not sufficiently obtained, and if it exceeds 0.7, the elongation at break (EB) and tensile strength (TB) after aging are good, but sufficient resistance is not obtained. Ozone property cannot be obtained.
Therefore, the rubber composition for tires of the present invention is excellent in ozone resistance, and has high retention rates of elongation at break (EB) and tensile strength (TB) after aging.

Further, in the rubber composition for tires of the present invention, the mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant (content of quinoline antioxidant / amine antioxidant content) of 0.27 to 0.7, it is possible to suppress adverse effects on rubber physical properties other than ozone resistance (such as heat build-up), making it suitable for tire applications.
Furthermore, from the viewpoint of increasing the ozone resistance of the rubber composition, and the elongation at break (EB) and tensile strength (TB) maintenance rate after aging, while suppressing adverse effects on rubber physical properties other than ozone resistance. Therefore, the mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant (content of quinoline antioxidant / content of amine antioxidant) is 0.27 to 0 0.63 is preferred, and 0.28 to 0.58 is more preferred.

Each component constituting the rubber composition of the present invention will be described below.
(rubber component)
The rubber composition for tires of the present invention contains a rubber component containing at least an isoprene skeleton rubber. The rubber component can thereby provide rubber elasticity to the composition.
The rubber component is not particularly limited as long as it contains at least an isoprene skeleton rubber. Here, the isoprene-skeletal rubber is a rubber having isoprene units as a main skeleton, and specific examples thereof include natural rubber (NR), synthetic isoprene rubber (IR), and the like.

The rubber component can also contain a diene rubber other than the isoprene skeleton rubber. Examples of the diene rubber other than the isoprene skeleton rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), and the like.

Further, when the rubber component contains an isoprene skeleton rubber, a diene rubber such as a styrene-butadiene rubber, a butadiene rubber, or a chloroprene rubber, the effect of the present invention (combined use of an amine antioxidant and a quinoline antioxidant The effect of improving ozone resistance and the effect of suppressing the decrease in elongation at break (EB) and tensile strength (TB) after aging) are likely to appear remarkably.

The content of the isoprene skeleton rubber in the rubber component is preferably 20 % by mass or more, more preferably 30 % by mass or more, and can be 100% by mass. The isoprene skeleton rubber in the rubber component may be used alone or in a blend of two or more.

一般式（１）で表されるアミン系老化防止剤は、Ｎ－フェニル－Ｎ’－（１，３－ジメチルブチル）－ｐ－フェニレンジアミン（老化防止剤６ＰＰＤ）と同様にフェニレンジアミン部分を含むものの、該フェニレンジアミン部分以外には二重結合を有しない点で、老化防止剤６ＰＰＤと異なるため、環境への負荷が少ない。
また、一般式（１）で表されるアミン系老化防止剤は、ゴム組成物の耐オゾン性を向上させ、老化後の切断時伸び（ＥＢ）及び引張強さ（ＴＢ）の維持率の低下を抑制する作用を有する。 (Amine anti-aging agent)
The rubber composition for tires of the present invention contains an amine anti-aging agent represented by general formula (1).

The amine antioxidant represented by the general formula (1) contains a phenylenediamine moiety like N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine (antioxidant 6PPD). However, since it differs from antiaging agent 6PPD in that it does not have double bonds other than the phenylenediamine moiety, it has less impact on the environment.
In addition, the amine anti-aging agent represented by the general formula (1) improves the ozone resistance of the rubber composition, and reduces the maintenance rate of elongation at break (EB) and tensile strength (TB) after aging. has the effect of suppressing

Here, in general formula (1) above, R ¹ and R ² are each independently a monovalent saturated hydrocarbon group. R ¹ and R ² may be the same or different, but are preferably the same from the viewpoint of synthesis.

The monovalent saturated hydrocarbon group preferably has 1 to 20 carbon atoms, more preferably 3 to 10 carbon atoms, and particularly preferably 6 and 7 carbon atoms. When the number of carbon atoms in the saturated hydrocarbon group is 20 or less, the number of moles per unit mass becomes large, so that the anti-aging effect becomes large and the ozone resistance of the rubber composition is improved.
Furthermore, from the viewpoint of further improving the ozone resistance of the rubber composition, R ¹ and R ² in the general formula (1) each independently represent a linear or cyclic saturated monovalent rubber having 1 to 20 carbon atoms. A hydrocarbon group is preferred.

Here, the monovalent saturated hydrocarbon group includes an alkyl group and a cycloalkyl group, and the alkyl group may be linear or branched. Furthermore, an alkyl group or the like may be bonded.
Examples of the alkyl group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl 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. Among these, a 1,4-dimethylpentyl group is preferred.
Examples of the cycloalkyl group include a cyclopentyl group, a methylcyclopentyl group, a cyclohexyl group, a methylcyclohexyl group, a cycloheptyl group, a cyclooctyl group, etc. Among these, a cyclohexyl group is preferred.

Further, as the amine antioxidant represented by the general formula (1), specifically, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD), N,N'-bis(1-ethyl-3-methylpentyl)-p-phenylenediamine, N,N'-dicyclohexyl-p-phenylenediamine (antiaging agent CCPD) and the like. Among these, N,N'-bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD) and N,N'-dicyclohexyl-p-phenylenediamine (CCPD) are preferred, and N,N '-Bis(1,4-dimethylpentyl)-p-phenylenediamine (antiaging agent 77PD) is particularly preferred. The amine anti-aging agents may be used singly or in combination of two or more.

The content of the amine anti-aging agent is not particularly limited, but is preferably 0.1 to 11 parts by mass with respect to 100 parts by mass of the rubber component. When the content of the amine anti-aging agent is 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component, the ozone resistance of the rubber composition can be sufficiently ensured, and after aging can sufficiently suppress the decrease in elongation at break (EB) and tensile strength (TB) of the rubber composition. On the other hand, when the content of the amine anti-aging agent is 11 parts by mass or less with respect to 100 parts by mass of the rubber component, adverse effects on rubber physical properties other than ozone resistance (exothermicity, etc.) are more reliably prevented. It can be suppressed and is suitable for tire applications.
The content of the amine anti-aging agent is more preferably 1 part by mass or more, more preferably 2 parts by mass or more with respect to 100 parts by mass of the rubber component, from the viewpoint of enhancing ozone resistance. 3 parts by mass or more is particularly preferable. In addition, the content of the amine antioxidant is more preferably 10.5 parts by mass or less with respect to 100 parts by mass of the rubber component, from the viewpoint of suppressing adverse effects on other rubber physical properties, and 10 parts by mass or less. is more preferable.

(Quinoline anti-aging agent)
The rubber composition for tires of the present invention contains a quinoline antioxidant. The quinoline anti-aging agent is an anti-aging agent having a quinoline moiety or a derivative thereof (such as a dihydroquinoline moiety).
The quinoline anti-aging agent has an effect of improving the ozone resistance by being contained in the rubber composition for tires and suppressing the decrease in the maintenance rate of elongation at break (EB) and tensile strength (TB) after aging. have

The quinoline antioxidant preferably has a dihydroquinoline moiety, more preferably a 1,2-dihydroquinoline moiety.
Specific examples of the quinoline antioxidant include a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antioxidant TMDQ), 6-ethoxy-2,2,4-trimethyl-1 ,2-dihydroquinoline, 6-anilino-2,2,4-trimethyl-1,2-dihydroquinoline and the like.
The quinoline antioxidant preferably contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline (antiaging agent TMDQ). A quinoline anti-aging agent containing a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline is said to be highly effective in improving the ozone resistance of a rubber composition, and is less likely to discolor the rubber composition. It also has advantages.
The polymer of 2,2,4-trimethyl-1,2-dihydroquinoline includes dimers, trimers and tetramers of 2,2,4-trimethyl-1,2-dihydroquinoline. mentioned.

The content of the quinoline antioxidant is such that the mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant is in the range of 0.27 to 0.7. is not particularly limited.
For example, while suppressing adverse effects on rubber physical properties other than ozone resistance, sufficiently ensure ozone resistance, and sufficiently reduce the elongation at break (EB) and tensile strength (TB) of the rubber composition after aging. From the viewpoint of suppression, the content of the quinoline antioxidant is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. When the content of the quinoline antioxidant is 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component, the ozone resistance of the rubber composition can be sufficiently ensured, and the A decrease in elongation at break (EB) and tensile strength (TB) of the rubber composition can be sufficiently suppressed. On the other hand, when the content of the quinoline antioxidant is 5 parts by mass or less with respect to 100 parts by mass of the rubber component, adverse effects on rubber properties other than ozone resistance (heat buildup, etc.) are suppressed, and tire applications can be suitable for
In addition, from the viewpoint of further increasing ozone resistance, the content of the quinoline antioxidant is more preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more with respect to 100 parts by mass of the rubber component. It is even more preferable to be Furthermore, from the viewpoint of more reliably suppressing adverse effects on other rubber physical properties, it is more preferably 4 parts by mass or less, more preferably 3 parts by mass or less per 100 parts by mass of the rubber component.

(wax)
The rubber composition for tires of the present invention preferably further contains wax. When the rubber composition for tires contains wax, the ozone resistance is further improved.
Examples of the wax include paraffin wax and microcrystalline wax.
Although the content of the wax is not particularly limited, it is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. When the content of the wax is 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component, the ozone resistance of the rubber composition is further improved. Further, when the content of the wax is 5 parts by mass or less with respect to 100 parts by mass of the rubber component, the effect on rubber physical properties other than ozone resistance is small.
In addition, the content of the wax is more preferably 0.5 parts by mass or more, more preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component, from the viewpoint of further improving the ozone resistance. . Furthermore, from the viewpoint of being able to further suppress adverse effects on other rubber physical properties, it is more preferably 4 parts by mass or less, and even more preferably 3 parts by mass or less with respect to 100 parts by mass of the rubber component.

(sulfur)
The tire rubber composition of the present invention preferably contains sulfur. When the rubber composition contains sulfur, it becomes vulcanizable, and the durability (in particular, elongation at break (EB) and tensile strength (TB)) of the rubber composition is improved.
As the sulfur, various types of sulfur can be used, but ordinary sulfur (soluble sulfur (powder sulfur), etc.) is preferable to insoluble sulfur, and oil treated sulfur, etc. are also preferable. Here, insoluble sulfur is sulfur insoluble in carbon disulfide (amorphous polymeric sulfur), and soluble sulfur (powder sulfur) is sulfur soluble in carbon disulfide.
The sulfur content is preferably in the range of 0.1 to 10 parts by mass, more preferably in the range of 1 to 5 parts by mass, per 100 parts by mass of the rubber component. If the sulfur content is 0.1 parts by mass or more with respect to 100 parts by mass of the rubber component, the vulcanized rubber can be ensured with better durability, and the sulfur content is 10 parts by mass or less with respect to 100 parts by mass of the rubber component. If so, better rubber elasticity can be ensured.

(Other ingredients)
The rubber composition for tires of the present invention may contain, in addition to the aforementioned rubber component, amine-based antioxidant, quinoline-based antioxidant, wax, sulfur, and, if necessary, various additives commonly used in the rubber industry. Ingredients (other ingredients) can be included. Other components include, for example, fillers such as silica and carbon black, silane coupling agents, softeners, processing aids, stearic acid, zinc oxide (zinc oxide), vulcanization accelerators, vulcanizing agents other than sulfur, and the like. may be appropriately selected and contained within a range that does not impair the object of the present invention. Commercially available products can be suitably used as these compounding agents.

In addition, the amine anti-aging agent represented by the general formula (1) may be supported on any carrier. For example, the amine anti-aging agent represented by the above general formula (1) may be supported on inorganic fillers such as silica and calcium carbonate.
Moreover, the amine anti-aging agent represented by the general formula (1) may be a masterbatch with a rubber component. Here, the rubber component used in forming the masterbatch is not particularly limited, and may be diene rubber such as natural rubber (NR), ethylene-propylene-diene rubber (EPDM), or the like. .
Moreover, the amine anti-aging agent represented by the general formula (1) may be a salt with an organic acid. Here, the organic acid used for forming the salt is not particularly limited, but stearic acid and the like can be mentioned.

(Method for producing rubber composition for tire)
The method for producing the rubber composition for tires of the present invention is not particularly limited. It can be produced by blending selected suitable ingredients and other ingredients, kneading, heating, extrusion, and the like.
Further, vulcanized rubber can be obtained by vulcanizing the obtained rubber composition.

The kneading conditions are not particularly limited, and various conditions such as the input volume of the kneading device, the rotation speed of the rotor, the ram pressure, the kneading temperature, the kneading time, the type of the kneading device, etc. It can be selected as appropriate. Examples of the kneading device include Banbury mixers, intermixes, kneaders, rolls, etc., which are usually used for kneading rubber compositions.

The heating conditions are also not particularly limited, and various conditions such as the heating temperature, the heating time, and the heating device can be appropriately selected according to the purpose. Examples of the heating device include a heating roll machine or the like which is usually used for heating the rubber composition.

The extrusion conditions are also not particularly limited, and various conditions such as extrusion time, extrusion speed, extrusion apparatus, and extrusion temperature can be appropriately selected according to the purpose. Examples of the extrusion device include an extruder or the like that is usually used for extrusion of a rubber composition. The extrusion temperature can be determined appropriately.

The vulcanization apparatus, method, conditions, etc. are not particularly limited and can be appropriately selected according to the purpose. As a vulcanization apparatus, a molding vulcanizer with a mold used for vulcanization of a rubber composition can be used. As a vulcanization condition, the temperature is, for example, about 100 to 190.degree.

<Tire>
The tire of the present invention is characterized by using the rubber composition for tires of the present invention described above.
As a result, the tire of the present invention has excellent ozone resistance and excellent durability after aging.
The site to which the rubber composition for tires is applied is not particularly limited. Can be used in one place. Among these, it is preferable to apply the tire rubber composition to the tread portion. This is because the effects of ozone resistance and durability after aging can be exhibited more remarkably.

Depending on the type of tire to be applied, the tire of the present invention may be obtained by vulcanizing after molding using an unvulcanized rubber composition, or using a semi-vulcanized rubber that has undergone a pre-vulcanization step or the like. After molding, it may be obtained by further vulcanization. The tire of the present invention is preferably a pneumatic tire, and the gas to be filled in the pneumatic tire may be normal air or oxygen partial pressure-adjusted air, or an inert gas such as nitrogen, argon, or helium. can be used.

EXAMPLES The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

<Examples 1-3, Comparative Examples 1-2>
A rubber composition is produced according to the formulation shown in Tables 1 and 2.
Examples 1 to 3 and Comparative Examples 1 and 2 are prediction data.

*1 NR: Natural rubber *2 SBR-1: Styrene-butadiene rubber, bound styrene content = 20% by mass, vinyl bond content in butadiene portion = 55% by mass, glass transition temperature (Tg) = -40°C
*3 SBR-2: Oil-extended rubber of styrene-butadiene rubber, amount of bound styrene = 45% by mass, amount of vinyl bond in butadiene portion = 19% by mass, glass transition temperature (Tg) = -30°C, oil content of 11% by mass *4 Carbon black: Asahi Carbon Co., Ltd., product name “Asahi #78”
*5 Silica: Manufactured by Tosoh Silica Industry Co., Ltd., trade name “Nip Seal AQ”
*6 Wax: Microcrystalline wax, total amount of Nippon Seiro Co., Ltd.'s trade name "Ozoace 0701" and Nippon Seiro Co., Ltd. trade name "Ozoace 0301" *7 Antioxidant 77PD: Amine antioxidant, N , N′-bis(1,4-dimethylpentyl)-p-phenylenediamine, manufactured by EASTMAN, trade name “Santoflex 77PD”
*8 Anti-aging agent TMDQ: Quinoline anti-aging agent, polymer of 2,2,4-trimethyl-1,2-dihydroquinoline, manufactured by Seiko Chemical Co., Ltd., trade name “Nonflex RD”
*10 Silane coupling agent: N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, manufactured by Shin-Etsu Chemical Co., Ltd., trade name "ABC-856"
*11 Stearic acid: manufactured by NOF Corporation, trade name “Kirijirushi stearic acid”
*12 Sulfur: Hosoi Chemical Industry Co., Ltd., product name “HK200-5”, 5% oil *13 Accelerator: Hakusui Tech Co., Ltd. zinc oxide and Sanshin Chemical Industry Co., Ltd. product name “Suncellar CM-G Total amount of accelerators containing at least * 14 Other chemicals: Total amount containing at least Kao Corporation's product name "MS-95"

<Evaluation>
The obtained rubber composition is evaluated for retention of elongation at break (EB) and tensile strength (TB) after aging, and ozone resistance by the following methods. Table 2 shows the results.

(1) Retention of Elongation at Break (EB) and Tensile Strength (TB) after Aging A rubber composition was vulcanized to prepare a vulcanized rubber test piece. A tensile test is performed on the test piece immediately after production in accordance with JIS K 6251 to measure initial elongation at break (EB) and tensile strength (TB).
Next, the vulcanized rubber test piece is left at 100 ° C. for 24 hours to age, and a tensile test is performed on the aged test piece in accordance with JIS K 6251 to determine the elongation at break (EB) after aging. and tensile strength (TB).
Then, from the initial elongation at break (EB) and tensile strength (TB), and the elongation at break (EB) and tensile strength (TB) after aging, the elongation at break (EB) after aging according to the following formula And the retention rate of tensile strength (TB) is calculated.
Maintenance rate of elongation at break (EB) after aging = elongation at break after aging (EB) / initial elongation at break (EB) x 100 (%)
Maintenance rate of tensile strength (TB) after aging = Tensile strength (TB) after aging / initial tensile strength (TB) x 100 (%)

(2) Ozone resistance In accordance with JIS K 6259, a dynamic ozone deterioration test (a test in which repeated strain was applied) and a static ozone deterioration test (a test in which a constant strain was applied and allowed to stand) were conducted to determine ozone resistance. Evaluate. Evaluation is performed by ranking according to the number of cracks and classifying them according to the following criteria (A to C), and also ranking according to the size and depth of the cracks, and classifying them according to the following criteria (1 to 5). .
The evaluation results are shown in Table 2 in the form of, for example, "A-1" and [B-2], in which the ranking according to the number of cracks and the ranking according to the depth are connected with a hyphen.

(2-1) Ranking by number of cracks A: few cracks B: many cracks C: countless cracks

(2-2) Ranking by size and depth of cracks 1: Cracks invisible to the naked eye but visible with a 10x magnifying glass.
2: Observable with the naked eye.
3: Deep and relatively large cracks (less than 1 mm).
4: Deep and large cracks (1 mm or more and less than 3 mm).
5: Those that are likely to cause cracks or cuts of 3 mm or more.

From the results in Table 2, it can be seen that the rubber compositions of each example are all excellent in ozone resistance and have high retention rates of elongation at break (EB) and tensile strength (TB) after aging. On the other hand, the rubber compositions of the respective comparative examples are inferior to those of the examples in any of the ozone resistance and the maintenance rate of elongation at break (EB) and tensile strength (TB) after aging. .

ADVANTAGE OF THE INVENTION According to the present invention, a rubber composition for a tire that has excellent ozone resistance and high maintenance rate of elongation at break (EB) and tensile strength (TB) after aging even when anti-aging agent 6PPD is not used. can provide things.
Moreover, according to the present invention, it is possible to provide a tire having excellent ozone resistance and excellent durability after aging.

Claims (5)

a rubber component containing an isoprene skeleton rubber;
The following general formula (1):

[Wherein, R ¹ and R ² are each independently a monovalent saturated hydrocarbon group];
and a quinoline antioxidant,
The mass ratio of the content of the quinoline antioxidant to the content of the amine antioxidant (content of quinoline antioxidant/content of amine antioxidant) is 0.27 to 0.7. A rubber composition for tires, characterized in that 2. The rubber composition for tires according to claim 1, wherein the quinoline anti-aging agent contains a polymer of 2,2,4-trimethyl-1,2-dihydroquinoline. Claim 1 or 2, wherein R ¹ and R ² in the general formula (1) are each independently a linear or cyclic monovalent saturated hydrocarbon group having 1 to 20 carbon atoms. The rubber composition for tires according to . The tire according to any one of claims 1 to 3, further comprising wax, and the content of the wax is 0.1 to 5 parts by mass with respect to 100 parts by mass of the rubber component. rubber composition for A tire comprising the tire rubber composition according to any one of claims 1 to 4.