Rubber composition

Abstract

To provide a rubber composition which is excellent in stain resistance and exhibits anti-aging properties equivalent or superior to those of a rubber composition containing a conventional amine-based antioxidant.SOLUTION: The rubber composition contains 100 pts.mass of a diene rubber and 0.1-10 pts.mass of a compound represented by the following formula (1). In the formula (1), R1 represents a hydrogen atom or a substituent; R2 represents a substituent; R3 represents a hydrogen atom or a substituent other than a hydroxy group; and R1-R3 may be bonded to each other to form a ring.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a rubber composition. [Background technology]

[0002] BACKGROUND ART Conventionally, rubber compositions containing an amine-based antioxidant (for example, N-phenyl-1-naphthylamine) as an antioxidant have been known (for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-095806 Summary of the Invention [Problem to be solved by the invention]

[0004] On the other hand, rubber compositions containing conventional amine-based antioxidants may discolor to brown or the like during use (they may have insufficient stain resistance).

[0005] In view of the above circumstances, an object of the present invention is to provide a rubber composition that is excellent in contamination resistance and exhibits antiaging properties equal to or better than those of rubber compositions containing conventional amine-based antiaging agents. [Means for solving the problem]

[0006] As a result of extensive research into the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by blending a specific compound in a predetermined amount, and have thus arrived at the present invention. That is, the present inventors have found that the above problems can be solved by the following configuration.

[0007] (1) A rubber composition containing 100 parts by mass of a diene rubber and 0.1 to 10 parts by mass of a compound represented by formula (1) described below. (2) The rubber composition according to (1) above, wherein the minimum bond energy of the XH bond in the compound is 71 kcal / mol or less, where X represents an atom other than a hydrogen atom, and the bond energy is calculated from the following formula using the density functional B3LYP / 6-31+G(d, p): (Bond energy) = (energy of the compound) - (energy of the hydrogen atom) - (energy of the radical obtained by abstracting a hydrogen atom from the compound) (3) The rubber composition according to (1) or (2) above, wherein the compound has at least one structure selected from the group consisting of a lactone structure, a thiolactone structure, and a cyclic amide structure. (4) The rubber composition according to any one of (1) to (3) above, wherein the compound is derived from a natural product. [Effects of the Invention]

[0008] As will be described below, the present invention can provide a rubber composition that is excellent in stain resistance and exhibits antiaging properties equal to or better than those of rubber compositions containing conventional amine-based antiaging agents. DETAILED DESCRIPTION OF THE INVENTION

[0009] The rubber composition of the present invention will be described below. In this specification, a numerical range expressed using "to" means a range that includes the numerical values ​​before and after "to" as the lower and upper limits. Each component may be used alone or in combination of two or more. When two or more components are used in combination, the content of the components refers to the total content unless otherwise specified. In addition, the term "excellent anti-aging properties" refers to rubber compositions that exhibit anti-aging properties equal to or greater than those of rubber compositions containing conventional amine-based anti-aging agents. Furthermore, excellent stain resistance, anti-aging properties, and compound dispersibility are also referred to as "excellent effects of the present invention."

[0010] The rubber composition of the present invention (hereinafter also referred to as "the composition of the present invention") is The rubber composition contains 100 parts by mass of a diene rubber and 0.1 to 10 parts by mass of a compound represented by formula (1) described below (hereinafter also referred to as a "specific compound").

[0011] It is believed that the composition of the present invention, which has such a constitution, solves the above-mentioned problems. The reason for this is not clear, but is thought to be as follows.

[0012] It is known that diene rubbers deteriorate due to the abstraction of hydrogen atoms to form radicals. As mentioned above, a technique for suppressing deterioration is known in which the compounding of an amine-based antioxidant such as N-phenyl-1-naphthylamine is used. In this regard, the inventors' studies have shown that amine-based antioxidants abstract hydrogen atoms more easily than diene rubbers. More specifically, the minimum bond energy of the XH bond (where X is an atom other than a hydrogen atom) in a diene rubber (rubber model) calculated by quantum chemical calculation is 71.1 kcal / mol, whereas the minimum bond energy of an amine-based antioxidant calculated similarly is approximately 70 kcal / mol, which is smaller than that of a diene rubber. Therefore, it is believed that the amine-based antioxidant forms radicals in place of the diene rubber, thereby suppressing the deterioration of the diene rubber. The present invention is based on such findings. Specifically, since the specific compound abstracts hydrogen atoms more easily than diene rubbers, it is believed that it suppresses the deterioration of diene rubbers in the same way as amine-based antioxidants. Specifically, it is believed that the bond energy of the C-H bond (hereinafter also referred to as the "specific bond") next to R1 in formula (1) described below is small, and the hydrogen atom of this C-H bond is easily abstracted. Furthermore, since R2 in formula (1) is a group other than a hydrogen atom and R3 is a group other than a hydroxy group, it is believed that compatibility with diene rubbers is high and the above-mentioned antiaging effect is fully exhibited. Furthermore, unlike amine-based antiaging agents such as N-phenyl-1-naphthylamine, the specific compound does not have a structure in which the amino group is sandwiched between aromatic rings, and therefore is less likely to form a resonance structure (which can lead to discoloration) even if a hydrogen atom is abstracted. As a result, it is believed that the composition of the present invention containing the specific compound exhibits excellent stain resistance and anti-aging properties.

[0013] Each component contained in the composition of the present invention will be described below.

[0014] [Diene rubber] The diene rubber contained in the composition of the present invention is not particularly limited. The diene rubber may be modified with an alkoxy group, an alkoxysilyl group, or the like. The composition of the present invention may contain one diene rubber or two or more diene rubbers.

[0015] [Specific example] Specific examples of the diene rubber include natural rubber (NR), butadiene rubber (BR), aromatic vinyl-conjugated diene copolymer rubber, isoprene rubber (IR), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), chloroprene rubber (CR), etc. Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene rubber (SBR), styrene-isoprene copolymer rubber, butyl rubber, etc.

[0016] [Molecular weight] The weight average molecular weight (Mw) of the diene rubber is not particularly limited, but in order to obtain better effects of the present invention, it is preferably 100,000 to 5,000,000, more preferably 200,000 to 3,000,000, and even more preferably 300,000 to 2,000,000.

[0017] In this specification, the weight average molecular weight (Mw) and number average molecular weight (Mn) are values ​​calculated as standard polystyrene obtained by gel permeation chromatography (GPC) measurement.

[0018] [Specific compound] The composition of the present invention contains a compound represented by the following formula (1).

[0019] Formula (1) [ka]

[0020] In formula (1), R1 represents a hydrogen atom or a substituent (for example, a specific example described later), R2 represents a substituent (for example, a specific example described later), and R3 represents a hydrogen atom or a substituent other than a hydroxy group (for example, a substituent other than a hydroxy group among the specific examples described later). R1 ​​to R3 may be bonded to each other to form a ring.

[0021] The above R1 is preferably a substituent, and more preferably a hydrocarbon group which may contain a heteroatom, for reasons such as better effects of the present invention. Examples of the hydrocarbon group include aliphatic hydrocarbon groups, aromatic hydrocarbon groups (aryl groups), and combinations thereof. The aliphatic hydrocarbon group may be linear, branched, or cyclic. Specific examples of the aliphatic hydrocarbon group include linear or branched alkyl groups (particularly having 1 to 30 carbon atoms), linear or branched alkenyl groups (particularly having 2 to 30 carbon atoms), and linear or branched alkynyl groups (particularly having 2 to 30 carbon atoms). Examples of the aromatic hydrocarbon group include aromatic hydrocarbon groups having 6 to 18 carbon atoms, such as phenyl, tolyl, xylyl, and naphthyl. R1 is preferably an alkyl group for reasons of better effects of the present invention, etc. The number of carbon atoms in the alkyl group is preferably 1 to 10, and more preferably 1 to 5, for reasons of better effects of the present invention, etc. The carbon atoms in the alkyl group may be substituted with -O-, -C(=O)-, -C(=O)-O-, -OC(=O)-O-, -S-, -S(=O)-, -SO2-, -NR- (R: hydrogen atom or substituent (for example, specific examples will be described later)), or a group formed by combining these groups.

[0022] Specific examples and preferred embodiments of R2 and R3 are the same as those of R1.

[0023] For reasons such as better effects of the present invention, it is preferable that any two of R1 to R3 are bonded to each other to form a ring, more preferable that R1 and R2 or R1 and R3 are bonded to each other to form a ring, and even more preferable that R1 and R2 are bonded to each other to form a ring.

[0024] [Preferred embodiment 1] For reasons such as better effects of the present invention, the specific compound preferably has at least one structure selected from the group consisting of a lactone structure (lactone ring), a thiolactone structure (thiolactone ring), and a cyclic amide structure (amide ring), more preferably has at least one structure selected from the group consisting of a thiolactone structure and a cyclic amide structure, and even more preferably has a cyclic amide structure.

[0025] [Preferred embodiment 2] For reasons such as better effects of the present invention, the specific compound is preferably a compound represented by any one of the following formulas (1-1) to (1-3), more preferably a compound represented by any one of the following formulas (1-1) to (1-2), and even more preferably a compound represented by the following formula (1-1). Note that the compound represented by formula (1-1) is an embodiment in which R1 and R2 in the above formula (1) are bonded to each other to form a ring, the compound represented by formula (1-2) is an embodiment in which R1 and R3 in the above formula (1) are bonded to each other to form a ring, and the compound represented by formula (1-3) is an embodiment in which R2 and R3 in the above formula (1) are bonded to each other to form a ring.

[0026] [ka]

[0027] The above L1 to L3 each independently represent a divalent linking group. Examples of the divalent linking group include divalent aliphatic hydrocarbon groups (particularly alkylene groups), divalent aromatic hydrocarbon groups (particularly arylene groups), -O-, -C(=O)-, -C(=O)-O-, -OC(=O)-O-, -S-, -S(=O)-, -SO2-, -NR- (R: hydrogen atom or substituent (for example, specific examples will be described later)), and groups combining these.

[0028] The definitions, specific examples and preferred embodiments of R1 to R3 are the same as those of R1 to R3 in the above formula (1).

[0029] [Preferred embodiment 3] The specific compound is preferably an amino acid derivative, since this will provide better effects of the present invention.

[0030] Preferred Embodiment 4 The specific compound is preferably derived from a natural product, because the effects of the present invention are more excellent. Whether or not the specific compound is derived from a natural product can be determined, for example, by 14 This can be determined by C dating. of a specific compound 14 The decay rate of C per gram per minute is preferably 0.1 dpm / gC or more, because the effects of the present invention are more excellent. 14 The C decay rate per gram per minute is measured by accelerator mass spectrometry (AMS) and liquid scintillation counting method (LSC).

[0031] [Minimum binding energy] The minimum bond energy of an XH bond (X represents an atom other than a hydrogen atom) in a specific compound (hereinafter also referred to as "minimum bond energy") is preferably 71 kcal / mol or less, more preferably 70 kcal / mol or less, and even more preferably 69 kcal / mol or less, for reasons such as better effects of the present invention. There is no particular lower limit for the minimum bond energy, but for reasons such as better effects of the present invention, it is preferably 50 kcal / mol or more, and more preferably 60 kcal / mol or more.

[0032] The above-mentioned binding energy is calculated from the following formula by the density functional B3LYP method using 6-31+G(d, p) as the basis function. (Bond energy) = (energy of a specific compound) - (energy of a hydrogen atom (radical hydrogen)) - (energy of the radical obtained by abstracting a hydrogen atom from a specific compound) That is, the energies of the specific compound, the hydrogen atom (radical hydrogen), and the radical obtained by abstracting any hydrogen atom from the specific compound are calculated by the quantum chemical calculation described above, and the bond energy is calculated from the above formula.

[0033] The bond energies of the XH bonds contained in a specific compound are calculated as described above, and the smallest bond energy is taken as the minimum bond energy. Usually, the bond energy of the C—H bond (specific bond) next to R1 in formula (1) is the smallest.

[0034] [Melting point] The melting point of the specific compound is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower, for reasons such as better effects of the present invention. There is no particular lower limit to the melting point, but for reasons such as better effects of the present invention, it is preferably 20°C or higher. The melting point is measured at 1 atmosphere.

[0035] [Content] In the composition of the present invention, the content of the specific compound is 0.1 to 10 parts by mass relative to 100 parts by mass of the diene rubber. The content is preferably 0.5 to 5 parts by mass, more preferably 1 to 3 parts by mass, for reasons such as better effects of the present invention.

[0036] [Specific examples of substituents] Specific examples of the substituent in this specification include a halogeno group (halogen atom), an alkyl group (for example, a tert-butyl group) (including a cycloalkyl group, a bicycloalkyl group, and a tricycloalkyl group), an alkenyl group (including a cycloalkenyl group and a bicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclic group (which may also be called a heterocyclic group), a cyano group, a hydroxy group, a nitro group, a carboxy group, a formyl group, an alkoxy group, an aryloxy group, a silyloxy group, a heterocyclic oxy group, an acyloxy group, a carbamoyl group, a carbamoyloxy group, an alkoxycarbonyloxy group, an aryloxycarbonyloxy group, an amino group (including an anilino group), an ammonio group, a dialkylamino group, an acylamino group, and an aminocarbonylamino group. Examples of substituents include an alkoxycarbonylamino group, an aryloxycarbonylamino group, a sulfamoylamino group, an alkyl or arylsulfonylamino group, a mercapto group, an alkylthio group, an arylthio group, a heterocyclic thio group, a sulfamoyl group, a sulfo group, an alkyl or arylsulfinyl group, an alkyl or arylsulfonyl group, an acyl group, an aryloxycarbonyl group, an alkoxycarbonyl group, an aryl or heterocyclic azo group, an imido group, a phosphino group, a phosphinyl group, a phosphinyloxy group, a phosphinylamino group, a phosphono group, a silyl group, a hydrazino group, a ureido group, a boronic acid group (-B(OH)), a phosphato group (-OPO(OH)), a sulfato group (-OSOH), and other known substituents.

[0037] [Optional ingredients] The composition of the present invention may further contain other components (optional components) as needed, provided that the effects and purposes of the composition are not impaired. Examples of the optional components include various additives commonly used in rubber compositions, such as fillers (e.g., silica, carbon black), silane coupling agents, terpene resins (e.g., aromatic modified terpene resins), thermally expandable microcapsules, zinc oxide (zinc white), stearic acid, antioxidants, waxes, processing aids, oils, liquid polymers, thermosetting resins, vulcanizing agents (e.g., sulfur), and vulcanization accelerators.

[0038] [Carbon black] The composition of the present invention preferably contains carbon black, as this will provide better effects of the present invention. The carbon black is not particularly limited, and various grades such as SAF-HS, SAF, ISAF-HS, ISAF, ISAF-LS, IISAF-HS, HAF-HS, HAF, HAF-LS, and FEF can be used. The nitrogen adsorption specific surface area (N2SA) of the carbon black is not particularly limited, but is preferably 50 to 200 m for reasons such as the superior effects of the present invention. 2 / g, and 70 to 150m 2 / g is more preferred. Here, the nitrogen adsorption specific surface area (N2SA) is the amount of nitrogen adsorbed onto the surface of carbon black measured according to JIS K6217-2:2001 "Part 2: Determination of specific surface area - Nitrogen adsorption method - Single point method."

[0039] <Content> When the composition of the present invention contains carbon black, the content thereof is not particularly limited, but in order to obtain better effects of the present invention, the content thereof is preferably 2 to 100 parts by mass, and more preferably 20 to 50 parts by mass, per 100 parts by mass of the diene rubber described above.

[0040] 〔silica〕 The composition of the present invention preferably contains silica, as this provides better effects of the present invention. The silica is not particularly limited, and any conventionally known silica can be used. Examples of the silica include wet silica, dry silica, fumed silica, and diatomaceous earth. Biomass-derived silica such as rice husks may also be used. The silica may be used alone or in combination of two or more types.

[0041] The cetyltrimethylammonium bromide (CTAB) adsorption specific surface area of ​​the silica (hereinafter, "CTAB adsorption specific surface area" may be simply referred to as "CTAB") is not particularly limited, but for the reasons of the superior effects of the present invention, it is preferred that the specific surface area be 100 to 300 m 2 / g, and 150 to 200m 2 / g is more preferred. Here, the CTAB adsorption specific surface area is a value measured in accordance with JIS K6430:2008, Appendix G.

[0042] <Content> When the composition of the present invention contains silica, the content thereof is not particularly limited, but in order to obtain better effects of the present invention, the content thereof is preferably 10 to 150 parts by mass, and more preferably 50 to 100 parts by mass, per 100 parts by mass of the diene rubber.

[0043] [Manufacturing method] The method for producing the composition of the present invention is not particularly limited, and specific examples thereof include a method of kneading the above-mentioned components using a known method or apparatus (e.g., a Banbury mixer, a kneader, a roll, etc.). When the composition of the present invention contains a vulcanizing agent (e.g., sulfur) and a vulcanization accelerator, it is preferable to first mix the components other than the vulcanizing agent and vulcanization accelerator at a high temperature (preferably 100 to 155°C), cool the mixture, and then mix the vulcanizing agent and vulcanization accelerator, because this will result in a more excellent effect of the present invention in the resulting composition. The composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[0044] [Application] The composition of the present invention is suitable for use as a rubber material. For example, it is suitable for use in tires (particularly pneumatic tires), conveyor belts, hoses, vibration-proof materials, rubber rolls, outer covers for railway vehicles, etc. Among these, it is particularly suitable for use in tires (particularly tire treads). [Example]

[0045] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0046] [Production of rubber composition] The components in Table 1 below were mixed in the composition (parts by mass) shown in the same table. Specifically, first, the components in Table 1 other than sulfur and the vulcanization accelerator were mixed in a 1.8 L internal mixer at 130°C for 5 minutes, and a masterbatch was discharged. Then, sulfur and the vulcanization accelerator were added to the masterbatch, and the mixture was mixed using an open roll at 80°C to produce each rubber composition.

[0047] [evaluation] The obtained rubber composition was press-vulcanized at 150° C. for 30 minutes to prepare a vulcanized rubber sheet, which was then evaluated as follows.

[0048] [Stain resistance] The appearance of the obtained vulcanized rubber sheet (6 x 6 inches, 2 mm thick) was visually observed after one month of outdoor exposure, and the stain resistance was evaluated according to the following criteria: ◯ indicates excellent stain resistance. ○: No discoloration was observed. ×: Discoloration was observed.

[0049] [How compounds mix] The obtained vulcanized rubber sheet was cut and the cross section was observed under an optical microscope, and the mixing state of the compounds (compound dispersibility) was evaluated according to the following criteria. ◎: No foreign matter was observed. ○: Almost no foreign matter was observed. ·△: A small amount of foreign matter was observed. ·×: Foreign matter was clearly observed.

[0050] [Breaking elongation and breaking elongation retention rate] From the obtained vulcanized rubber sheet, JIS No. 3 dumbbell-shaped test pieces (thickness: 2 mm) were punched out in accordance with JIS K6251:2010, and the elongation at break was evaluated at a temperature of 20°C and a tensile speed of 500 mm / min. The results are shown in Table 1 (elongation at break (before aging)). The results are expressed as an index, with the reference example being 100. The vulcanized rubber sheets thus obtained were subjected to an aging test (left to stand in an environment of 80°C for 192 hours) and similarly evaluated for elongation at break. The elongation at break retention rate was then calculated as follows. The results are shown in Table 1 (elongation at break retention rate). The results are expressed as an index, with the reference example being 100. Breaking elongation retention rate (%) = Breaking elongation after aging test / Breaking elongation before aging test × 100 A higher breaking elongation retention rate means better anti-aging properties. If the breaking elongation rate is 86% or higher, it can be said that the rubber composition exhibits anti-aging properties equal to or better than those of a rubber composition containing a conventional amine-based anti-aging agent.

[0051] [Table 1]

[0052] [Naphthylamine and Compounds 1 to 6] Among the components in Table 1, naphthylamine and compounds 1 to 6 are as follows. Note that naphthylamine, compounds 1 to 2, and compound 6 do not fall under the above-mentioned specific compounds, while compounds 3 to 5 fall under the above-mentioned specific compounds. Furthermore, compounds 3 to 5 are derivatives of natural products (amino acids), 14 The decay rate of C per gram per minute is 0.1 dpm / gC or more.

[0053] Naphthylamine: the following compound (melting point: 62°C) [ka]

[0054] Of the XH bonds in naphthylamine, the one with the lowest bond energy is the NH bond, with a bond energy of 69.6 kcal / mol.

[0055] Compound 1: Serine (compound shown below, melting point: 222°C (decomposition)) [ka]

[0056] When compound 1 is applied to formula (1), R2 becomes a hydrogen atom and R3 becomes a hydroxy group, and therefore, compound 1 does not fall under the above-mentioned specific compound. Among the XH bonds in compound 1, the specific bond has the smallest bond energy, which is 74.9 kcal / mol.

[0057] Compound 2: Proline (compound shown below, melting point: 209-228°C (decomposition)) [ka]

[0058] When compound 2 is applied to formula (1), R3 becomes a hydroxy group, and therefore does not fall under the category of the above-mentioned specific compounds. Among the XH bonds in compound 2, the specific bond has the smallest bond energy, which is 73.4 kcal / mol.

[0059] Compound 3: the following compound (wherein Boc represents a t-butoxycarbonyl group) (melting point: 30°C) [ka]

[0060] Compound 3 is a compound (specific compound) represented by formula (1), where R1 is a methyl group, R2 is a t-butoxycarbonyl group, and R3 is a methoxy group. Among the XH bonds in compound 3, the specific bond has the smallest bond energy, which is 70.7 kcal / mol.

[0061] Compound 4: the following compound (melting point: 55°C) [ka]

[0062] Compound 4 is a compound (specific compound) represented by formula (1). In formula (1), R1 and R2 are bonded to each other to form a ring (cyclic amide structure). R3 is an ethoxy group. Compound 4 corresponds to the compound represented by formula (1-1), where L1 is *1-C(=O)-C2H4-*2 (where *1 is the bonding position to the nitrogen atom, and *2 is the bonding position to the carbon atom), and R3 is an ethoxy group. Among the XH bonds in compound 4, the specific bond has the smallest bond energy, which is 67.9 kcal / mol.

[0063] Compound 5: the following compound (melting point: 110°C) [ka]

[0064] Compound 5 is a compound (specific compound) represented by formula (1). In formula (1), R1 and R3 are bonded to each other to form a ring (thiolactone structure). R3 is an ethoxy group. Compound 5 corresponds to the compound represented by formula (1-2), where L2 is *1-C2H4-S-*2 (where *1 is the bonding position to the carbon atom bonded to the nitrogen atom, and *2 is the bonding position to the carbon atom of the carbonyl group), and R2 is a methoxy group. Among the XH bonds in compound 5, the specific bond has the smallest bond energy, which is 69.3 kcal / mol.

[0065] Compound 6: The following compound (melting point: 110°C) [ka]

[0066] When compound 6 is applied to formula (1), R3 becomes a hydroxy group, and therefore does not fall under the category of the above-mentioned specific compounds. Among the XH bonds in compound 6, the specific bond has the smallest bond energy, which is 73.4 kcal / mol.

[0067] [Other ingredients] Other components in Table 1 are as follows. Natural rubber: Natural rubber Carbon black: Show Black N234 (manufactured by Showa Cabot Corporation) Zinc oxide: Three types of zinc oxide (manufactured by Seido Chemical Industry Co., Ltd.) Stearic acid: Beads Stearic Acid YR (manufactured by NOF Corporation) Oil: Process oil Sulfur: Oil-treated sulfur (Karuizawa Refinery Co., Ltd.) Vulcanization accelerator TBBS: Sancerer NS-G (manufactured by Sanshin Chemical Industry Co., Ltd.)

[0068] [Summary of Table 1] As can be seen from Table 1, Examples 1 to 3, which contained the specific compound, exhibited excellent stain resistance and anti-aging properties. Among them, Examples 2 and 3, in which the specific compound had at least one structure selected from the group consisting of a lactone structure, a thiolactone structure, and a cyclic amide structure, exhibited even better anti-aging properties. Among them, Example 2, in which the melting point of the specific compound was 100°C or lower, exhibited even better anti-aging properties.

[0069] On the other hand, Comparative Examples 2 to 4, which used compounds (amino acids) other than the specific compounds, showed insufficient antiaging properties. Also, Comparative Example 1, which used Compound 1, a conventional amine-based antiaging agent, showed insufficient stain resistance.

Claims

1. A rubber composition comprising 100 parts by mass of a diene rubber and 0.1 to 10 parts by mass of a compound represented by the following formula (1): 【Chemistry 1】 （１） In formula (1), R １ represents a hydrogen atom or a substituent, R ２ represents a substituent, R ３ represents a hydrogen atom or a substituent other than a hydroxy group. １ ~R ３ may be bonded to each other to form a ring.

2. 2. The rubber composition according to claim 1, wherein the minimum bond energy of an X-H bond in the compound is 71 kcal / mol or less, wherein X represents an atom other than a hydrogen atom, and the bond energy is calculated from the following formula using a density functional B3LYP / 6-31+G(d,p): (Bond energy) = (energy of the compound) - (energy of hydrogen atom) - (energy of radical obtained by abstracting hydrogen atom from the compound)

3. The rubber composition according to claim 1 or 2, wherein the compound has at least one structure selected from the group consisting of a lactone structure, a thiolactone structure, and a cyclic amide structure.

4. The rubber composition according to claim 1 or 2, wherein the compound is derived from a natural product.

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