JP2006291004A - Rubber composition and tire using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To develop an agent which improves a heat generation property of a rubber, applicable to a wide range of rubbers including natural rubbers and synthetic rubbers such as emulsification polymerized styrene-butadiene copolymer rubbers, and to provide a rubber composition with an improved heat generation property by mixing with the agent. <P>SOLUTION: The rubber composition contains an oxadiazole compound which is developed as an agent for improving heat generation of rubbers. The rubber composition with the above agent included in the rubber composition is excellent in low heat generation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber composition having improved heat generation and a tire using the same, and more particularly to a rubber composition containing a heat generation improving agent.

  In response to social demands for resource and energy savings, the development of fuel-efficient tires has been actively carried out in the rubber industry, particularly the tire industry, for the past several years. For the development of such a low fuel consumption tire, a rubber composition having a small hysteresis loss, that is, excellent in low heat generation property is indispensable.

  Patent Document 1 discloses a method for reducing the hysteresis loss of rubber using styrene-butadiene rubber (SBR) whose molecular terminal is modified with a special compound, particularly for the purpose of passenger car tires. Such a method for modifying the rubber itself to improve the heat buildup can be applied to solution polymerization SBR, but other rubbers, that is, natural rubber, and generally have higher temperature fracture characteristics than solution polymerization SBR. It cannot be applied to synthetic rubbers such as emulsion polymerization SBR, and a method other than the above-described method for modifying the rubber itself is desired as a method for improving the heat generation properties of a wide variety of rubbers including natural rubber and synthetic rubber. It was.

Japanese Patent Application Laid-Open No. 60-23409

  Accordingly, an object of the present invention is to develop a rubber exothermic improver that can be applied to a wide range of rubbers including natural rubber and synthetic rubber such as emulsion-polymerized SBR rubber, and by adding the rubber exothermic improver, exothermicity Is to provide an improved rubber composition.

  As a result of intensive studies to achieve the above object, the present inventors have developed an oxadiazole compound as a rubber exothermic improver, and by blending the oxadiazole compound into the rubber composition, The inventors have found that a rubber composition excellent in low heat build-up can be obtained by improving heat build-up, and completed the present invention.

（式中、Ｒ_１は芳香族基であり、Ｘはヒドロキシル基、アミノ基、メルカプト基であり、Ｒ_２は水素、モノ置換アミノ基もしくはジ置換アミノ基、又はアシル基であり、但し、ジ置換アミノ基は環状構造を形成していてもよい）、及び下記式（II）：

（式中、Ｒ_１は芳香族基であり、Ｘはヒドロキシル基、アミノ基又はメルカプト基であり、Ｚは−Ｓ_ｎ−で表されるポリスルフィド基（n＝１〜５）である）
で表わされるオキサジアゾール化合物からなる群より選ばれた少なくとも1種０．０１〜１０質量部を配合することを特徴とする。 That is, the rubber composition of the present invention has a reinforcing filler of 20 to 150 parts by mass and the following formula (I):

(Wherein R ₁ is an aromatic group, X is a hydroxyl group, an amino group, or a mercapto group, and R ₂ is hydrogen, a mono-substituted amino group, a di-substituted amino group, or an acyl group, provided that The substituted amino group may form a cyclic structure), and the following formula (II):

(In the formula, R ₁ is an aromatic group, X is a hydroxyl group, an amino group or a mercapto group, and Z is a polysulfide group (n = 1 to 5) represented by —S _n —)
At least one selected from the group consisting of oxadiazole compounds represented by the formula: 0.01 to 10 parts by mass.

で表されるオキサジアゾール化合物である。 In a preferred example of the rubber composition of the present invention, the oxadiazole compound of the formula (I) is represented by the following formula (III):

The oxadiazole compound represented by these.

で表されるオキサジアゾール化合物である。 In another preferred embodiment of the rubber composition of the present invention, the oxadiazole compound of the formula (I) is represented by the following formula (IV):

The oxadiazole compound represented by these.

（式中、Ｒ_３およびＲ_４は水素、第１級、第２級および第３級のアルキル基、シクロアルキル基又はフェニル基であり、Ｒ_３とＲ_４がアルキル基で環状構造を形成しても良い。）
で表されるオキサジアゾール化合物である。 In another preferred embodiment of the rubber composition of the present invention, the oxadiazole compound of the formula (I) is represented by the following formula (V):

Wherein R ₃ and R ₄ are hydrogen, primary, secondary and tertiary alkyl groups, cycloalkyl groups or phenyl groups, and R ₃ and R ₄ form a cyclic structure with an alkyl group. May be.)
The oxadiazole compound represented by these.

（式中、Ｒ_５は、炭素原子数１〜１８の飽和もしくは不飽和脂肪族炭化水素基、又は置換もしくは非置換のフェニル基である）で表されるオキサジアゾール化合物である。 In another preferred embodiment of the rubber composition of the present invention, the oxadiazole compound of the formula (I) is represented by the following formula (VI):

(Wherein R ₅ is a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, or a substituted or unsubstituted phenyl group).

（式中、ｎは１〜５の整数である）で表されるオキサジアゾール化合物である。 In another preferred embodiment of the rubber composition of the present invention, the oxadiazole compound of the formula (II) is represented by the following formula (VII):

(Wherein n is an integer of 1 to 5).

  In another preferred embodiment of the rubber composition of the present invention, 50 parts by mass or more of styrene-butadiene copolymer rubber or polybutadiene rubber is contained in 100 parts by mass of the rubber component.

  In another preferred embodiment of the rubber composition of the present invention, the reinforcing filler contains 20 parts by mass or more of carbon black.

  The tire according to the present invention is characterized in that the rubber composition is applied to a tire constituent member.

  According to the present invention, the exothermic properties of a wide range of rubbers including natural rubber and emulsion polymerized SBR are improved, and the exothermic low exothermicity in which the oxadiazole compound capable of reducing the hysteresis loss of the rubber is blended is excellent. The rubber composition and a fuel-efficient tire to which the rubber composition is applied can be provided.

（式中、Ｒ_１は芳香族基であり、Ｘはヒドロキシル基、アミノ基、メルカプト基であり、Ｒ_２は水素、モノ置換アミノ基もしくはジ置換アミノ基、又はアシル基であり、但し、ジ置換アミノ基は環状構造を形成していてもよい）、及び下記式（II）：

（式中、Ｒ_１は芳香族基であり、Ｘはヒドロキシル基、アミノ基又はメルカプト基であり、Ｚは−Ｓ_ｎ−で表されるポリスルフィド基（n＝１〜５）である）
で表わされるオキサジアゾール化合物からなる群より選ばれた少なくとも1種０．０１〜１０質量部を配合することを特徴とする。本発明のゴム組成物は、上記式（I）及び（II）で表されるオキサジアゾール化合物が配合されているため、低発熱性に優れている。 The present invention is described in detail below. The rubber composition of the present invention has a reinforcing filler of 20 to 150 parts by mass and the following formula (I) with respect to 100 parts by mass of a rubber component composed of at least one of natural rubber and synthetic rubber.

(Wherein R ₁ is an aromatic group, X is a hydroxyl group, an amino group, or a mercapto group, and R ₂ is hydrogen, a mono-substituted amino group, a di-substituted amino group, or an acyl group, provided that The substituted amino group may form a cyclic structure), and the following formula (II):

(In the formula, R ₁ is an aromatic group, X is a hydroxyl group, an amino group or a mercapto group, and Z is a polysulfide group (n = 1 to 5) represented by —S _n —)
At least one selected from the group consisting of oxadiazole compounds represented by the formula: 0.01 to 10 parts by mass. The rubber composition of the present invention is excellent in low heat build-up because it contains the oxadiazole compounds represented by the above formulas (I) and (II).

  Examples of the rubber component constituting the rubber composition of the present invention include natural rubber and various synthetic rubbers. Specific examples of the synthetic rubber include synthetic rubbers such as styrene-butadiene copolymer rubber (SBR), polybutadiene rubber, isoprene rubber, acrylonitrile-butadiene rubber, chloroprene rubber, ethylene propylene rubber, butyl rubber, and halogenated butyl rubber. . As the rubber component used in the rubber composition of the present invention, 50 parts of styrene-butadiene copolymer rubber (SBR) or polybutadiene rubber is used out of 100 parts by mass of the rubber component because the oxadiazole compound acts more effectively. A rubber component containing at least part by mass, preferably at least 70 parts by mass is desirable. In particular, among the styrene-butadiene copolymer rubber (SBR), an emulsion-polymerized styrene-butadiene copolymer rubber (SBR) excellent in high temperature fracture characteristics is preferable.

  Examples of the reinforcing filler used in the rubber composition of the present invention include carbon black and silica. Among these, carbon black is preferable.

  The type of carbon black is not particularly limited, and any carbon black can be selected and used from those conventionally used as reinforcing fillers for rubber. Examples of the carbon black include FEF, SRF, HAF, ISAF, and SAF.

The compounding amount of the reinforcing filler in the rubber composition of the present invention is 20 to 150 parts by mass with respect to 100 parts by mass of the rubber component. When the compounding amount of the reinforcing filler is less than 20 parts by mass, the reinforcing property of the rubber composition is inferior, and when it exceeds 150 parts by mass, not only the exothermic property is remarkably deteriorated but also physical properties such as wear resistance and workability are obtained. Remarkably worse. Here, the blending amount of the reinforcing filler is preferably 30 to 120 parts by mass from the viewpoint of achieving both reinforcing properties and various properties of rubber.

（式中、Ｒ_１は芳香族基であり、Ｘはヒドロキシル基、アミノ基、メルカプト基であり、Ｒ_２は水素、モノ置換アミノ基もしくはジ置換アミノ基、又はアシル基であり、但し、ジ置換アミノ基は環状構造を形成していてもよい）、及び下記式（II）：

（式中、Ｒ_１は芳香族基であり、Ｘはヒドロキシル基、アミノ基又はメルカプト基であり、Ｚは−Ｓ_ｎ−で表されるポリスルフィド基（n＝1〜5）である）
で表わされるオキサジアゾール化合物からなる群より選ばれた少なくとも１種である。 The oxadiazole compound used as the exothermic improver in the rubber composition of the present invention is represented by the following formula (I):

(Wherein R ₁ is an aromatic group, X is a hydroxyl group, an amino group, or a mercapto group, and R ₂ is hydrogen, a mono-substituted amino group, a di-substituted amino group, or an acyl group, provided that The substituted amino group may form a cyclic structure), and the following formula (II):

(In the formula, R ₁ is an aromatic group, X is a hydroxyl group, an amino group or a mercapto group, and Z is a polysulfide group (n = 1 to 5) represented by —S _n —)
And at least one selected from the group consisting of oxadiazole compounds represented by:

In the above formulas (I) and (II), R ₁ is an aromatic group, and specific examples of the aromatic group include aromatic hydrocarbon rings such as phenyl group and naphthyl group, pyridino group, pyrrolyl group, furyl And aromatic heterocycles such as a group, thienyl group, and triazolyl group. Among these, a phenyl group and a naphthyl group are preferable.

  X is at least one selected from a hydroxyl group, an amino group, and a mercapto group, and is preferably a hydroxyl group.

In the above formula (I), R ₂ is hydrogen, a mono-substituted amino group or a di-substituted amino group, or an acyl group. Examples of the substituent of the mono-substituted amino group and the di-substituted amino group include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, and n-pentyl. Primary, secondary and tertiary alkyl groups having 1 to 10 carbon atoms such as a group, n-hexyl group, n-heptyl group, n-octyl group and n-decyl group, cyclopropyl group, cyclobutyl Groups, cyclopentyl groups, cyclohexyl groups, cycloheptyl groups and the like, cycloalkyl groups having 3 to 7 carbon atoms, substituted or unsubstituted phenyl groups such as phenyl groups and tolyl groups, benzyl groups, and phenethyl groups. In the disubstituted amino group, two substituents may be bonded to each other to form, for example, a pyrrolidino group, a piperidino group, a morpholino group, or the like. Among these substituted amino groups having a substituent, a tert-butylamino group and a cyclohexylamino group are particularly preferable.

  As the acyl group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a pentanoyl group, a pivaloyl group, a dodecanoyl group, a tetradecanoyl group, an octadecanoyl group, etc., an aliphatic acyl group having 2 to 19 carbon atoms, Aromatic acyl groups such as benzoyl group and toluoyl group are exemplified. Among these, an acetyl group is particularly preferable.

で表されるオキサジアゾール化合物、及び下記式（IV）：

で表されるオキサジアゾール化合物、及び下記式（V）：

（式中、Ｒ_３およびＲ_４は水素、第１級、第２級および第３級のアルキル基、シクロアルキル基又は置換もしくは非置換のフェニル基であり、Ｒ_３とＲ_４がアルキル基で環状構造を形成しても良い。）
で表されるオキサジアゾール化合物、及び下記式（VI）：

（式中、Ｒ_５は、炭素原子数１〜１８の飽和もしくは不飽和脂肪族炭化水素基、又は置換もしくは非置換のフェニル基である）
で表されるオキサジアゾール化合物を挙げることができる。なお、上記式（V）で表されるオキサジアゾール化合物としては、上記式（V）中のＲ_３とＲ_４のいずれか一方が水素であり、他方がｔｅｒｔ−ブチル基又はシクロヘキシル基であるオキサジアゾール化合物が好ましく、上記式（VI）で表されるオキサジアゾール化合物としては、上記式（V）中のＲ_５がメチル基であるオキサジアゾール化合物が好ましい。 Specific examples of the oxadiazole compound represented by the above formula (I) include the following formula (III):

And an oxadiazole compound represented by the following formula (IV):

And an oxadiazole compound represented by the following formula (V):

Wherein R ₃ and R ₄ are hydrogen, primary, secondary and tertiary alkyl groups, cycloalkyl groups or substituted or unsubstituted phenyl groups, and R ₃ and R ₄ are alkyl groups (A ring structure may be formed.)
And an oxadiazole compound represented by the following formula (VI):

(In the formula, R ₅ is a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, or a substituted or unsubstituted phenyl group)
The oxadiazole compound represented by these can be mentioned. In addition, as an oxadiazole compound represented by the above formula (V), either one of R ₃ and R _{4 in} the above formula (V) is hydrogen, and the other is a tert-butyl group or a cyclohexyl group. An oxadiazole compound is preferable, and the oxadiazole compound represented by the above formula (VI) is preferably an oxadiazole compound in which R ₅ in the above formula (V) is a methyl group.

（式中、ｎは１〜５の整数である）
で表されるオキサジアゾール化合物が挙げられ、上記式（VII）中のｎが２又は３の整数であるオキサジアゾール化合物が好ましい。また、上記式（VII）中のｎが１〜５の整数である化合物が複数存在する混合物でも良い。 In the above formula (II), Z is a polysulfide group represented by the general formula: —S _n — (n is an integer of 1 to 5). In the general formula, n is preferably an integer of 2 or 3. Specific examples of such oxadiazole compounds represented by the above formula (II) include the following formula (VII):

(Where n is an integer from 1 to 5)
An oxadiazole compound represented by the formula (VII), wherein n is an integer of 2 or 3, is preferred. In addition, a mixture in which a plurality of compounds in which n in the formula (VII) is an integer of 1 to 5 exists may be used.

  The oxadiazole compound represented by the above formula (III), (IV), (V), (VI) or (VII) is particularly effective as an exothermic improver for rubber.

  The compounding quantity of the said oxadiazole compound mix | blended with the rubber composition of this invention is 0.01-10 mass parts with respect to 100 mass parts of said rubber components. Here, when the blending amount of the oxadiazole compound is less than 0.01 parts by mass, the exothermic improvement effect cannot be obtained, and when it exceeds 10 parts by mass, the physical properties such as strength at break of the rubber composition are reduced, and There is a risk of deterioration of workability due to an increase in viscosity.

  Further, the rubber composition of the present invention includes various chemicals usually used in the rubber industry, for example, vulcanizing agents, vulcanization accelerators, process oils, and anti-aging agents, as long as the object of the present invention is not impaired. An agent, an ozone degradation inhibitor, a silane coupling agent, a scorch inhibitor, zinc white, stearic acid, and the like can be blended.

  Furthermore, this invention is the tire which applied the rubber composition mentioned above to the tire structural member. As described above, since the rubber composition of the present invention is excellent in low heat build-up, it is particularly preferable to use the rubber composition for a tread.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples.

  The synthesis of various oxadiazole compounds as exothermic improvers used in this example will be described. Compounds A to F were synthesized according to Synthesis Examples 1 to 6 below.

(Synthesis Example 1)
Compound A: Synthesis of 2- (2-hydroxyphenyl) -5-mercapto-1,3,4-oxadiazole A four-necked flask (3 liters) equipped with a thermometer and a stirrer condenser was charged with 300 g of salicylic acid hydrazide (1. 97 mol), 220.6 g (3.94 mol) of potassium hydroxide, 1200 ml of ethanol, and 600 ml of deionized water were added and cooled to 10 ° C. Under stirring, 187.0 g (2.46 mol) of carbon disulfide was gradually added dropwise over 60 minutes. After completion of dropping, the mixture was heated and stirred for 12 hours under reflux (internal temperature 82 ° C.). Ethanol was distilled off under reduced pressure, and 400 ml of deionized water and 399.5 g (3.94 mol) of 36% hydrochloric acid aqueous solution were gradually added to the residue aqueous solution. The precipitated crystals were separated by filtration, washed with 1000 ml of deionized water, and then dried under reduced pressure to obtain the desired product (white crystals). The yield of this reaction was 286.6 g (1.48 mol), and the yield was 75%.
Melting point 230 ° C
¹ H-NMR (DMSO) 6.9 to 7.8 (m, 4H), 10.4 to 10.6 (s, 1H)
IR 1620cm ^-1 (C = N)
MS spectrum (FD) M ^<+> (194)

(Synthesis Example 2)
Compound B: Synthesis of 2- (3-hydroxy-2-naphthyl) -5-mercapto-1,3,4-oxadiazole Four-necked flask equipped with a thermometer and a stirrer condenser (in 1 liter) 3-hydroxy -2-Naphthoic acid hydrazide 100 g (0.495 mol), potassium hydroxide 55.4 g (0.99 mol), ethanol 400 ml, deionized water 200 ml were added and cooled to 10 ° C. Under stirring, 47.0 g (0.619 mol) of carbon disulfide was gradually added dropwise over 60 minutes. After completion of dropping, the mixture was heated and stirred for 12 hours under reflux (internal temperature 82 ° C.). Ethanol was distilled off under reduced pressure, and 200 ml of deionized water and 100.5 g (0.99 mol) of 36% aqueous hydrochloric acid were gradually added to the aqueous residue. The precipitated crystals were separated by filtration, washed with 400 ml of deionized water, and then dried under reduced pressure to obtain the desired product (white crystals). The shrinkage of this reaction was 113.9 g (0.448 mol), and the yield was 91%.
Melting point 239 ° C
¹ H-NMR (DMSO) 7.2 to 8.6 (m, 6H), 10.5 to 10.7 (s, 1H)
IR 1650cm ^-1 (C = N)
MS spectrum (FD) M ^<+> (244)

(Synthesis Example 3)
Compound C: Synthesis of bis [2- (2-hydroxyphenyl) -1,3,4-oxadiazol-5-yl] -disulfide In a four-necked flask (2 liters) equipped with a thermometer, stirrer and condenser 2- (2-hydroxyphenyl) -5-mercapto-1,3,4-oxadiazole 200 g (1.03 mol), 48% sodium hydroxide 94.2 g (1.13 mol), deionized water 700 Milliliter was added. While stirring, 128.0 g (1.13 mol) of 30% aqueous hydrogen peroxide was added dropwise over 30 minutes. After completion of dropping, the mixture was stirred at room temperature for 12 hours. Subsequently, 36% hydrochloric acid aqueous solution was gradually added until pH = 1 while suppressing exotherm. The precipitated crystals were separated by filtration, washed with 500 ml of deionized water, and then dried under reduced pressure to obtain the desired product (substantially white crystals). The yield of this reaction was 167.6 g (0.434 mol), and the yield was 84%.
Melting point 165 ° C
¹ H-NMR (DMSO) 6.9 to 7.8 (m, 8H), 10.2 to 10.6 (m, 2H)
IR 1620cm ^-1 (C = N)
MS spectrum (FD) M ^<+> (386)

(Synthesis Example 4)
Compound D: Synthesis of 2- (2-hydroxyphenyl) -5- (1,1-dimethylethylaminothio) -1,3,4-oxadiazole A four-necked flask equipped with a thermometer, a stirrer, and a condenser ( 3 liters), 2- (2-hydroxyphenyl) -5-mercapto-1,3,4-oxadiazole 58.5 g (0.3 mol), sodium hydroxide 13.0 g (0.33 mol), 1 liter of deionized water and 219.3 g (3.00 mol) of t-butylamine were added and cooled to 10 ° C. or lower. Under stirring, a solution prepared by mixing 83.0 g (0.5 mol) of potassium iodide and 76.1 g (0.6 mol) of iodine in 1 liter of deionized water was gradually added dropwise over 60 minutes. After completion of dropping, the mixture was stirred at 10 ° C. or lower for 1 hour. The precipitated crystals were separated by filtration, washed with 2 liters of deionized water, and then dried under reduced pressure to obtain the desired product (white crystals). The yield of this reaction was 60.5 g (0.228 mol), and the yield was 76%.
Melting point 83 ° C
¹ H-NMR (DMSO) 1.1 to 1.4 (m, 9H), 5.2 to 5.4 (s, 1H), 6.9 to 7.8 (m, 4H)
IR 1620 cm ⁻¹ (C = N), 3300 cm ⁻¹ (N−H)
MS spectrum (FD) M ^<+> (265)

(Synthesis Example 5)
Compound E: Synthesis of 2- (2-hydroxyphenyl) -5-cyclohexylaminothio-1,3,4-oxadiazole In a four-necked flask (1 liter) equipped with a thermometer, stirrer and condenser, 2- (2-hydroxyphenyl) -5-mercapto-1,3,4-oxadiazole 10.7 g (0.06 mol), sodium hydroxide 4.8 g (0.12 mol), deionized water 200 ml, cyclohexyl 18.0 g (0.18 mol) of amine was added and the mixture was cooled to 10 ° C. or lower. Under stirring, a solution prepared by mixing 16.5 g (0.10 mol) of potassium iodide and 15.3 g (0.12 mol) of iodine in 200 ml of deionized water was gradually added dropwise over 60 minutes. After completion of dropping, the mixture was stirred at 10 ° C. for 6 hours. The precipitated crystals were separated by filtration, washed with 50 ml of deionized water, and then dried under reduced pressure to obtain the desired product (white crystals). The yield of this reaction was 12.1 g (0.044 mol), and the yield was 73%.
Melting point 86 ° C
¹ H-NMR (DMSO) 1.0 to 2.0 (m, 10H), 2.9 to 3.1 (m, 1H), 5.2 to 5.4 (d, 1H), 6.9 to 7.8 (m, 4H)
^{IR 1650cm -1 (C = N)} , 3300cm -1 (N-H)
MS spectrum (FD) M ^<+> (291)

(Synthesis Example 6)
Compound F: Synthesis of bis [2- (2-hydroxyphenyl) -1,3,4-oxadiazol-5-yl] -trisulfide Four-necked flask (2 liters) equipped with a thermometer, stirrer and condenser To the mixture, 16.6 g (0.13 mol) of sulfur dichloride and 300 ml of ether (dehydrated solvent) were added and cooled to -30 to -40 ° C. Under stirring, 600 ml of ether (dehydrated solvent) was charged with 25.1 g (0.13 mol) of 2- (2-hydroxyphenyl) -5-mercapto-1,3,4-oxadiazole and 10.2 g (0.13 mol) of pyridine. 13 mol) was gradually added dropwise. After completion of dropping, the mixture was stirred at -30 to -40 ° C for 30 minutes. Subsequently, 25.1 g (0.13 mol) of 2- (2-hydroxyphenyl) -5-mercapto-1,3,4-oxadiazole and 10.2 g of pyridine (0.003 mol) were added to 600 ml of ether (dehydrated solvent). 13 mol) was gradually added dropwise. After completion of dropping, the mixture was stirred at room temperature for 12 hours. The precipitated crystals were separated by filtration, washed with 200 ml of deionized water, and then dried under reduced pressure to obtain the desired product (white crystals). The yield of this reaction was 45.7 g (0.109 mol), and the yield was 85%.
As a result of MS spectrum analysis, the obtained crystals were a mixture of disulfide, trisulfide, tetrasulfide, and pentasulfide, and the approximate mixing ratio was disulfide: trisulfide: tetrasulfide: The pentasulfide compound was 30: 55: 10: 5.
Melting point 180 ° C
¹ H-NMR (DMSO) 6.8 to 7.9 (m, 8H), 10.2 to 10.6 (m, 2H)
IR 1650cm ^-1 (C = N)
MS spectrum (FD) M ^<+> (386), M ^<+> (418), M ^<+> (450), M ^<+> (482)

(Examples 1 to 9, conventional examples)
According to the compounding prescription shown in Table 1 using each of Compounds A to F obtained in Synthesis Examples 1 to 6, various rubber compositions were prepared using a Banbury mixer, and the obtained rubber compositions were treated at 145 ° C for 30 minutes. A sample was prepared by vulcanization under conditions. For comparison, a rubber composition containing no oxadiazole compound was prepared using the same formulation as described above.

  These rubber compositions were evaluated for the strength at break and low heat build-up by the following methods. The results are shown in Table 2.

(1) Evaluation method of strength at break The dumbbell-shaped test piece of JIS No. 3 was punched out from vulcanized rubber, a tensile test was performed according to JIS K6301, and the tensile strength at break was measured. The measurement results were expressed as an index when the tensile strength at break of the conventional example was taken as 100. The larger the index value, the better the strength at break.

(2) Evaluation method of low exothermic property Using a viscoelasticity measuring tester, tan δ at 60 ° C. was measured under the condition of 1% dynamic strain, and the reciprocal number of each obtained tan δ was taken. The value was expressed as a low exothermic index when the value of oxadiazole compound additive-free formulation was 100. The larger the index value, the greater the effect of reducing heat generation.

  From Table 2, in any of Examples 1 to 9, the low heat build-up was improved as compared with the conventional example. The strength at break was slightly inferior to the conventional example in Examples 2, 4 and 6, but in other examples, it was equal to or improved from the conventional example.

Claims (15)

For 100 parts by mass of a rubber component comprising at least one of natural rubber and synthetic rubber, 20 to 150 parts by mass of a reinforcing filler and the following formula (I):

(Wherein R ₁ is an aromatic group, X is a hydroxyl group, an amino group, or a mercapto group, and R ₂ is hydrogen, a mono-substituted amino group, a di-substituted amino group, or an acyl group, provided that The substituted amino group may form a cyclic structure), and the following formula (II):

(In the formula, R ₁ is an aromatic group, X is a hydroxyl group, an amino group or a mercapto group, and Z is a polysulfide group (n = 1 to 5) represented by —S _n —)
A rubber composition comprising 0.01 to 10 parts by mass of at least one selected from the group consisting of oxadiazole compounds represented by the formula: The oxadiazole compound of the formula (I) is represented by the following formula (III):

2. The rubber composition according to claim 1, which is an oxadiazole compound represented by the formula: The oxadiazole compound of the formula (I) is represented by the following formula (IV):

2. The rubber composition according to claim 1, which is an oxadiazole compound represented by the formula: The oxadiazole compound of the formula (I) is represented by the following formula (V):

Wherein R ₃ and R ₄ are hydrogen, primary, secondary and tertiary alkyl groups, cycloalkyl groups, or substituted or unsubstituted phenyl groups, and R ₃ and R ₄ are alkyl groups To form a ring structure.
2. The rubber composition according to claim 1, which is an oxadiazole compound represented by the formula: The oxadiazole compound of the formula (I) is represented by the following formula (VI):

2. The oxadiazole compound represented by (wherein R ₅ is a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, or a substituted or unsubstituted phenyl group). Rubber composition. The oxadiazole compound of the formula (II) is represented by the following formula (VII):

2. The rubber composition according to claim 1, which is an oxadiazole compound represented by the formula: wherein n is an integer of 1 to 5.   The rubber composition according to any one of claims 1 to 6, comprising 50 parts by mass or more of styrene-butadiene copolymer rubber or polybutadiene rubber among 100 parts by mass of the rubber component.   The rubber composition according to any one of claims 1 to 7, which contains 20 parts by mass or more of carbon black as the reinforcing filler.   A tire to which the rubber composition according to any one of claims 1 to 8 is applied. The following formula (V):

(Wherein R ₃ and R ₄ are hydrogen, primary, secondary and tertiary alkyl groups, cycloalkyl groups, or substituted or unsubstituted phenyl groups, and R ₃ and R ₄ are alkyl groups and a cyclic structure. May be formed.)
An oxadiazole compound represented by the formula: The oxadiazole compound according to claim 10, wherein one of R ₃ and R _{4 in} the formula (V) is hydrogen and the other is a tert-butyl group. The oxadiazole compound according to claim 10, wherein one of R ₃ and R _{4 in} the formula (V) is hydrogen and the other is a cyclohexyl group. Following formula (VI):

(Wherein R ₅ is a saturated or unsaturated aliphatic hydrocarbon group having 1 to 18 carbon atoms, or a substituted or unsubstituted phenyl group). The oxadiazole compound according to claim 13, wherein R _{5 in the} formula (VI) is a methyl group. Formula (VII) below:

(In the formula, n is an integer of 1 to 5.)
An oxadiazole compound represented by the formula: