JP2011074323A - Rubber composition and pneumatic tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber composition made serviceable for a longer period by improving heat resistance and, particularly, suppressing the hardening deterioration of rubber without increasing the amount of antioxidant, and to provide a pneumatic tire made by using the rubber composition for respective members thereof. <P>SOLUTION: The rubber composition includes: a rubber component containing an isoprene-based rubber of 20 mass% or more; silica or carbon black having nitrogen adsorption relative surface area of 90 m<SP>2</SP>/g or more, or dibutyl phthalate absorption of 105 ml/100 g or more; and a compound represented by formula (1). In the formula, R<SP>1</SP>and R<SP>2</SP>are the same or different from each other and each present hydrogen atom, alkyl group, aryl group, or aralkyl group. Therein, such a case that the R<SP>1</SP>and R<SP>2</SP>are hydrogen atom at the same time is extruded. R<SP>3</SP>and R<SP>4</SP>are the same or different from each other and each present hydrogen atom, alkyl group, cyclic alkyl group, or cyclic ether group. Therein, the R<SP>3</SP>and R<SP>4</SP>may have ether group. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a rubber composition and a pneumatic tire using the same.

Conventionally, anti-aging agents have been widely used in rubber compositions used for tires and the like in order to increase the heat resistance of the rubber composition. Anti-aging agents include amines such as N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD) and N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD). Anti-aging agents are widely used.

However, in recent years, the demand for improved heat resistance has further increased, and further life extension has been demanded. Although a long life can be achieved by increasing the amount of the anti-aging agent, there is a problem that the surface is browned by the precipitation of 6PPD or IPPD on the tire surface, resulting in poor appearance of the tire. Therefore, it is desired to provide a rubber composition that can improve heat resistance and extend the life without increasing the amount of anti-aging agent.

Patent Document 1 discloses a rubber composition in which N- (1-methylheptyl) -N′-phenyl-p-phenylenediamine as an antiaging agent and a wax are blended with a diene rubber. However, there is still room for improvement in terms of improving heat resistance.

Japanese Patent Laid-Open No. 10-324779

The present invention solves the above-mentioned problems, improves the heat resistance without increasing the amount of anti-aging agent, particularly suppresses the curing deterioration of rubber, and can extend the life of the rubber composition, and to each member of the tire An object is to provide a used pneumatic tire.

（式（Ｉ）において、Ｒ^１及びＲ^２は、同一若しくは異なって、水素原子、アルキル基、アリール基又はアラルキル基を表す。但し、Ｒ^１及びＲ^２が同時に水素原子である場合を除く。Ｒ^３及びＲ^４は、同一若しくは異なって、水素原子、アルキル基、環状アルキル基又は環状エーテル基を表す。但し、Ｒ^３及びＲ^４はエーテル基を有してもよい。） The present invention relates to a rubber component containing 20% by mass or more of isoprene-based rubber, silica or carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more, or dibutyl phthalate oil absorption of 105 ml / 100 g or more, and the following formula (I): And a rubber composition containing the represented compound.

(In Formula (I), R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group, except that R ¹ and R ² are hydrogen atoms at the same time. R ³ and R ⁴ are the same or different and each represents a hydrogen atom, an alkyl group, a cyclic alkyl group or a cyclic ether group, provided that R ³ and R ⁴ may have an ether group.

The isoprene-based rubber is preferably at least one selected from the group consisting of isoprene rubber, natural rubber and modified natural rubber.

The compound is preferably a compound represented by the following formula (II) or the following formula (III).

The rubber composition preferably contains 20 to 100 parts by mass of the filler and 0.5 to 10 parts by mass of the compound represented by the formula (I) with respect to 100 parts by mass of the rubber component.

The rubber composition preferably further contains 0.5 to 10 parts by mass of sulfur.
The present invention also relates to a pneumatic tire produced using the rubber composition.

According to the present invention, the rubber component containing isoprene-based rubber contains the compound represented by the above formula (I) and silica and / or carbon black having specific characteristics, so that the heat resistance can be improved. In particular, it is possible to suppress curing deterioration of rubber. Such an improvement effect is greater than that of a styrene butadiene rubber (SBR) compounding system. Therefore, the life of the rubber composition can be extended without increasing the amount of anti-aging agent such as 6PPD, and can be suitably applied to each member of the tire.

The rubber composition of the present invention includes a rubber component containing isoprene-based rubber, silica, carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more, or dibutyl phthalate oil absorption of 105 ml / 100 g or more, and the above formula (I) And a compound represented by By blending the isoprene-based rubber with the compound represented by the above formula (I) and silica or carbon black having specific characteristics, the heat resistance can be improved, and in particular, the rubber can be prevented from being cured and deteriorated.

Here, the curing deterioration of rubber is a deterioration phenomenon in which the rubber becomes harder than the initial state when heat is applied under the condition where oxygen is present as a deterioration factor. Can be effectively suppressed. Such curing deterioration suppressing effect is different from so-called heat fatigue resistance (prevention of blow and chunk generation) and heat sag resistance, and isoprene-based rubber is combined with the compound of the above formula (I) and the silica. Or, it is produced when the above carbon black is blended.

Furthermore, when these components are used, the effect of improving heat resistance (particularly, the effect of suppressing curing deterioration) is generated synergistically, for example, compared to the case where the compound of the above formula (I) is added to the SBR compounding system. As a result, a great effect of suppressing curing deterioration occurs.
Therefore, in the present invention, since the heat resistance (particularly, the effect of inhibiting hardening deterioration) can be improved without increasing the amount of the anti-aging agent, it can be suitably used for each member of the tire, and the life of the tire can be extended.

In the present invention, isoprene-based rubber is used as the rubber component. In the present invention, the heat resistance (particularly, the effect of suppressing the curing deterioration) can be improved despite using a rubber having an isoprene skeleton. Examples of the isoprene-based rubber include isoprene rubber (IR), natural rubber (NR), and modified natural rubber. NR includes deproteinized natural rubber (DPNR) and high-purity natural rubber (HPNR). Modified natural rubber includes epoxidized natural rubber (ENR), hydrogenated natural rubber (HNR), and grafted natural rubber. Etc. Moreover, as NR, what is common in tire industry, such as SIR20, RSS # 3, TSR20, can be used, for example.

In the present invention, 100% by mass of the rubber component contains 20% by mass or more of isoprene-based rubber, preferably 30% by mass or more, more preferably 50% by mass or more, and still more preferably 60% by mass or more. If it is less than 20% by mass, the effect of suppressing curing deterioration may not be sufficiently obtained. The upper limit of the content of the isoprene-based rubber is not particularly limited, and may be 100% by mass, but is preferably 90% by mass or less, more preferably 80% by mass or less.

In addition to isoprene-based rubber, butadiene rubber (BR), styrene butadiene rubber (SBR), styrene isoprene butadiene rubber (SIBR), ethylene propylene diene rubber (EPDM), chloroprene rubber (CR) can be used as rubber components. And acrylonitrile butadiene rubber (NBR). It is preferable to use SBR and BR together with isoprene-based rubber. A rubber component may be used independently and may use 2 or more types together.

In the present invention, silica or carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more or a dibutyl phthalate oil absorption of 105 ml / 100 g or more is used.

Examples of the silica include, but are not limited to, dry method silica (anhydrous silicic acid), wet method silica (anhydrous silicic acid), and the like, and wet method silica is preferable because it has many silanol groups. By blending silica, heat resistance (particularly the effect of suppressing curing deterioration) can be improved. Silica may be used alone or in combination of two or more.

The BET specific surface area (BET) of silica is preferably 50 m ² / g or more, more preferably 80 m ² / g or more, and still more preferably 100 m ² / g or more. Further, N ₂ SA of silica is preferably 200 m ² / g or less, more preferably 150 m ² / g or less, and still more preferably 130 m ² / g or less. If it is less than 50 m ² / g, when more than 200 meters ² / g, there is a difficult possibility of sure hardening degradation inhibiting effect.
Incidentally, BET specific surface area _(N 2 SA) of the silica is a value determined by the BET method in accordance with ASTM D3037-81.

The DBP oil absorption (DBP) of silica is preferably 200 ml / 100 g or more, more preferably 220 ml / 100 g or more. Further, the DBP of silica is preferably 350 ml / 100 g or less, more preferably 300 ml / 100 g or less, still more preferably 280 ml / 100 g. If it is less than 200 ml / 100 g, and if it exceeds 350 ml / 100 g, it may be difficult to confirm the effect of inhibiting curing deterioration.
The DBP of silica is measured by the JIS K6217-4 (Brabender method) method.

The ratio of DBP oil absorption to the BET specific surface area of silica (DBP / BET) is preferably 1.80 or more, more preferably 2.00 or more, and further preferably 2.20 or more. Further, the DBP / BET of silica is preferably 3.00 or less, more preferably 2.50 or less, and still more preferably 2.30 or less. If it is less than 1.80, if it exceeds 3.00, it may be difficult to confirm the effect of inhibiting curing deterioration.

The average primary particle diameter of silica is preferably 10 nm or more, more preferably 15 nm, and still more preferably 18 nm or more. The average primary particle diameter of silica is preferably 30 nm or less, more preferably 25 nm or less, and still more preferably 22 nm or less. If it is less than 10 nm, if it exceeds 30 nm, it may be difficult to confirm the effect of inhibiting curing deterioration.
The average primary particle diameter of silica can be determined from the average value obtained by observing silica with an electron microscope and measuring the particle diameter of 50 arbitrary particles.

The content of silica is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 55 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, there is a possibility that the curing deterioration suppressing effect cannot be sufficiently obtained. Content of this silica becomes like this. Preferably it is 100 mass parts or less, More preferably, it is 80 mass parts or less, More preferably, it is 70 mass parts or less. When the amount exceeds 100 parts by mass, the dispersion of silica is deteriorated, and it may be difficult to confirm the effect of suppressing curing deterioration.

Examples of the carbon black having the above-described characteristics that can be used in the present invention include ISAF and SAF. By blending such carbon black, the reinforcing property can be enhanced and a good effect of suppressing curing deterioration can be obtained.

The nitrogen adsorption specific surface area (N ₂ SA) of carbon black is preferably 90 m ² / g or more, more preferably 100 m ² / g or more, and still more preferably 105 m ² / g or more. Also, _N 2 SA of the carbon black is preferably 150 meters ² / g or less, more preferably ^{130m 2 / g, 125m 2 /} g or less is more preferable. In the case of less than 90 m ² / g, in the case of exceeding 150 m ² / g, it may be difficult to confirm the effect of suppressing the curing deterioration.
The N ₂ SA of carbon black is determined by the A method of JIS K6217.

The carbon black dibutyl phthalate oil absorption (DBP) is preferably 105 ml / 100 g or more, more preferably 110 ml / 100 g or more, and even more preferably 112 ml / 100 g or more. Further, the DBP of carbon black is preferably 150 ml / 100 g or less, more preferably 130 ml / 100 g or less, and further preferably 125 ml / 100 g or less. If it is less than 105 ml / 100 g or more than 150 ml / 100 g, it may be difficult to confirm the effect of inhibiting curing deterioration.
In addition, DBP of carbon black is calculated | required by the measuring method of JISK6217-4.

The average particle size of carbon black is preferably 15 nm or more, more preferably 20 nm or more. The average particle size of carbon black is preferably 30 nm or less, more preferably 27 nm or less, and still more preferably 25 nm or less. If it is less than 15 nm, if it exceeds 30 nm, it may be difficult to confirm the effect of inhibiting curing deterioration.
In addition, the average particle diameter of carbon black is a number average particle diameter, and is measured with a transmission electron microscope.

The content of carbon black is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 55 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, the effect of suppressing curing deterioration may not be obtained satisfactorily. Moreover, this content becomes like this. Preferably it is 100 mass parts or less, More preferably, it is 80 mass parts or less, More preferably, it is 70 mass parts or less. If it exceeds 100 parts by mass, the dispersibility of the filler may be deteriorated.

In the present invention, other fillers may be blended in addition to the silica and carbon black. Examples of other fillers include inorganic fillers such as clay and calcium carbonate.

In the rubber composition of the present invention, the total content of the filler is preferably 20 parts by mass or more, more preferably 40 parts by mass or more, and further preferably 55 parts by mass or more with respect to 100 parts by mass of the rubber component. If it is less than 20 parts by mass, the effect of suppressing curing deterioration may not be obtained satisfactorily. The total content is preferably 100 parts by mass or less, more preferably 80 parts by mass or less, and still more preferably 70 parts by mass or less. When the amount exceeds 100 parts by mass, the dispersion of the filler is deteriorated, and it may be difficult to confirm the effect of suppressing the curing deterioration.

Further, when silica is blended in the rubber composition of the present invention, it is preferable to blend a silane coupling agent.
As the silane coupling agent, any silane coupling agent conventionally used in combination with silica can be used in the rubber industry. For example, bis (3-triethoxysilylpropyl) tetrasulfide, bis (2-tri Ethoxysilylethyl) tetrasulfide, bis (4-triethoxysilylbutyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, bis (4-trimethoxysilyl) Butyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (2-triethoxysilylethyl) trisulfide, bis (4-triethoxysilylbutyl) trisulfide, bis (3-trimethoxysilylpropyl) Trisulfi Bis (2-trimethoxysilylethyl) trisulfide, bis (4-trimethoxysilylbutyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, bis (2-triethoxysilylethyl) disulfide, bis (4 -Triethoxysilylbutyl) disulfide, bis (3-trimethoxysilylpropyl) disulfide, bis (2-trimethoxysilylethyl) disulfide, bis (4-trimethoxysilylbutyl) disulfide, 3-trimethoxysilylpropylbenzothiazoli And sulfide systems such as tetratetrasulfide and 3-triethoxysilylpropylbenzothiazole tetrasulfide. Moreover, mercapto type, vinyl type, glycidoxy type, nitro type, chloro type and the like can also be mentioned. Of these, bis (3-triethoxysilylpropyl) tetrasulfide and bis (3-triethoxysilylpropyl) disulfide are preferably used from the viewpoint of the reinforcing effect and processability of the silane coupling agent. These silane coupling agents may be used alone or in combination of two or more.

The content of the silane coupling agent is preferably 3 parts by mass or more and more preferably 7 parts by mass or more with respect to 100 parts by mass of silica. If it is less than 3 parts by mass, the fracture strength tends to be greatly reduced. Moreover, 15 mass parts or less are preferable, and, as for content of this silane coupling agent, 10 mass parts or less are more preferable. When the amount exceeds 15 parts by mass, effects such as an increase in fracture strength and a reduction in rolling resistance due to the addition of the silane coupling agent tend not to be obtained.

In the present invention, a compound represented by the following formula (I) is used as a vulcanization accelerator. By using the compound, the heat resistance (suppression of curing deterioration) of the vulcanized rubber can be improved.

（式（Ｉ）において、Ｒ^１及びＲ^２は、同一若しくは異なって、水素原子、アルキル基、アリール基又はアラルキル基を表す。但し、Ｒ^１及びＲ^２が同時に水素原子である場合を除く（即ち、同一の環に結合しているＲ^１及びＲ^２がともに水素原子である場合を除く）。Ｒ^３及びＲ^４は、同一若しくは異なって、水素原子、アルキル基、環状アルキル基又は環状エーテル基を表す。但し、Ｒ^３及びＲ^４はエーテル基を有してもよい。）

(In Formula (I), R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group, except that R ¹ and R ² are simultaneously hydrogen atoms ( That is, R ¹ and R ² bonded to the same ring are both hydrogen atoms.) R ³ and R ⁴ are the same or different and are a hydrogen atom, an alkyl group, a cyclic alkyl group, or a cyclic ether. Represents a group, provided that R ³ and R ⁴ may have an ether group.)

Regarding R ¹ and R ² , the alkyl group preferably has 1 to 10 carbon atoms, the aryl group has 6 to 10 carbon atoms, and the aralkyl group has 7 to 10 carbon atoms. Examples of the alkyl group (linear or branched) include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, iso-butyl group, sec-butyl group, tert-butyl group, pentyl group, Examples include a hexyl group, a heptyl group, a 2-ethylhexyl group, an octyl group, a nonyl group, and a decyl group. Examples of the aryl group include a phenyl group, a tolyl group, a xylyl group, a biphenyl group, a naphthyl group, an anthryl group, and a phenanthryl group. Examples of the aralkyl group include a benzyl group and a phenethyl group. Of the alkyl group, aryl group, and aralkyl group, an alkyl group is preferable, and the alkyl group preferably has 1 to 4 carbon atoms, more preferably 1 to 2 carbon atoms. Further, ^{R 1} is an alkyl group, ^{R 2} is preferably a hydrogen atom. In this case, the effect of suppressing curing deterioration can be obtained favorably.

Regarding R ³ and R ⁴ , the alkyl group preferably has 1 to 10 carbon atoms, the cyclic alkyl group has 3 to 12 carbon atoms, and the cyclic ether group has 3 to 10 carbon atoms. Specific examples of the alkyl group include the same groups as described above. Examples of the cyclic alkyl group include cyclopropyl group, cyclobutyl group, cyclopentyl group, cyclohexyl group, cycloheptyl group, cyclooctyl group, adamantyl group, 1-ethylcyclopentyl group, 1-ethylcyclohexyl group and the like. Examples of the cyclic ether group include an oxirane group, an oxetane group, an oxolane group, an oxane group, an oxepane group, an oxocan group, an oxonan group, an oxecan group, an oxet group, an oxole group, a dioxolane group, a dioxane group, a dioxepane group, and a dioxecan group. It is done. Of the alkyl group, cyclic alkyl group, and cyclic ether group, an alkyl group and a cyclic alkyl group are preferable, and the carbon number of the alkyl group is preferably 2 to 6, more preferably 3 to 5, and the cyclic alkyl group. The carbon number of is preferably 4 to 10, more preferably 5 to 7. Further, it is preferred that R ³ is an alkyl group or a cyclic alkyl group, R ⁴ is a hydrogen atom. In this case, the effect of suppressing curing deterioration can be obtained favorably.

Specific examples of the compound represented by the above formula (I) include N-tert-butyl-4-methyl-2-benzothiazolylsulfenamide, N-tert-butyl-4-ethyl-2-benzothiazolyl. Rusulfenamide, N-tert-butyl-4-propyl-2-benzothiazolylsulfenamide, N-tert-butyl-5-methyl-2-benzothiazolylsulfenamide, N-tert-butyl-5 Ethyl-2-benzothiazolylsulfenamide, N-tert-butyl-5-propyl-2-benzothiazolylsulfenamide, N-tert-butyl-6-methyl-2-benzothiazolylsulfenamide, N -Tert-butyl-6-ethyl-2-benzothiazolylsulfenamide, N-tert-butyl-6-propyl-2- Nzothiazolylsulfenamide, N-tert-butyl-4,6-dimethyl-2-benzothiazolylsulfenamide, N-tert-butyl-4,6-diethyl-2-benzothiazolylsulfenamide, And N-tert-butyl-4,6-dipropyl-2-benzothiazolylsulfenamide. In addition, N-cyclohexyl-4-methyl-2-benzothiazolylsulfenamide, N-cyclohexyl-4-ethyl-2-benzothiazolylsulfenamide, N-cyclohexyl-4-propyl-2-benzo Thiazolylsulfenamide, N-cyclohexyl-5-methyl-2-benzothiazolylsulfenamide, N-cyclohexyl-5-ethyl-2-benzothiazolylsulfenamide, N-cyclohexyl-5-propyl-2- Benzothiazolylsulfenamide, N-cyclohexyl-6-methyl-2-benzothiazolylsulfenamide, N-cyclohexyl-6-ethyl-2-benzothiazolylsulfenamide, N-cyclohexyl-6-propyl-2 -Benzothiazolylsulfenamide, N-cyclohexyl 4,6-dimethyl-2-benzothiazolylsulfenamide, N-cyclohexyl-4,6-diethyl-2-benzothiazolylsulfenamide, N-cyclohexyl-4,6-dipropyl-2-benzothiazolylsulfate Examples include phenamide. Among them, N-tert-butyl-4-methyl-2-benzothiazolylsulfenamide, N-tert-butyl-5-methyl-2-benzothiazolylsulfenamide, N-tert-butyl-6-methyl 2-benzothiazolylsulfenamide, N-cyclohexyl-4-methyl-2-benzothiazolylsulfenamide, N-cyclohexyl-5-methyl-2-benzothiazolylsulfenamide, N-cyclohexyl-6 Methyl-2-benzothiazolylsulfenamide is preferred. Furthermore, among the compounds described above, a compound (4m-TBBS) represented by the following formula (II) and a compound (4m-CBS) represented by the following formula (III) are particularly preferably used. When using the above compounds, the effect of suppressing curing deterioration can be obtained satisfactorily.

上記式（Ｉ）で表される化合物は、単独で用いてもよく、２種以上を併用してもよい。該化合物の市販品として、例えば、ＮＯＣＩＬ社の製品を使用することができる。

The compounds represented by the above formula (I) may be used alone or in combination of two or more. As a commercial product of the compound, for example, a product of NOCIL can be used.

The total content of the compounds represented by the above formula (I) is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, further preferably 1.3 parts by mass with respect to 100 parts by mass of the rubber component. More than part by mass. If it is less than 0.5 part by mass, the effect of suppressing curing deterioration may not be sufficiently obtained. The total content is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less. If it exceeds 10 parts by mass, it may be difficult to maintain an appropriate crosslinking density and crosslinking form.

In addition to the above components, the rubber composition of the present invention includes compounding agents conventionally used in the rubber industry, for example, stearic acid, zinc oxide, various anti-aging agents, vulcanizing agents such as wax, sulfur or sulfur compounds, Vulcanization accelerators and the like can be appropriately blended as necessary.

In the present invention, an amine-based anti-aging agent is preferably used as an anti-aging agent because of its excellent destructive properties, and heat resistance (especially an effect of inhibiting curing deterioration) can be improved without increasing the amount used. is there. Examples of amine-based antioxidants include diphenylamine-based and p-phenylenediamine-based amine derivatives. Examples of the diphenylamine derivative include p- (p-toluenesulfonylamide) -diphenylamine, octylated diphenylamine, and the like. Examples of p-phenylenediamine derivatives include N- (1,3-dimethylbutyl) -N′-phenyl-p-phenylenediamine (6PPD), N-phenyl-N′-isopropyl-p-phenylenediamine (IPPD). ), N, N′-di-2-naphthyl-p-phenylenediamine, and the like.

The content of the amine anti-aging agent is 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. If it is less than 0.5 parts by mass, the fracture characteristics may not be improved. Moreover, this content becomes like this. Preferably it is 6 mass parts or less, More preferably, it is 4 mass parts or less. If it exceeds 6 parts by mass, bloom may be generated on the surface.

In the present invention, sulfur can be suitably used as a vulcanizing agent. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur.
The sulfur content is preferably 0.5 parts by mass or more, more preferably 1.0 parts by mass or more, and still more preferably 1.5 parts by mass or more with respect to 100 parts by mass of the rubber component. If the amount is less than 0.5 parts by mass, the effect of the present invention may be small. Moreover, this content becomes like this. Preferably it is 10 mass parts or less, More preferably, it is 6 mass parts or less, More preferably, it is 4 mass parts or less. If it exceeds 10 parts by mass, the effect of suppressing the curing deterioration may not be sufficiently obtained.

In this invention, you may mix | blend another vulcanization accelerator with the compound represented by the said formula (I), and the curing deterioration inhibitory effect is obtained suitably also in this case.
Other vulcanization accelerators include N-tert-butyl-2-benzothiazolylsulfenamide (TBBS), N-cyclohexyl-2-benzothiazolylsulfenamide (CBS), N, N′-dicyclohexyl- Examples include 2-benzothiazolylsulfenamide (DZ), mercaptobenzothiazole (MBT), dibenzothiazolyl disulfide (MBTS), and diphenylguanidine (DPG). 0.1 to 2.0 parts by mass may be blended.

The rubber composition of the present invention is produced by a general method. That is, it can be produced by a method of kneading the above components with a Banbury mixer, a kneader, an open roll or the like and then vulcanizing.

The rubber composition of the present invention can be suitably used for tire members such as treads, sidewalls, and internal components.

The pneumatic tire of the present invention can be produced by a usual method using the rubber composition. That is, the rubber composition is extruded in accordance with the shape of the tire member at an unvulcanized stage, molded by a normal method on a tire molding machine, and bonded together with other tire members to form an unvulcanized tire. Form. This unvulcanized tire can be heated and pressurized in a vulcanizer to produce a tire.

The present invention will be specifically described based on examples, but the present invention is not limited to these examples.

Hereinafter, various chemicals used in Examples and Comparative Examples will be described together.
NR: TSR
ENR: ENR25 manufactured by MRB (epoxidation rate: 25 mol%)
SBR: S-SBR HPR355 manufactured by JSR Corporation
BR: Hisys BR150B manufactured by Ube Industries, Ltd.
Carbon Black: Dia Black I manufactured by Mitsubishi Chemical Corporation (ISAF carbon, N ₂ SA: 114 m ² / g, DBP oil absorption: 114 ml / 100 g, average particle diameter: 23 nm)
Silica: Silica 115Gr (BET (N ₂ SA): 110 m ² / g, DBP oil absorption: 250 ml / 100 g, DBP / BET: 2.23, average primary particle size: 20 nm) manufactured by Rhodia Japan Co., Ltd.
Silane coupling agent: Si266 (bis (3-triethoxysilylpropyl) disulfide) manufactured by Degussa
Zinc oxide: 2 types of zinc oxide manufactured by Mitsui Mining & Smelting Co., Ltd. Stearic acid: “Kashiwa” manufactured by NOF Corporation
Anti-aging agent: Anti-aging agent 6C (SANTOFLEX, 6PPD) manufactured by FLEXSYS Corporation
Sulfur: Powder sulfur vulcanization accelerator 1 (TBBS) manufactured by Tsurumi Chemical Co., Ltd .: Noxeller NS (N-tert-butyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator 2 (4m-TBBS): N-tert-butyl-4-methyl-2-benzothiazolylsulfenamide (formula (II)) manufactured by NOCIL
Vulcanization accelerator 3 (CBS): Noxeller CZ (N-cyclohexyl-2-benzothiazolylsulfenamide) manufactured by Ouchi Shinsei Chemical Co., Ltd.
Vulcanization accelerator 4 (4m-CBS): N-cyclohexyl-4-methyl-2-benzothiazolylsulfenamide (formula (III)) manufactured by NOCIL
Vulcanization accelerator 5 (DPG): Soxinol D (diphenylguanidine) manufactured by Sumitomo Chemical Co., Ltd.

Examples 1-8 and Comparative Examples 1-12
According to the blending contents shown in Tables 1 to 4, materials other than sulfur and a vulcanization accelerator were kneaded using a 1.7 L Banbury mixer. Sulfur and a vulcanization accelerator were added to the obtained kneaded product, and kneaded for 3 minutes at 80 to 90 ° C. using an open roll to obtain an unvulcanized rubber composition. The obtained unvulcanized rubber composition was press vulcanized at 170 ° C. for 10 to 20 minutes to obtain a vulcanized rubber composition. The obtained vulcanized rubber composition was used as a new sample.

(Deterioration conditions)
The new sample prepared above was thermally deteriorated in an oven at 80 ° C. for 7 days. The obtained sample was used as a deteriorated sample.

The following evaluation was performed using the obtained new samples and deteriorated samples. Each test result is shown in Tables 1-4. In the table, the value of the deteriorated sample when the new sample is set to 100 is shown as an index. The closer to 100, the less the deterioration, the hardness, swelling rate, and M100 compared to the new product, and the better the heat resistant deterioration performance. Indicates.

<Hardness>
Using the prepared sample, the hardness of the rubber was measured using a hardness meter at a temperature of 25 ° C. according to JIS K6253 (Shore-A measurement). It shows that it is so hard that a numerical value is large.

<Swelling rate>
The immersion test of the prepared sample was performed according to JIS K6258, and the volume of the sample after being immersed in toluene at 40 ° C. for 24 hours and swollen was measured and calculated from the volume change. The smaller the value, the higher the crosslink density.

<Stress at 100% elongation (M100)>
Using a No. 3 dumbbell-shaped test piece made of the prepared sample, a tensile test was performed at a pulling speed of 500 mm / min in accordance with JIS K6251 “vulcanized rubber and thermoplastic rubber—determining tensile properties”. The stress at 100% elongation at 23 ° C. (M100 (MPa)) was measured. Larger numbers indicate higher modulus and hardness. M100 is also an index of crosslink density.

From Table 1, when 4m-TBBS or 4m-CBS was blended with 100 parts by mass of NR and 60 parts by mass of silica or carbon black, a very large curing deterioration suppressing effect was obtained as compared with the case where TBBS or CBS was blended. Specifically, as the rate of change due to curing deterioration (for example, rate of change in hardness Hs = Hs ^aged / Hs ^new × 100), an improvement of about 5% in hardness and swelling rate and about 10-25% in M100 is seen. It was.

From Table 2, the same effect as in Table 1 was also observed in the mixed system of NR and SBR. On the other hand, in the blending system of 100 parts by mass of SBR, the effect of using 4m-TBBS was not observed for the hardness and M100.

From Table 3, the same effect as in Table 1 was also observed in the mixed system of NR and BR. On the other hand, in the system of BR 100 parts by mass, the effect of using 4m-CBS was small.

From Table 4, the same effect as in Table 1 was also observed in the blended system of ENR and silica or carbon black.

Claims (6)

A rubber component containing 20% by mass or more of isoprene-based rubber;
Silica, or carbon black having a nitrogen adsorption specific surface area of 90 m ² / g or more or dibutyl phthalate oil absorption of 105 ml / 100 g or more,
A rubber composition containing a compound represented by the following formula (I):

(In Formula (I), R ¹ and R ² are the same or different and each represents a hydrogen atom, an alkyl group, an aryl group, or an aralkyl group, except that R ¹ and R ² are hydrogen atoms at the same time. R ³ and R ⁴ are the same or different and each represents a hydrogen atom, an alkyl group, a cyclic alkyl group or a cyclic ether group, provided that R ³ and R ⁴ may have an ether group. The rubber composition according to claim 1, wherein the isoprene-based rubber is at least one selected from the group consisting of isoprene rubber, natural rubber and modified natural rubber. The rubber composition according to claim 1 or 2, wherein the compound is a compound represented by the following formula (II) or the following formula (III).

The filler according to any one of claims 1 to 3, comprising 20 to 100 parts by mass of a filler and 0.5 to 10 parts by mass of the compound represented by the formula (I) with respect to 100 parts by mass of the rubber component. Rubber composition. Furthermore, the rubber composition in any one of Claims 1-4 which contains 0.5-10 mass parts of sulfur. The pneumatic tire produced using the rubber composition in any one of Claims 1-5.