JP2021195492A - Rubber composition, rubber composition for tire, rubber composition for tire tread, crosslinked rubber for tire, tire tread, and tire - Google Patents

Abstract

To provide: a rubber composition which enables production of crosslinked rubber having a high dynamic storage elastic modulus; crosslinked rubber for a tire and a tire having high dynamic storage elastic moduli and a rubber composition for a tire which enables production of the same; and a tire tread having a high dynamic storage elastic modulus and a rubber composition for a tire tread which enables production of the same.SOLUTION: A rubber composition contains a rubber component containing diene-based rubber, a crosslinking agent, a benzoic acid derivative having an amino group or an acetoxy group at least a para position with respect to a carboxy group, and 20-120 pts.mass of a filler with respect to 100 pts.mass of the rubber component.SELECTED DRAWING: None

Description

The present invention relates to a rubber composition, a rubber composition for a tire, a rubber composition for a tire tread, a crosslinked rubber for a tire, a tire tread and a tire.

In recent years, under the social demand for energy saving, tires with low rolling resistance have been required in order to promote fuel efficiency for automobiles, and a rubber composition having lower heat generation (lower loss) than before has been desired. There is.
On the other hand, it is desired to improve the wear resistance of automobile tires, and a rubber composition having a large storage elastic modulus, particularly a dynamic storage elastic modulus (G'), is desired.

In Patent Document 1, a specific resin composition and a thermoplastic resin are specified with respect to natural rubber and synthetic isoprene rubber for the purpose of providing a rubber composition having low heat generation and high elasticity. The rubber compositions blended in proportion are described.

Japanese Unexamined Patent Publication No. 2012-92179

In Patent Document 1, a rubber composition having low heat generation and high elasticity with respect to a specific rubber component was obtained, but the rubber component used was limited. In addition, the amount of the resin composition and the thermoplastic resin to be added was large, and the selectivity of the formulation of the rubber composition was limited.

An object of the present invention is a rubber composition capable of producing a crosslinked rubber having a high dynamic storage elastic coefficient; a crosslinked rubber for a tire having a high dynamic storage elastic coefficient and a tire, and a rubber composition for a tire capable of producing the same. Moreover, it is an object of the present invention to provide a tire tread having a high dynamic storage elasticity and a rubber composition for a tire tread capable of producing the same, and to solve the problem.

As a result of diligent studies, the present inventor has found that the above-mentioned problems can be solved by blending a compound having a specific structure.
That is, the present invention relates to the following <1> to <8>.
<1> A rubber component containing a diene rubber, a cross-linking agent, a benzoic acid derivative having an amino group or an acetoxy group at least in the para position with respect to the carboxy group, and 20 to 120 to 100 parts by mass of the rubber component. A rubber composition containing a mass portion of a filler.

<2> The rubber composition according to <1>, wherein the content of the benzoic acid derivative is 0.05 to 10 parts by mass with respect to 100 parts by mass of the rubber component.
<3> The cross-linking agent contains a vulcanizing agent, further contains a vulcanization accelerator, and the mass ratio (a) of the content (a) of the vulcanization accelerator to the content (b) of the benzoic acid derivative. The rubber composition according to <1> or <2>, wherein / b) is 0.2 to 5.0.

<4> A rubber composition for a tire comprising the rubber composition according to any one of <1> to <3>.
<5> A rubber composition for a tire tread comprising the rubber composition according to any one of <1> to <3>.

<6> A cross-linked rubber for a tire obtained by cross-linking the rubber composition for a tire according to <4>.

<7> A tire tread obtained by cross-linking the rubber composition for tire tread according to <5>.
<8> A tire containing the crosslinked rubber for the tire according to <6>.

According to the present invention, a rubber composition capable of producing a crosslinked rubber having a high dynamic storage elastic coefficient; a crosslinked rubber for a tire having a high dynamic storage elastic coefficient and a tire, and a rubber composition for a tire capable of producing the same. Also, it is possible to provide a tire tread having a high dynamic storage elasticity and a rubber composition for a tire tread capable of producing the same.

Hereinafter, the present invention will be illustrated in detail based on the embodiments thereof. In the following description, the description of "A to B" indicating the numerical range represents the numerical range including the end points A and B, and is "A or more and B or less" (in the case of A <B) or ". It represents "A or less and B or more" (when A> B).

<Rubber composition>
The rubber composition of the present invention comprises a rubber component containing a diene-based rubber, a cross-linking agent, a benzoic acid derivative having an amino group or an acetoxy group at least in the para position with respect to the carboxy group, and 100 parts by mass of the rubber component. 20 to 120 parts by mass of filler.
Hereinafter, a benzoic acid derivative having an amino group or an acetoxy group at least in the para position with respect to the carboxy group is referred to as a benzoic acid derivative in the present invention.
As a result of diligent studies, the present inventors have found that the crosslinked rubber obtained by crosslinking the rubber composition containing the benzoic acid derivative in the present invention has a high dynamic storage elastic modulus (G'). The detailed mechanism by which such an effect is obtained is unknown, but some are presumed as follows.
In the process of crosslinking, it is considered that the benzoic acid derivative in the present invention and the rubber component form a pseudo-crosslink, and it is presumed that a high dynamic storage elastic modulus (G') was achieved.
Hereinafter, the present invention will be described in detail.

[Rubber component]
The rubber composition of the present invention contains a rubber component containing a diene-based rubber.
The rubber component can be appropriately selected from rubber components including diene-based rubber used in the rubber industry. The diene-based rubber may be a natural rubber or a synthetic rubber, and these may be used alone or in combination.
Examples of the diene synthetic rubber include styrene-butadiene copolymer (SBR), polybutadiene (BR), polyisoprene (IR), styrene-isoprene copolymer (SIR), butadiene-isoprene copolymer, and butadiene-styrene-. Examples thereof include isoprene copolymer, acrylonitrile-butadiene copolymer, chloroprene rubber, butyl rubber (IIR), halogenated butyl rubber and the like. Further, a part thereof may have a branched structure by using a polyfunctional modifier, for example, a modifier such as tin tetrachloride.
The rubber component is preferably made of a diene-based rubber, and preferably contains a styrene-butadiene copolymer or a natural rubber. The rubber component may be used alone or in combination of two or more.

[Benzoic acid derivative]
The rubber composition of the present invention contains a benzoic acid derivative having an amino group or an acetoxy group at least in the para position with respect to the carboxy group. The benzoic acid derivative in the present invention may further have an amino group or an acetoxy group at one or both of the ortho-position and the meta-position with respect to the carboxy group, and may have a halogen atom, a hydrocarbon group and the like. It may have a substituent.
The rubber composition of the present invention may contain only one kind of the benzoic acid derivative of the present invention, or may contain two or more kinds.

Among the above, the benzoic acid derivative in the present invention preferably has an amino group or an acetoxy group only at the para position, and specifically, p-aminobenzoic acid (pABA) and p-acetoxybenzoic acid having the following structures (p-aminobenzoic acid (pABA)). It is preferably pAcOBA).

The benzoic acid derivative in the present invention may be obtained as a commercial product or may be synthesized.

The content of the benzoic acid derivative in the present invention in the rubber composition is preferably 0.05 to 10 parts by mass with respect to 100 parts by mass of the rubber component. Within such a range, the storage elastic modulus (G') of the crosslinked rubber can be further improved, and the tan δ at 50 ° C. can be lowered. From the same viewpoint, the content of the benzoic acid derivative in the present invention in the rubber composition is more preferably 0.1 part by mass or more, further preferably 0.3 part by mass or more, and 0.5 part by mass. It is more preferably more than parts by mass, more preferably 5 parts by mass or less, further preferably 3 parts by mass or less, and even more preferably 2.5 parts by mass or less. ..

[Crosslinking agent]
The rubber composition of the present invention contains a cross-linking agent.
The cross-linking agent is not particularly limited as long as it is a component capable of cross-linking rubber molecules. Examples thereof include vulcanizing agents that crosslink sulfur, organic peroxides that crosslink peroxides, oxymu compounds that crosslink quinoids, and diamine compounds that crosslink amines. Usually, a vulcanizing agent is used.
Sulfur is usually used as the vulcanizing agent, and examples thereof include powdered sulfur, precipitated sulfur, colloidal sulfur, surface-treated sulfur, and insoluble sulfur.

In the rubber composition, the content of the cross-linking agent is preferably 0.1 part by mass or more, more preferably 0.3 part by mass with respect to 100 parts by mass of the rubber component from the viewpoint of sufficiently advancing the cross-linking between the rubber molecules. More than parts, more preferably 0.5 parts by mass or more, still more preferably 1 part by mass or more, and from the viewpoint of improving anti-aging resistance, preferably 10 parts by mass or less, more preferably 5 parts by mass or less. More preferably, it is 3 parts by mass or less.

[Vulcanization accelerator]
When the cross-linking agent contains a vulcanizing agent, the rubber composition of the present invention preferably further contains a vulcanization accelerator.
The vulcanization accelerator is not particularly limited and may be appropriately selected depending on the intended purpose. Specifically, CBS (N-cyclohexyl-2-benzothiazolesulfenamide), TBBS (N-t-butyl-2-benzothiazolesulfenamide), TBSI (N-t-butyl-2-benzothiazolesulfenamide) Sulfenamide-based vulcanization accelerator such as fenimide); guanidine-based vulcanization accelerator such as DPG (diphenylguanidine); thiuram-based vulcanization accelerator such as tetraoctylthiuram disulfide and tetrabenzylthiuram disulfide; MBT ( 2-mercaptobenzothiazole), a thiazole-based vulcanization accelerator such as MBTS (di-2-benzothiazolyl disulfide); a vulcanization accelerator such as zinc dialkyldithiophosphate; and the like. These may be used alone or in combination of two or more.
Among these, from the viewpoint of advancing appropriate vulcanization in the presence of the benzoic acid derivative in the present invention, it is preferable to contain at least a sulfenamide-based vulcanization accelerator as a vulcanization accelerator, and at least CBS. And, it is more preferable to contain either one or both of TBBS.

The content of the vulcanization accelerator in the rubber composition is preferably 0.1 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of advancing appropriate vulcanization at an appropriate vulcanization rate. It is preferably 0.3 parts by mass or more, more preferably 0.5 parts by mass or more, still more preferably 1 part by mass or more, and preferably 10 parts by mass or less, more preferably 7.5 parts by mass or less, further. It is preferably 5 parts by mass or less.

Further, the mass ratio (a / b) of the content (a) of the vulcanization accelerator to the content (b) of the benzoic acid derivative in the rubber composition in the rubber composition is the inhibition of vulcanization of the benzoic acid derivative in the present invention. From the viewpoint of suppressing the action, advancing appropriate vulcanization, and obtaining a crosslinked rubber composition having low heat generation, it is preferably 0.2 or more, more preferably 0.3 or more, still more preferably 1.0 or more. Yes, and preferably 5.0 or less, more preferably 3.0 or less, still more preferably 2.5 or less.

[Filler]
The rubber composition of the present invention contains 20 to 120 parts by mass of a filler with respect to 100 parts by mass of the rubber component.
When the rubber composition contains the filler in the above range, the reinforcing property of the crosslinked rubber can be improved and the tan δ at 50 ° C. can be further lowered.
Generally, when the rubber composition contains a large amount of filler, the crosslinked rubber tends to generate heat due to rubbing between the fillers. However, when the rubber composition contains the benzoic acid derivative in the present invention, the aggregation of the filler is enhanced. Fever can be suppressed. That is, it is easy to lower the tan δ at 50 ° C.
From the viewpoint of further improving the reinforcing property of the crosslinked rubber and further lowering the tan δ at 50 ° C., the total content of the filler in the rubber composition is preferably 30 parts by mass or more with respect to 100 parts by mass of the rubber component. It is more preferably 40 parts by mass or more, preferably 90 parts by mass or less, and more preferably 80 parts by mass or less.

As the filler, an organic filler such as carbon black, an inorganic filler such as silica, or a blend of these two types of filler may be used. Among these, one or more fillers selected from carbon black and silica are preferably used.
The carbon black is not particularly limited, and any carbon black that has been conventionally used as a filler for rubber can be appropriately selected and used. For example, SRF, GPF, FEF, HAF, ISAF, SAF and the like are used, and FEF, HAF, ISAF, SAF and the like, which are particularly excellent in bending resistance and fracture resistance, are preferably mentioned.
From the viewpoint of reinforcing property, carbon black has a nitrogen adsorption specific surface area N ₂ SA (based on JIS K 6217-2: 2001), preferably 30 m ² / g or more, and more preferably 35 m ² / g or more. , And ^{more preferably 150 m 2} / g or less, more preferably 130 m ² / g or less.
One type of carbon black may be used alone, or two or more types may be used in combination.

On the other hand, examples of silica include wet silica (hydrous silicic acid), dry silica (anhydrous silicic acid), calcium silicate, aluminum silicate, and the like, with wet silica being preferred.
The BET specific surface area (measured based on ISO 5794/1) of this wet silica is preferably 40 m ² / g or more, more preferably 80 m ² / g or more, and preferably 350 m from the viewpoint of reinforcing property. ^{It is 2} / g or less, more preferably 300 m ² / g or less. As such silica, commercially available products such as "Nipsil AQ" and "Nipsil KQ" manufactured by Tosoh Silica Co., Ltd. and "Ultrazil VN3" manufactured by Degussa Co., Ltd. can be used.
One type of silica may be used alone, or two or more types may be used in combination.
Examples of the inorganic filler other than silica include aluminum hydroxide, clay, talc, calcium carbonate, zeolite and the like.

In the present invention, it is preferable to use carbon black and silica together as a filler. In this case, the content of carbon black in the rubber composition of the present invention is a rubber component from the viewpoint of reinforcing property and low heat generation. With respect to 100 parts by mass, it is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, further preferably 15 parts by mass or more, and preferably 60 parts by mass or less, more preferably 55 parts by mass or less, further. It is preferably 50 parts by mass or less.
When carbon black and silica are used in combination, the content of silica in the rubber composition of the present invention is preferably 1 part by mass or more with respect to 100 parts by mass of the rubber component from the viewpoint of reinforcing property and low heat generation. , More preferably 3 parts by mass or more, further preferably 5 parts by mass or more, still more preferably 10 parts by mass or more, and preferably 50 parts by mass or less, more preferably 40 parts by mass or less, still more preferably 35 parts by mass. It is less than a part.

(Silane coupling agent)
When silica is used as a filler in the rubber composition of the present invention, it is preferable to add a silane coupling agent for the purpose of further improving the reinforcing property thereof.
Examples of the silane coupling agent include bis (3-triethoxysilylpropyl) tetrasulfide, bis (3-triethoxysilylpropyl) trisulfide, bis (3-triethoxysilylpropyl) disulfide, and bis (2-triethoxysilyl). Ethyl) tetrasulfide, bis (3-trimethoxysilylpropyl) tetrasulfide, bis (2-trimethoxysilylethyl) tetrasulfide, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 2-mercaptoethyltri Methoxysilane, 2-mercaptoethyltriethoxysilane, 3-trimethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-triethoxysilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, 2-triethoxysilyl Ethyl-N, N-dimethylthiocarbamoyltetrasulfide, 3-trimethoxysilylpropylbenzothiazolyl tetrasulfide, 3-triethoxysilylpropylbenzolyltetrasulfide, 3-triethoxysilylpropylmethacrylate monosulfide, 3-trimethoxy Cyrilpropyl methacrylate monosulfide, bis (3-diethoxymethylsilylpropyl) tetrasulfide, 3-mercaptopropyl dimethoxymethylsilane, dimethoxymethylsilylpropyl-N, N-dimethylthiocarbamoyltetrasulfide, dimethoxymethylsilylpropylbenzothiazolyl Examples thereof include tetrasulfide, and among these, bis (3-triethoxysilylpropyl) polysulfide and 3-trimethoxysilylpropylbenzothiaziltetrasulfide are preferable from the viewpoint of improving the reinforcing property.
These silane coupling agents may be used alone or in combination of two or more.

In the rubber composition of the present invention, the preferable blending amount of the silane coupling agent varies depending on the type of the silane coupling agent and the like, but from the viewpoint of improving the dispersibility of silica and suppressing the gelation of the rubber component, from the viewpoint of improving the dispersibility of silica. It is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, further preferably 2 parts by mass or more, and preferably 20 parts by mass or less, more preferably 15 parts by mass with respect to 100 parts by mass of silica. Hereinafter, it is more preferably 10 parts by mass or less.

[Other ingredients]
The rubber composition of the present invention may contain other additives in addition to the above-mentioned components as long as the object of the present invention is not impaired. Other additives may be appropriately selected from various additives usually used in the rubber industry, and specifically, vulcanization accelerators, antistatic agents, softeners, colorants, flame retardants, lubricants, etc. Examples thereof include foaming agents, plasticizers, processing aids, antioxidants, ultraviolet inhibitors, antistatic agents, anticoloring agents, and other compounding agents.

(Vulcanization acceleration aid)
From the viewpoint of promoting vulcanization, the rubber composition of the present invention may contain a vulcanization promoting aid such as zinc oxide and fatty acid. The fatty acid may be saturated or unsaturated, and may be linear or branched. Further, the number of carbon atoms is not particularly limited, and for example, one having 1 to 30 carbon atoms, preferably 15 to 30 carbon atoms can be used.
Specific examples of the fatty acid include cyclohexaneic acid (cyclohexanecarboxylic acid), naphthenic acid such as alkylcyclopentane having a side chain, hexanoic acid, octanoic acid, decanoic acid (including branched carboxylic acids such as neodecanoic acid), and dodecanoic acid. , Saturated fatty acids such as tetradecanoic acid, hexadecanoic acid and octadecanoic acid (stearic acid), unsaturated fatty acids such as methacrylic acid, oleic acid, linoleic acid and linolenic acid, resin acids such as rosin, tall oil acid and avietic acid. And stearic acid is preferred. These may be used alone or in combination of two or more. In the present invention, stearic acid and zinc oxide can be preferably used, and it is particularly preferable to use zinc oxide and stearic acid in combination.
The total content of these vulcanization accelerating aids in the rubber composition is not particularly limited, but from the viewpoint of kneading workability and vulcanization promotion, it is preferably 0. It is 5 parts by mass or more, more preferably 1 part by mass or more, further preferably 3 parts by mass or more, and preferably 15 parts by mass or less, more preferably 10 parts by mass or less, still more preferably 7 parts by mass or less.

(Anti-aging agent)
Examples of the antioxidant that can be used in the rubber composition of the present invention include 3C (N-isopropyl-N'-phenyl-p-phenylenediamine) and 6C [N- (1,3-dimethylbutyl) -N'-phenyl. -P-Phenylenediamine], TMDQ (2,2,4-trimethyl-1,2-dihydroquinoline polymer), AW (6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline), diphenylamine And high temperature condensates of acetone and the like.
The anti-aging agent may be used alone or in combination of two or more.
The blending amount of the antiaging agent in the rubber composition is preferably with respect to 100 parts by mass of the rubber component from the viewpoint of imparting sufficient weather resistance and ozone resistance and suppressing discoloration and deterioration of crack resistance. 0.1 part by mass or more, more preferably 0.3 part by mass or more, further preferably 1 part by mass or more, and preferably 6 parts by mass or less, more preferably 5 parts by mass or less, still more preferably 3 parts by mass. It is as follows.

The rubber composition of the present invention can be used in the production of various rubber products.
Examples of rubber products include vibration-proof rubber, seismic isolation rubber, belts such as conveyor belts, rubber crawlers, and various hoses, in addition to tires.

<Preparation of rubber composition>
The method for producing the rubber composition of the present invention is not particularly limited.
The rubber composition contains a rubber component, a cross-linking agent, a benzoic acid derivative in the present invention, and various compounding agents, and is kneaded, heated, and extruded by a Banbury mixer, a roll, an intensive mixer, a twin-screw extruder, or the like. It can be manufactured by the same.
From the viewpoint of suppressing the occurrence of vulcanization during the production of the rubber composition and improving the handleability during the production, the components contained in the rubber composition, excluding the cross-linking agent and the vulcanization accelerator, are pre-blended. It is preferable to prepare a rubber composition by mixing and mixing (first kneading step), and then blending and mixing a cross-linking agent and a vulcanization accelerator (second kneading step).

By preparing the rubber composition by the above method, vulcanization is unlikely to occur even if the first kneading step is performed under high temperature conditions, so that the rubber composition can be produced with high productivity.
The maximum temperature of the kneading temperature in the first kneading step is preferably 250 ° C. or lower, more preferably 200 ° C. or lower, still more preferably 180 ° C. or lower, from the viewpoint of suppressing thermal decomposition of each component. From the viewpoint of productivity, the kneading temperature in the first kneading step is preferably 100 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 140 ° C. or higher.
The maximum temperature of the kneading temperature in the second kneading step is preferably 150 ° C. or lower, more preferably 130 ° C. or lower, from the viewpoint of suppressing the occurrence of vulcanization during kneading. Further, from the viewpoint of productivity, the kneading temperature in the second kneading step is preferably 80 ° C. or higher, more preferably 100 ° C. or higher.

<Rubber composition for tires, rubber composition for tire tread>
The rubber composition for a tire of the present invention comprises the rubber composition of the present invention.
The rubber composition for a tire tread of the present invention comprises the rubber composition of the present invention.
Since the rubber composition of the present invention can produce a crosslinked rubber having an excellent balance between a high elastic modulus and a low tan δ, it is suitable for producing a tire, particularly a tire tread, and the rubber composition for a tire is particularly suitable for a tire. It is preferably used as a rubber composition for tread.

<Cross-linked rubber for tires>
The cross-linked rubber for a tire of the present invention is obtained by cross-linking the rubber composition for a tire of the present invention.
In the cross-linked rubber for tires, cross-linking is formed between the rubber molecules by a cross-linking agent, and in addition, pseudo-cross-linking by the benzoic acid derivative in the present invention may be formed.
The conditions for the cross-linking are not particularly limited and may be appropriately selected depending on the intended purpose, but the cross-linking temperature is preferably 120 to 200 ° C. and the cross-linking time is preferably 1 minute to 900 minutes.

<Tire tread and tires>
The tire tread and the tire of the present invention include the crosslinked rubber for a tire of the present invention.
The crosslinked rubber for a tire of the present invention is suitably used for manufacturing a tire.
The rubber composition for a tire tread of the present invention is suitably used for producing a tire tread. That is, the tire tread is obtained by cross-linking the rubber composition for tire tread of the present invention. The crosslinked rubber for tires of the present invention may be used for manufacturing a tire tread.
The application site of the crosslinked rubber for a tire of the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. For example, it may be used for the tread portion as described above, or may be suitably used for at least one member of the sidewall portion, the bead portion, the inner liner, and other reinforcing rubber portions.

Further, the tire of the present invention is not particularly limited except that the rubber composition for a tire or the rubber composition for a tire tread of the present invention is used, and can be produced according to a conventional method. That is, the rubber composition for tire tread of the present invention is extruded into a tread member at an unvulcanized stage, and is pasted and molded on a tire molding machine by a usual method to form a raw tire. The raw tire is manufactured by heating and pressurizing the raw tire in a vulcanizer. Further, as the gas to be filled in the tire, an inert gas such as nitrogen, argon or helium can be used in addition to normal air or air having an adjusted oxygen partial pressure.

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

<Examples 1 and 2 and Comparative Examples 1 to 3>
[Adjustment and cross-linking of rubber composition]
The components of the blending ratio shown in Table 1 are kneaded using a Banbury mixer to prepare a rubber composition, and further heated at 145 ° C. for 33 minutes at 145 ° C. for cross-linking (vulcanization) using a pressure-type vulcanizer to cross-link (vulcanize) the cross-linked rubber. (Vulcanized rubber) was obtained. The components shown in Table 1 are as follows.
・ NR: Natural rubber, RSS # 1
-Carbon black: Made by Tokai Carbon Co., Ltd., trade name "Seast 3", HAF, N ₂ SA = 79m ² / g
-Silica: Made by Tosoh Silica, trade name "Nipsil AQ", BET specific surface area = 205 m ² / g
・ Sulfen coupling agent: Ebonic, trade name “Si69”, bis [(3-triethoxysilyl) propyl] tetrasulfide ・ Anti-aging agent: Ouchi Shinko Kagaku Kogyo Co., Ltd., trade name “Nocrack 6C”, N-phenyl-N'-(1,3-dimethylbutyl) -p-phenylenediamine / vulcanization accelerator: manufactured by Sanshin Chemical Industry Co., Ltd., trade name "Sunceller NS-G", N- (t-butyl)- 2-Benzothiazole sulfenamide stearic acid: manufactured by Kao, trade name "Lunac S-70V",
・ Zinc oxide: manufactured by Wako Pure Chemical Industries, Ltd. ・ Sulfur: manufactured by Wako Pure Chemical Industries, Ltd.

Compound ・ pABA: p-aminobenzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)
-PAcOBA: p-acetoxybenzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd.)
・ BA: Benzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., structure below)
-PCBA: p-carboxybenzoic acid (manufactured by Tokyo Chemical Industry Co., Ltd., structure below)

〔evaluation〕
The storage elastic modulus (G'(50 ° C., 5%)) and loss tangent (tan δ (50 ° C., 5%)) were measured for the obtained crosslinked rubber.
Specifically, the obtained crosslinked rubber was subjected to a viscoelasticity measuring device "ARES-G2" (manufactured by TA Instruments) under the condition of a frequency of 10 Hz and a strain of 5% at 50 ° C. Dynamic storage elastic modulus (tensile dynamic storage elastic modulus, G'(50 ° C., 5%)) and loss tangent (tan δ (50 ° C., 5%)) were measured.
The dynamic storage elastic modulus (G') was expressed exponentially with the dynamic storage elastic modulus (G') of Comparative Example 1 as 100. The larger the value of G', the better the steering stability and wear resistance of the vehicle.
Further, regarding the loss tangent (tan δ), the loss tangent (tan δ) of Comparative Example 1 was set as 100 and displayed as an exponential notation. The smaller the value of tan δ, the lower the heat generation and the lower the rolling resistance when used in a tire.

From the results in Table 1, it was shown that a crosslinked rubber having a high dynamic storage elastic modulus (G') can be obtained by adding a compound having a specific structure.

INDUSTRIAL APPLICABILITY According to the present invention, a rubber composition for obtaining a crosslinked rubber having a high dynamic storage elastic modulus is provided, and the rubber composition and the crosslinked rubber can be applied to the production of a tire, and in particular, the production of a tire tread. It is useful for. A tire using the rubber composition or crosslinked rubber for a tire tread is expected to have excellent wear resistance, low heat generation, and excellent energy saving.

Claims (8)

Rubber components including diene rubber and
With a cross-linking agent,
A benzoic acid derivative having an amino group or an acetoxy group at least in the para position with respect to the carboxy group.
A rubber composition containing 20 to 120 parts by mass of a filler with respect to 100 parts by mass of the rubber component. The rubber composition according to claim 1, wherein the content of the benzoic acid derivative is 0.05 to 10 parts by mass with respect to 100 parts by mass of the rubber component. The cross-linking agent contains a vulcanizing agent, further contains a vulcanization accelerator, and the mass ratio (a / b) of the content (a) of the vulcanization accelerator to the content (b) of the benzoic acid derivative. The rubber composition according to claim 1 or 2, wherein the amount is 0.2 to 5.0. A rubber composition for a tire comprising the rubber composition according to any one of claims 1 to 3. A rubber composition for a tire tread comprising the rubber composition according to any one of claims 1 to 3. A cross-linked rubber for a tire obtained by cross-linking the rubber composition for a tire according to claim 4. A tire tread obtained by cross-linking the rubber composition for a tire tread according to claim 5. A tire containing the crosslinked rubber for the tire according to claim 6.