JP6135041B2 - Rubber composition and pneumatic tire - Google Patents

Description

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

In recent years, there has been a demand for reducing tire rolling resistance in order to improve fuel efficiency during vehicle travel. Therefore, a method is known in which diene rubber constituting the tread portion of the tire is mixed with silica to reduce hysteresis loss (particularly tan δ at high temperature) to reduce heat generation and reduce tire rolling resistance. Yes.
However, since silica has low affinity with diene rubbers and high cohesiveness between silicas, silica is not dispersed even if silica is simply blended with diene rubbers, reducing the rolling resistance of tires. There was a problem that could not be obtained sufficiently.

As means for solving such a problem, the present applicant, in Patent Document 1, described, “In addition to blending 5 to 100 parts by weight of silica with 100 parts by weight of diene rubber, a specific mercaptosilane (1) is added to the silica. 0.5 to 4.0% by weight of the blending amount and 0.5 to 10% by weight of the silica blending amount of the specific mercaptosilane (2) are blended at a temperature of 145 to 185 ° C. "Method for producing tire rubber composition" has been proposed ([Claim 1]).
Patent Document 1 describes that by using the rubber composition for tires produced by the above method, the hysteresis loss of the tire can be reduced and the rolling resistance can be sufficiently reduced.

JP 2010-270247 A

Under these circumstances, the present inventor examined a tire rubber composition containing a diene rubber, silica and mercaptosilane based on Patent Document 1, and found that tan δ (60 ° C.) as an index of rolling resistance was low. Although it was excellent in low rolling resistance, it was found that the scorch time was short and the scorch property (workability) was not sufficient.
In view of the above circumstances, an object of the present invention is to provide a rubber composition that is excellent in low rolling resistance and excellent in scorch properties when formed into a tire.

As a result of intensive studies on the above problems, the present inventors have blended a mercapto-based silane coupling agent and an acrylate having a specific structure, so that they have excellent low rolling resistance when made into tires, and scorch properties. The present inventors have found that a rubber composition excellent in the above can be obtained, and have reached the present invention.
That is, the present inventors have found that the above problem can be solved by the following configuration.

(1) Contains a diene rubber (A), silica (B), a mercapto silane coupling agent (C), and an acrylate (D) represented by the following formula (1),
Content of the said silica (B) is 5-150 mass parts with respect to 100 mass parts of said diene rubber (A),
The content of the mercapto-based silane coupling agent (C) is 0.1 to 15% by mass with respect to the content of the silica (B),
A rubber composition, wherein the content of the acrylate (D) is 0.01 to 10 parts by mass with respect to 100 parts by mass of the diene rubber (A).

(In the formula (1), R ¹¹ to R ¹⁵ each independently represent a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.)

(2) The mercapto-based silane coupling agent (C) is represented by the compound represented by the following formula (2) and / or the repeating unit represented by the following formula (3) and the following formula (4). The rubber composition as described in (1) above, which is a copolymer having a repeating unit.

(In formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms. R ²² represents a linear polyether group having 4 to 30 carbon atoms. R ²³ represents a hydrogen atom or a carbon atom. Represents an alkyl group having 1 to 8. R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, l represents an integer of 1 to 2, m represents an integer of 1 to 2, and n represents 0 to 1. Represents an integer, and l, m, and n satisfy the relationship of l + m + n = 3, and when R is 2, a plurality of R ²¹ may be the same or different, and m is 2. The plurality of R ²² may be the same or different.)

(In formulas (3) and (4), R ³¹ and R ⁴¹ each independently represents an alkylene group having 1 to 5 carbon atoms.
R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, or a linear or branched group. Represents a alkynylene group having 2 to 30 carbon atoms. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. A chain or branched alkynyl group having 2 to 30 carbon atoms is represented. When R ⁴² is a terminal, R ⁴² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight A chain or branched alkynyl group having 2 to 30 carbon atoms is represented.
R ³³ and R ⁴³ each independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, A linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal, or linear or branched A alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at its terminal.
R ³² and R ³³ may form a ring with R ³² and R ³³ .
R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ .
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms.
A plurality of R ³¹ , R ³² , R ³³ , R ³⁴ , R ⁴¹ , R ⁴² and R ⁴³ may be the same or different. )

(3) The rubber composition according to (1) or (2), wherein R ¹¹ in the formula (1) is a linear or branched alkyl group having 1 to 6 carbon atoms.

(4) A pneumatic tire using the rubber composition according to any one of (1) to (3) in a tire tread.

  As described below, according to the present invention, it is possible to provide a rubber composition excellent in low rolling resistance and excellent in scorch property when used as a tire, and a pneumatic tire using the rubber composition for a tire tread. it can.

It is a partial section schematic diagram of the tire showing an example of the embodiment of the pneumatic tire of the present invention.

Below, the rubber composition of this invention and the pneumatic tire using the rubber composition of this invention are demonstrated.
(Rubber composition)
The rubber composition of the present invention contains a diene rubber (A), silica (B), a mercapto silane coupling agent (C), and an acrylate (D) having a specific structure. The content is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber (A), and the content of the mercapto silane coupling agent (C) is relative to the content of the silica (B). It is a rubber composition which is 0.1-15 mass% and whose content of the said acrylate (D) is 0.01-10 mass parts with respect to 100 mass parts of said diene rubbers (A).

Generally, in a composition containing a polymer such as a rubber composition, the polymer generates radicals by the action of heat, mechanical shearing force, etc., and the generated radicals extract hydrogen from the polymer via peroxy radicals. It is thought that it changes to peroxide. Moreover, the produced | generated peroxide decomposes | disassembles and produces | generates a new radical, As a result, it is thought that a radical produces | generates in a chain.
When a radical is generated in this way, in the case of a polymer having a double bond such as a diene rubber, the cross-linking of the polymers proceeds due to the reaction between the radical and the double bond. As a result, the scorch time is shortened. The nature will decline.

Since the rubber composition of the present invention contains an acrylate having a specific structure as described above, the double bond of the acrylate captures radicals generated in the rubber composition, and further the phenol of the acrylate. Stabilizes the radicals captured by the neutral hydroxyl group. As a result, chain formation of radicals is suppressed and scorch properties are improved.
On the other hand, when the acrylate is simply blended, since the acrylate does not have a silica / polymer coupling function, the dispersibility of the silica is lowered, and the rolling resistance reduction effect due to the blending of silica cannot be sufficiently obtained. End up.
Since the rubber composition of the present invention contains a mercapto-based silane coupling agent together with the acrylate, the mercapto group improves the affinity between the rubber component and silica, improves the dispersibility of silica, and has excellent low rolling resistance. As the mercapto group acts on the phenolic hydroxyl group of the acrylate, the radical stabilizing ability of the acrylate is improved, and the amount of the acrylate does not adversely affect the rolling resistance. Is presumed to exhibit excellent scorch properties. In addition, as shown in the comparative examples described later, this is an amount that does not adversely affect the rolling resistance when the silane coupling agent that does not have a mercapto group is used. It is also inferred from the fact that there is no improvement in scorch properties.

  The diene rubber (A), silica (B), silane coupling agent (C) and acrylate (D) and other components that may be optionally contained are described in detail below.

<Diene rubber (A)>
The diene rubber (A) used in the rubber composition of the present invention is not particularly limited, and specific examples thereof include natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), aromatic vinyl-conjugated. Examples include diene copolymer rubber, acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (Br-IIR, Cl-IIR), and chloroprene rubber (CR). The diene rubber (A) may be a single diene rubber or a combination of two or more diene rubbers.

In the present invention, it is preferable to use an aromatic vinyl-conjugated diene copolymer rubber as the diene rubber (A) because an excellent tire is obtained due to wet performance and low rolling resistance. -It is more preferable to use butadiene rubber (BR) together with the conjugated diene copolymer.
Examples of the aromatic vinyl-conjugated diene copolymer rubber include styrene-butadiene copolymer rubber (SBR) and styrene-isoprene copolymer rubber. Among these, styrene-butadiene copolymer rubber (SBR) is preferable because a tire excellent in wet performance and low rolling resistance can be obtained.

The aromatic vinyl content (for example, styrene content) of the aromatic vinyl-conjugated diene copolymer is 20 to 45% by mass because both wet performance and low rolling resistance can be achieved when the tire is used. It is preferable and it is more preferable that it is 23-42 mass%.
Further, the vinyl bond content in the conjugated diene of the aromatic vinyl-conjugated diene copolymer is preferably 10 to 50% because the extrusion processability and silica dispersibility of the composition of the present invention are more excellent. More preferably, it is 25 to 48%. Here, the amount of vinyl bonds refers to the ratio of 1,2-vinyl bonds among cis-1,4-bonds, trans-1,4-bonds and 1,2-vinyl bonds, which are conjugated dienes. Say.
Further, the weight average molecular weight of the aromatic vinyl-conjugated diene copolymer is 100,000 to 1,500 because the extrusion processability of the composition of the present invention and the low rolling resistance when made into a tire can be compatible. Is preferably 1,000,000, more preferably 600,000 to 1,300,000. The weight average molecular weight (Mw) of the aromatic vinyl-conjugated diene copolymer is measured in terms of standard polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as a solvent.

The said aromatic vinyl-conjugated diene copolymer is not specifically limited about the manufacturing method, It can manufacture by a conventionally well-known method.
Moreover, the aromatic vinyl and conjugated diene as a monomer used when manufacturing the said aromatic vinyl-conjugated diene copolymer are not specifically limited.
Here, examples of the conjugated diene monomer include 1,3-butadiene, isoprene (2-methyl-1,3-butadiene), 2,3-dimethyl-1,3-butadiene, and 2-chloro-1. , 3-butadiene, 1,3-pentadiene and the like.
On the other hand, examples of the aromatic vinyl monomer include styrene, 2-methylstyrene, 3-methylstyrene, 4-methylstyrene, α-methylstyrene, 2,4-dimethylstyrene, 2,4-diisopropylstyrene, Examples include 4-tert-butylstyrene, divinylbenzene, tert-butoxystyrene, vinylbenzyldimethylamine, (4-vinylbenzyl) dimethylaminoethyl ether, N, N-dimethylaminoethylstyrene, and vinylpyridine.

In the present invention, the content in the case of using the aromatic vinyl-conjugated diene copolymer is 50% by mass or more of the diene rubber (A) because a tire excellent in low rolling resistance can be obtained. It is preferably 55% by mass or more, and more preferably 60% by mass or more.
Further, when the butadiene rubber (BR) is used in combination with the aromatic vinyl-conjugated diene copolymer, the content of the butadiene rubber (BR) makes it possible to obtain an excellent tire due to wear resistance and low rolling resistance. For the reason, it is preferably less than 50% by mass of the diene rubber (A), more preferably less than 45% by mass, and even more preferably less than 40% by mass.

<Silica (B)>
The silica (B) used in the rubber composition of the present invention is not particularly limited, and any conventionally known silica compounded in the rubber composition for use such as tires can be used.
Examples of the silica (B) include wet silica, dry silica, fumed silica, and diatomaceous earth. As the silica (B), one type of silica may be used alone, or two or more types of silica may be used in combination.
In the present invention, it is preferable that the silica (B) contains wet silica from the viewpoint of rubber reinforcement.

In the present invention, the silica (B) has a cetyltrimethylammonium bromide (CTAB) adsorption specific surface area because it is superior in mixing workability of the composition of the present invention, and wet performance and wear resistance when made into a tire. preferably 100~300m is ² / g, and more preferably 140~200m ² / g.
Here, the CTAB adsorption specific surface area is a surrogate property of the surface area that silica can be used for adsorption with the silane coupling agent, and the amount of CTAB adsorption on the silica surface is JIS K6217-3: 2001 “Part 3: Specific surface area of It is a value measured according to “How to obtain—CTAB adsorption method”.

  In the rubber composition of the present invention, the content of the silica (B) is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber (A), and a tire excellent in low rolling resistance is obtained. From the reason that the wear resistance and wet performance of the tire are also improved, it is preferably 20 to 140 parts by mass, and more preferably 35 to 130 parts by mass.

<Silane coupling agent (C)>
The silane coupling agent (C) of the present invention is a mercapto silane coupling agent and has a mercapto group and a hydrolyzable group.
Since the rubber composition of the present invention contains the silane coupling agent (C), as described above, the mercapto group improves the affinity between the rubber component and silica, improves the dispersibility of silica, and is excellent. Low rolling resistance is ensured. Moreover, the radical stabilization ability of the said acrylate (D) improves because the said mercapto group acts on the phenolic hydroxyl group of the acrylate (D) mentioned later.
Here, examples of the hydrolyzable group include an alkoxy group, a phenoxy group, a carboxyl group, and an alkenyloxy group. Among these, an alkoxy group is preferable because a tire excellent in low rolling resistance can be obtained. When the hydrolyzable group is an alkoxy group, the alkoxy group preferably has 1 to 16 carbon atoms, more preferably 1 to 4 carbon atoms. As a C1-C4 alkoxy group, a methoxy group, an ethoxy group, a propoxy group etc. are mentioned, for example.

The silane coupling agent (C) is a mercapto-based silane coupling agent having a polyether group because the scorch property of the rubber composition of the present invention is more excellent and a tire excellent in low rolling resistance can be obtained. It is preferable that
When the silane coupling agent (C) is a mercapto-based silane coupling agent having a polyether group, the polyether group protects the silica, so that the interaction between the acrylate (D) and the silica is suppressed. It becomes a rubber composition excellent in dispersibility, and exhibits excellent low rolling resistance when made into a tire.
Further, when the silane coupling agent (C) is a mercapto silane coupling agent having a polyether group, the polyether group together with the mercapto group acts on the phenolic hydroxyl group of the acrylate (D). The radical stabilizing ability of (D) is further improved, and a rubber composition having better scorch properties can be obtained.
Here, the polyether group is a group having two or more ether bonds, and specific examples thereof include groups having two or more structural units —R ^a —O—R ^b — in total. . Here, in the structural unit, R ^a and R ^b are each independently a linear or branched alkylene group, a linear or branched alkenylene group, a linear or branched alkynylene group, Alternatively, it represents a substituted or unsubstituted arylene group. Among these, a linear alkylene group is preferable because a tire excellent in low rolling resistance can be obtained.

  As a 1st suitable aspect of the said silane coupling agent (C), the compound represented by following formula (2) is mentioned.

In the above formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms. Among them, an alkoxy group having 1 to 3 carbon atoms is preferable because a tire excellent in low rolling resistance can be obtained. Examples of the alkoxy group having 1 to 3 carbon atoms include a methoxy group and an ethoxy group. A plurality of R ²¹ when l is 2 may be the same or different.
In the formula (2), R ²² represents a straight-chain polyether group having 4 to 30 carbon atoms. The polyether group is a group having two or more ether bonds, and specific examples thereof include a group having two or more structural units —R ^a —O—R ^b — in total. Definitions and preferred embodiments of R ^a and R ^b are the same as R ^a and R ^b as described above. When m is 2, the plurality of R ²² may be the same or different.
As a suitable aspect of a C4-C30 linear polyether group, group represented by following formula (5) is mentioned.

In the above formula (5), R ⁵¹ represents a linear alkyl group, a linear alkenyl group, or a linear alkynyl group, and among them, a linear alkyl group is preferable. As the linear alkyl group, a linear alkyl group having 1 to 20 carbon atoms is preferable, and a linear alkyl group having 8 to 15 carbon atoms is more preferable. Specific examples of the linear alkyl group having 8 to 15 carbon atoms include octyl group, nonyl group, decyl group, undecyl group, dodecyl group, tridecyl group and the like, and tridecyl group is particularly preferable.
In the above formula (5), R ⁵² represents a linear alkylene group, a linear alkenylene group or a linear alkynylene group, and among them, a linear alkylene group is preferable. As said linear alkylene group, a C1-C2 linear alkylene group is preferable and an ethylene group is more preferable.
In said formula (5), p represents the integer of 1-10 and it is preferable that it is 3-7.
In the above formula (5), * indicates a bonding position.

In the formula (2), R ²³ represents a hydrogen atom or an alkyl group having 1 to 8 carbon atoms.
In the above formula (2), R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, among them preferably an alkylene group having 1 to 12 carbon atoms, more preferably an alkylene group having 1 to 5 carbon atoms. Specific examples of the alkylene group having 1 to 5 carbon atoms include a methylene group, an ethylene group, and a propylene group.
In said formula (2), l represents the integer of 1-2 and it is preferable that it is 1. In said formula (2), m represents the integer of 1-2 and it is preferable that it is 2. n represents an integer of 0 to 1, and is preferably 0. l, m, and n satisfy the relationship of l + m + n = 3.

  As a 2nd suitable aspect of the said silane coupling agent (C), the copolymer which has a repeating unit represented by following formula (3) and a repeating unit represented by following formula (4) is mentioned.

In the above formulas (3) and (4), R ³¹ and R ⁴¹ each independently represent an alkylene group having 1 to 5 carbon atoms, and specific examples thereof include a methylene group, an ethylene group, and a propylene group. It is done. Of these, a propylene group is preferred. A plurality of R ³¹ and R ⁴¹ may be the same or different.
In the above formulas (3) and (4), R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, or a linear or branched carbon group having 2 to 30 carbon atoms. The alkenylene group or the linear or branched alkynylene group having 2 to 30 carbon atoms is preferable, and those having 3 to 20 carbon atoms are preferable. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. It represents a chain or branched alkynyl group having 2 to 30 carbon atoms, and among them, those having 3 to 20 carbon atoms are preferable. If R ⁴² is terminated, the definition of R ^42, specific examples and preferred embodiments are the same as above R ^32. A plurality of R ³² and R ⁴² may be the same or different.
In the above formulas (3) and (4), R ³³ and R ⁴³ are each independently a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched group. A alkenyl group having 2 to 30 carbon atoms, a linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms, and a hydroxyl group or a carboxyl group at the terminal Or a linear or branched alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal. R ⁴³ is preferably a group having a hydroxyl group at the terminal. R ³² and R ³³ may form a ring with R ³² and R ³³ . R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ . A plurality of R ³³ and R ⁴³ may be the same or different.
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms, and among them, an alkyl group having 3 to 10 carbon atoms is preferable. Specific examples of the alkyl group having 3 to 10 carbon atoms include a hexyl group, a heptyl group, and an octyl group. A plurality of R ³⁴ may be the same or different.

  The silane coupling agent (C) is excellent in the scorch and silica dispersibility of the composition of the present invention, and the above-mentioned two preferred embodiments (first) because a tire excellent in low rolling resistance can be obtained. Among the first preferred embodiment and the second preferred embodiment, the first preferred embodiment (compound represented by the above formula (2)) having a polyether group is preferable. The reason why the effect is more excellent by having a polyether group is as described above.

  In the rubber composition of the present invention, the content of the silane coupling agent (C) is 0.1 to 15% by mass with respect to the content of the silica (B), and the tire is more excellent in low rolling resistance. Is preferable, it is preferable that it is 1-14 mass%, and it is more preferable that it is 2-13 mass%.

<Acrylate (D)>
The acrylate (D) used in the rubber composition of the present invention is an acrylate represented by the following formula (1).

  Since the rubber composition of the present invention contains the acrylate (D), as described above, radicals are stabilized by the acrylate, and chain generation of radicals is suppressed. In addition, since the rubber composition of this invention contains a mercapto-type silane coupling agent (C) with the said acrylate (D) as mentioned above, the mercapto group of the said silane coupling agent is the phenol of the said acrylate (D). By acting on the functional hydroxyl group, the radical stabilizing ability of the acrylate (D) is improved, and even if the blending amount of the acrylate (D) is a specific small amount with respect to the rubber component, excellent scorch properties are exhibited.

In the above formula (1), R ¹¹ represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, tert-butyl group, 1,1-dimethylpropyl group). Among them, the scorch property of the rubber composition of the present invention is more excellent, and a tire excellent in low rolling resistance can be obtained. An alkyl group is preferable, and a methyl group is more preferable.
In the above formula (1), R ¹² and R ¹⁵ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms (for example, methyl group, ethyl group, tert-butyl group). In particular, the rubber composition of the present invention is more excellent in scorch properties and has a low rolling resistance, so that a tire excellent in low rolling resistance can be obtained. A linear or branched alkyl group is more preferable, a branched alkyl group having 1 to 6 carbon atoms is more preferable, a tert-butyl group or a 1,1-dimethylpropyl group is further preferable, and 1,1-dimethylpropyl group is more preferable. The group is particularly preferred.
In the above formula (1), R ¹³ and R ¹⁴ are each independently a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms (for example, a methyl group, an ethyl group, a tert-butyl group). In particular, the rubber composition of the present invention is more excellent in scorch properties and has a low rolling resistance, so that a tire excellent in low rolling resistance can be obtained. A linear or branched alkyl group is more preferable, a branched alkyl group having 1 to 6 carbon atoms is more preferable, and a 1,1-dimethylpropyl group is more preferable.

As a suitable aspect of the acrylate (D), for example, in the above formula (1), R ¹¹ is a hydrogen atom, R ¹² and R ¹⁵ are tert-butyl groups, and R ¹³ and R ¹⁴ are methyl groups. In addition, in the above formula (1), examples include compounds in which R ¹¹ is a methyl group, R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are 1,1-dimethylpropyl groups, among others, the rubber composition of the present invention. In the above formula (1), R ¹¹ is a methyl group, R ¹² , R ¹³ , R ^14, and R ¹⁵ are 1 for the reason that a tire having better scorch properties and lower rolling resistance can be obtained. , 1-dimethylpropyl group is preferred.

In the rubber composition of the present invention, the content of the acrylate (D) is 0.01 to 10 parts by mass with respect to 100 parts by mass of the diene rubber (A), and the scorch of the rubber composition of the present invention. From the reason that the tire is more excellent and the tire is more excellent in low rolling resistance, it is preferably 0.05 to 8 parts by mass, more preferably 0.1 to 7 parts by mass, and It is more preferable that it is 5-6 mass parts, and it is especially preferable that it is 1.5-4 mass parts.
When the content of the acrylate (D) is less than 0.01 parts by mass with respect to 100 parts by mass of the diene rubber (A), the scorch property of the resulting rubber composition becomes insufficient. Moreover, when content of the said acrylate (D) exceeds 10 mass parts with respect to 100 mass parts of said diene rubber (A), the low rolling resistance when it is set as a tire will become inadequate.

<Optional component>
If necessary, the rubber composition of the present invention may further contain an additive within a range that does not impair its effects and purposes.
Examples of the additive include a silane coupling agent other than the silane coupling agent (C) contained in the rubber composition of the present invention, a filler other than silica (B) (for example, carbon black), zinc oxide, Various additives commonly used in rubber compositions such as stearic acid, anti-aging agent, processing aid, aroma oil, liquid polymer, terpene resin, thermosetting resin, vulcanizing agent, vulcanization accelerator, etc. Can be mentioned.

<Method for producing rubber composition>
The method for producing the rubber composition of the present invention is not particularly limited, and specific examples thereof include, for example, kneading the above-described components using a known method and apparatus (for example, a Banbury mixer, a kneader, a roll, etc.). The method of doing is mentioned.
The rubber composition of the present invention can be vulcanized or crosslinked under conventionally known vulcanization or crosslinking conditions.

[Pneumatic tire]
The pneumatic tire of the present invention is a pneumatic tire using the above-described rubber composition of the present invention for a tire tread.
FIG. 1 shows a schematic partial sectional view of a tire representing an example of an embodiment of the pneumatic tire of the present invention, but the pneumatic tire of the present invention is not limited to the embodiment shown in FIG.

In FIG. 1, reference numeral 1 represents a bead portion, reference numeral 2 represents a sidewall portion, and reference numeral 3 represents a tire tread portion.
Further, a carcass layer 4 in which fiber cords are embedded is mounted between the pair of left and right bead portions 1, and the end of the carcass layer 4 extends from the inside of the tire to the outside around the bead core 5 and the bead filler 6. Wrapped and rolled up.
In the tire tread 3, a belt layer 7 is disposed over the circumference of the tire on the outside of the carcass layer 4.
Moreover, in the bead part 1, the rim cushion 8 is arrange | positioned in the part which touches a rim | limb.

  The pneumatic tire of the present invention is not particularly limited except that the rubber composition of the present invention is used for a tread of a pneumatic tire, and can be produced, for example, according to a conventionally known method. Moreover, as gas with which a tire is filled, inert gas, such as nitrogen, argon, helium other than the air which adjusted normal or oxygen partial pressure, can be used.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these.

( Reference Examples 1 to 3, Examples 4 to 7 and Comparative Examples 1 to 7)
The components shown in Table 1 below were blended in the proportions (parts by mass) shown in Table 1 below.
Specifically, first, among the components shown in Table 1 below, the components excluding sulfur and the vulcanization accelerator were mixed for 5 minutes using a 1.7 liter closed Banbury mixer, and reached 150 ± 5 ° C. Was released and cooled to room temperature to obtain a masterbatch. Furthermore, using the Banbury mixer, sulfur and a vulcanization accelerator were mixed with the obtained master batch to obtain a rubber composition.
In Table 1, regarding the amount of SBR, the upper value is the amount of SBR (oil-extended product) (unit: parts by mass), and the lower value is the net amount of SBR contained in SBR (unit: parts by mass) It is.
In the following, Examples 1 to 3 will be read as Reference Examples 1 to 3, respectively.

<Mooney viscosity>
For the prepared rubber composition (unvulcanized), Mooney was used in accordance with JIS K6300-1: 2001, using an L-shaped rotor, with a preheating time of 1 minute, a rotor rotation time of 4 minutes, and a test temperature of 100 ° C. The viscosity was measured.
The results are shown in Table 1. The results were expressed as an index with the value of Comparative Example 1 as 100. The smaller the index, the lower the viscosity and the better the workability.

<Mooney scorch> (Scorch index)
With respect to the prepared rubber composition (unvulcanized), the scorch time was measured in accordance with JIS K6300-1: 2001 using an L-shaped rotor at a test temperature of 125 ° C.
The results are shown in Table 1. The results were expressed as an index with the scorch time of Comparative Example 1 as 100. The larger the index, the longer the scorch time and the better the scorch property (workability).

<Tan δ (60 ° C.)> (Index of low rolling resistance)
The prepared rubber composition (unvulcanized) was press vulcanized at 160 ° C. for 20 minutes in a mold (15 cm × 15 cm × 0.2 cm) to prepare a vulcanized rubber sheet.
About the produced vulcanized rubber sheet, in accordance with JIS K6394: 2007, using a viscoelastic spectrometer (manufactured by Toyo Seiki Seisakusho Co., Ltd.), conditions of stretch deformation strain rate 10% ± 2%, frequency 20 Hz, temperature 60 ° C. Then, tan δ (60 ° C.) was measured.
The results are shown in Table 1. The results were expressed as an index with tan δ (60 ° C.) of Comparative Example 1 as 100. The smaller the index, the smaller the tan δ (60 ° C.), and the lower the rolling resistance when the tire is made.

<Pain effect>
The prepared rubber composition (unvulcanized) was vulcanized at 170 ° C. for 10 minutes using a strain shear stress measuring machine (RPA2000, manufactured by α-Technology Co., Ltd.), and then the strain shear modulus G having a strain of 0.28%. ′ And the strain shear modulus G ′ of 30.0% strain were measured, and the difference G′0.28 (MPa) −G′30.0 (MPa) was calculated as the Payne effect.
The results are shown in Table 1. The results were expressed as an index with the Payne effect of Comparative Example 1 as 100. A smaller index means a smaller Pain effect and better silica dispersibility.

Details of each component shown in Table 1 are as follows.
Diene rubber A1 (SBR): E581 (oil-extended product (including 37.5 parts by mass of oil-extended oil with respect to 100 parts by mass of SBR. The net content of SBR in SBR is 72.7% by mass), styrene content: 40 (Mass%, vinyl bond amount: 44%, weight average molecular weight: 1,260,000, manufactured by Asahi Kasei Corporation)
-Diene rubber A2 (BR): Nipol 1220 (manufactured by Nippon Zeon)
Silica B1: Zeosil 1165MP (CTAB adsorption specific surface area = 160 m ² / g, manufactured by Rhodia)
・ Carbon black: Seast 6 (Tokai Carbon Co., Ltd.)
Silane coupling agent C1: VP Si363 (manufactured by Evonik Degussa) (compound represented by the above formula (2). Here, R ²¹ : —OC ₂ H ₅ , R ²² : —O (C ₂ H ₄ O) ₅ —C ₁₃ H ₂₇ , R ²⁴ : — (CH ₂ ) ₃ —, l = 1, m = 2, n = 0.)
Silane coupling agent C2: NXT-Z45 (manufactured by Momentive) (a copolymer having a repeating unit represented by the above formula (3) and a repeating unit represented by the above formula (4). (The proportion of the repeating unit represented by (3) is 55 mol%, and the proportion of the repeating unit represented by the above formula (4) is 45 mol%.)
Silane coupling agent X1: VP Si69 (Evonik Degussa) (bis (3-triethoxysilylpropyl) tetrasulfide)
・ Zinc oxide: 3 types of zinc oxide (manufactured by Shodo Chemical Industry Co., Ltd.)
・ Stearic acid: Beads stearic acid (manufactured by NOF Corporation)
・ Anti-aging agent: 6PPD (manufactured by Flexis)
・ Oil: Extract No. 4 S (made by Showa Shell Sekiyu KK)
Acrylate D1: Sumilizer GM (manufactured by Sumitomo Chemical Co., Ltd.) (compound represented by the above formula (1). Here, R ¹¹ is a hydrogen atom, R ¹² and R ¹⁵ are tert-butyl groups, and R ¹³ and R ¹⁴ are Methyl group.)
Acrylate D2: Sumilizer GS (manufactured by Sumitomo Chemical Co., Ltd.) (compound represented by the above formula (1). Here, R ¹¹ is a methyl group, R ¹² , R ¹³ , R ¹⁴ and R ¹⁵ are 1,1-dimethyl. Propyl group.)
・ Methyl acrylate (Nippon Shokubai Co., Ltd.)
Radical scavenger: BHT (manufactured by Tokyo Chemical Industry Co., Ltd.) (2,6-di-tert-butyl-p-cresol)
・ Sulfur: Fine sulfur with Jinhua stamp oil (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization accelerator 1: Noxeller CZ-G (Ouchi Shinsei Chemical Co., Ltd.)
・ Vulcanization accelerator 2: Sunseller DG (manufactured by Sanshin Chemical Industry Co., Ltd.)

As can be seen from Table 1, the mercapto silane coupling agent (C) and the acrylate (C) are compared with Comparative Example 1 containing the mercapto silane coupling agent (C) but not the acrylate (D). Examples 1 to 7 containing D) showed excellent scorch properties while maintaining low rolling resistance. Among them, from the comparison of Examples 1-6, Example 4 in which R ¹¹ in the formula (1) contains an acrylate (D) is a linear or branched alkyl group having 1 to 6 carbon atoms No. 6 had a tendency to exhibit better scorch properties and better low rolling resistance. Moreover, from the comparison of Examples 1-6, the direction of Example 3 and 6 whose content of the said acrylate (D) is 1.5-4 mass parts with respect to 100 mass parts of said diene rubber (A). There was a tendency to exhibit better scorch and better low rolling resistance. Further, from comparison between Examples 5 and 7, Example 5 containing a mercapto-based silane coupling agent having a polyether group showed better scorch properties and better low rolling resistance.
On the other hand, Comparative Example 6 containing the acrylate (D) but not containing the mercapto silane coupling agent (C) (containing a non-mercapto silane coupling agent) had insufficient low rolling resistance. . Further, Comparative Example 4 containing methyl acrylate instead of acrylate (D) and Comparative Example 5 containing BHT instead of acrylate (D) had insufficient low rolling resistance. Moreover, although it contains a mercapto silane coupling agent (C) and the acrylate (D), the content of the acrylate (D) is less than 0.01 parts by mass with respect to 100 parts by mass of the diene rubber (A). In Comparative Example 2, the scorch property was insufficient. Moreover, the mercapto type | system | group silane coupling agent (C) and the said acrylate (D) are contained, but the content of the said acrylate (D) exceeds 10 mass parts with respect to 100 mass parts of said diene rubber (A). Example 3 was excellent in scorch, but low rolling resistance was insufficient.

1 Bead part 2 Side wall part 3 Tire tread part 4 Carcass layer 5 Bead core 6 Bead filler 7 Belt layer 8 Rim cushion

Claims (3)

Diene rubber (A), silica (B), mercapto silane coupling agent (C), and acrylate (D) represented by the following formula (1),
The content of the silica (B) is 5 to 150 parts by mass with respect to 100 parts by mass of the diene rubber (A),
The content of the mercapto silane coupling agent (C) is 0.1 to 15% by mass with respect to the content of the silica (B),
The rubber composition whose content of the acrylate (D) is 0.01 to 10 parts by mass with respect to 100 parts by mass of the diene rubber (A).

(In formula (1), R ¹¹ represents a methyl group. R ^{12 to} R ¹⁵ each independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 6 carbon atoms.) The mercapto-based silane coupling agent (C) is a compound represented by the following formula (2) and / or a repeating unit represented by the following formula (3) and a repeating unit represented by the following formula (4). The rubber composition according to claim 1, which is a copolymer having

(In formula (2), R ²¹ represents an alkoxy group having 1 to 8 carbon atoms. R ²² represents a linear polyether group having 4 to 30 carbon atoms. R ²³ represents a hydrogen atom or a carbon atom. Represents an alkyl group having 1 to 8. R ²⁴ represents an alkylene group having 1 to 30 carbon atoms, l represents an integer of 1 to 2, m represents an integer of 1 to 2, and n represents 0 to 1. Represents an integer, and l, m, and n satisfy the relationship of l + m + n = 3, and when R is 2, a plurality of R ²¹ may be the same or different, and m is 2. The plurality of R ²² may be the same or different.)

(In formulas (3) and (4), R ³¹ and R ⁴¹ each independently represents an alkylene group having 1 to 5 carbon atoms.
R ³² and R ⁴² are each independently a linear or branched alkylene group having 1 to 30 carbon atoms, a linear or branched alkenylene group having 2 to 30 carbon atoms, or a linear or branched group. Represents a alkynylene group having 2 to 30 carbon atoms. When R ³² is a terminal, R ³² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight chain. A chain or branched alkynyl group having 2 to 30 carbon atoms is represented. When R ⁴² is a terminal, R ⁴² is a hydrogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, or a straight A chain or branched alkynyl group having 2 to 30 carbon atoms is represented.
R ³³ and R ⁴³ each independently represents a hydrogen atom, a halogen atom, a linear or branched alkyl group having 1 to 30 carbon atoms, a linear or branched alkenyl group having 2 to 30 carbon atoms, A linear or branched alkynyl group having 2 to 30 carbon atoms, a linear or branched alkyl group having 1 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at the terminal, or linear or branched A alkenyl group having 2 to 30 carbon atoms and having a hydroxyl group or a carboxyl group at its terminal.
R ³² and R ³³ may form a ring with R ³² and R ³³ .
R ⁴² and R ⁴³ may form a ring with R ⁴² and R ⁴³ .
R ³⁴ represents an alkyl group having 1 to 13 carbon atoms.
A plurality of R ³¹ , R ³² , R ³³ , R ³⁴ , R ⁴¹ , R ⁴² and R ⁴³ may be the same or different. )   A pneumatic tire using the rubber composition according to claim 1 or 2 for a tire tread.