JP2019147915A - Tire rubber composition and pneumatic tire including the same - Google Patents

Abstract

To solve the problems in which: a racing tire for circuit traveling is required to have a high dry grip performance; therefore, a tread rubber composition is blended with a large amount of carbon black with a small particle size; however, such a rubber composition has an adverse effect on the dry grip performance when put in a high temperature condition, and also causes a deterioration of the workability.SOLUTION: In a tire rubber composition, a rubber component 100 pts.mass is blended with 90-180 pts.mass of carbon black having a nitrogen adsorption specific surface area of 145-400 m/g; in the rubber component 100 pts.mass, a solution polymerization styrene-butadiene copolymer rubber is 25-100 pts.mass; and the solution polymerization styrene-butadiene copolymer rubber is modified with a modification compound containing at least one alkoxysilyl group and at least two nitrogen atoms in the molecule.SELECTED DRAWING: None

Description

  The present invention relates to a tire rubber composition and a pneumatic tire using the same, and more particularly, even when a large amount of carbon black having a small particle diameter is blended, excellent processability is ensured. The present invention relates to a rubber composition for tires that can achieve dry grip performance and a pneumatic tire using the same.

It is known that the grip performance of a pneumatic tire is greatly affected by the tire temperature, and sufficient grip performance cannot be obtained at low temperatures. In particular, in a racing tire for circuit running, it is required that the rubber composition constituting the tread has a property of reaching a high temperature state as soon as possible after starting running. Therefore, a large amount of carbon black having a very small particle diameter (very high nitrogen adsorption specific surface area (N ₂ SA)) is blended in the tread rubber composition. However, a rubber composition containing a large amount of carbon black has a high hardness Hs and a storage elastic modulus E ′ at a high temperature, which adversely affects dry grip performance (maneuvering stability at high speeds). Furthermore, there is a problem that the viscosity of the rubber composition is increased during kneading and the processability is deteriorated. Therefore, the present amount of carbon black with a small particle size is limited.

  On the other hand, Patent Document 1 below discloses a tire rubber composition using a solution-polymerized styrene-butadiene copolymer rubber modified with a compound represented by the following formula (A) as a rubber component.

(Wherein R ¹ , R ² and R ³ are the same or different and each represents an alkyl group, an alkoxy group, a silyloxy group, an acetal group, a carboxyl group, a mercapto group or a derivative thereof. R ⁴ and R ⁵ are (The same or different, and represents a hydrogen atom or an alkyl group. N represents an integer.)

  However, in the tire rubber composition using the solution-polymerized styrene-butadiene copolymer rubber modified with the compound represented by the following formula (A), when a large amount of carbon black having a small particle diameter is blended, There is a problem that dry grip performance and workability cannot be compatible.

JP 2017-186462 A

  Accordingly, an object of the present invention is to provide a rubber composition for a tire that can provide excellent dry grip performance while ensuring processability even when a large amount of carbon black having a small particle diameter is blended, and an air using the same. The purpose is to provide tires.

As a result of intensive studies, the present inventors have formulated the above problems by blending a specific amount of carbon black having a specific nitrogen adsorption specific surface area and a specific solution-polymerized styrene-butadiene copolymer rubber with respect to the rubber component. We have found that this can be solved, and have completed the present invention.
That is, the present invention is as follows.

1. 90 to 180 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 145 to 400 m ² / g is blended with 100 parts by mass of the rubber component. -The butadiene copolymer rubber accounts for 25 to 100 parts by mass, and the solution-polymerized styrene-butadiene copolymer rubber is modified with a modifying compound containing at least one alkoxysilyl group and at least two nitrogen atoms in the molecule. A rubber composition for tires, characterized by being made.
2. The solution-polymerized styrene-butadiene copolymer rubber is represented by any one of the following general formulas (1) to (4) and satisfies the following conditions (A ′) to (C ′): 2. The rubber composition for tires according to 1 above.

In the general formula (1), P is the solution-polymerized styrene-butadiene copolymer rubber, R ¹ and R ² represent a hydrocarbon group having 1 to 12 carbon atoms, and an unsaturated bond may exist. They may be the same or different. R ³ represents a hydrocarbon group having 1 to 20 carbon atoms, and an unsaturated bond may be present. R ⁴ , R ⁵ , R ⁶ and R ^{7 each} contain Si, O or N and represent a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with an organic group having no active hydrogen, They may be present and may be the same or different. f is an integer of 1-2, d is an integer of 1-2, e is an integer of 0-1 (however, d + e + f = 3).

In general formula (2), the definitions of P, R ¹ , R ³ , R ⁴ , d, e, and f are the same as those in general formula (1). R ⁸ and R ⁹ each represent an aliphatic hydrocarbon group having 1 to 6 carbon atoms, may have an unsaturated bond, and may be the same or different from each other. R ¹⁰ contains Si, O or N and represents a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with an organic group having no active hydrogen, and may have an unsaturated bond.

In general formula (3), the definitions of P, R ³ , R ⁴ , R ⁷ , d, e, and f are the same as in general formula (1). The definitions of R ⁸ and R ¹⁰ are the same as those in the general formula (2). R ¹¹ represents a hydrocarbon group having 1 to 6 carbon atoms.

In general formula (4), the definitions of P, R ³ , R ⁵ and R ⁶ are the same as in general formula (1). R ¹² and R ¹³ each represent a hydrocarbon group having 1 to 12 carbon atoms, an unsaturated bond may be present, and may be the same or different. R ¹⁴ and R ^{15 each} contain Si, O, or N, represent a hydrocarbon group having 1 to 20 carbon atoms that may be substituted with an organic group having no active hydrogen, and may have an unsaturated bond. Each may be the same or different.
(A ′) One or more conjugated diene polymers are bonded to one modifying group.
(B ′) has at least two nitrogen atoms and one or more alkoxysilyl groups.
(C ′) One or more alkoxy groups are bonded per silicon atom.
3. The rubber composition for tires according to 1 or 2 above, further comprising 5-70 parts by mass of a resin having a softening point of 120 ° C. or higher.
4). 4. The tire rubber composition as described in 3 above, wherein the resin having a softening point of 120 ° C. or higher is a copolymer of an α-methylstyrene derivative and indene.
5. 5. The tire rubber composition according to any one of 1 to 4, which is used for a pneumatic tire for competition.
6). The pneumatic tire which used the rubber composition for tires in any one of said 1-4 for a cap tread.
7). A pneumatic tire for competition, wherein the rubber composition for tire according to 5 is used for a cap tread.

The rubber composition of the present invention uses a solution-polymerized styrene-butadiene copolymer rubber modified with a modifying compound containing at least one alkoxysilyl group and at least two nitrogen atoms in the molecule as a rubber component. Even when carbon black having a small particle diameter of 145 to 400 m ² / g of nitrogen adsorption specific surface area (N ₂ SA) is blended in a large amount of 90 to 180 parts by mass with respect to 100 parts by mass of the rubber component, processability is ensured. However, excellent dry grip performance can be obtained.
At least two nitrogen atoms contained in the modified compound interact with the carbon black having the small particle diameter, and it becomes possible to blend the carbon black in a large amount, thereby improving the dry grip performance, It is possible to suppress an increase in viscosity at the time of kneading the rubber composition because of increasing the affinity of the rubber composition.

  Hereinafter, the present invention will be described in more detail.

(Rubber component)
The rubber component used in the present invention includes a solution-polymerized styrene-butadiene copolymer rubber, and the solution-polymerized styrene-butadiene copolymer rubber has, for example, a terminal at least one alkoxysilyl group in the molecule. And a modified compound containing at least two nitrogen atoms.
Hereinafter, the solution-polymerized styrene-butadiene copolymer rubber particularly suitable in the present invention will be described.

(Solution-polymerized styrene-butadiene copolymer rubber)
The solution-polymerized styrene-butadiene copolymer rubber particularly suitable in the present invention is represented by any one of the general formulas (1) to (4) and satisfies the following conditions (A ′) to (C ′): To do.
(A ′) One or more conjugated diene polymers are bonded to one modifying group.
(B ′) has at least two nitrogen atoms and one or more alkoxysilyl groups.
(C ′) One or more alkoxy groups are bonded per silicon atom.

As described above, in general formula (1), general formula (2), general formula (3), and general formula (4), P and R ^{1 to} R ¹⁵ each have the following definitions.

P is a solution-polymerized styrene-butadiene copolymer rubber, and R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms. The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different. The hydrocarbon group may be an acyclic hydrocarbon group or a cyclic hydrocarbon group.

R ³ is a hydrocarbon group having 1 to 20 carbon atoms, may have an unsaturated bond, and may be an acyclic hydrocarbon group or a cyclic hydrocarbon group.

R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ¹⁰ , R ¹⁴ , R ¹⁵ each contain 1 to 20 carbon atoms and may be substituted with an organic group containing no active hydrogen and containing Si, O, or N It is a hydrocarbon group.
The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different.
Furthermore, the hydrocarbon group may be an acyclic hydrocarbon group or a cyclic hydrocarbon group. The active hydrogen is hydrogen that deactivates the living terminal such as SiOH, OH, NH, and NH ₂ .
Examples of the hydrocarbon group substituted with an organic group containing Si include a trialkylsilanylalkyl group, a dialkylarylsilanylalkyl group, a triarylsilanylalkyl group, a triarylsilanylaryl group, and a dialkylalkoxysilanylalkyl. There are groups.
Examples of the hydrocarbon group substituted with an organic group containing O include an alkoxyalkyl group, an aryloxyalkyl group, and an aryloxyaryl group.
Examples of the hydrocarbon group substituted with an organic group containing N include a dialkylaminoalkyl group, an alkylarylaminoalkyl group, a diarylaminoalkyl group, and a dialkylaminoaryl group.

R ⁸ and R ⁹ are each an aliphatic hydrocarbon group having 1 to 6 carbon atoms. The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different.
R ¹¹ is a hydrocarbon group having 1 to 6 carbon atoms.
R ^12, R ¹³ is a hydrocarbon group having 1 to 12 carbon atoms. The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different. The hydrocarbon group may be an acyclic hydrocarbon group or a cyclic hydrocarbon group.

The structure of R ¹ , R ¹² , and R ¹³ is a hydrocarbon group structure in which the distance between nitrogen and silicon in the tertiary amino group is 2 to 4 carbon atoms in the predetermined general formula. It is preferable to have. Specifically, general formula (9) is more preferable.

Here, R ^{16 to} R ³³ are hydrogen or a hydrocarbon group having 1 to 5 carbon atoms, and may be the same or different.

Moreover, about the structure of R < ² >, R <^8> , R < ⁹ >, in the predetermined general formula which comprises these, the distance between nitrogen of two tertiary amino groups is C1-C3 It preferably has a certain hydrocarbon group structure, and the carbon-carbon bond may be a single bond or a double bond.
Specifically, general formula (10) is more preferable.

Here, R ^{34 to} R ⁵¹ are hydrogen or a hydrocarbon group having 1 to 5 carbon atoms, and may be the same or different.

R ¹¹ is a trivalent hydrocarbon group having 1 to 6 carbon atoms, preferably a hydrocarbon group having 1 to 4 carbon atoms.

  The solution-polymerized styrene-butadiene copolymer rubber of the present embodiment is formed by modification with, for example, the following modifying compound. Examples of the modifying compound include the following general formulas (5) to (5) to ( The low molecular compound represented by 8), or these condensates are mentioned.

Here, in the general formula (5), R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms and may have an unsaturated bond, and may be the same or different from each other. Good. R ³ is a hydrocarbon group having 1 to 20 carbon atoms and may have an unsaturated bond. R ⁴ , R ⁵ , R ⁶ and R ⁷ are each a hydrocarbon group having 1 to 20 carbon atoms which contains Si, O, or N and may be substituted with an organic group having no active hydrogen, and is unsaturated Bonds may be present and may be the same or different. i is an integer of 1 to 3.

Here, in the general formula (6), the definitions of R ¹ , R ³ and R ⁴ are the same as those in the general formula (5), and R ⁸ and R ⁹ are aliphatic hydrocarbon groups having 1 to 6 carbon atoms. In addition, unsaturated bonds may be present and may be the same or different. R ¹⁰ comprises Si, O, or N, optionally substituted with an organic group having no active hydrogen is a hydrocarbon group which may having 1 to 20 carbon atoms, unsaturated bonds may be present. i is an integer of 1 to 3.

Here, in the general formula (7), the definitions of R ³ , R ⁴ and R ⁷ are the same as those in the general formula (5), and the definitions of R ⁸ and R ¹⁰ are the same as those in the general formula (6). , R ¹¹ is a hydrocarbon group having 1 to 6 carbon atoms, and i is an integer of 1 to 3.

Here, in the general formula (8), the definitions of R ³ , R ⁵ and R ⁶ are the same as those in the general formula (5). R ¹² and R ¹³ are each a hydrocarbon group having 1 to 12 carbon atoms and may have an unsaturated bond, and may be the same or different from each other. R ¹⁴ and R ¹⁵ are each a C 1-20 hydrocarbon group that contains Si, O, or N, and may be substituted with an organic group having no active hydrogen, and an unsaturated bond is present. It may be the same or different.

As described above, in the general formula (5), the general formula (6), the general formula (7), and the general formula (8), R ¹ and R ² are hydrocarbon groups having 1 to 12 carbon atoms. An unsaturated bond may exist in the hydrogen group, and each hydrocarbon group may be the same or different. The hydrocarbon group may be an acyclic hydrocarbon group or a cyclic hydrocarbon group. R ³ is a hydrocarbon group having 1 to 20 carbon atoms, may have an unsaturated bond, and may be an acyclic hydrocarbon group or a cyclic hydrocarbon group.

In the general formula (5), general formula (6), general formula (7), and general formula (8), R ⁴ , R ⁵ , R ⁶ , R ⁷ , R ¹⁰ , R ¹⁴ , and R ¹⁵ are Si , O or N, and a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with an organic group having no active hydrogen.

The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different. Further, the hydrocarbon group may be an acyclic hydrocarbon group or a cyclic hydrocarbon group.
The active hydrogen is hydrogen that deactivates the living terminal such as SiOH, OH, NH, and NH ₂ .
Examples of the hydrocarbon group substituted with an organic group containing Si include a trialkylsilanylalkyl group, a dialkylarylsilanylalkyl group, a triarylsilanylalkyl group, a triarylsilanylaryl group, and a dialkylalkoxysilanylalkyl. There are groups.
Examples of the hydrocarbon group substituted with an organic group containing O include an alkoxyalkyl group, an aryloxyalkyl group, and an aryloxyaryl group.
Examples of the hydrocarbon group substituted with an organic group containing N include a dialkylaminoalkyl group, an alkylarylaminoalkyl group, a diarylaminoalkyl group, and a dialkylaminoaryl group.

R ⁸ and R ⁹ are each an aliphatic hydrocarbon group having 1 to 6 carbon atoms. The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different.
R ¹¹ is a hydrocarbon group having 1 to 6 carbon atoms, preferably a hydrocarbon group having 1 to 4 carbon atoms.
R ^12, R ¹³ is a hydrocarbon group having 1 to 12 carbon atoms. The hydrocarbon group may have an unsaturated bond, and each hydrocarbon group may be the same or different. The hydrocarbon group may be an acyclic hydrocarbon group or a cyclic hydrocarbon group.

Examples of the condensate of the compounds represented by the general formulas (5) to (8) include structures having SiOR ³ groups condensed with each other.

The structures of R ¹ , R ¹² and R ¹³ constituting the low molecular weight compounds represented by the general formulas (5) to (8) are tertiary amino acids in the predetermined general formulas comprising them. It is preferable that the group has a hydrocarbon group structure in which the distance between nitrogen and silicon is 2 to 4 carbon atoms.
Specifically, the general formula (9) is more preferable.

Moreover, about the structure of R < ² >, R <^8> , R < ⁹ >, in the predetermined general formula which comprises these, the distance between nitrogen of two tertiary amino groups is C1-C3 It preferably has a certain hydrocarbon group structure, and the carbon-carbon bond may be a single bond or a double bond.
Specifically, the general formula (10) is more preferable.

Examples of the compound represented by the general formula (5) include N- [2- (trialkoxysilanyl) -ethyl] -N, N ′, N′-trialkylethane-1,2-diamine, N— [2- (alkyldialkoxysilanyl) -ethyl] -N, N ′, N′-trialkylethane-1,2-diamine, N- [3- (trialkoxysilanyl) -propyl] -N, N ', N'-trialkylpropane-1,3-diamine, N- [3- (alkyldialkoxysilanyl) -propyl] -N, N', N'-trialkylpropane-1,3-diamine, N -[3- (trialkoxysilanyl) -propyl] -2, N, N ', N'-tetraalkylpropane-1,3-diamine, N- [3- (alkyldialkoxysilanyl) -propyl]- 2, N, N ′, N′-Tetraalkyl group There are pan-1,3-diamine, and specific examples thereof include the following compounds.
That is, N- [2- (trimethoxysilanyl) -ethyl] -N, N ′, N′-trimethylethane-1,2-diamine, N- [2- (dimethoxymethylsilanyl) -ethyl] -N -Ethyl-N ', N'-dimethylethane-1,2-diamine, N- [3- (trimethoxysilanyl) -propyl] -N, N', N'-trimethylpropane-1,3-diamine, N- [3- (dimethoxymethylsilanyl) -propyl] -N-ethyl-N ′, N′-dimethylpropane-1,3-diamine, N- [3- (triethoxysilanyl) -propyl] -N , N ′, N′-triethyl-2-methylpropane-1,3-diamine, N- [3- (dimethoxymethylsilanyl) -propyl] -2, N, N ′, N′-tetramethylpropane-1 , 3-diamine, N- (2-dimethylamino ester ) -N '-[2- (trimethoxysilanyl) -ethyl] -N, N'-dimethylethane-1,2-diamine, N- [2- (diethoxypropylsilanyl) -ethyl] -N '-(3-Ethoxypropyl) -N, N'-dimethylethane-1,2-diamine, N- [2- (trimethoxysilanyl) -ethyl] -N'-methoxymethyl-N, N'-dimethyl Ethane-1,2-diamine, N- [2- (trimethoxysilanyl) -ethyl] -N, N′-dimethyl-N ′-(2-trimethylsilanylethyl) -ethane-1,2-diamine, N- [2- (triethoxysilanyl) -ethyl] -N, N′-diethyl-N ′-(2-dibutylmethoxysilanylethyl) -ethane-1,2-diamine and the like can be mentioned.
A preferred compound is N- [2- (trimethoxysilanyl) -ethyl] -N, N ′, N′-trimethylethane-1,2-diamine.

Examples of the compound represented by the general formula (6) include 1- [3- (trialkoxysilanyl) -propyl] -4-alkylpiperazine, 1- [3- (alkyldialkoxysilanyl) -propyl] -4. -Alkylpiperazine, 1- [3- (trialkoxysilanyl) -propyl] -3-alkylimidazolidine, 1- [3- (alkyldialkoxysilanyl) -propyl] -3-alkylimidazolidine, 1- [ 3- (trialkoxysilanyl) -propyl] -3-alkylhexahydropyrimidine, 1- [3- (alkyldialkoxysilanyl) -propyl] -3-alkylhexahydropyrimidine, 3- [3- (trialkoxy) Silanyl) -propyl] -1-alkyl-1,2,3,4-tetrahydropyrimidine, 3- [3- (alkyldials) Kishishiraniru) - propyl] -1-alkyl-1,2,3,4 have tetrahydropyrimidine, etc., and specific examples thereof include the following compounds.
That is, 1- [3- (triethoxysilanyl) -propyl] -4-methylpiperazine, 1- [3- (diethoxyethylsilanyl) -propyl] -4-methylpiperazine, 1- [3- (tri Methoxysilanyl) -propyl] -3-methylimidazolidine, 1- [3- (diethoxyethylsilanyl) -propyl] -3-ethylimidazolidine, 1- [3- (triethoxysilanyl) -propyl] -3-methylhexahydropyrimidine, 1- [3- (dimethoxymethylsilanyl) -propyl] -3-methylhexahydropyrimidine, 3- [3- (tributoxysilanyl) -propyl] -1-methyl-1 , 2,3,4-tetrahydropyrimidine, 3- [3- (dimethoxymethylsilanyl) -propyl] -1-ethyl-1,2,3,4-tetrahydro Limidine, 1- (2-ethoxyethyl) -3- [3- (trimethoxysilanyl) -propyl] -imidazolidine, (2- {3- [3- (trimethoxysilanyl) -propyl] -tetrahydropyrimidine -1-yl} -ethyl) dimethylamine and the like.
A preferred compound is 1- [3- (triethoxysilanyl) -propyl] -4-methylpiperazine.

Examples of the compound represented by the general formula (7) include 2- (trialkoxysilanyl) -1,3-dialkylimidazolidine, 2- (alkyldialkoxysilanyl) -1,3-dialkylimidazolidine, 2- (trialkoxysilanyl) -1,4-dialkylpiperazine, 2- (alkyldialkoxysilanyl) -1,4-dialkylpiperazine, 5- (trialkoxysilanyl) -1,3-dialkylhexahydropyrimidine , 5- (alkyl dialkoxysilanyl) -1,3-dialkylhexahydropyrimidine and the like, and specifically include the following compounds.
That is, 2- (trimethoxysilanyl) -1,3-dimethylimidazolidine, 2- (diethoxyethylsilanyl) -1,3-diethylimidazolidine, 2- (triethoxysilanyl) -1,4- Diethylpiperazine, 2- (dimethoxymethylsilanyl) -1,4-dimethylpiperazine, 5- (triethoxysilanyl) -1,3-dipropylhexahydropyrimidine, 5- (diethoxyethylsilanyl) -1, 3-diethylhexahydropyrimidine, {2- [3- (2-dimethylaminoethyl) -2- (ethyldimethoxysilanyl) -imidazolidin-1-yl] -ethyl} -dimethylamine, 5- (trimethoxysila Nyl) -1,3-bis- (2-methoxyethyl) -hexahydropyrimidine, 5- (ethyldimethoxysilanyl) -1,3 Bis - trimethylsilanyl hexahydropyrimidine and the like.
A preferred compound is 2- (trimethoxysilanyl) -1,3-dimethylimidazolidine.

Examples of the compound represented by the general formula (8) include bis- (3-dialkylaminopropyl) -dialkoxysilane, bis-[(3-dialkylamino-3-methyl) propyl] -dialkoxysilane, and the like. Specific examples include the following compounds.
That is, bis- (3-dimethylaminopropyl) -dimethoxysilane, bis- (3-ethylmethylaminopropyl) -diethoxysilane, bis-[(3-dimethylamino-3-methyl) propyl] -dimethoxysilane, bis -[(3-ethylmethylamino-3-methyl) propyl] -dimethoxysilane and the like.
A preferred compound is bis- (3-dimethylaminopropyl) -dimethoxysilane.

  The above-mentioned compounds can be reacted alone or in combination of two or more with the active terminal of the solution polymerized styrene-butadiene copolymer rubber. Furthermore, these compounds can be reacted alone or in combination of two or more with the active terminal of the solution-polymerized styrene-butadiene copolymer rubber as a condensate.

  The weight average molecular weight in terms of polystyrene of the solution-polymerized styrene-butadiene copolymer rubber is controlled according to the use and purpose, but is preferably 100,000 to 2,000,000 in view of processability and physical properties. Further, when the solution-polymerized styrene-butadiene copolymer rubber is non-oil extended, it is more preferably 200,000 to 1,000,000. The molecular weight distribution (Mw / Mn) is preferably 1 to 3, more preferably 1.1 to 2.5. When the solution-polymerized styrene-butadiene copolymer rubber is non-oil extended, it is more preferably 1.1 to 2.0.

  The conjugated diene polymer constituting the solution-polymerized styrene-butadiene copolymer rubber of the present embodiment has a vinyl bond amount (1,2-bond amount and / or 3,4-bond amount) of 10% to 90% is preferred. Furthermore, from the viewpoints of mechanical strength, wear resistance, etc., it is preferably 20% to 70%.

The solution-polymerized styrene-butadiene copolymer rubber used in the present invention can be obtained by reacting a modified compound as described above with an unmodified active end. A specific manufacturing method is known and disclosed in, for example, Japanese Patent Application Laid-Open No. 2013-82841.
Moreover, as the solution-polymerized styrene-butadiene copolymer rubber used in the present invention, commercially available ones can be used, and examples thereof include trade names F3420 and F3440 manufactured by Asahi Kasei Chemicals Corporation.

In the present invention, it is necessary that the solution polymerized styrene-butadiene copolymer rubber occupies 25 to 100 parts by mass in 100 parts by mass of the rubber component. When the solution-polymerized styrene-butadiene copolymer rubber is less than 25 parts by mass, when a large amount of carbon black having a small particle diameter is blended, the dry grip performance cannot be improved while ensuring processability.
The solution polymerized styrene-butadiene copolymer rubber preferably occupies 30 to 100 parts by mass in 100 parts by mass of the rubber component.
Other rubber components typically include diene rubbers such as natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene butadiene rubber (SBR), and acrylonitrile-butadiene copolymer. Examples include polymer rubber (NBR), ethylene-propylene-diene terpolymer (EPDM), and the like. These may be used alone or in combination of two or more. The molecular weight and microstructure are not particularly limited, and may be terminally modified with an amine, amide, silyl, alkoxysilyl, carboxyl, hydroxyl group or the like, or may be epoxidized.

(Carbon black)
Carbon black used in the present invention, from the viewpoint of increasing the dry grip performance, the nitrogen adsorption specific surface area _(N 2 SA) is required to be 145~400m ² / g, 160~380m ² / It is preferable that it is g, and it is more preferable that it is 180-360 m < ² > / g.
The nitrogen adsorption specific surface area (N ₂ SA) is determined according to JIS K6217-2.

  The compounding quantity of carbon black is 90-180 mass parts with respect to 100 mass parts of rubber components, 100-170 mass parts is preferable, and 110-165 mass parts is more preferable. If the blending amount of carbon black is less than 90 parts by mass, the dry grip performance cannot be improved, and if it exceeds 180 parts by mass, the workability deteriorates.

(resin)
The rubber composition for tires of the present invention preferably contains a resin having a softening point of 120 ° C. or higher. By blending such a resin, there is an effect of improving the grip resulting from the adhesiveness.
The softening point of the resin is more preferably 120 to 180 ° C.
In addition, the softening point of resin shall be measured based on JISK6220-1 (ring ball method).
Examples of resins having a softening point of 120 ° C. or higher include natural resins such as terpene resins and rosin resins, synthetic resins such as petroleum resins, coal resins, phenol resins, and xylene resins, aromatic modified terpene resins, and the like. Examples include α-methylstyrene derivatives and indene copolymers. In the present invention, from the viewpoint of further improving dry grip performance and processability, it is preferable to add an α-methylstyrene derivative and an indene copolymer. . Hereinafter, the α-methylstyrene derivative and indene copolymer will be described.

(Copolymer of α-methylstyrene derivative and indene)
The α-methylstyrene derivative can have the following general formula (I):

(In formula (I), R represents an alkyl group having 1 to 3 carbon atoms.)

  In the above general formula (I), R is methyl, ethyl, n-propyl or isopropyl, preferably methyl. The α-methylstyrene derivative and indene copolymer can be copolymerized by a commonly used method. Moreover, what is marketed can also be utilized, for example, Mitsui Chemicals, Inc. FMR0150 etc. are mentioned.

  The amount of the resin having a softening point of 120 ° C. or higher or the copolymer is preferably 5 to 70 parts by mass, and more preferably 7 to 60 parts by mass with respect to 100 parts by mass of the rubber component.

(Other ingredients)
In the rubber composition of the present invention, in addition to the above-described components, a vulcanization or crosslinking agent; a vulcanization or crosslinking accelerator; various fillers such as zinc oxide, silica, clay, talc, calcium carbonate; silane coupling Various additives that are generally blended in rubber compositions such as an anti-aging agent and a plasticizer can be blended, and these additives are kneaded by a general method to form a composition, vulcanized or Can be used to crosslink. The blending amounts of these additives can be set to conventional general blending amounts as long as the object of the present invention is not violated.

  The rubber composition of the present invention is suitable for producing a pneumatic tire according to a conventional method for producing a pneumatic tire, and is preferably applied to a cap tread, particularly a cap tread of a pneumatic tire for competition.

  EXAMPLES Hereinafter, although an Example and a comparative example further demonstrate this invention, this invention is not restrict | limited to the following example.

Examples 1-5 and Comparative Examples 1-8
Preparation of Sample In the formulation (parts by mass) shown in Table 1, the components other than the vulcanization accelerator and sulfur were kneaded for 5 minutes with a 1.8 liter closed Banbury mixer, and then the kneaded product was discharged out of the mixer at room temperature. Allow to cool. Thereafter, in the same Banbury mixer, a vulcanization accelerator and sulfur were added and further kneaded to obtain an unvulcanized rubber composition.

After vulcanizing the unvulcanized rubber obtained above, a pneumatic tire having a tire size of 225 / 40R18 was manufactured using the rubber composition in the tire tread portion. The dry grip performance of these pneumatic tires was evaluated by the following method.
Dry grip performance: The pneumatic tires obtained are assembled on rims of size 18 x 8 J, filled with air pressure of 240 kPa, mounted on four wheels of the test vehicle, and the test driver is on a dry circuit track (approximately 2 km per lap) ) For 10 laps continuously, the lap time for each lap was measured. The obtained result calculated the reciprocal number of average lap time. The results are shown as an index with the value of Comparative Example 1 being 100. The larger the index, the better the dry grip performance.

Mooney viscosity _{(ML 1 + 4, 100 ℃} ): unvulcanized rubber composition, JIS K6300-1: according to 2013, was measured Mooney viscosity _{(ML 1 + 4, 100 ℃} ). The results are shown as an index with the value of Comparative Example 1 being 100. The smaller the index, the lower the viscosity of the rubber and the better the processability. If the Mooney viscosity (ML _{1 + 4} , 100 ° C.) is 150 or more, it can be determined that there is no practical workability.
The results are also shown in Table 1.

* 1: SBR1 (Nipol 1749 manufactured by Nippon Zeon Co., Ltd., oil-extended E-SBR, oil-extended amount = 50 parts by mass with respect to 100 parts by mass of SBR, styrene content = 40%)
* 2: SBR2 (E581, manufactured by Asahi Kasei Corporation, oil-extended S-SBR, oil-extended amount = 37.5 parts by mass with respect to 100 parts by mass of SBR, styrene amount = 37%, vinyl amount = 43%)
* 3: SBR3 (Asahi Kasei Co., Ltd. F3440, oil-extended S-SBR, oil-extended amount = 37.5 parts by mass with respect to 100 parts by mass of SBR, styrene content = 37%, vinyl content = 43%)
* 4: Aroma oil (Extract No. 4 S manufactured by Showa Shell Sekiyu KK)
* 5: Aromatic modified terpene resin (TO-125 manufactured by Yasuhara Chemical Co., Ltd., softening point = 125 ° C., molecular weight = 1300)
* 6: α-methylstyrene indene resin (FMR0150 manufactured by Mitsui Chemicals, Copolymer of α-methylstyrene derivative and indene, softening point = 145 ° C., molecular weight = 2000)
* 7: Carbon Black 1 (Tokai Carbon Co., Ltd. Seest 9, Nitrogen adsorption specific surface area (N ₂ SA) = 142 m ² / g)
* 8: Carbon black 2 (Birla CD1919, nitrogen adsorption specific surface area (N ₂ SA) = 340 m ² / g)
* 9: Zinc Hana (Zinc Oxide, manufactured by Shodo Chemical Industry Co., Ltd.)
* 10: Stearic acid (industrial stearic acid N manufactured by Chiba Fatty Acid Co., Ltd.)
* 11: Anti-aging agent (Seiko Chemical Co., Ltd. Ozonon 6C)
* 12: Sulfur (Tsurumi Chemical Co., Ltd. Jinhua Indian Oil Fine Powdered Sulfur)
* 13: Vulcanization accelerator (Noxeller CZ-G manufactured by Ouchi Shinsei Chemical Co., Ltd.)
* 14: SBR4 (HPR355 manufactured by JSR Corporation (modified S-SBR, amount of bound styrene: 21% by mass, coupled with alkoxysilane, introduced at the end, modified with the compound represented by the formula (A) (formula ( 1) R ¹ = methoxy group, R ² = methoxy group, R ³ = methoxy group, R ⁴ = hydrogen atom, R ⁵ = hydrogen atom, n = 3))

From the results of Table 1, the rubber composition of the example ranges from 90 to 180 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 145 to 400 m ² / g with respect to 100 parts by mass of the rubber component. And, since the specific solution-polymerized styrene-butadiene copolymer rubber occupies 25 to 100 parts by mass in 100 parts by mass of the rubber component, a large amount of carbon black having a small particle diameter is blended. In addition, it suppresses the increase in viscosity to ensure processability and exhibits excellent dry grip performance. In particular, in Examples 2 and 3 using a copolymer of α-methylstyrene derivative and indene, the improvement in dry grip performance is remarkable.
On the other hand, Comparative Example 2 is an example in which the SBR used in Comparative Example 1 is changed to S-SBR, and there is not much change in dry grip performance and workability.
In Comparative Example 3, since the nitrogen adsorption specific surface area (N ₂ SA) of the carbon black is less than the lower limit specified in the present invention, the dry grip performance and workability are not so changed.
Comparative Example 4 was an example in which the carbon black used in the rubber composition of Comparative Example 1 was reduced in particle size, and the processability deteriorated.
Since the compounding quantity of the specific solution polymerization styrene-butadiene copolymer rubber used by this invention is less than the minimum prescribed | regulated by this invention, the comparative example 5 deteriorated workability.
In Comparative Example 6, since the carbon black content exceeds the upper limit specified in the present invention, even if the amount of the aroma oil is increased, the workability deteriorates and the vulcanized rubber test piece cannot be prepared. It was.
In Comparative Example 7, since the carbon black content was less than the lower limit specified in the present invention, the dry grip performance deteriorated.
Since Comparative Example 8 is an example using a solution-polymerized styrene-butadiene copolymer rubber modified with the compound represented by the formula (A) described in Patent Document 1 as a rubber component, the processability is Not only is it worse, but there is not much change in dry grip performance.

Claims (7)

90 to 180 parts by mass of carbon black having a nitrogen adsorption specific surface area (N ₂ SA) of 145 to 400 m ² / g with respect to 100 parts by mass of the rubber component,
In 100 parts by mass of the rubber component, 25-100 parts by mass of solution-polymerized styrene-butadiene copolymer rubber occupies at least one alkoxysilyl group in the molecule and at least A rubber composition for tires, which is modified with a modifying compound containing two nitrogen atoms. The solution-polymerized styrene-butadiene copolymer rubber is represented by any one of the following general formulas (1) to (4) and satisfies the following conditions (A ′) to (C ′): The tire rubber composition according to claim 1.

In the general formula (1), P is the solution-polymerized styrene-butadiene copolymer rubber, R ¹ and R ² represent a hydrocarbon group having 1 to 12 carbon atoms, and an unsaturated bond may exist. They may be the same or different. R ³ represents a hydrocarbon group having 1 to 20 carbon atoms, and an unsaturated bond may be present. R ⁴ , R ⁵ , R ⁶ and R ^{7 each} contain Si, O or N and represent a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with an organic group having no active hydrogen, They may be present and may be the same or different. f is an integer of 1-2, d is an integer of 1-2, e is an integer of 0-1 (however, d + e + f = 3).

In general formula (2), the definitions of P, R ¹ , R ³ , R ⁴ , d, e, and f are the same as those in general formula (1). R ⁸ and R ⁹ each represent an aliphatic hydrocarbon group having 1 to 6 carbon atoms, may have an unsaturated bond, and may be the same or different from each other. R ¹⁰ contains Si, O or N and represents a hydrocarbon group having 1 to 20 carbon atoms which may be substituted with an organic group having no active hydrogen, and may have an unsaturated bond.

In general formula (3), the definitions of P, R ³ , R ⁴ , R ⁷ , d, e, and f are the same as in general formula (1). The definitions of R ⁸ and R ¹⁰ are the same as those in the general formula (2). R ¹¹ represents a hydrocarbon group having 1 to 6 carbon atoms.

In general formula (4), the definitions of P, R ³ , R ⁵ and R ⁶ are the same as in general formula (1). R ¹² and R ¹³ each represent a hydrocarbon group having 1 to 12 carbon atoms, an unsaturated bond may be present, and may be the same or different. R ¹⁴ and R ^{15 each} contain Si, O, or N, represent a hydrocarbon group having 1 to 20 carbon atoms that may be substituted with an organic group having no active hydrogen, and may have an unsaturated bond. Each may be the same or different.
(A ′) One or more conjugated diene polymers are bonded to one modifying group.
(B ′) has at least two nitrogen atoms and one or more alkoxysilyl groups.
(C ′) One or more alkoxy groups are bonded per silicon atom.   The tire rubber composition according to claim 1 or 2, further comprising 5-70 parts by mass of a resin having a softening point of 120 ° C or higher.   The rubber composition for tire according to claim 3, wherein the resin having a softening point of 120 ° C or higher is a copolymer of an α-methylstyrene derivative and indene.   The tire rubber composition according to any one of claims 1 to 4, which is used for a pneumatic tire for competition.   The pneumatic tire which used the rubber composition for tires in any one of Claims 1-4 for cap tread.   A pneumatic tire for competition, wherein the rubber composition for tire according to claim 5 is used for a cap tread.