JPH1129658A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a pneumatic tire excellent in tire wet maneuvering stability and vibration comfortableness to drive from the initial period to the end of running by compounding a tread rubber with an SBR, a specific softener and a dithiophosphoric acid compound-based vulcanization accelerator. SOLUTION: This pneumatic tire is obtained by using a composition prepared by including (B) >=50 pts.wt. of an SBR, (C) 20-55 pts.wt. of a softener (in which 5-55 pts.wt. of the softener is a mineral oil-based softener selected from a straight and a blown asphalts, a coal tar and a pitch) and (D) 0.2-5.0 pts.wt. of a dithiophosphoric acid compound-based vulcanization accelerator selected from a metal dithiophosphate represented by formula I [R<1> and R<2> are each a 1-8C alkyl, etc.; M<1> is Zn, etc.; (n) is the valence of the metal] [e.g. a compound represented by formula II (M<2> is Zn, etc.)], an 0,0'-dialkyldithiophosphate disulfide and an 0,0'-dialkyldithiophosphate tetrasulfide in (A) 100 pts.wt. of a raw material rubber in a tread rubber.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to wet steering stability (hereinafter, simply referred to as "maneuverability") and vibration riding comfort (hereinafter, simply referred to as "ride comfort") of a tire from an early stage to a middle stage and an end stage. Pneumatic tires).

[0002]

2. Description of the Related Art In recent years, as automobiles have become higher in horsepower, higher in functionality and longer in life, tires have become highly compatible with both maneuverability and ride comfort. Is required to be maintained. In particular, in the case of passenger car tires, the bias tire is changed to a radial tire, and with the radial tire, the flatness is also changed from 82 to 70 and further to 65, and the maneuverability is greatly improved, but the riding comfort is not always improved. It is strongly demanded that both of these performances be highly compatible.

As one of the solutions, various rubber compounding agents for tire treads have been studied, but if attention is paid to vulcanization accelerators, JP-A-58-87138 discloses a specific vulcanization accelerator. It is disclosed that a rubber composition containing a specific anti-aging agent improves heat-resistant curing properties and improves the appearance of tires at the end of running. However, no studies have been made on tire performance and riding comfort. Also, Japanese Patent Application Laid-Open No. 56-1
Japanese Patent No. 39542 discloses that a rubber composition using a specific vulcanization accelerator improves sintering (scorchability) in rubber kneading, but there is no description or suggestion regarding the performance of a tire.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned facts, and an object of the present invention is to provide a pneumatic tire having excellent maneuverability and ride comfort from the beginning to the end of traveling. To provide.

[0005]

Means for Solving the Problems The present inventors have focused on polymers and various compounding agents to be compounded in tread rubber, and as a result of diligent studies, have found that the following means can solve the problems. It was completed.

That is, (1) The pneumatic tire of the present invention has a tread portion composed of two layers of a cap rubber layer disposed radially outward and a base rubber layer disposed radially inward, or a tread portion composed of one layer. In the pneumatic tire having the tread portion, at least one rubber of the cap rubber and the base rubber of the tread portion having two layers or the rubber of the tread portion having one layer has an SBR of 50 parts by weight in 100 parts by weight of the raw rubber. Contains more than parts by weight,
20 to 55 parts by weight of a softening agent is contained with respect to 100 parts by weight of the raw rubber, and 5 to 55 parts by weight of the softening agent is selected from the group consisting of straight asphalt, blown asphalt, coal tar and pitch. At least one
And a metal dithiophosphate represented by the following general formula (I), O, O'-dialkyldithiophosphate disulfide and O, O'-dialkyldithiophosphate tetrasulfide. It is characterized by comprising a rubber composition containing 0.2 to 5.0 parts by weight of at least one selected dithiophosphate compound-based vulcanization accelerator based on 100 parts by weight of the raw rubber.

[0007]

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Wherein R ¹ and R ² are each independently
Represents an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms. This alkyl group may be linear, branched or cyclic. M ¹ represents a Zn atom, an Sb atom, an Fe atom or a Cu atom, and n represents the number of valences of the metal to be bonded. (2) The metal dithiophosphate represented by the general formula (I) described in the above item (1) is preferably a dithiophosphate compound-based vulcanization accelerator represented by the following general formula (II).

[0009]

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(In the formula, M ² represents a Zn atom or an Sb atom, and n represents the number of valences of a metal to be bonded.) (3) The pneumatic tire of the present invention is disposed radially outward. In a pneumatic tire having a tread portion or a tread portion composed of two layers of a cap rubber layer and a base rubber layer disposed radially inward, the tread portion includes a cap rubber and a base of a tread portion composed of two layers. At least one of the rubbers or the rubber of the tread portion composed of one layer contains S in 100 parts by weight of the raw rubber.
BR contains 50 parts by weight or more, based on 100 parts by weight of the raw rubber, contains 20 to 55 parts by weight of a softener, and 5 to 55 parts by weight of the softener part by weight is straight asphalt;
At least one mineral oil-based softener selected from the group consisting of blown asphalt, coal tar and pitch, and each represented by the following general formulas (III), (IV), (V) and (VI) At least one benzothiazole compound-based vulcanization accelerator selected from the group consisting of
It is characterized by comprising a rubber composition containing 0.5 to 5.0 parts by weight with respect to 0 parts by weight.

[0011]

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[0012]

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[0013]

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[0014]

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(Wherein R ³ and R ⁴ are each independently
Hydrogen atom, alkyl group having 1 to 8 carbon atoms or 6 to 1 carbon atoms
Represents an aryl group of 0. However, the case where R ³ and R ⁴ are a hydrogen atom at the same time is excluded. R ⁵ represents an alkyl group, an alkenyl group or a cycloalkyl group having 1 to 8 carbon atoms, R ⁶
Represents a hydrogen atom or -N amino group represented by (R ⁷⁾ R ^8, an alkyl group or a cyclohexyl group of R ⁷ and R ⁸ are each independently a hydrogen atom or a C2-4. However, the case where R ⁷ and R ⁸ are a hydrogen atom at the same time is excluded.
R ⁹ and R ¹⁰ each independently represent an alkyl group, alkenyl group or cycloalkyl group having 1 to 8 carbon atoms. X is Z
represents n atom, an amino group represented by Cu atom or> N-R ^13, R ¹³ represents an alkyl group or a cyclohexyl group having 2 to 4 carbon atoms. R ¹¹ and R ¹² have the same meaning as R ⁹ . (4) R ³ and R ⁴ of the benzothiazole compound-based vulcanization accelerator represented by the general formula (III) described in the above item (3) each independently represent a hydrogen atom, a methyl group, an ethyl group or a phenyl group. It is preferable that R ³ and R ⁴ be a hydrogen atom at the same time.

(5) The general formula (III) described in the above item (3)
Are bis- (4-methylbenzothiazolyl-2) disulfide, bis- (5-methylbenzothiazolyl-2) disulfide, mercapto-4- It is preferably at least one selected from the group consisting of methylbenzothiazole and mercapto-5-methylbenzothiazole.

(6) The general formula (IV) described in the above item (3),
The position of the alkoxy group of the benzothiazole compound-based vulcanization accelerator represented by (V) and (VI) in the aromatic monocyclic ring is preferably the 4-position or 6-position, and more preferably the 4-position. preferable.

(7) General formula (IV) described in the above item (3),
The alkoxy group of the benzothiazole compound-based vulcanization accelerator represented by (V) and (VI) is preferably a group selected from the group consisting of a methoxy group, an ethoxy group and a butoxy group, and particularly preferably an ethoxy group. Is more preferred.

(8) The mineral oil-based softener described in the above item (1) or (3) is preferably straight asphalt or blown asphalt.

(9) The rubber composition described in the above item (1) or (3) is blended with SBR such that the styrene unit of SBR is 20% by weight or more in 100% by weight of the raw rubber. Preferably.

(10) The rubber composition according to the above item (1), (3) or (9) contains SBR having a styrene content of 30% by weight or more in 100 parts by weight of the raw rubber. Is preferred.

As described above, the present invention is particularly characterized in that a specific softener and a specific vulcanization accelerator are used in combination.

When the specific softening agent is not used in the present invention, the tire suppresses a decrease in the hardening of the tread rubber until the middle of running, but gradually hardens at the end. When the specific softener of the present invention is used in combination, that is, in the present invention, at the end of running of the tire, curing of the rubber due to transfer of the softener to another member is suppressed. For this reason, in the present invention, it is possible to suppress a decrease in maneuverability and ride comfort particularly at the end of running of the tire.

Conventionally, an aromatic oil is often used as a softening agent in a normal blending. However, the softening agent is transferred to another member (eg, a case) having a low oil content, and the softening agent is transferred to the tread rubber. Hardening occurs, which in turn reduces tire maneuverability and ride comfort. However, since the specific softener in the present invention hardly migrates to other members, it has come to a new finding that the curing of rubber can be significantly suppressed, and in combination with a specific vulcanization accelerator, excellent maneuverability and The pneumatic tire of the present invention having ride comfort is obtained.

[0025]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, at least one of the cap rubber and the base rubber of the tread portion composed of two layers or the tread portion rubber composed of one layer is contained in 100 parts by weight of raw material rubber by SBR (styrene butadiene). Rubber) must be contained in an amount of 50 parts by weight or more, preferably 70 parts by weight or more. If the blending amount of SBR is less than 50 parts by weight, the handling property and the riding comfort are inferior. As for the SBR, it is preferable to mix the SBR so that the styrene unit contained in the SBR is 20% by weight or more in 100% by weight of the raw rubber. For example, when 50 parts by weight of SBR and 50 parts by weight of natural rubber of another raw material rubber are compounded, it means that the styrene content of this SBR is 40% by weight or more.

In another embodiment, it is preferable that SBR having a styrene content of 30% by weight or more is contained in 100 parts by weight of the raw rubber. For example, when 10 parts by weight of SBR having a styrene content of 35% by weight, 40 parts by weight of SBR having a styrene content of 23.5% by weight, and 50 parts by weight of another raw rubber, natural rubber, are mixed.
Styrene units in 0% by weight are less than 20% by weight, indicating that such a blend may be used.

The SBR used in the present invention is not limited as long as it satisfies the above conditions, but commercially available emulsion-polymerized SBR, solution-polymerized SBR and the like can be used.

The raw rubber in the present invention includes, in addition to the SBR of the present invention, other SBRs, natural rubbers, synthetic rubbers such as isoprene rubber, butadiene rubber, butyl rubber (including halogenated butyl rubber), ethylene-propylene rubber and the like. Can be mentioned.

In the present invention, the total amount of the softener is 20 to 55 parts by weight based on 100 parts by weight of the raw rubber. 5 to 55 parts by weight of the softener, preferably 10 to 55 parts by weight from the viewpoint of the effect, are straight asphalt, blown asphalt (all petroleum-based), coal tar,
It is at least one mineral oil-based softener selected from the group consisting of pitch (above, coal-based). Among them, straight asphalt and / or blown asphalt are preferable from the viewpoint of the effect. If the amount of asphalt is less than 5 parts by weight, a sufficient effect cannot be obtained, and if it exceeds 55 parts by weight, workability (kneading) is deteriorated and abrasion resistance is deteriorated.

The dithiophosphate compound-based vulcanization accelerator used in one embodiment of the present invention is a metal dithiophosphate represented by the above formula (I), O, O'-dialkyldithiophosphate disulfide and O, O'- It is at least one selected from the group consisting of dialkyldithiophosphate tetrasulfide.

R ¹ and R ² of the metal dithiophosphate represented by the general formula (I) each independently have 1 to 8 carbon atoms.
An alkyl group or an aryl group having 6 to 10 carbon atoms,
This alkyl group may be linear, branched or cyclic. M ¹ is a Zn atom, Sb atom, Fe atom or Cu atom, and n is the number of valences of the metal to be bonded. Among them, R ¹ and R ² are preferably an alkyl group having 3 to 4 carbon atoms. Metal dithiophosphates having an alkyl group having 2 or less carbon atoms tend to have low solubility in rubber, and if the number of carbon atoms is 5 or more, the effect cannot be further improved. Is not always effective. As the metal, a Zn atom or an Sb atom is preferable. That is, a metal dithiophosphate represented by the formula (II) is preferable.

That is, these metal dithiophosphates include, for example, zinc O, O'-dipropyldithiophosphate, zinc O, O'-diisopropyldithiophosphate,
O'-di-n-butyl zinc dithiophosphate, O, O'-di-sec-butyl zinc dithiophosphate, O, O'-di-t
-Butyldithiophosphate, zinc O, O'-diphenyldithiophosphate, zinc O, O'-dicyclohexyldithiophosphate, antimony O, O'-dipropyldithiophosphate, antimony O, O'-diisopropyldithiophosphate, O, O Antimony '-di-n-butyldithiophosphate, antimony O, O'-di-sec-butyldithiophosphate, antimony O, O'-di-t-butyldithiophosphate, antimony O, O'-diphenyldithiophosphate
O, O'-dicyclohexylantimony antiphosphate; and the like. Among them, zinc O, O'-diisopropyldithiophosphate, zinc O, O'-di-n-butyldithiophosphate, antimony O, O'-diisopropyldithiophosphate, Antimony O, O'-di-n-butyldithiophosphate is preferred. These vulcanization accelerators can be used alone or in a mixture of two or more.

Examples of the O, O'-dialkyldithiophosphate disulfide or O, O'-dialkyldithiophosphate tetrasulfide include, for example, O, O'-dibutyldithiophosphate disulfide, O, O'-diisopropyldithiophosphate disulfide, O, O O'-dipropyldithiophosphate disulfide, O, O'-diethyldithiophosphate disulfide, O, O'-dimethyldithiophosphate disulfide, O, O'-bis (2-ethylhexyl) dithiophosphate disulfide, O, O'-bis (4-methylpentyl) dithiophosphate disulfide, O, O'-dioctadecyldithiophosphate disulfide, O, O'-dibutyldithiophosphate tetrasulfide, O, O'-diisopropyldithiophosphate tetrasulfide, O, O'-dipropyl Dithiophosphoric acid tetrasulfide, O, O′-diethyldithiophosphate tetrasulfide, O, O′-dimethyldithiophosphate tetrasulfide, O, O′-bis (2-ethylhexyl) dithiophosphate tetrasulfide, O,
O'-bis (4-methylpentyl) dithiophosphate tetrasulfide, O, O'-dioctadecyldithiophosphate tetrasulfide and the like can be mentioned. Above all, from the point of effect,
O, O'-dibutyldithiophosphoric acid tetrasulfide,
O, O'-diisopropyldithiophosphate tetrasulfide and O, O'-bis (2-ethylhexyl) dithiophosphate tetrasulfide are preferred.

The dithiophosphate compound-based vulcanization accelerator must be contained in an amount of 0.2 to 5.0 parts by weight based on 100 parts by weight of the raw rubber. If the amount is less than 0.2 parts by weight, the effect of improving the maneuverability and riding comfort after traveling is low, and even if the amount is more than 5.0 parts by weight, no further improvement in the effect is recognized, and from an economic point of view, The above increase is not effective.

The benzothiazole compound-based vulcanization accelerator used in another embodiment of the present invention has the general formula (III):
It is at least one selected from the group consisting of the compounds represented by (IV), (V) and (VI).

The above general formula (III) used in the present invention
R ^{3 of} a benzothiazole compound-based vulcanization accelerator represented by
And R ⁴ are each independently a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, except for the case where they are simultaneously a hydrogen atom. To 6 alkyl groups or 6 to 6 carbon atoms
10 aryl groups, each more preferably a hydrogen atom, a methyl group, an ethyl group or a phenyl group.

As these vulcanization accelerators, for example, 2
-Mercapto-4-methylbenzothiazole, 2-mercapto-4-ethylbenzothiazole, 2-mercapto-5-methylbenzothiazole, 2-mercapto-5
Ethyl benzothiazole, 2-mercapto-6-methylbenzothiazole, 2-mercapto-6-ethylbenzothiazole, 2-mercapto-4,5-dimethylbenzothiazole, 2-mercapto-4,5-diethylbenzothiazole, 2- Mercapto-4-phenylbenzothiazole, 2-mercapto-5-phenylbenzothiazole, 2-mercapto-6-phenylbenzothiazole,
Bis- (4-methylbenzothiazolyl-2) disulfide, bis- (4-ethylbenzothiazolyl-2) disulfide, bis- (5-methylbenzothiazolyl-)
2) disulfide, bis- (5-ethylbenzothiazolyl-2) disulfide, bis- (6-methylbenzothiazolyl-2) disulfide, bis- (6-ethylbenzothiazolyl-2) Disulfide, bis- (4
5-dimethylbenzothiazolyl-2) disulfide,
Bis- (4,5-diethylbenzothiazolyl-2) disulfide, bis- (4-phenylbenzothiazolyl-)
2) Disulfide, bis- (5-phenylbenzothiazolyl-2) disulfide, bis- (6-phenylbenzothiazolyl-2) disulfide, and the like.
Among them, bis- (4-methylbenzothiazolyl-2) disulfide, bis- (5-methylbenzothiazolyl-)
2) Disulfide, mercapto-4-methylbenzothiazole and mercapto-5-methylbenzothiazole are preferred. These vulcanization accelerators can be used alone or in a mixture of two or more.

Although the method for producing these vulcanization accelerators is not particularly limited, they can be easily produced by using, for example, JP-A-49-93361.

The general formula (IV) used in the present invention,
The benzothiazole compound-based vulcanization accelerator represented by (V) or (VI) is an alkoxy group-containing 2-mercaptobenzothiazole compound and is used alone or in a mixture of two or more.

Where R^FiveIs an alkyl group having 1 to 8 carbon atoms,
Represents an alkenyl group or a cycloalkyl group;⁶Is hydrogen
Atom or -N (R⁷) R⁸Represents an amino group represented by
R⁷And R⁸Are each independently a hydrogen atom or 2 to 2 carbon atoms
4 represents an alkyl group or a cyclohexyl group (provided that
R⁷And R⁸Are simultaneously hydrogen atoms). R
⁹And R^TenIs independently alkyl having 1 to 8 carbon atoms
Represents an alkenyl group or a cycloalkyl group. X is Z
n atom, Cu atom or> NR¹³The amino group represented by
Represents, R¹³Is an alkyl group having 2 to 4 carbon atoms or cyclohexyl
Represents a sil group. R ¹¹And R¹²Is R⁹Is synonymous with

In these general formulas, the alkoxy groups --OR ⁵ , --OR ⁹ , --OR ¹⁰ , --OR ¹¹ and --OR ¹²
Each group is preferably independently a methoxy group, an ethoxy group or a butoxy group from the viewpoint of the effect, and more preferably an ethoxy group.

Examples of the benzothiazole compound-based vulcanization accelerator represented by the general formula (IV) include 4-methoxy-2-mercaptobenzothiazole and 5-methoxy-2.
-Mercaptobenzothiazole, 6-methoxy-2-mercaptobenzothiazole, 7-methoxy-2-mercaptobenzothiazole, 4-ethoxy-2-mercaptobenzothiazole, 5-ethoxy-2-mercaptobenzothiazole, 6-ethoxy-2 -Mercaptobenzothiazole, 7-ethoxy-2-mercaptobenzothiazole, 4-butoxy-2-mercaptobenzothiazole, 5-butoxy-2-mercaptobenzothiazole,
6-butoxy-2-mercaptobenzothiazole, 7-
Butoxy-2-mercaptobenzothiazole, N-te
rt-butyl-4-methoxy-2-benzothiazolylsulfenamide, N-tert-butyl-5-methoxy-2-benzothiazolylsulfenamide, N-ter
t-butyl-6-methoxy-2-benzothiazolylsulfenamide, N-tert-butyl-7-methoxy-
2-benzothiazolylsulfenamide, N-tert
-Butyl-4-ethoxy-2-benzothiazolylsulfenamide, N-tert-butyl-5-ethoxy-2
-Benzothiazolylsulfenamide, N-tert-
Butyl-6-ethoxy-2-benzothiazolylsulfenamide, N-tert-butyl-7-ethoxy-2-
Benzothiazolylsulfenamide, N-tert-butyl-4-butoxy-2-benzothiazolylsulfenamide, N-tert-butyl-5-butoxy-2-benzothiazolylsulfenamide, N-tert-butyl -6-butoxy-2-benzothiazolylsulfenamide, N-tert-butyl-7-butoxy-2-benzothiazolylsulfenamide, N-ethyl-4-methoxy-2-benzothiazolylsulfenamide, N-ethyl-5-methoxy-2-benzothiazolylsulfenamide, N-ethyl-6-methoxy-2-benzothiazolylsulfenamide, N-ethyl-7-methoxy-2
-Benzothiazolylsulfenamide, N-ethyl-4
-Ethoxy-2-benzothiazolylsulfenamide,
N-ethyl-5-ethoxy-2-benzothiazolylsulfenamide, N-ethyl-6-ethoxy-2-benzothiazolylsulfenamide, N-ethyl-7-ethoxy-2-benzothiazolylsulfenamide , N-ethyl-4-butoxy-2-benzothiazolylsulfenamide, N-ethyl-5-butoxy-2-benzothiazolylsulfenamide, N-ethyl-6-butoxy-2-
Benzothiazolylsulfenamide, N-ethyl-7-
Butoxy-2-benzothiazolylsulfenamide, N
-Cyclohexyl-4-methoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-5-methoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-6-methoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-7-methoxy-2
-Benzothiazolylsulfenamide, N-cyclohexyl-4-ethoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-5-ethoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-
6-ethoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-7-ethoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-4-
Butoxy-2-benzothiazolylsulfenamide, N
-Cyclohexyl-5-butoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-6-butoxy-2-benzothiazolylsulfenamide, N-cyclohexyl-7-butoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-4-methoxy-2-benzothiazolylsulfenamide, N, N-
Dicyclohexyl-5-methoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-6
Methoxy-2-benzothiazolylsulfenamide,
N, N-dicyclohexyl-7-methoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-4-ethoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-5-ethoxy-2-
Benzothiazolylsulfenamide, N, N-dicyclohexyl-6-ethoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-7-ethoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl -4-butoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-5-butoxy-2-benzothiazolylsulfenamide, N,
N-dicyclohexyl-6-butoxy-2-benzothiazolylsulfenamide, N, N-dicyclohexyl-
7-butoxy-2-benzothiazolylsulfenamide; and the like.

Examples of the benzothiazole compound-based vulcanization accelerator represented by the general formula (V) include di-4-methoxy-2-benzothiazolyl disulfide and di-5-methoxy-2-benzothiazolyl. Disulfide, di-6-methoxy-2-benzothiazolyl disulfide, di-7-methoxy-2-benzothiazolyl disulfide, di-4-
Ethoxy-2-benzothiazolyl disulfide, di-5
-Ethoxy-2-benzothiazolyl disulfide, di-
6-ethoxy-2-benzothiazolyl disulfide, di-7-ethoxy-2-benzothiazolyl disulfide,
Di-4-butoxy-2-benzothiazolyl disulfide, di-5-butoxy-2-benzothiazolyl disulfide, di-6-butoxy-2-benzothiazolyl disulfide, di-7-butoxy-2- Benzothiazolyl disulfide, and the like.

Examples of the benzothiazole compound-based vulcanization accelerator represented by the general formula (VI) include zinc 4-methoxy-2-mercaptobenzothiazole, zinc 5-methoxy-2-mercaptobenzothiazole, -Methoxy-2-mercaptobenzothiazole zinc salt, 7-methoxy-2-mercaptobenzothiazole zinc salt, 4-
Ethoxy-2-mercaptobenzothiazole zinc salt, 5
-Ethoxy-2-mercaptobenzothiazole zinc salt,
6-ethoxy-2-mercaptobenzothiazole zinc salt, 7-ethoxy-2-mercaptobenzothiazole zinc salt, 4-butoxy-2-mercaptobenzothiazole zinc salt, 5-butoxy-2-mercaptobenzothiazole zinc salt, 6- Butoxy-2-mercaptobenzothiazole zinc salt, 7-butoxy-2-mercaptobenzothiazole zinc salt, 4-methoxy-2-mercaptobenzothiazole copper salt, 5-methoxy-2-mercaptobenzothiazole copper salt, 6-methoxy- 2-mercaptobenzothiazole copper salt, 7-methoxy-2-mercaptobenzothiazole copper salt, 4-ethoxy-2-mercaptobenzothiazole copper salt, 5-ethoxy-2-mercaptobenzothiazole copper salt, 6-ethoxy-2- Mercaptobenzothiazole copper salt, 7- Copper salt of toxic-2-mercaptobenzothiazole, copper salt of 4-butoxy-2-mercaptobenzothiazole, copper salt of 5-butoxy-2-mercaptobenzothiazole, copper salt of 6-butoxy-2-mercaptobenzothiazole, 7-butoxy- 2-mercaptobenzothiazole copper salt, N-ethyl- (4-methoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (5-
Methoxy-2-benzothiazolyl) sulfenimide,
N-ethyl- (6-methoxy-2-benzothiazolyl)
Sulfenimide, N-ethyl- (7-methoxy-2-
Benzothiazolyl) sulfenimide, Nt-butyl (4-methoxy-2-benzothiazolyl) sulfenimide, Nt-butyl (5-methoxy-2-benzothiazolyl) sulfenimide, Nt-butyl (6- Methoxy-2-benzothiazolyl) sulfenimide, N-
t-butyl (7-methoxy-2-benzothiazolyl) sulfenimide, N-cyclohexyl (4-methoxy-
2-benzothiazolyl) sulfenimide, N-cyclohexyl (5-methoxy-2-benzothiazolyl) sulfenimide, N-cyclohexyl (6-methoxy-2)
-Benzothiazolyl) sulfenimide, N-cyclohexyl (7-methoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (4-ethoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (5-ethoxy-2) -Benzothiazolyl) sulfenimide, N
-Ethyl- (6-ethoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (7-ethoxy-2-benzothiazolyl) sulfenimide, Nt-butyl (4-ethoxy-2-benzothiazolyl) sulfenimide , Nt-butyl (5-ethoxy-2-benzothiazolyl) sulfenimide, Nt-butyl (6-ethoxy-2-benzothiazolyl) sulfenimide, N-
t-butyl (7-ethoxy-2-benzothiazolyl) sulfenimide, N-cyclohexyl (4-ethoxy-
2-benzothiazolyl) sulfenimide, N-cyclohexyl (5-ethoxy-2-benzothiazolyl) sulfenimide, N-cyclohexyl (6-ethoxy-2)
-Benzothiazolyl) sulfenimide, N-cyclohexyl (7-ethoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (4-butoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (5-butoxy-2) -Benzothiazolyl) sulfenimide, N
-Ethyl- (6-butoxy-2-benzothiazolyl) sulfenimide, N-ethyl- (7-butoxy-2-benzothiazolyl) sulfenimide, Nt-butyl (4-butoxy-2-benzothiazolyl) sulfenimide , Nt-butyl (5-butoxy-2-benzothiazolyl) sulfenimide, Nt-butyl (6-butoxy-2-benzothiazolyl) sulfenimide, N-
t-butyl (7-butoxy-2-benzothiazolyl) sulfenimide, N-cyclohexyl (4-butoxy-
2-benzothiazolyl) sulfenimide, N-cyclohexyl (5-butoxy-2-benzothiazolyl) sulfenimide, N-cyclohexyl (6-butoxy-2)
-Benzothiazolyl) sulfenimide, N-cyclohexyl (7-butoxy-2-benzothiazolyl) sulfenimide, and the like.

Among these benzothiazole compound vulcanization accelerators, the position of the alkoxy group contained in the general formulas (IV), (V) and (VI) on the aromatic monocycle is the 4-position or the 6-position. And more preferably the 4-position. In addition, a benzothiazole compound having an alkoxy group at the 4- or 6-position of the aromatic monocycle is preferable in terms of availability of raw materials and ease of synthesis. Further, benzothiazolylsulfenamide, benzothiazolyl disulfide, and benzothiazolylsulfenimide having an alkoxy group at the 4- or 6-position of the aromatic monocycle are also preferable in view of scorch property. Further, a compound having an alkoxy group at the 4-position of the aromatic monocyclic ring is more preferable because it suppresses curing during thermal aging of the rubber composition.

The method for producing these vulcanization accelerators is not particularly limited, but they can be easily produced by using, for example, JP-A-49-93361.

The amount of the benzothiazole compound-based vulcanization accelerator used in the present invention is 0.2 to 10 parts by weight, preferably 0.5 to 5.0 parts by weight, based on 100 parts by weight of the rubber raw material. If the amount is less than 0.2 parts by weight, sufficient effects cannot be obtained. If the amount exceeds 10 parts by weight, not only no more effects can be obtained, but also workability such as scorch properties is reduced.

These vulcanization accelerators used in the present invention include, in addition to the above-mentioned general-purpose vulcanization accelerators, 2-mercaptobenzothiazolyl disulfide, Nt-butylbenzothiazolylsulfenamide, N-cyclohexyl Thiazole vulcanization accelerators such as benzothiazolyl sulfenamide and thiuram vulcanization accelerators such as tetra (2-ethylhexyl) thiuram disulfide and tetramethylthiuram disulfide can be appropriately compounded.

[0049] Carbon black, silica, zinc oxide, stearic acid, an antioxidant, W which is commonly used together with the above essential components as the rubber composition for a pneumatic tire of the present invention.
Components such as AX, a silane coupling agent, and a vulcanizing agent can be appropriately compounded as long as the effects of the present invention are not impaired.

Examples of the vulcanizing agent include sulfur. The amount of the vulcanizing agent is 0.1 to 5 parts by weight, preferably 1 to 2 parts by weight, based on 100 parts by weight of the raw rubber. If the amount is less than 0.1 part by weight, the breaking strength and abrasion resistance of the vulcanized rubber decrease, and if it exceeds 5 parts by weight, the rubber elasticity is impaired.

The rubber composition for a pneumatic tire of the present invention comprises:
It is obtained by kneading using a kneading machine such as a roll, an internal mixer, a Banbury mixer, and the like, and after forming, vulcanized and used for a tire tread and the like.

[0052]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, which should not be construed as limiting the scope of the present invention.

Various measurements were made according to the following methods. (1) Evaluation of maneuverability On a test course, the test driver comprehensively evaluated driving performance, braking performance, steering wheel responsiveness, and controllability during steering on a wet asphalt road surface using an FF4 door sedan on a FF4 door sedan. Of new tires (before running)
The maneuverability was evaluated. Further, the same tire was driven in a general market at 20,000 km and at 40,000 km, respectively, to evaluate the middle-stage maneuverability and the last-stage maneuverability.

(2) Evaluation of Riding Comfort An actual vehicle was run on a dry asphalt road surface using a FF 4-door sedan on a test course, and the overall evaluation was made based on the feeling of a test driver. This was also evaluated using new tires after running 20,000 km and after running 40,000 km.

As to the evaluation results, in both the maneuverability and the riding comfort, Examples 1 and 2 and Comparative Examples 2, 3, 4 and 5 used Comparative Example 1 as a control, and the difference from the control was ±. Shown by numerical values. The larger the value of +, the better the performance. Here, ± 0 means that the test driver cannot detect the difference in performance between the control tires, +1 means that the test driver has excellent performance to detect a significant difference in performance between the control tires, and +2 means The performance is so good that the test driver can clearly sense the performance difference, and +3 indicates that the performance is so good that the test driver can very clearly sense the performance difference. The larger the value of-, the lower the performance. -1, -2, -3
The degree of inferiority means that “excellent” is read as “inferior” in accordance with the above numerical value of +.

[Examples 1 and 2, Comparative Examples 1 to 5] Kneading and compounding were performed according to the compounding recipe shown in Table 1 below, and a tire of 195 / 60R14 size was prototyped using this tread rubber compound. Tire performance was measured. Table 1 shows the results
Shown in

[0057]

[Table 1]

The description of the numbering in the table is shown below. 1) SBR 1500 (styrene content 23.5% by weight, manufactured by Nippon Synthetic Rubber Co., Ltd.) 2) SBR 0120 (styrene content 35% by weight, 37.5% oil exhibition, manufactured by Japan Synthetic Rubber Co., Ltd.) 3) Carbon black: ISAF, SEAST 7H (Tokai Carbon Co., Ltd.) 4) TMDQ: 2,2,4-trimethyl-1,2-dihydroquinoline polymer 5) IPPD: N-isopropyl-N′-phenyl-p
-Phenylenediamine 6) Blown asphalt: Nippon Oil 10-20 Instep A blown asphalt 7) MBTS: Bis- (benzothiazolyl-2) disulfide 8) DPG: Diphenylguanidine 9) MMBTS: Bis- (4-methylbenzothiazolyl-) 2) Disulfide 10) TBBS: Nt-butyl-2-benzothiazolylsulfenamide 11) DIPDPZn: Zinc O, O'-diisopropyldithiophosphate 12) Weight% in raw rubber As shown in Table 1 In addition, the pneumatic tire of the present invention can maintain a high level of maneuverability and ride comfort until the middle and last stages of travel with respect to the maneuverability and ride comfort before traveling.

A conventional vulcanization accelerator (Comparative Example 2), a combination of an aromatic oil softener and a conventional vulcanization accelerator (Comparative Example 1), an aromatic oil softener and a vulcanization accelerator of the present invention, (Comparative Examples 3 and 4) and the combination of the asphalt softener of the present invention and the conventional vulcanization accelerator (Comparative Example 5) cannot provide sufficient effects. It is understood that excellent effects are exhibited in the present invention by the combination of the vulcanization accelerator.

[0060]

As described above, the pneumatic tire of the present invention has an excellent effect of maintaining a high level of maneuverability and ride comfort from the beginning to the middle and the end of traveling.

Claims (12)

[Claims] 1. A pneumatic tire having a tread portion composed of two layers or a tread portion composed of two layers, a cap rubber layer disposed radially outward and a base rubber layer disposed radially inward, wherein the tread portion is , At least one rubber of the cap rubber and the base rubber of the tread portion composed of two layers or the rubber of the tread portion composed of one layer, in 100 parts by weight of the raw rubber,
50 parts by weight or more of SBR, 20 to 55 parts by weight of a softening agent with respect to 100 parts by weight of raw rubber, and 5 to 55 parts by weight of the softening agent are straight asphalt, blown asphalt, and coal tar. And at least one mineral oil-based softener selected from the group consisting of: pitch, metal dithiophosphate, O, O'-dialkyldithiophosphate disulfide and O, O represented by the following general formula (I). Rubber composition containing 0.2 to 5.0 parts by weight of at least one dithiophosphate compound-based vulcanization accelerator selected from the group consisting of '-dialkyldithiophosphate tetrasulfide based on 100 parts by weight of raw rubber A pneumatic tire comprising: Embedded image (Wherein, R ¹ and R ² are each independently a C 1-8
Represents an alkyl group or an aryl group having 6 to 10 carbon atoms.
This alkyl group may be linear, branched or cyclic. M ¹ represents a Zn atom, an Sb atom, an Fe atom or a Cu atom, and n represents the number of valences of the metal to be bonded. ) 2. The method according to claim 1, wherein the metal dithiophosphate represented by the general formula (I) is a dithiophosphate compound-based vulcanization accelerator represented by the following general formula (II). Pneumatic tire. Embedded image (In the formula, M ² represents a Zn atom or an Sb atom, and n represents the number of valences of the metal to be bonded.) 3. A pneumatic tire having a tread portion composed of two layers or a tread portion composed of two layers of a cap rubber layer disposed radially outward and a base rubber layer disposed radially inward, wherein the tread portion is , At least one rubber of the cap rubber and the base rubber of the tread portion composed of two layers or the rubber of the tread portion composed of one layer, in 100 parts by weight of the raw rubber,
50 parts by weight or more of SBR, 20 to 55 parts by weight of a softening agent with respect to 100 parts by weight of raw rubber, and 5 to 55 parts by weight of the softening agent are straight asphalt, blown asphalt, and coal tar. And at least one mineral oil-based softener selected from the group consisting of pitch, and from the group consisting of the compounds represented by the following general formulas (III), (IV), (V) and (VI) A pneumatic tire comprising a rubber composition containing 0.5 to 5.0 parts by weight of at least one selected benzothiazole compound-based vulcanization accelerator based on 100 parts by weight of a raw rubber. Embedded image Embedded image Embedded image Embedded image (Wherein, R ³ and R ⁴ each independently represent a hydrogen atom, an alkyl group having 1 to 8 carbon atoms or an aryl group having 6 to 10 carbon atoms, provided that R ³ and R ⁴ are simultaneously a hydrogen atom. unless .R ⁵ represents an alkyl group having 1 to 8 carbon atoms, an alkenyl group or a cycloalkyl group, R ⁶ represents an amino group represented by hydrogen or ^{-N (R 7) R 8,} R 7 and R ⁸ each independently represent a hydrogen atom or an alkyl group or a cyclohexyl group having 2 to 4 carbon atoms. However, .R ⁹ and R ¹⁰ except when R ⁷ and R ⁸ are not hydrogen atoms at the same time
Each independently represents an alkyl group, alkenyl group or cycloalkyl group having 1 to 8 carbon atoms. X is a Zn atom, Cu
An amino group represented by atom or> N-R ^13, R ¹³ represents an alkyl group or a cyclohexyl group having 2 to 4 carbon atoms. R ¹¹ and R ¹² have the same meaning as R ⁹ . ) 4. The benzothiazole compound-based vulcanization accelerator represented by the general formula (III) according to claim 3, wherein R ³ and R ⁴ are each independently a hydrogen atom, a methyl group, an ethyl group or a phenyl group. ^4. The pneumatic tire according to claim 3, wherein the pneumatic tire is a group (except when R ³ and R ⁴ are simultaneously a hydrogen atom). 5. The benzothiazole compound-based vulcanization accelerator represented by the general formula (III) according to claim 3, wherein
(4-methylbenzothiazolyl-2) disulfide,
It is at least one selected from the group consisting of bis- (5-methylbenzothiazolyl-2) disulfide, mercapto-4-methylbenzothiazole and mercapto-5-methylbenzothiazole. 3. The pneumatic tire according to 3. 6. The general formula (IV) or (V) according to claim 3,
The pneumatic tire according to claim 3, wherein the position of the alkoxy group of the benzothiazole compound-based vulcanization accelerator represented by (VI) and the aromatic monocyclic ring is the 4-position or the 6-position. 7. The general formula (IV) or (V) according to claim 3,
4. The pneumatic tire according to claim 3, wherein the position of the alkoxy group of the benzothiazole compound-based vulcanization accelerator represented by (VI) and the aromatic monocycle is at the 4-position. 8. The general formulas (IV) and (V) according to claim 3.
The pneumatic tire according to claim 3, wherein the alkoxy group of the benzothiazole compound-based vulcanization accelerator represented by (VI) and (VI) is a group selected from the group consisting of a methoxy group, an ethoxy group and a butoxy group. . 9. The general formula (IV) or (V) according to claim 3,
The pneumatic tire according to claim 3, wherein the alkoxy group of the benzothiazole compound vulcanization accelerator represented by (VI) and (VI) is an ethoxy group. 10. The pneumatic tire according to claim 1, wherein the mineral oil softener is straight asphalt or blown asphalt. 11. The rubber composition according to claim 1, wherein the rubber composition is blended with SBR such that the styrene unit of SBR is not less than 20% by weight in 100% by weight of the raw rubber. Pneumatic tire. 12. The pneumatic tire according to claim 1, wherein the rubber composition contains SBR having a styrene content of 30% by weight or more in 100 parts by weight of the raw rubber.