JPH1077363A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject tire improved in both abrasion resistance and WET performance after a travel and capable of exhibiting good performances by using a specific rubber composition for a tire tread rubber. SOLUTION: This pneumatic tire is provided with a tread part. A rubber composition composing the tread part contains (A) >=70wt.% of a conjugated diene/vinyl aromatic hydrocarbon copolymer, (B) carbon black in an amount of 45-110 pts.wt. per 100 pts.wt. of the rubber component, and (C) a vulcanization accelerator of formula I or II (R<1> , R<2> are each independently H, an alkyl, an aryl, except the case wherein R<1> and R<2> are each simultaneously H) in an amount of 0.5-5.0 pts.wt. per 100 pts.wt. of the rubber component in the rubber component. The component B has a nitrogen adsorption specific surface area (N2 SA) of 100-160m<2> /g and a dibutyl phthalate(DBP) adsorbing amount of 120-200cm<3> /100g. Thereby, the tire is improved so as to be suitably used as a radial tire for a passenger car.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic tire, and more particularly, to a pneumatic tire using a specific rubber composition for a tire tread, which exhibits good performance while improving abrasion resistance after running and improving wettability. The present invention relates to a pneumatic tire suitable for a radial tire for a passenger car.

2. Description of the Related Art Hitherto, it has been known that the use of a high-structure carbon black in a rubber composition for a tire tread makes it possible to improve both the wear resistance and the wettability of a tire. However, there is a need for further improvement in wear resistance in the market, and according to the conventional method of adding the specific carbon black, when the addition amount is increased in order to improve wear resistance, the breaking energy after traveling decreases. It was difficult to further improve wear resistance. After further running, W
There is a problem such as a decrease in ET performance, and it is insufficient for maintaining performance over time. Japanese Patent Application Laid-Open No. 58-87138 discloses that a rubber composition is used in combination with a specific antioxidant and a vulcanization accelerator to suppress aging of tread / side rubber and improve terminal appearance. It has been proposed that the W after driving
The ET performance improvement was unknown. In addition, Japanese Unexamined Patent Publication No.
No. 6-139542 proposes a specific vulcanization accelerator,
It is described that the use of the rubber composition improves the processability of the rubber composition, but a tire using the rubber composition has not been studied. On the other hand, an effective vulcanization method (EV vulcanization system) is known as a method of suppressing the curing of rubber, but the effect of suppressing the curing is not sufficient, and on the contrary, the fracture energy after initial and aging is reduced. This is not preferable from the viewpoint of tire durability. Here, the breaking energy is an integrated value of the stress-strain curve.

As described above, an object of the present invention is to improve abrasion resistance and WET performance after running by improving a tread rubber composition for a pneumatic tire which could not be achieved by the prior art. It is also to obtain an improved pneumatic tire at the same time.

According to the pneumatic tire of the present invention, the rubber component contains 70% by weight or more of a conjugated diene / vinyl aromatic hydrocarbon copolymer and carbon black with respect to 100 parts by weight of the rubber component. A rubber composition containing 45 to 110 parts by weight, and 0.5 to 5.0 parts by weight of a vulcanization accelerator represented by the following general formula based on 100 parts by weight of the rubber component, as a tread rubber; The carbon black has a nitrogen adsorption specific surface area (hereinafter, referred to as N ₂ SA) of 100.
~ 160 m ² / g, and dibutyl phthalate (hereinafter, referred to as
Referred to as DBP) oil absorption amount 120~200cm ^3/10
0 g.

Embedded image In the above formula, R ¹ and R ² are each independently a hydrogen atom,
Represents an alkyl group or an aryl group, except when R ¹ and R ² are both hydrogen atoms. Where R ¹ , R
It is preferred that ² each independently represent a hydrogen atom, a methyl group, an ethyl group or a phenyl group. Also,
Specific examples of the vulcanization accelerator include mercapto-4
Methylbenzothiazole, mercapto-5-methylbenzothiazole, bis (4-methylbenzothiazolyl-
It is preferably at least one selected from the group consisting of 2) -disulfide and bis (5-methylbenzothiazolyl-2) -disulfide.

BEST MODE FOR CARRYING OUT THE INVENTION The pneumatic tire according to the present invention comprises, as a rubber composition for a tread rubber, 70% by weight or more of a conjugated diene / vinyl aromatic hydrocarbon copolymer and carbon black in a rubber component. 45 to 110 parts by weight per 100 parts by weight of the component, and 0.1 to 100 parts by weight of the vulcanization accelerator represented by the above general formula in the rubber component.
It contains 5 to 5.0 parts by weight. Here, the rubber component, which is the main material of the rubber composition, will be described. Here, the rubber component needs to contain 70% by weight or more of the conjugated diene / vinyl aromatic hydrocarbon copolymer. If the content of the conjugated diene / vinyl aromatic hydrocarbon copolymer is less than 70% by weight with respect to the rubber composition, the intended steering performance cannot be obtained, and especially the initial WET performance is reduced. Not preferred. In the present invention, the rubber component used as the main material of the rubber composition for a tire tread is a conjugated diene / vinyl aromatic hydrocarbon copolymer obtained by copolymerizing a vinyl aromatic hydrocarbon monomer and a conjugated diene monomer. Conjugated diene monomer, of which 4 to 12 carbon atoms per molecule.
And preferably 4 to 8 conjugated diene hydrocarbons. Specifically, for example, 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene,
Examples thereof include 1,3-pentadiene and octadiene.
These may be used alone or in combination of two or more. In particular, it is preferable to use a 1,3-butadiene monomer having excellent abrasion resistance and the like. As the vinyl aromatic hydrocarbon monomer copolymerized with the conjugated diene monomer, styrene,
α-methylstyrene, p-methylstyrene, o-methylstyrene, p-butylstyrene, vinylnaphthalene and derivatives thereof are included, and styrene is particularly preferred.
The method for producing the conjugated diene / vinyl aromatic hydrocarbon copolymer used in the present invention is not particularly limited, but the conjugated diene monomer may be prepared by a solution polymerization method, an emulsion polymerization method, a suspension polymerization method, or the like using an organolithium catalyst or the like. And a method of copolymerizing a vinyl aromatic hydrocarbon monomer with a vinyl aromatic hydrocarbon monomer.
As the copolymer, a butadiene / styrene copolymer (hereinafter, appropriately referred to as S) having excellent abrasion resistance and aging resistance, etc.
BR). The microstructure (cis-1,4 bond, trans-1,4 bond, vinyl bond) of the butadiene portion in the butadiene / styrene copolymer is not particularly limited, but is usually within the range obtainable with an organolithium catalyst system. Can take. The composition of the conjugated diene / vinyl aromatic hydrocarbon copolymer, for example, SBR is not particularly limited, but a weight ratio of 30/70 to 80/20 is preferable. If the vinyl aromatic hydrocarbon content is less than 20%,
It is not preferable because sufficient grip performance in wet and dry conditions cannot be obtained. The composition distribution of the conjugated diene / vinyl aromatic hydrocarbon copolymer can have a random structure, a block structure or an intermediate structure, but a random structure or an intermediate structure is preferable. In the present invention, the rubber component used as the main material of the rubber composition contains a conjugated diene /
It is necessary to contain the vinyl aromatic hydrocarbon copolymer in an amount of 70% by weight or more, but it is more preferable to contain the vinyl aromatic hydrocarbon copolymer in an amount of 80% by weight or more from the viewpoint of the effect. Further, the rubber component may be composed of a 100% conjugated diene / vinyl aromatic hydrocarbon copolymer. Among the rubber components of the rubber composition used for a tire tread of the present invention, the conjugated diene /
Examples of the polymer that can be used together with the vinyl aromatic hydrocarbon copolymer include natural rubber, isoprene rubber, butadiene rubber, butyl rubber (including halogenated butyl rubber), and synthetic rubber such as ethylene-propylene rubber. As long as the rubber component used in combination is less than 30% by weight, any content may be used as long as the effect of the present invention is not impaired, and not only one kind but also a combination of two or more kinds may be used. it can. The rubber composition used in the tread of the tire of the present invention contains 45 to 110 parts of a specific carbon black with respect to 100 parts by weight of the rubber component.
It is blended by weight. Carbon black is used as a reinforcing filler, whereby the effect of improving various physical properties is increased. If the total amount of carbon black used is less than 45 parts by weight, the initial handling stability (DR
(Y performance, WET performance) becomes difficult, and if it exceeds 110 parts by weight, abrasion resistance decreases and workability at the time of production also deteriorates. A more preferred content is 60 to 100 parts by weight.
The carbon black used here is ASTM D30
N ₂ SA measured according to 37 is 100 to 160 m ²
/ A g, DBP oil absorption and was measured according to ASTM D2414 are required to use a material having a characteristic of 120~200cm ³ / 100g. Preferably,
N ₂ SA is 100 to 150 m ² / g, and DB
P oil absorption and has a characteristic of 130~180cm ³ / 100g. If the N ₂ SA is less than 100 m ² / g, it is difficult to maintain the rigidity of the tread.
If it exceeds 60 m ² / g, a decrease in durability due to deterioration of heat buildup becomes a problem. Similarly DBP oil absorption 120 cm ^3/1
When carbon black is used is less than 00g tread stiffness retention becomes difficult, and when it exceeds 200 cm ^3/100 g, a significant increase of workability deterioration and modulus of occurs. ISAF, a commonly used carbon black
(According to ASTM old classification), N ₂ SA is 11
6 to 125 m ² / g, but the DBP oil absorption is 78 to 1
26cm ^3/100 g and relatively low, the desired effects of the present invention in combination with these carbon black is difficult to achieve. Silica may be used in combination as a reinforcing agent for the rubber composition used in the tire of the present invention. When silica is used in combination, it is preferable to further use a silane coupling agent because the reinforcing effect is enhanced. Further, the vulcanization accelerator used in the present invention is a vulcanization accelerator having a structure represented by the above general formula, and 0.5 parts by weight based on 100 parts by weight of the rubber component in the rubber composition.
It is contained in the range of up to 5.0 parts by weight. If the content is less than 0.5 parts by weight, the suppression of the decrease in the breaking energy after running, that is, the effect of improving the wear resistance is insufficient, and the curing due to running and the decrease in the WET performance after running cannot be suppressed. Further, if the amount is more than 5 parts by weight, no further improvement in the effect is recognized, and further increase in the amount is not effective from an economic viewpoint. In the above general formula, R ¹ and R ² are each independently a hydrogen atom, except when they are simultaneously a hydrogen atom,
Represents an alkyl group or an aryl group. Preferably, a hydrogen atom, an alkyl group having 1 to 6 carbon atoms 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. Specific examples of these vulcanization accelerators include 2-mercapto-4-methylbenzothiazole,
-Mercapto-4-ethylbenzothiazole, 2-mercapto-5-methylbenzothiazole, 2-mercapto-5-ethylbenzothiazole, 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) -di Sulfide, 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, mercapto-4-methylbenzothiazole, mercapto-5-methylbenzothiazole,
From the viewpoint of the effect, it is preferable that at least one selected from the group consisting of bis (4-methylbenzothiazolyl-2) -disulfide and bis (5-methylbenzothiazolyl-2) -disulfide is used. . These vulcanization accelerators can be used alone or as a mixture of two or more. Although the method for producing these vulcanization accelerators is not particularly limited, they can be easily produced, for example, by the method described in JP-A-49-93361. The rubber composition used in the tread of the pneumatic tire of the present invention contains, together with the essential components, a vulcanizing agent, a softening agent, zinc oxide, stearic acid, and an oxidizing agent used as an antioxidant, which are usually used in rubber compositions. An inhibitor, an ozone deterioration inhibitor, and the like can be appropriately compounded within a range that does not impair the effects of the present invention. Examples of the vulcanizing agent include sulfur and the like, and the amount of these used is 0.1 to 5 parts by weight, preferably 0.5 to 5 parts by weight, based on 100 parts by weight of the rubber component.
2 parts by weight. 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 lost. The rubber composition according to the present invention is obtained by kneading using a kneading machine such as a roll and an internal mixer, and after molding, vulcanization is performed, and the rubber composition is used for tire treads, undertreads, and the like. The pneumatic tire according to the invention is configured.

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. In the examples, parts and% mean parts by weight and% by weight, respectively, unless otherwise specified. The present invention will be described below with reference to examples and comparative examples. Rubber compositions [1] to [5] to be used for pneumatic tires of Examples and Comparative Examples were prepared by a conventional method using the formulations shown in Table 1 below. The used S
BR is as follows. SBR (A): Toughden 2530 (trade name) Asahi Kasei Kogyo
SBR (B): T0120 (trade name) Nippon Synthetic Rubber Co., Ltd.
The styrene content is 35%. The characteristics of the carbon black used are as follows. Carbon black N135: N ₂ SA 145 m ² /
g, DBP oil absorption of 135 cm ^3/100 g carbon black N234: N ^₂ SA 126m ₂ /
g, DBP oil absorption 125cm ³ / 100g

[Table 1] Next, a tire having a tread rubber consisting of the rubber compositions [1] to [5] shown in Table 1 was trial manufactured to have a size of 225 / 50R16, and the rim 8 was used as Examples 1 to 3 and Comparative Examples 1 and 2, respectively.
The test was performed using J-16. Various evaluations were based on the following methods. Evaluation method (a) WET steering stability evaluation A test driver evaluates the driving performance, braking performance, steering wheel responsiveness, and steering controllability on a test course on a wet road surface, and evaluates the driving performance. Was evaluated for steering stability. In addition, the same tire is 20,000k
m after running the same vehicle on the same wet road surface,
The steering stability at the time of WET after traveling was evaluated. The evaluation results are shown as indices with the steering stability evaluation at the time of initial WET of Example 1 as Comparative Example 1 and Examples 2 and 3 of Comparative Example 2 as 100. A large value indicates that the WET steering stability is excellent. (B) Abrasion resistance evaluation The market was run 20,000 km by actual vehicle evaluation, and the abrasion resistance was evaluated by measuring the height of the remaining groove of the tire (a 20,000 km traveling product) at that time. The result of Comparative Example 2 was indicated by an index with 100 being taken. The larger the value, the better the wear resistance. The evaluation results are shown in Table 2 below.

[Table 2] As is clear from the results in Table 2, the pneumatic tires of the examples all show excellent abrasion resistance and steering stability at the time of WET, and the steering stability at the time of WET decreases even after traveling 20,000 km. Hardly ever seen. On the other hand, the pneumatic tire obtained by the comparative example in which the vulcanization accelerator according to the present invention was not used had excellent handling stability at the time of initial WET, but had a
It was found that the WET performance after m running was greatly reduced.

As described above, the pneumatic tire of the present invention has the above-mentioned structure, and has an effect of being excellent in both abrasion resistance and wet performance after running.

Claims (3)

[Claims] 1. A pneumatic tire comprising a tread portion made of a rubber composition that comes into contact with a road surface, a carcass serving as a reinforcing member, and an end portion of the carcass wound around and fixed, and a bead core defining an inner size of the tire. In the rubber composition, the rubber component contains 70% by weight or more of a conjugated diene / vinyl aromatic hydrocarbon copolymer and 45 to 110 parts by weight of carbon black based on 100 parts by weight of the rubber component. The vulcanization accelerator represented by the following general formula is contained in an amount of 0.5 to 5.0 parts by weight based on 100 parts by weight of the rubber component, and the carbon black has a nitrogen adsorption specific surface area (N ₂ S).
A) is 100~160m ² / g, a dibutyl phthalate (DBP) oil absorption of 120~200cm ^3/100
g, a pneumatic tire. Embedded image (In the formula, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group or an aryl group, provided that R ¹ and R ² are not simultaneously a hydrogen atom.) 2. The vulcanization accelerator represented by the general formula, wherein R ¹ and R ² each independently represent a hydrogen atom, a methyl group, an ethyl group or a phenyl group. Pneumatic tires. (However, this excludes the case where R ¹ and R ² are simultaneously hydrogen atoms.) 3. The vulcanization accelerator comprises mercapto-4-methylbenzothiazole, mercapto-5-methylbenzothiazole, bis (4-methylbenzothiazolyl-2).
The pneumatic tire according to claim 1, wherein the pneumatic tire is at least one member selected from the group consisting of disulfide and bis (5-methylbenzothiazolyl-2) -disulfide.