JPH1087898A - Pneumatic tire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pneumatic tire which retains a low rolling resistance at a high degree and exhibits improved resistances to crack growth and rupture during from the initial stage of driving to the last stage by preparing a coating rubber for carcass plies from a rubber component contg. a specific vulcanization accelerator. SOLUTION: This tire has a pair of beads each having a bead filler 12 and a bead core 14, a carcass layer 16 which is folded from the inside to the outside of the tire and thus is fixed around the bead, a tread 18 positioned at the crown part of the carcass layer 16, and at least two belt layers 20 arranged in the inside of the tread 18. The carcass layer 16 has one or more carcass plies and the height h of the folding end of at least one carcass ply is in the range of 10-40mm from the lower end of the bead core 14. A coating rubber for the carcass plies is prepd. by compounding 100 pts.wt. rubber with 0.2-5.0 pts.wt. vulcanization accelerator represented by formula I or II (whereon R<1> and R<2> are each H, alkyl, or aryl provided the case when R<1> and R<2> are both H is excluded).

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 a pneumatic tire which maintains high rolling resistance at a high level, and
The present invention relates to a pneumatic tire having an improved ply end separation (hereinafter, simply referred to as a ply end separation) from an early stage to a late stage of tire running.

[0002]

2. Description of the Related Art As automobiles become more sophisticated and more sophisticated,
Improved tire lightness and low rolling resistance (lower fuel consumption)
There is a strong demand for improved durability.

[0003] For the purpose of reducing the weight of the tire, reducing the cost, and improving the riding comfort, a structure in which the folded end of the carcass ply is set closer to the bead core than the upper end of the bead filler is known. The ply end separator may be generated due to the large distortion in the portion, and the tire may be broken. As a means for preventing this, a side reverse bonding method in which side rubber is put under the rubber chafer to relieve distortion has been adopted.

[0004] As a countermeasure from the aspect of compounding a coating rubber for carcass ply (ply coating rubber), improvement in crack growth resistance and deterioration resistance of the rubber composition itself has been studied. In order to improve crack growth resistance, carbon black has been upgraded, and in terms of improvement in deterioration resistance, an effective vulcanization method (EV Cure) has been studied.

[0005] In the side reverse sticking method, in order to prevent the rubber chafer from being degraded by ozone, the rubber chafer is again placed on the rubber chafer.
Since side rubber must be attached, it is a burden on manufacturing. In the method of upgrading carbon black as an improvement from the viewpoint of compounding, the heat generation of the rubber increases, so that the low rolling resistance is likely to deteriorate. In addition, the workability of the calender during tire production is adversely affected. In addition, the method of improving the fracture resistance by EV Cure causes deterioration of the crack growth resistance.

Further, various rubber compounding agents for each member of a tire have been studied.
Japanese Patent No. 87138 discloses that a rubber composition for a tire tread containing a specific vulcanization accelerator and a specific antioxidant improves heat-resistant curing properties and improves the appearance at the end of tire running. There is no knowledge about rubber, and no studies have been made on low rolling resistance and durability of tires. Also, JP-A-56-1395
JP 42 Publication discloses that a rubber composition using a specific vulcanization accelerator improves sintering (scorchability) in rubber kneading, but there is no description about the performance of ply coating rubber or tires. No suggestion.

[0007]

DISCLOSURE 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 maintain a high level of low rolling resistance, and at the same time, a rubber property which controls a ply end separator. That is, it is an object of the present invention to provide a pneumatic tire in which the ply end separator is improved in various structures by improving the crack growth and fracture resistance of the rubber from the initial stage to the final stage of use of the tire.

[0008]

Means for Solving the Problems The present inventors have focused on ply coating rubber, vulcanization accelerator and the like in a tire having a structure in which the folded end of the carcass ply is set closer to the bead core than the upper end of the bead filler. As a result of intensive studies, they have found that the problems can be solved by the following means, and have completed the present invention.

That is, (1) The pneumatic tire of the present invention comprises a pair of beads having a bead filler and a bead core, a toroidal carcass layer extending over both beads, and a crown portion of the carcass layer. A carcass ply having at least one carcass ply, and at least one carcass ply folded back, wherein the carcass layer has at least one carcass ply In a pneumatic tire whose end is between 10 and 40 mm from the lower end of the bead core, the coating rubber for carcass ply contains a vulcanization accelerator represented by the following general formula in an amount of 0.2-5. 0 parts by weight, preferably 0.2 to 2.0 parts by weight.

[0010]

Embedded image

(Wherein R ¹ and R ² are each independently
Represents a hydrogen atom, an alkyl group or an aryl group. Where R
Except when ¹ and R ² are simultaneously hydrogen atoms. (2) In the pneumatic tire of the present invention, in the item (1), in the vulcanization accelerator represented by the general formula, R ¹ and R ² are each independently a hydrogen atom, a methyl group, or an ethyl group. Or a phenyl group. (However, R
Except when ¹ and R ² are simultaneously hydrogen atoms. (3) In the pneumatic tire of the present invention, in the above item (1), the vulcanization accelerator is bis (4-methylbenzothiazolyl-2) -disulfide, bis (5-methylbenzothiazolyl). -2) -Disulfide, mercapto-4-
At least one selected from the group consisting of methylbenzothiazole and mercapto-5-methylbenzothiazole
It is a seed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION The ply coating rubber used in the present invention needs to contain 0.2 to 5.0 parts by weight of a vulcanization accelerator represented by the above general formula based on 100 parts by weight of a rubber component. And preferably contains 0.2 to 2.0 parts by weight. If the amount is less than 0.2 parts by weight, there is no effect of improving the deterioration resistance.
If it exceeds 5.0 parts by weight, the elastic modulus of the rubber becomes too high,
It is not preferable because crack resistance deteriorates.

In the above general formula of the vulcanization accelerator used in the present invention, R ¹ and R ² each independently represent a hydrogen atom, an alkyl group or an aryl group, unless they are both hydrogen atoms. Preferably, a hydrogen atom and a carbon atom number of 1 to 6
And an aryl group having 6 to 10 carbon atoms, and more preferably a hydrogen atom, a methyl group, an ethyl group or a phenyl group, respectively.

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 Sulfide, 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.

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.

As the raw rubber for the ply coating rubber in the present invention, ordinary natural rubber and synthetic rubber such as isoprene rubber, butadiene rubber and butadiene-styrene rubber can be exemplified.

In the ply coating rubber of the pneumatic tire of the present invention, carbon black, silica, zinc oxide, stearic acid, an antioxidant, WAX, a coupling agent for silica, which are commonly used in the rubber industry together with the above essential components,
Components such as a vulcanizing agent 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. The amount of sulfur used is preferably 0.5 to 5 parts by weight, more preferably 1 to 4 parts by weight based on 100 parts by weight of the rubber component. Department. If the amount is less than 0.5 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 tends to be lost.

The rubber composition of the present invention is obtained by kneading using a kneading machine such as a roll, an internal mixer, a Banbury mixer, etc., and after molding, vulcanized to obtain a tire.

According to the present invention, the ply-end-separation resistance of the tire is improved because the use of the vulcanization accelerator as described above makes it possible to prevent cracks such as monosulfides and disulfides from occurring during EV Cure. It is considered that this is due to the fact that the deterioration of crack growth resistance due to aging and the decrease in fracture resistance are small because no vulcanized form having poor growth properties is produced.As a result, the ply coating rubber according to the present invention is a conventional ply coating rubber. In comparison with the above, it shows excellent crack growth resistance and has excellent deterioration resistance.

[0021]

EXAMPLES The present invention will be described below with reference to examples.
The present invention is not limited by these examples.

1 and 2 are schematic sectional views of pneumatic tires having different side structures. The pneumatic tire 10 or 22 has a pair of bead portions having a bead filler 12 and a bead core 14, a carcass layer 16 that is folded around the two bead portions from the inside of the tire to the outside, and a crown portion of the carcass layer 16. Tread part 18 located at
And at least two belt layers 20 disposed inside the tread portion 18, and the carcass layer 16
It has one or more carcass plies, and the height h of at least one carcass ply folded end is between 10 and 40 mm from the lower end of the beat core (the distance from the lower end of the bead core is h). The carcass layer 16 has fiber cords arranged in a direction substantially perpendicular to the circumferential direction. In the belt layer 20, non-extensible cords represented by aramid fibers and steel cords are arranged at an inclination angle of 10 ° to 30 ° with respect to the circumferential direction (or the equatorial plane of the tire), and at least two cords are provided. They are superimposed so that they intersect in different directions.

As for the side structure, FIG. 1 employs a side-adhered form in which the lower end of the side rubber 15 is disposed so as to cover the upper end of the rubber chafer 17 from the outside, and FIG. The side reverse bonding mode in which the upper end of the rubber chafer 17 is disposed so as to cover the lower end of the side rubber 15 from the outside is adopted. In FIG. 2, reference numeral 19 denotes a cover member arranged in a boundary area between the side rubber and the rubber chafer. Therefore, as can be seen from the side structure, the structure of FIG. 2 is different from the structure of FIG.
Work man-hours increase.

The tire used in this embodiment is 185/7
The carcass used was a single carcass ply reinforced with a polyester cord, and the number of shots was 50 pieces / 5 cm.

Various measurements were made according to the following methods. (1) Evaluation of ply-end separation resistance of tire This evaluation was performed using a pneumatic radial tire of 185 / 70R14 size and a tire inner pressure of 0.2MP with a drum.
a, 100,000 km with a load of 600 kg and a speed of 50 km / h
After running, the ply end crack length (mm) after running was measured. A ply end crack length of 5 mm or less is evaluated as a marketable level.

(2) Evaluation of Rolling Resistance The rolling resistance was measured using a new tire of 185 / 70R14 size and having an outer diameter of 1707.
Using a rotating drum of 6 mm and a width of 350 mm, 300 k
Under the action of a load of g, it was evaluated by measuring the coasting property when rotating at a speed of 0 to 180 km / h. The coasting property was measured every 20 km / hour, evaluated by the average value of the measured values at each speed, and the index was displayed with the control tire of Comparative Example 1 as 100. The larger the value, the better (low) the rolling resistance.

(3) Man-hours There is a difference in man-hours for molding depending on the form of the side structure.
○ indicates that the number of work steps is small, and X indicates that the number of work steps is large. [Examples 1-2, Comparative Examples 1-5] The ply coating rubber compositions A, B, C,
D, E and F were prepared. According to Table 2, this rubber composition, the tire side structure, and the height of the ply end from the lower end of the bead core were combined to prepare a pneumatic radial tire of 185 / 70R14, and the ply end crack length and rolling resistance were measured. . Table 2 shows the results.

[0028]

[Table 1]

[0029]

[Table 2]

As shown in Table 2, the pneumatic tire of the present invention maintains a high level of low rolling resistance, and has improved ply-end separation resistance from the beginning to the end of running, that is, the tire life is improved. You can see that

It can be seen that, in Comparative Examples which do not use the vulcanization accelerator specified in the present invention, low rolling resistance and improvement in ply end crack length are not compatible. Comparative Example 2 is not preferable because it requires a number of man-hours.

[0032]

As described above, the pneumatic tire of the present invention has the above-described structure, and therefore, without impairing low rolling resistance.
An excellent effect that the ply end separation resistance is improved from the beginning to the end of traveling is achieved.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing one embodiment of a pneumatic tire of the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the pneumatic tire of the present invention.

[Explanation of symbols]

10, 22 Pneumatic tire 12 Bead filler 14 Bead core 15 Side rubber 16 Carcass layer 17 Rubber chafer 18 Tread portion 19 Cover member 20 Belt layer h Distance from bead core lower end to carcass ply folded end

Claims (4)

[Claims] 1. A pair of beads having a bead filler and a bead core, a toroidal carcass layer extending over both beads, a tread located at a crown of the carcass layer, and an inner side of the tread. And at least two belt layers arranged, the carcass layer has one or more carcass plies,
In a pneumatic tire in which at least one folded end of the carcass ply is between 10 and 40 mm from the lower end of the bead core, the coating rubber for carcass ply comprises a vulcanization accelerator represented by the following general formula and a rubber component of 100 parts by weight. A pneumatic tire, comprising 0.2 to 5.0 parts by weight of the 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 bis (4-methylbenzothiazolyl-2) -disulfide, bis (5-methylbenzothiazolyl-2) -disulfide, mercapto-4-methylbenzo. Thiazole and mercapto-5
The pneumatic tire according to claim 1, wherein the pneumatic tire is at least one member selected from the group consisting of -methylbenzothiazole. 4. The pneumatic tire according to claim 1, wherein the vulcanization accelerator is contained in an amount of 0.2 to 2.0 parts by weight based on 100 parts by weight of the rubber component.