JP2000190713A - Pneumatic radial tire for passenger car - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve adhesive durability, corrosion/fatigue resistance, and carcass durability of a steel cord, by forming a carcass ply from a steel cord, forming a rubber layer of a side wall so that a plurality of layers have a laminated layer structure and a single layer of them is a low air permeable layer having a specific amount of butyl rubber. SOLUTION: A ply burying cord of a carcass 2 of a tire 1 comprises a steel cord. The rubber layer of a side wall 7 comprises at least two layers, as the inner layer 9 rubber composition familiarly used for side walls is used, and as the outer layer 8 a low air permeable layer containing a butyl rubber as a rubber component is used. Contents of the butyl rubber in the rubber component in this low air permeable layer is more than 30 wt.%, preferably more than about 50 wt.%. Thus, because moisture and oxygen are restrained to infiltrate from the outside of a side portion into a steel ply layer, adhesive resistance of a carcass layer is largely improved, and corrosion/fatigue resistance can be also improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic radial tire for a passenger car using a steel cord as a carcass, and more particularly to an adhesive durability (carcass durability) and a running performance between the steel cord and its coating rubber. And pneumatic radial tires for passenger cars.

[0002]

2. Description of the Related Art Generally, in a radial tire for trucks and buses, a steel cord is used as a reinforcing material for a belt and a carcass. In a radial tire for a passenger car,
A steel cord is used for the belt, and a textile cord such as polyester, nylon or rayon having excellent fatigue resistance is used for the carcass.

[0003] However, radial tires for passenger cars using a textile cord for the carcass have insufficient resistance to trauma, which is likely to occur when the tire side portion comes into contact with a curb, and poor adhesion between the cord and rubber tends to occur. This may lead to cord breakage or separation. Further, the textile cord generally has a low bending rigidity, and it is difficult to increase the rigidity of the side portion of the tire.

[0004] Therefore, it has been proposed to apply a steel cord instead of a textile cord to a carcass of a radial tire for a passenger car.
No. 0803 proposes to use, as a carcass, a steel cord having a 1 + n structure including one core filament and n sheath filaments arranged around the core filament. As a result, the above disadvantages are solved, but the following new problems arise.
That is, the steel cord used for the carcass is subjected to repeated bending and compression deformation over a long period of time along with the rolling of the tire, and particularly, the steel cord in the carcass portion adjacent to the belt is subjected to a lateral force when steering the vehicle. It is compressed and deformed, and by repeating this, the deterioration of the adhesion durability between the steel cord and its coating rubber progresses,
It leads to carcass separation failure. Therefore, in order to apply a steel cord to a carcass of a radial tire for a passenger car, it is important to improve the adhesion durability of the steel cord.

On the other hand, against the influence of the environment (mainly oxygen and moisture) from the inside of the tire, a rubber layer containing butyl rubber as a main component is used for the inner liner, or a low air permeability is used instead of the conventional inner liner. (Japanese Patent Application Laid-Open Nos. Hei 8-216285, Hei 8-258506, Hei 8-259741, etc.) have been attempted. Further, in order to cope with this effect, various measures have been taken from the structural and material aspects, such as the improvement of the corrosion resistance of the steel cord itself and the improvement of the adhesiveness from the viewpoint of compounding the coating rubber.

[0006]

However, these prior arts are not necessarily satisfactory solutions in an external environment, especially in a severe environment for a steel cord in a tire such as a high-temperature and high-humidity environment. Was.

Accordingly, an object of the present invention is to improve the athletic performance and at the same time to improve the carcass ply steel in any external environment, especially in a severe environment such as a hot and humid environment for a steel cord in a tire. It is an object of the present invention to provide a pneumatic radial tire for a car in which the steel cord is prevented from being adversely affected by moisture and the like, and the carcass durability is improved by improving the adhesion durability and corrosion fatigue resistance of the steel cord.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have adopted a steel cord for the carcass ply, and at the same time, made the rubber layer of the sidewall a laminated structure composed of at least two layers. It has been found that the above object can be achieved by forming one of the layers as a low air permeability layer containing a predetermined amount of butyl rubber as a rubber component, thereby completing the present invention.

That is, a pneumatic radial tire for a passenger car according to the present invention comprises: a carcass comprising at least one carcass ply folded back by a pair of bead cores and connected in a toroidal form; At least one pneumatic radial tire for a passenger car, comprising a belt composed of at least one steel cord belt ply disposed between a tread and the carcass, and a pair of sidewalls disposed on the left and right sides of the tread. The embedded cord of the carcass ply is made of a steel cord, and the side wall has a laminated structure of at least two rubber layers, one of which has a low air permeation containing 30% by weight or more of butyl rubber in a rubber component. Characterized in that it is a conductive layer.

In the pneumatic radial tire for a passenger car according to the present invention, the steel cord is 1 × N or 1 + N.
(2 ≦ N ≦ 7) It is preferable that the filament has a filament diameter of 0.125 to 0.25 mm.
Is preferably within the range.

The content of butyl rubber in the rubber component in the low air permeability layer is preferably at least 50% by weight, and the thickness of the layer is preferably 0.3 to 1.5 mm.

[0012]

Embodiments of the present invention will be described below. FIG. 1 shows a cross section of a pneumatic tire 1 for a passenger car according to an embodiment of the present invention. In the example shown,
The carcass 2 is composed of one ply arranged in a direction substantially perpendicular to the tire equatorial plane, and both ends thereof are wound around the bead ring 5 to form a winding end, and the carcass 2 on the bead ring 5 and the A hard rubber bead filler 6 is tapered between the ply winding end. The belt 4 has two belt cords arranged between the carcass 2 and the tread 3 with a belt cord inclined with respect to the tire equatorial plane (a first belt layer 4a and a second belt layer 4b).
Are overlapped so that the cords cross each other.

In the present invention, the rubber layer of the side wall 7 is composed of at least two layers. In the illustrated two-layer structure, for example, the inner layer 9 is made of a rubber composition commonly used for the side wall. In the outer layer 8, a low air permeable layer containing butyl rubber as a rubber component is used. Incidentally, such a low air permeable layer may of course be used as the inner layer. The content of butyl rubber in the rubber component of the low air permeability layer is 30% by weight or more, preferably 50% by weight or more, and the thickness (gauge) of the layer is preferably 0.3 to 3%.
1.5 mm. By providing such a low air permeable layer on the sidewall, without impairing athletic performance, even under a high-temperature and high-humidity environment, the penetration of moisture and oxygen from the outside of the side portion into the steel ply layer is suppressed. In addition, the adhesion resistance of the carcass is significantly improved, and the corrosion fatigue resistance is also improved. When the butyl rubber component in the rubber component in the low air permeable layer is less than 30% by weight, such an effect is insufficient, and when the layer thickness is less than 0.3 mm, the effect is also insufficient. On the other hand, 1.
If it exceeds 5 mm, the improvement effect is saturated, which is not preferable in terms of cost.

The low air permeable layer may be provided as any layer in the laminated structure, but is preferably the outermost layer. When the outermost layer is such a low air-permeable layer, moisture and oxygen can be blocked most effectively. In this case, in order to improve the weather resistance, the other rubber components are composed of natural rubber alone or natural rubber as described later.
It is preferred to use a blend with PDM.

The butyl rubber used for the low air permeability layer is
Preferably, it is at least one selected from the group consisting of butyl rubber, halogenated butyl rubber, and butyl rubber obtained by brominating a copolymer of isoolefin and p-methylstyrene. The rubber components other than the halogenated butyl rubber are not particularly limited. For example, natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), isoprene rubber (IR), ethylene propylene diene rubber (EPDM) ), Of which natural rubber is mainly used. In particular, when used as the outer layer, natural rubber alone or a blend of natural rubber and EPDM is preferable from the viewpoint of weather resistance, and particularly natural rubber / EPDM = 100/0 to 70/30. In addition, a compounding agent usually used in the rubber industry, for example, a reinforcing agent such as carbon black, a vulcanizing agent, a vulcanization aid, a vulcanization accelerator, an antioxidant, a softening agent and the like can be appropriately compounded. Of course.

In the present invention, the ply embedment cord of the carcass 2 is made of a steel cord, and preferably, the steel cord is 1 × N or 1 + N (2 ≦ N ≦
7, preferably 4 ≦ N ≦ 6), having a single twist or layer twist structure. The preferred twist pitch is between 6 mm and 12 mm. The filament diameter of the filament is preferably 0.1
It is in the range of 25 to 0.25 mm. This wire diameter is 0.1
If it is less than 25 mm, it is difficult to draw wire during production and it is difficult to produce tensile strength, so the cord strength is reduced, and as a result, the strength of the tire case member is reduced, while if it exceeds 0.25 mm, the fatigue resistance is reduced. It is not preferable because it deteriorates.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. Various types of pneumatic radial tires for passenger cars were manufactured by using a tire having a size of 195/65 R14 and a rim size of 6J × 14 and employing the conditions shown in Table 1 below as a carcass structure and a sidewall structure. As for the sidewall, Comparative Example 1 and Comparative Example 2 consisted of a single layer not containing butyl rubber as a rubber component, and Comparative Example 2 and Examples 1 to 5
It has a two-layer structure having a low air permeability layer containing butyl rubber as an outer layer. However, in Comparative Example 2, the butyl rubber content in the rubber component in the butyl rubber-containing layer was as low as 20% by weight, which is outside the scope of the present invention. The other rubber component of the sidewall is natural rubber, and as other compounding agents, 40 parts by weight of carbon black, 10 parts by weight of a softener (oil), 2 parts by weight of stearic acid, zinc, based on 100 parts by weight of the rubber component 5 parts by weight of flower, 2 parts by weight of a vulcanization accelerator, and 1.5 parts by weight of sulfur are blended. The belt is composed of two steel cords having a twisted structure of 1 × 3 × 0.30 (mm) arranged at an angle of 22 ° with respect to the equatorial plane of the tire (first belt layer 4a, second belt layer 4).
b: 30 to be inserted / 5 cm) were overlapped so that the cords crossed each other. About the obtained test tire,
The steering stability and the carcass ply adhesion resistance were evaluated.

Driving stability The test tire was placed on a drum having an outer diameter of 3000 mm, and after a load of 400 kg was applied to the tire, it was 30 km / h.
After preliminarily running at a speed of 30 minutes, the load was removed and the internal pressure was readjusted to ² kgf / cm ^2, and then, again under the same speed and the same load conditions, the slip angle on the drum was increased up to ± 4 °. Positive and negative were added consecutively.
Next, the cornering force (CF) at each positive and negative angle
Is measured, and the following equation is obtained: CP (kg / degree) = ｛CF (1 °) (kg) + CF (2
°) (kg) / 2 + CF (3 °) (kg) / 3 + CF
The cornering power (CP) was determined at (4 °) (kg) / 4 ° / 4. The evaluation results were expressed by an index when the CP of each test tire was set to 100 with the CP of the control tire (Comparative Example 1). The larger the index, the better the steering stability.

Ply cord adhesion resistance Each test tire is filled with air so that the internal pressure becomes 2 kgf / cm ² , and the speed is 60 km / min under JIS 100% load.
The vehicle was driven up to 50,000 km at h. After actual running, the four belt cords were peeled off from the rubber at room temperature, and the amount of rubber remaining on the cord was compared with that of the control tire (Comparative Example 1) at the portion where the amount of rubber was the most severe. Indicated by. The larger the value, the better the adhesion resistance.
The results obtained are shown in Table 1 below.

[0020]

[Table 1]

[0021]

As described above, in the pneumatic radial tire for a passenger car according to the present invention, the steel cord is used for the carcass ply, and at the same time, the rubber layer of the sidewall has a laminated structure of at least two layers. By making one layer a low air permeable layer containing butyl rubber as a rubber component, the exercise performance is improved, and at the same time, the tire tread can be used in a severe environment such as a hot and humid environment for the steel cord in the tire. The steel cord of the belt layer is not adversely affected by moisture or the like from under the groove, the adhesion durability and the corrosion fatigue resistance of the steel cord are improved, and the durability of the tire can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a pneumatic tire for a passenger car according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pneumatic tire 2 Carcass 3 Tread 4 Belt 4a First belt layer 4b Second belt layer 5 Bead ring 6 Bead filler 7 Side wall 8 Outer layer 9 Inner layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08L 21/00 C08L 21/00 23/22 23/22 // D07B 1/06 D07B 1/06 A

Claims (5)

[Claims] 1. A carcass comprising at least one carcass ply folded back by a pair of bead cores and connected in a toroidal shape, a tread arranged on a crown portion of the carcass, and arranged between the tread and the carcass. A pneumatic radial tire for a passenger car, comprising: a belt made of at least one steel cord belt ply; and a pair of sidewalls disposed on the left and right sides of the tread, wherein at least one embedment code of the carcass ply is a steel cord. Wherein the rubber layer of the sidewall has a laminated structure composed of at least two layers, and one of the layers is a low air permeable layer containing butyl rubber in a rubber component in an amount of 30% by weight or more. Pneumatic radial tire. 2. The steel cord is 1 × N or 1+
The pneumatic radial tire for a passenger car according to claim 1, wherein the pneumatic radial tire has a twisted structure of N (2 ≦ N ≦ 7). 3. The steel cord according to claim 1, wherein a filament diameter of the filament is in a range of 0.125 to 0.25 mm.
Or the pneumatic radial tire for a passenger car according to 2. 4. The low air permeable layer has a butyl rubber content of 50% by weight or more in a rubber component.
The pneumatic radial tire for a passenger car according to any one of claims 1 to 3. 5. The low air permeable layer has a thickness of 0.3 to 0.3.
The pneumatic radial tire for a passenger car according to any one of claims 1 to 4, which is 1.5 mm.