JP2000017588A - Rubber-steel cord composite and pneumatic tire for passenger car using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide pneumatic tires for passenger cars with excellent durability without occurrence of interfacial peeling from the adhesive layer during the car running, particularly in the run-flat driving. SOLUTION: This rubber-steel cord composite material has the rate of the filament area in the cord area in the 15 mm part in the arbitrarily selected cord-axis direction (in other words, the areal share of the filaments in R) is 0.45<=R<=0.95, where 15 mm in the cord axis direction means 15 mm long as actual cord length and the areal share R of the filament is represented by R=F/A when the area of the whole cords is represented as A and the area of the filaments is as F.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber-steel cord composite and a pneumatic tire for a passenger car, and more particularly, to a rubber-steel cord composite excellent in adhesiveness and durability at high temperatures. The present invention relates to a pneumatic tire for a passenger car which has excellent durability and can run safely even when the internal pressure is reduced.

[0002]

2. Description of the Related Art Tires, belts, hoses, and the like use a composite in which a steel cord for reinforcement is embedded in rubber. However, in order to improve durability and the like, a steel cord and a rubber composition are used. Stable adhesiveness with objects is required.
For this reason, conventionally, in order to bond a steel cord and a rubber composition, a direct bonding method in which a brass plating which is an alloy of copper and zinc is applied to the cord and reacted with sulfur in the rubber composition is generally used. is there. On the other hand, various attempts have been made to obtain adhesiveness from the structure of a steel cord.

[0003] For example, in a product reinforced by a steel cord, there is a problem that the durability of the product is shortened due to corrosion of the steel filament due to moisture entering the product. In other words, if there is a cavity in the steel cord, if it is injured, the water that has penetrated will propagate along the cavity in the steel cord and spread along the longitudinal direction of the cord,
As a result, rust caused by moisture is also diffused, and the adhesive strength between the rubber and the steel cord at that portion is reduced, which eventually causes the separation phenomenon.

[0004] In order to prevent such corrosion propagation, rubber is compressed inside the cord (between the metal filaments) through a gap between adjacent metal filaments by pressure vulcanization.
A code structure that fully penetrates has been proposed.

[0005] As one of the cord structures, a so-called 1 + 5 cord having one core filament and five sheath filaments has a gap between the sheath filaments, rubber easily penetrates, and a one-stage twisting process. Japanese Patent Application Laid-Open No. 60-38208 discloses a highly twistable cord.
It is disclosed in JP-A-59-1790.

However, in such a structure, even when the average sheath gap is sufficient, the arrangement of the sheath filaments is deviated, and a portion where the sheath filaments adhere to each other is formed.
There was a drawback in that there was a portion where rubber did not penetrate due to manufacturing variations.

Further, in the cord having a 1 + 5 structure disclosed in Japanese Patent Application Laid-Open No. 56-131404, it is suggested that the core filament may be formed by waving lightly. Is thinner than the sheath filament diameter, so the gap between sheath filaments is narrower, rubber is less likely to enter the gap, and the rigidity of the core filament is weaker, so the effect of corrugating is reduced, and the permeability of rubber When the type ratio is increased in order to improve the strength, there is a disadvantage that the strength is reduced.

[0008] Further, there is a method of increasing the diameter of the core filament larger than the diameter of the sheath filament, securing a certain gap or more between adjacent sheath filaments, and trying to infiltrate the rubber into the inside. The weight increases, the productivity also worsens, and the arrangement of the sheath filaments is partially biased and adheres to each other, so that the rubber does not penetrate and sufficient corrosion propagation resistance cannot be obtained.

On the other hand, running at low internal pressure with pneumatic tires,
In a tire capable of so-called run-flat running (referred to as a pneumatic safety tire), as a tire wheel, a core type in which a metal or synthetic resin annular core is attached to a rim portion in a tire air chamber, and a tire There is known a side reinforcement type in which a relatively hard rubber layer is disposed near a carcass and reinforced from a bead portion of a sidewall to a shoulder region to be reinforced. Of these two types, the core type is used for cargo transport vehicles and military vehicles that do not make ride comfort a problem because of its high load-bearing capacity in run-flat driving. It has a good reputation for vehicles with a light load and emphasis on riding comfort.

In the side reinforcing type, for example, a relatively hard reinforcing rubber layer having a crescent cross section is provided on the inner surface of the carcass layer on the side wall, and one end of the reinforcing rubber layer overlaps the belt layer with the carcass therebetween. , The other end
Arranged to overlap with the rubber filler and reinforced. If the tire punctures during running and the air escapes, the load is supported by the inherent rigidity of the sidewall reinforced by the reinforcing rubber layer, and although the speed must be slightly reduced, the run-flat running for a predetermined distance Can do it.

However, in the case of tires for passenger cars, the load burden is relatively small, but when the size of a passenger car is large, the load per tire becomes as large as about 500 kgf. Therefore, when a general-purpose pneumatic safety tire having a large flatness is run under run-flat conditions, the deformation of the sidewall is further increased, the internal temperature of the tire becomes 200 ° C. or higher, and the tire has excellent heat resistance. For example, it is said that even PET has insufficient adhesion to rubber at high temperatures. Specifically, in the case of a tire to which a PET carcass is applied, a failure during run flat running is caused at the PET / adhesive layer interface. Peeling is the main thing. Therefore, a higher level is desired in terms of run flat durability.

In addition, the sidewall is completely buckled due to a dynamic load several times that is received during traveling under run-flat conditions, and the vehicle travels while repeating this.
As a result, the bead portion on the side wall is pushed up by the flange of the rim, and the envelope rubber and the carcass folded portion sandwiched between the curved flange and the rubber filler generate heat, and the heat breaks the rubber blister and / or the carcass cord. Therefore, even if the part that caused the puncture is repaired, it cannot be used anymore.

[0013] Furthermore, it is naturally required to be able to perform run-flat running, that is, running when the internal pressure of the tire is low, and at the same time, to perform in normal running when filling the internal pressure.

[0014]

SUMMARY OF THE INVENTION The present invention provides a rubber-steel cord composite having excellent adhesion and durability at high temperatures.
Also, it is an object of the present invention to provide a pneumatic tire for a passenger car which does not cause interface delamination with an adhesive layer during running, particularly during run-flat running, and has excellent durability.

[0015]

Accordingly, the present inventors have developed a rubber-
After a thorough study of the structure of the steel cord composite, the rubber occupancy becomes easier by specifying the occupancy of filaments in the composite, and the adhesion between the rubber and the steel cord is impaired even at high temperatures. It has been found that a rubber-steel cord composite having excellent durability can be provided without using the rubber-steel cord composite, and a pneumatic tire for a passenger car having excellent durability can be provided by using the rubber-steel cord composite. Was completed.

That is, the present invention has the following configuration. (1) In the image obtained as a plane by X-ray transmission, the ratio of the filament area to the code area of the arbitrarily selected 15 mm portion in the code axis direction (filament area occupation ratio: R) is 0.45 or more and 0.95 The following rubber
Steel cord composite. However, 15 mm in the cord axis direction
Means the actual length of the cord is 15 mm, and when the area of the entire cord is A and the area occupied by the filament is F, the area occupancy R of the filament is
Is represented by R = F / A. (2) The rubber-steel cord composite according to (1), wherein each filament of the steel cord is substantially independently present in the rubber matrix. (3) The composite according to any one of (1) and (2), wherein the structure of the steel cord of the composite is a 1 × n structure or a 1 + n structure, and n is in a range of 2 ≦ n ≦ 7. A rubber-steel cord composite as described. (4) The rubber according to any one of (1) to (3), wherein the wire diameter of the steel cord filament of the composite is in a range of 0.125 to 0.275 mm.
Steel cord composite. (5) In or out of the tire,
In an image obtained as a plane by X-ray transmission, the ratio of the filament area to the code area of the arbitrarily selected 15 mm portion in the code axis direction (filament area occupation ratio: R) is 0.45 or more and 0.95 or less. A pneumatic tire for a passenger car using a rubber-steel cord composite. However, 15 mm in the cord axial direction means that the actual cord length is 15 mm, and when the area of the entire cord is A and the occupied area of the filament is F, the area occupancy R of the filament is R = F
/ A. (6) The pneumatic tire for a passenger car according to (5), wherein each filament of the steel cord is substantially independently present in the rubber matrix. (7) The steel cord according to (5) or (6), wherein the structure of the steel cord of the composite is a 1 × n structure or a 1 + n structure, and n is in a range of 2 ≦ n ≦ 7. A pneumatic tire for a passenger car as described. (8) The pneumatic tire for a passenger car according to any one of (5) to (7), wherein a wire diameter of the steel cord filament of the composite is in a range of 0.125 to 0.275 mm. . (9) The pneumatic tire for a passenger car according to any one of (5) to (8), wherein the composite is used for a carcass layer. (10) The pneumatic tire for a passenger car according to any one of (5) to (9), wherein the sidewall portion is reinforced with a rubber reinforcing layer.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION The rubber-steel cord composite of the present invention has the following features:
The ratio of the filament area to the cord area of the arbitrarily selected portion of 15 mm in the cord axis direction (the area occupancy of the filament: R) must be 0.45 or more and 0.95 or less. However, 15 mm in the cord axial direction means that the actual cord length is 15 mm.
When the area of the entire cord is A and the area occupied by the filament is F, the area occupancy R of the filament is R = F / A
Is represented by Here, the code area A is a portion indicated by oblique lines in FIG. 1, and the occupied area F of the filament is a black portion in FIG. The area occupancy of the filament is, for example, when the rubber-steel cord composite is used for a rubber article such as a tire, in the rubber article, directly or in a state of being taken out from the rubber article, Can be measured. When R is less than 4.5, the contact area between each filament and rubber increases,
Corrosion propagation due to moisture can be further suppressed,
On the other hand, the tensile modulus of the cord becomes low, and the rigidity requirement of the carcass cannot be satisfied. On the other hand, when R exceeds 9.5, the deformation of the steel filament itself is reduced, and the effect of improving the compression fatigue resistance is reduced. R is preferably from 0.50 to 0.90, more preferably from 0.55 to 0.75. As will be understood from the method of measuring and calculating the area occupancy R, which will be described later, when calculating R, the overlap is also included in one plane. 98 to 1.00.

Further, the rubber-steel cord composite of the present invention is a so-called open cord in which filaments do not come into contact with each other. Since the contact area of the steel cord can be changed, the intrusion of moisture between the steel cords can be suppressed by increasing the contact area. Further, by increasing the ratio of the contact area between each filament and the rubber, friction between filaments, so-called fretting, can be suppressed. As a result, corrosion propagation due to moisture, which is the main cause of the durability of the steel cord, can be suppressed, and the corrosion from fretting can be significantly improved.

The steel cord used in the present invention comprises:
× n structure or 1 + n structure, and n
Is preferably a natural number of 2 to 7, more preferably 3 to 6. When n exceeds 7, the filaments are likely to come into contact with each other, which may cause fretting,
It is not preferable in terms of adhesiveness, durability and corrosion resistance between the steel cord and the rubber. The filament diameter of the filament fiber of this steel cord is 0.125 to 0.275 m.
m, preferably 0.125 to 0.230 mm,
When the diameter is less than 0.125 mm, the wire is difficult to be drawn and the tensile strength is hardly produced during the production, so that the tensile strength of the cord is reduced, and as a result, the strength of the member using the composite is reduced. On the other hand, if the thickness exceeds 0.275 mm, the fatigue property is undesirably deteriorated.

[0020] The steel cord used in the present invention is, for example, when the filaments are twisted by a twisting machine (for example, in a tubular machine), the filaments are largely molded by a preformer, and the filaments are molded. It is produced by twisting filaments. When the molding amount is increased with respect to the filament pitch length of the cord, the tensile stress is low, and the elongation at the time of cutting is high.

The physical properties of the rubber composition used in the composite are appropriately selected depending on the intended use. For example, when the rubber composition is used for a carcass ply of a tire, the tensile stress (M ₅₀ ) at 50% elongation is determined. 1.2 to 6.0 MPa, 100%
Extension at the time of the tensile stress (M ₁₀₀₎ is 3.0~10.0MPa
It is preferred that

The rubber component used in the rubber-steel cord composite of the present invention is not particularly limited. For example, natural rubber (NR), butadiene rubber (BR), styrene-butadiene rubber (SBR), synthetic isoprene rubber ( IR)
Can be mentioned. Further, fillers and compounding chemicals usually used in the rubber industry may be appropriately compounded as needed.

The rubber-steel cord composite of the present invention can be used alone or together with other members for various rubber articles such as tires, belts, hoses, etc., and molded and vulcanized according to a conventional method. In this way, it becomes the final product.

Generally, since the steel cord is firmly bonded to the rubber, there is no problem in the adhesiveness even when the heat generation inside the composite is extremely high. For example, the steel cord is more durable than the polyethylene terephthalate (PET) -rubber composite. Sex becomes a high level. Also, how to reduce the heat generation inside the composite is very important. For example, when comparing PET cord and steel cord, the amount of deflection with respect to load becomes smaller because the steel cord has higher bending rigidity. In addition, the calorific value of the composite is reduced. Furthermore, since the above-mentioned steel cord has a low tensile stress at a constant elongation and a relatively high elongation at break, a significant improvement in compression fatigue resistance, which is generally a disadvantage of a steel cord, is seen. Since the cord can absorb the compression input by the deformation of the steel filament itself, the compression fatigue resistance is greatly improved.

Therefore, for example, when the rubber-steel cord composite of the present invention is used for a tire, there is no problem in adhesion even when the heat generated inside the tire is extremely high during run flat running (run flat). A trouble in running occurs in the rubber portion of the other portion), and the run flat running performance is at a higher level than, for example, PET. It is also very important to reduce the internal heat generation during run flat running. For example, when comparing PET cord and steel cord, the steel cord has higher bending rigidity, so the internal pressure of the tire decreases. The amount of deflection at the time is reduced, and the calorific value of the tire is reduced. Further, by reducing the tensile stress at the time of constant elongation of the steel cord and increasing the elongation at break, the compression fatigue resistance, which is generally a disadvantage of the steel cord, is greatly improved. That is, since the compression input can be absorbed by the deformation of the steel filament itself, the compression fatigue resistance is greatly improved. Therefore, a pneumatic safety tire having excellent run flat durability according to the present invention was obtained by using the steel cord thus prepared.

In order to obtain the above effects more efficiently,
The rubber-steel cord composite of the present invention is preferably used for a carcass ply of a tire.

In the present invention, a rubber reinforcing layer can be further provided on the sidewall portion. The shape and arrangement position of the rubber reinforcing layer are not particularly limited, as long as it is arranged at least in part of the side wall portion, and may extend to the shoulder portion. Further, it may be provided on the inner surface, the outer surface, or both of the carcass layers using the steel cord of the present invention. In particular, by arranging on the inner surface,
Run flat durability is further improved. The rubber composition of the side reinforcing layer, in particular is not limited, in order to increase the durability more effective is, M ₅₀ is 2.0~9.0MPa
It is preferably in the range of, M ₁₀₀ is in the range of 4.0～15.0MPa.

In the pneumatic safety tire according to the present invention, at least one of the down carcass layer is provided between the sidewall rubber and the outer surface of the carcass layer made of steel cord.
Sheets may be provided.

[0029]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but it should not be construed that the invention is limited thereto without departing from the gist of the present invention.

The tensile stress of the rubber composition used for the composite member is 24 ° C. in accordance with JIS K6301-1995.
Measured with

The area occupancy of the filaments was selected from 10 images obtained by irradiating X-rays from the normal direction of the surface of the rubber-filament fiber composite using K-2 type manufactured by Softex Corporation. It was measured and calculated, and the average value was obtained. The occupancy of the filament in the tire was measured and calculated in the same manner as in the case of the rubber-steel cord composite, with one layer of the carcass taken out.

The adhesive retention was determined by pulling a steel cord from a test sample obtained by vulcanizing and bonding a rubber composition and a steel cord to perform a peeling test. Were fixed between the upper and lower chucks, and peeled off using an Instron tensile tester at a tensile speed of 50 ± 5 mm / min. The value obtained by dividing the measured value by the number of tensile cords was used as the initial adhesion value. Next, the test sample was left in a thermo-hygrostat at a temperature of 70 ° C. and a humidity of 95% for 7 days, and then evaluated in the same manner as in the evaluation of the initial adhesive strength. Was taken as the adhesive retention.

Various performances of the tire were measured by the following methods. (1) Run flat durability After assembling the rim at an internal pressure of 3.0 kg / cm ² for 24 hours at room temperature of 38 ° C., the core of the valve was removed, the internal pressure was set to atmospheric pressure, the load was 570 kg, and the speed was 89 km / hrs. Room temperature 3
A drum running test was performed at 8 ° C. The running distance until the occurrence of a failure at this time was defined as run flat durability, and was represented by an index with the control being 100. The larger the index, the better the run flat durability.

(2) Normal internal pressure running durability Using a drum tester having a smooth drum surface made of steel and having a diameter of 1.707 m, the ambient temperature is controlled to 30 ± 3 ° C., and the standard rim size specified by JATMA is used. Using the rim of
At a maximum internal pressure of the JATMA standard, a load of twice the maximum load capacity of the JATMA standard was applied, and a durability drum running test was performed to measure the distance until the tire was broken. The evaluation of the practical application of the tire was evaluated as 20,000 km or less.
Those exceeding 10,000 km were rated as ○.

(3) Durability of Water-Containing Drum In addition to the same conditions as the normal internal pressure running durability described above, before the test was started, 300 cc of water was injected into the tire to perform a durability drum running test. The distance was measured.
The evaluation of the practical use of the tire was evaluated as x when it was 15,000 km or less and as ○ when it exceeded 15,000 km.

The composition of the rubber composition for the reinforcing rubber layer is shown in Table 1-1.
_{(M 50: 4.5MPa, M 100} : 10.5MPa) in,
The composition of the carcass ply coating rubber is shown in Table 1-2 (M
_{50: 2.4MPa, M 100: 4MPa} ) to show.

[0037]

[Table 1-1]

[0038]

[Table 1-2]

Using a rubber composition for a carcass ply coating rubber, a rubber-steel cord composite was prepared by combining three types of steel cords manufactured by changing the amount of molding, and their adhesive retention rates were measured. Table 2 shows the results. In addition,
The composite having an R of 0.98 has been conventionally referred to as an open structure.

[0040]

[Table 2]

As can be seen from Table 2, the rubber-steel cord composite of the present invention has better adhesion retention than the composite having the closed structure and the composite having the conventional open structure.

Next, a reinforcing rubber layer having a crescent cross section made of the rubber composition shown in Formulation Table 1-2 was arranged inside the carcass ply in the side wall portion.
Tire No. 6 was prepared by a conventional method.

As shown in FIG. 4, the carcass has the following five types. Structure: Two folded carcass plus one outside
It is a 3P structure in which two down carcass are arranged. Structure: A 2P structure in which one carcass is folded back to the tread portion in addition to one folded carcass. Structure: One folded carcass plus one outside
This is a 2P structure in which two down carcass are arranged. Structure: 1P structure in which the end of one carcass is turned up to the tread portion. Structure: 1P structure using one carcass. Although not shown, the tire of the present invention may be provided with a reinforcing layer covering the entire belt layer or a layer covering only the belt end on the outer periphery of the belt layer.

Table 3 shows the structure of each test tire.

[0045]

[Table 3]

Regardless of the structure of the carcass ply, by using the rubber-steel cord composite of the present invention for the carcass ply, compared with the case where a composite having a closed structure or a conventional open structure is used for the carcass ply,
It can be seen that the durability of the tire is improved.

[0047]

According to the present invention, a rubber-steel cord composite having excellent adhesiveness and durability at high temperatures, excellent durability, and running safely even when the internal pressure is reduced,
A pneumatic tire for a passenger car can be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing an area A of an entire cord.

FIG. 2 is a diagram showing an occupied area F of a filament.

FIG. 3 is a diagram illustrating an example of a tire according to the present invention.

FIG. 4-1 shows the structure of a carcass ply (I
FIG.

FIG. 4-2 shows the structure of a carcass ply used in Examples (IV
FIG.

[Explanation of symbols]

 1: pneumatic tire for passenger cars 2: carcass ply 2a: folded carcass ply 2b: down carcass ply 3, 3a, 3b: bead core 4: belt 5: tread surface 6: tread rubber 7, 7a, 7b: sidewall 8, 8a, 8b: bead filler 9, 9a, 9b: reinforcing rubber layer

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B60C 15/00 B60C 15/00 GH 17/00 17/00 B

Claims (10)

[Claims] 1. In an image obtained as a plane by X-ray transmission, a ratio of a filament area to a code area of an arbitrarily selected portion of 15 mm in a code axis direction (filament area occupation ratio: R) is 0.45 or more and 0 or more. A rubber-steel cord composite that is no greater than .95. However, 15 mm in the cord axial direction means that the actual cord length is 15 mm, and when the area of the entire cord is A and the occupied area of the filament is F, the area occupancy R of the filament is R = F / A. 2. The rubber-steel cord composite according to claim 1, wherein each filament of the steel cord is substantially independently present in a rubber matrix. 3. The structure of the composite steel cord,
3. The rubber-steel cord composite according to claim 1, wherein the rubber-steel cord composite has a 1 × n structure or a 1 + n structure, and n is in a range of 2 ≦ n ≦ 7. 4. The rubber according to claim 1, wherein a wire diameter of the steel cord filament of the composite is in a range of 0.125 to 0.275 mm. -Steel cord composite. 5. In an image obtained as a plane by X-ray transmission, a ratio of a filament area (filament area occupation ratio: R) to a code area of a portion 15 mm arbitrarily selected in the code axis direction is 0.45 or more and 0 or more. A pneumatic tire for a passenger car, characterized by using a rubber-steel cord composite having a diameter of 0.95 or less. However, the code axis direction 15
mm means 15 mm as the actual length of the cord, and when the area of the entire cord is A and the occupied area of the filament is F, the area occupancy R of the filament is R = F / A. Is represented. 6. The pneumatic tire for a passenger car according to claim 5, wherein each filament of the steel cord is substantially independently present in a rubber matrix. 7. The structure of the steel cord of the composite,
7. The pneumatic tire for a passenger vehicle according to claim 5, wherein the tire has a 1 × n structure or a 1 + n structure, and n is in a range of 2 ≦ n ≦ 7. 8. The passenger car according to claim 5, wherein a wire diameter of the steel cord filament of the composite is in a range of 0.125 to 0.275 mm. For pneumatic tires. 9. The pneumatic tire for a passenger car according to claim 5, wherein the composite is used for a carcass layer. 10. The pneumatic tire for a passenger car according to claim 5, wherein the side wall portion is reinforced with a rubber reinforcing layer.