JPH0390402A - Radial tire - Google Patents

Abstract

PURPOSE:To improve separation resistance of the end part by arranging a specific steel cord as a reinforcing cord at least in either of carcass or belt, and using a special rubber composition as the coating rubber of the cord. CONSTITUTION:A radial tire 1 is provided with at least carcass 7 and belt 8. In this case, at least the carcass 7 or the belt 8 has a single twisted steel cord of 1Xn construction (where n is integral number 2-6) twisted n pieces of filament of which diameter is of 0.1-0.5mm, and the steel cord is cobalt coated on its surface and arranged as a reinforcing cord. Further, as a coating rubber, a special rubber composite is used, in which organic cobalt metallic salt as a cobalt metal of 0-0.1 weight part and sulpher of 0.5-4.0 weight part against rubber component of 100 weight part are contained, and 100% modulus after valcanization is over 20kg/cm<2>.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention improves the metal cord and its coating rubber, which are applied to reinforcing materials such as belt cords and carcass ply cords of radial tires, thereby significantly extending the durability life. This relates to improved radial tires.

(Prior art) In tires using steel cords as reinforcing materials, belt end separation (Bus) and carcass ply end separation (PES) occur, which not only makes retreading impossible but also poses significant safety problems. In order to prevent such separation from the ends of the steel cord, for example,
No. 5 discloses an improvement technique for steel cords in which the bending rigidity of the steel cords is increased in order to prevent BBS.

However, the steel cord invented by this invention not only has a problem with fretting fatigue resistance, but also the bending rigidity of the cord itself has been reduced due to the increased strength of the steel cord in order to reduce the weight of radial tires, which is a social need in recent years. The current situation is that it cannot be said to be sufficient.

Here, it is necessary not only to improve the steel cord, but also to improve technology that combines the steel cord and rubber.
In particular, in order to prevent such separation, it is important to improve the rubber covering the steel cord and the rubber around the ends of the cord to suppress the growth of cracks in the rubber itself. JP-A-62-273237 and JP-A-63-2566
Publication No. 36 discloses a rubber composition with excellent crack growth resistance, but there is no mention of adhesion to steel cord as a covering rubber, making it unsuitable as a covering rubber.

Therefore, in order to suppress such BES and PES by other than using reinforcing members around the ends, it is necessary to suppress the growth of cracks in the rubber while maintaining the adhesion performance between the cord and the rubber better than before. be.

Conventionally, the method of bonding tire cord and rubber is as follows:
The most common method is direct adhesion, in which the tire cord is coated with positive plating, which is an alloy of copper and zinc, and reacts with the sulfur in the rubber.Organic cobalt salts such as cobalt naphthenate are added to the coating rubber to improve adhesion. I was trying to improve.

(Problems to be Solved by the Invention) Techniques for improving the plating of steel cords to improve the adhesion between the cord and rubber are disclosed in Japanese Patent Application Laid-open Nos. 54-89939, 54-89940, and 57-56110. However, in both cases, only a small amount of cobalt exists on the outermost surface of the cord due to thermal diffusion caused by wire drawing after the plating is formed, and therefore the role of cobalt in adhesion on the cord surface is extremely small. There was a problem in that the organic cobalt salt-free rubber did not exhibit good adhesion.In particular, the above-mentioned JP-A-57-5
After carefully studying the contents of Publication No. 6110 and forming a cobalt ternary alloy plating layer as described therein, a rich layer of cobalt was not formed on the surface but was diffused into the interior. Therefore, it was confirmed that rubber containing no organic cobalt salt did not exhibit good adhesion.

In view of this situation, in order to develop a radial tire that can significantly improve durability performance, the inventors of the present invention conducted intensive studies on the steel cord reinforcing material and the covering rubber for tires, and found that the conventional plastic plating It has been found that in the combination of a cord and a coated rubber containing organic acid cobalt salt, the rubber crack propagation rate is too fast, and therefore, there is a problem in that BES and PES are likely to occur in a radial tire to which such a cord and rubber are applied.

Therefore, an object of the present invention is to improve belt edge separation resistance (
An object of the present invention is to provide an improved technology for a radial tire that can significantly improve the performance of BES resistance) and carcass ply end separation resistance (PES resistance).

(Means for Solving the Problems) In order to achieve the above object, the radial tire of the present invention includes a toroidal carcass made of reinforcing cords arranged substantially parallel to the meridional cross section of the tire and rubber covering the cords; A reinforcing cord arranged outside the crown part of the carcass and inside the tread, and a belt made of rubber covering the cord, and at least one of the carcass or the belt has 2 to 6 filaments twisted together. A single-strand steel cord with a structure of n (n represents an integer of 2 to 6), the filament diameter being 0.15 to 0.
．． 5+am and having cobalt plating on the surface of the steel cord is provided as a reinforcing cord, and as a coating rubber, an organic cobalt metal salt is added as cobalt metal to 100 parts by weight of the rubber component.
A rubber composition containing 1 part by weight and 0.5 to 4.0 parts by weight of sulfur, with a 100% modulus of 20 kg/c- after vulcanization.
The above is what was used.

In the single-strand steel cord having the 1×n structure, n is preferably 2, and when n is 3 to 6, the elongation (Pl) when a load of 5.0 kg is applied to each steel cord is
) is preferably within the range of 0.2 to 1.2%.

As for the method of coating the above-mentioned cobalt, in addition to electroplating and dry plating, electroless plating (chemical plating) may also be used.

In the case of the rubber permeable cord with a single strand structure in the present invention,
Since the rubber penetrates into the inside of the cord, the adhesion between the cord and the rubber inside the cord is extremely important in terms of tire durability.

In a single-strand steel cord with a 1×2 structure made by twisting two filaments together, the coating process of depositing and forming a cobalt layer on the filament surface can be performed by either a wet method such as electroplating or a dry plating method. ,
It may be carried out either before or after the cord twisting process. The reason for this is that even if a single strand steel cord with a 1×2 structure is subjected to cobalt plating, the entire surface of the filament is coated with cobalt plating.

On the other hand, IX made by twisting 3 to 6 filaments together
For single strand steel cords with 3 to IX6 structure,
When using a wet method such as electroplating, it is possible to form cobalt plating on the surface inside the filament cord, but when using a dry plating method, this becomes difficult. However, even when using the wet method, there are technical issues in manufacturing with high productivity, such as tension control on the plating process line, and problems with the amount and uniformity of deposits. exists.

Therefore, in the case of a single-strand steel cord with a 1×3 to 1×6 structure, in the case of dry plating, it is preferable to form a cobalt plating layer on the surface of the filament after drawing, and then twist the filaments together. In the case of wet methods such as electroplating, the cobalt plating process can be performed either before or after the twisting process, but if anything, it is preferable to perform the cobalt plating process before the twisting process. is preferable.

In addition, the carbon content of the steel cord is 0.75~
From a practical standpoint, it is preferable to use a content within the range of 0.90% by weight. Further, as the base material for cobalt plating, any of iron and ironwork coated with copper, zinc, plasmid, etc. may be used.

(Function) As mentioned above, the steel cord for reinforcing the belt and/or carcass ply used in the present invention is 1×n (n is 2 to 6
A single-strand steel cord with a filament diameter of 0.15 to 0.5 mm.

Further, in the present invention, the number of filaments is 3 to 6.
The reason why the elongation (Pl) of the steel cord having a 1×3 to 1×6 structure is preferably within the range of 0.2 to 1.2% is that the elongation (P1) is 0.2%. If it is less than
It becomes difficult for the coating rubber to penetrate into the cord, and it also increases by 1 to 2%.
If the tension exceeds this, the tension tends to become uneven during the calendering process in which the steel cord is wrapped in rubber coating, causing the tire cord to become disordered, which tends to reduce conformity and cause problems with durability. This is because it is not desirable. In addition, in the case of the 1×2 structure, the covering rubber permeates well into the cord even if the twisted structure of the cord is not a single-twist rubber permeable structure as described above.

Next, in the present invention, the amount of sulfur in the coating rubber is 100! The reason for specifying the amount to be 0.5 to 4.0 parts by weight is that if it is less than 0.5 parts by weight, sufficient cross-linking reaction or adhesion reaction will not occur, while if it exceeds 4 parts by weight, the resistance will be poor. BES
This is because the effect of the present invention on improving the properties and PES resistance will be diminished.

In addition, the reason why the organic cobalt salt in the coating rubber is 0.1 part by weight or less in terms of cobalt metal is that if it exceeds 0.1 part by weight, it will not improve the adhesion but will actually reduce the adhesion. This is because it accelerates aging and reduces the durability of rubber. Preferably it is less than 0.05 part by weight.

Furthermore, the reason why the modulus of the covering rubber is set to 20 kg/cm2 or more is because if it is less than 20 kg/cm, the distortion of the covering rubber becomes too large due to the manual force applied to the belt and carcass ply, thus improving BES resistance and PES resistance. This is because not only the effect of the present invention is weakened, but also a problem arises in terms of durability.In particular, when applied to a belt for a radial tire for a passenger car, there is also a problem in that the steering stability is reduced.

Furthermore, in the present invention, the preferred thickness of the cobalt plating layer is defined as 0.05 to 0.40 μm when electroplating is used because if it is less than 0.05 μm, a stable film with a uniform plating thickness cannot be obtained. Sometimes the base material may be exposed, and the adhesion with the rubber may not be stabilized, while 0.40
This is because if the thickness exceeds μm, the gauge of cobalt plating becomes thick, which is unfavorable in terms of production efficiency and cost. Similarly, when using the dry plating method, the preferred thickness of the cobalt plating layer was specified as 0.001 to 0.15 μm.
．． If OO is less than 1 um, the plating layer will be in the state of bird-like crystals or network crystals, so stable adhesion with rubber cannot be obtained, while if it exceeds 0.15 μm, it is not only undesirable in terms of productivity and cost. On the contrary, it causes a decrease in adhesion,
This is because it is not desirable.

In the present invention, by coating the surface of the outermost layer of the steel cord with cobalt plating, the organic cobalt salt contained in the coating rubber, which was conventionally contained in the coating rubber to improve the adhesion with the cord with the outermost layer coated with a positive layer, can be removed. It has become possible to create a rubber compound that can be removed or reduced to a very small amount, thereby suppressing deterioration of adhesive strength over time and thermal aging of breaking strength, elongation, etc. caused by the addition of organic cobalt salts.

In addition, in order to maintain stable heat-resistant adhesion, the amount of sulfur component, which was previously contained in a relatively large amount (4 to 8 parts by weight), can now be reduced to less than 4 parts by weight. Heat aging can be prevented, crack propagation resistance has been significantly improved, and it has also become possible to improve the corrosion fatigue resistance of adjacent steel cords by reducing corrosive components.

Therefore, in the tire according to the present invention, not only the corrosion fatigue resistance, which has been a problem when using high-strength cords, is greatly improved, but also the bry end separation resistance can be significantly improved.

(Example) Hereinafter, the present invention will be specifically explained with reference to Examples.

As tires for evaluation, radial tire 1 for trucks and buses with tire size 11/70 R22.5 as shown in Fig. 1 and tire size 185SR as shown in Fig. 2 were used.
No. 14 radial tires for passenger cars 10 were used. In the figure, 2 is a bead part, 3 is a sidewall part, 4 is a part of a sigolder, 5 is a tread part, 6 is a bead wire part, 7 is a carcass layer, and 8 is a belt part, respectively.

The carcass ply structure of radial tires for trucks and buses is I x 5 xo, 25 mm, and the belt intersecting layer of radial tires for passenger cars is 1
mm, I X 2 Xo, 3 Onon and I X 3
Xo, 30mm structure was adopted. The steel cords used all had a carbon content of 0.82% by weight, and the number of strikes was constant.

Two methods were used to coat cobalt on the filaments before twisting them: electroplating and dry plating (sputtering).

Electroplating was performed under the following electroplating conditions after pretreatment of electrolytic degreasing and pickling. After forming the cobalt film, it was thoroughly cleaned with ultrasonic waves and dried.

pH of Wataru Bath: 4 Bath temperature: 40'CO current density: 5 A/dm'' On the other hand, dry plating was performed using a magnetron sputtering device as follows.

First, the vacuum level inside the chamber was set to 10-' Torr or less, and then a small amount of argon gas was introduced into the chamber to adjust the vacuum level to 0.1 Torr.
The surface of the test piece was cleaned for 5 minutes using a high frequency glow discharge of z. After cleaning, stop the high frequency glow discharge,
DC voltage 600 V to metal sample (cobalt) target
was applied, and sputtering was performed with argon plasma at a target current of 0.5 A to form a cobalt film.

In addition, the radial tires for trucks and buses (TBR)
The rubber compositions shown in Tables 1 to 3 below were used as the carcass ply coating rubber composition and the belt coating rubber composition of the passenger car radial tire (PSR). Further, the same rubber composition was used for the adjacent members at each cord end.

Incidentally, the variable values in Table 1 are shown in Tables 2 and 3.

The performance evaluation shown below was performed on the above-mentioned prototype tire.

The radial tire for a passenger car was dissected after running on the road, and the belt end crack length on the tread side of the intersecting belt cord layer was measured and evaluated. That is, the top of the cord of the belt layer was peeled off, the end of the belt cord was exposed, and the length of the crack that had occurred along the cord was measured using a caliper. The numerical value was set as 100 and expressed as an index.

The larger the value, the better the BES resistance.

The tread rubber of a prototype tire for trucks and buses was puffed, and the carcass ply end separation resistance was evaluated in a state where the belt layer did not fail due to heat generation in the belt layer. Specifically, each prototype tire was tested at a load of JIS 200% and a speed of 6.
0 klTl/hr, internal pressure 8.25 kg/mm" on the drum, separation occurred at the tip of the carcass ply cord, and the drum traveling distance was taken as the respective traveling distance. It was compared with that of the control tire and expressed as an index. The larger the value, the better the carcass blind separation resistance.

The performance evaluation results of the above solid prototype tires are shown in Tables 2 and 3 below.

The cobalt plating substrates shown in this example are all positive plated iron, but the substrates shown in Table 2 below and ironworks plated with copper and zinc can also be used. There is no change in the evaluation results shown in Table 3.

(Effects of the Invention) As is clear from the tire performance evaluation results shown in Tables 2 and 3 above, the radial tire of the present invention has a B resistance.
The performance of ES properties and PES resistance has been significantly improved, and as a result, the present invention can significantly extend the durability life of radial tires such as radial tires for passenger cars, radial tires for trucks and buses, and radial tires for light trucks. can be improved.

Furthermore, because the present invention has reduced the sulfur content in the rubber coating layer, it has become possible to reduce the sulfur in adjacent rubber members of the tire and to remove the adjacent members themselves, making it possible to create a new lightweight tire that has never existed before. can.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a truck/bus radial tire (TBR) used in the example, and FIG. 2 is a partial sectional view of a passenger car radial tire (PSR) used in the same example. 1...TBR2...Bead part 3...Side wall part 5...Tread part 7...Carcass layer 10...PSR 4...Shoulder part 6...Bead wire part 8...・Belt part

Claims (1)

[Scope of Claims] 1. A toroidal carcass made of reinforcing cords arranged substantially parallel to the meridional section of the tire and their covering rubber, and reinforcement arranged outside the crown portion of the carcass and inside the tread. In a radial tire comprising a cord and a belt made of a rubber covering the cord, at least one of the carcass or the belt has 1×n filaments twisted together.
(n is an integer of 2 to 6) structure, the filament diameter is 0.15 to 0.5 mm
and a steel cord having cobalt plating on the surface of the steel cord is arranged as a reinforcing cord, and as the coating rubber, an organic cobalt metal salt is added as cobalt metal of 0 to 0.1 with respect to 100 parts by weight of the rubber component. A rubber composition containing 0.5 to 4.0 parts by weight of sulfur,
A radial tire characterized by using a tire having a 100% modulus of 20 kg/cm^2 or more after vulcanization. 2. In the single-strand steel cord with the 1×n structure,
The radial tire according to claim 1, wherein n is 2. 3. In the single-strand steel cord with the 1×n structure,
n is 3 to 6, and 5.
Elongation (P_1) when applying a load of 0 kg is 0.2 to 1
．． The radial tire according to claim 1, wherein the radial tire is within the range of 2%. 4. The radial tire according to claim 1, wherein the cobalt plating layer is deposited by electroplating. 5. The thickness of the cobalt plating layer formed by the electroplating is 0.
．． The radial tire according to claim 2, wherein the radial tire has a diameter in the range of 0.05 to 0.40 μm. 6. The radial tire according to claim 1, wherein the cobalt plating layer is adhered and formed by a dry plating method. 7. The radial tire according to claim 4, wherein the thickness of the cobalt plating formed by the dry plating method is 0.001 to 0.15 μm.