JPH0790784A - Metal cord for reinforcing rubber article and conjugate material composed of the metal cord and rubber - Google Patents

Abstract

PURPOSE:To obtain a compact double-or triple-stranded metal cord for reinforcing rubber, enabling the weight-reduction and the durability-increasing of, e. g. a tire, a belt conveyor or a high-pressure hose and excellent in corrosion resistance, fatigue resistance and resistance to edge separation. CONSTITUTION:Metal filaments 1, 2 having metal plating on their surfaces are stranded in a tightly compacted state. Prior to stranding, the metal filament 1 is imparted with a spiral habit to wind in the same direction as to be stranded. Even after stranded, the cord is made to keep the wave shape, whose pitch (pw) is 0.2-0.5P (P=cord strand pitch) and height (h) is 0.05-0.35mm. Further, the metal filament 1 is imparted with inner stress which can be released on the breakage of the cord and the stress forces the metal filament 1 to protrude from the cord end.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal cord for reinforcing a rubber article which is excellent in corrosion resistance, fatigue resistance and edge separation resistance, and a tire and a conveyor made by embedding the metal cord in rubber as a reinforcing material. The present invention relates to a rubber compound such as a belt and a high pressure hose.

[0002]

2. Description of the Related Art Metal cords used for reinforcing rubber articles are usually made of high-carbon steel wire (JIS G3502 piano wire) and have brass, copper, zinc, etc. on the surface to provide adhesion to rubber. Is metal-plated and wire-drawn to a diameter of 0.1 to 0.5 mm, then single-twisted, double-twisted, or layer-twisted, which is widely used as a reinforcing material for automobile tires, conveyor belts, high-pressure hoses, etc. Has been. For example, radial tires for passenger cars use a metal cord having a 1 × 4 or 1 × 5 single twist structure in which 4 or 5 metal filaments are twisted together as a belt portion reinforcing material.

Quality characteristics required of the metal cord as the rubber reinforcing material include adhesiveness with rubber, corrosion resistance, fatigue resistance, and various other mechanical performances (cutting load, rigidity, etc.). . Among these, regarding corrosion resistance, when the rubber uncovered part is present in the metal cord embedded in rubber, when the tire is stepped on stones, nails, etc. while running, the scratch reaches the metal cord The cords corrode within a short period of time due to the moisture penetrating through the scratches, and the cutting load and fatigue resistance of the cords deteriorate. Further, the adhesion between the cord and the rubber may be deteriorated, and the cord may be peeled off to cause quality trouble due to separation of the tire.

The above-mentioned 1 × 4 or 1 × 5 closed cord, which is commonly used, has a cross-sectional shape as shown in FIG. 5, and has a cavity at the center of the cord. For this reason, when these metal cords are embedded in rubber, the rubber does not penetrate into the cords, and a hollow space where the rubber is not coated is generated. Such a composite of a metal cord and a rubber having a hollow space inside has a short service life because it causes quality troubles such as corrosion of the metal cord and separation of the metal cord and rubber due to permeation of water.

In order to solve this problem, attempts have been made to improve a metal cord which eliminates a rubber uncovered portion. For example, Japanese Laid-Open Patent Publication No. 55-90962 proposes an open cord in which metal filaments 2 are twisted so that there is a gap between them, as shown in FIG.
In No. 438, as shown in FIG. 7, a 2 (parallel) +2 cord having almost no cavities inside the cord is proposed, and both have already been put to practical use as a reinforcing material for tires.

On the other hand, due to the recent increase in environmental protection, various developments have been made to reduce the exhaust gas amount of automobiles. Since the reduction of fuel consumption is directly linked to the control of exhaust gas amount, the development in this aspect is particularly active, and there is also a strong demand for weight reduction of automobile tires from the viewpoint of reducing rolling resistance and weight. Therefore, attempts have been made to reduce the diameter of the metal cord and to simplify the twisted structure of the cord so that the thickness of the covering rubber can be reduced. For example, Japanese Patent Laid-Open No. Sho 62
-117893 and JP-A-62-234921,
As shown in FIG. 3, a very simple 1 × 2 cord is proposed in which two metal filaments 2 are twisted together. Since this cord has no cavity inside, the cord is covered with the embedded rubber except the filament contact portion, and has extremely excellent corrosion resistance. In addition, in Japanese Patent Laid-Open No. 2-229286,
Twisting of two metal filaments By setting the degree of squeezing to an appropriate range, a gap was partially provided between the two metal filaments, which further improved the rubber coverage and improved corrosion resistance. An improved code of x2 has been proposed.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The 1 × 2 cord disclosed in Japanese Patent No. 7893 and JP-A No. 62-234921 is not only excellent in corrosion resistance because it is covered with embedded rubber, but it is also composed of a minimum number of twists, so that it is lightweight for automobile tires. However, it has the following drawbacks. That is, when the 1 × 2 cord is used instead of the 1 × 4 cord or the 1 × 5 cord which is conventionally often used in passenger car tires, the number of twists is reduced in consideration of the strength and rigidity of the metal cord. In order to supplement the amount, a filament whose diameter is thicker than before is used. However, since the cut end surface of the metal cord placed in the rubber has no metal adhesion because it has no metal plating, the stress concentrated on this part when an external force is applied has a small number of twists and a filament diameter. Is larger as the diameter is larger. Therefore, when the 1x2 code is used, edge separation is more likely to occur than when the 1x4 or 1x5 code is used, which causes various quality troubles. Therefore, the product has a short life.

The 1 × 2 code is shown in FIG.
As can be seen from (c), the cross section of the cord has a form in which the metal filaments 2 are arranged horizontally or vertically, and has a nonuniform structure with large irregularities in the longitudinal direction.

Thus, the diameter of the filament is large,
Further, if the structure is non-uniform in the longitudinal direction, the fatigue resistance (bending fatigue and compression fatigue) of the cord deteriorates. In particular, when it is used for a belt portion of a passenger car tire, compressive stress is repeatedly applied to the metal cord due to the buckling phenomenon of the tire belt portion that occurs during rapid turning, but the compressive fatigue resistance to this repeated buckling phenomenon is poor. There's a problem.

Therefore, the present invention relates to a 2 to 3 twist cord represented by a 1 × 2 cord excellent in corrosion resistance and weight saving, and prevents edge separation due to a non-bonded portion of the cord end surface, which has been a problem in the past. To provide a metal cord having improved performance and fatigue resistance such as bending fatigue and compression fatigue, and a rubber composite such as a tire, a conveyor belt, and a high-pressure hose whose durability is improved by using this cord as a reinforcing material. Is.

[0011]

MEANS FOR SOLVING THE PROBLEMS The metal cord of the present invention developed in order to solve the above-mentioned problems comprises n (n = 2 or 3) metal filaments whose surface is plated with metal.
A metal cord formed by twisting a single twist structure of × n, in which each metal filament is twisted in a tightly twisted state, and at least one of the metal filaments A is attached by twisting. On the other hand, the other metal filaments B have a wave pitch pw of 0.
2 to 0.5 times, the wave height h is 0.05 to 0.35 mm, and the wave winding direction has a spiral wavy habit in the same direction as the twisting direction and internal stress released at the time of cutting both ends of the cord. However, when the internal stress is released, the end portion of the metal filament B projects in the cord longitudinal direction more than the metal filament A, and the cord end is constituted by only the metal filament B.

This metal cord preferably satisfies the following formula for the average value of the length of the metal filament B protruding from the end of the metal filament A when both ends are cut.

[0013]

[Equation 2]

Further, the metal filament B is twisted with a spiral wave-like habit before the cords are twisted together, but the height h ₁ of the wave of the previous habit is 0.18 to 0.18.
It should be within the range of 0.50 mm.

A tire, a conveyor belt, a high-pressure hose, etc. made by embedding such a metal cord as a reinforcing material in a rubber mainly composed of natural rubber or synthetic rubber is the rubber composite of the present invention. The product is more durable than the conventional composite product using the same two-stranded cord.

In addition to the above, the metal plating applied to the surface of the metal filament is brass, which has excellent adhesion to rubber, copper, zinc, or a ternary alloy in which elements such as Co, Ni and Sn are added to brass. desirable.

[0017]

The metal cord of the present invention is twisted in a tightly twisted state, and in this state, the metal filament B having a small wavy habit other than the habit of twisting is almost in contact locally with the adjacent filament. Then, between the contact points, a gap necessary for rubber penetration into the inside is generated between the adjacent filaments. In addition, since the small spiral wave-like habit causes the filament to have a margin of elongation and a spring effect for absorbing an external force, there is no decrease in bending fatigue and deterioration of twist stability.

In addition, the spiral wave-like habit before twisting can be simultaneously formed on a plurality of metal filaments by false twisting and untwisting by a false twisting device, or the individual metal filaments can be formed by staggered staggered pins. It can be formed by rotating the pin around the axis of the metal filament while applying it and applying a twist to the metal filament, and it can be easily obtained without any disadvantage in manufacturing.

Further, the internal stress of the metal filament B released at the time of cutting the cord can be easily retained by making a difference in the tension at the time of twisting (making the metal filament B smaller than the metal filament A). . Due to the stress, the ends of the metal filament B project outward from both ends of the metal filament A when the both ends of the cord are cut, so that the position of the unbonded portion of the cord end face with respect to the rubber is dispersed, and when the external force is applied, the cord ends The stress acting on is also dispersed. Therefore, according to the present invention, it is possible to improve the permeability of rubber without adversely affecting other properties required for a metal cord for reinforcing a rubber article, and at the same time prevent edge separation. It leads to a marked improvement in durability.

Here, regarding the spiral wave-like habit in the twisted state, the pitch pw is 0.2 to 0.5 times the twist pitch of the metal cord, and the wave height h is 0.05 to 0.35.
The reason for limiting to mm is as follows. That is, the pitch pw
If it is too large, the habit tends to disappear due to frictional resistance with various guides when the cords are twisted together, and the effect of improving fatigue resistance is diminished. On the other hand, if the pitch pw is too small, the amount of twist added to the metal filament B will be large and the cord strength will be significantly reduced, or the inter-filament gap will be too small and rubber permeability will be reduced.

As a preferable value for avoiding these problems, a peculiar pitch of 0.2 to 0.5 times the cord twist pitch P was selected. Further, the height h of the wave has a lowering limit of 0 in consideration of the size of the gap through which the rubber can permeate between the metal filaments as the wave height h increases the relaxation effect against external force and is effective in improving fatigue resistance. .05 mm
And Also, since the height h is excessively large, the cord diameter becomes large, and it becomes difficult to maintain the twisting uniformity of the cord. Therefore, the twisting pitch of the cord is generally set by using a metal filament whose diameter is in a general range. The upper limit of the case defined in the typical range is set to 0.35 mm.

Next, when the both ends of the cord are cut, the average value of the length Δl of the corrugated metal filament B protruding outward from the end of the non-corrugated filament A in the cord longitudinal direction satisfies the above-mentioned formula. The reason why it is preferable to set the range is described.

First, as a premise, the stress that is inherent in the twisted metal filaments and is released when the cord is cut is up to 2.5 m inward from the end of the cord, depending on various conditions at the time of manufacturing the cord. Since there is no influence, the cutting length l of the cord can be considered with the upper limit being 5 m.
Δl changes when l is 5 m or less.

The change in the length of Δl is equivalent to the difference in height Δh (h = h ₁ −h) before and after the twisting of the waves stiffened to the metal filament B at the pitch pw. It is thought to occur in. Therefore, assuming that the shape of the spiral wave is approximately circular, the lower limit is when Δh is min, and Δh is max.
If the upper limit is set to, the above equation holds for the average value of Δl. The wave height h ₁ before twisting is 0.1
When the range is 8 to 0.50 mm, Δh has a min of about 0.10 mm and a max of 0.30 under appropriate manufacturing conditions.
Since this is about mm, by substituting this into the above equation, a concrete number of the average value of Δl can be obtained.

On the other hand, in order to retain a small wavy habit in the twisted state, the metal filament B before twisting
The height h ₁ of the wavy habit of 0.
The reason why the wave winding direction is preferably 18 to 0.50 mm and the same direction as the twisting direction is preferable. First,
It is extremely important to make the spiral wave winding direction the same as the twisting direction. In the opposite direction, the spiral wave-like habit is returned at the time of twisting and the pitch of the wave becomes large, so it is necessary to add a wavy habit that is finer than the pitch of the twisted state, not only making it difficult to manufacture but also wavy Uneven curl tends to be uneven, and the buncher type twisting machine is difficult to stabilize the twist. In the same direction, a spiral wave-like habit is added during twisting, and the pitch of the peculiar wave is reduced, so a spiral wave-like habit that is larger than the pitch of the twisted wave may be added, facilitating manufacturing. . Also, the twist is stable. Therefore, it is desirable that the wave pitch before twisting is set larger than the pitch pw after twisting in consideration of the amount of addition at the time of twisting, and is 0.25 to 1.0 times the twisting pitch. In addition, the wave height h ₁ becomes smaller as the peculiar pitch decreases in the twisting process, and further decreases due to the ironing due to the contact of the twisting roller and the straightening roller after twisting. Considering the amount, it is set to 0.18 to 0.50 mm, which is larger than the height h in the twisted state.

The pitch and height of the spiral wave to be struck are defined as shown in FIG.

The diameter of the metal filament is usually 0.1
A range of 0.5 mm is used. 2 as in the present invention
In a metal cord formed by twisting metal filaments of a book, the filament diameter is more preferably in the range of 0.27 to 0.35 mm. Further, metal filaments having different diameters may be twisted together. Furthermore, the twist pitch of each metal filament is 5 to
It is desirable to make them the same within a range of 20 mm. If it is less than 5 mm, the productivity at the time of manufacturing the cord will be reduced, and if it exceeds 20 mm, the terminal will be loosened and the flexibility will be lowered when the cord is cut.

In the case of twisting two or three strands as in the present invention,
Practically, a twist pitch of 10 to 16 mm is desirable.

[0029]

1 and 2 show an example of the metal cord of the present invention. The metal cord of FIG. 1 has a 1 × 3 twist structure, and the metal cord of FIG. 2 has a 1 × 2 twist structure. These metal cords are metal filaments 1 (metal filament B in the present invention) to which a spiral wave-like habit has been applied beforehand.
And a metallic filament 2 with no spiral wave-like habit
The (metal filament A in the present invention) is twisted in a tighter twist state by making the tension of the metal filament 1 smaller than that of the metal filament 2. The metal filaments 1 and 2 are, of course, those whose surfaces are plated with metal. This code consists of points aa and cc in Fig. 1 (I).
When cut to a predetermined length (≦ 5 m) with the point as a cut point, the internal stress is released and the cut points aa and bb at both ends are released.
As shown in FIG. 1 (II), the metal filament 1 protrudes from the position of the outside in the longitudinal direction of the cord.

Further, even after the internal stress is released, the metal filament 1 draws a small spiral in the longitudinal direction of the filament while inscribed in the small circle d, and in this state, the great circle D
While inscribed in, it is in a state of drawing a large spiral in the longitudinal direction of the cord. Therefore, between the adjacent filaments,
Due to the diameter difference between the small circle d and the metal filament 2 (this becomes the remaining amount h of the height of the wave), a gap is created and the rubber penetrates into the inside of the cord. Further, since the habit imparted to the metal filament 1 has a small spiral wave shape, the bending fatigue property does not deteriorate. Furthermore, since the cord end is occupied only by the curled filament 1, the cross-sectional area of the end where rubber is not adhered can be reduced, which is effective in preventing edge separation.

In the three-stranded cord shown in FIG. 1, two metallic filaments may have a spiral wave-like habit.

A more detailed example will be described below.

Two of the three brass-plated metal filaments having a diameter of 0.27 mm were twisted with a spiral wave-like habit and twisted with the other one to obtain a metal cord having a 1 × 3 twist structure (Example 1). Obtained.

Also, the cords of Examples 2 and 3 and Comparative Example 2 were made by changing the dimensional specifications of the spiral wave to be stiffened.

Further, one of two brass-plated metal filaments having a diameter of 0.30 mm is provided with a spiral wave-like habit and twisted with the other one, and a metal cord having a 1 × 2 twist structure shown in FIG. 2 ( Example 4) was obtained. Also, with respect to this 1 × 2 cord, those in which the dimensions of the spiral wave were changed (Examples 5 and 6 and Comparative Example 4) were produced.

In addition to the above samples, a closed code of 1 × 3 × 0.27 (Comparative Example 1) and 1 × 2 shown in FIG.
A close code of × 0.30 (Comparative Example 3) was also prepared.

Next, using these samples, the rubber coverage when embedded in rubber, which is a substitute characteristic of corrosion resistance, was measured, and as a substitute characteristic of fatigue resistance, a cord for a composite of a cord and a rubber was measured. An axial compression fatigue test was conducted. Further, as an index of the edge separation resistance, the average value of the length Δl of the squeezed filament protruding outward in the cord longitudinal direction at the time of cutting both ends of the cord was measured.

The results are summarized in Table 1.

As can be seen from the table, in Examples 1 to 6, rubber permeability was improved as compared with the conventional cords of Comparative Examples 1 and 3, the rubber coverage was very good, and the fatigue resistance by the compression fatigue test was good. Also, the average value of the protruding length of the curled filament at the time of cutting the cord is superior to that of Comparative Examples 1, 2 or 3, 4.

[0040]

[Table 1]

[0041]

As described above, the metal cord of the present invention has the metal filament A having only the habit of being twisted, and the small spiral wave habit other than the habit of being twisted, and at the time of cutting both ends of the cord. The metal filaments B having the internal stress to be released are combined so that the total number of them is 2 to 3, and the filament gap is secured by the spiral wave and the external force is relaxed. To be Therefore, fatigue resistance related to simple bending and compression bending is improved. Further, the rubber coverage is improved by the gaps generated between the filaments, so that the corrosion resistance is improved and the fretting wear is reduced.

Further, since the cord end portion is composed only of the metal filament B and the cross-sectional area of the cord end portion where the rubber is not adhered is reduced during use, edge separation starting from the cord end portion is also suppressed.

Therefore, the rubber compound in which the metal cord of the present invention is embedded as a reinforcing material, such as a tire, a conveyor belt, and a high pressure hose, has improved fatigue resistance, corrosion resistance, and peeling resistance, and has improved durability. Weight reduction can also be realized.

[Brief description of drawings]

FIG. 1 is an external view showing an example of the metal cord of the present invention. (B) A cross-sectional view of the line bb of the same as above. (II) An external view of the above cord after cutting. (B) bb above. Cross section of line

[FIG. 2] (I) External view of another embodiment (b) Cross-sectional view of bb line section of the above (II) External view after cutting the above cord (b) Cross-section of bb line section of the same Figure

3A is a view showing a conventional closed cord. FIG. 3B is a sectional view taken along line bb of FIG. 3A. FIG. 3C is a sectional view taken along line cc of FIG.

FIG. 4 is a diagram showing the pitch and height of a spiral wave attached to a metal filament B.

5A is a cross-sectional view of a 1 × 5 closed cord, and FIG. 5B is a cross-sectional view of a 1 × 4 closed cord.

FIG. 6 is a sectional view of a 1 × 5 open cord.

FIG. 7 is a sectional view of 2 (parallel) +2 cords.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Metal filament with a spiral wave-like habit 2 Metal filament with no spiral wave-like habit 3 Metal cord of the present invention 4 Conventional closed cord

Claims (4)

[Claims] 1. n pieces (n = 2) whose surface is metal-plated
Or 3) a metal cord obtained by twisting the metal filaments of 1) into a single twist structure of 1 × n, wherein each metal filament is twisted in a tightly twisted state, and at least one metal filament A therein Has only a tendency to be attached by twisting, while the other metal filaments B have a wave pitch pw of 0.2 to 0.5 times the cord twisting pitch P and a wave height h in addition to being attached by twisting. Is 0.05 to 0.35 mm, the wave winding direction is the same as the twisting direction, and the internal stress is released when the both ends of the cord are cut, and the metal filament B is released when the internal stress is released. A metal cord for reinforcing a rubber article, characterized in that the end portion of the cord protrudes in the cord longitudinal direction from the metal filament A and the cord end is constituted by only the metal filament B. 2. The metal cord for reinforcing rubber articles according to claim 1, wherein the average value of the length of the metal filament B protruding from the end of the metal filament A when the both ends of the cord is cut satisfies the following formula. [Equation 1] 3. The metal filament B is twisted with a spiral wave-like habit having a wave height h of 0.18 to 0.50 mm before twisting the cords. Wave height is from h ₁ to h (= 0.05 to 0.35
mm), the metal cord for reinforcing a rubber article according to claim 1 or 2. 4. A tire, a conveyor belt, and a high pressure made by embedding the metal cord for reinforcing a rubber article according to claim 1, 2 or 3 in a rubber mainly composed of natural rubber or synthetic rubber as a reinforcing material. Rubber composites such as hoses.