JPH0115632B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention particularly relates to a metal cord having a novel twisted structure, and the corrosion resistance of the metal cord can be improved by using the present invention as a metal cord-rubber composite reinforced with a metal cord. This can significantly improve the service life of the composite. [Prior Art] Composites of metal cords and rubber are used as belt reinforcing layers, especially in steel radial tires. Steel cords of ×4 or 1×5 construction have been widely used in the past. When looking at the cross-sectional shape of these metal cords, their central portions are hollow as shown in FIG. [Problems to be Solved by the Invention] When a steel cord as described above is used as a belt reinforcing layer, if the tire receives trauma that reaches the metal cord from stones or nails while running on the road surface, the metal cord will be damaged. Moisture that enters through the wound easily penetrates into the cavity in the center of the cord, which corrodes the metal cord and reduces the adhesion between the cord and rubber, resulting in a phenomenon called separation between the cord and rubber. There was a drawback when it happened. To date, various studies have been made to improve these shortcomings, but among them, Japanese Patent Application Laid-Open No. 55-90692
As stated in the publication, by twisting the cord with a slightly larger diameter than the conventional cord, which has no gaps between each filament and has a compact cord diameter, as shown in FIG. A cord as shown in Fig. 2 was proposed, in which the filaments are not in contact with each other, a gap is provided between each filament, and the cord cross section has a uniform cross section inscribed in a circle. After being embedded in rubber, during the heat vulcanization process, when the rubber is in a fluid state at the initial stage of vulcanization, the rubber penetrates into the cavity in the center of the cord through the gaps between the filaments, and water that has entered from the external wound is removed. It is said that the corrosion resistance of metal cords is improved because the metal cords do not diffuse into the cords. However, according to the experience of the present inventors, the code described in the above-mentioned publication does not work because the hot vulcanization process is usually carried out under a pressure of 4 to 40 kg/ ^cm2 .
This pressure crushes the bulge in the cord, almost eliminating the air gap between the filaments, and as a result, the fluid rubber can hardly penetrate into the cavity in the center of the cord, and even if it does, it can only partially penetrate. If a product using such a cord is subjected to trauma even though only a small amount of rubber has penetrated, the interface between the partially penetrated rubber and the cord will corrode in a short period of time due to the moisture that has penetrated from the trauma. It is clear that this method has the disadvantage that moisture further diffuses in the length direction of the cord through the gaps, resulting in separation between the cord and the rubber. In view of the current situation, it is an object of the present invention to propose a metal cord of a completely new concept, which can be used as a metal cord in a metal cord-rubber composite, for example, and can solve the above-mentioned drawbacks. [Means for Solving the Problems] That is, the present invention consists of a twisted bundle of at least three metal filaments, and the arrangement of the metal filaments in a cross section perpendicular to the longitudinal direction of the twisted bundle is such that the arrangement of the metal filaments is equal to that of each adjacent filament. Irregular cross-sections in the longitudinal direction, including discrete areas spaced apart from one another, in particular between each filament, as well as partial contact areas spaced apart from each other in at least one neighbor and in contact with the remaining ones. Elongation when a load of 5.0Kg is applied to each cord.
P ₁ is in the range of 0.2 to 1.2%, and according to this elongation P ₁ , the elongation P ₂ when a load of 2.0 kg is applied is P ₂ (%) ≦
The present invention relates to a metal code characterized in that it satisfies the relationship expressed by 0.947P ₁ - 0.043. The metal cord of the present invention is, for example, a cord in _which various cross-sectional shapes shown in FIG. It is necessary that the elongation P ₂ (%) when a load of 2.0 kg is applied is 0.947P ₁ -0.043 or less, more preferably 0.947P ₁ -0.083 or less. The reason for this is that when used as a metal cord-rubber composite, if P ₁ is less than 0.2%, it is not much different from the conventional compact cord and the purpose of the present invention cannot be achieved, and if it exceeds 1.2%, the cut cord This is because the ends of the wire tend to be untwisted easily, which poses problems in terms of workability, which is undesirable. Among these, when emphasis is placed on workability, the range of 0.2 to 0.7% is more preferable, and when emphasis is placed on rubber permeability, the range is more preferable.
The range of 0.7 to 1.2% is more preferable. Also P ₂
0.947P ₁ - If it exceeds 0.043, after being buried in the rubber,
This is because, in the heat vulcanization process, the cord becomes more likely to have a cross-sectional shape that is easily crushed by the vulcanization pressure, and as a result, it becomes difficult for the rubber to penetrate, which is undesirable. The relationship between P ₂ and the permeability of rubber into the cord will be discussed in more detail below. Generally, in open-stranded cords, when a tensile stress is applied to the cord, each constituent filament tends to compress toward the center of the cord. Here, even if the elongation P ₁ is constant, the elongation P ₂ may be large or small. In the former case, as shown in Figure 2, the cross-sectional shape of the cord is uniform in the length direction (the filament gap is uniform).
In this case, each constituent filament tries to move freely toward the center, so when a load of 2 kg is applied, the elongation of the cord becomes relatively large. On the other hand, the latter is B to E in Figure 3 (1 x 5).
As shown in , the cross-sectional shape of the cord is uneven,
This is a case where the filaments are in contact with each other, and even if each filament tries to move toward the center, contact pressure (repulsive force) acts on each of the two contacting filaments, so when a load of 2 kg is applied, the cord elongates. becomes smaller. In the cross-sectional shape, if the number of contact points between filaments is the number of contacts, then the non-uniformity of the cross-sectional shape of the cord is expressed by the number of contacts. The cord with more contacts has a more uneven cross section. In the single-strand structure, the filament configuration is 1×
5, the number of contacts is 4 (E in Figure 3 1x5), 1x
When the number of contacts is 3 (D in 1×4 in FIG. 3), the non-uniformity of the cross-sectional shape becomes maximum. Therefore, in the metal cord of the present invention, in addition to discrete areas that are spaced apart between adjacent filaments or between each adjacent filament, there are also areas that are spaced apart between at least one adjacent filament and in contact between the remaining adjacent filaments. It has an irregular cross-sectional distribution in the longitudinal direction, including contact areas. In the metal cord of the present invention, the twist pitch is preferably 3 to 16 mm. The reason for this is that the twist pitch is 3mm.
If it is less than that, the productivity during cord manufacturing will decrease significantly,
This is because it is not practical for commercial use, and if it exceeds 16 mm, the cord bending resistance due to bending fatigue of the cord will be greatly reduced, which is undesirable in either case. Here, since a twist pitch of 8 mm or more is preferable from the viewpoint of productivity, it can be said that 8 to 16 mm is the optimum range for practical use. Further, it is preferable that the filament constituting the metal cord of the present invention has a diameter of 0.12 to 0.4 mm. This is because if it is less than 0.12 mm, the strength is too low, and if it exceeds 0.4 mm, the fatigue resistance will decrease and it is not suitable for practical use. The type of metal cord mentioned above is not limited, but steel cord is preferable because it is easily available and inexpensive.In this case, the filament is made of Cu, Sn, Zn, etc. so that the surface of the filament has good adhesion to rubber. Or to these
It may be coated with an alloy containing Ni or Co. Further, the metal cord of the present invention can be manufactured as follows. That is, it can be manufactured by compressing a filament that has been excessively curled in advance in the cord radial direction so as to have a predetermined P ₁ (elongation when loaded with 5 kg). In a tubular twisting machine, the fibers are produced by excessively curling and twisting with a preformer, and then compressing with a compression roller before winding onto a reel. In the bunchier type twisting machine,
The overtwist roller and/or compression roller are adjusted and manufactured as appropriate. As an example, Experiment No. 2 in Table 1
The cord has a P ₁ value of 1.8% immediately after twisting, is twisted using a normal tubular twisting machine, and then compressed to 0.87% using rollers. Finally, the rubber to be buried in order to use the metal cord of the present invention as a metal cord-rubber composite is natural rubber or synthetic rubber. When used in , it is preferable that the 50% modulus of the embedded rubber is 10 to 40 Kg/cm ² . The reason for this is that if the 50% modulus is less than 10 kg/ ^cm2 , the distortion at the end of the metal cord will increase and the resistance to belt end separation (referring to the growth of cracks in the belt coating rubber from the end of the belt cord) will decrease. This is because if it exceeds 40 kg/cm ² , the durability of the belt cord, that is, the cord is likely to break, and at the same time, the workability is significantly reduced, which is not preferable in either case. [Effects of the Invention] The metal cord of the present invention having the above-mentioned configuration is particularly advantageous in that it is a composite of a metal cord and rubber that is used as a reinforcing metal cord. This penetration prevents rust from spreading on the surface of the metal cord due to moisture intrusion due to trauma. Therefore, the separation phenomenon caused by a decrease in the adhesion between the cord and rubber due to corrosion of the metal cord is greatly improved, and the life of the composite of the present invention using the metal cord and rubber is significantly improved. Therefore, the metal cord of the present invention can be used not only in tires with excellent effects, but also in a wide range of industrial products such as agricultural tillers and belts. Note that the present invention applies to 2+7, 3+6, 3+9, 4+
Layered cord such as 10, 3+9+15 or 7×
It is also possible to apply the present invention to multi-strand cords such as 3, 7 x 4, etc. [Examples] Example 1 Twelve types of metal cords shown in Table 1 were created by twisting together brass-plated steel filaments. The twist pitch is 9.5mm in each case. 50% modulus 25kg/50% modulus using these metal cords as tire belt coating rubber
After embedding and vulcanizing with cm ² of rubber, take a metal cord, measure the length of the part where the rubber has almost completely penetrated into the center of the cord, and calculate the degree of rubber penetration as an index as a ratio to the total length of the cord. It was evaluated by For comparison, a conventional metal cord as shown in FIG. 1 was also evaluated in the same manner. The results are shown in Table 1. Here, P ₁ and P ₂ are the elongation (%) when a load of 5.0 kg and 2.0 kg is applied to a metal cord with a total length of 20 to 50 cm, respectively, and the cross-sectional shape is 5 mm in the length direction of the cord. The cross-sectional shape of the cord at the position of the interval was observed with a magnifying glass and indicated by the symbols shown in FIG.

[Table] Regarding the codes of experiments No. 1 to 12 in Table 1 above,
The degree of rubber penetration is measured by taking P ₁ on the horizontal axis and P ₂ on the vertical axis.
80-100 is 〇, 60-79 is ◇, 40-59 is □, 20-39
In Fig. 4, the graph is plotted as △ and 0 to 19 as ▽. As is clear from Table 1 and Figure 4, P ₂
≦0.947P ₁ -0.043 (preferably P ₂ ≦0.947P ₁ -
The metal cords of Experiments No. 1 to 8 (preferably Experiments No. 1 to 6) have a rubber penetration degree of 25
or more (preferably 55 or more), and the rubber penetrates well into the metal cord, whereas P ₂ >
It can be seen that the metal cords of Experiment Nos. 9 to 12 in the range of 0.947P ₁ -0.043 are close to cords with a uniform cross-sectional shape in which the filaments do not touch each other, and the degree of rubber penetration is poor. Next, the metal cords of experiments No. 1 to 12 in Table 1 above were added to the belt reinforcing layer (embedded rubber 50% modulus 25 kg/cm ²
A tire with a size of 175SR14 was created. For these tires, a hole with a diameter of 3 mm that reaches the metal cord was drilled in the ground contact area, and after running for 50,000 km on general roads, the metal cord corresponding to the position of the hole was taken, and The corrosion length of the cord is evaluated as the length of the adhesive interface over which the adhesion deteriorates, and the corrosion length of the cord is evaluated in the same manner using the metal cord of Experiment No. 13. Expressed as an index with 100. The smaller the value, the better. The results are shown in Table 1 above. From this, in the tires of Experiment Nos. 1 to 5 using the metal cord of the present invention, the corrosion resistance of the metal cord was improved, and the improvement was particularly remarkable in Nos. 1 to 2, so the service life was significantly improved. I understand that. Example 2 Consisting of 5 brass-plated steel filaments with a diameter of 0.25 mm, P ₁ = 0.70%, P ₂ =
A metal cord of the present invention having a cross-sectional shape of 0.52% and ABCC'DD'E was embedded in rubber having a 50% modulus of 10 to 40 kg, and evaluated in the same manner as in Example 1. The results are shown in Table 2.

[Table] As is clear from Table 2, it can be seen that the object of the present invention can be achieved without being affected by the modulus of the embedded rubber. Example 3 The metal cord used in Example 2 was used as a reinforcing agent for the rubber track of an agricultural tiller, and a running test was conducted for one year. The results also revealed that the metal cord of the present invention has significantly improved corrosion resistance.

[Brief explanation of drawings]

Fig. 1 is a sectional view of a conventional compact metal cord, Fig. 2 is a sectional view of a metal cord described in Japanese Patent Application Laid-Open No. 55-90692, Fig. 3 is a sectional view of a metal cord of the present invention, and Fig. 4 is a sectional view of a metal cord of the present invention. The figure is a diagram showing the relationship between P ₁ , P ₂ and the degree of rubber penetration. 1...cord, 2...filament, 3...contact point.

Claims (1)

[Scope of Claims] 1. Consisting of a twisted bundle of at least three metal filaments, the arrangement of the metal filaments in a cross section perpendicular to the longitudinal direction of the twisted bundle has discrete regions spaced apart from each other between adjacent filaments. In addition, the cord has an irregular cross-sectional distribution in the longitudinal direction, including a partial contact area where at least one adjacent cord is separated from the other and the remaining adjacent cords are in contact with each other, and a load of 5.0 kg per cord is applied. Elongation when hanging P ₁
ranges from 0.2 to 1.2%, and depending on this elongation P ₁
Elongation P ₂ when applying a load of 2.0Kg is P ₂ (%) ≦
0.947P _{1 -} A metal code that satisfies the relationship expressed by 0.043. 2. The metal cord according to claim 1, wherein the elongation P ₂ is in a range expressed by P ₂ ≦0.947P ₁ −0.083.