JP4031639B2 - Steel cord for reinforcing rubber articles and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a steel cord for reinforcing rubber articles used for a frame member of a steel radial tire and a method for manufacturing the same.
[0002]
[Prior art]
Steel cords for reinforcing rubber articles used for skeleton members of steel radial tires for vehicles are usually obtained by drawing a brass-plated wire to a desired wire diameter using a multi-step slip-type wet wire drawing method. In addition, a plurality of twisted steel filaments are widely used.
FIG. 4 is a diagram showing an outline of a wet wire drawing method using the multi-stage slip type wet wire drawing device 10, and this method includes two wet lubricants 11 m in the lubricating liquid tank 11 arranged so as to face each other. In the process of alternately passing the steel wires 13 between the drive capstans 12A and 12B between the multistage drive capstans 12A and 12B, the wire 14 is drawn by the die 14 at each stage. The steel wire (steel filament) that has been drawn through the die 14Z is sent from a driving capstan (not shown) outside the lubricating liquid tank 11 to the winding process.
[0003]
In general, when wet-drawing a brass-plated steel wire, a coating such as a zinc complex of phosphate ester is formed on the surface of the wire, and this is used as an extreme pressure coating to form a die for drawing. There is a way to control die and wire damage by reducing the friction between wires, which has played a huge role in producing steel cord filaments with high productivity. .
On the other hand, the adhesion between the steel cord and the rubber can be obtained by reacting copper contained in the filament surface with sulfur in the rubber in the vulcanization process of the molded green tire, There has been a problem that the coating film remaining on the filament surface hinders the copper-sulfur reaction.
Therefore, conventionally, the above problems have been solved by adding cobalt or nickel that promotes the diffusion of copper into the rubber.
[0004]
[Problems to be solved by the invention]
However, the addition of cobalt or nickel to the rubber is advantageous for accelerating the copper-sulfur reaction, but it has new problems such as reducing the vulcanization reactivity of the rubber and the durability of the tire. I have caused it.
In other words, cobalt or nickel added to rubber is effective in promoting the adhesion reaction between the brass-plated steel cord and rubber, but it may reduce workability due to chemical bloom of unvulcanized rubber, There was a problem that adhesion and adhesion to rubber were hindered. In addition, in the vulcanized rubber, the cobalt and nickel react with the vulcanization accelerator to cause vulcanization reversion, leading to a decrease in tire durability.
[0005]
The present invention has been made in view of conventional problems, and has a high adhesiveness and can suppress deterioration of vulcanized rubber and tire durability and a steel cord for reinforcing rubber articles and a method for manufacturing the same. The purpose is to provide.
[0006]
[Means for Solving the Problems]
As a result of intensive studies, the inventor has made an appropriate amount of cobalt that promotes copper diffusion in the vulcanization process adhere to the filament surface of the steel cord bonded to the rubber, and this cobalt causes the copper-sulfur during vulcanization. It has been found that by promoting the reaction, the adhesiveness between the steel cord and the rubber can be improved without deteriorating the rubber, and the present invention has been achieved.
That is, the invention according to claim 1 is a steel cord for reinforcing rubber articles formed by twisting a plurality of filaments, and the heat generation effect immediately after wet-drawing a brass-plated wire remains as the filament. During this time , a cobalt-added oiling treatment was performed, and a filament having cobalt adhered to the surface thereof was used. This makes it possible to attach an appropriate amount of cobalt to the filament surface, improve the adhesion of the steel cord for reinforcing rubber articles, and suppress deterioration of vulcanized rubber and tire durability. It becomes possible.
According to a second aspect of the present invention, in the steel cord for reinforcing a rubber article according to the first aspect, 0.1 to 5 parts by weight of a cobalt metal salt is used for the oiling treatment with respect to 100 parts by weight of the oil. It is a contained oil.
According to a third aspect of the present invention, in the steel cord for reinforcing rubber articles according to the first aspect, the adhesion amount of the cobalt is 0.1 to 5 mg / kg.
[0007]
The invention according to claim 4 is a method of manufacturing a steel cord for reinforcing a rubber article manufactured by twisting a plurality of filaments, and in the step of wet-drawing a brass-plated wire, Immediately after heating, the steel filament is subjected to a cobalt-added oiling treatment using an oil containing 0.1 to 5 parts by weight of a cobalt metal salt with respect to 100 parts by weight of the oil. It is characterized in that it is twisted after being attached.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing a method for manufacturing a steel cord for reinforcing rubber articles according to the present embodiment. In this example, the drawing process of the final die 14Z of the multi-stage slip type wet wire drawing device 10 shown in FIG. Later, a cobalt-added oiling treatment step by the oiling device 20 is provided so that cobalt is attached to the surface of a steel wire (hereinafter referred to as a filament) immediately after drawing.
As the cobalt salt used in the oiling treatment, for example, various cobalt salts such as cobalt naphthenate, cobalt stearate, cobalt oleate and the like can be used. Moreover, as oil, what contains fatty acid ester etc. mainly in mineral oil is used.
Also, simply applying a cobalt salt has an effect on initial adhesion, but since it cannot be expected to have an effect on durable adhesion, it is better to apply cobalt to oil by dispersing it in oil as in this example. In addition to initial adhesion, durability adhesion can be improved. At this time, by adding cobalt metal salt in the range of 0.1 to 5 parts by weight with respect to 100 parts by weight of oil, 0.1 to 5 mg / kg of cobalt is adhered to the filament surface immediately after wire drawing. Can do.
The cobalt-added oiling treatment is important to be performed on the filament immediately after the wet wire drawing treatment, and cobalt can be uniformly attached to the filament surface due to the heat generation effect immediately after the wire drawing. On the other hand, when cobalt is deposited in a process other than immediately after wire drawing, not only the cobalt deposition becomes non-uniform, but also the amount of cobalt deposition cannot be controlled sufficiently. Is also reduced.
[0009]
Fig. 2 shows the relationship between the amount of cobalt on the cord surface by the cobalt-added oiling treatment (the amount of Co per 1 kg of steel cord (steel filament)) and the durable adhesion between the cord and rubber to which no cobalt is added. Here, the rubber coverage (%) is used as the evaluation of the durable adhesion. As can be seen from this graph, the rubber coverage (%) increases from the vicinity where the amount of cobalt on the cord surface exceeds 0.1 mg / kg, particularly 0.5 mg / kg, and the durability adhesion is improved. On the other hand, when the amount of cobalt exceeds 3 mg / kg, the durable adhesiveness tends to decrease.
Also, FIG. 3 shows the vulcanization time and rubber coverage (%) when the cobalt-added oiling-treated cord and the rubber not added with cobalt are vulcanized and bonded at 145 ° C. when the amount of cobalt on the cord surface is different. )), And the amount of cobalt on the cord surface is 0.1 mg / kg, especially from the vicinity where it exceeds 0.5 mg / kg, the rubber coverage increases in a short vulcanization time, and the durability adhesion improves. I understand. On the other hand, from the point where the amount of cobalt exceeds 2 mg / kg, even if the amount of cobalt increases, the relationship between the vulcanization time and the rubber coverage hardly changes.
Moreover, since there exists a possibility that the problem with respect to rubber | gum degradation may arise when it exceeds 5 mg / kg, it is preferable to set it as 0.1-5 mg / kg as the amount of cobalt deposited on the filament surface immediately after wire drawing.
[0010]
<Example>
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples, but the present invention is not limited to the following.
About 0.82% wt. About the wire material prepared by adding a patenting treatment and a brass plating treatment to the high carbon steel wire material having a diameter of about 5.5 mm containing carbon of the above after repeated dry drawing until the diameter becomes about 1.4 mm. Multi-stage slip type wet wire drawing was performed until the diameter reached about 0.2 mm. Then, immediately after wire drawing, a cobalt addition oiling process is performed with an oil to which a predetermined amount of cobalt stearate is added, and cords of levels A to E with different surface cobalt amounts are prepared, and these cords and cobalt are not added. The rubber was vulcanized at 145 ° C. for 20 minutes. The results obtained by expressing the durable adhesive properties in terms of rubber coverage (%) at this time are shown in the table of FIG. 5, and the results of expressing the heat resistant adhesive properties in terms of rubber coverage (%) are shown in the table of FIG. Moreover, what gave the cobalt addition oiling process to the code | cord | chord before a vulcanization | cure as a comparative example was prepared, and durable adhesiveness and heat resistant adhesiveness were evaluated by the method similar to the above.
As is apparent from the tables of FIGS. 5 and 6, in the level A to D code in which the cobalt-added oiling treatment was performed immediately after the drawing, the durability adhesion and the heat-resistant adhesion were improved as the surface cobalt amount increased. Even in the case of the level D cord having the smallest surface cobalt content of 0.1 mg / kg, both the durable adhesiveness and the heat resistant adhesiveness are higher than those of the comparative example in which the cobalt content is 0.3 mg / kg. It was confirmed that it is important to perform a cobalt-added oiling treatment immediately after the line.
In addition, even in the cord subjected to the cobalt-added oiling treatment, when the amount of surface cobalt is extremely small (0.00 mg / kg in the table) as in the cord of level E, the durable adhesiveness and the heat resistant adhesiveness are It was not improved.
[0011]
【The invention's effect】
As described above, according to the present invention, in the steel cord for reinforcing rubber articles formed by twisting a plurality of filaments, as the filament, the heat generation effect immediately after wet-drawing the brass-plated wire remains. subjected to cobalt added oiling process while in. Thus using the filament was attached cobalt on the surface, Ru can be deposited a suitable amount of cobalt filament surface. Therefore , it is possible to improve the durable adhesiveness and heat resistant adhesiveness of the steel cord for reinforcing rubber articles, and to suppress the deterioration of the vulcanized rubber and the tire durability.
[Brief description of the drawings]
FIG. 1 is a view showing a method for manufacturing a steel cord for reinforcing rubber articles according to the present embodiment.
FIG. 2 is a graph showing the relationship between the amount of surface cobalt and durable adhesiveness (rubber coverage).
FIG. 3 is a graph showing the relationship between vulcanization time and rubber coverage when the amount of surface cobalt of a steel cord is changed.
FIG. 4 is a diagram showing a configuration of a multi-stage slip type wet wire drawing apparatus.
FIG. 5 is a table showing the results of evaluating durable adhesiveness of examples and comparative examples.
FIG. 6 is a table showing evaluation results of heat-resistant adhesion of Examples and Comparative Examples.
[Explanation of symbols]
10 multi-stage slip type wet wire drawing device, 11 lubricating liquid tank, 11 m wet lubricant,
12A, 12B drive capstan, 13 steel wire, 14 dies,
14Z final die, 20 oiling device.

Claims (4)

A cobalt-added oiling treatment is performed while a heat-generating effect remains immediately after wet-drawing a brass-plated wire, and a plurality of filaments having cobalt adhered thereto are twisted together. Steel cord for reinforcing rubber articles.   The steel cord for reinforcing rubber articles according to claim 1, wherein the oil used in the oiling treatment is an oil containing 0.1 to 5 parts by weight of a cobalt metal salt with respect to 100 parts by weight of the oil. .   The steel cord for reinforcing rubber articles according to claim 1, wherein the adhesion amount of cobalt is 0.1 to 5 mg / kg. An oil containing 0.1 to 5 parts by weight of a cobalt metal salt with respect to 100 parts by weight of oil in a steel filament in which a heat generation effect immediately after wire drawing remains in a wet drawing process of a brass-plated wire A method for producing a steel cord for reinforcing rubber articles, characterized in that after a cobalt-added oiling treatment using bismuth is applied and cobalt is adhered to the surface thereof, a plurality of the filaments are twisted together.

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