JPS6030543B2 - Steel cord for tires with improved adhesion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a steel cord for tires that has significantly improved adhesion to rubber in a humid environment, and in particular, the adhesion to rubber due to the composition ratio and surface crystal structure of the Marin plating applied to the steel cord. The present invention relates to a steel cord for tires with improved adhesion based on the findings.

Conventionally, steel cords used as tire reinforcing materials are coated with 7-3 masen (so-called 7-3 masen) plating, which has a copper content of about 7% by weight and the remaining zinc to improve adhesion. The steel cord coated with silver has excellent mechanical properties on its own, and also exhibits excellent adhesion to rubber in a dry environment.

However, when a steel cord plated with so-called 713 Marin is used as a tire reinforcing material, there is a problem in that the adhesion is significantly reduced by moisture during the tire manufacturing process.

In other words, tire reinforcing materials such as the carcass or breaker are plated with steel cord, coated with unvulcanized rubber, and then incorporated into the tire and heated. Coupled with the humid climate conditions, the adhesiveness of unvulcanized rubber decreases due to moisture absorption, and the adhesiveness decreases significantly after vulcanization. As a result of intensive research into the adhesion between Marin-plated steel cord and rubber under humid conditions, the present inventors discovered that the alloy composition ratio of true green plating and the crystal structure of the plating surface are sensitively affected.
Based on this knowledge, it is an object of the present invention to provide a steel cord that has excellent adhesion to rubber under humid conditions. In the present invention, the copper content is 6% by weight or more based on the total alloy amount.
This is an alloy with a composition of 0% by weight or less with the remainder being zinc, and the surface crystal structure of the alloy as determined by X-ray diffraction is a mixture of Q phase and 8 phases, and is a steel cord for tires with true plating. .

The copper component of the summer bell plating to be applied to the steel cord is at least 5% by weight and at most 6% by weight, preferably at least 55% by weight and at most 5% by weight of the total alloy component. When the copper content is less than 5% by weight, not only adhesiveness under humid conditions but also initial adhesiveness under dry conditions decreases, and the wire drawing process becomes difficult. Here, initial adhesion refers to the adhesion immediately after the steel cord is embedded in rubber and vulcanized and bonded. On the other hand, if the steel component exceeds 60% by weight, the adhesion of the vulcanized rubber decreases significantly with the time of moisture absorption. Furthermore, the surface structure of Shinsen plating needs to be a mixture of Q phase with a face-centered cubic structure and B phase with a body ○ cubic structure, and preferably 8 phases and an X phase with a Q phase.
The intensity ratio of line diffraction (8 phases/Q phase) is in the range of 0.2 or more and 2 or less.

Here, the surface crystal structure was determined by X-ray diffraction using copper as a target and using measurement conditions of 2-V and 3-skin A. When the Q phase is used alone, the adhesion after vulcanization is significantly reduced due to moisture absorption of the unvulcanized rubber, while when the 8 phases are used alone, the wire drawing process of the steel cord becomes difficult. It should be noted that as the steel component of true synthetic gold increases, the Q' in the surface crystal structure increases, and conversely, as the copper component decreases, the number of 8 phases tends to increase, but these two do not necessarily correspond to each other, and the steel cord's It varies depending on the plating method and processing conditions. Although there is no theoretical basis regarding the influence of the composition and surface crystal structure of the aforementioned Maruzu alloy on adhesive properties under humid conditions, initial adhesion and high humidity are affected only when the composition and surface crystal structure of the alloy are within the ranges described above. The decrease in adhesion of the vulcanized rubber steel cord composite under these conditions can be effectively prevented. In the present invention, the conventionally used cyan plating method and diffusion plating method can be employed as a method for applying marin plating to the steel cord.

The cyan plating method is a complete plating process using electroplating in cyanide, where copper and zinc are melted at the same time.
), soda cyanide (NaCN), etc. as main components. The diffusion plating method is a method in which a steel cord is coated with copper, then zinc plated, and the temperature is raised to about 50,000 ℃, so that the copper melts into the zinc and diffuses uniformly, forming true gold. In either method, the formation ratio of the Q phase and 8 phase of the surface crystals of the Marin plating is sensitively influenced by the processing conditions. It is desirable that the copper content of the Marin plating be substantially the same near the interface with steel and on the plating surface.
However, as a result of the fact that the deterioration of adhesion under humid conditions is significantly improved, when the Marasu-plated steel coat W of the present invention is used as a tire reinforcing material, the rubber does not peel off and the high-speed durability is significantly improved. Ta.

The present invention will be described below with reference to Examples. Example 1
Cyan plating was applied to a steel cord, which was buried parallel to the rubber compound shown in Table 1 so that the cut end was not exposed on the sample surface, and then vulcanized and bonded with 15,000.3 powder.

This sample piece was left in an atmosphere of 8'0 and relative humidity of 95%, and changes in adhesiveness over time were measured. In the adhesive peel test, the rubber on the surface of the sample piece was peeled off from the steel cord, and the rubber on the surface of the steel cord was measured with a copper ratio of 52% and 8 phases as the phase x linear diffraction intensity ratio (8 phases/Q phase). ) 3.0 (experiment number 7) was set as 100, and the relative value was determined. The results are shown in Table 2.・Table 2 As is clear from Table 2, the copper content of Marin plating is between 60 and 5.
When Q phase and 8 phase coexist at 0% by weight (experiment number 4)
~8), In addition to initial adhesion (standing time 0), no decrease in adhesiveness was observed with respect to standing time.

Example 2 Steel cords were plated with various steel ratios and surface crystal structures in the same manner as in Example 1, embedded in the rubber composition shown in Table 1, and then soaked in water at 2000°C in an unvulcanized state. The pieces were left in a desiccator (relative humidity 95%) for different times, and then vulcanized and bonded between three females at 150°C.

According to the above-mentioned standing time, the change in adhesion over time was measured by a peel test, and the results are shown in Table 3. Table 3 As is clear from Table 3, when the copper component of Marin plating is 60 to 5% by weight and Q phase and 8 phase are mixed (Experiment No. 12
- 14) There is little decrease in adhesiveness after vulcanization due to moisture absorption of the vulcanized rubber.

Example 3 Steel cord according to the present invention with a copper content of 55% by weight
So, the X-ray diffraction intensity ratio of the 8-phase and Q-phase (3-phase/Q-phase) is 1.
A 17$R14 tire was manufactured by using the tire No. 09 and, as a comparative example, a tire with a steel composition of 70% by weight and Q phase alone, which was subjected to machining plating and embedded in the rubber composition shown in Table 1 above, as a breaker.

Claims (1)

[Claims] 1 An alloy with a composition in which the copper content is 50% by weight or more and 60% by weight or less of the total alloy amount, and the balance is zinc, and the surface crystal structure of the alloy according to X-ray diffraction is a mixture of α and β phases. Ori,
The surface crystal structure determined by X-ray diffraction shows that the X-ray diffraction intensity ratio of β phase and α phase (β phase/α phase) is 0.2 or more Brass-plated steel cord for tires with improved adhesion. .