JPH01113233A - Compound of metal and rubber - Google Patents

Abstract

PURPOSE:To prevent an interruption of reaction between copper in a plating layer and sulfur in rubber at the initial stage of adhesion of the metal and the rubber, with realizing improvement in resisting properties against moisture and heat, by vulcanizing and adhering a metal coated with a ternary alloy plating layer of copper-zinc- cobalt of a specified composition whereby the cobalt containing ratio is gradually increased from the surface to the inside of the layer in a depth direction, and a rubber obtained by adding a predetermined rate of sulfur into natural rubber or synthetic isoprene rubber. CONSTITUTION:In a metal which is coated with a ternary alloy plating layer of copper- zinc-cobalt having copper 60-75weight%, cobalt 2-10weight% and zinc the rest, the cobalt containing ratio at the most surface of the plating layer is 0-5weight% which ratio is gradually increased to the depth 50-200Angstrom of the plating layer from the most surface. The ratio is generally constant in the plating layer deeper than the depth 50-200Angstrom from the most surface. Accordingly, in the case where rubber including natural rubber or synthetic isoprene rubber as its main component and sulfur, with or without addition or organic acid cobalt salt, silica or resorcin as an adhesion accelerator, is vulcanized and adhered with the metal, the adhesive property at the early stage is not obstructed, but the deterioration of the adhesive property during the use of the rubber product can be restricted.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a composite material that is used for a composite material made of metal and rubber, such as tires, hoses, and conveyor belts, and that has excellent adhesive properties between metal and rubber. It is something.

[Prior art and its problems]

Techniques for improving the strength and durability of rubber products by embedding various reinforcing materials in rubber are widely practiced.

Among these, rubber-metal composites are applied to automobile tires, high-pressure rubber hoses, conveyor belts, etc., and the required quality and performance is wide-ranging. This is a universal request.

In particular, for steel radial tires that use steel cords plated with a copper-zinc binary alloy as a reinforcing metal, with the development of expressways, there is a strong desire to improve the high-speed durability and high-speed stability of tires. In order to achieve this desire, it is extremely important to improve the adhesion between the steel cord and rubber.

Regarding this adhesion, research has been carried out to improve the plating layer coated on metal surfaces and rubber, and the adhesion during the manufacturing of rubber products, so-called initial adhesion, has been improved. There is a problem that the good initial adhesion gradually decreases when used, and the current situation is that it is not in a fully satisfactory state.

For example, there is a problem of reduced adhesion due to scratches in rubber and moisture infiltration, or in the case of automobile tires, the infiltration of salt water caused by salt used to prevent freezing. In this way, the adhesion (hereinafter referred to as heat and humidity resistance) during use of rubber products
A method has been proposed in which a ternary alloy plating layer made of copper-zinc with cobalt added thereto is coated to suppress the decrease in . (
For example, patent application No. 53-143282, patent application No. 5
4-114071).

However, metals coated with ternary alloys have problems such as wire breakage during wire drawing or damage to the plating layer due to the reduced workability of the ternary alloy itself.
In addition, there is a problem that the initial adhesion is reduced due to the addition of cobalt, so it has not been put into practical use.

The former problem related to wire drawing can be solved by improving the wire drawing conditions such as the shape of the wire drawing die and the lubricant.
New improvements are needed to address the latter problem of reduced initial adhesion due to the addition of cobalt. Therefore, the present inventors
As a result of research focusing on the surface composition of the plating layer that is involved in adhesion, we found a metal with a ternary alloy plating layer that can ensure good initial adhesion and improve heat and humidity resistance, and a metal that has a composition suitable for this. A composite material made of rubber was developed.

[Means for solving problems]

Adhesion between metal and rubber is formed by the reaction between the copper in the plating and the sulfur in the rubber, and the decrease in adhesion during use of rubber products is caused by the penetration of moisture or salt, which causes the zinc in the plating to become preferential at the bonding interface. It is known that this is caused by corrosion.

The present inventors took into account the adhesion mechanism and adhesion reduction mechanism and worked on improving the surface composition of the copper-zinc-cobalt ternary alloy plating layer. As a result, the cobalt plating content on the outermost surface of the plating was reduced. By lowering the cobalt content and gradually increasing the cobalt content to a certain depth, the reaction between the copper in the plating and the sulfur in the rubber is not hindered during the initial adhesion of metal and rubber, and the moisture and heat resistance can be improved. I found out.

That is, in a metal coated with a copper-zinc-cobalt ternary alloy plating layer having an average plating composition of 60 to 75% by weight of copper, 2 to 10% by weight of cobalt, and the remainder zinc, copper,
By optimizing the zinc and cobalt plating conditions and the subsequent diffusion conditions, the cobalt content on the outermost surface of the plating can be as low as 0 to 5% by weight, and 50 to 2% from the outermost surface.
A copper-zinc-cobalt ternary alloy plating layer is coated with a copper-zinc-cobalt ternary alloy plating layer whose content increases gradually up to a depth of 0.00 mm and remains approximately constant at deeper depths.

Here, the cobalt content on the outermost surface of the plating is 0 to 5% by weight.
The reason for limiting the cobalt content to 50 to 200 is that if it is larger than 5% by weight, the initial adhesion will decrease. This is because, if it exceeds 200 A, it will not be possible to improve the heat and humidity resistance. Furthermore, the plating average composition is fjA60-75% by weight.
The reason for this limitation is that if it is less than 60% by weight, the initial adhesion will decrease, and if it is more than 75% by weight, it will have an adverse effect on the heat and humidity resistance. The reason why we limited cobalt to 2 to 10% by weight is that if it is less than 2% by weight, it will have little effect on heat and humidity resistance, and if it exceeds 10% by weight, it will not be possible to reduce the cobalt content on the outermost surface of the plating to 5% or less. This is because wire drawability is extremely poor and it is not practical.

Next, the composition of the rubber used in the present invention will be described. Adhesion between metal and rubber is greatly influenced not only by the metal but also by the composition of the rubber. Therefore, it is important to have an appropriate rubber composition in order to obtain good adhesion.

Natural rubber or synthetic isoprene/rubber is used as the basic component of the rubber composition, and sulfur is added to cure the rubber by vulcanization and at the same time to provide an adhesive effect with the plating layer coated on the metal surface. The reason for limiting the amount of sulfur to 1 to 8 parts by weight based on 100 parts by weight of natural rubber or synthetic isoprene rubber is that if it is less than 1 part by weight, the adhesive reaction with the plating layer will be small and the initial adhesion will be reduced. This is because if it exceeds this amount, an excessive reaction occurs and the adhesive strength decreases, and the physical properties of the rubber are also adversely affected.

Furthermore, an organic acid cobalt salt, silica, resorcinol, or hexamethylenetetramine can be added as an adhesion promoter. Cobalt naphthenate as organic acid cobalt salt,
Cobalt stearate and the like can be used. The reason why the amount of organic acid cobalt salt is set to 6 parts by weight or less is that if it exceeds this amount, the physical properties of the rubber after heat aging during use of the rubber product will be significantly affected. In addition, the copper according to the present invention
When a metal having a zinc-cobalt ternary alloy plating layer is used, good initial adhesion and improved heat and humidity resistance can be achieved even with rubber to which no organic acid cobalt salt is added.

On the other hand, for rubbers containing silica, resorcinol, and hexamethylenetetramine, the upper limit was set for silica, and the upper and lower limits were set for resorcinol and hexamethylenetetramine. However, if the upper limit is exceeded, the moisture and heat resistance will decrease and the physical properties of the rubber will be adversely affected.

Furthermore, the rubber composition also includes vulcanization accelerators, vulcanization aids,
A reinforcing agent, an anti-aging agent, etc. may be added.

C action] When coating a metal surface with a copper-zinc-cobalt ternary alloy plating layer, the content of cobalt is small at the outermost surface of the plating and tends to gradually increase from the outermost surface toward the inner depth. When vulcanized adhesion is made with natural rubber or synthetic isoprene rubber with sulfur as the main component and rubber with or without addition of organic acid cobalt salt, silica, resolmin, or hexamethylenetetramine as an adhesion promoter, the initial adhesion is inhibited. Therefore, it is possible to suppress a decrease in adhesion during use of rubber products. Therefore, a composite formed by vulcanizing and adhering metal coated with such a plating layer and rubber maintains good initial adhesion and is excellent in heat and humidity resistance.

〔Example〕

IX5Xo, 25φ coated with a copper-zinc-cobalt ternary alloy plating layer whose average plating composition is shown in Table 1
A steel cord was used as well as a similar cord with a copper-zinc binary alloy plating layer as a comparison.

Furthermore, the composition of the plated surface was investigated by ESCA and the results are shown in FIG. Table 2 shows the rubber composition. After vulcanizing these steel cords and rubber at 150° C. for 30 minutes, an adhesion test was conducted according to ASTM standard D 2229-80. In addition, assuming the pull-out length to be 10 mm, n=15
The average value was used. Adhesion was investigated using initial adhesion and 80
The moisture and heat resistance was investigated when thermally degraded at 95% RH for 10 days at 120°C or 1 day at 120°C steam. Table 3 shows the results of the adhesiveness investigation.

From Table 1, Table 2, and Table 3, Sample 1.3 of the invention example has improved initial adhesion in each rubber compared to Samples 2 and 4 of the comparative example, and also has the same moisture and heat resistance as Sample 2.4. Samples 5 and 6 of comparative example
It can be seen that this is a significant improvement compared to .

〔Effect of the invention〕

The composite made of metal and rubber coated with a copper dizinc-cobalt ternary alloy plating layer according to the present invention can maintain good initial adhesion and greatly improve heat and humidity resistance.

[Brief explanation of the drawing]

Figure 1 shows the ES of copper-zinc=cobalt ternary alloy plated surface.
It is a graph showing changes in cobalt content due to CA. (Reference code)

Claims (7)

[Claims] (1) Copper whose plating average composition is 60 to 75% by weight of copper, 2 to 10% by weight of cobalt, and the remainder is zinc, and the cobalt content tends to gradually increase from the outermost surface of the plating to the inner depth direction. Metal coated with a ternary alloy plating layer of zinc-cobalt, natural rubber or synthetic isoprene rubber as main material, and sulfur as natural rubber or synthetic isoprene rubber 100%
A metal-rubber composite made by vulcanizing and adhering rubber containing 1 to 8 parts by weight. (2) In the copper-zinc-cobalt ternary alloy plating layer, the cobalt content is small at 0 to 5% by weight at the outermost surface of the plating, and gradually increases to a depth of 50 to 200 Å from the outermost surface and deeper than that. The metal-rubber composite according to claim 1, wherein the content is approximately constant in some places. (3) A composite of metal and rubber according to claim (1), characterized in that the average coating thickness of the copper-zinc-cobalt ternary alloy plating layer is 0.05 to 0.5 μm. thing. (4) A ternary alloy plating layer of copper-zinc-cobalt is formed by sequentially plating copper, zinc, and cobalt on the metal surface, then heating and diffusing it to form a ternary alloy, which is then wire-drawn. Claim No. 1 (1) characterized by
) A composite of metal and rubber as described in item 2. (5) Claim (1) characterized in that the rubber composition contains 0 to 6 parts by weight of organic acid cobalt salt as an adhesion promoter per 100 parts by weight of natural rubber or synthetic isoprene rubber. metal and rubber composite. (6) In the rubber composition, silica, resorcinol, and hexamethylenetetramine are used as adhesion promoters at 0 to 0 to 100 parts by weight of natural rubber or synthetic isoprene rubber, respectively.
20 parts by weight, 0.5 to 5 parts by weight, and 0.5 to 5 parts by weight of the metal-rubber composite according to claim (1). (7) The metal and rubber composition according to claim (1), wherein the metal shape is a wire as drawn, or a cord, wire mesh, or fabric obtained using these wires. Composite.