JPH0521990B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] This invention relates to a metal with improved adhesion to rubber used in tires, hoses, conveyor belts, etc., and a composite material composed of the metal and rubber that has excellent mutual adhesion between metal and rubber. It is related to. [Prior Art and its Problems] Techniques for improving the strength and durability of rubber products by embedding various reinforcing materials into rubber are widely practiced. Among these, rubber-metal composites are used in automobile tires, high-pressure rubber hoses, conveyor belts, etc., and the required quality and performance is wide-ranging. Improvement is a universal demand. In particular, for steel radial tires that use steel cords plated with copper-zinc binary alloy (brass) as a reinforcing metal, there is a strong demand to improve the high-speed durability and high-speed stability of tires as highways develop. In order to meet this demand, improving the adhesion between the steel cord and rubber has become an extremely important issue. Among various steel radial tires, large tires for trucks and buses may be used for a second or even a third time by repairing the tire tread after their first life, maintaining their adhesion over a long period of time. It has become important to do so. Normally, steel cord and rubber are bonded together during vulcanization when the copper in the plating of the steel cord and the sulfur mixed in the rubber react, producing sulfide at the interface between the steel cord and the rubber. . Regarding this adhesion, research has been carried out to improve the adhesive layer and rubber coated on metal surfaces, and the adhesion during the manufacturing of rubber products, so-called initial adhesion, has been improved. There is a problem in 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, when the adhesion is broken due to heat generation due to hysteresis loss of the rubber while the tire is running, the steam cord and its covering rubber layer separate, causing so-called separation, and the tire becomes unable to run. . Additionally, the tread or sidewall of the tire may be damaged during driving. If this damage reaches the steel cord, the water that has entered through the damage vaporizes due to the heat generated during running and enters between the filaments of the steel cord, destroying the adhesion between the steel cord and its covering rubber, and causing the separator to break down. Trigger Shion. Furthermore, if the air filled in the tire contains moisture, the moisture may enter from inside the tire, where the rubber is thin, and reach the steel cord, causing the same separation as described above. Conventionally, in order to prevent such a phenomenon, various techniques for improving the adhesion between rubber and steam cord have been disclosed. One of these is the technology of compounding the rubber that coats the steam cord. It has been discovered since the 1950s that the adhesion can be improved by adding an organic acid cobalt salt to rubber, and many techniques have been disclosed regarding the type and amount thereof. For example, JP-A-60-42440
The publication discloses improving adhesion by optimizing the respective amounts of sulfur and organic acid cobalt salt.
Furthermore, HRH compositions containing silica, resorcinol, and hexamethylenetetramine have been proposed. However, adding a large amount of organic acid cobalt salt causes deterioration of unvulcanized rubber, and decreases adhesive strength due to high temperature vulcanization, long vulcanization, or heat aging after running, and HRH rubber compositions may cause environmental pollution. , problems during production such as rubber burn. The other is an improved technique for plating steel cord. Patent Application No. 127847, Patent Application No. 1978-
No. 173,889 and US Pat. No. 4,226,918 disclose ternary alloy plating in which nickel is added to brass. However, ternary alloy plating has problems such as the plating layer being damaged during wire drawing due to decreased workability, and the problem of decreasing initial adhesion due to the addition of nickel, making it difficult to put into practical use. I haven't reached it yet. In particular, in order to improve the quality and performance of rubber and solve problems during tire production, organic acid cobalt salts, silica,
When using a rubber in which the amount of resorcinol or hexamethylenetetramine added is reduced or not added at all, the initial adhesion properties are significantly lowered due to the addition of nickel. The former problem regarding the wire drawing process can be solved by improving the wire drawing conditions such as the wire drawing die shape and lubricant, but the latter problem of reduced initial adhesion due to the addition of nickel can be solved by improving the plating composition and rubber. New improvements are needed from both sides of the formulation. The present invention improves the adhesion properties after moist heat aging and the adhesion properties after heat aging (hereinafter referred to as "moist heat resistance" and "heat resistance") without impairing the initial adhesion properties, and also prevents deterioration of rubber quality performance and tire production. The purpose is to provide a composite material made of metal and rubber that is further improved than the conventional one without causing any problems, and includes a metal with an improved stiffening layer and a rubber with an appropriate compounding content for the metal. In combination with this, this objective is achieved. [Means for Solving the Problems] The means for solving the problems provided by the present invention are as follows: (1) The average plating composition is 60 to 75% by weight of copper, 4 to 14% by weight of nickel, and the remainder is zinc; Copper-zinc-nickel with a nickel content of less than 4% by weight at the outermost surface, gradually increasing from the outermost surface to a depth of 50 Å, and falling into the range of approximately 4 to 14% by weight deeper than that. Metal with ternary alloy plating. (2) The metal and natural rubber or synthetic isoprene rubber
1 to 8 parts by weight of sulfur per 100 parts by weight, and 6 parts by weight or less of organic acid cobalt salt or 20 parts by weight or less of silica as an adhesion promoter, 5 parts by weight or less of resorcinol, and 5 parts by weight of hexamethylenetetramine. A metal-rubber composite made by vulcanizing and adhering the following rubbers. (3) The metal and natural rubber or synthetic isoprene rubber
The organic acid cobalt salt is limited to 0.5 parts by weight or less per 100 parts by weight, and 3 to 6 parts by weight of sulfur and N-tert-butyl-2-benzothiazolylsulfenamide or N-oxydiethylene are used as a vulcanization accelerator. These are three metal-rubber composites formed by vulcanization bonding with rubber containing 0.5 to 2 parts by weight of -2-benzothiazolylsulfenamide. Here, to explain about metal plating, the copper-zinc-nickel ternary alloy plating according to the present invention suppresses the decrease in initial adhesion due to the addition of nickel,
In addition, the plating surface layer has been improved in order to improve heat and humidity resistance and heat resistance. That is, in a metal coated with a copper-zinc-nickel ternary alloy plating layer in which the average composition of the entire plating layer is 60 to 75% by weight of copper, 4 to 14% by weight of nickel, and the remainder zinc, copper, zinc, By optimizing the nickel plating conditions and the subsequent diffusion conditions, and then performing the wire drawing process, the nickel content in the plating surface layer is small at the outermost surface and gradually increases toward the inner depth. It is to have a tendency. Specifically, the nickel content at the outermost surface of the plating is small, less than 4% by weight, and tends to increase up to a depth of 50 Å from the outermost surface, and at deeper depths it is approximately 4 to 14% by weight.
This is to ensure that it falls within the range of . To explain this in more detail,
ESCA (Electron Spectroscopy for Chemical
Analysis：Photoelectron spectroscopy)
When sputtering with Ar ions and analyzing from the plating surface in the internal depth direction, the concentration distribution of copper, zinc, and nickel in the depth direction can be obtained. This is limited to the range shown in Figure 1. That is, the present invention is characterized by having a concentration gradient in which the nickel content gradually increases in the plated surface layer.
In addition, at a depth of more than 50 Å from the surface, the nickel content should be within the range of approximately 4 to 14% by weight, and there is no need for a nearly uniform concentration distribution or a tendency to gradually increase or decrease. good. The nickel content shown here is the atomic occupancy of nickel determined from the analytical intensities of each element of copper, zinc, and nickel, converted into a weight ratio. When nickel is added to the conventionally used plastic plating, the adhesion reaction with rubber is reduced, resulting in a problem of reduced initial adhesion. On the other hand, it has the advantage of improved moisture and heat resistance and heat resistance. Therefore, in order to improve initial adhesion as well as moist heat resistance and heat resistance, the plating surface layer that takes part in the initial adhesion reaction should be made entirely of brass, which does not contain any nickel, and the inner layer should contain nickel. It is conceivable to use a copper-zinc-nickel ternary alloy. However, it is difficult to easily manufacture such a metal having two types of plating layers. Therefore, copper obtained by the production method described below -
In zinc-nickel ternary alloy plating, the nickel content of the plating surface layer has a concentration gradient as in the present invention, and furthermore, by combining with the rubber of the present invention, vulcanization of the metal and rubber is improved. Since the nickel content of the plating surface layer, which is involved in the initial adhesion reaction during adhesion, is low, good initial adhesion can be obtained. In addition, the adhesion after moist heat aging during use of a tire, which is a composite obtained by vulcanization adhesion of metal and rubber, and the heat resistance after heat aging are affected by corrosion of the plating layer. The progress of reactions and adhesion reactions is a problem, but as the plating layer contains more nickel, corrosion reactions can be suppressed, and the progress of adhesion reactions can also be suppressed, improving heat and humidity resistance and heat resistance. be able to. As described above, the feature of the present invention is that by improving the surface layer of copper-zinc-nickel ternary alloy plating, initial adhesion is improved and moist heat resistance and heat resistance are improved. In the conventional copper-zinc-nickel ternary alloy plating technology, there is no mention of the composition of the plating surface layer with regard to improving the initial adhesion to rubber. Here, the reason for limiting the plating composition will be explained. The reason why the nickel content on the plated surface was limited to less than 4% by weight is that if it exceeds 4% by weight, the initial adhesion will decrease. Further, the range in which the nickel content gradually increases from the surface in the direction of internal depth was limited to a depth of 50 Å from the surface because if the depth was less than 50 Å, the initial adhesion would be adversely affected. moreover,
The reason why the average plating composition is limited to 65 to 75% by weight of copper is because if it is less than 60% by weight, the adhesive reaction between the copper in the plating and the sulfur in the rubber is insufficient, resulting in a decrease in initial adhesion. On the other hand, if it exceeds 75% by weight, the reaction between copper and sulfur will proceed excessively, particularly during use of the tire, resulting in a significant decrease in heat and humidity resistance and heat resistance. In addition, the reason for limiting the amount of nickel to 4 to 14% by weight is that if it is less than 4% by weight, the initial adhesion is good, but it is not very effective in improving heat resistance or moisture resistance, whereas if it exceeds 14% by weight, the bonded surface The layer has more nickel,
This is because the nickel content on the outermost surface cannot be suppressed to less than 4% by weight, which adversely affects initial adhesion. Next, a method for manufacturing a metal plated with a copper-zinc-nickel ternary alloy according to the present invention will be described. To obtain a copper-zinc-nickel ternary alloy plating layer, copper plating → nickel plating → zinc plating,
Method of performing multilayer plating such as copper plating → zinc plating → nickel plating, zinc plating → nickel plating → copper plating, copper plating → zinc/nickel binary alloy plating, etc., followed by thermal diffusion. Another possible method is to perform copper/zinc/nickel ternary alloy plating in which the three elements are simultaneously precipitated without thermal diffusion. However, in the latter method of plating copper/zinc/nickel ternary alloy, it is extremely difficult to manage the plating bath to stably obtain a predetermined plating composition, and this is not practical. In addition, the plating composition is uniform from the surface to the inside, so the nickel content is 4% by weight.
If it is more than that, the initial adhesion will deteriorate. On the other hand, in the former method, which combines plating and thermal diffusion, it is important to create a plating structure that can easily diffuse between each plating layer and form a ternary alloy.
Diffusion between copper and nickel is more difficult than between copper and zinc or between nickel and zinc, so in a structure where copper and nickel are adjacent to each other, high temperature or long thermal diffusion is required to form a ternary alloy. It is not practical. In addition, if galvanizing is first performed on the steel wire as the base material, a hard and brittle iron-zinc alloy phase will be formed at the interface between the steel wire and the galvanized layer during thermal diffusion, which will cause the plating to fail. Also, it causes peeling of plating in the wire drawing process after thermal diffusion. Therefore, in order to obtain a copper-zinc-nickel ternary alloy plating layer, copper plating → zinc plating → nickel plating, nickel plating → zinc plating → copper plating,
Copper/nickel binary alloy plating → zinc plating, copper plating → zinc/nickel binary alloy plating, zinc/nickel binary alloy plating → copper plating, nickel plating → copper/zinc binary alloy plating A preferred method is to perform multilayer plating by plating, copper/zinc binary alloy plating and then nickel plating, followed by thermal diffusion. Among these plating methods, when combining copper/nickel binary alloy plating and copper/zinc binary alloy plating, it is difficult to manage these plating baths, and a cyan bath is used, which causes pollution problems. copper plating → zinc plating → nickel plating, nickel plating → zinc plating → copper plating, copper plating → zinc/nickel binary alloy plating, zinc/nickel binary alloy plating → A method using copper plating is more preferable. Here, a manufacturing method will be described in which the copper-zinc-nickel ternary alloy plating, which is a feature of the present invention, has a concentration gradient such that the nickel content in the surface layer gradually increases from the outermost surface toward the inner depth. When performing nickel plating → zinc plating → copper plating, zinc/nickel binary alloy plating → copper plating, the plating layer of the present invention can be formed by setting the temperature and time to appropriate conditions by thermal diffusion. can be obtained. On the other hand, when performing copper plating → zinc plating → nickel plating, or copper plating → zinc/nickel binary alloy plating, a ternary alloy layer is formed by heat diffusion after plating, and at the same time the outermost layer Then, zinc and nickel on the surface side are oxidized and an oxide film layer is formed. However, since this surface oxide film layer has poor workability, most of the oxide film is peeled off by wire drawing after thermal diffusion. Therefore, the nickel content of the plating surface layer after wire drawing is determined by the formation of a surface oxide film layer by controlling the thermal diffusion conditions, and the subsequent peeling of the oxide film layer by controlling the wire drawing conditions. can be more reduced and have a concentration gradient. For this reason, the plated layer of the present invention can be obtained by performing thermal diffusion and wire drawing under appropriate conditions. As described above, the plated layer of the present invention can be obtained by optimizing the thermal diffusion conditions and wire drawing processing conditions, but these conditions depend on the plating method, the thickness of the plated layer, and the plated composition. It changes over time. It is practical that the wire diameter after wire drawing of the metal coated with the copper-zinc-nickel ternary alloy plating according to the present invention is 0.1 to 1.0 mm, and the thickness of the plating layer is 0.05 to 0.50 μm. Further, the form may be a wire as drawn, a cord obtained using these wires, a wire mesh, a woven fabric, or the like. on the other hand,
In the cord obtained by twisting drawn wire,
Cords that have a two-layer structure of a center layer and an outermost layer, or cords that have a three-layer structure of a center layer, a middle layer, and an outermost layer, are composed of linear bodies that touch the rubber and linear bodies that do not touch the rubber. When coating the linear body in contact with rubber with a copper-zinc-nickel ternary alloy plating layer obtained by the method of the present invention, the linear body not in contact with rubber is coated with copper, zinc, or copper-zinc binary alloy. Other metal plating layers such as alloy plating may be applied. 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 at the same time as the rubber is vulcanized and cured to provide an adhesion effect to the cling layer coated on the metal surface. The amount of sulfur added to natural rubber or synthetic isoprene rubber
The content was limited to 1 to 8 parts by weight per 100 parts by weight.
If it is less than 1 part by weight, there is little adhesion reaction with the plating layer and the initial adhesion is reduced, and if it exceeds 8 parts by weight, there is an excessive reaction, which reduces the adhesion, especially the heat resistance, and may also have an adverse effect on the physical properties of the rubber. This is for the sake of coming. Furthermore, an organic acid cobalt salt, silica, resorcinol, or hexamethylenetetramine can be added as an adhesion promoter. As the organic acid cobalt salt, cobalt naphthenate, cobalt stearate, cobalt oleate, cobalt maleate, etc. are used, and those having a cobalt content of 8 to 10% are particularly preferred. 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. On the other hand, for rubbers containing silica, resorcinol, and hexamethylenetetramine, the upper limit of silica, resorcinol, and hexamethylenetetramine was set because exceeding the upper limit causes a decrease in heat and humidity resistance and has an adverse effect on the physical properties of the rubber. be. As mentioned above, the addition of organic acid cobalt salts, silica, resorcinol, and hexamethylenetetramine as adhesion promoters can cause problems in the quality performance of rubber and in the production of rubber products, and can also increase the cost of rubber products. Therefore, it is desirable to reduce or not add these adhesion promoters at all. However, in the prior art, it is said that the initial adhesion of cobalt salts of organic acids, which have been widely used in recent years, is poor unless the amount exceeds 0.5 parts by weight. In the copper-zinc-nickel ternary alloy plating according to the present invention, the initial adhesion is improved even when the organic acid cobalt salt is reduced or not added at all, but in order to obtain even better initial adhesion, the rubber compound is improved. I did this. That is, 0.5 parts by weight or less of an organic acid cobalt salt, 3 to 6 parts by weight of sulfur, and N-tert-butyl-2-benzothiazolyl sulfur as a vulcanization accelerator are added to 100 parts by weight of natural rubber or synthetic isoprene rubber. The rubber contains 0.5 to 2 parts by weight of phenamide or N-oxydiethylene-2-benzothiazolylsulfenamide. Here, the vulcanization accelerator is
If the amount is less than 0.5 parts by weight, rubber vulcanization will be slow, and adhesion will be particularly poor, and if it exceeds 2 parts by weight, the modulus of the rubber will become too large, resulting in a decrease in adhesion and the breaking strength of the rubber itself. [Function] By making the nickel content of the copper-zinc-nickel ternary alloy plating layer small at the outermost surface and gradually increasing from the outermost surface toward the inner depth, natural rubber or synthetic isoprene can be formed. When rubber is vulcanized and bonded to a rubber whose main component is sulfur, and to which organic acid cobalt salt, silica, resorcinol, or hexamethylenetetramine is added or not added at all as an adhesion promoter, the initial adhesion is not inhibited and the rubber is bonded. Decrease in adhesion during product use can be suppressed. Therefore, a composite obtained by vulcanizing and adhering metal coated with such a plating layer and rubber maintains good initial adhesion and has excellent moist heat resistance and heat resistance. [Example] In the following examples, comparative examples of steel cords and examples of the present invention are represented by numbers without dashes, and comparative examples of combinations of rubber and steel cords and examples of the present invention are represented by numbers with dashes. Example 1 Copper-zinc whose average plating composition is shown in Table 1
1×5× coated with nickel ternary alloy plating layer
A 0.25φ steel cord and a similar steel cord with a copper-zinc binary alloy plating layer were used. FIG. 2 shows the changes in the nickel content of the crimped surface layer of Inventive Examples 3 and 10 and Comparative Examples 4 and 11, which were investigated by ESCA. Table 2 also shows the formulations of the rubbers used. 150℃ using these steel cords and rubber,
After 30 minutes of vulcanization, an adhesion test was conducted according to ASTM standard D2229-80. In addition, the pull-out length is 10
The average value of n=15 was used as mm. Adhesion was investigated by examining initial adhesion and moist heat resistance when subjected to moist heat deterioration at 80°C and 95% RH for 10 days or 120°C steam for 1 day. Table 3 shows the results of the adhesiveness investigation. From Table 3, the steel cords coated with the copper-zinc-nickel ternary alloy plating layer of Inventions 3, 5, 6, 10, 12, and 13 are as follows: Comparative Example 4,
The initial adhesion was significantly improved compared to the steel cord coated with the copper-zinc-nickel ternary alloy plating layer of Comparative Examples 1 and 8, and the copper-zinc binary alloy plating layer of Comparative Examples 1 and 8 It can be seen that the moisture and heat resistance is much improved compared to the steel cord coated with .

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[Table] Enamide

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[Table] Example 2 Adhesion was investigated using a 1×5×0.25φ steel cord having the basic rubber composition shown in Table 4 and the average plating composition shown in Table 5. Test - Adhesion test specimens were prepared by vulcanization under certain conditions using the combinations of rubber compositions and steel cords shown in 1 to 4, and after aging under the conditions shown in Table 6, a peel test was conducted. . In the peel test, the peel force when the rubber was mechanically peeled off from the steel cord was measured, and the state of the rubber attached to the surface of the steel cord at that time was visually evaluated using a 10-point scale. As for the condition with rubber, a larger value indicates a better condition. In Test-5, a tire running test was conducted to examine quality performance. Table 7 shows the results of examining the vulcanization conditions in Test-1. When the rubber according to the present invention is combined with a steel cord, the initial adhesion, moist heat resistance, and heat resistance are good under any vulcanization conditions even without adding an organic acid cobalt salt to the rubber. Table 8 shows the results of examining the vulcanization accelerator in rubber in Test-2. The vulcanization accelerator according to the invention shows good adhesion. Table 9 shows the results of examining the amounts of cobalt stearate and sulfur in the rubber in Test-3. It can be seen that when 0.5 parts by weight or less of the organic acid cobalt salt and 3 to 6 parts by weight of sulfur according to the present invention are used, the initial adhesion is maintained in a good state and the moisture and heat resistance and heat resistance are excellent. Table 10 shows the results of examining the nickel content in plating and the amount of vulcanization accelerator in rubber in Test-4. At a nickel content of 4 to 14% by weight and a vulcanization accelerator amount of 0.5 to 2 parts by weight according to the present invention, initial adhesion,
Shows good results in both heat and humidity resistance and heat resistance. Table 11 shows the results of the examination of tires in Test-5. reducing the organic acid cobalt salt according to the present invention;
Furthermore, it can be seen that tires using a steel breaker in combination with rubber with no additives and steel cords exhibit extremely good quality and performance after running tests.

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〔Effect of the invention〕

The composite made of metal and rubber coated with a copper-zinc-nickel ternary alloy plating layer according to the present invention is
It maintains good initial adhesion and can significantly improve moisture and heat resistance and heat resistance. Furthermore, various problems such as environmental pollution and rubber burning during the production of rubber products can be solved.

[Brief explanation of the drawing]

FIG. 1 shows the range of the nickel content of the copper-zinc-nickel ternary alloy plated surface according to the method of the present invention. Figure 2 shows a specific example of the nickel content measured by ESCA on a copper-zinc-nickel ternary alloy plated surface. Reference numbers, A...Example of the present invention (sample 3), B...
Comparative example (sample 4), C...Invention example (sample 10), D
...Comparative example (sample 11).

Claims (1)

[Claims] 1. The average plating composition is 60 to 75% by weight of copper, 4 to 14% by weight of nickel, and the remainder is zinc, and the nickel content is as low as less than 4% by weight at the outermost plated surface, and from the outermost surface. Metal with a copper-zinc-nickel ternary alloy plating which increases gradually up to a depth of 50 Å and falls into a range of approximately 4-14% by weight at deeper depths. 2 The average plating composition is 60-75% by weight of copper, 4-14% by weight of nickel, and the rest is zinc, and the nickel content is small at less than 4% by weight at the outermost surface of the plating, and gradually increases from the outermost surface to a depth of 50 Å. metal with a copper-zinc-nickel ternary alloy plating, increasing to approximately 4-14% by weight at deeper depths, and natural rubber or synthetic isoprene rubber.
1 to 8 parts by weight of sulfur per 100 parts by weight, and 6 parts by weight or less of organic acid cobalt salt or 20 parts by weight or less of silica as an adhesion promoter, 5 parts by weight or less of resorcinol, and 5 parts by weight of hexamethylenetetramine. A metal-rubber composite made by vulcanizing and adhering the following rubbers. 3 The average plating composition is 60-75% by weight of copper, 4-14% by weight of nickel, and the rest is zinc, and the nickel content is small at less than 4% by weight at the outermost surface of the plating, and gradually decreases from the outermost surface to a depth of 50 Å. metal with a copper-zinc-nickel ternary alloy plating, increasing to approximately 4-14% by weight at deeper depths, and natural rubber or synthetic isoprene rubber.
The organic acid cobalt salt is limited to 0.5 parts by weight or less per 100 parts by weight, and 3 to 6 parts by weight of sulfur and N-tert-butyl-2-benzothiazolylsulfenamide or N-oxydiethylene are used as a vulcanization accelerator. -2
- 0.5 to 2 benzothiazolylsulfenamide
A metal-rubber composite made by vulcanizing and adhering rubber containing parts by weight.