JPS5927700B2 - Brasmetuki How to bond steel wire and rubber - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for adhering a plus-plated steel wire and rubber, and more specifically, the present invention is characterized by heat-treating a plus-plated steel wire under specific conditions using a cyan bath method. 2) Good initial adhesion under a wide range of vulcanization conditions; 3) During storage after vulcanization. The present invention also relates to a novel method for bonding rubber with a plus-plated steel wire that does not deteriorate in adhesiveness due to moisture during use.

In recent years, with the advent of steel tires that use plus-plated steel cords, adhesion between steel wire and rubber has become extremely important, and what is especially important when combining the two is sufficient adhesion to withstand stress concentration. It is to obtain.

Conventionally, various methods are known for bonding steel wire and rubber.

Among these, an adhesion method that involves bringing unvulcanized rubber into contact with a steel wire and vulcanizing it into a composite is often used.
Examples of these include general unvulcanized rubber in medium rubber,
Products that contain a large amount of sulfur and cause a chemical reaction between the sulfur and the copper in the plus plating (Journal of the Japan Rubber Association Vol. 45, No. 10)
No., pp. 920-931 (1972)) and a method of mixing specific adhesive chemicals such as cobalt naphthenate or resorcin and hexamethylenetetramine into unvulcanized rubber. They may also be used in combination to obtain a particularly high degree of adhesion. Even in the industrially effective adhesion between steel wire and rubber, there are difficulties in achieving the adhesion function through vulcanization.

The first problem is quality control. This is because slight variations in the process can sometimes cause a sudden drop in adhesive strength. This problem is particularly likely to occur during the humid summer months, and as a result, the running quality of steel tires may deteriorate significantly.After repeated research into the cause, we found that unvulcanized rubber due to humidity during the manufacturing process. It became clear that this was caused by the moisture inside. In other words, when unvulcanized rubber is brought into contact with a steel wire and then vulcanized, if moisture is present at the interface between the two, a large amount of reaction occurs between the steel wire and the unvulcanized rubber in the early stage of vulcanization. As a result, when the vulcanization reaction of the rubber is completed and the rubber is made into a composite, the bond at the interface is significantly weakened, resulting in easy breakage due to stress during use. The presence of moisture between the steel cord and the unvulcanized rubber is due to the moisture in the unvulcanized rubber, which is mostly contained in the unvulcanized rubber from the atmosphere during the manufacturing process. The entire manufacturing process from the rubber mixing process to the calendering process to the molding process to the force spotting process, especially everything necessary, taking into account the fact that moisture is stored during the process from one process to the next. Dehumidifying and air conditioning the process requires a large amount of capital investment and troublesome and difficult management, making it nearly impossible to control humidity industrially. Second
One problem is that rubber products, especially steel tires, after vulcanization are generally stored in a humid atmosphere for a long period of time before being used by consumers.

In particular, if tires are left in hot and humid areas during the summer, the surface tread rubber becomes scratched and moisture infiltrates when mounted on a car, weakening the adhesive bond, and further rusting occurs, reducing the quality of steel tires. In some cases. Of course, the first
It is desired that the problems associated with secondary moisture be solved, and at the same time that the initial adhesion is sufficiently strong over a wide range of vulcanization temperatures and vulcanization times.

In order to obtain the stability of these adhesives, there is a method of adjusting the chemicals related to rubber adhesion as mentioned above to make them stable against moisture and humidity, and then manufacturing rubber products industrially. There are many difficulties in solving these problems while satisfying the characteristics of a coated rubber that is required for industrial purposes and for rubber products, and at present we have not reached a state that is fully satisfied from all viewpoints. It's not working.

There is also a method of stabilizing using steel wire. Before entering into the details of the present invention, a method for brush plating steel wire will be briefly explained.

Regarding the Brasmetski method, see Journal of the Japan Society of Mechanical Engineers, Volume 78,
No. 685, pp. 962-965 (1975).

According to this document, plating is performed after a steel wire that has been subjected to heat treatment and the like is pickled. Brass plating methods include method 1, which uses a cyanide bath, and method 1, which uses an acid bath for cyanide-free plating. In the method using an acidic bath, instead of simultaneous electrodeposition, copper is electrodeposited in the first bath, zinc is electrodeposited on top of the copper in the second bath, and then the wire is heated to an appropriate temperature. Diffusion alloy copper and zinc to obtain brass plating. On the other hand, method 1 using a cyanide bath is simultaneous electrodeposition, and method 1 directly plating brass onto a wire produces a relatively uniform alloy, but it does not require heat treatment. In both cases, the adhesion between the rubber and steel wire is said to be influenced by the brass component, and the plating process is said to be carefully controlled.
To summarize the above, it is extremely difficult to supply effective rubber products made of composites of steel wire and vulcanized rubber to the market with stable quality from all points of view and to satisfy customers. This is an important problem that must be resolved.

The purpose of the present invention is to improve the adhesion between the brass wire (including the brass wire and steel cord) and the rubber during the manufacturing process, during the storage period of the rubber product after vulcanization, and during use. The objective is to obtain a new bonding method that maintains a high level of adhesion at all times, and to obtain a composite consisting of steel wire and vulcanized rubber that maintains a stable level of adhesion from the manufacturing process to the end of its service life. That's true.

The present inventors brought unvulcanized rubber into contact with a brass wire, and examined in more detail the influence of moisture on the adhesion method of vulcanization, and the influence of moisture after vulcanization bonding from the steel wire side. As a result of repeated research, we have found that by heat-treating steel wire obtained by the plating method using a cyan bath (method I above) under the following conditions, the effect of moisture when contacting unvulcanized rubber, The effects of moisture after bonding and even the effects of a wide range of vulcanization conditions have been sufficiently improved under test conditions similar to the environment in which the rubber product was manufactured and throughout its service life. Stino's wires were destroyed.

Heat treatment conditions Humidity conditions Heat treatment temperature in the atmosphere at a relative humidity of 20 to 80 m (
T℃) 160-4010gt≦T≦650-16010
The temperature within the range indicated by gt (where t (minutes) is the thermal heating time) The brass-plated steel wire or steel cord used in the present invention is suitable for severe dynamic applications of rubber products using them. They are preferred because they have excellent adhesion properties and variable adhesion stability against moisture.

In this case, the thickness of the brush plating layer is 0.1 μm or more, particularly preferably 0.2 μm or more.

The composition of Brasmetuki is 85-60% by weight of copper and 15% by weight of zinc.
~40% by weight. Copper: 85% by weight or less, zinc: 15% by weight
If the amount is more than 60% by weight, zinc acts to suppress the reaction and the reaction between sulfur and copper is controlled in an appropriate amount.
When the zinc content is 40% by weight or less, the alloy structure of the β phase is small, and the spread of brass plating is good, and it is easy to process the steel wire. The shape of the steel wire used in the present invention can be appropriately selected depending on the purpose of use of the composite material, but in general, solid wire, twisted wire, etc. are often used.

In addition, especially for steel tires, stranded wire coats are widely used as tire reinforcing materials for both trucks and passenger cars. Next, to explain the heat treatment conditions, when heat treating a steel wire that has been brass plated using the cyan bath method, for example, if the wire is heat treated at 150°C for about 1 minute or less, the surface of the brass plated surface will be heat treated. The brass plating surface of the steel wire that was not subjected to any polishing does not change. As a result, the adhesion to rubber, which is the object of the present invention, is not improved.

When the treatment conditions are further changed by raising the treatment temperature and lengthening the treatment time, first the zinc concentration on the surface gradually increases compared to the plated surface of the untreated cord, and then the hydroxide concentration on the plated surface increases. Dicopper (Cu(0H)2 → Cuprous oxide (Cu)
It is thought that copper oxides are precipitated in the order of 2O)→cupric oxide (CuO). In order to obtain the adhesion to rubber that is the objective of the present invention, it is necessary to heat treat the cord to such an extent that the zinc concentration is higher than that of the plating surface of the untreated cord, and that cupric hydroxide is precipitated on the plating surface. Desirably, heat treatment until cuprous oxide precipitates does not improve adhesion. Therefore, specifically, as described in the examples, 150°C for 10 minutes or more, 300°C for 1 minute or more, and 450°C for 5 minutes or more.
It is desirable that the heat treatment be performed for 2 minutes or less at 600°C, and 20 seconds or less at 750°C. However, if the heat treatment time is too long, it is disadvantageous economically and operationally. The present inventors investigated heat treatment conditions based on various experiments and their data, and as a result, the following formula: 160-4010gt≦T≦
650-16010gt However, T: Heating temperature (°C) t:
It has been found that the adhesion to rubber can be improved by heat-treating the plasmetized steel wire for a time that satisfies the heat treatment time (minutes).

Next, it was discovered that the adhesion of V1 was further improved by drawing the heat-treated plastic plated steel wire. The present invention is composed of a steel wire that has been heat-treated as described above}D. By bringing the steel wire obtained by this heat treatment into contact with unvulcanized rubber and vulcanizing it into a composite, the influence of moisture can be reduced. It is not affected by moisture in the protective opening, which reduces adhesion during the early stages of vulcanization, and it also enables strong adhesion between steel wire and rubber.

Additionally, the use of the heat treated steel wire of the present invention eliminates the need to modify the rubber product manufacturing process and does not require special adhesive formulations that take into account moisture. No special considerations are required during the molding process or when the steel wire according to the invention is brought into contact with the unvulcanized rubber. Furthermore, the use of the heat-treated steel wire of the present invention improves the moisture-resistant adhesion of rubber products after vulcanization compared to conventional untreated steel wires and maintains a high level of adhesion.

Therefore, there is less need to take special consideration where rubber products are used or stored. In other words, sufficient adhesion is ensured even if the rubber product is left unused for a long period of time. Furthermore, when selecting appropriate conditions for the heat treatment of the present invention, method 1 using a cyan bath under a wide variety of vulcanization conditions under normal conditions with little moisture, and acid bath as cyanide-free plating. (described above)
A better adhesion state can be obtained than either of the above. The effects of the present invention have been explained above, and based on these effects, the method of the present invention provides excellent adhesion between the wire and rubber, which cannot be obtained with conventional steel wire, always maintains a high adhesion level, and is inexpensive. This can be said to be a very useful method.

The application of the present invention is not limited to steel tires, but also extends to steel conveyors, belts, hoses, etc. It is an industrially very advantageous method for vulcanizing rubber products that are prone to partial overvulcanization. I can say it.

Example 1 As the steel wire, a steel cord for tires manufactured by Tokyo Steel Corporation [structure: (3+6), 7/3 brass plating, plating thickness 0.2 μm] was used.

Pass this cord through silica gel and dry air (
The relative humidity was 20% at 20°C. ) was heat-treated at various temperatures and times while being sent to a heating furnace. Table 2 shows the strength increase after these heat treatments. The unvulcanized rubber used had the formulation shown in Table 1.

The mixture was kneaded in a conventional manner using a mill roll according to the formulation, and a sheet of approximately 3.5 TI0 fL was prepared to obtain a dry unvulcanized rubber. The sheet was left in saturated steam at 30° C. for 6 days to produce a hydrous unvulcanized rubber. The weight moisture content of the sheet thus obtained was calculated using the electrolytic moisture method [Model D'Avrille].
Electrolyte Moisture Analyzer
Type LBWMOdelWEElectrOly
ticMOistumAnalyZerTypeLBY
(Manufacturers Engineering and Equipment Corp.
ngineeringandEquipmentC0r
It was found to be 1.2%. Also,
For comparison, a water-containing unvulcanized rubber with a water content of 0.4% was prepared. These were used as unvulcanized rubber to be bonded to the steel cord. Fifteen steel cords were arranged in parallel at 12.5 TI 1m intervals (the contact length between the unvulcanized rubber and the steel cord was 25 TWL), and the unvulcanized rubber was placed above and below in a mold that was fixed so that the mutual positions did not move. insert,
Integrated by vulcanization.

Vulcanization was performed at 160°C for 20 minutes.
-1L)j-Le Ifi! The rubber coverage rate (%) on ν is AS
Evaluation was performed using the TM standard pull-out test method (ASTM.D-2229). Adhesive strength was 3 using a load cell type tensile tester.
Measured twice and used the average value. The binding is shown in Cloth 2, and the adhesion level between the treated and untreated cords is almost the same when the moisture content is 0.4%, but when the moisture content is 1.2% (Ff
) clearly shows that there is a significant improvement. The heat treatment conditions for increasing the adhesive strength compared to the untreated cord are within the temperature and time range surrounded by the 10 gt curve, where the heating temperature is T (° C.) and the heat treatment time is t (minutes).

Adhesion of steel cord made in a cyanide-free bath (made by Kawasaki Steel Wire, same (3+6) cord as made by Tokyo Steel, and the copper content and plating thickness measured by fluorescent X-ray were the same) The force is 100 kg/Inc when the water content is 0.4%.
h, and when the moisture content was 1.2%, it was 80k9/Inch. Therefore, if the optimum conditions are selected as shown in Table 2, a higher adhesion level can be obtained by heat-treating the cyan bath method brush plating cord than the cyanide bath method brush plating cord. Does the coated surface of a cord heat-treated within the range mentioned above (for example, a cord heated at 300°C, 450°C, or 600°C for 1 minute) exhibit a yellow or golden color? When this cord is vulcanized with hydrous unvulcanized rubber, the interface of the cord does not change due to vulcanization, but when the untreated cord is used, it takes on a blue to iron gray color.

Furthermore, according to the results of electron beam diffraction analysis, the zinc concentration on the brass plated surface of this heat-treated cord was higher than that of the untreated cord. And the crystal grains are large? Example 2 The unprocessed code in Example 1 was converted to 3 by the method of Example 1.
Heat treatment was performed at 00°C for 30 minutes.

This cord and the untreated cord were brought into contact with the hydrous unvulcanized rubber of Example 1, and vulcanization was performed according to the method of Example 1 to prepare a test piece. After this test piece was left in an atmosphere of 70° C. and 95% relative humidity, the adhesive strength was measured. The results are shown in Table 3VC. The results in Table 3 show that the adhesion and rubber coverage of the heat-treated cord is improved compared to the untreated cord, and the adhesion level is maintained at a high level. Therefore, it is useful when actual rubber products containing heat treated cords are used under high humidity conditions. Example 3 The heat-treated cord of Example 2 and the untreated cord were brought into contact with the hydrous unvulcanized rubber of Example 1 and pressed at 100° C. for about 20 seconds to integrate them.

The shape of the test piece thus obtained differs from the test piece of Example 1 in that it has a thickness of 3.5 wrm. This test piece and the 3.5Tr of the hydrous unvulcanized rubber of Example 1
m sheet was left in an atmosphere of 90% relative humidity at 30°C. This sheet was placed above and below the test piece and vulcanized according to the method of Example 1 to prepare an adhesive test piece, and the adhesive strength and rubber coverage of the cord were measured. The results are shown in Table 4. The results in Table 4 show that while the adhesive strength and rubber coverage of the untreated cord are significantly reduced, the heat treated cord does not change over time and is stable against moisture in the unvulcanized rubber. Show that something is true.

It is also useful to use heat-treated cords even under conditions where moisture absorption is expected to occur significantly during the actual manufacturing process. Table 4 Example 4 Using the hydrous unvulcanized rubber of Example 1 and changing the vulcanization time,
Table 5 shows the results of measuring the adhesive strength.

The results in Table 5 show that in untreated cords, adhesive strength decreases due to over-vulcanization (in this case, about 20 minutes is the usual vulcanization condition), but in cords that have been heat-treated at high temperatures for a short time. Indicates that a high level of adhesion is maintained. When thick tires and the like are vulcanized, some parts become over-vulcanized, but heat treatment has been shown to be effective for these as well. Example 5 After leaving the cords prepared in Example 2 (untreated and heat treated) in air at 70°C and 95% relative humidity (the number of days of standing is also listed in Table 6), the cords prepared in Example 1 were dried and untreated. The sulfurized rubber was left in the air for 10 days to contact the unvulcanized rubber and vulcanize it.

The adhesive strength and the rubber coverage on the wire were measured and the results are shown in Table 6. The results in Table 6 show that the adhesion repals of the heat treated cords remain at a higher level compared to the untreated cords.

This means that the code is used in the actual manufacturing process,
Also, it is useful because there is little need to take special consideration regarding the place where it is stored. Example 620℃ and relative humidity 2
The untreated cord of Example 1 was heat-treated at 150° C. while supplying 0% and 80% air to the heating furnace (heat treatment times are also listed in Table 7).

This cord was vulcanized by contacting the dried unvulcanized rubber of Example 1 which had been left in air at 30° C. and a relative humidity of 90 (f) for 2 days. Table 7VC shows the measurement results of adhesive strength and rubber coverage on the wire. The results in Table 7 show that the relative humidity is 20
% to 80% indicates that the adhesive strength increases due to heat treatment. Example 7 The formulation in Table 1 was changed, and Table 8 was prepared according to the method of Example 1.
The adhesion strength of the hydrous unvulcanized rubber prepared according to the formulation and the cord of Example 2 (untreated and treated) was compared.

The results are shown in Table 9. The results in Table 9 show that the heat treated cord is also useful for adhesive rubbers formulated with cobalt naphthenate.

Example 8 Various cords heat-treated at 300°C for 1 minute and 30 minutes according to the method of Example 1 (the structure of the cord is also listed in Table 10) were brought into contact with the hydrous unvulcanized rubber of Example 1 and cured. Sulfurized.

Table 10 shows the adhesive strength and the rubber coverage of the cord. From the results in Table 10, it is clear that high adhesive strength can be obtained with various brass plating cords by appropriate heat treatment.

Example 9 A series of heat-treated wires (diameter 1.6TW1) with different heat treatment times at 300°C according to the method of Example 1 were wire-drawn (diameter 1.35i) at a wire-drawing speed of 10 cm/Sec.
did.

These wires (undrawn wires and wires subjected to wire drawing) were brought into contact with the hydrous unvulcanized rubber of Example 1 and vulcanized. The results in Table 11, which show the heat treatment time and adhesive strength for each, show that the adhesive strength increases when heat treatment is performed even on undrawn wire, and that the effect of heat treatment is significant even when heat-treated wire is drawn. This shows that it is expressed in

Claims (1)

[Claims] 1 A steel wire brass-plated by a cyan bath method is prepared using the following formula (160-40logt)≦T≦(650
-160logt) [In the above formula, T is the heating temperature (℃), t
is the heat treatment time (minutes)], the steel wire and the rubber are then brought into contact with unvulcanized rubber, and are integrated by vulcanization. Adhesion method. 2. The method according to item 1, wherein the brass plating comprises 85-60% by weight of copper and 15-40% by weight of zinc. 3 Brass-plated steel wire using the cyan bath method was prepared using the following formula (160-40logt)≦T≦(650
-160logt) [In the above formula, T is the heating temperature (℃), t
is the heat treatment time (minutes)], is subjected to wire drawing processing, is then brought into contact with unvulcanized rubber, and is integrated by vulcanization.
How to bond steel wire and rubber. 4. The method according to item 3, wherein the brass plating comprises 85 to 60% by weight of copper and 15 to 40% by weight of zinc.