JPH02145880A - Steel cord and said steel cord-rubber composite - Google Patents

Abstract

PURPOSE:To improve endurance of the title composite embedded in a rubber by attaching a cobalt metal layer having a specific plating thickness to a specific single twist open cord. CONSTITUTION:A cobalt metal plating layer having 500-4000Angstrom plating thickness is attached to a single twist open cord (elongation in 5kg load is 0.12-1.50% when n is 1 and 0.2-1.2% when n is 2-5) being 1-5 in filament numbers n. The cobalt metal plating layer is preferably attached by electrolytic plating.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention relates to steel cords for tires, belt conveyors, etc.
This invention relates to technology that significantly improves the durability of rubber composites.

(Prior art) In recent years, in order to meet social needs, efforts have been made to extend the life of rubber products reinforced with steel cords. For example, in the case of tires, single-strand rubber permeable cords Belts of radial tires (PSR) for passenger cars (JP-A-5643008, etc.), the outermost layer of radial tires (TBR) for trucks and buses on rough roads (JP-A-60-116504), and belts for trucks and buses. It is applied to the plies of radial tires (Japanese Patent Application No. 63-50390). The single-strand rubber permeable cord is a so-called open-strand cord in which the cord diameter is slightly larger and the cord is single-stranded so that the filaments do not come into contact with each other and gaps are created between each filament. If such a cord is embedded in rubber, during the heat vulcanization process, when the rubber is in a fluid state at the beginning of vulcanization, the rubber will penetrate into the cavity in the center of the cord from the gaps between the filaments. It is said that the corrosion resistance of steel cords is improved because water that has entered from external injuries does not diffuse into the cords.

However, conventionally, the above open twisted cord has +Ii
In reinforced rubber products, no consideration has been given to improving adhesion to members surrounding the cord, such as cord coating rubber or the rubber.

On the other hand, in order to improve the durability of rubber and adhesive durability of rubber products reinforced with steel cords, cobalt salt-free rubber, especially low sulfur content rubber, and cobalt-plated steel cords that can be bonded to the rubber are used. Composite materials have been studied (Japanese Unexamined Patent Publication No. 62-189117, etc.), but in this case no consideration was given to the cord twisted structure.

(Problems to be Solved by the Invention) As described above, the corrosion fatigue resistance and fretting resistance of the cord can be greatly improved by making it a single-stranded and open-stranded cord. Because the filament is shaped so that it is large, the degree of deformation of the filament is large when the amount of fluctuation that occurs during tire transfer is applied to the cord. For this reason, with conventional high-sulfur content rubber containing cobalt salt, the rubber deteriorated rapidly, and the rubber penetration effect, that is, the cushioning effect and the filament coating effect of rubber, etc., could not be fully demonstrated. It is known that rubber that does not contain cobalt salts and has a low sulfur content is good for reducing fatigue, but conventional steel cords with brass plating (plus plating) do not contain the above cobalt salts. It does not adhere to rubber.Also, Kobal I
・Cobalt-plated steel cord is known to be effective for adhesion to salt-free rubber, but cobalt plating cannot be applied to the inside of the cord using methods such as physical vapor deposition (PVD). There's a problem.

Therefore, an object of the present invention is to provide a technique that can significantly improve the durability of a steel cord-rubber composite reinforced with open twisted cords.

(Problems to be Solved by the Invention) The present inventors have conducted extensive research on methods that can significantly improve the durability of steel cord-rubber composites, and have found that a predetermined plating thickness is applied to a predetermined single-strand open cord by electrolytic plating. They have discovered that the durability of the composite can be greatly improved by attaching a cobalt metal layer to the cord, and in particular by combining the cord with a predetermined filler rubber and an adjacent rubber member, and have completed the present invention. I ended up doing it.

That is, in the present invention, the elongation (P+) of a single-strand open-stranded or monofilament steel cord with a filament number n of 1 to 5 at a load of 5 kg is 0.12% to 1.50% when n = 1, n = 0.2 when 2 to 5
% to 1.2%, and the cord has a plating thickness of 50%.
The present invention relates to a steel cord characterized by having a cobalt metal plating layer of 0 to 4000 people.

Furthermore, in order to further improve the corrosion fatigue resistance, fretting resistance, and adhesive deterioration resistance of the cord, the present invention provides the above-mentioned open twisted steel cord and an organic cobalt salt or an inorganic cobalt salt per 100 parts by weight of the rubber component. is 0 to 0.5 parts by weight as cobalt metal content, preferably not containing
Sulfur content is 0.5 to 5.0 parts, preferably 1.0 to 3.
This invention relates to a steel cord-rubber composite comprising 0 parts by weight of filler rubber (coating rubber).

In the present invention, by making the cord adjacent rubber member have the same cobalt salt content and sulfur content as the coating rubber, for example, ply end-resistant separation at the ply cord end of a TBR tire, or at the heald cord end of a TBR tire and a PSR tire, can be achieved. Belt end separation resistance can also be significantly improved.

In order to obtain good initial adhesion and heat-and-moisture resistant adhesion to cords coated with a metal cobalt layer by electrolytic plating, the moisture content in the coating rubber should be 0.3% or more for tires.
It is preferably within the range of 0.8%.

The plating treatment is carried out by twisting together filaments coated with base material or plus, etc., and applying metal cobalt electrolytic plating to the cord, which has a double-twisted structure.

When the present invention is applied to a TBR tire, the carcass ply cord has the following properties: Elongation (P, ) at 5 kg load: 0.35% to 1.0
% filament diameter: o, i3~0.32aa twisted structure
:lX3. lX4. It is preferable that the relationship of lX5 is satisfied.

In addition, the belt cord for TBR tires is 5 kg.
Elongation under load (P,): 0.3% to 1.2% Filament diameter: 0.30 to 0.40 + saliva twist structure:
lX4. It is preferable that the relationship of lX5 is satisfied.

Furthermore, as a belt cord for PSR tires, elongation at 5 kg load (P, ): 0.2% to 1.2% (excluding number of filaments n = 1) Filament diameter: o, is to 0.4 Peng twist Structure: lX2. It is preferable that the following relationship be satisfied: txa, lX4°X5.

(Function) The twisted structure of the steel cord of the present invention is 1X1°1X2.
The open twisted structure of lx3, 1x4 and 1x5 is required, but the reason for this is that when the twisted structure becomes lx6 or more, the twisted structure becomes unstable and the filament tends to fall into the inside of the cord. This is because it tends to become a twisted structure, and the rubber does not fully penetrate into the cord, making it impossible to take advantage of the advantages of the rubber-permeable cord.

The cord of the present invention, in which the rubber completely penetrates into the inside of the cord, overcomes the contact pressure between the filaments that make up the cord, significantly improving frentening resistance, fatigue resistance, and corrosion fatigue resistance against fluctuating input. can be improved. In addition, even if this cord is cut in one place, the rubber is completely filled inside the cord, so liquids such as water cannot diffuse through the inside of the cord, and the rubber acts as a cushion. , it also has the advantage of being difficult to cut.

A metallic cobalt layer is attached to the steel cord of the present invention by electrolytic plating, and the advantages of this electrolytic plating include:
The plating solution penetrates into the inside of the cord, making it possible to coat the side of the filament facing the center of the coat with cobalt.

However, if the thickness of the cobalt metal plating layer becomes less than 500 mm, no matter how thin the plating solution is or the current density is reduced, it will be affected by the underlying material and the plating will become a film with an uneven thickness. On the other hand, if the number of people exceeds 4,000, the adhesion cannot be improved, and even if the plating solution is made thicker (however, there is a limit to solubility) and the current density is increased, it is unclear whether this is due to the roughening of the crystal nuclei. However, the initial adhesion is still poor.

Next, regarding the coating rubber of the steel cord-rubber composite of the present invention, the sulfur content is 100% of the rubber component! i
If the amount exceeds 5 parts by weight, the heat deterioration resistance of the rubber suddenly deteriorates, so the amount must be 5 parts by weight or less. In particular, the amount is preferably 3 parts by weight or less, but if no sulfur is contained, the physical properties of the rubber itself, such as elastic modulus, etc. will deteriorate, so 0.5 parts by weight or more is necessary. Furthermore, if the amount of cobalt salt exceeds 0.5 parts by weight, 2. Since the heat deterioration resistance of the rubber deteriorates, the amount is preferably 0.5 parts by weight or less.

If the moisture content in the rubber is less than 0.3%, the reactivity of the adhesive will be low and the initial adhesion will be significantly reduced, while if it exceeds 0.8%, the moisture and heat deterioration resistance of the adhesive will deteriorate. , preferably within the range of <0.3% to 0.8% as described above.

Below, the case where the present invention is applied to tires will be described in more detail.

(1) In the case of carcass ply of TBR tire In the present invention, the elongation (pt) at 5 kg load is 0.35 to 1.0.
If a steel cord within the range of Since there is no contact between the two, the fretting resistance is also significantly improved. However, if the elongation (P, ) is less than 0.35%, it becomes difficult for the coating rubber to penetrate into the cord, and if it exceeds 1.0%, the tension is insufficient during the calendering process to wrap the steel cord with the coating rubber. It tends to become uniform, which tends to cause a decrease in uniformity due to disordered tire cords and a decrease in carcass durability, which is undesirable in any case.

Furthermore, when the steel filaments are twisted 1×2, the cord strength is low, and it is impossible to maintain case strength that can withstand damage to the side portion.

In this case, in order to maintain the strength of the case to withstand side trauma, it is necessary to increase the number of threads or make the filament diameter thicker than in 1×3, 1×4, and 1×5, but the former requires This is difficult due to problems in tire manufacturing technology and reduced bead durability.The latter is caused by bead lifting, where the cord comes off from the bead due to a significant increase in bending rigidity that is proportional to the fourth power of the filament diameter, or resistance due to increased input. There is a problem of decreased corrosion fatigue resistance. Therefore, in order to satisfy the required case strength, manufacturing suitability, etc., and to ensure corrosion fatigue resistance and fretting resistance, it is necessary to use a single layer of 1X3 twist, 1X4 twist, or 1X5 twist, preferably 1 ×4 twist or 1×5
Twist.

The lower limit of the diameter of such a filament is related to maintaining the necessary case strength and reducing the durability of the carcass ply end, and the upper limit is related to bead lifting and a decrease in corrosion fatigue resistance due to increased bending rigidity. Therefore, in the present invention, the filament diameter is set so that the load index is 10 as described above.
For heavy-duty radial tires with a diameter of 0 to 121, the length is limited to 0.13 to 0.25 m in the case of 1X5 twist. Preferably, it is within the range of 0.18 to 0.25 mm. In addition, in the case of lX4 twist, 0.1 to 0.25
m, preferably within the range of 0.19 to 0.25 mm. Furthermore, in the case of 1X3 twist, 0.15 to 0.
25III11, preferably 0.21 to 0.25III11.
within the range of 25am.

Similarly, for heavy-duty radial tires with a load index of 122 or higher, when the 1x5 twist is 0.
1 to 0.32 ma+. Preferably 0.21~
It shall be within the range of 0.32mm. In addition, in the case of 1×4 twist, the length is limited to 0.16 to 0.32 m, preferably 0.2 m.
It is within the range of 3 to 0.32 mm. Furthermore, in the case of 1X3 twist, it is limited to 0.17 to 0.32a+n+, preferably within the range of 0.27 to 0.3a+n+.

(2) In the case of a belt for a TBR tire In this example, as shown in FIG. things can be applied.

As a single layer twisted structure, lX3. 1X4 or 1X5 twists are used, of which 1X4 or 1X5 twists are preferred. Particularly preferred is a 1×4 or 1×5 twist having a filament diameter of 0.30 to 0.40 inches. In the case of single-layer twisting, the strength of the 1X3 twist is too low, and no matter how densely the belt is twisted, there is a limit to the number of twists that can be applied when actually manufacturing tires, resulting in low rigidity as a belt composite and poor abrasion resistance.

If the filament diameter is smaller than 0.30+s+, the cord will have poor cut resistance due to road stones, etc.
If it exceeds 40 aua, the cut resistance of the cord tends to deteriorate due to corrosion fatigue.

(3) In the case of belts for PSR tires In this example as well, as shown in Figure 2, the rubber composition according to the present invention is applied not only to the embedded rubber (coating rubber) but also to the rubber between the belts (b), which is an adjacent rubber member. Can be applied.

First, when the number n of filaments is other than 1, the elongation (P+) at a load of 5 kg is preferably within the range of 0.2% to 1.2% as described above. 2%
If it is less than 1% or 2%, there is no big difference from the conventional compact cord, and the purpose of the present invention cannot be achieved, and if it exceeds 1 or 2%, the ends of the cut cord tend to become untwisted, causing problems in workability. It's for a reason.

Next, when the number of filaments n is l, the above elongation (Pυ
is preferably within the range of 0.12% to 1.5%, and this is due to the following reasons.

In other words, 0.12% is for a straight filament, and the Young's modulus for iron-based metals is 21.000 kg.
/ am'', so if the filament diameter (d) is limited, it is determined to be (0.5 uun or less).Also, large elongation (Pl) can be obtained by using a wave-shaped filament, If it exceeds 1.5%, the filament will move violently, leading to a significant decrease in adhesive properties.

In addition, the filament diameter (d) is 0 in the case of a twisted structure of 1 x 2.
．． 2 to 0.4 mm is preferable, and in the case of IXI, 0
．． 3-0.5 mm is preferred. If the filament diameter is too small, the belt strength will be significantly reduced and the cut resistance of the tire will be reduced, and if the filament diameter is too large, the fatigue resistance will be reduced, so the preferred range is determined automatically.

(Example) Next, the present invention will be specifically explained based on examples.

For evaluation tires, 11R24 is used for TBR tires.
, 5 was used (see Figure 1). The carcass ply structure was 3 +9 in the control tire of Comparative Example 1.
Treat (before vulcanization) by driving a steel cord of
In the tires of other comparative examples and examples, the steel cords commonly used for each carcass ply shown in Table 1 were arranged at the same angle to the circumferential direction and in the tires of comparative example 1. The number of strokes was determined to match the case strength of the control tire.

Also, the belt structure is 1X5X0.3 as the first belt layer.
8 (an) open twisted cords are arranged at 52 degrees to the tire circumferential direction and upward to the right with 28 threads of 150M, and as the second belt layer and third belt i, the same cord is arranged at 20 degrees upward to the right and to the left. 30 shots 15 at 20° uphill
A control was prepared in which the same cords were arranged at 0 mm and the same cord was arranged as the fourth bell layer at an upward left angle of 20° with a number of 28 strokes and 150III11 (Comparative Example 4).

On the other hand, in the case of PSR tires as evaluation tires, 16
5SR13 was used (see Figure 2). This belt cord should be 20° to the circumferential direction so as to intersect with each other.
A control in which the cords were arranged at an angle of 38 and 150IlII11 was used as a control (Comparative Example 7).

Other conditions for the evaluation tires are shown in Tables 1 to 3.

The metal cobalt electrolytic plating treatments shown in these tables were performed as follows.

Using a positive-plated steel cord, the surface of the positive-plated steel cord is electrolytically degreased and washed with acid, and then electrolytically plated under the following electrolytic plating conditions to form a thin metal cobalt film on the surface of the steel cord. formed.

A steel cord having a cobalt thin film obtained by the above electrolytic plating method was thoroughly ultrasonically cleaned.

For plating thicknesses of 500 to 4000, each thickness was obtained by changing the current density and plating time.

A compounding example of the coating rubber for the steel cord and the rubber member adjacent to the cord is as follows. The amounts of sulfur and cobalt salts were varied as shown in Tables 1 to 3.

PLIu111 side natural rubber polyisoprene rubber Carbon black zinc oxide sulfur (2,5) The performance evaluation test for the sample tires was conducted as follows.

From Frenching prototype tires (same method for running tires and new tires)
The cord of the rubberized carcass cord layer from one bead part to the other bead part was pulled out and cut in half at a part of the crown center. Next, the rubber was dissolved in a solvent and the filaments were loosened one by one. The crown center side end and bead side end of each unraveled filament were held in a chuck, and the strength was measured using a tensile tester.The fractured surface of the filament was then set on a microscope so that it could be viewed from directly above. , I took an enlarged photo. Cover the obtained enlarged photograph with graph paper and draw a circle along the edge of the part where no fretting has occurred. The area S was measured, and the value divided by the cross-sectional area of the new steel filament was calculated for 10 steel cords, and the averaged value was taken as the amount of fretting.

The values are expressed as an index so that the smaller the amount of fretting, the larger the value.

The test method is as shown in Fig. 4. The rubber cord 3 taken out from the tire is hung on three pulleys 4 with a diameter of 40 mm as shown in the figure, and the fixed pulley 5 is Apply a tensile load to the weight 6 corresponding to 10% of the breaking load of the new cord through the
3 The pulley is repeatedly moved from side to side for 20 CIIl to repeatedly apply bending strain to the cord to cause it to break due to fatigue.The number of repetitions leading to cord breakage is determined as the average number of breaks for 10 cords, and that of the cord of a new tire is set as 100. The value obtained by determining the degree of decrease in comparison is the degree of decrease in corrosion fatigue resistance. The results are expressed as index values, and the larger the value, the better the corrosion fatigue resistance.

A sample with a width of 50 mm and a length of 300 mm was cut from the jiLuLL living image prototype tire, and a tension of 10% of the cord strength x number of strokes (i.e., treat strength) was applied to the sample, and the weight was 20 kg.
Let the blade type g fall naturally from above at right angles to the cord direction,
The side trauma resistance was compared based on the cutting height. The results are expressed as an index value, and the larger the value, the better the side trauma resistance.

First - Skin contact 1■ Peel the four cords from the rubber at low temperature (-60°C) from the cut section cut from the prototype tire, and measure the amount of rubber remaining on the cord to determine the amount of rubber remaining on the cord. The poor parts of each code were measured using an image analyzer and expressed as an index. The larger the value, the better the adhesion.

11 failures (moisture heat deterioration resistance) A prototype tire was filled with 300 cc of water and the load was JIS 2.
00%, speed 60km/hr, 11R24.5, internal pressure 7.25kg/cm'', rotate on a drum, stop after 1 in 20,000 runs, and heat at low temperature (-60'C).
), peel off the 4 cords from the rubber, and remove the old rubber remaining on the cords at the part where the amount of rubber attachment is the most severe.
Each code was measured using an image analyzer and compared with that of the control tire and expressed as an index.

The larger the value, the better the adhesion resistance.

The tread rubber of a carcass ply PES prototype tire was puffed, and the fracture resistance of the carcass ply ends was evaluated in a state where there was no failure of the belt layer due to heat generation in the belt layer. Specifically, each prototype tire was loaded at JIS 200%.
, speed 60ko+/hr, 11R24.5, internal pressure 8.25kg/cm'' on the drum, separation occurs at the tip of the carcass ply cord, and the drum traveling distance is measured when vibration becomes large. The distance traveled was compared with that of the control tire and expressed as an index. The larger the value, the better the bead durability.

The internal pressure for the prototype tire with a TBH resistance ratio is 7.25 kg/cm.
”, run at a JIS load of 150% and speed of 60 h/hr, stop after running 6000 km, and remove 3 from the tires.
For PSR's prototype tires, after driving on general roads at 100% load for 30,000 miles, the tires were stopped, two belt sections were cut out, and four cords were cut from the rubber at low temperatures (-60°C). After peeling off, the amount of rubber remaining on the cord was measured for each cord using an image analyzer at the part where the amount of rubber was most severely reduced, and compared with that of the control tire and expressed as an index. The larger the value, the better the heat deterioration resistance.

Belt L″′BEs Regarding TBR's prototype tires, low is used for general roads.

After running for 100,000 km at % load, the crack length at the end of the three belts was measured along the cord in units of length and expressed as an index in comparison with that of the control tire.

In addition, PSR's prototype tires were tested on general roads for 100
After running at a load of 30,000 i, the cracks at the ends of the two belts were measured along the longitudinal direction of the cord in units of 2 ++ u++,
It is expressed as an index in comparison with that of the control tire.

The larger the index value, the better the BES resistance.

After removing the rubber from the steel cord sample taken out from the tire, it was stretched at a tension speed of 5 mm with a length of 200 nun between the chucks.
A load of 0.25 to 5 kg was determined by a load-elongation test using an Instron type tensile tester at a full scale of 10 kg/min.
The elongation between f/piece was calculated, and the results of testing 50 pieces were arithmetic averaged to obtain the elongation (Pl) at a load of 5 kg.

The main raw ice content was measured by the Karl Finscher method, which is a general heat loss method.

The results obtained are shown in Table 1 for the carcass plies of TBR tires, Table 2 for the belts of TBR tires, and Table 3 for the belts of PSR tires.

First, the test results regarding carcass ply cords of TBR tires shown in Table 1 will be discussed.

Comparative Example 1 as a control is an example using a steel cord that can actually be made manually in the market, and unlike Comparative Example 2, it has a two-layer twisted structure, so the contact pressure is high and the rubber permeability into the cord is low. Therefore, it can be seen that compared to Comparative Example 2, everything except the initial adhesiveness was inferior.

Comparative example 2 uses a single-strand open cord, plus plating,
This is a combination with a conventional cobalt salt-containing high sulfur content peripheral rubber, and is generally better than Comparative Example 1, but the initial adhesion and heat deterioration resistance are still insufficient.

On the other hand, Example 1 is an example in which the cord of Comparative Example 2 was subjected to cobalt electrolytic plating treatment (plating thickness: 3000), and this was combined with a low sulfur content rubber containing no gobalt salt. In this example, the deterioration of the rubber and the decrease in adhesive properties are suppressed, and therefore, the side cut resistance, resistance to moist heat deterioration, and PES resistance are particularly good.

Example 2 is an example in which the sulfur content was increased to 5.0 parts by weight compared to Example 1. In this case, the improvement effect is not as great as in Example 1, but it is better than in Comparative Example 2.

Comparative Example 3 is an example in which a conventional cord was subjected to cobalt electrolytic plating treatment, and this was combined with a cobalt salt-free low sulfur content rubber. In this case, cobalt electrolytic plating and cobalt salt-free low sulfur content rubber are effective, but
It can be seen that compared to Comparative Example 2, everything except the adhesion-related performance was inferior.

Next, the test results regarding the belt cord of the TBR tire shown in Table 2 will be discussed.

In Examples 3 and 4, all results were better than in Comparative Example 6, which was the control, and it can be seen that the BES resistance in particular was significantly improved.

On the other hand, Comparative Example 4 is an example in which a 38 uu open twisted cord of I X 5 Xo is subjected to plus plating, and this is combined with a cobalt salt-containing high sulfur content rubber, and although it is better than Comparative Example 6, Adhesion and BES resistance are still insufficient.

Furthermore, in Comparative Example 5, the cobalt film formed by electrolytic plating is thinner than in the example, and it can be seen that both initial adhesion and heat deterioration resistance are inferior in this case.

Finally, the test results regarding belt cords of PSR tires, which are not shown in Table 3, will be discussed.

It can be seen that Examples 5 to 8, in which the number of filaments was changed, were all better than Comparative Example 7, which was the control.

On the other hand, in Comparative Example 8, the cobalt film formed by electrolytic plating is too thick compared to the example, and in this case, it can be seen that both initial adhesion and heat deterioration resistance are inferior.

(Effects of the Invention) As explained above, the steel cord and the steel cord-rubber composite of the present invention have the effect of significantly improving the durability of rubber products such as tires and belt conveyors. .

[Brief explanation of the drawing]

Figure 1 is a sectional view of a TBR tire, Figure 2 is a sectional view of a PSR tire, Figure 3 is an explanatory diagram of a fretting resistance test, and Figure 4 is an explanatory diagram of a corrosion resistance fatigue test. (a), (b)...Rubber between belts l...Non-wearing part 2...Fretting part 3...Rubber cord 4...Pulley 5...
Fixed pulley 6... Weight patent applicant Brideston Co., Ltd. Figure 1 Figure 2 tb

Claims (1)

[Claims] 1. 5k single-strand open-stranded or monofilament steel cord in which the number of filaments n is 1 to 5.
When the elongation under g load is n=1, it is 0.12% to 1.50%.
, 0.2% to 1.2% when n=2 to 5, and the steel cord has a cobalt metal plating layer having a plating thickness of 500 to 4000 Å. 2. The steel cord according to claim 1, wherein the cobalt metal plating layer is applied by electrolytic plating. 3. 5k single strand open strand or monofilament steel cord with filament number n from 1 to 5
When the elongation under g load is n=1, it is 0.12% to 1.50%.
, 0.2% to 1.2% when n = 2 to 5, and the cord has a cobalt metal plating layer with a plating thickness of 500 to 4000 Å, an open twisted or monofilament steel cord, and a rubber component of 100 Å. A steel cord rubber comprising a filler rubber containing 0 to 0.5 parts by weight of organic cobalt salt or inorganic cobalt salt as a cobalt metal content and 0.5 to 5.0 parts by weight of sulfur. complex. 4. The steel cord-rubber composite according to claim 3, wherein the cobalt metal plating layer is applied by electrolytic plating. 5. The steel cord-rubber composite according to claim 3 or 4, wherein the rubber member adjacent to the steel cord also uses the above rubber.