JP2004306788A - Cord-rubber complex and pneumatic tire using it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve an initial adhesive property of a steel cord and topping rubber and an adhesive property under heat and wet heat. <P>SOLUTION: This cord-rubber complex 21 is constituted of the steel cord 10 and covering rubber 12 and the steel cord 10 is made of a heat-treated cord using a wire applied with a heating process at heating temperature of 400 to 800°C and for heating time of 30 to 250 seconds after plating. The covering rubber contains moisture of 0.3 to 1.0% in an unvulcanized state. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００４３】
【表２】

【００４４】
実施例のものは、加熱処理をしない従来的な比較例１に対して、初期接着性及び湿熱接着性の双方を向上しうるのが確認できる。
【００４５】
【発明の効果】
叙上の如く本発明は、スチールコードとしてメッキ処理の後さらに所定の加熱処理を施した加熱処理コードを用る一方、被覆ゴムとして未加硫状態において水分を０．３〜１．０％含有したゴム組成物を用いているため、スチールコードと被覆ゴムとの初期接着性及び熱・湿熱接着性を向上でき、コード・ゴム複合体、及びそれを用いた空気入りタイヤ等の耐久性を高めうる。
【図面の簡単な説明】
【図１】本発明のコード・ゴム複合体を補強層に用いた空気入りタイヤの一実施例を示す断面図である。
【図２】そのコード・ゴム複合体を拡大して示す断面図である。
【符号の説明】
９ 補強層
１０ スチールコード
１２ 被覆ゴム
２１ コード・ゴム複合体[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a cord / rubber composite having improved initial adhesion and heat / wet heat adhesion between a steel cord and a coating rubber covering the same, and a pneumatic tire using the same.
[0002]
[Prior art]
Steel cord is widely used as a reinforcing element of rubber products from the viewpoint of high cord strength and excellent reinforcing effect.For example, even in pneumatic tires, carcass and belt layers of large tires, belt layers of tires for passenger cars. It is used for reinforcing layers such as. In the cord / rubber composite that forms the reinforcing layer, conventionally, in order to enhance the adhesion between the steel cord and the rubber, the steel cord side is subjected to brass plating and the like, and the rubber side is immersed in the rubber. Contains organic acid cobalt salt and the like.
[0003]
[Problems to be solved by the invention]
However, with the recent improvement of road networks, higher speeds and higher performance of vehicles, the performance required for tires is becoming more and more severe, and as a result, further improvement in the adhesion between the steel cord and the covering rubber is required. ing.
[0004]
In view of such a situation, as a result of research conducted by the present inventor, as a steel cord, a heat-treated cord that has been subjected to a predetermined heat treatment after plating has been used. By using the rubber composition containing 3 to 1.0% of water, it can be found that not only the initial adhesiveness but also the heat / wet heat adhesiveness which is the temporal adhesiveness under heat and wet heat can be improved. Was.
[0005]
The reason for this is that, first, an oxide film is generated on the plating surface by the heat treatment, and this oxide film optimizes the generation of sulfide (CuS) that develops adhesive strength, and the moisture contained in the rubber reduces Activating the plating surface and speeding up the formation of the sulfide during vulcanization are mentioned. It is presumed that the synergistic effect of these effects improves the initial adhesion and the heat / moisture heat adhesion. In the conventional case in which an oxide film is not formed, sulfide is excessively generated, causing cohesive failure such as enlargement of the sulfide layer, and impairing the initial adhesiveness. In addition, unreacted Zn remaining on the plating surface becomes Zn (OH) ₂ due to the influence of moisture and the like, causing adhesive deterioration, and the heat / moisture / heat adhesion is also reduced. On the other hand, if the water content in the rubber is low, the formation of sulfide during vulcanization is delayed, and the above-mentioned effect of the heat treatment cannot be exhibited effectively.
[0006]
Therefore, the present invention uses a heat-treated cord which has been subjected to a predetermined heat treatment after a plating treatment as a steel cord, while a rubber composition containing 0.3 to 1.0% of water in an unvulcanized state as a coating rubber. It is an object of the present invention to provide a cord / rubber composite that can improve the initial adhesion and the heat / wet heat adhesion between a steel cord and a covering rubber, and a pneumatic tire using the same, based on the use of a product. .
[0007]
[Patent Document 1]
JP-A-9-164604
[Means for Solving the Problems]
In order to achieve the above object, the invention of claim 1 of the present application is a cord / rubber composite including a steel cord and a covering rubber covering the steel cord,
The steel cord comprises a heat treatment code using a steel wire subjected to a heat treatment at a heating temperature of 400 to 800 ° C. and a heating time of 30 to 250 seconds after plating,
The coated rubber is characterized by comprising a rubber composition containing 0.3 to 1.0% of moisture in an unvulcanized state.
[0009]
In the invention of claim 2, the plating is brass plating, and the content of copper is 55 to 62%.
[0010]
Further, the invention of claim 3 is characterized in that the plating thickness of the steel wire is 0.1 to 0.3 μm.
[0011]
A fourth aspect of the present invention is an invention of a pneumatic tire, wherein the cord / rubber composite according to the first or second aspect is used for a reinforcing layer of a tire.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to illustrated examples. FIG. 1 is a cross-sectional view illustrating a pneumatic tire using the cord / rubber composite of the present invention.
In FIG. 1, a pneumatic tire 1 is provided with a carcass 6 extending from a tread portion 2 to a bead core 5 of a bead portion 4 through a sidewall portion 3, and an inside of the tread portion 2 and a radially outside of the carcass 6. Belt layer 7.
[0013]
In the present embodiment, the belt layer 7 of the reinforcing layer 9 including the carcass 6 and the belt layer 7 is formed of a cord / rubber composite 21 having a steel cord 10.
[0014]
In the present embodiment, the carcass 6 has a conventional structure, and is formed of one or more carcass plies 6A in which carcass cords of organic fibers are arranged at an angle of, for example, 75 ° to 90 ° with respect to the tire circumferential direction. You. The carcass ply 6A includes a ply folded portion 6b that is folded from the inside to the outside around the bead core 5 at both ends of the ply body 6a straddling between the bead cores 5 and 5. An apex rubber 8 for reinforcing a bead extending from the bead core 5 to the outside in the tire radial direction is disposed between the ply body 6a and the folded portion 6b.
[0015]
Next, the belt layer 7 includes two or more belt plies 7A and 7B in which belt cords are arranged at an angle of 10 to 45 ° with respect to the tire circumferential direction. By crossing each other, the rigidity of the belt is increased and the tread portion 2 is strongly reinforced. As shown in FIG. 2, the belt plies 7A and 7B have a sheet-like cord rubber in which steel cords 10 are arranged in parallel with each other and both sides of a cord array 11 are covered with a covering rubber 12 which is a topping rubber. It is formed by the complex 21.
[0016]
In the present invention, the steel cord 10 of the cord / rubber composite 21
A heat treatment cord made of a steel wire subjected to a predetermined heat treatment after plating is used, while a rubber composition containing 0.3 to 1.0% moisture in an unvulcanized state is used for the covering rubber 12. are doing.
[0017]
The steel cord 10 is made of at least one steel wire. In the present embodiment, for example, a steel cord having a 1 × 3 structure in which three steel wires are twisted is exemplified. In the steel cord 10, a steel wire is first subjected to a plating process, and thereafter, a wire drawing process is performed so as to have a predetermined thickness (diameter). Then, a heat-treated cord is formed by performing a heat treatment after twisting or before twisting a drawn steel wire having a predetermined thickness.
[0018]
Here, brass plating is employed as the plating, and in this example, a conventional diffusion plating method is employed for the brass plating.
[0019]
That is, first, a steel wire is passed through a copper plating bath and a galvanizing bath, respectively, and immersed in the bath to perform a plating process, and a copper plating layer and a zinc plating layer are laminated on the surface of the steel wire. Thereafter, the steel wire is subjected to a thermal diffusion process (for example, about 420 ° C.) by a heating device to diffuse the copper plating layer and the zinc plating layer, thereby forming an alloyed brass plating layer. At this time, the content (weight ratio) of copper in the brass plating is 55 to 62%, which is lower than the conventional range (62 to 70%), more preferably 55 to 60%, from the viewpoint of heat and wet heat adhesion. Further, it is preferable to keep the content within the range of 55 to 58%.
[0020]
The order of the plating may be “zinc plating” → “copper plating”. Copper plating baths include copper pyrophosphate baths and copper sulfate baths, zinc plating baths include zinc sulfate baths, and heating devices include electric heating devices, high-frequency heating devices, and fluidized bed heating furnaces.
[0021]
In the wire drawing process, as in the prior art, the plated steel wire is drawn out by a die and drawn in multiple stages until a wire having a predetermined thickness, which is the final finished dimension, is drawn.
[0022]
At this time, if the copper content in the brass plating is as low as 55 to 62%, the ductility tends to decrease and the wire drawing workability tends to decrease. In such a case, a thin copper plating layer having a thickness of, for example, 0.001 to 0.10 μm is further formed outside the brass plating layer to perform the wire drawing processability using the copper plating layer as a lubricant. It becomes possible. A part of the outermost copper plating layer disappears due to abrasion at the time of wire drawing, but the remaining part is thermally diffused into the brass plating by frictional heat.
[0023]
In the plating treatment, it is also important that the thickness of the plating on the steel wire having the final finished dimensions be kept within the range of 0.1 to 0.3 μm, preferably 0.15 to 0.25 μm.
[0024]
This is because if the thickness of the plating is thick, the adhesive properties, especially the heat and wet heat adhesive properties tend to be impaired, so that the effects of the present invention can be exerted particularly effectively, and especially in order to improve the heat and wet heat adhesive properties. It is preferable to regulate the plating thickness to be thinner in the range of 0.1 to 0.3 μm.
[0025]
Further, in the present invention, a heat treatment cord is formed by twisting a plurality of steel wires having the final finish dimensions into one and then performing a heat treatment. The heat-treated cord may be formed by subjecting the drawn steel wire to a heat treatment and then twisting the wire. Further, the heat treatment cord may be formed of one steel wire, in which case twisting is eliminated.
[0026]
The heat treatment is different from heating for heat diffusion in the plating process and frictional heat generated by wire drawing, and is intended to form an oxide film on the plating surface. In this heat treatment, it is necessary that the physical properties of the steel wire itself are not impaired as much as possible. Therefore, the heat treatment is performed at a heating temperature of 400 to 800 ° C. and a heating time of 30 to 250 seconds.
[0027]
Here, when an oxide film is not formed on the plating surface as in the related art, the generation of sulfide (CuS) that develops adhesive force with rubber becomes excessive, and the sulfide (CuS) layer becomes large. However, the initial adhesiveness tends not to be effectively exhibited, such as causing cohesive failure. Further, since a large amount of unreacted Zn remains on the plating surface, the heat and wet heat adhesion is reduced, for example, the Zn becomes Zn (OH) ₂ due to the influence of moisture or the like, causing adhesive deterioration.
[0028]
Therefore, by forming an oxide film on the plating surface by heat treatment, it is possible to optimize the generation of sulfide (CuS), to suppress unreacted Zn from becoming Zn (OH) _2, and to perform initial bonding. And both heat and wet heat adhesion can be effectively improved. If the heating time is less than 400 ° C. and the heating time is less than 30 seconds, the oxidation of the plating surface does not proceed. Conversely, if the heating time is more than 800 ° C. and the heating time is more than 250 seconds, the steel wire itself changes its composition. Cause the possibility of a drop in power. Therefore, more preferably, the heating time is 450 to 750 ° C. and the heating time is 40 to 200 seconds.
[0029]
The brass plating may partially include a third metal such as nickel or cobalt as long as the content is in the range of 10% or less.
[0030]
Next, in order to effectively exert the above-described effect by such a heat treatment, the uncoated rubber 12 has a weight of 0.3 to 1.0% based on the total weight of the coated rubber in an unvulcanized state. A rubber composition containing water is used.
[0031]
As the rubber base material of the rubber composition, natural rubber (NR), isoprene rubber (IR), butadiene rubber (BR), styrene-butadiene copolymer rubber (SBR), and the like are preferable. Polymerized rubber (EPM), ethylene-propylene-diene copolymer rubber (EPDM), acrylonitrile-butadiene copolymer rubber (NBR), butyl rubber (IIR), halogenated butyl rubber (X-IIR) and the like can also be used. These can be used alone or as a blend of two or more. In particular, when a heat-resistant cross-linking agent is used together with sulfur as a vulcanizing agent, NR, IR, BR, and SBR are used due to a cross-linking mechanism.
[0032]
The method for incorporating the above range of water into the rubber composition is not particularly limited, but it is preferable to mix water, for example, in the step of kneading the rubber composition.
[0033]
The water thus mixed activates the plating surface of the steel cord 10 and speeds up the generation of the sulfide (CuS) during vulcanization. As a result, the initial adhesion and the heat / wet heat adhesion can be improved by the synergistic action with the oxide film on the plating surface.
[0034]
If the water content is less than 0.3%, it is difficult to sufficiently exert the effect of the present invention. If the water content exceeds 1.0%, on the other hand, the water content becomes excessive and the rubber strength is impaired. It becomes a tendency.
[0035]
In addition to the water, the rubber base material may contain general rubber additives such as reinforcing fillers such as carbon black and silica, inorganic fillers such as calcium carbonate and zinc oxide, and sulfur. A sulfurizing agent, a softening agent such as stearic acid, a vulcanization accelerator, an antioxidant, a softening agent, a metal salt of an organic acid, and the like can be appropriately compounded.
[0036]
A cord / rubber composite 21 using such a steel cord 10 and a covering rubber 12 is provided with a bead reinforcing layer (not shown) for reinforcing the carcass 6, a band layer (not shown), or the bead portion 4 in addition to the belt layer 7. No) and various rubber products such as conveyor belts and hoses in addition to tires.
[0037]
As described above, particularly preferred embodiments of the present invention have been described in detail. However, the present invention is not limited to the illustrated embodiments, and can be implemented in various forms.
[0038]
【Example】
(1)
Both sides of an array of steel cords prepared according to the specifications in Table 1 are sandwiched between sheets of an unvulcanized rubber composition according to the specifications in Table 2, and heated and vulcanized (150 ° C., 30 minutes) in a pressed state to obtain a cord ply. Were prepared, and the initial adhesion and wet heat adhesion of the steel cord in each sample were tested. The water content of the rubber composition was determined by mixing water during the rubber kneading step, and the water content was quantitatively measured by the Karl Fischer method based on JIS K0068.
[0039]
The initial adhesiveness was evaluated by performing a peel test after naturally cooling the vulcanized sample at normal temperature and normal humidity (20 ° C., 50% (relative humidity)). The wet heat adhesion was evaluated by leaving the cured sample in an oven at a temperature of 80 ° C. and a humidity of 95% (relative humidity) for 5 days, then allowing it to cool naturally at normal temperature and normal humidity, and then performing a peeling test. Was evaluated. The evaluation criteria are as follows. Each sample was evaluated for 100 samples, and the average value is shown in Table 1.
5 ---- Completely covered with rubber and the plated surface of the steel cord is not visible.
4 ---- Plating surface is visible at 3 to 6 places.
3 ---- 13 to 20 plating surfaces are visible.
2 ---- Plating surface is visible at 21 or more places, but is covered by rubber at 60% or more as a whole.
1 ---- A portion covered with rubber is less than 30%.
[0040]
(2)
For Comparative Example 1 and Examples 1 and 2 in Table 1, a tire (size 180 / 55R17) in which a belt layer was formed with the cord / rubber composite of the specifications was prototyped, and the high-speed durability against moisture absorption of the tire was evaluated. Tested.
Belt layer, number of plies ---- 2 sheets, cord angle ------ (+ 20 °, -20 °)
・ Number of cords to be driven --------- 40 lines / 5cm
Carcass cord ----- 1100dtex / 2 (polyethylene terephthalate)
-Number of plies----1 sheet-Cord angle----(90 degrees)
・ The number of cords to be driven --- 38 lines / 5cm
[0041]
(A) High-speed durability against moisture absorption:
The tire was left in an atmosphere at a temperature of 70 ° C. and a humidity of 98% (relative humidity) for 7 days to absorb moisture. Thereafter, using a drum running tester, starting from a speed of 80 km / h under the conditions of an internal pressure (255 kPa) and a load (2.45 kN), the speed is increased by 10 km / h every 24 hours of running, and the tire is broken. The traveling distance up to the above was indicated by an index with Comparative Example 1 being 100. The higher the value, the better.
[0042]
[Table 1]

[0043]
[Table 2]

[0044]
It can be confirmed that in the example, both the initial adhesiveness and the wet heat adhesiveness can be improved as compared with the conventional comparative example 1 without heat treatment.
[0045]
【The invention's effect】
As described above, the present invention uses a heat-treated cord that has been subjected to a predetermined heat treatment after a plating treatment as a steel cord, while containing 0.3 to 1.0% of moisture in an unvulcanized state as a covering rubber. Because of the use of the rubber composition, it is possible to improve the initial adhesion and the heat / wet heat adhesion between the steel cord and the covering rubber, and to improve the durability of the cord / rubber composite and the pneumatic tire using the same. sell.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view showing one embodiment of a pneumatic tire using a cord / rubber composite of the present invention for a reinforcing layer.
FIG. 2 is an enlarged sectional view showing the cord / rubber composite.
[Explanation of symbols]
9 Reinforcement layer 10 Steel cord 12 Coated rubber 21 Cord / rubber composite

Claims (4)

A cord-rubber composite comprising a steel cord and a covering rubber covering the same,
The steel cord comprises a heat treatment code using a steel wire subjected to a heat treatment at a heating temperature of 400 to 800 ° C. and a heating time of 30 to 250 seconds after plating,
The cord-rubber composite, wherein the coated rubber comprises a rubber composition containing 0.3 to 1.0% of moisture in an unvulcanized state. The cord / rubber composite according to claim 1, wherein the plating is brass plating and the content of copper is 55 to 62%. The cord / rubber composite according to claim 1, wherein the steel wire has a plating thickness of 0.1 to 0.3 μm. A pneumatic tire using the cord / rubber composite according to any one of claims 1 to 3 for a reinforcing layer.

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