JP6623727B2 - Rubber cord composite and pneumatic tire using the same - Google Patents

Description

  TECHNICAL FIELD The present invention relates to a rubber-cord composite capable of improving the adhesion between a steel cord and topping rubber, and a pneumatic tire using the same.

  For example, steel cords are frequently used as reinforcing elements for rubber products such as pneumatic tires. In a rubber cord composite reinforced with a steel cord, a brass plating layer (binary plating of copper and zinc) is generally applied to the cord side in order to increase the adhesion between the steel cord and the topping rubber.

  The adhesiveness between the brass plating layer and the rubber is such that, during vulcanization, sulfur (S) compounded in the rubber and copper (Cu) in the brass plating layer undergo a cross-linking reaction and bond with the brass plating layer to form a topping. This is manifested when an adhesive reaction layer (CuS layer) is formed between the rubber and the rubber. However, in the brass plating, although the adhesiveness at the initial stage of vulcanization (hereinafter, sometimes referred to as “initial adhesiveness”) is good, the adhesiveness in a high-temperature, high-humidity, wet-heat environment (hereinafter, “wet-heat adhesiveness”). May worsen). This is considered to be because copper in the brass plating easily elutes into the rubber under a moist heat environment, and the eluted copper lowers the crosslink density in the adhesive reaction layer (CuS layer).

  Therefore, it is known to add an organic acid cobalt salt to the topping rubber in order to suppress the elution of copper and improve the wet heat adhesion. However, when such a topping rubber has a high temperature during the rubber kneading step, the deterioration is promoted by cobalt, so that the temperature needs to be reduced. For this reason, when the organic acid cobalt salt is blended in the topping rubber, a long kneading time is required, and the productivity is reduced.

  Therefore, in order to improve the wet heat adhesion of the topping rubber without blending the organic acid cobalt salt, for example, a steel cord having a ternary plating layer made of copper, zinc, and cobalt has been proposed. However, the rubber cord composite using the steel cord as described above has to be vulcanized at a high temperature of 170 ° C. or higher in order to obtain sufficient adhesiveness.

JP-A-2002-13081

  The present invention has been devised in view of the above situation, and based on improving a topping rubber, has a high initial adhesion and a wet heat adhesion even when vulcanized at a relatively low temperature of about 150 ° C. And a pneumatic tire using the same.

  The present invention is a rubber cord composite comprising a steel cord made of a plated wire and a topping rubber covering the steel cord, wherein the plated wire is formed on a surface of the core wire and the core wire, and A ternary plating layer made of copper (Cu), zinc (Zn), and cobalt (Co), wherein the ternary plating layer has a copper (Cu) content of 55 to 78 mass per 100 mass parts of plating. Parts, and cobalt (Co): 0.5 to 8.0 parts by mass, and the topping rubber is characterized by containing 5 parts by mass or more of silica with respect to 100 parts by mass of the rubber component.

  In the rubber-cord composite according to the present invention, it is desirable that the topping rubber does not contain a cobalt salt of an organic acid.

  In the rubber-cord composite according to the present invention, it is preferable that the topping rubber is vulcanized at 150 ° C. or higher.

  The present invention relates to a pneumatic tire, wherein the rubber-cord composite according to any one of claims 1 to 3 is used for a cord ply of a tire.

  The rubber-cord composite of the present invention comprises a steel cord composed of a plated wire and a topping rubber covering the steel cord. The plated element wire includes a core wire and a ternary plating layer formed on the surface of the core wire and made of copper (Cu), zinc (Zn), and cobalt (Co). The ternary plating layer contains 55 to 78 parts by mass of copper (Cu) and 0.5 to 8.0 parts by mass of cobalt (Co) based on 100 parts by mass of plating.

  In the present invention, a topping rubber containing 5 parts by mass or more of silica with respect to 100 parts by mass of the rubber component is employed. Thereby, even when the rubber / cord composite is vulcanized at about 150 ° C., the initial adhesiveness and wet heat adhesiveness can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS It is sectional drawing which shows one Example of the pneumatic tire which used the rubber code composite of this invention as a code ply. It is sectional drawing which shows the cord ply which is a rubber cord composite.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing an example of a pneumatic tire (hereinafter, sometimes simply referred to as “tire”) 1 in which a rubber cord composite 9 of the present embodiment is used as a cord ply for tire reinforcement. FIG. As the tire 1, various tires for heavy loads such as trucks and buses in addition to those for passenger cars can be adopted.

  The tire 1 of the present embodiment includes a carcass 6 extending from the tread portion 2 to the bead core 5 of the bead portion 4 through the sidewall portion 3 and a belt layer 7 disposed inside the tread portion 2 and radially outside the carcass 6. And with.

  The carcass 6 is formed, for example, from one carcass ply 6A having carcass cords arranged at an angle of 75 ° to 90 ° with respect to the tire circumferential direction. The carcass ply 6A includes a main body 6a extending from the tread portion 2 through the sidewall portion 3 to the bead core 5 embedded in the bead portion 4, and a folded portion 6b folded around the bead core 5.

  The belt layer 7 is formed, for example, from two belt plies 7A and 7B having belt cords arranged at an angle of 10 to 45 ° with respect to the tire circumferential direction. A tread rubber 2G that forms the outer surface 2a of the tread portion 2 is disposed outside the belt layer 7 in the tire radial direction. In the present embodiment, the rubber cord composite 9 of the present invention is used for the belt plies 7A and 7B.

  FIG. 2 is a cross-sectional view of a cord ply (belt ply 7A or 7B) that is a rubber / cord composite 9. As shown in FIG. 2, the rubber cord composite 9 is composed of a cord arrangement 11 in which steel cords 10 as belt cords are aligned in parallel with each other, and the cord arrangement 11 is coated on both sides and vulcanized. And a topping rubber 12.

  The steel cord 10 includes one or more plated wires 13. The steel cord 10 of the present embodiment is formed by a cord in which four plated wires 13 are twisted. Each plating strand 13 includes a core wire 13A and a ternary plating layer 13B formed on the surface of the core wire 13A.

  The core wire 13A is made of, for example, a steel wire and has a wire diameter of 0.1 to 0.7 mm. The core wire 13A is not limited to such an embodiment.

  The ternary plating layer 13B is made of copper (Cu), zinc (Zn), and cobalt (Co). The ternary plating layer 13B contains 55 to 78 parts by mass of copper and 0.5 to 8.0 parts by mass of cobalt with respect to 100 parts by mass of plating. When the content of copper is less than 55 parts by mass, it is difficult to sufficiently increase the crosslink density between copper and sulfur in the adhesive reaction layer, and both the initial adhesion and the wet heat adhesion become insufficient. When the content of copper exceeds 78 parts by mass, it is difficult to sufficiently suppress the elution of copper in a moist heat environment even with cobalt, which may cause rubber deterioration. When the content of cobalt is less than 0.5 part by mass, the hot-wet adhesion is reduced. When the cobalt content exceeds 8.0 parts by mass, the hardness of the ternary plating layer 13B increases, and cracks are easily generated during wire drawing. In addition, when the content of cobalt exceeds 8.0 parts by mass, the initial adhesiveness is reduced by vulcanization at a low temperature. From such a viewpoint, the content of copper is desirably from 64 to 72 parts by mass. Similarly, the content of cobalt is desirably 4.0 to 7.0 parts by mass.

  An example of a method for manufacturing the plated wire 13 is as follows. First, a plating process is performed on the core wire 13A of the plating wire 13 in the order of, for example, a copper layer, a cobalt layer, and a zinc layer. Next, the plated plating wire 13 is heat-treated at, for example, 500 to 650 ° C. and 5 to 25 seconds, so that copper, cobalt, and zinc are uniformly diffused throughout the plating layer. Next, a plated wire 13 having a predetermined wire diameter is formed by drawing the heat-treated material. The plating process is not limited to the order of the steps described above.

  The topping rubber 12 contains a rubber component and silica. As a result of various studies by the inventors, it has been found that the addition of silica to the topping rubber 12 improves the initial adhesiveness and wet heat adhesiveness of the rubber-cord composite 9 including the ternary plating layer 13B. did. According to the inventors, it is presumed that the water released from the silica during vulcanization improves the adhesion between the topping rubber 12 and the steel cord 10.

  As a result of further studies by the inventors, silica needs to be compounded in an amount of 5 parts by mass or more based on 100 parts by mass of the rubber component. When silica is less than 5 parts by mass with respect to 100 parts by mass of the rubber component, the amount of water released from the silica is not sufficient, and the initial adhesiveness and wet heat adhesiveness are significantly deteriorated. If the silica exceeds 60 parts by mass with respect to 100 parts by mass of the rubber component, the silica condenses and the topping rubber 12 generates a large amount of heat, so that the initial adhesion and the wet heat adhesion are deteriorated. From such a viewpoint, it is desirable that silica is contained in an amount of 10 to 55 parts by mass with respect to 100 parts by mass of the rubber component.

  The topping rubber 12 does not need to contain an organic acid cobalt salt. This is because the cobalt in the ternary plating layer 13B is expected to have the same effect as the organic acid cobalt salt in suppressing the elution of copper in the ternary plating layer 13B during vulcanization. In addition, the topping rubber 12 containing no organic acid cobalt salt can be kneaded at a high temperature in the rubber kneading step, and the kneading time is shortened, and the productivity is improved.

  As the rubber component, for example, a rubber component containing natural rubber (NR) or isoprene rubber (IR) in an amount of preferably 60 parts by mass or more, more preferably 70 parts by mass or more based on 100 parts by mass of the rubber component, more preferably 100 parts by mass Is most preferred. If the amount is less than 60 parts by mass, the breaking strength tends to be low. Examples of rubber components to be mixed with natural rubber or isoprene rubber include styrene-butadiene rubber (SBR), butadiene rubber (BR), ethylene-propylene-diene rubber (EPDM), chloroprene rubber (CR), butyl rubber (IIR), and acrylonitrile. -Butadiene rubber (NBR) and the like.

  Topping rubber 12 further contains sulfur and a vulcanization accelerator. As sulfur, sulfur generally used as a vulcanizing agent in the rubber industry can be used. The content of sulfur is not particularly limited, but is preferably 5 to 8 parts by mass with respect to 100 parts by mass of the rubber component in order to enhance the adhesiveness with the steel cord and to uniformly disperse the sulfur. preferable.

  As the vulcanization accelerator, for example, NS (N-ter-butyl-2-benzothiazylsulfenamide) in addition to the vulcanization accelerator DZ (NN-dicyclohexyl-2-benzothiazylsulfenamide) , TBSI (N-tert-butyl-2-benzothiazolylsulfenimide), BEHZ (N, N-di (2-ethylhexyl) -2-benzothiazolylsulfenamide), or 2 It is desirable to use one or more combinations.

  It is desirable that the topping rubber 12 further contains a well-known rubber additive. As such an additive, for example, a reinforcing agent (such as carbon black), a wax, an antioxidant, and the like are employed.

  The rubber / cord composite 9 formed of the above-described constituent materials exhibits excellent initial adhesion and wet heat adhesion even when vulcanized at a relatively low temperature of about 150 ° C. This point is clarified in an embodiment described later. The vulcanization temperature may be, for example, about 165 ° C., and desirably about 180 ° C. or less.

  In the present embodiment, a case is shown in which the rubber / cord composite 9 is applied to the belt plies 7A and 7B. However, the rubber-cord composite 9 of the present invention can be applied to other cord plies, such as a band ply and a bead reinforcing ply, in addition to the carcass ply 6A. Further, the rubber-cord composite 9 can be applied to rubber products other than tires, such as timing belts and hoses.

  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.

  A pneumatic tire for a passenger car having the basic structure shown in FIGS. 1 and 2 was prototyped based on the specifications in Table 1, and thereafter, inner and outer belt plies including the tire equator portion were sampled with a width of 25 mm in the tire axial direction. Was cut out. Then, the test piece was tested for adhesiveness. Test items are measurement of the peeling resistance of the sample piece and observation of the appearance of the sample piece after the measurement of the peeling resistance. The steel cord of the rubber cord composite was tested for wire drawing workability. The common specifications are as follows.

<Tire>
Size: 195 / 65R15
Belt cord angle: 24 °
<Rubber / cord composite>
Steel cord configuration: 2 + 2 × 0.23HT
Plating of plated wire: See Table 1 Ply thickness: 1.25 mm
Number of cords to drive: 38 / 5cm
<Basic compounding of topping rubber>
NR: 100 parts by mass Sulfur (20% oil treatment): 5.62 parts by mass Vulcanization accelerator DZ: 1 part by mass Zinc oxide: 8 parts by mass Antioxidant FR: 2 parts by mass

(1) Adhesion (peeling resistance)
Using a peeling tester, when the sample piece is peeled from one end side thereof at a speed of 50 mm / min along the inner and outer belt plies, the peeling resistance for initial adhesiveness, and the peeling resistance for wet heat adhesiveness are: Measured. In the measurement of the peeling resistance related to the initial adhesiveness, a sample piece cut out after vulcanizing the tire, naturally cooling it at normal temperature and normal humidity (20 ° C., 50% RH) is used. In the measurement of the peeling resistance relating to the wet heat adhesion, the cut sample piece is further left in an oven at a temperature of 80 ° C. and a relative humidity of 95% for 150 hours to be subjected to wet heat deterioration. The results are expressed as indices with the peel resistance at 100 when the vulcanization temperature of Comparative Example 2 is 150 ° C. As for the numerical value, the larger the value, the better.

(2) Adhesion (appearance)
After the peeling resistance test, the state of rubber adhesion on the cord surface on the peeled surface was observed. That is, in this test, the appearance of the sample piece used in the initial adhesion test and the appearance of the sample piece used in the wet heat adhesion test were observed. The results are indicated by a five-point method in which five points indicate that the entire surface of the steel cord is completely covered with rubber, and one point indicates that 30% or more of the surface of the steel cord is exposed. Three or more numerical values are good.

(3) Wire drawing workability The maximum wire drawing speed V1 at which wire drawing can be performed when forming a plated primary wire having a diameter of 1.7 mm from a primary drawn wire having a diameter of 1.7 mm, This was compared with the limit drawing speed Vo in forming the plated element wire of Comparative Example 1. When the ratio V1 / V0 is 0.1 or less, it is determined that mass production is difficult, and the result is represented by a three-point method, which is defined as "one point". Two or more points pass.

  As a result of the test, it was confirmed that the example had excellent initial adhesion and wet heat adhesion even when the vulcanization temperature was 150 ° C., as compared with the comparative example.

9 Rubber / Cord Composite 10 Steel Cord 12 Topping Rubber 13 Plated Wire 13A Core 13B Tri-Plating Layer

Claims (5)

A rubber cord composite comprising a steel cord formed of a plated wire and a topping rubber covering the steel cord,
The plating element wire includes a core wire, and a ternary plating layer formed on a surface of the core wire and made of copper (Cu), zinc (Zn), and cobalt (Co);
The ternary plating layer contains 55 to 78 parts by mass of copper (Cu) and 0.5 to 8.0 parts by mass of cobalt (Co) based on 100 parts by mass of plating.
The topping rubber contains 55 to 60 parts by mass of silica with respect to 100 parts by mass of the rubber component.   The rubber-cord composite according to claim 1, wherein the topping rubber does not contain a cobalt salt of an organic acid.   The rubber-cord composite according to claim 1, wherein the topping rubber is vulcanized at 150 ° C. or higher. The rubber-cord composite according to any one of claims 1 to 3, wherein the topping rubber does not contain carbon black. A pneumatic tire using the rubber-cord composite according to any one of claims 1 to 4 for a cord ply of a tire.

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