JP2005220188A - Radial tire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radial tire obtained by improving the initial adhesion and heat adhesion resistance between a metal cord and a coating rubber while keeping failure characteristics, heat-aging resistance and fatigue failure resistance of the coating rubber, in the radial tire having a belt layer and/or a carcass ply prepared by covering the metal cord with the coating rubber. <P>SOLUTION: This radial tire is obtained by using a rubber composition prepared by compounding 0.1-3.0 pts. mass of N, N'-diphenylmethanebismaleimide and 0.1-3.0 pts. mass of sodium pyrophosphate decahydrate with 100 pts. mass of a rubber component comprising a diene rubber as the rubber for covering the metal cord in at least one of the belt layer and the carcass ply. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radial tire having a belt layer and / or a carcass ply formed by coating a metal cord with a coating rubber, and in particular, while maintaining the fracture characteristics, heat aging resistance and fatigue fracture properties of the coating rubber, The present invention relates to a radial tire having improved initial adhesiveness and heat-resistant adhesiveness with a coating rubber.

  In recent years, a steel cord reinforced tire using a steel cord as a reinforcing material for at least one of a carcass and a belt has been widely used. Here, in the steel cord reinforced tire, it is important to secure the adhesion between the steel cord and the coating rubber covering the cord. If this adhesion is lowered, the durability of the carcass and / or the belt is lowered. As a result, there may be a problem in the durability of the tire.

  In addition, heavy duty tires such as off-road tires have recently been extended in service life, and the required severity has increased, and the use temperature of the tire has increased, so that the steel cord and the cord caused by heat are covered. Due to poor adhesion with the coating rubber, the tire may fail.

  Here, the deterioration due to the heat of adhesion between the steel cord and the coating rubber is caused by the fact that the adhesive layer made of copper sulfide between the steel cord and the coating rubber receives heat, and reacts with zinc that has melted from the plating, It is believed that a zinc sulfide layer is formed in the adhesive layer, and that the zinc sulfide layer reduces the adhesion between the steel cord and the coating rubber. Therefore, as a method for improving the heat-resistant life of adhesion, it is conceivable to apply a rubber composition in which the amount of sulfur added to the coating rubber is increased in order to prevent elution of zinc and suppress the destruction of copper sulfide. For the same reason, in order to promote the formation of an adhesive layer made of copper sulfide, it is conceivable to apply a rubber composition in which the amount of the organic acid cobalt salt is increased in the coating rubber.

  However, if a rubber composition with an increased amount of sulfur is used for the coating rubber, the heat resistance deterioration performance of the coating rubber will be reduced, and sulfur will be adjoined during vulcanization due to the difference in the amount of sulfur with the adjacent member. As a result, the effect of increasing sulfur is reduced, and the heat resistance deterioration performance of the adjacent member is also reduced. Moreover, when the rubber composition which increased organic acid cobalt salt is used for coating rubber, cobalt will accelerate | stimulate the thermal deterioration of coating rubber. Therefore, with these methods, while maintaining the heat aging resistance of the coating rubber, both the initial adhesion between the steel cord and the coating rubber (adhesion immediately after vulcanization) and the heat adhesion (adhesion after heat aging) are compatible. It was difficult to do.

  Also, by applying a rubber composition containing bismaleimide to the coating rubber, the rubber component can be cross-linked without sulfur, and the hardness of the coating rubber can be improved. A technique for improving the durability of a tire by suppressing shear strain is known (see Patent Document 1).

  Furthermore, by applying a rubber composition containing an inorganic hydrate salt to the coating rubber, moisture is released from the inorganic hydrate salt during vulcanization, and copper sulfide (adhesion layer) is formed between the steel cord and the coating rubber. A technique for promoting and improving initial adhesiveness is known (see Patent Document 2).

  However, even with the techniques described in Patent Documents 1 and 2, when used under harsh conditions such as off-road tires, the heat resistance adhesion between the steel cord and the coating rubber is not sufficient. Improvements are desired.

JP 2002-205506 A Japanese Patent Laid-Open No. 10-195237

  Accordingly, an object of the present invention is to solve the above-mentioned problems of the prior art in a radial tire provided with a belt layer and / or carcass ply formed by coating a metal cord with a coating rubber, and to provide the fracture characteristics and heat aging resistance of the coating rubber. It is another object of the present invention to provide a radial tire having improved initial adhesiveness and heat resistant adhesiveness between a metal cord and a coating rubber while maintaining fatigue fracture resistance.

  As a result of intensive studies to achieve the above object, the present inventor has obtained a rubber composition containing a predetermined amount of N, N'-diphenylmethane bismaleimide and sodium pyrophosphate decahydrate as a metal cord coating rubber. By using it, it was found that the initial adhesiveness and heat resistant adhesion between the metal cord and the coating rubber can be improved while maintaining the fracture characteristics, heat aging resistance and fatigue fracture resistance of the coating rubber, and the present invention has been completed. .

  That is, the radial tire of the present invention is a radial tire provided with a belt layer and / or a carcass ply made of a metal cord and a coating rubber covering the cord, and at least one of the belt layer and the carcass ply has a metal cord. The coating rubber to be coated is blended with 0.1 to 3.0 parts by mass of N, N'-diphenylmethane bismaleimide and 0.1 to 3.0 parts by mass of sodium pyrophosphate decahydrate with respect to 100 parts by mass of the rubber component made of diene rubber. It is characterized by using the rubber composition.

  In a preferred embodiment of the radial tire of the present invention, an insulation rubber is interposed between the metal cord and the coating rubber, and the rubber composition is used for the insulation rubber.

  The belt layer and / or carcass ply has a structure in which the surface of the metal cord is directly coated with the rubber composition and / or the periphery of the metal cord arranged in a substantially planar shape is coated with the rubber composition. Thus, a structure in which the cord is embedded is preferable.

  In another preferred embodiment of the radial tire of the present invention, the total amount of the N, N′-diphenylmethane bismaleimide and the sodium pyrophosphate decahydrate is 5.0 parts by mass with respect to 100 parts by mass of the rubber component. It is as follows. In this case, it is possible to reliably improve the initial adhesiveness and heat resistant adhesiveness between the metal cord and the coating rubber while ensuring the fracture characteristics, heat aging resistance and fatigue fracture resistance of the coating rubber.

  In another preferred embodiment of the radial tire of the present invention, the rubber composition has a tensile stress at 100% elongation after vulcanization of 3.0 MPa or more.

  The radial tire of the present invention is suitable as a heavy load tire such as an off-road tire.

  According to the present invention, in a radial tire having a belt layer and / or carcass ply formed by coating a metal cord with a coating rubber, N, N′-diphenylmethane bismaleimide and sodium pyrophosphate · 10 hydrate are used as the coating rubber. By using a rubber composition containing a predetermined amount of the product, the initial adhesiveness and heat resistant adhesion between the metal cord and the coating rubber were improved while maintaining the fracture characteristics, heat aging resistance and fatigue fracture resistance of the coating rubber. It is possible to provide a radial tire having high durability and long life.

  The present invention is described in detail below. The radial tire of the present invention includes a belt layer and / or a carcass ply made of a metal cord and a coating rubber that covers the cord, and at least one of the belt layer and the carcass ply includes a coating rubber that covers the metal cord. A rubber composition obtained by blending 0.1 to 3.0 parts by mass of N, N'-diphenylmethane bismaleimide and 0.1 to 3.0 parts by mass of sodium pyrophosphate decahydrate with respect to 100 parts by mass of a rubber component made of a diene rubber. It is used.

  In the radial tire of the present invention, an insulation rubber may be interposed between the metal cord and the coating rubber. In this case, the rubber composition is applied to the insulation rubber in addition to the coating rubber. Here, as the structure of the belt layer and / or the carcass ply, the metal cord surface is directly covered with the rubber composition, or a plurality of metal cords arranged in a substantially planar shape are covered with the rubber composition. A structure in which the cord is embedded is preferable.

  In the radial tire of the present invention, the metal cord cordin rubber contains N, N′-diphenylmethane bismaleimide, which is a heat-resistant cross-linking agent. Improves heat aging resistance. Also, since the metal cord cordin rubber contains sodium pyrophosphate decahydrate, moisture is released during vulcanization and the formation of copper sulfide (adhesion layer) between the metal cord and the coating rubber is promoted. , Initial adhesiveness is improved. Surprisingly, when N, N'-diphenylmethane bismaleimide and sodium pyrophosphate decahydrate are used in combination with the rubber composition for the coating rubber, the heat resistance adhesion between the metal cord and the coating rubber is improved. Even when used in harsh conditions such as off-road tires, the metal cord and the coating rubber have sufficient heat-resistant adhesiveness, extremely high durability and improved tire life Tires can be provided.

  The rubber component of the rubber composition used for the cordin rubber is a diene rubber, and examples of the diene rubber include natural rubber (NR) and synthetic diene rubbers such as synthetic polyisoprene rubber (IR). Of these rubber components, natural rubber is preferable. These rubber components may be used alone or as a blend of two or more.

で表される。ここで、Ｎ,Ｎ'-ジフェニルメタンビスマレイミドの配合量がゴム成分100質量部に対して0.1質量部未満では、長時間加硫による耐熱性の低下を抑制する効果が十分でないことがあり、3.0質量部を超えると、コーティングゴムの耐亀裂性が低下する傾向があると共に、加硫後のコーティングゴム中に未反応のＮ,Ｎ'-ジフェニルメタンビスマレイミドが残存して、熱的に安定な架橋構造を形成して、耐熱老化性を向上させる効果が十分に発揮されないことがある。 The rubber composition used for the cordin rubber contains 0.1 to 3.0 parts by mass of N, N′-diphenylmethane bismaleimide (BMI) with respect to 100 parts by mass of the rubber component. N, N′-diphenylmethane bismaleimide is known as a heat-resistant cross-linking agent, and can form a thermally stable cross-linked structure as compared with sulfur cross-linking. For example, the following formula (I):

It is represented by Here, if the blending amount of N, N′-diphenylmethane bismaleimide is less than 0.1 parts by mass with respect to 100 parts by mass of the rubber component, the effect of suppressing the decrease in heat resistance due to prolonged vulcanization may not be sufficient. Exceeding parts by mass tends to reduce the crack resistance of the coating rubber, and unreacted N, N'-diphenylmethane bismaleimide remains in the vulcanized coating rubber, resulting in thermally stable crosslinking. The effect of forming the structure and improving the heat aging resistance may not be sufficiently exhibited.

The rubber composition used for the cordin rubber contains 0.1 to 3.0 parts by mass of sodium pyrophosphate decahydrate (Na ₄ P ₂ O ₇ .10H ₂ O) with respect to 100 parts by mass of the rubber component. Sodium pyrophosphate decahydrate releases moisture during kneading and vulcanization of the rubber composition and promotes the formation of copper sulfide (adhesive layer) between the metal cord and the coating rubber, thereby providing initial adhesion. In addition to stabilizing and improving the properties, it is used in combination with the N, N′-diphenylmethane bismaleimide to greatly improve the heat resistant adhesion between the metal cord and the coating rubber. Here, when the blending amount of sodium pyrophosphate decahydrate is less than 0.1 parts by mass with respect to 100 parts by mass of the rubber component, the effect of improving the initial adhesion and heat-resistant adhesion between the metal cord and the coating rubber is sufficient. If the amount exceeds 3.0 parts by mass, the adhesive layer (copper sulfide) formed between the metal cord and the coating rubber is destroyed by the influence of acid, and the initial adhesiveness and the adhesive durability tend to decrease.

  In the rubber composition for cordin rubber, the total amount of N, N′-diphenylmethane bismaleimide and sodium pyrophosphate decahydrate is 5.0 parts by mass or less with respect to 100 parts by mass of the rubber component. Is preferred. Even if the total amount of N, N'-diphenylmethane bismaleimide and sodium pyrophosphate decahydrate exceeds 5.0 parts by mass with respect to 100 parts by mass of the rubber component, the performance is improved only by increasing the cost. I can't.

  As the physical properties after vulcanization, the rubber composition preferably has a tensile stress at 100% elongation of 3.0 MPa or more, more preferably 3.0 to 4.0 MPa. The tensile stress can be measured according to JIS K6301-1995.

  In addition to the rubber component, N, N'-diphenylmethane bismaleimide, sodium pyrophosphate decahydrate, the rubber composition contains compounding agents commonly used in the rubber industry, such as fillers, vulcanization accelerators. An agent, an antiaging agent, zinc white, stearic acid, a softening agent, an ozone deterioration preventing agent and the like can be appropriately selected and blended within a range that does not impair the object of the present invention. Examples of the filler include reinforcing fillers such as carbon black and silica, and inorganic fillers such as calcium carbonate and sodium carbonate. Examples of the vulcanization accelerator include 2-mercaptobenzothiazole (M) and dibenzothia. Thiazole vulcanization accelerators such as dil disulfide (DM) and N-cyclohexyl-2-benzothiazylsulfenamide (CZ), thiuram vulcanization accelerators such as tetramethylthiuram disulfide (TT), and diphenylguanidine ( And guanidine vulcanization accelerators such as DPG). As these compounding agents, commercially available products can be suitably used. The above rubber composition is prepared by blending the rubber component with various compounding agents appropriately selected as necessary together with N, N'-diphenylmethane bismaleimide and sodium pyrophosphate decahydrate, kneading and heating. It can be produced by extrusion or the like.

  Examples of the material of the metal cord used for the belt layer and / or the carcass ply of the radial tire of the present invention include iron, copper, aluminum, SUS, and brass. The metal cord is preferably a steel cord, particularly a steel cord that is brass coated and has improved adhesion to vulcanized rubber. The method for the coating treatment is not particularly limited, and a normal method such as a plating treatment method, various CVD methods, a PVD method, or the like can be used. The metal cord may be a single wire cord or a cord having a structure in which a plurality of metal filaments are twisted together. A plurality of such cords may be arranged side by side or may be a flat steel cord made of woven fabric.

  The belt layer and / or carcass ply has a structure in which the above rubber composition is directly coated on the surface of the metal cord and / or the cord is coated with the rubber composition around a plurality of metal cords arranged in a substantially planar shape. It is preferable that the structure is embedded. As shown in FIG. 1, the belt layer and / or carcass ply of the radial tire of the present invention includes an insulation rubber 2 made of the above rubber composition and the steel cord 1 when the steel cord 1 is arranged in a substantially planar shape. The surface can be directly coated. Here, the thickness of the insulation rubber 2 is preferably in the range of 0.1 to 3.0 mm, and more preferably in the range of 0.5 to 2.0 mm. The belt layer and / or the carcass ply may have a structure in which a plurality of steel cords 1 arranged in a substantially planar manner are covered with the coating rubber 3 made of the rubber composition. Here, the coating rubber 3 may be configured to directly contact the surface of the steel cord 1 without using the insulation rubber 2.

  A radial tire according to the present invention includes a pair of bead portions, a pair of side portions, a tread portion, a carcass extending in a toroid shape between bead cores embedded in the bead portions, and a crown portion of the carcass. A belt disposed radially outward. Here, the carcass is preferably composed of at least one carcass ply, and the belt is preferably composed of at least two belt layers. In the radial tire of the present invention, the above rubber composition excellent in initial adhesiveness and heat-resistant adhesiveness to the metal cord is applied to the coating rubber covering the metal cord with the belt layer and / or the carcass ply. Therefore, the durability of the belt layer and / or the carcass ply is very high. Therefore, the radial tire of the present invention is suitable as a heavy-duty tire that generates a large amount of heat and has a long service period, and is particularly suitable as an off-road tire among the heavy-duty tires.

  Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples.

  A rubber composition having the formulation shown in Table 1 was prepared, and the scorch characteristics, elongation at break during normal vulcanization and overvulcanization, tensile strength and tensile stress were measured by the following methods. These results are shown in Table 1.

(1) Scorch characteristics Based on JIS K6300, the time to reach the rising value from the minimum Mooney viscosity value was measured at 130 ° C to evaluate the scorch characteristics.

(2) Tensile test
A tensile test was carried out in accordance with JIS K6301 for both the sample that was normally vulcanized under the conditions of 145 ° C. × 60 minutes and the sample that was over-vulcanized under the conditions of 145 ° C. × 300 minutes, The elongation at break (E _B ), tensile strength (T _B ) and tensile stress (M ₃₀₀ ) were measured. Here, the tensile stress is a value at 300% elongation.

  Next, steel cords [1 × 5 × 0.25 mm (element diameter)] plated with brass (Cu: 63 wt%, Zn: 37 wt%) are arranged in parallel at intervals of 1.25 mm. The cord was coated with a rubber composition and vulcanized at 145 ° C. for 60 minutes to prepare a cord-rubber composite. The initial adhesion and heat-resistant adhesion between the cord and rubber in the composite were measured by the following methods, and the results shown in Table 1 were obtained.

(3) Initial adhesiveness In accordance with ASTM-D-2229, the steel cord is pulled out from each cord-rubber composite, and the rubber coating state of the exposed steel cord is visually observed. It was expressed in% and used as an index of initial adhesiveness. It shows that initial adhesiveness is so high that a numerical value is large.

(4) Heat-resistant adhesion After the cord-rubber composite was left in an environment of 100 ° C. and 20% RH for 7 days, the steel cord was pulled out of each composite and exposed in accordance with ASTM-D-2229. The rubber covering state of the steel cord was visually observed, and the covering ratio was displayed as 0 to 100% as an index of heat resistant adhesion. It shows that heat resistance adhesiveness is so high that a numerical value is large.

* 1 Nipol 2200.
* 2 Made by FLEXSIS, SANTOFLEX 6PPD.
* 3 Cobaltic acid cobalt.
* 4 No. 2 spindle oil, Idemitsu Kosan, Diana Process Oil NS-24.
* 5 Ouchi Shinsei Chemical, Noxeller DZ-G.
* 6 N, N'-diphenylmethane bismaleimide manufactured by Mitsui Chemicals.

  From Table 1, the rubber compositions of the examples have excellent fracture characteristics during normal vulcanization and overvulcanization, and the cord-rubber composites of the examples using the rubber compositions have initial adhesive properties. It can also be seen that the heat-resistant adhesiveness is significantly higher than that of Comparative Example 1. On the other hand, the cord-rubber composite using the rubber composition of the comparative example was inferior in initial adhesiveness and heat-resistant adhesiveness to the examples.

It is sectional drawing of an example of the belt layer and / or carcass ply of the radial tire of this invention.

Explanation of symbols

1 Steel cord 2 Insulation rubber 3 Coating rubber

Claims (6)

  In a radial tire provided with a belt layer and / or carcass ply comprising a metal cord and a coating rubber covering the cord, at least one of the belt layer and the carcass ply is coated with a diene rubber as the coating rubber covering the metal cord. A rubber composition comprising 0.1 to 3.0 parts by mass of N, N′-diphenylmethane bismaleimide and 0.1 to 3.0 parts by mass of sodium pyrophosphate decahydrate with respect to 100 parts by mass of the rubber component comprising A radial tire characterized by   The radial tire according to claim 1, wherein an insulation rubber is interposed between the metal cord and the coating rubber, and the rubber composition is used for the insulation rubber.   The belt layer and / or the carcass ply has a structure in which the surface of the metal cord is directly coated with the rubber composition and / or the periphery of a metal cord arranged in a substantially planar shape is coated with the rubber composition to coat the cord. The radial tire according to claim 1, wherein the radial tire has an embedded structure.   2. The total amount of the N, N′-diphenylmethane bismaleimide and the sodium pyrophosphate decahydrate is 5.0 parts by mass or less based on 100 parts by mass of the rubber component. Radial tires.   The radial tire according to claim 1, wherein the rubber composition has a tensile stress at 100% elongation after vulcanization of 3.0 MPa or more.   The radial tire according to claim 1, wherein the radial tire is an off-road tire.

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