JP6220529B2 - Rubber-metal composite manufacturing method, tire manufacturing method, industrial belt manufacturing method, and rubber crawler manufacturing method - Google Patents

Description

  The present invention relates to a rubber composition, a method for producing a rubber-metal composite, a rubber-metal composite, a tire, an industrial belt, and a rubber crawler.

  For rubber articles that require particularly high strength such as tires, industrial belts, rubber crawlers, etc., a rubber-metal composite in which a metal material is embedded in the rubber composition for the purpose of reinforcing the rubber and improving the strength and durability. The body is used. Here, in order for such a rubber-metal composite to exhibit a high reinforcing effect, it is necessary to bond the metal material and the rubber composition stably and strongly.

  In order to achieve high adhesion between the metal material and the rubber composition, a metal body such as a steel cord plated with zinc or brass is coated with a rubber composition containing sulfur, and the rubber composition is added. So-called direct vulcanization bonding, in which these are bonded together with vulcanization, is widely used. For example, in Patent Document 1, a steel cord with brass plating containing a specific amount of a metal such as phosphorus or zinc on the outermost surface is immersed in a solution containing a metal salt whose pH is usually in the range of 6.1 to 8.0. Then, it is reported that a steel cord-rubber composite excellent in initial adhesion and heat-resistant adhesion between the steel cord and the rubber composition can be obtained by coating with a rubber composition and then vulcanizing.

  Moreover, in order to implement | achieve the high adhesiveness between a metal material and a rubber composition, the method of mix | blending a cobalt compound with a rubber composition is used conventionally. For the same purpose, a method of blending resorcin or bis (3-hydroxyphenyl) adipate with a rubber composition is also known. However, since resorcin has sublimability, it was not practical from the viewpoint of environmental pollution and workability. Also, adipic acid bis (3-hydroxyphenyl) ester having improved sublimation properties is not practical from the viewpoint of cost.

  On the other hand, in the above-mentioned tire, industrial belt, rubber crawler and the like, it is preferable to reduce the thickness of the rubber-metal composite used in order to save resources and reduce fuel consumption. However, when the thickness of the rubber-metal composite is thin, there is a problem that the rubber-metal composite is easily deteriorated by permeated water / oxygen. Under such circumstances, a technique for further improving the adhesion between the metal material and the rubber composition is required.

International Publication No. 2011/030547

An object of the present invention is to provide a rubber composition having excellent adhesiveness after water / oxygen deterioration, that is, wet heat adhesiveness, while maintaining good initial adhesiveness with a metal material.
Another object of the present invention is to provide a method for producing a rubber-metal composite, which can obtain a rubber-metal composite having excellent wet heat adhesion while maintaining good initial adhesion between the metal material and the rubber composition. Is to provide.
Furthermore, the subject of this invention is providing the rubber-metal composite_body | complex which has the outstanding wet heat adhesiveness, maintaining the favorable initial adhesiveness of a metal material and a rubber composition.
Still another object of the present invention is to provide a tire, an industrial belt, and a rubber crawler that are excellent in durability particularly under high temperature and high humidity.

  The present inventor has found that by using both a benzoic acid compound and cobalt in the production of a rubber-metal composite, adhesion failure of the rubber composition due to water / oxygen deterioration can be greatly reduced, and the present invention has been completed. It came to do. The gist configuration of the present invention for solving the above problems is as follows.

The method for producing a rubber-metal composite according to the present invention includes a surface treatment step in which a metal material is brought into contact with a buffer having a pH in the range of 5.0 to 7.2, and the metal material after the surface treatment step. An adhesive step of bonding the rubber composition to the rubber composition, wherein the rubber composition is 0.001 to 10 parts by mass of benzoic acid and 0.001 of the cobalt compound in terms of cobalt with respect to 100 parts by mass of the rubber component. -10 mass parts is contained, It is characterized by the above-mentioned. The rubber-metal composite produced by the production method is excellent in initial adhesion and wet heat adhesion between the rubber composition and the metal material.
Further, when the pH of the buffer solution is in the range of 5.0 to 7.2, good durability of the metal material in the obtained rubber-metal composite can be maintained. In addition, the initial adhesiveness and wet heat adhesiveness between the rubber composition of the rubber-metal composite and the metal material can be further improved.

The buffer solution preferably contains at least one acid selected from acids having an acid dissociation constant pKa of 4 to 8 as a component constituting the buffer solution . With this configuration, it is possible to maintain good durability of the metal material in the obtained rubber-metal composite. In addition, the initial adhesiveness and wet heat adhesiveness between the rubber composition of the rubber-metal composite and the metal material can be further improved.

In the tire manufacturing method of the present invention, the rubber-metal composite manufactured by the above-described rubber-metal composite manufacturing method is used . The tire produced by the production method is particularly excellent in durability under high temperature and high humidity.

Method of manufacturing an industrial belt of the present invention, the rubber - using metal complexes - rubber manufactured by the manufacturing method of the metal complex. The industrial belt produced by the production method is particularly excellent in durability under high temperature and high humidity.

The method of manufacturing a rubber crawler of the present invention, the rubber - using metal complexes - rubber manufactured by the manufacturing method of the metal complex. The rubber crawler manufactured by the manufacturing method is particularly excellent in durability under high temperature and high humidity.

According to the present invention, it is possible to provide a rubber composition having excellent adhesiveness after water / oxygen deterioration, that is, wet heat adhesiveness, while maintaining good initial adhesiveness with a metal material.
According to the present invention, there is provided a method for producing a rubber-metal composite, in which a rubber-metal composite having excellent wet heat adhesion is obtained while maintaining good initial adhesion between the metal material and the rubber composition. can do.
According to the present invention, it is possible to provide a rubber-metal composite having excellent wet heat adhesion while maintaining good initial adhesion between the metal material and the rubber composition.
According to the present invention, it is possible to provide a tire, an industrial belt, and a rubber crawler that are excellent in durability particularly under high temperature and high humidity.

(Rubber composition)
Hereinafter, the present invention will be specifically described with reference to embodiments thereof.
The rubber composition of the present invention contains 0.001 to 10 parts by mass of a benzoic acid compound and 0.001 to 10 parts by mass of a cobalt compound in terms of cobalt with respect to 100 parts by mass of the rubber component. The rubber composition becomes a rubber material of the rubber-metal composite of the present invention.

[Benzoic acid compound]
The rubber composition of the present invention contains a benzoic acid compound in an amount of 0.001 to 10 parts by mass with respect to 100 parts by mass of a rubber component described later, and 0.01 to 5 parts by mass from the viewpoint of initial adhesiveness and wet heat adhesiveness. It is preferable to contain, and it is more preferable to contain 0.1-2 mass parts. If the content of the benzoic acid compound is less than 0.001 part by mass, sufficient wet heat adhesion cannot be obtained, and if it exceeds 10 parts by mass, the initial adhesiveness deteriorates.

  Here, the benzoic acid compound means benzoic acid or a derivative thereof, for example, a compound represented by the following formula.

(Wherein R _{1 to} R ₅ are each a hydrogen atom, a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, an iodine atom), a hydroxyalkyl group (for example, a hydroxymethyl group, a hydroxyethyl group), a hydroxy group, , Alkyl groups (for example, methyl group, ethyl group), aryl groups (for example, phenyl group, naphthyl group), alkenyl groups, alkynyl groups, carboxyl groups, alkoxycarbonyl groups (for example, methoxycarbonyl group), aryloxycarbonyl groups ( For example, phenoxycarbonyl group), alkoxy group (for example, methoxy group), aryloxy group (for example, phenoxy group), acyloxy group (for example, acetoxy group), alkylthio group (for example, methylthio group), arylthio group (for example, phenylthio group) ) Or a heterocyclic group Furthermore, the hydrogen atoms contained in the group described above, may be substituted herein-mentioned group or a halogen atom such as, and, R ₁ to R ₅ may each be the same or different.)

Among these benzoic acid compounds, from the viewpoint of initial adhesiveness and wet heat adhesiveness, it is preferable that at least one of benzoic acid and R _{1 to} R ₅ in the above formula is a hydroxyalkyl group (for example, a hydroxymethyl group, Hydroxyethyl group) or a benzoic acid derivative that is a hydroxy group is preferable, and benzoic acid, salicylic acid, and resorcinic acid are particularly preferable.

[Cobalt compound]
Although it does not specifically limit as a cobalt compound used for this invention, The cobalt salt of an organic acid, a cobalt metal complex, etc. are mentioned, The cobalt salt of an organic acid is preferable. Examples of organic acid cobalt salts include cobalt naphthenate, cobalt stearate, cobalt neodecanoate, cobalt rosinate, cobalt versatate, cobalt tall oil, cobalt oleate, cobalt linoleate, cobalt linolenate, cobalt palmitate Etc. Among these, from the viewpoint of the balance between initial adhesion and wet heat adhesion, cobalt salts of organic acids having 16 to 18 carbon atoms such as cobalt stearate, cobalt oleate, cobalt linoleate, cobalt linolenate, and cobalt versatate Is more preferable. The cobalt salt of the organic acid may be a complex salt in which part of the organic acid is replaced with boric acid. Examples of the cobalt metal complex include cobalt acetylacetonate. In the rubber composition of this invention, the said cobalt compound may be used individually by 1 type, and may be used in combination of 2 or more type.

  The rubber composition of the present invention contains the cobalt compound in an amount of 0.001 to 10 parts by mass in terms of cobalt with respect to 100 parts by mass of a rubber component to be described later, from the viewpoint of initial adhesiveness and wet heat adhesiveness. It is preferable to contain 5 parts by mass, and more preferably 0.1 to 2 parts by mass. In addition, in this invention, cobalt conversion means the mass of the cobalt atom contained in a cobalt compound. When the cobalt content is less than 0.001 part by mass, sufficient initial adhesiveness and wet heat adhesiveness cannot be obtained, and when it exceeds 10 parts by mass, the initial adhesiveness and wet heat adhesiveness are affected by the organic component contained in the cobalt compound. In addition, the rubber itself has poor heat resistance, moisture resistance, oxidation resistance, and crack resistance.

[Rubber component]
The rubber component used in the rubber composition of the present invention is not particularly limited. For example, natural rubber, polybutadiene rubber, polyisoprene rubber, styrene-butadiene copolymer rubber, acrylonitrile-butadiene copolymer rubber, ethylene-propylene copolymer Examples thereof include coalesced rubber, ethylene-propylene-diene terpolymer rubber, butyl rubber, halogenated butyl rubber, alkylated chlorosulfonated polyethylene rubber, isobutylene-isoprene copolymer rubber, and polychloroprene rubber. In the rubber composition of this invention, the said rubber component may be used individually by 1 type, and may be used in combination of 2 or more types.

[Other ingredients]
In addition to the benzoic acid compound, the cobalt compound, and the rubber component, the rubber composition of the present invention may be appropriately mixed with components that are usually employed in the rubber industry as long as the object of the present invention is not impaired. . Examples of other components include vulcanizing agents such as sulfur, fillers such as silica and carbon black, oils such as process oils, vulcanization accelerators, anti-aging agents, softeners, zinc oxide, and stearic acid. Can be mentioned.

  The rubber composition of the present invention can be produced by kneading these components by a conventional method, hot-heating and extruding.

(Method for producing rubber-metal composite-first embodiment)
A first aspect of the method for producing a rubber-metal composite according to the present invention includes a surface treatment step of bringing a metal material into contact with a buffer solution, and bonding the metal material after the surface treatment step and the rubber composition. Adhering step.

<Surface treatment process>
The surface treatment step in the first aspect of the method for producing a rubber-metal composite of the present invention refers to a step of bringing a metal material into contact with a buffer solution. By bringing the metal composition that has undergone the surface treatment step into contact with the rubber composition, the initial adhesion and wet heat adhesion between the metal material and the rubber composition can be further improved. In the method for producing a rubber-metal composite of the present invention, the mechanism for improving the adhesion between the rubber composition and the metal material is not limited by a specific theory, but is estimated as follows.

  The metal materials described below may have lubricant and rust preventives attached to their surfaces for the convenience of handling and to protect the metals from corrosion. In some cases, oxides of metals such as copper and zinc contained in the plating layer are adhered. It is considered that the coating made of these deposits hinders the adhesion between the metal material and the rubber composition. Therefore, the adhesion between the metal material and the rubber composition is improved by removing at least a part of the coating film present on the surface of the metal material. In the method for producing a rubber-metal composite according to the present invention, by pretreating the surface of the metal material with a buffer solution, at least a part of the coating film present on the surface of the metal material is removed, and the surface of the metal material Is moderately activated to a state suitable for adhesion to the rubber composition (that is, the state where the outermost surface composition of the metal material is optimized), so that the initial adhesion between the metal material and the rubber is improved. it is conceivable that. Moreover, it is thought that the said buffer solution does not have a bad influence on the surface of a metal material, and can also make favorable wet heat adhesiveness.

[Metal material]
Although it does not specifically limit as a metal material used for the 1st aspect of the manufacturing method of the rubber-metal composite_body | complex of this invention, For example, iron, steel (stainless steel), lead, aluminum, copper, brass, bronze, Monel Examples thereof include a linear shape made of a metal such as a metal alloy, nickel, and zinc, a plate shape, and a chain shape. The metal material may have a plating layer on the surface. The plating layer is not particularly limited, but includes, for example, a zinc plating layer, a copper plating layer, a brass plating layer, etc., among these, from the viewpoint of initial adhesion with the rubber composition, wet heat adhesion, A brass plating layer is preferred. The brass plating layer usually has a copper / zinc ratio of 60:40 to 70:30 on a mass basis. The metal material is a metal material of the rubber-metal composite of the present invention.

  As an example of the metal material, a metal steel wire will be described and described in detail. The metal steel wire is steel, that is, a linear metal containing iron as a main component (the mass of iron exceeds 50% by mass with respect to the total mass of the metal steel wire). The metal may include a metal other than iron described above. The metal steel wire preferably has a wire diameter of 0.1 mm to 5.5 mm, and more preferably 0.15 mm to 5.26 mm, from the viewpoints of workability and durability. Here, the wire diameter of the metal steel wire refers to the longest length between two points on the outer periphery in a cross-sectional shape perpendicular to the axis of the metal steel wire. The cross-sectional shape perpendicular to the axis of the metal steel wire is not particularly limited, and may be elliptical, rectangular, triangular, polygonal or the like, but is generally circular. When a steel cord in which the metal steel wire is twisted is used for the carcass or belt of a tire, the cross-sectional shape of the metal steel wire is preferably circular and the wire diameter is preferably 0.1 mm to 0.5 mm. When used for a bead core of a tire, the cross-sectional shape is preferably circular, and the wire diameter is preferably 1 mm to 1.5 mm. The metal steel wire may have a plating layer on the surface. Although the thickness of this plating layer is not specifically limited, For example, when it is a brass plating layer, it is 100-300 nm generally.

[Buffer solution]
In the first embodiment of the method for producing a rubber-metal composite of the present invention, a buffer solution is used in the surface treatment step. The buffer solution refers to a solution having a buffering action. Here, the buffering action refers to an action of maintaining a substantially constant hydrogen ion concentration despite the addition or removal of a certain amount of acid or base. When an acid solution is used for the surface treatment step, when a rubber-metal composite is continuously produced, or after immersing a metal material in the treatment solution, washing with water, etc., and then immersing in the treatment solution again The pH of the treatment liquid may fluctuate greatly due to elution of metal from the metal material surface or mixing of water. However, in the method for producing a rubber-metal composite according to the present invention, since the buffer solution is used in the surface treatment step, it is advantageous that the pH of the buffer solution hardly fluctuates.

  The buffer used in the present invention preferably has a pH in the range of 5.0 to 7.2, more preferably 5.2 to 7.0, and 5.4 to 6.8. Is more preferred, with 6.0 to 6.8 being particularly preferred. Since the pH of the buffer solution is 5.0 or more, the acid does not excessively corrode the metal material, and by being 7.2 or less, the coating existing on the surface of the metal material can be easily removed. Become. Further, when the pH of the buffer solution is 6.0 to 6.8, the storage stability (adhesiveness after leaving the treat) is also good.

  The buffer contains at least one acid. Although it does not specifically limit as an acid contained in the said buffer solution, From a viewpoint of the adhesiveness of a rubber composition and a metal material, and a durable viewpoint of a metal material, a weak acid is preferable and an acid dissociation constant (pKa) is 4-8. Certain acids are preferred. Examples of the weak acid include acetic acid, phosphoric acid, phthalic acid, succinic acid, citric acid, and carbonic acid. Among these, acetic acid and phosphoric acid are more preferable. These acids may be used alone or in combination of two or more.

  As a metal component contained in the buffer solution, sodium or potassium is preferable. Examples of the buffer solution include acetic acid-sodium acetate buffer solution, sodium dihydrogen phosphate-disodium hydrogen phosphate buffer solution, potassium hydrogen phthalate-sodium hydroxide buffer solution, sodium citrate-sodium hydroxide buffer solution. Liquid, succinic acid-sodium tetraborate buffer, and the like. Among these, from the viewpoint of initial adhesiveness between the rubber composition and the metal material and wet heat adhesiveness of the obtained rubber-metal composite, acetic acid-sodium acetate buffer solution, sodium dihydrogen phosphate-disodium hydrogen phosphate A buffer is preferred.

  The buffer solution may be prepared by adding an inorganic salt, alcohol or the like, if necessary, as long as the object of the present invention is not impaired.

  Examples of the method of bringing the metal material and the buffer solution into contact in the surface treatment step include a method of spraying a buffer solution on the metal material and a method of immersing the metal material in the buffer solution. The time during which the metal material and the buffer solution are in contact (hereinafter referred to as the surface treatment time) may be appropriately changed depending on the pH of the buffer solution, and is usually in the range of 0.5 seconds to 20 seconds, preferably The range is from 1 second to 15 seconds. When the pH of the buffer solution is low, the surface treatment time can be short. When the pH of the buffer solution is high, the surface treatment time can be increased. That is, by using a buffer solution having a high pH, the surface treatment time can be easily adjusted, that is, the degree of surface treatment of the metal material can be finely adjusted. Moreover, it is preferable that the temperature of a buffer solution is 10 to 40 degreeC, and it is more preferable that it is 15 to 30 degreeC.

<Adhesion process>
1st aspect of the manufacturing method of the rubber-metal composite_body | complex of this invention WHEREIN: An adhesion process means the process of adhere | attaching the metal material and the said rubber composition after passing through the said surface treatment process.

  Examples of the method for bonding the metal material and the rubber composition after the surface treatment step include a method of vulcanizing and bonding the metal material and the rubber composition under pressure and heating. Vulcanization conditions are not particularly limited, but the pressure is preferably 2 MPa to 15 MPa, more preferably 2 MPa to 5 MPa, and the temperature is preferably 120 to 200 ° C, and preferably 130 to 170 ° C. The vulcanization time is not particularly limited, but is preferably 3 minutes to 60 hours.

<Other processes>
The method for producing a rubber-metal composite of the present invention may have a washing step of washing the metal material brought into contact with the buffer solution with water after the surface treatment step and before the bonding step. By having this step, the buffer solution adhering to the metal material can be washed away, and corrosion of the metal material, particularly the plating layer, can be further prevented. The water used in the washing step may be ion exchange water or tap water, but is preferably ion exchange water.

(Method for producing rubber-metal composite -second embodiment)
The second aspect of the method for producing a rubber-metal composite of the present invention includes a surface treatment step for bringing a metal material into contact with a buffer solution containing cobalt, and the metal material and the rubber component after the surface treatment step. An adhesion step of adhering a rubber composition containing 0.001 to 10 parts by mass of a benzoic acid compound to 100 parts by mass.

<Surface treatment process>
In the surface treatment step in the second embodiment of the method for producing a rubber-metal composite of the present invention, the buffer solution in the first embodiment contains cobalt. The method for containing cobalt in the buffer solution is not particularly limited, and examples thereof include a method in which a cobalt salt is added to a buffer solution and dissolved or dispersed. The cobalt salt contained in the buffer solution is not particularly limited, and examples thereof include cobalt hydroxide, cobalt chloride, cobalt bromide, cobalt nitrate, cobalt sulfate, cobalt phosphate, cobalt acetate, and cobalt benzoate. The said cobalt salt may be used individually by 1 type, and may be used in combination of 2 or more type. Thus, by including cobalt in the buffer solution, the rubber-metal composite production method can supply cobalt to the surface of the metal material (that is, the contact surface between the metal material and the rubber composition). As in the first embodiment, the entire rubber composition need not contain a cobalt compound. Therefore, the usage-amount of cobalt which is a rare metal used as a whole can be reduced, which is preferable from the viewpoint of environment and cost. Furthermore, since the method for producing the rubber-metal composite can reduce the cobalt content contained in the rubber composition as a result, the crack resistance of the rubber in the rubber-metal composite obtained by the production method can be reduced. It can be excellent.

  The cobalt concentration in the buffer solution in the second embodiment of the method for producing a rubber-metal composite of the present invention is preferably 0.01 to 0.10 mol / L. When the cobalt concentration is 0.10 mol / L or less, the adhesiveness with the rubber composition is not deteriorated, and when it is 0.01 mol / L or more, the effect of this embodiment can be sufficiently obtained. . Moreover, it is preferable that cobalt salt etc. are fully melt | dissolved in the buffer solution.

  The buffer solution used in the surface treatment step in the second embodiment of the method for producing a rubber-metal composite of the present invention has the same properties and composition as the buffer solution in the first embodiment, except that cobalt is essential. Can be used. In the surface treatment step in the second aspect of the method for producing a rubber-metal composite of the present invention, the same method as in the first aspect can be used as the method for bringing the metal material and the metal material into contact with the buffer solution. .

<Adhesion process>
The adhesion step in the second aspect of the method for producing a rubber-metal composite of the present invention is a benzoic acid compound in an amount of 0.001 to 100 parts by mass of the metal material after the surface treatment step and 100 parts by mass of the rubber component. It refers to a step of bonding a rubber composition containing 10 parts by mass. In the second aspect of the present invention, the compounding amount of the cobalt compound in the rubber composition is preferably less than 0.1 parts by mass in terms of cobalt with respect to 100 parts by mass of the rubber component, and 0.001 part by mass. More preferably, it is less than part. When the compounding amount of the cobalt compound is less than 0.1 part by mass, the crack resistance of the rubber part of the obtained rubber-metal composite can be improved.

  The rubber composition used in the bonding step in the second embodiment of the method for producing a rubber-metal composite of the present invention has the same properties and blending as the rubber composition in the first embodiment except that a cobalt compound is not essential. Can be used. Further, in the second aspect of the method for producing a rubber-metal composite of the present invention, a cobalt compound is not essential in the rubber composition as described above, but it may of course be included. In the second aspect of the method for producing a rubber-metal composite of the present invention, the method for adhering the metal material and the rubber composition after the surface treatment step is the same as the method in the first aspect. Can be used.

(Rubber-metal composite)
The rubber-metal composite of the present invention is produced by the production method of the first aspect or the second aspect. The rubber-metal composite is excellent in initial adhesion and wet heat adhesion between the rubber composition and the metal material.

(Tire, industrial belt, rubber crawler)
The ply to which the rubber-metal composite is applied is preferably used as a tire carcass ply and a belt ply, and the rubber-metal composite is preferably used for a tire bead and the like. Similarly, the rubber-metal composite is suitably used for industrial belts such as conveyor belts and rubber crawlers. Since these tires, industrial belts, and rubber crawlers are excellent in wet heat adhesion between the rubber composition and the metal material, they are difficult to peel off. Therefore, they are particularly excellent in durability under high temperature and high humidity and have a long life.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

[Rubber composition]
Natural rubber (NR), HAF carbon (CB), zinc oxide, stearic acid, sulfur, anti-aging agent (Ouchi Shinsei Chemical Co., Ltd. Nocrack 6C), cobalt fatty acid salt (manufactured by OMG, Manobond) in the amounts shown in Table 1 C: Compound salt of organic acid cobalt salt mixed with boric acid), vulcanization accelerator (Ouchi Shinsei Chemical Co., Ltd., Noxeller DZ), benzoic acid, kneaded with Banbury mixer Then, the rubber compositions used in Reference Examples 1 to 3, Example 4 , and Comparative Examples 1 to 4 were obtained by heating and extruding by a conventional method.

[Metal material]
As the metal material, a brass-plated metal steel wire (copper / zinc mass ratio of the plating layer = 63/37, wire diameter 0.3 mm) was used. The metal steel wire was twisted to produce a 1 × 3 steel cord.

[Buffer A]
Buffer A containing cobalt was prepared by the following method.
Sodium acetate (special reagent grade) was dissolved in ion-exchanged water at a concentration of 0.1 mol / l, and acetic acid (special reagent grade) was added thereto. Furthermore, cobalt acetate is added so that the cobalt concentration in the buffer solution is 0.056 mol / l and sufficiently dissolved, and buffer solution A containing cobalt used in the surface treatment process of Reference Example 2 and Comparative Example 4 is used. (PH 6.0) was prepared. At that time, the buffer solution was prepared so that other ions were not substantially mixed.

[Buffer B]
Buffer B was prepared by the following method.
Sodium acetate (special reagent grade) is dissolved in ion-exchanged water at a concentration of 0.1 mol / l, and acetic acid (special reagent grade) is added thereto, and buffer B (pH 6.6) used in the surface treatment step of Example 4 is added. ) Was produced. At that time, the buffer was prepared with care so that other ions were not substantially mixed.

<Surface treatment and cleaning of metal materials>
The steel cord used in Reference Example 2 and Comparative Example 4 is immersed in the buffer solution A containing cobalt at 25 ° C. for 10 seconds, then washed with ion-exchanged water for 10 seconds, and immediately dried by blowing air (25 ° C.). I let you.
Further, the steel cord used in Example 4 was immersed in the above buffer B at 25 ° C. for 10 seconds, then washed with ion exchange water for 10 seconds, and immediately dried by blowing air (25 ° C.).

<Adhesion between metal material and rubber composition and evaluation>
-Initial adhesiveness Steel cords not subjected to surface treatment ( Reference Examples 1 and 3, Comparative Examples 1 to 3), the above-mentioned surface treatment, and washed steel cords ( Reference Example 2, Example 4 and Comparative Example 4) The steel cords were covered with rubber compositions from above and below at 12.5 mm intervals, and vulcanized at 160 ° C. for 20 minutes to bond the rubber compositions and the steel cords. Thus, a rubber-metal composite was obtained in which a steel cord was embedded in a rubber sheet having a thickness of 1 mm (the steel cord was 12.5 mm in the center of the rubber sheet in the thickness direction and parallel to the sheet surface. Lined up at intervals).
Thereafter, in accordance with ASTM D 2229, the steel cord was pulled out from each sample immediately after vulcanization, and the coverage of the rubber adhering to the steel cord was determined by visual observation from 0 to 100%. It was used as an index. A result shows that it is excellent in initial stage adhesiveness, so that a numerical value (%) is large.

-Wet heat adhesiveness Steel cords that have not been surface-treated ( Reference Examples 1 and 3, Comparative Examples 1 to 3), the above-mentioned surface treatment, and washed steel cords ( Reference Example 2, Example 4 and Comparative Example 4), The steel cords were covered with rubber compositions from above and below at 12.5 mm intervals, and vulcanized at 160 ° C. for 20 minutes to bond the rubber compositions and the steel cords. In this way, a rubber-metal composite in which a steel cord was embedded in a rubber sheet having a thickness of 1 mm was obtained (the steel cord was 12.5 mm apart in the center of the rubber sheet in the thickness direction and parallel to the sheet surface). Are lined up).
After this rubber-steel cord composite was left in a constant temperature and humidity maintained at 100 ° C. and 95% RH for 5 weeks, the steel cord was pulled out from each sample in accordance with ASTM D 2229 and adhered to the steel cord. The rubber coverage was determined from 0 to 100% by visual observation and used as an index of wet heat adhesion. A result shows that it is excellent in wet heat adhesiveness, so that a numerical value (%) is large.

The rubber-metal composites of Reference Examples 1 and 3 using a rubber composition containing a cobalt compound and benzoic acid are the same as Comparative Example 1 and benzoic acid using a rubber composition in which neither a cobalt compound nor benzoic acid is blended. Compared to the rubber-metal composite of Comparative Example 3 containing no cobalt compound, the initial adhesiveness and wet heat adhesiveness were significantly superior. The rubber-metal composites of Reference Examples 1 and 3 were remarkably superior in wet heat adhesion as compared with the rubber-metal composite of Comparative Example 2 containing a cobalt compound and not containing benzoic acid.
In addition, a cobalt compound and benzoic acid were used in Reference Example 2 in which a buffer solution containing cobalt was used for the surface treatment step and a rubber composition containing benzoic acid was used, and a buffer solution not containing cobalt was used in the surface treatment step. The rubber-metal composite of Example 4 using the rubber composition containing the comparative example 1 using the rubber composition containing no cobalt compound and benzoic acid was not subjected to the surface treatment process. Instead, the initial adhesiveness and wet heat adhesiveness were remarkably superior to those of the rubber-metal composite of Comparative Example 3 using a rubber composition containing benzoic acid without compounding a cobalt compound. The rubber-metal composites of Reference Example 2 and Example 4 were not subjected to a surface treatment step, and Comparative Example 2 using a rubber composition containing a cobalt compound and not containing benzoic acid, a buffer containing cobalt in the surface treatment step. The wet heat adhesiveness was remarkably excellent as compared with the rubber-metal composite of Comparative Example 4 using a liquid and using a rubber composition containing neither a cobalt compound nor benzoic acid.

Claims (5)

A surface treatment step of contacting the metal material with a buffer having a pH in the range of 5.0 to 7.2 ;
An adhesion step of bonding the metal material and the rubber composition after the surface treatment step;
Including
The rubber composition contains 0.001 to 10 parts by mass of benzoic acid and 0.001 to 10 parts by mass of a cobalt compound in terms of cobalt with respect to 100 parts by mass of the rubber component. Manufacturing method. The said buffer solution contains at least 1 sort (s) of acid selected from the acid whose acid dissociation constant pKa is 4-8 as a component which comprises the said buffer solution, The manufacturing of the rubber-metal complex of Claim 1 Method. A tire manufacturing method using the rubber-metal composite manufactured by the rubber-metal composite manufacturing method according to claim 1 . The manufacturing method of an industrial belt using the rubber-metal composite body manufactured by the manufacturing method of the rubber-metal composite body of Claim 1 or 2 . A method for producing a rubber crawler using the rubber-metal composite produced by the method for producing a rubber-metal composite according to claim 1 .