JP2884699B2 - Rubber joining method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method of bonding rubber to a base material such as a steel cord, and more particularly, to forming a metal thin film on a base material surface by a dry plating method or the like. The present invention relates to a method for improving the adhesive strength of a metal thin film and bonding a base material and rubber with good adhesiveness when vulcanizing and bonding a rubber composition.

2. Description of the Related Art When a rubber composition is bonded to a metal base such as a steel cord, in order to improve the adhesion between the metal base and the rubber composition, the present inventors apply a metal to the surface of the metal base by a dry plating method. Alternatively, a method has been proposed in which a metal alloy thin film is attached and formed, and then the rubber composition is heated and pressed to perform vulcanization bonding (Japanese Patent Application Laid-Open
62-87311 and 62-246278).

The bonding method can strongly bond the metal substrate and the rubber without using an adhesive.However, in order to further improve the adhesiveness between the dry plating thin film of the metal or the metal alloy and the metal substrate, the bonding method is usually used. The surface treatment is performed on the base material.

That is, a method of cleaning the surface of a metal substrate by a wet method such as solvent cleaning, ultrasonic cleaning, acid or alkali cleaning before performing dry plating, a plasma cleaning (bombard) performed in a vacuum, and a dry method such as a reverse sputtering method. Cleaning method is performed.

Further, in the method proposed in the above publication, when a sputtering method is employed as a dry plating method, a metal atom that has been beaten has a higher kinetic energy than a vacuum evaporation method. On the other hand, when the ion plating method is used, a part of the evaporated atoms is ionized, so that a bias potential is applied to the base material to electrically ionize the metal atoms. The dry plating method can be used to improve the adhesive strength of the dry plating thin film to the substrate by, for example, improving the adhesion of the dry plating thin film to the substrate by hitting the substrate with high energy. Can be improved.

Problems to be Solved by the Invention However, as a result of further studies by the present inventors, when a dry plating thin film is formed on a metal substrate surface, particularly when a cobalt metal thin film is formed as a dry plating thin film, the above-described appropriate pretreatment, Even when the dry plating method is adopted, under more severe conditions, the dry plating thin film portion that plays a role of bonding the base material and the rubber layer may occur before the rubber layer is destroyed, so that the rubber-based It has been found that the joint strength of the composite material may be reduced.

That is, when a cobalt metal thin film is formed on the surface of a metal base material, and then the rubber composition is bonded by heating and compression and sulfur vulcanization, a large amount of, for example, 5 to 6 parts of sulfur is blended and usually performed in about 40 minutes. For example, vulcanization is carried out for a long time of about 400 to 600 minutes, and the obtained rubber-based composite material is subjected to a peel test in a low-temperature atmosphere of about -60 ° C. It was found that the film was peeled off from the rubber layer to which the thin film adhered, and that this peeling was caused by a decrease in the strength of the film during vulcanization of the rubber.

The present invention has been made in view of the above circumstances, and in a method of bonding a rubber in which a rubber composition is heated and vulcanized after forming a cobalt metal thin film on a surface of a base material such as a metal, an adhesive function between the base material and the rubber layer is provided. It is an object of the present invention to provide a method for preventing the destruction of a cobalt metal thin film in a low-temperature peeling test after long-time vulcanization of a cobalt metal thin film having the above, and for firmly joining a substrate and rubber.

Means and Action for Solving the Problems The present inventors have conducted intensive studies to achieve the above object, and as a result, when forming a cobalt metal thin film on a substrate surface, for example, dry plating was performed in an oxidizing atmosphere. To form a cobalt metal thin film mixed with cobalt oxide (hereinafter referred to as a partially cobalt oxide thin film), heat-treating the thin film, and vulcanizing and bonding the thin film to a rubber layer. Even if the rubber composition mixed in a large amount such as ~ 6 parts is heated and pressed for about 400 minutes for a long time and vulcanized and bonded, it is possible to prevent the strength from being reduced in the thin film and improve the bonding strength. In this case, As shown in Examples described later, the formation of the above partial cobalt oxide thin film alone has almost no effect of improving the bonding strength, and when used in combination with the heat treatment of the thin film, the peeling test was conducted at a low temperature. Even in this case, it is found that destruction in the thin film can be surely prevented, so that the function of bonding the base material of the thin film and the rubber is not impaired, and that the base material and the rubber can be firmly bonded by exhibiting a sufficient function. The present invention has been accomplished.

Therefore, the present invention provides a method for bonding rubber, comprising forming a cobalt metal thin film containing a mixture of cobalt oxide on the surface of a substrate, heat-treating the thin film, and then vulcanizing and forming a rubber layer on the thin film. I will provide a.

 Hereinafter, the present invention will be described in more detail.

In the rubber bonding method of the present invention, the type of the target substrate is not particularly limited, and the present invention is applicable to metals, ceramics, plastics, and the like. In this case, examples of the type of the metal substrate include steel, stainless steel, titanium alloy, aluminum, aluminum alloy, copper, copper alloy, zinc, zinc alloy, and amorphous alloy.
It is not limited to these. Various ceramics and plastics can be selected according to the purpose.

The shape and size of the base material are appropriately selected depending on the purpose, for example, steel wire, steel cord,
Examples include steel tire cords, steel cables, steel strands, steel rods, steel plates, steel filaments, and the like (hereinafter, these are collectively referred to as steel cords), metal plates, metal fittings, and the like.

When a partial cobalt oxide thin film is formed on the surface of such a substrate, it is desirable that the above-described cleaning be performed on the substrate as a pre-treatment so as to enhance the adhesion to the partial cobalt oxide thin film.

As a method of forming the partial cobalt oxide thin film on the substrate, it is preferable to employ a dry plating method, for example, a vacuum evaporation method, an ion plating method, a DC and high frequency magnetron sputtering method, a two-electrode sputtering method, a high frequency sputtering method, Examples thereof include an arc discharge sputtering method and an electron cyclotron resonance (ECR) plasma method, and particularly preferred are an ion plating method, a DC and high-frequency magnetron sputtering method, and a high-frequency sputtering method.

When a partial cobalt oxide thin film is formed by these methods, a method of reacting with an oxidizing gas at the time of film formation is preferable, and a reactive sputtering method is generally employed. Alternatively, a method in which a film is formed from a substance containing an oxide in advance, such as a sputtering method using an oxide target, can be used. When the above reactive sputtering method is adopted, air or oxygen gas is mixed into the atmosphere gas,
By changing the concentration, the oxygen content (oxidation degree) of the thin film can be controlled.

The degree of oxidation of the partially cobalt oxide thin film obtained by the above method is preferably from 5 to 35 at%, particularly preferably from 10 to 25 at%, and if the oxidation degree is less than 5%, the effect of improving the bonding strength may not be exhibited. If the degree of oxidation is higher, the bonding strength may decrease.

The thickness of the above partial cobalt oxide thin film can be appropriately selected according to the purpose, but is usually preferably from 10 to 100 μm from the productivity of the thin film, and particularly preferably from 50 to 1 μm.

In the method of the present invention, the above-mentioned partial cobalt oxide thin film is formed on the surface of the substrate, and then the thin film is subjected to a heat treatment to obtain the effect of improving the bonding strength of the present invention.

Here, the conditions of the heat treatment are 100 to 400 ° C, particularly 150 to 300 ° C.
It is preferable to perform the treatment in the range of 1 second to 3 hours, but the treatment time is preferably long at a low temperature corresponding to the treatment temperature, and short at a high temperature. For example, 1 hour at 150 ° C. and 1 hour at 200 ° C. It can be about 30 seconds at 300 ° C. for 2 to 5 minutes. As the heat treatment method, a method such as resistance heating, oven heating, infrared heating, induction heating, etc. can be appropriately adopted,
The atmosphere may be any of air, vacuum, inert gas atmosphere and the like.

According to the method of the present invention, the partially cobalt oxide thin film is formed on the surface of the base material, and after the thin film is subjected to heat treatment, the rubber composition is vulcanized to join the base material and the rubber layer.

Here, the rubber component in the rubber composition is a natural rubber (N
R) and synthetic rubbers having a carbon-carbon double bond in the structural formula alone or as a blend of two or more thereof can be used. Examples of the synthetic rubber include polyisoprene rubber (IR), polybutadiene rubber (BR), which is a homopolymer of a conjugated diene compound such as isoprene, butadiene, and chloroprene.
Styrene-butadiene copolymer rubber (SBR), which is a copolymer of the conjugated diene compound and a vinyl compound such as styrene, acrylonitrile, vinylpyridine, acrylic acid, methacrylic acid, alkyl acrylates, and alkyl methacrylates, such as polychloroprene rubber; Vinyl pyridine butadiene styrene copolymer rubber, acrylonitrile butadiene copolymer rubber, acrylate butadiene copolymer rubber, methacrylate butadiene copolymer rubber, methyl acrylate butadiene copolymer rubber, methyl methacrylate butadiene copolymer rubber, ethylene, propylene, isobutylene Copolymers of olefins and diene compounds such as isobutylene-isoprene copolymer rubber (II
R)], copolymers of olefins and non-conjugated dienes (EPD
M) [e.g., an ethylene-propylene-cyclopentadiene terpolymer, an ethylene propylene-5-ethylidene-2-norbornene terpolymer, an ethylene propylene-1,4-hexadiene terpolymer], and a cycloolefin Examples include polyalkenamers (eg, polypentenamers) obtained by ring-opening polymerization, rubbers (eg, sulfur-vulcanizable polyepichlorohydrin rubber) obtained by ring-opening polymerization of oxirane rings, and polypropylene oxide rubbers. Also included are halides of the various rubbers, for example, chlorinated isobutylene isoprene copolymer rubber (Cl-IIR), brominated isobutylene isoprene copolymer rubber (Br-IIR), and the like. Further, a ring-opened polymer of norbornene may be used. Still further, as the blend rubber, a saturated elastic material such as epichlorohydrin rubber, polypropylene oxide rubber, chlorsulfonated polyethylene, or the like may be blended with the above rubber to be used.

The rubber component further according to a conventional method, carbon black, silica, calcium carbonate depending on the purpose, use, etc.,
Fillers such as calcium sulfate, clay, mica, mineral oil,
Softeners such as vegetable oils, sulfur and other crosslinking agents, vulcanization accelerators,
A rubber composition can be prepared by adding a vulcanization accelerator such as zinc white and stearic acid.

In the present invention, it is not necessary to particularly add an organic cobalt salt as a vulcanization adhesion promoter between the partially cobalt oxide and the rubber.

The bonding between the rubber composition and the partially cobalt oxide thin film on the surface of the substrate is performed by heating and pressing the rubber composition on the thin film and vulcanizing and bonding the same. The vulcanization method includes sulfur vulcanization and dithiol vulcanization. Organic sulfur vulcanization with an organic sulfur compound such as morpholine or tyrium vulcanization is employed, and heating can be performed according to a conventional method. Among these, the method by sulfur vulcanization is particularly preferred. In this case, the compounding amount of sulfur in the sulfur or the organic sulfur compound is preferably 0.5 to 7 parts by weight, particularly preferably 1 to 6 parts by weight based on 100 parts by weight of the rubber component.

In the method of the present invention, a rubber composition containing a large amount of the above-mentioned sulfur, for example, 5 to 6 parts, after performing vulcanization bonding for a long time, for example, even when a peel test is performed in a low-temperature atmosphere of about −60 ° C. The substrate and the rubber can be firmly bonded without destruction in the partially cobalt oxide thin film. Therefore, the method of the present invention requires a tire, a power transmission belt, It can be widely applied to the manufacture of various rubber products and parts such as a rubber-based composite material using a fibrous metal as a core material such as a conveyor belt and a hose, a vibration isolating rubber, a vibration isolator, a rubber crawler, a rubber screen, and a rubber roll.

Effect of the Invention As described above, the method of the present invention forms a partially cobalt oxide thin film on the substrate surface, and then performs a heat treatment on the thin film,
Then, by vulcanizing and forming a rubber layer on the thin film, the base material and the rubber layer can be firmly joined without being affected by the amount of sulfur as a rubber vulcanizing agent or the vulcanization adhesion time.

Hereinafter, the present invention will be described more specifically by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

(Examples, Comparative Examples)

Brass plated steel cord (diameter:
Using 0.18 mm, twist structure: 3 + 9), the surface of the steel cord was subjected to argon plasma treatment at a high frequency of 13.56 MHz and a power of 100 W for 5 minutes.

A cobalt thin film having a different degree of oxidation was applied to the steel cord subjected to the above treatment by DC magnetron sputtering.
It was formed with a thickness of 05 μm. Here, the sputtering conditions are such that argon gas is 90 to 95% as a reaction gas and oxygen gas is 10 to 95%.
5% volume ratio [measured with gas flow meter (mass flow meter)], gas pressure 5mTorr, power 0.5A × 400V, time
Performed in 30 seconds.

Next, the steel cord on which the dry plating was formed was heat-treated in an oven at 200 ° C. for 5 minutes in the air.

Next, the heat-treated cord was bonded to an unvulcanized rubber composition having the composition shown in Table 1 and then vulcanized at 145 ° C. for 400 minutes.

The vulcanized adhesive sample thus obtained was subjected to a peel test using a tensile tester in a low-temperature atmosphere at −60 ° C. to measure the adhesive strength, and the fracture surface was observed, and the adhesive performance was evaluated based on the following criteria. evaluated.

Adhesive performance F (%): Fracture area of dry plating thin film R (%): Fracture area of rubber F + R = 100% For comparison, vulcanized adhesion samples prepared in the same manner except that the above heat treatment was not performed A tensile test was performed.

The degree of oxidation of the dry plated thin film was determined as an average value of the entire dry plated thin film by X-ray photoelectron spectroscopy (XPS) using the 2S peak of cobalt and the 1S peak of 0 of cobalt oxide (CoO).

 Table 2 shows the above results.

As can be seen from the results in Table 2, the adhesive strength and the adhesive performance of the partial cobalt oxides without heat treatment (Comparative Examples 1 to 3) are inferior. On the other hand, according to the present invention (Examples 1 to 3)
Is excellent in adhesive strength and adhesive performance, and it is recognized that heat treatment of the partially cobalt oxide thin film is remarkably effective in improving bonding strength when vulcanization is performed for a long time.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-189117 (JP, A) JP-A-62-87310 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C08J 5/00-5/02 C08J 5/12-5/22 C09J 5/00 B32B 1/00-35/00

Claims (1)

(57) [Claims] 1. A method of bonding rubber, comprising forming a cobalt metal thin film containing cobalt oxide on a surface of a substrate, subjecting the thin film to heat treatment, and then vulcanizing and forming a rubber layer on the thin film. .