JPH03220242A - Method for bonding rubber - Google Patents

Abstract

PURPOSE:To improve the adhesive properties by forming a thin cobalt alloy film contg. a cobalt alloy oxide on a substrate material, thermally treating the film, and simultaneously forming and vulcanizing a rubber layer on the film. CONSTITUTION:100 pts.wt. rubber component (e.g. a natural rubber), 0.5-7 pts.wt. sulfur, a filler, a softener, an accelerator, a vulcanization aid, etc., are compounded to give a rubber compsn. Separately, a thin cobalt alloy (e.g. Co-Ni) film contg. a cobalt alloy oxide, with a degree of oxidation of 2-35atom%, and having a thickness of 10Angstrom -100mum is formed on the surface of a substrate material such as a metal, ceramic, or plastic by ion plating, high-frequency magnetron sputtering method, etc., and, if necessary, the film is thermally treated at 100-400 deg.C for 1sec to 3hr. Then, the rubber compsn. is thermally pressed onto the film, vulcanized, and bonded to the film.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the method of bonding rubber to a base material such as a steel cord. More specifically, the present invention relates to an improvement in the method of bonding rubber to a base material such as a steel cord. The present invention relates to a method for bonding a base material and rubber with good adhesiveness by improving the adhesive strength of a metal thin film when vulcanizing and adhering a rubber composition after formation.

14 When joining a rubber composition to a metal base material such as a steel cord, in order to improve the adhesion between the metal base material and the rubber composition,
The present inventors have proposed a method in which a metal or metal alloy thin film is deposited on the surface of a metal substrate by dry plating, and then a rubber composition is bonded under heat and vulcanization (JP-A-62
-87311, 62-246278).

The above bonding method can strongly bond the metal base material and rubber without using adhesives, but in order to further improve the adhesiveness between the dry plating thin film of metal or metal alloy and the metal base material, A surface treatment is performed on the base material.

In other words, there are two methods: cleaning the surface of the metal substrate with a wet method such as solvent cleaning, ultrasonic cleaning, alkali cleaning, etc. before applying dry plating, and plasma cleaning performed in a vacuum (
Dry cleaning methods such as bombardment) and reverse sputtering methods are used.

In addition, in the method proposed in the above-mentioned publication, when sputtering is used as the dry plating method, the ejected metal atoms have higher kinetic energy than in vacuum evaporation. On the other hand, when using the ion blating method, some of the evaporated atoms are ionized, so a bias potential is applied to the base material and the ionized metal atoms are electrically ionized. By accelerating and hitting the substrate with high energy, it is possible to improve the adhesion of the dry plating thin film to the substrate.Select and adopt dry plating methods as appropriate to improve the adhesion of the dry plating thin film to the substrate. can be done.

However, as a result of further investigation by the present inventors,
When forming a dry plating thin film, especially a cobalt metal thin film as a dry plating thin film, on the surface of a metal substrate, even if the above-mentioned appropriate pretreatment and dry plating method are adopted, under more severe conditions, the rubber layer may not be destroyed. It has been found that the dry plating thin film portion that serves to bond the base material and the rubber layer may be destroyed, resulting in a decrease in the bonding strength of the rubber-based composite material.

That is, after forming a cobalt metal thin film on the surface of the metal base material,
When a rubber composition is heat-pressed and bonded by sulfur vulcanization, a large amount of sulfur is blended, for example, 5 to 6 parts, and vulcanization, which normally takes about 40 minutes, is vulcanized for a long time, for example, about 600 minutes.
When the obtained rubber-based composite material was subjected to a peel test in a low temperature atmosphere of about -60° C., destruction occurred within the cobalt metal thin film.

It has been found that the bonding strength is significantly lowered, and it has also been found that this is caused by the lowering of the strength of the cobalt metal thin film during long-term vulcanization bonding.

The present invention was made in view of the above circumstances, and provides a rubber bonding method in which a metal thin film having an adhesive function between the base material and the rubber layer is formed on the surface of a base material such as metal, and then a rubber composition is heated and vulcanized. The object of the present invention is to provide a method for firmly bonding a base material and rubber by preventing a decrease in the strength of a metal thin film during rubber vulcanization.

In order to achieve the above object, the inventors of the present invention have conducted intensive studies and found that when forming a thin film of cobalt alloy on the surface of a substrate, 1, for example, dry plating is performed in an oxidizing atmosphere to remove cobalt. By forming a cobalt alloy thin film in which alloy oxides are mixed (hereinafter referred to as a partially oxidized cobalt alloy thin film), a rubber composition containing a large amount of 5 to 6 parts of sulfur can be mixed with 6 parts of sulfur.
Even when a rubber layer is formed by vulcanization for a long time of about 0.00 minutes, the partially oxidized cobalt alloy thin film does not break in a low-temperature peel test at about -60°C, and therefore the thin film's base material and rubber do not break. The present inventors have discovered that a rubber substrate can be firmly bonded to a base material without impairing its adhesion function, and the present invention has been completed based on this discovery.

Accordingly, the present invention provides a method for joining rubber, which comprises forming a partially oxidized cobalt alloy thin film on the surface of a base material, and then vulcanizing and forming a rubber layer on the thin film.

The present invention will be explained in more detail below.

In the rubber bonding method of the present invention, there are no particular restrictions on the type of base material to be used, and the method is applicable to metals, ceramics, plastics, etc. in this case.

Examples of the types of metal base materials include steel, stainless steel, titanium alloy, aluminum, aluminum alloy,
Examples include, but are not limited to, copper, copper alloys, zinc, zinc alloys, amorphous alloys, and the like. Furthermore, various ceramics and plastics can be selected depending on the purpose.

The shape, size, etc. of this base material can be selected as appropriate depending on the purpose. For example, steel wire, steel cord, steel tire cord, steel cable, steel strand, steel rod, steel plate, steel filament, etc. (generally referred to as steel cord), metal plates, metal fittings, etc.

When forming a partially oxidized cobalt alloy thin film on the surface of these substrates, it is desirable to perform the above-mentioned cleaning on the substrate as a pretreatment to improve the adhesion with the partially oxidized cobalt alloy thin film.

As a method for forming a partially oxidized cobalt alloy thin film on the above-mentioned base material, it is preferable to adopt a dry plating method,
Examples include vacuum evaporation method, ion plating method, DC and high frequency magnetron sputtering method, bipolar sputtering method, high frequency sputtering method, arc discharge sputtering method, electron cyclotron resonance (ECR) plasma method, etc. Preferred are the rating method, DC and high frequency magnetron sputtering method, and high frequency sputtering method.

The partially oxidized cobalt alloy thin film formed by the above method is made of cobalt as a base and other metals, and a portion of the alloy is uniformly oxidized.

Here, the alloy composition of the partially oxidized cobalt alloy thin film is 5, for example, Go-Ni, Co-Cr, Co-Ti,
C.

-Fe, Co-Zr, Co-Zn, Co-
Examples include Sn, Co-P, etc., but of course ternary, quaternary alloys, etc. may also be used. These compositions contain 5 cobalt
It is preferably 0 atomic % or more, and the upper limit is 9
It is desirable that the content be 9g%, and various selections can be made within that range. Specifically, in the case of Go-Ni, Ni is 5 to 40
% C, especially 10-25 atomic %.

In the case of -Cr, Cr is 5 to 25 at%, especially 7 to 15 at%, in the case of Co-Ti, T1 is 5 to 40 at%, especially 10 to 30 at%, and in the case of Co-Fe, Fe is 1 ~40
atomic %, especially 3 to 30 atomic %, C.

- In the case of Zr, Zr is 5 to 40 at%, especially 10 to 30
%, in the case of Co-Zn, Zn is 5 to 40 atomic %, especially 10 to 25 atomic %, and in the case of Co-3n, Sn is 5 to 4 atomic %.
A range of 0 atom %, particularly 10 to 25 atom %, is preferred.

In addition, the oxygen content (degree of oxidation) of the partially oxidized cobalt alloy thin film is 2 to 357! An oxidation degree of less than 2% may not produce an effect of improving bonding strength, while an oxidation degree higher than 35 atom% may result in a decrease in bonding strength. Note that the oxidation degree of the partially oxidized cobalt alloy thin film is the atomic % of oxygen atoms in all alloy elements.

When forming the partially oxidized cobalt alloy thin film by the above-mentioned dry plating method, the first alloy thin film can be formed by, for example, using an alloy target as a target in a sputtering method, or by using a chip target method in which another metal piece is placed on a base metal target. can be done. On the other hand, as a method for partially oxidizing the alloy thin film, a method of reacting with an oxidizing gas during film formation is suitable, and a reactive sputtering method is generally adopted. Alternatively, a method of forming a film from a substance containing an oxide in advance, such as a sputtering method using an oxide target, can also be used. When employing the above-mentioned reactive sputtering method, the degree of oxidation of the thin film can be controlled by mixing air or oxygen gas into the atmospheric gas and changing its concentration.

The film thickness of the partially oxidized cobalt alloy can be appropriately selected depending on the purpose, but it is usually preferably 10 to 100 mm from the viewpoint of thin film productivity, and particularly preferably 50 to 1 mm.

Note that before vulcanizing the partially oxidized cobalt alloy thin film and joining the base material and the rubber layer, if necessary, the partially oxidized cobalt alloy thin film is heat-treated at 100 to 400°C, preferably 150 to 300°C for 1 second to 3 hours. be able to.

In the method of the present invention, after forming a partially oxidized cobalt alloy thin film on the surface of a base material, the rubber composition is vulcanized to bond the base material and the rubber 1.

Here, the rubber component in the rubber composition is natural rubber (NR)
, and a synthetic rubber having a carbon-carbon double bond in its structural formula can be used alone or in a blend of two or more. The above synthetic rubbers include polyisoprene rubber (IR), which is a homopolymer of conjugated diene compounds such as isoprene, butadiene, and chloroprene, and polybutadiene rubber (BR).
, polyisoprene rubber, etc., the above conjugated diene compounds and styrene, acrylonitrile, vinylpyridine, acrylic acid, methacrylic acid, alkyl acrylates.

Styrene-butadiene copolymer rubber (SBR), which is a copolymer with vinyl compounds such as alkyl methacrylates, vinylpyridine-butadiene-styrene copolymer rubber, acrylonitrile-butadiene copolymer rubber, acrylic acid-butadiene copolymer rubber, methacrylic acid Copolymers of olefins such as ethylene, propylene, isobutylene, and diene compounds such as butadiene copolymer rubber, methyl acrylate butadiene copolymer rubber, methyl methacrylate butadiene copolymer rubber [e.g. isobutylene isoprene copolymer rubber ( IIR)), copolymers of olefins and non-conjugated dienes (EPDM) (e.g. ethylene-propylene-cyclopentadiene terpolymer, ethylene-propylene-5-
ethylidene-2-/rubornene terpolymer, ethylene propylene-1,4-hexadiene terpolymer], polyalkenamer obtained by ring-opening polymerization of cycloolefin [e.g. polypentenamer], ring-opening polymerization of oxirane ring (e.g., polyepichlorohydrin rubber that can be sulfur-cured), polypropylene oxide rubber, and the like. In addition, halides of the various rubbers mentioned above, such as chlorinated isobutylene isoprene copolymer rubber (C
Q-IrR), brominated isobutylene isoprene copolymer rubber (Br-IIR), and the like are also included. Furthermore, ring-opened polymers of norbornene may also be used. Furthermore, as a blended rubber, a saturated elastic material such as epichlorohydrin rubber, polypropylene oxide rubber, or chlorosulfonated polyethylene may be blended with the above-mentioned rubber.

In addition to the above rubber components, according to the purpose and use, fillers such as carbon black, silica, calcium carbonate, calcium sulfate, clay, and mica, softeners such as mineral oil and vegetable oil, crosslinkers such as sulfur, etc. A rubber composition can be prepared by adding a vulcanization accelerator, a vulcanization accelerator, a vulcanization accelerating aid such as zinc white, and stearic acid.

Note that in the present invention, it is not necessary to specifically incorporate organic cobalt salts as a vulcanization adhesion promoter between the partially cobalt oxide alloy and the rubber.

The above rubber composition and the partially oxidized cobalt alloy thin film on the surface of the base material are bonded by heat-pressing the rubber composition onto the thin film and vulcanizing the film. Organic sulfur vulcanization using an organic sulfur compound such as dithiomorpholine or thiuram vulcanization is employed, and vulcanization can be carried out according to a conventional method.

Among these, a method using sulfur vulcanization is particularly preferred. In this case, the amount of sulfur or sulfur in the organic sulfur compound is 0.5 to 7 parts by weight, especially 1 to 7 parts by weight, based on 100 parts by weight of the rubber component.
The amount is preferably 6 parts by weight.

In the method of the present invention, even when vulcanization bonding is performed for a long time with a rubber composition containing a large amount of sulfur, for example, 5 to 6 parts, the strength within the partially oxidized cobalt alloy thin film does not decrease, and the base material and rubber For this reason, the method of the present invention uses fibrous metal as the core material for tires, power transmission belts, conveyor belts, hoses, etc. that require strong bonding strength between base materials such as metal and rubber. It can be widely applied to the production of various rubber products and parts such as rubber composite materials, vibration-proof rubber, vibration-isolating materials, rubber crawlers, rubber screens, and rubber rolls.

As explained above, the method of the present invention involves forming a partially oxidized cobalt alloy thin film on the surface of a substrate, and then vulcanizing and forming a rubber layer on the thin film. The base material and the rubber layer can be firmly bonded without being affected by the blending amount or vulcanization adhesion time.

Next, Examples and Comparative Examples will be shown to further illustrate the present invention, but the present invention is not limited to the following Examples.

[Example, comparative example]

Steel cord with brass plating as base material (diameter: 0
．． 18m+, twisted structure: 3+9), the surface of this steel cord was used to generate a high frequency of 13.56MHz and a power of 100W.
Argon plasma treatment was performed for 5 minutes.

A partially oxidized cobalt alloy thin film having a composition shown in Table 1 was formed on the above-treated steel cord by DC magnetron sputtering to a thickness of 0.05-1 and an oxidation degree shown in the table. Here, the sputtering conditions were 1 alloy target, argon gas containing 5 to 10% by volume of oxygen gas, gas pressure of 5 mTorr, and power of 0.
．． The voltage was 5A x 400V and the time was 30 seconds.

Next, the cord was laminated with an unvulcanized rubber composition having the composition shown in Table 1, and then vulcanization bonding was performed at 145° C. for 600 minutes.

Table 1: A low-temperature peel test was carried out using a tensile tester in an atmosphere of 60°C to measure the adhesive strength and the ll! of the fractured surface.
The adhesive performance was evaluated based on the following criteria.

Chu' 111 F (%) Breakage area of Nidry plating thin film R (%): Breakage area of rubber F + R = 100% The composition of the alloy was determined by emission spectrometry, and the degree of oxidation of the dry plating thin film was determined by X-ray photoelectron spectroscopy. It was measured as the average value of the entire dry plating thin film by the (XPS) method.

The above results are shown in Table 2.

Note 1) Note 2>N-phenyl-N'-isopropyl-P-phenylenediamine N-oxydiethylene-2-benzothiazole sulfamide Regarding the vulcanized adhesive sample thus obtained, Table 2 From the results, in the case of cobalt single metal (comparative example)
In this case, poor adhesion was observed in the low-temperature peel test after long-term vulcanization.

On the other hand, when a cobalt alloy is used, it is recognized that it exhibits excellent adhesion performance even after long-term vulcanization, and a stable composite that is not affected by vulcanization time can be obtained.

Claims (1)

[Claims] 1. A rubber bonding method, which comprises forming a cobalt alloy thin film containing a cobalt alloy oxide on the surface of a base material, and then vulcanizing and forming a rubber layer on the thin film.