JPS5854665B2 - Method for manufacturing metal-rubber composite - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel method for manufacturing a metal-rubber composite, particularly a vibration-proof rubber element.

Anti-vibration rubber, which is a composite of metal and rubber, is widely used in many structures such as automobiles and ships.

For example, in order to prevent the corrosion of ferrous and other metals, anti-corrosion rubber for automobiles has traditionally been coated with a corrosion-resistant coating after the metal and rubber have been bonded together. In order to prevent physical deterioration, coating is done using low-temperature baking water-based paints such as melamine-alkyd paints or solvent-based paints such as lacquer paints.

However, in cold regions such as the northern United States and Canada, large amounts of rock salt and potassium chloride are sprayed on roads to prevent road surfaces from freezing, and in these areas, automobile underbody parts coated with the above coatings are not corrosion-resistant. However, there is a need for urgent countermeasures.

It is known that high-temperature baking resin paints such as powder coatings and electrodeposition coatings are suitable as corrosion protection measures for parts that are made only of metal without rubber composites, such as anti-vibration rubber.
Since these paints have a high baking temperature of approximately 150° C. or higher, when they are used in anti-vibration rubber made by bonding and combining rubber, there is a problem in that the bonded portion and the rubber portion deteriorate during baking.

In addition, anti-vibration rubber is also made by combining metal and rubber with only adhesives such as phenolic brimer adhesive, the most common vulcanization-adhesive adhesive, and chlorinated rubber cement adhesive. It is known that salt water greatly reduces adhesive strength due to the combined effects of corrosion of the metal at the adhesive interface and electrolytic action.

As described above, there is a strong demand for a method to improve the durability of anti-vibration rubber under usage conditions where it is affected by seawater, rock salt, etc.

The present invention is the result of various studies on conventional anti-corrosion measures, and as a result, a novel method for producing a metal-rubber composite with excellent corrosion resistance has been developed.

That is, a thermosetting resin-based coating composition is applied to the surface of the metal and cured at high temperatures to form a baked coating, and at least one surface of the baked coating and the vulcanized rubber surface are coated with epoxy or urethane. By joining with a system adhesive composition,
It manufactures composites of metal and rubber.

Generally, in the manufacturing method of composites of metal and rubber, the two are first glued together and finished with paint after the product is finished.Also, it is better to use a clean metal surface for the adhesive surface of the metal and rubber. It was commonly thought that the adhesive strength was more important than the film surface.

The manufacturing method of the present invention is significant in that it succeeded by breaking through these conventional common sense and adopting a completely opposite method, which was previously thought to be difficult to implement for composites of metal and rubber. It was possible to use a coating film baked at high temperatures, and unexpectedly good adhesive strength was obtained.

In the present invention, the thermosetting resin coating composition used to form a coating film on a metal surface includes coating compositions such as polyester resin, acrylic resin, and epoxy resin for powder coating, and anionic coating compositions such as polyester resin, acrylic resin, and epoxy resin for powder coating. The main types of paint compositions used are polybutadiene resins, polyester resins, etc. used in electrocoating, as well as epoxy resin coating compositions used in cationic electrocoating, but there are also others used in dip coating. Various resin-based coating compositions can be used.

However, when evaluating corrosion resistance, adhesiveness, etc., epoxy resin coating compositions for cationic electrodeposition coating are preferred.

The cationic epoxy resin coating composition includes a primer electrodeposition type in which a pigment is dispersed in a cationic medium made water-soluble or water-dispersible by adding an amine to an epoxy group, and an EPC in which an epoxy resin powder is further dispersed. (powder electrodeposition)
There are several types, all of which can achieve the purpose of the present invention.

Examples of the thermosetting method include a crosslinking method using a blocked isocyanate and a method of crosslinking by introducing a vinyl double bond into an amine-attached processed poquin resin.

The epoxy resin is preferably a known glycidyl ether of bisphenol A, but is not particularly limited.
It may be appropriately selected from other epoxy resins.

The coating composition may also contain other additives commonly used in coating compositions, such as rust preventives, various fillers, and solvents.

Suitable metals in the present invention include iron, non-ferrous metals such as iron, copper, aluminum, brass, and tin, and alloys thereof, and the shape may be cylindrical, plate-like, or processed in various ways. .

Rubbers used include natural rubber, polyisoprene, polybutadiene, polychloroprene, SBR, N
BR, ethylene-propylene-conjugated diene ternary copolymer, butylene-isogrene copolymer, etc., and these substances alone or in mixtures are the main components, and vulcanizing agents, fillers,
It goes without saying that other commonly used compounding agents are also included.

Furthermore, a portion of these vulcanized rubbers may be composited with metal, plastic, or other materials in advance.

When manufacturing a composite, the metal surface is first treated before painting so that the paint will easily adhere to it.

This is done by known methods, ie, degreasing with a solvent or alkaline solution and removing rust with an acid or mechanical polishing.

More preferably, an iron phosphate film or a zinc phosphate film is formed by chemical treatment.

As mentioned above, there are various methods for applying the thermosetting resin coating composition to the metal surface-treated in this manner.

The most suitable electrodeposition coating will be explained here.

Electrodeposition coatings are broadly divided into anionic and cationic types.

In anionic electrodeposition coating, the object to be coated is used as an anode, and the surface of the object becomes acidic due to the large amount of hydrogen ions generated at this anode, and the electrophoresed anionic water-soluble resin ions solidify and deposit a coating film. It is a mechanism.

On the other hand, in cationic electrodeposition coating, the object to be coated is used as a cathode, and at this cathode, the surface of the object is made alkaline by hydroxyl ions, and the electrophoresed cationic water-soluble resin ions harden to form a coating film and water. The mechanism is such that water is transferred to the tank by electric permeation.

These electrodeposited coating films are washed with water to remove excess paint, and then baked and dried at a high temperature of usually 160 to 200°C for 20 to 60 minutes.

The coating film thus obtained has extremely excellent corrosion resistance.

The rubber to be adhered to the metal on which the coating has been formed is first surface-treated by a known method.

That is, at least the adhesion surface of the vulcanized rubber or vulcanized rubber composite is improved in adhesion by cyclization with a strong acid, halogenation with a halogenated compound, or surface treatment by coating with a primer.

The thus surface-treated rubber is bonded to at least one surface of the baked metal film using an adhesive to form a composite.

Urethane-based or epoxy-based adhesives are suitable for use here.

Urethane adhesive compositions include two-component adhesive compositions consisting of a polyether or polyester base agent and an isocyanate curing agent, and one-component moisture-curing adhesives.

Epoxy adhesive compositions include two-component adhesive compositions containing bisphenol A glycidyl ether as a main ingredient and polyamine as a curing agent.

Any of these can achieve the purpose of the present invention,
It is applied to either or both of the rubber adhesion surface and the baked metal surface and then bonded together.

Next, a concrete and detailed explanation will be given using examples.

Example I In a round test piece shown in section 8-2-1 of JIS K6301 (see Figure 1), the steel test fitting 1 was subjected to alkaline degreasing, acid rust removal, and zinc phosphate film forming treatment. (1) As an example, an epoxy-based cationic electrodeposition primer paint (product name: Powercoat) was applied to this test metal fitting 1 by electrodeposition, and then baked and dried at 190°C for 30 minutes. On the other hand, a sulfur-cured natural rubber vulcanizate having a rubber hardness of 60° was prepared, which was immersed in concentrated sulfuric acid, left for 30 seconds, washed with water, and dried to perform surface treatment.

Next, a urethane adhesive made of a two-component mixture of polyether and diisocyanate was applied to the adhesion surfaces of the surface-treated vulcanized rubber 2 and the painted test metal fittings, and then the two were overlapped and bolted between two iron plates. 100 when crimped
A composite specimen was prepared by curing at ℃ for 30 minutes.

(2) As a comparative example, the same test fitting 1 was used, and a phenolic primer adhesive (trade name: Chemrock 205, manufactured by Hewson Chemical Company, USA) and a chlorinated rubber cement adhesive (trade name, manufactured by Hewson Chemical Co., Ltd., USA) were used on the adhesive surface with rubber. Kemrock 220)
After coating and drying, insert it into a mold and inject a sulfur-vulcanized natural rubber compound with a rubber hardness of 600.
Vulcanization was carried out at 0°C for 15 minutes.

This composite was immersed in a melamine alkyd water-based paint, dried at 130° C. for 30 minutes, and then painted to produce a composite of a comparative example corresponding to a conventional product.

A salt spray test according to JIS Z2371 was conducted on the samples of these Examples and Comparative Examples with the samples stretched by 20% of the rubber thickness in the tensile direction.

As a result, the comparative sample had an initial adhesive strength of 124 kg/c.
Rubber breakage was shown at d.

Then, it was peeled off by salt water spraying for 72 hours. The area of separation was between the metal and the primer adhesive.

On the other hand, the example sample had an initial adhesive strength of 80 to 9/ca and the rubber broke, no abnormality was observed after 144 hours of salt water spraying, and the adhesive strength after removal from the jig was 85 kg/ca and the rubber broke. Ta.

As described above, according to the method of the present invention, it is possible to produce a composite of metal and rubber that has excellent corrosion resistance.

Example 2 In a rubber bushing in which the inner cylinder 3 and the outer cylinder 5 are connected via rubber 4 as shown in FIG. It was subjected to alkaline degreasing, acid rust removal, and zinc phosphate film formation treatment in the same manner as in Example 1, and sulfur-vulcanized natural rubber having a hardness of 400 was vulcanized and bonded thereto in the same manner as in the comparative example of Example 1.

The outer diameter of the rubber at this time is 49171Eφ, and the outer cylinder 5
The adhesive surface was treated by applying concentrated sulfuric acid, leaving it for 1 minute, washing with water, and drying.

On the other hand, the outer cylinder 5 is made of carbon steel with an inner diameter of 44iiφ and a length of 40 mm, which has also been subjected to alkaline degreasing, acid rust removal, and zinc phosphate film forming treatment according to the usual method. 1) As an example, an epoxy-based cationic electrodeposition primer paint is applied by electrodeposition, and a urethane-based adhesive is used as a lubricant to apply the coating into the outer cylinder 5, which is made up of the above-mentioned inner cylinder 3 and rubber 4. After the surface-treated vulcanized rubber composite was press-fitted, it was allowed to stand at room temperature for 72 hours to cure.

(2) As a comparative example, a surface-treated vulcanized rubber composite was press-fitted into the outer cylinder 3 after the same phosphoric acid inversion, using a urethane adhesive as a lubricant, and then a melamine alkyd water-based paint was applied. and then dried and cured at 130° C. for 30 minutes.

When a comparative test was conducted between this example and the comparative example, the initial pull-out load of the comparative example was 2700 kg, the fractured part was near the outer cylinder, and some metal of the outer cylinder was exposed.

The pull-out load of this comparative example after 240 hours of salt water spraying was 225
0 kg, and more outer cylinder metal fittings were exposed at the fractured part than at the beginning.

In addition, there were scratch marks on the outer surface of the outer cylinder.
After 40 hours, there was rust with a width of 15 mm centered around the scratch marks, and there was also a lot of rust on areas where no scratch marks were made.

On the other hand, the initial pull-out load in the example is 3450 kg,
The broken part was near the outer cylinder, but there was no exposed metal or paint on the outer cylinder, and it was all rubber damage.

Moreover, the pull-out load after 240 hours of salt water spraying was 3900:9, and the fracture state was the same as the initial state.

Furthermore, the rust on the outer surface of the outer cylinder 9 was below the rim of one side from the scratch mark, and there was no rust on other parts.

Figures 4 and 5 show that both the rubber bushes of the example and comparative example are held down in the axial direction by eight springs 6 using the device shown in Figure 3, and a torsion angle of ±15° is repeatedly applied in the direction perpendicular to the axis. 3 is a graph showing the relationship between rotational torque and rotational speed until failure occurs.

Here, the repeated durability testing apparatus for a rubber bush shown in FIG. 3 (vertical cross-sectional view of the central portion) will be explained.

In this device, an outer cylinder 5 of a rubber bush 7 is fixed from the outside, and an inner cylinder 3 is inserted and fixed onto a rotating shaft 8.

One end of the rotating shaft 8 is pressed in the axial direction by a coil spring 6 via a bearing 10, while the other end is
It is connected to a repetitive rotary drive 9 that repeatedly rotates with a twist angle of 15°.

Therefore, this device can repeatedly rotate at a twisting angle of ±15° and apply rotational torque to the rubber bushing, and it is possible to determine the relationship between the number of repetitions and rotational torque until the rubber breaks.

As seen in this graph, the rotational torque value of the conventional product shown in Fig. 5 is low overall, and the 2X10' to 7
In contrast, in the embodiment of the present invention shown in FIG. 4, the variation is small and the overall torque value is high, and the breakage occurs in the range of 2×105 repetitions. It shows almost constant value.

As a result of observing the state of destruction, in the comparative example, the rubber on the outer cylinder side was damaged, whereas in the example of the present invention, the rubber on the inner cylinder side was damaged. This proves the superiority of the method of the present invention in which bonding is performed afterwards.

As is clear from the results detailed above, according to the method for producing a metal-rubber composite of the present invention, the adhesive strength between metal and rubber is not reduced even under corrosive conditions such as salt water. It has the advantage of significantly improving the durability of the composite.

[Brief explanation of the drawing]

FIG. 1 is a side view of the test piece composite. FIG. 2 is a central vertical cross-sectional view of the rubber bushing, and FIG. 3 is a central longitudinal cross-sectional view of the repeated durability test device. FIGS. 4 and 5 are graphs showing the relationship between rotational torque and rotational speed until failure occurs. 1... Test metal fittings, 2... Vulcanized rubber, 3
...Inner cylinder, 4...Rubber, 5...
・Outer cylinder, 6... Spring, 7... Rubber bush 8... Rotating shaft, 9...
Repetitive rotation drive unit, 10...Bearing.

Claims (1)

[Claims] 1. A thermosetting resin coating composition is applied to the surface of the metal and cured at high temperatures to form a baked coating, and at least one surface of the baked coating and the vulcanized rubber surface are coated with an epoxy or urethane coating. A method for producing a composite of metal and rubber, characterized in that the composite is bonded with an adhesive composition.