JP2659616B2 - Base treatment agent for forming organic resin layer on metal surface - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to aluminum, aluminum alloy, steel,
The present invention relates to an undercoating agent for pre-coating a metal surface when forming a resin adhesive layer or a resin coating layer on the surface of various metal products such as stainless steel and galvanized steel.

[Prior art] In many metal products, if it is an adhesive structure, the purpose is to improve the adhesive strength and durability of the bonded part, or if it is a painted product, its coating In order to improve the adhesion strength and durability of a coating film on a surface, a metal surface is generally subjected to a base treatment prior to adhesion or painting.

As a method of the undercoating treatment, for example, when the metal product is aluminum or an aluminum alloy, chromic acid anodizing treatment, phosphoric acid anodizing treatment, sulfuric acid.
There are sodium dichromate etching treatment, or chromate treatment with phosphoric acid chromate, chromate chromate, coating type chromate, etc.If the metal product is stainless steel, there is sulfuric acid / sodium dichromate etching treatment, etc. Further, when the metal product is steel, there is a dry blast treatment or the like.

By the way, as a method of treating the surface of aluminum or aluminum alloy for bonding, conventionally, a method utilizing the strong oxidizing power of chromic acid has been mainly used. In many cases, hexavalent chromium, which is a problem, is contained. For example, the Water Pollution Control Law has a wastewater standard of 0.5 mg / l or less for hexavalent chromium and 2.0 mg / l or less for trivalent chromium. There is a problem that it may require expensive equipment and costs.

Therefore, research on such a chromium-free surface treatment agent has been advanced, for example, a zirconium-based treatment agent, a treatment agent mainly containing an aqueous solution of a silicate containing molybdic acid, vanadic acid, permanganate, and the like. Low-polluting type surface treatment agents have also been proposed (JP-A-50-78,532, JP-A-5-78,532).
0-78,533).

However, these low-pollution-type surface treatment agents are mainly used for the surface treatment for forming a coating film layer, such as the surface treatment before coating the beverage can body, and the film obtained by this surface treatment Also, unlike a chromate film obtained by a base treatment using chromic acid, the corrosion resistance of the film itself can hardly be expected, and the main focus is on improving the adhesion of the coating film layer.

And especially in the surface treatment agent using permanganate, potassium permanganate which is industrially easily available is used as this permanganate, and this potassium permanganate has high solubility in water, When the adhesive layer or the coating layer is formed by directly bonding or coating after the undercoating treatment, the potassium in the undercoating due to the permeation of moisture reaching the undercoating through the adhesive layer or the coating layer. However, there is a problem that the base film is destroyed, the base material is corroded, and the adhesive strength and adhesion are reduced with time.

As a method for solving such a problem, for example, a method in which a base film is formed by a base treatment, followed by a water washing treatment, and potassium is eluted and removed from the formed base film in advance is considered to be effective. However, this method also requires an extra washing step, and also has the problem that the strength of the undercoat is reduced when potassium elutes from the undercoat in this washing step.

As the permanganate, sodium salts, barium salts, calcium salts, and the like may be used in addition to the potassium salts.However, any of these permanganates has a high solubility in water, and is different from the case of the potassium salt. There is a similar problem.

[Problems to be solved by the invention]

Therefore, the present inventors have conducted intensive studies to solve various problems in the conventional base treatment agent, and as a result,
When the treating agent containing a predetermined amount of permanganic acid and ultrafine anhydrous silica and having a pH adjusted to 3 or less is a non-polluting type, and is mainly composed of an aqueous solution of permanganate silicate It does not require a water-washing treatment of the underlying film, and
The present inventors have found that they have the same corrosion resistance as a chromate film and have excellent performance as an adhesive base or a paint base, and completed the present invention.

Accordingly, an object of the present invention is to provide a non-polluting type, which does not require a water-washing treatment of a base film as in the case of using a permanganate silicate aqueous solution as a main component, and has the same corrosion resistance as a chromate film. An object of the present invention is to provide a metal surface treatment agent for forming a base film having excellent performance as an adhesive base or a coating base.

Another object of the present invention is to provide a surface treating agent which exhibits excellent performance as an adhesive undercoating or coating undercoating when forming a resin adhesive layer or a resin coating layer on the surface of various metal products. Is to provide.

[Means for solving the problem]

That is, the present invention is a base treating agent for forming an organic resin layer on a metal surface containing 1 to 200 g / l of permanganic acid and 1 to 100 g / l of ultrafine anhydrous silica as main components and having a pH of 3 or less. is there.

In the present invention, the permanganate used itself cannot be obtained as an industrial chemical, but a permanganate which is easily obtainable as an industrial chemical, for example, using potassium permanganate, is easily obtained by the following method. Obtainable.

[A] Silver nitrate (AgNO ₃ ) is added to an aqueous solution of potassium permanganate (KMnO ₄ ), and the mixture is concentrated by heating, and silver permanganate (A
gMnO ₄ ) crystals were precipitated, and the crystals were separated and dissolved in water to form an aqueous solution. Barium chloride (Ba) was added to the aqueous solution.
Cl ₂ ) is added to produce barium permanganate [Ba (MnO ₄ ) ₂ ] and silver chloride (AgCl), and silver chloride which precipitates as a solid is separated and removed. (BaSO ₄ ) is separated and removed to obtain an aqueous solution of permanganate (HMnO ₄ ).

[B] Slowly cooled concentrated sulfuric acid is added to the potassium permanganate crystals to obtain oily permanganate.

[C] An aqueous solution of potassium permanganate is passed through a strongly acidic cation exchange resin and ion-exchanged to obtain an aqueous solution of permanganate.

The ultrafine anhydrous silica used in the present invention is obtained by reacting a volatile silicon compound such as silicon tetrachloride (SiCl ₄ ) in the gas phase in the presence of oxygen and hydrogen.
They usually have a particle size of 0.01 to 0.1 μm, and more preferably, spherical amorphous fine powder called fumed silica.
Such ultra-fine anhydrous silica is commercially available under the trade names of Aerosil (Nippon Aerosil Co., Ltd.) and Cabosil (Cabot Corporation). There are alkali silicate and colloidal silica as silicates. However, alkali silicate has a problem in water resistance of an undercoating film formed because a compound containing a water-soluble alkali metal is contained in the compound. However, there is a problem that the effect of improving the adhesiveness is small, which is not preferable.

The surface treating agent of the present invention contains the above-mentioned permanganic acid and ultrafine anhydrous silica at a predetermined ratio, and is prepared as an aqueous solution or aqueous dispersion having a hydrogen ion concentration (pH) of 3 or less.

Here, the addition amount of permanganate as HMnO ₄ 1~2
It is 00 g / l, preferably 3 to 150 g / l. If it is less than 1 g / l, a base film having excellent corrosion resistance cannot be obtained, and if it is more than 200 g / l, sufficient adhesive strength cannot be obtained. The amount of ultrafine particulate anhydrous silica, 1 to 100 g / l as SiO _2, is preferably 5~75g / l, is not sufficient wettability to less metal surface than 1 g / l, for the Sufficient adhesive strength cannot be obtained, and if it is more than 100 g / l, not only the corrosion resistance is not improved, but also the surface of the undercoat becomes powdery and the adhesive strength is rather reduced.

The surface treatment agent of the present invention is adjusted to a pH of 3 or less, preferably 0.5 to 2.0 using a pH adjuster at the time of its preparation, and the pH adjuster used at this time is preferably nitric acid or It is sulfuric acid. If the pH is higher than 3, there is a problem in its stability such as solidification of agar in a relatively short time after preparing the solution of the base treatment agent, and work such as uniform application and uniform dispersibility. The properties are also undesirably reduced. Since hydrochloric acid and phosphoric acid have an adverse effect on the reduction reaction of permanganate,
Cannot be used as a pH adjuster.

The base treating agent of the present invention is applied to a metal surface before applying an adhesive or a paint mainly containing an organic resin such as a synthetic resin or a natural resin, and forms a manganate base film on the metal surface.

As a method of this base treatment, it can be performed by a method similar to a conventionally known base treatment agent, for example, a dipping method, a brush,
There is a coating method using a roll coater, a bar coater, a spray or the like. The immersion method is, for example, a metal product is immersed in a base treatment agent at a temperature of room temperature to 85 ° C. for about 1 to 10 minutes and dried, and this immersion treatment is repeated a plurality of times as necessary,
A baking treatment is performed at a temperature of about 200 to 250 ° C. for 1 to 20 minutes. In addition, the coating method is to apply a base treatment agent to the surface of the metal product by an appropriate coating means, dry the coating, repeat the coating treatment as necessary a plurality of times, and then bake at a temperature of about 200 to 250 ° C. for 1 to 20 minutes. Perform processing. The baking treatment at the time of the undercoating treatment is a treatment necessary for reducing permanganic acid remaining in the formed undercoating film to manganese dioxide without being involved in the reaction with the metal surface, and fixing it to the metal surface. is there. The drying furnace used for this purpose may be any one that can be heated and dried at 200 to 250 ° C. In addition to a normal hot air drying furnace, a known drying furnace such as a far-infrared drying furnace is used. can do.

The undercoating agent of the present invention is useful for undercoating applied to the surface of various metal products for various purposes, particularly aluminum, aluminum alloys, steel, stainless steel,
When forming a resin adhesive layer or a resin coating layer on the surface of a metal product such as galvanized steel, it exerts excellent performance on an adhesion undercoating treatment or a coating undercoating treatment. For example, specific fields of application include automobiles, railway vehicles, electrical products, building materials,
Alternatively, it is suitably used for adhesion to a constituent member such as a beverage can or a base treatment at the time of painting.

The resin forming the resin adhesive layer and the resin coating layer is preferably a resin mainly composed of a thermosetting resin. The thermosetting resin may be a heat-curable resin or a room-temperature-curable resin. You may.

[Action]

The permanganic acid contained in the undercoating agent of the present invention is a stronger oxidizing agent than chromic acid. When it contacts a metal surface under acidic conditions, it is reduced to insoluble manganese dioxide and adheres to the metal surface. At this time, if there is an excess of permanganic acid in the formed base film, it dissolves in water and affects water resistance, but the permanganic acid remaining in the film by heating at a temperature of 200 ° C or more also It is easily reduced to manganese dioxide. The manganese dioxide formed in the undercoat in this manner has excellent water resistance and excellent adhesion to the metal surface, and is considered to contribute to the improvement of the corrosion resistance and adhesion of the undercoat.

〔Example〕

Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples.

[1] Examples 1 to 12 and Comparative Examples 1 to 13 5 g of potassium permanganate was dissolved in 1 pure water and passed through a strongly acidic ion-exchange resin column previously adjusted to RH type to obtain 5 g / l and A pH 2.1 permanganate aqueous solution (HMnO ₄ ) was obtained.

The permanganic acid aqueous solution (HMnO ₄ ) of 5 g / l and pH 2.1 thus obtained was concentrated by heating or diluted by adding pure water to obtain a predetermined solution corresponding to each of Examples and Comparative Examples. The concentration was adjusted and used in each of Examples and Comparative Examples.

Further, the pH adjustment of the adjusted base treatment agent was performed in Examples 1 to 3.
9, Examples 11 and 12, Comparative Examples 1 to 4 and Comparative Examples 6 and 7 were performed using nitric acid, and Example 10 and Comparative Examples 8 to 10 were performed using sulfuric acid. Comparative Examples 5 and 11 to 13 did not carry out such pH adjustment.

Permanganic acid, ultra-fine anhydrous silica (trade name, manufactured by Nippon Aerosil Co., Ltd .: Aerosil) in the proportions shown in Table 1,
Formulated with potassium permanganate or colloidal silica (Nissan Chemical Co., Ltd. product name: Snowtex 20)
The pH was adjusted to prepare the undercoating agents of Examples and Comparative Examples. In Comparative Example 11, the undiluted solution of Cosmer 150 (trade name, manufactured by Kansai Paint Co., Ltd.) was used as a coating type chromate treatment liquid.

Using the surface treatment agents of Examples and Comparative Examples thus prepared, test specimens were prepared by the following method, and subjected to a tensile shear adhesive strength test (according to JIS K-6850).
After bonding, the primary tensile shear bond strength (primary bond strength) after one day at room temperature, and after bonding in pure water at 30 ° C,
The secondary tensile shear adhesive strength (secondary adhesive strength) after immersion for 000 hours was measured. The results are shown in Table 1.

(1) Tensile shear adhesive strength test of Examples 1 to 10 and Comparative Examples 1 to 11 Aluminum alloy (JIS standard alloy A-5052) H34 tempered material with a thickness of 1.0 mm x 25 mm x 60 mm A test piece was prepared, and the surface thereof was degreased with acetone. Then, the base treating agents of Examples 1 to 10 and Comparative Examples 1 to 11 were applied by the method shown in Table 1. When the coating method at this time was the dipping method, the coating was immersed at room temperature for 1 minute, and when the coating method was the roll coater method, the coating was performed at room temperature so that the coating amount was 120 mg / m ² .

After applying the undercoating agent to the test piece in this way, if the baking treatment is "yes", perform the heat drying treatment in a 210 ° C hot air drying oven for 15 minutes, and if "no", leave it at room temperature Then, if the water washing process is “Yes”, the test piece is washed with water after this drying and dried again.
In the case of (1), a test piece having been subjected to a base treatment was prepared.

The two test pieces prepared by the base treatment in this manner were overlapped so that the overlap margin was 25 mm x 12.5 mm.
Cold-setting epoxy resin adhesive (two-component type) (Cemedine Co., Ltd. trade name: CEMEDINE 1500) was adhered using a 250 g / m ^2, a tensile shear bond strength test (according to JIS standard K-6850) went.

(2) Tensile shear bond strength test of Example 11 and Comparative Example 12 A test piece was prepared using rolled steel SS41, and the secondary bond strength was measured.
The test was conducted in the same manner as in the tensile shear adhesive strength test of Examples 1 to 10 and Comparative Examples 1 to 11 except that the test was performed after immersion for 6 hours.

(3) Tensile shear bond strength test of Example 12 and Comparative Example 13 A test piece was prepared using a galvanized steel sheet, and the secondary bond strength was measured.
The test was performed in the same manner as in the tensile shear adhesive strength test of Examples 1 to 8 and Comparative Examples 1 to 11 except that the test was performed after immersion for 480 hours.

[Effect of the Invention] The undercoating agent of the present invention has a water-resistant undercoat formed on a metal surface using the same, and a conventional potassium permanganate is used for forming this undercoat. Unlike the case of using a base treatment agent that uses chromic acid, it does not require a water washing treatment, and there is no need to worry about the problem of pollution as in the case of the base treatment agent that uses conventional chromic acid. No equipment is required and can be applied to on-site construction. In addition, since the underlying coating film itself has excellent corrosion resistance, when a resin adhesive layer or a resin coating layer is formed on the surface of various metal products, the adhesion to the organic resin layer can be improved. It has excellent performance that can be maintained for a long time.

Claims (2)

(57) [Claims] 1. An organic resin layer forming method on a metal surface, comprising 1 to 200 g / l of permanganic acid and 1 to 100 g / l of ultrafine anhydrous silica as main components and having a pH of 3 or less. Base treatment agent. 2. The undercoating agent for forming an organic resin layer on a metal surface according to claim 1, wherein nitric acid or sulfuric acid is added as a pH adjuster.