JPH04202674A - Surface preparation agent for forming organic resin layer on metal surface - Google Patents

Abstract

PURPOSE: To obtain a surface prepn. agent for forming an org. resin layer on a metallic surface which easily forms a ground surface film having excellent corrosion resistance and adhesiveness without pollution by forming the agent of specific contents of permanganic acid and superfine particulate anhydrous silica as essential components and specifying the pH thereof.

CONSTITUTION: This surface prepn. agent for forming the org. resin layer on the metallic surface is composed of 1 to 200 g/l permanganic acid and 1 to 100 g/l superfine particulate anhydrous silica as the essential components and is adjusted to pH of ≤3. The metallic surface is previously provided with the ground substrate film before the resin adhesive layer is formed thereon. The pH control agent is preferably nitric acid or sulfuric acid. The pH of the surface prepn. agent is adjusted to pH of ≤3, more preferably about 0.5 to 2.0 by adding the pH control agent to the agent. The surface prepn. agent is used at ordinary temp. to about 85°C. The metallic products are preferably immersed therein and are then subjected to a surface preparation by a baking treatment at about 200 to 250°C.

COPYRIGHT: (C)1992,JPO

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention is a method of applying a resin adhesive layer or a resin coating layer to the surface of various metal products such as aluminum, aluminum alloy, steel, stainless steel, and galvanized steel. The present invention relates to a surface treatment agent for applying a surface treatment to a metal surface in advance when forming the metal surface.

[Conventional technology]

For many metal products, the purpose is to improve the adhesive strength and durability of the bonded part if it is a bonded structure, or to improve the coating film on the painted surface if it is a painted product. In order to improve adhesive strength and durability, metal surfaces are generally pretreated prior to adhesion or painting.

For example, when the metal product is aluminum or an aluminum alloy, the surface treatment method includes chromic acid anodizing treatment, phosphoric acid anodizing treatment, sulfuric acid/dichromate soda etching treatment, or phosphoric acid chromate treatment. There is chromate treatment using chromate chromate, paint-on chromate, etc.If the metal product is stainless steel, there is sulfuric acid/soda dichromate etching treatment, etc.Furthermore, if the metal product is steel, there is chromate treatment. There are dry blasting treatments, etc.

By the way, conventional methods for adhering aluminum or aluminum alloys have mainly utilized the strong oxidizing power of chromic acid. In many cases, waste water contains hexavalent chromium, which poses a problem.For example, the Water Pollution Control Law has wastewater standards that limit hexavalent chromium to 0.5■/l or less and trivalent chromium to 2.0■/l or less. There has been a problem in that wastewater treatment sometimes requires a large amount of equipment and expense.

Therefore, research has been carried out on surface treatment agents that do not contain ROM, such as zirconium-based treatment agents and treatment agents whose main ingredient is an aqueous solution of silicate containing molybdic acid, vanadate, permancanate, etc. A low-pollution type surface treatment agent has also been proposed (Japanese Unexamined Patent Publication No. 50-78.532,
(Japanese Unexamined Patent Publication No. 1978-78.533).

However, these low-pollution surface treatment agents are mainly intended for surface treatment for coating layer formation, such as surface treatment before painting the bodies of beverage cans, and the film obtained by this surface treatment is However, unlike the chromate film obtained by surface treatment using chromic acid, the film itself cannot be expected to have much corrosion resistance, and the main focus is solely on improving the adhesion of the coating layer.

In particular, in surface treatment agents using permanganate, potassium permanganate, which is industrially easily available, is used as the permanganate, and this potassium permanganate has high solubility in water. When an adhesive layer or a paint layer is formed by adhering or painting as is after this base treatment, the potassium in the base film is absorbed by the penetration of moisture that passes through these adhesive layers or paint layers and reaches the base film. The problem was that the components were leached out, the underlying film was destroyed, the substrate was corroded, and the adhesive strength and adhesion decreased over time.

As a method for solving such problems, it is considered effective to, for example, perform a water washing treatment after forming a base film by surface treatment to elute and remove the potassium content from the formed base film in advance.

However, this method also requires an extra washing step and has the problem that the strength of the underlying film is reduced when potassium content is eluted from the underlying film in this washing step.

In addition, it may be possible to use sodium salts, barium salts, calcium salts, etc. in addition to potassium salts as permanganate salts.All of these permancanate salts have high solubility in water, and it is not possible to use potassium salts. I have a similar problem.

[Problem to be solved by the invention]

Therefore, as a result of intensive research to solve various problems with such conventional surface treatment agents, the present inventors have developed a method that contains a predetermined amount of permancanic acid and ultrafine particulate anhydrous silica, A treatment agent adjusted to 3 or less, or a non-polluting type, does not require water washing of the base film as in the case where the main ingredient is a permanganate formate aqueous solution, and
The present invention was completed based on the discovery that it has corrosion resistance equivalent to that of a chromate film, and has excellent performance as an adhesive base or painting base.

Therefore, the object of the present invention is to provide a non-polluting type film that does not require water washing treatment of the base film as in the case where the base film is based on an aqueous solution of silicate of permanganate, and has corrosion resistance equivalent to that of a chromate film. An object of the present invention is to provide a base treatment agent for metal surfaces for forming a base film having excellent performance as an adhesive base or a paint base.

Another object of the present invention is to provide a surface treatment agent that exhibits excellent performance as an adhesive base treatment or painting base treatment when forming a resin adhesive layer or a resin coating layer on the surface of various metal products. Our goal is to provide the following.

[Means to solve the problem]

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

° In the present invention, the permancanic acid used itself is not available as an industrial chemical, or a permanganate salt that is easily available as an industrial chemical, such as potassium permanganate, is used, and it can be easily obtained by the following method. can be obtained.

[A] Add silver nitrate (AgNO3) to an aqueous solution of permanganate (KMnO<), heat and concentrate to precipitate silver permanganate (AgMn04) crystals, separate these crystals, and dissolve in water. Barium chloride (BaC1z) is added to this aqueous solution to form barium permanganate rBa (MnO<L] and silver chloride (AgC1).
After separating and removing the silver chloride that precipitates as a solid, dilute sulfuric acid is added to precipitate barium sulfate (BaSO
4) is separated and removed to obtain an aqueous solution of permanganic acid (HMnO<).

[B” Gradually cooled concentrated sulfuric acid is added to the crystals of potassium permanganate to obtain oily permanganic acid.

[C] An aqueous permanganate solution is obtained by passing an aqueous solution of potassium permanganate through a strongly acidic cation exchange resin for ion exchange.

・Also, the ultrafine anhydrous silica used in the present invention is a volatile silicon compound, such as silicon tetrachloride (SiC/!)
It is obtained by reacting silica in the gas phase in the presence of oxygen and hydrogen, and it usually has a particle size of 0.01 to 0.1 pm, and preferably is a spherical amorphous fine powder called fumed silica. Such ultrafine anhydrous silica particles are commercially available under the trade names of Aerosil (Nippon Aerosil (Kikki)) and Cabosil (Cabot Corporation). There are colloidal silica, etc., but alkali silicates contain water-soluble alkali metals in their compounds, so there is a problem with the water resistance of the formed base film, and colloidal silica does not have the effect of improving adhesion. It is not desirable because there is a problem that it is too small.

The surface treatment agent of the present invention contains the permanganic acid and ultrafine anhydrous silica in predetermined proportions, and is prepared as an aqueous solution or a dispersion in water having a hydrogen ion concentration (pH) of 3 or less.

Here, the amount of permanganic acid added is 1 to 200 g/l, preferably 3 to 150 g/l as HMnO, and if it is less than 1 g/l, a base film with excellent corrosion resistance cannot be obtained. Further, if the amount exceeds 200 g/l, sufficient adhesive strength cannot be obtained. Further, the amount of ultrafine anhydrous silica particles added is 1 to 100 g/II as 5i02, preferably 5 to
75 g/12, and if it is less than Ig/12, the wettability to the metal surface will not be sufficient, and therefore sufficient adhesive strength will not be obtained, and if it is more than 100 g/I, there will be no improvement in corrosion resistance. Not only that, but the surface of the base film becomes powdery, which actually reduces the adhesive strength.

The surface treatment agent of the present invention uses a pH adjuster during its preparation to adjust the pH to 3 or less, preferably 0. The pH is adjusted to 5 to 2.0, and the pH adjusting agent used at this time is preferably nitric acid or sulfuric acid.

If the pH is higher than 3, after preparing the solution of the surface treatment agent,
Problems arise in its stability, such as solidification into agar-like form within a relatively short period of time, and workability such as uniform application and uniform dispersibility deteriorates, which is undesirable. Note that hydrochloric acid and phosphoric acid cannot be used as pH adjusters because they have an adverse effect on the reduction reaction of permanganic acid.

The surface treatment agent of the present invention is applied to a metal surface before applying an adhesive or paint whose main component is an organic resin such as a synthetic resin or a natural resin, and forms a mancanic acid base film on the metal surface.

This surface treatment can be carried out in the same manner as conventionally known surface treatment agents, such as a dipping method, a coating method using a brush, a roll coater, a bar coater, a spray, or the like. The dipping method is, for example, immersing the metal product in a base treatment agent for about 1 to 10 minutes at a temperature of room temperature to 85°C, drying it, repeating this dipping process multiple times as necessary, and then dipping it at a temperature of about 200 to 250°C. Baking treatment is carried out at a temperature of 1 to 20 minutes. In addition, the coating method involves applying a base treatment agent to the surface of the metal product using an appropriate coating method, drying it, repeating this coating process multiple times as necessary, and then heating the product at a temperature of 200 to 250°C.
Baking treatment is carried out for 1 to 20 minutes at a temperature of about 100 ml. This baking treatment during base treatment is a process that does not involve any reaction with the metal surface and is necessary to reduce the permanganate remaining in the formed base film to manganese dioxide and fix it to the metal surface. be. The drying oven used for this purpose may be one that can heat dry at 200 to 250°C, and in addition to a normal hot air drying oven, a known drying oven such as a far-infrared drying oven may be used. can be used.

The surface treatment agent of the present invention is useful as a surface treatment applied to the surfaces of various metal products for various purposes, but is particularly useful for surface treatment of metal products such as aluminum, aluminum alloy, steel, stainless steel, and galvanized steel. It exhibits excellent performance as an adhesive base treatment or painting base treatment when forming a resin adhesive layer or a resin coating layer on the surface. For example, as specific fields of application, it is suitably used for adhesion of structural members such as automobiles, railway vehicles, electrical appliances, construction materials, and beverage cans, and for surface treatment during painting.

It should be noted that the resin forming the resin adhesive layer and the resin coating layer is preferably one mainly composed of a thermosetting resin, and the thermosetting resin may be a thermosetting resin or a room temperature curing type. It's okay.

[For production]

Permanganic acid contained in the surface treatment agent of the present invention is a stronger oxidizing agent than chromic acid, and when it comes into contact with a metal surface under acidic conditions, it is reduced to insoluble manganese dioxide, which adheres to the metal surface. At this time, if excess permanganate exists in the formed base film, it will dissolve in water and affect the water resistance, or the permanganate that remains in the film when heated at a temperature of 200°C or higher. It is also easily reduced to manganese dioxide. The manganese dioxide formed in the base film in this way has excellent water resistance and adhesion to metal surfaces, and is thought to contribute to improving the corrosion resistance and adhesion of the base film.

〔Example〕

The present invention will be specifically described below based on Examples and Comparative Examples.

[1] Examples 1 to 12 and Comparative Examples 1 to 13 5 g of hydrium permanganate was dissolved in II pure water and passed through a strongly acidic ion exchange resin column previously adjusted to R-H type.
permanganic acid aqueous solution (HMnO
+) was obtained.

The thus obtained 5 g/z and pH 2.1 permanganic acid aqueous solution (HMnO<) is heated and concentrated, or
It was diluted by adding pure water, adjusted to a predetermined concentration corresponding to each Example and Comparative Example, and used in each Example and Comparative Example.

In addition, the pH adjustment of the prepared surface treatment agent was carried out in Examples I to
9. Examples 11 and 12, Comparative Examples 1 to 4, and Comparative Examples 6 and 7 were carried out using nitric acid, and Example 10 and Comparative Examples 8 to 10 were carried out using sulfuric acid. In Comparative Examples 5 and 11 to 13, such pH adjustment was not performed.

Permanganic acid, ultrafine anhydrous silica (Nippon Aerosil ■ part name: Aerosil), potassium permanganate, or colloidal silica (Nissan Chemical (Taru product name: Snotefux 20) are blended in the proportions shown in Table 1. The base treatment agents of Examples and Comparative Examples were prepared by adjusting the pH. In Comparative Example 11, Cosmer 150 (trade name, manufactured by Kansai Paint ■) was used as a undiluted solution as a coating mold 10M treatment solution.

Using the base treatment agents of the Examples and Comparative Examples prepared in this manner, test pieces were prepared in the following manner, subjected to a tensile shear adhesive strength test (according to JIS standard -6850), and bonded. The primary tensile shear adhesive strength after one day at room temperature (secondary adhesive strength) and the secondary tensile shear adhesive strength after immersion in pure water at 30°C for 1,000 hours after lamination (secondary adhesive strength). Strength) was measured. The results are shown in Table 1.

H of aluminum alloy (JIS standard alloy A-5052)
34 tempered material, thickness 1.0 mm x height 25 mm x width 60 mm
A test piece having the size of was prepared, and after degreasing the surface with acetone, the surface treatment agents of Examples 1-10 and Comparative Examples 1-11 were applied by the method shown in Table 1.

If the coating method is the dipping method, soak for 1 minute at room temperature, or if the roll coater method is used, the coating amount is 120 cm.
/M at room temperature.

After applying the base treatment agent to the test piece in this way, if baking treatment is “Yes”, heat drying for 15 minutes in a hot air drying oven at 210℃, or if “No baking treatment” is required, leave it at room temperature. Then, if water washing treatment is “with”, after this drying, the test piece is washed with water and dried again, and then “without”
In this case, the sample was used as it was, and a test piece with a surface treatment was prepared.

The two test pieces prepared by surface treatment in this way were
So that the thickness of the overlap is 25 mm x 12.5 mm, use 250 g of room temperature curing epoxy resin adhesive (two-component type) (product name: Cemeda 4-n 1500, manufactured by Cemedine ■).
rd and tensile shear adhesive strength test (JI
-6850 according to the S standard).

(2) Tensile shear adhesive strength test of Test 11 and Comparative Example 12 Test pieces were prepared using rolled steel 5S41, and for the measurement of secondary adhesive strength, they were soaked in pure water at 30°C after bonding. Example 1 above, except that after immersion for 336 hours
The test was carried out in the same manner as the tensile shear adhesive strength test of Comparative Examples 1 to 10 and Comparative Examples 1 to 11.

(3) Tensile shear adhesive strength test of Example 12 and Comparative Example 13 Test specimens were prepared using galvanized steel plates, and for the measurement of secondary adhesive strength, they were soaked in pure water at 30°C after lamination. The above Examples 1 to 1 except that after immersion for 480 hours.
The test was conducted in the same manner as the tensile shear adhesive strength test of Comparative Examples 1 to 11.

〔Effect of the invention〕

The base treatment agent of the present invention has excellent water resistance in the base film formed on the metal surface using the base treatment agent. Unlike chromic acid, it does not require washing with water, and there is no need to worry about pollution problems like with conventional base treatment agents that use chromic acid, so there is no need for specialized equipment. , applicable to on-site construction. In addition, the formed base film itself has excellent corrosion resistance, so when forming a resin adhesive layer or a resin coating layer on the surface 1 of various metal products, it is possible to avoid close contact with the organic resin layer. Patent applicant: Nippon Light Metal Co., Ltd. Same as above Nikkei Giken Co., Ltd. Same as above Alcan International Limited

Claims (2)

[Claims] (1) Base treatment for forming an organic resin layer on a metal surface, characterized by 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. agent. (2) The base treatment 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.