JPS5830372A - Production of aluminum plated steel plate coated with blister resistant paint - Google Patents

Abstract

PURPOSE:To improve blister resistance by treating a defatted aluminum plated steel plate with aq. amino silane, and drying the same by heating then coating and baking the paint. CONSTITUTION:An aluminum plated steel plate is defatted by alkali washing. An aq. soln. of aq. amino silane controlled to 8-10pH is coated thereon and is dried at 90-150 deg.C. Paint is coated on the treated aluminum plated steel plate and is baked. The concn. of the aq. amino silane is controlled to 0.1-10wt% and the treating time to 10-20sec. Epoxy, epoxy-polyester, epoxy-acrylic are used for the paint.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a manufacturing method for improving the blister resistance of a baking-painted steel plate using an aluminized steel plate as a base metal plate.

In general, in painted steel sheets that use galvanized steel sheets or aluminized steel sheets as base metals, zinc and aluminum exhibit a base potential compared to the underlying iron, so zinc and aluminum are selectively eluted due to the so-called sacrificial corrosion protection effect. Protects the steel substrate. In the case of coated steel sheets that are coated with zinc or aluminum as the base metal and coated on top of that, hydrogen gas generated as zinc or aluminum elutes and water vapor that permeates through the entire coating film from the outside world. This creates internal pressure between the paint film and the underlying metal surface, pushing the paint film upwards and causing so-called blisters.

Naturally, such blisters create a space between the paint film and the underlying metal surface, and moisture or various ions enter this space, accelerating corrosion. Similarly, when water enters from the defective parts of the coating film or from the end faces, it causes cracks from the surrounding areas and accelerates corrosion.

This tendency is greater for zinc, and aluminum is supposed to have better blister resistance, but impurities such as silicon segregate in the surface layer of painted steel sheets that use regular aluminized steel sheets as the base metal. For this reason, or due to plating defects on the plating surface, an optimal treatment method has not yet been proposed, and as a result, the adhesion of the coating film is not sufficient, and furthermore, the blister property is not good.

As pre-painting treatments for aluminized steel sheets, methods such as anodic oxidation, chromate treatment, and phosphoric acid film treatment have been proposed. However, chromate treatment has pollution problems such as chromium wastewater treatment, and phosphoric acid film treatment has problems with sludge treatment.

Therefore, the present inventors performed a pre-painting treatment on fully aluminum-plated steel sheets with aminosilane, which is water-based and has excellent long-term stability, to improve the adhesion between the aluminum-plated steel sheets and the paint and the water resistance of the chemical conversion coating. The inventors have discovered a method that works as a curing agent for paint at the interface and is also suitable from the viewpoint of pollution prevention.

The present invention proposes an improvement in the blister resistance of a painted steel plate whose base metal is an aluminized steel plate and which is sent after being painted and baked.

That is, the present invention requires (1) that the base metal is limited to an aluminized steel plate, (2) that it is treated with water-based aminosilane, and (3)
Adjust the pH of the aminosilane aqueous solution to a slightly alkaline range of 8 to 10 before use. (4) Form a silane film by heating before painting. (5) Paint a thermosetting paint on the top surface.・This relates to a method for manufacturing painted aluminized steel sheets with excellent blister resistance, which has the following main constituent requirements: ・No burn-out.

Next, these requirements will be explained in detail.

First, the aluminized steel plate used in the present invention is hot-dip plated,
It may be manufactured by vapor deposition plating or any other method. The paint used is mainly a thermosetting paint such as an epoxy/curing agent type paint from the viewpoint of adhesion to metals, corrosion resistance, etc.

In the present invention, the coating system is a 7-run coupling based on a modified epoxy or polyester system such as bisphenol A type epoxy, epoxy-polyester, epoxy-acrylic, or epoxy-urethane, or a combination system of a modified polyester system and a curing agent. It is preferable from the viewpoint of reactivity with the agent.

The mechanism of action of the silane coupling agent is well known, but when the silane coupling agent is expressed as 2 m soil x 6, it is hydrolyzed by moisture on the surface of an inorganic substance and becomes R8iXg +3H2
0-+ R81 (OHJ3-1-3HX) is adsorbed onto the surface of the p-inorganic substance and forms a complete film of siloxane bonds, resulting in a dense water-resistant film.

Furthermore, the organic functional group R reacts with the polymer of the paint and contributes to improving adhesion.

On the other hand, if a non-polluting water-based treatment can be used as a pre-painting treatment, there will be no need for pollution treatment or explosion-proof equipment. However, in the past, aqueous treatment of silane camping agents was not very effective;
It is significant that we used this method to explore its favorable conditions. That is, instead of the conventional method of adding a non-aqueous vehicle and a 7-run coupling agent to a pigment as an anchor material,
The present invention is characterized in that a film-like material formed using aqueous aminosilane is interposed between the coating film and the base metal, and the two technologies are fundamentally different.

Therefore, as an aminosilane, aminopropyl-
Trihydroxysilane is suitable.

NH2-CH2-0M2+ CH25i(OH).

This substance exists stably in an aqueous solution due to aqueous bonding, can be stably mixed with water at any ratio, and there is no need to treat it as a hazardous substance during storage, and it can be stored optionally diluted with water. In the case of fc paints, as mentioned above, the amino group containing all active hydrogen acts as a curing agent for the paint, so that strong adhesion can be obtained between the paint film and the underlying metal.

The concentration of water-soluble aminoprobyl trihydride-based oxysilane, which is a type of water-based aminosilane used in the present invention, is related to the amount of film after coating and drying on an aluminized steel plate. Since the crosslinked product itself may be destroyed or the effect may become saturated, the concentration of the treated aqueous solution should be within the range of 0.1 to 10% by weight, and the processing time should be 10% by weight.
It is necessary to control within the range of ~20 seconds.

Further, the pH of the treatment liquid needs to be in the range of 8 to 10 in order to lightly alkaline wash the steel plate surface.

As mentioned above, the hydroxyl group of aminosilane is adsorbed on the surface of the aluminized steel plate, and when heated, it forms a water-resistant film of dense siloxane bonds. After applying the aminosilane aqueous solution, it is necessary to dry it at 90 to 150°C for reasons such as the formation of wrinkles.

The present invention is a method for manufacturing painted metal sheets using aluminized steel sheets as a base material, which has a simple processing process and does not require pollution treatment, and has improved blister resistance compared to conventional chromate treatment, and as a result has improved corrosion resistance. We can expect an improvement in
It is considered to have high industrial value.

EXAMPLES Next, the present invention will be specifically explained with reference to examples, but the present invention is not limited to the following examples unless the gist of the invention is exceeded.

Example 1 Aluminized steel sheets with aluminum plating thickness of 8, 20, and 30 μm on one side, respectively, were degreased with alkali and treated with 1% by weight of aminopropyltrihydroxysilane (pH 8.5).
5 weight-1iL% (pH 9,1), 10i amount% (
The samples were immersed for 10 seconds in aqueous solutions of pH 10 and 0, respectively, and then squeezed with a roller. This treated plate was heat treated at 100° C. for 60 seconds.

Next, the above-treated aluminized steel plate was coated with 5μ of epoxy paint as a brimer and 15μ of polyester paint.
A complete C-steel cladding was prepared and tests were conducted on paint film adhesion, corrosion resistance, moisture resistance, etc.

In Table 1, Exp1-6, 10-12, and 19-21 are respectively from Example 1, and F+xp9, 18, and 27 are conventional chromate-treated materials, respectively.

As can be seen from Table 1, the present invention is superior in terms of the degree of blistering in the salt spray test and the wet test, that is, the degree of blistering progression from the end face and cross-cut portion. In addition, when the treatment concentration was 1 to 10% by weight, all were better than the comparative examples,
There is no difference within the scope of the invention.

Note that an improvement was also observed in heat adhesion.

Example 2 An aluminized steel plate that had been alkali-degreased in the same manner as in Example 1 was immersed in a 1-weight water attack solution of aminopropyltrihydroxysilane for 10 seconds, squeezed with a roller, and then various heating conditions were examined.

10 seconds and 60 seconds at 100°C; 10 seconds at 150°C.

Heat treatment was performed for 60 seconds and 60 seconds, respectively.

Exp 4 to 8, 16 to 17, and 22 to 26 are Example 2 of the present invention, and Exp 9, 18, and 27 are comparative examples.

As in Example 1, the blister resistance is superior to that of conventional materials, but within the scope of the present invention, it can be seen that the more heat treatment is sufficient, the more a dense layer is formed, and the blister resistance is improved. .

Claims (1)

[Claims] 1. A method for producing a rigid blister coated aluminized steel sheet, which comprises treating a degreased aluminized steel sheet with aqueous aminosilane adjusted to a pH of 8 to 10, heating and drying it, and then applying a baking coating. . 2. The method for producing a blister-resistant painted aluminized steel sheet according to claim 1, wherein the aqueous aminosilane is aminopropyltrihydroxysilane, and the treatment concentration is 0.1 to 10% by weight aqueous solution. 6. The method for producing a blister-resistant painted aluminized steel sheet according to claim 1 or 2, wherein the heating and drying conditions are 90 to 150°C and 10 to 60 seconds.