JPS62225341A - Coated steel plate for bonding - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a coated steel plate that has excellent adhesive durability when an adhesive is used during assembly.

(Prior art) When painted steel sheets are used for welding or caulking during assembly, the paint film is destroyed at the welded or caulked parts, reducing the benefit of using painted steel sheets by half. Metal adhesives have come to be used during assembly.

By the way, in the above-mentioned adhesive bonding, it goes without saying that the adhesive strength of each layer or surface of the painted steel plate must be maintained. Specifically, the layers and surfaces in such a case are as follows.

■ Adhesive layer ■ Adhesive/paint interface ■ Paint layer ■ Paint film/plating interface ■ Plating layer ■ Coating/base material interface (problem to be solved by the invention) Therefore, the present inventors conducted research, According to the results of experiments, when adhesively bonded, among the layers and surfaces described above,
It has been found that problems are likely to occur at each of the interfaces listed in , ■, and ■.

We will discuss each of them below.

(A) Adhesive/paint interface Depending on the heating conditions after applying the adhesive and bonding, the repainted steel plate may not adhere sufficiently, and peeling may easily occur at the adhesive/paint interface. This tendency is particularly remarkable in polyester-based and acrylic-based paints.

In order to prevent this peeling, it is necessary to sufficiently set the above-mentioned heating conditions, but as a method to sufficiently set these heating conditions,
There are two methods: ■ lengthen the heating time, and ■ raise the heating temperature.

However, method (2) is not practical due to production and equipment constraints. In addition, the method (2) has the problem of deterioration of the resin in the paint, in addition to equipment limitations.

That is, all of these methods have problems and are not practical.

On the other hand, epoxy-based and urethane-based paints do not have the same problems as the polyester-based and acrylic-based paints and have excellent adhesion stability. It is not suitable for cases where weather resistance is required, and the objects for which it can be used are limited.

(B) Regarding the two-film/plating interface, when two coated steel plates are bonded together with an adhesive and then kept in a wet state, the T-peel strength decreases over time.

However, when observing this peeling situation, it was found that peeling occurred at the coating/plating interface at the edge of the adhesive sample.
Cohesive failure of the adhesive occurred in the center. Then, the width of the interfacial peeling at the end portion became wider with the passage of time.

(C) Regarding the plating/base material interface In CB) above, peeling at the coating film/plating interface was explained, but if the holding time in a humid atmosphere becomes longer, peeling may occur at the plating/base material interface. In such a case, the T-peel strength will be very small.

For example, when an electrogalvanized steel sheet is used as the base material, peeling at the plating/base material interface as described above is unlikely to occur. Plated basis weight FF160 g
Corrosion resistance is inferior to that of lrd or higher.

Therefore, when a zinc-based hot-dip plated steel sheet with excellent corrosion resistance is used as a base material, it is necessary to suppress peeling at the plating/base material interface.

The present invention aims to provide a coated steel plate that satisfies the above three points (A) to (C), that is, has excellent adhesive durability.

(Means for Solving the Problems) The present invention provides plating that is formed by performing at least one of a zinc phosphate treatment with a coating weight of 1.5 g/% or less or a chromate treatment with a chromium adhesion amount of 20 to 150 cm/a as a base treatment. middle p
Apply epoxy paint, urethane paint, or epoxy resin to the adhesive-applied surface of a galvanized steel sheet or zinc-aluminum plated steel sheet with a b content of 0.05% by weight or less, based on the resin in the paint. This is a coated steel plate for adhesion, which is coated with either a polyester paint or an acrylic paint containing ~20% by weight.

In the present invention, the above-described materials are used for the base material, surface treatment, and paint in order to solve the problems at each interface described above, and the reason for this will be explained below.

(A) Adhesive/paint interface If the paint film is not required to have bendability or weather resistance, an epoxy or urethane paint is used.

If bending properties, weather resistance, etc. are required, 5 to 2
Use a paint containing 0ft1% epoxy resin.

In this case, if the amount of epoxy resin added is less than 5% by weight, the stability of adhesion is insufficient as shown in Table 1 below, and if it exceeds 20% by weight, it is also shown in Table 1 below. Since the rigidity of epoxy appears and impairs the workability of the coating film, the amount of epoxy resin added is set at 5 to 20%.

The type of epoxy resin is not particularly limited as long as it is compatible with the paint. However, when weather resistance is required for the coating film, aliphatic epoxy resins such as diglycidyl cyclohexanedicarboxylate epoxy resins are used rather than aromatic epoxy resins such as bisphenol A epoxy resins. It is preferable.

(B) About the coating film/plating interface Chromate treatment is performed as a base treatment for painting.

In this case, the amount of chromium deposited must be in the range of 20 to 150 .mu./d. That is, 20n+g/r
This is because if it is less than RF, the resistance against invading water is weak, and therefore the plating will corrode and the adhesive strength will decrease. On the other hand, if it exceeds 150 .mu./d, the bendability of the coated steel sheet deteriorates and the T-peel strength decreases, as shown in Table 2 below.

Note that similar results can be obtained even if the zinc phosphate treatment or the above-mentioned chromate treatment is performed after the zinc phosphate treatment. The present inventors have confirmed through experiments that the zinc phosphate treatment in this case needs to be 1.5 g/rrr or less.

Table 2 Effect of chromate deposition amount (C) Plating/base material interface 5% to 8-Zn-Mitshu metal plated steel Galfan (trade name), 55% Al-Zn plated steel plate Galvalume (trade name) (trade name), the plating will not peel off in a humid atmosphere.

Further, in the case of a general hot-dip galvanized steel sheet, peeling of the plating can be prevented by controlling the PB content in the plating to 0.05 or less. This is clear from Table 3 below.

Table 3: Plating audibility and adhesive strength change in a humid atmosphere (effects) The coated steel sheet for adhesion according to the present invention is treated with zinc phosphate of 1.5 g/d or less or has a chromium deposit of 20 to 150 μ/d.
Epoxy paint, Since it is constructed by applying either a urethane paint or a polyester paint or an acrylic paint containing 5 to 20% by weight of epoxy resin based on the resin in the paint, the plating/base material interface, Peeling at the paint film/plating interface and adhesive/paint film interface can be prevented.

(Example) After cleaning the surface by polishing 14 zinc-based hot-dip plated plates with a thickness of 0.5 mm using Scotch Brite (manufactured by Sumitomo 3M, trade name), Bonderite 1415A (manufactured by Nippon Barker Rising, trade name) was polished. ) was applied and dried. Thereafter, each of the paints shown below was coated to a dry film thickness of 10 μm, and the steel plate was baked to a temperature of 210 to 220°C. The adjustment of each paint is as shown below.

1) Epoxy paint Bakerit manufactured by Union Carbide Co.
e Phenoxy resin PK[l was used. PKH) was dissolved in 80 parts of a mixed solvent of cellosolve acetate/xylene=67/33 (weight ratio). Then, 16 parts of a titanium oxide pigment (Tiebake R-820 manufactured by Ishiya Sangyo Co., Ltd.) was added to 100 parts of this resin solution, and the pigment was dispersed using glass beads.

2) Urethane paint Desmodur L, Desmo manufactured by Bayer AG
phen 2001 was used. Desmophen 2
001 was dissolved in 150 parts of methyl ethyl ketone, 100 parts of the titanium oxide described above was added, and the pigment was dispersed using glass beads.

Immediately before painting, add 350 parts of this resin solution to Desm.
25 parts of odur L was added, stirred, and used.

3) Polyester paint Byron 103 manufactured by Toyobo was used. Byron 10302
For 0 parts, cellosolve acetate/xylene-67/33 (
The mixture was dissolved using 80 parts of a mixed solvent (weight ratio). and,
Four parts of methylolated melamine (Superbefkamine J 820, manufactured by Dainippon Ink Chemical) was added as a crosslinking agent. Further, 16 parts of the titanium oxide pigment described above was added to the resin solution and dispersed using glass beads.

The epoxy resin to be added was Epicoat 1004 manufactured by Yuka Shell Epoxy, and this was added when the polyester resin was dissolved.

In addition, when applying the polyester paint, the aforementioned phenoxy resin-based epoxy paint was used as a primer. Then, after applying epoxy paint to a dry thickness of 5 μm and baking, polyester paint was applied.

4) Acrylic paint Acryloi manufactured by Rohn and Haas Co.
d AT-56 was used. Acryloid AT
-5620 parts and 3 parts of Super Beckamine J820 were dissolved in 80 parts of cellosolve acetate. 16 parts of the titanium oxide pigment described above was added to the resin solution and dispersed using glass beads.

The epoxy resin to be added was Epicoat 1004 manufactured by Yuka Shell Epoxy, and this was added when the acrylic resin was dissolved.

Note that, as in the case of polyester paint, epoxy paint was used as a primer.

The coated steel plate described above was cut into pieces of 200 tl x 25 mm and then glued together using a urethane adhesive Hardofuku made by Denki Kagaku (I). At this time, apply adhesive to the coating surface to a thickness of 100 μm.
Two steel plates were bonded together and kept in a dryer at 150°C for 5 minutes.

Note that the adhesive that protruded from the test piece was removed using a cutter knife.

Then, the bonded test piece was placed at a temperature of 60°C and a relative humidity of 90%.
The adhesive strength was measured over time.

The results are shown in Table 1 above. Note that the adhesive strength was measured by a T-peel test based on JIS K-6854. Moreover, the peel strength was averaged over 5 repetitions. The bendability was evaluated by bending 180 parts of the coated plate and determining the number of plates that could be bent without causing any cracks in the coating film.

(Effects of the Invention) As explained above, the coated steel plate for adhesive according to the present invention has 1
．． Pb content 0 in plating formed by base treatment of at least one of zinc phosphate treatment with a chromium deposition amount of 5 g/nf or less or chromate treatment with a chromium deposition amount of 20 to 150 μ/d.
．． Apply epoxy paint, urethane paint, or epoxy resin at a concentration of 5 to 20% by weight based on the resin in the paint on the surface of the zinc-plated steel sheet or zinc-aluminum plated steel sheet where the adhesive is applied. Since the composition is coated with either polyester paint or acrylic paint, it is possible to prevent peeling at the plating/base material interface, paint film/plating interface, and adhesive/paint film interface, and the adhesive is durable. A coated steel plate for adhesion with excellent adhesive properties can be obtained.

Claims (1)

[Claims] (1) Pb content of 0.05 in plating formed by base treatment of at least one of zinc phosphate treatment with a 1.5 g/m^2 or less or chromate treatment with a chromium adhesion amount of 20 to 150 mg/m^2 Apply 5 to 20% by weight of epoxy paint, urethane paint, or epoxy resin to the surface of the zinc-plated steel sheet or zinc-aluminum-plated steel sheet to which the adhesive is applied, based on the resin in the paint.
A coated steel plate for adhesive use, characterized in that it is coated with either a polyester paint or an acrylic paint containing.