JPS607946B2 - Manufacturing method of highly durable painted metal plate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a highly durable coated metal plate, in which the surface of the metal plate is subjected to chemical conversion treatment, a primary primer paint is applied and baked, and then a coated metal plate of 1 to 100 coats in length is applied. A secondary primer paint for vinylidene fluoride resin paint to which glass fibers have been added is applied and baked, and then a vinylidene fluoride resin paint to which coloring pigments are added is applied and phosphoroused. The present invention relates to a method for producing a durable coated metal plate.

Currently, painted metal plates that guarantee maintenance-free durability of 13K or higher include vinyl fluoride film laminated metal plates, acrylic film laminated metal plates, polyvinyl chloride sol coated acrylic film composite laminated metal plates, and vinyl chloride fluoride film laminated metal plates. There are vinyl composite laminated metal plates, etc., and these are summarized in the technical document ``Durable synthetic resin-coated steel plates 1'' in Wang No. 7 of the ``Tetsu to Hagane'' Group 1.

Among these, fluororesin-coated metal plates have excellent waist resistance, heat resistance,
This product is coated with vinylidene fluoride resin paint, which has particularly excellent wear resistance.

This product is made by chemically treating the metal plate with a zinc phosphate or chromic acid treatment agent, and then applying a polymer epoxy primer for 7 to 70 minutes.
Apply with a 10 ta' roll coater to a plate temperature of 200 to 21.
After cooling at 0°C, a vinylidene fluoride resin containing 59% fluorine is further blended with an acrylic resin-based high boiling point plasticizer, pigment, and low boiling point solvent that are compatible with the vinylidene fluoride resin. Organosol paint of 25-4
Apply with a roll coater at 50% and plate temperature 240-250.
It is produced by dawning at qo and uniformly cooling with water sprayed in a mist cooler at 200oo or less. In this case, the standard thickness of the coating film is about 25r. Vinylidene fluoride resin paint itself has excellent weather resistance and corrosion resistance, and in particular, its heat resistance is the best among synthetic resin paints.
However, since the coated metal plate obtained in this way has a low coating hardness, the coating is easily scratched during processing such as bending or during construction, and it is necessary to use a protective film. Furthermore, since the workability is poor, the corrosion resistance of the bent portion may be poor. Furthermore, if the primer is a single layer as described above, it is currently impossible to use a primer that has good adhesion to both the chemical conversion coating and the vinylidene fluoride paint (polymer epoxy primer Adhesion is good with vinylidene fluoride resin coatings, but adhesion over time with chemical conversion coatings is not so good), which causes problems such as peeling of the coating. Furthermore, as a 3-coat, 3-bake coated metal plate, the present applicant et al. previously reported in Utility Model Publication No. 53-33977 that ``After surface-treating a thin metal plate, applying a primer paint and then adding glass fiber. To provide a painted metal plate on which a paint is applied and then a clear silicone polyester resin paint or silicone acrylic resin paint without the addition of coloring pigments is applied and baked.

With this product, it is possible to improve the hardness of the coating film using glass fibers, and it is conceivable that this invention can be applied directly to vinylidene fluoride resin paints to improve the hardness of the coating. There are the following problems. In other words, one application is to chemically treat a metal plate, then apply a blimmer coating, and apply various exterior paints as the second layer, such as oil-free polyester, thermosetting acrylic, epoxy, solution vinyl, and silicone. A competition was held to paint a mixture of polyester and other paints with glass fiber.
It is conceivable to apply and bake a clear pinylidene fluoride resin paint as the third layer, but with this, the adhesion between the second and third layers is poor, and in some cases, delamination may occur between the layers. There is a risk that this may occur. In another application, a metal plate is chemically treated, then a primer is applied, and then a second layer of vinylidene fluoride resin paint mixed with glass fiber is applied, and then It is conceivable to apply and bake a clear vinylidene fluoride resin paint as the third layer, but in this case, the primer is used to separate the chemical conversion coating and the second layer of glass fiber-containing vinylidene fluoride resin paint. Adhesion is poor and workability is poor. The present invention (shown in Comparative Example 4 below) has been made in view of the above points, and is a highly durable coated metal plate that is difficult to form in the coating film during processing and has excellent coating film adhesion. The purpose is to provide a manufacturing method.

The present invention will be explained in detail below.

First, a chemical conversion treatment is applied to the surface of a metal plate such as a galvanized steel plate, an aluminum-zinc alloy plated steel plate, an aluminum plated steel plate, or an aluminum plate.

Chemical conversion treatment is performed by treating with a lead phosphate-based or chromic acid-based treatment agent to form a chemical conversion coating.
Next, a primary primer paint having good adhesion to the chemical conversion coating, such as an epoxy urethane-based primary primer paint, is applied onto the treated surface of the metal plate and smeared.

The coating amount is preferably about 3 to 10 ta' (according to the field type). Next, in the second layer, a secondary primer paint that has good adhesion to both the primary primer paint and the vinylidene fluoride resin paint,
For example, a secondary primer paint of polymeric epoxy type is applied and baked. The coating amount is preferably about 3 to 10 coats per coat (solid content). Glass fiber is added and mixed in the secondary primer paint. By adding glass fiber to the secondary primer paint, the hardness of the coating applied to the metal plate is improved, and the ease with which the paint film sticks to the eaves is improved. The length of the glass fiber to be added is 1 to 100
〃 is optimal. That is, if the number is less than 1, the effect of improving the hardness of the coating film will be insufficient, and if it exceeds 100, the coating workability will deteriorate and the workability will also deteriorate. Note that the amount of glass fiber added is 0.00% relative to the solid content of the primer paint.
3 to 30% by weight is desirable. 0. If it is less than 3% by weight, it may not be sufficiently effective in improving hardness, and if it exceeds 3% by weight, painting workability tends to deteriorate, and it is not very effective in improving hardness, which affects corrosion resistance etc. may occur.

After the secondary primer paint is applied and baked, a third layer of vinylidene fluoride resin paint is applied thereon and baked. The coating amount is preferably 15 to 45 coats per coat (solid content).
Coloring pigments are added and mixed into the vinylidene fluoride resin paint to give it color, and this second layer serves as a decorative layer. The painted metal plate according to the present invention obtained as described above can be coated with a highly durable vinylidene fluoride resin paint, and a primary primer paint that has good adhesion to the chemical conversion coating can be applied. It is possible to use a secondary primer paint that has good adhesion to both the primary primer paint and the vinylidene fluoride resin paint, and as a result, the adhesion of the paint film to the metal plate is improved. The glass fiber added to the secondary primer paint can improve the hardness of the paint film and prevent the paint film from becoming scratchy during processing.

Here, it is possible to add glass fiber to the third layer of vinylidene fluoride resin paint in order to improve the hardness of the coating film, but it is also possible to surface-treat the glass fiber with chromium treatment, aminosilane treatment, vinylsilane treatment, etc. However, glass fiber is not compatible with resin paint, so the surface of the paint film becomes porous due to the addition of glass fiber, the water permeability increases, corrosion resistance becomes a window**, and the hardness of the paint film surface increases. However, durability cannot be obtained. (Shown in Comparative Examples 2 and 3 to be described later) Next, the present invention will be explained with reference to Examples.

A galvanized steel plate was coated with various paints shown in Table 1.

The film thickness and pricing conditions are as shown in Table 1. (No.
1 Table) Song 8VS; Glass fiber product name Surface Strand 8VSo manufactured by Nippon Sheet Glass Co., Ltd. Table 2 shows the performance evaluation results of Examples and Comparative Examples.

(Table 2) (Note) Test method/condition surface pencil hardness.・．． Using Mitsubishi Pencil 1 unit, JIS
-K, 5400, 6, and 14K show the highest hardness that will not tear the paint film.

Adhesion. ．． ．． Fold the test board 900 times, sandwich a board with the same thickness as the test temporary, tighten it with a vise, peel off the sellotape, and display the number of scissor boards that will not peel off. The condition before the tape is judged as if the tape is not present. Wear resistance
Characteristics: Taper abrasion tester used, one side load 500mm,
, Evaluate the wear loss after 250 rotations using a 4-tone value. Salt water spray... using 5% salt water, JIS-K-540
Perform salt spray test from 0.7.8K.

(10 drip point evaluation) Chemical resistance: sulfuric acid, hydrochloric acid,
Sodium hydroxide and acetic acid reagents were divided into 5% and soaked in an aqueous solution at 20°C for 500 hours. (10 drip point evaluation) Coin hitting...Rub the desert with the corner of a 10 yen coin,
Evaluate desert scars. Rotational scratch: Stack the painted surfaces so that they are in contact with each other, apply a 10K load on top of them, punish the lower painted plate, and rotate the upper painted plate 900 degrees to scratch the painted surfaces. Assess the condition. Eriksen injured...
Using the 318 type hardness scale manufactured by Eric Seso, the test was evaluated based on the load that would cause scratches on the painted surface.

Regarding rotary scratches and coin hits, the ratings are: ◎Excellent, ○Good, △Slightly poor.

From the results in Table 2, the examples have good adhesion, eaves sticking resistance,
It is confirmed that both water resistance and chemical resistance are superior to those of the comparative example*. Next, Table 3 shows the relationship between the amount of glass fiber added and the performance of the Examples shown in Table 1.

(Table 3) From the results in Table 3, the amount of glass fiber added is 0.3 to .

Claims (1)

[Claims] 1 After chemically treating the surface of the metal plate, apply and bake a primary primer paint, then apply and bake a secondary primer paint made of vinylidene fluoride resin paint with glass fibers of 1 to 100 μ in length added thereto. A method for producing a highly durable coated metal plate, which is then coated with a vinylidene fluoride resin paint to which a coloring pigment has been added and baked.