JPH0436475A - Production of surface treated steel sheet for adhesion base - Google Patents

Abstract

PURPOSE:To improve adhesion property of a steel sheet with resin, metal sheet, etc., by specifying the composition and drying conditions of chromate film applied on the steel sheet and then forming an org. resin film on the chromate film. CONSTITUTION:A chromate liquid containing silica by the weight ratio of SiO2/(Cr<3+>+Cr<6+>)>=0.5 is applied on a zinc or zinc-alloy plated steel sheet. Then, this sheet is dried at 150-300 deg.C sheet temp. to form a chromate film of 0.5-120mg/m<2> density in terms of Cr Then a water-soluble or water-dispersed, water-based or org. solvent-based org. polymer compd. is applied to form an org. resin film of 0.2-2.0g/m<2> dry weight. Thereby, the obtd. surface-treated steel sheet has good adhesion property as a base body for adhering a sheet material.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a surface-treated steel sheet that can be used as an adhesion base to obtain good layering properties when bonding a steel sheet to a sheet-like material such as resin or metal. Regarding the manufacturing method.

<Prior Art> In general, steel plates (laminated steel plates), which are made by pasting sheet-like resin onto steel plates with adhesive, are often used for automobiles, home appliances, and building materials. In recent years, these steel sheets are required to have high corrosion resistance, so zinc-based surface-treated steel sheets are used instead of cold-rolled steel sheets.

On the other hand, examples of bonding sheet-like materials such as metal to steel plates include vibration-damping steel plates and steel plates for printed circuit boards.
The situation is similar to that of laminated steel sheets, and galvanized steel sheets are often used.

When using a zinc-based surface-treated steel sheet as a base for adhesion, a steel sheet (bonde steel sheet) that has been subjected to phosphate treatment as a pretreatment for the base for painting (for example, Japanese Patent Publication No. 58-57511)
Alternatively, a steel plate subjected to chromate treatment (chromate steel plate) (for example, JP-A-5O-14550) is used.

However, these steel plates do not necessarily have sufficient performance. That is, bonded steel sheets have phosphate crystals formed on their surfaces, but these have poor toughness and are susceptible to deformation, resulting in peeling during bending.

Since the amount of chromate film deposited is small, adhesion during bending is good, unlike bonded steel sheets. However, 1
At high temperatures of 00° C. or higher or under high temperature and high humidity conditions, the adhesion deteriorates significantly.

<Problems to be Solved by the Invention> The present invention provides a method for manufacturing a surface-treated steel sheet for adhesive base having a chromate film that does not deteriorate in adhesion even at high temperatures of 100° C. or higher or under high temperature and humidity, which solves the above-mentioned problems. The purpose is to

Means for Solving the Problems> That is, the present invention provides a method for applying silica to a zinc or zinc-based alloy coated steel sheet at a weight ratio of 5i02/(Cr''+Cr'1).
．． Apply a chromate solution containing 5 or more and reach a plate temperature of 150℃
Dry in a temperature range of 300°C or higher to produce 0% Cr equivalent.
．． Forming a chromate film of 5 to 120 mg/m2,
Surface-treated steel sheet for adhesive base, characterized in that a water-soluble or water-dispersible water-based or organic solvent-based organic polymer compound is deposited thereon as an organic resin film of 0.2 to 2.0 g/m2 in dry weight. The present invention provides a method for manufacturing.

The present invention will be explained in more detail below.

The reason why conventional surface-treated steel sheets have poor adhesion is that the H2O in the chromate film dehydrates during heat bonding, generating gas and at the same time corrosion of the base plating occurs, and the adhesive strength between the adhesive and chromate is low. Therefore, the present invention was developed as a result of intensive studies focusing on the type of chromate and resin treatment. The reasons for this limitation will be described in detail below.

Any zinc or zinc-based alloy coated steel sheet can be used in the present invention, and Zn-Ni, Zn-Fe% Z
n-Al1. Representative examples include electroplating, hot-dip plating, and vapor deposition plating of zinc alloys such as Zn-Co and Zn-Cr. Although the basis weight is not particularly limited, it may be set to 5 to 100 g/m'.

In particular, electrogalvanized steel sheets, which are easily available and have excellent surface smoothness, are preferably used. Furthermore, since adhesion deteriorates due to oxidation of the plating surface, it is more preferable to make the plating surface difficult to oxidize. In order to suppress such oxidation of the electrogalvanized surface, it is effective to control the total amount of Ni'' and/or Co'' in the galvanized layer to 0.05 g/j2 or more. Electrogalvanizing produced using this plating bath has more stable adhesion.

Chromate can be applied to such zinc or zinc-based alloy coated steel sheets by the usual method, or by using a roll coater.
After application by spraying or squeezing with a gravure roll or air ringer, a certain amount of chromium hydrated oxide (chromate) is formed on the zinc or zinc-based alloy plating.

Silica in chromate solution is 5i02'/ (Cr”+C
r'°) The reason for limiting the weight ratio to 0.5 or more is 0.5
This is because if it is less than that, the secondary adhesion after the wet test will be poor. Regarding the upper limit, there is no problem from the viewpoint of adhesion. However, in order to keep the chromate solution stable,
It is desirable that the in2/(Cr"+Cr") weight ratio is 3 or less.

The amount of chromate film attached is 0.0 in terms of Cr. 5-120
The reason for limiting it to mg/rn2 is 0.5mg/m
If it is less than 2, the secondary adhesion after the wet test is poor;
This is because if it exceeds 0 mg/m'', the amount of Cr'' contained in the film will increase, causing deterioration of the resin when adhering and applying organic resin.

Since the amount of heat required for drying the chromate film can be reduced, CS”/(Cr”+(:r”) in the chromate solution
) The higher the ratio, the more desirable.

However, from the viewpoint of liquid stability, the upper limit is about 0.5.

Reduction to Cr'' can be achieved by adding an organic substance (e.g. ethylene glycol) or by adding an inorganic substance (e.g. H2O).
2 etc.).

The drying plate temperature of chromate should be in the range of 150 to 300°C. If the drying plate temperature is less than 150°C, H2O or cr(O) of Cr(OH)sH20 remaining in the chromate film
H) H, O, etc. from the dehydration reaction of s corrode the mesh layer during resin adhesion/coating, or generate bubbles, causing poor adhesion. This is because when the temperature exceeds 300° C., alloying of the plating begins, which makes the plating brittle and the adhesion deteriorates.

The water-soluble or water-dispersible water-based or solvent-based organic polymer compound to be applied on the chromate film is made of resin such as alkyd resin, amino alkyd resin, acrylic resin, epoxy ester resin, or urethane resin. This refers to an organic polymer compound in which a sol of silica, titania, alumina, etc. is added and dispersed for the purpose of improving corrosion resistance.

The presence of the organic polymer compound (resin) film improves corrosion resistance and adhesion.

However, the effect of the organic resin film appears at 0.2 g/m2 or more, and if it is less than 0.2 g/m', the improvement in corrosion resistance is not sufficient and is equivalent to that of chromate, and the effect of the organic resin film does not appear.

When the amount of resin attached is limited to 0.2 to 2.0 g/m', the corrosion resistance after adhesion is poor if the amount of resin is less than 0.2 g/m2. Moreover, if it exceeds 2.0 g/m', it becomes difficult to vent gas during bonding. Note that the method for applying these may be any commonly used method.

<Example> The present invention will be specifically described below based on Examples.

(Example 1) A 0.7 mm thick cold rolled steel sheet equivalent to SPCC was plated with various zinc or zinc-based alloys as shown in Table 1. In the table, EG represents electrogalvanizing, GI represents hot-dip Zn plating, and GA represents alloyed hot-dip Zn plating.

A chromate solution under the conditions shown in Table 's1 was applied onto these zinc or zinc-based alloy platings using a roll coater and dried. Thereafter, a water-dispersible acrylic resin was applied using a roll coater and dried.

A polyester adhesive was applied to the chromate steel sheet and organic coated steel sheet obtained as described above, and the sheet temperature was raised to 200°C.
The temperature was continued to rise, and a vinyl chloride sheet (200 μm) was crimped.

As a primary adhesion test, after 18% tensile deformation, a 2 mm square scratch was made on the substrate, tape was peeled off, and the following 4-stage evaluation was performed based on the peeled state of the coating film.

◎ No peeling at all ○ Peeling small △gU11 large A test was conducted and the same 4-level evaluation as above was performed.

The results are shown in Table 1.

(Example 2) A 0.7 mm thick cold rolled steel sheet equivalent to 5 pcc was plated at 20 g/m 2 using the following galvanizing bath and conditions.

Zn" 60g/m2 Ni"+Co" sulfate, current density 80-150A/dm2, pH 2, sulfuric acid bath. After that, a chromate solution under the conditions shown in Table 2 was applied and dried by roll squeezing with a Clavia roll. A solvent-based epoxy resin was applied using a roll coater and dried.

An epoxy resin sheet (100 μm) was applied to the chromate steel sheet and organic coated steel sheet obtained as described above.
Heat bonding was performed at 0°C for 20 minutes.

As an adhesion test, 24 hours at 134℃ and 3 atmospheres of vapor pressure were used.
r Within 30 minutes after standing, the same base test as in Example 1 was conducted and the same 4-level evaluation was performed (high pressure test).
.

In addition, after 120 hours of the wet (60° C., 90% or higher humidity) test, the board was immersed in a 260° C. solder bath for 1 minute and within 30 minutes, the board test was conducted and evaluated on a 4-grade scale (solder test). The results are shown in Table 2.

<Effects of the Invention> According to the method of the present invention, the composition and drying conditions of the applied chromate film on zinc or zinc-based alloy plating are appropriately selected to form an organic resin film, thereby solving the conventional problem of peeling. A surface-treated steel sheet for adhesion base with good adhesion that does not cause such problems can be obtained.

Claims (1)

[Claims] (1) Adding silica to zinc or zinc-based alloy coated steel sheet
O_2/(Cr^3^+Cr^6^+) weight ratio is 0.5
Apply a chromate solution containing the above and dry it at a temperature of 150°C to 300°C to obtain a Cr equivalent of 0.5
A chromate film of ~120 mg/m^2 is formed, and a water-soluble or water-dispersible water-based or organic solvent-based organic polymer compound is applied as an organic resin film on top of the chromate film, and the dry weight is 0.
．． A method for producing a surface-treated steel sheet for use as an adhesive base, characterized by adhesion of 2 to 2.0 g/m^2.