JP2000318087A - Precoated steel panel excellent in processing adhesion - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the coating properties of a point for a base material without chemically modifying a resin and to enhance the adhesion of the base material and a coating layer to enhance processing adhesion. SOLUTION: A precoated steel panel excellent in processing adhesion is constituted by providing a lower org. coating layer I and an upper org. coating layer II on at least the single surface of a steel panel and characterized by that the org. coating layer I contains 2-50 wt.% of a polytetrafluoroethylene resin. It is pref. that the org. coating film I further contains 20 wt.% or more of a polyether sulfone resin and the steel panel has one of or both of a chemical forming treatment layer and a plating layer containing 80 wt.% or more of zinc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precoated steel sheet having excellent processing adhesion and used for home appliances, building materials, automobiles and the like.

[0002]

2. Description of the Related Art Generally, thin steel sheet products are used after being painted. The purpose of this coating is to protect the base steel plate and at the same time to increase its durability and beautify it. Painted steel plates are used for everything from large structures such as buildings, ships, bridges, etc. to various machines, automobiles, furniture, small appliances and household goods, but painting of these steel plates is generally called post-coating. Performed after processing and assembly.
However, in the field of building materials and home appliances, there is a shift to a method of processing and assembling a so-called pre-coated steel sheet which has been painted in advance. In this precoated steel sheet, a polymerized resin having processability is used for the coating layer so that the coating film does not peel off during processing.

[0003] However, when a polymerized resin is applied in multiple layers and subjected to complicated processing, the coating film may be missing and sufficient film performance may not be obtained. In this case, in particular, the adhesion between the base material and the lower organic coating is required, but a method of adding a modifying group for improving the adhesion to the resin structure is generally used. However, there are disadvantages such as the cost of resin synthesis and the reduction in oxidative durability of the resin due to the addition of a chemically reactive group.

[0004]

SUMMARY OF THE INVENTION Accordingly, the present invention has been made to improve the wettability of a coating material on a substrate and to improve the adhesion between a substrate and a coating layer without performing chemical modification on a resin. The purpose is to provide a precoated steel sheet with improved adhesion.

[0005]

The gist of the present invention is as follows. "(1) At least one surface of a steel sheet has a lower organic coating layer I
And an upper organic coating layer II, wherein the organic coating layer I contains a polytetrafluoroethylene resin: 2 to 50% by weight.

(2) The precoated steel sheet having excellent work adhesion according to the above (1), wherein the organic coating layer I further contains 20% by weight or more of a polyether sulfone resin. (3) The precoated steel sheet having excellent working adhesion according to (1) or (2), wherein the steel sheet has a chemical conversion treatment layer as a further lower layer of the organic coating layer I.

(4) The above-mentioned (1) to (1), wherein the steel sheet has a plating layer containing 80% by weight or more of zinc.
The precoated steel sheet having excellent work adhesion according to any one of (3). ".

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The precoated steel sheet of the present invention comprises a steel sheet as a base material, a lower organic coating layer I, and an upper organic coating layer II.
A polytetrafluoroethylene resin (hereinafter referred to as PTFE) in the organic coating layer I in an amount of 2 to 50% by weight.
contains. As the base steel sheet, cold-rolled steel sheet, hot-rolled steel sheet, galvanized steel sheet, galvannealed steel sheet, zinc-iron alloy coated steel sheet, zinc-aluminum alloy coated steel sheet, aluminum-plated steel sheet, chrome-plated steel sheet, nickel-plated steel sheet,
Examples include a zinc-nickel alloy-plated steel sheet, a tin-plated steel sheet, a stainless steel sheet, an aluminum-plated stainless steel sheet, a lead-plated stainless steel sheet, and a zinc-plated stainless steel sheet.

The inventors of the present invention have confirmed that, in these inner-plated steel sheets, those having a plating composition containing 80% by weight or more of zinc have a high effect of improving the adhesion of the processed portion, and are most preferable as the base material. In order to secure the adhesion of the coating film, as a pretreatment for a further lower layer of the organic coating layer I,
It is preferable to perform a chemical conversion treatment on the plating or the steel sheet. As an example of this pretreatment, water washing, hot water washing, pickling, alkali degreasing, grinding and polishing are performed alone or in combination as required, chromate treatment, zinc phosphate treatment, water-soluble acrylic resin coating, water-soluble epoxy It is advisable to perform a chemical conversion treatment using a resin coating, a urethane resin coating, a hybrid coating treatment of each resin, a composite oxide film treatment alone or in combination. The conditions of each process to be selected are not particularly limited.

Next, as the organic coating layer I applied to at least one side of the steel sheet, a polyether sulfone resin (hereinafter referred to as PES), an epoxy resin, a polyester resin, a polyacryl resin, a polyurethane resin, a polynylon resin, a polyimide resin Resin, polystyrene resin, PVdF
There is no particular limitation on paints that can be used for pre-coated steel sheets, such as fluorine-based resins, but within the range examined by the inventors, resins containing 20% by weight or more of PES have few restrictions such as manufacturing conditions and contain PTFE. This is the most preferable resin for the formation. Organic coating layer I is made of PES and PTFE
The PES may be 50 to 98% by weight, which is the remaining amount of PTFE.

It is essential that PTFE be contained in the organic coating layer I in an amount of 2 to 50% by weight. 2% by weight of PTFE
If it is less than 30, adhesion based on the wettability between the substrate and the organic coating layer I cannot be secured. If the PTFE content is more than 50% by weight, the extensibility and elasticity of the coating layer will deteriorate, and the processing adhesion will rather decrease. The thickness of the organic coating layer I is not specifically defined, but is preferably 30 μm or less from the viewpoints of workability and coating workability. Thickness 3
If the thickness is larger than 0 μm, the coating film may be broken, which may cause peeling.

Although the composition, particle size, shape and distribution of PTFE are not particularly defined, generally, a fluorinated additive having a 1: 1 mixture of PTFE and WAX having an average particle size of about 1 to 5 microns is used. I do. Further, the organic coating layer II applied on the coating layer is not particularly limited as long as it is a paint that can be used for a precoated steel sheet, such as PES, a polyester resin, a polyacryl resin, a polyurethane resin, and a fluororesin such as PVdF.

Although the thickness of the organic coating layer II is not particularly specified, it is desirable that the dry film thickness be 50 μm or less from the viewpoint of securing workability and workability of coating. Film thickness is 50
If the thickness is larger than μm, the coating film may be broken and peeling may be induced. The organic coating layer I and the organic coating layer
Regarding any of II, there is no restriction on the use of additive components generally used in precoated steel sheets. Examples include color pigments and extender pigments, rust-preventive pigments and dyes,
Examples include leveling components and design components such as metallic, mica, and aggregates.

The above-mentioned precoated steel sheet of the present invention is processed into, for example, a roof wall panel, an outdoor advertising panel, a lighting reflection panel, a tunnel interior panel, an automobile exterior panel, a partition panel, an elevator interior panel, and the like. By applying to the accompanying parts, it becomes possible to obtain a thin steel plate product having better working adhesion than before.

[0015]

EXAMPLES Examples of the precoated steel sheet of the present invention will be described. A coating material containing a predetermined amount of PTFE was applied to the base material shown in Table 1 which had been subjected to alkali immersion degreasing and chromate treatment using a bar coater, and then baked by a high frequency induction heating method to form an organic coating layer I. An organic coating layer II was baked thereon in the same manner as above to obtain a test material.

The obtained precoated steel sheet was evaluated for processing adhesion under the following conditions. The processing adhesion test was performed under a 20 ° C atmosphere based on JIS G3312.
A T-bend test was performed, and the evaluation was made based on the degree of peeling of the coating film that occurred when the tape was peeled from the processed part. Table 1 shows the results. The evaluation of peeling was a 7-point scale of 7 points (no peeling), 5 points (peeling area was within 10%), 3 points (peeling area was within 30%), and 1 point (full peeling). The above was judged to be good.

As is clear from Table 1, the precoated steel sheet according to the present invention has excellent workability.

[0018]

[Table 1]

[0019]

According to the present invention, the lower resin coating layer I contains 2 to 50% by weight of a polytetrafluoroethylene resin, so that it can be used for roof walls, outdoor advertising, lighting reflection, tunnel interiors, automobile exteriors. A precoated steel sheet having extremely excellent work adhesion can be provided without using a special manufacturing method as a panel material for use in a building, a partition, an interior of an elevator, or the like. Therefore, it can be said that the present invention is an invention having extremely high industrial value.

Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat II (Reference) // B05D 3/10 B05D 3/10 A F-term (Reference) 4D075 AE03 BB73X CA13 DA06 DB05 DC02 DC12 DC18 EA05 EB17 EB37 EB56 4F100 AB03A AB18A AK01C AK18B AK18D AL05B AL05D AT00A BA03 BA07 BA10C BA10D EH71A EJ06A EJ46 GB07 GB32 GB48 JK06 JL01 JL11 YY00B YY00D 4K026 AA02 AA07 AA09 AA13 AA22 BB06 EB09 BB08

Claims (4)

[Claims] 1. A steel sheet having a lower organic coating layer I and an upper organic coating layer II on at least one side of a steel sheet, wherein the organic coating layer I contains 2 to 50% by weight of a polytetrafluoroethylene resin. Pre-coated steel sheet with excellent processing adhesion. 2. The precoated steel sheet according to claim 1, wherein the organic coating layer I further comprises 20% by weight or more of a polyether sulfone resin. 3. The precoated steel sheet having excellent work adhesion according to claim 1, wherein the steel sheet has a chemical conversion treatment layer as a further lower layer of the organic coating layer I. 4. The precoated steel sheet according to claim 1, wherein the steel sheet has a plating layer containing 80% by weight or more of zinc.