JP2987665B2 - High corrosion resistance painted steel sheet with excellent workability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated steel sheet having excellent corrosion resistance and workability, and this coated steel sheet can be used in many applications such as home appliances and building materials, similarly to a conventional coated steel sheet.

[0002]

2. Description of the Related Art Conventionally, various types of organic resin films have been applied to steel sheets for the purpose of improving the design properties and corrosion resistance of the steel sheets. In particular, in recent years, the use ratio of precoated materials (coated on steel plates before processing) has been increasing from the method of coating steel plates after processing them for the purpose of omitting the manufacturing process for home appliances and building materials.

At present, the demand for corrosion resistance is becoming increasingly sophisticated. As a method for ensuring such high corrosion resistance, a surface-treated steel sheet is used as an original plate for coating, or a coating film is formed into a multilayer to reduce the film thickness. A method of increasing the thickness has been implemented.

[0004] However adopting the method of thickening the coating film, dissolving a conventional such coatings resin in an organic solvent, or in a thermosetting resin coated steel sheets produced using the dispersed thermosetting coating was However, it is difficult in terms of its quality, particularly from the viewpoint of workability of the coated steel sheet, and the thickness of the coating film has been limited in order to ensure workability.

[0005] A coated steel sheet using a thermoplastic resin paint , such as a vinyl resin, generally has good workability even with a thick film. , it will require an is twice more than painting, I large film thickness
However, there is a disadvantage that the adhesion deteriorates as the temperature increases .

As a method of avoiding such a problem, a coated steel sheet is manufactured by a so-called laminating method in which a resin film which is colored in advance and where a picture is printed as necessary is manufactured, and the resin film is bonded to the steel sheet. ing.

However, this method has a drawback that only a film of a thermoplastic resin can be used, and the surface hardness of the coating film is insufficient.

[0008]

In a conventional thermosetting coated steel sheet, when the thermosetting resin coating film layer becomes thicker, the workability of the coating film layer is deteriorated, so that the film thickness is limited. Therefore, in recent years, a so-called laminated steel sheet in which a thermoplastic resin film is directly laminated on a steel sheet has been developed as a thick-film type coated steel sheet having improved workability.

In the former thermosetting resin coated steel sheet, by selecting the type of coating resin, the coating film properties such as hardness, stain resistance, weather resistance, etc. of the coating film can be arbitrarily controlled, and the corrosion resistance is good. However, the corrosion resistance, which is becoming more demanding year after year, is still insufficient. This is because it is necessary to increase the thickness of the organic resin coating layer in order to improve the corrosion resistance.

However, when the thickness of the thermosetting resin layer is increased,
Due to distortion during thermosetting, which occurs in the thermosetting resin coating film, there have been disadvantages such as deterioration in adhesion between the coating film and the steel sheet and deterioration in workability of the coating film layer.

The present invention is to provide a coated steel sheet having excellent corrosion resistance like the conventional thick film type coated steel sheet. The steel sheet of the present invention is excellent in workability and corrosion resistance, and has hardness, stain resistance, Surface physical properties such as weather resistance can be easily controlled.

[0012]

SUMMARY OF THE INVENTION The present invention provides a steel sheet having a first layer on at least one side of 30 to 200 μm , preferably
It has a thermoplastic resin laminate layer of 100 to 200 μm of polypropylene, polyethylene terephthalate, polyamide resin, etc., and a 10 to 30 μm ester-based layer as a second layer.
A highly corrosion-resistant coated steel sheet having excellent workability, characterized by having a coating layer of a thermosetting resin paint such as an alkyd resin .

[0013]

SUMMARY OF inventors have found a result of intensive studies, cold rolled steel or various surface treatments on the steel sheet, firstly a sufficient thickness to ensure corrosion resistance, Ekusutori the thermoplastic resin as the first layer
After that, a conventional thermosetting resin paint film layer is applied as a second layer on the thermoplastic resin laminate layer by coating.
It has been found that by forming the same, a thick-film type coated steel sheet having the same surface gloss, hardness, weather resistance, and design properties as the conventional coated steel sheet and having excellent corrosion resistance can be obtained.

That is, the present invention relates to a conventional thermosetting resin coating.
High corrosion resistance, which was difficult with a coated steel sheet having a coating film layer, has been changed to a coating film of a coated steel sheet having a coating layer of a thermosetting resin paint.
That the lower layer of the layer providing the laminate layer of the thermoplastic resin
More secure. Conversely, the weather resistance, surface hardness, stain resistance, etc., which are the drawbacks of thermoplastic resin-laminated steel sheets, which were generally used as conventional thick-film coated steel sheets, have been improved by thermoplastics.
Coating layer of thermosetting resin paint on the surface layer of resin laminated steel sheet
Imparting the corrosion resistance by providing the a coated steel plate excellent performance in processability.

Hereinafter, the contents of the present invention will be described in more detail.

[0016] Conventional consumer electronics, precoated coated steel sheet used in applications such as building materials, dispersed in an organic solvent, desiccants after the dissolved coating material was applied by roll coating, spraying, or flow coating method or the like method in a steel sheet・ It is hardened and has various quality characteristics required for painted steel sheet, namely corrosion resistance,
A paint having a composition adjusted to satisfy all properties such as surface hardness, stain resistance, weather resistance, and adhesion to a steel sheet is applied to the steel sheet.

However, the requirements for these quality characteristics required for coated steel sheets are becoming stricter every year, and the quality of paints is being improved accordingly. However, it has become difficult to satisfy all of these various quality characteristics with a single coating system. In particular, the quality requirements regarding corrosion resistance have become strict, and it is difficult to obtain high corrosion resistance with the above-mentioned conventional coated steel sheets. As a result, multilayer coated steel sheets coated twice or three times have been developed, High corrosion resistance is ensured by increasing the thickness and film thickness.

However, even in the method of coating a plurality of times, distortion in the resin due to a resin curing reaction or the like remaining in the coating film increases, and as the coating film thickness increases, the workability and the adhesion between the steel sheet and the coating film increase. There were disadvantages such as deterioration. Further, even a vinyl-coated steel sheet which is relatively easy to obtain a thick film has disadvantages such as the adhesion being deteriorated as the film thickness increases.

In order to solve this drawback , the present inventors have made a thermoplastic resin laminating film having excellent corrosion resistance and workability as the first layer.
A second layer, and then a second layer is formed on the first layer.
The same layer of thermosetting resin paint as ester, acrylic, alkyd, etc. used for conventional coated steel sheet
The invention of a two- layer coated steel sheet having a coating film layer has been reached.

The structure of the two- layer type coated steel sheet of the present invention and the quality characteristics required for each layer will be described in detail below.

FIG. 1 shows an example of the structure of a two- layer coated steel sheet according to the present invention. Reference numeral 1 denotes a cold rolled steel sheet or a surface-treated steel sheet. Reference numeral 2 denotes a first thermoplastic resin laminate layer.
Reference numeral 3 denotes a second coating layer.

FIG. 1 shows an example of laminating and painting only on one side, but the product of the present invention is a steel sheet having a laminating layer and a coating layer on both sides as shown in FIG. 3, or as shown in FIG. On the other hand, the opposite surface includes an example of a steel plate having the same coating layer as that of the conventional art.

First, the steel plate will be described. In the present invention, the steel sheet is not particularly limited, but a surface-treated steel sheet is desirable for improving adhesion to a coating film and corrosion resistance.
For example, a surface obtained by subjecting a cold-rolled steel sheet to a phosphate treatment, a chromate treatment, or the like, or a steel sheet subjected to a metal plating such as zinc, zinc-nickel alloy plating, and the like, similarly to a phosphate treatment, a chromate treatment, or the like. Treated steel sheet can be used.

In order to secure particularly high corrosion resistance, it is preferable to use a surface-treated steel sheet which has been subjected to the latter metal plating and further subjected to a phosphate treatment, a chromate treatment and the like.

Next, the constitution of the laminate layer and the coating layer, which are features of the present invention, will be described. Is a <br/> thermoplastic resins of the laminate layer of the first layer, (hereinafter abbreviated as PE) polyethylene, polypropylene (hereinafter abbreviated as PP), (hereinafter abbreviated as PET) polyethylene terephthalate, or polyamide ( (Hereinafter abbreviated as PA) or the like, alone or as a mixture, or as a copolymer resin.

In order to secure the adhesion between the thermoplastic resin and the steel sheet, it is preferable to appropriately modify the resin and arrange a resin layer having improved adhesion at the interface with the steel sheet. For example, in the case of a polyolefin resin such as PE or PP, a hydroxyl group (-OH) and a carboxyl group (-COOH)
And poor adhesion to steel sheets due to lack of functional groups.

As a method for solving this, PE or P
There is a method in which P is subjected to acid modification with an unsaturated carboxylic acid, an acid anhydride thereof, or a derivative thereof, and the above functional group is arranged in the molecule. By disposing such an acid-modified resin layer at the interface with the steel sheet and providing a general thermoplastic resin layer that does not undergo acid transformation on the interface, a thermoplastic resin laminate layer having excellent adhesion to the steel sheet ( 1) can be obtained at low cost.

The thickness of the thermoplastic resin laminate layer is
Limited to 30-200μ. If it is less than 30 μm, not only is it difficult to secure high corrosion resistance, which is the object of the present invention, but it is also difficult to obtain a coating layer having a uniform film thickness because the resin layer is thin. The reason why the upper limit is set to 200 μ is that the first
The effect of improving corrosion resistance required for the thermoplastic resin layer of the layer is saturated, no more Thickness is small the effect of improving corrosion resistance obtained compared to the increase in resin cost, because not economically advantageous.

Next, the second coating film layer (3 in FIG. 1) will be described. For the second layer, various paints used for ordinary coated steel sheets can be used. That is, dissolved in an organic solvent, dispersing the conventional coating can be used.

[0030] First is a kind of paint, if you want a good coating film formability may be selected port Riesuteru based paint or the like. When gloss and high hardness of the surface are required, an acrylic paint or a melamine-based thermosetting paint may be selected.

Next, with regard to the composition of the coating layer , when these paints are applied directly on the first thermoplastic resin laminate layer , the coating between the first layer laminate resin and the upper paint resin is removed. In some cases, excellent adhesion may not be obtained.
In such a case, first, a paint having excellent adhesion to both resins, such as an epoxy resin paint, is applied on the first layer, and then the second layer resin is applied. If a very high surface hardness is required, the second layer may be coated with an ultraviolet curable resin or the like.

[0032] Then it is for the thickness of the coating layer of the second layer, the thickness of the coating layer, since it greatly affects the corrosion resistance of the often painted steel, the thickness of the coating layer is required It is determined according to the corrosion resistance performance. However, in the product of the present invention, the corrosion resistance is ensured by the first thermoplastic resin laminate layer , and the second layer is mainly intended to ensure the quality of surface physical properties such as surface hardness, color tone, weather resistance and the like. .

Therefore, the thickness of the second coating layer should be sufficient to ensure these surface characteristics. For example it varies depending shades to ensure surface color is generally a sufficient 10～20Myu, also in order to ensure the weather resistance, by the paint 20~30μ according to the required weather resistance Good.

Although the coated steel sheet of the present invention has been described above, the feature of the coated steel sheet of the present invention is that various quality characteristics required for the coated steel sheet are determined by the first laminate layer and the second layer paint.
Of is intended to coating layer and to be allocated by function sharing, the adhesion between the first layer mainly steel, and the securing of corrosion resistance, and the second layer, hardness, color, weatherability, And surface quality characteristics such as designability are ensured.

Accordingly, even if the first layer is a thick film, a thermoplastic resin having excellent workability and adhesion is optimal, and a characteristic resin system having excellent surface properties can be selected for the upper layer.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The coated steel sheet of the present invention will be described below based on embodiments.

Example 1: A 0.6 mm low-carbon cold-rolled steel sheet is electrogalvanized (coating amount: 20 g / m ² ), and an electrogalvanized steel sheet whose upper layer is subjected to chromate treatment is used as an original sheet. After heating the electrogalvanized steel sheet to 200 ° C., a denatured PET (polyethylene terephthalate) resin (manufactured by Mitsui DuPont Polychemicals Co., Ltd., trade name: Shira PT) was melt-extruded on one side of the steel sheet by a melt extrusion method. , 150 μm in thickness.

Next thereon, an epoxy-based paint was 5μ coating by a roll coater method, also commercial port Riesuteru resin coating by a roll coater method after drying baking, melamine resin paint, acrylic resin paint, respectively 20μ
Paint and bake harden under baking conditions appropriate for each paint.
Workability and corrosion resistance of the coated steel sheet of the present invention thus manufactured were compared with those of the conventional steel sheet.

Conventional example: As a conventional example, a commercially available thermoplastic resin was laminated.
A steel plate and a steel plate coated with a thermoplastic resin were used.

Comparative Example: As a comparative example, the same epoxy-based paint was directly applied to the same electrogalvanized steel sheet used in the production of the coated steel sheet of the present invention without applying the thermoplastic resin layer as the first layer. 5μ
Paint, bake and dry. Thereafter, the same commercially available acrylic resin paint and the same commercially available
50,100,150μ each of vinyl resin paint
Paint, dry and cure under baking conditions appropriate for each paint.
In this case, the coating thickness of 50μ, 100μ, and 150μ was ensured by coating once, twice and three times, respectively, by a roll coating method.

Table 1 shows the measurement results of the corrosion resistance, workability, and surface hardness.

[0042]

[Table 1]

In Table 1: * 1) The coated steel plate is bent at 180 °, and the cracks at the bent portion are observed with a 20-power loupe. ◎ No cracks in the coating film were observed. ○ Fine cracks are observed. B: Cracks in the coating film are observed.

* 2) A test piece subjected to the same processing as the above processing test is sprayed with salt water. Evaluation is made on the state of rust occurrence after the salt spray test for 2000 hours. ◎ No rust is observed. ○ Some white rust (corrosion product of zinc) is observed. △ In addition to white rust, slightly red rust was observed. × Red rust is observed in 50% or more of the processed portion.

* 3) Pencil hardness when a scratch is formed on a coated steel plate with a pencil having a different hardness and the scratch begins to be formed.

As is clear from Table 1, the steel sheet of the present invention has improved workability, so that the corrosion resistance of the processed portion is also improved, and shows excellent performance as compared with conventional products and comparative materials.

Example 2 A 0.6 mm low-carbon cold-rolled steel sheet is electrogalvanized (coating amount: 20 g / m ² ), and an electrogalvanized steel sheet whose upper layer is subjected to chromate treatment is used as an original sheet. After heating this electrogalvanized steel sheet to 180 ° C., PP
(Polypropylene) -PE (polyethylene) copolymer resin (trade name: ADMER QE-0, manufactured by Mitsui Petrochemical Industries, Ltd.)
50) and PP (manufactured by Mitsui Petrochemical Industry Co., Ltd., trade name PP L-840) are melt-extruded with a two-layer extrusion type T die.

In this case, the steel plate side was made of a PP (polypropylene) -PE (polyethylene) copolymer resin having excellent adhesion, and the upper layer was made of a normal PP (L-840) film. The thickness of the laminate film was 30 μm for the lower Admer QE-050 and 70 μm for the L-840.
0 μ was used.

On the first PP resin layer, a polyester resin paint and an acrylic resin paint were applied in a thickness of 20 μm by a roll coater method and dried and cured under the respective curing conditions. The workability of the coated steel sheet of the present invention thus manufactured,
The corrosion resistance was investigated in comparison with conventional materials.

Conventional Example: As a conventional example, a commercially available PE (polyethylene) laminated steel sheet was used.

Table 2 shows the measurement results of the corrosion resistance, workability, and surface hardness.

[0052]

[Table 2]

As is evident from Table 2, by coating the second layer with a thermosetting paint, the surface hardness of the thermoplastic laminated steel sheet is improved, and the scratch resistance of the surface-treated steel sheet is improved.

[0054]

Coated steel plate of the present invention as described above, according to the present invention is a thermoplastic resin laminated with a d custo Rude or thermal laminating method, using a solvent type paint as a second layer and thereafter the first layer The first layer has excellent adhesion and workability to the steel sheet, and the second layer has a high corrosion resistance by applying a paint that imparts the required design and surface hardness to the coated steel sheet according to the purpose. excellent corrosion resistance coated steel Needing and Prospective,
In addition, a coated steel sheet having excellent surface characteristics can be obtained. The present invention
Despite being a thick film type coated steel sheet, most of it is a thermoplastic resin, which can reduce the use of organic solvents during coating, and provide a coated steel sheet with excellent workability and corrosion resistance as well as adhesion. .

[Brief description of the drawings]

FIG. 1 is a drawing showing a structural example of a two-layer coated steel sheet according to the present invention.

FIG. 2 is a drawing showing an example of the structure of a coated steel sheet in which only one side has a second-layer coating film.

FIG. 3 is a drawing showing a structural example of a coated steel plate having the same coating layer on both sides.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Steel plate 2 First layer of thermoplastic resin laminate layer 3 Second layer of solvent type paint coating layer

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B32B 15/08 B05D 7/14

Claims (3)

(57) [Claims] 1. A steel sheet having a thermoplastic resin laminated layer of 30 to 200 μm of polypropylene, polyethylene terephthalate, polyamide resin or the like as a first layer on at least one side of a steel sheet, and a 10 to 30 μm ester or alkyd resin as a second layer. A highly corrosion-resistant coated steel sheet having excellent workability, characterized by having a coating layer of a thermosetting resin paint such as 2. The method according to claim 1, wherein the thickness of the first laminated layer is 100 μm.
The highly corrosion-resistant coated steel sheet having excellent workability according to claim 1, characterized in that: 3. An epoxy resin system between a first layer and a second layer.
3. A coating film layer comprising a paint film layer.
High corrosion-resistant coated steel sheet with excellent workability described in 1.