JPH11291386A - Precoated steel plate with superior weatherability and processability and application thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a precoated steel plate having a superior whetherability and an outstanding processability through fabricating with a low-priced polyacrylic resin and a roofing wall panel, an outdoor advertising panel, a lighting reflection panel, a tunnel internal fitting panel, an exterior automotive trim panel, a partition panel and an elevator interior panel as use applications of the precoated steel plate. SOLUTION: The precoated steel plate has a layer 1 covered with a coating of a copolymerized acrylic polyol resin obtained by copolymerizing a polymerizable ultraviolet stable monomer, a cycloalkyl group-containing polymerizable monomer and a hydroxyl group-containing polymerizable monomer as essential polymerizable monomeric components. In addition, the precoated steel plate has a coated layer 11 with 10% or more coefficient of breaking extension by the tensile strength test under a room temperature environment between the steel plate and the coated layer 1. Thus it is possible to obtain the precoated steel plate with good weatherability and processability and various kinds of panel made of this steel plate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prepainted steel sheet having excellent weather resistance and workability used for home appliances, building materials, automobiles, and the like, and its use.

[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 sheets are used for everything from large structures such as buildings, ships, bridges, etc. to various machines, automobiles, furniture, small appliances and household goods, but the painting of these steel sheets 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 polymer resin is used for the coating layer so that the coating film does not peel off during processing. In particular, when a polyacrylic resin is used, a beautiful appearance can be obtained.

[0003]

However, ordinary polyacrylic resins cannot provide sufficient weather resistance.
In addition, weather resistance refers to durability performance against a change in appearance due to deterioration or deterioration of resin due to irradiation of sunlight or wind and rain when using a precoated steel sheet outdoors. On the other hand, when a fluorine-based resin is used, sufficient weather resistance can be obtained, but the cost is much higher than that of a polyacrylic resin-based paint.

In the case where the coating layer is composed of a plurality of layers, it is known that the workability of the entire coating layer is poor if the elongation percentage of the lowermost coating layer is low. An object of the present invention is to provide a prepainted steel sheet having excellent weather resistance and workability, and an application using the precoated steel sheet, in order to solve the above-mentioned problems.

[0005]

According to the present invention, there is provided a precoated steel sheet having a polymerizable ultraviolet-stable monomer (A) and a polymer having a cycloalkyl group. Coating layer essentially containing a copolymerized acrylic polyol resin (D) obtained by copolymerizing a polymerizable monomer component essentially containing a hydrophilic monomer (B) and a hydroxyl group-containing polymerizable monomer (C) I, a coating layer having a breaking elongation of 10% or more during a tensile test in a room temperature environment between the steel sheet and the coating layer I.
Achieved by having II.

At the same time, by using this pre-coated steel sheet for the external appearance of the product, it is possible to obtain a thin steel sheet product which is easy to process and has excellent weather resistance.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the precoated steel sheet of the present invention will be described in more detail. In addition, this invention is comprised from a steel plate and a coating layer. First, 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, aluminized steel sheet, chromium-coated steel sheet , A nickel-plated steel plate, a zinc-nickel alloy-plated steel plate, a tin-plated steel plate, a stainless steel plate, an aluminum-plated stainless steel plate, a lead-plated stainless steel plate, a zinc-plated stainless steel plate, and the like.

[0010] If necessary, the steel sheet can be subjected to a pretreatment. Examples of pretreatment include washing with water, washing with hot water, pickling, alkali degreasing, grinding, polishing, chromate treatment, zinc phosphate treatment, composite oxide film treatment, and the like, and the pretreatment may be performed alone or in combination. . Conditions for each pretreatment may be appropriately selected. Next, the coating layer I applied to at least one surface of the steel sheet is made of a copolymerized acrylic polyol resin (D) containing a polymer component for improving weather resistance. As an essential polymerizable monomer component, a polymerizable UV-stable monomer (A) containing a functional group such as a hindered amine having a UV-stabilizing ability, and the durability of the coating film without lowering the weather resistance of the resin And a hydroxyl group-containing polymerizable monomer (C) which can be a crosslinking group in the presence of a substrate adhesive and a crosslinking agent.

The polymerizable ultraviolet-stable monomer (A) is an essential compound for imparting excellent weatherability to the copolymer, and particularly comprises a sterically hindered piperidinyl group and a polymerizable unsaturated group. Those having at least one in the molecule are awarded, and among them, the substance represented by the formula (1) is most typically used.

[0010]

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Here, R ¹ is a hydrogen atom or a cyano group,
R ² and R ³ each independently represent a hydrogen atom or carbon atom 1
X is an imino group or an oxygen atom; Y is a hydrogen atom or an alkyl group having 1 to 18 carbon atoms or -C
Shows the O-CR ² = CHR ^3. For example, as a polymerizable ultraviolet-stable monomer (A), for example, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine , 4- (meta)
Acryloylamino-2,2,6,6-tetramethylpiperidine, 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloylamino-1,2,2 , 6,6-Pentamethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-
(Meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 1-crotonoyloxy-2,2,6,
6-tetramethylpiperidine and the like,
One or more of these can be used.

The cycloalkyl group-containing polymerizable monomer (B) is an essential compound for maintaining the durability of the coating film without deteriorating the weather resistance of the resin. The substances indicated are most typically used.

[0013]

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Here, R ⁴ in the formula (2) represents a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, and Z represents a cycloalkyl group which may have a substituent. Illustrative explanations will be given with reference to specific compound examples, for example, cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate
And tert-butylcyclohexyl (meth) acrylate, and one or more of these can be used.

Next, examples of the hydroxyl-containing polymerizable monomer (C) include, for example, hydroxyethyl (meth) acrylic acid.
And hydroxypropyl (meth) acrylate, caprolactone-modified hydroxy (meth) acrylate, and the like, and one or more of these can be used. Further, as other polymerizable monomers, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, isopropyl (meth) acrylate, t-butyl (meth) acrylate )
Acrylate, 2-ethylhexyl (meth) acrylate
(Meth) acrylic acid alkyl esters such as methacrylate, epoxy group-containing unsaturated monomers such as glycidyl (meth) acrylate, (meth) acrylimide, N, N'-dimethylaminoethyl (meth) acrylate, Vinyl pyridine,
Nitrogen-containing unsaturated monomers such as vinyl imidazole, aromatic unsaturated monomers such as styrene, α-methylstyrene and vinyl toluene, vinyl esters such as vinyl acetate, vinyl ether, (meth) acrylonitrile and the like. Examples thereof include unsaturated cyanide compounds, and one or more of these can be used as needed.

The copolymerization of the above polymerizable monomer components is not particularly limited, but the content ratio of each monomer component is from 0.1 to 0.1% of the UV-stable polymerizable monomer (A). 1
0.0% by weight, cycloalkyl group-containing polymerizable monomer (B) 5.0 to 97.9% by weight, hydroxyl group-containing polymerizable monomer (C) 2.0 to 35.0% by weight, other It is preferable to constitute 100% by weight of the copolymerized acrylic polyol resin (D) within the range of 0 to 92.9% by weight of the polymerizable monomer.

Further, a crosslinking agent can be added to the coating layer I if necessary. As a crosslinking agent, an aminoplast resin or a polyisocyanate compound can be used alone or in combination. Examples of the aminoplast resin include a methyletherified melamine resin, a butyletherified melamine resin, a butyletherified benzoguanamine resin, and a butyletherified cyclohexylbenzoguanamine resin. The mixing ratio of the aminoplast resin and the copolymerized acrylic polyol resin is preferably 10 to 100 parts by weight based on 100 parts by weight of the acrylic polyol.

Further, as the polyisocyanate compound,
It suffices that the molecule contains two or more isocyanate groups, for example, trimethylene diisocyanate, 1,6-hexamethylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate. Neat, isophorone diisocyanate, and trimethylolpropane adducts, derivatives of these diisocyanates;
Adduct polyisocyanate compounds such as ret-forms and isocyanurate-forms. Further, the isocyanate group of the isocyanate compound may be ε-caprolactam, phenol, cresol, oxime, or alcohol. And a blocked polyisocyanate compound blocked with a compound such as As for the blending of the polyisocyanate compound and the acrylic polyol resin, it is preferable that the isocyanate group is 0.3 to 2.0 mol per 1 mol of the OH group in the acrylic polyol.

When the curing agent is added, a curing catalyst such as dodecylbenzenesulfonic acid may be added as necessary. The compounding amount may be appropriately determined according to the expected firing conditions and the balance of the coating film performance. Further, in the coating layer I, a color pigment such as titanium white, an extender such as silica, a leveling effect agent, an antioxidant, an ultraviolet absorber, and the like may be appropriately added as long as it is an additive generally used in a paint. The required amount may be mixed and used.

Particularly, in order to improve the weather resistance, it is effective to use an additive capable of absorbing light at a specific wavelength. As an example, by using a benzotriazole-based or oxalic anilide-based ultraviolet absorber in the coating film, a wavelength of 200 nm can be obtained.
It is possible to improve the weather resistance of the coating film in an accelerated weather resistance test using a germicidal lamp or the like having a strong line in a region of up to 220 nm as a light source.

The thickness of the coating layer I is not specifically defined, but is preferably 30.0 μm or less in view of the drying limit in the manufacturing process and the workability of the precoated steel sheet. Next, as the coating layer II applied between the steel sheet and the coating layer I, an organic coating layer having a breaking elongation of 10% or more in a tensile test at room temperature is used. With respect to the coating material used for the coating layer II, there is no particular limitation on the type of resin and the presence or absence of a curing agent or an additive, provided that the breaking elongation after film formation is 10% or more.
Any paint generally used for pre-coated steel sheets may be used.

The method of the tensile test is based on JIS K
Performed according to 7113-1977. Specifically, the free film of the coating layer II prepared by the amalgam method was
The test piece was cut out in the shape of a No. 1 test piece using an NT cutter. The tensile test is performed at room temperature and the test speed is 50m
The elongation at break of the specimen at m / min was measured,
The elongation at break was taken.

The elongation at break of the coating layer II is preferably at least 10%. If the elongation at break is less than 10%, the workability of the entire coating layer is poor, causing cracks during processing, and the generated cracks serve as corrosion-causing points, causing problems such as a reduction in the corrosion resistance of the product. The thickness of the coating layer II is not particularly limited, but is preferably 20.0 μm or less from the viewpoint of the drying limit in the manufacturing process and ensuring the adhesion to the steel sheet.

A single or a plurality of organic coating layers may be formed between the coating layer I and the coating layer II as necessary. In this case, when the uppermost coating layer is a transparent layer having a low clearing or hiding power from the viewpoint of a design or the like, the second layer and lower layers may be required to have weather resistance. In this case, the above-mentioned copolymer acrylic polyol resin (D)
Can also be applied to the second and lower layers.

Similarly, from the viewpoint of design and the like, an organic coating layer having clearness and transparency can be added above the coating layer I. In this case, for the organic resin layer, the resin composition and the additive composition may be selected according to the required properties such as lubricity, hardness, workability and stain resistance, and required properties such as adhesion can be obtained. It may be used as appropriate. In addition,
There is no restriction on the use of commonly used additive components in any of the coating layers. Examples thereof include color pigments, extender pigments, rust preventive pigments and dyes, leveling components, and design components such as metallic, mica, and aggregate.

Further, the thickness of each organic coating layer is not particularly specified, but the drying limit in the manufacturing process and the pre-coating.
From the viewpoint of workability of the entire coated steel sheet, it is desirable that each layer be 20.0 μm or less. The above-mentioned precoated steel sheet of the present invention is, for example, a panel for a roof wall, a panel for an outdoor advertisement, a panel for lighting reflection, a panel for a tunnel interior, a panel for an automobile exterior, a partition panel, an elevator interior panel, and the like. By applying the present invention to parts exposed to the outdoor atmosphere, it is possible to obtain a product having better workability and better weather resistance than before.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a precoated steel sheet according to the present invention will be described. Alkaline degreasing / chromate treatment
A coating layer shown in Table 1 on a 6 mm thick galvanized steel sheet
Coating the paint of II so that the dry film thickness is 10 μm.
And then baked by a high-frequency induction heating method. On top of that, the coating of the coating layer I was dried to a thickness of 16 μm.
m was applied using a bar coater and then baked by a high frequency induction heating method to prepare a precoated steel sheet.

Similarly, a free film having a thickness of 10 μm was prepared from the coating material of the coating layer II by the amalgam method.
A test piece for a tensile test was prepared by cutting out the shape of a No. 1 test piece using an NT cutter. The obtained test material was evaluated for weather resistance, elongation at break, workability, and corrosion resistance of the processed part under the following conditions.

The weather resistance was evaluated by using a sunshine weather meter (SWOM) to measure the chromaticity difference (ΔE) and gloss retention (GR) before and after the test for 3000 hours. Table 2 shows the results. The chromaticity difference (ΔE) was measured using a chromaticity measuring device, and it was judged that ΔE was 1.0 or less as good.
The gloss retention (GR) was measured with a 60-degree reflectometer, and 60% or more was judged to be good.

The elongation at break was evaluated by measuring the elongation at break of the test material at a test speed of 50 mm / min in a room temperature environment according to the method described above. Table 2 shows the results. In addition,
A breaking elongation of 10% or more was regarded as good. Workability is JI
According to the method of SK5400, the degree of cracking of the coating film surface was measured in a 4T bending test in a room temperature environment, and the evaluation was made out of 5 points. In addition, five or more cracks were evaluated as good.

The corrosion resistance of the processed portion was evaluated by performing a salt spray corrosion test on the test piece subjected to 4T bending in accordance with the method of JIS Z2371 for 1,000 hours, and then measuring and evaluating the state of rust on the coated film surface of the processed portion. . Note that no rust was generated. As is clear from Table 2, the pre-copper according to the present invention was used.
It can be understood that the coated steel sheet has performance excellent in weather resistance and workability.

[0032]

[Table 1]

[0033]

[Table 2]

Next, the precoated steel sheet of the present invention shown in Table 1 was used for roof wall panels, outdoor advertising panels, lighting reflection panels, tunnel interior panels, automobile exterior panels, partition panels, elevators. ΔE and G before and after 3000 hours SWOM test
As a result of measuring the R and the degree of cracking of the coating film surface of the processed portion, good weather resistance and workability were exhibited as in the results of Table 2.

[0035]

The polymerizable ultraviolet-stable monomer (A), the cycloalkyl group-containing polymerizable monomer (B) and the hydroxyl group-containing polymerizable monomer (C) of the present invention are obtained by copolymerization. Having a copolymerized acrylic polyol resin (D) in the coating layer I, and a coating layer II having a breaking elongation of 10% or more at room temperature between the steel sheet and the coating layer I. By using the coated steel sheet, it is possible to manufacture a product that is inexpensive and has excellent weather resistance and workability. By applying this to the field of home appliances and building materials, it is possible to improve product quality and reduce manufacturing costs.

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Ryoji Nishioka 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Inside the Kimitsu Works (72) Inventor Masashi Takasugi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation (72) Inventor ▲ Yoshita Masaya 5-8 Nishiburi-cho, Suita-shi, Osaka Japan Co., Ltd. (72) Inventor Takao Minami 5-8 Nishi-Morita-cho, Suita-shi, Osaka In Japan Catalyst (72) Inventor Nakazaki Mitsuo 5-8 Nishiburi-cho, Suita-shi, Osaka Japan Co., Ltd.

Claims (13)

[Claims] At least one surface of a steel sheet essentially contains a polymerizable UV-stable monomer (A), a cycloalkyl group-containing polymerizable monomer (B), and a hydroxyl group-containing polymerizable monomer (C). It has a coating layer I containing a copolymerized acrylic polyol resin (D) obtained by copolymerizing a polymerizable monomer component, and breaks between the coating layer I and the steel sheet during a tensile test at room temperature. A coated steel sheet having excellent weather resistance and workability, comprising a coating layer II having an elongation of 10% or more. 2. The polymerizable ultraviolet-stable monomer (A) has the formula
(1)[However, R in the formula (1)¹Is a hydrogen atom or a cyano group, R
^Two, R^ThreeAre each independently a hydrogen atom or a carbon number 1 to
X is an imino group or an oxygen atom, Y is water
An atom or an alkyl group having 1 to 18 carbon atoms or -CO
-CR^Two= CHR ^Three(Where R^Two, R^ThreeIs the same as before)
Is shown. The weather resistance and workability according to claim 1, which is represented by the formula:
Excellent pre-coated steel sheet. 3. The polymerizable monomer having a cycloalkyl group (B) is represented by the formula (2): [However, R ⁴ in the formula (2) is a hydrogen atom or a carbon atom having 1 to 2 carbon atoms.
And Z represents a cycloalkyl group which may have a substituent. 3. A precoated steel sheet having excellent weather resistance and workability according to claim 1 or 2. 4. The precoated steel sheet according to claim 1, wherein the coating layer I comprises an aminoplast resin and / or a polyisocyanate compound as a crosslinking agent. 5. The coated steel sheet having excellent weather resistance and workability according to claim 1, wherein a chemical conversion treatment layer is provided between the coating layer II and the steel sheet. 6. The weather resistance according to claim 1, wherein an organic resin layer is provided between the coating layer I and the coating layer II and / or on the coating layer I. Precoated steel sheet with excellent workability and workability. 7. A panel for a roof wall using the pre-coated steel sheet according to any one of claims 1 to 6. 8. An outdoor advertising panel using the prepainted steel sheet according to any one of claims 1 to 6. 9. A lighting reflection panel using the precoated steel sheet according to any one of claims 1 to 6. 10. A panel for interior of a tunnel using the precoated steel sheet according to any one of claims 1 to 6. 11. An automotive exterior panel using the precoated steel sheet according to any one of claims 1 to 6. 12. A partition panel using the precoated steel sheet according to any one of claims 1 to 6. 13. An elevator interior panel using the precoated steel sheet according to any one of claims 1 to 6.