JPH10138392A - High hardness high corrosion resistance coated metal sheet which is excellent in chipping resistance and its use - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a metal sheet excellent in chipping resistance, high hardness, and high corrosion resistance by a method wherein a resin layer wherein nonwater soluble pigment is contained in coating and a film thickness and its hardness are specified, is provided as an under layer, and an electron beam curable film coated layer is provided as an upper layer. SOLUTION: Nonwater soluble pigment is indispensably contained an undercoat coating for primer applied onto one side of a metal sheet. As the undercoat coating for primer, there are polyester, epoxy, urethane, etc., which are coated with a roll coater, a curtain flow coater, etc., to obtain 4μm or over film thickness. Then, it is dried to be cured by standing at ordinary temperature or with a hot blast furnace, an induction heating furnace, a near infrared radiation furnace, an extreme infrared radiation furnace, etc. However, a hardness of the cured film shall be softer than F in pencil hardness. Then, an electron beam curable film coated layer as the upper layer is formed on the resin layer as the under layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coated metal sheet having high hardness and high corrosion resistance and excellent chipping resistance. The coated metal sheet of the present invention is suitable for a tunnel interior board or exterior building material.

[0002]

2. Description of the Related Art Painted metal sheets are used in various ways, such as white sheets, panels for home appliances, road guard boards, and tunnel interior boards, by imparting various characteristics to the coating film. Among them, the painted metal plate having high hardness and excellent stain resistance disclosed in Japanese Patent Publication No. 4-45342 is particularly useful as a tunnel interior plate.

[0003]

However, the coated metal sheet disclosed in the above-mentioned publication is used in a severely corrosive environment, for example, chloride (NaCl, CaCl ₂ ) for preventing freezing of a place facing a coast or a road. It was newly found that the corrosion resistance was not sufficient in a tunnel where dust was sprayed. As a result of investigating the cause of the insufficient corrosion resistance, it was presumed that the chipping phenomenon due to stepping stones or the like was the cause. Therefore, the present invention is excellent in chipping resistance, and high hardness, stain resistance,
An object of the present invention is to provide a coated metal sheet having excellent anti-glare properties and having sufficient corrosion resistance (for example, 5 years or more) even in a severe corrosive environment.

[0004]

According to the present invention, there is provided a coated metal plate according to the present invention, wherein a water-insoluble pigment is contained as a lower layer in a coating on at least one side of the metal plate.
It is characterized by having a resin layer with a hardness of at least μm, pencil hardness and softer than F, and having an electron beam-curable coating film coating layer as the upper layer, with excellent chipping resistance, high hardness, and corrosion resistance. is there. The electron beam-curable coating film coating layer comprises: A: 90 to 10 parts by weight of an oligo (meth) acrylate containing two or more (meth) acryloyl groups in a molecule and having a (meth) acryloyl group equivalent of 500 or less; B: 90 to 10 parts by weight of a polyhydric alcohol (meth) acrylate having two or more (meth) acryloyl groups in a molecule and having a (meth) acryloyl group equivalent of 150 or less,
And C: 0.5 to 20 parts by weight of a silica extender, D: 1 to 20 parts by weight of a polymer having a molecular weight of 5,000 or more, and A, B, C, D E: Desirable is E: 1 to 40 parts by weight based on 100 parts by weight of the mixture of components.
As the base metal plate, a stainless steel plate containing 13 wt% or more of Cr is preferable. In addition, the tunnel interior board manufactured using the coated metal sheet of the present invention has excellent performance even in the severe use environment as described above.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. First, the metal plate of the base metal used for the coated metal plate of the present invention may be a steel plate, an aluminum plate or any other metal plate. In particular, in terms of corrosion resistance and strength, stainless steel having a Cr content of 13 wt% or more is preferred. Preferably, a steel plate is applied. Usually, a chemical conversion treatment layer is first provided on at least one surface of the metal plate. As the chemical conversion treatment layer, there are a chromate treatment, a zinc phosphate treatment, a composite oxide film treatment and the like, and these may be used alone or in combination. These conditions may be appropriately selected. Further, the chemical conversion treatment layer may not be provided depending on the application.

Next, a primer layer of an undercoat film is provided as a lower layer. A primer layer can be formed by applying a primer undercoat on a metal plate and curing and drying. Primer undercoats include polyester, epoxy, and urethane coatings, which can be applied to roll coaters, curtain flow coaters, roller curtain coaters, electrostatic coating machines, brushes, blade coaters, die coaters, etc. Painted to become
Then, it is cured and dried at room temperature or in a hot-air oven, induction heating oven, near-infrared oven, far-infrared oven, energy beam curing oven such as electron beam or ultraviolet ray. However, the hardness of the cured coating must be softer than F in pencil hardness.
If F or harder than F, corrosion occurs in a corrosion resistance test after the chipping test.

In addition, it is essential that a water-insoluble pigment is contained in the primer undercoat. If a water-soluble pigment such as strontium chromate or barium chromate is contained, the pigment is eluted in a humid environment, and the adhesion of the undercoat film to the metal plate is reduced. And, chipping resistance is not obtained, resulting in deterioration of corrosion resistance. The film thickness is 4 μm or more. If the film thickness is smaller than 4 μm, the corrosion resistance after the simulation test for chipping resistance is deteriorated. In particular, a dry film thickness of about 5 to 12 μm is preferable.

Next, an electron beam-curable coating film coating layer is formed as an upper layer on the lower resin layer. The resin coating composition comprises: A: 90 to 10 parts by weight of an oligo (meth) acrylate having two or more (meth) acryloyl groups in a molecule and having a (meth) acryloyl group equivalent of 500 or less; To 90 to 10 parts by weight of a polyhydric alcohol (meth) acrylate having at least two (meth) acryloyl groups and having a (meth) acryloyl group equivalent of 150 or less, and 100 parts by weight of a mixture of the component A and the component B C: 0.5 to 20 parts by weight of a silica extender, D: 1 to 20 parts by weight of a polymer having a molecular weight of 5,000 or more, and 100 parts by weight of a mixture of components A, B, C, and D; It is preferable that the amount is 1 to 40 parts by weight of the powder. This upper layer paint is applied on the lower layer, and the oxygen concentration is 1%.
It is preferable to cure with an electron beam in the following inert gas.

Hereinafter, the composition of the upper resin coating will be described in detail. First, the oligo (meth) acrylate containing 90 to 10 parts by weight as the component A is obtained by esterifying (meth) acrylic acid with a polyester skeleton in the main chain. As a material used for the need to have a sufficient crosslinked network structure,
It is preferable that one molecule contains two or more (meth) acryloyl groups, more preferably three or more. Also, since the crosslink density must be sufficiently large,
(Meth) acryloyl group equivalent is also 500 or less,
More preferably, it is desirable to be 400 or less. If the number of (meth) acryloyl groups and the equivalent of (meth) acryloyl groups are within the scope of the present invention, polyhydric alcohol (meth)
In the combination with an acrylate, acrylic, epoxy, polyamide, silicone, urethane and the like generally fulfill the performance of the present invention. However, in consideration of the combination with a polymer, the polyester has the most preferable performance. As long as the oligo (meth) acrylate satisfies the requirements of the present invention, two or more of these may be used in combination.

Among the polyester oligomers having two (meth) acryloyl groups, di (meth) acrylates of polyester diols of tetrahydrophthalic acid or adipic acid with alkylene glycol or cycloalkylene glycol having 3 to 6 carbon atoms A polyester oligomer having the following structure and having a number average molecular weight of 350 to 800 and a number average molecular weight of 180 to 400 per (meth) acryloyl group is particularly suitable for this purpose.

Further, among polyester oligomers having two or more (meth) acryloyl groups, adipic acid or tetrahydrophthalic acid and trimethylolpropane;
Or, it has a structure of tetra (meth) acrylate, penta (meth) acrylate or hexa (meth) acrylate of a polyester polyol with pentaerythritol, a number average molecular weight of 550 to 2000, and a number average molecular weight of 100 per (meth) acryloyl group. Polyester oligomers of .about.350 are suitable for the purposes of the present invention.

Next, the polyhydric alcohol (meth) acrylate containing 90 to 10 parts by weight as the B component is obtained by reacting (meth) acrylic acid with the terminal hydroxyl group of the polyhydric alcohol to form a (meth) acryloyl group. It refers to the introduced one, which serves to obtain an extremely high crosslinking density in combination with oligo (meth) acrylate.
For this purpose, two (meth) acryloyl groups are contained in one molecule.
And the (meth) acryloyl group equivalent is 15
0 or less, more preferably about 130 or less. In addition,
In this case, a mixture of the above-mentioned polyhydric alcohol (meth) acrylate may be used.

Here, the mixing ratio of oligo (meth) acrylate to polyhydric alcohol (meth) acrylate will be described. The ratio of oligo (meth) acrylate / polyhydric alcohol (meth) acrylate is preferably in the range of 9/1 to 1/9 (weight ratio). The reason is that oligo (meth) acrylate alone does not provide a sufficient crosslink density, and therefore a polyhydric alcohol (meth) acrylate is added to increase the crosslink density. At least one or more must be added to the minimum oligo (meth) acrylate 9. Here, the upper limit of the polyhydric alcohol (meth) acrylate is oligo (meth) acrylate 1
However, if the coating is further added and the coating is hardened, the coating may crack or break after a lapse of time, possibly due to internal shrinkage stress.
When scratched, cracks increase. Therefore, the following is preferable.

Next, the silica extender which is the component C will be described. The silica of the present invention is added in an amount of 0.5 part by weight or more, preferably 1.0 part by weight or more, based on 100 parts by weight of the total of the component A: oligo (meth) acrylate and the component B: polyhydric alcohol (meth) acrylate. The present invention fulfills the purpose of preventing adhesion of dust from coating to curing of a coating film and gloss unevenness of electron beam irradiation curing. To give a concrete example, the thyroid series made by Fuji Devison Chemical,
Mizusukasil series and Mildon series manufactured by Mizusawa Chemical Industry, Relex series manufactured by Tokuyama Soda, Tokushir series Fine seal series, Shionogi Pharmaceutical carplex series, Nippon Aerosil series and the like. In the present invention, a mixed system of two or more extenders may be used.

Next, a polymer having a molecular weight of 5000 or more of the component D will be described. By this polymer, component A,
The lack of stickiness of the resin system composed of the component B is compensated for, so that good coating can be performed with an industrial coating machine, and the effect of the component C is remarkably enhanced. This polymer includes acrylic, polyester,
Urethane, epoxy, polyamide, melamine, silicone, alkyd, and the like, and modified products or combinations thereof may be used. It is a combination of them. In this case, a mixture of two or more kinds of the same resin may be used.

Here, component A: oligo (meth) acrylate, component B: polyhydric alcohol (meth) acrylate,
The quantitative relationship between the C component: silica-based extender and the D component: a polymer having a molecular weight of 5000 or more is described. The above two components are necessary for maintaining excellent film performance such as excellent stain resistance, chemical resistance, or hardness.Although the silica extender is effective for the aforementioned purpose, As a result of various studies, it has been found that the target coating film performance of the present invention is rather a negative factor.

Although the polymer itself improves the coatability, it has a negative effect on the coating film performance. That is, if the molecule has a large number of (meth) acryloyl groups active in an electron beam, for example, if it has the same degree as oligo (meth) acrylate and polyhydric alcohol (meth) acrylate, Although not so negative, such a thing is theoretically possible but cannot actually be synthesized. Although the limit is not clear, for example, Ford Motor Co., Ltd., Japanese Patent Publication No. 45-15630
According to the publication, there are three or more (meth) acryloyl groups in 1000 molecular weight, that is, the double bond equivalent is about 330 or more. Here, a quantitative relationship is required. As a result of various studies, the present inventors have found that, based on 100 parts by weight of the mixture of the A and B components, 0.5 to 20 parts by weight of the C component,
If it is in the range of 20 parts by weight, the object of the present invention is satisfied.

Next, the glass powder of the E component will be described.
Various studies were conducted to ensure high hardness (pencil hardness 9H <) as the upper layer and to obtain a coating film having high stain resistance and antiglare properties. As a result, glass powder was further used. Turned out to be the best. That is, from the viewpoint of increasing the hardness, it is conceivable that the powder itself is hard, for example, metal powder such as iron powder, copper powder, stainless steel powder, brass powder, bronze powder, zinc powder, nickel powder, etc. Because of the color, the color of the paint is restricted, or because of its high specific gravity, it precipitates in the paint, and the coating suitability with an industrial coating machine is not sufficient, or the curtain flow coater It has been found that a roll coater has the drawback that it precipitates and accumulates on the pipes and hoses of the paint circulation system, making it difficult to wash the coating machine, and is not suitable for industrial production.

What eliminates these drawbacks and meets the object of the present invention is glass powder. The term glass powder as used in the present invention refers to a spherical powder having a three-dimensional radius and a two-dimensional radius. And the other dimension refers to a fibrous material having a linear length. If we define the term radius here, it is not exactly the same radius regardless of whether it is spherical or fibrous, and although there are slight differences,
For example, an elliptical shape may be used.

Regarding the size of the glass powder, regardless of whether it is spherical or fibrous, the coating powder has no effect unless it is exposed above the coating film surface in order to increase the hardness with coating flaws. However, what is meant here is that the size of the glass powder does not have to be larger than the coating thickness, and even if it is smaller than the coating thickness, it floats in the coating as a result. What is necessary is just to expose from the coating film surface.

First, the appropriate size of the spherical glass powder is such that the paint viscosity at the time of coating is 10-100
It is preferable that the diameter of the spheroidized glass is 0.1 to 2.0 times the thickness of the coating film and the sphere diameter does not exceed 100 μm in the range of 15 to 120 μm in dry coating film thickness. If the sphere diameter of the glass is too small, the probability of exposure from the surface of the coating film becomes small, so that the hardness is hardly improved, the gloss is not significantly reduced, and the antiglare property is not good. On the other hand, if the glass sphere diameter is too large, the dispersibility in the paint will be poor, and the glass will tend to settle in the paint, which may cause trouble during painting. Note that the inside of the sphere may be hollow.

Next, the appropriate size of the fibrous glass powder is as follows:
Assuming that the coating viscosity and the coating thickness are in the ranges described above, the fiber diameter is 0.1 to 1.5 times the coating thickness and the length is 2
The range of 0 to 100 μm is good. The reason for the appropriate range is the same as that for the spherical glass powder. Regarding the amount of glass powder to be added, 10 to 40 parts by weight, preferably 3 to 30 parts by weight, of the present invention is added to 100 parts by weight of the coating mixture composed of the components A, B, C and D. It serves the purpose. In addition to the above resin coating composition, a plasticizer,
Pigments, difunctional difunctional monofunctional monomers, oligomers, solvents, polymers, and the like can be added as needed.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the coated metal plate of the present invention will be described. As the base plate, a ferritic stainless steel plate (Cr
18 wt% or more). After alkaline degreasing,
Chromate treatment was performed as necessary. Next, an epoxy-based, polyester-based, or urethane-based polymer resin was used as a primer layer, and its hardness was adjusted with a curing agent. A resin containing no strontium chromate and a resin containing 1% by weight were prepared. Next, paints I and II of the present invention were used as upper layer paints, and paint I was used as a comparative example.
II was used. The details of each paint are as follows.

(Paint I) An oligomer having a condensation molar ratio of phthalic acid, trimethylolpropane, and acrylic acid of about 1: 2: 4 (acryloyl group equivalent: about 155); B. trimethylolpropane trimethacrylate (acryloyl group equivalent: about 110); D. Silica extender pigment ("Syloid 308", manufactured by Fuji Devison Chemical Co., Ltd., oil absorption 170 g / 100 g), The copolymerization molar ratio of ethyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, acrylic acid is 7
An acrylic copolymer (number average molecular weight: about 20,000) consisting of 0: 24: 3: 3; Spherical glass powder (sphere diameter 18 μm), A, B,
The weight ratio of C, D, titanium white and E is 18.8: 18.
To a system consisting of 8: 1.8: 4.4: 44.2: 10, 30% of xylene (vs. the former) was added to obtain a paint. This paint system is applied with a curtain flow coater (effective width 60 cm).
Painted. The painted surface was beautiful and the garbage was hardly noticeable.

The coated plate was heated with hot air at 150 ° C. to a plate temperature of 80 ° C.
The solvent was scattered at a temperature of about 50 ° C. (in a furnace for about 50 seconds), and then cured by an electron beam. Curing conditions: voltage 300KV, current 25mA / 60cm
A dose of 3 Mrad and an oxygen concentration at the time of irradiation of 150 ppm (in a nitrogen stream) A coating film test such as stain resistance and hardness was performed on the cured coated plate.

(Paint II) An oligomer having a condensation molar ratio of adipic acid, pentaerythritol, and acrylic acid of about 1: 2: 4 (acryloyl group equivalent: about 122); C. diethylene glycol dimethacrylate (acryloyl group equivalent: about 121), C.I. Silica extender (Mizukasil NP manufactured by Mizusawa Chemical Industries)
-8, oil absorption 260 g / 100 g); E. Polyester (number-average molecular weight: about 15,000) having a condensation molar ratio of terephthalic acid, sebacic acid, and ethylene glycol of 3: 7: 10; Fibrous glass powder (diameter 13μm, average length 50μ)
m), and a coating was prepared by adding 30% (vs. xylene) to a system in which the weight ratios of A, B, C, D, titanium white and E were exactly the same as coating I. This paint system was applied using a curtain flow coater (effective width 60 cm). The painted surface was beautiful and the garbage was hardly noticeable.

The coated plate was heated at 150 ° C. with hot air at a plate temperature of 80 ° C.
The solvent was scattered at a temperature of about 50 ° C. (in a furnace for about 50 seconds), and then cured by an electron beam. Curing conditions: voltage 300KV, current 25mA / 60cm
A dose of 3 Mrad and an oxygen concentration at the time of irradiation of 150 ppm (in a nitrogen stream) A coating film test such as stain resistance and hardness was performed on the cured coated plate.

(Paint III) A paint was prepared under the same conditions as for paint I except for component E of paint I. Next, the evaluation test method will be described below. (Stain resistance) Magic ink (red, blue), curry, mustard, lipstick,
Apply crayon, colored pencils, and ink to the painted plate, wipe it with gauze soaked in ethanol 24 hours later, write a character with a whiteboard marker manufactured by Pilot Corporation, erase it with an eraser, Assuming oil fumes from automobiles, which are pollutants, 10 g of carbon black was sprinkled with 20 g of olive oil, applied, and one month later, wiped 10 times with a case covered with 0.3% washing water in all three methods. Those that were easily wiped without any trace were marked with 〇, and those that were not wiped were marked with x.

(Pencil hardness) A test was conducted based on JIS-K5400. (Gloss) Specular reflectance of 60 ° -60 ° was measured with a gloss meter. (Scratch resistance) 5 pieces of polypropylene fiber (1 mmφ, the same as the cleaning brush installed in the car in the tunnel)
× 5 × 5cm ³ copper piece, spread without gap, 0.3%
While the soapy water was applied to the coated plate, the coated surface was slid 1000 times with a copper piece to visually determine the scratched property of the coated surface.場合 when no scratches were found, × when slightly scratched
And

(Corrosion Resistance after Chipping Resistance) A DuPont impact test using a flat die side was used. Punch diameter 3.2m
m, 300g weight from 5cm to 50cm, 5c
Each was dropped from the height of m intervals, and the painted surface was scratched.
A total of 10 levels will be damaged. Thereafter, a composite cycle test was performed under the following conditions. The test period was set to 14 cycles, and the occurrence of red rust from the scratched part was visually observed. Δ: Of 10 scratches, no red rust was generated, x: Red rust was generated even with one piece. did.

Conditions for combined cycle test 35 ° C., 10% CaCl ₂ , 0.024% SO ₂ (4c
c / 1 aqueous sulfurous acid) for 4 hours, 8 hours in a dry atmosphere at 60 ° C. and 25% humidity, 4 hours in a humid atmosphere at 40 ° C. and 95% humidity,
One cycle was performed for 8 hours in a dry atmosphere at 60 ° C. and 25% humidity for a total of 24 hours. The above evaluation results are shown in Table 1 together with the coating conditions. As the lower layer of the present invention, those containing a water-insoluble pigment and having a predetermined film thickness and hardness are excellent in chipping resistance, and in combination with the upper layer, stain resistance, hardness, gloss, scratch resistance, etc. Thus, a highly corrosion-resistant coated metal plate having excellent coating film characteristics was obtained.

[0032]

[Table 1]

[0033]

The coated metal sheet of the present invention has high corrosion resistance in addition to chipping resistance, high hardness and high contamination resistance. It can be used for building materials in coastal areas exposed to extremely severe corrosive environments due to chloride ions coming from snowmelt salt and tunnel interior boards, etc., and repairs and replacements are reduced. The effect is great.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masashi Takasugi 1 Kimitsu, Kimitsu-shi, Chiba Nippon Steel Corporation Kimitsu Works (72) Inventor Hiroshi Kihira 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Technology Development Division, Inc.

Claims (4)

[Claims] 1. A resin layer having a thickness of 4 μm or more, a pencil hardness, and a hardness softer than F, wherein a water-insoluble pigment is contained in a paint as a lower layer on at least one surface of a metal plate. ,
A high hardness, high corrosion resistance coated metal sheet having excellent chipping resistance, having an electron beam-curable coating layer as an upper layer. 2. An electron beam-curable coating film coating layer comprising: A: an oligo (meth) acrylate having at least two (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 500 or less; 10 parts by weight, B: 90 to 10 parts by weight of a polyhydric alcohol (meth) acrylate containing two or more (meth) acryloyl groups in a molecule and having a (meth) acryloyl group equivalent of 150 or less,
And C: 0.5 to 20 parts by weight of a silica extender, D: 1 to 20 parts by weight of a polymer having a molecular weight of 5,000 or more, and A, B, C, D 2. The coated metal sheet according to claim 1, comprising: E: 1 to 40 parts by weight of glass powder with respect to 100 parts by weight of the mixture of the components. 3. The method according to claim 1, wherein the base metal plate has a Cr content of 13 wt% or more.
The coated metal sheet according to claim 1, which is a stainless steel sheet containing: 4. A tunnel interior plate comprising the painted metal plate according to claim 1.