JP3416260B2 - Painted metal sheet excellent in weather resistance and corrosion resistance and method for producing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention provides a flexible thermosetting material for the lowermost layer.
It has a coating film and one or more layers of electron beam hardness with good weather resistance.
Ionized acrylic poly (meth) acrylate
Permeation resistance is 500M ohm · cm² Corrosion resistance
Painted metal with excellent weather resistance, high hardness and high stain resistance
The present invention relates to a plate and a manufacturing method thereof.

[0002]

2. Description of the Related Art With respect to a coated metal sheet excellent in high hardness and high stain resistance and a method for producing the same, the technique disclosed in Japanese Patent Publication No. 4-45342 has already been put into practical use. The disclosed technique is a metal plate coated with an electron beam cured coating film.

[0003]

However, the above-mentioned coated metal sheet is used in a harsh environment, such as a place facing the coast or a lot of traffic, a large annual temperature difference, and a road freezing prevention. Corrosion resistance may be insufficient in a tunnel or the like in which chlorides (NaCl, CaCl ₂ ) are sprayed.

As a result of various studies on the cause of the deterioration of the corrosion resistance, it was found that microscopic cracks occur in a hard coating film and grow due to the large shrinkage of the coating film in the region where the difference in temperature is large.

It has also been found that in the tunnel, repeated micro-vibration of the road due to the passage of vehicles induces cracking of the hard coating film, and hits stones to cause cracking of the coating film.

Furthermore, recently, a case where a coated metal plate is used on a road outside a tunnel has recently occurred.

In this case, the coating film disclosed in Japanese Examined Patent Publication No. 4-45342 has insufficient weather resistance (chalking after 1000 hours of sunshine weatherometer test).
It has been found.

The present invention is a coated metal sheet which is resistant to the above-mentioned factors that induce corrosion and has sufficient corrosion resistance (for example, 5 years or more), and which is excellent in high weather resistance, high hardness, high stain resistance, and antiglare. And a method for manufacturing the same.

[0009]

In order to solve the above-mentioned problems, a coated metal sheet having excellent weather resistance and corrosion resistance according to the present invention is provided.
The lowermost layer of the metal plate is provided with a coating film having a glass transition point of 65 ° C. or lower and a coating film elongation of 30% or more, which is heat-cured into a solid or a state close to a solid. One or more layers comprising a (meth) acrylate and a composition containing two or more (meth) acryloyl groups in one molecule and a polyhydric alcohol (meth) acrylate having a (meth) acryloyl group equivalent of 150 or less as an essential component And the upper layer is cured by electron beam irradiation to have an ion permeation resistance of 500 M ohm · cm ² or more.

The manufacturing method is as follows: the glass transition point of the coating film is 65 ° C. or lower and the elongation of the coating film is 30% on the lowermost layer of the metal plate.
A coating having the above properties is applied, and a solid or nearly solid coating is formed by heat curing, and acrylic poly (meth) acrylate is formed on the upper layer thereof and two or more (meth) acryloyl groups in one molecule. And a (meth) acryloyl group equivalent of 150 or less, a coating film comprising a composition containing a polyhydric alcohol (meth) acrylate of 150 or less as an essential component is applied, and the upper layer is irradiated with an electron beam to be cured. It is characterized in that the ion permeation resistance is 500 M ohm · cm ² or more.

In the above-mentioned manufacturing method, it is effective to further heat the plate at a plate temperature of 200 ° C. or higher after electron beam irradiation when the curing degree of the lowermost thermosetting coating film is insufficient.

Further, as a coated metal plate, 13% or more of Cr is used.
The application of a stainless steel plate containing P is effective for ensuring corrosion resistance.

[0013]

The present invention will be described in detail below.

First, in the present invention, the glass transition point of the coating film is 65 ° C. or lower, preferably 40 ° C. or lower, in the lowermost layer of the metal plate.
A flexible thermosetting coating film having a coating film elongation of 30% or more, preferably 50% or more is provided.

By providing such a flexible coating film, cracking of the coating film due to differences in temperature and temperature, repeated vibration of the road, flying stones, etc. can be prevented, and the corrosion resistance can be remarkably improved. Unless the glass transition point and elongation are specified as described above, cracking of the coating film cannot be sufficiently prevented.

Examples of the thermosetting coating resin used in the present invention include polyester, acryl, polyurethane, epoxy resin and the like, and the former two are preferable.

As the polyester, linear polyester is desirable, and the molecular weight is preferably 5,000 or more. The following substances can be listed as the substances constituting this.

That is, as the alcohol, alkylene glycol type ethylene glycol, propylene glycol, chloropropylene glycol, butanediol (1,3- or 1,4- or 2,3-), 3-methylpentanediol, 2,2-diethylpropanediol, pentamethylene glycol, 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol, hexamethylene diol, etc. -Cyclohexanediol, cyclohexane-1,4-dimethanol, hydrogenated bisphenol A, etc., as polyalkylene glycol type, such as diethylene glycol, triethylene glycol, polyethylene glycol, diethylene glycol Ropylene glycol, polypropylene glycol, polytetramethylene glycol, polybutadiene diol, etc., and as the aromatic glycol type, 2,2'-bis (4-hydroxyphenyl) propane (also known as bisphenol A), bis (4-hydroxyphenyl) methane (Also known as bisphenol F), 4,4'-
Examples thereof include glycols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as dihydroxyphenyl, hydroquinone and resorcin.

As the carboxylic acid, a chain or branched 2
As carboxylic acid, oxalic acid, malonic acid, succinic acid,
Glutaric acid, itaconic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, dotecanoic acid, methyleneglutaric acid, methylmaleic acid, methylsuccinic acid, dodecenylsuccinic acid, etc. as aliphatic dicarboxylic acids, tetrahydrophthalic acid, hexahydrophthalic acid , 6-methyltetrahydrophthalic acid, 6-methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid, endoisopropylidenetetrahydrophthalic acid, 1,4,5,6,7,7-
Hexachloro-endo-5-norbornene-2,3-dicarboxylic acid (also called het acid), 1,4,5,6,7,7
-Hexabromo-endo-5-norbornene-2,3-
Dicarboxylic acids, cyclohexane, 1,4-dicarboxylic acid and the like, and aromatic dicarboxylic acids include phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, tetrabromophthalic acid, and their anhydrides.

Examples of the thermosetting acrylic resin include acrylic acid and α-substituted acrylates as follows, but are not limited thereto.

For example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, acrylic Acid-n-octyl and other acrylic acid alkyl esters, acrylic acid-2-chloroethyl, acrylic acid-3-chloropropyl and other alkyl halide acrylates, acrylic acid-2-hydroxyethyl, acrylic acid-2-hydroxypropyl, etc. OH-containing acrylic ester having OH group, methyl methacrylate, ethyl methacrylate, methacrylic acid-n-propyl, isopropyl methacrylate, methacrylic acid-n-butyl, isobutyl methacrylate, methacrylic acid-n-amyl, methacrylic acid Acid-n-octyl Such as lauryl methacrylate α-
Α-, such as alkyl acrylate alkyl ester, α-methyl chloroacrylate, α-ethyl chloroacrylate
Α of halogen acrylic acid ester, methacrylic acid-2-chloroethyl, methacrylic acid-3-chloropropyl, etc.
-Alkyl acrylic acid halogenated alkyl ester, methacrylic acid-2-hydroxyethyl, methacrylic acid-2
-Hydroxypropyl, methacrylic acid-1-chloro-2
-Α-alkyl acrylates having an OH group such as hydroxyethyl, and acrylic monomers such as glycidyl methacrylate.

Also in this case, the molecular weight is preferably 5000 or more.

Next, in the present invention, the coating of the lowermost layer is heat-cured to a state close to that of a solid so that when one or more layers are overcoated thereon, it is completely cured from the viewpoint of the adhesion between the lower layer and the upper layer. Because it must not be.

Next, on the lowermost layer, a polyvalent poly (meth) acrylate containing acrylic poly (meth) acrylate and two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 150 or less. At least one layer of a coating film composed of a composition containing alcohol (meth) acrylate as an essential component is applied.

The purpose of providing such a coating film is to improve the lowermost layer because it has poor scratch resistance and poor stain resistance. Further, even if a pinhole is formed in the lowermost coating film, it is crushed by applying multiple layers.

The acrylic poly (meth) acrylate used in the present invention is one obtained by esterification reaction of (meth) acrylic acid with an acrylic skeleton in the main chain, and 2 or more per 1000 molecular weight, Desirably, it has 3 or more (meth) acryloyl groups.

In order to obtain sufficient weather resistance, it is preferable to apply one or more electron beam-curable acrylic poly (meth) acrylates containing 1 mol or more of unsaturated carbon double bond per 1000 molecular weight.

Further details regarding this component will be given. The main chain is composed of the following monomers such as acrylic acid or α-substituted acrylate.

Acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, Acrylic acid-n-octyl and other acrylic acid alkyl esters, acrylic acid-2-chloroethyl, acrylic acid-3-chloropropyl and other alkyl halide acrylates, acrylic acid-2-hydroxyethyl, acrylic acid-2-hydroxypropyl OH group-containing acrylic acid ester having OH group such as, methyl methacrylate, ethyl methacrylate, methacrylate-n-propyl, isopropyl methacrylate, methacrylate-n-butyl, isobutyl methacrylate, methacrylate-n-amyl, Methacrylic acid-n-octane Le, α, such as lauryl methacrylate
-Alkyl acrylate alkyl ester, α-methyl chloroacrylate, α-ethyl chloroacrylate, etc.
Α-alkyl acrylic acid halogenated alkyl ester such as halogen acrylic acid ester, methacrylic acid-2-chloroethyl, methacrylic acid-3-chloropropyl,
Methacrylic acid-2-hydroxyethyl, methacrylic acid-
2-hydroxypropyl, methacrylic acid-1-chloro-
Included are α-alkyl acrylates having an OH group such as 2-hydroxyethyl, and acrylic monomers such as glycidyl methacrylate.

Also in this case, the molecular weight is preferably 5000 or more.

Next, the polyhydric alcohol (meth) acrylate refers to a polyhydric alcohol in which a (meth) acrylic acid is reacted with a hydroxyl group at a terminal of the polyhydric alcohol to introduce a (meth) acryloyl group, and is referred to as an oligo (meth) acrylate. Combined, it plays a role in obtaining an extremely high crosslinking density.

For this purpose, one molecule contains two or more (meth) acryloyl groups, and the (meth) acryloyl group equivalent is preferably 150 or less, more preferably about 130 or less.

In this case, a mixture of the above-mentioned polyhydric alcohol (meth) acrylate may be used. The polyhydric alcohol mentioned here means the following.

That is, as the dihydric alcohol, ethylene glycol, propylene glycol, chloropropylene glycol, butanediol (1,3-or 1,4- or 2,3-) in the form of alkylene glycol type, 3
-Methylpentanediol, 2,2-diethylpropanediol, pentamethylene glycol, 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol, hexamethylenediol, etc., alicyclic glycol type As 1,4-cyclohexanediol, cyclohexane-1,4-dimethanol, hydrogenated bisphenol A, etc., as a polyalkylene glycol type, diethylene glycol, triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol 2,2'-bis (4-hydroxyphenyl) propane (also known as bisphenol) Enol A), bis (4-hydroxyphenyl) methane (also known as bisphenol F), 4,
Examples thereof include glycols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as 4′-dihydroxyphenyl, hydroquinone and resorcin.

As the trihydric or higher alcohol, alkanetriol type glycerin, trimethylolmethane, trimethylolethane, trimethylolpropane,
1,2,6-hexanetriol, 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-2,3,4-butanetriol, 2-ethyl-
2,3,4-butanetriol, 2-methyl-1,2,
Alkanetetraols such as 3-butanetriol, 2-ethyl-1,2,3-butanetriol, 2,3,4-hexanetriol, pentamethylene glycol, etc. as erythritol, pentaerythritol, dipentaerythritol, toilet, 1, 2,3,4-pentane tetrol, 2,3,4,5-hexane tetrol,
2,5-Dimethyl-2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, 3-hexene-1,2,5,6-tetrol, 3-hexyne-1,
Ether group-containing fatty acids such as triols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to glycerin, trimethylolpropane, etc. as ether group-containing aliphatic triols such as 2,5,6-tetrol Examples of the group tetraol include tetraol obtained by adding alkylene oxide to erythritol or pentaerythritol, and aromatic triol include triol obtained by adding alkylene oxide to pyrogallol.

Of these, those having a (meth) acryloyl group equivalent of 150 or less are particularly preferable as a result.

The thickness of the coating film containing the oligo (meth) acrylate as an essential component is at least 15 μm or more, preferably 25 μm or more.

The number of layers to be overcoated is 1 or more, preferably 2 or more, more preferably 3 or more, and the thickness of each layer is preferably 2 μm or more and 10 μm or less.

The reason for this is that if it is too thin, the effect of compensating for coating film defects (pinholes) is weakened, and if it is too thick, the curability becomes large after electron beam curing and the shrinkage stress also becomes large, resulting in film cracking.
This is because delamination or the like is likely to occur.

Although the resin component of the composition constituting the present invention has been described above, a pigment, a solvent, a polymer and the like can be added in addition to the above, if necessary.

Inorganic color pigments include red iron oxide, yellow iron oxide, chrome vermillion, chromium oxide and carbon black, and organic color pigments include quinacridone, isoindolinone, indanthrene blue, phthalocyanine blue and phthalocyanine green. Can be given.

Other examples include titanium white, calcium carbonate, barium sulfate, alumina, silica and the like. It is also added to the overprinting varnish as needed.

Examples of the solvent include xylene, butyl acetate, cyclohexanone, methyl cellosolve, ethyl cellosolve, morpholine and olefin solvents.

As the polymer, which is sometimes used to improve the coating property, polyester, acrylic,
Urethane, epoxy, etc. are used. In this case, if the amount is too large, the performance will be deteriorated, so an appropriate amount is added.

A coating film having high hardness and stain resistance can be obtained with the above composition, but antiglare property is required depending on the use.

In this case, various measures are conceivable, but it has been found that a method of giving smooth geometric unevenness to the outermost surface layer of the coating film is preferable.

That is, although the extender pigment which is usually used can obtain the antiglare effect, the stain resistance is lowered.

As a method for providing a surface with smooth geometrical irregularities, the addition of glass or resin beads serves the purpose of the present invention. Specifically, the following are listed.

As the glass beads, soda-lime glass or low-alkali glass having a particle diameter of 2 μm to 70 μm is preferable depending on the required unevenness.

The soda-lime glass is very small in amount due to alkali or water, but it may elute when used for a long period of time, and it lowers the ion permeation resistance, so a low-alkali glass is preferable.

Examples of the resin beads include relatively hard beads such as melamine, styrene acryl, Teflon, polyacrylonitrile, etc. From the viewpoint of hardness, crosslinked acrylic resin beads are preferable, and depending on the required unevenness. A particle size of 2 μm to 100 μm is selected.

In addition, beads of nylon, urethane, etc. are also used depending on the use where high hardness (8H) is not required. If importance is attached to corrosion resistance, resin beads are more preferable.

Next, the ion permeation resistance of the coating film will be described. Focusing on the fact that corrosion is an electrochemical process,
The electrochemical permeation impedance measurement in an aqueous solution is performed, and the ion permeation resistance value of the coating film can be determined from the analysis of the result.

This value is the corrosive ionic species (C
_{^{l -, SO 4 2-, NO}} 3 -, the penetration into the interior of such), which the coating is quantitatively indicating the degree of how may suppressed how, as the measuring method Sho 60- Japanese Patent Laid-Open No. 1000075, Japanese Patent Laid-Open No. 62-229056, Japanese Patent Laid-Open No. 63-
It has been established as published in 126242.

As a device, a coating film deterioration degree diagnostic sensor (R, commercially available from Nittetsu Technos (Sagamihara City, Kanagawa Prefecture)
If ST Model 3) is used, the above value can be easily obtained by performing area correction.

The reason for limiting the ion permeation resistance value of the coating film to 500 M ohm · cm ² or more in the present invention is as follows.

In various coating systems, coating metal plates having different coating film ion permeation resistance values were prepared by changing the film thickness and the number of times of coating, and the time until the occurrence of point rust in the complex corrosion test of these samples was determined. It was measured.

In this composite test, 0.01N sulfuric acid,
Spray 0.01N nitric acid and 3% calcium chloride mixed aqueous solution at 40 degrees Celsius for 3 hours, then dry at 60 degrees Celsius for 3 hours, and continue at 60 degrees Celsius and 95% humidity for 6 hours. The cycle of doing was repeated.

As a result of the test, when applying the coating system of the present invention to stainless steel, in order to secure sufficient corrosion resistance, 500
It has been deduced that it is necessary to set it to be M ohm · cm ² or more, and it is desirable to be 1.5 G ohm · cm ² or more if possible.

In order to obtain the above resistance value, it is considered to select an appropriate resin structure and increase the film thickness.

Regarding the former, it is preferable that polar functional groups such as --COOH, --OH, --NH ₂ and the like are not present as much as possible in the resin structure of the cured coating film.

For this purpose, for the lowermost layer, one having few polar functional groups in the resin skeleton is selected, or even if there are many polar functional groups, reheating after electron beam irradiation to further promote the crosslinking reaction, etc. From the viewpoint of crosslink density, the latter is preferable.

With regard to oligo (meth) acrylates, those in which 85% or more, preferably 95% or more, of polar functional groups contained in the molecule of the monomer of the synthetic raw material are reacted are considered to be the main point of the present invention. It is a thing.

On the basis of such a concept, the above resistance value can be obtained by coating two or more layers with a coating thickness of 30 to 40 μm or more. However, even in this case, as described above, a multilayer coating film is obtained. Is better.

In this case, the film thickness of the lowermost layer is at least 20 μm or more, and the film thickness of the coating film overlaid thereon is at least 1 μm or more, preferably 3 μm or more, and the number of layers to be applied is preferably two or more. However, the total film thickness is preferably 70 μm or less.

The reason for this is that if it is too thick, the internal stress of the coating film becomes large and cracks may occur during long-term use, and it is economical.

Next, as the metal plate used in the present invention, Cr is used.
It is desirable to apply a stainless steel plate having a content of 13% or more.

Commercially available SUS410 (13% Cr), S
US430 (18% Cr), YUS180 (19Cr-
0.4Cu-0.4Nb-Low C-Low N), and YUS
220 (22Cr-0.8Mo-0.4Nb-0.5C
Using u) as a base material, a coating system having an ion permeation resistance value of 500 M ohm · cm ² is applied by the coating system according to claim 1, and the same complex corrosion test as described above is performed to measure the time until rust formation. did.

As a result, SUS410 generated spot rust after 1400 hours, whereas SUS430 produced 540 points of rust.
0 hours, YUS180 7900 hours, YUS220
In the case of 24,000 hours, the corrosion resistance was significantly improved with the increase of the respective contents of the base material chromium and molybdenum (SUS is a symbol specified in Japanese Industrial Standards, YUS is Nippon Steel Co., Ltd.). Trademark attached to stainless steel products).

Up to now, as a coated stainless steel having a life of more than 10 years in a tunnel which is a severe corrosive environment,
From the experience so far, 500 in the above-mentioned complex corrosion test
It has been said that 0 hour or more is desirable, and from this, it is desirable that the base material stainless contains 18% or more of Cr.

Here, by combining a coating system having a high coating film ion permeation resistance value and a base material with a further increased amount of corrosion-resistant alloy elements, it is possible to design and manufacture coated stainless steel with even higher corrosion resistance. Needless to say.

As a method of further coating more than one layer on the ground coat which has been cured in such a manner that it can be repeatedly coated, a roll coat method used for coating, a gravure offset method used for printing, a silk screen method, etc. are used. When coating two or more layers, the same method may be repeated or a combination with another method may be used. The ground coat and the overcoat layer may be colored or patterned if necessary.

The electron beam irradiation method in the above manufacturing method of the present invention will be described.

The irradiation device may be, for example, a scanning system, a curtain beam system, a broad beam system or the like, and the required acceleration voltage is selected depending on the coating film thickness. The electron beam irradiation atmosphere is replaced with an inert gas or the like.

In the present invention, a protective film made of vinyl chloride, polyethylene, polypropylene or the like may be laminated on the coating film.

If a stainless steel plate having a Cr content of 13% or more is used as the base metal plate, further high corrosion resistance can be obtained.

Next, a method for producing the coated metal plate of the present invention will be described.

In the coated metal plate of the present invention, it is preferable to use the stainless steel plate as described above as the original plate, but this may be a cut plate shape or a coil shape.

These are those that have been degreased in the steel plate manufacturing process, and those that have been subjected to a chemical conversion treatment such as chromic acid, phosphoric acid, and a silane coupling agent, or the above-mentioned treatment in the pretreatment process of the coating process. What has been given is used.

Further, it is better to use a primer between this original plate and the layer of the composition of the present invention. As the composition of this primer, any material such as epoxy, modified epoxy, epoxy acrylic, polyester, epoxy polyester, etc. may be used as long as it has good adhesion to the stainless steel plate.

The coating method is a usual method such as a roll coater, and the curing method may be any of heat, electron beam, ultraviolet ray and the like. The coating film thickness is about 1 to 10 μm, preferably about 2 to 8 μm.

As a method for applying the ground coat in the present invention, a coating method such as roll coating or curtain flow coating is used. The film thickness is as described above.

Here, the thermal curing of the ground coat will be described. The resin system of the present invention used for this is one which is heat-cured so that it can be overcoated.

The plate temperature during heat curing is 120 ° C. to 200 ° C.
A temperature of about 20 seconds to 3 minutes is suitable for this purpose.

The lowermost layer of the metal plate is cured to a solid state or a state close to a solid state before the electron beam irradiation, but is heated again after the electron beam irradiation in order to completely cure.

The temperature is the temperature at which the condensation reaction occurs,
The final plate temperature needs to be 200 ° C. or higher.

[0087]

【Example】

[0088]

Example 1 (Test No. 1) First, the following three types of coating materials were prepared as coating materials to be applied to the base material.

Layer A (ground coat): glass transition point of soft acrylic paint coating; -5 ° C., coating elongation; 300%,
Coating hardness; F

Layer B (first layer on Layer A): acrylic acid
Ethyl acrylate / 2-hydroxyethyl acrylate / glycidyl methacrylate copolymer (number average molecular weight: about 1
20,000, amount of dimeric bond: 2 pieces / 1,000 molecular weight) 1
A coating material was prepared by adding 120 parts of titanium oxide to 00 parts.

Layer C; (second layer on Layer A) 100 parts of titanium oxide was added to 100 parts of the polyacrylic copolymer used in Layer B to form a coating.

Layer D (third layer on Layer A); 100 parts of the polyacrylic copolymer used in Layer A was mixed with 1 part of trimethylolpropane trimethacrylate (equal to about 100 methacrylic groups).
A composition was prepared by adding 00 parts.

Next, a ferritic stainless steel plate (19Cr) coated with a thermosetting epoxy primer (3 μm) was used.
-0.4Cu-0.4Nb) layer A in dry film thickness of 30μ
It was applied with a curtain flow coater (manufactured by Iwata Co., Ltd.) so as to be m, and made into a soft solid under the conditions of a plate temperature of 140 ° C.

On this soft solid coating film, layer B was applied by a gravure offset printing machine to a dry film thickness of 5 μm, and layers C and D were further dried by a gravure offset printing machine to a dry film thickness of 5 μm. It was applied so that

After that, the three layers were simultaneously cured by electron beam irradiation. The condition is 160 mA / 1.2 m, the irradiation dose is 9
Mad and the oxygen concentration during irradiation were 150 ppm. The coated steel sheet was reheated to a plate temperature of 230 ° C. to completely cure the ground coat layer.

[0096]

Comparative Example 1 (Test No. 2) Layer A (ground coat layer) was made of hard polyester having a glass transition point of the coating film of 70 ° C. and elongation of the coating film of 10%, and layers B, C and D were formed thereon. A coated plate was prepared under the same conditions as in Example 1.

[0097]

[Comparative Example 2] (Test No. 3) 40 μm was applied only to layer A (layers B, C,
D was not applied), and the same treatment as in Example 1 was carried out to obtain a coated plate.

[0098]

Comparative Example 3 (Test No. 4) Example 1. The coated original plate in Example 1 was a hot-dip galvanized steel sheet (area weight: 180 g / cm ² ), and the coated plate was prepared under exactly the same conditions.

[0099]

Example 2 (Test No. 5) A glass transition point of 40 was added to the layer A of Example 1.
Tests were carried out by using a soft polyester paint having a coating film elongation of 150% at a temperature of ° C and using the same conditions as in Example 1 under other conditions.

[0100]

Comparative Example 4 (Test No. 6) Example 1. In Layer C of, the acrylic acid / ethyl acrylate / dihydroxyethyl acrylate / glycidyl methacrylate copolymer (number average molecular weight:
The number of double bonds of about 10,000) was set to 1 / 1,000 molecular weight), and 120 parts of titanium oxide was added to 100 parts of this to prepare a coating material. Other conditions are as in Example 1. A coated plate was prepared in the same manner as.

[0101]

Comparative Example 5 (Test No. 7) Example 1. Acrylic acid, which is layer D of
Ethyl acrylate / 2-hydroxyethyl acrylate / glycidyl methacrylate copolymer (number average molecular weight: about 1
Polyester having a condensation molar ratio of tetrahydrophthalic acid and trimethylolpropane / acrylic acid of 1: 2: 4 (acryloyl group equivalent of about 155) instead of 10,000, double bond amount: 2 pieces / 1,000 molecular weight) Other conditions were used in Example 1. A coated plate was prepared in the same manner as.

The following tests were carried out on the above coated plate. Pencil hardness test based on JISK5400.

Difficulty in removing after applying magic ink (red, black, blue) and ink (red, black, blue) and immersing in ethanol after 24 hours (⊚: complete removal, ∘: slight marks) Remaining, △: Remaining clear).

So-called chemical resistance after immersion in 5% hydrochloric acid and caustic soda for 240 hours (⊚: no change, ∘: slight mark, Δ: clear mark).

The corrosion resistance test was carried out according to the test method of Muto et al. (Procedures of the 37th Corrosion and Anticorrosion Symposium, P. 353, 1990). In this test method, one cycle consists of 5% NaCl
Spraying- (35 ° C; 4 hours) -Drying (60 ° C; 2 hours)-
It is a rigorous test in which humidity (45 ° C; relative humidity 95%, 2 hours) is 8 hours, and it is a severe test method. It is a test method that assumes a temperature difference when spraying chloride on the road to prevent freezing. Can be said.

Furthermore, assuming a microcrack that cannot be visually confirmed, a DuPont impact test (300 g, 20 c
The degree of red rust was also observed for the samples subjected to m) and those added to the test sample (⊚: no change, ∘: 1% or less red rust
Δ: 1 to 5 red rust% red rust, ×: 5 red rust% or more red rust).

Measurement of the ion permeation resistance of the coating film using a coating film deterioration diagnostic device RST Model-3 manufactured by Nippon Steel Technos Co., Ltd.

As the sunshine weatherometer, the Suga Test Instruments manufactured Ducycle Sunshine Super Long Life Weatherometer WEL-SUN-DC is used.
The degree of choking of the coating film was observed by using (◎: no change, ◯: slightly choking, Δ: fairly choking, ×: bad choking).

The evaluation results are shown in Table 1. The coated plate according to the present invention (Test No. 1) has extremely excellent corrosion resistance,
Pencil hardness, stain resistance and chemical resistance are also shown in Comparative Example 2 (Test NO.
It is improved compared to 3).

Hardness, stain resistance and chemical resistance are improved by E
It seems that the effect of the B cured coating layers B, C and D is obtained.

Further, it is considered that the corrosion resistance is excellent because the pinholes in the coating film are extremely phenomenon due to the multi-layer coating and the ion permeation resistance is increased.

[0112] Microcracks may be generated in the ground coat in the processed part of the system using the soft acrylic as the ground coat (test No. 2), or it may be dry or wet during the test.
It is thought that the corrosion resistance is not good because microcracks are promoted by the combination of the two, probably because of the temperature difference.

When a hot-dip galvanized steel sheet was used as the original sheet (Test No. 4), corrosion resistance and red rust occurred.

On the other hand, when the crosslink density is low (test NO.
Also in 6), sufficient performance is not obtained.

Further, instead of the acrylic copolymer,
Even when polyester is used (Test No. 7), the weather resistance is not good.

[0116]

[Table 1]

[0117]

According to the present invention, the ion permeation resistance is 500.
It is possible to obtain a coated metal plate having M ohm · cm ² or more, which is excellent in corrosion resistance and weather resistance, and has high hardness and high stain resistance.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI B32B 15/08 102 B32B 15/08 102Z 27/30 27/30 A C09D 4/02 C09D 4/02 5/00 5/00 5/08 5 / 08 (72) Inventor Hiroshi Kanai 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Co., Ltd. Technology Development Division (72) Inventor Hiroshi Kihira 20-1 Shintomi, Futtsu-shi, Chiba Nippon Steel Co., Ltd. Inside the Technology Development Headquarters (72) Yutaka Tadokoro 20-1 Shintomi, Futtsu City, Chiba Shin Nippon Steel Co., Ltd. Inside the Technology Development Headquarters (72) Inventor Katsuya Kusari 4013 Nakatsu, Aikawa-cho, Kanagawa Prefecture Dainippon Elio Co., Ltd. (72) Inventor Toshihiro Kano 4013 Nakatsu, Aikawa-cho, Aiko-gun, Kanagawa Dainippon Elio Co., Ltd. (72) Masato Horikiri 450 Aoto-cho, Midori-ku, Yokohama The Intec Co., Ltd. (72) Inventor, Tomoaki Mukaiyama 450 Aoto-cho, Midori-ku, Yokohama The inktech Co., Ltd. (56) Reference JP-A-6-47341 (JP, A) JP-A-60-40169 ( P, A) JP flat 2-242863 (JP, A) (58 ) investigated the field (Int.Cl. ^7, DB name) B05D 7/14 B05D 3/06 101 B05D 7/24 302 B32B 15/08 B32B 15/08 102 B32B 27/30 C09D 4/02 C09D 5/00 C09D 5/08

Claims (7)

(57) [Claims] 1. A lowermost layer of a metal plate is provided with a coating film having a glass transition point of 65 ° C. or lower and a coating film elongation of 30% or more, which is heat-cured into a solid or near solid state.
A composition in which an acrylic poly (meth) acrylate and a polyhydric alcohol (meth) acrylate containing two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 150 or less are essential components. A coated metal sheet having excellent weather resistance and corrosion resistance, characterized in that at least one coating film consisting of the above is provided and the upper layer is cured by electron beam irradiation to have an ion permeation resistance of 500 M ohm · cm ² or more. 2. A coated metal plate having excellent weather resistance and corrosion resistance, which comprises the acrylic poly (meth) acrylate according to claim 1 and contains 2 mol or more of double bonds per 1000 molecular weight. 3. A coated metal plate having excellent weather resistance and corrosion resistance according to claim 1, wherein the metal plate is a stainless steel plate containing 13% or more of Cr. 4. A coating film having a glass transition point of 65 ° C. or less and a coating film elongation of 30% or more is applied to the lowermost layer of a metal plate, and is applied in a solid or near solid state by heat curing. A film is formed, and an acrylic poly (meth) acrylate and a polyhydric alcohol (meth) acrylate containing two or more (meth) acryloyl groups in one molecule and having a (meth) acryloyl group equivalent of 150 or less are indispensable as an upper layer. After coating one or more layers of the composition as a component, the upper layer is irradiated with an electron beam to be cured to have an ion permeation resistance of 50.
A method for producing a coated metal sheet having excellent weather resistance and corrosion resistance, which is characterized in that it is 0 M ohm · cm ² or more. 5. The method for producing a coated metal plate according to claim 4, which has 2 mol or more of double bonds per 1000 molecular weight and is excellent in weather resistance and corrosion resistance. 6. The method for producing a coated metal plate having excellent weather resistance and corrosion resistance according to claim 4, wherein the metal plate is a stainless steel plate containing 13% or more of Cr. 7. The method for producing a coated metal plate having excellent weather resistance and corrosion resistance according to claim 4, further comprising heating at a plate temperature of 200 ° C. or higher after electron beam irradiation.