JPH0218708B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) The present invention relates to a method for producing a coated metal plate and a coating composition in which the coating film is cured with an electron beam. (Prior art) Generally, paints are soluble in solvents, and the solvent is scattered at room temperature or by heating, or by heating, ultraviolet rays, infrared rays, etc., a crosslinking/curing reaction is caused to cause insolubilization to form a cured coating. shall be. However, with these methods, it is difficult to obtain a product that does not undergo changes such as swelling or discoloration when exposed to any organic solvent, and has sufficient stain resistance against magic ink, whiteboard markers, and the like. The inventors of the present application have already applied a paint consisting of oligo(meth)acrylate and polyhydric alcohol(meth)acryloyl to a metal plate, as seen in Japanese Patent Application Laid-Open No. 126036/1982, and applied it using an electron beam curing method. By curing the coating film, we succeeded in obtaining a coated metal plate with high hardness, excellent solvent resistance, and stain resistance. However, it has been found that the above resin system has two problems when applied to actual industrial lines. In other words, dust tends to adhere after painting and before electron beam irradiation.Electron beam irradiation is performed in an inert gas, but due to subtle changes in the atmosphere, the painted surface after curing tends to have "uneven gloss". There are two points, and it has been found that when surface appearance is particularly important, there are problems in terms of production and commercial value. I will discuss these two points in more detail. Regarding the section, the resin system of JP-A-50-126036 is coated with an industrial coating method, such as a curtain flow coater, and after the coated plate is irradiated with an electric wire,
When looking at the charging property, it became clear that it was extremely high. This chargeability measurement is performed using the Static tester manufactured by Shishido Shokai Co., Ltd.
This was measured using an honestmeter Type S-4104, which is a constant voltage (here
8KV) is applied to the sample, and after the application is stopped, the attenuation of the electrostatic voltage on the sample is continuously measured to determine the time it takes for the electrostatic voltage to decrease by half (half-life). In this case, it can be determined that the longer the half-life, the more easily the substance is charged. Here, measurements are made on the coated board after curing. In reality, it would be appropriate to measure the painted board before curing, but the inventors have found a correlation between the chargeability of the painted board after curing and the amount of dust that adheres after painting until it hardens. It was experimentally discovered that there is a relationship. In other words, we have experimentally clarified the fact that when the half-life mentioned above is set to 100 seconds or less, preferably 80 seconds or less, dust is less likely to adhere. I will talk about the section. Coating film curing by electron beam irradiation is usually carried out in an inert gas atmosphere, and the same applies to the manufacturing method for the coated metal plate of the present invention. A simple conceptual diagram is shown in Figure 1. That is, an uncured painted plate 2 runs in the direction of the arrow on conveyors 1 ₁ to 1 ₁₂ (in the case of coils, it becomes a roller), and an inert gas atmosphere is supplied from inert gas supply pipes 4 ₁ to 4 ₇ . It is hardened by the electron beam that enters the inside and is taken out from the electron beam irradiation window 5 located at the bottom of the scan horn 6. Incidentally, in order to check the oxygen concentration, atmospheric gas is constantly sent to the analyzer from the gas sampling tube 3 for the oxygen analyzer. In this case, an inert gas control device as shown in FIG. 1 is installed under the irradiation window of the electron beam irradiation device to supply inert gas and lower the oxygen concentration.
A practical problem in industrial production lines is that when a painted board enters an inert gas control device, it brings in oxygen, and from a microscopic perspective, the oxygen concentration near the surface of the painted board varies depending on the location. This means that the oxygen concentration in the atmosphere is different from that captured in . Therefore, it is presumed that this is the cause, but the product after curing will have "uneven gloss".
There are even cases where the gloss value was 80 in some areas and 40 in others within the same painted board. As a solution, it was found that inert gas replacement should be performed at a low and uniform oxygen concentration, but this is technically difficult, and furthermore, from an operational cost perspective, it is necessary to reduce the amount of inert gas used as much as possible. Since this is more desirable, we tried to solve the problem from the perspective of paint. (Structure of the present invention) As a result of various studies, the present inventors have found that adding an extender pigment is effective in preventing "uneven luster". Among extender pigments, those that are even slightly effective include silica, white carbon, diatomaceous earth, calcium carbonate, clay, asbestin, and talc, but among these, silica is particularly effective. There are various types of silica, and the parameters that express their characteristics are, for example,
Examples include PH, average particle diameter, bulk specific gravity (g/cc), surface area (m ² /g), etc., but experiments have shown that oil absorption (g/100g) has the most influence for the purpose of the present invention. was found. In other words, the oil absorption amount
It has been found that adding 150g/100g or more of silica can prevent "uneven gloss" on the painted board after curing. Estimating the reason for this from a phenomenon perspective, the outermost surface area of a board coated with a paint containing silica, which has a large oil absorption capacity, is harder to the touch than one without silica. It is in a state close to a solid and is physically difficult to adsorb and dissolve oxygen, or chemically, the addition of these silica-based extender pigments makes it difficult to adsorb and dissolve, preventing uneven luster after curing. This may be due to other reasons, but in any case, we have experimentally discovered that adding a silica-based extender pigment can prevent uneven luster. In addition, when a silica-based extender pigment is added to polyester (meth)acrylate and polyhydric alcohol (meth)acrylate, which are other components in the present invention, the half-life can be shortened even in terms of the charging property mentioned above. We have also discovered that this can be done. The reason why it is difficult for dirt and dust to adhere is because this half-life can be shortened, and because the painted surface is harder (closer to a solid) than when no silica-based extender pigment is added.
It is presumed from experimental facts that it is physically difficult for them to adhere. As described above, the silica-based extender pigment of the present invention makes it difficult for "dirt" and "dust" to adhere to polyester (meth)acrylate and polyhydric alcohol (meth)acrylate, and also reduces "unevenness" during irradiation. ”, but naturally, depending on the amount added, it can also have the effect of eliminating luster. Next, we will discuss the effects of polymers with a molecular weight of 5000 or more. This makes the effect of the silica-based extender pigment more pronounced in the present invention, and further improves the coating properties when coating with an industrial coating machine. In this case, the polymer is solid or close to solid from the standpoint of improving paintability.
Its viscosity is 100,000 centipoise or more. Furthermore, when considering other parameters, this is limited to solid cases, but if the elongation of the resin is 100
% or more, the glass transition point of the resin is 40
The temperature is preferably 30°C or lower, preferably 30°C or lower.
In the present invention, which has a silica-based extender pigment as an essential component, if a system without the addition of a polymer is applied with an industrial coating machine, the paintability of this system will be poor due to lack of viscosity, so the addition of a polymer is an essential condition. It is. The polyester (meth)acrylate used in the present invention uses a polyester skeleton in the main chain,
The product obtained by esterifying this with (meth)acrylic acid is used in the present invention because it needs to have a sufficient crosslinked network structure, so two (meth)acryloyl groups are added to each molecule. It is preferable to include at least 1, more preferably 3 or more. Furthermore, since the crosslinking density must be sufficiently high, the (meth)acryloyl group equivalent is preferably 500 or less, more preferably 400 or less. In this case, two or more of these polyester (meth)acrylates may be used in combination as long as they satisfy the requirements of the present invention described above. Let's talk about this ingredient in more detail. Polyester (meth)acrylate with a polyester skeleton in the main chain is made of polyhydric alcohol and polycarboxylic acid, and the polyester has a hydroxyl group at the end, and is reacted with (meth)acrylic acid or its derivatives. (meth)acryloyl group is introduced. Here, we will further discuss the synthetic raw materials forming the polyester skeleton. That is, as dihydric alcohols, alkylene glycol types include ethylene glycol, propylene glycol, chloropropylene glycol,
Butanediol (1,3- or 1,4- or 2,3-), 3-methylpentanediol, 2,
1,4-cyclohexane as alicyclic glycol type such as 2-diethylpropanediol, pentamethylene glycol, 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol, hexamethylene diol, etc. diol, cyclohexane-1,4-dimethanol,
Hydrogenated bisphenol A and other polyalkylene glycol types include diethylene glycol, triethylene glycol, polyethylene glycol,
Dipropylene glycol, polypropylene glycol, polytetramethylene glycol polybutadiene diol, etc., as well as aromatic glycol types such as 2,2'-bis(4-hydroxyphenylpropane) (also known as bisphenol A), bis(4-hydroxyphenylpropane), and bis(4-hydroxyphenylpropane). Glycols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as enyl)methane (also known as bisphenol F), 4,4'-dihydroxyphenyl, hydroquinone, and resorcinol. can give. Examples of tri- to tetrahydric alcohols include glycerin, trimethylolmethane, trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol, 1,
2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-2,3,4-butanetriol, 2-methyl-2,3,4-butanetriol, 2-methyl-1,2, Alkantetraols such as 3-butanetriol, 2-ethyl-1,2,3-butanetriol, 2-3,4-hexanetriol, pentamethylene glycol, erythritol, pentaerythritol, toilette, 1,2,3, 4 pentanetetrol, 2,3,4,5 hexanetetrol, 2,
5-dimethyl-2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, 3
-Hexene-1,2,5,6-tetrol, 3-hexene-1,2,5,6-tetrol, etc. As ether group-containing aliphatic triols, alkylene oxides (ethylene oxide, propylene oxide, ether group-containing aliphatic tetraols, such as tetraols obtained by adding alkylene oxide to erythritol, pentaerythritol, etc.; and aromatic triols, such as tetraols obtained by adding alkylene oxide to pyrogallol. Examples include triols obtained by addition. Examples of carboxylic acids include chain or branched divalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, itaconic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, dodecanoic acid,
Methylene glutaric acid, methylmaleic acid, methylsuccinic acid, dodecenylsuccinic acid, etc., as alicyclic dicarboxylic acids, tetrahydrophthalic acid, hexahydrophthalic acid, 6-methyltetrahydrophthalic acid, 6-methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid Acid, endoisopropylidene tetrahydrophthalic acid, 1,4,5,6,
7,7-hexachloro-endo-5-norbornene-2,3-dicarboxylic acid (also known as hetts acid), 1,
4,5,6,7,7-hexapromo-endo-5
-norbornene-2,3-dicarboxylic acid, cyclohexane, 1,4-dicarboxylic acid, etc.; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, tetrabromophthalic acid, or anhydrides thereof; Things can be given. Specific examples of polyester oligomers having two (meth)acryloyl groups include di(meth)acryloyl groups of maleic acid and ethylene glycol;
Acrylate, di(meth)acrylate of polyester with maleic acid and diethylene glycol,
Di(meth)acrylate of polyester diol of adipic acid and diethylene glycol, di(meth)acrylate of polyester diol of tetrahydrophthalic acid and diethylene glycol, di(meth)acrylate of polyester diol of tetrahydrophthalic acid and propylene glycol,
Tetrahydrophthalic acid and butanediol (1,3
- or di(meth)acrylate of polyester diol with 1,4-), di(meth)acrylate of polyester diol with tetrahydrophthalic acid and 1,6-hexanediol, polyester with tetrahydrophthalic acid and neopentyl glycol Di(meth)acrylate of diol, di(meth)acrylate of polyester diol of tetrahydrophthalic acid and 1,4-cyclohexanediol, di(meth)acrylate of polyester diol of phthalic acid and diethylene glycol, phthalic acid and neopentyl glycol and di(meth)acrylates of polyester diols. Among these polyester oligomers, tetrahydrophthalic acid or adipic acid and 3 carbon atoms
A polyester oligomer having a di(meth)acrylate structure of a polyester diol with ~6 alkylene glycols or cycloalkylene glycols, with a number average molecular weight of 350 to 800 and a number average molecular weight of 180 to 400 per (meth)acryloyl group. are particularly suitable for the purposes of the invention. Further, specific examples of polyester oligomers having two or more (meth)acryloyl groups include tetra(meth)acrylate, penta(meth)acrylate, hexa(meth)acrylate of polyester polyol of adipic acid and pentaerythritol. ) acrylate, tetramethacrylate, penta(meth) of polyester polyol with tetrahydrophthalic acid and pentaerythritol
Acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol with phthalic acid and pentaerythritol, penta(meth)acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol with maleic acid and pentaerythritol Acrylate, penta(meth)acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol with adipic acid and trimethylolpropane, penta(meth)acrylate, hexa(meth)acrylate, tetrahydrophthalic acid and trimethylolpropane Tetra(meth)acrylate of polyester polyol with, penta(meth)acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol with tetrahydrophthalic acid and glycerin, penta(meth)acrylate, hexa(meth)acrylate, etc. can be given. Among these polyester oligomers, a polyester polyol with adipic acid or tetrahydrophthalic acid and trimethylolpropane, or pentaerythritol has a structure of tetra(meth)acrylate, penta(meth)acrylate or hexa(meth)acrylate with a number average Polyester oligomers having a molecular weight of 550 to 2000 and a number average molecular weight per (meth)acryloyl group of 100 to 350 are suitable for the purpose of the present invention. The polyhydric alcohol (meth)acrylate referred to in the present invention refers to one in which a (meth)acryloyl group is introduced by reacting (meth)acrylic acid with the terminal hydroxyl group of a polyhydric alcohol, and when combined with a polyester (meth)acrylate. This serves to obtain extremely high crosslinking density. For this purpose, it is necessary to use a product that contains two or more (meth)acryloyl groups in one molecule and has a (meth)acryloyl group equivalent.
It is 150 or less, more preferably about 130 or more. In this case, a mixture of the aforementioned polyhydric alcohol (meth)acrylates may be used. The polyhydric alcohol referred to here refers to the following. That is, as dihydric alcohols, alkylene glycol types include ethylene glycol, propylene glycol, chloropropylene glycol,
Butanediol (1,3- or 1,4- or 2,3-), 3-methylpentanediol, 2,
1,4-cyclohexane as alicyclic glycol type such as 2-diethylpropanediol, pentamethylene glycol, 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol, hexamethylene diol, etc. diol, cyclohexane-1,4-dimethanol,
Hydrogenated bisphenol A and other polyalkylene glycol types include diethylene glycol, triethylene glycol, polyethylene glycol,
Dipropylene glycol, polypropylene glycol, polytetramethylene glycol, polybutadiene diol, etc., and aromatic glycol types such as 2,2'-bis(4-hydroxyphenylpropane) (also known as bisphenol A), bis(4-
Glycol obtained by adding orkylene oxide (ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as hydroxyphenyl)methane (also known as bisphenol F), 4,4'-dihydroxyphenyl, hydroquinone, and resorcinol. Examples include the following. Examples of trihydric or higher alcohols include glycerin, trimethylolmethane, trimethylolethane, trimethylolpropane, 1,2,6-hexanetriol 1,
2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-2,3,4-butanetriol, 2-methyl-2,3,4-butanetriol, 2-methyl-1,2, Alkantetraols such as 3-butanetriol, 2-ethyl-1,2,3-butanetriol, 2-3,4-hexanetriol, pentamethylene glycol, erythritol, pentaerythritol, dipentaerythritol, toilette, 1,
2,3,4 pentanetetrol, 2,3,4,5
Hexanetetrol, 2,5-dimethyl-2,
3,4,5-hexanetetrol, 1,2,3,
5-pentanetetrol, 3-hexene-1,
2,5,6 tetrol, 3 hexyne-1,2,
Ether group-containing aliphatic tetraols such as 5,6-tetrol include triols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to glycerin, trimethylolpropane, etc. Examples of the ols include tetraols obtained by adding alkylene oxide to erythritol, pentaerythritol, etc., and aromatic triols include triols obtained by adding alkylene oxide to pyrogallol. Among these, those having a (meth)acryloyl group equivalent of 120 or less are particularly preferred. Furthermore, it is important to note that the addition of a polymer is an essential condition of the present invention, which, as mentioned earlier, results in a decrease in performance. In order to prevent this performance deterioration, it is particularly important that the average (meth)acryloyl group equivalent is in the range of 100 to 200 in the system in which polyester (meth)acrylate and polyhydric alcohol (meth)acrylate are mixed. What is also favorable is the point made clear in the present invention, where it is essential to add a polymer. Here, we will discuss the blending ratio of polyester (meth)acrylate and polyhydric alcohol (meth)acrylate. Polyester (meth)acrylate/Polyhydric alcohol (meth)acrylate 1/
A range of 0.5 to 1/10 (weight ratio) is desirable. This is because polyester (meth)acrylate alone does not increase the crosslinking density sufficiently, so polyhydric alcohol (meth)acrylate is added to improve the crosslinking density, but in order to meet the purpose of the present invention, The minimum amount must be 0.5 or more per 1 part of polyester (meth)acrylate.
Here, the upper limit of polyhydric alcohol (meth)acrylate is 10 to 1 to polyester (meth)acrylate, but if more than this is added and the coating film is cured, the , cracks will increase if the paint film is cracked or scratched. Therefore, it is preferably 10 or less. In addition, the amount of polyhydric alcohol (meth)acrylate added can be increased compared to the case of JP-A-50-126036, and the above-mentioned trouble can be prevented by adding a polymer with a molecular weight of 5000 or more, which will be described later. It is from. Next, I will talk about extender pigments. Although the materials that meet the purpose of the present invention have been mentioned above, silica is particularly effective, and has an oil absorption of 150 g/100 g or more. Regarding the amount, the total amount of polyester (meth)acrylate, polyhydric alcohol (meth)acrylate, and polymer referred to in the present invention
Preferably, the amount of silica is 0.5 parts or more per 100 parts.
Addition of 1.0 part or more satisfies the purpose of the present invention. Specifically, the names are: Fuji Davison Chemical's "Thyroid" series, Mizusawa Chemical's "Mizukasil" series, "Mildon" series, Tokuyama Soda's "Rerex series",
“Tokuseal” series, “Fine Seal” series, “Carplex” series manufactured by Shionogi Pharmaceuticals, “Aerosil” series manufactured by Nippon Aerosil,
etc. can be mentioned. In addition, in the present invention, a mixed system of two or more types of extender pigments may be used. Next, the polymer having a molecular weight of 5000 or more to be added as the fourth component in the present invention will be described. As long as the above-mentioned requirements are met, acrylic, polyester, urethane, epoxy, polyamide, melamine, silicone, alkyd, etc., and modified products or combinations thereof may be used.
Acrylic, polyester, and urethane alone or in combination are particularly effective in terms of both coating film performance and paintability. in this case,
It may be a mixture of two or more of the same type of resin. Here, the constituent components of the acrylic polymer will be described, but the present invention is not limited thereto. For example, acrylic acid, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate,
Isobutyl acrylate, n-amyl acrylate, n-hexyl acrylate, n-acrylate
-acrylic acid alkyl esters such as octyl;
2-chloroethyl acrylate, 3-acrylic acid
- Alkyl acrylate halides such as chloropropyl, OH group-containing esters of acrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate,
α-alkyl acrylic acid alkyl esters such as n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, n-octyl methacrylate, lauryl methacrylate, α - α-halogenated acrylic esters such as methyl chloroacrylate and α-ethyl chloroacrylate, α-alkyl acrylic acid halogenated alkyl esters such as 2-chloroethyl methacrylate, and 3-chloropropyl methacrylate, and methacrylic acid. 2-Hydroxylethyl, 2-hydroxylpropyl methacrylate, methacrylic acid-
α-alkyl acrylate esters with an OH group such as 1-chloro-2-hydroxyethyl, acrylic monomers containing epoxy groups such as glycidyl acrylate, glycidyl methacrylate, dimethylaminoethyl methacrylate, dimethylaminoethyl methacrylate, diethylaminoethyl Monomers having amino groups such as methacrylate and diethylaminoethyl acrylate are included. As component A of the present invention, one or more of these acrylic monomers may be used in an amount of 50% of the total monomers.
It is preferable to use mol % or more, and any remaining monomer can be used as long as it can be copolymerized. Next, the constituent components of polyester will be described, but they are not limited to those exemplified below. That is, the alkylene glycol type alcohols include ethylene glycol, dipropylene glycol, chloropropylene glycol, butanediol (1,3- or 1,4- or 2,3-), 3-methylpentanediol, 2,
1,4-cyclohexane as alicyclic glycol type such as 2-diethylpropanediol, pentamethylene glycol, 1,6-hexanediol, heptamethylene glycol, octamethylene glycol, nonamethylene glycol, neopentyl glycol, hexamethylene diol, etc. diol, cyclohexane-1,4-dimethanol,
Hydrogenated bisphenol A and other polyalkylene glycol types include diethylene glycol, triethylene glycol, polyethylene glycol,
Dipropylene glycol, polypropylene glycol, polytetramethylene glycol polybutadiene diol, etc., as well as aromatic glycol types such as 2,2'-bis(4-hydroxyphenylpropane) (also known as bisphenol A), bis(4-hydroxyphenylpropane), and bis(4-hydroxyphenylpropane). Glycols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to phenols such as enyl)methane (also known as bisphenol F), 4,4'-dihydroxyphenyl, hydroquinone, and resorcinol. can give. Furthermore, as alkantriol types, glycerin, trimethylolmethane, trimethylolethane, trimethylolpropane, 1,2,6-
Hexanetriol 1,2,3-butanetriol, 1,2,3-pentanetriol, 2-methyl-2,3,4-butanetriol, 2-methyl-2,3,4-butanetriol, 2-methyl-
1,2,3-butanetriol, 2-ethyl-
Alkanetraols such as 1,2,3-butanetriol, 2-3,4-hexanetriol, pentamethylene glycol, erythritol, pentaerythritol, toilette, 1,
2,3,4 pentanetetrol, 2,3,4,5
Hexanetetrol, 2,5-dimethyl-2,
3,4,5-hexanetetrol, 1,2,3,
5-pentanetetrol, 3-hexene-1,
2,5,6 tetrol, 3 hexyne-1,2,
Ether group-containing aliphatic tetraols such as ether group-containing aliphatic triols such as 5,6-tetrol include triols obtained by adding alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) to glycerin, trimethylolpropane, etc. Examples of the ols include tetraols obtained by adding alkylene oxide to erythritol, pentaerythritol, etc., and aromatic triols include triols obtained by adding alkylene oxide to pyrogallol. Examples of carboxylic acids include chain or branched divalent carboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, itaconic acid, maleic acid, fumaric acid, adipic acid, sebacic acid, dodecanoic acid,
Methylene glutaric acid, methylmaleic acid, methylsuccinic acid, dodecenylsuccinic acid, etc., as alicyclic dicarboxylic acids, tetrahydrophthalic acid, hexahydrophthalic acid, 6-methyltetrahydrophthalic acid, 6-methylhexahydrophthalic acid, endomethylenetetrahydrophthalic acid Acid, endoisopropylidene tetrahydrophthalic acid, 1,4,5,6,
7,7-hexachloro-endo-5-norbornene-2,3-dicarboxylic acid (also known as hetts acid), 1,
4,5,6,7,7-hexabromo-endo-5
-norbornene-2,3-dicarboxylic acid, cyclohexane, 1,4-dicarboxylic acid, etc.; aromatic dicarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, tetrachlorophthalic acid, tetrabromophthalic acid, or anhydrides thereof; Things can be given. Next, let's talk about polyurethane. This may be of any type, such as urethanized oil type, moisture curing type, block type, catalyst curing type, or two-component type. Here, I will talk about isocyanates. The constituent units of aliphatic diisocyanate are:
Ethane, propane, butene, thiodiethyl, pentane, β-methylbutane, hexane, ω, ω′ dipropyl ether, thiodipropyl, heptane,
2,2 dimethylpentane, 3 methoxyhexane,
Aliphatic diisocyanates with cyclic groups such as octane, 2,2,4 trimethylpentane, nonane, decane, 3-butoxyhexane, 1,4 butylene glycol dipropyl ether ω, ω′, undecane, dodecane, thiodihexyl, etc. The structural units include ω,ω' diisocyanate 1,3 dimethylbenzole, ω,ω' diisocyanate 1,2 dimethylbenzole, ω,ω' diisocyanate 1,
2 dimethylcyclohexane, ω, ω' diisocyanate 1,4 cyclohexane, ω, ω' diisocyanate 1,4 diethylbenzole, ω, ω' diisocyanate 1,4 dimethylnaphthalene, 1-
Examples of aromatic diisocyanates include ω-methylisocyanate-2-ω-n-pyropropyruisocyanato-3,5-dimethylcyclohexane, ω,ω′-diisocyanato-n-propyl-biphenyl, etc. Diisocyanate, 3,3' bitrylene 4,4' diisocyanate, diphenylmethane 4,4' diisocyanate, 3,3' dimethylphenylmethane 4,4' diisocyanate, 2,4 tolylene diisocyanate dimer , other structural units of aromatic isocyanate include 1,3 phenylene, 1,4 phenylene, 1 methylbenzole 2,4, 1,3 dimethylbenzole 2,4, 1 ethylbenzole 2,4, 1 isopropylbenzole, diisopropyl Examples of naphthalene isocyanates such as penzole include naphthalene 1, 4, 1,
1′ dinaphthyl 2,2′, etc., biphenyl isocyanates include biphenyl 2,4′, 3,3′ dimethylbiphenyl 4,4′, 2nitrobiphenyl 4,4′,
The constituent units of diisocyanate of di, triphenylmethane include diphenylmethane 4,4',
2,2'dimethyldiphenylmethane 4,4', etc., 1-methylbenzole 2,4,6, 1,3,5 as the structural unit of tri- and tetraisocyanate
Trimethylbenzole 2,4,6, naphthalene 1,3,7, biphenyl 2,4,4', diphenylmethane 2,4,4', 3-methyldiphenylmethane 4,6,4', triphenylmethane 4,4' , 4'', diphenyl 4,4' diisocyanate N-carbamic acid chloride, etc. Other isocyanates include organic phosphorus isocyanate, fluorinated isocyanate, sulfonyl isocyanate, etc. These isocyanates An appropriate molecular group or atomic group may be optionally introduced into the skeleton, or it may be modified. These contain RCOOH, H ₂ S, RSH, HCN, HCl,
HOH, HOH, ROH, R(OH) ₂ , NH ₃ , RNH ₂ ,
R( _NH2 ) ₂ , _{RSO2NH2 ,}

[Formula] NaHSO ₃ , RCONH ₂ , NH ₂ C ₂ H ₄ OH,
Active hydrogen compounds such as _R2CNOH , _{C6H6 - AlCl3} ,
That is, the activity (or reactivity) of hydroxyl groups, carboxyl groups, amino groups, active methylene groups, etc.
It is a compound with a hydrogen group. For example, as polyester, HOOC・
R′・CO・O・R・O・CO・R′・COOH or
It is represented by HO, R, O, CO, R', CO, O, R, OH, and the units already mentioned can be used as its constituent units. Polyether is represented by HO・R・O・R・O...R・O・R・OH, and its constituent units are:
Ethylene oxide, propylene oxide, trimethylene oxide, butylene oxide, α
-Manufactured by ring-opening polymerization or copolymerization of methyltrimethylene oxide, 3,3'-dimethyltrimethylene oxide, trimethylene oxide, tetrahydrofuran, dioxane, cyclic ether of dioxyamine, etc. (polyether glycol or (also called polyoxyalkylene glycol). Other active hydrogen compounds include polyols obtained by hydrogenation of carbon monoxide-olefin copolymers, formaldehyde-modified polymers thereof, phenolaldehyde polycondensates, aldehyde-polyol polycondensates, and polycondensates of bisphenol A and epichlorohydrin. Polythioethers, polyesteramides obtained from dicarboxylic acids and diamines or amino alcohols, etc. are used alone or in combination with other polymers. Above, the structural units of polyacrylic, polyester, and polyurethane have been described. What is important here is that, although not mentioned above, these polymers may have a C=C bond that is active to electron beams in the molecular skeleton, in the side chain, or at the end of the molecule. It is. Regarding the amount of C=C, when introducing it into a polymer, it is difficult to introduce a large amount because it is difficult to synthesize, but conceptually, the higher the amount as possible, the better the stain resistance and chemical resistance. Improves hardness. However, the silica-based extender pigments mentioned later,
The number of C═C bonds in the molecule may be 0 as long as the relationship between the amount of the polymer added and the average double bond equivalent of other components is within the range. Here, we will define the performance goals of the present invention, which are coated metal plates with high hardness, excellent chemical resistance, and excellent stain resistance. Excellent stain resistance is achieved using the standard test method, in which magic ink, curry, mustard, lipstick, crayons, colored pencils, ink, whiskey, and other daily necessities or substances commonly used in stain resistance tests are left for 24 hours after application. In addition, it can be erased without leaving any traces using benzine alcohol, water, other chemicals that dissolve contaminants, cloth, gauze, etc., and even if letters or figures are written with a whiteboard marker, they can be erased with an eraser. Regarding chemical resistance, 5% hydrochloric acid, acetic acid,
Add acids such as sulfuric acid, citric acid, nitric acid, 5% caustic soda, alkalis such as ammonia, ethanol, benzine, methyl ethyl ketone, acetone, xylene, ethyl acetate, and other organic solvents to the coating film for approximately 1 hour.
After dropping the cc and placing a cover glass (e.g. a watch glass) over it to prevent scattering, leave it for 24 hours.
No changes can be observed. In terms of hardness, it is 7H or higher on the pencil hardness scale. Here, polyester (meth)acrylate,
This article describes the quantitative relationship between polyhydric alcohol (meth)acrylate, silica-based extender pigments, and polymers with a molecular weight of 5000 or more. The above two components are necessary to maintain coating film performance such as excellent stain resistance, chemical resistance, and hardness. As a result of various studies, it has been found that although this method is effective in improving the performance of the coating film, it is rather a negative factor with respect to the objective coating performance of the present invention. Further, although the polymer itself improves paintability, it is a negative factor in terms of coating film performance. This is because if the molecule has as many (meth)acryloyl groups that are active to electron beams, for example to the same extent as polyester (meth)acrylate or polyhydric alcohol (meth)acrylate, then Although this is not a negative result, although something like this is theoretically possible, it is actually impossible to synthesize. Its limits are unclear, but for example, look at Ford Motor Co.'s Special Publication No. 15630.
There are about three (meth)acryloyl groups in a molecular weight of 1000, and the double bond equivalent is about 330 or more. Here, a quantitative relationship is needed. As a result of various studies, the inventors of the present application discovered that a close relationship exists between the (meth)acryloyl group equivalent and the amount of silica-based extender pigment and polymer added. When the average (meth)acryloyl group equivalent of polyester (meth)acrylate and polyhydric alcohol (meth)acrylate is x, the amount of silica extender added is y (%), and the amount of polymer added is z (%), x>0 ,z≧
At 0.1 -2/130x+3≦y+z≦-2/130x+12 (However, polyester (meth)acrylate,
Compared to the total amount of resin such as polyhydric alcohol (meth)acrylate and polymer, silica-based extender pigments
0.5 part or more), the purpose of the present invention is met, including the coating performance defined above. The four essential components have been described above, but in addition to these, plasticizers, pigments, diluent-like monofunctional monomers, oligomers, solvents, etc. can be added. Examples of plasticizers include dioctyl adipate,
Dioctyl phthalate, dibutyl phthalate, dioctyl sebacate, triisooctyl trimellitate, tri-2-ethylhexyl trimellitate, pyromellitic acid tetraester, 2,2-diphenolic acid ester, epoxidized linoleic acid,
Epoxidized soybean oil lacquer type resins and others may be mentioned, but they should be kept to the minimum necessary for imparting workability to the coated board, and 0 is preferable when using a flat board, for example, a white board. The pigment may be used for rust prevention, coloring, and other purposes. Regarding solvents, xylene, butyl acetate, methyl cellosolve, ethyl cellosolve, toluene,
Isopropyl alcohol, butyl alcohol, ethyl acetate, anone, morpholin, methyl ethyl ketone, acetone, olefinic solvents, etc.
One or more of them may be used as a mixed solvent. In the pre-painted steel sheet of the present invention, the original sheet may be a cut or coiled iron sheet, an electrogalvanized steel sheet, a hot-dip galvanized steel sheet, or a chemical conversion treatment such as chromic acid or phosphoric acid treatment that has already been applied to these sheets in the steel sheet manufacturing process. Aluminum plates, stainless steel plates, steel plates, etc. can be used; however, considering the balance of surface appearance of the coated product, cost, corrosion resistance, etc., (electro) galvanized steel plates are one of the most suitable. In addition, in the production of the present invention, the metal plate can be pretreated, if necessary, by various known methods. For treated steel plates, it is sufficient to simply pre-treat them with a cleaning treatment, and for those that have not been chemically treated, apply a chemical conversion treatment agent depending on the material, such as phosphate treatment. Examples include chromic acid treatment agents, composite oxide film treatment agents, and heavy metal replacement treatment agents. Further, it is better to use a primer between the original plate and the resin composition layer of the present invention.
It shows better performance when a primer that has good adhesion to the base plate, has rust prevention properties, and has good adhesion to the top coat resin composition is applied between the base plate and the resin composition of the present invention. . The composition of this primer may be any epoxy, modified epoxy, vinylphenol, epoxy acrylic, polyester, etc., and the curing method of the primer may be any of heat, electron beam, ultraviolet rays, infrared rays, and ultra-far infrared rays. The primer can be applied by any conventional method such as natural roll coating, reverse roll coating, curtain flow coating, or spray coating, and the thickness of the coating film is 1.
It is desirable that the thickness is about 10μ, preferably about 2 to 5μ. As curing conditions, appropriate conditions are used depending on the respective curing method or resin components. Furthermore, depending on the coating method, film thickness, and formulation conditions, a solvent may be added to the coating resin composition of the present invention in order to obtain an appropriate coating viscosity. It is desirable to scatter the solvent before irradiating the electron beam. The conditions for scattering this solvent are different from the conditions in the conventional method of producing coated metal plates using a thermosetting method, in which the paint is hardened by baking at a very high temperature, for example, close to 300°C, for a long period of time. That's fine. For example, dry hot air temperature 150℃,
A plate temperature of 120℃ or less is sufficient. Alternatively, if the setting is sufficient, the solvent may be scattered by leaving it alone, and heating may not be necessary. To explain the electron beam irradiation method after coating the resin composition in the present invention, the irradiation device is as follows:
Any known device can be used, such as a DC high-voltage electron gun or an electron beam irradiation device with an acceleration mechanism, and devices with accelerating voltages ranging from 100 kilovolts to several megavolts are currently being developed. However, in the present invention, a device of several hundred kilovolts is sufficient. Regarding the output current,
From the viewpoint of high-speed productivity, a large current is particularly desirable, and a current of 100 milliamperes/one accelerating tube or more is desirable. Regarding the appropriate irradiation dose in the present invention, approximately
A rough guideline is about 0.5 to 10 Mrad, but 1 to
It shows good performance at about 5 Mrad, although it depends on the resin composition. In general, when a coating film is cured by electron beam irradiation, it is known that oxygen acts as a polymerization inhibitor, so it is preferable to block this.
It is desirable to perform electron beam irradiation in an atmosphere substituted with an inert gas or the like. In particular, when the surface hardness, stain resistance/chemical resistance, water resistance, and weather resistance of the coating film are important, the above is of great significance. Examples of the inert gas include nitrogen gas, carbon dioxide, argon, helium, krypton, etc., but it is sufficient that the oxygen concentration during irradiation is about 1% or less, preferably about 0.1% or less. . In order to prevent the coating from being scratched on the pre-coated steel sheet of the present invention during loading, transporting, and processing of the coated product on the user's side, it is desirable to bond a protective film under pressure and heat. Examples of protective films include polyethylene, vinyl chloride,
Examples include polypropylene, polyester, and acrylic. Example 1 A: Oligomer with a condensation molar ratio of phthalic acid, trimethylolpropane, and acrylic acid of approximately 1:2:4 (acryloyl group equivalent: approximately 155), B: trimethylolpropane trimethacrylate (acryloyl group equivalent: approximately 110), C: silica Copolymerization molar ratio of D. ethyl acrylate, methyl methacrylate, hydroxyethyl methacrylate, and acrylic acid is 70:24:3:3. The weight ratio of acrylic copolymer (number average molecular weight approximately 20,000), A, B, C, D and titanium white is
A paint was prepared by adding 30% xylene (vs. the former) to a system consisting of 18.8:18.8:1.8:4.4:44.2. This paint system was applied to an electrogalvanized steel plate (1500 x 600 x 0.6 mm) coated with 2μ of thermosetting epoxy primer using a curtain flow coater (effective width 60 cm). The painted surface was beautiful, and there was hardly any visible dirt. This coated plate was sprayed with solvent under conditions such that the plate temperature reached 80°C with hot air at 150°C (about 50 seconds in the oven), and then cured with an electron beam. Curing conditions: voltage 300 KV, current 25 mA/60 cm, dose 3 Mrad, oxygen concentration 150 ppm during irradiation.
Chemical properties tests and coating film tests such as hardness were conducted. (Stain resistance) Magic ink (red, blue), curry, mustard,
Lipstick, crayons, colored pencils, and ink were applied to the painted board, and after 24 hours, they were wiped off easily with gauze soaked in ethanol, leaving no trace. Also, even if I wrote on it with a whiteboard marker made by Pilot Co., Ltd., I could completely erase it with an eraser. (Chemical resistance) Approximately 1 c.c. of 5% hydrochloric acid, acetic acid, sulfuric acid, citric acid, nitric acid, caustic soda, ammonia, etc., as well as ethanol, benzine, methyl ethyl ketone, acetone, xylene, and ethyl acetate, are dropped onto the coating film. After covering the shiso with a watch glass and leaving it for 24 hours to prevent scattering, washing with water and blowing with air, visual judgment was made, but no change was observed in the coating film. (Pencil hardness 8H) Reference example 1 In order to measure the chargeability of this coated plate, it was charged with an applied voltage of 8KV (charged voltage 17mV) using a Static honestmeter Type S-4104 manufactured by Shishido Shokai, and then the application was stopped and the charge was halved. period, that is, the charging voltage is
When the time to reach 8.5mV was measured, it was approximately 60 seconds. Comparative Example 1 In Example 1, the paint system excluding the C component was
It was created under exactly the same conditions as before. The performance after curing was almost the same as in Example 1, but dirt and dust were noticeable (visual observation: 2 pieces/10
When measuring the gloss within the same board, the highest value was 82 and the lowest value was 58, and even at first glance it seemed that the gloss was uneven. Furthermore, when the charging characteristics of this sample were measured, the half-life was 105 seconds. Comparative Example 2 In Comparative Example 1, a paint system was prepared under exactly the same conditions as before except for components C and D. The performance after curing was almost the same as in Example 1, but the surface of the painted board was not smooth and had "streaks", and dirt and dust were very noticeable (visual observation:
When measuring the gloss within the same board (4 pieces/10 x 10 cm), the highest value was 87 and the lowest value was 38, and at first glance it seemed that the gloss was noticeably uneven. Furthermore, when we measured the charging characteristics of this sample, we found that
The half-life was approximately 210 seconds. Example 2 A Polyester acrylate with a condensation molar ratio of adipic acid, pentaerythritol, and acrylic acid of approximately 1:2:4 (acryloyl group equivalent: 122) B: Diethylene glycol dimethacrylate (acryloyl group equivalent: 121), C: Silica-based extender pigment (Mizusawa) Mizukashiru NP-8 manufactured by Kagaku Kogyo, oil absorption 260g/100g) D Polyester with a condensation molar ratio of terephthalic acid, sebacic acid, and ethylene glycol of approximately 3:7:10 (molecular weight 15000) A, B, C, and D components A paint was prepared under exactly the same conditions as in Example 1, and after painting, the painted board was irradiated with an electron beam. The coating film performance and paintability were exactly the same as in Example 1,
The results were excellent. Example 3 A The condensation molar ratio of tetrahydrophthalic acid, trimethylolpropane, and acrylic acid is approximately 1:2:4
Polyester acrylate (acryloyl group equivalent: approx. 155) B Tetramethylolmethane tetraacrylate (acryloyl group equivalent: 88) C Silica-based extender pigment (Shionogi Pharmaceutical Carplex #100, oil absorption 220g/100g) D Condensation of isophthalic acid, sebacic acid, and diethylene glycol A polyester with a molar ratio of approximately 2:8:10 (molecular weight approximately 9000), a weight ratio of A, B, C, D and titanium white,
Approximately 20% xylene is added to a system consisting of 20:20:2:5:45.
% (compared to the former) and used as paint. A coated plate was prepared by curing this paint system with an electron beam under exactly the same conditions as in Example 1 (only the oxygen concentration during irradiation was different, here 500 ppm). The paintability and film performance showed the same results as in Example 1. Example 4 In place of component A of Example 3, an oligoacrylate with a condensation molar ratio of phthalic acid, glycerin, and acrylic acid of 1:2:4 (acryloyl group equivalent: approximately 130)
Even with the use of Example 1, the same results as in Example 1 were obtained in terms of paintability and film performance. Example 5 Even when half the amount of component A in Example 3 was replaced with component A in Example 2, the paintability and film performance were the same as in Example 3. Example 6 In Example 1, half of the C component was replaced with Example 2.
Even when the C component was replaced, the paintability and film performance were the same as in Example 1.

[Brief explanation of drawings]

FIG. 1 is an explanatory cross-sectional view of an electron beam irradiation device. 1 ₁ ~ ₁₂ ... Roll conveyor (or roller), 2 ... Painted plate, 3 ... Gas sampling tube for oxygen analyzer, 4 ₁ - ₇ ... Inert gas supply pipe, 5 ... Electron beam irradiation window, 6...Scyanhorn.

Claims (1)

[Claims] 1. Contains two or more (meth)acryloyl groups in one molecule, and has a (meth)acryloyl group equivalent of 500
The following polyester (meth)acrylates contain two or more (meth)acryloyl groups in one molecule,
And polyhydric alcohol (meth)acrylate with (meth)acryloyl group equivalent of 150 or less, oil absorption
150g/100g or more of silica-based extender pigment, molecular weight
1. A method for producing a coated metal plate, which comprises applying a paint containing a polymer of 5,000 or more as an essential component to an object to be coated, and curing it with an electron beam in an inert gas with an oxygen concentration of 1% or less. 2 Contains two or more (meth)acryloyl groups in one molecule and has a (meth)acryloyl group equivalent of 500
The following polyester (meth)acrylates contain two or more (meth)acryloyl groups in one molecule,
And polyhydric alcohol (meth)acrylate with (meth)acryloyl group equivalent of 150 or less, oil absorption
150g/100g or more of silica-based extender pigment, molecular weight
Electron beam curable coating composition containing 5000 or more polymers as essential components.