JPS6118583B2 - - Google Patents

Description

[Detailed description of the invention]

TECHNICAL FIELD The present invention relates to a pre-coated steel sheet mainly for indoor use which has excellent workability. In recent years, due to reasons such as non-pollution, labor saving, and process saving,
Manufacturers of home appliances, interior building materials, office equipment, vehicles, etc. are increasingly demanding pre-painted steel sheets, avoiding so-called post-coating, which involves painting after processing. At Millside, we are making every effort to meet these demands, but we are developing a pre-coat that has the same hardness, gloss, stain resistance and chemical resistance as post-coat, and is highly workable, such as withstanding impact over-the-air bending. It is difficult to manufacture steel plates. Therefore, when a manufacturer as mentioned above adopts a prepainted steel sheet in a limited field, the current situation is that one of the above characteristics is sacrificed. For example, if a thermosetting hard acrylic coating material is used, gloss, stain resistance, and chemical resistance are relatively good, but processability is not as good, and if a thermosetting PVC coating material is used, hardness and Processability is relatively good, but there is almost no gloss, and stain resistance, chemical resistance, etc. are not good. As described above, as long as the currently used thermosetting method is used as a coating film curing method, the current situation is that it is difficult to reach the performance range of conventional post coating materials. In order to overcome this problem, the present inventors used an electron beam irradiation method that has many features such as non-pollution, high performance, high-speed production, low cost, and non-heating. Shocking OT that was said to be there
It has high workability that can withstand bending, and also has other properties such as gloss, hardness, water resistance, stain/chemical resistance, corrosion resistance,
We have been trying to produce a pre-coated steel sheet with good aesthetic properties, and we have finally succeeded. That is, the present invention comprises: A: 100 parts of an acrylic copolymer mainly composed of acrylic acid, α-substituted acrylic acid, or a derivative thereof having a number average molecular weight in the range of 10,000 to 800,000; B: a dihydric alcohol; Dicarboxylic acid and (meth)
A polyester obtained by esterifying acrylic acid, having a number average molecular weight per (meth)acryloyl group of 400 or less and containing 1.5 to 2.0 (meth)acryloyl groups per molecule. 20 to 200 parts of oligomer, C: Number average molecular weight per (meth)acryloyl group obtained by esterifying three components: trivalent or tetrahydric alcohol, divalent carboxylic acid, and (meth)acrylic acid. is 350 or less, and there is a (meth)acryloyl group in one molecule.
Polyester oligomer containing 3.5 to 6.0, 1.0 to 1.0 to a mixture of both components A and B
This relates to a highly workable precoated steel sheet coated with a radiation-curable coating composition obtained by containing 30% of the composition as a main component and cured by electron beam. The main components will be described in detail below. The constituents of component A include the following, but are 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,
Acrylic acid-2-chloroethyl, acrylic acid-3
- Alkyl acrylic halides such as chloropropyl, OH group-containing acrylic acid esters such as 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, methacrylic acid, methyl methacrylate, ethyl methacrylate,
α-Alkylacrylic 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 OH groups 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 mitacrylate 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 monomers can be used as long as they can be copolymerized. It also includes polymers obtained by polymerizing an acrylic monomer as a main component in the coexistence of a non-acrylic polymer that is soluble in a polymerization solvent. Examples of such non-acrylic polymers include solvent-soluble polyurethane, ethylene-acetic acid copolymer, and solvent-soluble polyester. Among these polymers, polyester in particular often has good overall performance due to its compatibility with components B and C. Furthermore, polymers in which polymerizable double bonds are introduced into the side chains or both ends of the main chain by utilizing the reactivity of the functional groups are also possible. However, in the case of polymers having such unsaturated groups, in combination with component B and component C, the crosslinking density of the cured coating film becomes too high and the coating film becomes too hard, making it difficult to maintain good processability. Therefore, the monomers that leave double bonds should account for less than 10 mole percent of the total monomers. The copolymer preferably has a relatively large molecular weight of 10,000 to 800,000. The number molecular weight is
When it is less than 10,000, the processing adhesion of the coating film is insufficient, and when it is greater than 800,000, the fluidity of the coating material is extremely insufficient, and a coating film with a good surface condition cannot be obtained. The number average molecular weight, which is the B component of the present invention, is 400 or less, and the (meth)acryloyl group in one molecule is 1.5 to 1.
The polyester oligomer containing 2.0 polyesters has a number average molecular weight of 260 to 800, (meth) obtained by esterifying a dihydric alcohol, a dihydric carboxylic acid or its anhydride, and (meth)acrylic acid.
Number average molecular weight per acryloyl group 130-400
It is a polyester oligomer whose synthesis method, raw material composition and conditions are known [for example, AABerlin, “Polyester acrylates”,
Nauka, Moscow, 1967, Japanese Patent Publication No. 15883, etc.). Examples of each synthetic raw material include the following. That is, as dihydric alcohols, as alkylene glycol type, ethylene glycol,
Propylene glycol chlorpropylene glycol, butanediol (1,3- or 1,4- or 2,3-), 3-methylpentanediol,
1,4 as alicyclic glycol type, such as 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, diethylene glycol,
Triethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, polytetramethylene glycol polybutadiene diol, etc. Also, as an aromatic glycol type, 2,2'-bis(4-hydroxyphenylpropane) (also known as bisphenol A) , screw (4
-Hydroxyphenyl) methane (bisphenol F), 4,4'-dihydroxyphenyl, hydroquinone, resorcinol, and other phenols by adding orkylene oxide (ethylene oxide, propylene oxide, butylene soxide, etc.) Examples include glycols that can be obtained. As divalent carboxylic acids, chain or branched dicarboxylic acids
Examples of carboxylic acids include 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 the alicyclic dicarboxylic acid, 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 (betsumei hetsuto acid), 1,4,5,6,7,7-hexabromo-
Endo-5-norbornene-2,3-dicarboxylic acid, cyclohexane, 1,4-dicarboxylic acid, and aromatic dicarboxylic acids such as phthalic acid,
Examples include isophthalic acid, terephthalic acid, tetrachlorophthalic acid, and tetrabromophthalic acid. Specific examples of the polyester oligomers that are component B of the present invention include di(meth)acrylate of polyester diol of maleic acid and ethylene glycol, di(meth)acrylate of polyester of maleic acid and diethylene glycol, Polyester diol di(meth)acrylate 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 Di(meth)acrylate of polyester diol of and butanediol (1,3- or 1,4-), di(meth)acrylate of polyester diol of tetrahydrophthalic acid and 1,6-hexanediol, tetrahydrophthalic acid di(meth)acrylate of polyester diol with and neopentyl glycol, di(meth)acrylate of polyester diol with tetrahydrophthalic acid and 1,4-cyclohexanediol, di(meth)acrylate of polyester diol with phthalic acid and diethylene glycol , di(meth)acrylate of polyester diol of phthalic acid and neopentyl glycol. Among these polyester oligomers, it has the structure of di(meth)acrylate of polyester diol of tetrahydrophthalic acid and alkylene glycol or cycloalkylene glycol having 3 to 6 carbon atoms, and has a number average molecular weight of 350 to 800. Number average molecular weight per acryloyl group 180
-400 polyester oligomers are particularly suitable for the purposes of the present invention. The polyester oligomer having a number average molecular weight per (meth)acryloyl group of 350 or less and containing 3,5 to 6 (meth)acryloyl groups in one molecule, which is component C of the present invention, is trivalent or tetravalent. Number average molecular weight 450 to 2000, obtained by esterifying a divalent alcohol and a divalent carboxylic acid or its anhydride and (meth)acrylic acid, number average molecular weight per (meth)acryloyl group 100 to 350 It is a polyester oligomer whose synthesis method, raw material composition and conditions are known in the art [for example, AABerlin, “Polyesteracrylates”,
Nauka, Moscow, 1967, Japanese Patent Publication No. 50-15883, Special Publication No. 48-66679, etc.). Examples of each synthetic raw material include the following. That is, as tri- to tetrahydric alcohol,
Alkanetriol types 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-1,2,3-
Butanetriol, 2-ethyl-1,2,3-butanetriol, 2-3,4-hexanetriol, pentamethylene glycol, etc., as alkanetetraols, erythritol, pentaerythritol, toilette, 1,2,3,4pen Tantetrol, 2,3,4,5-hexanetetrol, 2,5-dimethyl-2,3,4,5-hexanetetrol, 1,2,3,5-pentanetetrol, 3-hexene-1, As ether group-containing aliphatic triols such as 2,5,6-tetrol and 3-hexyne-1,2,5,6-tetrol, alkylene oxides (ethylene oxide, propylene oxide, butylene oxide, etc.) are added to glycerin, trimethylolpropane, etc. Ether group-containing aliphatic tetraols such as tetraols obtained by adding alkylene oxide to erythritol, pentaerythritol, etc., and aromatic triols obtained by adding alkylene oxide to pyrogallol. Examples include triol. Further, examples of the divalent carboxylic acid include the divalent carboxylic acids mentioned in the section of component B above. Specific examples of polyester oligomers that are component C of the present invention include tetra(meth)acrylate, penta(meth)acrylate, hexa(meth)acrylate, and tetrahydrophthalic polyester polyol of adipic acid and pentaerythritol. Tetramethacrylate, penta(meth)acrylate, hexa(meth)acrylate of polyester polyol with acid and pentaerythritol, tetra(meth)acrylate, penta(meth)acrylate, hexa(meth)acrylate of polyester polyol with phthalic acid and pentaerythritol ) acrylate, tetra(meth)acrylate of polyester polyol with maleic acid and pentaerythritol, penta(meth)acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol with adipic acid and trimethylolpropane, penta( meth)acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol with tetrahydrophthalic acid and trimethylolpropane, penta(meth)acrylate
Examples include acrylate, hexa(meth)acrylate, tetra(meth)acrylate of polyester polyol of tetrahydrophthalic acid and glycerin, penta(meth)acrylate, and hexa(meth)acrylate. Among these polyester oligomers, polyester polyols of adipic acid or tetrahydrophthalic acid and pentaerythritol have a structure of tetra(meth)acrylate, penta(meth)acrylate or hexa(meth)acrylate and have a number average molecular weight of 550 to 2000; Polyester oligomers having a number average molecular weight per (meth)acryloyl group of 100 to 350 are suitable for the purposes of the present invention. Here, the fundamental idea of the present invention will be described below. The resin composition, which is one of the requirements of the present invention, consists of the three components A, B, and C mentioned above.
The roles of each and when combined are as follows. In other words, the highly formable precoated steel sheet according to the present invention can withstand impact OT bending and has a hardness of 2H.
or higher, gloss of 70 or higher, water resistance, stain resistance/chemical resistance, corrosion resistance, flat aesthetics, and other properties. However, component A of the resin composition of the present invention is mainly characterized by performance. In terms of processability, component B mainly improves the gloss and flat appearance of the paint film, but it also has effects on stain resistance, chemical resistance, and water resistance, and component C adjusts the appropriate crosslinking density of the paint film. However, only by combining the three components A, B, and C can a coating resin composition as excellent as the present invention for highly workable precoated steel sheets be obtained. was discovered experimentally. In other words, the acrylic copolymer of component A has high processability due to its high molecular weight, but the fluidity of the paint after painting is insufficient, and therefore the surface smoothness is at a disadvantage. , to compensate for this, it has a low molecular weight and relatively low particle size (approximately 100 centipoise to several thousand centipoise, preferably 100 centipoise to
1000 centipoise) Component B can be added to increase the fluidity of the coating film and improve the surface smoothness and gloss. In addition, component B is a monofunctional monomer that has two electron beam-active functional groups in the molecule and is common even when used alone.
It has a higher degree of crosslinking than monofunctional oligomers, and has considerably better stain resistance, chemical resistance, water resistance, etc. Even a coating composition that combines component B and component A has high processability (for example, impact OT bending).
However, the stain resistance, chemical resistance, hardness, and water resistance are not good enough, and by adding component C, the crosslinking density can be adjusted to reduce processability. The present invention has been achieved by experimentally discovering that the above-mentioned performance can be greatly improved. Here, the molecular weights and blending ratios of component A, component B, and component C are very important factors in the present invention, and will be described below. Regarding component A, the number average molecular weight is 10,000~
800,000 is suitable for the purpose of the present invention,
More preferably, it is between 20,000 and 300,000, and the amount of B component is small (for example, A/B>
1: weight ratio) In the above molecular weight range, it is desirable that the molecular weight is small, and when the amount of component B is large (for example, A/B<1: weight ratio), it is desirable that the molecular weight is large in the above molecular weight range. Regarding component B, (meth)acryloyl group 1
The range of number average molecular weight per unit is 130~
400, more preferably 180-400, and the number average molecular weight range is 260-800, more preferably 350-800. Regarding C component, (meth)acryloyl group 1
The number average molecular weight per unit is 100 to 350.
The number average molecular weight range is from 450 to
2000, more preferably 550 to 2000. Here, if the A component/B component>100/20, that is, if the A component is too large, the processability is good, but the fluidity of the paint film decreases, and the smoothness of the paint film decreases. This results in disadvantages such as a decrease in the gloss of the coating film, or an extremely poor stain resistance, chemical resistance, hardness, water resistance, etc. Also A
If component/B component <100/200, it will not withstand impact OT bending. Regarding component C, if it is less than 1% of the mixture of both components A and B, the crosslinking density of the coating film will be insufficient, and if it is more than 30%, it will be too excessive and the OT bending will occur. It cannot withstand processing. The blending ratio of component A and component B is component A/B.
Component = 100/20 to 100/200 (weight) is suitable for the present invention, and component C is 1.0 to 30% of the mixture of both components A and B, and depending on the conditions, 3 to 10% is the best. It is effective. In addition to these three components A, B, and C, plasticizer pigments, diluting solvents, monofunctional monomers, oligomers, and the like may be added as necessary. 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 octyl linoleate, epoxidized soybean oil, epoxidized cottonseed oil ,
Examples include Lutzker type polymer copolymers other than acrylic. Pigments used include coloring, rust prevention, and extender pigments, and solvents include xylene, butyl acetate, methyl cellosolve, toluene, isopropyl alcohol, butyl alcohol, ethyl acetate, olefinic solvents, etc. A mixed solvent may also be used. The amount of solvent is used to adjust the coating viscosity and is determined by the coating method, type of coating machine, coating speed, film thickness, etc., but of course there may be cases where it is not used. 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 coated steel plates, it is sufficient to simply pre-treat with cleaning treatment, and for those that have not been chemically treated, use a chemical conversion treatment agent depending on the material, such as:
ACP treatment agent Granozin #192 (Nippon Paint KK
(manufactured by Nippon Paint KK, chromic acid treatment agent for aluminum plates), Parker treatment agent Bonderite #133 (manufactured by Nippon Parkerizing KK, chromate treatment agent for aluminum plates)
The pretreatment can be carried out by a method of chemical conversion treatment using a compound salt treatment agent for galvanized steel sheets. Further, it is better to use a primer between the original plate and the resin composition layer of the present invention.
That is, the recent market may require corrosion resistance even for indoor use, and the resin composition of the present invention has a very large tensile elongation.
(100% or more) A primer that has high processability, good adhesion to the original plate, rust prevention, and good adhesion to the top coat resin composition is applied between the original plate and the resin composition of the present invention. shows better performance. The composition of this primer may be any one such as epoxy, modified epoxy, vinylphenol, epoxy acrylic, polyester, etc., and the curing method of the primer may be any of heat, electron beam, ultraviolet rays, far-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 be about 10μ, preferably about 2 to 5μ. As curing conditions, appropriate conditions are used depending on the respective curing method or resin components. The resin composition of the present invention may be applied to the coated plate immediately after the original plate or to the coated plate coated with a primer by any method such as curtain flow coater, spray coat, natural reverse coat, reverse roll coat, etc. The film thickness can range from 10 μm to several hundred μm, but it can be applied to ordinary home appliances such as refrigerators, electric washing machines, microwave ovens, etc.
For toasters, ovens, etc. or interior building materials such as unit baths, doors, partitions, etc., the thickness is usually around 30μ, but is not limited to this. Furthermore, other coatings shall be applied appropriately within the above-mentioned ranges. In addition, as mentioned above, the coating resin composition of the present invention may be difficult to obtain an appropriate coating viscosity depending on the coating method, film thickness, composition (A, B, C), etc. In some cases, a solvent is added, but in this case, it is desirable to scatter the solvent before coating and irradiating with an electron beam. The conditions for scattering this solvent are different from the conditions used in conventional thermosetting methods for manufacturing coated metal plates, in which the coating is hardened by baking at a very high temperature, for example, close to 300°C, for a long period of time, and the reaction between the resins is It is not necessary to raise the temperature at all; it is only necessary to disperse the solvent. For example, a drying hot air temperature of 150°C and a plate temperature of 120°C or less are 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 of 100 kilovolts and capacities ranging from several megabottles 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 heat radiation 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 film from being scratched during loading, transporting, and processing of the coated product on the pre-coated steel plate of the present invention, it is preferable to apply a protective film under pressure and heat. Examples of protective films include polyethylene, vinyl chloride, polypropylene, polyester, and others. Example 1 (Component A) Monomer ratio (mol%) of ethyl acrylate, methyl methacrylate, 2-hydroxylethyl methacrylate, and acrylic acid is 70:24:3:
100 parts of an acrylic copolymer with a number average molecular weight of approximately 80,000 (component B) phthalic acid, propylene glycol,
Monomer ratio (mole ratio) of acrylic acid is 1:2:2
70 parts of a polyester oligomer with a number average molecular weight of approximately 400 and an average molecular weight per double bond of approximately 200 (Component C) Monomers of tetrahydrophthalic acid, trimethylolpropane, and acrylic acid, quantitative ratio (mole ratio) is 1:2:4, and the number average molecular weight is approximately
600, consisting of 10 parts of polyester oligomer with an average molecular weight of approximately 150 per double bond, xylene-butyl acetate (equal weight mixture)
150 parts of titanium white is added to the resin system dissolved in 200 parts of solution.
The mixture was then dispersed into a paint using a three-roll paint-forming device. Electrogalvanized steel sheet (0.6m/
The previously obtained paint was applied using a curtain flow coater to a thickness of 25 μm on a 120°C solvent scattering oven for 1 minute to scatter the solvent, and then the coated plate was heated under a nitrogen stream (oxygen concentration 0.1%), voltage
A 3 Mrad electron beam was irradiated using an accelerator with a voltage of 300 KV and a current of 25 mA. The performance of the painted steel plate is shown in Table 1. As shown in the data in the table, the processability far exceeds that of conventional precoated materials, i.e., OT
It can withstand impact bending and has other good performance as well. Example 2 The conditions were exactly the same as in Example 1 except for the B component and C component, and the following compositions were used for the B component and C component. An improvement of one rank was observed in the magic ink and mustard, and a half rank improvement in the hair tonic, and the other results were the same as in Example 1. (Component B) The monomer ratio (mole ratio) of tetrahydrophthalic acid, neopentyl glycol, and acrylic acid is 1:2:2, and the number average molecular weight is approximately
450, 60 parts of polyester oligomer with a molecular weight of approximately 225 per double bond (Component C) adipic acid, pentaerythritol,
Monomer ratio (mole ratio) of acrylic acid is 1:2:6
5 parts of a polyester oligomer with a number average molecular weight of about 710 and a number average molecular weight per double bond of about 118 Example 3 (Component A) Butyl acrylate, ethyl acrylate, methyl methacrylate, acrylic acid, The monomer ratio (mole ratio) of glycidyl methacrylate is 26:
100 parts of an acrylic copolymer consisting of 18:52:2:2 and having a number average molecular weight of approximately 200,000 (Component B) Het's acid, diethylene glycol,
Monomer ratio (mole ratio) of methacrylic acid is 1:2:2
120 parts of a polyester oligomer with a number average molecular weight of about 700 and a number average molecular weight of about 350 per double bond (Component C) Monomers (molar ratio) of maleic acid, trimethylolpropane, and acrylic acid. 1:2:4
consisting of 5 parts of polyester oligomer with a number average molecular weight of approximately 550 and a number average molecular weight of approximately 275 per double bond, xylene-butyl acetate (equal weight mixture)
200 parts of titanium white is added to the resin system dissolved in 300 parts of solution.
and dispersed in a ball mill to form a paint. Electrogalvanized steel sheet coated with a dry coating of 3μ of thermosetting epoxy acrylic primer (0.8m
The previously obtained paint was applied using a curtain flow coater to a thickness of 20 μm on a 140°C solvent scattering oven for about 40 seconds to scatter the solvent, and then the coated plate was heated under a nitrogen stream ( Oxygen concentration 0.05%), voltage
A 300KV, 25mA current accelerator was used to irradiate a 2Mrad electron beam. Its performance is shown in Table 1. Example 4 (Component A) Monomer ratio (mole ratio) of methyl methacrylate, ethyl acrylate, and acrylic acid: 27:
100 parts of an acrylic copolymer with a ratio of 70:3 and a number average molecular weight of approximately 50,000 (Component B) Monomer molar ratio of tetrahydrophthalic acid, neopentyl glycol, and acrylic acid is 1:
2:2 polyester oligomer with a number average molecular weight of approximately 450 and an average molecular weight per double bond of approximately 225 (Component C) Monomer moles of tetrahydrophthalic acid, pentoerythritol, and acrylic acid The ratio is 1:2:
A pre-coated steel sheet was prepared using 10 parts of a polyester oligomer consisting of 6, having a number average molecular weight of about 730 and a molecular weight per double bond of about 122, using the same method as in Example 1 except for the other conditions. Its performance is table-
Shown in 1. Example 5 A pre-coated steel plate was prepared using the following components in place of the B and C components of Example 4, and under the same conditions as Example 4 except for the following components. Its performance is similar to Example 4. (Component B) Polyester oligomer 50 consisting of a monomer molar ratio of adipic acid, hexanediol, and methacrylic acid of 1:2:2, a number average molecular weight of approximately 480, and an average molecular weight per double bond of approximately 240.
Part (Component C) Hettic acid, pentaerythritol,
A polyester oligomer 10 having a monomer molar ratio of acrylic acid of 1:2:6, a number average molecular weight of approximately 800, and an average molecular weight per double bond of approximately 135.
Part Example 6 (Component A) The molar ratio of monomers of ethyl acrylate, methyl acrylate, methyl methacrylate, and 2-hydroxylethyl methacrylate is 60:20:
A pre-coated steel sheet was prepared using 100 parts of an acrylic copolymer consisting of 18:2 and having a number average molecular weight of about 70,000. The ingredients and other conditions were exactly the same as in Example 1. Its performance was also similar to that of Example 1. Example 7 (Component A) Monomer ratio (molar ratio) of propyl acrylate, methyl methacrylate, and acrylic acid is 70:
100 parts of an acrylic copolymer having a ratio of 25:5 and a number average molecular weight of approximately 150,000. A precoated steel sheet was prepared under exactly the same conditions as in Example 1, except for the B and C components and other conditions. Its performance is shown in Table 1. Example 8 A test material was prepared in the same manner by adding 1% diallyl phthalate (based on solid content) as a plasticizer to the coating system of Example 1, and a performance test was conducted. It showed the same result as 1.

[Table] Comparative Example 1 in Table 1 is the performance result when the C component of the resin in Example 1 was not added. The gloss and processability show the same performance as Example 1, but the other performances are inferior. In this case, even if the amount of B component is increased, similar results are obtained. The method for determining pencil hardness in this performance table is to scratch the surface of the paint film with a pencil under a load of approximately 300g, wipe it with a cloth, and observe the presence or absence of scratches under a 10x magnifying glass. This is a great method. As explained above, according to the present invention, a precoated steel sheet having excellent hardness, gloss, stain resistance/chemical resistance, and workability can be obtained.

Claims (1)

[Claims] 1 A: 100 parts of an acrylic copolymer mainly composed of acrylic acid, α-substituted acrylic acid, or a derivative thereof having a number average molecular weight in the range of 10,000 to 800,000, B: Dihydric alcohol and dicarboxylic acid (meth)
A polyester oligomer obtained by esterifying acrylic acid, having a number average molecular weight per (meth)acryloyl group of 400 or less and containing 1.5 to 2.0 (meth)acryloyl groups in one molecule. 20 to 200 parts, C: Obtained by esterifying a trihydric or tetrahydric alcohol, a dihydric carboxylic acid, and (meth)acrylic acid, and the number average molecular weight per (meth)acryloyl group is 350 or less A polyester oligomer containing 3.5 to 6.0 (meth)acryloyl groups in one molecule,
A pre-coated steel sheet coated with a resin composition obtained mainly from 1.0 to 30% of a mixture of both components A and B, and cured with an electron beam.