JPS6220908B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a highly workable precoated steel plate. In recent years, in addition to traditional outdoor building materials, home appliances,
In the industry that manufactures products for interior building materials, utensils, and other high-end uses, there is a strong momentum to use prepainted steel sheets in more areas. The coater side is also working diligently to meet this demand, but the required coating film performance is extremely high.For example, it maintains the hardness, stain resistance, chemical resistance, and corrosion resistance of a post coat, and has good processability. There are even examples of such things. From the perspective of pre-coated steel plate manufacturers, this is extremely difficult, and requires consideration of pre-treatment of the steel plate, materials such as paint, and various coating film curing methods such as electron beam curing, heat curing, ultraviolet curing, and other coating film curing methods. However, at present, there is no product that has coating film properties comparable to postcoats and can be processed freely. One possible method to solve this problem is to stop the curing of the coating film at a stage where it can withstand processing, process it into the desired shape, and then heat it again to completely cure it. JP-A-53-85827 is an invention based on this idea;
The key point is that the main ingredients are very specific paints, namely epoxy resin and allyl etherified methylol phenol, and if necessary, acetalized polyvinyl alcohol, cellulose derivatives, resol-type phenolic resins, amino resins, etc. can be added. The amount of these ingredients used is also limited. Moreover, as stated in the detailed description of the invention in the above-mentioned publication, it is actually quite difficult to stop the thermosetting reaction at the desired stage, and the coating film may become sticky due to insufficient curing, or may be difficult to process due to excessive curing. There were many cases where it was inappropriate and unsuitable, and it was not practical. As a result of many years of study, the inventors of the present invention intended to develop a pre-coated steel sheet having a semi-cured coating film that solved the drawbacks of the previous invention, and they succeeded in that goal. The present invention has 0.1 (meth)acryloyl group per 1000 molecular weight in the molecule, which reacts and completely cures the coating film by heating after processing into the desired shape.
A resin system with a functional group that reacts with heating is added to a resin system that has unsaturated carbon double bonds that are active in electron beams at a ratio of ~10, or a resin system that has unsaturated carbon double bonds in the molecule. The main component is a Lutzker type resin system with no bonds, and the dynamic elastic modulus E' after semi-curing with an electron beam is 1.
×10 This is a highly formable pre-coated steel sheet coated with a coating film with a glass transition temperature of 70°C or less and a glass transition temperature of ¹⁰ dyne/cm ² or less.This steel sheet is processed into the desired shape by the user and then heated to completely After being cured, it is used as home appliances, building materials, and other products. While comparing the features of the present invention, the contents of the above-mentioned Japanese Patent Laid-Open No. 53-85827, which is an example of the prior art, will be described and examined in more detail. In other words, the specification of this publication states that (1) it is important to set the conditions at which the coating film should be in a semi-cured state before curing is stopped, and an inappropriate semi-cured state will result in unsatisfactory results. (2) The range of optimal semi-curing conditions for ordinary thermosetting paints is narrow, making it difficult to put it into practical use when considering the fluctuations in drying conditions that can occur in ordinary industrial paint drying equipment. described as difficult. In Japanese Patent Application Laid-Open No. 53-85827, it is thought that the solution to this problem was the use of a paint that uses a very limited resin system and has a specific composition ratio. The greatest feature of the present invention is that in pre-coated steel sheets, which are coated with a paint film in a semi-hardened state after coating the steel sheet, the semi-hardening method utilizes radical polymerization for the curing reaction of the paint polymer. be.
More specifically, if the electron beam curing method is used as the drying and curing method, the semi-curing conditions of the coating film can be freely selected.In other words, compared to ordinary thermosetting paints, it is possible to select the optimum semi-curing conditions. It is practical that the range can be greatly expanded, and the range of fluctuations in drying conditions that can occur in thermosetting industrial paint drying equipment can be significantly reduced even when applied to a practical line by using an electron beam accelerator. This is what I found. Here, the paint that can be used is one that contains a radically polymerizable unsaturated double bond in its molecule. When semi-curing the coating film, condensation due to heating,
When using curing reactions such as addition and polyaddition reactions, it is difficult to overcome the problems mentioned in the above-mentioned Japanese Patent Application Laid-Open No. 53-85827. This seems natural from the perspective of controlling the curing equipment. When semi-curing a coating film, consider the most common industrial hot air drying oven as an example of a thermal curing method.
Even if the temperature and time are set, it would be very difficult to apply it to an actual industrial line. First, in industrial lines, even if the temperature of the drying oven is set to a certain level, it is unavoidable that the ambient temperature meter will fluctuate by more than ±5°C. Furthermore, the wind speed of hot air,
In addition to unavoidable fluctuations in air volume, etc., the initial temperature of the board during threading, the movement of the board due to the catenary during threading, etc., combined with the synergistic effect with the conditions mentioned above, can lead to drying. It is difficult to set the state upon exiting the furnace, for example, the final plate temperature (=set value of curing conditions) within a very small range. Furthermore, it is impossible to suddenly change the baking conditions in response to a change in line speed due to line trouble before the baking process. Even when the coating film is completely cured, the coated surface is still hot, so it remains soft and to prevent blocking, it is rapidly cooled and then rolled up in the case of a coil or laminated in the case of a cut plate. In this case, the purpose is only to cool the hardened coated steel sheet, but in the case of semi-hardening, even this cooling condition causes a problem in that the degree of hardening varies. Furthermore, in addition to the factors mentioned above, the influence of plate thickness also plays a large role. As mentioned above, from the equipment point of view, as long as thermosetting equipment is used, stopping the curing reaction at an intermediate stage has many unstable factors. In addition, from the perspective of paint curing reactions, most of the curing reactions by heating belong to sequential reactions among the polymerization reactions shown in Table 1 below.
Taking the polycondensation reaction (crosslinking reaction), which is a typical reaction example of a normal thermosetting coating film, as an example, the relationship between the reaction time (curing time) and the molecular weight of the product (degree of crosslinking or degree of curing) is It is schematically represented as shown in Figure 1 (Kyoritsu Zensho "Organic Electron Theory", page 281, published in 1960).

[Table] Here, the degree of curing of a normal thermosetting coating film is usually controlled at a reaction time T _A and a molecular weight M _A point, as explained using the example of FIG.
That is, in other words, the coating film is cured in a region where the relationship between curing time and degree of curing is relatively smooth. In this region, the coating film has been completely cured, so it has good hardness, stain resistance, chemical resistance, etc., but as a matter of course, the processability is poor. In the case of semi-curing, the reaction is controlled below the T _A and M _A points in Figure 1, but in conjunction with the equipment factors mentioned above, the desired degree of curing can be stably achieved. That is extremely difficult. The most important feature of the present invention is that the paint applied to steel sheets is a resin (component A) that has an unsaturated carbon double bond that is active to electron beams in its molecule, and a resin (component B) that has a functional group that reacts with heating. This is a system in which a catalyst that enables radical polymerization by thermal decomposition is added to a resin composition formed by adding a component (component) to which a catalyst that enables radical polymerization by thermal decomposition is added depending on the case. After processing into the desired shape, as a complete hardening reaction,
The condensation reaction of component B and the radical polymerization reaction of component A are carried out by heating. Here, in the first stage of semi-curing, using radical polymerization for the curing reaction makes it much easier to control the degree of curing and expands the range of curing conditions compared to sequential reactions, especially for electron beam curing. We have experimentally discovered that the degree of reaction can be controlled extremely easily by using the method, and that from an equipment standpoint, an electron beam irradiator can significantly narrow the range of variation in physical conditions than a heating oven. This is the gist of the present invention. The content of the present invention will be described in more detail. The A component of the resin constituting the paint used in the present invention is a resin having an unsaturated carbon double bond in its molecule that is active to electron beams, for example, by esterification reaction with (meth)acrylic acid at the molecular end or side chain. or those having a double bond in the molecule, such as those introduced by or diene systems, and one or more of these can be used. Component B, a resin having a functional group that reacts when heated, includes, for example, a carboxyl group, a hydroxyl group, an isocyanate group, a glycidyl group, a methylol group, a methoxy group, an ethoxymethyl group, a butoxymethyl group, an amide group, and an imide group in the molecule. It has one or more types of functional groups that enable thermal reactions such as groups, and one or more of these can be used. A
Any resin such as polyester, acrylic, epoxy, urethane, silicone, melamine, alkyd, etc. may be used as long as both the resin systems of Component and Component B satisfy the conditions mentioned above. What is important here is the amount of unsaturated carbon double bonds in component A and the amount of functional groups that enable thermal reaction in component B. Since the first-stage semi-curing reaction is performed using an electron beam, the amount of unsaturated double bonds involved in the reaction is important, and according to experiments conducted by the present inventors, the molecular weight
0.1 to 10 (meth)acryloyl groups per 1000
It is appropriate that there be 0.4 to 6, preferably 0.4 to 6. In other words, the amount of unsaturated double bonds is 10 per 1000 molecular weight.
If the number is more than 1, there will be too many crosslinking points and the curability of the coating film will be too high, causing problems such as cracking during processing after semi-curing. In this case, it is possible to loosen the semi-curing conditions, that is, reduce the electron beam irradiation dose, but the degree of curing relative to the dose becomes too steep, and even if electron beam curing is used, it is difficult to control the curing. may not be easy. Furthermore, if the number of double bonds is less than 0.1 per 1000 molecular weight, the number of crosslinking points will be too small and the film will be too soft to be used as a semi-cured coating, making it unsuitable for use as a pre-coated steel sheet. and is not industrially practical. Next, the number of functional groups that react during the second stage of heating is 0.05 to 1000 per molecular weight.
50 pieces, preferably 0.1 to 40 pieces. If the amount is less than 0.05, the coating film performance will not be sufficient even if it is heated and cured, and for example, the hardness, stain resistance, chemical resistance, etc. will be poor. If the number is 50 or more, the crosslinking density after heating becomes too high, and as a result, cracks and cracks in the processed portion occur over time, although it is unclear whether this is due to an increase in internal reactions or not. Furthermore, the molecular weights of component A and component B will be discussed. Regarding component A, the number average molecular weight is 200~
200000 preferably 300-100000. Regarding component B, the number average molecular weight is 60 to 200,000, preferably 100 to 500,000. In this case, if it is below each lower limit, when a resin system consisting of both components A and B is semi-cured with an electron beam, the coating film generally does not elongate and has insufficient workability. Also,
If it exceeds the upper limit, the viscosity will increase, requiring a large amount of solvent to be added during coating, and heating to a considerably high temperature during the solvent scattering process, reducing economic efficiency. Furthermore, in the present invention, a lacquer type resin having no unsaturated carbon bond in its molecule can be added. This lacquer-type resin includes (polymer) acrylic, polyester, urethane, acrylamide, diene, melamine, rubber-based resin, and others, but in this case, the main purpose is to impart flexibility to the coating film. In the first stage of semi-curing and the second stage of complete curing, no curing reaction is expected, so free functional groups such as hydroxyl groups, carboxyl groups, isocyanate groups, amide groups and other stain-resistant and chemical-resistant groups are used. It is better to have zero or as little amount as possible of substances that may adversely affect properties, water resistance, etc., and it is sufficient that the amount is only necessary to increase the affinity with pigments or other resins when making a paint.
Even if it is hot, it is sufficient that it is several mol% or less. still,
The viscosity of this resin is preferably solid or close to solid, and the viscosity of the resin is preferably 10,000 centipoise or more, and the elongation of the resin is preferably 100% or more. The purpose of adding this resin is to compensate for the lack of flexibility and elongation when resins with active unsaturated carbon double bonds in their molecules are semi-cured by electron beam irradiation. Alternatively, this is to relieve internal shrinkage stress during semi-curing. Here, a catalyst that enables radical polymerization by thermal decomposition may be added as necessary, but this is because the double bonds do not react sufficiently when the coating film is semi-cured by the electron beam in the first step. Therefore, it is added in advance to completely cure the coating film by heating after processing into the desired shape in the second stage. Examples of catalysts that enable radical polymerization through thermal decomposition include the following. That is, examples thereof include Kent peroxide, peroxyketanol, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, peroxyester type, and the like. However, the decomposition temperature of these catalysts must be at least 50°C or higher, preferably 70°C or higher. This is because after the first stage of semi-curing of the coating film, the pre-coated steel sheet is shipped to users of home appliances, building materials, etc., and before it is processed into the desired shape, the radical polymerization hardening reaction due to thermal decomposition of the catalyst takes place. For you must not proceed. The present inventors conducted a follow-up experiment on coating film performance for 12 months after the first stage of semi-curing, and found that in the resin system mentioned above, the decomposition temperature of the catalyst was 50℃ or higher. We have found that some of them are good. However, even if the decomposition temperature of the catalyst is too high, it is inappropriate from the viewpoint of energy saving and cost, even if it does not affect the performance of the coating film, and the temperature is preferably about 20° C. or lower. Further, since both the A component and the B component can be cured by heating, a catalyst may be added in advance as necessary to promote the reaction. In addition, the following additives may be added when the above resin system is made into a paint. That is, polyhydric alcohol (meth)acrylates for adjusting crosslinking density and viscosity, such as ethylene glycol di(meth)acrylate, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, pentaerythritol tetra or Tri(meth)acrylate or monofunctional oligo(meth)acrylate, such as phenylglycidyl(meth)acrylate,
Phenoxyethyl (meth)acrylate, phenylcarbitol (meth)acrylate, nonylphenoxyethyl (meth)acrylate, nonylphenol ethylene oxide adduct (meth)acrylate, benzoyloxyethyl (meth)acrylate, nonylphenol ethylene oxide Adduct (meth)acrylate, cresol glycidyl ether (meth)acrylate, cresol/propylene oxide adduct (meth)acrylate, styrenated cresol/ethylene glycol (meth)acrylate, butanol/propylene oxide adduct (meth)acrylate,
Dialkyl ethanol (meth)acrylate and the like. Furthermore, a phthalic acid-based or phosphoric acid-based plasticizer such as dibutyl phthalate, dioctyl phthalate, dioctyl terephthalate, and dibutyl terephthalate may be used. Naturally, pigments and, if necessary, conventional thinners may also be added. When adding thinner, leave it alone or blow jet air or hot air,
It is necessary to scatter the thinner using infrared electromagnetic induction heating, but even if heat is applied, it must be kept below the decomposition temperature of the radical polymerization catalyst. Conditions must be set carefully to prevent this from happening. The above-mentioned paint is applied to a steel plate and semi-cured with an electron beam.The degree of curing in this case requires that the paint film be tack-free, but there are other conditions as well. Glass transition point (peak value of loss tangent tanδ in viscoelasticity measurement) is 70℃
The dynamic elastic modulus E′ is 1×10 ¹⁰ dyne/cm ² at the processing temperature during post-processing by the user.
It has been experimentally found that the object of the present invention is preferably about 9×10 ⁹ dyne/cm ² or less. As a further supplement, the glass transition point of the coating film after semi-curing is preferably 98% or less when expressed in terms of absolute temperature compared to that during heat curing after the second stage of processing (=complete curing). It must be 95% or less. In addition, the glass transition point of the coating film after complete curing is 70℃ or higher, and the dynamic elastic modulus E' is 2×
It has also been experimentally found that it must be at least 10 ¹⁰ dyne/cm ² . In the present invention, the painted base plate includes, for example, a steel plate, an electrogalvanized steel plate, a hot-dip galvanized steel plate,
Alternatively, steel plates whose surfaces have already been subjected to chemical conversion treatment with chromic acid, phosphoric acid, etc. in the manufacturing process, stain-free steel, tinplate, aluminum plates, stainless steel plates, etc. can be used. In addition, various known methods can be used to pre-treat the metal plate as necessary. For example, if the metal plate is a steel plate that has already been chemically treated in the manufacturing process, , a pretreatment such as simply a cleaning treatment may be performed, or if the material has not been subjected to a chemical conversion treatment, a pretreatment can be performed using a chemical conversion treatment agent appropriate for the material. Further, in the present invention, it is preferable to apply a primer to the original plate, and any primer can be used as long as it has good adhesion to the painted original plate and does not cause any trouble with the paint applied thereon. For example, epoxy, epoxy acrylic, epoxy polyester, polyester, acrylic, vinylphenol-based paints may be heat-curable, ultraviolet-curable, or electron beam-curable, and are cured by their respective curing means. . As a precaution, if the ultraviolet ray or electron beam curable primer contains a solvent, a setting and flash-off process may be included to scatter the solvent. These primers can be applied by conventional methods such as natural roll coating, reverse roll coating, curtain flow coating, and spray coating, and the coating thickness is as follows: It is about 1 to 10μ, preferably about 3μ.
The coating system of the present invention may be applied by conventional roll coating, curtain flow coating, spray coating, etc., and heating coating may be used as long as the coating has a very high viscosity. Regarding the electron beam irradiation method, any known equipment can be used, and currently developed and commercially available accelerating voltages
Any voltage from 150kV to several MV can be used. To set the accelerating voltage, film thickness, film specific gravity, and known knowledge (Depth-Dose curve) may be used. For example,
A 300kV, 200mA accelerator is sufficient. In addition, when curing a coating film by irradiating an electron beam, it is known that oxygen or ozone acts as a polymerization inhibitor, so it is desirable to block this, and the oxygen concentration in the electron beam irradiation atmosphere is known to act as a polymerization inhibitor. The content is preferably 5% or less, preferably 0.5% or less. It is also possible to print on the coating film of this product, and furthermore, it is desirable to laminate a protective film to protect the surface of the coating film. This product can also be printed, and the same resin-based ink as mentioned above is suitable as the printing ink. As the protective film, polyvinyl chloride, polypropylene, polyethylene or other materials are used. Example 1 As component A, the monomer molar ratio of derivatives in which acrylic acid was added to ethyl acrylate, methyl methacrylate, and glycidyl methacrylate was 65:30:
5, the number average molecular weight is approximately 10,000, the molecular weight
B is added to 100 parts (parts by weight, same hereinafter) of an acrylic resin containing approximately 0.48 acryloyl groups per 1000.
As ingredients, 100 parts of Toyobo "Vylon"P-300" (molecular weight 20000, OH value: 100-150 eq./10 ⁶ g), 12.6 parts of Nippon Polyurethane "Coronate L-75" (that is, component B contains NCO/ OH=3),
Add 210 parts of titanium white to
200 parts were dispersed using three rolls to form a paint. This paint was coated with a thermosetting epoxy/acrylic primer (film thickness: 2 μm) in advance, and then applied to a cured electrogalvanized steel sheet using a bar coater to a dry film thickness of 25 μm, and xylol was scattered with jet air. This painted board was coated under a nitrogen atmosphere (oxygen concentration
0.1%), with an accelerator with a voltage of 300 kV and a current of 25 mA,
A coated steel plate with a semi-cured coating film was obtained by irradiation with an electron beam at a dose of 5 Mrad. The hardness of this coated steel plate was F, and when it was shockingly bent to 90° (R=0) using a bending machine, no cracks were observed and the workability was good. This same board was tested for stain resistance. After applying Magizu ink (red, black, blue) and keeping it at room temperature for 24 hours, I tried wiping it with gauze soaked in ethanol, but it left a strong mark (rating × - △) and the areas where Magizu ink was not applied , “Glossiness” occurred. Next, this processed board was placed in an atmosphere of 230°C for 3
After holding it for a minute, it was taken out from the open and the hardness was measured, and it was 3H, and there was no change such as cracking in the processed part. In addition, when a stain resistance test was conducted in the same way as before, traces of contamination could be easily wiped off (rating: ◎), and no "shininess" occurred. Reference example 1 Instead of electrogalvanized steel sheet, use tin foil (25μ
The same paint as in Example 1 was applied on the foil (thickness) under the same conditions to obtain a tin foil having a semi-cured film, and the tin was dissolved using the amalgam method to obtain a free film. About this film, Toyo Baldwin Co., Ltd.
When the viscoelastic behavior was examined using a Viblon DDV-EA type tester manufactured by Manufacturer, the dynamic elastic modulus E' was 6.0×
10 ⁹ dyne/cm ² (20°C), and the temperature showing the loss tangent tanδ _nax was 35°C. Furthermore, when the viscoelastic behavior of the semi-cured coating film was heated under the same heating conditions as in Example 1, E' was 3.0×10 ¹⁰ dyne/cm ² (20°C), tan δ _nax
The temperature was 90℃. Example 2 The monomer molar ratio of phthalic acid, trimethylolpropane, and acrylic acid was 1:2:4, the number average molecular weight was about 600, and the number of double bonds per 1000 molecules was about 6.
ke polyester oligomer as component A,
The B component and other conditions were completely the same as in Example 1 to obtain a coated plate having a semi-cured coating film. The hardness of this coated plate was F ⁺ , and when it was shockingly bent to 90° (R=0) using a bending machine, no cracks were observed and the workability was good. When we conducted a stain resistance test on this board, we applied Magic Ink (red, black, and blue) and lipstick, kept it at room temperature for 24 hours, and then wiped it with gauze soaked in ethanol, but it left a strong mark. (Rating △). Next, this processed plate was held in an atmosphere of 250°C for 3 minutes, and then taken out from the oven and its hardness was measured to be 3H, and there were no changes such as cracks in the processed area. In addition, when a stain resistance test was conducted as before, traces of stain were easily wiped away (rating: ◎). Reference example 2 Instead of electrogalvanized steel sheet, use tin foil (25μ
The same paint as in Example 2 was applied on the foil (thickness) under the same conditions to obtain a tin foil having a semi-cured coating, and the tin was dissolved using an amalgam method to obtain a free film. When the viscoelastic behavior of this film was investigated (Toyo Baldwin Co., Ltd.: Vibron DDV--EA type tester), the dynamic elastic modulus E' was 9.5×10 ⁹ dyne/
cm ² (20°C), the temperature showing the loss tangent tanδ _nax is 30
It was warm at ℃. Furthermore, when the viscoelastic behavior of the semi-cured coating film was heated under the same heating conditions as in Example 1, E' was 2.8×10 ¹⁰ dyne/cm ² (20°C), and the temperature of tanδ _nax was It was 85℃. Example 3 In Example 1, hexamethoxymethylolmelamine (molecular weight 390, molecular weight
Except for using 15 methoxy groups per 1000
A coated steel plate having a semi-cured coating film was obtained under the same conditions as in Example 1. The hardness of this coated steel plate was HB, and when it was shockingly bent to 90° (R=0) using a bending machine, no cracks were observed and the workability was good. This same board was tested for stain resistance. After applying Magizu ink (red, black, blue) and keeping it at room temperature for 24 hours, I tried wiping it with gauze soaked in ethanol, but it left a strong mark (rating × - △) and the areas where Magizu ink was not applied “Glossiness” occurred. Next, after holding this processed steel plate in an atmosphere of 230°C for 3 minutes, it was taken out from the oven and its hardness was measured, and it was found to be 3H, and there were no changes such as cracks in the processed area. In addition, when a stain resistance test was conducted in the same manner as before, traces of contamination were easily seen (scored ◎), and no "glossy" was observed at all. Comparative example 1 In Example 1, a paint containing only component B was created by omitting component A, and the dose was adjusted under exactly the same conditions and procedures.
A painted steel plate irradiated with 5 Mrad was obtained. However, this painted steel plate is sticky,
The hardness was also less than 4B, making it unsuitable for use as a prepainted steel sheet. Example 4 To the resin system of Example 1, an additional 100 parts of a Lutzker type resin having a monomer mole ratio of ethyl acrylate and methyl methacrylate of 60:40 and a number average molecular weight of approximately 50,000 (solid) was added. Then, titanium white was added to make a paint with the same pigment. This paint system was applied under exactly the same conditions as in Example 1, and then irradiated with an electron beam to obtain a coated steel plate having a semi-cured coating film. The hardness of this coated steel plate was HB, and when it was shockingly bent to 180° (R=0) using a bending machine, no cracks were observed and the workability was good. This same steel plate was subjected to a stain resistance test. After applying Magizu ink (red, black, blue) and keeping it at room temperature for 24 hours, I tried wiping it with gauze soaked in ethanol, but it left a strong mark (rating × - △) and the areas where Magizu ink was not applied Next, after holding this processed steel plate in an atmosphere of 260℃ for 5 minutes, it was taken out of the oven and its hardness was measured, and it was found to be 2H, and there were no changes such as cracks in the processed part. In addition, when we conducted the stain resistance test as before, traces of contamination were easily wiped away (score: ◎).
Moreover, no "shininess" occurred.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating the relationship between the reaction time and the molecular weight of the product in a polymer reaction.

Claims (1)

[Claims] 1 It has a molecular weight of 1000 in the molecule, which reacts and completely cures the coating film by heating after processing into the desired shape.
A resin system containing 0.1 to 10 (meth)acryloyl groups in a ratio of 0.1 to 10 electron beam-active unsaturated carbon double bonds to which a resin system having a functional group that reacts upon heating is added, or Furthermore, the main component is a Lutzker type resin system that does not have unsaturated carbon bonds in the molecule, and the dynamic elastic modulus E' after semi-curing with an electron beam is 1×10 ¹⁰ dyne/cm ²
The following is a highly workable pre-coated steel sheet coated with a coating film with a glass transition point of 70°C or less.