Coil steel coating and steel sheet for forming electron beam-cured coating

Abstract

The application discloses a kind of for forming electron beam curing coating coil steel coating, effective component includes: composite matrix resin A: 40-60 parts by weight;Organosilicon compound B: 3-10 parts by weight;Monofunctional olefinic unsaturated polymerizable monomer C: 15-25 parts by weight;Acrylic acid phosphate ester compound D: 5-15 parts by weight;Titanium salt or zirconium salt of acrylic acid compound E: 0.2-3 parts by weight;Wherein, A includes 20-30wt% isobornyl acrylate containing aliphatic polyurethane acrylate oligomer A1 and 30-40wt% dipropylene glycol diacrylate containing amine modified epoxy diacrylate oligomer A2, the mass fraction ratio of A1 and A2 is: 1.0-5.0.Correspondingly, the application also discloses the steel plate with the electron beam curing coating formed by the coil steel coating on the surface.

Description

Technical Field

[0001] This invention relates to a coating, and more particularly to an electron beam curable coating for steel plates. Background Technology

[0002] Coated steel sheets, also known as pre-coated steel sheets, are steel sheets made by coating one or more layers of organic coatings onto the surface of metal coils (cold-rolled sheets, hot-dip galvanized sheets, aluminized sheets, zinc-aluminum-magnesium sheets, etc.) and then curing them.

[0003] Traditional pre-coated steel sheet production processes involve applying water-based or solvent-based coatings to the surface of steel strips and then drying or curing them into a film through heat curing. This production method boasts high technological maturity and stable quality, making it the preferred choice in the coil steel industry. However, limitations imposed by the curing rate of heat-cured coatings and the space requirements of the equipment restrict further improvements in the production efficiency of traditional pre-coated sheets. Furthermore, heat curing methods are energy-intensive, have high infrastructure costs, and high operating costs; moreover, solvent evaporation causes environmental pollution, and incineration produces large amounts of CO2.

[0004] To overcome this problem, low-energy, rapid curing, and solvent-free processes have become the current development trends, with electron beam (EB) curing being the most superior. EB curing utilizes the energy of an electron beam as the excitation source for the coating curing process, enabling solvent-free coatings to instantly cure into a film at room temperature. Compared to traditional heat curing methods, EB curing offers numerous advantages, including environmental friendliness, energy efficiency, high efficiency, and low carbon footprint. Currently, EB curing has found some applications in fields such as wood, paper, and optical fibers. Coatings cured by EB in these fields generally do not require further processing and operate in relatively gentle environments.

[0005] However, in the field of steel plate coating, the cured coating still needs to undergo subsequent processing steps such as rolling and stamping. In addition, it also needs to face the harsh outdoor service environment. This requires the EB cured coating to have excellent adhesion performance on the metal substrate, especially the adhesion performance after molding and the wet adhesion after water penetration, as well as corrosion resistance. However, the existing EB cured coating cannot achieve this performance on the metal substrate. Summary of the Invention

[0006] One of the objectives of this invention is to provide a coil coating for forming an electron beam cured coating. When applied to a steel plate, this product can give the steel plate excellent dry and wet adhesion properties and resistance to underfilm erosion.

[0007] To achieve the above objectives, the present invention provides a coil coating for forming an electron beam cured coating, the effective components of which include:

[0008] Composite matrix resin A: 40-60 parts by weight;

[0009] Organosilicon compound B: 3-10 parts by weight;

[0010] Monofunctional olefinic unsaturated polymerizable monomer C: 15-25 parts by weight;

[0011] Acrylic phosphate compound D: 5-15 parts by weight;

[0012] Titanium or zirconium salts of acrylic acid, E: 0.3-2 parts by weight;

[0013] The composite matrix resin A includes an aliphatic polyurethane acrylate oligomer A1 containing 20-30 wt% isoborneol acrylate and an amine-modified epoxy diacrylate oligomer A2 containing 30-40 wt% dipropylene glycol diacrylate, wherein the mass ratio of A1 to A2 is 1.0-5.0.

[0014] The present invention also provides a coil coating for forming an electron beam cured coating, the effective components of which consist of the following:

[0015] Composite matrix resin A: 40-60 parts by weight;

[0016] Organosilicon compound B: 3-10 parts by weight;

[0017] Monofunctional olefinic unsaturated polymerizable monomer C: 15-25 parts by weight;

[0018] Acrylic phosphate compound D: 5-15 parts by weight;

[0019] Titanium or zirconium salts of acrylic acid, E: 0.2-3 parts by weight;

[0020] The composite matrix resin A includes an aliphatic polyurethane acrylate oligomer A1 containing 20-30 wt% isoborneol acrylate and an amine-modified epoxy diacrylate oligomer A2 containing 30-40 wt% dipropylene glycol diacrylate, wherein the mass ratio of A1 to A2 is 1.0-5.0.

[0021] The coil coating of this invention is applied to the surface of a coated steel sheet and formed by electron beam curing (EB) to create an electron beam (EB) cured coating. The flexibility exhibited by the entire EB cured coating, as well as its dry and wet adhesion properties at the interface with the metal substrate and its adhesion properties at the interface with the topcoat coating, are inseparable from the composite matrix resin A. The polyurethane segments in the aliphatic polyurethane acrylate oligomer A1, containing 20-30 wt% isoborneol acrylate, provide excellent coating flexibility, while the amine-modified epoxy diacrylate oligomer A2, containing 30-40 wt% dipropylene glycol diacrylate, provides the interfacial adhesion properties between the coating and the metal substrate, as well as the interfacial adhesion properties between the coating and the topcoat.

[0022] In this invention, the mass percentage of A1 to A2 is 1.0-5.0 because: if it is less than 1.0, the flexibility of the coating may decrease, and if it is more than 5.0, the adhesion between the coating and the metal substrate and the topcoat may deteriorate.

[0023] In addition, the weight of composite matrix resin A, which is composed of A1 and A2, is 40-60 parts because: if it is less than 40 parts, the flexibility of the coating and its adhesion to the metal substrate will decrease; if it is more than 60 parts, the adhesion of the coating to the subsequent topcoat coating and its wet adhesion to the metal substrate may decrease.

[0024] In this invention, the aliphatic polyurethane acrylate oligomer A1 containing 20-30% isobornyl acrylate (IBOA) can have the following properties: a viscosity of 15000-25000 mPa·s at 25°C, a molecular weight of 2000-4000, a functionality of 2, a density of 1.0-1.2 g / m2, and a glass transition temperature Tg of 35-55°C.

[0025] In this invention, the amine-modified epoxy diacrylate oligomer A2 containing 30-40% dipropylene glycol diacrylate (DPGDA) can have the following properties: a viscosity of 500-1500 mPa·s at 25°C, a functionality of 2, a density of 1.0-1.2 g / m2, a glass transition temperature Tg of 70-90°C, and an acid value of 2-4 mgKOH / g.

[0026] In this invention, the role of organosilicon compound B is to further enhance the wet adhesion performance and resistance to underfilm corrosion between the EB-cured coating and the metal substrate. On one hand, the vinyl groups in the organosilicon compound can participate in the reaction during radiation curing, combining with the composite matrix resin A. On the other hand, when water or water vapor, or water or water vapor carrying corrosive media, penetrates through the coating and reaches the substrate interface, the organosilicon compound B in the cured coating undergoes a hydrolysis reaction in the presence of water, generating Si-OH groups. These Si-OH groups undergo a condensation reaction with the Me-OH (Me represents metal) groups on the metal surface, forming a strong Si-O-Me covalent bond at the metal interface. This prevents further spread of corrosive media and the resulting increase in underfilm corrosion, and further enhances the wet adhesion performance between the coating and the metal substrate. Furthermore, another role of organosilicon compound B is to improve the adhesion between the EB-cured coating and the subsequent topcoat (solvent-based or radiation-cured topcoat).

[0027] The weight percentage of organosilicon compound B is 3-10 because: if it is less than 3 parts, sufficient wet adhesion and resistance to underfilm erosion cannot be obtained; if it is more than 10 parts, the surface energy of the cured coating will be reduced, resulting in pinhole defects during the application or curing of subsequent topcoat coatings and a decrease in the adhesion between the EB coating and the topcoat coating.

[0028] In this invention, the monofunctional olefin unsaturated polymerizable monomer C is an acrylic monomer with high Tg and monofunctional reactivity. Monofunctional olefin unsaturated polymerizable monomer C can participate in cross-linking reactions during electron beam curing. Its monofunctional reactivity results in a low shrinkage rate during curing, ensuring good adhesion between the coating and the metal substrate. The weight fraction of monofunctional olefin unsaturated polymerizable monomer C is 15-25 parts because: if it is less than 15 parts, the coating curing degree is low, and dry and wet adhesion are reduced; if it is more than 25 parts, the curing shrinkage rate of the coating will increase, which is also detrimental to the dry adhesion performance between the coating and the metal substrate.

[0029] In this invention, acrylate phosphate compound D is used as an adhesion promoter. This adhesion promoter, through micro-phosphating with the metal surface, significantly improves the dry and wet adhesion properties between the EB cured coating and the metal substrate. The weight percentage of acrylate phosphate compound D is 5-15 parts because: if it is less than 5 parts, the dry and wet adhesion properties between the cured coating and the metal substrate will deteriorate; if it is more than 15 parts, the adhesion properties between the cured coating and the subsequent topcoat coating will deteriorate.

[0030] In this invention, a titanium or zirconium salt compound E of acrylic acid is used as an interface corrosion inhibitor. The main function of this interface corrosion inhibitor is to improve the resistance of the primer coating to under-film corrosion. On the one hand, the acrylic component participates in film formation during electron beam curing; on the other hand, when water or water vapor, or water or water vapor carrying corrosive media, penetrates through the coating or through defects to the interface between the coating and the metal, the metal salt compounds therein will undergo a passivation reaction with the metal substrate surface under the action of water, thereby preventing further propagation of water or other corrosive media. The weight percentage of the titanium or zirconium salt compound E of acrylic acid is 0.3-2.0 parts because: if it is less than 0.3 parts, the resistance to under-film corrosion is not significant; if it is more than 2.0 parts, it will affect the flexibility of the cured coating.

[0031] Furthermore, in some embodiments of the present invention, the effective components of the coil coating of the present invention further include at least one of the following:

[0032] Rust-preventive pigment F: 2-5 parts by weight;

[0033] Opacifying pigment G: 5-10 parts by weight;

[0034] Additive H: 0.2-1 parts by weight.

[0035] The rust-preventing principle of rust-preventing pigments is that when corrosive media (such as water and oxygen) penetrate the paint film and reach the coating / metal interface, a corrosion reaction occurs. At the interface, metal atoms are oxidized, lose electrons to form metal ions, while oxygen gains electrons and is reduced to OH-. - The ions create an alkaline environment at the cured coating / metal interface. The weight percentage of the rust-preventive pigment is 2.0-5.0 parts because: if it is less than 2.0 parts, the rust-preventive effect is not obvious; if it is more than 5.0 parts, it will affect the flexibility of the cured coating.

[0036] The purpose of masking pigment is to provide a certain degree of coverage to the metal substrate, which is beneficial to the uniformity of the appearance after the topcoat is applied. The weight of masking pigment is 5.0-10.0 parts because: if it is less than 5.0 parts, the covering effect will not be obvious; if it is more than 10 parts, it will lead to a decrease in the adhesion of the cured coating.

[0037] Furthermore, in the coil coating of the present invention, the mass ratio of A1 to A2 is 1.5-4.0.

[0038] Furthermore, in the coil coating of the present invention, the organosilicon compound B includes at least one of the following: vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, methylvinyldimethoxysilane, vinyltriacetoxysilane, propoxytriacetoxysilane methacrylate, triethoxysilane propyl methacrylate, and triethoxysilane methacrylate.

[0039] Furthermore, in the coil coating of the present invention, the monofunctional olefinic unsaturated polymerizable monomer C includes at least one of the following: hydroxypropyl methacrylate, cyclotrimethylolpropane methyl acetal acrylate, cyclotrimethylolpropane methyl acetal monoacrylate, isobornyl acrylate, lauryl acrylate, methyl methacrylate lauric acid, and octyl acrylate decyl acrylate.

[0040] Furthermore, in the coil coating of the present invention, the acrylate phosphate compound D includes at least one of the following: polyethylene glycol methacrylate phosphate, di(hydroxyethyl) phosphate, 2-methyl-2-hydroxyethyl acrylate phosphate, and di(methacryloyloxyethyl) hydrogen phosphate.

[0041] Furthermore, in the coil coating of the present invention, the titanium or zirconium salt compound E of acrylic acid includes at least one of the following: titanium triisopropoxide methacrylate, zirconium acrylate, and zirconium tetramethacrylate.

[0042] Furthermore, in the coil coating of the present invention, the anti-rust pigment F comprises ion-exchange type alkaline silica powder.

[0043] This ion-exchange alkaline silica powder has a low density and a high specific surface area. It can dissolve in an alkaline environment into silicic acid or silicate ions. These soluble parts can react with metal ions at the coating / metal interface to form a protective layer of metal silicate salt, thereby preventing further corrosion of the metal at the interface.

[0044] Furthermore, in the coil coating of the present invention, the ion-exchange alkaline silica powder has an average particle size of 2-6 μm and a pH of 8-10.

[0045] Furthermore, in the coil coating of the present invention, the covering pigment G comprises titanium dioxide.

[0046] Furthermore, in the coil coating of the present invention, the additive H includes at least one of a leveling agent, a wetting agent, and an anti-settling agent.

[0047] Another objective of this invention is to provide a steel plate with excellent dry and wet adhesion properties and resistance to under-film corrosion. It can be used alone while meeting the requirements of subsequent processing and service, or it can be used as a substrate for the initial coating of double-coated color-coated steel plates, and it can form good adhesion and overall corrosion resistance with the topcoat coating.

[0048] To achieve the above objectives, the present invention provides a steel plate comprising a substrate, a plating layer plated on the surface of the substrate, and an electron beam curable coating coated on the surface of the plating layer, wherein the electron beam curable coating is formed by coating the surface of the plating layer with the coil coating as described above and then curing it with an electron beam.

[0049] It should be noted that the effective components and their proportions in the electron beam cured coating are exactly the same as those in coil coatings.

[0050] Furthermore, in the steel plate described in this invention, the electron beam cured coating is a single-layer structure.

[0051] Furthermore, in the steel plate described in this invention, the thickness of the electron beam cured coating is 3-30 μm.

[0052] Furthermore, in the steel plate described in this invention, the thickness of the electron beam cured coating is 3-10 μm.

[0053] Furthermore, in the steel plate described in this invention, the coating is a hot-dip galvanized layer, a hot-dip aluminum-zinc layer, a hot-dip zinc-aluminum-magnesium layer, or an electro-galvanized layer.

[0054] Furthermore, in the steel plate described in this invention, the process parameters for electron beam curing are as follows: under a protective atmosphere of nitrogen + oxygen mixed gas with an oxygen content ≤200ppm, the electron beam voltage is 90-150KV and the electron beam dose is 10-60KGy.

[0055] The coil coating for forming an electron beam cured coating described in this invention, when applied to a steel plate to form an electron beam cured coating, can give the steel plate excellent dry and wet adhesion properties and resistance to under-film erosion. Detailed Implementation

[0056] The following will further explain and illustrate the coil coating and steel plate for forming electron beam curing coating according to the present invention with reference to specific embodiments. However, such explanation and illustration do not constitute an undue limitation on the technical solution of the present invention.

[0057] Examples 1-9 and Comparative Examples 1-9

[0058] To verify the effectiveness of the present invention, the inventors prepared the coil coatings for forming electron beam curable coatings of Examples 1-9 and the coil coatings of Comparative Examples 1-9.

[0059] These coil coatings are applied to cold-rolled strip steel with a coating layer, and then an electron beam curing process is used to form an electron beam cured coating on the surface of the strip steel. This electron beam cured coating is a single-layer structure.

[0060] The process parameters for electron beam curing are as follows: under a protective atmosphere of nitrogen + oxygen mixed gas with an oxygen content of ≤200ppm, the electron beam voltage is 90-150KV and the electron beam dose is 10-60KGy.

[0061] Table 1 lists the composition of the coatings and electron beam cured coatings of the steel plates of Examples 1-9 and Comparative Examples 1-9. It should be noted that the composition of the electron beam cured coating is the same as that of the coil coating, so it will not be described again here.

[0062] Table 1.

[0063]

[0064]

[0065] Note: A1 in Table 1 refers to an aliphatic polyurethane acrylate oligomer containing 30 wt% isobornyl acrylate (IBOA), with a viscosity of 21000 mPa·s at 25°C, a molecular weight of 2700 g / mol, a functionality of 2, a density of 1.1 g / m², and a glass transition temperature of 46°C. Although the examples listed in Table 1 all use an aliphatic polyurethane acrylate oligomer containing 30 wt% isobornyl acrylate (IBOA), other aliphatic polyurethane acrylate oligomers containing 20-30 wt% isobornyl acrylate are also feasible for this invention.

[0066] Table 1 shows A2 as an amine-modified epoxy diacrylate oligomer containing 35% dipropylene glycol diacrylate (DPGDA), with a viscosity of 1100 mPa·s at 25°C, a functionality of 2, a density of 1.14 g / m², a glass transition temperature of 80°C, and an acid value of 3 mg KOH / g. Although the examples listed in Table 1 all use amine-modified epoxy diacrylate oligomers containing 35% dipropylene glycol diacrylate (DPGDA), other amine-modified epoxy diacrylate oligomers containing 30-40% dipropylene glycol diacrylate (DPGDA) are also feasible for this invention.

[0067] The types of organosilicon compounds (B) in Table 1 are as follows:

[0068] B1 Vinyltrimethoxysilane B2 Vinyltris(2-methoxyethoxy)silane B3 Vinyltriisopropoxysilane B4 methylvinyldimethoxysilane B5 Vinyltriacetoxysilane B6 methacrylate propoxytriacetoxysilane B7 Triethoxysilane propyl methacrylate B8 Triethoxysilane methacrylate

[0069] The types of monofunctional olefinic unsaturated polymerizable monomers (C) listed in Table 1 are as follows:

[0070] C1 Hydroxypropyl methacrylate C2 Cyclotrimethylolpropane methyl acetal acrylate C3 Cyclotrimethylolpropane methyl acetal monoacrylate C4 Isoborneol acrylate C5 Lauryl acrylate C6 methyl methacrylate lauric acid C7 Octyl acrylate decyl acrylate

[0071] The types of adhesion promoters (D) listed in Table 1 are as follows:

[0072] D1 Polyethylene glycol methacrylate D2 Di(hydroxyethyl) phosphate D3 2-Methyl-2-acrylate-2-hydroxyethyl phosphate D4 Di(methacryloyloxyethyl) hydrogen phosphate

[0073] Interfacial corrosion inhibitors in Table 1

[0074] E1 Titanium triisopropoxide methacrylate E2 Zirconium acrylate E3 Zirconium tetramethylacrylate

[0075] The rust-preventive pigment F in Table 1 is an ion-exchange type alkaline silica powder with an average particle size of 3 μm and a pH of 8.5. It should be noted that in other embodiments, other ion-exchange type alkaline silica powders with an average particle size of 2-6 μm and a pH of 8-10 are also feasible. Furthermore, other pigments known to those skilled in the art that can achieve rust-preventive functions are also feasible and are within the scope of protection of this invention.

[0076] In Table 1, the masking pigment G is titanium dioxide. It should be noted that other pigments known to those skilled in the art that can achieve the masking function are also feasible and are within the scope of protection of this invention.

[0077] Additives H in Table 1 include: leveling agents, wetting agents, anti-settling agents, or combinations thereof.

[0078] It should be noted that although each of the embodiments in Table 1 uses only one substance for B, C, D and E, it is also possible to use them in combination. For example, component B can be a mixture of B1 and B2, component C can be a mixture of C2, C4 and C7, etc., which will not be listed here.

[0079] It should be noted that the present invention focuses on the superior performance of the electron beam cured coating formed by the designed coil coating, and there are no special limitations on the steel substrate used. Therefore, in practical applications, those skilled in the art can select the required steel substrate according to specific needs.

[0080] Table 2 lists the parameters of the electron beam curing process for Examples 1-9 and Comparative Examples 1-9.

[0081] Table 2.

[0082]

[0083]

[0084] Note: Electron beam curing is performed under a nitrogen protective atmosphere with an oxygen content of ≤200ppm.

[0085] Accordingly, to verify the beneficial effects of the coil coating designed in this invention and the electron beam cured coating formed therefrom, steel plates from Examples 1-9 and Comparative Examples 1-9 were sampled, cut into standard-sized samples, and subjected to the following tests. The test data for evaluating various properties are listed in Table 3. The specific test items and methods are as follows:

[0086] 1. Dry adhesion

[0087] 1.1T Bending: Conducted according to section 7. Bending Test standard of GB / T 13448, with the following evaluation criteria:

[0088] ◎: T-bend rating ≤3T that prevents coating from peeling off from the substrate

[0089] ○: T-bend rating that prevents coating from peeling off the substrate = 4T

[0090] Δ: T-bend rating that prevents coating from peeling off the substrate = 5T

[0091] ×: T-bend rating ≥6T that prevents coating from peeling off from the substrate.

[0092] 1.2 Cross-cut Test: The test shall be conducted according to the cross-cut test standard in GB / T 13448, and the rating shall be based on Table 1 of GB / T 13448. The evaluation criteria are as follows:

[0093] ◎: The cross-cut test rating is level 0 as specified in Table 1 of GB / T 13448.

[0094] ○: The cross-cut test rating is level 1-2 as specified in Table 1 of GB / T 13448.

[0095] Δ: The cross-cut test rating is level 3-4 as specified in Table 1 of GB / T 13448.

[0096] ×: The cross-cut test rating is 5 as specified in Table 1 of GB / T 13448.

[0097] 1.3 Impact: The impact test shall be conducted in accordance with the standard of 8. Reverse impact test in GB / T 13448, and the evaluation criteria are as follows:

[0098] ◎: Impact energy ≥9J that prevents coating from detaching from the substrate

[0099] ○: The impact energy required to prevent the coating from detaching from the substrate is 7-8 J.

[0100] Δ: The impact energy required to prevent the coating from detaching from the substrate is 6-7 J.

[0101] ×: The impact energy that prevents the coating from detaching from the substrate is ≤6J.

[0102] 2. Wet adhesion

[0103] 2.1 Boiling: Immerse the sample in boiling water for 2 hours. After removal, first evaluate the appearance of the coating, including blistering or peeling. Then, conduct a cross-cut test according to GB / T 13448, section 13. The evaluation criteria are as follows:

[0104] ◎: The coating shows no blistering or peeling, and its cross-cut test rating is grade 0 as specified in Table 1 of GB / T 13448.

[0105] ○: The coating has minor blistering but no peeling, and the cross-cut test rating is level 1-2 as specified in Table 1 of GB / T 13448.

[0106] Δ: The coating exhibits extensive blistering but no peeling, and its cross-cut test rating is 3-4 as specified in Table 1 of GB / T 13448.

[0107] ×: Extensive coating peeling, cross-cut test rating is level 5 as specified in Table 1 of GB / T 13448.

[0108] 2.2 Saltwater Immersion: Immerse the sample in a 5% NaCl solution for 72 hours. After removal, evaluate the appearance of the coating, including blistering or peeling. The evaluation criteria are as follows:

[0109] ◎: The coating is free of bubbles and peeling.

[0110] ○: Minor bubbling of the coating, no peeling.

[0111] Δ: Excessive blistering of the coating, no peeling.

[0112] ×: Extensive coating peeling

[0113] 3. Resistance to undercoat corrosion: Before the test, use a knife to draw a single straight line parallel to the long side of the sample on the central part of the sample. The line should be no less than 50 mm long and penetrate the coating. The line should be no less than 30 mm from the edge. Then, conduct a salt spray test according to ASTM B117 for 1000 hours. The evaluation criteria are as follows:

[0114] ◎: The average erosion width on one side of the marked area is less than or equal to 3mm.

[0115] ○: The average erosion width on one side of the marked area is greater than 3mm and less than or equal to 10mm.

[0116] Δ: The average erosion width on one side of the scribed area is greater than 10mm and less than or equal to 15mm.

[0117] ×: The average erosion width on one side of the marked area is greater than 15mm.

[0118] 4. Adhesion to the topcoat and overall corrosion resistance

[0119] For the electron beam cured coated steel plates in Examples 1-9 and Comparative Examples 1-9, a topcoat was applied and cured. The topcoat was a conventional solvent-based polyester coating with a film thickness of 15 μm. The curing conditions were PMT 241-254℃ and a curing time of 20-30 s. The fully coated samples were then subjected to the following tests. The test results can directly reflect the interfacial adhesion performance between the EB-cured coating and the topcoat coating, as well as the overall corrosion resistance provided by the topcoat coating together.

[0120] 4.1T Bending: Conducted according to section 7. Bending Test standard of GB / T 13448, with the following evaluation criteria:

[0121] ◎: T-bend rating ≤3T that ensures no peeling between the EB-cured coating and the topcoat coating.

[0122] ○: T-bend rating that ensures no peeling between the EB-cured coating and the topcoat coating = 4T

[0123] Δ: T-bend rating that ensures no peeling between the EB-cured coating and the topcoat = 5T

[0124] ×: T-bend rating ≥6T that prevents EB-cured coating from peeling off from topcoat.

[0125] 4.2 Cross-cut Test: The test shall be conducted according to the cross-cut test standard in GB / T 13448, and the rating shall be based on Table 1 of GB / T 13448. The evaluation criteria are as follows:

[0126] ◎: The cross-cut adhesion test result for EB-cured coatings and topcoat coatings that prevents peeling is grade 0.

[0127] ○: The cross-cut adhesion test result for preventing peeling between the EB-cured coating and the topcoat is grade 1-2.

[0128] Δ: The cross-cut adhesion test score of 3-4 ensures that there is no peeling between the EB-cured coating and the topcoat.

[0129] ×: The cross-cut adhesion test result for preventing peeling between the EB-cured coating and the topcoat coating is level 5.

[0130] 4.3 Impact: The impact test shall be conducted according to section 8. Reverse impact test standard in GB / T 13448, and the evaluation criteria are as follows:

[0131] ◎: Impact energy ≥9J that prevents detachment between the EB-cured coating and the topcoat coating.

[0132] ○: The impact energy required to prevent detachment between the EB-cured coating and the topcoat is 7-8J.

[0133] Δ: The impact energy required to prevent detachment between the EB-cured coating and the topcoat is 6-7 J.

[0134] ×: Impact energy resulting in no detachment between the EB-cured coating and the topcoat coating ≤ 6J

[0135] 4.4 Corrosion resistance provided with the topcoat coating

[0136] The plate neutral salt spray test, conducted according to ASTM B117, lasted 1000 hours, and the evaluation criteria are as follows:

[0137] ◎: The bubble density grade and bubble size should not exceed grade 2 as specified in Table 21 of GB / T 1766.

[0138] ○: Bubble density and size should not exceed level 3 as specified in Table 21 of GB / T 1766. Δ: Bubble density and size should not exceed level 4 as specified in Table 21 of GB / T 1766. ×: Bubble density and size should not exceed level 5 as specified in Table 21 of GB / T 1766.

[0139] Table 3 shows the relevant test data of the electron beam cured coated steel sheets in Examples 1-9 and Comparative Examples 1-9 after the above tests.

[0140] Table 3.

[0141]

[0142]

[0143] As can be seen from Tables 1 and 3, in Comparative Example 1, the insufficient content of composite matrix resin A and the excessive content of monofunctional olefin unsaturated polymerizable monomer C are both detrimental to the dry adhesion performance of the electron beam cured coating steel plate. The lack of dry adhesion directly affects the wet adhesion and resistance to underfilm erosion.

[0144] In Comparative Example 2, the excessive content of organosilicon compound B reduced the surface energy of the electron beam cured coating and decreased the adhesion between the electron beam cured coating and the subsequent topcoat coating; while the excessive content of covering pigment G was detrimental to the dry adhesion performance of the pre-coated board.

[0145] In Comparative Example 3, the excessive content of acrylic phosphate compound D, which acts as an adhesion promoter, resulted in poor adhesion between the pre-coated plate and the subsequent topcoat coating. The insufficient content of anti-rust pigment F resulted in an insignificant anti-rust effect, manifested in a reduction in the resistance to under-film corrosion of the electron beam cured coated steel plate, as well as a reduction in the corrosion resistance provided together with the topcoat coating.

[0146] The excessive A1 / A2 ratio in composite matrix resin A in Comparative Example 4 indicates that the content of amine-modified epoxy acrylate oligomers, which mainly provide adhesion performance in the coating, is too low, which has an adverse effect on both dry and wet adhesion performance. On the other hand, the excessive content of titanium salt or zirconium salt compounds E of acrylic acid will affect the flexibility of the coating and thus also affect the dry adhesion performance of the pre-coated steel plate.

[0147] In Comparative Example 5, the high content of composite matrix resin A means that the content of components that provide adhesion and corrosion inhibition is relatively lower than that of resin, which is not conducive to the dry and wet adhesion performance of the coating. The low content of monofunctional olefin unsaturated polymerizable monomer C results in insufficient cross-linking and reduced dry adhesion performance of the pre-coated steel plate.

[0148] In Comparative Example 6, the content of organosilicon compound B was too low, which prevented the achievement of sufficient wet adhesion performance and resistance to underfilm corrosion.

[0149] In Comparative Example 7, the content of the titanium or zirconium salt compound E of acrylic acid, which is used as an interface corrosion inhibitor, is too low, and its anti-under-film corrosion effect is not obvious; the content of the hiding pigment G is too low, which affects the hiding effect of the coating.

[0150] In Comparative Example 8, the low content of acrylic phosphate compound D, which acts as an adhesion promoter, leads to poor dry and wet adhesion of the pre-coated steel plate; excessive addition of rust-preventive pigment F will damage the flexibility of the coating, thereby affecting the dry adhesion performance.

[0151] In Comparative Example 9, the absence of polyurethane acrylate oligomer A1 affected the coating's flexibility, which in turn impacted the dry adhesion performance of the pre-coated panel. Furthermore, because the coating thickness was smaller than the average particle size of the rust-inhibiting pigment silica in the coating, the wet adhesion performance of the pre-coated panel decreased, as did the overall corrosion resistance along with the topcoat coating.

[0152] The electron beam cured coated steel plates in Examples 1-9 of this invention all exhibit excellent dry and wet adhesion performance and resistance to underfilm corrosion, and can form good adhesion and overall corrosion resistance with the topcoat coating.

[0153] It should be noted that the embodiments listed above are merely specific embodiments of the present invention. Obviously, the present invention is not limited to the above embodiments, and similar changes or modifications made thereto are those that can be directly derived or easily conceived by those skilled in the art from the content disclosed in the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A coil coating for forming an electron beam cured coating, characterized in that, Its active ingredients include: Composite matrix resin A: 40-60 parts by weight; Organosilicon compound B: 3-10 parts by weight; said organosilicon compound B includes at least one of the following: vinyltrimethoxysilane, vinyltri(2-methoxyethoxy)silane, vinyltriisopropoxysilane, methylvinyldimethoxysilane, vinyltriacetoxysilane, propoxytriacetoxysilane methacrylate, triethoxysilane propyl methacrylate, and triethoxysilane methacrylate; Monofunctional olefinic unsaturated polymerizable monomer C: 15-25 parts by weight; wherein the monofunctional olefinic unsaturated polymerizable monomer C includes at least one of the following: hydroxypropyl methacrylate, cyclotrimethylolpropane methyl acetal acrylate, cyclotrimethylolpropane methyl acetal monoacrylate, isobornyl acrylate, lauryl acrylate, methyl methacrylate lauric acid, octyl acrylate decyl acrylate; Acrylic phosphate compound D: 5-15 parts by weight; said acrylic phosphate compound D includes at least one of the following: polyethylene glycol methacrylate, di(hydroxyethyl) phosphate, 2-methyl-2-hydroxyethyl acrylate phosphate, di(methacryloyloxyethyl) hydrogen phosphate. Titanium or zirconium salt compound E of acrylic acid: 0.3-2 parts by weight; said titanium or zirconium salt compound E of acrylic acid includes at least one of the following: titanium triisopropoxide methacrylate, zirconium acrylate, zirconium tetramethacrylate; The composite matrix resin A includes an aliphatic polyurethane acrylate oligomer A1 containing 20-30 wt% isoborneol acrylate and an amine-modified epoxy diacrylate oligomer A2 containing 30-40 wt% dipropylene glycol diacrylate, wherein the mass ratio of A1 to A2 is 1.0-5.

0.

2. The coil coating as described in claim 1, characterized in that, Its active ingredients consist of the following: Composite matrix resin A: 40-60 parts by weight; Organosilicon compound B: 3-10 parts by weight; Monofunctional olefinic unsaturated polymerizable monomer C: 15-25 parts by weight; Acrylic phosphate compound D: 5-15 parts by weight; Titanium or zirconium salts of acrylic acid, E: 0.3-2 parts by weight; The composite matrix resin A includes an aliphatic polyurethane acrylate oligomer A1 containing 20-30 wt% isoborneol acrylate and an amine-modified epoxy diacrylate oligomer A2 containing 30-40 wt% dipropylene glycol diacrylate, wherein the mass ratio of A1 to A2 is 1.0-5.

0.

3. The coil coating as described in claim 1, characterized in that, Its active ingredients also include at least one of the following: Rust-preventive pigment F: 2-5 parts by weight; Opacifying pigment G: 5-10 parts by weight; Additive H: 0.2-1 parts by weight.

4. The coil coating as described in any one of claims 1-3, characterized in that, The mass ratio of A1 to A2 is 1.5-4.

0.

5. The coil coating as described in claim 3, characterized in that, The rust-preventive pigment F comprises ion-exchange type alkaline silica powder.

6. The coil coating as described in claim 5, characterized in that, The ion-exchange alkaline silica powder has an average particle size of 2-6 μm and a pH of 8-10.

7. The coil coating as described in claim 3, characterized in that, The masking pigment G includes titanium dioxide.

8. The coil coating as described in claim 3, characterized in that, The additive H includes at least one of the following: leveling agent, wetting agent, and anti-settling agent.

9. A steel plate comprising a substrate, a plating layer plated on the surface of the substrate, and an electron beam cured coating applied to the surface of the plating layer, characterized in that, The electron beam cured coating is formed by applying the coil coating as described in any one of claims 1-8 to the coating surface and then curing it with an electron beam.

10. The steel plate as described in claim 9, characterized in that, The electron beam cured coating has a single-layer structure.

11. The steel plate as described in claim 9, characterized in that, The thickness of the electron beam cured coating is 3-30 μm.

12. The steel plate as described in claim 11, characterized in that, The thickness of the electron beam cured coating is 3-10 μm.

13. The steel plate as described in claim 9, characterized in that, The coating is a hot-dip galvanized layer, a hot-dip aluminum-zinc layer, a hot-dip zinc-aluminum-magnesium layer, or an electro-galvanized layer.

14. The steel plate as described in claim 9, characterized in that, The process parameters for electron beam curing are as follows: under a protective atmosphere of nitrogen + oxygen mixed gas with an oxygen content of ≤200ppm, the electron beam voltage is 90-150KV and the electron beam dose is 10-60KGy.

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