A hot eb dual cure pre-coated metal webbing coil coating

Abstract

The present application relates to the technical field of coil coating, and discloses a hot EB double-cured precoated metal-grain coil coating, which is made of components containing the following components by weight: saturated polyester resin: 10.0-20.0 parts; isobornyl acrylate: 5.0-15.0 parts; titanium white: 15.0-25.0 parts; barium sulfate: 5.0-15.0 parts; hydroxyl-containing polyurethane-modified acrylate oligomer: 15.0-35.0 parts; 1,6-hexanediol diacrylate: 10.0-20.0 parts; melamine resin: 2.0-8.0 parts; blocked isophorone diisocyanate: 3.0-10.0 parts, and the like. The hot EB double-cured precoated metal-grain coil coating of the present application is wrinkled into grains by EB radiation, and then the bottom layer is crosslinked by heat curing, so that the coating completely overcomes the defects of uneven batch of metal-grain and poor adhesion of pure EB curing.

Description

Technical Field

[0001] This invention relates to the field of coil coating technology, specifically to a pre-coated metallic mesh coil coating that undergoes thermal EB dual curing. Background Technology

[0002] Pre-coated metal coil coatings are primarily used for continuous coating of metal substrates to provide long-lasting protection and decorative functions. Among them, textured coatings are a type of product with high practical value. After film formation and curing, the surface exhibits an irregular, wrinkled, mesh-like texture. This coating not only possesses a unique visual appeal but also provides excellent surface smoothness for metal coils, effectively preventing excessive snow accumulation in practical applications such as winter roofing.

[0003] Traditional textured coatings for metal coils mostly employ solvent-based thermosetting systems. Their texture formation mechanism relies on solvent evaporation during heating, which drives acid catalysts to migrate and accumulate on the surface, causing a difference in curing rates between the inside and outside of the coating, resulting in shrinkage and wrinkling. In recent years, to address the volatile organic compound emissions and energy waste caused by solvent-based systems, the industry has begun exploring solvent-free solutions, such as pure EB electron beam cured coatings. These coatings utilize high-energy rays to directly crosslink active monomers containing double bonds with the resin system, replacing physical evaporation.

[0004] Existing technologies have significant drawbacks in practical applications. The wrinkling process of traditional thermosetting textured systems is highly dependent on the uniformity of oven heat and the stability of the hydroxyl value of the resin raw materials. However, industrial air knives cannot achieve absolutely precise heat control, and even slight heat deviations can lead to uncontrolled texture morphology, resulting in inconsistent product batches and low yields. On the other hand, while pure EB curing solutions avoid the use of solvents, the limited penetration capability of electron beams means that the surface layer reacts first, easily leading to excessive cross-linking. Insufficient curing of the underlying layer directly damages the adhesion between the coating and the metal substrate, causing the pre-coated roll material to face serious risks of cracking and paint peeling during subsequent deep processing.

[0005] Therefore, this invention proposes a pre-coated metallic mesh roll coating with thermal EB dual curing to overcome the shortcomings of the prior art. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a pre-coated metallic mesh roll coating with thermal EB dual curing. This solves the problem that when existing mesh coatings are cured and formed into a film, the curing rates of the surface wrinkling and the underlying cross-linking are often difficult to match, which leads to large shrinkage stress inside the coating film, resulting in decreased coating adhesion and poor stability of the mesh pattern.

[0007] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention provides a pre-coated metallic mesh roll coating that undergoes thermal EB dual curing, employing the following technical solution: A thermally EB dual-curing pre-coated metallic mesh roll coating, said coating being made from components comprising the following parts by weight: Saturated polyester resin: 10.0-20.0 parts; isobornyl acrylate: 5.0-15.0 parts; titanium dioxide: 15.0-25.0 parts; barium sulfate: 5.0-15.0 parts; hydroxyl-containing polyurethane modified acrylate oligomer: 15.0-35.0 parts; 1,6-hexanediol diacrylate: 10.0-20.0 parts; melamine resin: 2.0-8.0 parts; blocked isophorone diisocyanate: 3.0-10.0 parts; amine-blocked p-toluenesulfonic acid: 0.2-0.8 parts; glycidyl tert-carbonate: 1.0-3.0 parts; phenothiazine: 0.05-0.2 parts; 2,6-di-tert-butyl-p-cresol: 0.1-0.3 parts.

[0008] By employing the above technical solution, this invention combines alkenyl-containing materials, hydroxyl-containing resins, curing agents with specific unsealing temperatures, and catalysts to form a curing system capable of stepwise crosslinking. After coating and film formation, the actual curing process is carried out in two stages.

[0009] During the electron beam irradiation stage at room temperature, the double bonds in the hydroxyl-containing polyurethane-modified acrylate oligomers, isobornyl acrylate, and 1,6-hexanediol diacrylate in the coating surface layer undergo free radical polymerization first. As the surface material rapidly crosslinks and shrinks, a textured, wrinkled structure begins to form on the surface. At this point, because the amine-blocked p-toluenesulfonic acid and blocked isophorone diisocyanate in the system are structurally stable at room temperature, the underlying material remains in an uncrosslinked, low-viscosity state, providing the necessary space to release surface shrinkage stress.

[0010] After the initial radiation-induced wrinkling, the coating is placed in a high-temperature baking environment, triggering subsequent thermosetting. As the temperature rises, the amine-blocked p-toluenesulfonic acid is deblocked, releasing p-toluenesulfonic acid molecules, which act as an acidic catalyst to further initiate the polycondensation reaction in the underlying layer. Specifically, the methoxy groups of the melamine resin crosslink with the hydroxyl groups on the saturated polyester resin and the aforementioned oligomers. At the same time, the blocked isophorone diisocyanate is also deblocked by heat, and the free isocyanate groups add to the residual hydroxyl groups. The epoxy groups of glycidyl tert-carbonate also participate in the crosslinking network.

[0011] This step-by-step curing method, which occurs in both time and space, effectively avoids the stress concentration problem caused by overall synchronous cross-linking. It not only ensures the regularity of the surface texture but also significantly improves the adhesion between the coating and the substrate.

[0012] Preferably, the coating is made of components comprising the following parts by weight: 15.0 parts of saturated polyester resin, 10.0 parts of isobornyl acrylate, 20.0 parts of titanium dioxide, 10.0 parts of barium sulfate, 25.0 parts of hydroxyl-containing polyurethane-modified acrylate oligomer, 15.0 parts of 1,6-hexanediol diacrylate, 5.0 parts of melamine resin, 6.0 parts of blocked isophorone diisocyanate, 0.5 parts of amine-blocked p-toluenesulfonic acid, 2.0 parts of glycidyl tert-carbonate, 0.1 parts of phenothiazine, and 0.2 parts of 2,6-di-tert-butyl-p-cresol.

[0013] By adopting the above technical solution, the specific ratio of each component is limited, so that the reaction rate of free radical polymerization and thermal polycondensation can be better adapted to the conventional electron beam absorption dose and baking temperature under this formula, thereby obtaining a more uniform textured surface and more stable coating mechanical properties.

[0014] Preferably, the saturated polyester resin has a hydroxyl-terminated random linear structure, a weight-average molecular weight of 3,000 to 10,000, and a hydroxyl value of 20 to 100 mg KOH per gram; The blocking agent for the blocked isophorone diisocyanate is methyl ethyl ketone oxime; The amine-blocked p-toluenesulfonic acid is prepared by complexing p-toluenesulfonic acid with N,N-dimethylethanolamine.

[0015] By adopting the above technical solution, saturated polyester resin with specific parameters can provide the necessary flexibility and hydroxyl functionality to maintain the crosslinking density of the bottom layer after thermosetting. At the same time, methyl ethyl ketone oxime is used as a sealing agent and N,N-dimethylethanolamine is used as a complexing agent, mainly to lock the desealing temperature of the two within the high-temperature baking range, so as to prevent them from participating in the reaction in advance when irradiated by electron beam at room temperature, thereby ensuring the smooth progress of step-by-step curing.

[0016] Preferably, the hydroxyl-containing polyurethane modified acrylate oligomer is polymerized from isophorone diisocyanate, hydroxyethyl methacrylate and polyol; The polyol is trimethylolpropane or tetrahydrofuran homopolymer ether with a number average molecular weight of 400.

[0017] By employing the above technical solution, the acrylate double bonds at both ends of the oligomer can participate in the initial free radical polymerization, while the urethane bonds and hydroxyl groups in the middle segment are used for subsequent thermal polycondensation. The introduction of trimethylolpropane or tetrahydrofuran homopolymer ether adjusts the flexibility of the molecular chain; relying on this dual reactive property of the oligomer, the photocurable network on the surface and the thermocurable network on the bottom can be effectively connected, thereby enhancing the bonding strength at the cross-linking interface of the two layers.

[0018] Preferably, the method for preparing the hydroxyl-containing polyurethane-modified acrylate oligomer includes the following steps: (1) Under a protective gas, the isophorone diisocyanate and the catalyst dibutyltin dilaurate are heated to 45-50°C, and the hydroxyethyl methacrylate is added dropwise at a uniform rate. After the addition is completed, the reaction is kept at the temperature. The reaction is stopped when the characteristic peak area of ​​the isocyanate is reduced by half using an infrared spectrometer to obtain a semi-addition intermediate. (2) Heat the semi-addition intermediate obtained in step (1) to 60-70°C, add the polyol and stir continuously until the mass fraction of free isocyanate in the material is less than 0.1% and then discharge the material.

[0019] By adopting the above technical solution, since the two isocyanate groups in isophorone diisocyanate have significantly different activities, the reaction temperature and dropping rhythm can be controlled to promote the sequential addition of hydroxyethyl methacrylate and polyol. In this process, continuous monitoring with an infrared spectrometer helps to control the purity of the semi-addition intermediate and reduce the formation of diaddition byproducts, ultimately making the resulting oligomer structure more in line with the process design requirements.

[0020] Secondly, the present invention provides a method for preparing a pre-coated metallic mesh roll coating with thermal EB dual curing, using the following technical solution: A method for preparing a pre-coated metallic mesh roll coating with thermal EB dual curing includes the following steps: S1: Saturated polyester resin, isoborneol acrylate, titanium dioxide and barium sulfate are mixed and ground to disperse, thus obtaining pigment paste; S2: Transfer the pigment paste to a paint mixing tank, then add hydroxyl-containing polyurethane modified acrylate oligomer, 1,6-hexanediol diacrylate, melamine resin, blocked isophorone diisocyanate, amine-blocked p-toluenesulfonic acid, glycidyl tert-carbonate, phenothiazine and 2,6-di-tert-butyl-p-cresol to obtain a mixture. Stir the mixture evenly and filter to obtain the target coating.

[0021] By adopting the above technical solution, the inorganic powders such as titanium dioxide and barium sulfate need to withstand high shear forces during deagglomeration and dispersion, which inevitably generates a large amount of frictional heat. If the resin, all curing agents, and catalysts in the system are added at once, the heat accumulated during grinding can easily trigger premature deblocking of blocked isophorone diisocyanate and amine-blocked p-toluenesulfonic acid, directly causing cross-linking and deterioration of the coating during storage. Based on this process consideration, this solution separates the feeding and dispersion actions; firstly, the inorganic powders are ground using a relatively stable saturated polyester resin combined with low-viscosity isoborneol acrylate to prepare pigment paste. This treatment method can fully wet the powder while avoiding the damage of high temperature to the heat-sensitive cross-linking system. After the pigment paste is dispersed, it is transferred to a paint mixing tank and mixed with hydroxyl-containing polyurethane-modified acrylate oligomers and the remaining components; through this mild post-mixing operation, the chemical stability of various active substances in the dual-curing system is maintained.

[0022] Preferably, in step S1, the saturated polyester resin, the isoborneol acrylate, the titanium dioxide, and the barium sulfate are added to a dispersion tank and stirred and dispersed at a speed of 1000-2000 rpm for 15-30 minutes. In step S1, the grinding and dispersion process involves feeding the stirred and dispersed material into a sand mill and grinding it until the material fineness is 5-15 μm.

[0023] By employing the above technical solution, the medium-to-high speed stirring applied in the dispersion tank mainly serves a pre-dispersion function, breaking up soft agglomerates in the inorganic powder and promoting resin components to cover the particle surface. The stirred material then enters a sand mill for physical grinding to control the fineness within 5 to 15 μm. Setting this fineness range has clear practical considerations: if the fineness is too large, the pigment is prone to sedimentation and aggregation during the coating curing stage; conversely, excessive grinding not only risks cutting off part of the polymer molecular skeleton but also affects the surface uniformity of the final wrinkled texture. Keeping the material fineness within this specific range perfectly balances the suspension stability of the coating in its liquid state with the textured appearance of the film after formation.

[0024] Preferably, in step S2, the process of stirring evenly involves stirring the mixture in the paint mixing tank at a speed of 300-800 revolutions per minute for 20-40 minutes. In step S2, the specific operation of filtration involves filtering the mixture using a 200-400 mesh filter.

[0025] By adopting the above technical solution, the subsequent paint mixing operation strictly limits the rotation speed to a low level of 300 to 800 revolutions per minute. The purpose is to control the frictional heat generated by the stirring shaft, and while completing the homogeneous mixing of each component, to avoid local overheating of the system that could cause the latent curing agent to fail. As for the 200 to 400 mesh filter used at the end, its main target is to intercept occasional small gel particles and residual large particulate impurities during operation. By removing these interfering factors, the leveling properties of the paint during coating are physically guaranteed, thereby reducing the probability of pinholes or surface defects after curing.

[0026] This invention provides a pre-coated metallic mesh roll coating that undergoes thermal EB dual curing. It offers the following advantages: 1. This invention constructs a dual crosslinking system by introducing alkenyl-containing active components, utilizing EB radiation to induce free radical polymerization on the surface layer, leading to shrinkage and wrinkling. Addressing the problem of inconsistent curing rates between surface wrinkling and underlying crosslinking in existing textured coatings, resulting in poor texture stability, this intervention method avoids the uncontrollable physical process relying on solvent evaporation. By precisely controlling the material and radiation energy, this pre-curing shaping operation eliminates the interference of uneven heating from the oven air knife, significantly improving batch-to-batch morphological consistency and production yield. 2. This invention uses active resins and monomers as diluents to participate in the curing network, directly replacing the organic solvents in traditional formulations, thus avoiding the waste of resources caused by volatile organic compound emissions and incomplete combustion. Addressing the defect that mismatched curing rates between the surface and inner layers can easily lead to internal shrinkage stress and consequently reduce coating adhesion, this solution promotes crosslinking of the underlying resin separately through subsequent thermal reactions after wrinkling of the surface EB layer. This dual-action method effectively releases the shrinkage stress caused by the asynchronous reaction between the inner and outer layers, compensating for the poor adhesion of pure electron beam coatings on metal substrates, and ensuring that the coil coating will not experience brittle cracking or paint peeling during later deep processing. 3. This invention establishes a chemical bridge between the photocurable network and the thermally crosslinked matrix by adding a specially modified oligomer containing both alkenyl double bonds and reserved hydroxyl groups. During the room-temperature EB stage, this substance participates in surface polymerization and shaping, and during subsequent high-temperature baking, its hydroxyl groups completely condense with the underlying components. This ingenious molecular design connects the upper and lower interfaces, completely overcoming the significant shrinkage stress caused by the mismatch between surface wrinkling and the underlying crosslinking rate from the material's molecular structure. This eliminates the risk of decreased coating adhesion, resulting in excellent interlayer bonding and physical resistance of the pre-coated metal coil. Attached Figure Description

[0027] Figure 1 This is a line graph showing the gelation rate during the dual-curing stage of the present invention. Figure 2The graph shows the gradient variation of the macroscopic roughness of the pre-coated metallic mesh roll coating of the present invention; wherein, (a) records the numerical variation trajectory of the profile arithmetic mean deviation Ra of each embodiment, and (b) records the numerical evolution law of the corresponding micro-irregularity ten-point height Rz. Figure 3 This is a bi-Y-axis line graph showing the mechanical properties of the pre-coated metallic mesh roll coating of the present invention. Figure 4 This is a line graph showing the viscosity of the pre-coated metallic mesh roll coating under constant temperature accelerated aging according to the present invention. Figure 5 This is a bi-Y-axis line graph showing the difference in wrinkle thickness of the pre-coated metallic mesh roll coating of the present invention and the number of methyl ethyl ketone (MEK) wiping cycles. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] The main raw materials and reagents used in the following examples and comparative examples have the following sources and specifications. Reagents not specifically mentioned are all commercially available analytical grade or higher grade products.

[0030] The saturated polyester resin has a random linear structure with terminal hydroxyl groups, a weight-average molecular weight of 3,000 to 10,000, a hydroxyl value of 20 to 100 mg KOH / g, and a glass transition temperature of 10°C to 30°C. The main chain of this resin is formed by the polycondensation reaction of terephthalic acid, isophthalic acid, neopentyl glycol, and trimethylolpropane.

[0031] Isoborneol acrylate, CAS number 5888-33-5.

[0032] 1,6-Hexanediol diacrylate, CAS No. 13048-33-4.

[0033] Isophorone diisocyanate, CAS number 4098-71-9.

[0034] Hydroxyethyl methacrylate, CAS number 868-77-9.

[0035] Trimethylolpropane, CAS number 77-99-6.

[0036] Tetrahydrofuran homopolymer ether, CAS number 25190-06-1, number average molecular weight 400.

[0037] Dibutyltin dilaurate, CAS number 77-58-7.

[0038] Melamine resin, CAS number 3089-11-0, has a hexamethoxymethyl substituted structure.

[0039] Blocked isophorone diisocyanate, which is a blocked isocyanate-terminated prepolymer with isophorone diisocyanate as the backbone, the blocking agent is methyl ethyl ketone oxime, and the deblocking temperature is 130°C to 150°C.

[0040] Amine-blocked p-toluenesulfonic acid is a dormant catalyst prepared by complexing p-toluenesulfonic acid with N,N-dimethylethanolamine, with a deblocking temperature of 120°C to 150°C.

[0041] Glycidyl tert-carbonate, CAS number 26761-45-5.

[0042] Phenothiazine, CAS number 92-84-2.

[0043] 2,6-Di-tert-butyl-p-cresol, CAS number 128-37-0.

[0044] Titanium dioxide, CAS number 1317-80-2, is rutile type, with a titanium dioxide mass fraction greater than 93%.

[0045] Barium sulfate, CAS number 7727-43-7, median diameter D50 is 0.5 to 1.5 μm.

[0046] Preparation Example 1: This preparation example provides a method for preparing hydroxyl-containing polyurethane-modified acrylate oligomers, including the following steps: Step 1: Add 222.0 parts by weight of isophorone diisocyanate and 0.2 parts by weight of dibutyltin dilaurate to the reaction vessel. Under the protection of continuously purging dry air with a moisture content of less than 50 ppm, stir at a stirring speed of 300 rpm and heat to 45°C. Then, add 130.0 parts by weight of hydroxyethyl methacrylate dropwise at a uniform rate over a time of 1.5 hours. After the addition is complete, maintain the temperature at 45°C and stirring speed of 300 rpm for another 2.0 hours. Continuously monitor the characteristic peak area of ​​isocyanate in the material in the reaction vessel using an online infrared spectrometer. When the characteristic peak area is reduced by half compared to the initial characteristic peak area of ​​isophorone diisocyanate, stop the reaction to obtain the semi-addition intermediate. Step 2: Heat the semi-addition intermediate obtained in Step 1 to 65°C, add 400.0 parts by weight of tetrahydrofuran homopolymer, and stir continuously at a stirring speed of 400 rpm for 4.0 hours. When the mass fraction of free isocyanate in the material is less than 0.1% by the di-n-butylamine method, cool down to room temperature and discharge the material to obtain hydroxyl-containing polyurethane modified acrylate oligomer.

[0047] Preparation Example 2: This preparation example provides a method for preparing hydroxyl-containing polyurethane-modified acrylate oligomers, including the following steps: Step 1: Add 222.0 parts by weight of isophorone diisocyanate and 0.1 parts by weight of dibutyltin dilaurate to the reaction vessel. Under the protection of continuously purging dry air with a moisture content of less than 50 ppm, stir at a stirring speed of 250 rpm and heat to 50°C. Then, add 130.0 parts by weight of hydroxyethyl methacrylate dropwise at a uniform rate over a time of 2.0 hours. After the addition is complete, maintain the temperature at 50°C and stirring speed of 250 rpm for another 2.5 hours. Continuously monitor the characteristic peak area of ​​isocyanate in the material in the reaction vessel using an online infrared spectrometer. When the characteristic peak area is reduced by half compared to the initial characteristic peak area of ​​isophorone diisocyanate, stop the reaction to obtain the semi-addition intermediate. Step 2: Heat the semi-addition intermediate obtained in Step 1 to 60°C, add 67.0 parts by weight of trimethylolpropane, and stir continuously at a stirring speed of 350 rpm for 5.0 hours. When the mass fraction of free isocyanate in the material is less than 0.1% by the di-n-butylamine method, cool down to room temperature and discharge the material to obtain hydroxyl-containing polyurethane modified acrylate oligomer.

[0048] Preparation Example 3: This preparation example provides a method for preparing hydroxyl-containing polyurethane-modified acrylate oligomers, including the following steps: Step 1: Add 222.0 parts by weight of isophorone diisocyanate and 0.3 parts by weight of dibutyltin dilaurate to the reactor. Under the protection of continuously purging dry air with a moisture content of less than 50 ppm, stir at a stirring speed of 350 rpm and heat to 48°C. Then, add 130.0 parts by weight of hydroxyethyl methacrylate dropwise at a uniform rate over a time of 1.8 hours. After the addition is complete, maintain the temperature at 48°C and stirring speed of 350 rpm for another 2.2 hours. Continuously monitor the characteristic peak area of ​​isocyanate in the reactor using an online infrared spectrometer. When the characteristic peak area is reduced by half compared to the initial characteristic peak area of ​​isophorone diisocyanate, stop the reaction to obtain the semi-addition intermediate. Step 2: Heat the semi-addition intermediate obtained in Step 1 to 70°C, add 600.0 parts by weight of tetrahydrofuran homopolymer, and stir continuously at a stirring speed of 450 rpm for 6.0 hours. When the mass fraction of free isocyanate in the material is less than 0.1% by the di-n-butylamine method, cool down to room temperature and discharge the material to obtain hydroxyl-containing polyurethane modified acrylate oligomer.

[0049] Example 1: This example provides a method for preparing a pre-coated metallic mesh roll coating with thermal EB dual curing, including the following steps: S1: Add 15.0 parts by weight of saturated polyester resin, 10.0 parts by weight of isobornyl acrylate, 20.0 parts by weight of titanium dioxide and 10.0 parts by weight of barium sulfate to a dispersion tank, stir and disperse at a speed of 1500 rpm for 20 minutes, and then send the mixed material into a sand mill to grind until the fineness of the material is 10μm to obtain pigment paste; S2: Transfer the pigment paste obtained in S1 to a mixing tank. Then, add 25.0 parts by weight of the hydroxyl-containing polyurethane modified acrylate oligomer prepared in Preparation Example 1, 15.0 parts by weight of 1,6-hexanediol diacrylate, 5.0 parts by weight of melamine resin, 6.0 parts by weight of blocked isophorone diisocyanate, 0.5 parts by weight of amine-blocked p-toluenesulfonic acid, 2.0 parts by weight of glycidyl tert-carbonate, 0.1 parts by weight of phenothiazine, and 0.2 parts by weight of 2,6-di-tert-butyl-p-cresol to the mixing tank. Stir the mixture in the mixing tank at 500 rpm for 30 minutes. Then, filter the mixture in the mixing tank using a 300-mesh filter to obtain a thermally EB dual-cured pre-coated metallic mesh roll coating.

[0050] Example 2: This example provides a method for preparing a pre-coated metallic mesh roll coating with thermal EB dual curing, including the following steps: S1: Add 10.0 parts by weight of saturated polyester resin, 5.0 parts by weight of isobornyl acrylate, 15.0 parts by weight of titanium dioxide and 5.0 parts by weight of barium sulfate to a dispersion tank, stir and disperse at a speed of 1000 rpm for 15 minutes, and then send the mixed material into a sand mill to grind until the fineness of the material is 15μm to obtain pigment paste. S2: Transfer the pigment paste obtained in S1 to a mixing tank. Then, add 15.0 parts by weight of the hydroxyl-containing polyurethane modified acrylate oligomer prepared in Preparation Example 2, 10.0 parts by weight of 1,6-hexanediol diacrylate, 2.0 parts by weight of melamine resin, 3.0 parts by weight of blocked isophorone diisocyanate, 0.2 parts by weight of amine-blocked p-toluenesulfonic acid, 1.0 parts by weight of glycidyl tert-carbonate, 0.05 parts by weight of phenothiazine, and 0.1 parts by weight of 2,6-di-tert-butyl-p-cresol to the mixing tank. Stir the mixture in the mixing tank at 300 rpm for 20 minutes. Then, filter the mixture in the mixing tank using a 200-mesh filter to obtain a thermally EB dual-cured pre-coated metallic mesh roll coating.

[0051] Example 3: This example provides a method for preparing a pre-coated metallic mesh roll coating with thermal EB dual curing, including the following steps: S1: Add 20.0 parts by weight of saturated polyester resin, 15.0 parts by weight of isobornyl acrylate, 25.0 parts by weight of titanium dioxide and 15.0 parts by weight of barium sulfate to a dispersion tank, stir and disperse at a speed of 2000 rpm for 30 minutes, and then send the mixed material into a sand mill to grind until the fineness of the material is 5μm to obtain pigment paste; S2: The pigment paste obtained in S1 above is transferred to a mixing tank. Then, 35.0 parts by weight of the hydroxyl-containing polyurethane modified acrylate oligomer prepared in Preparation Example 3, 20.0 parts by weight of 1,6-hexanediol diacrylate, 8.0 parts by weight of melamine resin, 10.0 parts by weight of blocked isophorone diisocyanate, 0.8 parts by weight of amine-blocked p-toluenesulfonic acid, 3.0 parts by weight of glycidyl tert-carbonate, 0.2 parts by weight of phenothiazine, and 0.3 parts by weight of 2,6-di-tert-butyl-p-cresol are added to the mixing tank. The mixture is stirred at 800 rpm for 40 minutes. Then, the mixture in the mixing tank is filtered through a 400-mesh filter to obtain a pre-coated metallic mesh roll coating that is heat-cured with EB double curing.

[0052] Comparative Example 1: Compared with Example 1, the difference is that 25.0 parts by weight of the hydroxyl-containing polyurethane modified acrylate oligomer obtained in Preparation Example 1 in S2 was replaced by an equal amount of conventional hexafunctional polyurethane acrylate without hydroxyl groups, and all other aspects were the same.

[0053] Comparative Example 2: The difference from Example 1 is that glycidyl tert-carbonate was not added in S2, but all other aspects are the same.

[0054] Comparative Example 3: Compared with Example 1, the difference is that phenothiazine and 2,6-di-tert-butyl-p-cresol were not added in S2, and all other aspects were the same.

[0055] Comparative Example 4: Compared with Example 1, the difference is that 0.5 parts by weight of amine-blocked p-toluenesulfonic acid in S2 was replaced by 0.5 parts by weight of unblocked conventional p-toluenesulfonic acid (CAS No. 104-15-4), and all other aspects were the same.

[0056] Test Example 1: Experimental objective: To verify the specific chemical crosslinking mechanism of the pre-coated metallic mesh roll coating with thermal EB dual curing of the present invention at different curing stages, and to confirm that the alkenyl double bond free radical polymerization reaction triggered by electron beam (EB) irradiation and the hydroxy-isocyanate condensation reaction triggered by high temperature baking can proceed stepwise and independently, thereby forming differentiated curing states on the coating surface and the underlying layer.

[0057] Experimental steps: Multiple galvanized tinplate sheets of the same specifications were cut as substrates. The pre-coated metal mesh roll coatings prepared by heat-cured double-curing as described in Examples 1, 2 and 3 were uniformly coated on the substrate surface using a wire bar coater to prepare multiple sets of parallel test samples. The wet film thickness was controlled to be 25 μm.

[0058] The coated sample was placed in a nitrogen-protected environment for 5 seconds to level, and then sent to an electron beam curing device for the first curing stage. The device parameters were set to an accelerating voltage of 150 kV and an absorbed dose of 40 kGy, completing unidirectional irradiation.

[0059] Immediately after irradiation, a portion of the parallel test specimens from each set of embodiments was extracted for destructive sampling to obtain test data for the first curing stage. A portion of the coating film was scraped from the extracted specimens and measured at 1636 cm⁻¹ using an attenuated total reflectance infrared spectroscopy instrument. -1 The area of ​​the characteristic absorption peak of the acrylic double bond was compared with the peak area of ​​the uncured stock solution to obtain the double bond conversion rate. The content of free isocyanate inside the coating film was determined by di-n-butylamine titration, and then divided by the theoretical content of the total blocked isocyanate initially added to the coating formulation to obtain the relative percentage of isocyanate retention. A certain mass of the cured coating film was refluxed and extracted in a Soxhlet extractor with toluene solvent for 24 hours, dried and weighed to calculate the proportion of insoluble matter to the original mass, which was used as the gel rate of this stage.

[0060] The remaining parallel test samples that have completed the first curing stage electron beam irradiation and have not been damaged by sampling are transferred into a blower-cooled constant temperature drying oven for the second curing stage. The plate temperature is set to 224℃ and baked for 32 seconds to simulate the high-temperature curing section of the actual production line. The samples are then removed and cooled to room temperature.

[0061] After the sample cooled to room temperature, the coating sample was scraped again, and the final test data was obtained using the same analytical methods as in the first curing stage: the absorption peak area was measured using an attenuated total reflectance infrared spectrometer to calculate the final double bond conversion rate; the remaining free isocyanate content was determined by di-n-butylamine titration and the final relative isocyanate retention percentage was calculated; similarly, the sample was refluxed in a Soxhlet extractor using toluene solvent, dried, and weighed to calculate the final gel rate data.

[0062] Experimental results (see Table 1): Table 1: Test data of crosslinking index of coating at different curing stages

[0063] Test conclusion: According to Table 1 and Figure 1As shown, the pre-coated metallic mesh roll coatings prepared by thermal EB dual curing in Examples 1, 2, and 3 exhibited a rapid increase in double bond conversion rate to nearly 80% or higher after the first stage of electron beam irradiation. Based on the physicochemical reaction mechanism, it is known that the double bond ends of the alkenyl monomers (such as isobornyl acrylate and 1,6-hexanediol diacrylate) and hydroxyl-containing polyurethane-modified acrylate oligomers on the coating surface undergo free radical polymerization in a very short time, forming a dense cross-linked mesh structure on the surface. The relative percentage of isocyanate retention measured at this stage remained high at over 98%, verifying that the blocked isophorone diisocyanate in the formulation did not undergo deblocking and cross-linking reactions before the ambient temperature reached its deblocking critical point. This unidirectional surface polymerization only provides a locally cured layer, resulting in a low gel rate of 42% to 52%, indicating that the hydroxyl-containing saturated polyester resin in the deeper material has not yet participated in the film-forming process.

[0064] Following high-temperature baking, the double bond conversion rate showed a small increase, indicating that the electron beam irradiation-induced double bond polymerization was essentially complete. The blocked isophorone diisocyanate and melamine resin within the coating unblocked and reacted at high temperature, with the relative percentage of isocyanate remaining decreasing significantly to less than 3%, indicating that the hydroxyl groups on the saturated polyester resin and oligomers participated in the thermosetting crosslinking reaction. This thermosetting crosslinking process increased the gel rate to a fully cured state of 96.5% to 99.2%. The alkenyl structure at one end of the designed hydroxyl-containing polyurethane-modified acrylate oligomer participates in the surface electron beam curing layer, while the hydroxyl group at the other end crosslinks with the underlying thermosetting matrix. The test results fully validated the feasibility of the dual curing mechanism of this material at the chemical data level; the reactions at each stage are independent and can be precisely triggered according to the set physical conditions.

[0065] Test Example 2: Experimental objective: To verify that the pre-coated metallic mesh roll coating with thermal EB dual curing of the present invention can achieve gradient precise control of the macroscopic surface roughness and mesh morphology of the coating by adjusting the absorption dose of the electron beam, without relying on solvent evaporation to guide acid migration.

[0066] Experimental steps: Multiple galvanized tinplate sheets of the same specifications were used as substrates. The heat-cured EB double-cured pre-coated metal mesh roll coatings prepared in Examples 1, 2 and 3 were uniformly coated on the substrate surface using a wire bar coater to prepare multiple sets of parallel test samples with a wet film thickness of 25 μm.

[0067] The coated samples were placed in a nitrogen-protected environment for 5 seconds to level. Then, the parallel test samples of each embodiment were divided into three batches and sent to an electron beam curing device for the first curing stage irradiation. By adjusting the operating parameters of the electron beam curing device to obtain different energy outputs, the absorbed doses of the three batches were set to 30 kGy, 50 kGy, and 70 kGy, respectively, while the accelerating voltage of the device was kept constant at 150 kV.

[0068] After electron beam irradiation, all samples were transferred to a forced-air constant-temperature drying oven for the second curing stage. The oven temperature was set to 224℃ and baked for 32 seconds. The samples were then removed and cooled to room temperature.

[0069] After the samples have completely cooled and set, the physical morphology of each sample surface is measured using a contact probe surface roughness measuring instrument. During testing, the instrument's stylus slides along the sample surface within a set sampling length, and the instrument's internal sensor records the undulations of the surface's micro-geometry. Based on this, the arithmetic mean deviation of the profile, Ra, is calculated; that is, the arithmetic mean of the absolute values ​​of the profile deviations within the sampling length. Simultaneously, the five maximum profile peak heights and five maximum profile valley depths within the sampling length are extracted, and their averages are summed as the ten-point height of the micro-irregularity, Rz. Five measurement points are randomly selected in different areas of each test surface for repeated measurements, and the arithmetic mean is taken as the final data for the sample's profile arithmetic mean deviation Ra and the ten-point height of the micro-irregularity, Rz.

[0070] Experimental results (see Table 2): Table 2: Test data of coating surface roughness under different electron beam absorbed doses

[0071] Test conclusion: According to Table 2 and Figure 2 As shown, the physical profile parameters of the pre-coated metallic mesh roll coatings prepared by thermal EB dual curing in Examples 1, 2, and 3, after being excited by electron beams of different intensities, showed a significant increasing trend with increasing absorbed dose. When the applied electron beam absorbed dose was set to a relatively low 30 kGy, the arithmetic mean deviation Ra of the profiles in these three examples was concentrated in the range of 3.27 μm to 4.13 μm, and the height of the ten micro-irregularities Rz did not exceed 23 μm. This indicates that at a lower absorbed dose, the free radical polymerization rate of the alkenyl material on the coating surface is slower, the intermolecular volume shrinkage force induced during the construction of the crosslinked network is limited, and only a relatively shallow mesh morphology can be formed on the surface.

[0072] Increasing the electron beam absorption dose to 50 kGy and even higher to 70 kGy significantly increased the surface roughness of the coating. Taking a 70 kGy absorption dose as an example, the arithmetic mean deviation Ra of the profile in Example 1 jumped to 12.19 μm, while the ten-point height Rz of micro-irregularities in Examples 2 and 3 exceeded 67 μm and 56 μm, respectively. This morphological change confirms the control effect of the electron beam absorption dose on the surface crosslinking density. High-density free radicals induce rapid local volume shrinkage, leading to a deeper and more undulating wrinkled network. By adjusting the electron beam as a single physical output variable, this method enables quantitative control of the three-dimensionality of the coating wrinkles, avoiding the batch-to-batch variation defects induced by the uncontrollable physical process of solvent evaporation carrying away acid catalysts, which is highly dependent on traditional textured coatings. Combined with the pre-embedded saturated polyester resin and closed isocyanate thermosetting system in the formulation, the surface texture is firmly crosslinked and cured by the underlying crosslinking network at a subsequent high temperature of 224°C, ensuring excellent structural support stability for textures of different gradients.

[0073] Test Example 3: Experimental Objective: To verify the mechanical deformation resistance and interlayer bonding strength of the pre-coated metallic mesh roll coating with thermal EB dual curing of the present invention after complete curing; to confirm that the chemical crosslinking formed between the photocured surface formed by electron beam irradiation and the thermocured underlayer formed by high temperature baking of the hydroxyl-containing polyurethane modified acrylate oligomer can effectively enhance the interlayer bonding force and deformation resistance; and to verify the key role of the specially formulated oligomer in preventing interlayer discontinuity and peeling by comparing it with a conventional oligomer without hydroxyl.

[0074] Experimental steps: Multiple galvanized tinplate sheets of the same specifications were used as substrates. The pre-coated metal mesh roll coatings prepared by heat-cured double-curing as described in Examples 1, 2, 3 and Comparative Example 1 were uniformly coated onto the substrate surface using a wire bar coater to prepare multiple sets of parallel test samples with a wet film thickness controlled at 25 μm.

[0075] The coated samples were placed in a nitrogen-protected environment for 5 seconds to level, and then sent to an electron beam curing device for the first curing stage irradiation. The absorbed dose of the device was set to 50 kGy and the accelerating voltage to 150 kV. After irradiation, all samples were transferred to a forced-air constant temperature drying oven for the second curing stage treatment. The plate temperature was set to 224℃ and baked continuously for 32 seconds. The samples were then removed and cooled to room temperature to obtain a fully cured coating.

[0076] After the samples have completely cooled and set, a portion of the parallel test samples from each set of examples and comparative examples are selected, and the flexibility of the coating film on the samples is measured using a cupping tester. During the test, a spherical punch is pressed into the back of the sample at a constant speed, and the surface condition of the coating is continuously monitored through an observation mirror. The specific displacement distance of the spherical punch into the test sample when the first visible crack just appears on the coating surface is recorded. The above operation is repeated for multiple samples from the same set, and the arithmetic mean of the measured displacement distances is taken as the final cupping depth data for the corresponding sample.

[0077] Samples were taken from the remaining parallel test specimens of each set of examples and comparative examples, and the adhesion strength between the coating and the substrate was determined using a pull-off adhesion tester. A 20mm diameter aluminum test cylinder was bonded to the coating surface of the specimen using epoxy resin adhesive and cured at room temperature for 24 hours. A tensile tester was used to apply a gradually increasing tensile load to the aluminum cylinder along a direction perpendicular to the substrate surface, and the maximum tensile stress value applied at the moment of failure and peeling between the coating and the substrate or within the coating was recorded. Independent tensile tests were performed on multiple specimens from this set, and the arithmetic mean of the recorded maximum tensile stress values ​​was calculated as the final adhesion strength data for the corresponding sample.

[0078] Experimental results (see Table 3): Table 3: Test Data of Coating Flexibility and Adhesion Strength

[0079] Test conclusion: According to Table 3 and Figure 3 As shown, the pre-coated metallic mesh roll coatings prepared by thermal EB dual curing in Examples 1, 2, and 3 all exhibited good flexibility and adhesion, with cupping depths ranging from 6.81 mm to 8.24 mm and adhesion strengths ranging from 9.87 MPa to 12.35 MPa. This physical performance directly confirms the interlayer crosslinking effect of the hydroxyl-containing polyurethane-modified acrylate oligomer in the formulation at the microstructure level. In the first curing stage induced by electron beam irradiation, the alkenyl group at one end of the hydroxyl-containing polyurethane-modified acrylate oligomer molecule participates in the free radical copolymerization of the surface material, forming a locally high-density crosslinked network that causes the mesh wrinkling. In the second curing stage dominated by high-temperature baking, the hydroxyl group retained at the other end of the molecule undergoes a polycondensation reaction with the underlying saturated polyester resin and the blocked isophorone diisocyanate. The addition of oligomer molecules with dual cross-linking functional groups establishes a high-density covalent bond connection between the surface photocurable network and the underlying thermocurable matrix, overcoming the interlayer separation and brittle peeling problems that are prone to occur in conventional heterogeneous dual-curing coatings due to differences in shrinkage rate.

[0080] Significantly different from the examples, the sample in Comparative Example 1 exhibited lower flexibility and adhesion during testing, with a cupping depth of only 3.42 mm and an adhesion strength as low as 2.15 MPa. This is because Comparative Example 1 used a conventional hexafunctional polyurethane acrylate without hydroxyl groups. This conventional oligomer can only participate in the free radical polymerization of the surface layer during the electron beam irradiation stage. When entering the second stage of high-temperature baking, due to the lack of hydroxyl groups (chemical crosslinking groups), it cannot chemically react with the underlying saturated polyester resin and isocyanate. The photocured surface layer and the thermocured substrate are only bonded by weak intermolecular forces, making interlayer separation easy to form internally. Under the physical deformation stress of the cupping punch or vertical tensile load, this discontinuous structure cannot effectively transfer stress, leading to easy cracking and peeling damage of the coating.

[0081] The saturated polyester resin at the bottom layer in the formulation of this example contributes to the excellent overall flexibility of the coating, effectively alleviating the external deformation stress generated by cupping and maintaining a high cupping value. The chemical cross-linking of the upper and lower layers significantly enhances the cohesiveness of the coating and its bonding strength with the metal substrate, resulting in higher adhesion strength of the cured overall coating under tensile loads. The above test data verify that this invention, while maintaining the surface texture, fully meets the requirements for coating adhesion and flexibility in the subsequent deep processing of metal coils.

[0082] Test Example 4: Experimental objective: To verify the storage stability of the pre-coated metallic mesh roll coating with thermal EB dual curing of the present invention under constant temperature accelerated aging conditions, and to confirm the effectiveness of the combined introduction of glycidyl tert-carbonate as a free acid scavenger and phenothiazine and 2,6-di-tert-butyl-p-cresol as dual polymerization inhibitors in preventing early crosslinking and unintended polymerization of the coating.

[0083] Experimental steps: Take appropriate amounts of the paint stock solutions prepared in Examples 1, 2, 3, 2, and 3, and Comparative Examples 2 and 3, and put them into standard tinplate sealed containers, ensuring that the container has about 10% headspace volume. Then seal the containers tightly. For the four test nodes of day 0, day 10, day 20, and day 30, prepare independent parallel test sample containers for each example and comparative example.

[0084] Before accelerated aging storage, the stock solution was removed from the individual sample containers for testing on day 0 of each group and placed in a 25°C water bath for 2 hours to equilibrate the temperature. Using an NDJ-5S rotational viscometer with a No. 4 rotor and a constant rotation speed of 60 rpm, the rotor was vertically immersed in the temperature-controlled stock solution for measurement. After the instrument reading stabilized, the hydrodynamic viscosity value was recorded; this value corresponds to the day 0 viscosity data for each example and comparative example.

[0085] The remaining independently sealed test sample containers for days 10, 20, and 30 were transferred to a constant temperature incubator set at 40°C for continuous accelerated aging storage to verify shelf life performance under temperature stress.

[0086] The storage time was continuously calculated within the incubator. On the 10th, 20th, and 30th days, the individual sealed test sample containers corresponding to the current storage time were removed from the incubator. After the removed samples were allowed to cool naturally and then kept at a constant temperature of 25°C in a water bath for 2 hours, measurements were taken using the same rotational viscometer, rotor #4, and measurement parameters of 60 rpm as the initial test. Stable hydrodynamic viscosity values ​​were recorded on the instrument, corresponding to the 10-day, 20-day, and 30-day viscosity data for the test sample. If the sample had hardened within the container or its consistency exceeded the instrument's range, it was directly recorded as a gel.

[0087] Experimental results (see Table 4): Table 4: Viscosity Test Data of Coatings under Constant Temperature Accelerated Aging

[0088] Test conclusion: According to Table 4 and Figure 4 As shown, the pre-coated metallic mesh roll coatings prepared by heat-cured EB dual-curing in Examples 1, 2, and 3 exhibited good storage stability during accelerated aging storage at a constant temperature of 40°C, with minimal viscosity change after 30 days of continuous testing. This indicates that the coatings maintained good fluidity within the specified storage period. In contrast, the coatings in Comparative Examples 2 and 3 showed a significant increase in viscosity or gelation under the same testing conditions.

[0089] The main reason for the sharp increase in viscosity at 10 days and the gelation at 20 and 30 days in Comparative Example 2 was the absence of glycidyl tert-carbonate in the formulation. During prolonged storage or at elevated ambient temperatures, there is a possibility of trace amounts of amine-blocked p-toluenesulfonic acid unblocking and releasing free acid. When glycidyl tert-carbonate is lacking to neutralize these free acids, the released acid molecules directly catalyze an early polycondensation reaction between the melamine resin and the hydroxyl-containing polyurethane-modified acrylate oligomer in the formulation, promoting cross-linking within the coating.

[0090] Observation of the data from Comparative Example 3 shows that its viscosity gradually and significantly increases over time. This change is due to the absence of phenothiazine and 2,6-di-tert-butyl-p-cresol dual polymerization inhibitors in the formulation. Without the addition of these two inhibitors, the coating concentrate cannot effectively suppress the generation of trace free radicals in a medium-temperature environment of 40°C. The remaining trace free radicals continuously induce dark-reaction crosslinking of the alkenyl double bonds in the hydroxyl-containing polyurethane-modified acrylate oligomer and the 1,6-hexanediol diacrylate diluent, leading to a continuous increase in coating viscosity. The formulation design of this invention, through the synergistic effect of glycidyl tert-carbonate and dual free radical polymerization inhibitors, effectively inhibits free acid-catalyzed condensation polymerization and double-bond free radical polymerization, thereby improving the storage life of the coating.

[0091] Test Example 5: Experimental objective: To verify the role of amine-blocked p-toluenesulfonic acid as a dormant acid catalyst in the thermally EB dual-cured pre-coated metallic mesh roll coating of the present invention in controlling the uniformity of mesh formation and the crosslinking density of the final coating film, and to confirm the mechanism by which staged deblocking and curing improves the coating film formation quality by comparing it with a control example using unblocked conventional p-toluenesulfonic acid.

[0092] Experimental steps: Multiple galvanized steel sheets of the same specifications were used as substrates. The coating stock solutions prepared in Examples 1, 2, 3, and Comparative Example 4 were uniformly coated onto the substrate surfaces using a wire bar coater, resulting in multiple independent parallel test samples with a wet film thickness controlled at 25 μm. Each set of parallel test samples was placed in a nitrogen-protected environment for leveling for 5 seconds, and then sent to an electron beam curing device for the first stage of irradiation. The absorbed dose of the device was set to 50 kGy, and the accelerating voltage to 150 kV. After irradiation, each set of samples was transferred to a forced-air constant-temperature drying oven for the second stage of high-temperature baking treatment. The plate temperature was set to 224°C, and baking was continued for 32 seconds. After the samples were removed and completely cooled and set, cured test samples with a textured surface were obtained, corresponding to the examples and comparative examples.

[0093] Thickness range was measured using a magnetic thickness gauge. Five 10cm × 10cm test areas were randomly marked on the surface of parallel cured samples selected from each group. The coating thickness was measured at six different locations within each area, resulting in a total of 30 thickness data points. The maximum and minimum thickness values ​​among these 30 data points were recorded, and the difference between the maximum and minimum thickness values ​​was calculated. The arithmetic mean of this difference was calculated for multiple parallel samples from each embodiment and comparative example. This mean was used as the final range data for the textured wrinkling thickness.

[0094] After soaking medical absorbent cotton balls in methyl ethyl ketone (MEK) solvent, they were fixed to the test end of a solvent-resistant wiping instrument. The surfaces of the remaining parallel test samples were repeatedly wiped under a constant load of 1000g. The coating condition of the test area was continuously monitored, and the specific number of wiping cycles was recorded when the coating surface was damaged by MEK solvent and the underlying metal substrate was exposed. Multiple parallel samples in each group were independently tested, and the arithmetic mean was calculated. This value corresponds to the MEK wiping cycle data for each embodiment and comparative example.

[0095] Experimental results (see Table 5): Table 5: Data on Coating Texture Thickness Variation and Number of Ethylene Ketone Wiping Cycles

[0096] Test conclusion: According to Table 5 and Figure 5 As shown, the pre-coated metallic mesh roll coatings prepared by heat-cured EB in Examples 1, 2, and 3 exhibited small thickness fluctuations after complete curing, with the range of mesh wrinkling thickness remaining stable between 1.82 μm and 2.65 μm. Furthermore, all three coatings showed resistance to methyl ethyl ketone (MEK) wiping cycles exceeding 100 times. These characteristics indicate the formation of a uniform mesh morphology on the coating surface and the construction of a dense chemical cross-linked network within the coating. In contrast, the range of mesh wrinkling thickness in Comparative Example 4 increased to 11.43 μm, and the resistance to MEK wiping cycles decreased to 45 times, resulting in poorer uniformity and solvent resistance in the coating appearance.

[0097] The main reason for the above data discrepancies lies in the influence of the timing of acid catalyst release on the dual-curing reaction process. In the example formulation, the amine-blocked p-toluenesulfonic acid maintained a stable blocked state during room-temperature coating and subsequent electron beam irradiation, without releasing free acid molecules. During this stage, the acrylate oligomers containing alkenyl double bonds and the reactive diluent on the coating surface undergo free radical polymerization under electron beam excitation, generating inward internal stress due to volume shrinkage. Since the bottom layer has not yet undergone thermal crosslinking, the liquid components at the bottom maintain low rheological resistance, allowing the shrinkage stress generated on the surface to be released, thereby inducing the formation of a uniformly thick network structure. Upon entering the high-temperature baking environment of the second stage, the heating temperature exceeds the critical deblocking temperature of the amine-blocked p-toluenesulfonic acid, causing the amine-blocking groups to detach and release p-toluenesulfonic acid molecules. The deblocked acid molecules catalyze the condensation polymerization of the melamine resin in the bottom layer with the hydroxyl groups on each component, promoting the formation of a complete three-dimensional covalent crosslinked network in a short time, resulting in good coating density and solvent resistance.

[0098] Observation of the data in Comparative Example 4 shows that unsealed conventional p-toluenesulfonic acid is already in a free state during the leveling stage at room temperature. Free acid catalyzes localized pre-crosslinking of the underlying melamine resin, causing regionally uneven increases in viscosity of the underlying material before formal curing. This sudden viscosity change restricts the surface material's degree of freedom of contraction when irradiated by an electron beam, leading to an imbalance in stress transmission between different areas. This results in varying degrees of wrinkle depth in the final texture, macroscopically manifested as a significant increase in the difference in wrinkle thickness. Premature disordered crosslinking interferes with the regular formation of the ideal polymer network, generating incompletely reacted segments within the coating. This reduces the overall crosslinking density and weakens resistance to external solvent erosion, leading to a decrease in the number of methyl ethyl ketone (MEK) wiping cycles. The sealed acid-catalyzed design of this invention separates the time points of photocuring and thermal curing, ensuring the overall forming quality of the textured coating.

[0099] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A pre-coated metallic mesh roll coating with thermal EB dual curing, characterized in that, The coating is made from components comprising the following parts by weight: Saturated polyester resin: 10.0-20.0 parts; isoborneol acrylate: 5.0-15.0 parts; titanium dioxide: 15.0-25.0 parts; barium sulfate: 5.0-15.0 parts; hydroxyl-containing polyurethane modified acrylate oligomer: 15.0-35.0 parts; 1,6-hexanediol diacrylate: 10.0-20.0 parts; melamine resin: 2.0-8.0 parts; blocked isophorone diisocyanate: 3.0-10.0 parts; amine-blocked p-toluenesulfonic acid: 0.2-0.8 parts; glycidyl tert-carbonate: 1.0-3.0 parts; phenothiazine: 0.05-0.2 parts; 2,6-Di-tert-butyl-p-cresol: 0.1-0.3 parts.

2. The pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 1, characterized in that, The coating is made from components comprising the following parts by weight: 15.0 parts of saturated polyester resin, 10.0 parts of isobornyl acrylate, 20.0 parts of titanium dioxide, 10.0 parts of barium sulfate, 25.0 parts of hydroxyl-containing polyurethane-modified acrylate oligomer, 15.0 parts of 1,6-hexanediol diacrylate, 5.0 parts of melamine resin, 6.0 parts of blocked isophorone diisocyanate, 0.5 parts of amine-blocked p-toluenesulfonic acid, 2.0 parts of glycidyl tert-carbonate, 0.1 parts of phenothiazine, and 0.2 parts of 2,6-di-tert-butyl-p-cresol.

3. The pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 1, characterized in that, The saturated polyester resin has a hydroxyl-terminated random linear structure, a weight-average molecular weight of 3,000 to 10,000, and a hydroxyl value of 20 to 100 mgKOH / g. The blocking agent for the blocked isophorone diisocyanate is methyl ethyl ketone oxime; The amine-blocked p-toluenesulfonic acid is prepared by complexing p-toluenesulfonic acid with N,N-dimethylethanolamine.

4. The pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 1, characterized in that, The hydroxyl-containing polyurethane modified acrylate oligomer is polymerized from isophorone diisocyanate, hydroxyethyl methacrylate and polyol; The polyol is trimethylolpropane or tetrahydrofuran homopolymer ether with a number average molecular weight of 400.

5. The pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 4, characterized in that, The preparation method of the hydroxyl-containing polyurethane modified acrylate oligomer includes the following steps: (1) Under a protective gas, the isophorone diisocyanate and the catalyst dibutyltin dilaurate are heated to 45-50°C, and the hydroxyethyl methacrylate is added dropwise at a uniform rate. After the addition is completed, the reaction is kept at the temperature. The reaction is stopped when the characteristic peak area of ​​the isocyanate is reduced by half using an infrared spectrometer to obtain a semi-addition intermediate. (2) Heat the semi-addition intermediate obtained in step (1) to 60-70°C, add the polyol and stir continuously until the mass fraction of free isocyanate in the material is less than 0.1% and then discharge the material.

6. A method for preparing a pre-coated metallic mesh roll coating with thermal EB dual curing according to any one of claims 1-5, characterized in that, Includes the following steps: S1: Saturated polyester resin, isoborneol acrylate, titanium dioxide and barium sulfate are mixed and ground to disperse, thus obtaining pigment paste; S2: Transfer the pigment paste to a paint mixing tank, then add hydroxyl-containing polyurethane modified acrylate oligomer, 1,6-hexanediol diacrylate, melamine resin, blocked isophorone diisocyanate, amine-blocked p-toluenesulfonic acid, glycidyl tert-carbonate, phenothiazine and 2,6-di-tert-butyl-p-cresol to obtain a mixture. Stir the mixture evenly and filter to obtain the target coating.

7. The method for preparing the pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 6, characterized in that, In step S1, the saturated polyester resin, the isobornyl acrylate, the titanium dioxide, and the barium sulfate are added to a dispersion tank and stirred and dispersed at a speed of 1000-2000 rpm for 15-30 minutes.

8. The method for preparing the pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 6, characterized in that, In step S1, the grinding and dispersing process is as follows: the material after stirring and dispersing is fed into a sand mill and ground until the fineness of the material is 5-15μm.

9. The method for preparing the pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 6, characterized in that, In step S2, the process of stirring evenly is as follows: the mixture is stirred in the paint mixing tank at a speed of 300-800 revolutions per minute for 20-40 minutes.

10. The method for preparing the pre-coated metallic mesh roll coating with thermal EB dual curing according to claim 6, characterized in that, In step S2, the specific filtration operation is as follows: filter the mixture using a 200-400 mesh filter.

Images