Radiation curing powder coating as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of coatings, and particularly relates to a radiation curing powder coating as well as a preparation method and application thereof. The radiation curing powder coating is prepared from the following raw materials in parts by mass: 56 to 65 parts of resin, 5 to 25 parts of novolac epoxy resin coated ammonium polyphosphate, 5 to 25 parts of magnesium-aluminum layered double hydroxide mechanochemical intercalation modified aluminum tripolyphosphate, 2 to 10 parts of zinc phosphate, 1 to 10 parts of photoinitiator, 1 to 2 parts of flatting agent and 0 to 1 part of defoaming agent. The powder coating provided by the invention is strong in adhesive force, a coating body is easy to form after being sprayed on a metal matrix material, the coating body is excellent in impact resistance, salt mist resistance, hardness and the like, the flame retardant grade reaches UL94 V-0 grade, the fireproof and antirust performance is excellent, and the long-term stable performance can be maintained.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a radiation-cured powder coating, its preparation method, and its application. Background Technology

[0002] The main materials for power battery casings include steel, aluminum alloys, composite materials (such as SMC and carbon fiber), and high-performance plastics. The choice is made based on a trade-off between strength, lightweight, and corrosion resistance, depending on the application scenario. Steel possesses high physical stability and compressive strength, providing reliable physical protection for the battery and effectively resisting external collisions and impacts. Furthermore, steel processing technology is mature, and production costs are relatively low, making it suitable for mass production. However, steel is prone to rusting in humid environments, requiring the application of anti-rust coatings. Only after rust prevention treatment can long-term stability and safety be maintained.

[0003] Radiation-cured powder coatings are a type of powder coating that does not require high-temperature baking but relies primarily on ultraviolet (UV) or electron beam (EB) irradiation to rapidly cure into a film. Existing radiation-cured powder coatings use limited raw materials, and the rapid curing process directly affects the full wetting of the coating with the substrate, as well as the orderly arrangement of the molecular chains. Consequently, the coating's mechanical strength, toughness, and adhesion to metal substrates are all suboptimal. Summary of the Invention

[0004] To provide a high-performance radiation-cured powder coating, this invention provides a radiation-cured powder coating, its preparation method, and its application. The powder coating provided by this invention exhibits strong adhesion, easily forms a coating body when sprayed onto a metal substrate, and possesses excellent impact resistance, salt spray resistance, and hardness. It also achieves a UL94 V-0 flame retardant rating, demonstrating excellent fire and rust prevention properties and maintaining long-term performance stability.

[0005] This invention provides a radiation-cured powder coating, which is made from the following raw materials in parts by weight: 56 to 65 parts of resin, 5 to 25 parts of phenolic epoxy resin-coated ammonium polyphosphate, 5 to 25 parts of magnesium-aluminum layered double hydroxide mechanically and chemically intercalated aluminum tripolyphosphate, 2 to 10 parts of zinc phosphate, 1 to 10 parts of photoinitiator, 1 to 2 parts of leveling agent, and 0 to 1 part of defoamer.

[0006] The powder coating provided by this invention has strong adhesion and can easily form a coating body when sprayed on metal substrate materials. The coating body has excellent impact resistance, salt spray resistance and hardness, and the flame retardant rating reaches UL94 V-0 level. It has excellent fireproof and rustproof performance and can maintain long-term performance stability.

[0007] Furthermore, the radiation-cured powder coating is made from the following raw materials in parts by weight: 64.5 parts resin, 20 parts phenolic epoxy resin-coated ammonium polyphosphate, 7 parts magnesium aluminum layered double hydroxide mechanically and chemically intercalated modified aluminum tripolyphosphate, 6 parts zinc phosphate, 1 part photoinitiator, 1.5 parts leveling agent, and 0.5 parts defoamer.

[0008] Furthermore, the resin is composed of 80% semi-crystalline polyester acrylate resin, 0%~20% polyurethane acrylate and 0%~20% epoxy acrylate; wherein the contents of polyurethane acrylate and epoxy acrylate are not both 0%.

[0009] Furthermore, the photoinitiator is composed of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:1 to 3; the leveling agent is an acrylate leveling agent or an organosilicone leveling agent; and the defoamer is an organosilicone defoamer.

[0010] The present invention also provides a method for preparing the radiation-cured powder coating, comprising the following steps: The in-situ polymerization method was used to cure phenolic epoxy resin on the surface of ammonium polyphosphate to form a dense coating layer, thus obtaining ammonium polyphosphate coated with phenolic epoxy resin. A mechanochemical method was used to drive aluminum tripolyphosphate or its derivatives to intercalate into the interlayer structure of magnesium-aluminum layered double hydroxides through ball milling, thereby obtaining magnesium-aluminum layered double hydroxide mechanochemically intercalated aluminum tripolyphosphate. Premixing resin, phenolic epoxy resin-coated ammonium polyphosphate, magnesium aluminum layered double hydroxide mechanical and chemical intercalation modified aluminum tripolyphosphate, zinc phosphate, photoinitiator, leveling agent and defoamer yields a premix. The premixed material is melt-extruded to obtain strips at a melt-extruded temperature of 110℃~130℃. The material strips are pressed into tablets, crushed, and sieved to obtain radiation-cured powder coatings.

[0011] Furthermore, the preparation steps of the phenolic epoxy resin-coated ammonium polyphosphate are as follows: phenolic epoxy resin and dicyandiamide curing agent are directly added to the ammonium polyphosphate suspension; and stirred at 50℃~70℃ for 3 to 5 hours to allow the resin to directly undergo cross-linking and curing reaction on the particle surface and be coated.

[0012] Furthermore, the preparation steps of the magnesium-aluminum layered double hydroxide mechanochemical intercalation modified aluminum tripolyphosphate are as follows: Aluminum tripolyphosphate was dried at 100℃~110℃ to obtain aluminum tripolyphosphate powder; The magnesium-aluminum layered double hydroxide was pulverized, passed through a 325-mesh sieve, and the magnesium-aluminum layered double hydroxide powder was collected. Aluminum tripolyphosphate powder and magnesium aluminum layered double hydroxide powder are mixed at a weight ratio of 2 to 6:1, and then ground with grinding media. After grinding, the grinding media is removed by passing the powder through a 200-mesh sieve. The resulting powder is then dried to obtain the magnesium-aluminum layered double hydroxide mechanically and chemically intercalated aluminum tripolyphosphate.

[0013] Furthermore, the grinding media consists of zirconia grinding balls with a diameter of 5 mm and zirconia grinding balls with a diameter of 10 mm in a mass ratio of 2:3.

[0014] The present invention also provides the application of the radiation-cured powder coating to form a coating body on a metal substrate material, the coating body having the properties of impact resistance, salt spray resistance, high hardness, fire resistance and rust prevention.

[0015] Furthermore, the coating thickness is 90μm to 100μm, and the metal substrate material is a steel substrate material.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The powder coating provided by this invention has strong adhesion and easily forms a coating body when sprayed onto metal substrates. The coating exhibits excellent impact resistance, salt spray resistance, and hardness, achieving a UL94 V-0 flame retardant rating. It also demonstrates excellent fire and rust prevention properties, maintaining long-term performance stability. Furthermore, it possesses both good early and long-term rust prevention capabilities and combines the advantages of high powder coating utilization with the low-temperature curing of radiation-cured coatings. It is suitable for protecting the metal casings of power batteries and other applications requiring high fire and rust resistance.

[0017] In the powder coating provided by this invention, the resin is composed of semi-crystalline polyester acrylate resin and functional acrylates (polyurethane acrylate, epoxy acrylate). Both the semi-crystalline polyester acrylate resin and the functional acrylates contain unsaturated groups, which can be cured under ultraviolet light irradiation and the action of a photoinitiator to form a coating matrix (resin matrix). The core of the phenolic epoxy resin-coated ammonium polyphosphate is ammonium polyphosphate, which has excellent fire-retardant properties. Its outer shell is a phenolic epoxy resin coating layer, which can block the penetration of external moisture or water, prevent the precipitation of ammonium polyphosphate, and thus ensure that the coating has a long-lasting and stable fire-retardant capability. The loose interlayer structure of the magnesium-aluminum layered double hydroxide-modified aluminum tripolyphosphate facilitates the release of rust-preventing ions (phosphate ions), improving rust-preventive performance. Furthermore, the enhanced interaction between the neutralized aluminum tripolyphosphate and the resin matrix is ​​beneficial to improving the mechanical properties of the coating and its adhesion to the substrate, as well as the storage stability of the coating. Aluminum tripolyphosphate (APP) has a relatively fast rust-preventive effect, while zinc phosphate rust-preventive paint is slower but more durable. Using both together helps the coating maintain a high level of rust prevention throughout its service life. Additionally, APP and zinc phosphate themselves have flame-retardant properties and can act as synergists with ammonium polyphosphate as the primary flame retardant. However, more ammonium polyphosphate, APP, and zinc phosphate are not necessarily better; they must be controlled within a reasonable range. When the dosage of ammonium polyphosphate is below 5%, APP below 5%, and zinc phosphate below 2%, the content of the anti-corrosion active components in the coating is insufficient, failing to form a stable and effective rust-preventive system, resulting in poor coating corrosion resistance. While the corrosion resistance of the coating improves when the dosage of ammonium polyphosphate exceeds 25%, APP exceeds 25%, or zinc phosphate exceeds 10%, excessive addition of any of these three fillers will weaken the coating's impact resistance to varying degrees. Therefore, it is crucial to minimize the amount added while meeting performance requirements, and thus, control the dosage of all three within an appropriate range.

[0018] The radiation-cured powder coating of this invention contains APP, ATP, MgAl-CO3 LDH, and zinc phosphate, all of which have dual functions of flame retardancy and rust prevention. This allows the coating to maintain excellent fire resistance (UL94 V-0 rating, limiting oxygen index ≥25%) and rust prevention (salt spray resistance ≥1000h) even under extreme conditions, such as thermal runaway in new energy vehicles, thermal runaway or combustion of power batteries, high-temperature summer seasons, high-humidity autumn seasons, and water immersion or heavy rain. Specifically, ammonium polyphosphate decomposes upon heating to generate polyphosphoric acid (a strong dehydrating agent), promoting dehydration and carbonization of organic surfaces to form a carbonized film. Simultaneously, the gases and heat generated during decomposition cause the coating to expand and bubble, forming a foam insulation layer that isolates external oxygen and heat transfer. The decomposition process releases non-combustible gases such as nitrogen and ammonia, diluting the oxygen concentration in the surrounding air and blocking the combustion chain reaction. The carbonized film and the expanded foam layer cover the substrate surface, effectively isolating air and preventing oxygen from entering the combustion zone. At high temperatures, aluminum tripolyphosphate dehydrates, forming water vapor that carries away a significant amount of energy and lowers the surrounding temperature. Furthermore, dehydration promotes the formation of a carbon layer, which helps to isolate the air. Magnesium-aluminum layered double hydroxides also have a similar effect. Therefore, these fillers also provide synergistic flame retardancy.

[0019] The phenolic epoxy resin-coated ammonium polyphosphate of this invention offers several beneficial effects: First, ammonium polyphosphate has poor thermal stability; coating improves its thermal stability, preventing high-temperature decomposition during powder coating preparation and ensuring the actual effective content of ammonium polyphosphate. Second, ammonium polyphosphate is an inorganic salt with poor compatibility with organic resins; coating with an organic resin layer improves compatibility with the matrix resin, facilitating uniform dispersion in the coating and preventing migration to the coating surface, thus improving the coating's flame retardancy and mechanical properties. Third, the highly cross-linked coating layer impedes water penetration, preventing APP from decomposing into phosphoric acid upon contact with water, which would cause corrosion of steel.

[0020] This invention utilizes magnesium-aluminum layered double hydroxide mechanochemical intercalation modified aluminum tripolyphosphate, which expands the interlayer spacing of ATP, thereby increasing the rust-inhibiting ions (PO4). 3- / Al 3+The release rate of ATP is increased by more than 3 times, and the nanosheets formed after intercalation can be oriented in the coating to form a labyrinthine barrier, significantly reducing oxygen permeability and thus increasing the salt spray tolerance time of the coating to over 1000 hours. Furthermore, intercalation gives ATP an alkaline surface, eliminating the "flash rust" phenomenon, and its use in combination with zinc phosphate gives the coating both early and long-term rust prevention capabilities. In addition, the ball milling collision energy is used to forcibly peel off the MgAl-CO3 LDH sheets and insert them into the ATP interlayer, achieving interlayer spacing expansion (>2.0 nm) and surface alkalization (pH>7.0) in one step, reducing the process time to less than 3 hours, compared to 72 hours for the traditional hydrothermal method.

[0021] In this invention, during the curing of the powder coating, the semi-crystalline polyester acrylate resin polymerizes to form a "rigid skeleton." Increasing its content significantly improves curing speed and efficiency, and substantially increases coating hardness, abrasion resistance, and chemical resistance. The functional acrylate forms a "flexible network." Increasing its content significantly enhances flexibility, impact resistance, and adhesion to the substrate, greatly improving adhesion and balancing internal stress and shrinkage. By varying the amounts of semi-crystalline polyester acrylate resin and functional acrylate in the formulation, a series of customized formulations can be created, resulting in coatings with different film properties and curing processes to meet the requirements of various applications. Detailed Implementation

[0022] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods, and the materials and reagents used in the following embodiments are commercially available unless otherwise specified. The aluminum tripolyphosphate has a D50 ≤ 5 μm, and the magnesium-aluminum layered double hydroxide belongs to MgAl-CO3. 2- Type, Mg / Al molar ratio 2:1, specific surface area ≥20m² 2 / g; the epoxy value of the phenolic epoxy resin is 0.45~0.50. Table 1 lists the source and specifications of the raw materials in the examples.

[0023] Example 1 A phenolic epoxy resin-coated ammonium polyphosphate and its preparation method include the following steps: 100g of ammonium polyphosphate (APP) was dispersed in 250mL of 70% ethanol aqueous solution and stirred at 60℃ to dissolve. The mixture was then treated with ultrasound at 40kHz for 30min. After that, 15g of phenolic epoxy resin (EPN) was added and stirred evenly. Then, 150mL of 1% dicyandiamide ethanol solution was added dropwise. The mixture was stirred at 300rpm and 60℃ for 4h. After the reaction was completed, the mixture was centrifuged at 4000rpm for 10min, and the solid product was collected. The solid product was washed three times with 70% ethanol aqueous solution and then dried in a vacuum oven at 60℃ for 12h. Finally, it was air-jet pulverized to D50≦10μm to obtain phenolic epoxy resin-coated ammonium polyphosphate.

[0024] The degree of polymerization of the ammonium polyphosphate is ≥1000.

[0025] In the above preparation steps: Dicyandiamide in the dicyandiamide ethanol solution, acting as an amine curing agent for epoxy resin, readily undergoes a curing reaction with the epoxy resin at 60°C, forming a cross-linked structure. The initially formed flocculent cross-linked structure carries a large amount of ammonium polyphosphate along with it to settle. As dicyandiamide continues to be added dropwise, the cross-linking density gradually increases, forming a dense phenolic epoxy resin coating layer that completely encapsulates the ammonium polyphosphate, preventing direct contact with the external environment. After the reaction is complete, the mixture is centrifuged, washed, vacuum dried at 60°C, and then air-jet pulverized to D50 ≤ 10 μm to obtain phenolic epoxy resin-coated ammonium polyphosphate. In the preparation of phenolic epoxy resin-coated ammonium polyphosphate, the dosage of phenolic epoxy resin and dicyandiamide curing agent ensures the formation of a dense cross-linked structure and a moderate coating thickness, balancing flame retardancy and compatibility. Excessive dosage of phenolic epoxy resin and dicyandiamide curing agent results in an overly thick coating, reducing the flame retardant efficiency of the coating. Conversely, insufficient dosage leads to incomplete coating, making the ammonium polyphosphate prone to migration and hydrolysis. During curing, excessively high reaction temperatures result in overly rapid reactions and uneven cross-linking network formation. Conversely, excessively low temperatures lead to incomplete curing, insufficient cross-linking density, and inability to form an effective coating.

[0026] Example 2 A phenolic epoxy resin-coated ammonium polyphosphate and its preparation method are disclosed. The preparation method is the same as that in Example 1, except that the amount of phenolic epoxy resin used is 25g, the amount of dicyandiamide used is 2.5g, the reaction temperature is 50℃, and the reaction time is 5h.

[0027] Example 3 A phenolic epoxy resin-coated ammonium polyphosphate and its preparation method are disclosed. The preparation method is the same as that in Example 1, except that the amount of phenolic epoxy resin used is 35g, the amount of dicyandiamide used is 3.5g, the reaction temperature is 70℃, and the reaction time is 3h.

[0028] Example 4 A magnesium-aluminum layered double hydroxide mechanically and chemically intercalated modified aluminum tripolyphosphate and its preparation method include the following steps: Aluminum tripolyphosphate (ATP) was dried at 105°C until the moisture content was less than 0.5% to obtain aluminum tripolyphosphate powder for later use; the D50 of the aluminum tripolyphosphate was ≤5μm.

[0029] Magnesium-aluminum layered double hydroxide (MgAl-CO3 LDH) was pulverized and passed through a 325-mesh sieve to collect the MgAl-CO3 LDH powder; the magnesium-aluminum layered double hydroxide belongs to MgAl-CO3. 2- Type, Mg / Al molar ratio 2:1, specific surface area ≥20m² 2 / g.

[0030] Take 300g of aluminum tripolyphosphate powder and 100g of MgAl-CO3 LDH powder, mix them, and put them into a ball mill jar. Then add 2000g of zirconia grinding balls with a diameter of 5mm and 3000g of zirconia grinding balls with a diameter of 10mm. Grind with a planetary ball mill for 2 hours at a speed of 400rpm and a jar temperature of ≤45℃. After grinding, remove the grinding balls by passing them through a 200-mesh sieve and dry them to obtain magnesium-aluminum layered double hydroxide mechanochemically intercalated aluminum tripolyphosphate.

[0031] The aforementioned magnesium-aluminum layered double hydroxide is alkaline and contains hydroxide ions (OH-). - ) and carbonate ions (CO3) 2- Aluminum tripolyphosphate is acidic and contains H+. + And Al 3+ Both are layered inorganic salts, and their blending and grinding can form intercalation structures. Due to the strong interlayer forces of aluminum tripolyphosphate and the weak interlayer forces of magnesium aluminum layered double hydroxides, magnesium aluminum layered double hydroxides are typically intercalated into aluminum tripolyphosphate. The intercalation driving force is the synergy of mechanical grinding and acid-base neutralization. When the amount of hydrotalcite is too small, intercalation is insufficient, the interlayer spacing is not widened enough, and the release of rust-preventing ions is slow; while when the amount of hydrotalcite is too large, excessive hydrotalcite tends to agglomerate, reducing coating adhesion. If the grinding time is too long, the particles are excessively crushed and prone to agglomeration; while if the time is too short, the layers are not completely peeled off, resulting in poor intercalation.

[0032] Example 5 A magnesium-aluminum layered double hydroxide mechanically and chemically intercalated modified aluminum tripolyphosphate and its preparation method are disclosed. The method is prepared according to Example 4, except that the amount of aluminum tripolyphosphate used is 400g and the grinding time is 1h.

[0033] Example 6 A magnesium-aluminum layered double hydroxide mechanically and chemically intercalated modified aluminum tripolyphosphate and its preparation method are disclosed. The method is prepared according to Example 4, except that the amount of aluminum tripolyphosphate used is 500g and the grinding time is 3h.

[0034] Example 7 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts of D resin, 20 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 1, 7 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 4, 6 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320).

[0035] The photoinitiator is prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:1; the D resin is composed of 80% semi-crystalline polyester acrylate resin and 20% polyurethane acrylate.

[0036] The preparation of the above-mentioned radiation-cured powder coating includes the following steps: Weigh the raw materials according to the mass fractions and mix them to obtain a premix. Use a twin-screw extruder to melt-extrude the premix at a barrel temperature of 120°C. The melt-extruded strands are directly fed into a two-roll plasticizer for sheeting. The strands are then crushed by a pulverizer and sieved through a 200-mesh sieve. The powder that passes through the 200-mesh sieve is collected to obtain powder coating.

[0037] Example 8 A radiation-curable powder coating is made from the following raw materials in parts by weight: 64.5 parts of D resin, 20 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 2, 7 parts of aluminum tripolyphosphate mechanically and chemically intercalated with magnesium aluminum layered double hydroxide obtained in Example 4, 6 parts of zinc phosphate, 1 part of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320). The photoinitiator is the same as in Example 7, and the preparation steps are the same as in Example 7.

[0038] Example 9 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts of E resin, 20 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 3, 7 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 4, 6 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320); The photoinitiator is the same as in Example 7; Resin E is composed of 80% semi-crystalline polyester acrylate resin and 20% epoxy acrylate. The preparation steps are the same as in Example 7.

[0039] Example 10 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts of F resin, 15 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 1, 12 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 5, 6 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320); The photoinitiator is the same as in Example 7; resin F is composed of 80% semi-crystalline polyester acrylate resin, 10% polyurethane acrylate, and 10% epoxy acrylate. The preparation steps are the same as in Example 7.

[0040] Example 11 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts of G resin, 15 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 2, 12 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 5, 6 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320); The photoinitiator is the same as in Example 7; Resin G is composed of 80% semi-crystalline polyester acrylate resin and 20% epoxy acrylate. The preparation steps are the same as in Example 7.

[0041] Example 12 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts of H resin, 15 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 2, 12 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 5, 6 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320); The photoinitiator is the same as in Example 7; Resin H is composed of 80% semi-crystalline polyester acrylate resin, 10% polyurethane acrylate, and 10% epoxy acrylate. The preparation steps are the same as in Example 7.

[0042] Example 13 A radiation-cured powder coating is made from the following raw materials in parts by weight: 56 parts of resin I, 5 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 1, 25 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 6, 2 parts of zinc phosphate, 10 parts of photoinitiator, 1 part of acrylate leveling agent (BYK-3902 P), and 1 part of silicone defoamer (KP-320). The photoinitiator was prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:2; Resin I was composed of 80% semi-crystalline polyester acrylate resin, 10% polyurethane acrylate, and 10% epoxy acrylate. The preparation steps were the same as in Example 7.

[0043] Example 14 A radiation-curable powder coating is made from the following raw materials in parts by weight: 56 parts J resin, 25 parts ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 2, 5 parts aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 6, 10 parts zinc phosphate, 1 part photoinitiator, 1 part acrylate leveling agent (BYK-3902 P), and 1 part silicone defoamer (KP-320); wherein, the photoinitiator is prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:3; J resin is composed of 80% semi-crystalline polyester acrylate resin, 10% polyurethane acrylate, and 10% epoxy acrylate. The preparation steps are the same as in Example 7.

[0044] Example 15 A radiation-cured powder coating is made from the following raw materials in parts by weight: 65 parts of K resin, 25 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 3, 5 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 6, 2 parts of zinc phosphate, 1 part of photoinitiator, and 2 parts of acrylate leveling agent (BYK-3902 P). The photoinitiator was prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:3; the K resin was prepared by mixing 80% semi-crystalline polyester acrylate resin and 20% polyurethane acrylate. The preparation steps were the same as in Example 7.

[0045] Comparative Example 1 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts D resin, 20 parts ammonium polyphosphate, 7 parts aluminum tripolyphosphate, 6 parts zinc phosphate, 4.5 parts photoinitiator, 1.5 parts acrylate leveling agent (BYK-3902 P), and 0.5 parts silicone defoamer (KP-320). The photoinitiator is prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a 1:1 mass ratio. The D resin is composed of 80% semi-crystalline polyester acrylate resin and 20% polyurethane acrylate. The preparation steps are the same as in Example 7.

[0046] Comparative Example 2 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts of E resin, 20 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 1, 7 parts of aluminum tripolyphosphate, 6 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320). The photoinitiator was prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:1; the D resin was composed of 80% semi-crystalline polyester acrylate resin and 20% polyurethane acrylate. The preparation steps were the same as in Example 7.

[0047] Comparative Example 3 A radiation-cured powder coating is made from the following raw materials in parts by weight: 61 parts F resin, 20 parts ammonium polyphosphate, 7 parts aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 4, 6 parts zinc phosphate, 4.5 parts photoinitiator, 1.5 parts acrylate leveling agent (BYK-3902 P), and 0.5 parts silicone defoamer (KP-320); The photoinitiator was prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:1; the D resin was composed of 80% semi-crystalline polyester acrylate resin and 20% polyurethane acrylate. The preparation steps were the same as in Example 7.

[0048] Comparative Example 4 A radiation-cured powder coating is made from the following raw materials in parts by weight: 75.5 parts of G resin, 4 parts of ammonium polyphosphate coated with phenolic epoxy resin obtained in Example 2, 4 parts of aluminum tripolyphosphate modified by mechanical and chemical intercalation of magnesium aluminum layered double hydroxide obtained in Example 5, 10 parts of zinc phosphate, 4.5 parts of photoinitiator, 1.5 parts of acrylate leveling agent (BYK-3902 P), and 0.5 parts of silicone defoamer (KP-320); The photoinitiator was prepared by mixing bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:1; the G resin was composed of 80% semi-crystalline polyester acrylate resin and 20% epoxy acrylate. The preparation steps were the same as in Example 7.

[0049] Application Example 1 Taking the radiation-cured powder coatings prepared in Examples 7-15 and Comparative Examples 1-4 as examples, they were sprayed onto a metal substrate (steel) according to the following steps to study their effect on the metal substrate. Specifically, the steps included are as follows:

[0050] Step 1: Pre-treatment of the steel surface: Take SPCC cold-rolled steel sheet, grind it with 120# sandpaper to a roughness Ra=1.5~3.0μm, then spray it with an alkaline aqueous solution (4wt% sodium hydroxide, pH=10~12) at 60℃ for 3 minutes, then rinse it with pure water until pH=7, and immerse it in a 1,2-bis(trimethoxysilyl ethane) (BTSE) solution (5wt% BTSE + 40wt% ethanol + 55wt% water) at room temperature for 1 minute. After taking it out, dry it with hot air at 100℃ for 10 minutes.

[0051] Step 2, electrostatic spraying: The radiation-cured powder coating is loaded into an electrostatic powder spraying device and uniformly sprayed onto the pretreated steel plate surface under the conditions of electrostatic voltage of 80kV, atomizing gas pressure of 0.4MPa, and spray gun distance of 230mm, with an average film thickness of 95μm±5μm.

[0052] Step 3, melt leveling and radiation curing: Infrared heating is used to melt the coating, and the surface temperature reaches 120°C. For Comparative Examples 1-4, Examples 7, 9, 10, and 12, and Examples 13-15, UV irradiation was used, with the irradiation dose controlled at 750 mJ / cm². 2 Approximately. For Examples 8 and 11, electron accelerator irradiation was used, with an absorbed dose of 100 kGy.

[0053] Performance testing: The radiation-cured powder coatings prepared in the above embodiments and comparative examples were subjected to relevant performance tests. Adhesion testing was conducted according to GB / T 9286-2021, using the cross-cut test. Impact resistance testing was conducted according to GB / T 1732-2020. Salt spray resistance testing was conducted and evaluated according to GB / T 31588.1-2015, using cyclic D mode, and the time to reach the Ri1 rust level was recorded. Extreme environment testing involved cycling the samples from -40℃ to 85℃ 50 times, and the surface was observed for cracks using a magnifying glass. Flame retardancy testing was conducted using the UL94 vertical burning method. Coating hardness testing was performed using the pencil hardness method (GB / T6739-2006 / ISO 15184:2012), and limiting oxygen index testing was performed using GB / T 2406.2-2009 / ISO 4589-2:2017. The test results are shown in Table 2.

[0054] The above test results show that, compared with Comparative Examples 1 to 4, the radiation-cured powder coatings prepared in Examples 7 to 15 have significantly enhanced adhesion, all reaching level 0; impact resistance, salt spray resistance, and hardness are all significantly improved, and no cracks appeared under extreme environmental test conditions; the flame retardancy rating of the examples all reached UL94 V-0, and the limiting oxygen index was around 30%.

[0055] This invention provides a radiation-curable powder coating comprising a semi-crystalline polyester acrylate resin, functional acrylate, phenolic epoxy resin-coated ammonium polyphosphate, magnesium aluminum layered double hydroxide mechanically and chemically intercalated aluminum tripolyphosphate, zinc phosphate, a photoinitiator, a leveling agent, and a defoamer. Its preparation method includes premixing, melt extrusion, tableting, pulverizing, and sieving. Its application steps on metal substrates include electrostatic spraying, infrared preheating melting, and radiation curing. The radiation curing is one of ultraviolet curing and electron beam curing. The coating provided by this invention has excellent fire and rust prevention properties, maintains long-term performance stability, possesses both good early and long-term rust prevention capabilities, and combines the advantages of high utilization rate of powder coatings and low-temperature curing of radiation-cured coatings. It is suitable for the protection of metal casings of power batteries and other applications requiring high fire and rust resistance.

[0056] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the inventive concept of the present invention, can make other changes and modifications to these embodiments, all of which fall within the scope of the present invention.

[0057] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. If such modifications and variations fall within the scope of equivalents of this invention, then this invention also intends to include these modifications and variations.

Claims

1. A radiation-cured powder coating, characterized in that, It is made from the following raw materials in parts by weight: 56 to 65 parts resin, 5 to 25 parts phenolic epoxy resin coated ammonium polyphosphate, 5 to 25 parts magnesium aluminum layered double hydroxide mechanically and chemically intercalated aluminum tripolyphosphate, 2 to 10 parts zinc phosphate, 1 to 10 parts photoinitiator, 1 to 2 parts leveling agent, and 0 to 1 part defoamer.

2. The radiation-cured powder coating according to claim 1, characterized in that, It is made from the following raw materials in parts by weight: 64.5 parts resin, 20 parts phenolic epoxy resin coated ammonium polyphosphate, 7 parts magnesium aluminum layered double hydroxide mechanically and chemically intercalated modified aluminum tripolyphosphate, 6 parts zinc phosphate, 1 part photoinitiator, 1.5 parts leveling agent, and 0.5 parts defoamer.

3. The radiation-cured powder coating according to claim 2, characterized in that, The resin is composed of 80% semi-crystalline polyester acrylate resin, 0%~20% polyurethane acrylate and 0%~20% epoxy acrylate; wherein the contents of polyurethane acrylate and epoxy acrylate are not both 0%.

4. The radiation-cured powder coating according to claim 2, characterized in that, The photoinitiator is composed of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 1-hydroxycyclohexylphenyl ketone in a mass ratio of 1:1 to 3; the leveling agent is an acrylate leveling agent or an organosilicone leveling agent; and the defoamer is an organosilicone defoamer.

5. A method for preparing a radiation-cured powder coating according to any one of claims 1 to 4, characterized in that, Includes the following steps: The in-situ polymerization method was used to cure phenolic epoxy resin on the surface of ammonium polyphosphate to form a dense coating layer, thus obtaining ammonium polyphosphate coated with phenolic epoxy resin. A mechanochemical method was used to drive aluminum tripolyphosphate or its derivatives to intercalate into the interlayer structure of magnesium-aluminum layered double hydroxides through ball milling, thereby obtaining magnesium-aluminum layered double hydroxide mechanochemically intercalated aluminum tripolyphosphate. Premixing resin, phenolic epoxy resin-coated ammonium polyphosphate, magnesium aluminum layered double hydroxide mechanical and chemical intercalation modified aluminum tripolyphosphate, zinc phosphate, photoinitiator, leveling agent and defoamer yields a premix. The premixed material is melt-extruded to obtain strips at a melt-extruded temperature of 110℃~130℃. The material strips are pressed into tablets, crushed, and sieved to obtain radiation-cured powder coatings.

6. The method for preparing radiation-cured powder coating according to claim 5, characterized in that, The preparation steps of the phenolic epoxy resin coated ammonium polyphosphate are as follows: phenolic epoxy resin and dicyandiamide curing agent are directly added to the ammonium polyphosphate suspension; and stirred at 50℃~70℃ for 3 to 5 hours to allow the resin to directly undergo cross-linking and curing reaction on the particle surface and be coated.

7. The method for preparing radiation-cured powder coating according to claim 5, characterized in that, The preparation steps of the magnesium-aluminum layered double hydroxide mechanochemical intercalation modified aluminum tripolyphosphate are as follows: Aluminum tripolyphosphate was dried at 100℃~110℃ to obtain aluminum tripolyphosphate powder; The magnesium-aluminum layered double hydroxide was pulverized, passed through a 325-mesh sieve, and the magnesium-aluminum layered double hydroxide powder was collected. Aluminum tripolyphosphate powder and magnesium aluminum layered double hydroxide powder are mixed at a weight ratio of 2 to 6:1, and then ground with grinding media. After grinding, the grinding media is removed by passing the powder through a 200-mesh sieve. The resulting powder is then dried to obtain the magnesium-aluminum layered double hydroxide mechanically and chemically intercalated aluminum tripolyphosphate.

8. The method for preparing radiation-cured powder coating according to claim 7, characterized in that, The grinding media consists of zirconia grinding balls with a diameter of 5 mm and zirconia grinding balls with a diameter of 10 mm in a mass ratio of 2:

3.

9. The application of the radiation-cured powder coating according to any one of claims 1 to 4 in forming a coating body on a metal substrate material, characterized in that, The coating has the properties of impact resistance, salt spray resistance, high hardness, fire resistance and rust prevention.

10. The application according to claim 9, characterized in that, The coating thickness is 90μm to 100μm, and the metal substrate material is a steel substrate material.

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