A UV-curable powder coating and a method for preparing and using the same

Abstract

The application relates to the technical field of powder coatings, and particularly discloses a UV-cured powder coating as well as a preparation method and application thereof. The UV-cured powder coating disclosed by the application comprises the following components: 60-80 parts of powder resin, 2-10 parts of a curing agent, 5-10 parts of a filler, 1-2 parts of a leveling agent, 0.5-1 part of a degassing agent and 0.5-10 parts of 184 initiator; the filler is obtained by mixing montmorillonite, calcium carbonate and aluminum oxide, then being pretreated by an ammonium salt solution of an acrylate copolymer, and then being fired; and the degassing agent is composed of 3910-micronized amide wax degassing agent and ketose degassing agent in a weight ratio of 3-5:1-1.5. According to the technical scheme, the UV-cured powder coating is cured into a coating, the coating has excellent gloss, adhesion and smoothness, and the coating has high chemical corrosion resistance.

Description

A UV-curable powder coating, its preparation method and application Technical Field

[0001] This application relates to the technical field of powder coatings, specifically to a UV-curable powder coating, its preparation method, and its application. Background Technology

[0002] Powder coatings, as an environmentally friendly green coating, have advantages such as high utilization rate and excellent film performance, and are widely used in metal furniture, home appliances, building materials, and the automotive industry. Traditional thermosetting powder coatings, such as epoxy, polyester / TGIC, and polyurethane systems, require baking at a certain high temperature (usually 160-200℃) for 10-30 minutes to melt, level, and undergo a cross-linking curing reaction to form a coating film. This high-temperature, long-duration curing process greatly limits its application on heat-sensitive substrates (such as wood, plastics, composite materials, and pre-assembled metal parts), because these substrates cannot withstand prolonged high-temperature heating, leading to problems such as deformation, scorching, and performance degradation.

[0003] To expand the application of powder coatings to heat-sensitive substrates, the industry has developed low-temperature curing powder coating technology. Existing technologies mainly achieve this through two approaches: First, the traditional method of lowering the curing temperature. This method primarily relies on developing highly reactive resin systems or using efficient catalytic systems to reduce the crosslinking reaction temperature of the resin. For example, using special polyurethane systems or epoxy / polyhydric anhydride systems can lower the curing temperature to around 120-140℃. However, this method still has significant limitations: the curing time is still relatively long, typically requiring 10-20 minutes even at lower temperatures, hindering production efficiency; storage stability is a challenge, as high reactivity often leads to agglomeration of powder coatings during storage and transportation, resulting in poor stability and demanding requirements for packaging and storage conditions; and the lower temperature limit is difficult to overcome, as 120℃ is still too high for some extremely heat-sensitive plastics (such as PP and ABS) or precision electronic components. Second, low-temperature curing is achieved through UV curing technology. The principle is that the formula contains photopolymerizable unsaturated bonds (such as acrylic double bonds) and photoinitiators. After the powder is melted and leveled at a low temperature (such as 100-120℃), it is not heat-cured, but is irradiated by ultraviolet (UV) light to excite the photoinitiator to generate free radicals or cations, which triggers the unsaturated resin to undergo a rapid polymerization reaction, thus achieving rapid curing and film formation. This technology combines the advantages of powder coatings being VOC-free and UV curing being highly efficient and energy-saving, and is theoretically very suitable for heat-sensitive substrates. However, the existing UV-cured powder coating technology still has the following technical bottlenecks: (1) There is a contradiction between the melting and leveling process and the curing process. The UV curing process of powder is extremely fast, and the leveling of the powder is insufficient after melting, which affects the gloss of the film and the appearance of the coating will have defects such as orange peel and pinholes; (2) Small molecule byproducts may be generated during the curing process of the coating, which can easily lead to yellowing of the coating and affect the adhesion to the substrate, while also reducing the chemical corrosion resistance of the coating. Summary of the Invention

[0004] To address the aforementioned technical problems, this application provides a UV-curable powder coating, its preparation method, and its application.

[0005] In a first aspect, this application provides a UV-curable powder coating, specifically comprising the following components in parts by weight: 60-80 parts powder resin, 2-10 parts curing agent, 5-10 parts filler, 1-2 parts leveling agent, 0.5-1 part degassing agent, and 1-8 parts 184 initiator;

[0006] The filler is prepared by mixing montmorillonite, calcium carbonate, and alumina in a weight ratio of 80-90:8-12:1-3, pretreating with an ammonium salt solution of acrylate copolymer, and then firing. The degassing agent is composed of 3910-micronized amide wax degassing agent and ketose degassing agent in a weight ratio of 3-5:1-1.5.

[0007] By utilizing the technical solution provided in this application, and by optimizing the formulation of fillers, degassing agents, and initiators, and by optimizing the dosage of each raw material component, the UV-curable powder coating prepared exhibits excellent gloss, adhesion, and smoothness after curing, and also demonstrates high chemical corrosion resistance.

[0008] Specifically, montmorillonite, calcium carbonate, and alumina are mixed in a specific ratio and then organically pretreated with an ammonium salt solution of acrylate copolymer. This allows for the initial organication of the filler through the polymeric ammonium salt, improving dispersibility. Through high-temperature calcination, alumina reacts with silica produced from the decomposition of montmorillonite and calcium oxide from the decomposition of calcium carbonate, generating high-temperature stable phases such as mullite, resulting in a stable, porous, and highly active composite inorganic framework. In the coating, this activated filler forms a strong bond with the resin through a microporous anchoring effect. Simultaneously, its chemical inertness and lamellar / particle reinforcement effect work together to ultimately achieve superior performance in terms of gloss, adhesion, smoothness, and chemical resistance.

[0009] During the melting and leveling stage, powder coatings can trap air and moisture that have escaped from the substrate surface. If the trapped gas does not have time to escape, it can easily form tiny bubbles or pinholes, which can seriously affect the appearance (smoothness, gloss) and performance (adhesion, chemical resistance) of the coating.

[0010] Therefore, after numerous experiments, this application demonstrates that the specific ratio of 3910-micronized amide wax and ketose-based degassing agents in the degassing agent formulation can reduce the surface tension of the molten coating, decrease the pressure within air bubbles, and make the bubbles more prone to expansion, deformation, and coalescence, thereby accelerating their migration to the surface. It also reduces the melt viscosity of the coating, allowing small molecule gases sufficient time to escape from the coating film. Simultaneously, it lubricates the coating, increasing the free volume between layers and reducing the resistance to the movement of small molecule gases. Furthermore, it has a certain adsorption or complexation effect on some small molecule gases, altering their state in the melt and making them easier to expel. Thus, the synergistic effect of the two degassing agents achieves thorough and efficient degassing within the extremely short melt leveling time required for UV curing, resulting in a pinhole-free, high-gloss coating with good adhesion and excellent chemical resistance.

[0011] Preferably, the UV-curable powder coating specifically comprises the following components in parts by weight: 65-75 parts powder resin, 4-8 parts curing agent, 6-9 parts filler, 1.2-1.8 parts leveling agent, 0.6-0.9 parts degassing agent, and 4-6 parts initiator.

[0012] Preferably, the filler is prepared by mixing and stirring ball-milled and sieved montmorillonite, calcium carbonate, and alumina to obtain a solid material. Then, 3-5 wt% of an ammonium salt solution of acrylate copolymer and 5-7 wt% of distilled water are added to the material system and stirred thoroughly. The mixture is then subjected to a pressure of 40-60 kN for 25-40 seconds and placed in an oven to dry to constant weight. Finally, the sample is calcined at 1000-1200℃ for 4-7 hours to obtain the final product.

[0013] Preferably, the degassing agent is selected from one or more of dihydroxyacetone and D-fructose.

[0014] Preferably, the degassing agent is composed of a mixture of 3910-micronized amide wax and dihydroxyacetone in a weight ratio of 4-6:1-1.2.

[0015] In one specific implementation, the weight ratio of 3910-micronized amide wax and dihydroxyacetone in the degassing agent can be 3:1, 4:1, 5:1, 3:1.2, 4:1.2, 5:1.2, 3:1.5, 4:1.5, or 5:1.5.

[0016] Experimental analysis shows that the degassing agent composed of the above-mentioned weight ratio of 3910-micronized amide wax and dihydroxyacetone can further improve the performance of powder coatings after curing.

[0017] Preferably, the powdered resin is UVECOAT® 2100; the curing agent is UVECOAT® 9010.

[0018] Preferably, the leveling agent is selected from one or more of polyacrylate leveling agents, cellulose acetate butyrate leveling agents, and polydimethylsiloxane leveling agents.

[0019] Secondly, this application provides a method for preparing the UV-curable powder coating, which specifically includes the following steps in sequence: weighing each component according to the weight parts and mixing them evenly; then melting and extruding at a temperature of 90-120℃, and then pressing, crushing, grinding and sieving to obtain a powder coating with a particle size of 40±5μm.

[0020] Preferably, the process parameters for melt extrusion are: screw speed of 70-90 r / min, feed speed of 20-30 r / min; zone 1 temperature: 90-100℃, zone 2 temperature: 100-110℃, zone 3 temperature: 110-120℃, and die head temperature: 105-115℃.

[0021] Thirdly, this application provides the application of the UV-curable powder coating in the field of coating the surface of heat-sensitive substrates.

[0022] In summary, the technical solution of this application has the following effects:

[0023] The UV-curable powder coating provided in this application has outstanding environmental protection properties, with no solvent evaporation pollution; it has high curing efficiency, with a short curing time under UV light irradiation, much faster than traditional thermosetting powder coatings; it is applicable to a wide range of substrates, requiring no high-temperature baking, and can be used on temperature-sensitive substrates such as wood, plastics, and paper, breaking through the application limitations of traditional powder coatings.

[0024] The UV-curable powder coating provided in this application exhibits excellent gloss, adhesion, and smoothness, and the coating can resist the erosion of chemicals such as acids, alkalis, and solvents, making it suitable for applications in harsh chemical environments.

[0025] The UV-curable powder coating provided by this invention has a simple and easy preparation method, readily available raw materials, low price, is suitable for large-scale production, and has high value for promotion and use. Detailed Implementation

[0026] The present application will be further described in detail below with reference to embodiments, comparative examples and performance test results. These embodiments should not be construed as limiting the scope of protection claimed in this application.

[0027] Powdered resin UVECOAT® 2100 and curing agent UVECOAT® 9010 were purchased from Zhanxin; montmorillonite (item number RM-015) was purchased from Shijiazhuang Ruiming Mineral Products Co., Ltd.; ammonium salt solution of acrylate copolymer (model BYK-155) was purchased from BYK, Germany; RF-7101 polyacrylate leveling agent was purchased from Qingdao Shengshi New Materials Co., Ltd.; the remaining raw materials were all available through commercial purchase.

[0028] Example

[0029] Examples 1-5

[0030] Examples 1-5 provide a UV-curable powder coating and its preparation method, respectively.

[0031] The difference in the above embodiments is that the amount of each raw material component is different, as shown in Table 1.

[0032] The specific preparation method of the UV-curable powder coating in the above embodiments is shown below.

[0033] (1) The preparation method of the packing is as follows:

[0034] Montmorillonite, calcium carbonate, and alumina were separately loaded into the grinding jars of a planetary ball mill. Zirconia balls were used as the grinding media, with a ball diameter ratio of large balls (10-15 mm): medium balls (5-8 mm): small balls (2-4 mm) = 2:3:5, and the material-to-ball ratio was controlled at 1:6. 6% anhydrous ethanol (by weight of the raw materials) was added as a dispersant to prevent particle agglomeration. The ball mill speed was set to 300 r / min, and the grinding time was 3 hours. During this time, the mill was stopped every 30 minutes, the jar lid was opened, and the mixture was stirred thoroughly to ensure uniform grinding.

[0035] After ball milling, the material is removed and placed in an oven to dry at 80-100℃ for 2 hours to remove dispersant residue. Each ball-milled raw material is then passed through a 600-mesh sieve to obtain ball-milled and sieved montmorillonite, calcium carbonate, and alumina.

[0036] According to the weight ratio of 85:10:2, montmorillonite, calcium carbonate, and alumina after ball milling and sieving were put into a mixer at 200 r / min and mixed evenly to obtain a solid material. Then, 4 wt% of ammonium salt solution of acrylate copolymer and 6 wt% distilled water were added to the material system and stirred thoroughly. The mixture was kept under a pressure of 50 kN for 30 s and the prepared sample was placed in an oven to dry to constant weight. Then, the sample was fired at 1100℃ for 5 h to obtain the final product.

[0037] (2) The preparation method of UV-curable powder coating is as follows:

[0038] According to Table 1, weigh out the corresponding weights of powder resin UVECOAT® 2100, curing agent UVECOAT® 9010, filler, RF-7101 polyacrylate leveling agent, degassing agent (composed of 3910-micronized amide wax degassing agent and dihydroxyacetone in a weight ratio of 5:1), and 184 initiator, and place them in a mixer with a speed of 1000 r / min. Stir for 30 min and mix evenly.

[0039] Melt extrusion: The mixture is poured into a twin-screw extruder for melt extrusion; the screw diameter is 35 mm and the length-to-diameter ratio is 36:1; the screw speed is set to 80 r / min and the feed speed is 25 r / min; the temperature of zone 1 is 95℃, the temperature of zone 2 is 105℃, the temperature of zone 3 is 115℃, and the die head temperature is 110℃.

[0040] Tableting with a tablet press: The extruded material is fed into the tablet press, and the pressure of the roller press is adjusted to 4MPa to compress the material into uniform thin sheets with a thickness of 2-3mm. During the tableting process, the material temperature is controlled at 80-90℃ to prevent the thin sheets from cooling too quickly and causing cracks.

[0041] Coarse crushing: The compressed flakes are fed into the coarse crusher, and the crushing particle size is adjusted to 2-10mm. The crushed material particles are uniform and there are no large pieces of unbroken flakes.

[0042] Fine grinding mill: Feed the crushed material into the fine grinding mill, adjust the feed speed to 6kg / h, and the grinding time to 20-30min to ensure that the material is fully ground and refined.

[0043] Sieving: Pass the ground material through a 35μm sieve to collect coarse particles; then pass it through a 45μm sieve to collect the undersized material, which is a powder coating with a particle size of 40±5μm; pack it into a sealed plastic bucket and store it in a dry, ventilated warehouse with the warehouse temperature controlled at 15-28℃.

[0044] Table 1. Amounts of each raw material component in Examples 1-5 and Comparative Examples 1-2

[0045]

[0046] Examples 6-8

[0047] Examples 6-8 respectively provide a UV-curable powder coating and its preparation method.

[0048] The difference between the above embodiments and Embodiment 1 is that the preparation methods of the fillers are different, as shown below.

[0049] In Example 6, the weight ratio of montmorillonite, calcium carbonate, and alumina was 80:12:1.

[0050] In Example 7, the weight ratio of montmorillonite, calcium carbonate, and alumina was 90:8:3.

[0051] In Example 8: The filler was prepared as follows: Montmorillonite, calcium carbonate, and alumina, after ball milling and sieving, were added to a mixer at 200 r / min according to a weight ratio of 85:10:2 and mixed evenly to obtain a solid material; then 8 wt% of an ammonium salt solution of acrylate copolymer and 2 wt% distilled water were added to the material system and stirred thoroughly. The mixture was kept under a pressure of 50 kN for 30 s and the prepared sample was placed in an oven to dry to constant weight; then the sample was calcined at 1100℃ for 5 h to obtain the final product.

[0052] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0053] Examples 9-11

[0054] Examples 9-11 provide a UV-curable powder coating and its preparation method, respectively.

[0055] The difference between the above embodiments and Embodiment 1 is that the types of degassing agents are different, as detailed below.

[0056] In Example 9: the degassing agent is composed of 3910-micronized amide wax degassing agent and dihydroxyacetone in a weight ratio of 3:1.5.

[0057] In Example 10: the degassing agent is composed of 3910-micronized amide wax degassing agent and D-fructose in a weight ratio of 5:1.

[0058] In Example 11: the degassing agent is composed of 3910-micronized amide wax degassing agent and dihydroxyacetone in a weight ratio of 4:1.2.

[0059] All other process parameters in the above embodiments are the same as those in Embodiment 1.

[0060] Comparative Example

[0061] Comparative Examples 1-2

[0062] Comparative Examples 1 and 2 respectively provide a UV-curable powder coating and its preparation method.

[0063] The difference between the above comparative example and Example 1 is that the amount of each raw material component is different, as shown in Table 1.

[0064] All other process parameters in the above comparative examples are the same as those in Example 1.

[0065] Comparative Examples 3-5

[0066] Comparative Examples 3-5 each provide a UV-curable powder coating and its preparation method.

[0067] The difference between the above comparative example and Example 1 is as follows:

[0068] In Comparative Example 3, an equal amount of ball-milled and sieved montmorillonite was used as filler.

[0069] In Comparative Example 4, the packing material was composed of ball milled and sieved montmorillonite, calcium carbonate, and alumina in a weight ratio of 85:10:2.

[0070] In Comparative Example 5: the degassing agent was composed of 3910-micronized amide wax degassing agent and dihydroxyacetone in a weight ratio of 1:5.

[0071] All other process parameters in the above comparative examples are the same as those in Example 1.

[0072] Performance testing

[0073] The powder coatings prepared in the examples or comparative examples were sprayed onto aluminum plates (substrate size 100mm×150mm×3mm) using compressed air through a spray gun. The plates were first heated to 100°C for 2 minutes, and then subjected to a 1000mJ / cm² spray. 2 Ultraviolet light irradiation causes the coating to cure and cross-link, forming a coating layer.

[0074] Gloss: The gloss of the coating is tested according to the method specified in GB-T 9754-2007.

[0075] Adhesion: The coating adhesion was tested according to the method specified in GB / T 9286-2021.

[0076] Smoothness: The coating was tested using a BYK orange peel tester and evaluated using the LW value.

[0077] Chemical corrosion resistance: The coating was immersed in 8% hydrochloric acid and 10% sodium hydroxide solution at 40°C for 168 hours. After the specified immersion time, the sample was taken out, the surface was rinsed with distilled water to remove the residual chemical medium, and then gently wiped dry with a clean soft cloth. After being placed in a standard environment for 2 hours, the smoothness was tested to evaluate the chemical corrosion resistance of the coating.

[0078] Test results are shown in Table 2.

[0079] Table 2. Test results of coatings in the examples and comparative examples.

[0080]

[0081] As can be seen from the test results in Table 2 above, the UV-curable powder coating prepared using the technical solution provided in this application exhibits excellent gloss, adhesion, and smoothness after curing, and also has high chemical corrosion resistance.

[0082] By comparing the test results of Examples 1-5 and Comparative Examples 1-2, it can be seen that the dosage of each raw material component has a significant impact on the performance of the powder coating. In Comparative Examples 1-2, the dosages of each raw material component were mismatched, resulting in powder coating materials with poor performance. In contrast, the powder coating prepared in this application, by optimizing the dosage formulation of each raw material component, exhibits excellent performance.

[0083] By comparing the test results of Examples 1, 6-8, and Comparative Examples 3-4, it can be seen that the type of filler has a significant impact on the performance of powder coatings. In Comparative Example 3, equal amounts of ball-milled and sieved montmorillonite were used as fillers. In Comparative Example 4, the filler consisted of a mixture of ball-milled and sieved montmorillonite, calcium carbonate, and alumina in a weight ratio of 85:10:2, resulting in powder coating materials with poor performance. In contrast, this application utilizes a mixture of montmorillonite, calcium carbonate, and alumina in a weight ratio of 80-90:8-12:1-3, pretreated with an ammonium salt solution of acrylate copolymer, and then calcined to obtain the filler. The resulting powder coating exhibits excellent performance.

[0084] By comparing the test results of Examples 1, 9-11, and Comparative Example 5, it can be seen that the type of degassing agent has a significant impact on the performance of powder coatings. In Comparative Example 5, the degassing agent was composed of a mixture of 3910-micronized amide wax degassing agent and dihydroxyacetone in a weight ratio of 1:5, resulting in powder coating materials with poor performance. In contrast, the powder coating prepared in this application, composed of a mixture of 3910-micronized amide wax degassing agent and ketose degassing agent in a weight ratio of 3-5:1-1.5, exhibits excellent performance.

[0085] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A UV-curable powder coating, characterized in that, Specifically, it includes the following components in parts by weight: 60-80 parts powder resin, 2-10 parts curing agent, 5-10 parts filler, 1-2 parts leveling agent, 0.5-1 part degassing agent, and 1-8 parts 184 initiator; the powder resin is UVECOAT® 2100; the curing agent is UVECOAT® 9010; the filler is obtained by mixing montmorillonite, calcium carbonate, and alumina in a weight ratio of 80-90:8-12:1-3, pretreating with an ammonium salt solution of acrylate copolymer, and then firing; the degassing agent is composed of 3910-micronized amide wax degassing agent and ketose degassing agent in a weight ratio of 3-5:1-1.

5.

2. The UV-curable powder coating according to claim 1, characterized in that, Specifically, it includes the following components by weight: 65-75 parts powder resin, 4-8 parts curing agent, 6-9 parts filler, 1.2-1.8 parts leveling agent, 0.6-0.9 parts degassing agent, and 4-6 parts 184 initiator.

3. The UV-curable powder coating according to claim 1, characterized in that, The filler is prepared by mixing and stirring ball-milled and sieved montmorillonite, calcium carbonate, and alumina to obtain a solid material. Then, 3-5 wt% of an ammonium salt solution of acrylate copolymer and 5-7 wt% of distilled water are added to the material system and stirred thoroughly. The mixture is then subjected to a pressure of 40-60 kN for 25-40 seconds and placed in an oven to dry to constant weight. Finally, the sample is calcined at 1000-1200℃ for 4-7 hours to obtain the final product.

4. The UV-curable powder coating according to claim 1, characterized in that, In the degassing agent, the ketose degassing agent is selected from one or more of dihydroxyacetone and D-fructose.

5. The UV-curable powder coating according to claim 1, characterized in that, The degassing agent is composed of a mixture of 3910-micronized amide wax and dihydroxyacetone in a weight ratio of 4-5:1-1.

2.

6. The UV-curable powder coating according to claim 1, characterized in that, The leveling agent is selected from one or more of polyacrylate leveling agents, cellulose acetate butyrate leveling agents, and polydimethylsiloxane leveling agents.

7. A method for preparing a UV-curable powder coating as described in any one of claims 1-6, characterized in that, Specifically, the process includes the following steps: weighing each component according to its weight and mixing them evenly; then melting and extruding them at a temperature of 90-120℃, followed by tableting, crushing, grinding, and sieving to obtain a powder coating with a particle size of 40±5μm.

8. The method for preparing UV-curable powder coating according to claim 7, characterized in that, The process parameters for melt extrusion are as follows: screw speed is 70-90 r / min, feed speed is 20-30 r / min; zone 1 temperature: 90-100℃, zone 2 temperature: 100-110℃, zone 3 temperature: 110-120℃, and die head temperature: 105-115℃.

9. The application of the UV-curable powder coating as described in any one of claims 1-6 in the field of coating the surface of heat-sensitive substrates.

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