Method for preparing layered functional powder coating

Abstract

Disclosed is a method for preparing a powder coating, and in particular, a method for preparing a layered functional powder coating. The method comprises: separately crushing both a functional material and a layering-promoting material by a crusher, and then binding or combining the crushed materials, to form a first mixture; then crushing the first mixture into a material having a medium particle size of 1-20 μm by means of the crusher, to obtain a layered functional powder material; evenly mixing the obtained layered functional powder material and a powder coating primer, to form a second mixture, and then forming the second mixture into particles having a medium particle size of 20-50 μm by means of extrusion, crushing, pressure bonding, or crushing, to obtain layered functional powder coating particles; electrostatically spraying a metal or non-metal substrate with the obtained layered functional powder coating particles, and then performing high-temperature heating on the sprayed substrate, to cure the powder coating adsorbed on a surface of the substrate into a film; and gathering a functional material in an upper-layer region of the coating, so that the amount of the functional material used can be reduced, so as to achieve the purposes of reducing the cost and improving the basic performance of the coating.

Description

A preparation method of layered functional powder coating Technical Field

[0001] The present invention relates to the field of powder coating preparation, in particular to a method for preparing layered functional powder coating. Background Art

[0002] Powder coatings have gained widespread industrial application due to their zero VOC emissions, excellent film properties, low cost, and low energy consumption. Functional powder coatings, in particular, offer additional special properties such as antimicrobial, hydrophobic, corrosion-resistant, conductive, insulating, and thermally insulating properties, making them widely used in the medical, aerospace, marine, automotive, building materials, furniture, and electronics industries. Due to these special properties, the market for these powder coatings is growing annually.

[0003] Functional powder coatings are typically made by adding functional materials to a powder coating base. These coatings possess specialized properties or functions, and have a wide range of applications to meet specific needs. These include powder coatings that offer various physical, chemical, and biochemical properties, such as antimicrobial powder coatings, hydrophobic powder coatings, and fluorescent powder coatings. Antimicrobial powder coatings, primarily composed of an antimicrobial agent and a powder coating base, possess bactericidal or bacterial growth-inhibiting properties and are widely used in a variety of applications, including medical devices, food packaging equipment, and public health facilities. Antimicrobial powder coatings help prevent cross-infection and disease transmission, providing additional hygiene protection. Especially in medical equipment and hospital environments, they can significantly reduce the risk of bacterial infection, enhance public health and wellness standards, and help protect people from disease. Hydrophobic powder coatings impart a strong hydrophobic property to surfaces, causing liquid water to bead up on them. This makes the surface water- and moisture-resistant, providing additional protection and reducing corrosion and wear. They also prevent dirt and liquids from adhering to the surface, imparting a degree of self-cleaning ability. It is primarily used in outdoor equipment, building materials, automotive parts, and other fields. Fluorescent powder coatings are fluorescent coatings that absorb external light energy and convert it into visible light. They are widely used in visual warnings, decoration, identification, and nighttime visibility enhancement applications, such as safety signs, traffic signs, display screens, and decorative items. Fluorescent coatings not only enhance the appeal and uniqueness of a product but also significantly improve visibility at night or in low-light conditions, playing a vital role in warning and safety. In summary, functional powder coatings impart special functions and performance to products and equipment, playing a vital role in a variety of fields.

[0004] The functionality of a coating is primarily achieved by incorporating corresponding functional materials into the coating. Melt extrusion and dry mixing are common methods for adding functional material additives to powder coatings. Functional materials are typically sized at the micron or nanometer scale. For example, antimicrobial agents are often made from porous materials loaded with inorganic or organic antimicrobial substances. Hydrophobic additives are typically materials with low surface energy, such as modified nano-silica and polytetrafluoroethylene. Commonly used fluorescent materials in powder coatings include organic and inorganic fluorescent pigments, such as coumarin, zinc sulfide, silicates, and phosphates.

[0005] Currently, these functional materials are essentially uniformly dispersed throughout the powder coating system after curing. This leads to two problems: 1) coating performance, such as adhesion and impact resistance, is compromised; 2) functional materials located at the bottom of the coating are covered by the coating and cannot fulfill their functions, resulting in waste of functional materials. These issues further lead to unstable performance, high prices, and low market acceptance of functional coatings.

[0006] This invention proposes a layered functional powder coating that concentrates functional materials in the upper layer of the coating, placing them closer to the external environment and effectively releasing the coating's functions. Furthermore, due to the layering effect of the functional materials, the functional material content can be significantly reduced, thereby reducing the cost of the functional powder coating. Since the lower layer of the coating contains only a small amount of functional material, the coating's basic properties, such as adhesion and impact resistance, are unaffected. To enhance the performance of functional powder coatings and promote their market application, it is necessary to develop a high-performance, low-cost method that overcomes the many shortcomings of current methods.

[0007] Summary of the Invention

[0008] The purpose of the present invention is to provide a method for preparing a layered functional powder coating to solve the problems of high cost, reduced adhesion and impact resistance of existing functional powder coatings.

[0009] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0010] A method for preparing a layered functional powder coating comprises the following steps:

[0011] (1) The functional material and the delamination-promoting material are respectively crushed by a crusher, and then the crushed materials are bonded or combined together to form a first mixture; the first mixture is then crushed by a crusher into a material with a medium particle size of 1-20 μm to obtain a delaminated functional powder material;

[0012] (2) uniformly mixing the layered functional powder material obtained in step (1) with a powder coating base powder to form a second mixture, and then crushing the second mixture into particles with a medium particle size of 20-50 μm by extrusion, crushing or pressure binding, to obtain layered functional powder coating particles;

[0013] (3) electrostatically spraying the layered functional powder coating particles obtained in step (2) onto a metal or non-metal substrate, and then heating the sprayed substrate at a high temperature to solidify the powder coating into a film;

[0014] (4) placing the metal or non-metal substrate in air and cooling it at room temperature to obtain a layered functional coating on the surface of the substrate.

[0015] Compared with the prior art, the beneficial results of the present invention are:

[0016] (1) The present invention combines the delamination-promoting material with the functional material, so that the functional material is concentrated in the upper layer of the coating. Compared with the prior art, the functional material is evenly distributed in the coating, which can reduce the amount of functional material used and achieve the purpose of reducing costs;

[0017] (2) Compared with existing common functional powder coatings, the basic properties of the adhesion interface between the coating and the substrate are not affected by the functional materials, such as adhesion and impact resistance;

[0018] (3) The functional materials of layered functional powder coatings are concentrated in the upper layer of the coating, making the functional materials closer to the external environment, which is conducive to the effective release of the coating function;

[0019] (4) Layered functional powder coatings can achieve functional multi-layer coatings in one spraying, reducing the spraying process and significantly saving manpower and equipment resources. DETAILED DESCRIPTION

[0020] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0021] In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention may also be implemented in other ways different from those described herein. Those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0022] A method for preparing a layered functional powder coating of the present invention comprises the following steps:

[0023] (1) The functional material and the delamination-promoting material are respectively crushed by a crusher, and then the crushed materials are bonded or combined together to form a first mixture; the first mixture is then crushed by a crusher into a material with a medium particle size of 1-20 μm to obtain a delaminated functional powder material;

[0024] (2) uniformly mixing the layered functional powder material obtained in step (1) with a powder coating base powder to form a second mixture, and then crushing the second mixture into particles with a medium particle size of 20-50 μm by extrusion, crushing or pressure binding, to obtain layered functional powder coating particles;

[0025] (3) electrostatically spraying the layered functional powder coating particles obtained in step (2) onto a metal or non-metal substrate, and then heating the sprayed substrate at a high temperature to solidify the powder coating into a film;

[0026] (4) placing the metal or non-metal substrate in air and cooling it at room temperature to obtain a layered functional coating on the surface of the substrate.

[0027] In the present invention, in step (1),

[0028] The median particle size of the functional material is 0.05-20 μm; the median particle size of the delamination-promoting material is 0.05-20 μm when pressure-bound; and 0.05-5000 μm when melt-extruded; there is no requirement for the solution rule.

[0029] As a preferred embodiment, in the step (1), the functional material and the stratification-promoting material are crushed separately by a crusher, and then the crushed materials are bonded together to form a first mixture.

[0030] The bonding or combining methods are one or more methods selected from the group consisting of solution bonding, pressure bonding, and melt extrusion.

[0031] When the bonding or combining method is a solution method, the stratification-promoting material is first dissolved in a liquid solvent, and then mixed with functional material particles, dried, and crushed to obtain a stratified functional material.

[0032] When the bonding or combining method is a pressure binding method, the pressure of the pressure binding of the functional material and the delamination-promoting material is 3-50 MPa.

[0033] When the bonding or combining method is a melt extrusion method, the functional material and the delamination-promoting material are extruded through a single-screw or twin-screw extruder at an extrusion temperature of 80-300°C.

[0034] In the step (2), the method for uniformly mixing the layered functional powder material and the powder coating base powder is one or more of melt extrusion, pressure binding or dry mixing.

[0035] In the present invention, when the layered functional powder material and the powder coating base powder are uniformly mixed by melt extrusion, the layered functional powder material and the powder coating base powder are extruded through a single-screw or twin-screw extruder at an extrusion temperature of 80-120°C.

[0036] When the layered functional powder material and the powder coating base powder are mixed evenly by dry mixing, the layered functional powder material and the powder coating base powder are dry mixed by a dry mixer at a stirring rate of 500-10000 rpm for 1-30 minutes.

[0037] The temperature range of the high temperature heating in step (3) is 140-350° C., and the heating time is 5-30 minutes.

[0038] Example 1

[0039] In this embodiment, an antibacterial-silicone resin-polyester-TGIC hybrid layered powder coating is prepared, and the preparation process is as follows:

[0040] 1. Weigh 1g of a silver-based solid antimicrobial agent (median particle size of approximately 0.05μm) and 9g of a silicone resin (as a delamination-promoting material, median particle size of approximately 1cm) in a grinder. Grind for 1 minute to crush the silicone resin and mix the two evenly to obtain a mixture with a median particle size of approximately 20μm.

[0041] 2. The mixture obtained in step 1 was melt-extruded and then crushed into powder with a medium particle size of 10 μm;

[0042] 3. The powder in step 2 was mixed evenly with 20 g of polyester powder coating with a medium particle size of 20 μm (as a powder coating base) using a mixer, and then the two were pressed into blocks under high pressure (8 MPa), and finally crushed to a powder with a medium particle size of about 35 μm to obtain a layered antibacterial powder coating;

[0043] 4. The powder obtained in 3 was electrostatically sprayed onto an aluminum plate and baked at 200°C for 20 minutes to solidify the powder into a paint film to obtain a layered antibacterial coating.

[0044] Example 2

[0045] The process for preparing the antibacterial-silicone resin-polyester-TGIC hybrid layered powder coating is as follows:

[0046] 1. Weigh 1g of a silver-based solid antimicrobial agent (median particle size of approximately 0.05μm) and 9g of a silicone resin (as a delamination-promoting material, median particle size of approximately 1cm) in a grinder. Grind for 1 minute to crush the silicone resin and mix the two evenly to obtain a mixture with a median particle size of approximately 20μm.

[0047] 2. The mixture obtained in step 1 was melt-extruded and then crushed into powder with a medium particle size of 10 μm;

[0048] 3. The powder in step 2 was mixed evenly with 30 g of polyester powder coating with a medium particle size of 20 μm (as a powder coating base) using a mixer, and then the two were mixed evenly by melt extrusion. After cooling, flakes were obtained, and finally pulverized to a powder with a medium particle size of about 35 μm to obtain a layered antibacterial powder coating;

[0049] 4. The powder obtained in 3 was electrostatically sprayed onto an aluminum plate and baked at 200°C for 20 minutes to solidify the powder into a paint film to obtain a layered antibacterial coating.

[0050] Example 3

[0051] The process for preparing a hydrophobic polyester-epoxy hybrid layered powder coating is as follows:

[0052] 1. Weigh 5g of polytetrafluoroethylene particles (as a hydrophobic material, with a median particle size of about 1μm) and 1g of stearic acid (as a delamination-promoting material), add them to 100mL of anhydrous ethanol, stir at room temperature for 30 minutes, then heat and stir at 50℃ until all the ethanol evaporates, and grind the solid to a median particle size of about 10μm;

[0053] 2. Weigh 4g of the powder from step 1 and 32g of epoxy powder coating primer, melt-extrude at 100-120°C, cool to room temperature, and then grind to a powder with a medium particle size of about 35μm to obtain a layered hydrophobic powder coating;

[0054] 3. The powder obtained in 2 was electrostatically sprayed onto an aluminum plate and baked at 200°C for 18 minutes to solidify the powder into a paint film to obtain a layered hydrophobic coating.

[0055] Example 4

[0056] The process for preparing a hydrophobic polyester-epoxy hybrid layered powder coating is as follows:

[0057] 1. Weigh 5g of polytetrafluoroethylene particles (as a hydrophobic material, with a median particle size of approximately 1μm) and 1g of paraffin wax and silicone resin as delamination-promoting materials) and add them to 50mL of a chloroform and ethyl acetate mixture. Stir at room temperature for 30 minutes, then heat and stir at 50°C until the solution is completely evaporated. Grind the solid to a median particle size of approximately 10μm.

[0058] 2. Weigh 4g of the powder from step 1 and 32g of epoxy powder coating primer, mix well, press into blocks under a high pressure of 10MPa, and then crush to a powder with a medium particle size of about 35μm to obtain a layered hydrophobic powder coating;

[0059] 3. The powder obtained in 2 was electrostatically sprayed onto an aluminum plate and baked at 200°C for 18 minutes to solidify the powder into a paint film to obtain a layered hydrophobic coating.

[0060] Example 5

[0061] The process for preparing fluorescent-silicone-polyester-TGIC-layered powder coating is as follows:

[0062] 1. Weigh 1g of inorganic fluorescent pigment (as fluorescent material) and 5g of silicone resin (as delamination-promoting material), stir and mix them evenly, melt and extrude at 100-110°C, cool to room temperature, and then grind into powder with a medium particle size of about 10μm;

[0063] 2. Weigh 25g of polyester TGIC powder coating base powder, crush it to a medium particle size of about 10μm, then stir and mix it evenly with the powder in step 1. Use high pressure of 8Mpa to press the two into blocks, and finally crush them to a powder with a medium particle size of about 30μm to obtain a layered fluorescent powder coating;

[0064] 3. The powder coating obtained in 2 was electrostatically sprayed onto an aluminum plate and baked at 190°C for 25 minutes to solidify the powder into a paint film to obtain a layered fluorescent coating.

[0065] Example 6

[0066] The process for preparing wear-resistant silicone resin-nylon layered powder coating is as follows:

[0067] 1. Weigh 3g of stearic acid and dissolve it in 50mL of chloroform. Then add 10g of wear-resistant pigment (as wear-resistant material) and 5g of silicone resin (as delamination-promoting material) and mix them evenly. Heat at 40°C in a ventilated place until the chloroform is completely evaporated. Grind the resulting solid into powder with a medium particle size of about 10μm.

[0068] 2. Weigh 48g of nylon powder (PA11, used as powder coating base, with a median particle size of about 45μm) and grind it to a median particle size of about 20μm. Then stir and mix it evenly with the powder obtained in step 1. Use high pressure 7Mpa to press the two into blocks, and finally grind them to a powder with a median particle size of about 40μm to obtain a layered wear-resistant nylon coating;

[0069] 3. The powder coating obtained in 2 was electrostatically sprayed onto an aluminum plate and baked at 240°C for 15 minutes to solidify the powder into a paint film to obtain a layered wear-resistant coating.

[0070] For the above Example 1, without adding silicone resin, the same antibacterial polyester TGIC non-delamination paint and coating were prepared, and the prepared coating was used as a reference coating.

[0071] For the above Example 2, without adding silicone resin, the same antibacterial polyester TGIC non-delamination paint and coating were prepared, and the prepared coating was used as a reference coating.

[0072] For the above Example 3, paraffin wax and silicone resin were not added, and the same hydrophobic polyester-epoxy hybrid non-delamination paint and coating were prepared, and the prepared coating was used as a reference coating.

[0073] For the above Example 4, paraffin wax and silicone resin were not added, and the same hydrophobic polyester-epoxy hybrid non-stratified coating and coating were prepared, and the prepared coating was used as a reference coating.

[0074] For the above Example 5, without adding silicone resin, the same fluorescent polyester TGIC non-delamination paint and coating were prepared, and the prepared coating was used as a reference coating.

[0075] For the above Example 6, without adding stearic acid and silicone resin, the same wear-resistant nylon non-layered coating and coating were prepared, and the prepared coating was used as a reference coating.

[0076] The following experiments were performed to test the layered functional powder coatings prepared in Examples 1-6:

[0077] The layered functional powder coatings of Examples 1-6 and the reference coating were tested for their performance. Antibacterial performance was tested according to ASTM E2180; hydrophobicity was tested according to ASTM D5946; fluorescence intensity was tested according to ASTM D4388; and wear resistance was tested according to ASTM D4060. Three parallel experiments were performed. The specific results are shown in the following table:

[0078] The analysis shows that the comparison between Examples 1-6 and their corresponding reference samples shows that the functional effects of the functional materials are significantly improved after layered aggregation, indicating that the layered aggregation effect of the present invention is excellent, and better performance is achieved by using the same amount of functional materials.

[0079] Evaluation criteria for the surface quality of the sprayed and cured coating include, but are not limited to, impact resistance (ASTM D2794) and adhesion (ISO 2409). A film approximately 60 μm thick was sprayed onto an aluminum panel (Q-panel A-2-3.5). The impact resistance of the coating was compared using a 15.9 mm diameter, 1 kg punch dropped from a height of 50 cm. Adhesion between the coating and the substrate was tested using the cross-hatch method. The results are shown in the table below:

[0080] Comparison of the impact resistance and adhesion of Examples 1-6 with their corresponding reference samples shows that the delamination and aggregation of the functional materials significantly improves the impact resistance and adhesion of the coatings. This demonstrates that the functional materials of the present invention are well delaminated and have minimal impact on the coating's performance. Adhesion also improves by 0-2 levels after delamination.

[0081] The above-listed embodiments do not limit the equipment parameters and operating parameters of the present invention, which are further described as follows:

[0082] In the embodiments of the present invention, the stratification-promoting materials used include silicone resin, fluororesin, fluorosilicone copolymer resin, paraffin and stearic acid, such as methyl polysiloxane and other organic silanes, polytetrafluoroethylene, polyvinylidene fluoride, fluorinated propylene and fluorinated polyether and fluororesin copolymer resin, petroleum wax, paraffin wax hydrocarbon and microcrystalline wax, lactic acid stearate and hydroxystearic acid, etc. Other types of stratification-promoting materials can also be used.

[0083] The functional type in the embodiment of the present invention is not limited to antibacterial, hydrophobic, fluorescent and performance, and may also include other functions. The powder coating in the present invention is not limited to that used in the embodiment, and includes common powder coatings on the market.

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a layered functional powder coating, characterized in that: The preparation method comprises the following steps: (1) The functional material and the delamination-promoting material are respectively crushed by a crusher, and then the crushed materials are bonded or combined together to form a first mixture; and the first mixture is crushed by a crusher to a material with a medium particle size of 1-20 μm to obtain a delaminated functional powder material; (2) uniformly mixing the layered functional powder material obtained in step (1) with a powder coating base powder to form a second mixture, and then extruding, crushing or pressure binding the second mixture to obtain particles with a medium particle size of 20-50 μm to obtain layered functional powder coating particles; (3) electrostatically spraying the layered functional powder coating particles obtained in step (2) onto a metal or non-metal substrate, and then heating the sprayed substrate at a high temperature to cure the powder coating into a film; (4) The metal or non-metal substrate is placed in air and cooled at room temperature, thereby obtaining a layered functional coating on the surface of the substrate.

2. The method for preparing a layered functional powder coating according to claim 1, characterized in that: In the step (1), the functional material and the stratification-promoting material are respectively crushed by a crusher, and then the crushed materials are bonded together to form a first mixture. The method of bonding or combining them together is one or more methods selected from the group consisting of solution method, pressure bonding, and melt extrusion.

3. The method for preparing the layered functional powder coating according to claim 1, characterized in that: In the step (1), the median particle size of the functional material is 0.05-20 μm, and the median particle size of the stratification-promoting material is 0.05-20 μm during pressure binding and 0.05-5000 μm during melt extrusion.

4. The method for preparing a layered functional powder coating according to claim 1, characterized in that: In the step (2), the layered functional powder material and the powder coating base powder are uniformly mixed by one or more of melt extrusion, pressure binding or dry mixing.

5. The method for preparing the layered functional powder coating according to claim 2, characterized in that: In the step (1), when the bonding or combining method is a solution method, the stratification-promoting material is first dissolved in a liquid solvent, and then mixed with functional material particles, dried, and crushed to obtain a stratified functional material.

6. The method for preparing the layered functional powder coating according to claim 2, characterized in that: In the step (1), when the bonding or combining method is a pressure binding method, the pressure of the pressure binding of the functional material and the stratification-promoting material is 3-50 MPa.

7. The method for preparing a layered functional powder coating according to claim 2, characterized in that: In the step (1), when the method of bonding or combining together is a melt extrusion method, the functional material and the delamination-promoting material are extruded through a single-screw or twin-screw extruder at an extrusion temperature of 80-300°C.

8. The method for preparing the layered functional powder coating according to claim 4, characterized in that: In the step (2), when the method for uniformly mixing the layered functional powder material and the powder coating base powder is a melt extrusion method, the layered functional powder material and the powder coating base powder are extruded through a single-screw or twin-screw extruder at an extrusion temperature of 80-120°C.

9. The method for preparing the layered functional powder coating according to claim 4, characterized in that: In the step (2), when the method for uniformly mixing the layered functional powder material and the powder coating base powder is a dry mixing method, the layered functional powder material and the powder coating base powder are dry mixed by a dry mixer at a stirring rate of 500-10000 rpm and a stirring time of 1-30 minutes.

10. The method for preparing the layered functional powder coating according to claim 1, characterized in that: In the step (3), the high temperature heating temperature range is 140-350° C., and the heating time is 5-30 minutes.

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