A polydopamine / nanosilver spherical antibacterial powder coating and its preparation method and application

Abstract

The present invention relates to a polydopamine nanosilver spherical antibacterial powder coating, and its preparation method and application. The present invention prepares a spherical powder coating by treating resin powder with a barrier agent under microwave conditions, then forms spherical particles with micro- and nanopore structures in situ under etchant treatment and removes the barrier agent, utilizes the self-polymerization of dopamine to form active sites in situ in the nanopores, and finally constructs a polydopamine / nanosilver spherical antibacterial powder coating by in situ reduction of silver ions, which can effectively improve the fluidity and coating performance of the antibacterial powder. At the same time, the coating has an antibacterial effect on Escherichia coli and Staphylococcus aureus, and the antibacterial rate can reach more than 99.9%. The preparation method of the present invention is simple, low-cost, highly repeatable, and has universal applicability, and can be widely used for antibacterial treatment of object surfaces.

Description

Technical Field

[0001] The invention belongs to the technical field of antibacterial powder coatings and relates to a polydopamine / nanosilver spherical antibacterial powder coating and a preparation method and application thereof. Background Art

[0002] As people's health awareness increases, antimicrobial coatings, as a new type of material with antimicrobial properties, have received increasing attention. Antimicrobial coatings have a wide range of applications, such as medical institutions, schools, office spaces, furniture, and public transportation. However, as countries continue to issue regulations restricting volatile organic compounds (VOCs), strict requirements and prevention and control technical measures have been formulated for the emission of VOCs during the coating process. Compared with traditional liquid coatings, antimicrobial powder coatings, as a coating variety with high production efficiency, excellent coating performance, eco-friendly and economical properties, have inherent advantages in preventing and controlling VOCs, and their recovery rate can reach 98%.

[0003] Antimicrobial powder coatings are a special type of powder coating that has been developed in recent years. Among them, nanosilver is a highly efficient, broad-spectrum inorganic antimicrobial agent with many advantages, such as long-lasting antimicrobial properties, high safety, strong antimicrobial effects, and low resistance to drug resistance. Powder coatings with nanosilver as an antimicrobial additive not only have the inherent advantages of powder coatings, but also have surface antimicrobial properties, which play a positive role in reducing the spread of pathogens and have broad application prospects. However, due to its large specific surface area, nanosilver has a certain degree of agglomeration, and the lack of active groups on the surface of nanosilver makes it difficult to effectively combine with the coating matrix. At the same time, the poor fluidity of conventional powder coatings can lead to uneven distribution during the spraying process, resulting in bubbles and orange peel in the coating, which ultimately affects the appearance and performance of the coating. Therefore, finding an appropriate method to introduce nanosilver particles into the powder coating matrix and solve the fluidity of the powder coating is an urgent problem to be solved. Summary of the Invention

[0004] The present invention aims to address the problems of prior art antibacterial powder coating preparation, such as nanosilver agglomeration, poor interfacial interaction between nanosilver and the substrate, and the orange peel phenomenon resulting from insufficient fluidity of the antibacterial coating. The present invention provides a method for preparing a polydopamine / nanosilver spherical antibacterial powder coating. The method comprises preparing a spherical powder coating using a barrier agent, then in situ forming a nanopore structure under acid etching, utilizing dopamine self-polymerization to form active sites in the nanopores, and finally constructing the polydopamine / nanosilver spherical antibacterial powder coating through in situ reduction of silver ions. The spherical powder coating can effectively improve the fluidity of the powder coating. The polydopamine loading can act as a "bridge" to strengthen the bonding between the coating substrate and the nanosilver. At the same time, the active groups of the polydopamine can complex silver ions, which helps reduce nanosilver agglomeration, thereby effectively improving the fluidity, coating performance, and antibacterial properties of the antibacterial powder coating.

[0005] In order to solve the above technical problems, the present invention is achieved through the following technical solutions.

[0006] The present invention provides a method for preparing a polydopamine / nanosilver spherical antibacterial powder coating, comprising the following steps:

[0007] (1) The resin powder coating matrix and the barrier agent are mixed evenly and placed in a microwave oven, and stirred at an output power of 500-1000W; then water and an etchant are added and stirred for 6-24 hours; after the reaction is completed, an alkaline solution is added and the reaction is continued for 6-24 hours, and then washed and dried to obtain a spherical resin powder with a nanoporous structure;

[0008] (2) placing the spherical resin powder with a nanoporous structure obtained in step (1) in a container, adding water and tris(hydroxymethyl)aminomethane, and adjusting the pH to 8-9 using a pH adjuster; then adding dopamine hydrochloride and stirring to react to obtain a polydopamine-functionalized spherical powder;

[0009] (3) The polydopamine functionalized spherical powder is washed and placed in a container together with water, and a silver nitrate solution is slowly added for stirring reaction; then a reducing agent is slowly added for heating and stirring reaction, and then washed and dried to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0010] Preferably, the resin powder coating matrix in step (1) is selected from one or more of triglycidyl isocyanurate (TGIC), polyester resin, epoxy resin E12, polyurethane resin (PU), polyamide resin (PA), polyethylene resin (PE), and fluorocarbon resin (PVDF).

[0011] Preferably, the barrier agent in step (1) is selected from one or more of fumed nano-silicon dioxide, fumed nano-silicon dioxide, nano-zinc oxide, nano-ferroferric oxide, and nano-aluminum oxide.

[0012] Preferably, the etchant in step (1) is selected from one or more of HCl, HF, LiF, and H2SO4.

[0013] Preferably, the alkaline solution in step (1) is selected from one or more of NaOH solution, KOH solution, NaHCO3 solution, and Na2CO3 solution.

[0014] Preferably, the molar ratio of the etchant to the barrier agent in step (1) is 1:1-4.

[0015] Preferably, the molar ratio of the etchant to the solute in the alkaline solution in step (1) is 1:1-5.

[0016] Preferably, in step (1), the output power of the microwave oven is 600-900 W, and the stirring time is 80-150 s; more preferably, the output power of the microwave oven is 700 W, and the stirring time is 110-130 s.

[0017] Preferably, water and an etchant are added in step (1) and stirred to react for 9-18 hours; more preferably, water and an etchant are added and stirred to react for 12 hours.

[0018] Preferably, in step (1), the alkaline solution is added and the reaction is continued for 9-18 hours; more preferably, the alkaline solution is added and the reaction is continued for 12 hours.

[0019] Preferably, the washing in step (1) is performed using water; more preferably, the washing is performed using deionized water for 1-6 times; most preferably, the washing is performed using deionized water for 4 times.

[0020] Preferably, the drying temperature in step (1) is 30-60°C and the drying time is 12-72h; more preferably, the drying temperature is 35-50°C and the drying time is 24-54h; most preferably, the drying temperature is 40°C and the drying time is 48h.

[0021] Preferably, the pH adjuster in step (2) is selected from one or more of hydrochloric acid, nitric acid, sulfuric acid and acetic acid.

[0022] Preferably, the stirring reaction in step (2) is carried out at a temperature of 18-30° C. and for a time of 12-48 h; more preferably, the stirring reaction is carried out at a temperature of 20-25° C. and for a time of 18-30 h.

[0023] Preferably, the mass ratio of the spherical resin powder with a nanoporous structure to dopamine hydrochloride in step (2) is 0.2-5:1; more preferably, the mass ratio of the spherical resin powder with a nanoporous structure to dopamine hydrochloride is 0.5-3:1.

[0024] Preferably, in step (3), the polydopamine-functionalized spherical powder is washed under reduced pressure with deionized water; more preferably, the polydopamine-functionalized spherical powder is washed under reduced pressure with deionized water for 1-6 times; most preferably, the polydopamine-functionalized spherical powder is washed under reduced pressure with deionized water for 3 times.

[0025] Preferably, the mass ratio of the polydopamine functionalized spherical powder to silver nitrate in step (3) is 1-20:1; more preferably, the mass ratio of the polydopamine functionalized spherical powder to silver nitrate is 4-16:1.

[0026] Preferably, the reducing agent in step (3) is selected from one or more of DMF, glucose, ascorbic acid, and NaBH4.

[0027] Preferably, the molar ratio of the reducing agent to Ag in the silver nitrate solution in step (3) is 1:0.5-2; more preferably, the molar ratio of the reducing agent to Ag in the silver nitrate solution is 1:1.

[0028] Preferably, the stirring reaction in step (3) is carried out at a temperature of 18-30° C. and for a time of 2-12 h; more preferably, the stirring reaction is carried out at a temperature of 20-25° C. and for a time of 4-8 h.

[0029] Preferably, the temperature of the heating and stirring reaction in step (3) is 40-60°C, and the time is 1-7 hours; more preferably, the temperature of the heating and stirring reaction is 45-55°C, and the time is 3-5 hours.

[0030] Preferably, the washing in step (3) is performed using water; more preferably, the washing is performed using deionized water for 1-6 times; most preferably, the washing is performed using deionized water for 4 times.

[0031] Preferably, the drying temperature in step (3) is 30-60°C and the drying time is 12-72h; more preferably, the drying temperature is 35-50°C and the drying time is 24-54h; most preferably, the drying temperature is 40°C and the drying time is 48h.

[0032] The second aspect of the present invention provides a polydopamine / nanosilver spherical antibacterial powder coating prepared according to the above preparation method.

[0033] A third aspect of the present invention provides an antibacterial powder coating, comprising a polydopamine / nanosilver spherical antibacterial powder coating prepared according to the above preparation method.

[0034] Preferably, the antibacterial powder coating is prepared by the following method: spraying polydopamine / nanosilver spherical antibacterial powder coating to form a coating, followed by curing, heating and melt leveling to obtain the coating.

[0035] Preferably, the spraying is electrostatic spraying.

[0036] Preferably, the coating has a thickness of 70-100 μm.

[0037] Preferably, the curing heat treatment is performed at a temperature of 170-200° C. and for a time of 5-20 minutes.

[0038] Compared with the existing technology, the present invention has the following beneficial effects:

[0039] (1) The present invention prepares spherical powder by treating resin powder with a barrier agent, and then treating with an etchant to remove the barrier material, thereby forming a porous structure on the polyamide surface. On the one hand, the spherical structure can significantly improve the fluidity of the powder, avoiding the orange peel phenomenon caused by insufficient fluidity of the antibacterial powder; on the other hand, the formation of the porous structure is conducive to the subsequent loading of silver, improving the interfacial interaction between nanosilver and the powder matrix, while preventing and reducing silver agglomeration.

[0040] (2) The polydopamine loading used in the present invention can be used as a "bridge" to strengthen the combination of the powder matrix and nanosilver. At the same time, the active groups of polydopamine can complex silver ions, which is beneficial to reduce the agglomeration of nanosilver, thereby effectively improving the fluidity, coating performance and antibacterial performance of the antibacterial powder coating.

[0041] (3) The antibacterial powder coating prepared by the present invention has good fluidity, stable performance, and an antibacterial rate of more than 99.9%. It can be directly used as an antibacterial agent in various types of scenarios, and can also be further processed according to actual needs, such as coating to form an antibacterial coating for use. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 Schematic diagram of the reaction process of microwave spheroidization of the present invention.

[0043] Figure 2 These are SEM morphologies of the polyamide powder obtained before and after treatment with the barrier agent and etchant in Example 1 of the present invention.

[0044] Figure 3 This is the XRD pattern of Ag@PDA@PA prepared in Example 1 of the present invention.

[0045] Figure 4 These are the board surface diagrams of Example 1 and Comparative Examples 2-4 of the present invention.

[0046] Figure 5 These are graphs showing the anti-E. coli effects of the antibacterial coatings of Example 1 and Comparative Example 4 after culturing for 1 hour and 6 hours.

[0047] Figure 6 This is a diagram showing the anti-E. coli effect of the antibacterial coating of Example 1 and Comparative Examples 1 and 4 of the present invention after culturing for 6 hours. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail with reference to the following examples. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0049] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the scope of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

[0050] Example 1

[0051] A polydopamine / nanosilver spherical antibacterial powder coating, the spherical reaction process is as follows Figure 1 As shown, the preparation method comprises the following steps:

[0052] (1) 120 g of polyamide PA powder and 30 g of fumed nano-silica R972 were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 110 s; then taken out and added with 600 mL of deionized water and 40% hydrofluoric acid solution, and stirred for 12 h, wherein the molar ratio of HF to fumed nano-silica was 1.5:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of HF to NaOH was 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyamide powder with a nanoporous structure.

[0053] (2) 50 g of the spherical polyamide powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.6 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.2 using 0.5 M HCl; then 25 g of dopamine hydrochloride was added and stirred at room temperature for 24 h to obtain a polydopamine-functionalized spherical polyamide powder.

[0054] (3) The polydopamine functionalized spherical polyamide powder was washed with deionized water under reduced pressure for 3 times and then placed in a 1000 mL beaker with 400 mL of deionized water. 2 g / L of silver nitrate solution was slowly added and stirred at room temperature for 6 hours, wherein the mass ratio of the polydopamine functionalized spherical polyamide powder to AgNO3 was 8:1; then DMF was slowly added and heated at 50°C with stirring for 4 hours, wherein the molar ratio of AgNO3 to DMF in the AgNO3 solution was 1:1; then the powder was washed with deionized water for 4 times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0055] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 100 μm, and then heat-treated at 170° C. for 10 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0056] Example 2

[0057] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0058] (1) 116.67 g of polyester resin / TGIC mixture (wherein the mass ratio of polyester resin to TGIC is 96:4) and 33.33 g of nano-ferroferric oxide were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 120 s; then taken out and added with 600 mL of deionized water and 40% hydrochloric acid solution, and stirred for 12 h, wherein the molar ratio of HCl to nano-ferroferric oxide was 1.5:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of HCl to NaOH was 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyester TGIC powder with a nanoporous structure.

[0059] (2) 50 g of the spherical polyester TGIC powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.65 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.4 using 0.75 M HCl; then 50 g of dopamine hydrochloride was added and the mixture was stirred and reacted at room temperature for 24 h to obtain a polydopamine-functionalized spherical polyester TGIC powder.

[0060] (3) The polydopamine-functionalized spherical polyester TGIC powder was washed with deionized water under reduced pressure three times and then placed in a 1000 mL beaker with 400 mL of deionized water. 1.5 g / L of silver nitrate solution was slowly added and stirred at room temperature for 5 hours, wherein the mass ratio of polydopamine-functionalized spherical polyester TGIC powder to AgNO3 was 8:2; glucose was then slowly added and heated and stirred at 50°C for 4.5 hours, wherein the molar ratio of AgNO3 to glucose in the AgNO3 solution was 1:1; it was then washed with deionized water four times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0061] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 75 μm, and then heat-treated at 180° C. for 15 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0062] Example 3

[0063] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0064] (1) 112.5 g of polyurethane (PU) powder and 37.5 g of nano-alumina were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 130 s; then taken out and added with 600 mL of deionized water and 40% dilute sulfuric acid solution, and stirred for 12 h, wherein the molar ratio of H2SO4 to nano-alumina was 1.5:2; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of H2SO4 to NaOH was 1:5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyurethane powder with a nanoporous structure.

[0065] (2) 50 g of the spherical polyurethane powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.7 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.5 with 1 M HCl; then 100 g of dopamine hydrochloride was added and the mixture was stirred and reacted at room temperature for 24 h to obtain a polydopamine-functionalized spherical polyurethane powder.

[0066] (3) The polydopamine-functionalized spherical polyurethane powder was washed with deionized water under reduced pressure three times and then placed in a 1000 mL beaker with 400 mL of deionized water. 3 g / L of silver nitrate solution was slowly added and stirred at room temperature for 5.5 hours, wherein the mass ratio of the polydopamine-functionalized spherical polyurethane powder to AgNO3 was 9:1; then ascorbic acid was slowly added and heated and stirred at 50°C for 4 hours, wherein the molar ratio of AgNO3 to ascorbic acid in the AgNO3 solution was 1:1; then the powder was washed with deionized water four times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0067] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 90 μm, and then heat-treated at 200° C. for 20 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0068] Example 4

[0069] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0070] (1) 127.5 g of polyamide PA powder and 22.5 g of fumed nano-silica 200 were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 120 s; then taken out and added with 600 mL of deionized water and 40% hydrofluoric acid solution, stirred and reacted for 12 h, wherein the molar ratio of HF to fumed nano-silica was 2:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of HF to NaOH was 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyamide powder with a nanoporous structure.

[0071] (2) 50 g of the spherical polyamide powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.75 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.4 using 0.25 M HCl; then 16.67 g of dopamine hydrochloride was added and stirred at room temperature for 24 h to obtain a polydopamine-functionalized spherical polyamide powder.

[0072] (3) The polydopamine functionalized spherical polyamide powder was washed with deionized water under reduced pressure for 3 times and then placed in a 1000 mL beaker with 400 mL of deionized water. 2.5 g / L of silver nitrate solution was slowly added and stirred at room temperature for 6.5 h, wherein the mass ratio of the polydopamine functionalized spherical polyamide powder to AgNO3 was 9:2; then NaBH4 was slowly added and heated and stirred at 50°C for 3 h, wherein the molar ratio of AgNO3 to NaBH4 in the AgNO3 solution was 1:1; then the powder was washed with deionized water for 4 times and dried in a vacuum oven at 40°C for 48 h to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0073] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 85 μm, and then heat-treated at 170° C. for 15 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0074] Example 5

[0075] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0076] (1) 133.33 g of polyester resin / TGIC mixture (wherein the mass ratio of polyester resin to TGIC is 96:4) and 16.67 g of nano-alumina were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 120 s; then taken out and added with 600 mL of deionized water and 40% hydrochloric acid solution, and stirred for 12 h, wherein the molar ratio of HCl to nano-alumina is 2:1; after the reaction is completed, 5 M NaOH solution is slowly added and the reaction is continued for 12 h, wherein the molar ratio of HCl to NaOH is 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyester TGIC powder with a nanoporous structure.

[0077] (2) 50 g of the spherical polyester TGIC powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.8 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.6 using 0.5 M HCl; then 33.33 g of dopamine hydrochloride was added and stirred at room temperature for 24 h to obtain a polydopamine-functionalized spherical polyester TGIC powder.

[0078] (3) The polydopamine-functionalized spherical polyester TGIC powder was washed with deionized water under reduced pressure for three times and then placed in a 1000 mL beaker with 400 mL of deionized water. 1 g / L silver nitrate solution was slowly added and stirred at room temperature for 6 hours, wherein the mass ratio of the polydopamine-functionalized spherical polyester TGIC powder to AgNO3 was 10:1; then DMF was slowly added and heated and stirred at 50°C for 3.5 hours, wherein the molar ratio of AgNO3 to DMF in the AgNO3 solution was 1:1; then it was washed with deionized water for 4 times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0079] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 90 μm, and then heat-treated at 170° C. for 5 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0080] Example 6

[0081] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0082] (1) 131.25 g of polyurethane and 18.75 g of fumed nano-silica A200 were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 110 s; then taken out and added with 600 mL of deionized water and 40% dilute sulfuric acid solution, and stirred for 12 h, wherein the molar ratio of H2SO4 to fumed nano-silica was 1:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of H2SO4 to NaOH was 1:5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyurethane powder with a nanoporous structure.

[0083] (2) 50 g of the spherical polyurethane powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.85 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.7 with 0.75 M HCl; then 20 g of dopamine hydrochloride was added and stirred at room temperature for 24 h to obtain a polydopamine-functionalized spherical polyurethane powder.

[0084] (3) The polydopamine-functionalized spherical polyurethane powder was washed with deionized water under reduced pressure three times and then placed in a 1000 mL beaker with 400 mL of deionized water. 1 g / L silver nitrate solution was slowly added and stirred at room temperature for 5 hours, wherein the mass ratio of the polydopamine-functionalized spherical polyurethane powder to AgNO3 was 7:1; glucose was then slowly added and heated and stirred at 50°C for 4 hours, wherein the molar ratio of AgNO3 to glucose in the AgNO3 solution was 1:1; then the powder was washed with deionized water four times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0085] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 80 μm, and then heat-treated at 170° C. for 8 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0086] Example 7

[0087] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0088] (1) 128.57 g of polyester resin / E12 mixture (wherein the mass ratio of polyester resin to E12 is 50:50) and 21.43 g of fumed nano-silica R972 were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 120 s; then taken out and added with 600 mL of deionized water and 40% hydrochloric acid solution, and stirred for 12 h, wherein the molar ratio of HCl to fumed nano-silica was 4:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of HCl to NaOH was 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyester E12 powder with a nanoporous structure.

[0089] (2) 50 g of the spherical polyester E12 powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.55 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.8 with 1 M HCl; then 75 g of dopamine hydrochloride was added and the mixture was stirred and reacted at room temperature for 24 h to obtain polydopamine-functionalized spherical polyester E12 powder.

[0090] (3) The polydopamine-functionalized spherical polyester E12 powder was washed with deionized water under reduced pressure three times and then placed in a 1000 mL beaker with 400 mL of deionized water. 3 g / L of silver nitrate solution was slowly added and stirred at room temperature for 5.5 hours, wherein the mass ratio of the polydopamine-functionalized spherical polyester E12 powder to AgNO3 was 5:1; then ascorbic acid was slowly added and heated at 50°C with stirring for 4 hours, wherein the molar ratio of AgNO3 to ascorbic acid in the AgNO3 solution was 1:1; then the powder was washed with deionized water four times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0091] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 80 μm, and then heat-treated at 170° C. for 8 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0092] Example 8

[0093] A polydopamine / nanosilver spherical antibacterial powder coating, the preparation method of which comprises the following steps:

[0094] (1) 125 g of a polyester resin and E12 mixture (wherein the mass ratio of polyester resin to E12 is 50:50) and 25 g of nano-ferroferric oxide were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 130 s; then taken out and added with 600 mL of deionized water and 40% hydrofluoric acid solution, and stirred for 12 h, wherein the molar ratio of HF to nano-ferroferric oxide was 4:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of HF to NaOH was 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyester E12 powder with a nanoporous structure.

[0095] (2) 50 g of the spherical polyester E12 powder with a nanoporous structure obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.5 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 9.0 using 0.25 M HCl; then 30 g of dopamine hydrochloride was added and the mixture was stirred and reacted at room temperature for 24 h to obtain polydopamine-functionalized spherical polyester E12 powder.

[0096] (3) The polydopamine-functionalized spherical polyester E12 powder was washed with deionized water under reduced pressure three times and then placed in a 1000 mL beaker with 400 mL of deionized water. 1.5 g / L of silver nitrate solution was slowly added and stirred at room temperature for 6.5 hours, wherein the mass ratio of the polydopamine-functionalized spherical polyester E12 powder to AgNO3 was 8:0.5; then NaBH4 was slowly added and heated and stirred at 50°C for 4 hours, wherein the molar ratio of AgNO3 to NaBH4 in the AgNO3 solution was 1:1; then it was washed with deionized water four times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

[0097] Furthermore, the polydopamine / nanosilver spherical antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 80 μm, and then heat-treated at 170° C. for 15 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0098] Comparative Example 1

[0099] An antibacterial powder coating, the preparation method of which comprises the following steps:

[0100] (1) 120 g of polyamide PA powder and 30 g of fumed nano-silica R972 were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 110 s; then taken out and added with 600 mL of deionized water and 40% hydrofluoric acid solution, and stirred for 12 h, wherein the molar ratio of HF to fumed nano-silica was 1.5:1; after the reaction was completed, 5 M NaOH solution was slowly added and the reaction was continued for 12 h, wherein the molar ratio of HF to NaOH was 1:2.5; washed with deionized water 4 times and placed in a vacuum oven at 40 ° C for 48 h to obtain spherical polyamide powder with a nanoporous structure.

[0101] (2) 50 g of the mixture obtained in step (1) and 400 mL of deionized water were placed in a 1000 mL beaker, and 2 g / L of silver nitrate solution was slowly added and stirred at room temperature for 6 h, wherein the mass ratio of the mixture to AgNO3 was 8:1; then DMF was slowly added and heated and stirred at 50°C for 4 h, wherein the molar ratio of AgNO3 to DMF was 1:1; then the mixture was washed with deionized water 4 times and dried in a vacuum oven at 40°C for 48 h to obtain an antibacterial powder coating.

[0102] Furthermore, the antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 80 μm, and then heat-treated at 170° C. for 10 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0103] Comparative Example 2

[0104] An antibacterial powder coating, the preparation method of which comprises the following steps:

[0105] (1) 50 g of polyamide powder was placed in a 1000 mL beaker, 500 mL of deionized water and 0.6 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.4 using 0.5 M HCl. Subsequently, 25 g of dopamine hydrochloride was added and stirred at room temperature for 24 h to obtain polydopamine-functionalized polyamide powder.

[0106] (2) The polydopamine functionalized polyamide powder was washed with deionized water under reduced pressure for 3 times and then placed in a 1000 mL beaker with 400 mL of deionized water. 2 g / L of silver nitrate solution was slowly added and stirred at room temperature for 5 h, wherein the mass ratio of the polydopamine functionalized polyamide powder to AgNO3 was 8:1; then DMF was slowly added and heated and stirred at 50°C for 5 h, wherein the molar ratio of AgNO3 to DMF in the AgNO3 solution was 1:1; then the powder was washed with deionized water for 4 times and dried in a vacuum oven at 40°C for 48 h to obtain an antibacterial powder coating.

[0107] Furthermore, the antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 80 μm, and then heat-treated at 170° C. for 15 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0108] Comparative Example 3

[0109] An antibacterial powder coating, the preparation method of which comprises the following steps:

[0110] (1) 120 g of polyamide PA powder and 30 g of fumed nanosilica R972 were mixed evenly using a wall breaker, placed in a microwave oven equipped with a rotary drum, and stirred at an output power of 700 W for 110 s; washed with deionized water four times and then placed in a vacuum oven at 40 ° C and dried for 48 h to obtain polyamide powder.

[0111] (2) 50 g of the polyamide powder obtained in step (1) was placed in a 1000 mL beaker, 500 mL of deionized water and 0.6 g of tris(hydroxymethyl)aminomethane were added, and the pH was adjusted to 8.2 using 0.5 M HCl; then 25 g of dopamine hydrochloride was added and stirred at room temperature for 24 h to obtain polydopamine-functionalized polyamide powder.

[0112] (3) The polydopamine functionalized polyamide powder was washed with deionized water under reduced pressure for 3 times and then placed in a 1000 mL beaker with 400 mL of deionized water. 2 g / L of silver nitrate solution was slowly added and stirred at room temperature for 6 hours, wherein the mass ratio of polydopamine functionalized polyamide powder to AgNO3 was 8:1; then DMF was slowly added and heated at 50°C with stirring for 4 hours, wherein the molar ratio of AgNO3 to DMF in the AgNO3 solution was 1:1; then the powder was washed with deionized water for 4 times and dried in a vacuum oven at 40°C for 48 hours to obtain a polydopamine / nanosilver antibacterial powder coating.

[0113] Furthermore, the polydopamine / nanosilver antibacterial powder coating prepared above was electrostatically sprayed on a tinplate to form a coating with a thickness of 100 μm, and then heat-treated at 170° C. for 10 min to melt and level the coating, thereby obtaining an antibacterial powder coating.

[0114] Comparative Example 4

[0115] The polyamide PA powder was electrostatically sprayed onto the tinplate to form a coating with a thickness of 80 μm, and then heat-treated at 170° C. for 15 minutes to melt and level the tinplate, thereby obtaining the PA powder coating.

[0116] Verification Example 1

[0117] The polyamide powder obtained before and after treatment with the barrier agent and the etchant in step (1) of Example 1 was taken, and its morphology was detected using a scanning electron microscope. The results are as follows: Figure 2 As shown. Figure 2 (a) and Figure 2 (c) is untreated polyamide raw powder, Figure 2 (b) and Figure 2 (d) is the spherical polyamide powder with nanoporous structure obtained after treatment. The results show that after the polyamide powder is treated with the barrier agent, the spherical change of its surface is obvious. After sphericalization, it is further treated with an etchant to remove the barrier material, thereby forming a porous structure on the polyamide surface, which is conducive to the subsequent loading of silver. The spherical antibacterial powder coating prepared in Example 1 was tested using an X-ray diffractometer. The results are as follows: Figure 3 The results show that the antibacterial powder coating obtained is successfully loaded with the required content of silver component.

[0118] Subsequently, the powder coatings prepared in Examples 1-8 and Comparative Examples 1-4 were respectively tested for their angle of repose, angle of collapse, angle of difference and flow index as well as the antibacterial rate of the boards prepared therefrom. The test results are shown in Table 1 and Figure 4 shown.

[0119] Table 1 Performance data of antibacterial powder coatings of Examples 1-8 and Comparative Examples 1-4

[0120] sample Angle of repose Collapse Angle Difference Angle Liquidity Index Antibacterial properties Example 1 35° 18.9° 16.1° 131.8 99.9％ Example 2 34.6° 18.8° 15.8° 138.9 98.6％ Example 3 34.4° 18.9° 15.5° 141.2 95.7％ Example 4 37.3° 21.1° 16.2° 129.3 98.9％ Example 5 41.5° 21.1° 20.4° 98.6 96.3％ Example 6 39.7° 20.9° 18.8° 103.7 99.7％ Example 7 38.7° 21.5° 17.2° 112.8 95.82％ Example 8 37.4° 20.6° 16.8° 119.7 97.38％ Comparative Example 1 38.3° 21.4° 16.9° 116.6 80.70％ Comparative Example 2 44.5° 21.2° 23.3° 67.74 91.67％ Comparative Example 3 32.5° 18.6° 13.9° 149.8 \ Comparative Example 4 42.9° 20.8° 22.1° 73.96 \

[0121] The spherical preparation process and mechanism of the polydopamine nanosilver spherical antibacterial powder coating of the present invention can be found in Figure 1 When the surface tension of a fluid is significantly higher than gravity or other forces, the fluid will take on a spherical shape. In the absence of other forces, surface tension will minimize the surface of a given volume, causing the droplets to take on a spherical shape. A spherical powder coating is obtained by utilizing the surface tension of molten droplets or solution droplets to transform irregularly shaped powder coating particles into spherical particles. In order to reduce the stacking of powders during the spheroidization process, a barrier agent is added for dispersion. The barrier agent itself is a flow aid. The more it is added, the better the fluidity of the powder itself. Since the amount of the barrier agent added is more than 15%, and the amount of powder coating nanoparticles added should not exceed 0.8%, if it exceeds 0.8%, the more it is added, the coating will have many pinholes, shrinkage holes, and air holes. In severe cases, the coating film cannot be formed and the leveling of the coating decreases, so an etchant is needed to remove the barrier agent. Comparative Example 2, despite the addition of polydopamine, did not spheronize the powder, resulting in significantly lower surface leveling than Example 1 of the present invention, and numerous cracks appeared on the surface of the film formed. Comparative Example 3, despite the use of a barrier agent to spheronize the powder, did not further treat the barrier agent with an etchant. Although the fluidity was optimal, the barrier agent content far exceeded the requirements for powder coatings, making it difficult to form a film and causing it to fall apart upon contact. Therefore, subsequent antibacterial testing of the board surface was unfeasible. Comparative Example 4, using untreated polyamide powder, also suffered from poor leveling, with numerous bubbles appearing on the surface of the film formed. This shows that spheronizing the powder with a barrier agent and removing the barrier agent are key factors in improving coating leveling and film formation.

[0122] The antibacterial tests in the chart all used Escherichia coli liquid, which was cultured on the coating for 6 hours and then diluted 10 times, 100 times, 1000 times, and 10,000 times respectively, and then applied on the culture medium. Comparative Example 4 was used as a blank control group, and the antibacterial rate was calculated based on the difference in colony counts. Subsequently, the antibacterial coating synthesized in Example 1 and the pure polyamide powder coating synthesized in Comparative Example 4 were taken for antibacterial testing. Specifically, this test used Escherichia coli liquid, which was cultured on the coating for 1 hour and 6 hours and then diluted 10 times, 100 times, 1000 times, and 10,000 times respectively, and then applied on the culture medium. The results are shown in Figure 2. Figure 5 As shown, Figure 5 (a) and Figure 5 (c) is a graph showing the number of colonies on the plate of the coating of Comparative Example 4 at the corresponding dilution multiples after 1 hour and 6 hours of bacterial culture; Figure 5 (b) and Figure 5(d) shows the plate counts of the AgNPs@PDA@PA coating prepared in Example 1 at corresponding dilution factors after 1 and 6 hours of bacterial culture. The results show that the coating in Comparative Example 4, consisting solely of polyamide PA powder without any treatment and serving as a blank control, achieved an antibacterial efficacy of 36.95% after 1 hour of culture, and 99.9% after 6 hours of culture. The significant improvement in antibacterial efficacy over time demonstrates the synergistic antibacterial effect of the Ag loading.

[0123] Since the leveling performance of the board surface in Comparative Examples 2 and 3 was poor, especially in Comparative Example 3, which could not even form a film, the subsequent antibacterial test of the board surface could not be carried out. Therefore, Example 1 and Comparative Example 1 were further used for antibacterial performance comparison (E. coli liquid was cultured on the coating for 6 hours), and Comparative Example 4 was used as a blank control. The results are as follows: Figure 6 As shown. The results show that the antibacterial rate of Example 1 is significantly improved compared with that of Comparative Example 1. Since polydopamine is not used as a carrier in Comparative Example 1, its antibacterial performance is not as good as that of polydopamine under the condition of the same Ag addition amount. The main reason is that polydopamine has effective loading sites for silver ions and can effectively disperse silver ions. Direct addition of nanosilver reduces the utilization rate of silver ions due to the easy agglomeration of nano-scale substances. In contrast, the role of polydopamine is more evident. In Comparative Example 2, the powder is not spheroidized, and the fluidity of the powder is far inferior to that of other spheroidized powder particles. The leveling property of the final board surface is also inferior to that of the spheroidized powder coating.

[0124] The above detailed description of the technical solutions involved in the present invention is provided in detail. It should be noted that the above description is intended only to help those skilled in the art better understand the methods and concepts of the present invention, and is not intended to limit the relevant content. Without departing from the principles of the present invention, those skilled in the art may also make appropriate adjustments or modifications to the present invention, and such adjustments and modifications shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polydopamine / nanosilver spherical antibacterial powder coating, characterized in that: The steps include: (1) The resin powder coating matrix and the barrier agent are mixed evenly and placed in a microwave oven, and stirred at an output power of 500-1000W; then water and an etchant are added and stirred to react for 6-24 hours; after the reaction is completed, an alkaline solution is added and the reaction is continued for 6-24 hours, and then washed and dried to obtain a spherical resin powder with a nanoporous structure; the barrier agent is selected from one or more of fumed nano-silicon dioxide, nano-zinc oxide, nano-ferroferric oxide, and nano-aluminum oxide; (2) placing the spherical resin powder with a nanoporous structure obtained in step (1) in a container, adding water and tris(hydroxymethyl)aminomethane, and adjusting the pH to 8-9 using a pH regulator; then adding dopamine hydrochloride and stirring to react to obtain a polydopamine-functionalized spherical powder; (3) The polydopamine functionalized spherical powder is washed and placed in a container together with water, and a silver nitrate solution is slowly added for stirring reaction; then a reducing agent is slowly added for heating and stirring reaction, and then washed and dried to obtain a polydopamine / nanosilver spherical antibacterial powder coating.

2. The preparation method according to claim 1, characterized in that The resin powder coating matrix in step (1) is selected from one or more of polyester resin, epoxy resin E12, polyurethane resin, polyamide resin, polyethylene resin, and fluorocarbon resin.

3. The preparation method according to claim 1, characterized in that The etchant in step (1) is selected from one or more of HCl, HF, LiF, and H2SO4.

4. The preparation method according to claim 1, characterized in that In step (1), the output power of the microwave oven is 600-900W, and the stirring time is 80-150s.

5. The preparation method according to claim 1, characterized in that The stirring reaction in step (2) is carried out at a temperature of 18-30° C. and for a time of 12-48 hours.

6. The preparation method according to claim 1, characterized in that The reducing agent in step (3) is selected from one or more of glucose, ascorbic acid, and NaBH4.

7. The preparation method according to claim 1, characterized in that The temperature of the heating and stirring reaction in step (3) is 40-60°C and the time is 1-7h.

8. The polydopamine / nanosilver spherical antibacterial powder coating prepared according to the preparation method according to any one of claims 1 to 7.

9. An antibacterial powder coating, characterized in that: The invention comprises a polydopamine / nanosilver spherical antibacterial powder coating prepared according to the preparation method according to any one of claims 1 to 7.

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