Preparation method of antibacterial wear-resistant waterborne polyurethane coating

Abstract

The invention relates to the technical field of polyurethane coatings, and discloses a preparation method of an antibacterial wear-resistant waterborne polyurethane coating, which comprises the following steps: taking concentrated hydrochloric acid, p-phenylenediamine, sodium nitrite, formaldehyde, amino modified nano silicon dioxide and hexamethylene diisocyanate as raw materials; the preparation method comprises the following steps: taking 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide as a raw material, carrying out diazotization coupling reaction, substitution reaction, Mannich reaction and addition reaction to prepare modified polyisocyanate, then taking 9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and ((2-aminoethyl) azadiyl) dimethanol as raw materials, carrying out substitution reaction to prepare DOPO-based dihydric alcohol, and carrying out reaction to prepare the DOPO-based dihydric alcohol. Finally, the modified polyisocyanate, DOPO-based dihydric alcohol and polyethylene glycol 400 are used as raw materials, an antibacterial wear-resistant polyurethane emulsion is prepared through a prepolymerization reaction and a chain extension reaction, and the prepared polyurethane coating has good antibacterial, anti-ultraviolet, flame-retardant and wear-resistant properties.

Description

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 24, 2024, with application number 202411908780.X and invention name “A method for preparing an antibacterial and wear-resistant water-based polyurethane coating”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The invention relates to the technical field of polyurethane coatings, in particular to a method for preparing an antibacterial and wear-resistant water-based polyurethane coating. Background Art

[0003] Waterborne polyurethane uses water as the dispersion medium. Due to the advantages of water being non-toxic, odorless, non-flammable, non-explosive, non-polluting to the environment, significantly reducing product costs, and not endangering the health of operators, it has attracted more and more attention. As a material with excellent performance, good compatibility, and environmental friendliness, waterborne polyurethane has been widely used in leather, textile coating and other fields.

[0004] At present, the market mostly uses a combination of halogen flame retardants and water-based polyurethane to perform flame retardant finishing on coated objects. This has the disadvantages of opaque coatings, large amounts of flame retardants added, and the generation of toxic gases and thick smoke when burned.

[0005] For example, the patent with authorization announcement number CN113088114A discloses a wear-resistant polyurethane coating and its preparation method. The invention uses polyurethane matrix resin, acrylate, polyketone resin, nitrocellulose, nano-silica, nano-calcium carbonate, additives and solvents, polyurethane matrix resin. The coating composition prepared by the invention is easy to prepare and use, can effectively resist friction, wear, scratch and scrape, and enhance the scratch resistance of the coating surface. However, the coating prepared by this invention is not suitable for humid or wet environments. In such environments, bacteria are easily bred, the service life is shortened, and the anti-ultraviolet performance is poor. Summary of the Invention

[0006] (1) Technical problems solved

[0007] In view of the shortcomings of the existing technology, the present invention provides a method for preparing an antibacterial and wear-resistant water-based polyurethane coating, and the prepared polyurethane coating has good antibacterial, anti-ultraviolet, flame retardant and wear-resistant properties.

[0008] (2) Technical solution

[0009] A method for preparing an antibacterial and wear-resistant water-based polyurethane coating comprises the following steps: adding a polyurethane emulsion into a stirrer, stirring at high speed for 15-30 minutes, adding a cosolvent (ethanol butyl ether), a slip agent (DC-56), a leveling agent (H-140), and a defoaming agent (W-0506), mixing the mixture evenly, adding a diluent (ZP-110), and stirring at high speed for 15-30 minutes to prepare the antibacterial and wear-resistant polyurethane coating.

[0010] Preferably, the polyurethane emulsion preparation method is:

[0011] (1) Add 37% concentrated hydrochloric acid to deionized water, add 1,3,5-triaminobenzene, cool to -5 to 0°C, stir and react for 30-50 minutes, then dropwise add an aqueous solution of sodium nitrite, and react for 50-90 minutes. After the reaction is complete, remove impurities, filter, add deionized water, and then add 4-hydroxy-2,6-dimethylbenzyl alcohol, sodium hydroxide, and anhydrous sodium carbonate. Stir and mix evenly and react for 2-4 hours. After the reaction is complete, filter, wash with hot deionized water and ethanol, and dry to obtain intermediate 1.

[0012] (2) Add formaldehyde to chloroform solvent, add calcium hydride, heat to 20-30°C, react for 20-40 minutes, then heat to 50-70°C, add amino-modified nano-silica, heat to 75-85°C, add intermediate 1, react for 50-90 minutes, filter, column chromatography, and low-pressure distillation to obtain intermediate 2;

[0013] (3) Add intermediate 2, hexamethylene diisocyanate, to butyl acetate solvent, stir evenly, add catalyst dibutyltin dilaurate (DBTDL), heat to 70-90°C, react for 2-4 hours, cool, and distill under low pressure to obtain modified polyisocyanate;

[0014] (4) Under nitrogen atmosphere, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), triethylamine (TEA), and ((2-aminoethyl)azadiyl)dimethanol to dichloromethane solvent, cool to -10 to 0°C, add carbon tetrachloride, and heat to 5-15°C. After the addition is complete, heat to 20-30°C, react for 10-14 hours, filter, wash with deionized water, and dry to obtain DOPO-based diol;

[0015] (5) Under nitrogen atmosphere, add modified polyisocyanate, polyethylene glycol 400 (PEG400), and DOPO-based diol into a three-necked flask, stir and mix evenly, heat to 80-90℃, react for 2-4h, cool to 35-55℃, add dihydroxymethylpropionic acid (DMPA) and 1,4-butanediol (BDO), heat to 70-90℃, react for 30-90min, cool to 35-50℃, add catalyst dibutyltin dilaurate and stannous octoate, heat to 60-80℃, react for 3-5h, and after the reaction is complete, cool to 30-50℃, neutralize with triethylamine, emulsify with deionized water, chain extend with ethylenediamine (EDA), and distill under reduced pressure to obtain a polyurethane emulsion.

[0016] Preferably, the ethanol butyl ether accounts for 3% to 10% of the mass of the polyurethane emulsion, the slip agent accounts for 0.2% to 0.5% of the mass of the polyurethane emulsion, the defoaming agent accounts for 0.6% to 1% of the mass of the polyurethane emulsion, the leveling agent accounts for 0.3% to 0.5% of the mass of the polyurethane emulsion, and the diluent accounts for 15% to 20% of the mass of the polyurethane emulsion.

[0017] Preferably, in step (1), the molar ratio of concentrated hydrochloric acid, 1,3,5-triaminobenzene, sodium nitrite, deionized water, 4-hydroxy-2,6-dimethylbenzyl alcohol, sodium hydroxide, and anhydrous sodium carbonate is 35.5-36.5:1:4-5:160-170:2.5-3.5:2.5-3.5:8-10.

[0018] Preferably, in step (2), the molar ratio of the intermediate 1, calcium hydride, formaldehyde, and amino-modified nano-silica is 1:4-5:5.5-7:3-3.5.

[0019] Preferably, in step (3), the molar ratio of intermediate 2, DBDTDL, and hexamethylene diisocyanate is 1:0.0005-0.0015:3-3.5.

[0020] Preferably, in step (4), the molar ratio of DOPO, TEA, ((2-aminoethyl)azadiyl)dimethanol, and carbon tetrachloride is 1:0.8-1.2:0.35-0.45:0.8-1.2.

[0021] Preferably, in step (5), the molar mass ratio of DOPO-based diol, modified polyisocyanate, PEG400, DMPA, BDO, dibutyltin dilaurate, stannous octoate, and ethylenediamine is 1:9-9.5:1.8-2.2:0.8-1.2:1.3-1.7:0.07-0.1:0.12-0.16:1.5-2.

[0022] (3) Beneficial technical effects

[0023] The invention uses concentrated hydrochloric acid, p-phenylenediamine, sodium nitrite, formaldehyde, amino-modified nano-silica and hexamethylene diisocyanate as raw materials, and carries out diazotization coupling reaction, substitution reaction and Manniene reaction to prepare modified polyisocyanate. Then, uses 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and ((2-aminoethyl)azadiyl)dimethanol as raw materials, and carries out substitution reaction to prepare DOPO-based diol. Finally, uses the modified polyisocyanate, DOPO-based diol and polyethylene glycol 400 as raw materials, and carries out prepolymerization reaction and chain extension reaction to prepare antibacterial and wear-resistant polyurethane coating.

[0024] The antibacterial and wear-resistant polyurethane coating prepared by the present invention contains quaternary ammonium salt groups, which have positive charges and can be adsorbed on the surface of microorganisms to form micelles and gradually penetrate into the lipid layer and protein layer of the cytoplasm, thereby changing the permeability of the cell membrane and causing the cell contents to extravasate, leading to the death of the microorganisms. At the same time, the coating coagulates proteins, denatures enzymes and structural proteins, disrupts the metabolism of the microorganisms, and kills the microorganisms, thereby improving the antibacterial properties of the coating.

[0025] The antibacterial and wear-resistant polyurethane coating prepared by the present invention contains nano-silica, and a network structure is formed between the nano-silica and the organic matrix, which can change the stress concentration of the polyurethane coating. When the material is impacted, it triggers more yield deformation of the surrounding matrix, increases the crack propagation resistance of the matrix, and enhances the toughness. At the same time, when the coating is cured, the polymer chain links and covalent bonds themselves shrink. The addition of the non-shrinking component nano-silica can fill the gaps generated by the shrinkage of the organic component, thereby achieving the effect of reducing the internal stress of the material, and thus having better wear resistance.

[0026] The antibacterial and wear-resistant polyurethane coating prepared by the present invention contains azo groups, which exhibit photochromic and photoinduced cis-trans isomerization properties. The azo groups also have a distinct absorption peak in the ultraviolet region (particularly between 200 and 400 nm). This is because the π electrons within the azo groups readily undergo transitions from a lower energy level to a higher energy level under ultraviolet light. This transition absorbs ultraviolet light, reducing its penetration and thus achieving an anti-ultraviolet effect. Introducing these groups into coatings can enhance their UV resistance.

[0027] The antibacterial and wear-resistant polyurethane coating prepared by the present invention contains phosphorus, nitrogen, and silicon elements. Nitrogen decomposes during combustion to produce a large amount of non-combustible gas, which can dilute the oxygen concentration around the coating. Silicon migrates to the outside of the material during combustion, converting Si-O bonds in its molecules into Si-C bonds. The generated white combustion residue and carbides form a covering layer on the coating surface, preventing the escape of combustion volatiles and preventing oxygen from contacting the substrate material, thereby improving the flame retardant properties of the coating. Phosphorus releases a large amount of gas or high-density steam when heated or burned, which can dilute oxygen and gaseous combustibles in the air and reduce the surface temperature of the burning material, causing combustion to stop. At the same time, the phosphorus component in the structure of the present invention captures H and OH free radicals formed during the combustion process, thereby producing a good quenching effect and carbonization effect. The formation of the carbon layer reduces the release of volatiles. The antibacterial and wear-resistant polyurethane coating prepared by the present invention has good wear resistance, antibacterial properties, flame retardant properties, and UV resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is the synthetic route of intermediate 2;

[0029] Figure 2 It is a modified polyisocyanate synthesis route;

[0030] Figure 3 This is a synthetic route for DOPO-based diols. DETAILED DESCRIPTION

[0031] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention, in conjunction with the embodiments of the present invention. It should be understood that the embodiments described herein are merely a portion of the embodiments of the present invention, and not all of them. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are intended to fall within the scope of protection of the present invention.

[0032] Preparation method of amino-modified nano-silica:

[0033] Add 1 mL of 3-aminopropyltrimethoxysilane and 3.6 mL of anhydrous ethanol to 0.4 mL of distilled water to prepare a silane solution, let it stand for 10 minutes, add 12.5 mL of anhydrous ethanol and 1.0 g of nano-silica to 0.21 mL of the silane solution, ultrasonically disperse, mechanically stir, heat to 78°C, react for 2 hours, filter, dry, and grind to obtain amino-modified nano-silica.

[0034] Example 1

[0035] (1) Add 3.55 mol of 37% concentrated hydrochloric acid to 150 ml of deionized water, add 0.1 mol of 1,3,5-triaminobenzene, cool to -5 °C, stir and react for 50 min, then add 0.5 mol of sodium nitrite aqueous solution dropwise, and react for 60 min. After the addition is complete, remove impurities, filter, add 16 mol of deionized water, 0.3 mol of 4-hydroxy-2,6-dimethylbenzyl alcohol, 0.25 mol of sodium hydroxide, and 1 mol of anhydrous sodium carbonate, stir and mix evenly, and react for 3 h. After the reaction is complete, filter, wash with hot deionized water and ethanol, and dry to obtain intermediate 1.

[0036] (2) Add 0.7 mol of formaldehyde to 100 ml of chloroform solvent, add 0.45 mol of calcium hydride, heat to 30 ° C, react for 20 min, then heat to 60 ° C, add 0.35 mol of amino-modified nano-silica, heat to 85 ° C, add 0.1 mol of intermediate 1, react for 90 min, filter, column chromatography, and low-pressure distillation to obtain intermediate 2.

[0037] (3) Add 0.1 mol of intermediate 2 and 0.35 mol of hexamethylene diisocyanate to 200 ml of butyl acetate solvent, stir evenly, add 0.05 mmol of catalyst dibutyltin dilaurate (DBTDL), heat to 90 °C, react for 2 h, cool, and distill under low pressure to obtain modified polyisocyanate.

[0038] (4) Under nitrogen atmosphere, add 0.1 mol of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), 0.08 mol of triethylamine (TEA), and 0.045 mol of ((2-aminoethyl)azadiyl)dimethanol to 100 ml of dichloromethane solvent, cool to -10 °C, add 0.12 mol of carbon tetrachloride, and heat to 15 °C. After the addition is complete, heat to 20 °C and react for 14 h. Filter, wash with deionized water, and dry to obtain DOPO-based diol.

[0039] (5) Under nitrogen atmosphere, 0.95 mol of modified polyisocyanate, 0.2 mol of polyethylene glycol 400 (PEG400), and 0.1 mol of DOPO-based diol were added to a three-necked flask, stirred and mixed evenly, heated to 85 °C, reacted for 2 h, cooled to 55 °C, 0.08 mol of dihydroxymethylpropionic acid (DMPA) and 0.15 mol of 1,4-butanediol (BDO) were added, heated to 70 °C, reacted for 90 min, cooled to 50 °C, 0.01 mol of catalyst dibutyltin dilaurate and 0.015 mol of stannous octoate were added, heated to 80 °C, reacted for 3 h, the reaction was completed, cooled to 30 °C, neutralized with triethylamine, emulsified with deionized water, chain extended with 0.15 mol of ethylenediamine (EDA), and distilled under reduced pressure to obtain a polyurethane emulsion.

[0040] (6) Add 10 parts by weight of polyurethane emulsion into a stirrer and stir at high speed for 30 minutes. Then add 0.03 parts of cosolvent ethanol butyl ether, 0.05 parts by weight of slip agent (DC56), 0.03 parts by weight of leveling agent (H-140) and 0.06 parts by weight of defoaming agent (W-0506), mix them evenly, then add 1.5 parts by weight of diluent (ZP-110), stir at high speed for 15 minutes to prepare an antibacterial and wear-resistant polyurethane coating.

[0041] Example 2

[0042] (1) Add 3.65 mol of 37% concentrated hydrochloric acid to 150 ml of deionized water, add 0.1 mol of 1,3,5-triaminobenzene, cool to 0°C, stir and react for 30 min, then add 0.4 mol of sodium nitrite aqueous solution dropwise, and react for 50 min. After the addition is complete, remove impurities, filter, add 17 mol of deionized water, 0.35 mol of 4-hydroxy-2,6-dimethylbenzyl alcohol, 0.3 mol of sodium hydroxide, and 0.8 mol of anhydrous sodium carbonate, stir and mix evenly, and react for 4 h. After the reaction is complete, filter, wash with hot deionized water and ethanol, and dry to obtain intermediate 1.

[0043] (2) Add 0.5 mol of formaldehyde to 100 ml of chloroform solvent, add 0.4 mol of calcium hydride, heat to 30 ° C, react for 20 min, then heat to 70 ° C, add 0.3 mol of amino-modified nano-silica, heat to 75 ° C, add 0.1 mol of intermediate 1, react for 30 min, filter, column chromatography, and low-pressure distillation to obtain intermediate 2.

[0044] (3) Add 0.1 mol of intermediate 2 and 0.3 mol of hexamethylene diisocyanate to 200 ml of butyl acetate solvent, stir evenly, add 0.15 mmol of DBTDL as a catalyst, heat to 70 °C, react for 4 h, cool, and distill under low pressure to obtain modified polyisocyanate.

[0045] (4) Under nitrogen atmosphere, add 0.1 mol of DOPO, 0.12 mol of TEA, and 0.035 mol of ((2-aminoethyl)azadiyl)dimethanol to 100 ml of dichloromethane solvent, cool to 0 °C, add carbon tetrachloride, and heat to 5 °C. After the addition is complete, heat to 30 °C and react for 10 h. Filter, wash with deionized water, and dry to obtain DOPO-based diol.

[0046] (5) Under nitrogen atmosphere, 0.9 mol of modified polyisocyanate, 0.22 mol of PEG400 and 0.1 mol of DOPO-based diol were added to a three-necked flask, stirred and mixed evenly, heated to 90 °C, reacted for 4 h, cooled to 35 °C, 0.12 mol of DMPA and 0.13 mol of BDO were added, heated to 90 °C, reacted for 30 min, cooled to 35 °C, 0.007 mol of catalyst dibutyltin dilaurate and 0.012 mol of stannous octoate were added, heated to 80 °C, reacted for 3 h, the reaction was completed, cooled to 50 °C, neutralized with triethylamine, emulsified with deionized water, chain extended with 0.2 mol of EDA, and distilled under reduced pressure to obtain a polyurethane emulsion.

[0047] (6) Add 10 parts by weight of polyurethane emulsion into a stirrer and stir at high speed for 15 minutes. Add 1 part by weight of cosolvent ethanol butyl ether, 0.02 parts by weight of slip agent, 0.05 parts by weight of leveling agent and 0.1 parts by weight of defoaming agent, mix well, add diluent, stir at high speed for 20 minutes to prepare antibacterial and wear-resistant polyurethane coating.

[0048] Example 3

[0049] (1) Add 3.6 mol of concentrated hydrochloric acid (mass fraction: 37%) to 150 ml of deionized water, add 0.1 mol of 1,3,5-triaminobenzene, cool to -2°C, stir and react for 40 min, then dropwise add 0.45 mol of an aqueous solution of sodium nitrite. After the addition is complete, react for 90 min. After the reaction is complete, remove impurities, filter, add 16.5 mol of deionized water, 0.25 mol of 4-hydroxy-2,6-dimethylbenzyl alcohol, 0.35 mol of sodium hydroxide, and 0.9 mol of anhydrous sodium carbonate, stir and mix evenly, react for 2 h. After the reaction is complete, filter, wash with hot deionized water and ethanol, and dry to obtain intermediate 1.

[0050] (2) Add 0.6 mol of formaldehyde to 100 ml of chloroform solvent, add 0.5 mol of calcium hydride, heat to 20 ° C, react for 40 min, then heat to 50 ° C, add 0.31 mol of amino-modified nano-silica, heat to 80 ° C, add 0.1 mol of intermediate 1, react for 60 min, filter, column chromatography, and low-pressure distillation to obtain intermediate 2.

[0051] (3) Add 0.1 mol of intermediate 2 and 0.31 mol of hexamethylene diisocyanate to 200 ml of butyl acetate solvent, stir evenly, add 0.1 mmol of DBTDL as a catalyst, heat to 80 °C, react for 3 h, cool, and distill under low pressure to obtain modified polyisocyanate.

[0052] (4) Under nitrogen atmosphere, add 0.1 mol of DOPO, 0.1 mol of TEA, and 0.04 mol of ((2-aminoethyl)azadiyl)dimethanol to 100 ml of dichloromethane solvent, cool to -8 °C, add carbon tetrachloride, and heat to 10 °C. After the addition is complete, heat to 25 °C and react for 12 h. Filter, wash with deionized water, and dry to obtain DOPO-based diol.

[0053] (5) Under nitrogen atmosphere, 0.92 mol of modified polyisocyanate, 0.18 mol of PEG400 and 0.1 mol of DOPO-based diol were added to a three-necked flask, stirred and mixed evenly, heated to 85 °C, reacted for 3 h, cooled to 40 °C, 0.1 mol of DMPA and 0.17 mol of BDO were added, heated to 80 °C, reacted for 60 min, cooled to 40 °C, 0.008 mol of dibutyltin dilaurate and 0.016 mol of stannous octoate as catalyst were added, heated to 70 °C, reacted for 4 h, the reaction was completed, cooled to 40 °C, neutralized with triethylamine, emulsified with deionized water, chain extended with 1.7 mol of EDA, and distilled under reduced pressure to obtain a polyurethane emulsion.

[0054] (6) Add 10 parts by weight of polyurethane emulsion into a stirrer and stir at high speed for 25 minutes. Add 0.5 parts by weight of cosolvent ethanol butyl ether, 0.03 parts by weight of slip agent, 0.04 parts by weight of leveling agent and 0.08 parts by weight of defoaming agent, mix well, then add 1.8 parts by weight of diluent and stir at high speed for 20 minutes to prepare an antibacterial and wear-resistant polyurethane coating.

[0055] Example 4

[0056] The difference between this embodiment and embodiment 1 is that the amount of each raw material used in step (5) of embodiment 4 is twice that of embodiment 1.

[0057] Example 5

[0058] The difference between this embodiment and embodiment 1 is that the amount of each raw material used in step (5) of embodiment 5 is four times that of embodiment 1.

[0059] Example 6

[0060] The difference between this embodiment and embodiment 1 is that the amount of each raw material used in step (5) of embodiment 6 is six times that of embodiment 1.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that in step (5) of Comparative Example 1, the modified polyisocyanate is replaced by isophorone diisocyanate.

[0063] Comparative Example 2

[0064] The difference between this comparative example and Example 1 is that no DOPO-based diol is added in step (5) of Comparative Example 2.

[0065] Preparation of paint film

[0066] According to the national standard GB1727-92, paint films were prepared by brushing on tinplate substrates that had been previously sanded to remove rust and oil. The coatings from Examples 1-6 and Comparative Examples 1-2 were then brushed with the emulsions to a dry film thickness of 40 μm. The coatings were applied quickly and evenly in both the horizontal and vertical directions to prevent the emulsion from overflowing and leaving no white spots on the substrate. The applied paint films from Examples 1-6 and Comparative Examples 1-2 were then cured in a constant temperature (30°C) and humidity (40% relative humidity) room for 7 days before testing the film properties.

[0067] Wear resistance testing

[0068] According to the national standard GB / T178-2006, the wear resistance of the paint film was tested using a paint film abrasion tester (BGD-523).

[0069] Procedure: A pair of 750g weights were placed on the paint films of Examples 1-6 and Comparative Examples 1-2. The paint films were pre-grinded with sandpaper on a CS-10 grinding wheel for 50 r / min. The paint film surfaces were then polished with a pair of CS-10 grinding wheels at 60 r / min. The surfaces were vacuumed to remove debris. After the instrument was operated for 500 r, the surfaces were cleaned. The weight changes before and after polishing were recorded. This weight change data served as the wear resistance data for the paint films.

[0070] Paint film pencil hardness test

[0071] According to the national standard GB / T6739-2006, the pencil hardness of the paint film was tested using a trolley-type pencil hardness tester (BGD-506 / 2).

[0072] Steps: Sand the tip of a pencil with sandpaper, rotate it to smooth it, and insert it into a hardness tester with both ends placed horizontally at a 45° angle until it touches the surface of the paint film. Remove the pad at the front end of the hardness tester and push the trolley forward 7-10mm at a speed of 0.5mm / s-1mm / s. Visually inspect and feel whether there are scratches or breaks on the surface of the paint film. Test three times in parallel at different positions. The hardest pencil model that does not cause scratches on the paint film surface is regarded as the hardness of the paint film.

[0073] Paint film impact resistance test

[0074] According to the national standard GB / T 1732-1993, the impact resistance of the paint film was tested using a tubular paint film impactor (BGD-302).

[0075] Steps: Prepare paint films with a dry film thickness of about 40 μm in Examples 1-6 and Comparative Examples 1-2, respectively, and place them at the bottom of a tubular impactor. Allow a 1 kg hammer to slide freely from different heights in the tube to impact an iron sheet. The impact point should be greater than 1.5 cm from the edge of the test plate or other test points. Perform three forward or reverse impacts on each example or comparative example. The highest impact height corresponding to no cracking or peeling is used as an impact resistance indicator of the paint film.

[0076] Table 1: Test data of various embodiments and comparative examples

[0077] Pencil hardness Abrasion resistance (750g / 500r) Impact resistance (Kg.cm) Example 1 2H 0.016 50 Example 2 2H 0.018 50 Example 3 2H 0.017 50 Example 4 2H 0.016 50 Example 5 2H 0.016 50 Example 6 2H 0.015 50 Comparative Example 1 H 0.030 40 Comparative Example 2 2H 0.017 50

[0078] As can be seen from Table 1, the wear resistance, impact resistance, and pencil hardness of Comparative Example 1 are relatively poor compared to those of the other Examples and Comparative Examples. This is because Examples 1-6 and Comparative Example 2 all contain nano-silica, which can form a network structure with the organic matrix, thereby changing the stress concentration of the polyurethane coating. When the material is impacted, it causes more yield deformation in the surrounding matrix, increases the matrix crack propagation resistance, and enhances toughness. At the same time, when the coating cures, the polymer chain links and covalent bonds themselves shrink. The addition of the non-shrinking component, nano-silica, can fill the gaps created by the shrinkage of the organic components, thereby reducing the internal stress of the material, thereby achieving better wear resistance.

[0079] Antibacterial testing

[0080] The antibacterial activity was tested according to the AATCC 100-2012 immersion method. Escherichia coli and Aspergillus niger were selected as test bacteria. Equal amounts of bacterial solution were evenly dripped onto the paint films of Examples 1-6 and Comparative Examples 1-2. A blank control group (Sankeshu paint) was also set up. After 24 hours of incubation, the bacterial count reduction rate, i.e., the antibacterial rate, was calculated.

[0081] R (%) = [(BA) / B] × 100

[0082] Where: R------bacteria reduction rate, %;

[0083] A------The number of bacteria in the paint film sample after contact culture;

[0084] B-------The number of bacteria in the paint film sample that has not been cultured.

[0085] Table 2: Antibacterial test results of various embodiments and comparative examples

[0086] A (cfu / ml) B (cfu / ml) R（%） Example 1 <![CDATA[1.46×10 3 ]]> <![CDATA[9.10×10 3 ]]> 84 Example 2 <![CDATA[1.85×10 3 ]]> <![CDATA[9.25×10 3 ]]> 80 Example 3 <![CDATA[0.98×10 3 ]]> <![CDATA[8.94×10 3 ]]> 89 Example 4 <![CDATA[1.32×10 3 ]]> <![CDATA[8.83×10 3 ]]> 85 Example 5 <![CDATA[1.23×10 3 ]]> <![CDATA[9.46×10 3 ]]> 87 Example 6 <![CDATA[1.38×10 3 ]]> <![CDATA[9.83×10 3 ]]> 86 Comparative Example 1 <![CDATA[1.72×10 3 ]]> <![CDATA[9.58×10 3 ]]> 82 Comparative Example 2 <![CDATA[1.73×10 3 ]]> <![CDATA[9.10×10 3 ]]> 81 Blank control group <![CDATA[8.33×10 3 ]]> <![CDATA[9.25×10 3 ]]> 10

[0087] As can be seen from Table 2, the antibacterial rates of Examples 1-6 and Comparative Examples 1-2 are both higher than 80%, while the blank control group is Sankeshu paint purchased on the market, with an antibacterial rate of 10%, which is poor in antibacterial properties. Therefore, Examples 1-6 and Comparative Examples 1-2 have certain antibacterial properties. The reason is that both Examples 1-6 and Comparative Examples 1-2 contain quaternary ammonium groups, which are positively charged and can be adsorbed on the surface of microorganisms to form micelles and gradually penetrate into the lipid layer and protein layer of the cytoplasm, thereby changing the permeability of the cell membrane and causing the cell contents to extravasate, leading to the death of the microorganisms. At the same time, they coagulate proteins, denature enzymes and structural proteins, destroy the metabolism of microorganisms, and kill microorganisms, thereby improving the antibacterial properties of the coatings.

[0088] UV resistance testing

[0089] Take 3 samples of each of Examples 1-6 and Comparative Examples 1-2, and place them in a QUV accelerated aging tester according to the test method specified in Q / JLY J7110279. 2 / nm) is 0.76, the UV wavelength is 340nm, the temperature is 60℃, and the test time is 1200h. After the test, the appearance is inspected, the color difference is evaluated, and the gloss and adhesion are measured.

[0090] Glossiness testing

[0091] The glossiness test method manufactured by Three Enshi Technology Co., Ltd. was adopted, and the glossiness tester was used for testing. The glossiness of the paint film at 60° was measured with reference to GB1743-1979 "Determination of gloss of paint films".

[0092] Color difference detection

[0093] The DS-600 spectrophotometer was used to test the color difference of the samples before and after light aging and record them.

[0094] Table 3: UV resistance test results of various embodiments and comparative examples

[0095] Color difference (ΔE) Adhesion / Grade (Before aging) gloss / ° (After aging) gloss / ° Example 1 41.2 1 83.6 78.9 Example 2 39.5 1 82.0 77.8 Example 3 39.8 1 83.1 78.4 Example 4 40.9 1 82.9 78.8 Example 5 40.7 1 83.5 79.2 Example 6 41.1 1 82.9 78.6 Comparative Example 1 17.3 0 74.3 64.7 Comparative Example 2 38.9 1 83.3 78.5

[0096] As shown in Table 3, the paint film of Comparative Example 1 has an uneven surface, resulting in a decrease in its refractive index. Calculations show a gloss loss of 12.7% for Comparative Example 1, while the average gloss loss for the other examples and the comparative example is 5.1%. A comparison of color difference ΔE reveals that Comparative Example 1 exhibits weak UV aging resistance. This is because the other examples and the comparative example contain azo groups, which exhibit photochromic and photoinduced cis-trans isomerization properties and exhibit a distinct absorption peak in the UV region (particularly between 200 and 400 nm). This is because the π electrons within the azo group readily undergo transitions from lower energy levels to higher energy levels under UV irradiation. This transition absorbs UV light, reducing its penetration and thus achieving UV resistance. Introducing azo groups into coatings can enhance their UV resistance.

[0097] Flame retardant performance testing

[0098] The paint films of Examples 1-6 and Comparative Examples 1-2 were prepared into a size of 100 mm×6.5 mm×3 mm, and LOI tests were performed using an oxygen index meter according to ASTM D2863.

[0099] Table 4: LOI test results of various embodiments and comparative examples

[0100] LOI / % Example 1 34.2 Example 2 32.8 Example 3 33.1 Example 4 33.8 Example 5 33.7 Example 6 34.1 Comparative Example 1 29.3 Comparative Example 2 27.1

[0101] As can be seen from Table 4, the oxygen index of Comparative Example 2 is lower than that of the other examples and comparative examples. The reason is that Examples 1-6 contain phosphorus, nitrogen, and silicon elements. The nitrogen element will decompose and produce a large amount of non-combustible gas when burning. The non-combustible gas can dilute the concentration of oxygen around the coating. The silicon element can migrate to the outside of the material when burning. The Si-O bond in its molecule will be converted into a Si-C bond. The generated white combustion residue and carbide form a covering layer on the surface of the coating, preventing the escape of combustion volatiles and preventing oxygen from contacting the base material, thereby improving the flame retardant performance of the coating. The phosphorus element will release carbon dioxide when heated or burned. Releasing a large amount of gas or high-density steam can dilute the oxygen and gaseous combustibles in the air and reduce the surface temperature of the burning material, causing the combustion to stop. The reason why the oxygen index of Comparative Example 1 is higher than that of Comparative Example 2 is that the phosphorus component in the structure of Comparative Example 1 can capture the H· and ·OH free radicals formed during the combustion process, thereby producing a better quenching effect and carbonization effect. The formation of the carbon layer reduces the release of volatiles. At the same time, the carbonized layer can isolate the fire source and the paint film, limit the volatilization of combustible gases, prevent the generation of new free radicals, reduce the combustion rate, reduce the amount of heat release, and achieve a flame retardant effect.

Claims

1. A method for preparing an antibacterial and wear-resistant waterborne polyurethane coating, characterized in that: The preparation method comprises the following steps: adding the modified polyurethane emulsion into a stirrer, stirring at high speed for 15-30 minutes, adding a cosolvent (ethanol butyl ether), a slip agent (DC-56), a leveling agent (H-140) and a defoaming agent (W-0506), mixing them evenly, adding a diluent (ZP-110), stirring at high speed for 15-30 minutes, and preparing the antibacterial and wear-resistant polyurethane coating.

2. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 1, wherein: The modified polyurethane emulsion preparation method is: (1) Add 37% concentrated hydrochloric acid to deionized water, add 1,3,5-triaminobenzene, cool to -5 to 0°C, stir and react for 30-50 minutes, then dropwise add an aqueous solution of sodium nitrite, and react for 50-90 minutes. After the reaction is complete, remove impurities, filter, add deionized water, and then add 4-hydroxy-2,6-dimethylbenzyl alcohol, sodium hydroxide, and anhydrous sodium carbonate. Stir and mix evenly and react for 2-4 hours. After the reaction is complete, filter, wash with hot deionized water and ethanol, and dry to obtain intermediate 1. (2) Add formaldehyde to chloroform solvent, add calcium hydride, heat to 20-30°C, react for 20-40 minutes, then heat to 50-70°C, add amino-modified nano-silica, heat to 75-85°C, add intermediate 1, react for 50-90 minutes, filter, separate by column chromatography, and distill at low pressure to obtain intermediate 2; (3) Add intermediate 2, hexamethylene diisocyanate, to butyl acetate solvent, stir evenly, add catalyst dibutyltin dilaurate (DBTDL), heat to 70-90°C, react for 2-4 hours, cool, and distill under low pressure to obtain modified polyisocyanate; (4) Under nitrogen atmosphere, add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), triethylamine (TEA), and ((2-aminoethyl)azadiyl)dimethanol to dichloromethane solvent, cool to -10 to 0°C, add carbon tetrachloride, and heat to 5-15°C. After the addition is complete, heat to 20-30°C, react for 10-14 hours, filter, wash with deionized water, and dry to obtain DOPO-based diol; (5) Under nitrogen atmosphere, add modified polyisocyanate, polyethylene glycol 400 (PEG400), and DOPO-based diol into a three-necked flask, stir and mix evenly, heat to 80-90℃, react for 2-4h, cool to 35-55℃, add dihydroxymethylpropionic acid (DMPA) and 1,4-butanediol (BDO), heat to 70-90℃, react for 30-90min, cool to 35-50℃, add catalyst dibutyltin dilaurate and stannous octoate, heat to 60-80℃, react for 3-5h, and after the reaction is complete, cool to 30-50℃, neutralize with triethylamine, emulsify with deionized water, chain extend with ethylenediamine (EDA), and distill under reduced pressure to obtain a modified polyurethane emulsion.

3. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 1, characterized in that: The ethanol butyl ether accounts for 3% to 10% of the polyurethane emulsion by mass, the slip agent accounts for 0.2% to 0.5% of the polyurethane emulsion by mass, the defoamer accounts for 0.6% to 1% of the polyurethane emulsion by mass, the leveling agent accounts for 0.3% to 0.5% of the polyurethane emulsion by mass, and the diluent accounts for 15% to 20% of the polyurethane emulsion by mass.

4. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 2, wherein: In the step (1), the molar ratio of concentrated hydrochloric acid, 1,3,5-triaminobenzene, sodium nitrite, deionized water, 4-hydroxy-2,6-dimethylbenzyl alcohol, sodium hydroxide, and anhydrous sodium carbonate is 35.5-36.5:1:4-5:160-170:2.5-3.5:2.5-3.5:8-10.

5. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 2, wherein: In the step (2), the molar ratio of the intermediate 1, calcium hydride, formaldehyde, and amino-modified nano-silica is 1:4-5:5.5-7:3-3.

5.

6. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 2, characterized in that: In the step (3), the molar ratio of the intermediate 2, DBDTDL, and hexamethylene diisocyanate is 1:0.0005-0.0015:3-3.

5.

7. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 2, characterized in that: In the step (4), the molar ratio of DOPO, TEA, ((2-aminoethyl)azadiyl)dimethanol, and carbon tetrachloride is 1:0.8-1.2:0.35-0.45:0.8-1.

2.

8. The method for preparing the antibacterial and wear-resistant waterborne polyurethane coating according to claim 2, characterized in that: In the step (5), the molar mass ratio of DOPO-based diol, modified polyisocyanate, PEG400, DMPA, BDO, dibutyltin dilaurate, stannous octoate, and ethylenediamine is 1:9-9.5:1.8-2.2:0.8-1.2:1.3-1.7:0.07-0.1:0.12-0.16:1.5-2.

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