Flame-retardant epoxy resin coating and preparation method thereof

Abstract

The invention relates to the technical field of coatings, and discloses a flame-retardant epoxy resin coating and a preparation method thereof.The flame-retardant epoxy resin coating is prepared by adding bisphenol A type epoxy resin, propylene glycol, phosphorus-containing modified imidazolyl benzoxazine, a chitosan-based flame retardant, titanium dioxide, a BYK-071 defoaming agent, a BYK-345 flatting agent, a BYK-220S wetting dispersant and water into a stirrer, stirring, adding a curing agent, stirring, adding a curing agent, and stirring to obtain the flame-retardant epoxy resin coating. The flame-retardant epoxy resin coating is obtained after the reaction is finished. Phosphorus, silicon and benzoxazine structures in the phosphorus-containing modified imidazolyl benzoxazine and the chitosan-based flame retardant all have better flame-retardant effects, and the phosphorus, silicon and benzoxazine structures in the phosphorus-containing modified imidazolyl benzoxazine and the chitosan-based flame retardant have better flame-retardant effects. Chitosan in the chitosan-based flame retardant also has a good flame retardant effect and an antibacterial effect. Benzoxazine can form a heat-resistant phenolic resin structure at high temperature, so that the benzoxazine has a relatively good flame-retardant effect; and an imidazole group in the phosphorus-containing modified imidazolyl benzoxazine also has a relatively good antibacterial effect.

Description

Technical Field

[0001] The invention relates to the technical field of coatings, in particular to a flame retardant epoxy resin coating and a preparation method thereof. Background Art

[0002] Epoxy resin has excellent adhesion, electrical insulation, mechanical strength and other characteristics, and is widely used in coatings, adhesives and other fields. However, epoxy resin is flammable, which limits its application in coatings, and its antibacterial effect also needs to be improved. Therefore, how to avoid this phenomenon is the key to solving the problem.

[0003] For example, patent CN108517170A discloses a flame-retardant epoxy coating and a preparation method thereof. The invention first uses ammonium polyphosphate as a raw material and disperses it in dimethylethanolamine, thereby improving its dispersion compatibility with various raw materials and enhancing the surface strength and flame retardant properties of the finished coating; however, its antibacterial effect is not improved. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies of the prior art, the present invention provides a flame retardant epoxy resin coating and a preparation method thereof, which has good flame retardant and antibacterial effects.

[0006] (II) Technical solution

[0007] To achieve the above object, the present invention provides the following technical solution: a flame retardant epoxy resin coating, comprising the following components by weight: 40-65 parts by weight of bisphenol A epoxy resin, 1-3 parts by weight of propylene glycol, 4-8 parts by weight of phosphorus-modified imidazole benzoxazine, 6-9 parts by weight of chitosan-based flame retardant, 0.8-1.3 parts by weight of titanium dioxide, 0.2-0.5 parts by weight of BYK-071 defoamer, 0.4-0.7 parts by weight of BYK-345 leveling agent, 0.5-0.7 parts by weight of BYK-220S wetting and dispersing agent, and 5-10 parts by weight of water;

[0008] The preparation method of the phosphorus-modified imidazolyl benzoxazine is as follows:

[0009] Step 1: Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole and triethylamine catalyst to dichloromethane solvent, stir mechanically for 10-12 minutes, add carbon tetrachloride under ice bath conditions, add dropwise within 1-1.5 hours, then remove the ice bath, continue to react at room temperature for 10-14 hours, after the reaction is completed, wash with deionized water 2-4 times, and vacuum dry at 40-60° C. for 18-24 hours to obtain intermediate 1;

[0010] Step 2: Add 4-hydroxybenzyl chloride and intermediate 1 to isopropanol solvent, reflux at 60-85°C for 12-15h, and after the reaction, perform rotary evaporation and recrystallize from ethanol to obtain phenolic imidazole;

[0011] Step 3: Add 7-12 parts by weight of phenolic imidazole, 5-10 parts by weight of aniline, and 12-16 parts by weight of formaldehyde aqueous solution to a reaction bottle, condense and reflux at 60-85° C., stir evenly, add 1-2 parts by weight of oxalic acid catalyst, react, add water after the reaction, let stand and separate, filter and dry to obtain phosphorus-modified imidazole benzoxazine.

[0012] Preferably, in the step 1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole, triethylamine catalyst and carbon tetrachloride is 1.1-1.3:1:0.01-0.02:0.5-0.8.

[0013] Preferably, in step 2, the mass ratio of 4-hydroxybenzyl chloride to intermediate 1 is 1.5-1.8:1.

[0014] Preferably, the reaction time in step three is 4-8h.

[0015] Preferably, the preparation method of the chitosan-based flame retardant is:

[0016] S1. Add octamethylcyclotetrasiloxane and 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane to the reactor, introduce nitrogen protection, and then continue to add tetramethylammonium hydroxide catalyst, react at 60-80°C for 2-6h, and cool the material after the end to obtain a double-terminal epoxy silicone oil;

[0017] S2. Add double-terminal epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stir and mix, continue to add boron trifluoride ether catalyst, react at 80-95° C. for 6-12 hours, filter after completion, wash with deionized water and ethanol, and dry to obtain intermediate 2;

[0018] S3. 6-12 parts by weight of diphenylmethane diisocyanate is added to a toluene solvent, nitrogen is introduced, 8-14 parts by weight of intermediate 2 is added thereto, the reaction is carried out at 75-85 ° C for 4-6h, 5-9 parts by weight of purified chitosan is added thereto, the reaction is carried out at 60-75 ° C for 5-7h, and a chitosan-based flame retardant is obtained after completion;

[0019] The preparation method of the purified chitosan is as follows: 50 g of chitosan and 300 mL of distilled water are added into a 500 mL reactor, stirred and dissolved at 90° C., filtered while hot, cooled and crystallized, and vacuum dried at 80° C. for 24 hours to obtain purified chitosan.

[0020] Preferably, the mass ratio of octamethylcyclotetrasiloxane, 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide catalyst in S1 is 0.8-1.2:1:0.02-0.03.

[0021] Preferably, the mass ratio of the double-terminal epoxy silicone oil, 4-hydroxymethyl caged bicyclic phosphate, and boron trifluoride etherate catalyst in S2 is 1:1.4-1.7:0.01-0.023.

[0022] Preferably, the preparation method of the flame-retardant epoxy resin coating is: add bisphenol A epoxy resin, propylene glycol, phosphorus-modified imidazole benzoxazine, chitosan-based flame retardant, titanium dioxide, BYK-071 defoamer, BYK-345 leveling agent, BYK-220S wetting dispersant, and water into a stirrer, stir for 4-6 minutes, and obtain the flame-retardant epoxy resin coating.

[0023] (III) Beneficial technical effects

[0024] The invention provides a flame-retardant epoxy resin coating by adding bisphenol A epoxy resin, propylene glycol, phosphorus-modified imidazole benzoxazine, chitosan-based flame retardant, titanium dioxide, BYK-071 defoamer, BYK-345 leveling agent, BYK-220S wetting dispersant and water into a stirrer and stirring the mixture.

[0025] The phosphorus, silicon and benzoxazine structures in phosphorus-modified imidazole benzoxazine and chitosan-based flame retardants all have good flame retardant effects. Chitosan in chitosan-based flame retardants also has good flame retardant and antibacterial effects. When burning, phosphorus can generate polyphosphoric acid and metaphosphoric acid with strong dehydration. Since polyphosphoric acid and metaphosphoric acid are not easy to volatilize, they can form a dense protective layer on the surface of the coating, thus playing a flame retardant effect. When heated, silicon can produce a glass-like substance on the surface of the material, isolating material transport and energy transfer. Benzoxazine will form a heat-resistant phenolic resin structure at high temperature, which makes it have a good flame retardant effect; the phenolic hydroxyl group in the formed phenolic resin will cross-link and cure with the epoxy group of bisphenol A epoxy resin, which improves the compatibility between each other, and at the same time, it forms a curing system with the imidazole group in phosphorus-modified imidazole benzoxazine. The imidazole group in phosphorus-modified imidazole-based benzoxazine also has good antibacterial effect; and after the double-terminal epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate react, the degree of substitution of the phosphorus element is increased, further improving its flame retardant effect. DETAILED DESCRIPTION

[0026] Example 1

[0027] (1) 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole and triethylamine catalyst were added to dichloromethane solvent, and mechanically stirred for 10 minutes. Carbon tetrachloride was added thereto under ice bath conditions, wherein the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole, triethylamine catalyst and carbon tetrachloride was 1.1:1:0.01:0.5, and the addition was completed within 1 hour. Then the ice bath was removed and the reaction was continued at room temperature for 10 hours. After the reaction was completed, the mixture was washed with deionized water twice and vacuum dried at 40° C. for 18 hours to obtain intermediate 1;

[0028] (2) adding 4-hydroxybenzyl chloride and intermediate 1 to an isopropanol solvent, wherein the mass ratio of 4-hydroxybenzyl chloride to intermediate 1 is 1.5:1, and reacting under reflux at 60° C. for 12 h. After the reaction, rotary evaporation is performed, and recrystallization is performed with ethanol to obtain phenolic imidazole;

[0029] (3) Add 7 parts by weight of phenolic imidazole, 5 parts by weight of aniline, and 12 parts by weight of formaldehyde aqueous solution to a reaction bottle, condense and reflux at 60° C., stir evenly, add 1 part by weight of oxalic acid catalyst, react for 4 hours, add water after reaction, let stand to separate, filter and dry to obtain phosphorus-modified imidazole benzoxazine;

[0030] (4) Add octamethylcyclotetrasiloxane and 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane to the reaction kettle, introduce nitrogen protection, and then continue to add tetramethylammonium hydroxide catalyst, wherein the mass ratio of octamethylcyclotetrasiloxane, 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide catalyst is 0.8:1:0.02, react at 60° C. for 2 hours, and cool and discharge after completion to obtain double-terminal epoxy silicone oil;

[0031] (5) Adding double-ended epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stirring and mixing, and continuously adding boron trifluoride etherate catalyst thereto, wherein the mass ratio of double-ended epoxy silicone oil, 4-hydroxymethyl caged bicyclic phosphate, and boron trifluoride etherate catalyst is 1:1.4:0.01, reacting at 80°C for 6h, filtering after completion, washing with deionized water and ethanol in turn, and drying to obtain intermediate 2;

[0032] (6) 6 parts by weight of diphenylmethane diisocyanate were added to a toluene solvent, nitrogen was introduced for protection, 8 parts by weight of the intermediate 2 were added thereto, the reaction was carried out at 75° C. for 4 h, 5 parts by weight of the purified chitosan were added thereto, the reaction was carried out at 60° C. for 5 h, and a chitosan-based flame retardant was obtained after the reaction was completed;

[0033] (7) 40 parts by weight of bisphenol A epoxy resin, 1 part by weight of propylene glycol, 4 parts by weight of phosphorus-modified imidazole benzoxazine, 6 parts by weight of chitosan-based flame retardant, 0.8 parts by weight of titanium dioxide, 0.2 parts by weight of BYK-071 defoamer, 0.4 parts by weight of BYK-345 leveling agent, 0.5 parts by weight of BYK-220S wetting and dispersing agent, and 5 parts by weight of water are added into a stirrer and stirred for 4 minutes to obtain a flame-retardant epoxy resin coating.

[0034] Example 2

[0035] (1) 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole and triethylamine catalyst were added to dichloromethane solvent, and mechanical stirring was performed for 10-12 minutes. Carbon tetrachloride was added thereto under ice bath conditions, wherein the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole, triethylamine catalyst and carbon tetrachloride was 1.3:1:0.02:0.8, and the addition was completed within 1.5 hours. Then, the ice bath was removed, and the reaction was continued at room temperature for 14 hours. After the reaction was completed, the mixture was washed with deionized water 4 times, and vacuum dried at 60° C. for 24 hours to obtain intermediate 1;

[0036] (2) adding 4-hydroxybenzyl chloride and intermediate 1 to an isopropanol solvent, wherein the mass ratio of 4-hydroxybenzyl chloride to intermediate 1 is 1.8:1, and reacting under reflux at 85° C. for 15 h. After the reaction, rotary evaporation is performed, and recrystallization is performed with ethanol to obtain phenolic imidazole;

[0037] (3) Add 12 parts by weight of phenolic imidazole, 10 parts by weight of aniline, and 16 parts by weight of formaldehyde aqueous solution to a reaction bottle, condense and reflux at 85° C., stir evenly, add 2 parts by weight of oxalic acid catalyst, react for 8 hours, add water after the reaction, let stand to separate, filter and dry to obtain phosphorus-modified imidazole benzoxazine;

[0038] (4) adding octamethylcyclotetrasiloxane and 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane to the reaction kettle, introducing nitrogen protection, and then continuing to add tetramethylammonium hydroxide catalyst, wherein the mass ratio of octamethylcyclotetrasiloxane, 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide catalyst is 1.2:1:0.03, reacting at 80° C. for 6 hours, cooling and discharging after completion, to obtain a double-terminal epoxy silicone oil;

[0039] (5) Adding double-ended epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stirring and mixing, and continuously adding boron trifluoride etherate catalyst thereto, wherein the mass ratio of double-ended epoxy silicone oil, 4-hydroxymethyl caged bicyclic phosphate, and boron trifluoride etherate catalyst is 1:1.7:0.023, reacting at 95° C. for 12 h, filtering after completion, washing with deionized water and ethanol in turn, and drying to obtain intermediate 2;

[0040] (6) 12 parts by weight of diphenylmethane diisocyanate was added to a toluene solvent, nitrogen was introduced for protection, 14 parts by weight of the intermediate 2 was added thereto, and the reaction was carried out at 85° C. for 6 h, and 9 parts by weight of the purified chitosan was added thereto, and the reaction was carried out at 75° C. for 7 h. After the reaction, a chitosan-based flame retardant was obtained;

[0041] (7) 65 parts by weight of bisphenol A epoxy resin, 3 parts by weight of propylene glycol, 8 parts by weight of phosphorus-modified imidazole benzoxazine, 9 parts by weight of chitosan-based flame retardant, 1.3 parts by weight of titanium dioxide, 0.5 parts by weight of BYK-071 defoamer, 0.7 parts by weight of BYK-345 leveling agent, 0.7 parts by weight of BYK-220S wetting and dispersing agent, and 10 parts by weight of water are added into a stirrer and stirred for 6 minutes to obtain a flame-retardant epoxy resin coating.

[0042] Example 3

[0043] (1) 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole and triethylamine catalyst were added to dichloromethane solvent, and mechanical stirring was performed for 11 minutes. Carbon tetrachloride was added thereto under ice bath conditions, wherein the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole, triethylamine catalyst and carbon tetrachloride was 1.2:1:0.015:0.7, and the addition was completed within 1.2 hours. Then the ice bath was removed and the reaction was continued at room temperature for 12 hours. After the reaction was completed, the mixture was washed with deionized water 3 times and vacuum dried at 50° C. for 22 hours to obtain intermediate 1;

[0044] (2) adding 4-hydroxybenzyl chloride and intermediate 1 to an isopropanol solvent, wherein the mass ratio of 4-hydroxybenzyl chloride to intermediate 1 is 1.6:1, and refluxing at 75° C. for 14 h. After the reaction, rotary evaporation is performed, and recrystallization is performed with ethanol to obtain phenolic imidazole;

[0045] (3) Add 10 parts by weight of phenolic imidazole, 8 parts by weight of aniline, and 14 parts by weight of formaldehyde aqueous solution to a reaction bottle, condense and reflux at 75° C., stir evenly, add 1 part by weight of oxalic acid catalyst, react for 6 hours, add water after reaction, let stand to separate, filter and dry to obtain phosphorus-modified imidazole benzoxazine;

[0046] (4) adding octamethylcyclotetrasiloxane and 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane to the reaction kettle, introducing nitrogen protection, and then continuing to add tetramethylammonium hydroxide catalyst, wherein the mass ratio of octamethylcyclotetrasiloxane, 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide catalyst is 0.9:1:0.02, reacting at 70° C. for 5 hours, cooling and discharging after completion, and obtaining double-terminal epoxy silicone oil;

[0047] (5) Adding double-ended epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stirring and mixing, and continuously adding boron trifluoride etherate catalyst thereto, wherein the mass ratio of double-ended epoxy silicone oil, 4-hydroxymethyl caged bicyclic phosphate, and boron trifluoride etherate catalyst is 1:1.5:0.02, reacting at 75° C. for 10 h, filtering after completion, washing with deionized water and ethanol in turn, and drying to obtain intermediate 2;

[0048] (6) 10 parts by weight of diphenylmethane diisocyanate was added to a toluene solvent, nitrogen was introduced for protection, 12 parts by weight of the intermediate 2 was added thereto, the reaction was carried out at 78° C. for 5 h, 7 parts by weight of purified chitosan was added thereto, the reaction was carried out at 65° C. for 6 h, and a chitosan-based flame retardant was obtained after the reaction was completed;

[0049] (7) 55 parts by weight of bisphenol A epoxy resin, 2 parts by weight of propylene glycol, 6 parts by weight of phosphorus-modified imidazole benzoxazine, 8 parts by weight of chitosan-based flame retardant, 0.9 parts by weight of titanium dioxide, 0.4 parts by weight of BYK-071 defoamer, 0.6 parts by weight of BYK-345 leveling agent, 0.6 parts by weight of BYK-220S wetting and dispersing agent, and 8 parts by weight of water are added into a stirrer and stirred for 5 minutes to obtain a flame-retardant epoxy resin coating.

[0050] Example 4

[0051] (1) 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole and triethylamine catalyst were added to dichloromethane solvent, and mechanically stirred for 10 minutes. Carbon tetrachloride was added thereto under ice bath conditions, wherein the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole, triethylamine catalyst and carbon tetrachloride was 1.1:1:0.01:0.5, and the addition was completed within 1 hour. Then the ice bath was removed and the reaction was continued at room temperature for 10 hours. After the reaction was completed, the mixture was washed with deionized water twice and vacuum dried at 40° C. for 18 hours to obtain intermediate 1;

[0052] (2) adding 4-hydroxybenzyl chloride and intermediate 1 to an isopropanol solvent, wherein the mass ratio of 4-hydroxybenzyl chloride to intermediate 1 is 1.5:1, and reacting under reflux at 60° C. for 12 h. After the reaction, rotary evaporation is performed, and recrystallization is performed with ethanol to obtain phenolic imidazole;

[0053] (3) Add 12 parts by weight of phenolic imidazole, 10 parts by weight of aniline, and 16 parts by weight of formaldehyde aqueous solution to a reaction bottle, condense and reflux at 85° C., stir evenly, add 2 parts by weight of oxalic acid catalyst, react for 8 hours, add water after the reaction, let stand to separate, filter and dry to obtain phosphorus-modified imidazole benzoxazine;

[0054] (4) adding octamethylcyclotetrasiloxane and 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane to the reaction kettle, introducing nitrogen protection, and then continuing to add tetramethylammonium hydroxide catalyst, wherein the mass ratio of octamethylcyclotetrasiloxane, 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide catalyst is 1.2:1:0.03, reacting at 80° C. for 6 hours, cooling and discharging after completion, to obtain a double-terminal epoxy silicone oil;

[0055] (5) Adding double-ended epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stirring and mixing, and continuously adding boron trifluoride etherate catalyst thereto, wherein the mass ratio of double-ended epoxy silicone oil, 4-hydroxymethyl caged bicyclic phosphate, and boron trifluoride etherate catalyst is 1:1.5:0.02, reacting at 75° C. for 10 h, filtering after completion, washing with deionized water and ethanol in turn, and drying to obtain intermediate 2;

[0056] (6) 10 parts by weight of diphenylmethane diisocyanate was added to a toluene solvent, nitrogen was introduced for protection, 12 parts by weight of the intermediate 2 was added thereto, the reaction was carried out at 78° C. for 5 h, 7 parts by weight of purified chitosan was added thereto, the reaction was carried out at 65° C. for 6 h, and a chitosan-based flame retardant was obtained after the reaction was completed;

[0057] (7) 55 parts by weight of bisphenol A epoxy resin, 2 parts by weight of propylene glycol, 6 parts by weight of phosphorus-modified imidazole benzoxazine, 8 parts by weight of chitosan-based flame retardant, 0.9 parts by weight of titanium dioxide, 0.4 parts by weight of BYK-071 defoamer, 0.6 parts by weight of BYK-345 leveling agent, 0.6 parts by weight of BYK-220S wetting and dispersing agent, and 8 parts by weight of water are added into a stirrer and stirred for 5 minutes to obtain a flame-retardant epoxy resin coating.

[0058] Comparative Example 1

[0059] This comparative example is different from Example 4 in that phosphorus-modified imidazolyl benzoxazine is not added.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 4 is that no chitosan-based flame retardant is added.

[0062] The oxygen index meter was used to test the limiting oxygen index of the coating, and the horizontal and vertical combustion instrument was used to test the combustion grade of the coating. The test results are shown in Table 1.

[0063] Table 1: Flame retardancy tests.

[0064] project Limiting oxygen index (%) Combustion level Example 1 31.4 V-0 Example 2 32.6 V-0 Example 3 31.5 V-0 Example 4 31.9 V-0 Comparative Example 1 21.4 V-1 Comparative Example 2 20.3 V-1

[0065] It can be seen from Table 1 that Examples 1-4 of the present invention have better flame retardant effects than Comparative Examples 1-2.

[0066] Pipette 1 mL of a 10 8 CFU / mL of Staphylococcus aureus was added to PBS buffer, and then diluted 10-fold to 10 5 CFU / mL, then add the coating sample (1cm×1cm×0.2mm), and then culture it in a constant temperature incubator at 37℃ with shaking for 24h. After culture, add PBS buffer to dilute the bacterial solution 10 times in sequence, and then transfer 0.5mL of the bacterial solution to the agar medium, and continue to culture it at 37℃ with shaking for 24h. After culture, count the colonies and count the antibacterial rate.

[0067] Table 2: Antibacterial performance test.

[0068] project Antibacterial rate (%) Example 1 98.3 Example 2 99.9 Example 3 98.7 Example 4 98.4 Comparative Example 1 81.2 Comparative Example 2 80.6

[0069] It can be seen from Table 2 that Examples 1-4 of the present invention have better antibacterial effects than Comparative Examples 1-2.

[0070] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific implementation methods described. Obviously, many modifications and changes can be made according to the content of this specification. This specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can understand and use the present invention well. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A flame retardant epoxy resin coating, characterized in that: The invention comprises the following components by weight: 40-65 parts by weight of bisphenol A epoxy resin, 1-3 parts by weight of propylene glycol, 4-8 parts by weight of phosphorus-modified imidazole benzoxazine, 6-9 parts by weight of chitosan-based flame retardant, 0.8-1.3 parts by weight of titanium dioxide, 0.2-0.5 parts by weight of BYK-071 defoamer, 0.4-0.7 parts by weight of BYK-345 leveling agent, 0.5-0.7 parts by weight of BYK-220S wetting and dispersing agent, and 5-10 parts by weight of water; The preparation method of the phosphorus-modified imidazolyl benzoxazine is as follows: Step 1: Add 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole and triethylamine catalyst to dichloromethane solvent, stir mechanically for 10-12 minutes, add carbon tetrachloride under ice bath conditions, add dropwise within 1-1.5 hours, then remove the ice bath, continue to react at room temperature for 10-14 hours, after the reaction is completed, wash with deionized water 2-4 times, and vacuum dry at 40-60° C. for 18-24 hours to obtain intermediate 1; Step 2: Add 4-hydroxybenzyl chloride and intermediate 1 to isopropanol solvent, reflux at 60-85°C for 12-15h, and after the reaction, perform rotary evaporation and recrystallize from ethanol to obtain phenolic imidazole; Step 3: Add 7-12 parts by weight of phenolic imidazole, 5-10 parts by weight of aniline, and 12-16 parts by weight of formaldehyde aqueous solution to a reaction bottle, condense and reflux at 60-85° C., stir evenly, add 1-2 parts by weight of oxalic acid catalyst, react, add water after the reaction, let stand and separate, filter and dry to obtain phosphorus-modified imidazole benzoxazine.

2. The flame retardant epoxy resin coating according to claim 1, characterized in that: In the step 1, the mass ratio of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, 1-(3-aminopropyl)imidazole, triethylamine catalyst and carbon tetrachloride is 1.1-1.3:1:0.01-0.02:0.5-0.

8.

3. The flame retardant epoxy resin coating according to claim 1, characterized in that: In the step 2, the mass ratio of 4-hydroxybenzyl chloride to intermediate 1 is 1.5-1.8:

1.

4. The flame retardant epoxy resin coating according to claim 1, characterized in that: The reaction time in step 3 is 4-8h.

5. The flame retardant epoxy resin coating according to claim 1, characterized in that: The preparation method of the chitosan-based flame retardant is: S1. Add octamethylcyclotetrasiloxane and 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane to the reactor, introduce nitrogen protection, and then continue to add tetramethylammonium hydroxide catalyst, react at 60-80°C for 2-6h, and cool the material after the end to obtain a double-terminal epoxy silicone oil; S2. Add double-terminal epoxy silicone oil and 4-hydroxymethyl caged bicyclic phosphate to N,N-dimethylformamide solvent, stir and mix, continue to add boron trifluoride ether catalyst, react at 80-95° C. for 6-12 hours, filter after completion, wash with deionized water and ethanol, and dry to obtain intermediate 2; S3. Add 6-12 parts by weight of diphenylmethane diisocyanate to toluene solvent, introduce nitrogen protection, continue to add 8-14 parts by weight of intermediate 2, react at 75-85°C for 4-6h, continue to add 5-9 parts by weight of purified chitosan, react at 60-75°C for 5-7h, and obtain chitosan-based flame retardant after completion.

6. The flame retardant epoxy resin coating according to claim 5, characterized in that: The mass ratio of octamethylcyclotetrasiloxane, 1,3-diglycidyloxypropyl-1,1,3,3-tetramethyldisiloxane and tetramethylammonium hydroxide catalyst in S1 is 0.8-1.2:1:0.02-0.

03.

7. The flame retardant epoxy resin coating according to claim 5, characterized in that: The mass ratio of the double-terminal epoxy silicone oil, 4-hydroxymethyl caged bicyclic phosphate, and boron trifluoride etherate catalyst in S2 is 1:1.4-1.7:0.01-0.

023.

8. A method for preparing a flame retardant epoxy resin coating according to any one of claims 1 to 7, characterized in that: The preparation method of the flame-retardant epoxy resin coating is as follows: bisphenol A epoxy resin, propylene glycol, phosphorus-modified imidazole benzoxazine, chitosan-based flame retardant, titanium dioxide, BYK-071 defoamer, BYK-345 leveling agent, BYK-220S wetting dispersant, and water are added into a stirrer, and stirred for 4-6 minutes to obtain the flame-retardant epoxy resin coating.