Bio-based hydrophobically modified flame retardant for transparent fire-retardant coating and preparation method thereof

Abstract

The present invention provides a bio-based hydrophobically modified flame retardant for transparent fire-retardant coatings and a preparation method thereof. The preparation method comprises the following steps: S1, sequentially adding phytic acid and urea to an aqueous solution in a reactor, heating to 80-110°C with stirring, subjecting the mixture to condensation and reflux reaction for 30-150 minutes, purifying the mixture with anhydrous ethanol, and drying the mixture to obtain ammonium phytate, wherein the molar ratio of phytic acid to urea is 1:6-12; S2, adding gelatin to the ammonium phytate solution for adsorption self-assembly to obtain a reaction solution; S3, adding an aqueous citric acid solution to the reaction solution for cross-linking, cooling the reaction solution to room temperature, filtering the mixture, washing with deionized water, and drying the mixture to obtain the bio-based hydrophobically modified flame retardant.

Description

Technical Field

[0001] The invention relates to a bio-based hydrophobically modified flame retardant for transparent fire-retardant coating and a preparation method thereof. Background Art

[0002] Currently, many hotels, hospitals, theaters, computer labs, and historic buildings are renovated using wooden structures. However, wooden structures present a fire hazard. Fires in these structures not only cause significant national damage but also lead to the demise of cultural heritage and history. With increasing attention to environmental protection, green, environmentally friendly transparent fire retardant coatings are becoming increasingly popular. Transparent fire retardant coatings not only offer excellent fire protection but also maintain their transparency, effectively preserving the original texture and color of the substrate.

[0003] However, the commonly used ordinary transparent fire-retardant coatings with flame retardants have poor water resistance and can only be used in dry environments, which limits their application. Summary of the Invention

[0004] The present invention provides a bio-based hydrophobically modified flame retardant for transparent fire-retardant coatings and a preparation method thereof, which can effectively solve the above-mentioned problems.

[0005] The present invention is achieved in that:

[0006] The present invention provides a method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating, comprising the following steps:

[0007] S1. Add phytic acid and urea to a reactor in sequence, add them to an aqueous solution, stir, heat to 80-110° C., condense and reflux for 30-150 minutes, purify with anhydrous ethanol and dry to obtain ammonium phytate, wherein the molar ratio of phytic acid to urea is 1:6-12; S2. Add gelatin to the ammonium phytate solution for adsorption self-assembly to obtain a reaction solution; S3. Add citric acid aqueous solution to the reaction solution for cross-linking, cool to room temperature, filter, wash with deionized water, and then dry to room temperature to obtain a bio-based hydrophobically modified flame retardant.

[0008] The present invention further provides a bio-based hydrophobically modified flame retardant for transparent fire retardant coatings, the structural formula of which is:

[0009] , where R1 is: , R is an alkyl group.

[0010] The beneficial effects of the present invention are as follows: the bio-based hydrophobically modified flame retardant for transparent fire-retardant coatings provided by the present invention and the preparation method thereof, the prepared bio-based hydrophobically modified flame retardant for transparent fire-retardant coatings having good hydrophobicity and water resistance, so that it can be used not only in dry environments, but also in relatively humid southern environments, greatly expanding its scope of use; further, the bio-based hydrophobically modified flame retardant for transparent fire-retardant coatings provided by the present invention and the preparation method thereof also have the characteristics of simple preparation method and easy industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0012] Figure 1 This is a flow chart of a method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire-retardant coating provided by an embodiment of the present invention.

[0013] Figure 2 This is a flow chart of a method for preparing a bio-based hydrophobically modified transparent fire retardant coating provided by an embodiment of the present invention.

[0014] Figure 3 These are photos of hydrophobicity tests of a bio-based hydrophobically modified transparent fire retardant coating provided by an embodiment of the present invention and a comparative example.

[0015] Figure 4 This is a schematic diagram of the flame retardant principle of a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the invention for which protection is sought, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0017] In the description of the present invention, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0018] Reference Figure 1 As shown, an embodiment of the present invention provides a method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating, comprising the following steps:

[0019] S1, adding phytic acid and urea to a reaction kettle in sequence, adding the aqueous solution to the mixture and heating to 80-110° C. under stirring, condensing and refluxing for 30-150 minutes, purifying with anhydrous ethanol and drying to obtain ammonium phytate, wherein the molar ratio of phytic acid to urea is 1:6-12;

[0020] S2, adding gelatin to the ammonium phytate solution for adsorption and self-assembly to obtain a reaction solution;

[0021] S3, adding a citric acid aqueous solution to the reaction solution for cross-linking, cooling to room temperature, filtering, washing with deionized water, and drying to room temperature to obtain a bio-based hydrophobically modified flame retardant.

[0022] In step S1, the reaction equation of phytic acid and urea is as follows:

[0023] In order to improve the conversion rate of phytic acid, it is preferred that the proportion of urea be appropriately increased. Preferably, the molar ratio of phytic acid to urea is 1:7 to 10. In one embodiment, the molar ratio of phytic acid to urea is about 1:8.

[0024] Preferably, phytic acid and urea are added sequentially to a reactor, added to an aqueous solution, and heated to 95-105° C. with stirring. More preferably, phytic acid and urea are added sequentially to a reactor, added to an aqueous solution, and heated to 98-102° C. with stirring. In one embodiment, phytic acid and urea are added sequentially to a reactor, added to an aqueous solution, and heated to about 100° C. with stirring.

[0025] In step S1, preferably, the condensation reflux reaction is carried out for 50 to 70 minutes. In one embodiment, the condensation reflux reaction is carried out for about 60 minutes. It is understood that by controlling the reaction amount, reaction temperature, and reaction time, a better conversion rate can be obtained, and the conversion rate can be increased from about 20% to more than 80%.

[0026] In step S2, the main purpose of introducing gelatin is to increase the nitrogen source, increase the expansion ratio of the flame retardant coating, reduce the hydrophilic group -NH4 of ammonium phytate, and improve hydrophobicity. The reaction equation is as follows:

[0027]

[0028] wherein R is an alkyl group. Preferably, the molar ratio of gelatin to ammonium phytate is 0.9 to 1.5:1. In one embodiment, the molar ratio of gelatin to ammonium phytate is about 1.1:1.

[0029] In step S3, the flame retardant is made into a coating. The biggest problem is water resistance. In order to reduce the hydrophilicity of the self-assembling structural group and enhance the hydrophobicity of the flame retardant, thereby improving the water resistance of the coating, citric acid is added to perform a cross-linking reaction to reduce the hydrophilicity. The reaction equation is as follows:

[0030]

[0031] Among them, preferably, the molar ratio of citric acid to ammonium phytate in the reaction solution is 3.5~4.5:1. In one embodiment, the molar ratio of citric acid to ammonium phytate in the reaction solution is 4.3:1. The reaction temperature of the citric acid and the reaction solution is 30℃~70℃, preferably, the reaction temperature of the citric acid and the reaction solution is 50℃~60℃. The reaction time of the citric acid and the reaction solution is 30min~120min, preferably, the reaction time of the citric acid and the reaction solution is 30min~120min. More preferably, the reaction time of the citric acid and the reaction solution is 60min~80min. The concentration of the ammonium phytate solution should not be too high or too low. Preferably, the concentration of the ammonium phytate solution is 150g / L~250g / L.

[0032] The embodiment of the present invention further provides a bio-based hydrophobically modified flame retardant for transparent fire retardant coatings, the structural formula of the bio-based hydrophobically modified flame retardant for transparent fire retardant coatings is:

[0033] , where R1 is: .

[0034] See Figure 4 As shown, the flame retardant mechanism of the bio-based hydrophobically modified flame retardant for transparent fire-retardant coating provided by the present invention is as follows: when the bio-based flame retardant is heated, it will decompose into a strong acid, which will react with the hydroxyl groups on the carbon-carbon chain in the polymer to produce a dehydration reaction. At the same time, it will decompose into inert gases such as nitrogen, ammonia, and carbon dioxide to form a honeycomb carbonized layer, thereby preventing the spread of fire.

[0035] Example A-1:

[0036] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 100°C with stirring, and refluxed under condensation for 60 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 83.1%.

[0037] Example A-2:

[0038] 1 mol of phytic acid and 6 mol of urea were added to an aqueous solution, heated to 100°C with stirring, and refluxed under condensation for 60 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 79.2%.

[0039] Example A-3:

[0040] 1 mol of phytic acid and 10 mol of urea were added to an aqueous solution, heated to 100°C with stirring, and refluxed under condensation for 60 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 81.2%.

[0041] Example A-4:

[0042] 1 mol of phytic acid and 12 mol of urea were added to an aqueous solution, heated to 100°C with stirring, and refluxed under condensation for 60 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 80.7%.

[0043] It can be seen from Examples A-1 to A-4 that the optimal molar ratio of the reaction is about 1:8.

[0044] Example A-5:

[0045] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 60°C under stirring, condensed and refluxed for 60 minutes, purified with anhydrous ethanol and freeze-dried for 24 hours, and the conversion rate of phytic acid was about 0, with almost no reaction.

[0046] Example A-6:

[0047] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 80°C with stirring, condensed and refluxed for 60 minutes, purified with anhydrous ethanol and freeze-dried for 24 hours, and the conversion rate of phytic acid was about 20.2%.

[0048] Example A-7:

[0049] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 90°C with stirring, condensed and refluxed for 60 minutes, purified with anhydrous ethanol and freeze-dried for 24 hours, and the conversion rate of phytic acid was about 67.9%.

[0050] Example A-8:

[0051] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 110°C with stirring, and refluxed under condensation for 60 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 57.4%.

[0052] From Examples A-6 to A-8, it can be seen that the conversion rate decreases significantly with increasing reaction temperature.

[0053] Example A-9:

[0054] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 100°C with stirring, and refluxed under condensation for 30 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 60.1%.

[0055] Example A-10:

[0056] 1 mol of phytic acid and 8 mol of urea were added to an aqueous solution, heated to 100°C with stirring, and refluxed under condensation for 90 minutes. The solution was purified with anhydrous ethanol and freeze-dried for 24 hours to obtain a phytic acid conversion rate of approximately 71.6%.

[0057] From Examples A-9 to A-10, it can be seen that the optimal reaction time is about 60 minutes.

[0058] Example B-1:

[0059] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 60°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility of the bio-based hydrophobically modified flame retardant (at 25°C) was tested to be 23.1%.

[0060] Example B-2:

[0061] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 30°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility (25°C) of the bio-based hydrophobically modified flame retardant was tested to be 75.4%.

[0062] Example B-3:

[0063] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 40°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility (25°C) of the bio-based hydrophobically modified flame retardant was tested to be 71.2%.

[0064] Example B-4:

[0065] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 50°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility of the bio-based hydrophobically modified flame retardant (at 25°C) was tested to be 23.4%.

[0066] Example B-5:

[0067] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 70°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility (25°C) of the bio-based hydrophobically modified flame retardant was tested to be 60.7%.

[0068] It can be seen from Examples B-1 to B-5 that when the reaction temperature is 50-60°C, the solubility of the obtained bio-based hydrophobically modified flame retardant is the lowest, and it has good water resistance and hydrophobicity.

[0069] Example B-6:

[0070] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 60°C for 30 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility (25°C) of the bio-based hydrophobically modified flame retardant was tested to be 55.1%.

[0071] Example B-7:

[0072] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) and adsorbed and self-assembled at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution and a cross-linking reaction was carried out at 60°C for 120 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1). The reaction solution was cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility (25°C) of the bio-based hydrophobically modified flame retardant was tested to be 45.4%.

[0073] It can be seen from Examples B-6 and B-7 that when the reaction time is too long, certain side reactions occur, which reduces the water resistance and hydrophobicity.

[0074] Example B-8:

[0075] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 0.9:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 60°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility of the bio-based hydrophobically modified flame retardant (at 25°C) was tested to be 34.6%.

[0076] Example B-9:

[0077] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.5:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 60°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.3:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility of the bio-based hydrophobically modified flame retardant (at 25°C) was tested to be 24.8%.

[0078] It can be seen from Examples B-8 and B-9 that as the amount of gelatin added decreases, its water resistance and hydrophobicity decrease.

[0079] Example B-10:

[0080] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 60°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 3.5:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility of the bio-based hydrophobically modified flame retardant (at 25°C) was tested to be 35.6%.

[0081] Example B-11:

[0082] Gelatin was added to a 200 g / L ammonium phytate solution (wherein the molar ratio of gelatin to ammonium phytate was 1.1:1) for adsorption self-assembly at room temperature to obtain a reaction solution; then, a citric acid aqueous solution was added to the reaction solution for a cross-linking reaction at 60°C for 70 minutes (wherein the molar ratio of citric acid to ammonium phytate in the reaction solution was 4.5:1), cooled to room temperature, filtered, washed with deionized water, and dried to room temperature to obtain a bio-based hydrophobically modified flame retardant. The solubility of the bio-based hydrophobically modified flame retardant (at 25°C) was tested to be 22.7%.

[0083] It can be seen from Examples B-10 and B-11 that as the amount of citric acid added decreases, the reaction is insufficient, resulting in reduced water resistance and hydrophobicity.

[0084] The present invention further provides a method for preparing a bio-based hydrophobically modified transparent fire-retardant coating. The bio-based hydrophobically modified transparent fire-retardant coating of the present invention is directly developed and designed based on existing traditional transparent fire-retardant coatings, and directly replaces the flame retardants in traditional transparent fire-retardant coatings. Of course, the application of the bio-based hydrophobically modified flame retardant of the present invention is not limited to the present invention; the use of the bio-based hydrophobically modified flame retardant of the present invention in other types of transparent fire-retardant coatings is also within the scope of protection of the present invention.

[0085] See Figure 2 As shown, the preparation method of the bio-based hydrophobically modified transparent fire retardant coating specifically comprises the following steps:

[0086] S4, adding 1-3 parts by weight of organically modified refined hectorite clay to 600-700 parts by weight of an aqueous epoxy resin to disperse, adding 300-350 parts by weight of a bio-based hydrophobically modified flame retardant and stirring to prepare component A;

[0087] S5, adding 20-35 parts by weight of ammonia water to component A and stirring evenly, then adding 80-120 parts by weight of an aqueous curing agent to component A and stirring evenly to obtain a bio-based hydrophobically modified transparent fire retardant coating.

[0088] In step S4, preferably, 1-3 parts by weight of organically modified refined hectorite clay are added to 600-700 parts by weight of waterborne epoxy resin and dispersed at 500rpm-900rpm for 1-5min, 300-350 parts by weight of bio-based hydrophobically modified flame retardant are added and stirred at 1200rpm-1900rpm for 20-30min to make component A. This is because, as the viscosity of the bio-based hydrophobically modified flame retardant is added as a whole, faster stirring speed and time are required. Preferably, in a plurality of embodiments thereof, 2 parts by weight of organically modified refined hectorite clay are added to 650-680 parts by weight of waterborne epoxy resin, and the bio-based hydrophobically modified flame retardant is 310-320 parts by weight.

[0089] In step S5, preferably, 25-30 parts by weight of ammonia water is added to component A and stirred evenly, and then 90-110 parts by weight of an aqueous curing agent is added to component A and stirred evenly to obtain a bio-based hydrophobically modified transparent fire retardant coating.

[0090] Example C-1:

[0091] 2 parts by weight of organically modified refined hectorite clay were added to 670 parts by weight of water-based epoxy resin and dispersed at 800 rpm for 1 minute. 310 parts by weight of a bio-based hydrophobically modified flame retardant (Example A-1) were added and stirred at 1500 rpm for 25 minutes to prepare component A. 28 parts by weight of ammonia water were then added to component A and stirred evenly. 100 parts by weight of a water-based curing agent was then added to component A and stirred evenly to obtain a bio-based hydrophobically modified transparent fire retardant coating.

[0092] Comparative Example 1:

[0093] 2 parts by weight of organically modified refined hectorite clay were added to 670 parts by weight of water-based epoxy resin and dispersed at 800 rpm for 1 minute, 310 parts by weight of a traditional transparent fire-retardant coating flame retardant was added and stirred at 1500 rpm for 25 minutes to prepare component A; then 28 parts by weight of ammonia water was added to component A and stirred evenly, and then 100 parts by weight of a water-based curing agent was added to component A and stirred evenly to obtain a traditional transparent fire-retardant coating.

[0094] Test Example: Example C-1 and Comparative Example 1 were tested according to National Standard 12441-2018. The test data are shown in Table 1.

[0095] Table 1 shows the test data after 1 hour of water resistance test

[0096]

[0097] Please also see Figure 3 Comparative testing shows that coatings made with the bio-based hydrophobically modified flame retardant provided by the present invention exhibit better water resistance, transparency, and gloss than coatings made with traditional transparent fire-retardant flame retardants. Furthermore, the expansion ratio of the bio-based hydrophobically modified flame retardant provided by the present invention is essentially comparable to the state-of-the-art.

[0098] Example C-2:

[0099] Component A was prepared by adding 2 parts by weight of organically modified refined hectorite clay to 670 parts by weight of water-based epoxy resin and dispersing the mixture at 800 rpm for 1 minute. 300 parts by weight of a bio-based hydrophobically modified flame retardant (Example A-1) was then added and stirred at 1500 rpm for 25 minutes. Component A was then prepared. 28 parts by weight of aqueous ammonia was then added to component A and stirred thoroughly. Finally, 100 parts by weight of a water-based curing agent was added to component A and stirred thoroughly to produce a bio-based hydrophobically modified transparent fire retardant coating. Testing showed an expansion ratio of 69.7.

[0100] Example C-3:

[0101] Component A was prepared by adding 2 parts by weight of organically modified refined hectorite clay to 670 parts by weight of water-based epoxy resin and dispersing the mixture at 800 rpm for 1 minute. 320 parts by weight of a bio-based hydrophobically modified flame retardant (Example A-1) was then added and stirred at 1500 rpm for 25 minutes. Component A was then prepared. 28 parts by weight of aqueous ammonia was then added to component A and stirred thoroughly. Finally, 100 parts by weight of a water-based curing agent was added to component A and stirred thoroughly to produce a bio-based hydrophobically modified transparent fire retardant coating. Testing showed an expansion ratio of 74.4.

[0102] Example C-4:

[0103] Component A was prepared by adding 2 parts by weight of organically modified refined hectorite clay to 670 parts by weight of water-based epoxy resin and dispersing the mixture at 800 rpm for 1 minute. 350 parts by weight of a bio-based hydrophobically modified flame retardant (Example A-1) was then added and stirred at 1500 rpm for 25 minutes. Component A was then prepared. 28 parts by weight of aqueous ammonia was then added to component A and stirred thoroughly. Finally, 100 parts by weight of a water-based curing agent was added to component A and stirred thoroughly to produce a bio-based hydrophobically modified transparent fire retardant coating. Testing showed an expansion ratio of 75.1.

[0104] Comparative Example 2:

[0105] Component A was prepared by adding 2 parts by weight of organically modified refined hectorite clay to 670 parts by weight of water-based epoxy resin and dispersing the mixture at 800 rpm for 1 minute. Component A was then prepared by adding 280 parts by weight of a bio-based hydrophobically modified flame retardant (Example A-1) and stirring at 1500 rpm for 25 minutes. Component A was then prepared by adding 28 parts by weight of aqueous ammonia to the mixture and stirring thoroughly. Finally, 100 parts by weight of a water-based curing agent was added to the mixture and stirred thoroughly to produce a bio-based hydrophobically modified transparent fire retardant coating. Testing showed an expansion ratio of 59.3.

[0106] Comparative Example 4:

[0107] Component A was prepared by adding 2 parts by weight of organically modified refined hectorite clay to 670 parts by weight of water-based epoxy resin and dispersing the mixture at 800 rpm for 1 minute. Component A was then prepared by adding 400 parts by weight of a bio-based hydrophobically modified flame retardant (Example A-1) and stirring at 1500 rpm for 25 minutes. Component A was then prepared by adding 28 parts by weight of aqueous ammonia to component A and stirring thoroughly. Finally, 100 parts by weight of a water-based curing agent was added to component A and stirred thoroughly to produce a bio-based hydrophobically modified transparent fire retardant coating. Testing showed an expansion ratio of 73.2.

[0108] As can be seen from Examples C2-C4 and Comparative Examples 2-3, as the bio-based hydrophobically modified flame retardant concentration falls below 300 phr, the expansion ratio decreases significantly, remaining far below that of the prior art. However, when the bio-based hydrophobically modified flame retardant concentration exceeds 350 phr, the expansion ratio not only does not increase but actually decreases.

[0109] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating, characterized in that: The following steps are involved: S1, adding phytic acid and urea to a reaction kettle in sequence, adding the aqueous solution to the mixture and heating to 80-110° C. under stirring, condensing and refluxing for 30-150 minutes, purifying with anhydrous ethanol and drying to obtain ammonium phytate, wherein the molar ratio of phytic acid to urea is 1:6-12; S2, adding gelatin to the ammonium phytate solution for adsorption self-assembly to obtain a reaction solution, wherein the molar ratio of gelatin to ammonium phytate is 0.9-1.5:1; S3, adding a citric acid aqueous solution to the reaction solution for cross-linking, cooling to room temperature, filtering, washing with deionized water, and drying to room temperature to obtain a bio-based hydrophobically modified flame retardant, wherein the molar ratio of citric acid to ammonium phytate in the reaction solution is 3.5-4.5:

1.

2. The method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating as claimed in claim 1, characterized in that: In step S1, the molar ratio of phytic acid to urea is 1:7-10.

3. The method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating as claimed in claim 1, characterized in that: In step S1, phytic acid and urea are sequentially added to an aqueous solution in a reactor and heated to 95-105° C. under stirring.

4. The method for preparing a bio-based hydrophobically modified flame retardant for a transparent fire retardant coating as claimed in claim 1, wherein: In step S1, the reaction is carried out under condensation and reflux for 50 to 70 minutes.

5. A bio-based hydrophobically modified flame retardant for transparent fire retardant coating, characterized in that: The structural formula of the bio-based hydrophobically modified flame retardant for transparent fire retardant coating is: , where R1 is: , R is an alkyl group.

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