Enhanced high-thermal-conductivity fireproof coating based on modified boron nitride and bio-based flame-retardant coating modified UiO-66

Abstract

The invention discloses an enhanced high-thermal-conductivity fireproof coating based on modified boron nitride and bio-based flame-retardant coating modified UiO-66, and belongs to the field of flame-retardant materials. The preparation method comprises the following steps: firstly, coating the surface of BN with polysilazane (PSZ) and silane through hydrolysis and condensation to obtain surface-treated BN, then preparing UiO-66, and then adsorbing two bio-based materials, namely CS and PA, on the UiO-66 through electrostatic attraction. The enhanced fireproof coating based on the modified boron nitride and the bio-based modified UiO-66 is obtained by compounding the modified boron nitride and the surface-treated boron nitride with the epoxy resin, the flame-retardant resin expansive carbon layer is high in strength and compact, the flame-retardant effect is remarkable, meanwhile, the preparation method is simple, the preparation process is green and environment-friendly, and the application prospect is wide. The method is suitable for wide application and industrial production in the flame-retardant field.

Description

Technical Field

[0001] The present invention relates to the technical field of fire retardant coatings, and in particular to an enhanced high thermal conductivity fire retardant coating based on modified boron nitride and bio-based flame retardant coating modified UiO-66. Background Art

[0002] In recent years, nano flame retardant technology has attracted much attention and has been used to modify many materials. Metal organic frameworks (MOFs) are porous nanomaterials with a periodic network skeleton formed by the combination of metal ions and organic ligands. Compared with traditional flame retardants, MOFs-based flame retardants have the advantages of high thermal stability, good compatibility with the matrix, high porosity, strong structural designability, and little effect on the mechanical properties of the matrix. As a zirconium-based metal organic framework material, UiO-66 has a wide range of application potential due to its porosity, high specific surface area, chemical stability and controllability. However, due to the lack of flame retardant elements (such as phosphorus, nitrogen and silicon), the flame retardant effect of using only MOF is usually limited. Therefore, it is necessary to organically combine MOFs with compounds containing flame retardant elements to further improve their flame retardant efficiency through chemical modification.

[0003] Among the current technologies, the technologies used in UiO-66 include CN 118878852 A, which discloses a metal organic framework-based porous liquid functional flame retardant, but its peak heat release rate is only 45.2% lower than that of pure polyurea, and the effect can still be improved; Patent CN 118562255 A discloses a polymer metal organic framework-modified flame retardant epoxy resin, but its final measured PHRR value is greater than 600kW·m 2 , the effect can still be improved. The chemical modification technology includes the technology of using chitosan and phytic acid. Patent CN 114703667 B discloses a method for preparing flame-retardant cotton fabrics based on attapulgite layer-by-layer self-assembly technology, as well as "The influence of chitosan / sodium phytate coated ammonium polyphosphate complex on the flame retardant properties of polylactic acid composite materials", but these technologies are all aimed at the exploration of fabric flame retardancy, and the substrates used are all fabrics, not flowing liquids, and they do not involve the use of flame retardant coatings. The technology related to the modification and use of boron nitride is "Research on environmentally friendly phenolic resin composite materials modified by boron nitride hybridization", but the article only explores the flame retardant effect of boron nitride particles after modification by silane coupling agent, and is not used in combination with other substances. In addition, patent CN 118772683 A discloses a layer-by-layer self-assembled MOFs intumescent high-efficiency fire retardant coating, which mentions the impregnation modification of MOFs nanomaterials, but the specific scheme does not involve the exploration of UiO-66 materials. Summary of the invention

[0004] Technical issues

[0005] UiO-66 is a zirconium-based organic metal framework material. Due to the lack of flame retardant elements (such as phosphorus, nitrogen and silicon), the flame retardant effect of using only MOF is usually limited. Therefore, it needs to be chemically modified to further improve its flame retardant efficiency and broaden its scope of application.

[0006] Technical content

[0007] In order to solve the above problems, the present invention provides an enhanced fire retardant coating based on modified boron nitride and bio-based modified UiO-66. The enhanced fire retardant coating consists of 50-60% epoxy resin, 10-15% 4,4-diaminodiphenylmethane, 1-5% bio-based flame retardant coating modified UiO-66 nanomaterials, and 25-35% modified boron nitride by mass fraction.

[0008] Preferably, the enhanced fire retardant coating is composed, by mass fraction, of 53-57% epoxy resin, 11-13% 4,4-diaminodiphenylmethane, 1-3% bio-based flame retardant coating modified UiO-66 nanomaterial, and 27-32% modified boron nitride.

[0009] Specifically, the enhanced fire retardant coating is composed, by mass fraction, of 55.84% epoxy resin, 12.16% 4,4-diaminodiphenylmethane, 2% bio-based flame retardant coating modified UiO-66 nanomaterial, and 30% modified boron nitride.

[0010] Furthermore, the bio-based flame retardant coating modified UiO-66 nanomaterial is a UiO-66 nanomaterial wrapped with a chitosan layer and a phytic acid layer from the inside to the outside; one chitosan layer and one phytic acid layer are counted as one layer of bio-based flame retardant coating, and there are a total of 1 to 5 layers of bio-based flame retardant coating, preferably 2 to 4 layers of bio-based flame retardant coating, and most preferably 3 layers of bio-based flame retardant coating.

[0011] Furthermore, the UiO-66 nanomaterial is prepared as follows:

[0012] Zirconium chloride is dissolved in N, N-dimethylformamide to obtain a zirconium chloride solution; 2-aminoterephthalic acid is dissolved in N, N-dimethylformamide to obtain a 2-aminoterephthalic acid solution; the two solutions are mixed, added with acetic acid and stirred, and then sealed and heated for reaction; after cooling, the solid is collected by centrifugation, and finally vacuum activated to obtain UiO-66 nanomaterials;

[0013] Further, the concentration of zirconium chloride in the zirconium chloride solution is 0.75-2wt%;

[0014] Further, the concentration of 2-aminoterephthalic acid in the 2-aminoterephthalic acid solution is 0.35 to 1.5 wt %;

[0015] Further, the volume ratio of the acetic acid to the total N,N-dimethylformamide in the zirconium chloride solution and the 2-aminoterephthalic acid solution is 1:4 to 3:8;

[0016] Furthermore, the sealed heating reaction temperature is 100-200°C and the time is 6-16h;

[0017] Furthermore, the vacuum activation conditions are a temperature of 20 to 180° C. and an activation time of 1 to 12 hours.

[0018] Furthermore, the preparation of the modified boron nitride is as follows: boron nitride is added to ethanol and mixed to obtain a mixed solution, and the pH of the mixed solution is adjusted using aqueous ammonia; a certain amount of 3-aminopropyltriethoxysilane is weighed and added to the mixed solution for reaction, and after the reaction is completed, ethanol is added to the reaction solution for centrifugal washing to remove unreacted ammonia and 3-aminopropyltriethoxysilane; the precipitate after centrifugation is collected, dried, and then ground to obtain modified boron nitride.

[0019] Furthermore, the concentration of boron nitride in the mixed solution is 1-5wt%.

[0020] Furthermore, the pH is adjusted to 7-12.

[0021] Furthermore, the mass ratio of the 3-aminopropyltriethoxysilane to boron nitride is 1 to 5:1.

[0022] Furthermore, the reaction temperature is 55-70° C. and the reaction time is 3-6 hours.

[0023] Furthermore, the centrifugal washing is performed at 3500-6000 rpm for 4 times.

[0024] Furthermore, the drying temperature is 40-70° C. and the drying time is 36-60 hours.

[0025] The enhanced fire retardant coating provided by the present invention is used in the field of fire prevention or flame retardancy.

[0026] Furthermore, the application includes applying the enhanced fire retardant coating to the surface of buildings, furniture, equipment or materials requiring fire protection, and then heating to cure it.

[0027] The present invention also provides an enhanced fireproof board based on modified boron nitride and bio-based modified UiO-66, wherein the enhanced fireproof board is obtained by introducing the enhanced fireproof coating into a mold and then heating and curing it.

[0028] Furthermore, the heat curing includes first drying at 100-150° C. for 1-3 hours, and then drying at 150-200° C. for 1-3 hours.

[0029] The present invention also provides a method for preparing the fire retardant coating, the method comprising the following steps:

[0030] S1. Preparation of base material: taking epoxy resin and curing agent, mixing to obtain base material;

[0031] S2, adding boron nitride to ethanol and mixing to obtain a mixed solution, and adjusting the pH of the mixed solution with ammonia water; weighing a certain amount of 3-aminopropyltriethoxysilane and adding it to the mixed solution for reaction, and after the reaction is completed, adding ethanol to the reaction solution for centrifugal washing to remove unreacted ammonia and 3-aminopropyltriethoxysilane; collecting the precipitate after centrifugation, drying it, and grinding it to obtain modified boron nitride;

[0032] S3. Preparation of bio-based flame retardant coating modified UiO-66 nanomaterials: taking the UiO-66 nanomaterials and immersing them in a chitosan acetic acid aqueous solution, then taking out the UiO-66 nanomaterials and immersing them in a phytic acid aqueous solution, and then taking out the UiO-66 nanomaterials;

[0033] The UiO-66 nanomaterials after two-step impregnation are modified with one layer, and the two-step impregnation is repeated to obtain UiO-66 nanomaterials modified with multiple layers;

[0034] S4. Preparation of flame retardant resin: take the modified multilayer UiO-66 nanomaterial, the modified boron nitride and the base material, mix them, heat and stir to disperse them evenly to obtain the fire retardant coating.

[0035] Furthermore, the curing agent in step S1 includes one or a mixture of polyamide, liquid acid anhydride, aliphatic polyamine, cardanol modified amine, and aromatic polyamine curing agents.

[0036] Furthermore, in step S1, the mass ratio of the epoxy resin to the curing agent is 2:1 to 5:1.

[0037] Furthermore, the concentration of boron nitride in the mixed solution in step S2 is 1-5 wt %.

[0038] Furthermore, the pH in step S2 is adjusted to 7-12.

[0039] Furthermore, in step S2, the mass ratio of 3-aminopropyltriethoxysilane to boron nitride is 1 to 5:1.

[0040] Furthermore, the reaction temperature in step S2 is 55-70° C. and the reaction time is 3-6 hours.

[0041] Furthermore, the centrifugal washing in step S2 is centrifugal washing at 3500-6000 rpm for 4 times.

[0042] Furthermore, the drying temperature in step S2 is 40-70° C. and the drying time is 36-60 hours.

[0043] Furthermore, the preparation of the UiO-66 nanomaterial in step S3 is as follows:

[0044] Zirconium chloride is dissolved in N, N-dimethylformamide to obtain a zirconium chloride solution; 2-aminoterephthalic acid is dissolved in N, N-dimethylformamide to obtain a 2-aminoterephthalic acid solution; the two solutions are mixed, added with acetic acid and stirred, and then sealed and heated for reaction; after cooling, the solid is collected by centrifugation, and finally vacuum activated to obtain UiO-66 nanomaterials;

[0045] The concentration of zirconium chloride in the zirconium chloride solution is 0.75-2wt%;

[0046] The concentration of 2-aminoterephthalic acid in the 2-aminoterephthalic acid solution is 0.35 to 1.5 wt %;

[0047] The volume ratio of the acetic acid to the total N,N-dimethylformamide in the zirconium chloride solution and the 2-aminoterephthalic acid solution is 1:4 to 3:8;

[0048] The sealed heating reaction is carried out at a temperature of 100 to 150°C for a period of 6 to 16 hours;

[0049] The vacuum activation conditions are a temperature of 20 to 140° C. and an activation time of 1 to 12 hours.

[0050] Furthermore, the concentration of chitosan in the chitosan acetic acid aqueous solution in step S3 is 0.5-5 wt%.

[0051] Furthermore, the concentration of acetic acid in the chitosan acetic acid aqueous solution in step S3 is 0.5-2 wt %.

[0052] Furthermore, the concentration of phytic acid in the phytic acid aqueous solution in step S3 is 2-7 wt %.

[0053] Furthermore, the immersion time in step S3 is 1 to 10 minutes.

[0054] Furthermore, the number of modified layers of the multi-layered UiO-66 nanomaterial modified in step S3 is 1 to 5.

[0055] Preferably, the number of modified layers of the multi-layered UiO-66 nanomaterial modified in step S3 is 2 to 4.

[0056] Most preferably, the number of modified layers of the multi-layered UiO-66 nanomaterial modified in step S3 is 3.

[0057] Furthermore, in step S4, the fire retardant coating modified with multiple layers of UiO-66 nanomaterials accounts for 0.5 to 2 wt%;

[0058] Furthermore, in step S4, the modified boron nitride accounts for 10-30wt% in the fire retardant coating;

[0059] Furthermore, in step S4, the base material accounts for 68% to 89.5wt% of the fire retardant coating.

[0060] Furthermore, the heating and stirring in step S4 is stirring at 60-105° C. for 1.5-12 hours.

[0061] The present invention has the following beneficial effects:

[0062] (1) The boron nitride nanomaterial modified by silane coupling agent grafting in the present invention can effectively solve the dispersibility of boron nitride in the matrix, and the modification of boron nitride by silane coupling agent also helps to reduce the thermal resistance of the interface between the boron nitride nanomaterial and the matrix, and improve its thermal conductivity. In addition, the present invention uses a bio-based flame retardant coating to modify UiO-66. This method is green, environmentally friendly, and low in toxicity. The obtained bio-based flame retardant coating modified UiO-66 is more efficient and safe, and is conducive to the construction of an intumescent flame retardant coating.

[0063] (2) The boron nitride nanomaterial obtained in the present invention has excellent heat resistance and sheet barrier effect. The bio-based flame retardant coating modified UiO-66 has the effects of porous adsorption, smoke suppression and toxicity reduction, catalytic carbonization and expansion flame retardancy. The combination of the two will greatly improve the fire resistance of the substrate and reduce combustion toxicity, and achieve a synergistic effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] Figure 1 This is the infrared spectrum of UiO-66 before and after bio-based flame retardant modification.

[0065] Figure 2 XRD diagram of UiO-66 before and after bio-based flame retardant modification.

[0066] Figure 3 This is the SEM image of unmodified UiO-66 in Comparative Example 2.

[0067] Figure 4 This is the SEM image of the modified UiO-66-3 in Example 2.

[0068] Figure 5 This is a photograph of the fire retardant coating obtained in Comparative Example 1 after the cone calorimetry test.

[0069] Figure 6 This is a photograph of the fire retardant coating obtained in Example 4 after the cone calorimetry test. DETAILED DESCRIPTION

[0070] The present invention is further explained and illustrated below in conjunction with the attached tables and examples, but the protection scope of the present invention is not limited to the following examples.

[0071] Example 1

[0072] A fire retardant coating comprises the following steps:

[0073] 1. Preparation of base material

[0074] Weigh 40.24 g of epoxy resin and 8.76 g of 4,4-diaminodiphenylmethane to obtain a base material;

[0075] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0076] (1) Preparation of UiO-66 nanomaterials

[0077] Weigh 0.714g zirconium chloride (ZrCl4) and dissolve it in 80mL N,N dimethylformamide (DMF); weigh 0.5075g 2-aminoterephthalic acid and dissolve it in 80mL DMF; pour the two solutions into a beaker together and add 42mL acetic acid for ultrasonic stirring, then pour into a polytetrafluoroethylene beaker and seal it, react at an oven temperature of 120°C for 12h, then cool it down, collect the product by centrifugation, wash it with DMF and methanol for 3 times and 2 times respectively, and finally activate it at 120°C in vacuum for 2h to obtain UiO-66 nanomaterials;

[0078] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials

[0079] 1 g of chitosan (CS) powder was stirred and dissolved in 100 mL of 1% acetic acid solution to form bio-based solution 1; 70% phytic acid (PA) solution (7.17 g) was ultrasonically stirred and dissolved in 92.83 mL of deionized water to form bio-based solution 2;

[0080] 1 g of UiO-66 nanomaterial was immersed in bio-based solution 1, immersed for 5 minutes, and then centrifuged at 6000 r / min for 8 minutes to retain the solid; the obtained solid was immersed in bio-based solution 2, immersed for 5 minutes, and then centrifuged at 6000 r / min for 8 minutes to retain the solid, completing the first layer after electrostatic attraction adsorption; the solid after immersion and centrifugation of bio-based solution 2 was vacuum dried at 80°C for 2 hours to obtain bio-based modified UiO-66-1 nanomaterial;

[0081] 3. Preparation of fire retardant coating

[0082] Weigh 1 g of bio-based modified UiO-66-1 nanomaterial and mix it with the base material, then heat it in an oil bath at 105° C. and stir it at a stirring speed of 350 r / min for 3 h to obtain a fire retardant coating.

[0083] Example 2

[0084] A fire retardant coating comprises the following steps:

[0085] 1. Preparation of base material: refer to step 1 in Example 1;

[0086] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0087] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0088] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials

[0089] 1 g of chitosan (CS) powder was stirred and dissolved in 100 mL of 1% acetic acid solution to form bio-based solution 1; 70% phytic acid (PA) solution (7.17 g) was ultrasonically stirred and dissolved in 92.83 mL of deionized water to form bio-based solution 2;

[0090] 1 g of UiO-66 nanomaterial was immersed in bio-based solution 1, immersed for 5 min, and then centrifuged at 6000 r / min for 8 min to retain the solid; the obtained solid was immersed in bio-based solution 2, immersed for 5 min, and then centrifuged at 6000 r / min for 8 min to retain the solid, completing the first layer after electrostatic attraction adsorption;

[0091] Repeat the above two impregnation steps twice, shortening the impregnation time to 1 min; vacuum drying the solid obtained after the final impregnation centrifugation at 80° C. for 2 h to obtain the bio-based modified UiO-66-3 nanomaterial;

[0092] 3. Preparation of fire retardant coating

[0093] Weigh 1 g of bio-based modified UiO-66-3 nanomaterial and mix it with the base material, then heat it in an oil bath at 105° C. and stir it at a stirring speed of 350 r / min for 3 h to obtain a fire retardant coating.

[0094] Example 3

[0095] A fire retardant coating comprises the following steps:

[0096] 1. Preparation of base material: refer to step 1 in Example 1;

[0097] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0098] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0099] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials

[0100] 1 g of chitosan (CS) powder was stirred and dissolved in 100 mL of 1% acetic acid solution to form bio-based solution 1; 70% phytic acid (PA) solution (7.17 g) was ultrasonically stirred and dissolved in 92.83 mL of deionized water to form bio-based solution 2;

[0101] 1 g of UiO-66 nanomaterial was immersed in bio-based solution 1, immersed for 5 min, and then centrifuged at 6000 r / min for 8 min to retain the solid; the obtained solid was immersed in bio-based solution 2, immersed for 5 min, and then centrifuged at 6000 r / min for 8 min to retain the solid, completing the first layer after electrostatic attraction adsorption;

[0102] Repeat the above two impregnation steps 4 times, shortening the impregnation time to 1 min; vacuum drying the solid obtained after the final impregnation centrifugation at 80° C. for 2 h to obtain the bio-based modified UiO-66-5 nanomaterial;

[0103] 3. Preparation of fire retardant coating

[0104] Weigh 1 g of bio-based modified UiO-66-5 nanomaterial and mix it with the base material, then heat it in an oil bath at 105° C. and stir it at a stirring speed of 350 r / min for 3 h to obtain a fire retardant coating.

[0105] Example 4

[0106] A fire retardant coating comprises the following steps:

[0107] 1. Preparation of base material

[0108] Weigh 27.92 g of epoxy resin and 6.08 g of 4,4-diaminodiphenylmethane to obtain a uniformly mixed base material;

[0109] 2. Preparation of modified boron nitride

[0110] 5 g of boron nitride was added to 100 mL of ethanol to obtain a 5 wt% mixed solution, which was then dispersed using ultrasound, and then the pH of the mixed solution was adjusted to 10 using ammonia water; 20 g of 3-aminopropyltriethoxysilane was weighed and slowly added to the mixed solution, and after the addition was completed, the solution was placed in a water bath at 70° C. for 3 h; the above solution was then transferred to a centrifuge tube, and centrifuged and washed 4 times at 4500 rpm with ethanol to remove unreacted ammonia and 3-aminopropyltriethoxysilane; the collected precipitate was placed in a vacuum oven at 50° C. and dried for 48 h. After drying, it was gently ground with an agate mortar to make it evenly dispersed and prevent agglomeration for subsequent use;

[0111] 3. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0112] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0113] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials: refer to the corresponding steps in Example 2;

[0114] 4. Preparation of fire retardant coating

[0115] Weigh 1 g of bio-based flame retardant modified UiO-66-3 nanomaterial and 15 g of modified boron nitride and mix them with the base material, then heat them in an oil bath at 105°C and stir them at a stirring speed of 350 r / min for 3 hours to obtain a fire retardant coating.

[0116] Comparative Example 1

[0117] A fire retardant coating comprises the following steps:

[0118] 1. Preparation of base material

[0119] Weigh 41.06 g of epoxy resin and 8.94 g of 4,4-diaminodiphenylmethane to obtain a uniformly mixed base material;

[0120] 2. Preparation of resin

[0121] After the base material is mixed evenly, pour it into the mold and dry it at 100℃ for 2h, then at 150℃ for 2h; after it is completely cooled, demould it.

[0122] Comparative Example 2

[0123] A fire retardant coating comprises the following steps:

[0124] 1. Preparation of base material: refer to step 1 in Example 1;

[0125] 2. Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0126] 3. Preparation of fire retardant coating

[0127] Weigh 1 g of UiO-66 nanomaterial and mix it with the base material, then heat it in an oil bath at 105°C and stir it at a stirring speed of 350 r / min for 3 hours to obtain a fire retardant coating.

[0128] Comparative Example 3

[0129] A fire retardant coating comprises the following steps:

[0130] 1. Preparation of base material: refer to step 1 in Example 1;

[0131] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0132] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0133] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials

[0134] 1 g of chitosan (CS) powder was stirred and dissolved in 100 mL of 1% acetic acid solution to form bio-based solution 1;

[0135] 1 g of UiO-66 nanomaterial was weighed and immersed in the bio-based solution 1. After immersion for 5 min, the solid was centrifuged at 6000 r / min for 8 min to retain the solid. The solid was vacuum dried at 80 ° C for 2 h to obtain the bio-based modified CS@UiO-66-1 nanomaterial.

[0136] 3. Preparation of fire retardant coating

[0137] Weigh 1 g of CS@UiO-66-1 nanomaterial and mix it with the base material, then heat it in an oil bath at 105°C and stir it at a stirring speed of 350 r / min for 3 h to obtain the fire retardant coating.

[0138] Comparative Example 4

[0139] A fire retardant coating comprises the following steps:

[0140] 1. Preparation of base material: refer to step 1 in Example 1;

[0141] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0142] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0143] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials

[0144] 70% phytic acid solution (7.17 g) was dissolved in 92.83 mL of deionized water by ultrasonic stirring to form bio-based solution 2;

[0145] 1 g of UiO-66 nanomaterial was weighed and immersed in the bio-based solution 2. After immersion for 5 min, the solid was centrifuged at 6000 r / min for 8 min to retain the solid. The solid was vacuum dried at 80 ° C for 2 h to obtain the bio-based modified PA@UiO-66-1 nanomaterial.

[0146] 3. Preparation of fire retardant coating

[0147] Weigh 1 g of PA@UiO-66-1 nanomaterial and mix it with the base material, then heat it in an oil bath at 105°C and stir it at a stirring speed of 350 r / min for 3 h to obtain a fire retardant coating.

[0148] Comparative Example 5

[0149] A fire retardant coating comprises the following steps:

[0150] 1. Preparation of base material: refer to step 1 in Example 1;

[0151] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0152] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0153] (2) Preparation of blended nanomaterials

[0154] Disperse 0.6gUiO-66 in 20mL pure water and ultrasonicate for 30min to form a well-dispersed suspension. Add 0.07g chitosan (CS) to the above suspension and stir until the mixed solution is homogeneous. Under stirring, add 0.33g phytic acid (PA) dropwise to the mixed suspension and stir magnetically at room temperature for 24h. After stirring, centrifuge at 6000r / min for 8min to retain the solid. Vacuum dry the obtained solid at 80°C for 2h to obtain a blended nanomaterial;

[0155] 3. Preparation of fire retardant coating

[0156] Weigh 1g of blended nanomaterials (including 7wt% chitosan, 33wt% phytic acid and 60wt% UiO-66) and mix it with the base material, then heat it in an oil bath at 105°C and stir it at a stirring speed of 350r / min for 3h to obtain a fire retardant coating.

[0157] Comparative Example 6

[0158] A fire retardant coating comprises the following steps:

[0159] 1. Preparation of base material

[0160] Weigh 28.92 g of epoxy resin and 6.08 g of 4,4-diaminodiphenylmethane to obtain a uniformly mixed base material;

[0161] 2. Preparation of modified boron nitride

[0162] 5 g of boron nitride was added to 100 mL of ethanol to obtain a 5 wt% mixed solution, which was then dispersed using ultrasound, and then the pH of the mixed solution was adjusted to 10 using ammonia water; 20 g of 3-aminopropyltriethoxysilane was weighed and slowly added to the mixed solution, and after the addition was completed, the solution was placed in a water bath at 70° C. for 3 h; the above solution was then transferred to a centrifuge tube, and centrifuged and washed 4 times at 4500 rpm with ethanol to remove unreacted ammonia and 3-aminopropyltriethoxysilane; the collected precipitate was placed in a vacuum oven at 50° C. and dried for 48 h. After drying, it was gently ground with an agate mortar to make it evenly dispersed and prevent agglomeration for subsequent use;

[0163] 3. Preparation of fire retardant coating

[0164] Weigh 15 g of modified boron nitride and mix it with the base material, then heat it in an oil bath at 105° C. and stir it at a stirring speed of 350 r / min for 3 hours to obtain a fire retardant coating.

[0165] Comparative Example 7

[0166] A fire retardant coating comprises the following steps:

[0167] 1. Preparation of base material: refer to step 1 in Example 1;

[0168] 2. Preparation of UiO-66 nanomaterials modified with bio-based flame retardant coating

[0169] (1) Preparation of UiO-66 nanomaterials: refer to the corresponding steps in Example 1;

[0170] (2) Preparation of bio-based solution and modification of UiO-66 nanomaterials

[0171] 1 g of chitosan (CS) powder was stirred and dissolved in 100 mL of 1% acetic acid solution to form bio-based solution 1; 70% phytic acid (PA) solution (7.17 g) was ultrasonically stirred and dissolved in 92.83 mL of deionized water to form bio-based solution 2;

[0172] 1 g of UiO-66 nanomaterial was immersed in bio-based solution 1, immersed for 5 min, and then centrifuged at 6000 r / min for 8 min to retain the solid; the obtained solid was immersed in bio-based solution 2, immersed for 5 min, and then centrifuged at 6000 r / min for 8 min to retain the solid, completing the first layer after electrostatic attraction adsorption;

[0173] The above two impregnation steps were repeated for 6 times, and the impregnation time was shortened to 1 min. The solid obtained after the final impregnation centrifugation was vacuum dried at 80° C. for 2 h to obtain the bio-based modified UiO-66-7 nanomaterial.

[0174] However, due to the 7-layer self-assembly modification of UiO-66-7 nanomaterial, the obtained nanoparticles have agglomerated and cannot be used for subsequent applications.

[0175] Table 1 Comparative Examples 1 to 6 and Examples 1 to 4 Sample Formulas

[0176]

[0177]

[0178] Cone calorimetry test process:

[0179] The composite material samples prepared in Examples 1 to 4 and Comparative Examples 1 to 6 were respectively installed on the test device, the power of the radiation cone was set to 35 kW, the cone calorimeter was started, thermal radiation was performed and test data was collected in real time, and parameters such as the heat release rate, total heat release and carbon monoxide release rate of the material were calculated. After the preset test time was reached, the thermal radiation of the radiation cone was stopped, and the test results are shown in the following table:

[0180] Table 2 Cone calorimetry test data of comparative examples 1 to 6 and examples 1 to 4

[0181]

[0182] The peak heat release rate (PHRR) is an important fire characteristic parameter of the material. The initial maximum peak represents the typical combustion characteristics of the material. The total heat release (THR) refers to the total amount of heat released by the material from ignition to flame extinction. The larger the value, the more violent the combustion reaction. The total smoke generation (TSR) refers to the total cumulative smoke generation per unit sample area during combustion. The larger the value, the more smoke generated by the combustion. The real-time mass (MASS) reflects the trend of decomposition and weight loss during the combustion process of the material. The greater the weight loss, the more violent the combustion reaction.

[0183] The results show that compared with pure epoxy resin (Comparative Example 1), the PHRR values ​​of Examples 1 to 4 are low, proving that the flame retardant properties can be improved after adding the bio-based flame retardant modified UiO-66 nano flame retardant system and modified boron nitride (BN).

[0184] In Examples 1 to 3, the PHRR value increases first and then decreases with the increase in the number of layers of bio-based flame retardant modified UiO-66, proving that within a certain range, the flame retardant performance first increases and then weakens with the increase in the number of layers of bio-based flame retardant modified UiO-66. When the number of layers of bio-based flame retardant modified UiO-66 reaches five layers (Example 3), the flame retardant performance deteriorates, which may be caused by the agglomeration of nano molecules caused by too many layers and the internal closure. At the same time, when the number of layers reaches 7 layers, the nano molecules will undergo serious agglomeration, which directly affects subsequent use. Therefore, the number of layers of layer-by-layer self-assembly modification should be controlled at 1 to 5 layers, preferably 3 layers.

[0185] Compared with Comparative Example 2, Examples 1 to 3 and Comparative Examples 3 to 5 all have improved flame retardant properties based on the addition of the same proportion of nanomaterials, which illustrates the necessity of bio-based modification. At the same time, compared with Comparative Examples 3 to 5, Example 2 has better effects, which illustrates that only using chitosan or phytic acid, or only using blending without layer-by-layer modification, cannot achieve excellent flame retardant effect improvement.

[0186] In addition, compared with Example 2 and Comparative Example 6, Example 4 is significantly better than Example 2 and Comparative Example 6, achieving the synergistic effect of modified BN and UiO-66-3 of "one plus one is greater than two". The specific calculation is: in terms of PHRR, Example 2 only uses UiO-66-3 more than Comparative Example 1, and its PHRR value decreases by 329.04kW·m 2 , the decline rate was 25.4% (E A ), Comparative Example 6 only uses modified boron nitride compared to Comparative Example 1, and its PHRR value decreases by 412.808kW·m 2 , the decline rate is 31.9% (E B ), Example 4 has UiO-66-3 and modified boron nitride combined compared with Comparative Example 1, and its PHRR value decreases by 789.64kW·m 2 , the decline rate is 61.0% (E A+B ), applying the Jin Zheng average Q value calculation formula, it can be obtained that Q>1.15. Therefore, in Example 4, a synergistic enhancement effect is achieved.

[0187]

[0188] E A 、E B A and B are the effects of each other, E A+B It is the combined effect of A and B. Q<0.85 indicates that A and B have an antagonistic effect; 0.85≤Q≤1.15 indicates that A and B have an additive effect; Q≥1.15 indicates that A and B have a synergistic effect.

[0189] The UiO-66 nano flame retardant modified with bio-based flame retardant is an integrated bio-based flame retardant system. The expansion effect of the composite material is as follows Figure 6 As shown, the system synergistically acts as a dehydrating agent / foaming agent to form a stable expanded char layer to protect the base material from continuous impact of flame and heat.

[0190] In summary, the composite materials of UiO-66-3 nanomaterials modified with a certain amount of bio-based flame retardant and modified boron nitride (BN) exhibited excellent flame retardant properties.

[0191] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. An enhanced fire retardant coating based on modified boron nitride and bio-based modified UiO-66, characterized in that: The enhanced fire retardant coating is composed of 50-60% epoxy resin, 10-15% 4,4-diaminodiphenylmethane, 1-5% bio-based flame retardant coating modified UiO-66 nanomaterial, and 25-35% modified boron nitride by mass fraction; The bio-based flame retardant coating modified UiO-66 nanomaterial is a UiO-66 nanomaterial that wraps a chitosan layer and a phytic acid layer from the inside to the outside; one chitosan layer and one phytic acid layer are counted as one layer of bio-based flame retardant coating, and there are 1 to 5 layers of bio-based flame retardant coating in total; The preparation of the modified boron nitride comprises the following steps: adding boron nitride to ethanol and mixing to obtain a mixed solution, and adjusting the pH value of the mixed solution with ammonia water; weighing a certain amount of 3-aminopropyltriethoxysilane and adding it to the mixed solution for reaction, and after the reaction is completed, adding ethanol to the reaction solution for centrifugal washing to remove unreacted ammonia and 3-aminopropyltriethoxysilane; collecting the precipitate after centrifugation, drying it, and grinding it to obtain the modified boron nitride.

2. The enhanced fire retardant coating according to claim 1, characterized in that: The enhanced fire retardant coating is composed of 53-57% epoxy resin, 11-13% 4,4-diaminodiphenylmethane, 1-3% bio-based flame retardant coating modified UiO-66 nanomaterials, and 27-32% modified boron nitride, by mass fraction.

3. The enhanced fire retardant coating according to claim 1, characterized in that: The bio-based flame retardant coating has 2 to 4 layers in total.

4. Use of the enhanced fire retardant coating according to any one of claims 1 to 3 in the field of fire prevention or flame retardancy.

5. An enhanced fireproof board based on modified boron nitride and bio-based modified UiO-66, characterized in that: The enhanced fireproof board is made by introducing the enhanced fireproof coating according to any one of claims 1 to 3 into a mold and then heating and curing it.

6. A method for preparing the fire retardant coating according to any one of claims 1 to 3, characterized in that: The preparation method comprises the following steps: S1. Preparation of base material: taking epoxy resin and curing agent, mixing to obtain base material; S2. Preparation of modified boron nitride: boron nitride is added to ethanol to obtain a mixed solution, and the pH of the mixed solution is adjusted with aqueous ammonia; a certain amount of 3-aminopropyltriethoxysilane is weighed and added to the mixed solution for reaction, and after the reaction is completed, ethanol is added to the reaction solution for centrifugal washing to remove unreacted ammonia and 3-aminopropyltriethoxysilane; the precipitate after centrifugation is collected, dried, and then ground to obtain modified boron nitride; S3. Preparation of bio-based flame retardant coating modified UiO-66 nanomaterials: taking the UiO-66 nanomaterials and immersing them in a chitosan acetic acid aqueous solution, then taking out the UiO-66 nanomaterials and immersing them in a phytic acid aqueous solution, and then taking out the UiO-66 nanomaterials; The UiO-66 nanomaterials after two-step impregnation are modified with one layer, and the two-step impregnation is repeated to obtain UiO-66 nanomaterials modified with multiple layers; S4. Preparation of flame retardant resin: take the modified multilayer UiO-66 nanomaterial, the modified boron nitride and the base material, mix them, heat and stir to disperse them evenly to obtain the fire retardant coating.

7. The preparation method according to claim 6, characterized in that: In step S1, the curing agent includes one or a mixture of polyamide, liquid acid anhydride, aliphatic polyamine, cardanol modified amine, and aromatic polyamine curing agents.

8. The preparation method according to claim 6, characterized in that: In step S2, the concentration of boron nitride in the mixed solution is 1-5wt%; the pH is adjusted to 7-12; the mass ratio of 3-aminopropyltriethoxysilane to boron nitride is 1-5:1; the reaction temperature is 55-70°C, and the reaction time is 3-6h.

9. The preparation method according to claim 6, characterized in that: In step S3, the concentration of chitosan in the chitosan acetic acid aqueous solution is 0.5-5wt%; the concentration of acetic acid in the chitosan acetic acid aqueous solution is 0.5-2wt%; the concentration of phytic acid in the phytic acid aqueous solution is 2-7wt%; and the immersion time is 1-10 minutes.

10. The preparation method according to claim 6, characterized in that: In step S4, the heating and stirring is stirring at 60-105° C. for 1.5-12 hours.

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