Preparation of green and environment-friendly bio-based CS (at) SA (at) ZIF-67 nano hybrid material epoxy intumescent fire retardant coating

Abstract

The invention discloses preparation of an environment-friendly bio-based CS (SA) ZIF-67 nano hybrid material epoxy intumescent fire retardant coating, and belongs to the technical field of fire retardant coatings. According to the preparation method disclosed by the invention, the interaction among active groups on biomass chitosan, sodium alginate and a metal organic framework ZIF-67 is utilized, a chitosan and sodium alginate biomass flame-retardant layer is loaded on the surface of the ZIF-67 in situ on the basis of an electrostatic adsorption or coordination complexing principle, and finally a green and environment-friendly bio-based CS (SA) ZIF-67 core-shell structure nano hybrid material is constructed; and the method is beneficial to improving agglomeration and improving the dispersity of the metal organic framework nano material, the compatibility of the metal organic framework nano material with a matrix and the flame-retardant efficiency of the metal organic framework nano material.

Description

Technical Field

[0001] The invention relates to the technical field of fire retardant coatings, and in particular to the preparation of a green and environmentally friendly bio-based CS@SA@ZIF-67 nano-hybrid material epoxy intumescent fire retardant coating. Background Art

[0002] Flame retardants are mainly used in the fields of plastics, rubber, textiles and coatings. There are many types of flame retardants, among which the most representative ones are halogen, phosphorus, nitrogen, silicon, inorganic hydroxide and intumescent flame retardants; at the same time, bio-based flame retardant materials have also become a hot spot in the field of flame retardancy. Bio-based flame retardant materials are environmentally friendly, renewable raw materials and biodegradable. Bio-based flame retardant materials such as cellulose, starch, cyclodextrin and chitosan have high carbon content and excellent carbon-forming properties. They can act as carbon sources in intumescent flame retardants and are currently a hot topic for research on new flame retardant materials. The flame retardant elements of bio-based materials are usually mainly C and N, but the content of flame retardant elements is not enough to make them play an ideal flame retardant role in the matrix. It is usually necessary to modify them to introduce other flame retardant elements, or to use them in combination with other flame retardants to achieve excellent synergistic flame retardant effects.

[0003] Metal-Organic Frameworks (MOFs) are a class of highly crystalline porous nanomaterials with a periodic network framework formed by the combination of metal ions and organic ligands, which usually show good catalytic oxidation and carbonization performance. Zeolite imidazolate framework (ZIF) is a subclass of metal-organic framework (MOFs), which is composed of metal nodes and imidazole derivatives as connectors and is usually used in polymer composites. The flame retardant effect of ZIF-67 nanomaterials without flame retardant modification is usually poor, so it needs to be flame retardantly modified to improve its flame retardant properties.

[0004] At present, CN 118772683 A discloses the preparation and application of a layer-by-layer self-assembled MOFs intumescent high-efficiency fire-retardant coating, in which ZIF-67 micro-nano material, polyethyleneimine (PEI) and sodium alginate are specifically selected for modification, and mixed with ammonium polyphosphate / calcium gluconate system to obtain a fire-retardant composite material. However, more development can be done for the modification of ZIF-67. In addition, in the technology related to the use of chitosan and sodium alginate, such as "Research on Flame Retardant Modification of Polyester Fabric and Its Combustion Mechanism", the use of biomass polyelectrolyte chitosan, alginate gel and one-dimensional inorganic nanomaterial sepiolite is disclosed, and flame-retardant polyester fabric is obtained by layer-by-layer self-assembly technology. However, its exploration of fabric flame retardancy uses a fabric as the substrate rather than a flowing liquid, and does not involve the use in flame-retardant coatings, and the application surface is not wide enough. Therefore, further exploration can be done for the chemical modification of ZIF and its application in flame-retardant coatings. Summary of the invention

[0005] Technical issues

[0006] Since ZIF-67 lacks flame retardant elements (such as phosphorus, nitrogen and silicon), the flame retardant effect of MOF alone is usually limited, so it needs to be chemically modified to further improve its flame retardant efficiency and broaden its scope of application.

[0007] Technical content

[0008] The present invention utilizes the interaction between biomass and active groups on the metal organic framework ZIF-67, loads a biomass flame retardant layer on the surface of ZIF-67 in situ based on the principle of electrostatic adsorption or coordination complexation, and performs flame retardant modification on the ZIF-67 nanomaterial. Subsequently, the flame retardant modified ZIF-67 nanomaterial is compounded with an epoxy resin system as a filler to obtain a composite fireproofing system with enhanced flame retardant effect.

[0009] The first aspect of the present invention provides a method for preparing a bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material, comprising the following steps:

[0010] (1) Immersing the ZIF-67 nanomaterial in a chitosan solution for a certain period of time, and collecting the precipitate by centrifugation;

[0011] (2) immersing the precipitate obtained in (1) in a sodium alginate solution for a certain period of time, collecting the precipitate by centrifugation, completing the loading modification, and obtaining a modified ZIF-67 sample;

[0012] (3) The modified ZIF-67 sample is dried to obtain the bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material.

[0013] In one embodiment of the present invention, the ZIF-67 nanomaterial in step (1) is prepared according to the following steps:

[0014] S1, dissolving 2-methylimidazole in a solvent and mixing evenly, adding the transition metal compound solution dropwise under stirring, and reacting under a certain temperature condition to obtain a suspension;

[0015] S2, centrifuging the suspension in step S1 to collect the precipitate, and washing it with methanol;

[0016] S3, drying the solid washed in step S2 to obtain a metal organic framework material.

[0017] Furthermore, in the preparation of ZIF-67 nanomaterials, the solvent is one or more of deionized water, acetone, ethanol, anhydrous methanol or N,N-dimethylformamide.

[0018] Furthermore, in the preparation of ZIF-67 nanomaterials, the transition metal compound in step S1 is one or more of metal cobalt salts such as cobalt nitrate, cobalt sulfate, and cobalt oxide.

[0019] Furthermore, in the preparation of ZIF-67 nanomaterials, the solvent in the transition metal compound solution in step S1 is one or more of deionized water, acetone, ethanol, anhydrous methanol or N,N-dimethylformamide.

[0020] Furthermore, in the preparation of ZIF-67 nanomaterials, the molar ratio of the transition metal compound to 2-methylimidazole in step S1 is 16:1 to 2:1.

[0021] Furthermore, in the preparation of ZIF-67 nanomaterials, the certain temperature in step S1 is 80-140°C.

[0022] Furthermore, in the preparation of ZIF-67 nanomaterials, the reaction time in step S1 is 2 to 14 hours.

[0023] In one embodiment of the present invention, the concentration of chitosan in the chitosan solution in step (1) is 0.5-5 wt%.

[0024] In one embodiment of the present invention, the concentration of chitosan in the chitosan solution in step (1) is 0.5-2 wt%.

[0025] In one embodiment of the present invention, the concentration of chitosan in the chitosan solution in step (1) is 0.5-1 wt%.

[0026] In one embodiment of the present invention, the concentration of chitosan in the chitosan solution in step (1) is 1 wt %.

[0027] In one embodiment of the present invention, the concentration of sodium alginate in the sodium alginate solution in step (2) is 0.4-3 wt %.

[0028] In one embodiment of the present invention, the concentration of sodium alginate in the sodium alginate solution in step (2) is 0.4-0.6 wt %.

[0029] In one embodiment of the present invention, the concentration of sodium alginate in the sodium alginate solution in step (2) is 0.4 wt %.

[0030] In one embodiment of the present invention, the immersion time in steps (1) and (2) is 3 to 20 minutes.

[0031] In one embodiment of the present invention, the immersion time in step (1) is 3 to 10 minutes.

[0032] In one embodiment of the present invention, the immersion time in step (2) is 15 to 20 minutes.

[0033] The second aspect of the present invention provides a method for preparing an epoxy intumescent fire retardant coating based on CS@SA@ZIF-67 core-shell structure nano hybrid material, comprising the following steps:

[0034] Ⅰ. Mix the CS@SA@ZIF-67 core-shell structure nano-hybrid material, acid source, gas source and acetone solution, and stir to form a dispersed system;

[0035] II. Preheating the epoxy resin; adding the epoxy resin to the dispersed system obtained in step (I) when the epoxy resin can flow, stirring until the mixture is uniform, and then volatilizing the solvent under a certain temperature condition to obtain a mixed system;

[0036] III. Take the curing agent and add it into the mixed system, stir and mix to obtain the epoxy intumescent fire retardant coating.

[0037] Furthermore, the acid source in step I is one or more of ammonium polyphosphate, ammonium sulfate, ammonium chloride or phytic acid.

[0038] Furthermore, the gas source in step I is one or more of ammonium polyphosphate, melamine, dicyandiamide, glycine or ammonium borate.

[0039] Furthermore, the mass proportion of the flame retardant modified ZIF-67 nanomaterial in the epoxy intumescent fire retardant coating is 0.5% to 6%.

[0040] Preferably, the mass proportion of the flame retardant modified ZIF-67 nanomaterial in the epoxy intumescent fire retardant coating is 0.5% to 2%.

[0041] Most preferably, the mass proportion of the flame retardant modified ZIF-67 nanomaterial in the epoxy intumescent fire retardant coating is 1%.

[0042] Furthermore, the mass proportion of the acid source in the epoxy intumescent fire retardant coating is 0.01% to 6%.

[0043] Furthermore, the mass proportion of the gas source in the epoxy intumescent fire retardant coating is 0.01% to 8%.

[0044] Specifically, optionally, the acid source and gas source in step I are ammonium polyphosphate.

[0045] Specifically, the mass proportion of ammonium polyphosphate in the epoxy intumescent fire retardant coating is 0.5-1.5%.

[0046] Furthermore, the mass proportion of epoxy resin in the epoxy intumescent fire retardant coating is 80-85%.

[0047] Furthermore, the certain temperature in step II is 60-100° C.; and the volatilization time is 1-3 hours.

[0048] Furthermore, the curing agent in step III is one or more of 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, diaminodiphenyl sulfone, methyltetrahydrophthalic anhydride, diethylenetriamine and ethylenediamine.

[0049] Furthermore, the mass proportion of the curing agent in the epoxy intumescent fire retardant coating is 15-20%.

[0050] The third aspect of the present invention is to provide the application of the epoxy intumescent fire retardant coating obtained by the above preparation method in the field of fire prevention and fire retardant product preparation.

[0051] The present invention has the following beneficial effects:

[0052] (1) The present invention utilizes the interaction between biomass chitosan, sodium alginate and the active groups on the metal organic framework ZIF-67, and in situ loads chitosan and sodium alginate biomass flame retardant layers on the surface of ZIF-67 based on the principle of electrostatic adsorption or coordination complexation, and finally constructs a green and environmentally friendly bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material, which is in line with the concept of sustainable green chemistry; in addition, the method also helps to improve agglomeration, and improve the dispersibility of metal organic framework nanomaterials, compatibility with the matrix and flame retardant efficiency.

[0053] (2) CS@SA@ZIF-67 core-shell structured nanohybrid material has excellent catalytic carbonization, smoke suppression and toxicity reduction, and heat resistance properties, and can act as a carbon source. In combination with the acid source / gas source of the traditional intumescent flame retardant system, such as ammonium polyphosphate, it not only plays a synergistic flame retardant role, but also improves the intumescent flame retardant properties of the fire retardant coating, promotes the coating to expand into a protective intumescent carbon layer at high temperature, can block heat and effectively control the spread of fire, thereby helping to extend precious rescue time. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 XRD patterns of ZIF-67 before and after modification;

[0055] Figure 2 FTIR images of ZIF-67 before and after modification;

[0056] Figure 3 These are the SEM images of ZIF-67 before and after modification, where a is the SEM image of ZIF-67 before modification, and b is the SEM image of ZIF-67 after modification. DETAILED DESCRIPTION

[0057] 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.

[0058] Source of raw materials

[0059] The ammonium polyphosphate (APP) used in the following examples has a purity of 99.8% and was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0060] Example 1

[0061] The preparation method of the epoxy intumescent fire retardant coating based on the bio-based CS@SA@ZIF-67 core-shell structure nano hybrid material comprises the following steps:

[0062] 1. Preparation of ZIF-67 nanomaterials

[0063] (1) 6.552 g of cobalt nitrate and 3.696 g of 2-methylimidazole were dissolved in 60 mL of methanol to form a cobalt nitrate solution and a 2-methylimidazole solution, respectively. The 2-methylimidazole solution was then added dropwise to the cobalt nitrate solution under stirring, and the mixture was reacted at 120° C. for 4 h to obtain a suspension;

[0064] (2) The suspension in step (1) was centrifuged at a speed of 6000 r / min for 8 min to collect the precipitate, and the precipitate was washed three times with methanol;

[0065] (3) Drying the washed solid in step (2) in an oven at 80° C. for 12 h to obtain ZIF-67 nanomaterials.

[0066] 2. Preparation of biomass modification solution

[0067] 1 g of chitosan was dissolved in 100 mL of 1% acetic acid solution to prepare a chitosan solution with a concentration of 1 wt %; 0.4 g of sodium alginate was dissolved in 100 mL of deionized water to prepare a sodium alginate solution with a concentration of 0.4 wt %.

[0068] 3. Preparation of CS@SA@ZIF-67 core-shell structured nanohybrid materials

[0069] (1) The ZIF-67 nanomaterial was immersed in the prepared 1 wt% chitosan solution for 5 min, and the precipitate was collected by centrifugation;

[0070] (2) immersing the precipitate obtained in (1) in a prepared 0.4 wt% sodium alginate solution for 20 min, collecting the precipitate by centrifugation, and completing the loading modification;

[0071] (3) The loaded modified ZIF-67 sample was placed in an oven at 90°C and dried for 12 h to obtain the CS@SA@ZIF-67 core-shell structured nanohybrid material.

[0072] 4. Preparation of epoxy intumescent fire retardant coating

[0073] (1) 0.5 g of bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material, 5 mL of APP aqueous solution (containing 0.5 g of APP) and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0074] (2) Preheat 40.2365 g of epoxy resin (EP) in an oven at 80° C. for 10 min; add the epoxy resin to the dispersion system described in step (1) when the epoxy resin is flowable, and stir for 35 min;

[0075] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0076] (4) Add 8.7635 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nanohybrid material.

[0077] Example 2

[0078] The preparation method of the epoxy intumescent fire retardant coating based on the bio-based CS@SA@ZIF-67 core-shell structure nano hybrid material comprises the following steps:

[0079] Steps 1 to 3 are prepared by referring to the steps in Example 1.

[0080] 4. Preparation of epoxy intumescent fire retardant coating

[0081] (1) 0.5 g of bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0082] (2) Preheat 40.6471 g of epoxy resin (EP) in an oven at 80° C. for 10 min; add the epoxy resin to the dispersion system described in step (1) when the epoxy resin is flowable, and stir for 35 min;

[0083] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0084] (4) Add 8.8529 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nanohybrid material.

[0085] Example 3

[0086] The preparation method of the epoxy intumescent fire retardant coating based on the bio-based CS@SA@ZIF-67 core-shell structure nano hybrid material comprises the following steps:

[0087] Steps 1 to 3 are prepared by referring to the steps in Example 1.

[0088] 4. Preparation of epoxy intumescent fire retardant coating

[0089] (1) 0.25 g of bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0090] (2) Preheat 40.8524 g of epoxy resin (EP) in an oven at 80° C. for 10 min; add the epoxy resin to the dispersion system described in step (1) when the epoxy resin is flowable, and stir for 35 min;

[0091] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0092] (4) Add 8.8976 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nanohybrid material.

[0093] Example 4

[0094] The preparation method of the epoxy intumescent fire retardant coating based on the bio-based CS@SA@ZIF-67 core-shell structure nano hybrid material comprises the following steps:

[0095] Steps 1 to 3 are prepared by referring to the steps in Example 1.

[0096] 4. Preparation of epoxy intumescent fire retardant coating

[0097] (1) 1.0 g of bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0098] (2) Preheat 40.2365 g of epoxy resin (EP) in an oven at 80° C. for 10 min; add the epoxy resin to the dispersion system described in step (1) when the epoxy resin is flowable, and stir for 35 min;

[0099] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0100] (4) Add 8.7635 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nanohybrid material.

[0101] Comparative Example 1

[0102] 41.0577 g of epoxy resin (EP) was preheated in an oven at 80°C for 10 min, and added into the flask when the epoxy resin was able to flow. 8.9423 g of 4,4-diaminodiphenylmethane was stirred continuously for 2 min to obtain an epoxy fire retardant coating.

[0103] Comparative Example 2

[0104] 0.5 g of ZIF-67 nanomaterial and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed ZIF-67 system; 40.6471 g of epoxy resin (EP) was preheated in an oven at 80°C for 10 min and added to the flask when the epoxy resin was able to flow. 8.8529 g of 4,4-diaminodiphenylmethane was stirred for 2 min to obtain an epoxy intumescent fire retardant coating.

[0105] Comparative Example 3

[0106] Steps 1 and 2 are prepared by referring to the steps in Example 1.

[0107] 3. Preparation of CS@ZIF-67 core-shell structured nanohybrid materials

[0108] The ZIF-67 nanomaterial was immersed in the prepared 1wt% chitosan solution for 5 minutes, and the precipitate was collected by centrifugation; the loaded and modified ZIF-67 sample was placed in a 90°C oven and dried for 12 hours to obtain the CS@SA@ZIF-67 core-shell structure nanohybrid material;

[0109] 4. Preparation of epoxy intumescent fire retardant coating

[0110] (1) 0.5 g of bio-based CS@ZIF-67 core-shell structured nanohybrid material and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0111] (2) Preheat 40.6471 g of epoxy resin (EP) in an oven at 80°C for 10 min and add it into the flask when the epoxy resin is flowable;

[0112] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0113] (4) Add 8.8529 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nanohybrid material.

[0114] Comparative Example 4

[0115] Steps 1 and 2 are prepared by referring to the steps in Example 1.

[0116] 3. Preparation of SA@ZIF-67 core-shell structured nanohybrid materials

[0117] The ZIF-67 nanomaterial was immersed in the prepared 0.4wt% sodium alginate solution for 20 minutes, and the precipitate was collected by centrifugation to complete the loading modification; the loaded ZIF-67 sample was placed in a 90°C oven and dried for 12 hours to obtain the SA@ZIF-67 core-shell structure nanohybrid material;

[0118] 4. Preparation of epoxy intumescent fire retardant coating

[0119] (1) 0.5 g of bio-based SA@ZIF-67 core-shell structured nanohybrid material and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0120] (2) Preheat 40.6471 g of epoxy resin (EP) in an oven at 80°C for 10 min and add it into the flask when the epoxy resin is flowable;

[0121] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0122] (4) Add 8.8529 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nanohybrid material.

[0123] Comparative Example 5

[0124] 0.5g ZIF-67 nanomaterial, 5mL APP aqueous solution (containing 0.5g APP) and 60mL acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniform ZIF-67 dispersion system; 40.2365g epoxy resin (EP) was preheated in an oven at 80°C for 10min and added to the flask when the epoxy resin could flow. 8.7635g 4,4-diaminodiphenylmethane was added to the flask, stirred continuously for 2min, poured into the template, and dried at 100°C for 2h, and at 150°C for 2h, and demolded after cooling to obtain the epoxy fire retardant coating.

[0125] Comparative Example 6

[0126] 0.5g ZIF-67 nanomaterial, 5mL APP and calcium gluconate mixed aqueous solution (ammonium polyphosphate: calcium gluconate = 4:1, total 0.5g) and 60mL acetone solution were mixed in a three-necked flask, and ultrasonic stirring was performed to form a uniform ZIF-67 dispersion system; 40.2365g epoxy resin (EP) was preheated in an oven at 80°C for 10min, and added to the flask when the epoxy resin could flow. 8.7635g 4,4-diaminodiphenylmethane was added to the flask, stirred continuously for 2min, poured into the template, and dried at 100°C for 2h, and at 150°C for 2h, and demolded after cooling to obtain the epoxy fire retardant coating.

[0127] Comparative Example 7

[0128] Step 1 is prepared by referring to the steps in Example 1.

[0129] 2. Preparation of biomass modification solution

[0130] 1 g of polyethyleneimine (PEI) was added to 100 mL of deionized water to prepare a polyethyleneimine solution with a concentration of 1 wt %; 0.4 g of sodium alginate was dissolved in 100 mL of deionized water to prepare a sodium alginate solution with a concentration of 0.4 wt %.

[0131] 3. Preparation of PEI@SA@ZIF-67 core-shell structured nanohybrid materials

[0132] (1) The ZIF-67 nanomaterial was immersed in the prepared 1 wt % polyethyleneimine solution for 5 min, and the precipitate was collected by centrifugation;

[0133] (2) immersing the precipitate obtained in (1) in a prepared 0.4 wt% sodium alginate solution for 20 min, collecting the precipitate by centrifugation, and completing the loading modification;

[0134] (3) The loaded modified ZIF-67 sample was placed in an oven at 90°C and dried for 12 h to obtain the PEI@SA@ZIF-67 core-shell structured nanohybrid material.

[0135] 4. Preparation of epoxy intumescent fire retardant coating

[0136] (1) 0.5 g of bio-based PEI@SA@ZIF-67 nanohybrid material, 5 mL of APP aqueous solution (containing 0.5 g of APP) and 60 mL of acetone solution were mixed in a three-necked flask and ultrasonically stirred to form a uniformly dispersed system of modified ZIF-67;

[0137] (2) Preheat 40.2365 g of epoxy resin (EP) in an oven at 80° C. for 10 min; add the epoxy resin to the dispersion system described in step (1) when the epoxy resin is flowable, and stir for 35 min;

[0138] (3) placing the mixed system in (2) in an oil pan and volatilizing at 105°C for 3 h;

[0139] (4) Add 8.7635 g of 4,4-diaminodiphenylmethane and continue stirring for 2 min to obtain an epoxy intumescent fire retardant coating based on PEI@SA@ZIF-67 core-shell structure nanohybrid material.

[0140] Comparative Example 8

[0141] The ZIF-67 nanomaterial, 1wt% ZIF-67 / CS / SA blend solution (ZIF-67 nanomaterial: chitosan solution: sodium alginate solution = 2.5:2.5:1, 0.5g in total) and 60mL acetone solution were mixed in a three-necked flask, and ultrasonically stirred to form a uniform ZIF-67 dispersion system; 40.6471gg epoxy resin (EP) was preheated in an oven at 80°C for 10min, and added to the flask when the epoxy resin could flow. 8.8529g 4,4-diaminodiphenylmethane was added to the flask, stirred continuously for 2min, poured into the template, and dried at 100°C for 2h, and dried at 150°C for 2h, and demolded after cooling to obtain the epoxy fire retardant coating.

[0142] Comparative Example 9

[0143] The preparation was carried out according to the steps and parameters in Example 1, wherein only the concentration of the sodium alginate solution in step 2 was adjusted to 1 wt %, and then the immersion was carried out, and the nanoparticles eventually disintegrated and could not be prepared subsequently.

[0144] Comparative Example 10

[0145] The preparation was carried out with reference to the steps and parameters in Example 1, wherein only the concentration of the sodium alginate solution in step 2 was adjusted to 2 wt % and then impregnated. As a result, the nanoparticles eventually disintegrated and subsequent preparation could not be carried out.

[0146] Comparative Example 11

[0147] The preparation was carried out according to the steps and parameters in Example 1, wherein only (1) and (2) in step 2 were repeated once more to obtain a ZIF-67 sample loaded with two modified layers. Eventually, the nanoparticles disintegrated and subsequent preparation could not be performed.

[0148] Comparative Example 12

[0149] The preparation was carried out according to the steps and parameters in Example 1, wherein only (1) and (2) in step 2 were repeated twice to obtain a ZIF-67 sample loaded with three modified layers. Eventually, the nanoparticles disintegrated and subsequent preparation could not be carried out.

[0150] Table 1 Sample formula of Examples 1 to 4 and Comparative Examples 1 to 8

[0151]

[0152]

[0153] The fire retardant coatings prepared in Examples 1 to 4 and Comparative Examples 1 to 8 were poured into a mold and then heated and cured (dried at 100°C for 2 hours and dried at 150°C for 2 hours) to obtain composite material samples, which were then subjected to cone calorimetry testing. The samples were mounted on a 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 the heat release rate, total heat release and other parameters of the material were calculated. After the preset test time was reached, the thermal radiation of the radiation cone was stopped.

[0154] The test results are shown in the following table:

[0155] Table 2 Cone calorimetry test data of Examples 1 to 4 and Comparative Examples 1 to 8

[0156]

[0157]

[0158] Among them, 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 sum of the heat released from the material from ignition to the flame extinction. The larger the value, the more intense the combustion reaction. 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 intense the combustion reaction. The same conclusion as above can be drawn from THR and MASS.

[0159] The results show that compared with pure epoxy resin (Comparative Example 1), the PHRR of the unmodified intumescent nano fire retardant coating (Comparative Example 2) is reduced, indicating that the addition of nanomaterials improves the flame retardant properties of epoxy resin. Compared with pure epoxy resin (Comparative Example 1) and unmodified intumescent nano fire retardant coating (Comparative Example 2), the PHRR of the epoxy intumescent fire retardant coating based on bio-based CS@SA@ZIF-67 core-shell structure nano hybrid material (Examples 2 to 4) is significantly reduced, proving that the flame retardant properties of the flame retardant modified ZIF-67 are enhanced.

[0160] For Examples 2 to 4, the more CS@SA@ZIF-67 is contained, the better the flame retardant performance is. However, the performance of Example 2 is similar to that of Example 4, and the ideal effect has been achieved. In order to reduce the cost, the mass fraction of the bio-based CS@SA@ZIF-67 core-shell structure nano hybrid material prepared by the present invention in the intumescent fire retardant coating should be 1.0%. APP (Example 1) is added on the basis of CS and SA flame retardant modification. Compared with Example 2, APP is used as an acid source and a gas source in this flame retardant system, which improves the flame retardancy of the composite material and significantly reduces its PHRR.

[0161] Compared with pure epoxy resin (Comparative Example 1), the PHRR of epoxy resin composites of CS-modified ZIF-67, SA-modified ZIF-67, APP-modified ZIF-67, and APP / calcium gluconate-modified ZIF-67 (Comparative Examples 3 to 6) are all reduced, but compared with Example 1, their PHRR is still at a relatively high level and their flame retardant properties are poor.

[0162] Comparative Example 7 is a ZIF-67 modified by PEI and SA, and APP is added on the basis of flame retardant modification. Its PHRR is significantly increased compared with Example 1, and the flame retardant performance is poor.

[0163] Comparative Example 8 is a composite material formed by blending ZIF-67, CS, and SA (ZIF-67:CS:SA=2.5:2.5:1) with epoxy resin. The PHRR of the composite material is much higher than that of the epoxy intumescent fire retardant coating based on the bio-based CS@SA@ZIF-67 core-shell structure nano-hybrid material (Example 2), which proves that the flame retardant modification of the nanomaterial is better than the direct physical blending, and the flame retardant performance of the fire retardant coating prepared by the present invention is improved due to the modification of the nanomaterial.

[0164] It can be seen from Comparative Examples 9 to 12 that the concentration of the sodium alginate solution and the number of immersions of the biomass modified solution in the preparation of the CS@ZIF-67 core-shell structured nanohybrid material have an important influence on the structure of the core-shell structured nanohybrid material. The concentration of the sodium alginate solution should not be too high and should be maintained at 0.4wt%. At the same time, the number of immersion modifications should not be too many and only one immersion modification is sufficient.

[0165] 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. A method for preparing a bio-based CS@SA@ZIF-67 core-shell structure nanohybrid material, characterized in that: The following steps are involved: (1) impregnating the ZIF-67 nanomaterial in a 0.5-1 wt% chitosan solution and collecting the precipitate by centrifugation; (2) immersing the precipitate obtained in (1) in a 0.4-0.6 wt % sodium alginate solution, collecting the precipitate by centrifugation, completing the loading modification, and obtaining a modified ZIF-67 sample; (3) drying the modified ZIF-67 sample to obtain the bio-based CS@SA@ZIF-67 core-shell structured nanohybrid material; The ZIF-67 nanomaterial described in step (1) is prepared according to the following steps: S1. Dissolve 2-methylimidazole in a solvent and mix well, add cobalt nitrate solution dropwise under stirring, and react under a certain temperature condition to obtain a suspension; S2, centrifuging the suspension in step S1 to collect the precipitate, and washing it with methanol; S3, drying the solid washed in step S2 to obtain a metal organic framework material.

2. The preparation method according to claim 1, characterized in that: In the preparation of ZIF-67 nanomaterials, the molar ratio of the transition metal compound to 2-methylimidazole in step S1 is 16:1 to 2:1; the certain temperature in step S1 is 80 to 140° C.; and the reaction time in step S1 is 2 to 14 hours.

3. The preparation method according to claim 1, characterized in that: The immersion time in step (1) is 3 to 10 minutes.

4. The preparation method according to claim 1, characterized in that The immersion time in step (2) is 15 to 20 minutes.

5. A method for preparing an epoxy intumescent fire retardant coating based on the CS@SA@ZIF-67 core-shell structure nano-hybrid material according to any one of claims 1 to 4, characterized in that: The following steps are involved: Ⅰ. Mix the CS@SA@ZIF-67 core-shell structure nanohybrid material, ammonium polyphosphate and acetone solution, and stir to form a dispersed system; II. Preheating the epoxy resin; adding the epoxy resin to the dispersed system obtained in step (I) when the epoxy resin can flow, stirring until the mixture is uniform, and then volatilizing the solvent under a certain temperature condition to obtain a mixed system; III. Take the curing agent and add it into the mixed system, stir and mix to obtain the epoxy intumescent fire retardant coating.

6. The preparation method according to claim 5, characterized in that: The mass proportion of flame retardant modified ZIF-67 nanomaterials in epoxy intumescent fire retardant coatings is 0.5% to 2%.

7. The preparation method according to claim 5, characterized in that: The mass proportion of ammonium polyphosphate in epoxy intumescent fire retardant coating is 0.5-1.5%.

8. The preparation method according to claim 5, characterized in that: The mass proportion of epoxy resin in epoxy intumescent fire retardant coating is 80-85%.

9. The preparation method according to claim 5, characterized in that: The curing agent in step III is one or more of 4,4-diaminodiphenylmethane, 4,4-diaminodiphenyl ether, diaminodiphenyl sulfone, methyltetrahydrophthalic anhydride, diethylenetriamine and ethylenediamine; the mass proportion of the curing agent in the epoxy intumescent fire retardant coating is 15-20%.

10. Use of the epoxy intumescent fire retardant coating prepared by the preparation method according to any one of claims 5 to 9 in the field of fire prevention and fire retardant product preparation.

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