A preparation method and product of modified spray polyurea

Abstract

The present invention belongs to the technical field of spray polyurea materials, specifically to a method for preparing a modified spray polyurea and its product. The coupling agent-modified zinc cobaltate @ZnCe-LDH, prepared by a specific method, is compounded with melamine polyphosphate and found to have a synergistic effect, effectively reducing the delayed release and improving flame retardancy. Furthermore, the use of a specific coupling agent improves the dispersibility of the zinc cobaltate @ZnCe-LDH while also improving the mechanical properties of the polyurea material.

Description

Technical Field

[0001] The present invention belongs to the technical field of spray polyurea materials, and more specifically relates to a preparation method and product of modified spray polyurea. Background Art

[0002] Spray polyurea materials are widely used in roofing waterproofing, petrochemical tank corrosion protection, and foam prop protection due to their solvent-free, environmentally friendly nature, high mechanical strength, fast construction speed, and excellent corrosion and waterproofing properties. When polyurea is exposed to high heat, its macromolecular chains break, and the resulting small hydrocarbon molecules undergo a violent oxidation reaction with oxygen, causing combustion. The heat generated by the combustion exacerbates the decomposition and combustion of the polyurea material.

[0003] Melamine polyphosphate (MPP), a nitrogen-based flame retardant, is widely used in flame retardant applications for materials such as plastics and synthetic rubber due to its advantages of being drip-free, non-toxic, and having low smoke density. Dai Jing et al. coated ADP with melamine-formaldehyde (MF) resin to obtain MF@ADP microcapsules, which were then compounded with MPP at a mass ratio of 2:1. When the mass fraction of the compounded flame retardant was 25%, the limiting oxygen index (LOI) of the flame-retardant low-density polyethylene (PE-LD) composite material increased to 30.6%, forming a more stable P / N / O polymer carbon layer, reducing the amount of smoke generated by PE-LD and enabling the material's flame retardancy to reach UL 94V-0.

[0004] CN115260819B discloses a method for preparing flame-retardant spray polyurea and a product thereof. The flame-retardant spray polyurea is composed of component A and component B. The raw materials of component A are proportioned as follows by weight: 40-60 parts of polyether polyol; 40-60 parts of isocyanate; the raw materials of component B are proportioned as follows by weight: 35-55 parts of amino-terminated polyether; 30-40 parts of chain extender; 20-40 parts of composite flame retardant; 0.1-0.5 parts of dispersant; 0.5-1.0 parts of defoamer; the composite flame retardant is proportioned as follows by weight percentage: 15-25 parts of hexaphenoxycyclotriphosphazene; 15-25 parts of Ti3C2Tx-loaded cerium oxide, ytterbium oxide and molybdenum oxide; wherein the loading amount of cerium oxide is 3-7wt%; the loading amount of ytterbium oxide is 4-8wt%; and the loading amount of molybdenum oxide is 2-6wt%; 10-20 parts of halloysite nanotubes; and 10-20 parts of DOPO. The flame retardant spray polyurea of the present invention has excellent mechanical properties and flame retardant properties and has a strong application prospect. However, the invention only has good flame retardant properties by adding multiple flame retardant ingredients, which is costly.

[0005] CN114874689A discloses a primer-free spray polyurea material and a preparation method thereof, belonging to the technical field of paint spray polyurea materials. The primer-free spray polyurea material of the present invention is composed of component A and component B, with the volume ratio of component A to component B being 1:1; component A includes an isocyanate, a modified polyol, and a reactive diluent; component B includes a chain extender, a modified chain extender, an amino-terminated polyether, a color paste, an antioxidant, a UV absorber, and a light stabilizer; the modified polyol is a graft copolymer of a silane coupling agent containing an isocyanate group and a trifunctional polyol; and the modified chain extender is a copolymer of an epoxy silane coupling agent and a secondary amino chain extender. The primer-free spray polyurea material of the present invention has excellent adhesion to various metals without the need for a matching primer, and also has excellent physical and mechanical properties, corrosion resistance, media and chemical resistance, and aging resistance, which can significantly improve construction efficiency, safety performance, and quality stability. The invention is able to have excellent mechanical properties by adding coupling agents and grafting modifications.

[0006] The flame retardant material prepared by the specific method of the present invention is applied to polyurea, has low preparation cost, significantly improves the flame retardant properties of the polyurea material, and also improves the mechanical properties of the polyurea material. Summary of the Invention

[0007] The present invention aims to overcome the defects and shortcomings of the prior art by providing a method for preparing and producing a modified spray polyurea. The coupling agent-modified zinc cobaltate@ZnCe-LDH, prepared by a specific method, is found to exhibit a synergistic effect when combined with melamine polyphosphate, effectively reducing the delayed release and enhancing flame retardancy. Furthermore, the use of a specific coupling agent improves the dispersibility of the zinc cobaltate@ZnCe-LDH while also enhancing the mechanical properties of the polyurea.

[0008] The object of the present invention is to provide a method for preparing a modified spray polyurea.

[0009] Another object of the present invention is to provide a modified spray polyurea.

[0010] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0011] A method for preparing a modified spray polyurea, comprising the following steps:

[0012] (1) The preparation method of component A is as follows:

[0013] Add polyether polyol into the reaction kettle, dehydrate under reduced pressure at 110-120°C for 2-4 hours, cool to 50°C, add isocyanate, stir evenly, then heat to 75-85°C, keep warm for 2-4 hours, degas and cool to obtain component A;

[0014] (2) The preparation method of component B is as follows:

[0015] Add the amino-terminated polyether, chain extender, composite flame retardant, dispersant and defoamer into a reaction kettle, heat to 65-85° C. for high-speed dispersion, stir for 30-50 min, and rotate at 700-900 r / min to obtain component B;

[0016] (3) Stir components A and B separately and evenly, then mix them in a volume ratio of 1:1, with the equivalent ratio of components A and B being such that the isocyanate index is between 0.95 and 1.05. After stirring evenly, spray them with a polyurea sprayer to obtain a modified spray polyurea;

[0017] The flame retardant consists of melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH; the mass ratio of the melamine polyphosphate to the coupling agent-modified zinc cobaltate @ZnCe-LDH is 1:3-5.

[0018] In the present invention, the preferred technical solution is that in step (1), the raw materials of component A are proportioned by weight as follows:

[0019] 40-50 parts of polyether polyol;

[0020] 60-70 parts of isocyanate

[0021] In a further preferred technical solution, the polyether polyol is polyether polyol N330; and the isocyanate is at least one of toluene diisocyanate (TDI), dicyclohexylmethane diisocyanate (HMDI), and lysine diisocyanate (LDI).

[0022] In the present invention, the preferred technical solution is that the raw materials of the B component are proportioned by weight as follows:

[0023] 50-70 parts of amino-terminated polyether;

[0024] 35-45 parts of chain extender;

[0025] Dispersant 0.2-0.6 parts;

[0026] 1-1.4 parts of defoaming agent.

[0027] 10 to 20 parts of flame retardant.

[0028] In a further preferred technical solution, the amino-terminated polyether is amino-terminated polyether D-2000; the chain extender is one or more of 1,4-bis-sec-butylaminobenzene, 4,4′-bis-sec-aminodiphenylmethane, and N,N′-bis-sec-pentylcyclohexanediamine; the dispersant is Disperbyk 162; and the defoamer is Airex 930.

[0029] In the present invention, a further preferred technical solution is that the preparation method of the coupling agent-modified zinc cobaltate @ZnCe-LDH comprises the following steps:

[0030] (a) drying corn stalks at 60-80° C. and grinding them to pass through a 200-mesh sieve;

[0031] (b) adding the straw, zinc salt, cobalt salt and urea obtained in step (a) to deionized water and ultrasonically treating for 30 to 50 minutes; then transferring to a hydrothermal kettle, reacting at 100 to 140° C. for 12 to 16 hours, centrifuging, washing, and vacuum drying at 60 to 90° C. for 10 to 16 hours, and then calcining at 500 to 600° C. in an air atmosphere for 4 to 8 hours, and grinding to obtain zinc cobaltate;

[0032] (c) adding the zinc cobaltate, zinc salt, cerium salt, and urea obtained in step (b) to deionized water and ultrasonically treating for 20 to 40 minutes; then transferring to a hydrothermal reactor, reacting at 100 to 140° C. for 12 to 16 hours, centrifuging, washing, and vacuum drying at 60 to 90° C. for 10 to 16 hours to obtain zinc cobaltate@ZnCe-LDH;

[0033] (d) adding the zinc cobaltate@ZnCe-LDH and coupling agent obtained in step (c) to ethanol and ultrasonically dispersing them for 20 to 40 minutes; then reacting at 50 to 70° C. for 4 to 8 hours, filtering, washing, and vacuum drying at 70 to 90° C. for 8 to 16 hours to obtain coupling agent-modified zinc cobaltate@ZnCe-LDH.

[0034] In certain embodiments, in step (b), the ratio of the straw, zinc salt, cobalt salt and urea obtained in step (1) is: 0.2-0.4 g: 1 mol: 3-4 mol: 8-16 mol; the zinc salt is at least one of zinc nitrate, zinc chloride and zinc acetate; and the cobalt salt is one of cobalt nitrate, cobalt chloride and cobalt acetate.

[0035] In certain embodiments, in step (c), the ratio of the zinc cobaltate, zinc salt, cerium salt and urea obtained in step (b) is: 15 g: 10 mmol: 25 mmol~35 mmol: 60~150 mmol: the zinc salt is at least one of zinc nitrate, zinc chloride and zinc acetate; the cerium salt is at least one of cerium nitrate, cerium chloride and cerium acetate.

[0036] In certain embodiments, in step (d), the mass ratio of the zinc cobaltate-loaded ZnCe-LDH obtained in step (c) to the coupling agent is 100:4-8; and the coupling agent is at least one of triethanolamine borate and KH-560.

[0037] In certain embodiments, in step (d), the coupling agent is triethanolamine borate and KH-560; the mass ratio of triethanolamine borate to KH-560 is 3:1.

[0038] The modified spray polyurea is prepared based on the above-mentioned preparation method of the modified spray polyurea.

[0039] The present invention has the following beneficial effects:

[0040] (1) By using corn straw as a template to prepare zinc cobalt oxide, the pore structure of the straw is retained, so that when ZnCe-LDH is loaded, it can be loaded both inside and outside the pores. Compared with simple mixing, the flame retardant properties of the spray polyurea are significantly improved;

[0041] (2) Modification of the coupling agent by zinc cobaltate @ZnCe-LDH can improve its dispersibility, thereby affecting the flame retardant and mechanical properties of the spray polyurea; and the modification of the coupling agent also introduces B and / or Si, thereby promoting the improvement of the performance of the spray polyurea;

[0042] (3) By combining melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH, the two synergistically improve the flame retardant properties of spray polyurea. DETAILED DESCRIPTION

[0043] The present invention is further described below with reference to specific examples, which, however, are not intended to limit the present invention in any way. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the art.

[0044] Unless otherwise specified, the reagents and materials used in the following examples were commercially available.

[0045] Example 1

[0046] A method for preparing a modified spray polyurea, comprising the following steps:

[0047] (1) The preparation method of component A is as follows:

[0048] Add polyether polyol into the reaction kettle, dehydrate under reduced pressure at 120°C for 2 hours, cool to 50°C, add isocyanate, stir evenly, then heat to 85°C, keep warm for 2 hours, degas and cool to obtain component A;

[0049] (2) The preparation method of component B is as follows:

[0050] Add the amino-terminated polyether, chain extender, composite flame retardant, dispersant and defoamer into a reactor, heat to 85° C. for high-speed dispersion, stir for 30 min, and rotate at 900 r / min to obtain component B.

[0051] (3) Stir components A and B separately and evenly, then mix them in a volume ratio of 1:1, with the equivalent ratio of components A and B being such that the isocyanate index is between 1.05, and spray them with a polyurea sprayer after stirring evenly to obtain a modified spray polyurea;

[0052] The flame retardant is composed of melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH; the mass ratio of the melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH is 1:5;

[0053] The raw materials of the A component are proportioned as follows by weight:

[0054] 50 parts of polyether polyol; the polyether polyol is polyether polyol N330;

[0055] 60 parts of isocyanate; the isocyanate is dicyclohexylmethane diisocyanate (HMDI);

[0056] The raw materials of the B component are proportioned as follows by weight:

[0057] 70 parts of amino-terminated polyether; the amino-terminated polyether is amino-terminated polyether D-2000;

[0058] 35 parts of chain extender; the chain extender is N,N′-bis-secondary pentylcyclohexanediamine;

[0059] 0.6 parts of dispersant; the dispersant is Disperbyk 162;

[0060] 1 part of defoaming agent; the defoaming agent is Airex 930;

[0061] 20 parts of flame retardant;

[0062] The preparation method of the coupling agent-modified zinc cobaltate @ZnCe-LDH comprises the following steps:

[0063] (a) Corn stalks were dried at 70°C and ground to pass through a 200-mesh sieve;

[0064] (b) adding 0.3 g of the straw obtained in step (a), 1 mol of zinc nitrate, 3.5 mol of cobalt acetate, and 12 mol of urea to 200 mL of deionized water and ultrasonically treating for 40 min; then transferring to a hydrothermal reactor, reacting at 120° C. for 14 h, centrifuging, washing, and vacuum drying at 80° C. for 14 h, and then calcining at 550° C. in air atmosphere for 6 h, and grinding to obtain zinc cobaltate;

[0065] (c) 15 g of zinc cobaltate obtained in step (b), 10 mmol of zinc acetate, 30 mmol of cerium nitrate, and 100 mmol of urea were added to 150 mL of deionized water and sonicated for 30 min; then transferred to a hydrothermal reactor, reacted at 120°C for 14 h, centrifuged, washed, and vacuum-dried at 80°C for 12 h to obtain zinc cobaltate@ZnCe-LDH;

[0066] (d) 100 g of zinc cobaltate@ZnCe-LDH obtained in step (c) and 6 g of KH-560 were added to 200 mL of ethanol and ultrasonically dispersed for 30 min; then, the mixture was reacted at 60°C for 5 h, filtered, washed, and vacuum dried at 80°C for 12 h to obtain coupling agent-modified zinc cobaltate@ZnCe-LDH.

[0067] Example 2

[0068] A method for preparing a modified spray polyurea, comprising the following steps:

[0069] (1) The preparation method of component A is as follows:

[0070] Add polyether polyol into the reaction kettle, dehydrate under reduced pressure at 115°C for 3 hours, cool to 50°C, add isocyanate, stir evenly, then heat to 80°C, keep warm for 3 hours, degas and cool to obtain component A;

[0071] (2) The preparation method of component B is as follows:

[0072] Add the amino-terminated polyether, chain extender, composite flame retardant, dispersant and defoamer into a reactor, heat to 75° C. for high-speed dispersion, stir for 40 min, and rotate at 800 r / min to obtain component B.

[0073] (3) Stir components A and B separately and evenly, then mix them in a volume ratio of 1:1, with the equivalent ratio of components A and B being such that the isocyanate index is between 1, and after stirring evenly, spray them with a polyurea sprayer to obtain a modified spray polyurea;

[0074] The flame retardant is composed of melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH; the mass ratio of the melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH is 1:4;

[0075] The raw materials of the A component are proportioned as follows by weight:

[0076] 45 parts of polyether polyol; the polyether polyol is polyether polyol N330;

[0077] 65 parts of isocyanate; the isocyanate is dicyclohexylmethane diisocyanate (HMDI);

[0078] The raw materials of the B component are proportioned as follows by weight:

[0079] 60 parts of amino-terminated polyether; the amino-terminated polyether is amino-terminated polyether D-2000;

[0080] 40 parts of chain extender; the chain extender is 4,4'-bis-secondary aminodiphenylmethane;

[0081] 0.4 parts of dispersant; the dispersant is Disperbyk 162;

[0082] 1.2 parts of defoaming agent; the defoaming agent is Airex 930;

[0083] 15 parts of flame retardant;

[0084] The preparation method of the coupling agent-modified zinc cobaltate@ZnCe-LDH is the same as the preparation process and conditions in Example 1.

[0085] Example 3

[0086] A method for preparing a modified spray polyurea, comprising the following steps:

[0087] (1) The preparation method of component A is as follows:

[0088] Add polyether polyol into the reaction kettle, dehydrate under reduced pressure at 110°C for 4 hours, cool to 50°C, add isocyanate, stir evenly, then heat to 75°C, keep warm for 4 hours, degas and cool to obtain component A;

[0089] (2) The preparation method of component B is as follows:

[0090] Add the amino-terminated polyether, chain extender, composite flame retardant, dispersant and defoamer into a reactor, heat to 65° C. for high-speed dispersion, stir for 50 min, and rotate at 700 r / min to obtain component B.

[0091] (3) Stir components A and B separately and evenly, then mix them in a volume ratio of 1:1, with the equivalent ratio of components A and B being such that the isocyanate index is between 0.95, and spray them with a polyurea sprayer after stirring evenly to obtain a modified spray polyurea;

[0092] The flame retardant is composed of melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH; the mass ratio of the melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH is 1:3;

[0093] The raw materials of the A component are proportioned as follows by weight:

[0094] 40 parts of polyether polyol; the polyether polyol is polyether polyol N330;

[0095] 70 parts of isocyanate; the isocyanate is toluene diisocyanate (TDI);

[0096] The raw materials of the B component are proportioned as follows by weight:

[0097] 50 parts of amino-terminated polyether; the amino-terminated polyether is amino-terminated polyether D-2000;

[0098] 45 parts of a chain extender; the chain extender is 1,4-bis-sec-butylaminobenzene;

[0099] 0.2 parts of dispersant; the dispersant is Disperbyk 162;

[0100] 1.4 parts of defoaming agent; the defoaming agent is Airex 930;

[0101] 10 parts of flame retardant;

[0102] The preparation method of the coupling agent-modified zinc cobaltate@ZnCe-LDH is the same as the preparation process and conditions in Example 1.

[0103] Example 4

[0104] Same as Example 2, except that 6 g of triethanolamine borate was used as the coupling agent instead of 6 g of KH-560.

[0105] Example 5

[0106] Same as Example 2, except that the coupling agent is a combination of 4.5 g triethanolamine borate and 1.5 g KH-560 instead of 6 g KH-560.

[0107] Comparative Example 1

[0108] Same as Example 2, except that no flame retardant is contained.

[0109] Comparative Example 2

[0110] Same as Example 2, except that the flame retardant is only melamine polyphosphate.

[0111] Comparative Example 3

[0112] Same as Example 2, except that the flame retardant is composed only of zinc cobaltate@ZnCe-LDH modified by a coupling agent.

[0113] Comparative Example 4

[0114] Same as Example 2, except that:

[0115] The preparation method of the coupling agent-modified zinc cobaltate @ZnCe-LDH comprises the following steps:

[0116] (a) 1 mol zinc nitrate, 3.5 mol cobalt acetate, and 12 mol urea were added to 200 mL deionized water and sonicated for 40 min. The mixture was then transferred to a hydrothermal reactor and reacted at 120°C for 14 h. The mixture was centrifuged, washed, and vacuum-dried at 80°C for 14 h. The mixture was then calcined at 550°C in air for 6 h and ground to obtain zinc cobaltate.

[0117] (b) 15 g of the zinc cobaltate obtained in step (b), 10 mmol of zinc acetate, 30 mmol of cerium nitrate, and 100 mmol of urea were added to 150 mL of deionized water and ultrasonicated for 30 min; then transferred to a hydrothermal reactor, reacted at 120° C. for 14 h, centrifuged, washed, and vacuum-dried at 80° C. for 12 h to obtain zinc cobaltate@ZnCe-LDH;

[0118] (d) 100 g of zinc cobaltate@ZnCe-LDH obtained in step (c) and 6 g of KH-560 were added to 200 mL of ethanol and ultrasonically dispersed for 30 min; then, the mixture was reacted at 60°C for 5 h, filtered, washed, and vacuum dried at 80°C for 12 h to obtain coupling agent-modified zinc cobaltate@ZnCe-LDH.

[0119] Comparative Example 5

[0120] Same as Example 2, except that an equal amount of coupling agent-modified zinc cobaltate is used instead of coupling agent-modified zinc cobaltate@ZnCe-LDH.

[0121] The preparation method of the coupling agent-modified zinc cobaltate comprises the following steps:

[0122] (a) Corn stalks were dried at 70°C and ground through a 200-mesh sieve;

[0123] (b) adding 0.3 g of the straw obtained in step (a), 1 mol of zinc nitrate, 3.5 mol of cobalt acetate, and 12 mol of urea to 200 mL of deionized water and ultrasonically treating for 40 min; then transferring to a hydrothermal reactor, reacting at 120° C. for 14 h, centrifuging, washing, and vacuum drying at 80° C. for 14 h, and then calcining at 550° C. in air atmosphere for 6 h, and grinding to obtain zinc cobaltate;

[0124] (d) 100 g of the zinc cobaltate obtained in step (b) and 6 g of KH-560 were added to 200 mL of ethanol and ultrasonically dispersed for 30 min; then the mixture was reacted at 60° C. for 5 h, filtered, washed, and vacuum dried at 80° C. for 12 h to obtain coupling agent-modified zinc cobaltate.

[0125] The limiting oxygen index (LOI) and mechanical properties of the samples of Examples 1-5 and Comparative Examples 1-5 were measured. The specific test results are shown in Table 1:

[0126] The limiting oxygen index (LOI) is GB / T10707-2008.

[0127] Tensile strength: GB / T23446-2009.

[0128] Table 1:

[0129] Limiting oxygen index (LOI) / % Tensile strength (MPa) Example 1 31.7 30.1 Example 2 32.4 29.6 Example 3 32.1 29.4 Example 4 34.6 31.7 Example 5 37.5 32.4 Comparative Example 1 22.4 27.4 Comparative Example 2 25.6 20.5 Comparative Example 3 27.1 32.1 Comparative Example 4 29.5 28.8 Comparative Example 5 28.7 28.3

[0130] As can be seen from Table 1, by comparing Example 2 with Comparative Example 1, the addition of a flame retardant can improve the flame retardant properties and tensile stress. By comparing Example 2 with Comparative Example 2, when melamine polyphosphate is used alone as a flame retardant, the tensile stress is reduced and the improvement in flame retardant properties is not obvious. By comparing Example 2 with Comparative Examples 3-5, it can be seen that the combination of melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH can have excellent flame retardant properties while ensuring mechanical strength.

[0131] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for preparing a modified spray polyurea, characterized in that: The preparation method comprises the following steps: (1) The preparation method of component A is as follows: Add polyether polyol into the reaction kettle, dehydrate under reduced pressure at 110-120°C for 2-4 hours, cool to 50°C, add isocyanate, stir evenly, then heat to 75-85°C, keep warm for 2-4 hours, degas and cool to obtain component A; (2) The preparation method of component B is as follows: Add the amino-terminated polyether, chain extender, composite flame retardant, dispersant and defoamer into a reactor, heat to 65-85° C., stir and disperse at high speed for 30-50 min at a speed of 700-900 rpm to obtain component B; (3) Stir components A and B separately and evenly, then mix them in a volume ratio of 1:

1. The equivalent ratio of components A and B is such that the isocyanate index is between 0.95 and 1.

05. After stirring evenly, spray them with a polyurea sprayer to obtain a modified spray polyurea. The composite flame retardant is composed of melamine polyphosphate and coupling agent-modified zinc cobaltate @ZnCe-LDH; the mass ratio of the melamine polyphosphate to the coupling agent-modified zinc cobaltate @ZnCe-LDH is 1:3-5; The preparation method of the coupling agent-modified zinc cobaltate @ZnCe-LDH comprises the following steps: (a) Oven-dry corn stalks at 60-80°C and grind them through a 200-mesh sieve; (b) adding the straw, zinc salt, cobalt salt, and urea obtained in step (a) to deionized water and ultrasonically treating the mixture for 30 to 50 minutes; then transferring the mixture to a hydrothermal reactor, reacting the mixture at 100 to 140° C. for 12 to 16 hours, centrifuging, washing, and vacuum drying the mixture at 60 to 90° C. for 10 to 16 hours; then calcining the mixture at 500 to 600° C. in an air atmosphere for 4 to 8 hours, and grinding the mixture to obtain zinc cobaltate; (c) adding the zinc cobaltate, zinc salt, cerium salt, and urea obtained in step (b) to deionized water and ultrasonically treating for 20-40 minutes; then transferring the mixture to a hydrothermal reactor, reacting at 100-140°C for 12-16 hours, centrifuging, washing, and vacuum drying at 60-90°C for 10-16 hours to obtain zinc cobaltate@ZnCe-LDH; the ratio of the zinc cobaltate, zinc salt, cerium salt, and urea obtained in step (b) is: 15 g: 10 mmol: 25 mmol-35 mmol: 60-150 mmol: (d) Adding the zinc cobaltate@ZnCe-LDH and coupling agent obtained in step (c) to ethanol and ultrasonically dispersing them for 20-40 minutes; then reacting at 50-70°C for 4-8 hours, filtering, washing, and vacuum drying at 70-90°C for 8-16 hours to obtain coupling agent-modified zinc cobaltate@ZnCe-LDH.

2. The method for preparing a modified spray polyurea according to claim 1, wherein: In step (1), the raw materials of component A are proportioned as follows by weight: 40-50 parts of polyether polyol; 60-70 parts of isocyanate 3. The method for preparing a modified spray polyurea according to claim 1 or 2, characterized in that: In step (1), the polyether polyol is polyether polyol N330; and the isocyanate is at least one of toluene diisocyanate TDI, dicyclohexylmethane diisocyanate HMDI, and lysine diisocyanate LDI.

4. The method for preparing a modified spray polyurea according to claim 1, wherein: In step (2), the raw materials of component B are proportioned as follows by weight: 50-70 parts of amino-terminated polyether; 35-45 parts of chain extender; Dispersant 0.2-0.6 parts; 1-1.4 parts of defoaming agent; 10~20 parts of composite flame retardant.

5. The method for preparing a modified spray polyurea according to claim 1 or 4, characterized in that: The amino-terminated polyether is amino-terminated polyether D-2000; the chain extender is one or more of 1,4-bis-sec-butylaminobenzene, 4,4'-bis-sec-aminodiphenylmethane, and N,N'-bis-sec-pentylcyclohexanediamine; the dispersant is Disperbyk 162; and the defoamer is Airex 930.

6. The method for preparing a modified spray polyurea according to claim 1, wherein: In step (b), the ratio of the straw, zinc salt, cobalt salt and urea obtained in step (a) is: 0.2-0.4 g: 1 mol: 3-4 mol: 8-16 mol; the zinc salt is at least one of zinc nitrate, zinc chloride and zinc acetate; the cobalt salt is one of cobalt nitrate, cobalt chloride and cobalt acetate; in step (c), the zinc salt is at least one of zinc nitrate, zinc chloride and zinc acetate; the cerium salt is at least one of cerium nitrate, cerium chloride and cerium acetate.

7. The method for preparing a modified spray polyurea according to claim 1, wherein: In step (d), the mass ratio of the zinc cobaltate @ZnCe-LDH obtained in step (c) to the coupling agent is 100:4-8; the coupling agent is at least one of triethanolamine borate and KH-560.

8. The method for preparing a modified spray polyurea according to claim 1, wherein: In step (d), the coupling agents are triethanolamine borate and KH-560; the mass ratio of triethanolamine borate to KH-560 is 3:

1.

9. The spray polyurea prepared by the method for preparing a modified spray polyurea according to any one of claims 1 to 8.