Preparation method of cyclic phosphazene schiff base carboxylic acid rare earth complex and application thereof in preparation of flame-retardant polymer materials

Abstract

The application discloses a preparation method of a cyclotriphosphazene Schiff base carboxylic acid rare earth complex and application of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex in preparation of a flame-retardant high polymer material, which is prepared by reacting raw materials including p-hydroxybenzaldehyde, anhydrous potassium carbonate, hexachlorocyclotriphosphazene, p-aminobenzoic acid and a rare earth chloride salt with seven waters, and is obtained directly. The cyclotriphosphazene Schiff base carboxylic acid rare earth complex prepared by the application plays a role of catalyzing carbonization and capturing free radicals based on the joint action of rare earth elements and phosphorus elements, plays a high-efficiency flame-retardant role, and has a small adding amount, so that the total adding amount of the flame retardant can be effectively reduced when the flame retardant is compounded with other halogen-free flame retardants.

Description

Technical Field

[0001] The invention belongs to the technical field of flame retardant materials, and particularly relates to a preparation method of a cyclotriphosphazene Schiff base carboxylic acid rare earth complex and an application thereof in the preparation of flame retardant polymer materials. Background Art

[0002] In recent years, polymers have been widely used in numerous fields, including electronics, high-speed rail, ships, and aerospace, due to their advantages such as light weight, high strength, and ease of processing. However, most polymers are composed of elements such as carbon (C), hydrogen (H), and oxygen (O), making them inherently flammable or combustible, making them prone to fires and causing property damage. Furthermore, polymers produce large amounts of smoke and toxic gases when burned. Therefore, flame-retardant modification of polymers is of great significance to expand their application areas and protect life and health.

[0003] Halogen-free flame retardants are currently primarily used to modify polymer materials for flame retardancy, mitigating the environmental and human health hazards posed by halogen-based flame retardants. However, the primary technical challenge facing halogen-free flame retardants is their lower flame retardancy compared to halogen-based flame retardants. This requires a larger addition amount to meet the required flame retardancy, often leading to a significant decrease in the material's mechanical properties. Consequently, industry professionals are actively exploring new flame retardant compounds and flame retardant synergists to enhance the flame retardancy of halogen-free flame retardants. Summary of the Invention

[0004] The present invention aims to overcome the defects of the prior art and provide a method for preparing a cyclotriphosphazene Schiff base carboxylic acid rare earth complex.

[0005] Another object of the present invention is to provide the use of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex prepared by the above preparation method

[0006] The technical solutions of the present invention are as follows:

[0007] A method for preparing a cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps:

[0008] (1) Add p-hydroxybenzaldehyde and anhydrous potassium carbonate to N,N-dimethylformamide and stir evenly at room temperature;

[0009] (2) adding hexachlorocyclotriphosphazene to the material obtained in step (1) and stirring at room temperature for reaction;

[0010] (3) pouring the material obtained in step (2) into water, dispersing and filtering, washing the obtained precipitate with water and ethanol, and then drying to obtain compound a;

[0011] (4) Dissolve compound a in tetrahydrofuran at room temperature, then add p-aminobenzoic acid, and stir to react at room temperature;

[0012] (5) removing tetrahydrofuran from the material obtained in step (4) by rotary evaporation, adding dichloromethane, washing the precipitate, and then filtering and separating it, adding ethanol to wash the precipitate, and then drying to obtain SCCP;

[0013] (6) After mixing the SCCP prepared in step (5), N,N-dimethylformamide and deionized water, sodium hydroxide is added, and the mixture is heated to 55-65° C. and stirred until dissolved. Then, rare earth chloride heptahydrate is added and stirred evenly. After cooling, the mixture is filtered and the precipitate is washed with DMF and ethanol respectively and then dried to obtain the product.

[0014] In a preferred embodiment of the present invention, the molar ratio of p-hydroxybenzaldehyde, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 36-72:36-72:5-10; the molar ratio of compound a to p-aminobenzoic acid is 2-3:7-9; and the molar ratio of SCCP, sodium hydroxide and rare earth chloride heptahydrate is 6-9:15-20:15-20.

[0015] Further preferably, the volume ratio of N,N-dimethylformamide to deionized water in step (6) is 2:1.

[0016] In a preferred embodiment of the present invention, the rare earth chloride heptahydrate is selected from lanthanum chloride heptahydrate, cerium chloride heptahydrate, yttrium chloride heptahydrate, scandium chloride heptahydrate, praseodymium chloride heptahydrate and neodymium chloride heptahydrate.

[0017] The cyclotriphosphazene Schiff base carboxylic acid rare earth complex prepared by the preparation method is used in the preparation of flame retardant polymer materials.

[0018] In a preferred embodiment of the present invention, the raw materials of the flame retardant polymer material include a polymer substrate, the cyclotriphosphazene Schiff base carboxylic acid rare earth complex and a phosphorus-nitrogen flame retardant, and the weight ratio of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex to the phosphorus-nitrogen flame retardant is 1:1-6.

[0019] Further preferably, the polymer substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polycarbonate, polylactic acid, acrylonitrile-butadiene-styrene copolymer and ethylene-vinyl acetate copolymer, and the phosphorus-nitrogen flame retardant is selected from at least one of ammonium polyphosphate, piperazine pyrophosphate, diethyl aluminum hypophosphite, aluminum hypophosphite, melamine cyanurate, melamine polyphosphate, triethyleneimine phosphate, diaminomethyl phosphate, polyol pyrophosphate and N,N'-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxane-2-yl)ethylenediamine.

[0020] A flame retardant polymer material, the raw materials of which include a polymer substrate, the cyclotriphosphazene Schiff base carboxylic acid rare earth complex and a phosphorus-nitrogen flame retardant.

[0021] The content of polymer matrix is ​​82-96.5wt%,

[0022] The weight ratio of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex to the phosphorus-nitrogen flame retardant is 1:1-6.

[0023] In a preferred embodiment of the present invention, the polymer substrate is at least one selected from polypropylene, polyethylene, polyamide, polyester, polycarbonate, polylactic acid, acrylonitrile-butadiene-styrene copolymer and ethylene-vinyl acetate copolymer.

[0024] In a preferred embodiment of the present invention, the phosphorus-nitrogen flame retardant is selected from at least one of ammonium polyphosphate, piperazine pyrophosphate, diethylaluminum hypophosphite, aluminum hypophosphite, melamine cyanurate, melamine polyphosphate, triethyleneimine phosphate, diaminomethyl phosphate, polyol pyrophosphate and N,N'-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxane-2-yl)ethylenediamine.

[0025] The beneficial effects of the present invention are as follows: the cyclotriphosphazene Schiff base carboxylic acid rare earth complex prepared by the present invention plays the role of catalyzing carbonization and capturing free radicals based on the joint action of rare earth elements and phosphorus elements, and has a highly efficient flame retardant effect, and the addition amount is small. When combined with other halogen-free flame retardants, the total addition amount of the flame retardant can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The infrared spectra of Compound a, SCCP and the complex La@SCCP in Examples 1 to 4 of the present invention are shown.

[0027] Figure 2 1 is the H NMR spectrum of Compound a and SCCP in Examples 1 to 4 of the present invention.

[0028] Figure 3 TG / DTG curves of the complexes La@SCCP in Examples 1 to 4 of the present invention under argon atmosphere (a) and air atmosphere (b).

[0029] Figure 4 Figure 3 is a graph showing the relationship between HRR (a), THR (b), SPR (c), and TSP (d) versus time in cone calorimetry experiments of PLA and flame-retardant polymer materials in Examples and Comparative Examples of the present invention. The PLA-3, PLA-7, and PLA-8 curves correspond to the flame-retardant polymer materials prepared in Examples 6, 7, and 8, respectively. DETAILED DESCRIPTION

[0030] The technical solution of the present invention is further illustrated and described below through specific implementation methods in conjunction with the accompanying drawings.

[0031] Example 1

[0032] (1) 72 mmol of p-hydroxybenzaldehyde and 72 mmol of anhydrous potassium carbonate were added to 400 mL of N,N-dimethylformamide and stirred at room temperature for 2 h;

[0033] (2) 10 mmol of hexachlorocyclotriphosphazene was added to the material obtained in step (1), and the reaction was stirred at room temperature for 12 h, and then the reaction was stopped;

[0034] (3) The material obtained in step (2) was poured into 400 mL of water, dispersed, and filtered. The precipitate was washed three times with water and then three times with ethanol, and dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 2 Compound a shown (Compound a);

[0035] (4) Compound a (23.2 mmol) was added to 300 mL of tetrahydrofuran and dissolved at room temperature. 88.6 mmol of p-aminobenzoic acid was then added and stirred at room temperature for 12 h.

[0036] (5) Remove tetrahydrofuran from the material obtained in step (4) by rotary evaporation, add 200 mL of dichloromethane, wash the precipitate, filter and separate, add ethanol to wash the precipitate, and dry it to obtain Figure 1 and Figure 2 The compound shown is 2,2,4-tris(4-(4-carboxyphenyliminomethyl)phenoxy)-4,6,6-tris(4-formyl)-phenoxy)cyclotriphosphazene (abbreviated as SCCP);

[0037] (6) 8.21 mmol of the product obtained in step (5) was added to 200 mL of N,N-dimethylformamide and 100 mL of deionized water, and then 17.1 mmol of sodium hydroxide was added. The mixture was heated to 60°C and stirred for 0.5 h until dissolved. Then, 16.2 mmol of lanthanum chloride heptahydrate was added and stirred for 6 h. After cooling, the mixture was filtered and the precipitate was washed with DMF and ethanol respectively. The precipitate was dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 3 The cyclotriphosphazene Schiff base lanthanum carboxylate complex La@SCCP is shown.

[0038] Example 2

[0039] (1) 36 mmol of p-hydroxybenzaldehyde and 36 mmol of anhydrous potassium carbonate were added to 400 mL of N,N-dimethylformamide and stirred at room temperature for 2 h;

[0040] (2) 10 mmol of hexachlorocyclotriphosphazene was added to the material obtained in step (1), and the reaction was stirred at room temperature for 12 h, and then the reaction was stopped;

[0041] (3) The material obtained in step (2) was poured into 400 mL of water, dispersed, and filtered. The precipitate was washed three times with water and then three times with ethanol, and dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 2 Compound a shown (Compound a);

[0042] (4) Take 20 mmol of compound a and dissolve it in 300 mL of tetrahydrofuran at room temperature. Then add 70 mmol of p-aminobenzoic acid and stir the reaction at room temperature for 12 h.

[0043] (5) Remove tetrahydrofuran from the material obtained in step (4) by rotary evaporation, add 200 mL of dichloromethane, wash the precipitate, filter and separate, add ethanol to wash the precipitate, and dry it to obtain Figure 1 and Figure 2 The compound shown is 2,2,4-tris(4-(4-carboxyphenyliminomethyl)phenoxy)-4,6,6-tris(4-formyl)-phenoxy)cyclotriphosphazene (abbreviated as SCCP);

[0044] (6) 6 mmol of the product obtained in step (5) was added to 200 mL of N,N-dimethylformamide and 100 mL of deionized water, and then 15 mmol of sodium hydroxide was added. The mixture was heated to 60°C and stirred for 0.5 h until dissolved. Then, 15 mmol of lanthanum chloride heptahydrate was added and stirred for 6 h. After cooling, the mixture was filtered and the precipitate was washed with N,N-dimethylformamide and ethanol respectively, and dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 3 The cyclotriphosphazene Schiff base lanthanum carboxylate complex La@SCCP is shown.

[0045] Example 3

[0046] (1) Add 50 mmol of p-hydroxybenzaldehyde and 50 mmol of anhydrous potassium carbonate to 400 mL of N,N-dimethylformamide and stir at room temperature for 2 h;

[0047] (2) 10 mmol of hexachlorocyclotriphosphazene was added to the material obtained in step (1), and the reaction was stirred at room temperature for 12 h, and then the reaction was stopped;

[0048] (3) The material obtained in step (2) was poured into 400 mL of water, dispersed, and filtered. The precipitate was washed three times with water and then three times with ethanol, and dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 2Compound a shown (Compound a);

[0049] (4) 30 mmol of compound a was added to 300 mL of tetrahydrofuran and dissolved at room temperature. 90 mmol of p-aminobenzoic acid was then added and stirred at room temperature for 12 h.

[0050] (5) Remove tetrahydrofuran from the material obtained in step (4) by rotary evaporation, add 200 mL of dichloromethane, wash the precipitate, filter and separate, add ethanol to wash the precipitate, and dry it to obtain Figure 1 and Figure 2 The compound shown is 2,2,4-tris(4-(4-carboxyphenyliminomethyl)phenoxy)-4,6,6-tris(4-formyl)-phenoxy)cyclotriphosphazene (abbreviated as SCCP);

[0051] (6) 9 mmol of the product obtained in step (5) was added to 200 mL of N,N-dimethylformamide and 100 mL of deionized water, and then 15 mmol of sodium hydroxide was added. The mixture was heated to 90°C and stirred for 0.5 h until dissolved. Then, 15 mmol of lanthanum chloride heptahydrate was added and stirred for 8 h. After cooling, the mixture was filtered and the precipitate was washed with N,N-dimethylformamide and ethanol respectively, and dried in a vacuum oven at 80-90°C to obtain the following: Figure 1 and Figure 3 The cyclotriphosphazene Schiff base lanthanum carboxylate complex La@SCCP is shown.

[0052] Example 4

[0053] (1) Add 50 mmol of p-hydroxybenzaldehyde and 50 mmol of anhydrous potassium carbonate to 400 mL of N,N-dimethylformamide and stir at room temperature for 2 h;

[0054] (2) 10 mmol of hexachlorocyclotriphosphazene was added to the material obtained in step (1), and the reaction was stirred at room temperature for 12 h, and then the reaction was stopped;

[0055] (3) The material obtained in step (2) was poured into 400 mL of water, dispersed, and filtered. The precipitate was washed three times with water and then three times with ethanol, and dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 2 Compound a shown (Compound a);

[0056] (4) 30 mmol of compound a was added to 300 mL of tetrahydrofuran and dissolved at room temperature. 90 mmol of p-aminobenzoic acid was then added and stirred at room temperature for 12 h.

[0057] (5) Remove tetrahydrofuran from the material obtained in step (4) by rotary evaporation, add 200 mL of dichloromethane, wash the precipitate, filter and separate, add ethanol to wash the precipitate, and dry it to obtain Figure 1 and Figure 2 The compound shown is 2,2,4-tris(4-(4-carboxyphenyliminomethyl)phenoxy)-4,6,6-tris(4-formyl)-phenoxy)cyclotriphosphazene (abbreviated as SCCP);

[0058] (6) 9 mmol of the product obtained in step (5) was added to 200 mL of N,N-dimethylformamide and 100 mL of deionized water, and then 15 mmol of sodium hydroxide was added. The mixture was heated to 90°C and stirred for 0.5 h until dissolved. Then, 15 mmol of cerium chloride heptahydrate was added and stirred for 8 h. After cooling, the mixture was filtered and the precipitate was washed with N,N-dimethylformamide and ethanol respectively, and dried in a vacuum oven at 80-90°C to obtain the following: Figure 1 and Figure 3 The cyclotriphosphazene Schiff base lanthanum carboxylate complex Ce@SCCP is shown.

[0059] Example 5

[0060] (1) 72 mmol of p-hydroxybenzaldehyde and 72 mmol of anhydrous potassium carbonate were added to 400 mL of N,N-dimethylformamide and stirred at room temperature for 2 h;

[0061] (2) 10 mmol of hexachlorocyclotriphosphazene was added to the material obtained in step (1), and the reaction was stirred at room temperature for 12 h, and then the reaction was stopped;

[0062] (3) The material obtained in step (2) was poured into 400 mL of water, dispersed, and filtered. The precipitate was washed three times with water and then three times with ethanol, and dried in a vacuum oven at 80°C to obtain the following: Figure 1 and Figure 2 Compound a shown (Compound a);

[0063] (4) Compound a (23.2 mmol) was added to 300 mL of tetrahydrofuran and dissolved at room temperature. 88.6 mmol of p-aminobenzoic acid was then added and stirred at room temperature for 12 h.

[0064] (5) Remove tetrahydrofuran from the material obtained in step (4) by rotary evaporation, add 200 mL of dichloromethane, wash the precipitate, filter and separate, add ethanol to wash the precipitate, and dry it to obtain Figure 1 and Figure 2 The compound shown is 2,2,4-tris(4-(4-carboxyphenyliminomethyl)phenoxy)-4,6,6-tris(4-formyl)-phenoxy)cyclotriphosphazene (abbreviated as SCCP);

[0065] (6) 8.21 mmol of the product obtained in step (5) was added to 200 mL of N,N-dimethylformamide and 100 mL of deionized water, and then 17.1 mmol of sodium hydroxide was added. The mixture was heated to 60°C and stirred for 0.5 h until dissolved. Then, 16.2 mmol of cerium chloride heptahydrate was added and stirred for 6 h. After cooling, the mixture was filtered and the precipitate was washed with DMF and ethanol respectively. The precipitate was dried in a vacuum oven at 80°C to obtain cyclotriphosphazene Schiff base carboxylic acid cerium complex Ce@SCCP.

[0066] Example 6

[0067] A flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex, comprising the following components:

[0068] 96.5% polylactic acid, 0.5% cyclotriphosphazene Schiff base carboxylate lanthanum complex prepared in Example 1, 3% phosphorus-nitrogen flame retardant, wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate.

[0069] The preparation method of the flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps: premixing the components through a high-speed mixer, melting and extruding the components through a twin-screw extruder, granulating the components into strands, and drying the components to obtain the final product.

[0070] Example 7

[0071] A flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex, comprising the following components:

[0072] 96% polylactic acid, 1% cyclotriphosphazene Schiff base carboxylate lanthanum complex prepared in Example 1, 3% phosphorus-nitrogen flame retardant, wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate.

[0073] The preparation method of the flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps: premixing the components through a high-speed mixer, melting and extruding the components through a twin-screw extruder, granulating the components into strands, and drying the components to obtain the final product.

[0074] Example 8

[0075] A flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex, comprising the following components:

[0076] 96% polylactic acid, 2% cyclotriphosphazene Schiff base carboxylate lanthanum complex prepared in Example 1, and 2% phosphorus-nitrogen flame retardant, wherein the phosphorus-nitrogen flame retardant is ammonium polyphosphate.

[0077] The preparation method of the flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps: premixing the components through a high-speed mixer, melting and extruding the components through a twin-screw extruder, granulating the components into strands, and drying the components to obtain the final product.

[0078] Example 9

[0079] A flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex, comprising the following components:

[0080] 82% polyethylene, 3% cyclotriphosphazene Schiff base carboxylate lanthanum complex prepared in Example 1, 15% phosphorus-nitrogen flame retardant, wherein the phosphorus-nitrogen flame retardant is piperazine pyrophosphate.

[0081] The preparation method of the flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps: premixing the components through a high-speed mixer, melting and extruding the components through a twin-screw extruder, granulating the components into strands, and drying the components to obtain the final product.

[0082] Example 10

[0083] A flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex, comprising the following components:

[0084] 82% polyamide, 2% cyclotriphosphazene Schiff base carboxylate lanthanum complex prepared in Example 1, 12% phosphorus-nitrogen flame retardant, wherein the phosphorus-nitrogen flame retardant is diethyl aluminum hypophosphite.

[0085] The preparation method of the flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps: premixing the components through a high-speed mixer, melting and extruding the components through a twin-screw extruder, granulating the components into strands, and drying the components to obtain the final product.

[0086] Example 11

[0087] A flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex, comprising the following components:

[0088] 96.5% polylactic acid, 0.5% cyclotriphosphazene Schiff base carboxylic acid cerium complex prepared in Example 5, 3% phosphorus-nitrogen flame retardant. The phosphorus-nitrogen flame retardant is ammonium polyphosphate.

[0089] The preparation method of the flame retardant polymer material based on cyclotriphosphazene Schiff base carboxylic acid rare earth complex comprises the following steps: premixing the components through a high-speed mixer, melting and extruding the components through a twin-screw extruder, granulating the components into strands, and drying the components to obtain the final product.

[0090] Comparative Example 1

[0091] The relationship between HRR, THR, SPR and TSP and time in cone calorimetry experiment of pure polylactic acid (PLA) is as follows: Figure 4 shown.

[0092] Comparative Example 2

[0093] The invention discloses a flame retardant polyethylene, which is composed of 82% polyethylene and 18% piperazine pyrophosphate. The components are premixed in a high-speed mixer and then melt-extruded in a twin-screw extruder. The final product is obtained after being drawn into strands and granulated and dried.

[0094] Comparative Example 3

[0095] A flame retardant polyamide is composed of 82% polyamide and 18% diethyl aluminum hypophosphite. The components are premixed in a high-speed mixer and then melt-extruded through a twin-screw extruder. The product is then drawn into strands and granulated, and dried to obtain the final product.

[0096]

[0097] The above description is merely a preferred embodiment of the present invention and therefore cannot be used to limit the scope of the present invention. In other words, equivalent changes and modifications made within the scope of the present invention and the contents of the specification should still fall within the scope of the present invention.

Claims

1. A method for preparing a cyclotriphosphazene Schiff base carboxylic acid rare earth complex, characterized by: The steps include: (1) Add p-hydroxybenzaldehyde and anhydrous potassium carbonate to N,N-dimethylformamide and stir evenly at room temperature; (2) adding hexachlorocyclotriphosphazene to the material obtained in step (1) and stirring at room temperature for reaction; (3) The material obtained in step (2) was poured into water, dispersed, and then filtered. The resulting precipitate was washed with water and ethanol, and then dried to obtain compound a, whose structural formula is (4) Dissolve compound a in tetrahydrofuran at room temperature, then add p-aminobenzoic acid, and stir to react at room temperature; (5) removing tetrahydrofuran from the material obtained in step (4) by rotary evaporation, adding dichloromethane, washing the precipitate, and filtering and separating it, adding ethanol to wash the precipitate, and drying it to obtain SCCP, whose structural formula is (6) After mixing the SCCP prepared in step (5), N,N-dimethylformamide and deionized water, sodium hydroxide is added, and the mixture is heated to 55-65° C. and stirred until dissolved. Then, rare earth chloride heptahydrate is added and stirred evenly. After cooling, the mixture is filtered and the precipitate is washed with DMF and ethanol respectively and then dried to obtain the product; The rare earth chloride heptahydrate is selected from lanthanum chloride heptahydrate, cerium chloride heptahydrate, yttrium chloride heptahydrate, scandium chloride heptahydrate, praseodymium chloride heptahydrate and neodymium chloride heptahydrate.

2. The preparation method according to claim 1, wherein: The molar ratio of p-hydroxybenzaldehyde, anhydrous potassium carbonate and hexachlorocyclotriphosphazene is 36-72:36-72:5-10; the molar ratio of compound a and p-aminobenzoic acid is 2-3:7-9; and the molar ratio of SCCP, sodium hydroxide and rare earth chloride heptahydrate is 6-9:15-20:15-20.

3. The preparation method according to claim 2, wherein: The volume ratio of N,N-dimethylformamide to deionized water in step (6) is 2:

1.

4. Use of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex prepared by the preparation method according to any one of claims 1 to 3 in the preparation of flame retardant polymer materials.

5. The use according to claim 4, characterized in that: The raw materials of the flame retardant polymer material include a polymer substrate, the cyclotriphosphazene Schiff base carboxylic acid rare earth complex and a phosphorus nitrogen flame retardant, and the weight ratio of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex to the phosphorus nitrogen flame retardant is 1:1-6.

6. The use according to claim 5, characterized in that: The polymer substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polycarbonate, polylactic acid, acrylonitrile-butadiene-styrene copolymer and ethylene-vinyl acetate copolymer, and the phosphorus-nitrogen flame retardant is selected from at least one of ammonium polyphosphate, piperazine pyrophosphate, diethyl aluminum hypophosphite, aluminum hypophosphite, melamine cyanurate, melamine polyphosphate, triethyleneimine phosphate, diaminomethyl phosphate, polyol pyrophosphate and N,N'-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxane-2-yl)ethylenediamine.

7. A flame retardant polymer material, characterized in that: The raw materials include a polymer substrate, a cyclotriphosphazene Schiff base carboxylic acid rare earth complex prepared by the preparation method according to any one of claims 1 to 3, and a phosphorus-nitrogen flame retardant. The content of polymer matrix is ​​82-96.5wt%, The weight ratio of the cyclotriphosphazene Schiff base carboxylic acid rare earth complex to the phosphorus-nitrogen flame retardant is 1:1-6.

8. The flame retardant polymer material according to claim 7, characterized in that: The polymer substrate is selected from at least one of polypropylene, polyethylene, polyamide, polyester, polycarbonate, polylactic acid, acrylonitrile-butadiene-styrene copolymer and ethylene-vinyl acetate copolymer.

9. The flame retardant polymer material according to claim 7, characterized in that: The phosphorus-nitrogen flame retardant is selected from at least one of ammonium polyphosphate, piperazine pyrophosphate, diethyl aluminum hypophosphite, aluminum hypophosphite, melamine cyanurate, melamine polyphosphate, triethyleneimine phosphate, diaminomethyl phosphate, polyol pyrophosphate and N,N'-bis(5,5-dimethyl-2-phospha-2-thio-1,3-dioxane-2-yl)ethylenediamine.

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