Preparation method and application of functionalized diatomite grafted polyurethane elastomer with high flame retardance

Abstract

The invention relates to the technical field of new materials, and discloses a high-flame-retardance functionalized diatomite grafted polyurethane elastomer, polyurethane is subjected to in-situ polymerization on the surface of diatomite through an in-situ polymerization method, and polyurethane and diatomite are organically combined through a covalent bond connection method, so that the compatibility between the polyurethane and the diatomite is enhanced, and the flame retardance of the elastomer is improved. The diatom ooze is added into the diatom ooze, so that the diatom ooze is highly dispersed in a polyurethane elastomer matrix, the reinforcing effect of the diatom ooze as a filler is better played, the tensile strength and the elongation at break of the polyurethane elastomer are obviously improved, and the mechanical property of the elastomer material is enhanced; the flame retardant can promote charring during combustion to form a stable carbon layer, and the stable carbon layer and highly dispersed diatomite form a continuous barrier layer, so that the flame retardant polyurethane elastomer has good smoke suppression and molten drop prevention effects, and the flame retardant property of the polyurethane elastomer is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of new materials, in particular to a preparation method and application of a highly flame-retardant functionalized diatomaceous earth grafted polyurethane elastomer. Background Art

[0002] Polyurethane is a new type of polymer material that can be made into elastomers, foams, coatings and other materials. It is widely used in construction, automobile manufacturing, aviation industry and other fields. However, traditional polyurethane elastomers and other materials are easy to burn and have low mechanical properties, which limits the practical application of polyurethane materials. Using inorganic nanofillers as filling and reinforcing agents is an effective way to improve the comprehensive performance of polyurethane and other polymer materials, such as graphene and nano-silica.

[0003] Diatomaceous earth is a natural nano-mineral with the advantages of porosity and large specific surface area. It is widely used in polymer materials such as epoxy resins and can improve the mechanical strength and thermal stability of materials. In order to improve the dispersibility of diatomaceous earth, in-situ polymerization has been widely studied and applied in recent years. By introducing polymerization sites in inorganic nanofillers, monomers can be induced to undergo in-situ polymerization. Organophosphorus flame retardants such as 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) are excellent organophosphorus flame retardant precursors. The document "Synthesis and Characterization of a New Phosphorus-Containing Flame Retardant DOPO-ITA" published in the Journal of Wuhan University of Science and Technology discloses the reaction of DOPO with itaconic acid to obtain a carboxyl-containing DOPO-ITA compound with excellent flame retardant properties. Therefore, the DOPO-ITA compound can be compounded with diatomaceous earth to improve the flame retardant and mechanical properties of polyurethane elastomers.

[0004] 1. Technical issues to be resolved In view of the deficiencies in the prior art, the present invention provides a method for preparing and applying a functionalized diatomaceous earth grafted polyurethane elastomer with high flame retardancy, thereby solving the problem of low flame retardancy and mechanical properties of the polyurethane elastomer.

[0005] (II) Technical solution To achieve the above object, the present invention provides the following technical solution: a highly flame-retardant functionalized diatomite grafted polyurethane elastomer, wherein the preparation method of the highly flame-retardant functionalized diatomite grafted polyurethane elastomer is as follows: (1) Add 1500-4000 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 15-40 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 2-5 hours, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0006] (2) Add a solvent and a co-solvent to a reaction bottle, add amino diatomaceous earth and DOPO-ITA compound, stir to dissolve, add 4-dimethylaminopyridine and dicyclohexylcarbodiimide, and then undergo an amidation reaction. Centrifuge to remove the solvent, wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0007] (3) Add xylene solvent, carboxyl DOPO-modified diatomaceous earth and trimethylolpropane to a reaction bottle, heat and stir to dissolve, add p-toluenesulfonic acid as a catalyst, stir to react, filter the solvent, wash with chloroform and ethanol, and obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0008] (4) Add polycaprolactone diol, 4,4'-diphenylmethane diisocyanate, and dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add dibutyltin dilaurate in a nitrogen atmosphere, heat to 75-85 °C, react for 2-4 h, then add 1,4-butanediol and react for 20-40 min. Pour the product into a mold for heat curing, then place it in a flat vulcanizer for vulcanization, and finally heat for aging to obtain a highly flame-retardant functionalized diatomaceous earth-grafted polyurethane elastomer.

[0009] Preferably, in step (2), the mass fractions of the solvent are 2500-6000 parts, the co-solvent is 800-2000 parts, the amino diatomaceous earth is 100 parts, the DOPO-ITA compound is 65-120 parts, the 4-dimethylaminopyridine is 3-8 parts, and the dicyclohexylcarbodiimide is 40-100 parts.

[0010] Preferably, in step (2), the solvent is N,N-dimethylformamide solvent, and the co-solvent is xylene solvent.

[0011] Preferably, the reaction in step (2) is carried out at 60-85° C. for 12-36 h.

[0012] Preferably, in step (3), the weight proportions are 3500-8000 parts of xylene solvent, 100 parts of carboxyl DOPO-modified diatomaceous earth, 30-65 parts of trimethylolpropane, and 0.15-0.4 parts of p-toluenesulfonic acid.

[0013] Preferably, the reaction in step (3) is carried out at 80-120° C. for 10-20 h.

[0014] Preferably, the weight proportions of polycaprolactone diol in step (4) are 100 parts, 4,4'-diphenylmethane diisocyanate is 22-28 parts, dihydroxymethyl DOPO modified diatomaceous earth is 1.5-6 parts, dibutyltin dilaurate is 0.1-0.18 parts, and 1,4-butanediol is 3-5 parts.

[0015] Preferably, in step (4), the vulcanization is carried out at 8-12 MPa for 20-40 min, and the heating and aging is carried out at 90-120° C. for 18-24 h.

[0016] 3. Beneficial technical effects Compared with the prior art, the present invention has the following beneficial technical effects: The highly flame-retardant functionalized diatomite grafted polyurethane elastomer comprises the following steps: γ-aminopropyltriethoxysilane is used to modify diatomite, active amino groups are introduced, and then amidation reaction is carried out with the amino groups of diatomite and a carboxyl group of DOPO-ITA in a solvent system of N,N-dimethylformamide and xylene under the catalytic action of 4-dimethylaminopyridine and dicyclohexylcarbodiimide to obtain carboxyl DOPO-modified diatomite; further, under the catalytic action of p-toluenesulfonic acid, the carboxyl DOPO modified with the diatomite undergoes an esterification reaction with one of the hydroxyl groups of trimethylolpropane to obtain dimethylol DOPO-modified diatomite containing two hydroxymethyl groups; the dimethylol group is used as an in-situ polymer site to cause polycaprolactone diol and 4,4'-diphenylmethane diisocyanate to undergo in-situ polymerization on the surface of diatomite, thereby obtaining the highly flame-retardant functionalized diatomite grafted polyurethane elastomer.

[0017] The highly flame-retardant functionalized diatomite-grafted polyurethane elastomer is prepared by in-situ polymerization of polyurethane on the surface of diatomite, and organically combining polyurethane and diatomite through covalent bonding, thereby enhancing the compatibility between the two, so that the diatomite is highly dispersed in the polyurethane elastomer matrix, and the reinforcing effect of diatomite as a filler is better exerted, and the tensile strength and elongation at break of the polyurethane elastomer are significantly improved, thereby enhancing the mechanical properties of the elastomer material. Moreover, the modified DOPO in the diatomite group is used as a phosphorus-based flame retardant, which can promote carbonization during combustion to form a stable carbon layer, and form a continuous barrier layer with the highly dispersed diatomite, so as to have good smoke suppression and anti-drip effects, and enhance the flame retardant properties of the polyurethane elastomer. DETAILED DESCRIPTION

[0018] To achieve the above object, the present invention provides the following embodiments and examples: A method for preparing a highly flame-retardant functionalized diatomite-grafted polyurethane elastomer is as follows: (1) Add 1500-4000 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 15-40 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 2-5 hours, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0019] (2) Add 2500-6000 parts by weight of N,N-dimethylformamide solvent and 800-2000 parts by weight of xylene co-solvent into a reaction bottle, add 100 parts of amino-modified diatomaceous earth and 65-120 parts of DOPO-ITA compound, stir to dissolve, add 3-8 parts of 4-dimethylaminopyridine and 40-100 parts of dicyclohexylcarbodiimide, and then carry out amidation reaction at 60-85°C for 12-36 hours, centrifuge to remove the solvent, and wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0020] (3) Add 3500-8000 parts by weight of xylene solvent, 100 parts by weight of carboxyl DOPO-modified diatomaceous earth and 30-65 parts by weight of trimethylolpropane into a reaction bottle, heat and stir to dissolve, add 0.15-0.4 parts of catalyst p-toluenesulfonic acid, and then stir at 80-120 °C for esterification reaction for 10-20 h, filter the solvent, wash with chloroform and ethanol to obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0021] (4) Add 100 parts by weight of polycaprolactone diol, 22-28 parts by weight of 4,4'-diphenylmethane diisocyanate, and 1.5-6 parts by weight of dihydroxymethyl DOPO modified diatomaceous earth into a reaction bottle, add 0.1-0.18 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 75-85 °C, react for 2-4 h, then add 3-5 parts of 1,4-butanediol, react for 20-40 min, pour the product into a mold for heat curing, and then place it in a flat vulcanizer and vulcanize it at 8-12 MPa for 20-40 min, and finally heat it at 90-120 °C for 18-24 h to obtain a functionalized diatomaceous earth grafted polyurethane elastomer with high flame retardancy. Example

[0022] (1) Add 1500 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 15 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 2 h, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0023] (2) Add 2500 parts by weight of N,N-dimethylformamide solvent and 800 parts by weight of xylene co-solvent into a reaction bottle, add 100 parts of amino-modified diatomaceous earth and 65 parts of DOPO-ITA compound, stir to dissolve, add 3 parts of 4-dimethylaminopyridine and 40 parts of dicyclohexylcarbodiimide, and then carry out amidation reaction at 60°C for 12 hours. Centrifuge to remove the solvent, wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0024] (3) Add 3500 parts by weight of xylene solvent, 100 parts by weight of carboxyl DOPO-modified diatomaceous earth and 30 parts by weight of trimethylolpropane into a reaction bottle, heat and stir to dissolve, add 0.15 parts of catalyst p-toluenesulfonic acid, and then stir at 80 °C for esterification reaction for 10 h. Filter the solvent and wash with chloroform and ethanol to obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0025] (4) Add 100 parts by weight of polycaprolactone diol, 22 parts by weight of 4,4'-diphenylmethane diisocyanate, and 1.5 parts by weight of dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add 0.1 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 75 °C, react for 2 h, then add 3 parts of 1,4-butanediol and react for 20 min. Pour the product into a mold for heat curing, then place it in a flat vulcanizer and vulcanize it at 8 MPa for 20 min. Finally, heat it at 90 °C and mature it for 18 h to obtain a functionalized diatomaceous earth grafted polyurethane elastomer with high flame retardancy. Example

[0026] (1) Add 2000 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 22 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 2 h, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0027] (2) Add 3500 parts by weight of N,N-dimethylformamide solvent and 1200 parts by weight of xylene co-solvent into a reaction bottle, add 100 parts of amino-modified diatomaceous earth and 80 parts of DOPO-ITA compound, stir to dissolve, add 4 parts of 4-dimethylaminopyridine and 55 parts of dicyclohexylcarbodiimide, and then carry out amidation reaction at 60 °C for 12 h. Centrifuge to remove the solvent, wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0028] (3) Add 4500 parts by weight of xylene solvent, 100 parts by weight of carboxyl DOPO-modified diatomaceous earth and 38 parts by weight of trimethylolpropane into a reaction bottle, heat and stir to dissolve, add 0.22 parts of catalyst p-toluenesulfonic acid, and then stir at 100 °C for esterification reaction for 10 h. Filter the solvent and wash with chloroform and ethanol to obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0029] (4) Add 100 parts by weight of polycaprolactone diol, 24 parts by weight of 4,4'-diphenylmethane diisocyanate, and 2 parts by weight of dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add 0.12 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 85 °C, react for 3 h, then add 3.5 parts of 1,4-butanediol, react for 30 min, pour the product into a mold for heat curing, and then place it in a flat vulcanizer and vulcanize it at 10 MPa for 30 min, and finally heat it at 120 °C for 18 h to obtain a functionalized diatomaceous earth grafted polyurethane elastomer with high flame retardancy. Example

[0030] (1) Add 3000 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 28 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 4 h, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0031] (2) Add 4500 parts by weight of N,N-dimethylformamide solvent and 1500 parts by weight of xylene co-solvent into a reaction bottle, add 100 parts of amino-modified diatomaceous earth and 100 parts of DOPO-ITA compound, stir to dissolve, then add 5.5 parts of 4-dimethylaminopyridine and 70 parts of dicyclohexylcarbodiimide, and then carry out amidation reaction at 75°C for 24 hours. Centrifuge to remove the solvent, wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0032] (3) Add 6000 parts by weight of xylene solvent, 100 parts by weight of carboxyl DOPO-modified diatomaceous earth and 45 parts by weight of trimethylolpropane into a reaction bottle, heat and stir to dissolve, add 0.25 parts of catalyst p-toluenesulfonic acid, and then stir at 100 °C for esterification reaction for 12 h. Filter the solvent and wash with chloroform and ethanol to obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0033] (4) Add 100 parts by weight of polycaprolactone diol, 25 parts by weight of 4,4'-diphenylmethane diisocyanate, and 4 parts by weight of dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add 0.15 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 80°C, react for 3 h, then add 4 parts of 1,4-butanediol, react for 30 min, pour the product into a mold for heat curing, and then place it in a flat vulcanizer and vulcanize it at 10 MPa for 30 min, and finally heat it at 100°C for aging for 20 h to obtain a highly flame retardant functionalized diatomaceous earth grafted polyurethane elastomer. Example

[0034] (1) Add 3500 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 35 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 4 h, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0035] (2) Add 5500 parts by weight of N,N-dimethylformamide solvent and 1800 parts by weight of xylene co-solvent into a reaction bottle, add 100 parts of amino-modified diatomaceous earth and 110 parts of DOPO-ITA compound, stir to dissolve, add 7 parts of 4-dimethylaminopyridine and 85 parts of dicyclohexylcarbodiimide, and then carry out amidation reaction at 75°C for 24 hours. Centrifuge to remove the solvent, wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0036] (3) Add 7500 parts by weight of xylene solvent, 100 parts by weight of carboxyl DOPO-modified diatomaceous earth and 55 parts by weight of trimethylolpropane into a reaction bottle, heat and stir to dissolve, add 0.35 parts of catalyst p-toluenesulfonic acid, and then stir at 120 °C for esterification reaction for 12 h. Filter the solvent, wash with chloroform and ethanol to obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0037] (4) Add 100 parts by weight of polycaprolactone diol, 27 parts by weight of 4,4'-diphenylmethane diisocyanate, and 5.2 parts by weight of dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add 0.17 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 85 °C, react for 3 h, then add 4.5 parts of 1,4-butanediol, react for 40 min, pour the product into a mold for heat curing, and then place it in a flat vulcanizer and vulcanize it at 12 MPa for 40 min, and finally heat it at 120 °C for 24 h to obtain a highly flame retardant functionalized diatomaceous earth grafted polyurethane elastomer. Example

[0038] (1) Add 4000 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 40 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 5 h, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0039] (2) Add 6000 parts by weight of N,N-dimethylformamide solvent and 2000 parts by weight of xylene co-solvent into a reaction bottle, add 100 parts of amino-modified diatomaceous earth and 120 parts of DOPO-ITA compound, stir to dissolve, then add 8 parts of 4-dimethylaminopyridine and 100 parts of dicyclohexylcarbodiimide, and then carry out amidation reaction at 85°C for 36 hours. Centrifuge to remove the solvent, wash with chloroform and ethanol to obtain carboxyl DOPO-modified diatomaceous earth.

[0040] (3) Add 8000 parts by weight of xylene solvent, 100 parts by weight of carboxyl DOPO-modified diatomaceous earth and 65 parts by weight of trimethylolpropane into a reaction bottle, heat and stir to dissolve, add 0.4 parts of catalyst p-toluenesulfonic acid, and then stir at 120 °C for esterification reaction for 20 h. Filter the solvent, wash with chloroform and ethanol to obtain dihydroxymethyl DOPO-modified diatomaceous earth.

[0041] (4) Add 100 parts by weight of polycaprolactone diol, 28 parts by weight of 4,4'-diphenylmethane diisocyanate, and 6 parts by weight of dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add 0.18 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 85 °C, react for 4 h, then add 5 parts of 1,4-butanediol and react for 40 min. Pour the product into a mold for heat curing, then place it in a flat vulcanizer and vulcanize it at 12 MPa for 40 min. Finally, heat it at 120 °C and mature it for 24 h to obtain a highly flame retardant functionalized diatomaceous earth grafted polyurethane elastomer.

[0042] Comparative Example 1 (1) Add 2500 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 30 parts by weight of γ-aminopropyltriethoxysilane into a reaction bottle, react under ultrasound for 3 h, filter the solvent, wash with ethanol, and obtain amino diatomaceous earth.

[0043] (4) Add 100 parts by weight of polycaprolactone diol, 25 parts by weight of 4,4'-diphenylmethane diisocyanate, and 3.5 parts by weight of amino diatomaceous earth into a reaction bottle, add 0.12 parts of dibutyltin dilaurate in a nitrogen atmosphere, heat to 85 °C, react for 3 h, then add 4 parts of 1,4-butanediol and react for 30 min. Pour the product into a mold for heat curing, then place it in a flat vulcanizer and vulcanize it at 10 MPa for 30 min. Finally, heat it at 100 °C and mature it for 20 h to obtain a diatomaceous earth-polyurethane elastomer.

[0044] The urethane elastomers prepared in the examples and comparative examples were cut into slices, and 0.2 g of the slices were placed in a cone calorimeter at a heating rate of 20°C / min and a maximum test temperature of 800°C to test the combustion performance.

[0045]

[0046] The urethane elastomer was made into a standard specimen of 50 mm×10 mm×10 mm, and the tensile strength and elongation at break of the standard specimen were tested by an HZ tensile testing machine.

[0047]

Claims

1. A highly flame retardant functionalized diatomite-grafted polyurethane elastomer, characterized in that: The preparation method of the highly flame-retardant functionalized diatomite-grafted polyurethane elastomer is as follows: (1) adding 1500-4000 parts by weight of ethanol solvent, 100 parts by weight of diatomaceous earth and 15-40 parts by weight of γ-aminopropyltriethoxysilane to a reaction bottle, reacting under ultrasound for 2-5 hours, filtering the solvent, washing with ethanol, and obtaining amino diatomaceous earth; (2) Adding a solvent and a co-solvent to a reaction flask, adding amino diatomite and DOPO-ITA compound, stirring to dissolve, adding 4-dimethylaminopyridine and dicyclohexylcarbodiimide, and then undergoing an amidation reaction, centrifuging to remove the solvent, washing with chloroform and ethanol, and obtaining carboxyl DOPO-modified diatomite; (3) Add xylene solvent, carboxyl DOPO modified diatomaceous earth and trimethylolpropane to a reaction bottle, heat and stir to dissolve, add p-toluenesulfonic acid as a catalyst, stir to react, filter the solvent, wash with chloroform and ethanol to obtain dihydroxymethyl DOPO modified diatomaceous earth; (4) Add polycaprolactone diol, 4,4'-diphenylmethane diisocyanate, and dihydroxymethyl DOPO-modified diatomaceous earth into a reaction bottle, add dibutyltin dilaurate in a nitrogen atmosphere, heat to 75-85 °C, react for 2-4 h, then add 1,4-butanediol and react for 20-40 min. Pour the product into a mold for heat curing, then place it in a flat vulcanizer for vulcanization, and finally heat for aging to obtain a highly flame-retardant functionalized diatomaceous earth-grafted polyurethane elastomer.

2. The highly flame-retardant functionalized diatomite-grafted polyurethane elastomer according to claim 1, characterized in that: In the step (2), the mass fractions of the solvent are 2500-6000 parts, the co-solvent is 800-2000 parts, the amino diatomaceous earth is 100 parts, the DOPO-ITA compound is 65-120 parts, the 4-dimethylaminopyridine is 3-8 parts, and the dicyclohexylcarbodiimide is 40-100 parts.

3. The highly flame-retardant functionalized diatomite-grafted polyurethane elastomer according to claim 1, characterized in that: In the step (2), the solvent is N,N-dimethylformamide solvent, and the co-solvent is xylene solvent.

4. The highly flame-retardant functionalized diatomaceous earth grafted polyurethane elastomer according to claim 1, characterized in that: The reaction in step (2) is carried out at 60-85°C for 12-36 hours.

5. The highly flame-retardant functionalized diatomaceous earth grafted polyurethane elastomer according to claim 1, characterized in that: In the step (3), the weight proportions are 3500-8000 parts of xylene solvent, 100 parts of carboxyl DOPO modified diatomaceous earth, 30-65 parts of trimethylolpropane, and 0.15-0.4 parts of p-toluenesulfonic acid.

6. The highly flame-retardant functionalized diatomaceous earth grafted polyurethane elastomer according to claim 1, characterized in that: The reaction in step (3) is carried out at 80-120° C. for 10-20 h.

7. The highly flame-retardant functionalized diatomaceous earth grafted polyurethane elastomer according to claim 1, characterized in that: The mass fractions of the polycaprolactone diol in step (4) are 100 parts, 4,4'-diphenylmethane diisocyanate is 22-28 parts, dihydroxymethyl DOPO modified diatomaceous earth is 1.5-6 parts, dibutyltin dilaurate is 0.1-0.18 parts, and 1,4-butanediol is 3-5 parts.

8. The highly flame-retardant functionalized diatomaceous earth-grafted polyurethane elastomer according to claim 1, characterized in that: In the step (4), the vulcanization is carried out at 8-12 MPa for 20-40 min, and the heating and aging is carried out at 90-120° C. for 18-24 h.

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