An environment-friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects, its preparation method and application

Abstract

The present invention discloses an environment-friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects, and its preparation method and application. First, nanoparticles graft-modified with a silane coupling agent are prepared. Then, after heating and refluxing a methanol solution dissolving polyethyleneimine and benzaldehyde, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide is added and the reaction continues. The nanoparticles modified with the silane coupling agent are added. After complete reaction, a yellowish-brown suspension is obtained. After vacuum drying the suspension, it is washed, filtered with a hot ethanol solution, dried and ground into powder. After the powder fully absorbs carbon dioxide, an environment-friendly polyurethane foam foaming agent with both flame retardant and wave-absorbing effects can be obtained. The product is simple to synthesize and has a relatively high yield, solving the problems of the single function and environmental pollution of traditional polyurethane foaming agents, and the difficulty in the process of preparing environment-friendly granular foaming agents with modified polyethyleneimine.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation and application of blowing agents, and particularly relates to an environment-friendly polyurethane foam blowing agent with flame retardant and wave-absorbing effects, its preparation method and application. Background Art

[0002] The global annual output of polyurethane has exceeded 22 million tons, and 65% of the market share comes from polyurethane foam. Polyurethane foam is widely used in fields such as sofas, mattresses, refrigerators, pipelines, building insulation, and wave-absorbing materials, and blowing agents are one of the indispensable auxiliary materials in its production process.

[0003] Traditional blowing agents are low-boiling chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) compounds, which contain chlorine atoms in their structures and can damage the ozone layer; the currently used blowing agents include hydrofluorocarbon (HFC) compounds and hydrofluoroolefin (HFO) compounds, but the former has a strong greenhouse effect and can cause global warming, and the decomposition products of the latter in the atmosphere contain trifluoroacetic acid (CF3COOH) and hydrofluoric acid (HF), which may cause acid pollution and damage the ecological environment. Common blowing agents also include alkane blowing agents (such as cyclopentane), and the performance of such blowing agents is similar to that of HFO. Although they have less impact on the environment, there is a risk of explosion and combustion.

[0004] Recently, a series of CO2 adducts of hydrophobically modified polyethyleneimine (PEI) have been developed by researchers and used as polyurethane blowing agents, which is an environment-friendly blowing agent. However, hydrophobically modified polyethyleneimine is a very viscous liquid, and it needs to pass through carbon dioxide gas and be continuously stirred to form blowing agent particles. Therefore, a large amount of kinetic energy and carbon dioxide gas are consumed in the preparation process of this blowing agent, and this blowing agent has a single function, which limits its wide application.

[0005] CN 114507362 A discloses a method for preparing modified polyethyleneimine carbon dioxide adduct microsphere blowing agents by spraying. In this invention, hydrophobically modified polyethyleneimine is first dissolved in an organic solvent, and the obtained solution is sprayed into a reactor with a certain temperature and CO2 concentration through a pressure pump and a sprayer to obtain mist-like droplets. As the solvent volatilizes and hydrophobically modified polyethyleneimine reacts fully with CO2, the CO2 adduct microspheres of hydrophobically modified polyethyleneimine are obtained. However, the microsphere blowing agents prepared by the above method need to consume low-boiling organic solvents such as ether, dichloromethane, methyl tert-butyl ether, and acetone. There is a certain risk of leakage of organic solvents during the production process, which pollutes the environment and brings fire hazards, and also damages the physical health of production personnel. Moreover, this microsphere blowing agent has a single function, complex production equipment, and high preparation cost. Summary of the Invention

[0006] Technical problems to be solved by the present invention: Aiming at the disadvantages that traditional polyurethane foaming agents can cause greenhouse effects and environmental pollution, and the production of environmentally friendly polyurethane foaming agent particles by hydrophobic modified polyethyleneimine is complex and has a single function, an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, its preparation method and application are provided. The product is easy to synthesize, has a relatively high yield, and the final yield is not less than 85%. In the process of preparing polyurethane foam, the use method is simple, and the prepared polyurethane foam not only has high strength and uniform cell structure, but also has good flame retardant and wave absorption properties.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] An environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects and its preparation method, comprising the following steps:

[0009] a. Modifying nanoparticles with a silane coupling agent:

[0010] Disperse the nanoparticles in anhydrous ethanol, add water and a silane coupling agent, mix well, and heat and keep warm for reflux reaction to obtain silane coupling agent-modified nanoparticles;

[0011] b. Preparing a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0012] Completely dissolve the cationic water-soluble polymer in organic solvent I, add aromatic aldehyde, mix well to form a reaction system, stir, heat and keep warm for reflux;

[0013] Dissolve 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in solvent I, and dropwise add it into the reaction system within 1 hour. After the dropping is completed, continue to heat and reflux at a constant temperature. After the reaction is completed, a flame retardant intermediate graft-modified cationic polymer is obtained;

[0014] c. Preparing a suspension of an intermediate for an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0015] Add the silane coupling agent-modified nanoparticles to the flame retardant intermediate graft-modified cationic polymer obtained in step b, continue to keep warm for reaction, and obtain a suspension of an intermediate for an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects;

[0016] d. Preparing a powder of an intermediate for an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0017] Dry the suspension, wash, filter, dry and grind it to obtain a powder of an intermediate for an environmentally friendly polyurethane foam foaming agent with both flame retardant and wave absorption effects;

[0018] e. Preparing an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0019] Stir the powder of the polyurethane foam foaming agent intermediate in a carbon dioxide atmosphere until the powder fully absorbs carbon dioxide, and an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects is obtained.

[0020] Furthermore, in step a, the mass ratio of the nanoparticles to absolute ethanol is 1:2 to 1:20; the mass ratio of water to the silane coupling agent is 5:1 to 1:1; the mass ratio of the nanoparticles to the silane coupling agent is 10:1 to 1:1.

[0021] Furthermore, in step a, the silane coupling agent includes 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0022] Furthermore, in step a, the nanoparticles include nano-ferroferric oxide.

[0023] Furthermore, in step a, the temperature of the heating and heat preservation reflux reaction is 60-100°C; the time of the heating reflux reaction is 2-16 h; after the heating and heat preservation reflux reaction is completed, the product needs to be filtered and the filter cake is rinsed successively with absolute ethanol and deionized water; the silane coupling agent-modified nanoparticles need to be dried at 80°C.

[0024] Furthermore, in step b, the cationic water-soluble polymer includes polyethyleneimine; the average molecular weight of the cationic water-soluble polymer is 500-100000 Da; the organic solvent I includes one or more of methanol, ethanol, and propanol; the aromatic aldehyde includes one or more of benzaldehyde and phenylacetaldehyde; the mass ratio of the cationic water-soluble polymer to the aromatic aldehyde is 10:1 to 1:1; the grafting degree of the cationic polymer grafted and modified by the flame retardant intermediate is 5%-40%.

[0025] Furthermore, in step b, the temperature of the stirring, heating, and heat preservation reflux is 70-120°C; the time of the stirring, heating, and heat preservation reflux is 4-20 h; the time of continuing the heating reflux while maintaining the temperature constant is 2-24 h.

[0026] Furthermore, in step c, the nanoparticles in the suspension account for 2%-60% of the total mass of the foaming agent; the temperature of the continuing heat preservation reaction is 70-120°C; the time of the continuing heat preservation reaction is 4-24 h.

[0027] Furthermore, in step d, the stirring time in the carbon dioxide atmosphere is 24 h.

[0028] The present invention provides an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects prepared by the preparation method described in any one of the above.

[0029] The present invention also provides the application of the above-mentioned environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects in automobile manufacturing, transportation, civil engineering, light industry, textile, mechanical and electrical, or petrochemical industry.

[0030] Compared with the prior art, the present invention has the following characteristics and beneficial effects:

[0031] (1) For the preparation method of the environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects of the present invention, first, an aromatic aldehyde, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, and a cationic water-soluble polymer (polyethyleneimine is used in the present invention) are reacted to graft a flame retardant intermediate onto the polyethyleneimine molecular chain. Then, it continues to react with nano-sized magnetite particles modified by a silane coupling agent KH-560 to graft nano-sized particles onto the polyethyleneimine molecular chain, and the powder of the foaming agent intermediate is fully absorbed with carbon dioxide in a carbon dioxide atmosphere, finally obtaining a polyurethane foam foaming agent integrating environmental protection, flame retardancy, wave absorption and other characteristics. During the synthesis of this product, by modifying a typical water-soluble cationic polymer, the flame retardant intermediate and nano-functional particles with the characteristic of absorbing electromagnetic waves are grafted onto a highly branched polymer, realizing the unity of environmental protection, flame retardancy, wave absorption and enhanced performance, and solving the common technical problems in the industry such as the traditional polyurethane foam foaming agent causing greenhouse effect and environmental pollution, and the production of environment-friendly polyurethane foaming agent particles by hydrophobic modified polyethyleneimine being complex and having a single function. When used for producing polyurethane foam, it can greatly improve the flame retardant performance and compressive strength of the foam, and at the same time endow the foam with certain wave absorption characteristics.

[0032] (2) Compared with the prior art, the preparation process of the present invention is more simple, further shortens the preparation time, and while improving the yield, reduces the preparation cost, and is suitable for large-scale industrial production.

[0033] (3) The advantages of the present invention are as follows: a. No volatile toxic organic solvents are used in the preparation process of this polyurethane foaming agent, which can maximize the health of production personnel and environmental safety; b. Compared with hydrophobically modified polyethyleneimine, the powder of this polyurethane foaming agent intermediate has a higher specific surface area, can quickly and fully absorb carbon dioxide, and the operation is simple and efficient; c. In the process of preparing polyurethane foam, this foaming agent can release carbon dioxide gas through the reaction heat of polyurethane black material and white material, without generating halogen-containing gases, and is truly environmentally friendly and pollution-free; d. A certain amount of flame retardant intermediate is grafted on the chain of this polyurethane foaming agent, making the polyurethane foam product have good flame retardant performance; e. Since nano-ferroferric oxide particles are a widely used wave-absorbing material, and it is connected with highly branched polyethyleneimine through a silane coupling agent to prepare a foaming agent, which can endow the polyurethane foam with certain wave-absorbing performance; f. During the foaming process of polyurethane foam, the bubbles are nucleated by nano-ferroferric oxide particles, which can improve the pore uniformity of the polyurethane foam. And filling a certain amount of nano-ferroferric oxide particles can further improve the mechanical strength of the foam.

[0034] (4) During the production process of polyurethane foam, the operation of using this product is simple. Just add the powder of this foaming agent into the polyurethane white material and stir evenly. The process is simple and there is no need to carry out large-scale rectification on the existing production process and equipment. Description of the Drawings

[0035] Figure 1 It is a simple device diagram for the powder of the intermediate of the polyurethane foam foaming agent with flame retardant and wave-absorbing effects to absorb carbon dioxide gas.

[0036] Figure 2 It is a transmission electron microscope (TEM) image of the environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects prepared in Example 5, magnified 30,000 times and dispersed in ethanol.

[0037] Figure 3 It is a transmission electron microscope (TEM) image of the environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects prepared in Example 9, magnified 10,000 times and dispersed in ethanol.

[0038] Figure 4 It is the infrared absorption spectrum (FT-IR) before and after the reaction of the flame retardant intermediate grafted and modified cationic water-soluble polymer in Example 1. Among them, DOPO represents 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; BZL represents benzaldehyde; PEI represents polyethyleneimine; DPI represents the final reaction product.

[0039] Figure 5 It is the infrared absorption spectrum before and after the powder of the intermediate of the environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects prepared in Example 2 absorbs carbon dioxide.

[0040] Figure 6 It is the thermogravimetric-differential scanning calorimetry curve of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%) from 35 to 600 °C.

[0041] Figure 7 Scanning electron micrograph of polyurethane foam prepared from an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, magnified 30 times (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%).

[0042] Figure 8 Scanning electron micrograph of polyurethane foam prepared from an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, magnified 100 times (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%)

[0043] Figure 9 It is the curve of the real part (ε') and the imaginary part (ε") of the dielectric constant of polyurethane foam prepared from an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%) varying with frequency.

[0044] Figure 10 It is the curve of the magnetic permeability (μ) and the dielectric loss tangent (tanε) of polyurethane foam prepared from an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%) varying with frequency. Detailed implementation manners

[0045] The following examples are intended to further illustrate the present invention, but should not be construed as limiting the protection scope of the present invention. Some non-essential improvements and adjustments made by those skilled in the art to the present invention based on the above content of the present invention still fall within the protection scope of the present invention.

[0046] Example 1

[0047] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0048] a. Modifying nano-particles with a silane coupling agent:

[0049] Weigh 10.000 g of nano-ferroferric oxide and 20.000 g of absolute ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonicate the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonication, pour 5.000 g of water and 1.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 60 °C and keep it under reflux. Continue the reaction for 2 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake successively with absolute ethanol and deionized water. Place the filter cake in a vacuum oven at 50 °C to dry, and the nano-ferroferric oxide particles modified by silane coupling agent KH-560 are obtained.

[0050] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0051] After completely dissolving 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, add 1.234 g of benzaldehyde. After mixing evenly, add all of it to the reaction vessel, stir and heat to 85 °C and keep it under reflux for 10 h.

[0052] Dissolve 2.514 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol. Dropwise add the methanol solution containing DOPO into the reaction system drop by drop through a constant pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 85 °C and continue to heat and reflux for 8 h. After the reaction is completed, the DOPO graft-modified polyethyleneimine with a grafting degree of 5% is obtained.

[0053] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0054] Add 0.281 g of modified nano-ferroferric oxide to the reaction system and continue the reaction at 85 °C for 6 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a nano-particle mass ratio of 2%.

[0055] d. Prepare a powder of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0056] Place the suspension prepared in step c in a vacuum drying oven at 70 °C and dry it for 36 h to obtain a gray granular solid. Wash the solid with a hot ethanol solution, then filter, dry the filter cake and grind it into powder, and the powder of the polyurethane foam foaming agent intermediate with both flame retardant and wave absorption effects can be obtained.

[0057] e. Prepare a polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0058] Utilize the attached Figure 1The device stirs the powder of the polyurethane foam foaming agent intermediate in a carbon dioxide atmosphere for 24 hours until the powder fully absorbs carbon dioxide, and then an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects is obtained.

[0059] The high-pressure CO2 gas enters the reaction device after washing and drying. Under magnetic stirring, the powder of the polyurethane foam foaming agent intermediate fully absorbs CO2, and a polyurethane foam foaming agent with flame retardant and wave absorption effects can be prepared through a 24-hour reaction.

[0060] Example 2

[0061] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0062] a. Modify nanoparticles with a silane coupling agent:

[0063] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of absolute ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonically irradiate the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonic irradiation ends, pour 6.000 g of water and 2.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 80 °C and keep it under reflux for 8 hours while maintaining a constant temperature. After the reaction ends, filter the product and wash the filter cake with absolute ethanol and deionized water successively, and place the filter cake in a vacuum oven at 80 °C to dry, and then nano-ferroferric oxide particles modified with silane coupling agent KH-560 are obtained.

[0064] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0065] Completely dissolve 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, then add 6.170 g of benzaldehyde, mix evenly and add all of it to the reaction vessel, stir and heat to 85 °C and keep it under reflux for 10 h.

[0066] Dissolve 12.559 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol, and gradually add the methanol solution dissolved with DOPO dropwise into the reaction system through a constant pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 85 °C unchanged and continue to heat and reflux for 8 h. After the reaction is completed, DOPO graft-modified polyethyleneimine with a grafting degree of 25% is obtained.

[0067] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0068] Add 0.586 g of modified nano-ferroferric oxide into the reaction system, and continue the reaction at 85 °C for 6 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a nano-particle mass ratio of 2%.

[0069] d. Prepare the powder of the intermediate of the polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0070] Place the suspension prepared in step c in a vacuum drying oven at 70 °C for drying for 36 h to obtain gray granular solid. Wash the solid with a hot ethanol solution, then filter, dry the filter cake and grind it into powder to obtain the powder of the intermediate of the polyurethane foam foaming agent with both flame retardant and wave absorption effects.

[0071] e. Prepare the polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0072] Utilize the Figure 1 attached device to stir the powder of the intermediate of the polyurethane foam foaming agent in a carbon dioxide atmosphere for 24 h until the powder fully absorbs carbon dioxide, and then the environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects is obtained.

[0073] Example 3

[0074] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, and the steps are as follows:

[0075] a. Modify nano-particles with a silane coupling agent:

[0076] Weigh 10.000 g of nano-ferroferric oxide and 200.000 g of anhydrous ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonicate the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonication ends, pour 10.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 100 °C and keep it under reflux, and continue the reaction for 16 hours under the condition of constant temperature. After the reaction ends, filter the product and wash the filter cake successively with anhydrous ethanol and deionized water, and place the filter cake in a vacuum oven at 120 °C for drying to obtain the nano-ferroferric oxide particles modified with silane coupling agent KH-560.

[0077] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0078] Completely dissolve 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, then add 9.872 g of benzaldehyde, mix evenly and add all of them into the reaction vessel, stir and heat to 85 °C and keep it under reflux for 10 h.

[0079] Dissolve 20.094 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol. Dropwise add the methanol solution containing DOPO into the reaction system through a constant-pressure dropping funnel within 1 h. After the dropping is completed, continue heating under reflux at 85 °C for 8 h. After the reaction is completed, DOPO-grafted modified polyethyleneimine with a grafting degree of 40% is obtained.

[0080] c. Prepare a suspension of the intermediate of the polyurethane foam foaming agent with flame retardant and wave-absorbing effects:

[0081] Add 0.816 g of modified nano-ferroferric oxide into the reaction system and continue to react at 85 °C for 6 h to obtain a suspension of the multifunctional wet strength agent with flame retardant effect with a mass ratio of nano-particles of 2%.

[0082] d. Prepare a powder of the intermediate of the polyurethane foam foaming agent with flame retardant and wave-absorbing effects:

[0083] Place the suspension prepared in step c in a vacuum drying oven at 70 °C for 36 h to obtain gray granular solids. Wash the solids with a hot ethanol solution, then filter, dry the filter cake and grind it into powder to obtain the powder of the intermediate of the polyurethane foam foaming agent with both flame retardant and wave-absorbing effects.

[0084] e. Prepare an environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects:

[0085] Using the attached Figure 1 device, continuously stir the powder of the intermediate of the polyurethane foam foaming agent in a carbon dioxide atmosphere until the powder fully absorbs carbon dioxide to obtain an environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects.

[0086] Example 4

[0087] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects, the steps are as follows:

[0088] a. Modify nano-particles with a silane coupling agent:

[0089] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of absolute ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonicate the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After ultrasonication, pour 20.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 80 °C and keep it under reflux. Continue the reaction for 8 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake successively with absolute ethanol and deionized water. Place the filter cake in a vacuum oven at 80 °C to dry, and nano-ferroferric oxide particles modified with silane coupling agent KH-560 are obtained.

[0090] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0091] After completely dissolving 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, add 1.234 g of benzaldehyde. After mixing evenly, add all of it to the reaction vessel, stir and heat to 70 °C and keep it under reflux for 4 h.

[0092] Dissolve 2.514 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol. Dropwise add the methanol solution containing DOPO into the reaction system drop by drop through a constant pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 70 °C unchanged and continue to heat and reflux for 4 h. After the reaction is completed, DOPO graft-modified polyethyleneimine with a grafting degree of 5% is obtained.

[0093] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0094] Add 5.892 g of modified nano-ferroferric oxide to the reaction system and continue the reaction at 70 °C for 4 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a nano-particle mass ratio of 30%.

[0095] d. Prepare a powder of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0096] Place the suspension prepared in step c in a vacuum drying oven at 70 °C for 36 h to obtain a gray granular solid. Wash the solid with a hot ethanol solution, then filter, dry the filter cake and grind it into powder, and a powder of a polyurethane foam foaming agent intermediate with both flame retardant and wave absorption effects can be obtained.

[0097] e. Prepare a polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0098] Utilize the attached Figure 1The device stirs the powder of the polyurethane foam foaming agent intermediate in a carbon dioxide atmosphere for 24 hours until the powder fully absorbs carbon dioxide, thus obtaining an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects.

[0099] Example 5

[0100] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0101] a. Modify nanoparticles with a silane coupling agent:

[0102] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of absolute ethanol solution. Pour the ethanol into a beaker containing nano-ferroferric oxide, and ultrasonically treat the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonic treatment, pour 20.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 80 °C and keep it under reflux, and continue the reaction for 8 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake successively with absolute ethanol and deionized water, and place the filter cake in a vacuum oven at 80 °C to dry, thus obtaining nano-ferroferric oxide particles modified with silane coupling agent KH-560.

[0103] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0104] Completely dissolve 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, then add 6.170 g of benzaldehyde, mix evenly and add all of it to the reaction vessel, stir and heat to 95 °C and keep it under reflux for 10 h.

[0105] Dissolve 12.559 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol, and gradually add the methanol solution dissolved with DOPO dropwise into the reaction system through a constant pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 95 °C unchanged and continue heating under reflux for 12 h. After the reaction is completed, DOPO graft-modified polyethyleneimine with a grafting degree of 25% is obtained.

[0106] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0107] Add 12.312 g of modified nano-ferroferric oxide to the reaction system, and continue the reaction at 95 °C for 14 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a nano-particle mass ratio of 30%.

[0108] d. Preparation of powder of polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0109] Place the suspension prepared in step c in a vacuum drying oven at 70 °C and dry for 36 h to obtain gray granular solid. Wash the solid with hot ethanol solution, then filter, dry the filter cake and grind it into powder to obtain the powder of polyurethane foam foaming agent intermediate with both flame retardant and wave absorption effects.

[0110] e. Preparation of polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0111] Utilize the Figure 1 attached device to stir the powder of polyurethane foam foaming agent intermediate in a carbon dioxide atmosphere for 24 h until the powder fully absorbs carbon dioxide, thus obtaining the environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects.

[0112] Example 6

[0113] A preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0114] a. Modification of nanoparticles with silane coupling agent:

[0115] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of anhydrous ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonically treat the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonic treatment, pour 20.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat to 80 °C and keep it under reflux, and continue to react for 8 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake successively with anhydrous ethanol and deionized water, and place the filter cake in a vacuum oven at 80 °C to dry, thus obtaining the nano-ferroferric oxide particles modified with silane coupling agent KH-560.

[0116] b. Preparation of flame retardant intermediate graft-modified cationic water-soluble polymer:

[0117] Completely dissolve 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, then add 9.872 g of benzaldehyde, mix evenly and add all of it to the reaction vessel, stir and heat to 120 °C and keep it under reflux for 20 h.

[0118] Dissolve 20.094 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol. Dropwise add the methanol solution containing DOPO into the reaction system through a constant-pressure dropping funnel within 1 h. After the dropping is completed, continue heating under reflux at 85 °C for 24 h. After the reaction is completed, DOPO-grafted modified polyethyleneimine with a grafting degree of 40% is obtained.

[0119] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0120] Add 17.128 g of modified nano-ferroferric oxide into the reaction system and continue the reaction at 120 °C for 24 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a mass ratio of nano-particles of 30%.

[0121] d. Prepare a powder of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0122] Place the suspension prepared in step c in a vacuum drying oven at 70 °C and dry for 36 h to obtain gray granular solids. Wash the solids with a hot ethanol solution, then filter, dry the filter cake and grind it into powder to obtain the powder of the polyurethane foam foaming agent intermediate with both flame retardant and wave absorption effects.

[0123] e. Prepare an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0124] Use the attached Figure 1 device to stir the powder of the polyurethane foam foaming agent intermediate in a carbon dioxide atmosphere for 24 h until the powder fully absorbs carbon dioxide to obtain an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects.

[0125] Example 7

[0126] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0127] a. Modify nano-particles with a silane coupling agent:

[0128] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of absolute ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonicate the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After ultrasonication, pour 20.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After mixing well, pour the mixture into a flask equipped with a stirring device, heat it to 80 °C and keep it refluxing. Continue the reaction for 8 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake successively with absolute ethanol and deionized water. Place the filter cake in a vacuum oven at 80 °C to dry, and nano-ferroferric oxide particles modified with silane coupling agent KH-560 are obtained.

[0129] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0130] Completely dissolve 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of ethanol, add 1.234 g of benzaldehyde, mix well and then add all of it to the reaction vessel, stir and heat to 85 °C and keep it refluxing for 10 h.

[0131] Dissolve 2.514 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of ethanol, and gradually add the ethanol solution dissolved with DOPO dropwise into the reaction system through a constant pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 85 °C and continue heating and refluxing for 8 h. After the reaction is completed, DOPO graft-modified polyethyleneimine with a grafting degree of 5% is obtained.

[0132] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0133] Add 20.622 g of modified nano-ferroferric oxide to the reaction system, and continue the reaction at 85 °C for 6 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a nano-particle mass ratio of 60%.

[0134] d. Prepare a powder of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0135] Place the suspension prepared in step c in a vacuum drying oven at 70 °C to dry for 36 h to obtain a gray granular solid. Wash the solid with a hot ethanol solution, then filter, dry the filter cake and grind it into powder, and a powder of a polyurethane foam foaming agent intermediate with both flame retardant and wave absorption effects can be obtained.

[0136] e. Prepare a polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0137] Utilize the attached Figure 1The device stirs the powder of the polyurethane foam foaming agent intermediate in a carbon dioxide atmosphere for 24 hours until the powder fully absorbs carbon dioxide, thus obtaining an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects.

[0138] Example 8

[0139] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0140] a. Modify nanoparticles with silane coupling agent:

[0141] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of absolute ethanol solution, pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonically treat the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonic treatment, pour 20.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 80 °C and keep it under reflux, and continue the reaction for 8 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake successively with absolute ethanol and deionized water, and place the filter cake in a vacuum oven at 80 °C to dry, thus obtaining nano-ferroferric oxide particles modified with silane coupling agent KH-560.

[0142] b. Prepare a flame retardant intermediate graft-modified cationic water-soluble polymer:

[0143] Completely dissolve 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of propanol, then add 6.986 g of phenylacetaldehyde, mix evenly and add all of them to the reaction vessel, stir and heat to 85 °C and keep it under reflux for 10 h.

[0144] Dissolve 12.559 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of propanol, and gradually add the propanol solution dissolved with DOPO dropwise into the reaction system through a constant pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 85 °C unchanged and continue heating under reflux for 8 h. After the reaction is completed, DOPO graft-modified polyethyleneimine with a grafting degree of 25% is obtained.

[0145] c. Prepare a suspension of a polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0146] Add 43.094 g of modified nano-ferroferric oxide to the reaction system, and continue the reaction at 85 °C for 6 h to obtain a suspension of a multifunctional wet strength agent with a flame retardant effect and a nano-particle mass ratio of 60%.

[0147] d. Preparation of powder of polyurethane foam foaming agent intermediate with flame retardant and wave absorption effects:

[0148] The suspension prepared in step c was placed in a vacuum drying oven at 70 °C and dried for 36 h to obtain gray granular solid. The solid was washed with hot ethanol solution, then filtered, and the filter cake was dried and ground into powder to obtain the powder of polyurethane foam foaming agent intermediate with both flame retardant and wave absorption effects.

[0149] e. Preparation of polyurethane foam foaming agent with flame retardant and wave absorption effects:

[0150] Using the attached Figure 1 device, the powder of polyurethane foam foaming agent intermediate was stirred in a carbon dioxide atmosphere for 24 h until the powder fully absorbed carbon dioxide, and the environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects was obtained.

[0151] Example 9

[0152] A preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects, the steps are as follows:

[0153] a. Modification of nanoparticles with silane coupling agent:

[0154] Weigh 10.000 g of nano-ferroferric oxide and 100.000 g of absolute ethanol solution. Pour the ethanol into the beaker containing nano-ferroferric oxide, and ultrasonically irradiate the mixture for 30 minutes to fully disperse the nano-ferroferric oxide in the ethanol solution. After the ultrasonic irradiation, pour 20.000 g of water and 10.000 g of silane coupling agent KH560 into the above mixture. After fully mixing evenly, pour the mixture into a flask equipped with a stirring device, heat it to 80 °C and keep it refluxing, and continue to react for 8 hours under the condition of constant temperature. After the reaction, filter the product and wash the filter cake with absolute ethanol and deionized water successively, and place the filter cake in a vacuum oven at 80 °C to dry, and the nano-ferroferric oxide particles modified with silane coupling agent KH-560 are obtained.

[0155] b. Preparation of flame retardant intermediate grafted and modified cationic water-soluble polymer:

[0156] After completely dissolving 10.000 g of polyethyleneimine (PEI) with a molecular weight of 500 in 100 ml of methanol, add 9.872 g of benzaldehyde, mix evenly and then add all of it to the reaction vessel, stir and heat to 85 °C and keep it refluxing for 10 h.

[0157] Dissolve 20.094 g of 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) in 50 ml of methanol. Dropwise add the methanol solution containing DOPO into the reaction system through a constant-pressure dropping funnel within 1 h. After the dropping is completed, keep the temperature at 85 °C and continue heating under reflux for 8 h. After the reaction is completed, DOPO-grafted modified polyethyleneimine with a grafting degree of 40% is obtained.

[0158] c. Prepare a suspension of the intermediate of the polyurethane foam foaming agent with flame retardant and wave-absorbing effects:

[0159] Add 59.949 g of modified nano-ferroferric oxide into the reaction system and continue to react at 85 °C for 6 h to obtain a suspension of the multifunctional wet strength agent with flame retardant effect with a mass ratio of nano-particles of 60%.

[0160] d. Prepare the powder of the intermediate of the polyurethane foam foaming agent with flame retardant and wave-absorbing effects:

[0161] Place the suspension prepared in step c in a vacuum drying oven at 70 °C for 36 h to obtain gray granular solids. Wash the solids with a hot ethanol solution, then filter, dry the filter cake and grind it into powder to obtain the powder of the intermediate of the polyurethane foam foaming agent with both flame retardant and wave-absorbing effects.

[0162] e. Prepare the polyurethane foam foaming agent with flame retardant and wave-absorbing effects:

[0163] Using the attached Figure 1 device, stir the powder of the intermediate of the polyurethane foam foaming agent in a carbon dioxide atmosphere for 24 h until the powder fully absorbs carbon dioxide to obtain an environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects.

[0164] Figure 2 Transmission electron microscope (TEM) image at 30,000 times magnification of the environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects prepared in Example 5 dispersed in ethanol. Figure 3 Transmission electron microscope (TEM) image at 10,000 times magnification of the environmentally friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects prepared in Example 9 dispersed in ethanol. Through Figure 2 and Figure 3 it can be observed that the foaming agent is spherical, with an average particle size of 20 nm, and is evenly dispersed and not easy to agglomerate.

[0165] Figure 4FT-IR spectra before and after the reaction of the flame retardant intermediate graft-modified cationic water-soluble polymer in Example 1. Among them, DOPO represents 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide; BZL represents benzaldehyde; PEI represents polyethyleneimine; DPI represents the final reaction product. As can be seen from the figure, for the infrared spectrum of DOPO, the absorption peaks generated at wavenumbers of 3054 cm-1, 2437 cm-1, 1597 cm-1, 1450 cm-1, 1250 cm-1, and 1048 cm-1 are the characteristic vibration peaks of CAr-H, P-H, P-Ph, P-C, P=O, and P-O, respectively. After the reaction, the characteristic absorption peak of the P-H bond at 2437 cm-1 completely disappears, indicating that all P-H bonds have reacted with the carbonyl group of benzaldehyde and the amino group of polyethyleneimine.

[0166] Figure 5 FT-IR spectra of the powder of the environmentally friendly polyurethane foam blowing agent intermediate with flame retardant and wave absorption effects prepared in Example 2 before and after absorbing carbon dioxide. The infrared absorption curve shows absorption peaks at 1100 cm -1 , 1049 cm -1 which are the characteristic vibration peaks of -Si-O- and -Si-O-Si-, respectively. The absorption peaks at 1448 cm -1 , 1377 cm -1 are the bending vibration peaks of amino cations, indicating that the powder of the blowing agent intermediate has successfully absorbed CO2.

[0167] Figure 6 TG-DSC curve of the environmentally friendly polyurethane foam blowing agent with flame retardant and wave absorption effects (grafting degree of DOPO is 25%, mass ratio of nano-ferroferric oxide particles is 10%) from room temperature to 600 °C. It can be seen from the TG-DSC curve that the blowing agent has an exothermic peak at 35-150 °C and a thermal weight loss of nearly 6%, indicating that the blowing agent can release CO2 when heated.

[0168] Figure 7 SEM image of the polyurethane foam prepared from the environmentally friendly polyurethane foam blowing agent with flame retardant and wave absorption effects magnified 30 times (grafting degree of DOPO is 25%, mass ratio of nano-ferroferric oxide particles is 10%). Figure 8 SEM image of the polyurethane foam prepared from the environmentally friendly polyurethane foam blowing agent with flame retardant and wave absorption effects magnified 100 times (grafting degree of DOPO is 25%, mass ratio of nano-ferroferric oxide particles is 10%). From Figure 7 and Figure 8It can be seen that the environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects can successfully prepare polyurethane foam. The obtained cell shapes are all spherical, the cell sizes are uniform, and it has a closed-cell structure.

[0169] Figure 9 It is the curve of the real part (ε') and the imaginary part (ε") of the dielectric constant of the polyurethane foam prepared by the environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%) varying with frequency. As can be seen from the figure, the wave-absorbing foam has good dielectric properties in the frequency range of 2 - 18 GHz. The variation range of the real part of the dielectric constant is about 12.5 - 6.5, and the imaginary part oscillates around 3.

[0170] Figure 10 It is the curve of the magnetic permeability (μ) and the dielectric loss tangent (tanε) of the polyurethane foam prepared by the environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects (the grafting degree of DOPO is 25%, and the mass ratio of nano-ferroferric oxide particles is 10%) varying with frequency. As can be seen from the figure, the wave-absorbing foam has a relatively high magnetic permeability in the frequency range of 2 - 18 GHz. Because there is a certain amount of loss medium in the wave-absorbing foam and there are a large number of closed-cell structures, it endows the foam with good dielectric loss ability, and its loss tangent value oscillates around 0.5.

[0171] To verify the performance of the polyurethane foam prepared by the foaming agents of each example, the products of each example were used as foaming agents, and the foam of the application example was prepared according to the polyurethane foam formula in Table 1; the product 25% DPI-PEI-CO2 that did not add Fe3O4 but absorbed CO2 in Example 5 was used as the foaming agent, and the foam of the comparative example was prepared according to the polyurethane foam formula in Table 1. The performance of each example and the comparative example is shown in Table 2.

[0172] Table 1

[0173]

[0174] Table 2

[0175]

[0176] Polyurethane is an organic polymer with a basic structure of -C-C- bonds and is extremely flammable when exposed to fire. Therefore, improving the flame retardancy of polyurethane foam is extremely important for expanding its application fields. DOPO is an important phosphorus-based flame retardant. By analyzing the relevant data in Table 2, it can be found that as the grafting degree of DOPO in the foaming agent increases, the limiting oxygen index of the foam also increases. The wave-absorbing particles in the foam can not only serve as a loss medium for electromagnetic waves but also act as fillers in the foam, which is also of great significance for improving the compression performance of the foam. When the grafting degree of DOPO in the polyurethane foam foaming agent with flame retardant and wave-absorbing effects is increased from 5% to 40% and the content of nano-Fe3O4 particles is increased from 2% to 60%, the limiting oxygen index of the prepared foam is increased from 21% to 34%, and the compression performance is increased from 794 kPa to 1354 kPa.

Claims

1. A preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave-absorbing effects, characterized in that, It includes the following steps: a. Modifying nano-ferroferric oxide particles with a silane coupling agent: Disperse nano-ferroferric oxide particles in absolute ethanol, add water and a silane coupling agent, mix them evenly, and heat and keep warm for reflux reaction to obtain nano-ferroferric oxide particles modified with a silane coupling agent; b. Preparing a flame-retardant intermediate graft-modified polyethyleneimine: Completely dissolve polyethyleneimine in organic solvent I, then add aromatic aldehyde, mix them evenly to form a reaction system, stir, heat and keep warm for reflux; Dissolve 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide in solvent I, and dropwise add it into the reaction system within 1 hour. After the dropping is completed, continue heating and refluxing at a constant temperature. After the reaction is completed, a flame-retardant intermediate graft-modified polyethyleneimine is obtained; c. Preparing a suspension of a polyurethane foam blowing agent intermediate with flame-retardant and wave-absorbing effects: Add the nano-ferroferric oxide particles modified with a silane coupling agent to the flame-retardant intermediate graft-modified polyethyleneimine obtained in step b, and continue to keep warm for reaction to obtain a suspension of a polyurethane foam blowing agent intermediate with flame-retardant and wave-absorbing effects; d. Preparing a powder of a polyurethane foam blowing agent intermediate with flame-retardant and wave-absorbing effects: Dry the suspension, wash, filter, dry and grind it to obtain a powder of a polyurethane foam blowing agent intermediate with both flame-retardant and wave-absorbing effects; e. Preparing a polyurethane foam blowing agent with flame-retardant and wave-absorbing effects: Stir the powder of the polyurethane foam blowing agent intermediate in a carbon dioxide atmosphere until the powder fully absorbs carbon dioxide, and a green polyurethane foam blowing agent with flame-retardant and wave-absorbing effects is obtained.

2. The preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step a, the mass ratio of the nano-ferroferric oxide particles to absolute ethanol is 1:2 to 1:20; the mass ratio of water to the silane coupling agent is 5:1 to 1:1; the mass ratio of the nano-ferroferric oxide particles to the silane coupling agent is 10:1 to 1:

1.

3. The preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step a, the silane coupling agent includes 3-(2,3-epoxypropoxy)propyltrimethoxysilane.

4. The preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step a, the nano-ferroferric oxide particles include nano-ferroferric oxide.

5. The preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step a, the temperature of the heating and keeping warm for reflux reaction is 60 to 100 °C; the time of the heating and reflux reaction is 2 - 16 h; after the heating and keeping warm for reflux reaction, the product needs to be filtered and the filter cake is washed successively with absolute ethanol and deionized water; the nano-ferroferric oxide particles modified with a silane coupling agent need to be dried at 80 °C.

6. The preparation method of an environmentally friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step b, the average molecular weight of the polyethyleneimine is 500 to 100,000 Da; the organic solvent I includes methanol, ethanol, and propanol; the aromatic aldehyde includes benzaldehyde and phenylacetaldehyde; the mass ratio of the polyethyleneimine to the aromatic aldehyde is 10:1 to 1:1; the grafting degree of the flame-retardant intermediate graft-modified polyethyleneimine is 5% to 40%.

7. The preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step b, the temperature of the stirring, heating and keeping warm for reflux is 70 to 120 °C; the time of the stirring, heating and keeping warm for reflux is 4 to 20 h; the time of continuing heating and refluxing at a constant temperature is 2 to 24 h.

8. The preparation method of an environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 1, characterized in that, In step c, the nano-ferroferric oxide particles in the suspension account for 2% to 60% of the total mass of the foaming agent; the temperature for the continued heat preservation reaction is 70 to 120 °C; the time for the continued heat preservation reaction is 4 to 24 h; in step e, the stirring time under a carbon dioxide atmosphere is 24 h.

9. An environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects prepared by the preparation method according to any one of claims 1-8.

10. Application of the environment-friendly polyurethane foam foaming agent with flame retardant and wave absorption effects according to claim 9 in automobile manufacturing, transportation, civil engineering, light industry, textile, mechanical and electrical engineering or petrochemical industry.

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