Preparation method of a flame-retardant aerogel derived from a flame-retardant unsaturated polyester

Abstract

The present invention provides a crosslinked gas-phase flame retardant. By introducing structures containing silicon, nitrogen, phosphorus in the +1 oxidation state, etc., the flame retardant efficiency of the crosslinked gas-phase flame retardant with the specific structure is enhanced, and the flame retardant properties of the subsequently prepared flame-retardant unsaturated polyester composite material and flame-retardant aerogel are greatly improved. The present invention uses the crosslinked gas-phase flame retardant and waste materials made of unsaturated polyester as raw materials to prepare a flame-retardant unsaturated polyester with excellent flame retardant properties; then uses the flame-retardant unsaturated polyester as a raw material to directly degrade and prepare a flame-retardant aerogel with excellent flame retardancy and a double crosslinked network structure, which helps to realize the high-value upgrading and recycling of flame-retardant unsaturated polyester after it has been in long-term service and becomes waste.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogel materials, and particularly to a preparation method of a flame-retardant aerogel derived from flame-retardant unsaturated polyester. Background Art

[0002] Aerogel is currently recognized as the solid material with the lowest density in the world. Due to its characteristics such as low density, high porosity, and large surface area, it has received great attention and is widely used in fields such as thermal insulation, catalysis, adsorption and separation, etc. Aerogels are often prepared by the sol-gel method. Through a specific drying method, gas replaces the liquid phase in the hydrogel without changing the three-dimensional network structure of the aerogel itself, and finally a nanoscale porous solid material is formed. Currently, there are various types of aerogels, such as nanocellulose aerogel, silica aerogel, graphene aerogel, etc. However, the types of raw materials for preparing aerogels are still relatively few at present, and materials such as graphene and nanocellulose are expensive, which greatly increases their costs and limits their large-scale applications. Therefore, obtaining starting materials from renewable resources or waste resources is becoming an attractive way.

[0003] Unsaturated polyester is one of the most widely used thermosetting materials. Due to the three-dimensional network structure formed by the copolymerization cross-linking reaction of unsaturated bonds, the cured unsaturated polyester materials have excellent mechanical, corrosion-resistant, thermal-stable, and chemical-stable properties, etc., and thus are highly favored in fields such as chemical anticorrosion, rail transit, and building materials. At the same time, the excellent properties have led to a sharp increase in the demand for unsaturated polyester. In recent years, the annual output of unsaturated polyester in China has continued to grow. However, while it is being produced and used in large quantities, the waste and obsolete products of thermosetting unsaturated polyester and its composites are also rapidly accumulating. At present, when environmental protection and green development have become the theme of the times, recycling unsaturated polyester to produce high-value-added products is an attractive and feasible environmental and economic attempt. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation method of a flame-retardant aerogel derived from flame-retardant unsaturated polyester. By using the excellent flame-retardant performance of the cross-linked gas-phase flame retardant provided by the present invention, and using it and the waste of unsaturated polyester and unsaturated polyester materials as raw materials, a flame-retardant unsaturated polyester with excellent flame-retardant performance is prepared, realizing the high-value utilization of the waste of unsaturated polyester materials, and then the flame-retardant aerogel prepared by using the flame-retardant unsaturated polyester as a raw material has excellent flame-retardant performance.

[0005] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0006] The present invention provides a cross-linked gas-phase flame retardant, which has a chemical structure as shown in Formula 1 below:

[0007]

[0008] In the formula 1, n is from 1 to 10.

[0009] The present invention also provides a preparation method of the cross-linked gas-phase flame retardant described in the above technical solution, including the following steps:

[0010] After mixing 3-aminopropyltriethoxysilane, paraformaldehyde, diphenylphosphine oxide and an organic solvent, a first reaction and solvent removal are carried out in sequence to obtain an intermediate shown in the following formula 2:

[0011]

[0012] After mixing the intermediate with a mixed solution containing ethanol and water, a polymerization reaction is carried out to obtain a cross-linked gas-phase flame retardant.

[0013] Preferably, the molar ratio of 3-aminopropyltriethoxysilane, paraformaldehyde and diphenylphosphine oxide is 1:(0.5 - 0.8):2.

[0014] Preferably, the volume ratio of ethanol to water in the mixed solution of ethanol and water is 1:1 - 3:1, the pH value of the mixed solution is 2 - 5 or 9 - 12; the temperature of the polymerization reaction is 70 - 90 °C, and the time of the polymerization reaction is 6 - 10 h.

[0015] The present invention also provides a preparation method of a flame-retardant aerogel derived from a flame-retardant unsaturated polyester, using the cross-linked gas-phase flame retardant described in the above technical solution as a raw material. The preparation method of the flame-retardant aerogel includes the following steps:

[0016] (1) After mixing the cross-linked gas-phase flame retardant with an unsaturated polyester resin and waste of the unsaturated polyester resin material, curing is carried out to obtain a flame-retardant unsaturated polyester;

[0017] (2) The flame-retardant unsaturated polyester obtained in step (1) is sliced and soaked in dichloromethane in sequence to obtain a pretreated flame-retardant unsaturated polyester;

[0018] (3) The pretreated flame-retardant unsaturated polyester obtained in step (2) is added to a mixed alkaline solution of diethylenetriamine and potassium hydroxide, and then heated and stirred and filtered in sequence to obtain a solid;

[0019] (4) The solid obtained in step (3) is soaked in water and freeze-dried in sequence to obtain a flame-retardant aerogel derived from a flame-retardant unsaturated polyester.

[0020] Preferably, the mass ratio of the cross-linked gas-phase flame retardant in step (1) to the total mass of the unsaturated polyester resin and the waste of the unsaturated polyester resin material is 1.5:8.5 - 3:7.

[0021] Preferably, in the step (1), the curing temperature is 25-120 °C, and the curing time is 0.5-7 h.

[0022] Preferably, in the step (3), the temperature of heating and stirring is 70-100 °C, and the time of heating and stirring is 2-4 h.

[0023] Preferably, during the freeze-drying process in the step (4), the cold trap temperature is -70 to -50 °C, the temperature of the sample to be freeze-dried is 10-20 °C, and the vacuum degree is 1-5 Pa; the freeze-drying time is 24-48 h.

[0024] The present invention also provides a flame-retardant aerogel derived from flame-retardant unsaturated polyester prepared by the above preparation method.

[0025] The present invention provides a crosslinked gas-phase flame retardant. By introducing structures containing silicon, nitrogen, phosphorus in the +1 oxidation state, etc., the flame retardancy efficiency of the crosslinked gas-phase flame retardant with the specific structure is enhanced, and the flame retardant performance of the subsequent prepared flame-retardant aerogel is greatly improved. The present invention uses the crosslinked gas-phase flame retardant and waste of unsaturated polyester and unsaturated polyester materials as raw materials to prepare a flame-retardant unsaturated polyester with excellent flame retardant performance, and then uses the flame-retardant unsaturated polyester as a raw material to directly degrade and prepare a flame-retardant aerogel derived from flame-retardant unsaturated polyester with excellent flame retardant performance and a double-crosslinked network structure, realizing the high-value recycling of unsaturated polyester. Description of the Drawings

[0026] Figure 1 1H NMR spectrum of the crosslinked gas-phase flame retardant prepared in Example 1;

[0027] Figure 2 31P NMR spectrum of the crosslinked gas-phase flame retardant prepared in Example 1;

[0028] Figure 3 Thermogravimetric curve of the crosslinked gas-phase flame retardant prepared in Example 1;

[0029] Figure 4 TGA curves of pure unsaturated polyester and the flame-retardant unsaturated polyester prepared in Example 2 of the present invention;

[0030] Figure 5 Heat release rate curves of pure unsaturated polyester and the flame-retardant unsaturated polyester prepared in Example 2 of the present invention;

[0031] Figure 6 Heat release rate curves of non-flame-retardant aerogel and the flame-retardant aerogel derived from flame-retardant unsaturated polyester prepared in Example 2 of the present invention;

[0032] Figure 7 Thermal release rate curve of the flame retardant unsaturated polyester prepared as a comparative example;

[0033] Figure 8 Thermal release rate curve of the flame retardant aerogel derived from the flame retardant unsaturated polyester as a comparative example. Detailed implementation manners

[0034] In the present invention, unless otherwise specified, the raw materials used are all conventional commercially available products in the art.

[0035] The present invention provides a crosslinked gas-phase flame retardant having a chemical structure shown in Formula 1 below:

[0036]

[0037] In the present invention, in Formula 1, n is 1 to 10, more preferably 2 to 9.

[0038] The present invention also provides a preparation method of the crosslinked gas-phase flame retardant described in the above technical solution, including the following steps:

[0039] After mixing 3-aminopropyltriethoxysilane, paraformaldehyde, diphenylphosphine oxide and an organic solvent, a first reaction and solvent removal are carried out in sequence to obtain an intermediate shown in Formula 2 below:

[0040]

[0041] After mixing the intermediate and a mixed solution containing ethanol and water, a polymerization reaction is carried out to obtain a crosslinked gas-phase flame retardant.

[0042] In the present invention, the molar ratio of 3-aminopropyltriethoxysilane, paraformaldehyde and diphenylphosphine oxide is preferably 1:(0.5 to 0.8):2, more preferably 1:0.67:2. The present invention controls the molar ratio of 3-aminopropyltriethoxysilane, paraformaldehyde and diphenylphosphine oxide within the above range, so that each component reacts fully to prepare an intermediate with a high yield.

[0043] In the present invention, the organic solvent is preferably chloroform, tetrahydrofuran or dichloromethane.

[0044] In the present invention, the temperature of the first reaction is preferably 40 to 60°C, more preferably 45 to 55°C. In the present invention, the time of the first reaction is preferably 10 to 15 h, more preferably 11 to 14 h. The present invention controls the temperature and time of the first reaction within the above range, so that each component reacts fully to prepare an intermediate with a high yield.

[0045] In the present invention, the preferred method for removing the solvent is rotary evaporation. The present invention has no special limitation on the selected method, as long as the residual solvent can be removed.

[0046] In the present invention, the volume ratio of ethanol to water in the mixed solution containing ethanol and water is 1:1 to 3:1.

[0047] In the present invention, the polymerization reaction is preferably carried out under stirring conditions. The present invention has no special limitation on the stirring method, as long as the components can be mixed evenly. In the present invention, the pH value of the mixed solution is preferably 2 to 5 or 9 to 12, more preferably 3 to 4 or 9 to 10. In the present invention, the temperature of the polymerization reaction is preferably 70 to 90 °C, more preferably 75 to 85 °C. In the present invention, the time of the polymerization reaction is preferably 6 to 10 h, more preferably 7 to 9 h. By controlling the pH value of the mixed solution, the temperature and time of the polymerization reaction within the above ranges in the present invention, the raw materials can react fully, and a cross-linked gas-phase flame retardant with high yield and excellent performance can be prepared.

[0048] The present invention also provides a preparation method of a flame-retardant aerogel derived from a flame-retardant unsaturated polyester. Using the cross-linked gas-phase flame retardant described in the above technical solution as a raw material, the preparation method of the flame-retardant aerogel includes the following steps:

[0049] (1) After mixing the cross-linked gas-phase flame retardant with an unsaturated polyester resin and waste materials made of unsaturated polyester resin, curing is carried out to obtain a flame-retardant unsaturated polyester;

[0050] (2) The flame-retardant unsaturated polyester obtained in step (1) is successively subjected to slicing and soaking in dichloromethane to obtain a pretreated flame-retardant unsaturated polyester;

[0051] (3) The pretreated flame-retardant unsaturated polyester obtained in step (2) is added to a mixed alkali solution containing diethylenetriamine and potassium hydroxide, and then heated and stirred and filtered successively to obtain a solid;

[0052] (4) The solid obtained in step (3) is successively subjected to water soaking and freeze-drying to obtain a flame-retardant aerogel derived from a flame-retardant unsaturated polyester.

[0053] In the present invention, the cross-linked gas-phase flame retardant is mixed with an unsaturated polyester resin and waste materials made of unsaturated polyester resin, and then cured to obtain a flame-retardant unsaturated polyester.

[0054] In the present invention, the ratio of the mass of the crosslinked gas-phase flame retardant to the total mass of the unsaturated polyester resin and the waste made of unsaturated polyester resin is 1.5:8.5 to 3:7. The present invention controls the ratio of the mass of the crosslinked gas-phase flame retardant to the total mass of the unsaturated polyester resin and the waste made of unsaturated polyester resin within the above range to achieve high flame retardancy of the flame-retardant unsaturated polyester and good flame retardancy of the aerogel prepared from the flame-retardant unsaturated polyester as a raw material.

[0055] In the present invention, the curing temperature is preferably 25 to 120 °C, and the curing time is preferably 0.5 to 7 h. In the present invention, the type of the flame-retardant unsaturated polyester is preferably room-temperature curing unsaturated polyester and high-temperature curing unsaturated polyester; when the type of the flame-retardant unsaturated polyester is room-temperature curing unsaturated polyester, the curing is preferably carried out at room temperature for 0.5 to 3 h; when the type of the flame-retardant unsaturated polyester is high-temperature curing unsaturated polyester, the curing is preferably carried out by first curing at 70 °C for 4 h and then curing at 120 °C for 3 h.

[0056] After obtaining the flame-retardant unsaturated polyester, the present invention successively subjects the flame-retardant unsaturated polyester to slicing and dichloromethane soaking treatment to obtain pretreated flame-retardant unsaturated polyester.

[0057] In the present invention, the size of the fragments obtained by slicing is preferably <100 mesh. In the present invention, the temperature of the dichloromethane soaking treatment is preferably room temperature. In the present invention, the time of the dichloromethane soaking treatment is preferably 18 to 30 h, more preferably 20 to 28 h. The present invention controls the temperature and time of the dichloromethane soaking treatment within the above range to fully swell the flame-retardant unsaturated polyester and dissolve the uncured part, facilitating subsequent degradation operations.

[0058] After the dichloromethane soaking treatment is completed, the present invention preferably separates the solid and liquid of the product of the dichloromethane soaking treatment to obtain pretreated flame-retardant unsaturated polyester.

[0059] The present invention has no special limitation on the method of the solid-liquid separation, and any well-known technical solution in the art can be adopted.

[0060] After obtaining the pretreated flame-retardant unsaturated polyester, the present invention adds the pretreated flame-retardant unsaturated polyester to a mixed alkali solution containing diethylenetriamine and potassium hydroxide, and then successively carries out heating and stirring and filtration to obtain a solid.

[0061] In the present invention, the ratio of the mass of the pretreated flame-retardant unsaturated polyester to the mass of the mixed alkali solution containing diethylenetriamine and potassium hydroxide is preferably (2 - 4) g:100 g.

[0062] In the present invention, the mixed alkali solution containing diethylenetriamine and potassium hydroxide is preferably an aqueous solution of diethylenetriamine and potassium hydroxide with a mass fraction of 30 wt% to 50 wt%. In the present invention, the mass ratio of diethylenetriamine to potassium hydroxide is preferably (15 to 20):1.

[0063] In the present invention, the temperature of the heating and stirring is preferably 60 to 100 °C, more preferably 70 to 90 °C. In the present invention, the time of the heating and stirring is preferably 1 to 4 h, more preferably 2 to 3 h. The present invention controls the temperature and time of the heating and stirring within the above ranges to regulate the number of broken ester bonds in the unsaturated polyester material.

[0064] The present invention has no special limitation on the filtration method, and the well-known technical solutions in the art can be adopted.

[0065] After obtaining the solid, the present invention sequentially soaks the solid in water and freeze-dries it to obtain a flame-retardant aerogel derived from the flame-retardant unsaturated polyester.

[0066] In the present invention, the temperature of the water soaking is preferably 20 to 60 °C, more preferably 25 to 40 °C. In the present invention, the time of the water soaking is preferably 0.5 to 3 h, more preferably 1 to 2 h. The present invention controls the temperature and time of the water soaking within the above ranges to enable the degradation product, i.e., the solid, to fully absorb water and expand.

[0067] After the water soaking is completed, the present invention preferably separates the solid and liquid of the product of the water soaking to obtain a separation product.

[0068] The present invention has no special limitation on the method of the solid-liquid separation, and the well-known technical solutions in the art can be adopted.

[0069] After obtaining the separation product, the present invention freeze-dries the separation product to obtain a flame-retardant aerogel derived from the flame-retardant unsaturated polyester.

[0070] In the present invention, during the freeze-drying process, the temperature of the cold trap is preferably -70 to -50 °C, the temperature of the sample to be freeze-dried is preferably 10 to 20 °C, and the vacuum degree is preferably 1 to 5 Pa; the time of the freeze-drying is 24 to 48 h. The present invention controls the conditions and time of the freeze-drying within the above ranges to obtain a flame-retardant aerogel derived from the flame-retardant unsaturated polyester with excellent performance.

[0071] The preparation method of the flame-retardant aerogel derived from the flame-retardant unsaturated polyester provided by the present invention is simple in operation, mild in reaction conditions, low in cost, and suitable for large-scale production.

[0072] The present invention also provides a flame-retardant aerogel derived from the flame-retardant unsaturated polyester prepared by the preparation method described in the above technical solution.

[0073] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0074] Example 1

[0075] A crosslinked gas-phase flame retardant having the chemical structure shown in Formula 1 below:

[0076]

[0077] In Formula 1, n is 3;

[0078] The preparation route of the crosslinked gas-phase flame retardant having the structure shown in Formula 1 is as follows:

[0079]

[0080] The preparation method of the crosslinked gas-phase flame retardant having the structure shown in Formula 1 comprises the following steps:

[0081] Add 3-aminopropyltriethoxysilane (0.1 mol), paraformaldehyde (0.067 mol), diphenylphosphine oxide (0.2 mol) and chloroform (175 mL) into a 500 mL three-necked round-bottom flask, and carry out the first reaction at 50 °C for 12 h; after the first reaction is completed, rotary evaporate to remove the solvent to obtain an intermediate;

[0082] Mix the intermediate with a mixed solution containing ethanol and water (the volume ratio of ethanol to water is 2:1), and carry out a polymerization reaction at 80 °C with vigorous stirring for 8 h; after the polymerization reaction is completed, rotary evaporate to remove the solvent to obtain a yellow solid powder, which is the crosslinked gas-phase flame retardant;

[0083] The molar ratio of the 3-aminopropyltriethoxysilane, paraformaldehyde and diphenylphosphine oxide is 1:0.67:2.

[0084] The nuclear magnetic resonance hydrogen spectrum of the crosslinked gas-phase flame retardant prepared in Example 1 was detected by a nuclear magnetic resonance spectrometer as Figure 1 shown; from Figure 1 it can be seen that the aromatic proton peaks of the crosslinked gas-phase flame retardant prepared in Example 1 are in the range of 7-8 ppm, and the aliphatic hydrogen atoms are at positions such as 3.76, 3.38, 2.78, 1.41 ppm, etc.

[0085] The nuclear magnetic resonance phosphorus spectrum of the crosslinked gas-phase flame retardant prepared in Example 1 was detected by a nuclear magnetic resonance spectrometer as Figure 2 shown; from Figure 2It can be seen that the crosslinked gas-phase flame retardant prepared in Example 1 has a main peak at the position of 28.21 ppm.

[0086] The thermogravimetric curve of the crosslinked gas-phase flame retardant prepared in Example 1 was detected by thermogravimetric analysis method as shown in Figure 3 ; It can be seen from Figure 3 that the crosslinked gas-phase flame retardant prepared in Example 1 has good thermal stability, the temperature at its maximum weight loss rate is 310 °C, and the char residue rate at 800 °C is 29%.

[0087] Example 2

[0088] A preparation method of a flame-retardant aerogel derived from a flame-retardant unsaturated polyester uses the crosslinked gas-phase flame retardant prepared in Example 1 as a raw material. The preparation method of the flame-retardant aerogel is as follows:

[0089] (1) After mixing the crosslinked gas-phase flame retardant with unsaturated polyester resin, it is cured at 30 °C for 3 h to obtain a flame-retardant unsaturated polyester;

[0090] In the step (1), the mass ratio of the crosslinked gas-phase flame retardant to the mass of the unsaturated polyester resin is 1:5;

[0091] (2) The flame-retardant unsaturated polyester obtained in the step (1) is sliced into fragments, immersed in dichloromethane at room temperature for 24 h for dichloromethane immersion treatment, and after filtration, a pretreated flame-retardant unsaturated polyester is obtained;

[0092] (3) After mixing 2 g of the pretreated flame-retardant unsaturated polyester obtained in the step (2) with a mixed alkali solution containing diethylenetriamine and potassium hydroxide, it is heated and stirred at 80 °C for 3 h, and after filtration, a solid is obtained;

[0093] The mixed alkali solution containing diethylenetriamine and potassium hydroxide is obtained by mixing 200 g of diethylenetriamine, 10 g of potassium hydroxide and 210 g of water;

[0094] (4) The solid obtained in the step (3) is immersed in water for 1 h of water immersion, and then freeze-dried for 48 h to obtain a flame-retardant aerogel derived from a flame-retardant unsaturated polyester;

[0095] During the freeze-drying process in the step (4), the cold trap temperature is -60 °C, the temperature of the sample to be freeze-dried is 15 °C, and the vacuum degree is 1 Pa.

[0096] The vertical burning grade of the flame-retardant unsaturated polyester prepared in the step (1) of Example 2 was detected by vertical burning test to be V0 level.

[0097] The thermogravimetric curves of pure unsaturated polyester and the flame-retardant unsaturated polyester prepared in Example 2 of the present invention were detected by a thermogravimetric analyzer as shown in Figure 4 the figure. The left figure is pure unsaturated polyester (i.e., non-flame-retardant), and the right figure is the flame-retardant unsaturated polyester prepared in Example 2 (i.e., flame-retardant); as can be seen from Figure 4 the figure, compared with pure unsaturated polyester, the flame-retardant unsaturated polyester prepared in Example 2 has higher high-temperature char-forming property. The char residue rate of the flame-retardant unsaturated polyester at 800 °C is 12%, while the char residue rate of pure unsaturated polyester (non-flame-retardant) at 800 °C is 4%.

[0098] The heat release rate curves of pure unsaturated polyester and the flame-retardant unsaturated polyester prepared in Example 2 of the present invention were detected by a microcalorimeter as shown in Figure 5 the figure; as can be seen from Figure 5 the figure, compared with pure unsaturated polyester, the heat release rate of the flame-retardant unsaturated polyester prepared in Example 2 is significantly inhibited, and the peak value of the heat release rate drops from 365 to 184 W / g, indicating that the flame-retardant property of the flame-retardant unsaturated polyester prepared in Example 2 is significantly improved.

[0099] According to the same method as in Example 2, non-flame-retardant aerogel derived from pure unsaturated polyester (abbreviated as non-flame-retardant aerogel) was prepared using non-flame-retardant unsaturated polyester as the raw material.

[0100] The heat release rate curves of the above non-flame-retardant aerogel and the flame-retardant aerogel derived from the flame-retardant unsaturated polyester prepared in Example 2 of the present invention were detected by a microcalorimeter as shown in Figure 6 the figure; as can be seen from Figure 6 the figure, compared with the non-flame-retardant aerogel, the heat release rate of the flame-retardant aerogel prepared in Example 2 is significantly inhibited, and the peak value of the heat release rate drops from 336 to 103 W / g, indicating that the flame-retardant property of the flame-retardant aerogel prepared in Example 2 is significantly improved.

[0101] Comparative Example

[0102] In the prior art, there is a flame retardant with the chemical structure shown in Formula 3 below, which is used for flame retardant modification of materials such as epoxy resin (J. Mater. Chem. A, 2016, 4, 3462; RSC Adv., 2017, 7, 46139);

[0103]

[0104] According to the same methods as in Example 1 and Example 2 of the present invention respectively, the flame retardant shown in Formula 3 was prepared, and then used as the raw material to prepare comparative flame-retardant unsaturated polyester and comparative flame-retardant aerogel respectively. The steps are as follows:

[0105] 3 - aminopropyltriethoxysilane (0.1 mol), paraformaldehyde (0.067 mol), 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide (0.2 mol) and chloroform (175 mL) were added to a 500 mL three - necked round - bottom flask, and the first reaction was carried out at 50 °C for 12 h; after the first reaction was completed, the solvent was removed by rotary evaporation to obtain an intermediate; after mixing the intermediate with a mixed solution containing ethanol and water (the volume ratio of ethanol to water was 2:1), a polymerization reaction was carried out with vigorous stirring at 80 °C for 8 h; after the polymerization reaction was completed, the solvent was removed by rotary evaporation to obtain a yellow solid powder, that is, the flame retardant with the structure shown in Formula 3 was obtained; after mixing the cross - linked gas - phase flame retardant with unsaturated polyester resin at a mass ratio of 1:5, curing was carried out at 30 °C for 3 h to obtain a comparative flame - retardant unsaturated polyester;

[0106] The comparative flame - retardant unsaturated polyester was sliced into fragments, immersed in dichloromethane at room temperature for 24 h for dichloromethane immersion treatment, and after filtration, a pretreated comparative flame - retardant unsaturated polyester was obtained; 2 g of the pretreated comparative flame - retardant unsaturated polyester, 200 g of diethylenetriamine, 10 g of potassium hydroxide and 210 g of water were mixed, and then heated and stirred at 80 °C for 3 h, and after filtration, a solid was obtained; the obtained solid was immersed in water for 1 h of water immersion, and then freeze - dried for 48 h to obtain a comparative flame - retardant aerogel;

[0107] During the freeze - drying process, the temperature of the cold trap was - 60 °C, the temperature of the sample to be freeze - dried was 15 °C, and the vacuum degree was 1 Pa.

[0108] Comparing the flame retardant with the structure shown in Formula 3 with the cross - linked gas - phase flame retardant with the structure shown in Formula 1 of the present invention, it can be seen that there are the following differences between the two: (1) The flame retardant with the structure shown in Formula 3 uses 9,10 - dihydro - 9 - oxa - 10 - phosphaphenanthrene - 10 - oxide as a phosphorus - containing monomer, and its phosphorus structure is in the + 1 oxidation state, while the cross - linked gas - phase flame retardant with the structure shown in Formula 1 of the present invention uses diphenylphosphine oxide with a - 1 phosphorus oxidation state structure, which has significant gas - phase flame - retardant characteristics; (2) The cross - linked gas - phase flame retardant with the structure shown in Formula 1 of the present invention has a higher phosphorus content and higher flame - retardant efficiency; (3) The cross - linked gas - phase flame retardant with the structure shown in Formula 1 of the present invention is used for the preparation of flame - retardant unsaturated polyester and the corresponding flame - retardant aerogel, while the flame retardant with the structure shown in Formula 3 is only used for the flame - retardant modification of materials such as epoxy.

[0109] The vertical combustion test was used to detect that the vertical combustion grade of the comparative flame - retardant unsaturated polyester was non - combustion level, indicating that the flame - retardant performance of the flame - retardant unsaturated polyester in Example 2 of the present invention was significantly better than that of the comparative flame - retardant unsaturated polyester.

[0110] The heat release rate curve of the comparative flame - retardant unsaturated polyester prepared in the comparative example was detected by a micro - calorimeter as Figure 7as shown; by Figure 7 As can be seen, compared with the peak heat release rate of 184 W / g of the flame-retardant unsaturated polyester in Example 2 of the present invention, the peak heat release rate of the comparative flame-retardant unsaturated polyester has increased significantly to 295 W / g, indicating that the flame-retardant performance of the flame-retardant unsaturated polyester in Example 2 of the present invention is significantly better than that of the comparative flame-retardant unsaturated polyester in the comparative example.

[0111] The heat release rate curve of the comparative flame-retardant aerogel prepared in the comparative example was detected by a microcalorimeter as Figure 8 shown; by Figure 8 As can be seen, compared with the peak heat release rate of 103 W / g of the flame-retardant aerogel in Example 2 of the present invention, the peak heat release rate of the comparative flame-retardant aerogel has increased significantly to 269 W / g, indicating that the flame-retardant performance of the flame-retardant aerogel in Example 2 of the present invention is significantly better than that of the comparative flame-retardant aerogel.

[0112] In summary, the crosslinked gas-phase flame retardant of the present invention has excellent flame retardancy efficiency and significantly enhances the flame-retardant performance of the flame-retardant unsaturated polyester prepared therefrom; then, using the flame-retardant unsaturated polyester as a raw material to directly degrade and prepare a flame-retardant aerogel with excellent flame retardancy and a double-crosslinked network structure helps to realize the high-value upgrading and recycling of the flame-retardant unsaturated polyester after long-term service and becoming waste.

[0113] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a flame-retardant aerogel derived from a flame-retardant unsaturated polyester, characterized in that, It includes the following steps: (1) Mix the crosslinked gas-phase flame retardant with unsaturated polyester resin and waste materials made of unsaturated polyester resin, and then cure them to obtain flame-retardant unsaturated polyester; The crosslinked gas-phase flame retardant is obtained by mixing an intermediate with a mixed solution containing ethanol and water, and then carrying out a polymerization reaction; The chemical formula of the intermediate is: ； (2) Slice and soak the obtained flame-retardant unsaturated polyester in dichloromethane successively to obtain pretreated flame-retardant unsaturated polyester; (3) Add the obtained pretreated flame-retardant unsaturated polyester to a mixed alkali solution containing diethylenetriamine and potassium hydroxide, and then carry out heating and stirring and filtration successively to obtain a solid; (4) Soak the obtained solid in water and carry out freeze-drying successively to obtain a flame-retardant aerogel derived from flame-retardant unsaturated polyester.

2. The preparation method according to claim 1, characterized in that, The mass ratio of the crosslinked gas-phase flame retardant to the total mass of the unsaturated polyester resin and the waste materials made of unsaturated polyester resin is 1.5:8.5 to 3:

7.

3. The preparation method according to claim 1, characterized in that, The curing temperature is 25 to 120 °C, and the curing time is 0.5 to 7 h.

4. The preparation method according to claim 1, characterized in that, The temperature of heating and stirring is 70 to 100 °C, and the time of heating and stirring is 2 to 4 h.

5. The preparation method according to claim 1, wherein During the freeze-drying process, the cold trap temperature is -70 to -50 °C, the temperature of the sample to be freeze-dried is 10 to 20 °C, and the vacuum degree is 1 to 5 Pa; the freeze-drying time is 24 to 48 h.

6. The preparation method according to claim 1, characterized in that, The preparation method of the intermediate includes the following steps: Mix 3-aminopropyltriethoxysilane, paraformaldehyde, diphenylphosphine oxide and an organic solvent, and then carry out a first reaction and remove the solvent successively to obtain the intermediate.

7. The preparation method according to claim 6, characterized in that, The molar ratio of 3-aminopropyltriethoxysilane, paraformaldehyde and diphenylphosphine oxide is 1:(0.5 to 0.8):

2.

8. The preparation method according to claim 1, wherein The volume ratio of ethanol to water in the mixed solution containing ethanol and water is 1:1 to 3:1, and the pH value of the mixed solution containing ethanol and water is 2 to 5 or 9 to 12; The temperature of the polymerization reaction is 70 to 90 °C, and the time of the polymerization reaction is 6 to 10 h.

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