Degradation method and recycling method of waste polyisocyanurate

Abstract

The invention relates to a degradation method and a recycling method of waste polyisocyanurate, and the degradation method is as follows: aliphatic amine and basic hydroxide are used as degradation agents, and degradation is carried out under the synergistic effect of the aliphatic amine and the basic hydroxide. The recycling method comprises the following steps: mixing a product B obtained by degradation with an organic compound, and introducing gas generated by reaction of activated carbon and chlorine to obtain a product C; fully mixing and stirring a foaming agent, a catalyst, a foam stabilizer and the degraded product A to obtain a component A; and stirring the component A and the product C, and pouring into a foaming mold for foaming to prepare the flame-retardant foam. According to the method disclosed by the invention, the waste polyisocyanurate material can be efficiently degraded and recycled.

Description

Technical Field

[0001] The present invention relates to the technical field of recycling and reuse of waste polyisocyanurate, and specifically to a method for degrading and recycling waste polyisocyanurate. Background Art

[0002] Polyisocyanurate materials are rigid foam materials formed by the reaction of polyisocyanates with polyether polyols or (and) polyester polyols under the action of catalysts. Its structure consists of countless tiny closed cells that do not communicate with each other, and has a series of characteristics such as low thermal conductivity, low water absorption, light weight and shock resistance, and strong adaptability, making it one of the organic materials widely used in the field of thermal insulation. At present, natural gas has become one of the main energy sources in China, and a large amount of polyisocyanurate thermal insulation materials are required in natural gas cryogenic and pipeline transportation, resulting in a large amount of solid waste. These wastes are difficult to degrade, and landfill treatment will cause serious environmental pollution and waste of resources.

[0003] Most of the existing technologies are for the recycling and utilization of waste polyurethane (PU) materials. For example, Chinese Patent CN113292700A discloses a method for recycling waste polyurethane to prepare polyurethane thermal insulation materials. The waste rigid polyurethane foam is mixed and reacted with an alcoholysis agent, a co-alcoholysis agent, and a modifier to obtain a degradation product, and the degradation product is mixed and stirred with a foaming agent, a catalyst, a stabilizer, and isocyanate to foam, obtaining a polyurethane thermal insulation material. This method can achieve the degradation of waste polyurethane and synthesize new polyurethane thermal insulation materials.

[0004] Polyisocyanurate (PIR) materials are a kind of foam materials containing a typical carbon-nitrogen six-membered rigid heterocyclic characteristic structure, such as Figure 1 As Figure 2 shown, the PU polymer chain is a linear molecular structure, and the PIR polymer chain contains a rigid ring structure. Polyisocyanurate is formed by the trimerization reaction of isocyanate and has a six-membered ring structure with a repeating structural unit of urethane chain segments and a high crosslinking density. There is no active hydrogen on the six-membered ring structure, and the molecular structure contains a benzene ring structure with a large steric hindrance, which hinders the movement of molecular chain segments during heating. Compared with PU, the PIR molecular structure is more stable, the decomposition temperature and flash point temperature are higher, PIR has a lower thermal decomposition rate, and the decomposition conditions are more severe. The national standard GB 50264 has more strict performance requirements for PIR products. The compressive strength of PU products shall not be less than 0.20 MPa and the volume water absorption shall not be greater than 5%, while the compressive strength of PIR products shall not be less than 0.22 MPa and the volume water absorption shall not be greater than 4%. The flame retardancy requirements for PIR materials during use are generally higher than those for PU materials.

[0005] Therefore, the differences in chemical structure, physical properties, and product requirements between PIR materials and PU materials determine the differences in their degradation and preparation methods. The technology required for the degradation and preparation of PIR materials is more complex, and the reaction conditions are more stringent. If the degradation method of PU materials is used to degrade PIR materials, problems such as too high reaction temperature, incomplete degradation, many by-products, and too high viscosity of degradation products that cannot be reused will occur. Therefore, the degradation methods of PU materials in the prior art are not applicable to the degradation of PIR materials, and moreover, there is no specific method for the efficient degradation, recycling, and reuse of waste polyisocyanurate in the prior art. Summary of the Invention

[0006] The present invention aims to provide a degradation method and a recycling method that are simple in process and can efficiently degrade and recycle waste polyisocyanurate materials.

[0007] To solve the above technical problems, the specific solution adopted by the present invention is a degradation method of waste polyisocyanurate: using fatty amines and alkaline hydroxides as degradation agents, and carrying out degradation under the synergistic action of fatty amines and alkaline hydroxides.

[0008] As an optimized scheme of the above degradation method of waste polyisocyanurate: it specifically includes the following steps:

[0009] S1: Take the waste polyisocyanurate, after being crushed and washed, add it to a sodium hydroxide solution for reaction, The reaction products are successively filtered, washed, and dried;

[0010] S2: Place the reaction products obtained in S1 and fatty amines in a hydrothermal reaction kettle, heat up to 120 - 150 °C and stir;

[0011] S3: Add the alkaline hydroxide to the hydrothermal reaction kettle, heat up to 170 - 220 °C and stir, and then cool to room temperature;

[0012] S4: Add a non-polar solvent to the hydrothermal reaction kettle, stir and let it stand, then it is stratified into a non-polar solvent layer and an aqueous layer; then, distill the non-polar solvent layer to obtain product A; evaporate and crystallize the aqueous layer to obtain product B.

[0013] As an optimized scheme of the above degradation method of waste polyisocyanurate: the fatty amine is one of ethylenediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

[0014] As another optimized scheme of the above degradation method of waste polyisocyanurate: the alkaline hydroxide is one or more of NaOH, KOH, LiOH, Al(OH)3, Ca(OH)2, and Mg(OH)2.

[0015] As another optimization scheme of the above-mentioned method for degrading waste polyisocyanurate: the non-polar solvent is one of benzene, toluene, chloroform, ethylene dichloride, ethyl acetate and DMF.

[0016] As another optimization scheme of the above-mentioned method for degrading waste polyisocyanurate: in step S2, the mass ratio of fatty amine to waste polyisocyanurate is 0.1-0.3:1; in step S3, the mass ratio of alkaline hydroxide to waste polyisocyanurate is 0.1-0.7:1.

[0017] A method for recycling waste polyisocyanurate comprises the following steps:

[0018] S1: taking the product B obtained by the above degradation method and mixing it with an organic compound to obtain a mixed liquid; passing the gas generated by the reaction of activated carbon and chlorine at 200°C into the mixed liquid, raising the temperature to 100-200°C, and obtaining the product C after reduced pressure distillation;

[0019] S2: fully mixing and stirring the foaming agent, the catalyst, the foam leveling agent and the product A obtained by the above-mentioned degradation method to obtain component A;

[0020] S3: Component A and product C in S1 are mixed and stirred in proportion, and poured into a foaming mold for foaming to obtain a flame retardant foam; and then the flame retardant foam is placed in an oven at 60° C. for aging treatment.

[0021] As an optimization scheme for the above-mentioned method of recycling waste polyisocyanurate: the organic compound is chlorobenzene, dichlorobenzene or trichlorobenzene; the foaming agent is one of HCFC141b, HCFC-22, cyclopentane and petroleum ether; the foaming agent is one of silicone oil SD611, silane foaming agent AK8803, silane foaming agent AK880 and silane foaming agent L580.

[0022] As another optimization scheme for the above-mentioned method for recycling waste polyisocyanurate: the catalyst is one of triethylamine, triethyleneimine, N,N-dimethylcyclohexylamine, triethanolamine, N-methylmorpholine, N,N'-diethyl-3-methylpiperazine, pyridine, bis(2-dimethylaminoethyl) ether, 2-(N,N-dimethylamino)-ethyl-3-(N',N'-dimethyl)propyl ether, 2-(N,N-dimethylamino)-ethyl-2-(N',N'-dimethyl)-1-methylethyl ether, dimethylethanolamine, dibutyltin dilaurate, dibutyltin diacetate, potassium oleate and stannous octoate.

[0023] As another optimization scheme of the above method for recycling waste polyisocyanurate: in step S2, the mass ratio of the blowing agent to product A is 0.15 - 0.2:1; the mass ratio of the catalyst to product A is 0.05 - 0.15:1; the mass ratio of the foam stabilizer to product A is 0.03 - 0.06:1.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The alkaline hydroxide in the present invention is used as a degradation agent, which is inexpensive and can effectively promote the generation of ionic bonds, accelerate the reaction process, and obtain high-purity products. However, a relatively high temperature and strong alkalinity are required during its degradation reaction. As a degradation agent, fatty amine can degrade and crosslink waste polyisocyanurate particles at a lower temperature due to the strong reactivity of its amine group and the low-temperature activity of amidation. Therefore, adding fatty amine can open some chemical bonds and degrade them into oligomers. When fatty amine and alkaline hydroxide are used together as degradation agents to degrade waste polyisocyanurate, it can not only improve the degradation efficiency and obtain high-purity products, but also reduce the requirements for reaction equipment, making this method for degrading waste polyisocyanurate applicable to industrial production.

[0026] 2. Through the synergistic effect of alkaline hydroxide and fatty amine, the present invention can effectively reduce the reaction temperature required and increase the reaction rate. First, the carbamate group decomposes to generate the corresponding isocyanate and alcohols. With the addition of the degradation agent and the increase of the reaction temperature, the isocyanate bond and urea bond break, generating polyols, polyamines, and aromatic compounds. The intermediate product of degradation, isocyanate, contains an isocyanate group (-NCO), which has a resonance effect, making its charge distribution uneven, generating a nucleophilic center and an electrophilic center, and can react with substances containing active hydrogen. The greater the electron cloud density of the nucleophilic center of the substance containing active hydrogen, the stronger its electronegativity, the higher the reaction activity, and the faster the reaction rate. That is, the reaction activity of the substance containing active hydrogen (RNH2) is related to the nature of R. When R is an electron-donating substituent, the reaction activity is high. As a substance containing active hydrogen, fatty amine has a high reaction activity with the isocyanate group. When it reacts with the isocyanate group by providing an electron group from its hydrocarbon group, it can enhance the reaction activity and increase the reaction rate.

[0027] 3. By recycling and utilizing the degradation products, the present invention achieves the recycling of waste polyisocyanurate, which can not only reduce the environmental pollution caused by waste polyisocyanurate waste, but also reduce the production cost of raw materials for producing flame-retardant foams. Description of the Drawings

[0028] Figure 1 It is a schematic diagram of the molecular structure of the PIR material;

[0029] Figure 2 Schematic diagram of the molecular structure of the PU material. Detailed implementation manners

[0030] The degradation method and recycling method in the present invention are specifically described through the following multiple embodiments:

[0031] A degradation method of waste polyisocyanurate in the present invention: using fatty amine and alkaline hydroxide as degradation agents, and carrying out degradation under the synergistic action of fatty amine and alkaline hydroxide.

[0032] The degradation method of waste polyisocyanurate includes the following steps:

[0033] S1: Take the waste polyisocyanurate, after crushing and cleaning, add it to the sodium hydroxide solution for reaction, and the reaction product is successively filtered, washed and dried.

[0034] S2: Place the reaction product obtained in S1 and the fatty amine in a hydrothermal reaction kettle, heat up to 120 - 150 °C and stir.

[0035] The above-mentioned fatty amine is one of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

[0036] The mass ratio of the above-mentioned fatty amine to the waste polyisocyanurate is 0.1 - 0.3:1.

[0037] S3: Add the alkaline hydroxide to the hydrothermal reaction kettle, heat up to 170 - 220 °C and stir, and then cool to room temperature.

[0038] The above-mentioned alkaline hydroxide is one or more of NaOH, KOH, LiOH, Al(OH)3, Ca(OH)2 and Mg(OH)2.

[0039] The mass ratio of the above-mentioned alkaline hydroxide to the waste polyisocyanurate is 0.1 - 0.7:1.

[0040] S4: Add the non-polar solvent to the hydrothermal reaction kettle, stir and let it stand, then it is layered into a non-polar solvent layer and an aqueous layer; then, distill the non-polar solvent layer to obtain product A; evaporate and crystallize the aqueous layer to obtain product B.

[0041] The above-mentioned non-polar solvent is one of benzene, toluene, chloroform, dichloroethane, ethyl acetate and DMF.

[0042] A recycling method of waste polyisocyanurate in the present invention includes the following steps:

[0043] S1: Take the waste polyisocyanurate, after crushing and cleaning, add it to the sodium hydroxide solution for reaction, and the reaction product is successively filtered, washed and dried.

[0044] S2: Place the reaction product obtained in S1 and fatty amine in a hydrothermal reaction kettle, heat to 120-150° C. and stir.

[0045] The above-mentioned fatty amine is one of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

[0046] The mass ratio of the above-mentioned fatty amine to the waste polyisocyanurate is 0.1-0.3:1.

[0047] S3: Add alkaline hydroxide into a hydrothermal reactor, heat to 170-220° C. and stir, then cool to room temperature.

[0048] The alkaline hydroxide is one or more of NaOH, KOH, LiOH, Al(OH)3, Ca(OH)2 and Mg(OH)2.

[0049] The mass ratio of the alkaline hydroxide to the waste polyisocyanurate is 0.1-0.7:1.

[0050] S4: Add a non-polar solvent into a hydrothermal reactor, stir, let stand, and then separate into a non-polar solvent layer and a water layer; then, distill the non-polar solvent layer to obtain product A; evaporate and crystallize the water layer to obtain product B.

[0051] The non-polar solvent is one of benzene, toluene, chloroform, dichloroethane, ethyl acetate and DMF.

[0052] S5: taking the product B obtained by the above degradation and mixing it with an organic compound to obtain a mixed liquid; introducing the gas generated by the reaction of activated carbon and chlorine at 200° C. into the mixed liquid, heating it to 100-200° C., and obtaining product C after reduced pressure distillation.

[0053] The organic compound is chlorobenzene, dichlorobenzene or trichlorobenzene; the foaming agent is one of HCFC141b, HCFC-22, cyclopentane and petroleum ether.

[0054] S6: Fully mix and stir the foaming agent, catalyst, foam leveling agent and the product A obtained by the above degradation method to obtain component A.

[0055] The above-mentioned foaming agent is one of HCFC141b, HCFC-22, cyclopentane and petroleum ether. The foam stabilizer is one of silicone oil SD611, silane foam stabilizer AK8803, silane foam stabilizer AK880 and silane foam stabilizer L580. The catalyst is one of triethylamine, triethyleneimine, N,N-dimethylcyclohexylamine, triethanolamine, N-methylmorpholine, N,N'-diethyl-3-methylpiperazine, pyridine, bis(2-dimethylaminoethyl) ether, 2-(N,N-dimethylamino)-ethyl-3-(N',N'-dimethyl) propyl ether, 2-(N,N-dimethylamino)-ethyl-2-(N',N'-dimethyl)-1-methylethyl ether, dimethylethanolamine, dibutyltin dilaurate, dibutyltin diacetate, potassium oleate and stannous octoate.

[0056] The mass ratio of the above-mentioned foaming agent to product A is 0.15 - 0.2:1; the mass ratio of the catalyst to product A is 0.05 - 0.15:1; the mass ratio of the foam stabilizer to product A is 0.03 - 0.06:1.

[0057] S7: Mix component A and product C in S5 in proportion, stir, and pour them into a foaming mold for foaming to obtain a flame-retardant foam; then place the flame-retardant foam in an oven at 60 °C for curing treatment.

[0058] Example 1

[0059] First, mechanically crush the waste polyisocyanurate and grind it to 60 - 100 mesh. Wash the waste polyisocyanurate with clean water, add a 1mol / L NaOH solution to the waste polyisocyanurate, stir, and then wash it with clean water until neutral, and then place it in a drying oven for drying. Then, weigh 200g of waste polyisocyanurate and 20g of diethylenetriamine and add them to a hydrothermal reaction kettle, stir and heat up to 120 °C. After reacting for 1h, weigh 20g of NaOH and add it to the hydrothermal reaction kettle, continue to stir and heat up to 180 °C, and react for 5h. After the temperature in the hydrothermal reaction kettle cools to room temperature, add toluene and stir. After the solution stands for 1h, it is layered into a water layer and a non-polar solvent layer, and they are extracted and separated, and the non-polar solvent layer is distilled to obtain polyol. Evaporate and crystallize the water layer to obtain diamine.

[0060] The gas generated by the reaction of activated carbon and chlorine at 200 °C is introduced into the mixed solution of diamine and chlorobenzene. The mixed solution is heated up to 120 °C, and the gas is continuously introduced during the heating process. Then, the product obtained by the reaction is subjected to vacuum distillation to obtain isocyanate.

[0061] Secondly, weigh 50 g of the above-mentioned product polyol, 10 g of HCFC141b, 5 g of triethylamine, and 2.5 g of silicone oil SD611 in sequence, mix them evenly and stir well. Weigh 57.5 g of the above-mentioned product isocyanate and add it. After quickly stirring for 20 s, pour it into a foaming mold for foaming, and place the obtained foam in an oven at 60 °C for 24 h for curing treatment.

[0062] Example 2

[0063] First, mechanically crush the waste polyisocyanurate and grind it to 60-100 mesh. Wash the waste polyisocyanurate with clean water, add 1 mol / L NaOH solution to the waste polyisocyanurate, stir and then wash it with clean water until it is neutral, and then place it in a drying oven for drying. Then, weigh 200 g of the waste polyisocyanurate and 30 g of triethylenetetramine and add them to a hydrothermal reaction kettle, stir and heat up to 120 °C. After reacting for 1 h, weigh 20 g of KOH and add it to the hydrothermal reaction kettle, continue to stir and heat up to 180 °C, and react for 4 h. After the temperature in the hydrothermal reaction kettle cools to room temperature, add chloroform and stir. After the solution stands for 1 h, it is stratified into an aqueous layer and a non-polar solvent layer, which are extracted and separated, and the non-polar solvent layer is distilled to obtain polyol. The aqueous layer is evaporated to crystallize to obtain diamine.

[0064] The gas generated by the reaction of activated carbon and chlorine at 200 °C is introduced into the mixed solution of diamine and chlorobenzene. The mixed solution is heated to 150 °C, and the gas is continuously introduced during the heating process. Then, the product obtained by the reaction is subjected to vacuum distillation to obtain isocyanate.

[0065] Secondly, weigh 50 g of the above-mentioned product polyol, 7.5 g of HCFC-22, 3.5 g of stannous octoate, and 2 g of silicone oil SD611 in sequence, mix them evenly and stir well. Weigh 57.5 g of the above-mentioned product isocyanate and add it. After quickly stirring for 20 s, pour it into a foaming mold for foaming, and place the obtained foam in an oven at 60 °C for 24 h for curing treatment.

[0066] Example 3

[0067] First, the waste polyisocyanurate is mechanically crushed and ground to 60-100 mesh. Use clean water to wash the waste polyisocyanurate, add 1mol / L NaOH solution to the waste polyisocyanurate, stir and wash it with clean water until it is neutral, and then place it in a drying oven for drying. Then, weigh 200g of waste polyisocyanurate and 40g of tetraethylenepentamine in turn and add them to the hydrothermal reactor, stir and heat to 130°C. After it reacts for 1h, weigh 40gNaOH and 20gKOH and add them to the hydrothermal reactor, continue to stir and heat to 200°C, and react for 3h. After the temperature in the hydrothermal reactor cools to room temperature, add dichloroethane and stir. After the solution is left to stand for 1h, separate the layers and extract and separate. Distill the non-polar solvent layer to obtain polyols. Evaporate and crystallize the water layer to obtain diamines.

[0068] The gas generated by the reaction of activated carbon and chlorine at 200°C is introduced into a mixed solution of diamine and chlorobenzene, the mixed solution is heated to 150°C, and the gas is continuously introduced during the heating process. Then, the product obtained by the reaction is distilled under reduced pressure to obtain isocyanate.

[0069] Secondly, 50g of the above-mentioned polyol, 8.5g of cyclopentane, 4g of triethanolamine, and 0.5g of silane foaming agent AK8803 were weighed in sequence, mixed evenly and stirred thoroughly. 57.5g of the above-mentioned isocyanate was weighed and added, stirred rapidly for 20s, and then poured into a foaming mold for foaming, and the obtained foam was placed in a 60°C oven for 24h for aging.

[0070] Example 4

[0071] First, the waste polyisocyanurate is mechanically crushed and ground to 60-100 mesh. Use clean water to wash the waste polyisocyanurate, add 1mol / L NaOH solution to the waste polyisocyanurate, stir and wash it with clean water until it is neutral, and then place it in a drying oven for drying. Then, weigh 200g of waste polyisocyanurate and 40g of diethylenetriamine in turn and add them to the hydrothermal reactor, stir and heat to 120°C. After it reacts for 2h, weigh 80gNaOH and 20gCa(OH)2 and add them to the hydrothermal reactor, continue to stir and heat to 210°C, and react for 4h. After the temperature in the hydrothermal reactor cools to room temperature, add toluene and stir. After the solution is left to stand for 1h, separate the layers and extract and separate. Distill the non-polar solvent layer to obtain polyols. Evaporate and crystallize the water layer to obtain diamines.

[0072] The gas generated by the reaction of activated carbon and chlorine at 200°C is introduced into a mixed solution of diamine and chlorobenzene, the mixed solution is heated to 170°C, and the gas is continuously introduced during the heating process. Then, the product obtained by the reaction is distilled under reduced pressure to obtain isocyanate.

[0073] Secondly, 50g of the above-mentioned polyol, 10g of petroleum ether, 6g of N,N-dimethylcyclohexylamine, and 2.5g of silane foam leveler L580 were weighed in sequence, mixed evenly and stirred thoroughly. 57.5g of the above-mentioned isocyanate was weighed and added, stirred rapidly for 20s, and then poured into a foaming mold for foaming, and the obtained foam was placed in a 60°C oven for 24h for aging.

[0074] Example 5

[0075] First, the waste polyisocyanurate is mechanically crushed and ground to 60-100 mesh. Use clean water to wash the waste polyisocyanurate, add 1mol / L NaOH solution to the waste polyisocyanurate, stir and wash it with clean water until it is neutral, and then place it in a drying oven for drying. Then, weigh 200g of waste polyisocyanurate and 50g of triethylenetetramine in turn and add them to the hydrothermal reactor, stir and heat to 135°C. After it reacts for 2h, weigh 60gNaOH, 40gKOH and 20gAl(OH)2 and add them to the hydrothermal reactor, continue to stir and heat to 210°C, and react for 4h. After the temperature in the hydrothermal reactor cools to room temperature, add chloroform and stir. After the solution is left to stand for 1h, separate the layers and extract and separate. Distill the non-polar solvent layer to obtain polyols. Evaporate and crystallize the water layer to obtain diamines.

[0076] The gas generated by the reaction of activated carbon and chlorine at 200°C is introduced into a mixed solution of diamine and chlorobenzene, the mixed solution is heated to 180°C, and the gas is continuously introduced during the heating process. Then, the product obtained by the reaction is distilled under reduced pressure to obtain isocyanate.

[0077] Secondly, 50g of the above-mentioned polyol, 9g of HCFC141b, 6g of triethanolamine, and 3g of silane foaming agent AK8803 were weighed in sequence, mixed evenly and stirred thoroughly. 60g of the above-mentioned isocyanate was weighed and added, stirred rapidly for 20s, and then poured into a foaming mold for foaming, and the obtained foam was placed in a 60°C oven for 24h for aging.

[0078] In summary, the following table shows the test results of compressive strength, volume water absorption and thermal conductivity of the foam materials prepared in Examples 1-5.

[0079] It can be seen from the data in the table that the degradation method of the present invention can effectively degrade waste polyisocyanurate and can recycle its degradation products to prepare PIR flame-retardant foam, and the comprehensive properties of the prepared foam materials are better than the national standards. The tensile strength of the prepared PIR foam material is ≥0.22 MPa, the volume water absorption rate is ≤4%, and the thermal conductivity (25°C) is ≤0.029 W / (m·°C). The comprehensive properties are excellent, meeting and exceeding the national and industrial standards.

Claims

1. A method for degrading waste polyisocyanurate, characterized in that: Fatty amine and alkaline hydroxide are used as degradation agents, and the degradation is carried out under the synergistic effect of the fatty amine and the alkaline hydroxide.

2. The degradation method of waste polyisocyanurate according to claim 1, characterized in that: The specific steps include: S1: taking waste polyisocyanurate, crushing and washing it, and then adding sodium hydroxide solution to react, and filtering, washing and drying the reaction product in sequence; S2: placing the reaction product obtained in S1 and aliphatic amine in a hydrothermal reaction kettle, heating to 120-150° C. and stirring; S3: adding alkaline hydroxide into a hydrothermal reactor, heating to 170-220° C. and stirring, and then cooling to room temperature; S4: Add a non-polar solvent into a hydrothermal reactor, stir, let stand, and then separate into a non-polar solvent layer and a water layer; then, distill the non-polar solvent layer to obtain product A; evaporate and crystallize the water layer to obtain product B.

3. A method for degrading waste polyisocyanurate according to claim 2, characterized in that: The fatty amine is one of ethylenediamine, diethylenetriamine, triethylenetetramine and tetraethylenepentamine.

4. A method for degrading waste polyisocyanurate according to claim 2, characterized in that: The alkaline hydroxide is one or more of NaOH, KOH, LiOH, Al(OH)3, Ca(OH)2 and Mg(OH)2.

5. A method for recycling waste polyisocyanurate according to claim 2, characterized in that: The non-polar solvent is one of benzene, toluene, chloroform, dichloroethane, ethyl acetate and DMF.

6. The method for recycling waste polyisocyanurate according to claim 2, wherein: In step S2, the mass ratio of the fatty amine to the waste polyisocyanurate is 0.1-0.3:1; and in step S3, the mass ratio of the alkaline hydroxide to the waste polyisocyanurate is 0.1-0.7:

1.

7. A method for recycling waste polyisocyanurate, characterized in that: The specific steps include: S1: mixing the product B obtained by the degradation method according to any one of claims 2 to 6 with an organic compound to obtain a mixed solution; introducing the gas generated by the reaction of activated carbon and chlorine at 200° C. into the mixed solution, heating the mixture to 100-200° C., and performing reduced pressure distillation to obtain a product C; S2: Fully mixing and stirring the foaming agent, the catalyst, the foam leveling agent and the product A obtained by the degradation method according to any one of claims 2 to 6 to obtain component A; S3: Component A and product C in S1 are mixed and stirred in proportion, and poured into a foaming mold for foaming to obtain a flame retardant foam; and then the flame retardant foam is placed in an oven at 60° C. for aging treatment.

8. The recycling method of waste polyisocyanurate according to claim 7, characterized in that: The organic compound is chlorobenzene, dichlorobenzene or trichlorobenzene; the foaming agent is one of HCFC141b, HCFC-22, cyclopentane and petroleum ether; and the foaming agent is one of silicone oil SD611, silane foaming agent AK8803, silane foaming agent AK880 and silane foaming agent L580.

9. The recycling method of waste polyisocyanurate according to claim 7, characterized in that: The catalyst is one of triethylamine, triethyleneimine, N,N-dimethylcyclohexylamine, triethanolamine, N-methylmorpholine, N,N'-diethyl-3-methylpiperazine, pyridine, bis(2-dimethylaminoethyl) ether, 2-(N,N-dimethylamino)-ethyl-3-(N',N'-dimethyl)propyl ether, 2-(N,N-dimethylamino)-ethyl-2-(N',N'-dimethyl)-1-methylethyl ether, dimethylethanolamine, dibutyltin dilaurate, dibutyltin diacetate, potassium oleate and stannous octoate.

10. A method for recycling waste polyisocyanurate according to claim 7, characterized in that: In step S2, the mass ratio of the blowing agent to product A is 0.15 - 0.2:1; the mass ratio of the catalyst to product A is 0.05 - 0.15:1; the mass ratio of the foam stabilizer to product A is 0.03 - 0.06:1.

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