Method for recycling thermosetting polyurethane resin

Abstract

The present invention provides a method for recycling and reusing thermosetting polyurethane resin, comprising the following steps: providing a thermosetting polyurethane resin and a degradation system; adding the thermosetting polyurethane resin to the degradation system, allowing the system to stand at room temperature to obtain a degradation product solution; post-treating the degradation product solution to obtain a degradation product; and reacting the degradation product with an isocyanate to obtain a polyurethane material. This invention solves the problem of high temperature requirements for recycling and reusing thermosetting polyurethane resins in the prior art.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane resins, and in particular to a method for recycling thermosetting polyurethane resins. Background Art

[0002] Polyurethane resin, a resin containing carbamate groups in its molecular chain, has been one of the fastest-growing resin materials in recent years. Domestic demand is rapidly increasing, and its applications are widespread. Examples include foam soles and organic leather uppers in common athletic shoes, adhesives used to bond shoe components, caulking or potting compounds, thermal insulation foam, and various coatings in the construction industry, as well as seat cushions, sponges, and sealants in automobiles, and structural components on high-speed trains and aircraft. The use of polyurethane resin in these areas is limited by the product's inherent lifespan, which means that products made from polyurethane resin generate significant amounts of waste. Furthermore, the processing and use of polyurethane resin also produces significant amounts of scrap or defective products. Directly discarding or incinerating these materials wastes resources and pollutes the environment, necessitating the recycling and reuse of used or unusable polyurethane resin.

[0003] Thermoplastic polyurethane resins can be simply heated and reprocessed into various other products, making them relatively easy to recycle and reuse. However, thermosetting polyurethane resins are relatively stable to both temperature and solvents. Traditional recycling methods involve crushing thermosetting polyurethane resins and reusing them as fillers. These traditional recycling methods are not very valuable. Thermal decomposition, hydrolysis, and the most commonly used alcoholysis method all have the disadvantages of high energy consumption and low economic benefits, which cannot fully reflect the recycling and reuse value of polyurethane resins.

[0004] Chinese patent publication number CN113402770A discloses a method for recycling and reusing polyurethane degradation. The method involves first compounding a small molecule alcohol and a titanium catalyst into an alcoholysis agent. The polyurethane and alcoholysis agent are then mixed uniformly and heated to 100-200 degrees Celsius for alcoholysis to obtain a regenerated polyether polyol. Finally, the polyether polyol, a foaming agent, a foam stabilizer, and water are mixed uniformly to obtain a white material, which is then added to a black material for reaction to obtain the polyurethane insulation material. Chinese patent publication number CN106977765A discloses a method for recycling and reusing polyurethane materials. An alcoholysis agent, a catalyst, and an alcoholysis aid are added to the recovered polyurethane material and heated to 150-200 degrees Celsius for 5-10 hours. Existing methods for recycling and reusing thermosetting polyurethane resins suffer from high temperature requirements, high energy consumption, and complex processes, resulting in low economic benefits.

[0005] Therefore, it is necessary to provide a method for recycling and reusing thermosetting polyurethane resin to solve the above problems existing in the prior art. Summary of the Invention

[0006] The object of the present invention is to provide a method for recycling and reusing thermosetting polyurethane resin to solve the problem in the prior art that recycling and reusing thermosetting polyurethane resin has high temperature requirements.

[0007] To achieve the above object, the method for recycling and reusing thermosetting polyurethane resin of the present invention comprises the following steps:

[0008] S0: Providing a thermosetting polyurethane resin and a degradation system, wherein the degradation system comprises any one of a first system and a second system, wherein the first system comprises a reducing agent and an organic solvent, and the second system comprises an acidic substance and the organic solvent, and some urethanes of the thermosetting polyurethane resin are connected by weak coupling bonds;

[0009] S1: adding the thermosetting polyurethane resin to the degradation system, allowing the system to stand at room temperature to obtain a degradation product solution, and post-treating the degradation product solution to obtain a degradation product;

[0010] S2: reacting the degradation product with isocyanate to obtain a polyurethane material.

[0011] The beneficial effects of the thermosetting polyurethane resin recycling method of the present invention are as follows: by adding a thermosetting polyurethane resin to a degradation system, allowing it to stand at room temperature to obtain a degradation product solution, and then post-treating the degradation product solution to obtain a degradation product, the weak coupling bonds in the thermosetting polyurethane resin are automatically degraded in the degradation system at room temperature, and the degradation process has low temperature requirements; the degradation product is then reacted with an isocyanate to obtain a polyurethane material, and the performance of the obtained polyurethane material is comparable to that of the thermosetting polyurethane resin. The thermosetting polyurethane resin recycling method of the present invention solves the problem of high temperature requirements in the recycling and reuse of thermosetting polyurethane resins in the prior art.

[0012] Optionally, the reducing agent includes at least one of a thiol compound and a phosphine compound, the organic solvent includes at least one of N,N-dimethylformamide and tetrahydrofuran, and the acidic substance includes at least one of hydrochloric acid, hydrobromic acid, phosphoric acid, and acetic acid. This advantageously allows for the degradation of weak coupling bonds without damaging other bonds.

[0013] Optionally, the weak coupling bond includes at least one of an ester bond, a sulfinic acid bond, a persulfonic acid structure, a phosphate bond, a disulfide bond, a ketal structure, an imine structure, an alkoxyamine, an aminal, a histamine bond, a tertiary aminoformic acid, an acylhydrazone structure, an orthoester acid, an acetal structure, an orthocarbonate bond, a peroxide bond, an orthocarbonate bond, a Dials-Alder structure, and a boron ester bond.

[0014] Optionally, the weak coupling bond includes at least one of a ketal structure, a disulfide bond and an imine structure.

[0015] Optionally, step S0 further includes the following steps:

[0016] S000: Provide isocyanates, polyether polyols and small molecule polyols containing weak coupling bonds;

[0017] S011: reacting the isocyanate and the polyether polyol to obtain an isocyanate-terminated prepolymer;

[0018] S012: reacting the isocyanate-terminated prepolymer with the polyether polyol and the small molecule polyol containing a weak coupling bond to obtain the thermosetting polyurethane resin.

[0019] Optionally, step S0 further includes the following steps:

[0020] S000: Provide isocyanates, polyether polyols and small molecule polyols containing weak coupling bonds;

[0021] S021: reacting the isocyanate with the small molecule polyol containing a weak coupling bond to obtain an isocyanate-terminated prepolymer;

[0022] S022: reacting the isocyanate-terminated prepolymer with the polyether polyol and the small molecule polyol containing a weak coupling bond to obtain the thermosetting polyurethane resin.

[0023] Optionally, the isocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, carbonized carbonyl modified toluene diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

[0024] Optionally, the polyether polyol includes at least one of difunctional polyether polyol, trifunctional polyether polyol and tetrafunctional polyether polyol.

[0025] Optionally, step S2 further includes the following steps:

[0026] S211: reacting the dehydrated degradation product with the isocyanate to obtain a first prepolymer, wherein the molar ratio of the dehydrated degradation product to the isocyanate is (3-7):1;

[0027] S212: reacting the first prepolymer and the isocyanate to obtain a polyurethane material.

[0028] Optionally, step S2 further includes the following steps:

[0029] S221: reacting the dehydrated degradation product with the isocyanate to obtain a second prepolymer, wherein the molar ratio of the dehydrated degradation product to the isocyanate is 1:(2-7);

[0030] S222: reacting the second prepolymer with a difunctional polyether polyol to obtain a polyurethane material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is the infrared spectrum of a small molecule diol containing an imine structure. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be the common meanings understood by people with ordinary skills in the field to which the invention belongs. The words "including" and similar words used in this article mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects.

[0033] By introducing weak coupling bonds into thermosetting polyurethane resins, recycling and reuse of the thermosetting polyurethane resin requires only a simple treatment with a low-concentration reducing agent or organic solution to disrupt the internal structure of the thermosetting polyurethane resin, degrading it into small molecule raw materials. The resulting small molecule raw materials can then be reused in the production of polyurethane resins. This present invention provides a novel, economical, and environmentally friendly recycling and reuse method. Prior art applications of weak coupling bonds in polyurethane resins have been limited to self-repairing, with limited research on their direct application in the recycling and reuse of thermosetting polyurethane resins.

[0034] An embodiment of the present invention provides a method for recycling and reusing thermosetting polyurethane resin, comprising the following steps:

[0035] S0: Providing a thermosetting polyurethane resin and a degradation system, wherein the degradation system comprises any one of a first system and a second system, wherein the first system comprises a reducing agent and an organic solvent, and the second system comprises an acidic substance and the organic solvent, and some urethanes of the thermosetting polyurethane resin are connected by weak coupling bonds;

[0036] S1: adding the thermosetting polyurethane resin to the degradation system, allowing the system to stand at room temperature to obtain a degradation product solution, and post-treating the degradation product solution to obtain a degradation product;

[0037] S2: Dehydrating the degradation product and reacting it with isocyanate to obtain a polyurethane material.

[0038] Specifically, a thermosetting polyurethane resin is added to a degradation system, allowed to stand at room temperature to obtain a degradation product solution, and the degradation product solution is post-treated to obtain a degradation product. This allows the weak coupling bonds in the thermosetting polyurethane resin to automatically degrade in the degradation system at room temperature, and the degradation process has low temperature requirements. The degradation product is then dehydrated and reacted with an isocyanate to obtain a polyurethane material, which has a hardness comparable to that of the thermosetting polyurethane resin. The method for recycling and reusing thermosetting polyurethane resins of the present invention solves the problem of high temperature requirements in the prior art for recycling and reusing thermosetting polyurethane resins.

[0039] In some embodiments of the present invention, the reducing agent includes at least one of a thiol compound and a phosphine compound, the organic solvent includes at least one of N,N-dimethylformamide and tetrahydrofuran, and the acidic substance includes at least one of hydrochloric acid, hydrobromic acid, phosphoric acid, and acetic acid. These can degrade weak coupling bonds without damaging other bonds.

[0040] In some specific embodiments of the present invention, the thiol compound includes at least one of 2-mercaptoethanol, thioglycolic acid, dithiothreitol, dithioerythritol and reduced glutamine, and the phosphine compound includes at least one of tributylphosphine, triphenylphosphine and tris(2-carboxyethyl)phosphine hydrochloride.

[0041] In some embodiments of the present invention, the weak coupling bond includes at least one of an ester bond, a sulfinic acid bond, a persulfonic acid structure, a phosphate bond, a disulfide bond, a ketal structure, an imine structure, an alkoxyamine, an aminal, a histamine bond, a tertiary aminoformic acid, an acylhydrazone structure, an orthoester acid, an acetal structure, an orthocarbonate bond, a peroxide bond, an orthocarbonate bond, a Dials-Alder structure, and a boron ester bond.

[0042] In some embodiments of the present invention, the weak coupling bond includes at least one of a ketal structure, a disulfide bond, and an imine structure.

[0043] In some embodiments of the present invention, step S0 further includes the following steps:

[0044] S000: Provide isocyanates, polyether polyols and small molecule polyols containing weak coupling bonds;

[0045] S011: reacting the isocyanate and the polyether polyol to obtain an isocyanate-terminated prepolymer;

[0046] S012: reacting the isocyanate-terminated prepolymer with the polyether polyol and the small molecule polyol containing a weak coupling bond to obtain the thermosetting polyurethane resin.

[0047] In some embodiments of the present invention, step S0 further includes the following steps:

[0048] S000: Provide isocyanates, polyether polyols and small molecule polyols containing weak coupling bonds;

[0049] S021: reacting the isocyanate with the small molecule polyol containing a weak coupling bond to obtain an isocyanate-terminated prepolymer;

[0050] S022: reacting the isocyanate-terminated prepolymer with the polyether polyol and the small molecule polyol containing a weak coupling bond to obtain the thermosetting polyurethane resin.

[0051] In some embodiments of the present invention, the isocyanate includes at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, carbonized carbonyl modified toluene diisocyanate, and 4,4-dicyclohexylmethane diisocyanate.

[0052] In some embodiments of the present invention, the polyether polyol includes at least one of a difunctional polyether polyol, a trifunctional polyether polyol, and a tetrafunctional polyether polyol.

[0053] In some embodiments of the present invention, step S2 further includes the following steps:

[0054] S211: reacting the dehydrated degradation product with the isocyanate to obtain a first prepolymer, wherein the molar ratio of the dehydrated degradation product to the isocyanate is (3-7):1;

[0055] S212: reacting the first prepolymer and the isocyanate to obtain a polyurethane material.

[0056] In some specific embodiments of the present invention, the molar ratio of the dehydrated degradation product to the isocyanate is any one of 4:1, 5:1 and 6:1.

[0057] In some embodiments of the present invention, step S2 further includes the following steps:

[0058] S221: reacting the dehydrated degradation product with the isocyanate to obtain a second prepolymer, wherein the molar ratio of the dehydrated degradation product to the isocyanate is 1:(2-7);

[0059] S222: reacting the second prepolymer with a difunctional polyether polyol to obtain a polyurethane material.

[0060] In some specific embodiments of the present invention, the molar ratio of the dehydrated degradation product to the isocyanate is any one of 1:3, 1:4, 1:5 and 1:6.

[0061] The technical solutions of the embodiments of the present invention are described in detail below through specific examples.

[0062] The products used in the examples include: vanillin, ethanolamine and tetrahydrofuran were purchased from Shanghai Titan Technology Co., Ltd., dibutyltin dilaurate was purchased from Shanghai Koraman Reagent Co., Ltd.; isophorone diisocyanate was purchased from Sigma-Aldrich (Shanghai) Trading Co., Ltd.; trifunctional polyether polyol EP330NG, trifunctional polyether polyol MN3050D, trifunctional polyether polyol MN1000, difunctional polyether diol with a molecular weight of 1000, and PTMEG1000 polyether polyol were purchased from Shandong Bluestar Dongda; carbonized subcarbon-modified toluene diisocyanate was purchased from Wanhua Chemical Group Co., Ltd.; and triethyl phosphate was purchased from Shanghai Jizhi Biochemical Technology Co., Ltd.

[0063] Example 1

[0064] Preparation of a small molecule diol containing an imine structure: 15.2 g (0.1 mol) of vanillin was weighed into a 500 ml three-necked flask, 200 ml of dried dichloromethane (DCM) was added, and the mixture was stirred until the vanillin was completely dissolved. 6.1 g (0.1 mol) of ethanolamine was then slowly added dropwise. The mixture was stirred at room temperature for 1 hour to form a yellow precipitate. After removing the solvent, the product was washed with 100 ml of DCM and dried under vacuum to obtain a small molecule diol containing an imine structure (abbreviated as MEA-V) with a yield of approximately 90%. The reaction equation is as follows:

[0065]

[0066] Figure 1 This is the infrared spectrum of a small molecule diol containing an imine structure, 1640-1690 cm-1 The C=N double bond stretching vibration region, that is, in the infrared spectrum, if 1640-1690cm -1 The presence of a peak indicates that there is C=N in the compound. Figure 1 , at 1641cm -1 There is a peak at , indicating that there is an imine structure in the obtained MEA-V.

[0067] 50g of trifunctional polyether polyol EP330NG with a molecular weight of 5000 was stirred and dehydrated at 110 degrees for 2 hours, cooled to room temperature, and 33g of carbonized carbon modified toluene diisocyanate was slowly added. The reaction was carried out at 65 degrees for two hours to obtain an isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer was cooled to room temperature and mixed with 9.6g of dehydrated MEA-V and 49.4g of PTMEG1000 polyether polyol. After vacuum degassing, it was injected into a mold and reacted and cured at 80 degrees to obtain a thermosetting polyurethane resin. The reaction equation of the process is as follows:

[0068]

[0069] 40g of thermosetting polyurethane resin was crushed into particles approximately 5mm in diameter and added to 200ml of a second system. The mixture was allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then nitrogen-purged to remove the solvent. The degradation product was then dehydrated with stirring at 120°C for 2 hours. This product was then used as a polyamine raw material. 10g of the dehydrated degradation product was reacted with 2g of a 1000 molecular weight difunctional polyether diol, 1.1g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate to obtain a polyurethane material. The second system consisted of hydrochloric acid and tetrahydrofuran, with a volume ratio of 1M hydrochloric acid to tetrahydrofuran of 1:9.

[0070] Example 2

[0071] 50g of trifunctional polyether polyol MN3050D with a molecular weight of 3000 was stirred and dehydrated at 110 degrees for 2 hours, cooled to room temperature, and 37.5g of carbonized subcarbon-modified toluene diisocyanate was slowly added. The reaction was carried out at 65 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 10.1g of dehydrated MEA-V and 52.2g of PTMEG1000 polyether polyol. After vacuum degassing, it was injected into a mold and reacted and cured at 80 degrees to obtain a thermosetting polyurethane resin.

[0072] 40g of thermosetting polyurethane resin was crushed into particles approximately 5mm in diameter and added to 200ml of the second system. The solution was allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then nitrogen-purged to remove the solvent. The degradation product was then dehydrated at 120°C for 2 hours, which was then used as a polyamine raw material. 10g of the dehydrated degradation product was reacted with 2g of a difunctional polyether diol with a molecular weight of 1000, 1.2g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate to obtain a polyurethane material. The second system consisted of hydrochloric acid and tetrahydrofuran, with a volume ratio of 1M hydrochloric acid to tetrahydrofuran of 1:9.

[0073] Example 3

[0074] 50g of trifunctional polyether polyol MN3050D with a molecular weight of 3000 was stirred and dehydrated at 110 degrees for 2 hours, cooled to room temperature, and 37.5g of carbonized subcarbon-modified toluene diisocyanate was slowly added. The reaction was carried out at 65 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 10.1g of dehydrated MEA-V and 52.2g of PTMEG1000 polyether polyol. After vacuum degassing, it was injected into a mold and reacted and cured at 80 degrees to obtain a thermosetting polyurethane resin.

[0075] 40g of thermosetting polyurethane resin was crushed into particles approximately 5mm in diameter and added to 200ml of a second system. The mixture was allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then nitrogen-purged to remove the solvent. The degradation product was then dehydrated at 120°C for 2 hours with stirring, and then used as a polyamine raw material. 10g of the dehydrated degradation product was reacted with 2g of a 1000 molecular weight difunctional polyether diol, 1.2g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate to obtain a polyurethane material. The second system consisted of hydrobromic acid and tetrahydrofuran, with a volume ratio of 1M hydrobromic acid to tetrahydrofuran of 1:9.

[0076] Example 4

[0077] 50g of trifunctional polyether polyol MN3050D with a molecular weight of 3000 was stirred and dehydrated at 110 degrees for 2h, cooled to room temperature, 0.05g of dibutyltin dilaurate, and 25.9g of isophorone diisocyanate were slowly added and reacted at 80 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 8.8g of dehydrated MEA-V and 45.1g of PTMEG1000 polyether polyol, vacuum degassed and injected into a mold, and reacted and cured at 90 degrees to obtain a thermosetting polyurethane resin.

[0078] 40g of thermosetting polyurethane resin was crushed into particles approximately 5mm in diameter and added to 200ml of a second system. The mixture was allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then subjected to high-temperature treatment to remove the solvent. The degradation product was then dehydrated at 120°C for 2 hours to serve as a polyamine raw material. 10g of the dehydrated degradation product was reacted with 2g of a 1000 molecular weight difunctional polyether diol, 1.0g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate to obtain a polyurethane material. The second system consisted of hydrochloric acid and tetrahydrofuran, with a volume ratio of 1M hydrochloric acid to tetrahydrofuran of 1:9.

[0079] Example 5

[0080] 50g of trifunctional polyether polyol EP330NG with a molecular weight of 5000 was stirred and dehydrated at 110 degrees for 2h, cooled to room temperature, and 33g of carbonized carbon modified toluene diisocyanate was slowly added. The reaction was carried out at 65 degrees for two hours to obtain an isocyanate-terminated prepolymer. The isocyanate-terminated prepolymer was cooled to room temperature and mixed with 8.8g of hydroxyethyl disulfide and 41.9g of PTMEG1000 polyether polyol. After vacuum degassing, it was injected into a mold and reacted and cured at 80 degrees to obtain a thermosetting polyurethane resin. The reaction equation of the process is as follows:

[0081]

[0082] 40g of thermosetting polyurethane resin was crushed into particles with a diameter of approximately 5mm, added to 200ml of the first system, and allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then subjected to high-temperature treatment to remove the solvent, and then the degradation product was obtained. The degradation product was then dehydrated by stirring at 120°C for 2 hours, which could be used as a polyol raw material. 10g of the dehydrated degradation product, 2g of a difunctional polyether diol with a molecular weight of 1000, 1.8g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate were reacted to obtain a polyurethane material. The first system consisted of tributylphosphine dissolved in tetrahydrofuran, with the amount of tributylphosphine per liter of tetrahydrofuran being 0.1 mol.

[0083] Example 6

[0084] 50g of trifunctional polyether polyol EP330NG with a molecular weight of 5000 was stirred and dehydrated at 110 degrees for 2h, cooled to room temperature, 0.05g of dibutyltin dilaurate, 22.9g of isophorone diisocyanate were slowly added, and reacted at 80 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 7.9g of hydroxyethyl disulfide and 36g of PTMEG1000 polyether polyol, vacuum degassed and injected into a mold, and reacted and cured at 90 degrees to obtain a thermosetting polyurethane material.

[0085] 40g of thermosetting polyurethane material was crushed into particles with a diameter of approximately 5mm, added to 200ml of the first system, and allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then subjected to high-temperature treatment to remove the solvent, and then the degradation product was obtained. The degradation product was then dehydrated by stirring at 120 degrees for 2 hours, which could be used as a polyol raw material. 10g of the dehydrated degradation product, 2g of a difunctional polyether diol with a molecular weight of 1000, 1.9g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate were reacted to obtain a polyurethane material. The first system consisted of tributylphosphine dissolved in tetrahydrofuran, with the amount of tributylphosphine per liter of tetrahydrofuran being 0.1 mol.

[0086] Example 7

[0087] 50g of trifunctional polyether polyol MN3050D with a molecular weight of 3000 was stirred and dehydrated at 110 degrees for 2h, cooled to room temperature, and 37.5g of carbonized subcarbon-modified toluene diisocyanate was slowly added. The reaction was carried out at 65 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 10g of hydroxyethyl disulfide and 49.7g of PTMEG1000 polyether polyol. After vacuum degassing, it was injected into a mold and reacted and cured at 80 degrees to obtain a thermosetting polyurethane resin.

[0088] 40g of thermosetting polyurethane material was crushed into particles with a diameter of approximately 5mm, added to 200ml of the first system, and allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then subjected to high-temperature treatment to remove the solvent, and then the degradation product was obtained. The degradation product was then dehydrated by stirring at 120°C for 2 hours, which could be used as a polyol raw material. 10g of the dehydrated degradation product, 2g of a difunctional polyether diol with a molecular weight of 1000, 1.9g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate were reacted to obtain a polyurethane material. The first system consisted of tributylphosphine dissolved in tetrahydrofuran, with the amount of tributylphosphine per liter of tetrahydrofuran being 0.1 mol.

[0089] Example 8

[0090] 50g of trifunctional polyether polyol MN3050D with a molecular weight of 3000 was stirred and dehydrated at 110 degrees for 2h, cooled to room temperature, 0.05g of dibutyltin dilaurate, and 25.9g of isophorone diisocyanate were slowly added and reacted at 80 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 7.0g of hydroxyethyl disulfide and 45.1g of PTMEG1000 polyether polyol, vacuum degassed, injected into a mold, and reacted and cured at 90 degrees to obtain a thermosetting polyurethane resin.

[0091] 40g of thermosetting polyurethane material was crushed into particles with a diameter of approximately 5mm, added to 200ml of the first system, and allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then nitrogen-purged to remove the solvent, and then the degradation product was obtained. The degradation product was then stirred and dehydrated at 120°C for 2 hours, which could be used as a polyol raw material. 10g of the dehydrated degradation product, 2g of a difunctional polyether diol with a molecular weight of 1000, 1.9g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate were reacted to obtain a polyurethane material. The first system consisted of tributylphosphine dissolved in tetrahydrofuran, with the amount of tributylphosphine per liter of tetrahydrofuran being 0.1 mol.

[0092] Example 9

[0093] 50g of trifunctional polyether polyol MN1000 with a molecular weight of 1000 was stirred and dehydrated at 110 degrees for 2h, cooled to room temperature, 0.05g of dibutyltin dilaurate, 41.27g of isophorone diisocyanate were slowly added, and reacted at 80 degrees for two hours to obtain an isocyanate-terminated prepolymer. After the isocyanate-terminated prepolymer was cooled to room temperature, it was mixed with 8.4g of hydroxyethyl disulfide and 54.3g of PTMEG1000 polyether polyol, vacuum degassed and injected into a mold, and reacted and cured at 90 degrees to obtain a thermosetting polyurethane resin.

[0094] 40g of thermosetting polyurethane material was crushed into particles with a diameter of approximately 5mm, added to 200ml of the first system, and allowed to stand at room temperature for 24 hours to obtain a degradation product solution. The degradation product solution was then nitrogen-purged to remove the solvent, and then the degradation product was obtained. The degradation product was then stirred and dehydrated at 120°C for 2 hours, which could be used as a polyol raw material. 10g of the dehydrated degradation product, 2g of a difunctional polyether diol with a molecular weight of 1000, 1.9g of carbonized carbon-modified toluene diisocyanate, and 1g of triethyl phosphate were reacted to obtain a polyurethane material. The first system consisted of tributylphosphine dissolved in tetrahydrofuran, with the amount of tributylphosphine per liter of tetrahydrofuran being 0.1 mol.

[0095] The properties of the thermosetting polyurethane resin, degradation products, and polyurethane materials in Examples 1-9 are shown in Table 1. The hardness test instrument was purchased from Naibo Testing Technology (Shanghai) Co., Ltd., model THR-150DX, the viscosity test instrument was purchased from Guangdong Beidou Precision Instrument Co., Ltd., model PT-502C, and the molecular weight test instrument was purchased from Agilent, model Agilent 7100.

[0096] Table 1

[0097]

[0098]

[0099] As shown in Table 1, the viscosity and molecular weight of the degradation product obtained after degradation of the thermosetting polyurethane resin are more suitable for preparing polyurethane materials again, and the performance of the recycled polyurethane material is comparable to that of the original thermosetting polyurethane resin.

[0100] While the embodiments of the present invention have been described in detail above, it will be apparent to those skilled in the art that various modifications and variations of these embodiments are possible. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as set forth in the claims. Furthermore, the invention described herein is susceptible to other embodiments and may be practiced or implemented in a variety of ways.

Claims

1. A method for recycling thermosetting polyurethane resin, characterized in that: The following steps are involved: S0: Provide thermosetting polyurethane resin and degradation system, Some of the carbamates of the thermosetting polyurethane resin are connected by weak coupling bonds. S0 includes providing isocyanate, polyether polyol and a small molecule polyol containing a weak coupling bond. The small molecule polyol containing a weak coupling bond for preparing the thermosetting polyurethane is MEA-V or 2-hydroxyethyl disulfide. The structural formula of the MEA-V is ； The degradation system includes any one of a first system and a second system, wherein the first system includes a reducing agent and an organic solvent, and the second system includes an acidic substance and the organic solvent; S1: adding the thermosetting polyurethane resin to the degradation system, allowing the system to stand at room temperature to obtain a degradation product solution, and post-treating the degradation product solution to obtain a degradation product; S2: reacting the degradation product with isocyanate to obtain a polyurethane material, S2 includes: S211: reacting the dehydrated degradation product with the isocyanate to obtain a first prepolymer, wherein the molar ratio of the dehydrated degradation product to the isocyanate is (3-7):1; S212: reacting the first prepolymer with the isocyanate to obtain a polyurethane material; Alternatively, S2 includes: S221: reacting the dehydrated degradation product with the isocyanate to obtain a second prepolymer, wherein the molar ratio of the dehydrated degradation product to the isocyanate is 1:(2-7); S222: reacting the second prepolymer with a difunctional polyether polyol to obtain a polyurethane material.

2. The method for recycling thermosetting polyurethane resin according to claim 1, characterized in that: The reducing agent includes at least one of a mercapto compound and a phosphine compound, the organic solvent includes at least one of N,N-dimethylformamide and tetrahydrofuran, and the acidic substance includes at least one of hydrochloric acid, hydrobromic acid, phosphoric acid and acetic acid.

3. The method for recycling thermosetting polyurethane resin according to claim 1, characterized in that: Step S0 further includes the following steps: S000: Provide isocyanates, polyether polyols and small molecule polyols containing weak coupling bonds; S011: reacting the isocyanate and the polyether polyol to obtain an isocyanate-terminated prepolymer; S012: reacting the isocyanate-terminated prepolymer with the polyether polyol and the small molecule polyol containing a weak coupling bond to obtain the thermosetting polyurethane resin.

4. The method for recycling thermosetting polyurethane resin according to claim 1, characterized in that: Step S0 further includes the following steps: S000: Provide isocyanates, polyether polyols and small molecule polyols containing weak coupling bonds; S021: reacting the isocyanate with the small molecule polyol containing a weak coupling bond to obtain an isocyanate-terminated prepolymer; S022: reacting the isocyanate-terminated prepolymer with the polyether polyol and the small molecule polyol containing a weak coupling bond to obtain the thermosetting polyurethane resin.

5. The method for recycling and reusing thermosetting polyurethane resin according to claim 3 or 4, wherein the isocyanate comprises at least one of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, polymethylene polyphenyl isocyanate, and 4,4-dicyclohexylmethane diisocyanate.

6. The method for recycling thermosetting polyurethane resin according to claim 3 or 4, characterized in that: The polyether polyol includes at least one of a difunctional polyether polyol, a trifunctional polyether polyol and a tetrafunctional polyether polyol.

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