A method of catalyzing depolymerization of polyurethane with a carboxylate salt
By using carboxylate catalysts in a diester medium for polyurethane depolymerization, the problems of equipment corrosion and product separation difficulties in existing technologies have been solved, achieving efficient and green resource recycling of polyurethane waste, which has potential for industrial application.
Patent Information
- Application Number
- CN202511472728.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-15
- Publication Date
- 2026-11-06
- Estimated Expiration
- 2045-10-15
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of chemical recycling technology of waste polymer materials, specifically relating to a method for catalytic depolymerization of polyurethane into its monomers or high-value chemicals, and more specifically, a method for catalytic depolymerization of polyurethane using carboxylate substances in diester carbonate. Background Technology
[0002] Polyurethane (PU) is an important class of polymer materials prepared by reacting isocyanates with polyols. Due to its excellent mechanical properties, abrasion resistance, processability, and formulation flexibility, it is widely used in fields such as foamed plastics, elastomers, coatings, adhesives, synthetic leather, and fibers. With the continuous growth of global polyurethane consumption, the amount of waste generated has also increased year by year, leading to increasingly serious environmental burdens and resource waste problems.
[0003] Traditional methods for treating polyurethane waste include landfilling and incineration, but these methods not only consume land resources but may also generate harmful gases, causing secondary pollution. Therefore, developing efficient and green chemical recycling technologies to depolymerize waste polyurethane into original monomers or other high-value chemicals is a key approach to achieving resource recycling and sustainable development of the industry.
[0004] Currently, the main chemical depolymerization methods for polyurethane include hydrolysis, alcoholysis, aminolysis, and acidolysis. However, these methods generally have some limitations: for example, hydrolysis requires strong acid or strong base conditions, which severely corrodes equipment and makes product separation and purification difficult; alcoholysis usually requires high reaction temperatures and large amounts of alcohol solvent, resulting in high energy consumption and the formation of complex mixtures; aminolysis and acidolysis also suffer from harsh reaction conditions, high reagent costs, and environmental pollution. Furthermore, existing catalytic systems mostly employ metal oxides, strong acid-base compounds, or organometallic catalysts, whose catalytic efficiency, selectivity, and stability still need improvement, and some catalysts are inherently toxic or difficult to recover, limiting their large-scale application.
[0005] Carboxylate compounds have attracted widespread attention in the field of catalysis due to their wide availability, low cost, low toxicity, and high designability. In particular, carboxylate metal salts and carboxylate ionic liquids have demonstrated excellent catalytic activity and selectivity in various reactions such as esterification, polymerization, and degradation. Their application in the depolymerization process of polyurethane holds promise for achieving efficient and highly selective depolymerization under mild conditions, while simultaneously reducing environmental impact.
[0006] Dicarbonates (such as dimethyl carbonate and diethyl carbonate) are environmentally friendly green solvents and reagents, characterized by moderate boiling points and low toxicity. This invention proposes a novel and promising method for the resource-based recycling of polyurethane waste by using carboxylate catalysts in a diester medium to achieve efficient depolymerization of polyurethane. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide a polyurethane depolymerization method with mild reaction conditions, high efficiency, and environmental friendliness.
[0008] The polyurethane depolymerization method provided by the present invention includes the following steps: chemically depolymerizing polyurethane or polyurethane-containing composite materials in a diester under the condition of a carboxylate as a catalyst.
[0009] The above method can be used to depolymerize polyurethane under mild conditions and convert it into valuable chemicals such as urethane derivatives.
[0010] In the above method, the reaction conditions for the chemical depolymerization reaction are: a reaction time of 0.5 to 36 hours at a temperature of room temperature to 200°C, wherein the room temperature range is 15 to 30°C.
[0011] In the above method, the carboxylate substance can be selected from any one of the following: carboxylate anionic metal salts, carboxylate anionic ionic liquids, and composite systems based on carboxylate anionic metal salts and carboxylate anionic ionic liquids.
[0012] The carboxylic acid anion metal salt has anions including, but not limited to, formic acid anion, acetate anion, propionic acid anion, lactic acid anion, trifluoroacetic acid anion, benzoic acid anion, etc.; and metal cations including, but not limited to, sodium ion, potassium ion, zinc ion, magnesium ion, calcium ion. Specifically, the carboxylic acid anionic metal salts include, but are not limited to, sodium formate, potassium formate, zinc formate, sodium acetate, potassium acetate, zinc acetate, magnesium acetate, calcium acetate, zinc propionate, zinc lactate, zinc trifluoroacetate, sodium trifluoroacetate, potassium trifluoroacetate, sodium benzoate, etc. The carboxylic acid anionic ionic liquid has anions including, but not limited to, formic acid anion, acetate anion, trifluoroacetic acid anion, lactate anion, etc.; and cations including, but not limited to, imidazole cation, pyridinyl cation, piperidinyl cation, tetraalkylammonium cation, tetraalkylphosphine cation, guanidinyl cation, alkylpyridinyl cation, alkylpiperidine cation, alkylpyrrole cation, etc.; wherein the alkyl groups in the tetraalkylammonium cation, tetraalkylphosphine cation, alkylpyridinyl cation, alkylpiperidine cation, and alkylpyrrole cation can be independently selected from C1-C8 straight-chain or branched alkyl groups; Specifically, the carboxylic acid anionic ionic liquid includes, but is not limited to, [N 1111 ]OAc (tetramethylammonium acetate), [N 4444 ]OAc (tetrabutylammonium acetate), [P 4444 OAc (tetrabutylphosphine acetate), [Py 14]OAc (N-butyl-N-methylpyrrole acetate), [PP 14 [OAc (N-butyl-N-methylpiperidine acetate), [BMIm]OAc (1-butyl-3-methylimidazolium acetate), [EMIm]OAc (1-ethyl-3-methylimidazolium acetate), [N 4444 [CF3COO] (tetrabutylammonium trifluoroacetate), [P] 4444 [CF3COO] (tetrabutylphosphine trifluoroacetate), [N 4444 [Lac] (Tetrabutylammonium lactate).
[0013] In the above method, the diester carbonate may be selected from at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, dibutyl carbonate, diphenyl carbonate, dibenzyl carbonate, etc.
[0014] In the above method, the polyurethane includes various types of polyurethane materials and their waste.
[0015] The polyurethanes described in this invention include, but are not limited to: polyether-type polyurethanes, polyester-type polyurethanes, MDI (4,4'-diphenylmethane diisocyanate) type polyurethanes, HDI (1,6-hexamethylene diisocyanate) type polyurethanes, TDI (2,4-toluene diisocyanate / 2,6-toluene diisocyanate) type polyurethanes, and IPDI (3-isocyanatomethylene-3,5,5-trimethylcyclohexyl diisocyanate) type polyurethanes. The polyurethane-containing composite materials include, but are not limited to, at least one of all samples, physical samples, or mixtures thereof containing polyurethane components.
[0016] Furthermore, the polyurethane is an MDI-type polyurethane, and even more specifically, it can be a polyether-type MDI-type polyurethane or a polyester-type MDI-type polyurethane.
[0017] In the above method, other solvents may be added to the chemical depolymerization reaction system. The other solvents may be selected from at least one of the following: toluene, n-hexane, tetrahydrofuran, alcohol solvents (such as methanol, ethanol, isopropanol, etc.), and N,N-dimethylformamide.
[0018] Furthermore, the ratio of the other solvents to the diester is 1 ml / 5 mmol to 20 mL / 1 mmol.
[0019] In the above method, the molar ratio of the diester to the polyurethane structural unit can be 1:1 to 25:1, specifically 10:1 to 15:1, 10:1, 15:1 or 20:1, etc. In the above method, the molar ratio of the carboxylate substance to the polyurethane structural unit can be 1% to 20%, specifically 1%, 5%, 10% or 20%, etc.
[0020] Furthermore, in the above method, the reaction conditions for the chemical depolymerization reaction are: a temperature of 60–200°C for 0.5–36 h.
[0021] Preferably, when a carboxylic acid anionic metal salt is added as a catalyst, the reaction temperature can be 100–200°C (specifically, 120°C–160°C, 120°C, 140°C, or 160°C, etc.); and the time can be 4–36 h (specifically, 12–24 h, 8 h, 12 h, or 24 h).
[0022] Preferably, when a carboxylic acid anionic ionic liquid is added as a catalyst, the reaction temperature can be 80–160°C (specifically, 120°C–140°C, 80°C, 100°C, 120°C, 140°C, or 160°C, etc.); the time can be 0.5–24 h (specifically, 4–8 h, 2 h, 4 h, or 8 h, etc.).
[0023] Preferably, when a composite system formed by adding a carboxylic acid anionic metal salt and a carboxylic acid anionic ionic liquid is used as a catalyst, the reaction temperature can be 80–140°C (specifically, 80°C, 100°C, 120°C, etc.); the time can be 0.5–8h (specifically, 1–2h, 0.5h, 1h, 2h, etc.).
[0024] In this invention, the polyurethane structural unit refers to the basic repeating unit constituting the polyurethane polymer compound. Its core is a structural segment containing characteristic functional groups connected by urethane bonds (-NH-CO-O-), which can usually be represented as -ORO-CO-NH-R'-NH- (where R and R' can be aliphatic or aromatic hydrocarbon groups). Specifically, polyurethane is formed by a stepwise addition polymerization reaction of polyisocyanates (such as 4,4'-diphenylmethane diisocyanate, MDI) and polyols (such as polyether glycol or polyester glycol). During the reaction, no small molecules are precipitated. The isocyanate group (-NCO) and hydroxyl group (-OH) directly add to form urethane bonds, which are then linked to form a polymer chain. This repeating structural segment connected by urethane bonds is the structural unit of polyurethane.
[0025] Furthermore, the specific operation of the above method is as follows: polyurethane or a polyurethane-containing composite material is placed in a diester, and under the condition of adding a carboxylate as a catalyst, it is heated at a certain temperature for a set time to obtain the corresponding product.
[0026] The method further includes the following operations: filtering and separating unreacted solids; then collecting excess diester and the generated product sequentially by conventional vacuum distillation, and recovering catalysts, etc.
[0027] The recovered catalyst can be reused.
[0028] Regarding the separation of products after the reaction, it also includes adopting appropriate separation methods according to the different catalysts used.
[0029] Examples of products obtained through the above methods are described below: For polyester-type polyurethanes, such as PBA-type and MDI-type polyurethanes (PBA represents polybutylene adipate, and MDI represents 4,4'-diphenylmethane diisocyanate), after depolymerization with DMC, methyl methylene bis(4,1-phenylene) dicarboxylate (MDC), dimethyl adipate (DMA), and dimethyl 1,4-butanediol carbonate (BDD) are obtained; after depolymerization with DEC, PBA-type and MDI-type polyurethanes are obtained, ethyl methylene bis(4,1-phenylene) dicarboxylate, diethyl adipate, and diethyl 1,4-butanediol carbonate are obtained; and after depolymerization with DMC, PEA-type and MDI-type polyurethanes (PEA represents polyethylene adipate, and MDI represents 4,4'-diphenylmethane diisocyanate) are obtained, MDC, DMA, BDD, ethylene carbonate (EC), and dimethyl 2,5-dioxadipic acid (DD) are obtained.
[0030] For polyether-type polyurethanes, such as polytetrahydrofuran-type MDI-type polyurethanes, depolymerization with DMC yields MDC, BDD, tetrahydrofuran (THF), etc.
[0031] This invention utilizes the reaction of diester with polyurethane to achieve the depolymerization of polyurethane under mild conditions to prepare chemicals. It is applicable to the research and development of related technologies for the chemical recovery of polyurethane monomers from any polyurethane and its mixtures. The method provided by this invention has advantages such as high efficiency, environmental friendliness, and mild reaction conditions, depolymerizing polyurethane to generate its monomers, and has strong industrial application value. Attached Figure Description
[0032] Figure 1 This is a product obtained by depolymerizing polyurethane in dimethyl carbonate. Detailed Implementation
[0033] The present invention will now be described in further detail with reference to specific embodiments. The given embodiments are merely illustrative of the invention and not intended to limit its scope. The embodiments provided below can serve as a guide for further improvements by those skilled in the art and do not constitute a limitation on the invention in any way.
[0034] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Unless otherwise specified, the materials and reagents used in the following examples are commercially available.
[0035] Examples 1-11: Catalytic depolymerization of dimethyl carbonate by carboxylic acid anion metal salts in PBA-type and MDI-type polyurethanes Experimental procedure: 240 mg (containing approximately 1 mmol of polyurethane structural units) of PBA-type MDI-type polyurethane, 0.05 mmol of metal salt, and 900 mg (approximately 10 mmol) of dimethyl carbonate were added to a 20 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at a set temperature and reacted for a certain time. After cooling in an ice-water bath, pyrazine was added as an internal standard and deuterated DMSO as a deuteration reagent. The product yield was analyzed by NMR, and the following results were obtained.
[0036] Table 1. Reaction conditions and results of Examples 1-11
[0037] Examples 12-21: Catalysis of dimethyl carbonate depolymerization by carboxylic acid anionic liquids in PBA-type and MDI-type polyurethanes Experimental procedure: 240 mg (containing approximately 1 mmol of polyurethane structural units) of PBA-type MDI-type polyurethane, 0.05 mmol of ionic liquid, and 900 mg (approximately 10 mmol) of dimethyl carbonate were added to a 20 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at a set temperature and reacted for a certain time. After cooling in an ice-water bath, pyrazine was added as an internal standard and deuterated dimethyl sulfoxide (DMSO-d6) as a deuteration reagent. The product yield was analyzed by NMR, and the following results were obtained.
[0038] Table 2 Reaction conditions and results of Examples 12-21
[0039] Examples 22-28: Catalytic depolymerization of PBA-type MDI-type polyurethane using composite systems Experimental procedure: 240 mg (containing approximately 1 mmol of polyurethane structural units) of PBA-type MDI-type polyurethane, 0.05 mmol of metal carboxylate, 0.01 mmol of carboxylic acid anionic ionic liquid, and 900 mg (approximately 10 mmol) of dimethyl carbonate were added to a 20 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at a set temperature and reacted for a certain time. After cooling to room temperature, pyrazine was added as an internal standard and deuterated dimethyl sulfoxide as a deuteration reagent. The product yield was analyzed by NMR, and the following results were obtained.
[0040] Table 3 Reaction conditions and results of Examples 22-28
[0041] Examples 29-36: Depolymerization of PBA-type and MDI-type polyurethanes with DMC in other solvent systems The experimental procedure involved adding 240 mg (1 mmol of polyurethane structural unit) of PBA-type MDI-type polyurethane, 0.05 mmol of zinc acetate, 270 mg (approximately 3 mmol) of dimethyl carbonate, and 1 mL of other solvent to a 15 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at a set temperature and allowed to react for a certain period of time. After cooling to room temperature, pyrazine was added as an internal standard and deuterated dimethyl sulfoxide as a deuteration reagent. The product yield was analyzed by NMR, yielding the following results.
[0042] Table 4. Reaction conditions and results of Examples 29-36
[0043] Examples 37-38: Depolymerization of other types of polyurethane in DMC catalyzed by zinc acetate Experimental procedure: Approximately 1 mmol of polyurethane containing polyurethane structural units, 0.05 mmol of zinc acetate, and 900 mg of DMC (approximately 10 mmol) were added to a 15 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at 120 °C and reacted for 12 hours. After cooling in an ice-water bath, pyrazine was added as an internal standard and deuterated dimethyl sulfoxide as a deuteration reagent. The yield was then determined by NMR analysis using the internal standard method.
[0044] Example 37: Depolymerization of PEA-type MDI-type polyurethane yielded methyl methylene bis(4,1-phenylene)dicarbamate (MDC) with a yield of 94.5%, dimethyl adipate (DMA) with a yield of 93.7%, diethyl 1,4-butanediol carbonate (BDD) with a yield of 94.5%, ethylene carbonate (EC) with a yield of 84.3%, and dimethyl 2,5-dioxa-adipate (DD) with a yield of 6.2%.
[0045] Example 38: Depolymerization of polytetrahydrofuran-type MDI polyurethane yielded methyl methylene bis(4,1-phenylene)dicarbamate (MDC) with a yield of 93.5%, 1,4-butanediol diethyl carbonate (BDD) with a yield of 90.2%, and tetrahydrofuran (THF) with a yield of 90.7%.
[0046] Example 39: Zinc acetate-catalyzed depolymerization of polytetrahydrofuran-type MDI-type spandex yarn in DMC Experimental procedure: 113 mg of polytetrahydrofuran-type MDI-type spandex yarn (containing 1 mmol of polyurethane structural units), 0.05 mmol of zinc acetate, and 900 mg of dimethyl carbonate (approximately 10 mmol) were added to a 15 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at 120 °C and reacted for 12 hours. After cooling in an ice-water bath, pyrazine was added as an internal standard and deuterated dimethyl sulfoxide as a deuteration reagent. The product yields were analyzed by NMR, yielding methyl methylene bis(4,1-phenylene)dicarbamate (MDC) with a yield of 90.4%, 1,4-butanediol diethyl carbonate (BDD) with a yield of 88.9%, and tetrahydrofuran (THF) with a yield of 80.9%.
[0047] Example 40: Depolymerization of PBA-type MDI-type polyurethane in diethyl carbonate (DEC) catalyzed by zinc acetate Experimental procedure: 240 mg of PBA-type MDI-type polyurethane (containing 1 mmol of polyurethane structural unit), 0.05 mmol of zinc acetate, and 1200 mg of diethyl carbonate (approximately 10 mmol) were added to a 50 mL pressure-resistant reaction tube. The reaction tube was then placed in a heating device at 120 °C and reacted for 12 hours. After cooling in an ice-water bath, pyrazine was added as an internal standard and deuterated dimethyl sulfoxide as a deuteration reagent. The product yields were analyzed by NMR, yielding ethyl methylenebis(4,1-phenylene)dicarbamate (90.5%), diethyl adipate (89.5%), and diethyl 1,4-butanediol carbonate (87.6%).
[0048] The present invention has been described in detail above. For those skilled in the art, the invention can be practiced in a wide range of ways with equivalent parameters, concentrations, and conditions without departing from its spirit and scope, and without requiring unnecessary experiments. Although specific embodiments have been given, it should be understood that further modifications can be made to the invention. In summary, according to the principles of the invention, this application is intended to include any changes, uses, or improvements to the invention, including changes made using conventional techniques known in the art that depart from the scope disclosed herein. Some of the essential features can be applied within the scope of the following appended claims.
Claims
1. A method for depolymerizing polyurethane, comprising the following steps: chemically depolymerizing polyurethane or a polyurethane-containing composite material in a diester under conditions where a carboxylate is used as a catalyst; The carboxylate substances are selected from any one of the following: carboxylate anionic ionic liquids and composite systems formed based on carboxylate anionic metal salts and carboxylate anionic ionic liquids; The carboxylic acid anion metal salt has an anion selected from at least one of the following: formic acid anion, acetate anion, propionic acid anion, lactic acid anion, trifluoroacetic acid anion, benzoic acid anion; and a metal cation selected from at least one of the following: sodium ion, potassium ion, zinc ion, magnesium ion, calcium ion. The carboxylic acid anionic ionic liquid has an anion selected from at least one of the following: formic acid anion, acetate anion, trifluoroacetic acid anion, and lactate anion; and a cation selected from at least one of the following: imidazole cation, pyridinyl cation, piperidinyl cation, tetraalkylammonium cation, tetraalkylphosphine cation, guanidinyl cation, alkylpyridinyl cation, alkylpiperidine cation, and alkylpyrrole cation; wherein... The alkyl groups in the tetraalkylammonium cation, tetraalkylphosphine cation, alkylpyridinium cation, alkylpiperidine cation, and alkylpyrrole cation are all independently selected from C1-C8 straight-chain or branched alkyl groups. The molar ratio of the diester to the polyurethane structural unit is 1:1 to 25:
1. When a carboxylic acid anionic liquid is added as a catalyst, the reaction temperature for the chemical depolymerization is 120–140°C, and the reaction time is 4–8 h. When a composite system formed by adding anionic metal salts of carboxylic acid and anionic ionic liquids of carboxylic acid is used as a catalyst, the reaction temperature of the chemical depolymerization is 80–140 °C and the reaction time is 0.5–24 h. The specific operating steps of the method are as follows: polyurethane or polyurethane-containing composite material is placed in diester carbonate, heated for a certain time at a set reaction temperature under the condition that carboxylate is used as a catalyst, and then cooled to obtain the corresponding product.
2. The method according to claim 1, characterized in that: The carbonate diester is selected from at least one of dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate, diphenyl carbonate, and dibenzyl carbonate; And / or, the polyurethane includes various types of polyurethane materials and their waste.
3. The method according to claim 1, characterized in that: The carboxylic acid anion metal salt is selected from at least one of the following: sodium formate, potassium formate, zinc formate, sodium acetate, potassium acetate, zinc acetate, magnesium acetate, calcium acetate, zinc propionate, zinc lactate, zinc trifluoroacetate, sodium trifluoroacetate, potassium trifluoroacetate, and sodium benzoate. And / or, the carboxylic acid anionic ionic liquid is selected from at least one of the following: [N 1111 ]OAc (tetramethylammonium acetate), [N 4444 ]OAc (tetrabutylammonium acetate), [P 4444 OAc (tetrabutylphosphine acetate), [Py 14 ]OAc (N-butyl-N-methylpyrrole acetate), [PP 14 [OAc (N-butyl-N-methylpiperidine acetate), [BMIm]OAc (1-butyl-3-methylimidazolium acetate), [EMIm]OAc (1-ethyl-3-methylimidazolium acetate), [N 4444 [CF3COO] (tetrabutylammonium trifluoroacetate), [P] 4444 [CF3COO] (tetrabutylphosphine trifluoroacetate), [N 4444 [Lac] (Tetrabutylammonium lactate).
4. The method according to claim 1, characterized in that: The polyurethane is selected from at least one of the following: polyether polyurethane, polyester polyurethane, MDI polyurethane, HDI polyurethane, TDI polyurethane, IPDI polyurethane; the polyurethane-containing composite material is selected from at least one of all samples, physical objects, or mixtures thereof containing polyurethane components.
5. The method according to claim 1, characterized in that: The molar ratio of the carboxylate to the polyurethane structural unit is 1% to 20%.
6. The method according to claim 1, characterized in that: The method further includes the following steps: filtering and separating unreacted solids; and then collecting excess diester, catalyst, and the resulting products, such as carbamate derivatives, polyols, or esters, by conventional vacuum distillation.
7. The method according to claim 1, characterized in that: The polyurethane is a PBA-type MDI-type polyurethane, which is chemically depolymerized in dimethyl carbonate to obtain methyl methylene bis(4,1-phenylene)dicarbamate (MDC), dimethyl adipate (DMA), and dimethyl 1,4-butanediol carbonate (BDD). And / or, the polyurethane is a PBA-type or MDI-type polyurethane, which is chemically depolymerized in diethyl carbonate to obtain ethyl methylene bis(4,1-phenylene)dicarbamate, diethyl adipate, and diethyl 1,4-butanediol carbonate. And / or, the polyurethane is a PEA-type or MDI-type polyurethane, which is chemically depolymerized in dimethyl carbonate to obtain methyl methylene bis(4,1-phenylene)dicarbamate (MDC), dimethyl adipate (DMA), dimethyl 1,4-butanediol carbonate (BDD), ethylene carbonate (EC), and dimethyl 2,5-dioxadipic acid (DD). And / or, the polyurethane is a polytetrahydrofuran-type MDI polyurethane, which is chemically depolymerized in dimethyl carbonate to obtain methyl methylene bis(4,1-phenylene)dicarbamate (MDC), dimethyl 1,4-butanediol carbonate (BDD), and tetrahydrofuran (THF).