Method for recovering polyester through high-efficiency selective alcoholysis of alcohol amine compound

Abstract

The invention provides a method for recovering polyester through high-efficiency selective alcoholysis of an alcohol amine compound, aiming at the problems existing in the prior art for recovering polyester from the alcohol amine compound. According to the method, by combining factors such as an amino protection strategy and a solvent effect, selective alcoholysis of the alcohol amine compound on the polyester is realized, so that when the alcohol amine compound is used for degrading and recycling the polyester, the energy consumption in a separation process can be reduced in a degradation process, the recovery rate and the purity of an alcoholysis product are improved, and moreover, the production cost is reduced. The alcoholysis product obtained by the method provided by the invention also contains amino groups and ester groups, and can be used as a high-value chemical raw material for synthesizing high-performance polymers or fine chemicals and realizing upgraded recovery of polyester, so that environmental protection and resource recycling can be greatly promoted undoubtedly, and development and popularization of circular economy are promoted.

Description

Technical Field

[0001] The invention relates to the technical field of solid waste recovery, and in particular to a method for recovering polyester through efficient and selective alcoholysis of an alcoholamine compound. Background Art

[0002] Polyester is a general term for polymers obtained by polycondensation of polyols and polyacids. It has excellent tensile strength, chemical resistance, transparency, processability and thermal stability, and is widely used in plastics, textiles and other fields. With the continuous increase in demand, the amount of waste polyester has also increased significantly. Taking polyethylene terephthalate (PET), the largest type of waste, as an example, waste PET materials account for 8% of the total mass and 12% of the total volume of the world's solid waste. Its recycling can not only reduce environmental pollution, but also improve resource utilization. At present, the main recycling method for polyester is physical recycling. During the recycling process, the performance of the recycled product decreases due to heat, mechanical and other effects, and most of them are downgraded recycling. In comparison, chemical recycling methods are flexible and have a wide range of applications. It is expected to achieve polyester upgrading and recycling, and is a recycling method with development prospects.

[0003] The current chemical recovery methods of polyester are mainly solvent hydrolysis, including hydrolysis, alcoholysis and ammonia / amine hydrolysis. Among them, alcoholysis is widely used, and usually uses methanol, ethylene glycol, etc. to carry out ester exchange reactions to prepare monomers such as dibasic acid methyl ester or ethylene glycol ester respectively. These monomers can be further polymerized to obtain polyester, thereby realizing the recycling of polyester. In addition to recycling, researchers have begun to pay attention to the upgrading and recycling of polyester in recent years, that is, introducing active groups while degrading polyester, and the obtained degradation products can be further reconstructed to obtain various high-value products. For example, while alcoholamine compounds can undergo degradation reactions with polyester, they may also bring such active groups, which can not only achieve the degradation and recycling of polyester, but also obtain degradation products as high-value chemical raw materials, which can be used to synthesize high-performance polymers or fine chemicals, and are expected to be used for the upgrading and recycling of polyester. However, since alcoholamine compounds are more inclined to undergo amidation reactions with polyester in thermodynamics, it is difficult to obtain degradation products with active groups that can be used as high-value chemical raw materials, and their application is limited.

[0004] Therefore, a method for recycling polyester using amine compounds and achieving upgraded recycling is proposed, which will greatly expand the application prospects of polyester, promote environmental protection and resource recycling, and promote the development of a circular economy. Summary of the invention

[0005] The present invention aims at the problems existing in the prior art of polyester recovery by alcoholamine compounds, and provides a method for recovering polyester by efficient and selective alcoholysis of alcoholamine compounds. The method realizes the selective alcoholysis of polyester by alcoholamine compounds by creatively and synergistically applying amino protection strategy, solvent effect and reaction system design theory, so that when polyester is degraded and recovered by alcoholamine compounds, the energy consumption of the separation process is reduced, and the recovery rate and purity of alcoholysis products are improved. Moreover, the alcoholysis products obtained by the method provided by the present invention also contain amino groups and ester groups, which can be used as high-value chemical raw materials for synthesizing high-performance polymers or fine chemicals, realizing polyester upgrading and recovery, which can greatly promote environmental protection and resource recycling, and promote the development and promotion of circular economy; the method provided by the present invention can also reduce the reaction temperature and improve the reaction efficiency by activating the ester group, thereby avoiding side reactions at higher reaction temperatures and improving the selectivity of the alcoholysis products; when the alcoholysis products obtained by the method provided by the present invention are used as high-value chemical raw materials for preparing new materials, in addition to the primary amino groups in the alcoholysis products giving the new materials good reactivity, the ester groups in the alcoholysis products also give the new materials easy recyclability, thus realizing a closed-loop cycle. This method provides a new idea for recycling polyester materials. The process is simple to operate, the reaction conditions are mild, and the alcoholysis product has high added value.

[0006] The present invention is achieved through the following specific technical solutions: A method for recovering polyester by high-efficiency selective alcoholysis of alcoholamine compounds comprises the following steps: protecting alcoholamine compounds with amino-protecting agents to obtain amino-protected alcoholamine compounds, mixing the amino-protected alcoholamine compounds with polar aprotic solvents to form a mixed solution, adding polyester and a catalyst, heating to cause degradation reaction, and pouring the reaction solution into a poor solvent after the degradation reaction is completed, and the amino-protected alcoholysis product is precipitated from the reaction solution. After precipitation, filtering and collecting are performed to obtain a recovered product. The poor solvent refers to a solvent in which the amino-protected alcoholysis product can be completely precipitated.

[0007] The specific method of protecting with an amino protecting agent is a method in the prior art: for example, amino protection can be carried out according to the prior art (such as the method described in the public literature, the journal information is: Chem. Rev., 2009, 109, 2455). In the present invention, the amino protecting agent is used to react with the amino group in the alcoholamine compound by amidation reaction with the amino group, thereby reducing the reactivity of the amino group to achieve the purpose of protecting the amino group.

[0008] Furthermore, the alcoholamine compound includes at least one of ethanolamine, n-propanolamine, isopropanolamine, butanolamine, isobutanolamine, and 4-aminomethylbenzyl alcohol.

[0009] Furthermore, the polar aprotic solvent includes at least one of N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, acetonitrile, methyl ethyl ketone, dimethyl sulfoxide, N-methylpyrrolidone, dimethylformamide, gamma-butyrolactone, gamma-valerolactone, delta-valerolactone, dihydro-levoglucosyl ketone, N-butylpyrrolidone, hexamethylphosphoric triamide, and 1,4-dioxane.

[0010] Furthermore, the catalyst includes at least one of tetrabutylammonium bromide, betaine, metformin, tetramethylguanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), and 1,5,7-triazidobicyclo[4,4,0]dec-5-ene (TBD).

[0011] Furthermore, the mass ratio of the amino-protected alcohol amine compound to the polar aprotic solvent is 1:0.5-10, the amount of polyester used is 1%-20% of the mass of the mixed solution; and the amount of the catalyst used is 1%-30% of the mass of the mixed solution.

[0012] Furthermore, the temperature of the degradation reaction is 80-200° C., and the reaction time is 10-300 min.

[0013] Furthermore, in the method for efficiently and selectively alcoholyzing alcoholamine compounds to recover polyester, the poor solvent is water.

[0014] Furthermore, the amino protecting agent includes one of di-tert-butyl dicarbonate, p-toluenesulfonyl chloride, trifluoroacetic anhydride, and phthalic anhydride.

[0015] Further, the polyester includes polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polypentylene terephthalate (PPT), polyethylene succinate (PES), polypropylene succinate (PPS), polybutylene succinate (PBS), polyneopentyl succinate (PNS), polycyclohexylene dimethylene terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyethylene adipate (PEA), polypropylene adipate (PPA), polybutylene adipate (PBA), polyneopentyl adipate (PNA), polyethylene 2,5-furandicarboxylate (PEF) , poly(1,3-propylene-2,5-furandicarboxylate) (PTF), poly(butylene-2,5-furandicarboxylate) (PBF), poly(hexanediol adipate) (PHA), and a copolymer of butylene adipate and butylene terephthalate (PBAT) or more thereof.

[0016] Furthermore, in the method for efficiently and selectively alcoholyzing alcoholamine compounds to recover polyester, the degradation reaction temperature is 100-150°C.

[0017] After filtering and collecting the amino-protected alcoholysis product precipitated from the reaction solution, the following steps may also be included: the collected amino-protected alcoholysis product can be used after removing the amino protecting group by heating deprotection (for example, the technology described in the following public documents: Angew. Chem. Int. Ed., 2010, 49,4598) or acid deprotection according to the prior art, and the heating deprotection or acid deprotection method is the prior art, for example, the prior art described in the following public documents: Chem. Rev., 2009, 109, 2455; RSC Adv., 2020, 10, 24017; Mol. Divers., 2005, 9, 291-293; J. Org. Chem., 1998, 63, 3471, and the amino-linked ester group is removed by utilizing the difference in activity between the amino-linked ester group and the benzene ring-linked ester group.

[0018] The present invention has the following beneficial results: 1. The present invention creatively applies the amino protection strategy, solvent effect, and reaction system design theory of alcoholamine compounds, and fully considers and utilizes the mutual influence and synergistic effect between various factors to achieve the selective alcoholysis reaction of polyester. Since alcoholamine compounds contain hydroxyl and amino groups in the molecules at the same time, alcoholysis or aminolysis can occur with polyester, and when alcoholysis occurs, alcoholysis products with amino and ester groups that can be used as high-value chemical raw materials can be obtained on the basis of realizing the degradation and recovery of polyester, and are used for the upgrading and recovery of polyester. However, since alcoholamine compounds are more inclined to undergo amidation reaction rather than transesterification reaction with polyester in thermodynamics, it is difficult to obtain selective alcoholysis products. According to the method provided by the present invention, after amino protection, the amino activity of the amino-protected alcoholamine compound decreases, which increases the selectivity of the alcoholysis reaction. However, under amino protection, due to the high alcoholysis reaction temperature of the polyester, the protective group decomposes at high temperature, and further amidation reaction will occur, which will hinder the occurrence of alcoholysis reaction. The reaction system containing polar aprotic solvent provided by the present invention has an activation effect on polyester, reduces the conditions of transesterification reaction, avoids the aminolysis reaction caused by the decomposition of the amino protective group at high temperature, and further improves the selectivity of alcoholysis reaction. At the same time, the present invention fully considers the reactant characteristics of the entire reaction system (including the use of amino protection and the full consideration of solvent effects, etc.), designs applicable and preferred reaction conditions and catalysts, reduces the energy consumption of the separation process, and improves the recovery rate and purity of the alcoholysis product.

[0019] 2. The present invention uses alcoholamine compounds as alcoholysis reagents, and selective alcoholysis products can be obtained through amino protection reactions. The selective alcoholysis products can be deprotected by heat or acid to obtain diamino structure products, which can be used as raw materials for the preparation of high-performance fine chemicals and polymer materials. At the same time, the ester group in the product structure makes the new material easy to recycle. Therefore, the present invention not only solves the problem of recycling waste polyester materials, but also further increases the added value of the recycled products, and gives the new materials recyclability, thereby realizing the upgraded recycling of polyester.

[0020] 3. The operation method of the present invention is simple, the reaction conditions are mild, the reaction time is short, and the product selectivity is high. The resource utilization rate of waste polyester is greatly improved. Specific embodiments

[0021] The following examples are given to further illustrate the present invention. It is necessary to point out that the following examples cannot be understood as limiting the scope of protection of the present invention. If a person skilled in the art makes some non-essential improvements and adjustments to the present invention based on the above content of the present invention, it still falls within the scope of protection of the present invention.

[0022] It is worth mentioning that: 1. The degradation rate D of polyester in the examples and comparative examples is calculated according to the following formula: D = (W0-W1) / W0×100% Where: W0 is the initial mass of the polyester; W1 is the mass of the undegraded polyester after filtering and separating the degradation liquid after the reaction is completed and then washed and dried.

[0023] 2. The yield Y of the alcoholysis product of amino protection in the examples and comparative examples is calculated according to the following formula: Y=W2 / W3×100% Wherein: W3 is the theoretical mass of the amino-protected alcoholysis product; W2 is the mass of the amino-protected alcoholysis product obtained after the reaction is completed.

[0024] Example 1 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with N,N-dimethylacetamide to form a mixed solution, and then PET and tetrabutylammonium bromide were added. The mass ratio of amino-protected ethanolamine and N,N-dimethylacetamide was 1:0.5, the amount of tetrabutylammonium bromide was 1% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 100°C for 300 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 100%, and the yield of amino-protected diaminoethyl terephthalate was 60%.

[0025] Example 2 The amino group of ethanolamine was protected with di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with 1,3-dimethyl-2-imidazolidinone to form a mixed solution, and then PET and betaine were added. The mass ratio of amino-protected ethanolamine and 1,3-dimethyl-2-imidazolidinone was 1:5, the amount of betaine was 5% of the mass of the mixed solution, and the amount of PET was 5% of the mass of the mixed solution. The reaction was carried out at 200°C for 10 min. After the reaction, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 84%, and the yield of amino-protected diaminoethyl terephthalate was 55%.

[0026] Example 3 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with acetonitrile to form a mixed solution, and then PET and metformin were added. The mass ratio of amino-protected ethanolamine and acetonitrile was 1:1, the amount of metformin was 5% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 100%, and the yield of amino-protected diaminoethyl terephthalate was 70%.

[0027] Example 4 The amino group of ethanolamine was protected by p-toluenesulfonyl chloride, and then the amino-protected ethanolamine was mixed with dihydro-levoglucosyl ketone to form a mixed solution, and then PET and 1,5-diazabicyclo[4.3.0]-5-nonene were added. The mass ratio of amino-protected ethanolamine and dihydro-levoglucosyl ketone was 1:1, the amount of 1,5-diazabicyclo[4.3.0]-5-nonene was 5% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 150°C for 30 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 100%, and the yield of amino-protected diaminoethyl terephthalate was 42%.

[0028] Example 5 The amino group of ethanolamine was protected by p-toluenesulfonyl chloride, and then the amino-protected ethanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PET and tetramethylguanidine were added. The mass ratio of amino-protected ethanolamine and N-methylpyrrolidone was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 100%, and the yield of amino-protected diaminoethyl terephthalate was 67%.

[0029] Example 6 The amino group of ethanolamine was protected by p-toluenesulfonyl chloride, and then the amino-protected ethanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and N-methylpyrrolidone was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 20% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 70%, and the yield of amino-protected diaminoethyl terephthalate was 66%.

[0030] Example 7 The amino group of ethanolamine was protected by p-toluenesulfonyl chloride, and then the amino-protected n-propanolamine was mixed with hexamethylphosphoric acid triamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and hexamethylphosphoric acid triamide was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 10% of the mass of the mixed solution. The reaction was carried out at 130°C for 30 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminopropyl terephthalate. The degradation rate of PET was 92%, and the yield of amino-protected diaminopropyl terephthalate was 55%.

[0031] Example 8 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and N-methylpyrrolidone was 1:4, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 10% of the mass of the mixed solution, and the amount of PET was 5% of the mass of the mixed solution. The reaction was carried out at 130°C for 60 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 56%, and the yield of amino-protected diaminoethyl terephthalate was 38%.

[0032] Example 9 The amino group of n-propanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected n-propanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected n-propanolamine and N-methylpyrrolidone was 1:5, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 10% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 10 min, and water was added after the reaction to precipitate the amino-protected diaminopropyl terephthalate. The degradation rate of PET was 50%, and the yield of amino-protected diaminopropyl terephthalate was 35%.

[0033] Example 10 The amino group of isopropanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected isopropanolamine was mixed with N,N-dimethylformamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected isopropanolamine and N,N-dimethylformamide was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 10% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 80°C for 40 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoisopropyl terephthalate. The degradation rate of PET was 21%, and the yield of amino-protected diaminoisopropyl terephthalate was 4%.

[0034] Embodiment 11 The amino group of butanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected butanolamine was mixed with 1,4-dioxane to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected butanolamine and 1,4-dioxane was 1:5, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 20% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 20 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminobutyl terephthalate. The degradation rate of PET was 42%, and the yield of amino-protected diaminobutyl terephthalate was 18%.

[0035] Example 12 The amino group of 4-aminomethylbenzyl alcohol was protected by di-tert-butyl dicarbonate, and then the amino-protected 4-aminomethylbenzyl alcohol was mixed with N,N-dimethylformamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected 4-aminomethylbenzyl alcohol and N,N-dimethylformamide was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 5% of the mass of the mixed solution. The reaction was carried out at 130°C for 30 min. After the reaction was completed, water was added to precipitate the amino-protected dimethylamino-p-phenylenediphthalate. The degradation rate of PET was 100%, and the yield of amino-protected terephthalic acid-4-aminomethyl-p-phenylenediphthalate was 65%.

[0036] Example 13 The amino group of ethanolamine was protected by trifluoroacetic anhydride, and then the amino-protected ethanolamine was reacted with N,N-dimethylformamide was mixed to form a mixed solution, and then PET, 1,5,7-triazidobicyclo[4,4,0]dec-5-ene and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and N,N-dimethylformamide was 1:5, the amount of 1,5,7-triazidobicyclo[4,4,0]dec-5-ene and 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% and 10% of the mass of the mixed solution, respectively, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 150°C for 10 min. After the reaction, water was added to precipitate amino-protected diaminoethyl terephthalate. The degradation rate of PET was 71%, and the yield of amino-protected diaminoethyl terephthalate was 48%.

[0037] Embodiment 14 The amino group of ethanolamine was protected by trifluoroacetic anhydride, and then the amino-protected ethanolamine was mixed with dimethyl sulfoxide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and dimethyl sulfoxide was 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 100%, and the yield of amino-protected diaminoethyl terephthalate was 52%.

[0038] Embodiment 15 The amino group of ethanolamine was protected by trifluoroacetic anhydride, and then the amino-protected ethanolamine was reacted with Gamma-valerolactone was mixed to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and gamma-valerolactone was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 min. After the reaction, water was added to precipitate amino-protected diaminoethyl terephthalate. The degradation rate of PET was 100%, and the yield of amino-protected diaminoethyl terephthalate was 35%.

[0039] Example 16 The amino group of ethanolamine was protected by trifluoroacetic anhydride, and then the amino-protected ethanolamine was mixed with methyl ethyl ketone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and methyl ethyl ketone was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 10% of the mass of the mixed solution, and the amount of PET was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 80 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PET was 79%, and the yield of amino-protected diaminoethyl terephthalate was 43%.

[0040] Embodiment 17 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PBAT and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and N-methylpyrrolidone was 1:2, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PBAT was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 60 minutes. After the reaction, water was added to precipitate amino-protected diaminoethyl terephthalate and amino-protected diaminoethyl succinate. The degradation rate of PBAT was 90%, and the yields of amino-protected diaminoethyl terephthalate and amino-protected diaminoethyl adipic acid were 41% and 32%, respectively.

[0041] Embodiment 18 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with dimethyl sulfoxide to form a mixed solution, and then PTT and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and N,N-dimethylformamide was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PTT was 5% of the mass of the mixed solution. The reaction was carried out at 140°C for 30 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PTT was 76%, and the yield of amino-protected diaminoethyl terephthalate was 38%.

[0042] Embodiment 19 Phthalic anhydride was used to protect the amino group of ethanolamine, and then the amino-protected isobutanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PBT and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine to N,N-dimethylformamide was 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PBAT was 1% of the mass of the mixed solution. The reaction was carried out at 150°C for 20 min. After the reaction, water was added to precipitate the amino-protected diaminoisobutyl terephthalate. The degradation rate of PBT was 71%, and the yield of amino-protected diaminoisobutyl terephthalate was 42%.

[0043] Embodiment 20 Phthalic anhydride was used to protect the amino group of ethanolamine, and then the amino-protected ethanolamine was mixed with N-methylpyrrolidone and dimethyl sulfoxide to form a mixed solution, and then PPT and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine, N-methylpyrrolidone and dimethyl sulfoxide was 1:1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PBS was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 minutes. After the reaction was completed, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rate of PPT was 100%, and the yield of amino-protected diaminoethyl terephthalate was 60%.

[0044] Embodiment 21 Phthalic anhydride was used to protect the amino group of ethanolamine, and then the protected product was mixed with N,N-dimethylformamide to form a mixed solution, wherein the mass ratio of amino-protected ethanolamine and N,N-dimethylformamide was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PBS was 1% of the mass of the mixed solution. The reaction was carried out at 140°C for 30 minutes, and water was added after the reaction to precipitate the amino-protected diaminoethyl succinate. The degradation rate of PBS was 81%, and the yield of amino-protected diaminoethyl succinate was 45%.

[0045] Embodiment 22 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with N-butylpyrrolidone to form a mixed solution, and then PEN and 1,5,7-triazidobicyclo[4,4,0]dec-5-ene were added. The mass ratio of amino-protected ethanolamine and N-butylpyrrolidone was 1:1, the amount of 1,5,7-triazidobicyclo[4,4,0]dec-5-ene was 30% of the mass of the mixed solution, and the amount of PEN was 5% of the mass of the mixed solution. The reaction was carried out at 100°C for 100 minutes. After the reaction, water was added to precipitate the amino-protected diaminoethyl naphthalene dicarboxylate. The degradation rate of PEN was 100%, and the yield of amino-protected diaminoethyl naphthalene dicarboxylate was 63%.

[0046] Embodiment 23 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with delta-butyrolactone to form a mixed solution, and then PCT and 1,5,7-triazidobicyclo[4,4,0]dec-5-ene were added. The mass ratio of amino-protected ethanolamine and delta-butyrolactone was 1:2, the amount of 1,5,7-triazidobicyclo[4,4,0]dec-5-ene was 5% of the mass of the mixed solution, and the amount of PCT was 1% of the mass of the mixed solution. The reaction was carried out at 130°C for 60 min. After the reaction, water was added to precipitate the amino-protected diaminoethyl terephthalate. The PCT degradation rate was 84%, and the yield of amino-protected diaminoethyl terephthalate was 52%.

[0047] Embodiment 24 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with N-butylpyrrolidone to form a mixed solution, and then PEF and 1,5,7-triazidobicyclo[4,4,0]dec-5-ene were added. The mass ratio of amino-protected ethanolamine and N-butylpyrrolidone was 1:1, the amount of 1,5,7-triazidobicyclo[4,4,0]dec-5-ene was 10% of the mass of the mixed solution, and the amount of PEF was 5% of the mass of the mixed solution. The reaction was carried out at 200°C for 30 minutes. After the reaction, water was added to precipitate the amino-protected 2,5-furandicarboxylic acid diaminoethyl ester. The degradation rate of PEF was 100%, and the yield of amino-protected 2,5-furandicarboxylic acid diaminoethyl ester was 68%.

[0048] Embodiment 25 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected n-butanolamine was combined with delta-valerolactone to form a mixed solution, and then PET, PTT and 1,5,7-triazidobicyclo[4,4,0]dec-5-ene were added. The mass ratio of amino-protected n-butanolamine and delta-valerolactone was 1:1, the amount of 1,5,7-triazidobicyclo[4,4,0]dec-5-ene was 10% of the mass of the mixed solution, the amount of PET and PTT was 5% and 10% of the mass of the mixed solution, respectively, and the reaction was carried out at 130°C for 60 min. After the reaction, water was added to precipitate the amino-protected diaminoethyl terephthalate. The degradation rates of PET and PTT were 100%, and the yield of amino-protected diaminoethyl terephthalate was 55%.

[0049] Embodiment 26 The amino group of ethanolamine was protected by di-tert-butyl dicarbonate, and then the amino-protected ethanolamine was mixed with N-methylpyrrolidone to form a mixed solution, and then PET, PBS and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and N-methylpyrrolidone was 1:4, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 10% of the mass of the mixed solution, and the amounts of PET and PBS were both 5% of the mass of the mixed solution. The reaction was carried out at 130°C for 60 min. After the reaction was completed, water was added to precipitate amino-protected diaminoethyl terephthalate and amino-protected diaminoethyl succinate. The degradation rates of PET and PBS were 100%, and the yields of amino-protected diaminoethyl terephthalate and amino-protected diaminoethyl succinate were 62% and 50%, respectively.

[0050] Embodiment 27 The amino group of ethanolamine was protected by p-toluenesulfonyl chloride, and then the amino-protected ethanolamine was mixed with gamma-butyrolactone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene were added. The mass ratio of amino-protected ethanolamine and gamma-butyrolactone was 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene was 5% of the mass of the mixed solution, and the amount of PET was 10% of the mass of the mixed solution. The reaction was carried out at 130°C for 40 min. After the reaction, acetonitrile was added to precipitate amino-protected diaminoethyl terephthalate. The degradation rate of PET was 90%, and the yield of amino-protected diaminoethyl terephthalate was 50%.

Claims

1. A method for recovering polyester by highly efficient and selective alcoholysis of an olamine compound, characterized in that: The following steps are involved: The alcohol amine compound is protected by an amino protecting agent to obtain an amino protected alcohol amine compound, the amino protected alcohol amine compound and a polar aprotic solvent are mixed to form a mixed solution, polyester and a catalyst are added, and the mixture is heated to cause a degradation reaction. After the degradation reaction is completed, the reaction solution is poured into a poor solvent, and the amino protected alcoholysis product is precipitated from the reaction solution.

2. The method for recovering polyester by highly efficient and selective alcoholysis of an alcoholamine compound according to claim 1, characterized in that: The alcoholamine compound includes at least one of ethanolamine, n-propanolamine, isopropanolamine, butanolamine, isobutanolamine and 4-aminomethylbenzyl alcohol.

3. A method for recovering polyester by highly efficient and selective alcoholysis of an alcoholamine compound according to claim 1 or 2, characterized in that: The polar aprotic solvent includes at least one of N,N-dimethylformamide, N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, acetonitrile, methyl ethyl ketone, dimethyl sulfoxide, N-methylpyrrolidone, gamma-butyrolactone, gamma-valerolactone, delta-valerolactone, dihydro-levoglucosenone, N-butylpyrrolidone, hexamethylphosphoric triamide, and 1,4-dioxane.

4. The method for recovering polyester by highly efficient and selective alcoholysis of an alcoholamine compound according to claim 3, characterized in that: The catalyst includes at least one of tetrabutylammonium bromide, betaine, metformin, tetramethylguanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), 1,5-diazabicyclo[4.3.0]-5-nonene (DBN), and 1,5,7-triazidobicyclo[4,4,0]dec-5-ene (TBD).

5. The method for recovering polyester by highly efficient and selective alcoholysis of alcoholamine compounds according to claim 4, characterized in that: The polyester includes polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), polypentylene terephthalate (PPT), polyethylene succinate (PES), polypropylene succinate (PPS), polybutylene succinate (PBS), polyneopentyl succinate (PNS), polycyclohexylene dimethylene terephthalate (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyethylene adipate (PEA), polypropylene adipate (PPA), polybutylene adipate (PBA), polyneopentyl adipate (PNA), polyethylene 2,5-furandicarboxylate (PEF) , poly(1,3-propylene-2,5-furandicarboxylate) (PTF), poly(butylene-2,5-furandicarboxylate) (PBF), poly(hexanediol adipate) (PHA), and a copolymer of butylene adipate and butylene terephthalate (PBAT) or more thereof.

6. The method for recovering polyester by highly efficient and selective alcoholysis of an alcoholamine compound according to claim 5, characterized in that: The mass ratio of the amino-protected alcohol amine compound to the polar aprotic solvent is 1:0.5-10, the amount of polyester used is 1%-20% of the mass of the mixed liquid; and the amount of the catalyst used is 1%-30% of the mass of the mixed liquid.

7. The method for recovering polyester by highly efficient and selective alcoholysis of alcoholamine compounds according to claim 6, characterized in that: The temperature of the degradation reaction is 80-200° C., and the reaction time is 10-300 min.

8. The method for recovering polyester by highly efficient and selective alcoholysis of alcoholamine compounds according to claim 7, characterized in that: The degradation reaction temperature is 100-150°C.

9. The method for recovering polyester by highly efficient and selective alcoholysis of alcoholamine compounds according to claim 1, characterized in that: The poor solvent is water.

10. A method for recovering polyester by highly efficient and selective alcoholysis of an alcoholamine compound according to any one of claims 1-2, 4-9, characterized in that: The amino protecting agent includes at least one of di-tert-butyl dicarbonate, p-toluenesulfonyl chloride, trifluoroacetic anhydride and phthalic anhydride.