Method for recovering polyesters by selective alcoholysis of an alcohol amine compound

Abstract

The present application provides a kind of alcohol amine compound high-efficiency selective alcoholysis method for recycling polyester to solve the problems in prior art of alcohol amine compound recycling polyester.The method combines amine group protection strategy and solvent effect to realize the selective alcoholysis of alcohol amine compound to polyester, which can reduce the energy consumption of separation process during degradation, improve the recovery rate and purity of alcoholysis product, and the alcoholysis product obtained by the method also contains amino and ester groups, which can be used as high-value chemical raw materials to synthesize high-performance polymers or fine chemicals, realize polyester upgrading and recycling, which can undoubtedly greatly promote environmental protection and resource recycling, and promote the development and popularization of circular economy.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of solid waste recycling, and particularly relates to a method for recycling polyester through high-efficiency selective alcoholysis of alcohol amine compounds. BACKGROUND

[0002] Polyesters are polymers obtained by polycondensation of polyols and polyacids, and have excellent tensile strength, chemical resistance, transparency, processability and thermal stability, and are widely used in the fields of plastics, textiles and the like. With the increasing demand, the amount of waste polyesters also increases substantially. Taking the most used type of polyethylene terephthalate (PET) as an example, waste PET materials account for 8% of the total mass and 12% of the total volume of solid waste in the world. Recycling and utilization of waste PET materials not only reduce environmental pollution, but also improve resource utilization. At present, the main recycling method of polyesters is physical recycling, and the performance of the recycled products is reduced due to heat and mechanical effects during the recycling process, and most of the recycled products are downcycled. In comparison, the chemical recycling method is flexible and has a wide range of applications, and is expected to realize upcycling of polyesters, which is a promising recycling method.

[0003] The current chemical recycling method of polyesters is mainly solventysis, including hydrolysis, alcoholysis and ammonia / amineysis. Among them, alcoholysis is widely used, and ester exchange reactions are usually carried out using methanol, ethylene glycol and the like to prepare monomers such as dimethyl acid or ethylene glycol ester. These monomers can be further polymerized to obtain polyesters, thereby realizing the cyclic recycling of polyesters. In addition to cyclic recycling, researchers have begun to focus on upcycling of polyesters in recent years, that is, introducing active groups while degrading polyesters, and the degradation products obtained can be further reconfigured to obtain various high-value products. For example, alcohol amine compounds can not only undergo degradation reactions with polyesters, but also can bring such active groups, which can realize the degradation and recycling of polyesters, and also can 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 upcycling of polyesters. However, due to the thermodynamic tendency of alcohol amine compounds to undergo amidation reactions with polyesters, 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 polyesters using alcohol amine compounds and realizing upcycling is proposed, which will greatly expand the application prospect of polyesters, promote environmental protection and resource recycling, and promote the development of circular economy. SUMMARY

[0005] The present application provides a method for high-efficiency and selective alcoholysis of polyesters by alcohol amine compounds, aiming at solving the problems in the prior art of alcohol amine compounds in the field of polyester recycling. The method realizes the selective alcoholysis of polyesters by alcohol amine compounds by creatively and cooperatively applying amino protection strategy, solvent effect and reaction system design theory, so that the energy consumption of the separation process is reduced, the recovery rate and purity of the alcoholysis product are improved when the alcohol amine compound is used to degrade and recycle the polyester, and the alcoholysis product obtained by the method provided by the present application also contains amino and ester groups, which can be used as a high-value chemical raw material to synthesize high-performance polymers or fine chemicals, realize the upgrading and recycling of polyesters, greatly promote environmental protection and resource recycling, and promote the development and popularization of circular economy; the method provided by the present application can also activate the ester group, reduce the reaction temperature and improve the reaction efficiency, thereby avoiding side reactions at higher reaction temperatures and improving the selectivity of the alcoholysis product; when the alcoholysis product obtained by the method provided by the present application is used as a high-value chemical raw material to prepare new materials, in addition to the primary amino group of the alcoholysis product imparting good reactivity to the new materials, the ester group in the alcoholysis product also imparts easy recyclability to the new materials, realizing the closed loop of recycling. The method provides a new idea for recycling polyester materials, and has the advantages of simple process operation, mild reaction conditions and high added value of alcoholysis products.

[0006] The present application is realized by the following specific technical solutions:

[0007] A method for high-efficiency and selective alcoholysis of polyesters by alcohol amine compounds, comprising the following steps: protecting the alcohol amine compound with an amino protecting reagent to obtain an amino-protected alcohol amine compound, mixing the amino-protected alcohol amine compound and a polar aprotic solvent to form a mixed solution, adding polyesters and a catalyst, heating to occur a degradation reaction, pouring the reaction liquid into a poor solvent after the degradation reaction is completed, and the amino-protected alcoholysis product is precipitated from the reaction liquid. After precipitation, filtration is performed to collect the recovered product. The poor solvent refers to a solvent in which the amino-protected alcoholysis product can be completely precipitated.

[0008] The specific method for protecting the amino group with an amino protecting reagent is a method in the prior art: for example, amino protection can be performed according to the prior art (such as the method described in the published literature, Journal Information: Chem. Rev., 2009, 109,2455), and in the present application, the method is specifically as follows: the higher electrophilicity of the amino protecting reagent is used to react with the amino group in the alcohol amine compound to form an amide, so as to reduce the reactivity of the amino group and achieve the purpose of protecting the amino group.

[0009] Further, the alcohol amine compound includes at least one of ethanolamine, n-propanolamine, isopropanolamine, butanolamine, isobutanolamine and 4-aminomethyl benzyl alcohol.

[0010] Further, the polar aprotic solvent includes at least one of N,N-dimethylacetamide, 1,3-dimethyl-2-imidazolidinone, acetonitrile, methyl ethyl ketone, dimethyl sulfoxide, N-methyl pyrrolidone, dimethylformamide, gamma-butyrolactone, gamma-valerolactone, delta-valerolactone, dihydrolevoglucosenone, N-butyl pyrrolidone, hexamethylphosphoramide, 1,4-dioxane.

[0011] Further, 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), 1,5,7-triazabicyclo[4,4,0]dec-5-ene (TBD).

[0012] Further, the mass ratio of the amino-protected alcohol amine compound and the polar aprotic solvent is 1:0.5-10, the amount of the polyester is 1%-20% of the mass of the mixed solution, and the amount of the catalyst is 1%-30% of the mass of the mixed solution.

[0013] Further, the temperature of the degradation reaction is 80-200°C, and the reaction time is 10-300 min.

[0014] Further, the one alcohol amine compound high-efficiency selective alcoholysis recovery polyester method, the poor solvent is water.

[0015] Further, the amino-protecting reagent includes one of di-tert-butyl dicarbonate, p-toluenesulfonyl chloride, trifluoroacetic anhydride, phthalic anhydride.

[0016] Further, the polyester includes one or more of polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), poly(pentylene terephthalate) (PPT), polyethylene succinate (PES), polypropylene succinate (PPS), polybutylene succinate (PBS), poly(neopentylene succinate) (PNS), poly(cyclohexylene dimethylene terephthalate) (PCT), polyethylene naphthalate (PEN), polybutylene naphthalate (PBN), polyethylene adipate (PEA), polypropylene adipate (PPA), polybutylene adipate (PBA), poly(neopentylene adipate) (PNA), poly(ethylene 2,5-furandicarboxylate) (PEF), poly(1,3-propylene 2,5-furandicarboxylate) (PTF), poly(butylene 2,5-furandicarboxylate) (PBF), poly(hexamethylene adipate) (PHA), and a copolymer of poly(butylene adipate) and poly(butylene terephthalate) (PBAT).

[0017] Further, the alcohol amine compound is used for the selective alcoholysis of the polyester, and the degradation reaction temperature is 100-150°C.

[0018] After the amino-protected alcoholysis product separated from the reaction solution is collected by filtration, the following step can be further included: the collected amino-protected alcoholysis product can be used after the amino-protecting group is removed according to the application needs by the existing technology such as heating deprotection (for example, the technology described in the following published literature: Angew. Chem. Int. Ed., 2010, 49, 4598) or acid deprotection, which is the existing technology such as the existing technology described in the following published literature: Chem. Rev., 2009, 109, 2455; RSC Adv., 2020, 10, 24017; Mol. Divers., 2005, 9, 291-293; J. Org. Chem., 1998, 63, 3471, which realizes the removal of the amino-attached ester group by utilizing the activity difference of the amino-attached ester group and the benzene ring-attached ester group.

[0019] The present application has the following beneficial results:

[0020] 1. The present application creatively uses the amino protection strategy of alcohol amine compounds, solvent effect, and reaction system design theory, and fully considers and utilizes the mutual influence and synergistic effect between various factors to realize the selective alcoholysis of the polyester. Since the alcohol amine compound molecule contains both hydroxyl and amino groups, it can undergo alcoholysis or aminolysis with the polyester, and when the alcoholysis reaction occurs, the alcoholysis product with amino and ester groups, which can be used as a high-value chemical raw material, is obtained on the basis of the degradation and recovery of the polyester, for the upgrading and recovery of the polyester. However, since the alcohol amine compound is more inclined to undergo amidation reaction with the polyester than transesterification reaction in thermodynamics, it is difficult to obtain a selective alcoholysis product. By using the method provided by the present application, on the one hand, the activity of the amino group of the amino-protected alcohol amine compound is reduced after the amino protection, which increases the selectivity of the alcoholysis reaction, but the decomposition of the protecting group at high temperature will further cause the amidation reaction under the amino protection, which will hinder the occurrence of the alcoholysis reaction. The reaction system containing the polar aprotic solvent provided by the present application has an activating effect on the polyester, reduces the transesterification reaction conditions, avoids the aminolysis reaction caused by the decomposition of the amino-protecting group at high temperature, and further improves the selectivity of the alcoholysis reaction. At the same time, the present application fully considers the characteristics of the reactants of the entire reaction system (including the use of amino protection and full consideration of the solvent effect), designs suitable 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.

[0021] 2、The application uses alcohol amine compounds as alcoholysis reagents, and can obtain selective alcoholysis products through amino protection reaction. The double amino structure products can be obtained through thermal or acid deprotection of the selective alcoholysis products, and can be used as raw materials for preparation of high-performance fine chemicals and polymer materials. The ester groups in the product structure make the new materials easy to recycle. Therefore, the application not only solves the recycling problem of waste polyester materials, but also further increases the added value of the recycled products, and endows the new materials with recyclability, realizing the upgrading and recycling of polyesters.

[0022] 3、The application has simple operation method, mild reaction condition, short reaction time, and high product selectivity.

[0023] The resource utilization rate of waste and old polyesters is greatly improved. Specific embodiments

[0024] The following examples are given to further illustrate the application. It is necessary to point out here that the following examples cannot be understood as limiting the scope of protection of the application. If some non-essential improvements and adjustments are made to the application by skilled persons in the field according to the above content of the application, they still belong to the protection scope of the application.

[0025] It is worth noting that:

[0026] 1. The degradation rate D of the polyester in the examples and comparative examples is calculated according to the following formula:

[0027] D= (W0-W1) / W0 x 100%

[0028] In the formula: W0 is the initial mass of the polyester; W1 is the mass of the undegraded polyester after water washing and drying after filtering and separating the degradation liquid at the end of the reaction.

[0029] 2. The yield Y of the amino-protected alcoholysis product in the examples and comparative examples is calculated according to the following formula:

[0030] Y=W2 / W3 x 100%

[0031] In the formula: W3 is the theoretical mass of the amino-protected alcoholysis product; W2 is the mass of the amino-protected alcoholysis product obtained at the end of the reaction.

[0032] Example 1

[0033] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with N,N-dimethylacetamide to form a mixed solution, and then PET and tetrabutylammonium bromide are added. The mass ratio of amino-protected ethanolamine and N,N-dimethylacetamide is 1:0.5, the amount of tetrabutylammonium bromide is 1% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 100°C for 300 min, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 60%.

[0034] Example 2

[0035] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with 1,3-dimethyl-2-imidazolidinone to form a mixed solution, and then PET and betaine are added. The mass ratio of amino-protected ethanolamine and 1,3-dimethyl-2-imidazolidinone is 1:5, the amount of betaine is 5% of the mass of the mixed solution, and the amount of PET is 5% of the mass of the mixed solution. The reaction is carried out at 200°C for 10 min, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 84%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 55%.

[0036] Example 3

[0037] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with acetonitrile to form a mixed solution, and then PET and metformin are added. The mass ratio of amino-protected ethanolamine and acetonitrile is 1:1, the amount of metformin is 5% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 70%.

[0038] Example 4

[0039] The amino group of ethanolamine is protected using p-toluenesulfonyl chloride, and then the amino-protected ethanolamine is mixed with dihydrolevoglucosenone to form a mixed solution, and then PET and 1,5-diazabicyclo[4.3.0]-5-nonene are added. The mass ratio of the amino-protected ethanolamine and the dihydrolevoglucosenone is 1:1, the amount of 1,5-diazabicyclo[4.3.0]-5-nonene is 5% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 150°C for 30 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 42%.

[0040] Example 5

[0041] The amino group of ethanolamine is protected using p-toluenesulfonyl chloride, and then the amino-protected ethanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PET and tetramethylguanidine are added. The mass ratio of the amino-protected ethanolamine and the N-methylpyrrolidone is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 67%.

[0042] Example 6

[0043] The amino group of ethanolamine is protected using p-toluenesulfonyl chloride, and then the amino-protected ethanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of the amino-protected ethanolamine and the N-methylpyrrolidone is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 20% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 70%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 66%.

[0044] Example 7

[0045] The amino group of ethanolamine is protected using p-toluenesulfonyl chloride, and then the amino-protected n-propanolamine is mixed with hexamethylphosphorus triamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and hexamethylphosphorus triamide is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 10% of the mass of the mixed solution. The reaction is carried out at 130°C for 30 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 92%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 55%.

[0046] Example 8

[0047] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and N-methylpyrrolidone is 1:4, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 5% of the mass of the mixed solution. The reaction is carried out at 130°C for 60 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 56%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 38%.

[0048] Example 9

[0049] The amino group of n-propanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected n-propanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected n-propanolamine and N-methylpyrrolidone is 1:5, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 10 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 50%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 35%.

[0050] Example 10

[0051] The amino group of isopropanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected isopropanolamine is mixed with N,N-dimethylformamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected isopropanolamine and N,N-dimethylformamide is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 80°C for 40 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisopropyl ester. The PET degradation rate is 21%, and the yield of amino-protected terephthalic acid diaminoisopropyl ester is 4%.

[0052] Example 11

[0053] The amino group of isopropanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected isopropanolamine is mixed with N,N-dimethylformamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected isopropanolamine and N,N-dimethylformamide is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 80°C for 40 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisopropyl ester. The PET degradation rate is 21%, and the yield of amino-protected terephthalic acid diaminoisopropyl ester is 4%.

[0054] Example 12

[0055] The amino group of isopropanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected isopropanolamine is mixed with N,N-dimethylformamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected isopropanolamine and N,N-dimethylformamide is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 80°C for 40 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisopropyl ester. The PET degradation rate is 21%, and the yield of amino-protected terephthalic acid diaminoisopropyl ester is 4%.

[0056] Example 13

[0057] The amino group of isopropanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected isopropanolamine is mixed with N,N-dimethylformamide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected isopropanolamine and N,N-dimethylformamide is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 80°C for 40 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisopropyl ester. The PET degradation rate is 21%, and the yield of amino-protected terephthalic acid diaminoisopropyl ester is 4%.

[0058] N,N-dimethylformamide to form a mixed solution, and then PET, 1,5,7-triazido bicyclo[4,4,0]decane-5-ene and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of the amino-protected ethanolamine and N,N-dimethylformamide is 1:5, the amount of 1,5,7-triazido bicyclo[4,4,0]decane-5-ene and 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% and 10% of the mass of the mixed solution, respectively, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 150°C for 10 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 71%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 48%.

[0059] Example 14

[0060] The amino group of ethanolamine is protected using trifluoroacetic anhydride, and then the amino-protected ethanolamine is mixed with dimethyl sulfoxide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of the amino-protected ethanolamine and dimethyl sulfoxide is 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 52%.

[0061] Example 15

[0062] The amino group of ethanolamine is protected using trifluoroacetic anhydride, and then the amino-protected ethanolamine is mixed with dimethyl sulfoxide to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of the amino-protected ethanolamine and dimethyl sulfoxide is 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 52%.

[0063] gamma-valerolactone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of the amino-protected ethanolamine and gamma-valerolactone is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and then water is added to precipitate the amino-protected terephthalic acid diaminoethyl ester. The PET degradation rate is 100%, and the yield of the amino-protected terephthalic acid diaminoethyl ester is 35%.

[0064] Example 16

[0065] The amino group of ethanolamine is protected using trifluoroacetic anhydride, and then the amino-protected ethanolamine is mixed with methyl ethyl ketone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and methyl ethyl ketone is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 10% of the mass of the mixed solution, and the amount of PET is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 80 min, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The degradation rate of PET is 79%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 43%.

[0066] Example 17

[0067] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with N-methyl pyrrolidone to form a mixed solution, and then PBAT and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and N-methyl pyrrolidone is 1:2, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PBAT is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 60 min, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl ester and amino-protected succinic acid diaminoethyl ester. The degradation rate of PBAT is 90%, and the yields of amino-protected terephthalic acid diaminoethyl ester and amino-protected adipic acid diaminoethyl ester are 41% and 32%, respectively.

[0068] Example 18

[0069] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with dimethyl sulfoxide to form a mixed solution, and then PTT and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and N,N-dimethylformamide is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PTT is 5% of the mass of the mixed solution. The reaction is carried out at 140°C for 30 min, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The degradation rate of PTT is 76%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 38%.

[0070] Example 19

[0071] The amino group of ethanolamine is protected using phthalic anhydride, and then the amino-protected isobutanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PBT and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and N,N-dimethylformamide is 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PBAT is 1% of the mass of the mixed solution. The reaction is carried out at 150°C for 20 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisobutanol ester. The degradation rate of PBT is 71%, and the yield of amino-protected terephthalic acid diaminoisobutanol ester is 42%.

[0072] Example 20

[0073] The amino group of ethanolamine is protected using phthalic anhydride, and then the amino-protected isobutanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PBT and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and N,N-dimethylformamide is 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PBAT is 1% of the mass of the mixed solution. The reaction is carried out at 150°C for 20 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisobutanol ester. The degradation rate of PBT is 71%, and the yield of amino-protected terephthalic acid diaminoisobutanol ester is 42%.

[0074] Example 21

[0075] The amino group of ethanolamine is protected using phthalic anhydride, and then the amino-protected isobutanolamine is mixed with N-methylpyrrolidone to form a mixed solution, and then PBT and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine and N,N-dimethylformamide is 1:10, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PBAT is 1% of the mass of the mixed solution. The reaction is carried out at 150°C for 20 min, and then water is added to precipitate amino-protected terephthalic acid diaminoisobutanol ester. The degradation rate of PBT is 71%, and the yield of amino-protected terephthalic acid diaminoisobutanol ester is 42%.

[0076] Example 22

[0077] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with N-butylpyrrolidone to form a mixed solution, and then PEN and 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene are added. The mass ratio of amino-protected ethanolamine and N-butylpyrrolidone is 1:1, the amount of 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene is 30% of the mass of the mixed solution, and the amount of PEN is 5% of the mass of the mixed solution. The reaction is carried out at 100°C for 100 minutes, and then water is added to precipitate amino-protected naphthalene-diaminoethyl succinate. The degradation rate of PEN is 100%, and the yield of amino-protected naphthalene-diaminoethyl succinate is 63%.

[0078] Example 23

[0079] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with delta-butyrolactone to form a mixed solution, and then PCT and 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene are added. The mass ratio of amino-protected ethanolamine and delta-butyrolactone is 1:2, the amount of 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene is 5% of the mass of the mixed solution, and the amount of PCT is 1% of the mass of the mixed solution. The reaction is carried out at 130°C for 60 minutes, and then water is added to precipitate amino-protected terephthalic acid diaminoethyl succinate. The degradation rate of PCT is 84%, and the yield of amino-protected terephthalic acid diaminoethyl succinate is 52%.

[0080] Example 24

[0081] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected ethanolamine is mixed with N-butylpyrrolidone to form a mixed solution, and then PEF and 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene are added. The mass ratio of amino-protected ethanolamine and N-butylpyrrolidone is 1:1, the amount of 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene is 10% of the mass of the mixed solution, and the amount of PEF is 5% of the mass of the mixed solution. The reaction is carried out at 200°C for 30 minutes, and then water is added to precipitate amino-protected 2,5-furanic acid diaminoethyl succinate. The degradation rate of PEF is 100%, and the yield of amino-protected 2,5-furanic acid diaminoethyl succinate is 68%.

[0082] Example 25

[0083] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected n-butanolamine is mixed with delta-valerolactone to form a mixed solution, and then PET, PTT and 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene are added. The mass ratio of amino-protected n-butanolamine to delta-valerolactone is 1:1, the amount of 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene is 10% of the mass of the mixed solution, and the amounts of PET and PTT are 5% and 10% of the mass of the mixed solution, respectively. The reaction is carried out at 130°C for 60 min, and after the reaction is completed, water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The degradation rates of PET and PTT are 100%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 55%.

[0084] Example 26

[0085] The amino group of ethanolamine is protected using di-tert-butyl dicarbonate, and then the amino-protected n-butanolamine is mixed with delta-valerolactone to form a mixed solution, and then PET, PTT and 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene are added. The mass ratio of amino-protected n-butanolamine to delta-valerolactone is 1:1, the amount of 1,5,7-triazido-bicyclo[4,4,0]dec-5-ene is 10% of the mass of the mixed solution, and the amounts of PET and PTT are 5% and 10% of the mass of the mixed solution, respectively. The reaction is carried out at 130°C for 60 min, and after the reaction is completed, water is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The degradation rates of PET and PTT are 100%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 55%.

[0086] Example 27

[0087] The amino group of ethanolamine is protected using p-toluenesulfonyl chloride, and then the amino-protected ethanolamine is mixed with gamma-butyrolactone to form a mixed solution, and then PET and 1,8-diazabicyclo[5.4.0]undec-7-ene are added. The mass ratio of amino-protected ethanolamine to gamma-butyrolactone is 1:1, the amount of 1,8-diazabicyclo[5.4.0]undec-7-ene is 5% of the mass of the mixed solution, and the amount of PET is 10% of the mass of the mixed solution. The reaction is carried out at 130°C for 40 min, and after the reaction is completed, acetonitrile is added to precipitate amino-protected terephthalic acid diaminoethyl ester. The degradation rate of PET is 90%, and the yield of amino-protected terephthalic acid diaminoethyl ester is 50%.

Claims

1. A method for selectively alcoholystopping polyesters using alkanolamine compounds, characterized in that: Includes the following steps: Aminoamine compounds are protected with an amino-protecting reagent to obtain amino-protected aminoamine compounds. The amino-protected aminoamine compounds are mixed with a polar aprotic solvent to form a mixture. A polyester and a catalyst are added, and the mixture is heated to induce a degradation reaction. After the degradation reaction is complete, the reaction solution is poured into a poor solvent, and the amino-protected alcoholysis products precipitate from the reaction solution. The aminoamine compounds are selected from at least one of ethanolamine, n-propanolamine, isopropanolamine, butanolamine, isobutanolamine, and 4-aminomethylbenzyl alcohol. The polar aprotic solvent is selected from N,N-dimethylformamide and N,N-dimethylacetamide. The catalyst is selected from at least one of the following: amide, 1,3-dimethyl-2-imidazolinone, acetonitrile, methyl ethyl ketone, dimethyl sulfoxide, N-methylpyrrolidone, gamma-butyrolactone, gamma-valerolactone, delta-valerolactone, dihydro-L-glucoselenone, N-butylpyrrolidone, hexamethylphosphoric triamine, and 1,4-dioxane; the catalyst is selected from at least one of tetrabutylammonium bromide, betaine, metformin, tetramethylguanidine, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and 1,5-diazabicyclo[4.3.0]-5-nonene (DB). N), 1,5,7-triazidobiscyclo[4,4,0]dec-5-ene (TBD); the polyester is selected from polyethylene terephthalate (PET), polypropylene terephthalate (PTT), polybutylene terephthalate (PBT), polypentyl terephthalate (PPT), polyethylene succinate (PES), polypropylene succinate (PPS), polybutylene succinate (PBS), polypentylene glycol succinate (PNS), polycyclohexanedimethyl terephthalate (PCT), polyethylene naphthalate (BND), and polyethylene terephthalate (PET). One or more of the following: poly(ethylene ester) (PEN), polybutylene naphthalene dicarboxylate (PBN), polyethylene adipate (PEA), polypropylene adipate (PPA), polybutylene adipate (PBA), polyneoprene adipate (PNA), polyethylene 2,5-furandicarboxylate (PEF), poly(1,3-propanediol 2,5-furandicarboxylate) (PTF), polybutylene 2,5-furandicarboxylate (PBF), polyhexane adipate (PHA), and copolymer of butylene adipate and butylene terephthalate (PBAT).

2. The method for selective alcoholysis of amine compounds to recover polyester according to claim 1, characterized in that: The mass ratio of the amino-protected alkanolamine compound to the polar aprotic solvent is 1:0.5 to 10, the amount of polyester is 1% to 20% of the mass of the mixture, and the amount of catalyst is 1% to 30% of the mass of the mixture.

3. The method for selective alcoholysis of amine compounds to recover polyester according to claim 2, characterized in that: The degradation reaction is carried out at a temperature of 80–200°C for a time of 10–300 min.

4. The method for selective alcoholysis of amine compounds to recover polyester according to claim 3, characterized in that: The degradation reaction temperature is 100–150°C.

5. The method for selective alcoholysis of amine compounds to recover polyester according to claim 1, characterized in that: The unsuitable solvent is water.

6. A method for selective alcoholysis of amine compounds to recover polyester according to any one of claims 1-5, characterized in that: The amino protecting agent includes at least one of ditert-butyl dicarbonate, p-toluenesulfonyl chloride, trifluoroacetic anhydride, and phthalic anhydride.