Method for decomposing and recycling polyester polymer material

Abstract

The invention provides a method for decomposing and recycling a polyester polymer material, and belongs to the field of polyester polymer material recycling. The preparation method comprises the following steps: mixing a polyester polymer material, a solvent and a catalyst to obtain a mixed solution; after the reaction is finished, filtering and separating to obtain a depolymer solution; and separating the depolymerization solution to obtain a reaction solvent and a small molecule depolymerization product. According to the degradation method provided by the invention, the depolymerization speed of the polyester polymer material is greatly improved under the action of the solvent, the catalyst and the rays, and compared with the prior art, the degradation temperature can be reduced to room temperature, and the reaction is normal pressure reaction, so that the energy consumption is greatly reduced, and the production cost is reduced. The solvent in the degradation method provided by the invention can be alcohol, ammonia and the like, so that the rapid depolymerization of the polyester high polymer material is promoted, the reaction time is greatly shortened, and the recovery efficiency is improved. The method provided by the invention has selectivity to a target material, the purity of the product is very high, and redundant impurities and side reactions are not generated.

Description

Technical Field

[0001] The invention belongs to the field of polyester macromolecular material recovery, and in particular relates to a method for decomposing and recovering polyester macromolecular materials. Background Art

[0002] The recycling problem of polymer materials has attracted wide attention, and how to turn waste into treasure is the key point that needs to be solved. Polymer materials include various plastics, engineering plastics, synthetic materials, etc. Among them, polyethylene terephthalate ranks first in terms of degradation difficulty.

[0003] Polyester polymer material is the synthetic material with the largest output and the most extensive application, accounting for more than 80% of the total synthetic fiber, which makes the proportion of its waste also grow rapidly. Although domestic and foreign enterprises have achieved chemical recycling of polyester polymer in industry, the recycling rate is still less than 20%. Most of the polyester polymer is incinerated and landfilled, which not only wastes a lot of natural resources, but also causes environmental pollution.

[0004] At present, the chemical recycling methods of polyester polymers mainly include ammonolysis, hydrolysis and alcoholysis. Among them, the ammonolysis method is to use ammonia (amine) substances to depolymerize polyester polymers into small molecules such as terephthalamide. Although ammonia (amine) compounds have high reactivity and mild reaction conditions, they cannot obtain the raw monomers for synthesizing PET. The hydrolysis method and alcoholysis method can depolymerize polyester polymers into monomers, and the monomers can continue to be repolymerized to prepare recycled polyester, realizing the closed-loop cycle of polyester polymers. Therefore, it is the most studied depolymerization method. The hydrolysis method is to depolymerize polyester polymers into terephthalic acid-based monomers. Although the solvent is water, due to the harsh reaction conditions of the depolymerization process, it is generally required to be carried out under high temperature and high pressure [temperature>130℃, pressure 1~4MPa——GreenChem., 2022, 24, 1362; J.Clean.Prod., 2019, 2081469]. At the same time, strong acids and alkalis are required as catalysts, which are easy to cause corrosion to equipment. Alcoholysis is mainly divided into two categories: methanolysis and glycolysis. Methanolysis is the depolymerization of polyester polymers into monomer dimethyl terephthalate. Although it is easy to sublime, due to the low boiling point of methanol, the reaction requires harsh high temperature [temperature>160°C, Polym. Degrad. Stab., 2002, 75, 185; US Pat, 5414022A, 1995 US Pat, 3403115A, 1968.] and high pressure conditions. Glycol alcoholysis is the depolymerization of polyester polymers to obtain monomer diethylene glycol terephthalate. Although ethylene glycol has a high boiling point, the reaction can usually be carried out at 180-220°C under normal pressure [Green Chem., 2022, 24, 1294; Polymer Degradation and Stability 183 (2021) 109463; ACS Sustain.Chem.Eng.2019,7,3292】, but the recovered monomers often contain oligomers, which makes the purification process relatively complicated, that is, firstly, it is necessary to add excess water to the ethylene glycol alcoholysis solution to dissolve the diethylene glycol terephthalate therein, and the insoluble part is the polyester and oligomers that are not completely depolymerized, and then the diethylene glycol terephthalate solution is separated by filtration, and then the diethylene glycol terephthalate solution is concentrated under reduced pressure to remove the water in the solution, and finally the diethylene glycol terephthalate is precipitated by cold crystallization.

[0005] The existing hydrolysis and alcoholysis technologies have harsh depolymerization conditions. In addition to depolymerizable polyester polymers, they are not selective for other non-polyester polymer components and can also depolymerize them. Therefore, it is almost impossible to achieve selective depolymerization of polyester polymer composites, resulting in complex recycled components, which makes it impossible to recycle and waste resources. At present, in order to avoid the influence of these non-polyester polymer components, raw materials with extremely high pure polyester polymer content are often selected for depolymerization and recycling, resulting in a small recovery yield of this part of raw materials. Therefore, achieving selective depolymerization of polyester in polyester polymer composites in industry is a problem that needs to be solved urgently. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for decomposing and recovering polyester polymer materials, which can achieve selective depolymerization of target composite materials during the recovery process, and non-target composite materials do not undergo chemical changes; not only can the recovery rate and purity of the depolymerization products of polyester polymer materials be improved, but non-target composite materials as well as solvents and catalysts can also be recycled again, which is undoubtedly of great significance for the recycling of resources and environmental protection.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for decomposing and recycling polyester polymer materials, comprising the following steps:

[0009] A polyester polymer material, a solvent and a catalyst are mixed under the condition that the oxygen concentration is less than 5% to obtain a mixed solution, and then a high-energy ray is used for reaction;

[0010] After the reaction is completed, filtering and separating to obtain a depolymerized product solution;

[0011] The depolymerization solution is separated to obtain a reaction solvent and a small molecule depolymerization product.

[0012] The inventors of the present invention have discovered that the interaction between radiation and catalysts and polymer materials can affect the materials through different mechanisms, while the catalyst accelerates or guides these reactions through its chemical properties. Radiation, especially high-energy radiation (such as electron beams, X-rays, etc.), can have direct or indirect effects on polymer materials: Direct effect: The radiation directly collides with the polymer chain, resulting in the breaking of chemical bonds and the generation of free radicals or excited molecules. These free radicals or excited substances can further trigger degradation reactions, such as chain breaking, cross-linking, and recombination. Indirect effect: The radiation triggers the ionization of the solvent or surrounding gas through radiation, generating more reactive substances (such as hydrated free radicals, OH free radicals, etc.), which can react with the polymer material and cause degradation.

[0013] Catalysts work in the radiation degradation process mainly through the following mechanisms:

[0014] Free radical capture and guided degradation: Some catalysts can capture free radicals generated by radiation, change the reaction path of free radicals, and thus achieve selective degradation. For example, some metal catalysts can combine with free radicals to prevent free radicals from further initiating chain extension or cross-linking, and selectively promote chain breakage. Changing the reaction path: Catalysts may guide polymer materials toward specific degradation pathways by providing low-energy reaction channels, rather than producing random breaks or cross-links. For example, some acidic or basic catalysts can accelerate the hydrolysis or aminolysis reactions of polymer materials such as polyesters and polyamides. Adjusting degradation rate and selectivity: Some catalysts achieve selective degradation by changing the local electronic environment of polymer materials, making them particularly sensitive to certain chemical bonds (such as ester bonds, amide bonds, etc.) under the action of radiation.

[0015] Preferably, the reaction condition is anaerobic condition.

[0016] Preferably, the polyester polymer material can be obtained by conventional purchasing methods; the processing method of the polyester polymer material is:

[0017] (1) Pre-cleaning: 5-10 g of polyester polymer material and 100-150 mL of anhydrous ethanol are mixed and sealed, stirred at room temperature for 10-20 h, 0.1-1.0 L of deionized water is added, filtered, and dried; the above pre-cleaning process is repeated 2-3 times to obtain a pretreated polyester polymer material;

[0018] (2) Ultrasonic cleaning: ultrasonically cleaning the pre-cleaned polyester polymer material in step (1) at 25-40° C. for 5-15 min to obtain a cleaned polyester polymer material;

[0019] (3) Mix 1-8 g of the polyester polymer material of step (2) with 5-10 mL of anhydrous ethanol and dry in vacuum at 40-60° C. to obtain a clean polyester polymer material.

[0020] Preferably, the mass ratio of the polyester polymer material, the solvent and the catalyst is 1:(1-1000):(0.1-100), and more preferably the mass ratio is 1:(1-800):(0.1-80).

[0021] Preferably, the solvent is an ammonia solution and / or an amine solution;

[0022] The mass percentage of the water-soluble compound in the mixed solution is 2-90%, more preferably 10-80%, specifically 20%, 30%, 40%, 50%, 60%, 70%.

[0023] Preferably, the ammonia solution is aqueous ammonia; the water-soluble compound of the amine solution is one or more of monoamines with 1 to 4 carbon atoms, diamines with 2 to 8 carbon atoms, triamines with 3 to 4 carbon atoms, and polyamines.

[0024] Preferably, the monoamine having 1 to 4 carbon atoms is a primary amine and / or a secondary amine; more preferably, it is a primary amine.

[0025] Preferably, the catalyst is an alkaline reagent.

[0026] Preferably, the high-energy rays include cobalt-60 gamma rays or electron beam rays.

[0027] Preferably, the irradiation dose of the high-energy rays is 10-2000 kGy; more preferably, it is 50-1000 kGy, specifically, it can be 80 kGy, 150 kGy, 300 kGy, 600 kGy; the dose rate is 0.1-10 kGy / h, more preferably, it is 2-8 kGy / h, specifically, it can be 2 kGy / h, 4 kGy / h6 kGy / h, 8 kGy / h.

[0028] Preferably, the small molecule depolymerization product contains amide compounds and small molecule polymer esters.

[0029] Preferably, the oxygen concentration is controlled by introducing nitrogen and / or argon for deoxygenation.

[0030] Preferably, the filtration separation can separate the incompletely reacted PET waste.

[0031] Preferably, the separation method is precipitation or cooling crystallization.

[0032] Contains at least the following beneficial technical effects:

[0033] 1. The present invention uses a one-step radiation method to decompose polyester polymer materials. The radiation reduction reaction is carried out at ambient temperature, the operation is simple, and it is expected to realize the industrialization of the technology.

[0034] 2. The raw materials used in the present invention are polyester polymer materials and ammonia / amine solutions, which have a wide range of sources and a high utilization rate. The ammonia / amine raw materials used are completely liquid after the reaction, and the raw materials can be effectively separated; the preparation process is simple, does not involve harsh chemical reaction conditions, and avoids complex and difficult chemical reactions and purification processes.

[0035] 3. The polyester polymer material decomposition and recovery method of the present invention combines the characteristics of ester functional groups that are easily attacked by nucleophiles and the good nucleophilic properties of ammonia / amine substances. The degradation method provided by the present invention greatly improves the depolymerization rate of the polymer material under the action of solvents, catalysts and radiation. Compared with the prior art, the present invention can not only reduce the degradation temperature to room temperature, but also react at normal pressure, which not only greatly reduces energy consumption, but also can achieve a high depolymerization rate of the target material. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a scanning electron microscope photograph of the degradation product of Example 1;

[0037] Figure 2 These are macroscopic photographs of Example 1 before and after degradation. DETAILED DESCRIPTION

[0038] The technical solution of the present invention is further illustrated by the following examples.

[0039] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0040] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the main idea or essential features of the present invention. Therefore, from all points of view, the embodiments should be regarded as exemplary and non-restrictive, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims are included in the present invention, and any reference numerals in the claims should not be regarded as limiting the claims involved.

[0041] In addition, it should be understood that although this specification is described according to the implementation modes, not every implementation mode includes only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation modes that can be understood by those skilled in the art. These other implementation modes are also covered within the protection scope of the present invention.

[0042] It should also be understood that the specific embodiments described above are only used to explain the present invention, and the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, can make equivalent replacements or changes based on the technical solutions and inventive concepts of the present invention, which should be covered by the protection scope of the present invention / invention.

[0043] Examples 1-28

[0044] (1) 6 g of PET or PBT or PC or PTT is mixed with 150 mL of anhydrous ethanol and sealed, stirred at room temperature for 20 h, 0.5 L of deionized water is added, filtered, and dried; the above pre-cleaning process is repeated 3 times to obtain pre-treated PET or PBT or PC or PTT; the pre-treated PET or PBT or PC or PTT is ultrasonically cleaned at 35° C. for 10 min to obtain cleaned PET or PBT or PC or PTT; then 4 g of the cleaned PET or PBT or PC or PTT is mixed with 5 mL of anhydrous ethanol and vacuum dried at 60° C. to obtain a clean polyester polymer material;

[0045] (2) 4 g of the clean PET or PBT or PC or PTT prepared in step (1) is mixed with a catalyst and an ammonia / amine compound, sealed and allowed to stand for 24 hours; in the mixed solution, the mass ratio of PET or PBT or PC or PTT to concentrated ammonia water, the mass ratio of PET or PBT or PC or PTT to sodium hydroxide, and the mass percentage of ammonia / amine in the mixed solution are as shown in Table 1;

[0046] (3) injecting the mixed solution obtained in step (2) into a cylindrical irradiation reactor and passing nitrogen gas to remove oxygen;

[0047] (4) The sealed irradiation reactor is irradiated with a cobalt 60 gamma ray source. The absorbed dose and the absorbed dose rate of the irradiation reaction are shown in Table 1. After irradiation, a depolymerized polyester mixed solution can be obtained.

[0048] (5) filtering the mixed solution obtained in step (4), and drying to obtain a depolymerization product.

[0049] Comparative Examples 1-20

[0050] (1) The treatment method of PET, PBT, PC or PTT is the same as that in Example 1.

[0051] (2) mixing the PET or PBT or PC or PTT prepared in step (1) with a catalyst and using water as a solvent; in the mixed solution, the mass ratio of PET or PBT or PC or PTT to sodium hydroxide is 1:1, and the mass ratio of PET or PBT or PC or PTT to water is 1:800.

[0052] (3) Inject the mixed solution obtained in step (2) into a cylindrical irradiation reactor and pass nitrogen to remove oxygen; irradiate the sealed irradiation reactor with a cobalt 60 gamma ray source; the absorbed dose is 50 kGy.

[0053] See Table 1 for specific parameters.

[0054] Table 1 Mixtures and irradiation conditions of Examples 1-28 and Comparative Examples 1-20

[0055]

[0056]

[0057]

[0058] Experimental Example 1

[0059] The yields of the depolymerization products obtained in Examples 1-28 and the yields of the products obtained in Comparative Examples 1-20 were measured. The test results are shown in Table 2.

[0060] The formula for calculating the yield in a chemical reaction mainly includes two key parts: theoretical yield and actual yield: Definition of actual yield and theoretical yield: Theoretical yield: The mass or mole number of the target product obtained according to stoichiometric calculations assuming that the reaction is completely carried out. Actual yield: The mass or mole number of the target product actually obtained in the experiment.

[0061] Yield formula:

[0062] Yield = theoretical yield / actual yield × 100%

[0063] Table 2 Yield data of depolymerization products of Examples 1-28 and Comparative Examples 1-20

[0064] project Yield / % Example / Comparative Example No. Yield / % Example 1 98 Embodiment 25 95 Example 2 97 Embodiment 26 90 Example 3 98 Embodiment 27 85 Example 4 97 Embodiment 28 95 Example 5 96 Comparative Example 1 0 Example 6 95 Comparative Example 2 0 Example 7 96 Comparative Example 3 0 Example 8 97 Comparative Example 4 0 Example 9 98 Comparative Example 5 0 Example 10 99 Comparative Example 6 0 Embodiment 11 97 Comparative Example 7 0 Example 12 92 Comparative Example 8 0 Example 13 97 Comparative Example 9 0 Embodiment 14 96 Comparative Example 10 0 Embodiment 15 99 Comparative Example 11 45 Example 16 97 Comparative Example 12 50 Embodiment 17 96 Comparative Example 13 46 Embodiment 18 94 Comparative Example 14 50 Embodiment 19 97 Comparative Example 15 50 Embodiment 20 94 Comparative Example 16 44 Embodiment 21 90 Comparative Example 17 50 Embodiment 22 97 Comparative Example 18 35 Embodiment 23 96 Comparative Example 19 48 Embodiment 24 97 Comparative Example 20 49

[0065] Figure 1 is a scanning electron microscope photograph of the degradation product of Example 1, Figure 2 The macroscopic photographs of Example 1 before and after degradation are shown in Table 2. The degradation products obtained by Examples 2-28 are similar to those of Example 1. It can be seen from Table 2 that the degradation yield of the ammonia / amine decomposition reaction of Comparative Examples 1-20 is very low and no degradation occurs only under irradiation conditions. However, Examples 1-28 show that complete degradation can be basically achieved under combined irradiation conditions.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for decomposing and recovering polyester polymer materials, characterized in that: The following steps are involved: A polyester polymer material, a solvent and a catalyst are mixed under the condition that the oxygen concentration is less than 5% to obtain a mixed solution, and then a high-energy ray is used for reaction; After the reaction is completed, filtering and separating to obtain a depolymerized product solution; The depolymerization solution is separated to obtain a reaction solvent and a small molecule depolymerization product.

2. The method according to claim 1, characterized in that The mass ratio of the polyester polymer material, the solvent and the catalyst is 1:(1-1000):(0.1-100).

3. The method according to claim 2, characterized in that The solvent is an ammonia solution and / or an amine solution; The mass percentage of the water-soluble compound in the mixed solution is 2-90%.

4. The method according to claim 3, characterized in that The ammonia solution is ammonia water; the water-soluble compound of the amine solution is one or more of monoamines with 1 to 4 carbon atoms, diamines with 2 to 8 carbon atoms, triamines with 3 to 4 carbon atoms, and polyamines.

5. The method according to claim 4, characterized in that The monoamine having 1 to 4 carbon atoms is a primary amine and / or a secondary amine.

6. The method according to claim 1, characterized in that The catalyst is an alkaline reagent.

7. The method according to claim 1, characterized in that The high-energy rays include cobalt-60 gamma rays or electron beam rays.

8. The method according to claim 1, characterized in that The irradiation dose of the high-energy rays is 10-2000 kGy, and the dose rate is 0.1-10 kGy / h.

9. The method according to claim 1, characterized in that: The small molecule depolymerization product contains amide compounds and small molecule polymerized esters.

10. The method according to claim 1, characterized in that The oxygen concentration is controlled by introducing nitrogen and / or argon to remove oxygen.

Images