Depolymerization regeneration method of amido-containing polymer

Abstract

The invention relates to a depolymerization regeneration method of an amido-containing polymer. The depolymerization regeneration method comprises depolymerization, and the depolymerization comprises the following steps: mixing an amido-containing polymer, a dicarboxylic acid depolymerization agent and water, sealing, and heating to a depolymerization temperature to degrade the amido-containing polymer into small molecular compounds. The depolymerization regeneration method disclosed by the invention can also comprise hydrolysis, separation and purification or repolymerization. The depolymerization and repolymerization process is simple, does not use an organic solvent, is low in cost, safe and environment-friendly, is easy to realize large-scale stable regeneration of the amido-containing polymer, especially polyamide, polyurethane and polyesteramide, shows wide application prospects and important economic values, and has remarkable social benefits and economic benefits.

Description

Technical Field

[0001] The invention belongs to the field of polymer materials, relates to a method for regenerating and utilizing polymer materials, and particularly relates to a method for depolymerizing and regenerating an amide-containing polymer. Background Art

[0002] Amide-containing polymers mainly include polyurethane, polyamide and polyesteramide. Polyurethane is a high molecular compound made by the reaction of isocyanate and polyol. It has excellent physical and chemical properties and is widely used in construction, transportation, electronics, medical equipment, aerospace and other fields. Downstream products mainly include foam plastics, shoe leather resins, fibers, coatings, adhesives, sealants and elastomers, etc. It is known as the fifth most common plastic after polyethylene, polyvinyl chloride, polypropylene and polystyrene. Polyamide, commonly known as nylon, contains repeated amide groups (-NHCO-) ​​on its molecular chain and is generally a semi-crystalline thermoplastic polymer. Since DuPont industrialized polyamide 66 (PA66) in 1939, polyamide, as a high-performance engineering plastic, has been widely used in automobile manufacturing, electronics and electrical, textile industry, medical equipment and other fields due to its excellent mechanical strength, wear resistance, chemical corrosion resistance and thermal stability. However, with the mass production and consumption of amide-containing polymer products such as polyurethane and polyamide, the treatment of waste polyurethane and polyamide has become increasingly prominent. Therefore, the recycling of amide-containing polymers has become one of the important ways to solve resource shortages and environmental pollution. Among them, the depolymerization and regeneration of polyurethane and polyester amide has just started and is still very immature; while the recycling technology of polyamide has many problems, but it is relatively mature.

[0003] The regeneration technology of polyamide mainly includes three categories: physical regeneration, biological regeneration and chemical regeneration. The physical method converts polyamide products into recycled slices through processes such as cleaning, sorting, crushing, melting, extrusion, and granulation, and then recycles them; this method is simple to operate and has low production costs, and is currently the mainstream regeneration preparation method. The biological regeneration method uses the action of microorganisms or enzymes to decompose polyamide into small molecular compounds, and then further converts them into new polyamide materials; this method is environmentally friendly and sustainable, but the technology is not yet mature and is in the research stage. The chemical regeneration method first depolymerizes the polyamide material, and then obtains high-quality recycled slices through purification, separation, polymerization and other processes, which is conducive to the high-value recycling of polyamide, and is also the main research direction in the field of polyamide regeneration at home and abroad; this method can more thoroughly recycle polyamide molecules and the quality of the recycled slices is the same as that of the original slices, but the process is complicated and the cost is high, and it is still a long way from large-scale application.

[0004] Chemical regeneration of polyamide often involves its chemical depolymerization. Depending on the depolymerizing agent, medium and means used, chemical depolymerization of polyamide can be divided into pyrolysis, aminolysis, glycolysis, alcoholysis, hydrogenolysis, enzymolysis, hydrolysis and ionic liquid recovery, among which hydrolysis can be divided into three types: neutral, acidic and alkaline hydrolysis.

[0005] Chinese patents CN200710156491 and CN200910097552 respectively disclose methods for preparing regenerated adipic acid and hexamethylenediamine by acidolysis of polyamide 66 using sulfuric acid and hydrochloric acid as catalysts, but there is the problem of complicated separation of adipic acid, hexamethylenediamine and catalysts. CN202111431061 discloses a process system for chemically regenerating waste polyester and polyamide into PBAT, including a waste polyester depolymerization system, a depolymerization product purification system, an ester exchange system, a polyamide depolymerization system, adipic acid purification system, adipic acid drying system, an esterification system, a pre-condensation system, a final condensation system and a post-processing system, etc. Obviously, this process and equipment system are too complicated, which will inevitably lead to high regeneration costs. CN202211490612 will use a small molecule acid containing an ether oxygen bond structure to depolymerize polyamide, prepare a carboxyl-terminated polyamide oligomer, and react with a polyether component to prepare a polyetheramide elastomer. CN202111427961 recovers and purifies caprolactam after depolymerization under the condition that the dynamic viscosity of the polyamide 6 / subcritical water system is not higher than 10Pa·s, and then regenerates polyamide 6 by polymerization. CN202310917811 uses steam containing caprolactam to hydrolyze and depolymerize polyamide 6 melt to obtain a caprolactam aqueous solution, and dopes caprolactam in superheated steam as a depolymerization aid, which can effectively reduce the viscosity of the depolymerization system, increase the depolymerization rate and yield. CN202311774566 and CN202311226678 control the chemical equilibrium by adjusting the amount of water to synthesize polyamide oligomers, and then polymerize to prepare regenerated polyamide. CN202311788970 uses zinc acetate and zinc chloride as catalysts to catalyze and hydrolyze polyamide 6 to recover caprolactam monomer. CN202410248100 discloses a method for efficiently depolymerizing polyamide 6 using an organic catalyst t-BuP4. CN202410298885 discloses a method for preparing caprolactam by cleaning waste PA6 fishing nets with sodium hydroxide solution, and then performing immersion, extraction, melt depolymerization and separation.

[0006] Internationally, DuPont disclosed in U.S. Patent US5310905A a method for depolymerizing polyamide using acetic acid, propionic acid, butyric acid, valeric acid or caproic acid as a catalyst. BASF disclosed in PCT patent WO2023187045 that a polyamide melt containing caprolactam units is hydrolyzed in a high-temperature aqueous fluid to achieve the regeneration of caprolactam. In WO2023120427, Asahi Kasei Corporation heats and degrades polyamide in a solvent containing inorganic salts and polyols to regenerate lactam, dicarboxylic acid and diamine monomers. Toray disclosed in WO2023074437 a method for efficiently recovering caprolactam and polyamide 6 oligomers by depolymerizing polyamide 6 using only a small amount of water and solid-liquid separation. In WO2024056584, Solvay disclosed a method for recovering monomers from AABB-type polyamides, which first contacted the polyamide melt with a C2-C18 carboxylic acid to reduce the molecular weight of the polyamide, then carried out acid-, alkali- or enzyme-catalyzed hydrolysis in an aqueous phase, and recovered dicarboxylic acid and diamine monomers.

[0007] In summary, the depolymerization and regeneration of amide-containing polymers represented by polyamide is an important research direction in the field of polymer materials in recent years. It is a hot spot of competition among various enterprises and research institutions. A large number of invention patents have been continuously disclosed, and the technical system is also constantly improving. However, there are still a series of problems that restrict large-scale regeneration, such as the need for high temperature and pressure, catalysts, long time, high energy consumption, complex separation of depolymerization products, difficult purification, low recovery rate, and difficulty in high-value utilization. Summary of the invention

[0008] In view of the above-mentioned difficulties existing in the existing depolymerization and regeneration technologies of amide-containing polymers, the purpose of the present invention is to provide a low-cost, high-value regeneration solution for amide-containing polymers, and in particular to provide a method for rapidly depolymerizing amide-containing polymers, efficiently preparing amide carboxylic acid or amide dicarboxylic acid, and separating and purifying amide carboxylic acid or amide dicarboxylic acid at low cost.

[0009] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0010] The invention provides a depolymerization and regeneration method for an amide-containing polymer, which comprises depolymerization: the depolymerization comprises: sealing a mixture of an amide-containing polymer, a dicarboxylic acid depolymerizing agent and water, and heating the mixture to a depolymerization temperature to degrade the mixture into small molecular compounds; wherein the amide-containing polymer is one of polyamide, polyurethane or polyester amide; the ratio of the mole number of the dicarboxylic acid depolymerizing agent to the mole number of amide groups in the amide-containing polymer is 1 to 3, and the ratio of the mole number of water to the mole number of amide groups in the amide-containing polymer is 1 to 40.

[0011] The present invention has no particular restrictions on the amide-containing polymer. Considering the scale, polyamide, polyurethane or polyesteramide is generally preferred, more preferably polyamide or polyurethane, and most preferably polyamide. The depolymerization temperature in the present invention is not particularly limited. Considering that too low a depolymerization temperature may result in too slow a depolymerization speed, too high a depolymerization temperature may result in excessive energy consumption and too high a system pressure, it is generally appropriate to use 100 to 300°C, preferably 120 to 290°C, and more preferably 150 to 270°C. The small molecule compound of the depolymerization product of polyamide in the present invention is preferably one or more of imide carboxylic acid or amide dicarboxylic acid small molecule compounds; and the degradation products of polyurethane and polyesteramide also contain small molecule compounds such as diols, polyols, hydroxy acids or lactones. In the depolymerization and regeneration method of the present invention, since the dicarboxylic acid depolymerizer has good compatibility with amide-containing polymers such as polyamide, it can quickly diffuse into the amorphous phase of amide-containing polymers such as polyamide and then attack the amide bonds, resulting in rapid depolymerization of amide-containing polymers such as polyamide. Therefore, the time required for complete depolymerization in the present invention is generally not more than 24 hours; if the depolymerization time is too short, the depolymerization temperature is too high, which is easy to cause side reactions, and if it is too long, the depolymerization efficiency is affected. Therefore, the depolymerization time is generally 0.5 to 24 hours; preferably 0.5 to 5 hours.

[0012] The present invention has no particular restrictions on the dicarboxylic acid depolymerizing agent: when polyamide or other amide-containing polymers contain dicarboxylic acid units, the dicarboxylic acid depolymerizing agent may be the same as or different from the dicarboxylic acid monomers used to prepare the polyamide, polyurethane, or polyesteramide, but in order to simplify the separation and purification process, the dicarboxylic acid depolymerizing agent is preferably one of the dicarboxylic acid monomers used to prepare the polymer. On the other hand, especially for polyamide, the dicarboxylic acid depolymerizing agent is preferably the same as the dicarboxylic acid monomer used to prepare the polyamide; considering the cost and availability, the dicarboxylic acid depolymerizing agent may be a C4-C10 dicarboxylic acid, preferably adipic acid, sebacic acid, or terephthalic acid, more preferably adipic acid or sebacic acid, and most preferably adipic acid.

[0013] The molar number of the dicarboxylic acid depolymerizing agent in the present invention should not be less than the molar number of the amide group in the amide group-containing polymer. If it is less than the molar number of the amide group in the amide group-containing polymer, the depolymerization will be incomplete, and if it is too much, the atom economy will be low; therefore, generally, the ratio of the molar number of the dicarboxylic acid depolymerizing agent to the molar number of the amide group in the amide group-containing polymer is 1 to 3; and the molar ratio should be appropriately adapted to the type of amide group-containing polymer, generally preferably 1 for polyamide or polyesteramide, and preferably 2 for polyurethane. In particular, for the depolymerization of polyamide, the dicarboxylic acid depolymerizing agent is preferably adipic acid or sebacic acid, and the ratio of its molar number to the molar number of the amide group in the amide group-containing polymer is 1 as the best.

[0014] In the present invention, water, on the one hand, acts as a plasticizer for the amide-containing polymer, which is beneficial to improve the reactivity of the amide-containing polymer and promote depolymerization. On the other hand, it acts as a solvent for the small molecular compounds of the depolymerization product (such as imide carboxylic acid or amide dicarboxylic acid, etc.), so the role of water is very important. Too low a water amount affects the depolymerization efficiency, and too high a water amount leads to high energy consumption. Therefore, the ratio of the number of moles of water to the number of moles of amide groups in the amide-containing polymer is generally preferably 1 to 40, preferably 10 to 30. The present invention has no restrictions on whether water is gaseous or liquid at the depolymerization temperature. It can be a mixture of liquid water and water vapor, or only water vapor. In view of the fact that amide-containing polymers generally have good hydrophilicity, no matter water exists in liquid or water vapor, it can quickly diffuse into the amide-containing polymer to participate in and promote its depolymerization.

[0015] The depolymerization product imidocarboxylic acid small molecule compound described in the present invention has a molecular structure shown in Formula 1:

[0016]

[0017] In Formula 1, R and R1 are independently an alkylene group or an arylene group.

[0018] The depolymerization product amide dicarboxylic acid small molecule compound described in the present invention generally has a molecular structure shown in Formula 2 or Formula 3:

[0019]

[0020] R, R2, R3 and R4 in Formula 2 and Formula 3 are independently one or more of alkylene groups or arylene groups. The present invention has no other special restrictions on R, R1, R2, R3 and R4, wherein R is derived from a dicarboxylic acid depolymerizer, and R1, R2, R3 and R4 are derived from amide-containing polymers such as polyamide.

[0021] The depolymerization and regeneration method of an amide-containing polymer provided by the present invention also includes hydrolysis, wherein the hydrolysis is to add an inorganic strong acid or an inorganic strong base solution to one or more depolymerization products of the aforementioned imide carboxylic acid or amide dicarboxylic acid to cleave the imide bond or amide bond, and then separate and purify to obtain two or more regenerated monomers. The present invention has no particular restrictions on the inorganic strong acid or inorganic strong base solution, which can be dilute sulfuric acid or hydrochloric acid, NaOH or KOH aqueous solution, etc.; the regenerated monomers include more than one regenerated dicarboxylic acid monomer, and one or more selected from diamine, lactam or amino acid monomers.

[0022] The depolymerization and regeneration method of an amide-containing polymer provided by the present invention also includes separation and purification, wherein the separation and purification is to perform hot filtration on the system after the depolymerization is completed, cool the filtrate until the product precipitates, and then filter and wash to obtain purified imide carboxylic acid or amide dicarboxylic acid. After systematic research, the present invention has found that imide carboxylic acid and amide dicarboxylic acid are both easy to dissolve in hot water and easy to precipitate in cold water. Based on this characteristic, the present invention provides a simple and efficient method for separating and purifying imide carboxylic acid and amide dicarboxylic acid: after the depolymerization is completed, the system is hot filtered, the filtrate is cooled until the product precipitates, and then filtered and washed to obtain high-purity imide carboxylic acid or amide dicarboxylic acid. The present invention has no special restrictions on the temperature and pressure of hot filtration, which is generally determined by the solubility characteristics of imide carboxylic acid or amide dicarboxylic acid. Considering the convenience of operation, it is generally suitable to filter at normal pressure and cool to 80°C to 95°C; on the other hand, the present invention has no special restrictions on the temperature and pressure of cooling precipitation, which is generally suitable at normal temperature and pressure.

[0023] The depolymerization and regeneration method of an amide-containing polymer provided by the present invention also includes repolymerization: adding one or more of diamine, amino alcohol, amino acid, lactam, diol, hydroxy acid, lactide or lactone monomer to the depolymerization product amide dicarboxylic acid for polycondensation to prepare regenerated polyamide or polyesteramide. The present invention has no particular restrictions on the addition of diamine, amino alcohol, amino acid, lactam, diol, hydroxy acid, lactide or lactone monomer. Considering the cost and availability, C4-C10 diamine, C2-C6 amino alcohol, C4-C6 amino acid, C4-C6 lactam, C2-C10 diol, C2-C6 hydroxy acid, C4-C6 lactide or C4-C6 lactone monomer is preferred. A polymerization catalyst may be added during repolymerization, or a catalyst may not be added; but for the polyesteramide system, in order to improve the repolymerization speed and efficiency, a catalyst is preferably added; the added catalyst is one or more of tin, titanium or antimony catalysts. The present invention has no particular limitation on the repolymerization temperature, and the conventional polycondensation temperature of polyester and polyamide can be adopted, which is generally between 160 and 300° C. The specific temperature is comprehensively considered based on the properties of the repolymerization system and the melting point of the repolymerization product.

[0024] The present invention is applicable to the depolymerization and regeneration of amide-containing polymers, and the amide-containing polymers may be one or more of PA6, PA46, PA56, PA66, PA510, PA610, PA1010, PA11, PA12, PA6T or PA10T. However, considering the efficiency of separation and purification and the difficulty of high-value regeneration, the method provided by the present invention is more suitable for the depolymerization and regeneration of one or more of PA46, PA56, PA66, PA510, PA610 or PA1010. In the depolymerization, in order to simplify the process and reduce energy consumption, the ratio of the number of moles of water to the number of moles of amide groups in the amide-containing polymer is preferably 10 to 30.

[0025] The present invention has no particular limitation on the form of the amide-containing polymer, which may be in the form of fibers, films, powders, slices or blocks. However, for ease of operation, especially for large-scale and continuous depolymerization and regeneration, amide-containing polymer pellets or powders are generally preferred. In other words, the amide-containing polymer may be pretreated, for example, the amide-containing polymer fibers and films may be preprocessed into foam materials.

[0026] The principle of the present invention is as follows:

[0027] In view of the technical difficulties that the depolymerization and regeneration of existing polyamide and other amide-containing polymers generally require high temperature and high pressure, catalysts, high energy consumption, complex separation of depolymerization products, difficult purification, low recovery rate, and difficulty in high-value utilization, the present invention uses a dicarboxylic acid depolymerizer with excellent compatibility with the amide-containing polymer to quickly depolymerize the amide-containing polymer into imide carboxylic acid or amide dicarboxylic acid containing one or two amide groups in the presence of water, and then uses the characteristics of imide carboxylic acid and amide dicarboxylic acid that are easy to dissolve in hot water and easy to precipitate in cold water to achieve efficient separation and purification of imide carboxylic acid or amide dicarboxylic acid, and finally repolymerizes the purified amide dicarboxylic acid with monomers such as diamines or diols to achieve high-value regeneration, thereby providing a complete set of high-efficiency and low-cost depolymerization and regeneration technical solutions for polyamide and other amide-containing polymers that are easy to scale up, and its basic principle is as follows:

[0028] (1) Efficient depolymerization: Dicarboxylic acids, especially aliphatic dicarboxylic acids, have good compatibility with amide-containing polymers, so they can diffuse quickly into amide-containing polymers at high temperatures (depolymerization temperature) and attack amide groups; on the other hand, they will show high acidity in high-temperature water, thereby playing a role in efficient catalytic depolymerization. Furthermore, the depolymerization product, imide carboxylic acid or amide dicarboxylic acid, is soluble in the water phase, which is conducive to its diffusion from the polymer organic phase and promotes the depolymerization. In short, the present invention uses a combination of dicarboxylic acid depolymerizer and water to depolymerize amide-containing polymers such as polyamides in a closed high temperature environment, which can have a significant synergistic effect, thereby achieving efficient depolymerization of amide-containing polymers such as polyamides.

[0029] (2) Efficient purification: First, no catalyst and non-aqueous solvent are added in the depolymerization of the present invention, which provides the possibility for efficient purification of imidocarboxylic acid or amide dicarboxylic acid. Secondly, the depolymerization product of the amide-containing polymer depolymerization method provided by the present invention is imidocarboxylic acid or amide dicarboxylic acid containing 1 or 2 amide groups, and its molecular structure contains both hydrophilic and hydrophobic groups, thus giving its water solubility a certain controllability from the structure. Through systematic research, we found and confirmed that these imidocarboxylic acids or amide dicarboxylic acids have the characteristics of being easy to dissolve in hot water and easy to precipitate in cold water; using this characteristic, the present invention can simply and efficiently separate imidocarboxylic acid and amide dicarboxylic acid solutions from other solid impurities through hot filtration, and then separate them from water and other water-soluble impurities through cooling, precipitation, filtration, washing and drying, thereby achieving low energy consumption and efficient purification of the depolymerization product. Furthermore, the present invention does not necessarily need to hydrolyze the amide-containing polymer into dicarboxylic acid (salt) and diamine (salt), which can avoid the separation and purification of dicarboxylic acid and diamine with complicated process, high energy consumption and low yield.

[0030] Beneficial effects of the present invention:

[0031] The present invention utilizes a dicarboxylic acid depolymerizer having excellent compatibility with amide-containing polymers to rapidly depolymerize polyamide and other amide-containing polymers into imide carboxylic acid or amide dicarboxylic acid containing one or two amide groups in the presence of water; then utilizes the characteristics of imide carboxylic acid or amide dicarboxylic acid being easy to dissolve in hot water and easy to precipitate in cold water to achieve efficient separation and purification of the depolymerization product; finally, the amide dicarboxylic acid is repolymerized with monomers such as diamine or diol to achieve high-value regeneration, thereby providing a complete set of technical solutions for efficient and low-cost depolymerization and regeneration of amide-containing polymers that are easy to scale up. The depolymerization and repolymerization process of the present invention is simple, does not use organic solvents, is safe and environmentally friendly, is easy to achieve large-scale stable regeneration of amide-containing polymers such as polyamide, has low regeneration cost, shows broad application prospects and important economic value, and has significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Depolymerization diagram of PA66 in depolymerization example A1;

[0033] Figure 2 H NMR spectra of amide dicarboxylic acid J666, adipic acid AA and PA66 in depolymerization example A1;

[0034] Figure 3 DSC curve of the first heating of the amide dicarboxylic acid J666 in depolymerization example A1;

[0035] Figure 4DSC curves of the polyester amide of the repolymerization example C1 during the first cooling and the second heating. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading content of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0037] The types and sources of monomers used in the examples are summarized in Table 1.

[0038] Table 1. Types and sources of amide-containing polymers and depolymerizing agents

[0039]

[0040] H NMR ( 1 H NMR): diamide diacid and polymer 1 HNMR was tested on a Bruker Avance 600 NMR spectrometer, the solvent was deuterated trifluoroacetic acid (TFAA, 11.50 ppm), and the number of scans was 16. The number average molecular weight Mn of some polymers was calculated from the resonance peak of the terminal group in the hydrogen spectrum.

[0041] Differential Scanning Calorimetry (DSC): A Perkin-Elmer Pyris-1 DSC instrument was used to test the crystallization and melting behavior of the samples. Specifically, about 5.5-6.0 mg of the sample was sealed in an aluminum crucible and placed in the instrument, with nitrogen as the purge gas and protective gas (20 mL / min); the first heating was from 30 °C at a heating rate of 20 °C / min to 20 °C above the melting point (T m +20), and keep it for 3min to eliminate the thermal history of the sample; cooling: cooling down to 30℃ at a cooling rate of 20℃ / min, and also keeping it for 3min; second heating: repeating from 30℃ to Tm+20 at a heating rate of 20℃ / min. Crystallization temperature Tc and crystallization enthalpy ΔH of the sample c Parameters such as melting point T m and melting enthalpy ΔH m The parameters are determined by the secondary heating curve.

[0042] Relative viscosity (ηr) determination: The measurement was performed using an Ubbelohde viscometer with a capillary diameter of 1.0 mm. The polyamide sample was dissolved in concentrated sulfuric acid at a concentration of 1 g / dL, and the polyesteramide sample was dissolved in a solution of phenol and 1,1,2,2-tetrachloroethane at a mass ratio of 1:1, with a concentration c of 5 mg / ml. The samples were then placed in a constant temperature water bath at 25.00±0.01°C and stabilized for 30 minutes before testing. The outflow times t1 and t2 of the pure solvent and polyamide solution were measured respectively. Relative viscosity η r The calculation formula is:

[0043] η r =t2 / t1 (1)

[0044] Intrinsic viscosity (η sp ) Determination: Tested with reference to the capillary viscometer method in 5.1 of GB / T 14190-2017 Test Method for Fiber-Grade Polyester Chips. The formula for calculating the intrinsic viscosity is:

[0045] η sp =(η-η0) / η 0. (2)

[0046] Where η is the solution viscosity, η0 is the solvent viscosity, and η sp It is the intrinsic viscosity, and the unit is usually dl / g.

[0047] Depolymerization Example:

[0048] Depolymerization Example A1

[0049] 400g of PA66 slices (3.54mol of amide groups), 517g of adipic acid (3.54mol, depolymerizer / amide molar ratio of 1) and 1274g of water (70.8mol, water / amide molar ratio of 20) were added to a 5l autoclave, nitrogen purged 3 times and then sealed and stirred, heated to 180°C for 2h for depolymerization; after stopping the reaction, the temperature was lowered to 90°C to obtain a homogeneous aqueous solution of the depolymerization product amide dicarboxylic acid J666 (specific structure see Table 2); after cooling to room temperature and standing overnight, the depolymerization product J666 was precipitated from the water, filtered, washed with water and vacuum dried to obtain 853g of J666 product, with a degradation yield of 93%. The depolymerization diagram of PA66 in depolymerization example A1 is shown in Figure 1 After depolymerization, PA66 is completely converted into amide dicarboxylic acid J666 (structure see Table 2) and forms a homogeneous aqueous solution (90°C). After cooling, J666 precipitates from the water.

[0050] Depolymerization Example A2

[0051] 40.0 g of PA56 slices (0.377 mol of amide group), 55.1 g of adipic acid (0.377 mol, depolymerizing agent / amide group molar ratio of 1) and 135.8 g of water (7.55 mol, water / amide group molar ratio of 20) were added to a 600 ml high-pressure reactor, and the mixture was nitrogen purged three times and stirred in a closed state, and the mixture was heated to 180° C. for depolymerization for 2 h; after stopping the reaction, the mixture was cooled to 90° C. to obtain a homogeneous aqueous solution of the depolymerization product amide dicarboxylic acid J656 (Table 2); after cooling to room temperature and standing overnight, the depolymerization product was precipitated from the water, and 81.8 g of the J656 product was obtained after filtration, washing with water and vacuum drying, and the degradation yield was 86%.

[0052] Depolymerization Example A3

[0053] 40.0 g of PA46 slices (0.404 mol of amide group), 59.0 g of adipic acid (0.404 mol, depolymerizing agent / amide group molar ratio of 1) and 145.5 g of water (8.08 mol, water / amide group molar ratio of 20) were added to a 600 ml high-pressure reactor, and the mixture was nitrogen purged three times and stirred in a closed state, and the mixture was heated to 250° C. for depolymerization for 2 h; after stopping the reaction, the mixture was cooled to 90° C. to obtain a homogeneous aqueous solution of the depolymerization product amide dicarboxylic acid J646 (Table 2); after cooling to room temperature and standing overnight, the depolymerization product was precipitated from the water, and 77.3 g of J646 product was obtained after filtration, washing with water and vacuum drying, and the degradation yield was 78%.

[0054] Depolymerization Example A4

[0055] 40.0 g of PA510 slices (0.299 mol of amide group), 60.4 g of sebacic acid (0.299 mol, depolymerizing agent / amide group molar ratio of 1) and 161.2 g of water (8.96 mol, water / amide group molar ratio of 30) were added to a 600 ml high-pressure reactor, and the mixture was nitrogen-purged three times and stirred in a closed state. The mixture was heated to 180° C. for depolymerization for 2 h. After the reaction was stopped, the mixture was cooled to room temperature and allowed to stand overnight. The depolymerization product was precipitated from the water, and 94.4 g of J10510 (Table 2) product was obtained after filtration, washing with water and vacuum drying. The degradation yield was 94%.

[0056] Depolymerization Example A5

[0057] 40.0 g of PA610 slices (0.284 mol of amide group), 57.4 g of sebacic acid (0.284 mol, depolymerizing agent / amide group molar ratio of 1) and 102.1 g of water (5.67 mol, water / amide group molar ratio of 20) were added to a 600 ml high-pressure reactor, and the mixture was nitrogen purged three times and stirred in a closed state. The mixture was heated to 180° C. for depolymerization for 1 h. After the reaction was stopped, the mixture was cooled to room temperature and allowed to stand overnight. The depolymerization product was precipitated from the water, and 93.5 g of J10610 (Table 2) product was obtained after filtration, washing with water and vacuum drying. The degradation yield was 96%.

[0058] Depolymerization Example A6

[0059] 40.0 g of PA1010 slices (0.237 mol of amide group), 47.9 g of sebacic acid (0.299 mol, depolymerizer / amide group molar ratio of 1) and 85.2 g of water (4.73 mol, water / amide group molar ratio of 20) were added to a 600 ml high-pressure reactor, and the mixture was nitrogen-purged three times and stirred in a closed state. The mixture was heated to 180° C. for depolymerization for 2 h. After the reaction was stopped, the mixture was cooled to room temperature and allowed to stand overnight, and the depolymerization product was precipitated from the water. After filtration, washing and vacuum drying, 85.2 g of J101010 (Table 2) product was obtained, and the degradation yield was 94%.

[0060] Depolymerization Example A7

[0061] 40.0 g of PA6 / 6T (6 / 6T molar ratio is 1) slices (0.334 mol of amide group), 146.3 g of adipic acid (1.001 mol, depolymerizer / amide group molar ratio is 3) and 120.2 g of water (6.680 mol, water / amide group molar ratio is 20) were added to a 600 ml high pressure reactor, and the mixture was stirred in a sealed manner after nitrogen replacement for 3 times, and the mixture was heated to 260° C. for depolymerization for 2 h. After the reaction was stopped, the mixture was cooled to room temperature and allowed to stand overnight, and the depolymerization product was precipitated from the water. After filtration, washing with water and vacuum drying, 77.2 g of a mixed product of J66 and J66T (Table 2) was obtained.

[0062] Depolymerization Example A8

[0063] 40.0 g of PA6 waste fiber foam material (amide group ~ 0.354 mol), 51.7 g of adipic acid (0.354 mol, depolymerizer / amide group molar ratio is ~ 1) and 127.4 g of water (7.08 mol, water / amide group molar ratio is 20) were added to a 600 ml high-pressure reactor, nitrogen substituted 3 times and then sealed and stirred, and the temperature was raised to 180° C. for depolymerization for 2 h; after stopping the reaction, the temperature was lowered to 90° C. and filtered while hot to obtain a homogeneous aqueous solution of the depolymerization product amide dicarboxylic acid J66 (Table 2); the filtrate was slowly cooled to room temperature and allowed to stand overnight, and the depolymerization product was precipitated from the water; after filtering, washing with water and vacuum drying, 65.2 g of J66 (Table 2) product was obtained, and the degradation yield was 71%.

[0064] Depolymerization Example A9

[0065] 40.0 g of PA5T powder (0.344 mol of amide group), 57.2 g of terephthalic acid PTA (0.344 mol, depolymerizer / amide group molar ratio of 1) and 247.9 g of water (13.77 mol, water / amide group molar ratio of 40) were added to a 600 ml high-pressure reactor, and the mixture was nitrogen-purged three times and stirred in a closed state. The mixture was heated to 290° C. for depolymerization for 6 h. After stopping the reaction, the mixture was slowly cooled to room temperature and allowed to stand overnight. The depolymerization product was precipitated from the water, and 97.3 g of JT5T (Table 2) product was obtained after filtration, washing with water and vacuum drying, with a degradation yield of 95%.

[0066] Depolymerization Example A10

[0067] 40.0 g (amide group 0.353 mol) of PA6 / 66 (6 / 66 molar ratio is 1) slices, 103.3 g (0.707 mol, depolymerizing agent / amide group molar ratio is 2) of adipic acid and 6.36 g (0.353 mol, water / amide group molar ratio is 1) of water were added into a 600 ml autoclave, and the mixture was stirred in a sealed state after nitrogen replacement for 3 times, and the mixture was heated to 150° C. for depolymerization for 3 h; after stopping the reaction, the mixture was cooled to 90° C. to obtain a homogeneous aqueous solution of a mixture of depolymerization products J66 and J666 (Table 2); after cooling to room temperature and standing overnight, the depolymerization product was precipitated from the water, and 82.6 g of a mixed product was obtained after filtration, washing with water and vacuum drying, and the degradation yield was 74%.

[0068] Depolymerization Example A11

[0069] 40.0 g of PA6 waste fiber foam material (amide group ~ 0.354 mol), 41.8 g of succinic acid (0.354 mol, depolymerizer / amide group molar ratio is ~ 1) and 127.4 g of water (7.08 mol, water / amide group molar ratio is 20) were added to a 600 ml high-pressure reactor, nitrogen substituted 3 times and then sealed and stirred, and the temperature was raised to 220° C. for depolymerization for 0.5 h; after stopping the reaction, the temperature was lowered to 90° C. and filtered while hot to obtain a homogeneous aqueous solution of the depolymerization product, imidocarboxylic acid J64 (Table 2); the filtrate was slowly cooled to room temperature and allowed to stand overnight, and the depolymerization product was precipitated from the water; after filtering, washing with water and vacuum drying, 63.5 g of imidocarboxylic acid J64 (Table 2) product was obtained, and the degradation yield was >92%.

[0070] Depolymerization Example A12

[0071] 40.0 g of TPU slices (0.129 mol of amide group), 37.8 g of adipic acid (0.258 mol, depolymerizer / amide group molar ratio of 2) and 45.62 g of water (2.58 mol, water / amide group molar ratio of 20) were added to a 600 ml high-pressure reactor, and the mixture was stirred in a closed state after nitrogen replacement for 3 times, and the temperature was raised to 100° C. for depolymerization for 24 h; the reaction was stopped and the temperature was lowered to obtain a mixture of depolymerization products of amide diacid J666, butanediol and polytetrahydrofuran.

[0072] Depolymerization Example A12

[0073] 40.0 g of polyester amide PEA62 chips (0.201 mol of amide group), 29.4 g of adipic acid (0.201 mol, depolymerizing agent / amide group molar ratio of 1) and 72.3 g of water (4.02 mol, water / amide group molar ratio of 20) were added to a 600 ml high-pressure reactor, and the mixture was stirred in a closed state after nitrogen replacement for 3 times, and the temperature was raised to 160° C. for depolymerization for 6 h; the reaction was stopped and the temperature was lowered to obtain a mixture of depolymerization products, amide diacid J666 and ethylene glycol.

[0074] Table 2. Types and structures of depolymerization products in various depolymerization examples

[0075]

[0076] Hydrolysis Example

[0077] Hydrolysis Example B1

[0078] 20 ml of 0.1 M dilute sulfuric acid solution was added to 20 g of depolymerization product J66 (from depolymerization example A8), and the mixture was heated to 200°C and refluxed for 4 h for hydrolysis. Thereafter, 7.5 g of caprolactam was obtained after hot filtration and cooling of the filtrate, and 10.3 g of adipic acid was obtained after washing and drying the filter residue.

[0079] Hydrolysis Example B2

[0080] 20 ml of 0.1 M NaOH solution was added to 20 g of depolymerization product J64 (from depolymerization example A11), and the temperature was raised to 190°C and refluxed for 3 h for hydrolysis. Thereafter, 7.2 g of caprolactam was obtained after hot filtration and cooling of the filtrate; 10.5 g of succinic acid was obtained after the filter residue was washed with water, acid washed and dried.

[0081] Repolymerization Example:

[0082] Repolymerization Example C1

[0083] 100g of depolymerization product J666 and 25.6g of ethylene glycol were added to the reactor. After nitrogen replacement for 3 times, the mixture was sealed and stirred. The catalyst ethylene glycol antimony was added and the temperature was raised to 180°C for esterification for 3h under nitrogen flow. The pressure was gradually reduced to below 100Pa within 1h and the temperature was raised to 240°C for condensation for 3h to obtain 101g of PEA62 polyester amide resin with a characteristic viscosity of 1.2.

[0084] Repolymerization Example C2

[0085] 100 g of the depolymerization product J666 (from depolymerization example A1), 50 g of water and 31.9 g of hexamethylenediamine were added to a high-pressure reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 200° C. for reaction for 2 h, and then the pressure was slowly released to normal pressure, and the temperature was gradually raised to 300° C. within 1.5 h under a nitrogen flow for condensation for 2 h; finally, the reaction was further condensed under vacuum for 0.5 h to obtain 107 g of PA66 polyamide resin with a relative viscosity of 2.3.

[0086] Repolymerization Example C3

[0087] 100g of the depolymerization product J666, 50g of water and 33.1g of 6-aminohexanol were added to a high-pressure reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 180°C and the reaction was carried out for 2h, and then the pressure was slowly released to normal pressure, and a catalyst stannous chloride was added and esterified for 3h under a nitrogen flow; the pressure was gradually reduced to below 100Pa within 1h, and then the temperature was raised to 240°C for condensation for 3h to obtain 101g of PEA66 polyester amide resin with a characteristic viscosity of 1.1.

[0088] Repolymerization Example C4

[0089] 100g of depolymerization product J666, 5g of aminobutyric acid and 21.7g of ethylene glycol were added to the reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 200°C and the reaction was carried out for 2h, and then the pressure was slowly released to normal pressure, and the catalyst tetrabutyl titanate was added and esterified for 3h under nitrogen flow; the pressure was gradually reduced to below 100Pa within 1h, and then the temperature was raised to 260°C for condensation for 3h to obtain 108g of PEA642 polyester amide resin with a characteristic viscosity of 1.1.

[0090] Repolymerization Example C5

[0091] 100g of depolymerization product J666, 5g of caprolactam and 21.7g of ethylene glycol were added to the reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 210°C and the reaction was carried out for 1.5h, and then the pressure was slowly released to normal pressure, and the catalyst tetrabutyl titanate was added and esterified for 3.5h under nitrogen flow; the pressure was gradually reduced to below 100Pa within 1h, and then the temperature was raised to 260°C for condensation for 3h to obtain 105g of PEA662 polyester amide resin with a characteristic viscosity of 0.95.

[0092] Repolymerization Example C6

[0093] 100g of depolymerization product J666, 5g of lactic acid and 21.7g of ethylene glycol were added to the reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 180°C and the reaction was carried out for 2h, and then the pressure was slowly released to normal pressure, and the catalyst ethylene glycol antimony was added and esterified for 3h under nitrogen flow; the pressure was gradually reduced to below 100Pa within 1h, and then the temperature was raised to 250°C and polycondensed for 3h to obtain 101g of PEA622 polyester amide resin with a characteristic viscosity of 1.0.

[0094] Repolymerization Example C7

[0095] 100g of depolymerization product J666, 5g of glycolide and 21.7g of ethylene glycol were added to the reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 200°C and the reaction was carried out for 2h, and then the pressure was slowly released to normal pressure, and the catalyst ethylene glycol antimony was added and esterified for 3h under nitrogen flow; the pressure was gradually reduced to below 100Pa within 1h, and then the temperature was raised to 260°C for condensation for 3h to obtain 105g of PEA262 polyester amide resin with a characteristic viscosity of 0.95.

[0096] Repolymerization Example C8

[0097] 100g of depolymerization product J666, 5g of caprolactone and 21.7g of ethylene glycol were added to the reactor, and the atmosphere was replaced with nitrogen three times and then stirred in a closed state; the temperature was raised to 190°C and the reaction was carried out for 2h, and then the pressure was slowly released to normal pressure, and a catalyst stannous chloride was added and esterified for 3h under a nitrogen flow; the pressure was gradually reduced to below 100Pa within 1h, and then the temperature was raised to 250°C and polycondensed for 3h to obtain 106g of PEA662 polyester amide resin with a characteristic viscosity of 1.0.

Claims

1. A method for depolymerization and regeneration of an amide-containing polymer, characterized in that The method comprises depolymerization, wherein the depolymerization comprises mixing an amide group-containing polymer, a dicarboxylic acid depolymerizing agent and water, sealing the mixture, and heating the mixture to a depolymerization temperature to degrade the mixture into small molecular compounds; wherein the amide group-containing polymer is one of polyamide, polyurethane or polyester amide; the ratio of the mole number of the dicarboxylic acid depolymerizing agent to the mole number of the amide group in the amide group-containing polymer is 1 to 3, and the ratio of the mole number of the water to the mole number of the amide group in the amide group-containing polymer is 1 to 40.

2. The depolymerization and regeneration method of an amide-containing polymer according to claim 1, characterized in that The depolymerization temperature is 120-290° C., the small molecule compound is one or more of amide carboxylic acid or amide dicarboxylic acid, and the depolymerization time is 0.5-24 hours.

3. The depolymerization and regeneration method of an amide-containing polymer according to claim 2, characterized in that It also includes hydrolysis, wherein the hydrolysis is to add an inorganic strong acid or an inorganic strong base solution to one or more of the imidocarboxylic acid or amide dicarboxylic acid to cleave the imido bond or amide bond, and then separate and purify to obtain two or more regenerated monomers.

4. The depolymerization and regeneration method of an amide-containing polymer according to claim 2, characterized in that It also includes separation and purification, wherein after the depolymerization is completed, the system is hot-filtered, the filtrate is cooled until the product is precipitated, and then filtered and washed to obtain purified imide carboxylic acid or amide dicarboxylic acid.

5. The depolymerization and regeneration method of an amide-containing polymer according to claim 2, characterized in that The imidocarboxylic acid has a molecular structure shown in Formula 1: ii. R and R1 in Formula 1 are independently one or more of an alkylene group or an arylene group iii. The amide dicarboxylic acid has a molecular structure shown in Formula 2 or Formula 3: iv. R, R2, R3 and R4 in Formula 2 and Formula 3 are independently one or more of an alkylene group or an arylene group.

6. The depolymerization and regeneration method of an amide-containing polymer according to claim 2 or 4, characterized in that The method further comprises repolymerization: adding one or more of diamine, amino alcohol, amino acid, lactam, diol, hydroxy acid, lactide or lactone monomers to the amide dicarboxylic acid for polycondensation to prepare recycled polyamide or polyester amide.

7. The depolymerization and regeneration method of an amide-containing polymer according to claim 1, characterized in that: The amide-containing polymer is a polyamide and contains more than one dicarboxylic acid unit on its main chain; the dicarboxylic acid depolymerizing agent is the same as one of the dicarboxylic acid monomers used to prepare the polyamide.

8. The depolymerization and regeneration method of an amide-containing polymer according to claim 7, characterized in that: The dicarboxylic acid depolymerizing agent is adipic acid or sebacic acid, and the ratio of the molar number of the dicarboxylic acid depolymerizing agent to the molar number of the amide groups in the amide group-containing polymer is 1.

9. The depolymerization and regeneration method of an amide-containing polymer according to claim 7, characterized in that: The amide group-containing polymer is one or more of PA46, PA56, PA66, PA510, PA610 or PA1010.

10. The depolymerization and regeneration method of an amide-containing polymer according to claim 6, characterized in that: One or more of tin, titanium or antimony catalysts are added during the repolymerization, and the temperature of the repolymerization is 160-300°C.

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