Method for preparing high-heat-resistance and high-transparency polyesteramide by recycling waste PET (Polyethylene Terephthalate)

Abstract

The invention provides a method for preparing high-heat-resistance and high-transparency polyesteramide by recycling waste PET (polyethylene terephthalate), which comprises the following steps: (1) carrying out alcoholysis reaction on a first raw material system comprising waste PET, an alcoholysis agent and an alcoholysis catalyst to obtain an alcoholysis system; (2) carrying out aminolysis reaction on a second raw material system containing the alcoholysis system, a diamine aminolysis agent and an aminolysis catalyst to obtain an aminolysis system; (3) carrying out exchange reaction on the aminolysis system to obtain an exchange system and an alcoholysis agent recovery system; the exchange reaction comprises ester exchange reaction and / or amide exchange reaction; and (4) carrying out polymerization reaction on the to-be-polymerized system comprising the exchange system to obtain regenerated polyesteramide. The PET recovery method provided by the invention is simple and efficient, and the waste polyester can be effectively upgraded into a high-added-value and high-functionalization material.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, and in particular to a method for preparing high heat-resistant and high-transparency polyesteramide by recycling waste PET. Background Technology

[0002] Polyethylene terephthalate (PET), as a widely used general-purpose plastic, has brought corresponding environmental pressures due to its massive consumption in packaging, textiles, and other fields. Waste PET is difficult to degrade in the natural environment, and improper disposal can cause long-term "white pollution." Furthermore, its production relies on petroleum resources. Therefore, developing efficient PET chemical recycling technologies to depolymerize it into original monomers or intermediates to achieve a closed-loop cycle is of urgent need and significant importance for reducing environmental pollution, conserving fossil resources, and promoting the sustainable development of the plastics economy.

[0003] However, the current industrialization path for PET chemical depolymerization and recycling still faces significant challenges. On the one hand, existing depolymerization processes are often complex, involving multiple reactions and cumbersome separation and purification steps, resulting in high energy consumption, stringent operational requirements, and a difficulty in balancing overall efficiency and economics. On the other hand, and more critically, the recycled polymers produced by repolymerizing monomers or intermediates recovered using existing technologies are typically significantly inferior to petroleum-based virgin polymers in key physicochemical properties, especially in terms of heat resistance and optical transparency, making it difficult to meet the stringent material quality requirements of high-end packaging, high-performance fibers, and other fields. This forces recycled PET to be used in a downgraded manner, preventing the realization of a high-value-added closed-loop cycle and hindering the economic feasibility and large-scale promotion of chemical recycling processes.

[0004] Therefore, in view of the core problems of the existing PET depolymerization technology, such as the complexity of the process and the poor material properties (especially heat resistance and optical properties) of the depolymerized products after repolymerization, there is an urgent need to develop a new depolymerization and purification method that is simpler, more efficient and can retain the structural integrity of the product with high quality. Summary of the Invention

[0005] This invention provides a method for preparing high heat-resistant and high-transparency polyesteramide by recycling waste PET. This method is applicable to the recycling of waste PET and has the advantages of being simple, efficient, and able to effectively upgrade waste polyester into high-value-added and high-functionality materials.

[0006] This invention provides a method for preparing high heat-resistant and high-transparency polyesteramide by recycling waste PET, comprising the following steps: (1) subjecting a first raw material system including waste PET, an alcoholysis agent, and an alcoholysis catalyst to an alcoholysis reaction to obtain an alcoholysis system; (2) subjecting a second raw material system including the alcoholysis system, a diamine-based aminolysis agent, and an aminolysis catalyst to an aminolysis reaction to obtain an aminolysis system; (3) subjecting the aminolysis system to an exchange reaction to obtain an exchange system and an alcoholysis agent recovery system; the exchange reaction includes an ester exchange reaction and / or an amide exchange reaction; (4) subjecting a polymerization system including the exchange system to a polymerization reaction to obtain recycled polyesteramide; the aminolysis system includes bis(2-hydroxyethyl) terephthalate and a compound shown in Formula 1.

[0007] Formula 1;

[0008] n is an integer from 1 to 5, R comes from the diamine hydrolysate, and R is a C10 to C15 alicyclic ring.

[0009] Optionally, the diamine hydrolysate has the structure shown in Formula 2, NH2-R-NH2 (Formula 2).

[0010] Optionally, the diamine-based aminolytic agent includes at least one of 4,4'-diaminodicyclohexylmethane, isophorone diamine, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and 4,4'-isopropyldicyclohexylamine.

[0011] Optionally, the amount of the diamine-based aminolysis agent is 30% to 90% of the amount of terephthalic acid in the waste PET.

[0012] Optionally, in the alcoholysis reaction, the reaction temperature is 200°C~240°C and the time is 1h~2h; and / or, in the aminolysis reaction, the reaction temperature is 200°C~220°C and the time is 2h~6h; and / or, in the exchange reaction, the reaction temperature is 250°C~260°C and the time is 2h~5h, and the pressure is 50kPa~150kPa; and / or, in the polymerization reaction, the reaction temperature is 265°C~280°C and the time is 2h~5h, and the pressure is 20Pa~60Pa; and / or, the reaction further includes a step of returning the alcoholysis agent recovery system to participate in the alcoholysis reaction.

[0013] Optionally, the alcoholysis agent comprises ethylene glycol; and / or, the alcoholysis catalyst comprises at least one of zinc acetate, sodium acetate, and cobalt acetate; and / or, the aminolysis catalyst comprises at least one of 1,5,7-triazabicyclo[4.4.0]decen-5-ene, tetramethylguanidine, and 1,8-diazabicyclo[5.4.0]undec-7-ene; and / or, the mass ratio of the alcoholysis agent to the waste PET is (1~3):1; and / or, the mass ratio of the alcoholysis catalyst to the waste PET is 0.1%~0.5%; and / or, the mass ratio of the aminolysis catalyst to the waste PET is 0.5%~1.0%.

[0014] Optionally, the polymerization system further includes one or more of a polymerization catalyst, a stabilizer, and an antioxidant; wherein the polymerization catalyst includes one or more of antimony trioxide, antimony glycolide, titanium glycolide, tetrabutyl titanate, tetraisopropyl titanate, and germanium dioxide; and / or, the stabilizer includes one or more of phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and triphenyl phosphite; and / or, the antioxidant includes one or more of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and tris[2,4-di-tert-butylphenyl]phosphite.

[0015] Optionally, in the polymerization catalyst, the mass ratio of the metal element to the recycled polyesteramide is 5ppm to 150ppm, the mass ratio of the stabilizer to the recycled polyesteramide is 5ppm to 25ppm, and the mass ratio of the antioxidant to the recycled polyesteramide is 100ppm to 3000ppm.

[0016] The present invention also provides a recycled polyesteramide, which is prepared according to the above-described method for recycling waste PET.

[0017] Optionally, the heat distortion temperature of the recycled polyesteramide is 80.4°C to 161.3°C; and the transmittance is 87.1% to 93.6%.

[0018] This invention provides a method for preparing high-heat-resistant and high-transparency polyesteramide from waste PET recycling, which has at least the following beneficial effects: The waste PET recycling method of this invention achieves one-pot depolymerization and functionalized regeneration of waste polyester through a series of alcoholysis and ammonolysis reactions, combined with exchange reactions (ester exchange and / or amide exchange) and polymerization processes. Simultaneously, by controlling the amount and type of diamine ammonolysis agent added, the chain segment structure and properties (such as heat resistance and light transmittance) of the regenerated polyesteramide can be flexibly adjusted, ultimately obtaining a high-value-added regenerated polyesteramide material with high heat resistance and high transparency. Specifically, this invention employs a synergistic depolymerization method combining sequential alcoholysis and ammonolysis. This method first depolymerizes PET through alcoholysis, and then the key step is to further ammonolyze the alcoholysis system, precisely converting the intermediate into bis(2-hydroxyethyl) terephthalate (BHET) and the product shown in Formula 1. The aminolysis product of the compound (BHET-A-BHET monomer or polymer) serves as a monomer precursor for subsequent repolymerization. This product can more effectively recombine into high-quality recycled polyester with a regular molecular chain structure and extremely low impurity content, thereby achieving the dual goals of simplifying the process and improving the key physicochemical properties of recycled materials (especially heat resistance and optical properties). This avoids multiple separation and purification steps, simplifying the process flow. At the same time, the introduction of diamine-based aminolysis agents disrupts the regularity of the molecular chain segments of the alcoholysis product, reducing crystallinity. Simultaneously, amide bonds are introduced to enhance intermolecular forces, thereby synergistically improving the heat resistance and transparency of the material. Through exchange reactions (ester exchange and / or amide exchange reactions), the exchange system is transformed into recycled polyesteramide with a controllable chain segment structure. Combined with the polymerization process, the molecular weight and distribution are further optimized, achieving targeted regulation of the performance of waste PET materials. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the present invention and are not intended to limit the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] To ensure the recycled products retain excellent properties (especially heat resistance and optical properties), the inventors analyzed current recycling methods and concluded that the root cause of performance defects likely lies in the relatively limited way traditional single depolymerization pathways cut PET molecular chains. This results in insufficient structural purity and regularity of the obtained monomers / oligomers, and makes it difficult to fully restore the original polymer chain structure and sequence regularity during subsequent repolymerization. Therefore, a process that can more precisely control the structure of the depolymerized products is needed to overcome these limitations.

[0021] Based on this, embodiments of the present invention provide a method for recycling waste PET, comprising the following steps: (1) subjecting a first raw material system including waste PET, an alcoholysis agent, and an alcoholysis catalyst to an alcoholysis reaction to obtain an alcoholysis system; (2) subjecting a second raw material system including the alcoholysis system, a diamine-based aminolysis agent, and an aminolysis catalyst to an aminolysis reaction to obtain an aminolysis system; (3) subjecting the aminolysis system to an exchange reaction to obtain an exchange system and an alcoholysis agent recovery system; the exchange reaction includes an ester exchange reaction and / or an amide exchange reaction; (4) subjecting a polymerization system including the exchange system to a polymerization reaction to obtain recycled polyesteramide; the aminolysis system includes bis(2-hydroxyethyl) terephthalate and the compound shown in Formula 1.

[0022] Formula 1;

[0023] n is an integer from 1 to 5, R comes from diamine aminolytic agents, and R is a C10 to C15 alicyclic ring.

[0024] (1) The first raw material system, including waste PET, alcoholysis agent and alcoholysis catalyst, is subjected to alcoholysis reaction to obtain alcoholysis system.

[0025] For example, step (1) may specifically include: cleaning and drying waste PET, and then carrying out an alcoholysis reaction of a first raw material system including waste PET, alcoholysis agent and alcoholysis catalyst under a nitrogen atmosphere to obtain an alcoholysis system.

[0026] Alcohololysis can break down PET molecular chains into oligomers, and a nitrogen atmosphere can suppress side reactions.

[0027] Specifically, waste PET can include one or more of waste PET bottle flakes and polyester filaments.

[0028] The alcoholysis reaction can be carried out in a stainless steel reactor.

[0029] (2) A second raw material system, including an alcoholysis system, a diamine aminolysis agent and an aminolysis catalyst, is subjected to an aminolysis reaction to obtain an aminolysis system.

[0030] For example, step (2) may specifically include: subjecting a second raw material system, including an alcoholysis system, a diamine aminolysis agent and an aminolysis catalyst, to an aminolysis reaction under a nitrogen atmosphere to obtain an aminolysis system (depolymerization liquid).

[0031] Amine hydrolysis can further depolymerize oligomers obtained from alcoholysis into an aminolytic system.

[0032] The aminolysis system may include one or more of bis(2-hydroxyethyl) terephthalate (BHET) and compounds of Formula 1 (BHET-A-BHET monomers or polymers).

[0033] Formula 1,

[0034] Where n can be an integer from 1 to 5, R can come from a diamine aminolytic agent, and R can be a C10 to C15 alicyclic ring.

[0035] n can be an integer from 1 to 5, such as 1, 2, 3, 4, 5, or any combination of two of them.

[0036] R can be an alicyclic ring of C10 to C15.

[0037] (3) The aminolysis system is subjected to an exchange reaction to obtain an exchange system and an alcoholysis agent recovery system.

[0038] For example, step (3) may specifically include: subjecting the amine hydrolysis system to an exchange reaction under heating conditions, and obtaining the exchange system and the alcoholysis agent recovery system after liquid phase separation.

[0039] Exchange reactions can promote the recombination of PET segments by dynamically regulating the structure of the aminolysis system.

[0040] Specifically, the exchange reaction can include ester exchange reaction and / or amide exchange reaction.

[0041] Furthermore, alcoholysis reactions can include transesterification reactions, and aminolysis reactions can include amide exchange reactions.

[0042] Liquid phase separation can separate the alcoholysis agent recovery system in the esterification tower through fractionation.

[0043] The alcoholysis agent recovery system may include the alcoholysis agent in step (1).

[0044] Based on alcoholysis, diamine aminolysis agents and aminolysis catalysts are introduced to carry out a series of depolymerization reactions, which can improve the depolymerization efficiency. The resulting aminolysis system (depolymerization liquid) can be directly carried out exchange reactions without the need for cumbersome separation and purification steps. The process is simple, with high depolymerization efficiency and low energy consumption.

[0045] (4) The polymerizing system, including the exchange system, is subjected to a polymerization reaction to obtain recycled polyesteramide.

[0046] For example, step (4) may specifically include: mixing the system to be polymerized, including the exchange system, removing the alcoholysis agent under a low vacuum environment of 5 kPa to 20 kPa, and then carrying out the polymerization reaction to obtain recycled polyesteramide.

[0047] Polymerization can further transform the exchange system into regenerated polyesteramide with a controllable chain segment structure.

[0048] The pressure of a low vacuum can be 5 kPa to 20 kPa, for example, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20 kPa or any combination thereof.

[0049] Vacuum conditions within the above range can promote the removal of small molecule byproducts (such as alcoholysis agents) and increase the molecular weight of recycled polyesteramide.

[0050] Furthermore, the temperature for removing the alcoholysis agent can be 250°C to 265°C, for example, 250, 255, 260, 265°C or any combination thereof.

[0051] When the temperature for removing the alcoholysis agent meets the above-mentioned range, the alcoholysis agent can be removed more effectively.

[0052] The time for removing the alcoholysis agent can be 1h to 2h, for example, 1, 1.5, 2h or any combination thereof.

[0053] If the time required to remove the alcoholysis agent meets the above-mentioned range, the alcoholysis agent can be completely removed.

[0054] According to research and analysis, the waste PET recycling method of this invention achieves one-pot depolymerization and functional regeneration of waste polyester through a series of alcoholysis and ammonolysis reactions, combined with exchange reactions (ester exchange and / or amide exchange) and polymerization processes. Simultaneously, by controlling the amount and type of diamine ammonolysis agent added, the chain segment structure and properties (such as heat resistance and light transmittance) of the recycled polyester amide can be flexibly adjusted, ultimately obtaining a high-value-added recycled polyester amide material with high heat resistance and high transparency. Specifically, this invention employs a synergistic depolymerization method combining sequential alcoholysis and ammonolysis. This method first depolymerizes PET through alcoholysis, and then the key step is to further ammonolyze the alcoholysis system, precisely converting the intermediate into bis(2-hydroxyethyl) terephthalate (BHET) and the compound shown in Formula 1 (BHET-A-BH). The aminolysis product of ET monomers or polymers can be used as a monomer precursor for subsequent repolymerization. This product can be more effectively repolymerized into high-quality recycled polyester with regular molecular chain structure and extremely low impurity content. This achieves the dual goals of simplifying the process and improving the key physicochemical properties of recycled materials (especially heat resistance and optical properties). It avoids multiple separation and purification steps and simplifies the process flow. At the same time, by introducing diamine aminolysis agents, the regularity of the molecular chain segments of the alcoholysis product is destroyed, the crystallinity is reduced, and amide bonds are introduced to enhance intermolecular forces, thereby synergistically improving the heat resistance and transparency of the material. Through exchange reactions (ester exchange and / or amide exchange reactions), the exchange system is converted into recycled polyester amide with a controllable chain segment structure. Combined with the polymerization process, the molecular weight and distribution are further optimized to achieve targeted regulation of the performance of waste PET materials.

[0055] In some embodiments, the diamine aminolysis agent has the structure shown in Formula 2, NH2-R-NH2 Formula 2.

[0056] Diamine-based aminolysis agents can introduce the structure shown in Formula 2. Furthermore, they can introduce amide bonds (-NH-CO-) into the aminolysis system. The higher thermal decomposition temperature, stronger rigidity, and tunable transparency of amide bonds can provide better heat resistance and mechanical and optical properties for recycled polyesteramides.

[0057] In some specific embodiments, Formula 2 refers to the "A" component in BHET-A-BHET above. Specifically, BHET-A-BHET is BHET-NH-R-NH-BHET.

[0058] Furthermore, when n is 1, the structure in Equation 1 can represent the monomer of BHET-NH-R-NH-BHET; when n is an integer from 2 to 5, the structure in Equation 1 can represent BHET-(NH-R-NH-BHET). n - polymers.

[0059] In some specific embodiments, in Formula 2, R can be an alicyclic ring of C10 to C15.

[0060] Specifically, diamine-based aminosolvents may include at least one of 4,4'-diaminodicyclohexylmethane, isophorone diamine, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and 4,4'-isopropyldicyclohexylamine.

[0061] The aforementioned diamine hydrolysants are alicyclic diamines, whose alicyclic structure has excellent thermal stability and is light in color and does not easily turn yellow. They can impart excellent high-temperature resistance and high transparency to recycled polyester amides.

[0062] In some embodiments, the amount of diamine-based aminosolvent can be 30% to 90% of the amount of terephthalic acid in waste PET, for example, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, or any combination thereof.

[0063] When the amount of diamine-based aminolytic agents added meets the above-mentioned range, it can better achieve the depolymerization and chain breaking of PET chains in waste PET, better control the content of ester bonds and amide bonds in PET and the chain segment structure of PET, and realize the controllability of the heat resistance and light transmittance of recycled polyester amide. Furthermore, it provides a new method for the recycling and high-value utilization of waste PET, which is of great significance.

[0064] In some specific embodiments, the reaction temperature in the alcoholysis reaction can be 200°C to 240°C, and the reaction time can be 1 hour to 2 hours.

[0065] The temperature for alcoholysis can be 200°C to 240°C, for example, 200, 210, 220, 230, 240°C or any combination thereof.

[0066] When the temperature of the alcoholysis reaction meets the above range, the rate of the alcoholysis reaction can be increased, the viscosity of the first raw material system can be reduced, and the mass transfer and mixing of the first raw material system can be facilitated.

[0067] The alcoholysis reaction can take 1 to 2 hours, for example, 1, 1.5, 2 hours or any combination thereof.

[0068] If the alcoholysis reaction time meets the above range, it can ensure the complete progress of the alcoholysis reaction, so that waste PET is converted into oligomers or monomers, which is conducive to more complete depolymerization of waste PET.

[0069] In the aminolysis reaction, the reaction temperature can be 200°C to 220°C, and the time can be 2h to 6h.

[0070] The temperature for the aminolysis reaction can be 200°C to 220°C, for example, 200, 205, 210, 215, 220°C or any combination thereof.

[0071] The temperature range of the aminolysis reaction is within the above range, which is conducive to the formation of amide bonds, inhibits the occurrence of side reactions, and further improves the depolymerization degree of waste PET.

[0072] In the exchange reaction, the reaction temperature can be 250°C~260°C, the time can be 2h~5h, and the pressure can be 50kPa~150kPa.

[0073] The temperature of the exchange reaction can be 250°C to 260°C, for example, 250, 251, 252, 253, 254, 255, 256, 257, 258, 259, 260°C or any combination thereof.

[0074] When the exchange reaction temperature meets the above range, the rate of the exchange reaction can be increased, which is beneficial to the further depolymerization of waste PET.

[0075] The exchange reaction time can be 2h to 5h, for example, 2, 3, 4, 5h or any combination thereof.

[0076] The exchange reaction time meets the above range, enabling the prepolymerization (precondensation) reaction of bis(2-hydroxyethyl) terephthalate (BHET) and the compound shown in Formula 1 (BHET-A-BHET monomer or polymer) to facilitate subsequent further polymerization (condensation) into recycled polyester.

[0077] The pressure for the exchange reaction can be 50 kPa to 150 kPa, for example, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 kPa or any combination thereof.

[0078] When the pressure of the exchange reaction meets the above range, it is beneficial to remove volatile byproducts and some alcoholysis agents, improve the purity of the recycled polyesteramide, and thus further improve the physical properties of the recycled polyesteramide.

[0079] In the polymerization reaction, the reaction temperature can be 265°C~280°C, the time can be 2h~5h, and the pressure can be 20Pa~60Pa.

[0080] The polymerization temperature can be 265°C to 280°C, for example, 265, 270, 275, 280°C or any combination thereof.

[0081] When the polymerization temperature meets the above range, the polymerization rate (condensation reaction) can be increased, the viscosity of the polymerizable system including the exchange system can be reduced, the removal of by-products can be facilitated, the purity of recycled polyesteramide can be improved, and the physical properties such as high temperature resistance and optical properties of recycled polyesteramide can be further improved.

[0082] The polymerization reaction can take 2 to 5 hours, for example, 2, 3, 4, 5 hours or any combination thereof.

[0083] If the polymerization reaction time meets the above range, the polymerization reaction can be completed, and the molecular weight of the recycled polyesteramide can reach the target (100kDa~200kDa).

[0084] The pressure for the polymerization reaction can be 20 Pa to 60 Pa, for example, 20, 30, 40, 50, 60 Pa or any combination thereof.

[0085] The polymerization reaction, by meeting the aforementioned high vacuum environment, can efficiently remove low-molecular-weight byproducts and alcoholysis agents, thereby increasing the molecular weight of the recycled polyesteramide product and further obtaining recycled polyesteramide with high heat resistance and high transparency.

[0086] In some specific embodiments, the method also includes a step of returning the alcoholysis agent recovery system to participate in the alcoholysis reaction, thereby realizing the recycling of the alcoholysis agent.

[0087] In some embodiments, the alcoholysis agent may include ethylene glycol.

[0088] The alcoholysis agent meets the above requirements, is inexpensive and has few side reactions, which is conducive to the generation of bis(2-hydroxyethyl) terephthalate (BHET) monomer, and further, is conducive to the synthesis of recycled polyesteramide.

[0089] The mass ratio of the hydrolysis agent to the waste PET can be (1~3):1, for example, 1:1, 2:1, 3:1 or any combination thereof.

[0090] The addition of alcoholysis agent within the above range is beneficial to the generation of oligomers with hydroxyl (-OH) end groups, thus providing a precursor with a well-defined structure and suitable reactivity for the subsequent preparation of recycled polyesteramide.

[0091] The alcoholysis catalyst may include at least one of zinc acetate, sodium acetate, and cobalt acetate.

[0092] The alcoholysis catalyst meets the above criteria, can rapidly catalyze the alcoholysis reaction, is inexpensive, has good selectivity for the depolymerization of PET, and reduces the occurrence of side reactions.

[0093] The mass ratio of the alcoholysis catalyst to the waste PET is 0.1% to 0.5%, for example, 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, or any combination thereof.

[0094] The amount of alcoholysis catalyst added meets the above range, which can both improve the rate of alcoholysis reaction and reduce costs.

[0095] The aminolysis catalyst may include at least one of 1,5,7-triazabicyclo[4.4.0]decen-5-ene, tetramethylguanidine, and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0096] Amine hydrolysis catalysts that meet the above criteria can overcome the reaction bottleneck of the aminolysis reaction and improve the reaction rate of the aminolysis reaction.

[0097] Furthermore, the mass ratio of the amine hydrolysis catalyst to the waste PET can be 0.5% to 1.0%, for example, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or any combination thereof.

[0098] When the amount of aminolysis catalyst added meets the above range, it can increase the reaction rate of the aminolysis reaction and enable the waste PET to be completely depolymerized.

[0099] In some embodiments, the polymerization system may further include one or more of a polymerization catalyst, a stabilizer, and an antioxidant.

[0100] Specifically, the polymerization catalyst may include one or more of antimony trioxide, antimony glycolate, titanium glycolate, tetrabutyl titanate, tetraisopropyl titanate, and germanium dioxide.

[0101] Polymer catalysts that meet the above criteria can improve the activity of polymerization reactions, reduce the generation of side reactions, and improve the optical properties of regenerated polyesteramide (high transparency and white color).

[0102] Stabilizers may include one or more of phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and triphenyl phosphite.

[0103] Stabilizers that meet the above criteria can prevent over-catalysis in the early stages of polymerization and inhibit the binding of metal ions (such as antimony and titanium) in the polymerization catalyst in the later stages of polymerization, thereby reducing the activity of metal ions in catalyzing the degradation of ester bonds and / or amide bonds.

[0104] In some specific embodiments, the antioxidant may include one or more of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant 1010), octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate (antioxidant 1076), N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine (antioxidant 1098), bis(2,4-dicumylphenyl)pentaerythritol diphosphite (antioxidant 608), and tris[2,4-di-tert-butylphenyl]phosphite (antioxidant 168).

[0105] Antioxidants that meet the above criteria can inhibit the thermal oxidative degradation caused by oxygen during the polymerization process, prevent the breakage, cross-linking and yellowing of recycled polyester amide molecular chains, and improve the heat resistance and optical properties of recycled polyester amide.

[0106] Furthermore, in the polymerization catalyst, the mass ratio of the metal element to the mass of the recycled polyesteramide can be 5 ppm to 150 ppm, calculated as a metal element.

[0107] Metallic elements may include one or more of titanium, antimony, and germanium.

[0108] The amount of polymerization catalyst added can be calculated as a metal element, and the mass ratio of the metal element to the mass of the regenerated polyester amide can be 5 ppm to 150 ppm, for example, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, 150 ppm or any combination thereof.

[0109] The addition amount of polymerization catalyst within the above range can avoid excessive catalysis leading to accelerated thermal degradation and color deterioration, which is beneficial to improving the heat resistance and optical properties of recycled polyester amide.

[0110] In some embodiments, the mass ratio of the stabilizer to the recycled polyesteramide, based on phosphorus content, can be 5 ppm to 25 ppm, for example, a range of 5, 10, 15, 20, 25 ppm or any combination thereof.

[0111] When the amount of stabilizer added meets the above range, it can effectively passivate the metal in the residual polymerization catalyst, significantly reduce thermal degradation in the later stage of polymerization, improve the hue of the recycled polyester amide, and further improve the optical properties of the recycled polyester amide.

[0112] Furthermore, the mass ratio of the antioxidant to the recycled polyester amide can be 100ppm to 3000ppm, for example, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1500, 2000, 2500, 3000ppm or any combination thereof.

[0113] When the amount of antioxidant added meets the above range, it can provide sufficient oxidative stability for the polymerization process, which is beneficial to improving the optical properties of recycled polyester amide.

[0114] This invention also provides a recycled polyesteramide, prepared according to the above-described waste PET recycling method.

[0115] The aforementioned recycled polyesteramide exhibits excellent heat resistance and optical properties.

[0116] In some specific embodiments, the heat distortion temperature of the recycled polyesteramide can be 80.4°C to 161.3°C, for example, 80.4, 125.7, 127.8, 137.7, 161.3°C or any combination thereof.

[0117] The heat distortion temperature of recycled polyesteramide meets the above range, proving that it has excellent heat resistance.

[0118] Furthermore, the transmittance of the recycled polyesteramide can be 87.1% to 93.6%, for example, 87.1%, 90.1%, 91.3%, 92.2%, 93.6% or any combination thereof.

[0119] The transmittance of recycled polyesteramide meets the above range, proving that it has excellent optical properties.

[0120] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0121] Example 1

[0122] This embodiment provides a method for recycling waste PET, the specific process of which is as follows:

[0123] (1) 1 kg of waste PET bottle flakes and polyester filaments (waste PET) are cleaned and dried. The first raw material system, including waste PET, 1 kg of ethylene glycol (EG, alcoholysis agent) and 5 g of zinc acetate (alcoholysis catalyst), is added to a 5 L stainless steel reactor and alcoholysis reaction is carried out at 200°C for 2 h under nitrogen atmosphere to obtain alcoholysis system.

[0124] (2) The second raw material system, including the alcoholysis system, 1.56 mol of 4,4'-diaminodicyclohexylmethane (a diamine aminolysis agent, the amount of which accounts for 30% of the amount of terephthalic acid in PET), and 5 g of 1,5,7-triazabicyclo[4.4.0]decene-5-ene (aminolysis catalyst), is subjected to aminolysis at 200°C for 2 h under a nitrogen atmosphere to obtain the aminolysis system (depolymerization liquid);

[0125] (3) The amine hydrolysis system (depolymerization liquid) is subjected to ester exchange and / or amide exchange (exchange reaction) at 250°C and 50 kPa nitrogen pressure for 2 h. After liquid phase separation, the exchange system and ethylene glycol (alcoholization agent recovery system) are obtained.

[0126] (4) Mix the polymerization system including the exchange system, tetrabutyl titanate (polymerization catalyst, Ti=5ppm), antimony trioxide (polymerization catalyst, Sb=30ppm), phosphoric acid (stabilizer, P=3ppm), triphenyl phosphate (stabilizer, P=2ppm), 1200 ppm pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant, antioxidant 1010) and 1800 ppm tris[2,4-di-tert-butylphenyl] phosphite (antioxidant, antioxidant 168), react for 1 h at 250°C and 10 kPa to remove excess ethylene glycol (alcoholization agent), and then carry out the polymerization reaction at 265°C and 30 Pa for 2 h. After the reaction is completed, pull the pellets and dry them to obtain recycled polyesteramide chips.

[0127] Example 2

[0128] This embodiment provides a method for recycling waste PET, the specific process of which is as follows:

[0129] (1) 1 kg of waste PET bottle flakes and polyester filaments (waste PET) are cleaned and dried, and the first raw material system including waste PET, 1.5 kg of ethylene glycol (EG, alcoholysis agent) and 3 g of zinc acetate (alcoholysis catalyst) is added to a 5 L stainless steel reactor and alcoholysis reaction is carried out at 240°C for 1 h under nitrogen atmosphere to obtain alcoholysis system;

[0130] (2) The second raw material system, including the alcoholysis system, 3.38 mol of 4,4'-diaminodicyclohexylmethane (a diamine aminolysis agent, the amount of which accounts for 65% of the amount of terephthalic acid in PET), and 7.4 g of 1,5,7-triazabicyclo[4.4.0]decene-5-ene (aminolysis catalyst), is subjected to aminolysis at 210°C for 4 h under a nitrogen atmosphere to obtain the aminolysis system (depolymerization liquid);

[0131] (3) The amine hydrolysis system (depolymerization liquid) is subjected to ester exchange and / or amide exchange (exchange reaction) at 255°C and 100kPa nitrogen pressure for 4 hours. After liquid phase separation, the exchange system and ethylene glycol (alcoholization agent recovery system) are obtained.

[0132] (4) Mix the polymerization system including the exchange system, titanium glycol (polymerization catalyst, Ti=6ppm), antimony glycol (polymerization catalyst, Sb=100ppm), trimethyl phosphate (stabilizer, P=25ppm), 50ppm pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant, antioxidant 1010) and 50ppm bis(2,4-dicumylphenyl)pentaerythritol-diphosphite (antioxidant, antioxidant 608), react for 1h at 260°C and 10kPa to remove excess ethylene glycol (alcoholization agent), and then carry out the polymerization reaction at 275°C and 40Pa for 4h. After the reaction is completed, pull the pellets and dry them to obtain recycled polyesteramide chips.

[0133] Example 3

[0134] This embodiment provides a method for recycling waste PET, the specific process of which is as follows:

[0135] (1) 1 kg of waste PET bottle flakes and polyester filaments (waste PET) are washed and dried, and the first raw material system including waste PET, 2 kg of ethylene glycol (EG, alcoholysis agent) and 2 g of zinc acetate (alcoholysis catalyst) is added to a 5 L stainless steel reactor. The alcoholysis reaction is carried out at 220 °C for 1.5 h under nitrogen atmosphere to obtain the alcoholysis system.

[0136] (2) The second raw material system, including the alcoholysis system, 4.68 mol of 4,4'-diaminodicyclohexylmethane (a diamine aminolysis agent, the amount of which accounts for 90% of the amount of terephthalic acid in PET), and 10 g of 1,5,7-triazabicyclo[4.4.0]decene-5-ene (aminolysis catalyst), is subjected to aminolysis at 220°C for 6 h under a nitrogen atmosphere to obtain the aminolysis system (depolymerization liquid);

[0137] (3) The amine hydrolysis system (depolymerization liquid) is subjected to ester exchange and / or amide exchange (exchange reaction) at 260℃ and 150kPa nitrogen pressure for 5h. After liquid phase separation, the exchange system and ethylene glycol (alcoholization agent recovery system) are obtained.

[0138] (4) Mix the system to be polymerized, which includes the exchange system, tetraisopropyl titanate (polymerization catalyst, Ti=10ppm), triethyl phosphate (stabilizer, P=25ppm), 900ppm β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol (antioxidant, antioxidant 1076) and 1100ppm tris[2,4-di-tert-butylphenyl]phosphite (antioxidant, antioxidant 168), and react it for 1h at a low vacuum of 265°C and 10kPa to remove excess ethylene glycol (alcoholization agent). Then, polymerize it at 280°C and a high vacuum of 20Pa for 5h to obtain recycled polyesteramide. After the reaction is completed, pull the strips, cut them into pellets and dry them to obtain recycled polyesteramide chips.

[0139] Example 4

[0140] This embodiment provides a method for recycling waste PET, the specific process of which is as follows:

[0141] (1) 1 kg of waste PET bottle flakes and polyester filaments (waste PET) are cleaned and dried. The first raw material system, including waste PET, 3 kg of ethylene glycol (EG, alcoholysis agent) and 1 g of zinc acetate (alcoholysis catalyst), is added to a 5 L stainless steel reactor and alcoholysis reaction is carried out at 200°C for 2 h under nitrogen atmosphere to obtain alcoholysis system;

[0142] (2) The second raw material system, including the alcoholysis system, 3.64 mol of isophorone diamine (a diamine aminolysis agent, whose amount accounts for 70% of the amount of terephthalic acid in PET), and 8.6 g of tetramethylguanidine (aminolysis catalyst), is subjected to aminolysis reaction at 215 °C for 5 h under nitrogen atmosphere to obtain the aminolysis system (depolymerization liquid).

[0143] (3) The amine hydrolysis system (depolymerization liquid) is subjected to ester exchange and / or amide exchange (exchange reaction) at 258°C and 80 kPa nitrogen pressure for 5 h. After liquid phase separation, the exchange system and ethylene glycol (alcoholization agent recovery system) are obtained.

[0144] (4) Mix the polymerization system including the exchange system, germanium dioxide (polymerization catalyst, Ge=150ppm), triphenyl phosphite (stabilizer, P=15ppm), and 800ppm tris[2,4-di-tert-butylphenyl]phosphite (antioxidant, antioxidant 168), and react it for 1h at 265°C and 10kPa to remove excess ethylene glycol (alcoholization agent). Then, carry out the polymerization reaction at 275°C and 60Pa for 3h. After the reaction is completed, pull the strips, cut them into pellets and dry them to obtain recycled polyesteramide chips.

[0145] Example 5

[0146] This embodiment provides a method for recycling waste PET, the specific process of which is as follows:

[0147] (1) 1 kg of waste PET bottle flakes and polyester filaments (waste PET) are cleaned and dried, and the first raw material system including waste PET, 1.8 kg of ethylene glycol (EG, alcoholysis agent) and 2.5 g of zinc acetate (alcoholysis catalyst) is added to a 5 L stainless steel reactor and alcoholysis reaction is carried out at 200°C for 2 h under nitrogen atmosphere to obtain alcoholysis system;

[0148] (2) The second raw material system, including the alcoholysis system, 2.60 mol of isophorone diamine (a diamine aminolysis agent, the amount of which accounts for 50% of the amount of terephthalic acid in PET), and 6.1 g of 1,8-diazabicyclo[5.4.0]undec-7-ene (aminolysis catalyst), is subjected to aminolysis at 205 °C for 3 h under a nitrogen atmosphere to obtain the aminolysis system (depolymerization liquid);

[0149] (3) The amine hydrolysis system (depolymerization liquid) is subjected to ester exchange and / or amide exchange (exchange reaction) at 253°C and 90 kPa nitrogen pressure for 3 h. After liquid phase separation, the exchange system and ethylene glycol (alcoholization agent recovery system) are obtained.

[0150] (4) Mix the polymerization system including the exchange system, tetrabutyl titanate (polymerization catalyst, Ti=6ppm), antimony glycolate (polymerization catalyst, Sb=60ppm), phosphoric acid (stabilizer, P=3ppm), triethyl phosphate (stabilizer, P=2ppm), 400ppm β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl alcohol (antioxidant, antioxidant 1076) and 1200ppm bis(2,4-dicumylphenyl)pentaerythritol-diphosphite (antioxidant, antioxidant 608), react for 1h at 255°C and 10kPa to remove excess ethylene glycol (alcoholization agent), and then polymerize at 280°C and 25Pa for 2h. After the reaction is completed, pull the pellets and dry them to obtain recycled polyesteramide chips.

[0151] Example 6

[0152] This embodiment is basically the same as that of Example 1, except that: 1.04 mol of 4,4'-diaminodicyclohexylmethane (a diamine hydrolysate, the amount of which accounts for 20% of the amount of terephthalic acid in PET) is used in step (2), and the rest of the steps are the same as those of Example 1.

[0153] Example 7

[0154] This embodiment is basically the same as that of embodiment 3, except that: 4.99 mol of 4,4'-diaminodicyclohexylmethane (a diamine hydrolysate, the amount of which accounts for 96% of the amount of terephthalic acid in PET) is used in step (2), and the rest of the steps are the same as those in embodiment 3.

[0155] Example 8

[0156] This embodiment is basically the same as embodiment 4, except that: no antioxidant is added in step (4), and the rest of the steps are the same as in embodiment 4.

[0157] Example 9

[0158] This embodiment is basically the same as that of embodiment 5, except that the aminolysis catalyst used in step (2) is sodium acetate, and the rest of the steps are the same as those of embodiment 5.

[0159] Example 10

[0160] This embodiment is basically the same as that of embodiment 2, except that the polymerization catalyst used in step (4) and the amount added are titanium glycol (polymerization catalyst, Ti=10ppm) and antimony glycol (polymerization catalyst, Sb=300ppm), and the rest of the steps are the same as those of embodiment 2.

[0161] Example 11

[0162] This embodiment is basically the same as embodiment 5, except that: no stabilizer is added in step (4), and the rest of the steps are the same as in embodiment 5.

[0163] Example 12

[0164] This embodiment is basically the same as embodiment 4, except that: no stabilizer and antioxidant are added in step (4), and the rest of the steps are the same as in embodiment 4.

[0165] Comparative Example 1

[0166] The process is basically the same as in Example 1, except that the alcoholysis reaction in step (1) is not performed; instead, the aminolysis reaction is carried out directly. The specific steps are as follows:

[0167] (1) 1 kg of waste PET bottle flakes or polyester filaments (waste PET) is cleaned and dried, and the raw material system including waste PET, 1 kg of ethylene glycol (EG, alcoholysis agent), 1.56 mol of 4,4'-diaminodicyclohexylmethane (diamine aminolysis agent, the amount of which accounts for 30% of the amount of terephthalic acid in PET), and 5 g of 1,5,7-triazabicyclo[4.4.0]decene-5-ene (aminolysis catalyst) is subjected to aminolysis reaction at 200°C for 2 h under nitrogen atmosphere to obtain aminolysis system (depolymerization liquid);

[0168] (2) The amine hydrolysis system (depolymerization solution) is subjected to amide exchange (exchange reaction) at 250°C and 50 kPa nitrogen pressure for 2 h to obtain the exchange system;

[0169] (3) Mix the polymerization system including the exchange system, tetrabutyl titanate (polymerization catalyst, Ti=5ppm), antimony trioxide (polymerization catalyst, Sb=30ppm), phosphoric acid (stabilizer, P=3ppm), triphenyl phosphate (stabilizer, P=2ppm), 1200 ppm pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant, antioxidant 1010) and 1800 ppm tris[2,4-di-tert-butylphenyl] phosphite (antioxidant, antioxidant 168), react for 1 h at 250°C and 10 kPa to remove excess ethylene glycol (alcoholization agent), and then polymerize for 2 h at 265°C and 30 Pa. After the reaction is completed, pull the pellets and dry them to obtain recycled polyesteramide chips.

[0170] Comparative Example 2

[0171] The process is basically the same as in Example 3, except that the diamine hydrolysate used in step (2) is 4.68 mol hexamethylenediamine (which accounts for 90% of the amount of terephthalic acid in PET), and the rest of the steps are the same as in Example 3.

[0172] Test case

[0173] The intrinsic viscosity [η] and glass transition temperature (T) of the recycled polyesteramides prepared in Examples 1-12 and Comparative Examples 1-2 were measured respectively. g The heat distortion temperature (HDT), light transmittance, and mechanical properties were tested, and the test results are shown in Table 1.

[0174] The intrinsic viscosity [η] of recycled polyesteramide chips was tested according to GB / T 14190-2017.

[0175] To of recycled polyesteramide was tested using differential scanning calorimetry. g ;

[0176] HDT of recycled polyesteramide was tested according to GB / T 1634.1-2019;

[0177] The transmittance of the injection-molded sample obtained after injection molding of recycled polyesteramide chips is tested according to GB / T 2410-2008.

[0178] The mechanical properties of injection-molded samples obtained by injection molding of polyesteramide chips were tested according to GB / T 1040.1-2018.

[0179] Table 1 Test results of the examples and comparative examples

[0180]

[0181] Conclusion Analysis:

[0182] (1) Examples 1-5 show that the recycled polyesteramide synthesized using alicyclic diamines as aminolysis agents possesses excellent heat resistance (HDT>80.4℃) and transparency (transmittance>87.1%). This result indicates that the introduction of alicyclic structures can effectively disrupt the regularity of PET molecular chains and reduce their crystallinity; at the same time, the newly formed amide bonds can enhance intermolecular interactions through a large number of hydrogen bonds, thereby increasing the glass transition temperature (T0) of the material. g The heat resistance and light transmittance of polyesteramide both show a gradual increasing trend with the increase in the amount of alicyclic diamine used.

[0183] (2) The comparison between Example 1 and Example 6 shows that, under the same process conditions, if the amount of alicyclic diamine added is too low, the amide bond content in the resulting recycled polyester amide will be significantly reduced, the interaction between molecular chains will be weakened, and its heat resistance, light transmittance and mechanical properties will all be significantly reduced.

[0184] (3) A comparison between Example 3 and Example 7 shows that, under the same process conditions, after the amount of alicyclic diamine exceeds the preferred range, further increasing its addition amount does not further improve the heat resistance, light transmittance, and mechanical properties of the recycled polyester amide. This is because aminolysis is an equilibrium reaction, and excessive aminolysis agent cannot continuously improve the aminolysis efficiency or introduce more amide bonds.

[0185] (4) The comparison between Example 4 and Example 8 confirms that if an antioxidant is not added during the polymerization reaction (condensation) stage, the resulting recycled polyesteramide is more prone to thermal oxidation and photo-oxidation degradation during subsequent processing and use, leading to molecular chain breakage and decreased mechanical properties. At the same time, the formation of active chromophores will cause the material to yellow and reduce light transmittance.

[0186] (5) Comparison between Example 5 and Example 9 shows that, under the same process conditions, using sodium acetate as an aminolysis catalyst will lead to a significant decrease in aminolysis efficiency. The overall performance of the prepared polyesteramide is significantly worse than that of the system using the preferred catalyst, but it is still better than the comparative example.

[0187] (6) The comparison results between Example 2 and Example 10 show that adding excessive polymerization catalyst during the polymerization reaction (condensation) stage leads to excessively high catalytic activity, violent reaction, and increased system temperature, which in turn triggers severe thermal degradation and side reactions. The resulting recycled polyesteramide has low intrinsic viscosity, short molecular chains, weakened entanglement network, and decreased heat distortion temperature. Furthermore, due to the widened molecular weight distribution and insufficient chain segment entanglement, the material exhibits brittle fracture characteristics, with a significant reduction in elongation at break, impact resistance, and tensile strength.

[0188] (7) The comparison between Example 5 and Example 11 further shows that the absence of a stabilizer during the polymerization (condensation) stage can also cause runaway catalytic activity, overheating of the reaction and increased degradation, resulting in a decrease in the intrinsic viscosity of the recycled polyester amide, a shortening of the molecular chain, a weakening of the entanglement network, a decrease in the heat distortion temperature, and a significant deterioration of mechanical properties (such as elongation at break, impact resistance and tensile strength).

[0189] (8) A comparison between Example 4 and Example 12 shows that the stabilizer mainly stabilizes the reaction process by controlling the activity of the polymerization catalyst during the polymerization stage; while the antioxidant mainly plays the role of inhibiting side reactions and preventing yellowing during processing. When both are missing (as in Example 12), the system's performance in terms of reaction controllability and product color stability is significantly deteriorated, which in turn leads to a significant deterioration in the mechanical and optical properties of the material.

[0190] (9) The comparison between Example 1 and Comparative Example 1 shows that when only the aminolysis reaction is used for depolymerization, the degree of depolymerization of the system is insufficient, which directly leads to the limitation of molecular weight growth in the subsequent polymerization stage and the failure to reach the expected value. Therefore, the overall performance of the recycled polyester amide obtained in the end is poor.

[0191] (10) The comparison between Example 3 and Comparative Example 2 shows that, under the same process conditions, if the alicyclic diamine is replaced with a linear aliphatic diamine (such as hexamethylenediamine), the transmittance of the resulting recycled polyesteramide is only 72.9%. The carbon chain structure of the linear aliphatic diamine is more regular, and its destructive effect on the regularity of the PET molecular chain segments is weaker. Therefore, the crystallinity of the product decreases only slightly, and the transmittance is correspondingly lower.

[0192] (11) In summary, this invention employs a “alcohololysis-amineolysis” tandem process: firstly, waste PET is initially depolymerized through alcohololysis, then through amineolysis, and finally through esterification / amide exchange and polymerization (condensation) processes, a recycled polyesteramide with both high heat resistance and high transparency is successfully prepared. This method realizes the high-value conversion and upgrading of waste polyester resources.

[0193] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing polyesteramide from recycled waste PET, characterized in that the steps include... include: (1) The first raw material system, including waste PET, alcoholysis agent and alcoholysis catalyst, is subjected to alcoholysis reaction to obtain alcoholysis system; (2) A second raw material system comprising the alcoholysis system, a diamine aminolysis agent, and an aminolysis catalyst is subjected to an aminolysis reaction to obtain an aminolysis system; (3) The aminolysis system is subjected to an exchange reaction to obtain an exchange system and an alcoholysis agent recovery system; the exchange reaction includes ester exchange reaction and / or amide exchange reaction; (4) The polymerizable system including the exchange system is subjected to a polymerization reaction to obtain recycled polyesteramide; The aminolysis system comprises bis(2-hydroxyethyl) terephthalate and the compound shown in Formula 1. Formula 1; n is an integer from 1 to 5, R comes from the diamine hydrolysate, and R is a C10 to C15 alicyclic ring.

2. The method for preparing polyesteramide from recycled waste PET according to claim 1, characterized in that, The diamine-based aminolysis agent has the structure shown in Formula 2. NH2-R-NH2 Equation 2.

3. The method for preparing polyesteramide from waste PET according to claim 1 or 2, characterized in that, The diamine-based aminolytic agents include at least one of 4,4'-diaminodicyclohexylmethane, isophorone diamine, 3,3'-dimethyl-4,4-diaminodicyclohexylmethane, and 4,4'-isopropyldicyclohexylamine.

4. The method for preparing polyesteramide from waste PET according to any one of claims 1-3, characterized in that, The amount of the diamine-based aminolysis agent is 30% to 90% of the amount of terephthalic acid in the waste PET.

5. The method for preparing polyesteramide from waste PET according to any one of claims 1-4, characterized in that, In the alcoholysis reaction, the reaction temperature is 200°C~240°C, and the time is 1h~2h; and / or, In the aforementioned aminolysis reaction, the reaction temperature is 200°C~220°C, and the time is 2h~6h; and / or, In the exchange reaction, the reaction temperature is 250°C~260°C, the time is 2h~5h, and the pressure is 50kPa~150kPa; and / or, In the polymerization reaction, the reaction temperature is 265°C ~ 280°C, the time is 2h ~ 5h, and the pressure is 20Pa ~ 60Pa; and / or, It also includes the step of returning the alcoholysis agent recovery system to participate in the alcoholysis reaction.

6. The method for preparing polyesteramide from waste PET according to any one of claims 1-5, characterized in that, The alcoholysis agent includes ethylene glycol; and / or, The alcoholysis catalyst includes at least one of zinc acetate, sodium acetate, and cobalt acetate; and / or, The aminolysis catalyst comprises at least one selected from 1,5,7-triazabicyclo[4.4.0]decen-5-ene, tetramethylguanidine, and 1,8-diazabicyclo[5.4.0]undec-7-ene; and / or, The mass ratio of the alcoholysis agent to the waste PET is (1~3):1; and / or, The mass ratio of the alcoholysis catalyst to the waste PET is 0.1% to 0.5%; and / or, The mass ratio of the aminolysis catalyst to the waste PET is 0.5% to 1.0%.

7. The method for preparing polyesteramide from waste PET according to any one of claims 1-6, characterized in that, The polymerization system further includes one or more of a polymerization catalyst, a stabilizer, and an antioxidant; wherein the polymerization catalyst includes one or more of antimony trioxide, antimony glycolate, titanium glycolate, tetrabutyl titanate, tetraisopropyl titanate, and germanium dioxide; and / or, Stabilizers include one or more of phosphoric acid, trimethyl phosphate, triethyl phosphate, triphenyl phosphate, and triphenyl phosphite; and / or, Antioxidants include one or more of the following: pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], octadecyl β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, bis(2,4-dicumylphenyl)pentaerythritol diphosphite, and tris[2,4-di-tert-butylphenyl]phosphite.

8. The method for preparing polyesteramide from waste PET according to claim 7, characterized in that, In the polymerization catalyst, the mass ratio of the metal element to the recycled polyesteramide is 5ppm to 150ppm, the mass ratio of the stabilizer to the recycled polyesteramide is 5ppm to 25ppm, and the mass ratio of the antioxidant to the recycled polyesteramide is 100ppm to 3000ppm.

9. A recycled polyesteramide, characterized in that, It is prepared according to the recycling method of waste PET according to any one of claims 1-8.

10. The recycled polyesteramide according to claim 9, characterized in that, The recycled polyesteramide has a heat distortion temperature of 80.4°C to 161.3°C and a transmittance of 87.1% to 93.6%.

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