Preparation method of film base material grade regenerated polyester chip

Abstract

The invention relates to a preparation method of a film-based material-grade regenerated polyester chip, and belongs to the technical field of preparation of high polymer materials for films. The method comprises the following steps: by taking a waste polyester (PET) product as a main raw material, firstly carrying out ethylene glycol (EG) depolymerization and pre-impurity removal to obtain an alcoholysis solution, and then preparing a monomer solution in which the content of bis (2-hydroxyethyl) terephthalate (BHET) is greater than or equal to 96.5 wt% and the content of diethylene glycol (DEG) is 2.5-3.2 wt% through a microwave radiation induced film evaporation separation and molecular distillation refining continuous process; the preparation method comprises the following steps: preparing a monomer solution, adding a copolymerization component 1, 4-butanediol into the monomer solution, and carrying out pre-polycondensation and final polycondensation to prepare the film-base-material-grade regenerated polyester chip, so that the film-base-material-grade regenerated polyester chip has good two-way stretching film-forming property, and the performance index of the film-base-material-grade regenerated polyester chip reaches the superior product grade of a primary film-base-material-grade polyester chip. Compared with the preparation process of the film base material grade regenerated polyester chip with the same quality, the method has the advantages of mild overall process parameters, short flow, good continuity, clean process and low consumption, and also has the advantages of convenience in EG internal recycling and obvious comprehensive efficiency advantage.

Description

Technical Field

[0001] The invention relates to a method for preparing film base material-grade recycled polyester chips, and belongs to the technical application of preparing base material chips for polyester films. Background Art

[0002] Polyester film, due to its excellent overall performance, is widely used in various packaging applications, with annual consumption exceeding 3 million tons. The primary raw material for polyester film is film-based polyester (PET) chips, which are primarily produced by direct esterification of terephthalic acid, ethylene glycol, and a certain amount of modifying monomers. The main structure is polyethylene terephthalate (PET). However, since polyester film is mostly a fast-moving consumer product, coupled with its dependence on petroleum and resistance to degradation, the corresponding environmental and resource issues are becoming increasingly serious. Therefore, the production technology of film-based recycled polyester has attracted much attention in the industry.

[0003] The most common recycling technology for film-grade polyester uses post-consumer polyester bottles as raw material. This process involves washing and drying the waste PET, then melting and homogenizing it, mixing it with a modifier, and then pelletizing or directly drawing it into film. However, this method requires extremely high purity and molecular weight grade for the waste PET, and the molecular weight and quality of the recycled material are significantly degraded. This is particularly true for film-grade polyesters that require high transparency. Currently, the only chemical method for producing film-grade polyester with comparable performance to virgin chips from waste polyester products, which are high in impurities and difficult to separate directly, is chemical. This involves using a specific chemical reaction to depolymerize PET macromolecules to specific monomers that can be effectively separated from impurities and refined. The refined monomers are then used as raw materials for repolymerization to produce PET macromolecules of comparable quality to virgin chips. Currently, the three main depolymerization methods for PET recycling are water depolymerization, methanol depolymerization, and ethylene glycol depolymerization. Ethylene glycol (EG) depolymerization offers significant advantages over the other two methods in terms of mild reaction conditions, reaction safety, equipment cost, and operating and maintenance costs, making it a popular choice in the industry.

[0004] Currently, the preparation method of membrane-based regenerated polyester chips that is comparable to the original still has problems such as long production processes, low efficiency, and high consumption. The key to improvement lies first in how to more efficiently prepare the depolymerization monomer bis(2-hydroxyethyl) terephthalate (BHET) that can meet the polymerization requirements of membrane-based materials. BHET is separated and refined from the mixture after the EG depolymerization of waste PET. The composition of this mixed system includes: EG, BHET, oligomers (mainly dimers) inevitably formed due to the depolymerization equilibrium, the by-product of EG self-polymerization, diethylene glycol (DEG), coloring and modifier fragments (mainly small molecules containing phthalocyanine, azo, and anthraquinone structures), anions and cations (mainly all catalysts for polymerization and depolymerization), and filterable impurities (inorganic powders, metal oxides, other miscellaneous polymers that do not depolymerize). The main separation and refinement technologies for BHET in the polyester regenerated ethylene glycol depolymerization system are as follows: The separation and refinement of BHET mentioned in the invention patents US4609608, US6630601, and CN104710601B are mainly achieved by controlling the solubility of BHET. That is, after the crude separation of BHET by cooling crystallization in the system, water is introduced for recrystallization refinement. Although this method can improve the purity of BHET, the temperature required for the aqueous-phase recrystallization of BHET is much lower than room temperature, the process takes a long time and consumes a lot of energy, and it is also difficult to recycle the solvent. Moreover, for systems with high contents of coloring and modifier fragments and anion and cation impurities, it is very difficult to obtain BHET that meets the polymerization requirements of membrane-based materials even by repeating the aqueous-phase recrystallization multiple times.

[0005] The invention patent WO2002 / 010117 first filters out filterable impurities, then uses activated carbon to adsorb and remove coloring and modifier fragments in the system, and uses ion exchange resin to remove cationic and anionic impurities in the system. After that, the BHET in the system is cooled and crystallized to obtain crude BHET. For the crude BHET, a three-stage step-by-step refining process is adopted, that is, first vacuum distillation is used to remove part of the EG, then thin-film evaporation is carried out under a higher vacuum state to thoroughly remove low-boiling substances, and finally high-vacuum molecular distillation is used to condense and collect BHET to complete the refining. The three-stage step-by-step refining process can effectively inhibit the occurrence of side reactions, and the obtained refined BHET can meet the polymerization requirements of the film base material level. However, the overall process is too long, the efficiency is low, the overall optimization control complexity is high, and the EG reuse is difficult. The invention patent WO2003 / 101929, in order to further inhibit side reactions, on the basis of WO2002 / 010117, in the three-stage step-by-step refining link, the evaporation process is further classified, and the control of the fraction-to-bottoms ratio is also increased in the molecular distillation link. The obtained refined BHET has a higher purity, but the efficiency has not been improved. The invention patent WO2022 / 003990, on the basis of WO2003 / 101929, for the removal of nitrogen-containing disperse dyes, ethylene glycol monoethers or diethers with 4 to 12 carbon atoms are introduced for extraction and decolorization. Although the homogeneous phase can improve the decolorization efficiency, the decolorizing agents with such chemical structures will inevitably increase the separation difficulty from the alcoholysis agent ethylene glycol, which will hinder the reuse of ethylene glycol and decolorizing agents in the system. At the same time, there is no improvement in the overall separation and refining efficiency.

[0006] Compared with WO2002 / 010117, WO2003 / 101929, and WO2022 / 003990, the invention patent CN1135846441B adopts a more general separation and refining route to improve efficiency. The refining of crude BHET is divided into two steps: removing low-boiling substances at a low vacuum degree and high-temperature flash evaporation and condensation to collect BHET at a high vacuum degree. However, this method does not mention the control of side reactions during the process and the actual purity of BHET, only stating that the obtained polyester can be used for spinning processing, and it does not explain whether the relevant quality products can be comparable to the original spinning-grade PET chips. Similarly, the invention patent CN107189044A only mentions rectification for the refining of BHET and then directly polymerizes, but also points out that a toner needs to be added. Therefore, it can be judged that the efficiency improvement obtained by such streamlining measures comes at the cost of quality, and there are still difficulties in inhibiting side reactions.

[0007] Patent inventions CN115894223A and CN116284710 propose a method for creating the sublimation conditions of BHET crystals to achieve purification. Although the process flow of this method is short, due to the strong intermolecular hydrogen bonding of BHET molecules, its saturated vapor pressure is very low. Therefore, the process window for the sublimation purification of BHET in a strict thermodynamic sense is very narrow, and it is difficult to achieve large-scale production. For large-scale sublimation purification, a more practical operation route is to first convert crude BHET into dimethyl terephthalate (DMT) through transesterification with methanol. Since DMT has no intermolecular hydrogen bonding and its saturated vapor pressure is much higher than that of BHET, large-scale purification can be relatively smoothly completed. Then, the purified DMT is converted back into BHET through transesterification with ethylene glycol, and then polymerized to prepare recycled film base-grade PET with quality comparable to the original. Patent inventions WO / 2003 / 033581A1, CN109503818A, CN110964188B, CN114437328A, CN114044892B, and CN114149574B all contain recycled polyester preparation technologies developed based on this idea. However, these methods also have one of the most significant common defects, that is, they introduce two additional transesterification reactions, which not only increases the use of catalysts, but also involves the management and reuse of highly flammable and volatile methanol during the process. The process is long and the production cost is high.

[0008] On the other hand, the preparation of recycled polyester chips for film base grade not only has high requirements for the purity of recycled BHET, but also has certain special requirements for the molecular structure of the final product. PET for film base applications requires good biaxial stretching and crystallization properties, and it is necessary to control a certain amount of more flexible chain segment structures in the PET macromolecular structure. The preparation of virgin film base grade polyester chips can be achieved by directly esterifying terephthalic acid, ethylene glycol, and a modified monomer together and then further co-polycondensing to achieve specific adjustment of the PET macromolecular structure. However, during recycled preparation, it usually starts with high-purity BHET for polymerization. Since there is no process of co-esterifying with a modified monomer, even if a modified monomer is added for co-polycondensation, it is very difficult to form a copolymer structure that can meet the requirements of film stretching processing. Summary of the Invention

[0009] The object of the present invention is to provide a preparation method of film base material grade recycled polyester chips in view of the deficiencies of the above-mentioned existing technologies. This preparation method uses waste polyester (PET) products as the main raw material. First, it undergoes glycolysis (EG) and preliminary impurity removal to obtain an alcoholysis solution. Then, through a continuous process of microwave radiation-induced thin-film evaporation separation and molecular distillation refining, a monomer solution with a bis(2-hydroxyethyl) terephthalate (BHET) content ≥ 96.5 wt% and a diethylene glycol (DEG) content of 2.5 - 3.2 wt% is produced. Subsequently, 1,4-butanediol, a copolymerization component, is added to the monomer solution, and through pre-polycondensation and final polycondensation, film base material grade recycled polyester chips can be prepared. The product has good biaxial stretching film-forming properties, and its performance indicators reach the excellent grade of virgin film base material grade polyester chips. Compared with the preparation processes of film base material grade recycled polyester chips of the same quality, the overall process parameters of this method are mild, the process flow is short and has good continuity, the process is clean and low in energy consumption, and at the same time, it has the advantages of convenient internal recycling of EG and obvious comprehensive efficiency advantages.

[0010] The present invention achieves the above object through the following technical solutions: A preparation method of film base material grade recycled polyester chips, characterized in that it comprises the following steps: 1) Uniformly mix waste polyester material, EG, catalyst, stabilizer, and activated carbon in a certain proportion, then feed them into an alcoholysis device. Under the protection of inert gas at a temperature of 185 - 200 °C and a pressure of 100 - 200 kPa, uniformly stir for a depolymerization reaction for 2 - 5 h. Then, at 60 - 100 °C, filter out the activated carbon and other filterable impurities, and maintain the filtrate at 60 - 100 °C. Flow through cation exchange resin and anion exchange resin in sequence for ion demineralization until the total concentration of cations and anions ≤ 50 ppm. The resulting liquid is denoted as the alcoholysis solution.

[0011] 2) Under the protection of inert gas, preheat the alcoholysis solution obtained in step 1) to 110 - 120 °C, then transfer it to a wiped film evaporator with microwave radiation for microwave radiation-induced thin-film evaporation treatment to remove substances in the alcoholysis solution with boiling points lower than BHET. Then, control the air pressure in the thin-film evaporation chamber to be 400 - 600 Pa through a vacuum system, control the residence time of the alcoholysis solution on the evaporation surface under the action of microwave irradiation to be 20 - 100 s through the feed flow rate and the scraper rotation speed, and control the temperature of the concentrated finished liquid at the concentration outlet to be maintained at 145 - 155 °C through the microwave power to obtain a concentrated finished liquid with EG < 0.1 wt% and a DEG content of 2.0 - 2.6 wt%. The resulting concentrated finished liquid is denoted as the separation liquid. At the same time, condense and collect the low-boiling substances removed in this step, and transfer the low-boiling substances to a conventional distillation separation device to obtain EG with a purity ≥ 99.0 wt% through conventional distillation separation. The obtained EG is denoted as recycled EG.

[0012] 3) Transfer the separation liquid obtained in step 2) into a molecular distillation apparatus. Under the conditions that the heating surface temperature is 215 - 220 °C, the pressure is ≤25 Pa, and the condensation surface temperature is 110 - 120 °C, by controlling the residence time of the separation liquid on the heating surface, maintain the mass ratio of the distillate to the residue at 7.5:2.5 - 8:2. The main component of the obtained residue is oligomer, denoted as alcoholysis refined residue. After collecting the alcoholysis refined residue, transfer it into the alcoholysis apparatus in step 1) to participate in the depolymerization reaction in the next production cycle. The obtained distillate is denoted as monomer liquid, and the BHET content in the monomer liquid is ≥96.5 wt%, and the DEG content is 2.5 - 3.2 wt%.

[0013] 4) Mix the monomer liquid obtained in step 3) with a 1,4 - butanediol dispersion containing a certain amount of catalyst and stabilizer in a certain proportion under the conditions of a temperature of 170 - 180 °C, a pressure of 101 kPa, and nitrogen protection, and maintain the temperature and transfer it into a prepolycondensation reactor. The prepolycondensation reaction temperature is 235 - 240 °C, the reaction time is 1.5 - 2.5 h, the pressure in the reactor is 101 kPa at the beginning, keep it unchanged for 0.5 - 1 h first, and then the pressure linearly decreases from 101 kPa to 1 kPa with the reaction time. Then transfer it into a final polycondensation reactor and react at a temperature of 265 - 285 °C and a pressure of 20 - 50 Pa for 1.5 - 2.5 h, and then cool, pelletize, and dry the obtained melt to obtain film - base - grade recycled polyester chips.

[0014] For the preparation method of the above - mentioned film - base - grade recycled polyester chips, the waste polyester material in step 1) is a post - consumer polyester product or production waste with a PET component content ≥85 wt%, preferably a post - consumer polyester product or production waste with 95 wt%. The EG is a mixture of polyester - grade EG and the recycled EG obtained in step 2) of the present invention in a ratio of 1:0.1 - 1:1. The catalyst in step 1) is one of sodium carbonate, zinc acetate, tetra - n - butyl titanate, and tetra - isopropyl titanate. The stabilizer in step 1) is one of sodium acetate and potassium acetate. The so - called "in a certain proportion" in step 1) means that based on the mass of PET contained in the waste polyester material, the addition amount of EG is 200 - 400 wt%, the addition amount of the catalyst is 0.5 - 1.5 wt%, the addition amount of the stabilizer is 0.5 - 5×10 -2 wt%, and the addition amount of activated carbon is 1 - 5 wt%.

[0015] As described above, in the preparation method of a film base material grade recycled polyester chip, the structural features of the scraper thin film evaporator with microwave radiation in step 2) are as follows: Microwaves are generated by a microwave generator with adjustable power and transmitted to the evaporator cavity through a waveguide connected to the inner wall of the evaporator. The materials of the inner wall of the evaporator and the rotor scraper need to be microwave-transparent materials. The gap between the rotor scraper and the inner wall of the evaporator is 0.5 - 2 mm. Microwave reflection blocking and heat insulation treatments are carried out at each interface on the inner wall and the outer wall. The evaporation gas condensation system and the concentrated liquid collection system connected through the interfaces are both located outside the cavity where the liquid film is formed and are not affected by microwave radiation.

[0016] As described above, in the preparation method of a film base material grade recycled polyester chip, the contents of each substance in the 1,4-butanediol dispersion containing a certain amount of catalyst and stabilizer in step 4) are as follows: the catalyst is 100 - 1000 ppm, and the stabilizer is 200 - 1000 ppm; the catalyst is one of antimony glycolate, germanium acetate, and tetra-n-butyl titanate; the stabilizer is one of trimethyl phosphate, triphenyl phosphate, or triphenyl phosphite; the mixing ratio of the monomer liquid to the 1,4-butanediol dispersion is 90:10 - 95:5 by mass; the evaluation of the performance and quality of the obtained recycled film base material grade polyester is carried out in accordance with the national standard of the People's Republic of China GB / T 17932 - 2013 (Film grade polyester chips (PET)).

[0017] The following explains the substantial features and related principles of the present invention: The substantial features of the preparation method of a film base material grade recycled polyethylene terephthalate (PET) provided by the present invention are mainly reflected in that: while efficiently obtaining high-purity BHET from the alcoholysis solution obtained by the glycolysis method, the content of DEG therein can be controlled to be exactly at a level where it can form a more sufficient copolymer structure with BHET and 1,4-butanediol with an addition amount of 5 - 10 wt% to meet the application requirements of film processing, that is, efficiently preparing a monomer liquid with a BHET content ≥ 96.5 wt% and a DEG content of 2.5 - 3.2 wt%. On this basis, the copolymer component 1,4-butanediol is added to the monomer liquid, and after the processes of pre-polycondensation and final polycondensation, the preparation of a film base material grade recycled polyester chip with quality comparable to that of the original can be achieved.

[0018] The reason why the present invention can efficiently and stably produce the monomer liquid is as follows: Firstly, through step 1), the basic components of the alcoholysis liquid (components: EG, DEG, BHET and oligomers) can be standardized. On this basis, through step 2), the combined advantages of thin-film evaporation and microwave radiation induction are formed. According to the different microwave absorption abilities and kinetic energy conversion characteristics of different polar molecules, combined with thin-film evaporation that can minimize diffusion limitations, the separability and separation controllability of each component in the alcoholysis liquid are comprehensively improved. At the same time, since microwaves can promote the relaxation and breakage of hydrogen bonds between molecules, the process can effectively avoid the separation entrainment between the EG, DEG and BHET components, and inhibit side reactions such as the self-polymerization of EG into DEG and the transesterification between DEG and BHET during the separation process. Compared with conventional thin-film evaporation treatment, there is no need to go through time-consuming processes such as step-by-step gradual evaporation to avoid entrainment and side reactions, and the efficient and controllable removal of low-boiling substances can be achieved in one step. Then, through step 3), molecular distillation is used to separate oligomers, and light components are extracted during the extraction process to achieve the high-efficiency refining of monomers. Based on this principle, through the comprehensive control of the process parameter ranges in steps 1), 2) and 3) determined by the practice of the system, the efficient and stable production of the monomer liquid can be achieved.

[0019] On the other hand, the reason why a DEG content of 2.5 - 3.2 wt% is beneficial for BHET to form a more sufficient copolymerization structure with 1,4-butanediol added in an amount of 5 - 10 wt% is as follows: In principle, during the transesterification reaction, DEG is closer to EG in terms of functional group activity. Compared with 1,4-butanediol, it can enter the main chain more easily and uniformly. At the same time, the chain flexibility of DEG is closer to that of 1,4-butanediol, and it can undergo transesterification with 1,4-butanediol better. Therefore, DEG can better help 1,4-butanediol enter the main chain uniformly. In terms of effects, through the practice of the system, it is determined that DEG must be within the above content range to significantly improve the success rate and uniformity of the copolymerization of 1,4-butanediol within the above addition range into the macromolecular chain, and at the same time obtain ideal intrinsic viscosity, melting point and color value. Only then can the finally formed copolymer product have good biaxial drawability. Therefore, on the basis of the efficient and stable production of the monomer liquid, through step 4), the preparation of film-based recycled polyester chips with quality comparable to that of virgin materials can be finally achieved, which is also unattainable by previous recycled polymerization processes.

[0020] In the publicly disclosed preparation technologies of membrane base material grade recycled polyester CN107793560B, CN114044892B, CN115232300A, and the aforementioned related PET alcoholysis monomer purification technologies, the utilization of microwave radiation induction methods is not involved, and during the purification of monomers, the specific regulation of the DEG content towards membrane base material grade recycled polymerization is not achieved synchronously. Among the related polyester glycolysis methods, only patents CN108602974B and CN112940344A mention the utilization of microwave radiation means, and the goal is only to speed up the depolymerization process, without any microwave-related operations in the depolymerization monomer purification link, which is essentially different from the technical solution of the present invention. Therefore, there is no technical inspiration for the technical solution of the present invention in the prior art.

[0021] Generally speaking, compared with the background technology, the present invention has a shorter and more efficient process. The process does not need to go through complex and time-consuming steps such as cooling crystallization and multi-stage evaporation and gradual concentration of crude BHET in order to avoid problems such as evaporation separation entrainment and side reactions. And based on the significant improvement in the separation accuracy and adjustable performance of substances in the alcoholysis solution of the present invention, it can synchronously achieve the transformation from blindly improving the purity of BHET to specifically controlling the DEG content in BHET for membrane base material applications, which is more economical, efficient and stable. In addition, due to the concentrated distillation of low-boiling substances and few side reactions in the process of the present invention, it is easier to recycle EG in the system compared with the background technology, with less raw material consumption; the operation of transferring the alcoholysis refined residue generated in step 3) into the alcoholysis device to participate in the depolymerization reaction of the next production cycle can, on the one hand, due to the similar compatibility effect, the addition of the alcoholysis refined residue can improve the solubility of waste polyester materials in the depolymerization system, enabling the reaction to enter the homogeneous state more quickly, significantly shortening the reaction time required for depolymerization in step 1), reducing side reactions, and at the same time can also improve the recycling yield.

[0022] The beneficial effects of the present invention are: (1) The method for preparing recycled membrane base material grade PET provided by the present invention can solve the problems of long process, poor continuity, many side reactions, low purity and low yield existing in the direct separation and refining of BHET in the alcoholysis solution based on the gas-liquid equilibrium separation method. At the same time, it can control the content of the product monomer liquid BHET in the refining link ≥ 96.5 wt%, and the DEG content is 2.5 - 3.2 wt%, which exactly meets the specific requirements for the preparation of 1,4-butanediol copolymerization type membrane base material grade PET. Compared with the background technology, it can significantly shorten the production process and be more efficient and economical while ensuring high-quality product output.

[0023] (2) The preparation method of the recycled film base grade PET provided by the present invention is easier to achieve the efficient and sufficient reuse of EG and oligomer residues during the production process compared with the background technology. At the same time, based on the significant improvement in the separation accuracy and adjustable performance of substances in the alcoholysis solution by the present invention, the transformation from blindly high-purity monomer purification to controlled monomer purification for the specific requirements of film base grade recycling has been realized. All of these can significantly reduce the raw material and waste treatment costs, and are cleaner and lower in consumption.

[0024] (3) The preparation method of the recycled film base grade PET provided by the present invention has mild overall process parameter requirements, a short process, good continuity, a moderate investment cost for production equipment, obvious comprehensive efficiency advantages, and good industrial application prospects.

[0025] The technical solution of the present invention will be further described in detail below with specific embodiments. Example 1

[0026] 1) After uniformly mixing waste polyester materials, EG, a catalyst, a stabilizer, and activated carbon in a certain proportion, feed them into an alcoholysis device. Under the protection of inert gas and uniform stirring at a temperature of 185 °C and a pressure of 100 kPa, carry out a depolymerization reaction for 5 h. Then, at 70 °C, filter out the activated carbon and other filterable impurities, and maintain the filtrate at 70 °C. Flow it through a cation exchange resin and an anion exchange resin in sequence for ion reduction. The total concentration of cations and anions in the obtained liquid is 25 ppm, which is recorded as the alcoholysis solution.

[0027] Among them, the waste polyester material is a waste film dense material with a PET component content of 96.2 wt%; the EG is a 1:1 mixture of polyester polymerization grade EG and the recycled EG in step 2); the catalyst is tetrabutyl titanate; the stabilizer is sodium acetate; the certain proportion means that based on the mass of PET, the addition amount of EG is 400 wt%, the addition amount of the catalyst is 1.5 wt%, the addition amount of the stabilizer is 5×10 -2 wt%, and the addition amount of activated carbon is 2 wt%.

[0028] 2) Under the protection of inert gas, preheat the alcoholysis solution obtained in step 1) to 110 °C, transfer it to a wiped film evaporator with microwave radiation, and carry out microwave radiation-induced thin film evaporation treatment to remove substances in the alcoholysis solution with boiling points lower than BHET. The gap between the rotor scraper and the inner wall of the evaporator is 2 mm. This treatment controls the air pressure in the thin film evaporation cavity to be 400 Pa through the vacuum system, controls the residence time of the alcoholysis solution on the evaporation surface under the action of microwave irradiation to be 100 s through the feed flow rate and the scraper rotation speed, controls the temperature of the completed solution at the concentration outlet to be maintained at 145 °C through the microwave power. The EG content in the concentrated completed solution is 0.05 wt%, and the DEG content is 2.6 wt%, which is recorded as the separated liquid; at the same time, condense and collect the low-boiling substances removed in this step, and transfer them to a conventional distillation separation device to obtain EG with a purity of 99.1 wt%, which is recorded as the recovered EG.

[0029] 3) Transfer the separated liquid obtained in step 2) to a molecular distillation device. At a heating surface temperature of 220 °C, a pressure of 15 Pa, and a condensing surface temperature of 110 °C, by controlling the residence time of the separated liquid on the heating surface to be 125 s, the mass ratio of the distillate to the residue can be stabilized at 8:2. The main component of the obtained residue is oligomer, which is recorded as the alcoholysis refined residue, collected and transferred to the alcoholysis device to participate in the depolymerization reaction in the next production cycle; the obtained distillate is recorded as the monomer liquid, and the BHET content of the monomer liquid is 96.5 wt% and the DEG content is 3.2 wt%.

[0030] 4) Uniformly mix the monomer liquid obtained in step 3) with a 1,4-butanediol dispersion containing 100 ppm tetrabutyl titanate and 1000 ppm triphenyl phosphate at a mass ratio of 90:10 under the protection of nitrogen at 170 °C and 101 kPa, and maintain the temperature and transfer it to a pre-polycondensation reactor. At 235 °C, react for 2.5 h. The pressure is maintained at 101 kPa for the first 1 h, and then linearly decreases from 101 kPa to 1 kPa with the reaction time; then transfer it to a final polycondensation reactor. At 265 °C, 50 Pa, react for 2.5 h, cool, pelletize and dry the obtained melt to obtain film base material grade recycled polyester chips with an intrinsic viscosity of 0.637 ± 0.003 dL / g, a melting point of 240.1 ± 1 °C, and a hue L / b value of 81.3 / 1.94 ± 0.09. Example 2

[0031] 1) Uniformly mix waste polyester material, EG, catalyst, stabilizer, and activated carbon in a certain proportion, then feed them into the alcoholysis device. Under the protection of inert gas and uniform stirring at a temperature of 200 °C and a pressure of 200 kPa, carry out the depolymerization reaction for 2 h. Then, at 70 °C, filter to remove activated carbon and other filterable impurities, and keep the filtrate at 70 °C. Flow it through cation exchange resin and anion exchange resin in sequence for ion removal and reduction. The total concentration of anions and cations in the obtained liquid is 50 ppm, which is recorded as the alcoholysis solution.

[0032] Among them, the waste polyester material is a dense waste film with a PET component content of 98.5 wt%; the EG is a mixture of polyester polymerization-grade EG and the EG recovered in step 2) at a ratio of 1:0.1; the catalyst is sodium carbonate; the stabilizer is potassium acetate; the "in a certain proportion" means based on the mass of PET, the addition amount of EG is 200 wt%, the addition amount of the catalyst is 0.5 wt%, the addition amount of the stabilizer is 0.5×10 -2 wt%, and the addition amount of activated carbon is 1 wt%.

[0033] 2) Under the protection of inert gas, preheat the alcoholysis solution obtained in step 1) to 120 °C, then transfer it to a wiped film evaporator with microwave radiation for microwave radiation-induced film evaporation treatment to remove substances in the alcoholysis solution with boiling points lower than BHET. The gap between the rotor scraper and the inner wall of the evaporator is 0.5 mm. This treatment controls the air pressure in the film evaporation chamber to be 600 Pa through the vacuum system, controls the residence time of the alcoholysis solution on the evaporation surface under the action of microwave irradiation to be 20 s through the feed flow rate and the scraper rotation speed, and controls the temperature of the concentrated finished liquid at the concentration outlet to be maintained at 155 °C through the microwave power. The EG content in the concentrated finished liquid is 0.02 wt%, and the DEG content is 2.0 wt%, which is recorded as the separation liquid; at the same time, condense and collect the low-boiling substances removed in this step, and transfer them to a conventional distillation separation device to obtain EG with a purity of 99.2 wt%, which is recorded as the recovered EG.

[0034] 3) Transfer the separation liquid obtained in step 2) to a molecular distillation device. At a heating surface temperature of 215 °C, a pressure of 25 Pa, and a condensation surface temperature of 120 °C, by controlling the residence time of the separation liquid on the heating surface to be 105 s, the mass ratio of the distillate to the residue can be stabilized at 7.5:2.5. The main component of the obtained residue is oligomer, which is recorded as the alcoholysis refined residue, collected and transferred to the alcoholysis device to participate in the depolymerization reaction in the next production cycle; the obtained distillate is recorded as the monomer liquid, and the BHET content of the monomer liquid is 97.3 wt% and the DEG content is 2.5 wt%.

[0035] 4) The monomer liquid obtained in step 3) and the ethylene glycol dispersion containing 500 ppm germanium acetate and 200 ppm trimethyl phosphate were uniformly mixed at a mass ratio of 95:5 under nitrogen protection at 180 °C and 101 kPa, and then transferred to a pre-polycondensation reactor while maintaining the temperature. The reaction was carried out at 240 °C for 1.5 h. The pressure was maintained at 101 kPa for the first 0.5 h, and then linearly decreased from 101 kPa to 1 kPa with the reaction time. Then it was transferred to a final polycondensation reactor, and the reaction was carried out at 285 °C and 20 Pa for 1.5 h. The obtained melt was cooled, pelletized and dried to obtain film base grade recycled polyester chips with an intrinsic viscosity of 0.658 ± 0.008 dL / g, a melting point of 247.8 ± 0.8 °C, and a hue L / b value of 84.5 / 0.84 ± 0.05. Example 3

[0036] 1) The waste polyester material, EG, catalyst, stabilizer and activated carbon were uniformly mixed in a certain proportion and then fed into an alcoholysis device. Under the protection of inert gas and uniform stirring at a temperature of 195 °C and a pressure of 150 kPa, the depolymerization reaction was carried out for 3 h. Then at 60 °C, the activated carbon and other filterable impurities were removed by filtration, and the filtrate was maintained at 60 °C and passed through a cation exchange resin and an anion exchange resin in turn for ion reduction. The total concentration of cations and anions in the obtained liquid was 20 ppm, which was recorded as the alcoholysis liquid.

[0037] Among them, the waste polyester material was a waste film compact material with a PET component content of 95.4 wt%; the EG was a mixture of polyester polymerization grade EG and the recycled EG in step 2) at a ratio of 1:0.5; the catalyst was zinc acetate; the stabilizer was sodium acetate; the certain proportion meant that based on the mass of PET, the addition amount of EG was 300 wt%, the addition amount of the catalyst was 0.8 wt%, the addition amount of the stabilizer was 3×10 -2 wt%, and the addition amount of activated carbon was 2 wt%.

[0038] 2) The alcoholysis liquid obtained in step 1) was preheated to 115 °C under the protection of inert gas and then transferred to a wiped film evaporator with microwave radiation for microwave radiation-induced film evaporation treatment to remove substances with boiling points lower than BHET in the alcoholysis liquid. The gap between the rotor scraper and the inner wall of the evaporator was 1.5 mm. This treatment controlled the pressure in the film evaporation chamber to 500 Pa through a vacuum system, controlled the residence time of the alcoholysis liquid on the evaporation surface under the action of microwave irradiation to 50 s through the feed flow rate and the scraper rotation speed, and controlled the temperature of the concentrated product at the outlet to 150 °C through the microwave power. The EG content in the concentrated product liquid was 0.03 wt%, and the DEG content was 2.2 wt%, which was recorded as the separated liquid; at the same time, the low-boiling substances removed in this step were condensed and collected and transferred to a conventional distillation separation device to obtain EG with a purity of 99.2 wt%, which was recorded as the recycled EG.

[0039] 3) Transfer the separation liquid obtained in step 2) to a molecular distillation device. At a heating surface temperature of 218 °C, a pressure of 22 Pa, and a condensation surface temperature of 115 °C, by controlling the residence time of the separation liquid on the heating surface to be 115 s, the mass ratio of the distillate to the residue can be stabilized at 7.7:2.3. The main component of the obtained residue is oligomer, denoted as alcoholysis refined residue, which is collected and transferred to an alcoholysis device to participate in the depolymerization reaction in the next production cycle; the obtained distillate is denoted as monomer liquid, and the BHET content of the monomer liquid is 97.0 wt% and the DEG content is 2.8 wt%.

[0040] 4) Uniformly mix the monomer liquid obtained in step 3) with an ethylene glycol dispersion containing 1000 ppm of antimony glycolate and 600 ppm of triphenyl phosphite at a mass ratio of 93:7 under nitrogen protection at 175 °C and 101 kPa, and maintain the temperature and transfer it to a prepolycondensation reactor. At 237 °C, react for 2 h, and keep the pressure at 101 kPa for the first 0.8 h, and then linearly decrease from 101 kPa to 1 kPa with the reaction time; then transfer it to a final polycondensation reactor, at 275 °C, 30 Pa, react for 2 h, cool, pelletize and dry the obtained melt, and thus obtain film base material grade recycled polyester chips with an intrinsic viscosity of 0.642 ± 0.007 dL / g, a melting point of 245.1 ± 0.9 °C, and a hue L / b value of 82.5 / 1.14 ± 0.06. Example 4

[0041] 1) Uniformly mix waste polyester material, EG, catalyst, stabilizer and activated carbon in a certain proportion, and feed them into an alcoholysis device. At a temperature of 195 °C and a pressure of 120 kPa, under inert gas protection and uniform stirring, carry out a depolymerization reaction for 3 h. Then at 100 °C, filter to remove activated carbon and other filterable impurities, and maintain the filtrate at 100 °C, and flow through a cation exchange resin and an anion exchange resin in sequence for ion removal. The total concentration of cations and anions in the obtained liquid is 26 ppm, denoted as alcoholysis liquid.

[0042] Among them, the waste polyester material is a colored cloth foam material with a PET component content of 91.7 wt%; the EG is a mixture of polyester polymerization grade EG and the recycled EG in step 2) at a ratio of 1:0.5; the catalyst is tetraisopropyl titanate; the stabilizer is sodium acetate; the certain proportion means based on the mass of PET, the addition amount of EG is 300 wt%, the addition amount of the catalyst is 0.8 wt%, the addition amount of the stabilizer is 4×10 -2 wt%, and the addition amount of activated carbon is 4 wt%.

[0043] 2) Under the protection of inert gas, preheat the alcoholysis solution obtained in step 1) to 115 °C, transfer it to a wiped film evaporator with microwave radiation, and carry out microwave radiation-induced thin film evaporation treatment to remove substances with boiling points lower than BHET in the alcoholysis solution. The gap between the rotor scraper and the inner wall of the evaporator is 1 mm. This treatment controls the air pressure in the thin film evaporation chamber to be 550 Pa through the vacuum system, controls the residence time of the alcoholysis solution on the evaporation surface under the action of microwave irradiation to be 40 s through the feed flow rate and the scraper rotation speed, and controls the temperature of the concentrated product at the outlet to be maintained at 152 °C through the microwave power. The EG content in the concentrated product is 0.02 wt%, and the DEG content is 2.1 wt%, which is recorded as the separated liquid; at the same time, condense and collect the low-boiling substances removed in this step, and transfer them to a conventional distillation separation device to obtain EG with a purity of 99.0 wt%, which is recorded as the recovered EG.

[0044] 3) Transfer the separated liquid obtained in step 2) to a molecular distillation device. At a heating surface temperature of 216 °C, a pressure of 23 Pa, and a condensing surface temperature of 115 °C, by controlling the residence time of the separated liquid on the heating surface to be 113 s, the mass ratio of the distillate to the residue can be stabilized at 7.6:2.4. The main component of the obtained residue is oligomer, which is recorded as the alcoholysis refined residue, collected and transferred to the alcoholysis device to participate in the depolymerization reaction in the next production cycle; the obtained distillate is recorded as the monomer liquid, and the BHET content of the monomer liquid is 97.1 wt% and the DEG content is 2.7 wt%.

[0045] 4) Uniformly mix the monomer liquid obtained in step 3) with an ethylene glycol dispersion containing 500 ppm tetrabutyl titanate and 400 ppm trimethyl phosphate at a mass ratio of 92:8 under the protection of nitrogen at 175 °C and 101 kPa, and maintain the temperature and transfer it to a prepolymerization reactor. React at 238 °C for 2.1 h, and keep the pressure at 101 kPa for the first 0.9 h, and then linearly decrease from 101 kPa to 1 kPa with the reaction time; then transfer it to a final polymerization reactor, react at 278 °C, 35 Pa for 2.2 h, cool and granulate the obtained melt and dry it to obtain film base material grade recycled polyester chips with an intrinsic viscosity of 0.652 ± 0.005 dL / g, a melting point of 244.9 ± 0.8 °C, and a hue L / b value of 84.1 / 1.01 ± 0.05. Example 5

[0046] 1) The waste polyester material, EG, catalyst, stabilizer, and activated carbon are uniformly mixed in a certain proportion and then fed into the alcoholysis device. Under the protection of inert gas and uniform stirring, a depolymerization reaction is carried out at a temperature of 192 °C and a pressure of 160 kPa for 4 h. Then, at 80 °C, the activated carbon and other filterable impurities are removed by filtration, and the filtrate is maintained at 80 °C and sequentially flows through a cation exchange resin and an anion exchange resin for ion removal and reduction. The total concentration of cations and anions in the obtained liquid is 30 ppm, which is denoted as the alcoholysis solution.

[0047] Among them, the waste polyester material is a colored cloth foam material with a PET component content of 85.2 wt%; the EG is a mixture of polyester polymerization-grade EG and the EG recovered in step 2) at a ratio of 1:0.8; the catalyst is zinc acetate; the stabilizer is potassium acetate; the "in a certain proportion" means that based on the mass of PET, the addition amount of EG is 350 wt%, the addition amount of the catalyst is 1 wt%, the addition amount of the stabilizer is 2×10 -2 wt%, and the addition amount of activated carbon is 5 wt%.

[0048] 2) The alcoholysis solution obtained in step 1) is preheated to 115 °C under the protection of inert gas and then transferred to a wiped film evaporator with microwave radiation for microwave radiation-induced film evaporation treatment to remove substances in the alcoholysis solution with boiling points lower than BHET. The gap between the rotor scraper and the inner wall of the evaporator is 1.5 mm. This treatment controls the air pressure in the film evaporation chamber to be 500 Pa through a vacuum system, controls the residence time of the alcoholysis solution on the evaporation surface under the action of microwave irradiation to be 40 s through the feed flow rate and the scraper rotation speed, and controls the temperature of the concentrated finished liquid at the outlet to be maintained at 150 °C through the microwave power. The EG content in the concentrated finished liquid is 0.03 wt%, and the DEG content is 2.3 wt%, which is denoted as the separation liquid; at the same time, the low-boiling substances removed in this step are condensed and collected and transferred to a conventional distillation separation device to obtain EG with a purity of 99.0 wt%, which is denoted as the recovered EG.

[0049] 3) The separation liquid obtained in step 2) is transferred to a molecular distillation device. At a heating surface temperature of 218 °C, a pressure of 20 Pa, and a condensation surface temperature of 115 °C, by controlling the residence time of the separation liquid on the heating surface to be 120 s, the mass ratio of the distillate to the residue can be stabilized at 7.9:2.1. The main component of the obtained residue is oligomer, which is denoted as the alcoholysis refined residue, collected and transferred to the alcoholysis device to participate in the depolymerization reaction in the next production cycle; the obtained distillate is denoted as the monomer liquid, and the BHET content of the monomer liquid is 96.9 wt% and the DEG content is 2.9 wt%.

[0050] 4) The monomer liquid obtained in step 3) and the ethylene glycol dispersion containing 400 ppm tetrabutyl titanate and 800 ppm triphenyl phosphate were uniformly mixed at a mass ratio of 91.5:8.5 under nitrogen protection at 175 °C and 101 kPa, and then transferred to a prepolymerization reactor while maintaining the temperature. The reaction was carried out at 237 °C for 2 h. The pressure was maintained at 101 kPa for 0.7 h at the beginning, and then linearly decreased from 101 kPa to 1 kPa with the reaction time. Then it was transferred to a final polymerization reactor, and the reaction was carried out at 280 °C and 35 Pa for 2 h. The obtained melt was cooled, granulated and dried to obtain film base grade recycled polyester chips with an intrinsic viscosity of 0.648 ± 0.006 dL / g, a melting point of 242.5 ± 0.9 °C, and a hue L / b value of 83.5 / 0.95 ± 0.06. Example 6

[0051] 1) The waste polyester material, EG, catalyst, stabilizer and activated carbon were uniformly mixed in a certain proportion and then fed into an alcoholysis device. Under the protection of inert gas and uniform stirring at a temperature of 192 °C and a pressure of 125 kPa, the depolymerization reaction was carried out for 4 h. Then at 80 °C, the activated carbon and other filterable impurities were removed by filtration, and the filtrate was maintained at 80 °C and passed through a cation exchange resin and an anion exchange resin in turn for ion reduction. The total concentration of cations and anions in the obtained liquid was 28 ppm, which was recorded as the alcoholysis liquid.

[0052] Among them, the waste polyester material was waste packaging bottle flakes with a PET component content of 92.8 wt%; the EG was a mixture of polyester polymerization grade EG and the recycled EG in step 2) at a ratio of 1:0.8; the catalyst was zinc acetate; the stabilizer was sodium acetate; the certain proportion was based on the mass of PET, the addition amount of EG was 350 wt%, the addition amount of the catalyst was 1 wt%, and the addition amount of the stabilizer was 1×10 -2 wt%; the addition amount of activated carbon was 3 wt%.

[0053] 2) The alcoholysis liquid obtained in step 1) was preheated to 115 °C under the protection of inert gas and then transferred to a wiped film evaporator with microwave radiation for microwave radiation-induced thin film evaporation treatment to remove substances with boiling points lower than BHET in the alcoholysis liquid. The gap between the rotor scraper and the inner wall of the evaporator was 1 mm. This treatment controlled the air pressure in the thin film evaporation chamber to 550 Pa through a vacuum system, controlled the residence time of the alcoholysis liquid on the evaporation surface under microwave irradiation to 80 s through the feed flow rate and the scraper rotation speed, and controlled the temperature of the concentrated product at the outlet to 148 °C through the microwave power. The EG content in the concentrated product liquid was 0.03 wt%, and the DEG content was 2.5 wt%, which was recorded as the separated liquid; at the same time, the low-boiling substances removed in this step were condensed and collected, and transferred to a conventional distillation separation device to obtain EG with a purity of 99.3 wt%, which was recorded as the recycled EG.

[0054] 3) Transfer the separation liquid obtained in step 2) into a molecular distillation device. At a heating surface temperature of 219 °C, a pressure of 23 Pa, and a condensing surface temperature of 115 °C, by controlling the residence time of the separation liquid on the heating surface to be 117 s, the mass ratio of the distillate to the residue can be stabilized at 7.8:2.2. The main component of the obtained residue is oligomer, denoted as the alcoholysis refined residue, which is collected and transferred into the alcoholysis device to participate in the depolymerization reaction in the next production cycle; the obtained distillate is denoted as the monomer liquid, and the BHET content of the monomer liquid is 96.7 wt% and the DEG content is 3.1 wt%.

[0055] 4) Uniformly mix the monomer liquid obtained in step 3) with an ethylene glycol dispersion containing 500 ppm tetrabutyl titanate and 700 ppm triphenyl phosphite at a mass ratio of 91:9 under nitrogen protection at 175 °C and 101 kPa, and then transfer the mixture while maintaining the temperature into a prepolycondensation reactor. React at 235 °C for 2.3 h. The pressure is maintained at 101 kPa for 0.9 h at the beginning, and then linearly decreases from 101 kPa to 1 kPa with the reaction time; then transfer it into a final polycondensation reactor, react at 282 °C and 35 Pa for 2 h, cool, pelletize, and dry the obtained melt to obtain film base grade recycled polyester chips with an intrinsic viscosity of 0.651 ± 0.004 dL / g, a melting point of 241.6 ± 0.9 °C, and a hue L / b value of 82.9 / 0.89 ± 0.06.

[0056] The above is only the preferred embodiment of the present invention. The above examples do not impose any formal restrictions on the essence of the present invention. Any simple modification or deformation made by those of ordinary skill in the art in the technical field after reading this specification based on the technical essence of the present invention, and any equivalent embodiments that may be changed or modified by using the above-disclosed technical content into equivalent variations, still fall within the scope of the technical solution of the present invention without departing from the essence and scope of the present invention.

Claims

1. A preparation method of membrane-based recycled polyester chips, characterized in that, It includes the following steps: 1) After uniformly mixing waste polyester materials, EG, catalyst, stabilizer and activated carbon in a certain proportion, feed them into an alcoholysis device. Under the protection of inert gas at a temperature of 185 - 200 °C and a pressure of 100 - 200 kPa, stir evenly for 2 - 5 h for depolymerization reaction. Then at 60 - 100 °C, filter to remove activated carbon and other filterable impurities, and maintain the filtrate at 60 - 100 °C, and flow through cation exchange resin and anion exchange resin in sequence for ion removal until the total concentration of cations and anions ≤ 50 ppm. The obtained liquid is recorded as alcoholysis liquid; 2) Under the protection of inert gas, preheat the alcoholysis liquid obtained in step 1) to 110 - 120 °C, transfer it to a scraped - surface thin - film evaporator with microwave radiation, and carry out microwave - radiation - induced thin - film evaporation treatment to remove substances in the alcoholysis liquid with boiling points lower than BHET. Then control the air pressure in the thin - film evaporation cavity to be 400 - 600 Pa through a vacuum system, control the residence time of the alcoholysis liquid on the evaporation surface under the action of microwave irradiation to be 20 - 100 s through the feed flow rate and the scraping speed, and control the temperature of the finished liquid at the concentration outlet to be maintained at 145 - 155 °C through the microwave power to obtain a concentrated finished liquid with EG < 0.1wt% and a DEG content of 2.0 - 2.6wt%. The obtained concentrated finished liquid is recorded as separation liquid; At the same time, condense and collect the low - boiling substances removed in this step, and transfer the low - boiling substances to a conventional distillation separation device, and obtain EG with a purity ≥ 99.0wt% through conventional distillation separation. The obtained EG is recorded as recycled EG; 3) Transfer the separation liquid obtained in step 2) to a molecular distillation device. At a heating - surface temperature of 215 - 220 °C, a pressure of ≤ 25 Pa, and a condensing - surface temperature of 110 - 120 °C, by controlling the residence time of the separation liquid on the heating surface, make the mass ratio of the distillate to the residue maintain at 7.5:2.5 - 8:2; The main component of the obtained residue is oligomer, which is recorded as alcoholysis refined residue. After collecting the alcoholysis refined residue, transfer it to the alcoholysis device in step 1) to participate in the depolymerization reaction in the next production cycle; The obtained distillate is recorded as monomer liquid, and the BHET content of the monomer liquid ≥ 96.5wt% and the DEG content is 2.5 - 3.2wt%; 4) Uniformly mix the monomer liquid obtained in step 3) with a 1,4 - butanediol dispersion containing a certain amount of catalyst and stabilizer in a certain proportion at a temperature of 170 - 180 °C, a pressure of 101 kPa, and under the protection of nitrogen, and maintain the temperature and transfer it to a pre - polycondensation reactor. The pre - polycondensation reaction temperature is 235 - 240 °C, the reaction time is 1.5 - 2.5 h, the pressure in the reactor is 101 kPa at the beginning, keep it unchanged for 0.5 - 1 h first, and then the pressure linearly drops from 101 kPa to 1 kPa with the reaction time; Then transfer it to a final - polycondensation reactor, and react at a temperature of 265 - 285 °C and a pressure of 20 - 50 Pa for 1.5 - 2.5 h, and then cool, pelletize and dry the obtained melt to obtain film - base - grade recycled polyester chips.

2. The preparation method of a film-based recycled polyester chip according to claim 1, characterized in that, The waste polyester material described in step 1) is a post-consumer polyester product or production waste with a PET component content of ≥ 85 wt%; the catalyst described in step 1) is one of sodium carbonate, zinc acetate, tetra-n-butyl titanate, and tetra-isopropyl titanate; the stabilizer described in step 1) is one of sodium acetate and potassium acetate; the statement that the waste polyester material, EG, catalyst, stabilizer, and activated carbon are in a certain proportion in step 1) means that based on the mass of PET contained in the waste polyester material, the addition amount of EG is 200 - 400 wt%, the addition amount of the catalyst is 0.5 - 1.5 wt%, the addition amount of the stabilizer is 0.5 - 5×10 -2 wt%, and the addition amount of activated carbon is 1 - 5 wt%.

3. The preparation method of a film-based recycled polyester chip according to claim 1, characterized in that, The EG is a mixture of polyester polymerization grade EG and the recycled EG obtained in step 2) of the present invention at a ratio of 1:0.1 to 1:

1.

4. The method for preparing a film base material grade recycled polyester chip according to claim 1, characterized in that: The contents of the various substances in the 1,4-butanediol dispersion containing a certain amount of catalyst and stabilizer described in step 4) are: 100-1000 ppm of catalyst, and 200-1000 ppm of stabilizer; the mixing ratio of the monomer liquid described in step 4) to the 1,4-butanediol dispersion is 90:10-95:5 by mass.

5. The preparation method of a film-based recycled polyester chip according to claim 1, characterized in that, The catalyst in step 4) is one of ethylene glycol antimony, germanium acetate, and tetra-n-butyl titanate, and the stabilizer is one of trimethyl phosphate, triphenyl phosphate, or triphenyl phosphite.