Synthesis process of polyethylene glycol oxalate

Abstract

The invention provides a synthesis process of polyethylene glycol oxalate. The invention also provides a synthesis system of polyethylene glycol oxalate. The invention further provides the polyethylene glycol oxalate. The invention further provides application of the polyethylene glycol oxalate in industrial application materials. According to the synthesis process of polyethylene glycol oxalate provided by the invention, parameters such as concentration ratio, temperature, pressure and the like in the ester exchange stage, the pre-polycondensation stage and the final polycondensation stage of the synthesis process of polyethylene glycol oxalate are accurately controlled, and a special double-layer sleeve type reactor, an efficient vacuum system and a solvent recovery system are combined; the method realizes efficient synthesis of polyethylene glycol oxalate, improves the thermal stability and mechanical properties of the product, reduces the production cost and environmental pollution, and has significant industrial application value and environmental protection benefits.

Description

Technical Field

[0001] This invention belongs to the technical field of polyester material preparation, and relates to a synthesis process of polyoxoethylene glycol ester, specifically a synthesis process of biodegradable polyoxoethylene glycol ester. Background Technology

[0002] Polyethylene oxalate (PEOx) is an important biodegradable polyester material with good environmental performance and biodegradability. However, the synthesis of PEOx in existing technologies faces several problems: First, the reaction conditions are not precisely controlled, resulting in low molecular weight and poor thermal stability of the product; second, the reactor structure design is not reasonable enough, leading to low heat and mass transfer efficiency; third, the vacuum system configuration is not optimized, making it difficult to achieve efficient removal of small molecules; fourth, the solvent recovery system is imperfect, leading to resource waste and environmental pollution. These problems seriously restrict the industrial production and application of PEOx.

[0003] The synthesis process of traditional polyester materials such as polyethylene terephthalate (PET) is relatively mature, mainly prepared through esterification and polycondensation reactions. PET processes are typically carried out under high temperature and high pressure conditions, requiring efficient heat and mass transfer equipment, such as falling film reactors or tubular reactors. However, PET is difficult to degrade in the natural environment, requiring over 400 years to fully degrade, and the recycling process is complex, making closed-loop recycling difficult. In contrast, PEOx is biodegradable, complies with global plastic bans and restrictions, and is particularly suitable for the production of single-use packaging materials. However, optimizing the PEOx synthesis process remains a pressing issue. Summary of the Invention

[0004] In view of the characteristics of the prior art described above, the purpose of this invention is to provide a synthesis process for poly(ethylene oxalate), which achieves efficient synthesis of poly(ethylene oxalate) by precisely controlling the reaction conditions at each stage, combined with a specially designed reactor structure and an efficient solvent recovery system, thereby improving the thermal stability, mechanical properties and biodegradability of the product.

[0005] To achieve the above and other related objectives, the first aspect of the present invention provides a process for synthesizing poly(ethylene oxalate), comprising the following steps: 1) Dimethyl oxalate and ethylene glycol are mixed and then subjected to transesterification under the action of a catalyst to obtain oligomeric ethylene glycol oxalate and methanol; The reaction formula is shown in equation (1): n (COOCH3)2 + n HOCH2CH2OH → n HOCH2CH2COOCCOOH + 2n CH3OH; 2) The oligomeric oxalate glycol ester is subjected to a pre-condensation reaction to obtain medium molecular weight polyoxalate glycol ester; The reaction formula is shown in equation (2): 2n HOCH2CH2COOCCOOH → (COOCH2CH2)2COOCCOOH + n H2O; 3) Medium molecular weight polyoxoethylene glycol ester is subjected to a final polycondensation reaction to obtain high molecular weight polyoxoethylene glycol ester. The reaction formula is shown in equation (3): (COOCH2CH2)2COOCCOOH → [O-CH2CH2-O-CO-CO-O-CH2CH2-O] n + (n-1) H2O, In formulas (1), (2) or (3), n is a positive integer; the weight-average molecular weight of the oligomeric oxalate glycol ester is 1-15 kDa; the weight-average molecular weight of the medium molecular weight polyoxalate glycol ester is 25-50 kDa; and the weight-average molecular weight of the high molecular weight polyoxalate glycol ester is 80-100 kDa.

[0006] A second aspect of the present invention provides a synthesis system for poly(ethylene oxalate), comprising, in sequence along the reaction direction, a mixing device, an ester exchange reaction unit, a pre-polymerization reaction unit, a purification unit, and a final polymerization reaction unit. The ester exchange reaction unit is connected to a CO2 treatment device and is also connected to a methanol recovery device to form a circulation loop. The purification unit, in sequence along the reaction direction, includes a washing component, a filtering component, and a drying component. The filtering component is connected to a solvent recovery unit, and the solvent recovery unit is also connected to the washing component to form a circulation loop.

[0007] The third aspect of the present invention provides a polyoxin glycol ester, which is prepared by the synthesis process of the polyoxin glycol ester provided in the first aspect of the present invention.

[0008] The fourth aspect of this invention provides the use of poly(ethylene oxalate) in industrial application materials.

[0009] As described above, the synthesis process of polyoxoethylene glycol ester provided by the present invention has the following beneficial effects: (1) The present invention provides a synthesis process for polyoxoethylene glycol ester. By precisely controlling the reaction conditions at each stage, including optimizing key parameters such as the concentration ratio, temperature control, catalyst selection, reactor structure, vacuum system and solvent recovery system at stages such as transesterification, pre-condensation and final condensation, combined with a specially designed reactor structure and a high-efficiency solvent recovery device, the high-efficiency synthesis of polyoxoethylene glycol ester is achieved. The product has excellent thermal stability, good mechanical properties and good biodegradability.

[0010] (2) The synthesis process of polyoxoethylene glycol ester provided by the present invention improves the reaction efficiency and molecular weight of the product by precisely controlling the concentration ratio, temperature and pressure of the transesterification, pre-condensation and final condensation stages. The synthesized polyoxoethylene glycol ester has a thermal decomposition temperature of 5% above 240℃, a crystallization temperature of about 137℃, and an intrinsic viscosity of 0.6-1.5dL / g, exhibiting excellent thermal stability and good mechanical properties.

[0011] (3) The synthesis process of polyoxoethylene glycol ester provided by the present invention adopts a double-layer shell reactor and a top condenser coil design, which improves the heat and mass transfer efficiency, reduces side reactions, and ensures the purity and uniformity of the product.

[0012] (4) The synthesis process of polyoxoethylene glycol ester provided by the present invention optimizes the mixing effect in the reactor through the anchor-type stirring paddle design, thereby improving the reaction rate and product molecular weight.

[0013] (5) The synthesis process of polyoxoethylene glycol ester provided by the present invention adopts a vacuum system with molecular pump and mechanical pump in series, which realizes efficient removal of small molecules in the final polycondensation stage and improves the molecular weight of the product.

[0014] (6) The synthesis process of polyoxoethylene glycol ester provided by the present invention achieves efficient recovery and recycling of solvents through the optimized design of methanol and solvent recovery devices such as ethanol, thereby reducing production costs and environmental pollution.

[0015] (7) The synthesis process of polyoxoethylene glycol ester provided by the present invention realizes the resource utilization of CO2 through the application of CO2 by-product treatment device, further reduces carbon emissions and improves the environmental performance of the process.

[0016] (8) The synthesis process of polyoxadenyl glycol ester provided by the present invention improves reaction efficiency, shortens reaction time and reduces energy consumption by precisely controlling reaction conditions and optimizing reactor structure; and reduces production costs and improves economic benefits by optimizing process parameters and recycling solvents. Attached Figure Description

[0017] Figure 1 The diagram shown is a structural diagram of a synthesis system for polyoxoethylene glycol ester according to the present invention.

[0018] Figure 2 The diagram shows the structure of a double-walled reactor in the synthesis system of polyoxoethylene glycol ester according to the present invention, wherein 1 is the inner tube; 2 is the outer tube; 3 is the cooling channel; 4 is the condenser coil; 5 is the agitator; and 6 is the impeller. Detailed Implementation

[0019] The following detailed description discloses an embodiment of the synthesis process of poly(ethylene oxalate) glycol ester according to this application. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of actually identical structures may be omitted. This is to avoid making the following description unnecessarily lengthy and to facilitate understanding by those skilled in the art. Furthermore, the following description is provided to enable those skilled in the art to fully understand this application and is not intended to limit the subject matter of the claims.

[0020] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the particular range. The range defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range.

[0021] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0022] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0023] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0024] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0025] The first aspect of this invention provides a process for synthesizing poly(ethylene oxalate), comprising the following steps: 1) Dimethyl oxalate and ethylene glycol are mixed and then subjected to transesterification under the action of a catalyst to obtain oligomeric ethylene glycol oxalate and methanol; The reaction formula is shown in equation (1): n (COOCH3)2 + n HOCH2CH2OH → n HOCH2CH2COOCCOOH + 2n CH3OH; 2) The oligomeric oxalate glycol ester is subjected to a pre-condensation reaction to obtain medium molecular weight polyoxalate glycol ester; The reaction formula is shown in equation (2): 2n HOCH2CH2COOCCOOH → (COOCH2CH2)2COOCCOOH + n H2O; 3) Medium molecular weight polyoxoethylene glycol ester is subjected to a final polycondensation reaction to obtain high molecular weight polyoxoethylene glycol ester. The reaction formula is shown in equation (3): (COOCH2CH2)2COOCCOOH → [O-CH2CH2-O-CO-CO-O-CH2CH2-O] n + (n-1) H2O, In formulas (1), (2) or (3), n is a positive integer; the weight-average molecular weight of the oligomeric oxalate glycol ester is 1-15 kDa; the weight-average molecular weight of the medium molecular weight polyoxalate glycol ester is 20-50 kDa; and the weight-average molecular weight of the high molecular weight polyoxalate glycol ester is 80-100 kDa.

[0026] In the above formulas (1), (2) or (3), n represents the degree of polymerization, that is, the number of repeating units. In the transesterification reaction, pre-condensation reaction or final condensation reaction, the polymer chain is gradually formed by releasing methanol.

[0027] In formulas (1), (2), or (3) above, the viscosity of the oligomeric oxalate glycol ester is ≥1.46 Pa·s and <50 Pa·s; the viscosity of the medium molecular weight polyoxalate glycol ester is ≥50 Pa·s and ≤300 Pa·s; and the viscosity of the high molecular weight polyoxalate glycol ester is 732 Pa·s-1200 Pa·s.

[0028] The innovation of the above synthesis process mainly lies in its stepwise and controllable synthesis strategy. By decomposing the entire polymerization process into three stages, it cleverly avoids the two major challenges faced by polyoxoethylene glycol ester: (a1) Oxalic acid is unstable: Oxalic acid is very easy to decarboxylate (decompose into CO, CO2 and H2O) at high temperatures during polycondensation, which leads to chain termination and the inability to increase molecular weight.

[0029] (a2) The polymer chain is unstable: the oxalate bonds on the main chain of polyoxalate are sensitive to heat and hydrolysis, and are prone to chain breakage and degradation under high temperature and long-term reaction.

[0030] The three-step process in this invention systematically solves these problems by changing the starting materials and finely controlling the reaction process, as detailed below: (b1) In step 1), dimethyl oxalate is used instead of oxalic acid as the starting monomer. Dimethyl oxalate is a stable ester compound that does not undergo decarboxylation side reactions at the reaction temperature.

[0031] (b2) In step 2), the initial (oxalic acid-ethylene glycol) bond is constructed via "ester exchange" rather than "direct esterification." The byproduct released by this reaction is methanol, not water. The core objective of this stage is to generate oligomers with well-defined structures and controllable end groups, rather than pursuing high molecular weight. This lays a pure and stable foundation for subsequent reactions.

[0032] This step, under relatively mild conditions, condenses the oligomer obtained in the previous step, releasing water molecules and allowing the molecular weight (degree of polymerization n) to be initially and controllably increased, resulting in a "medium molecular weight" prepolymer.

[0033] This step can also be considered a crucial "purification and shaping" stage. While moderately increasing the molecular weight, it allows for more effective removal of residual small molecules (such as water and trace amounts of methanol) from the reaction system, and the molecular weight distribution and end-group structure of the prepolymer can potentially be adjusted by controlling conditions (such as temperature and vacuum). This avoids the high temperatures and prolonged reaction times that would result from attempting to achieve high molecular weights in the initial stages, thus reducing the risk of thermal degradation.

[0034] (b3) In step 3), molecular weight is increased under optimal conditions, which is usually carried out under high vacuum and strict temperature control. High vacuum is used to remove the byproduct water ((n-1) H2O) to the maximum extent and continuously, driving the polycondensation equilibrium reaction toward the formation of high molecular weight polymers.

[0035] Since pure and stable prepolymers have already been generated in steps 1) and 2), the final polycondensation can focus on the single objective of "chain growth." The materials in the reactor at this point are mainly prepolymers with identical active end groups, resulting in fewer side reactions. This allows for the achievement of higher molecular weights in a relatively shorter time and with minimal damage to the polymer chains. This is a significant improvement over the traditional one-pot direct polycondensation method.

[0036] In step 1) above, the molar ratio of dimethyl oxalate to ethylene glycol is 1:1-2, preferably 1:1. The key to this step is controlling the monomer molar ratio precisely to 1:1 to ensure that the oligomeric ethylene glycol oxalate produced by the reaction has the maximum degree of polymerization.

[0037] In step 1) above, the catalyst is a stannous oxalate or rare earth titanate composite solid catalyst.

[0038] In one embodiment, the molar amount of stannous oxalate is 3.9-4.1‰ of dimethyl oxalate, preferably 4‰. Stannous oxalate is a classic catalyst for transesterification and polycondensation, exhibiting high activity and good selectivity.

[0039] In one embodiment, the rare earth titanate composite solid catalyst comprises a rare earth element compound, a titanium-containing compound, and stannous oxalate. The molar ratio of rare earth element to stannous oxalate in the rare earth element compound is 0.5-2:1; the molar ratio of titanium element to rare earth element in the titanium-containing compound is 0.5-2:1; and the molar amount of stannous oxalate is 3.9-4.1‰ of dimethyl oxalate, preferably 4‰.

[0040] In a preferred embodiment, the rare earth element in the rare earth-containing compound is selected from at least one of lanthanum (La) or cerium (Ce), and the rare earth element in the compound is selected from at least one of La2O3, CeO2, La2(C2O4)3 or Ce(C2O4)2.

[0041] The aforementioned rare earth element-containing compounds typically exist in the form of their oxides (such as La2O3, CeO2) or oxalates, and may form specific surface structures or lattices through combination with titanium.

[0042] In a preferred embodiment, the titanium-containing compound is a titanium complex or titanium oxide.

[0043] In a further preferred embodiment, the titanium complex is a tetraalkyl titanate.

[0044] In the most preferred embodiment, the tetraalkyl titanate is selected from at least one of tetrabutyl titanate, tetraisopropyl titanate, or titanium acetylacetonate.

[0045] In a further preferred embodiment, the titanium oxide is TiO2.

[0046] The aforementioned rare earth titanate composite solid catalyst is a multi-metal synergistic composite solid catalyst. Its core is the "rare earth (La / Ce)-titanium (Ti)" framework, which is responsible for providing stable structure and basic catalytic activity; stannous oxalate (Sn) is introduced as a highly efficient co-catalyst, and by optimizing the ratio of the two (0.5-2:1), precise control of reaction rate, product selectivity and polymer molecular weight distribution can be achieved.

[0047] Specifically, lanthanum and cerium, as rare earth elements, are moderately strong Lewis acids that can effectively activate the carbonyl groups (C=O) in dimethyl oxalate and ethylene glycol, promoting nucleophilic attack and thus catalyzing transesterification reactions. At the same time, the introduction of rare earth elements can improve the thermal stability of the catalyst, enabling it to maintain its activity at higher temperatures during subsequent pre-condensation and final condensation.

[0048] Titanium is a known highly efficient catalyst for transesterification and polycondensation (widely used in PET polyester production). It provides strong Lewis acid sites and exhibits synergistic effects with rare earth elements, forming more stable and highly active catalytic centers. It exists as a "titanium ester" structure, which is a titanium complex or a titanium oxide (such as TiO2) supported on a carrier, forming the core framework or support portion of the catalyst. Compounds containing rare earth elements typically exist as their oxides (such as La2O3, CeO2) or oxalates, and through complexation with titanium in titanium-containing compounds, specific surface structures or lattices are formed, resulting in rare earth-titanium systems.

[0049] The composite of stannous oxalate and rare earth-titanium is designed to finely control catalytic activity and selectivity, avoiding excessive side reactions (such as thermal degradation or cyclization) that may occur with a single tin catalyst. As another key active component, it is physically mixed with or composited with the aforementioned rare earth-titanium framework through surface interactions.

[0050] In step 1) above, a third monomer, isosorbide, is added to the transesterification reaction. This allows for the convenient synthesis of copolymerized modified polyethylene oxalate.

[0051] In one embodiment, the molar amount of the third monomer is 4-6% of dimethyl oxalate, preferably 5%.

[0052] In step 1) above, the reaction temperature of the transesterification reaction is 120-160℃, preferably 160℃.

[0053] In step 1) above, the heating program for the transesterification reaction is as follows: heating to 70-80°C, preferably 80°C, at a heating rate of 9-11°C / min, preferably 10°C / min, and stirring for 55-65 minutes, preferably 60 minutes, and then heating to 120-160°C, preferably 160°C, at a heating rate of 9-11°C / min, preferably 10°C / min.

[0054] In one embodiment, the stirring rate is 10-50 rpm, preferably 30-40 rpm, to ensure uniform mixing of the reactants.

[0055] In step 1) above, the reaction time for the transesterification reaction is 160-290 minutes.

[0056] In step 1) above, the transesterification reaction is timed to the point at which the first drop of small molecule methanol is produced.

[0057] In step 2) above, the reaction temperature of the pre-condensation reaction is 120-130℃, preferably 130℃.

[0058] In step 2) above, the reaction pressure of the pre-condensation reaction is 2-3 kPa absolute pressure.

[0059] In step 2) above, the reaction time of the pre-condensation reaction is 30-60 minutes, preferably 45 minutes.

[0060] In step 2) above, after the pre-condensation reaction, the monomers are washed, filtered, and dried in sequence to remove unreacted monomers and impurities.

[0061] In one embodiment, the solvent used for washing is an organic solvent with a boiling point below 80°C, preferably ethanol.

[0062] In one embodiment, the solvent used for washing is 2-4 times the mass of medium molecular weight polyoxoethylene glycol ester.

[0063] In one embodiment, the filtration is a reduced pressure filtration, wherein the pressure of the reduced pressure filtration is 1-2 kPa absolute pressure.

[0064] In one embodiment, the filtering is repeated at least three times, preferably three times.

[0065] In one embodiment, the vacuum degree of the drying process is ≤1 kPa.

[0066] In one embodiment, the drying temperature is 50-80°C.

[0067] In one embodiment, the drying time is 6-12 hours.

[0068] In one embodiment, the drying process is carried out until the moisture content is below 200 ppm.

[0069] Because poly(ethylene oxalate) is heat-sensitive, excessively high drying temperatures can cause thermal degradation and a decrease in molecular weight, so temperature control is essential. Using a specific vacuum level serves three purposes: first, to rapidly remove residual solvent and trace amounts of water, thus accelerating the drying process; second, to create conditions for solvent vaporization at low temperatures; and third, to isolate oxygen and prevent the polymer from oxidizing and turning yellow under heating conditions. Moisture is a terminator of the polycondensation reaction, and extremely low moisture content is an absolute prerequisite for achieving high molecular weight in the subsequent final polycondensation reaction; therefore, it is necessary to control moisture content. Moisture control can be monitored using online or offline moisture analyzers (such as the Karl Fischer method).

[0070] In step 3) above, the reaction temperature of the final polycondensation reaction is 185-195℃, preferably 185℃. The resulting high molecular weight polyethylene oxalate is a high thermal stability polyethylene oxalate copolyester, with a 5% thermal decomposition temperature above 240℃.

[0071] In step 3) above, the heating program for the final polycondensation reaction is as follows: the temperature is increased to 185-195°C, preferably 185°C, at a heating rate of no more than 1°C / min. The final polycondensation temperature is reached at a slow heating rate to avoid side reactions caused by excessively rapid heating.

[0072] In step 3) above, the final polycondensation reaction is carried out in a vacuum, and the reaction pressure of the final polycondensation reaction is no greater than 100 Pa absolute pressure.

[0073] In step 3) above, the reaction time of the final polycondensation reaction is 120-240 minutes, preferably 180 minutes.

[0074] In step 3) above, the stirring rate during the final polycondensation reaction is 10-50 rpm, preferably 40 rpm, to ensure uniform mixing of the reactants.

[0075] A second aspect of the present invention provides a system for synthesizing poly(ethylene oxalate), such as... Figure 1 As shown, a mixing device, an ester exchange reaction unit, a pre-polymerization reaction unit, a purification unit, and a final polymerization reaction unit are connected sequentially along the reaction direction. The ester exchange reaction unit is connected to a CO2 treatment device and is also connected to a methanol recovery device to form a circulation loop. The purification unit includes a washing component, a filtering component, and a drying component sequentially along the reaction direction. The filtering component is connected to a solvent recovery unit, and the solvent recovery unit is also connected to the washing component to form a circulation loop.

[0076] In the above system, the mixing device is a conventional mixing reactor, which can achieve the mixing of dimethyl oxalate, ethylene glycol, and catalyst.

[0077] In the above system, such as Figure 1 As shown, the transesterification reaction unit is a double-walled reactor. This double-walled reactor is a conventionally used double-walled reactor and can be purchased commercially.

[0078] Specifically, such as Figure 2 As shown, the double-layered tube reactor is provided with an inner tube and an outer tube connected sequentially from the inside to the outside. A cooling channel is formed between the inner tube and the outer tube. A condenser coil is provided at the top of the inner tube. An agitator is also provided inside the inner tube. The blades of the agitator are located at 1 / 3 to 2 / 3 of the vertical height of the reactor.

[0079] In a preferred embodiment, the inner tube is made of titanium alloy and the outer tube is made of stainless steel.

[0080] In a preferred embodiment, the condenser coil is a conventionally used condenser coil.

[0081] In a preferred embodiment, the condenser coil is made of stainless steel. It can be used to condense methanol produced during the transesterification reaction.

[0082] In a preferred embodiment, the stirring paddle is an anchor-type stirring paddle, which is capable of uniformly mixing the reactants.

[0083] The methanol release during the transesterification reaction in the aforementioned transesterification unit is an exothermic process. If the heat cannot be removed in time, excessively high local temperatures will directly exacerbate the thermal degradation of the polyoxalate chains and the decarboxylation side reaction of the raw materials / intermediates, damaging the molecular chain structure, resulting in the inability to increase molecular weight and a darker product color. When the reaction is carried out in a double-walled reactor, the cooling channel between the inner and outer tubes forms a jacket surrounding the entire reaction zone. By circulating a cooling medium (such as heat transfer oil or cold water) into this channel, the heat of reaction can be efficiently and uniformly removed from the reactor wall, ensuring that the entire reaction system is maintained within the optimal and stable temperature window. This is the foundation for achieving the first step of high-quality oligomerization.

[0084] The transesterification reaction in the aforementioned transesterification unit is a reversible reaction. Timely removal of the byproduct methanol (2nCH3OH) is crucial for driving the reaction towards oligomer formation and improving conversion rate. The condenser coil at the top of the inner tube (usually circulated with cooling water) acts as a partial reflux condenser. The evaporated methanol vapor is condensed into liquid here. Through design, the reflux ratio can be controlled—allowing some condensate to reflux and maintain reactant concentration, while excess methanol is distilled off the system, thereby continuously disrupting the reaction equilibrium and driving the forward reaction. This is more effective and controllable than simply relying on tail gas condensation. Initially, the reaction is a liquid-liquid homogeneous phase, but the system viscosity gradually increases as oligomers are formed. Good mixing is essential for heat transfer (avoiding local overheating), mass transfer (small molecule diffusion), and maintaining uniform catalyst dispersion. The impeller blades are positioned at 1 / 3-2 / 3 of the reactor's vertical height, typically in the main region of the reactants, enabling the most effective radial and axial mixing. It lifts the bottom material upwards and forms a circulation, ensuring uniform temperature and concentration within the reactor. If the agitator is positioned too high, the material at the bottom may stagnate; if it is too low, there may be insufficient disturbance to the liquid surface, which is not conducive to methanol distillation. This design takes into account both whole-bottle mixing and surface renewal, which promotes mass transfer and assists in the escape of methanol.

[0085] In the above system, such as Figure 1 As shown, the transesterification reaction unit is equipped with a first online monitoring device, which is selected from one or more combinations of an online gas chromatograph (Online GC), an online viscometer, and a distributed temperature sensor. This device enables the achievement of the core monitoring objectives of the transesterification reaction unit: reaction conversion rate, prevention of local overheating, byproduct (methanol) removal efficiency, and early warning of decarboxylation side reactions (CO2 generation).

[0086] In one embodiment, the distributed temperature sensor is selected from any one or more combinations of PT100 resistance temperature sensors or thermocouples.

[0087] In the above system, such as Figure 1 As shown, the methanol recovery device is a sieve plate tower. It is used for distillation to recover methanol for recycling.

[0088] In one embodiment, the reflux ratio in the sieve plate tower is 0.1-3.0 times the minimum reflux ratio.

[0089] In one embodiment, the top condensation temperature of the sieve plate tower is -10 to 70°C, preferably 10°C.

[0090] In the above system, such as Figure 1 As shown, the CO2 treatment device includes a chemical absorption section and a desorption / regeneration section in sequence along the CO2 input direction. The chemical absorption section is an absorption tower, and the desorption / regeneration section is a desorption tower.

[0091] In one embodiment, the absorbent used in the chemical absorption section is a lean amine solution, preferably an ethanolamine (MEA) solution. The CO2 generated during the transesterification reaction is absorbed via chemical absorption. The absorbed CO2 can be regenerated using a desorption tower, achieving a purity of over 99%, and can be used for food-grade dry ice production or industrial storage.

[0092] In a preferred embodiment, the ethanolamine (MEA) solution is an aqueous solution with a weight percentage concentration of 15-30 wt% ethanolamine. It is added and controlled at a stoichiometric ratio of 1.1-1.5 times the CO2 molar flow rate at the absorber inlet, depending on the absorber tower design. In actual absorber towers, the mass transfer process is not ideal. To ensure CO2 absorption rate (typically designed values ​​>90% or even >99%), an excess of amine solution must be provided to maintain sufficient driving force (i.e., free amine concentration) in each section of the tower.

[0093] In one embodiment, in the desorption and regeneration section, the bottom temperature of the desorption tower is 110-130°C, and the top pressure is 0.1-0.3 MPa (absolute pressure). Indirect heating is achieved using saturated steam. In the aforementioned desorption and regeneration section, increasing the temperature shifts the reaction equilibrium of the amine-CO2 compound in the reverse direction to release CO2. Operating under a slightly positive pressure facilitates the discharge of CO2 gas from the top of the tower to subsequent equipment.

[0094] The CO2-containing gas drawn from the non-condensable gas in the transesterification reaction unit or condensation system in the above-mentioned chemical absorption section enters from the bottom of the absorption tower and comes into countercurrent contact with the absorbent lean amine liquid (such as cold MDEA solution) sprayed down from the top of the tower; the CO2 is chemically absorbed by the amine liquid, and the purified tail gas (mainly inert gases such as N2) is discharged from the top of the tower.

[0095] The aforementioned desorption and regeneration section is used to absorb CO2 generated during the transesterification reaction for resource utilization. In this section, the CO2-rich amine solution is discharged from the bottom of the absorption tower, heated, and then enters the top of the desorption tower (regeneration tower). Inside the desorption tower, it is heated by a steam reboiler (typically 100-120°C), releasing the CO2, which is then collected or vented from the top of the tower. The regenerated lean amine solution is cooled and pumped back to the top of the absorption tower for recycling.

[0096] The aforementioned CO2 treatment device demonstrates that the process actively monitors and treats key by-reaction products, ensuring the acquisition of high molecular weight, high-quality polymers. It prevents potential pressure fluctuations, equipment corrosion, and indirect impacts on polycondensation equilibrium caused by CO2 accumulation in the system. The absorbent is recyclable, reflecting the process's environmental friendliness and economic efficiency. Its parameter settings embody the principles of "refined process control" and "full-process green design" in the polyoxoethylene glycol ester synthesis process. The purified exhaust gas obtained can be emitted, and the high-purity CO2 can be utilized as a resource.

[0097] The aforementioned CO2 treatment device is a key component in achieving the "full-process green design" of the synthesis system of this invention. It not only actively removes CO2 generated by side reactions, ensuring the stable operation of the main reaction system and product quality, but also achieves efficient utilization of the absorbent through a closed-loop absorption-regeneration process, reducing operating costs and demonstrating the environmental friendliness and atom economy of the process. This device, together with the methanol recovery device, constitutes a complete system for the treatment and resource utilization of byproducts from the main reaction.

[0098] In the above system, such as Figure 1 As shown, the prepolymerization reaction unit is a batch reactor, which is equipped with a stirring paddle and a vacuum device.

[0099] In one embodiment, the vacuum pumping device is selected from one or a combination of two of molecular pumps or mechanical pumps.

[0100] In a preferred embodiment, the vacuum pumping device is a combination of a molecular pump and a mechanical pump connected in series.

[0101] In one embodiment, the batch reactor is also internally or externally connected to a fractionation column.

[0102] The batch reactor used as the pre-polymerization reaction unit is a conventional batch reactor. Specifically, as a batch reactor equipped with powerful stirring, a high vacuum system, and internal / external fractionation columns, it is a key unit in the synthesis system that receives transesterification products (oligomers) and converts them into refined precursors. It seamlessly connects with the preceding transesterification reaction unit (double-walled type), the subsequent purification unit (washing, filtration, drying), and the final polycondensation reaction unit, forming a continuous, closed, and material-recyclable advanced polymer synthesis system.

[0103] In the above system, such as Figure 1 As shown, the prepolymerization reaction unit is equipped with a second online monitoring device, which is selected from one or more combinations of an online moisture analyzer, an online viscometer, a stirring torque sensor, and a high-precision vacuum pressure sensor. This device enables the prepolymerization reaction unit to achieve its core monitoring objectives: degree of dehydration, molecular weight increase, and system vacuum level.

[0104] In the above system, such as Figure 1 As shown, the washing component is a stirring washing vessel.

[0105] In the above system, such as Figure 1 As shown, the filtering component is a vacuum filter.

[0106] In the above system, such as Figure 1 As shown, the drying component is a vacuum drying oven.

[0107] In the above system, such as Figure 1 As shown, the solvent recovery unit is a packed tower.

[0108] In one embodiment, the packing material in the packed tower is polypropylene stepped ring packing.

[0109] In one embodiment, the height of the packed tower is 7-9 meters, preferably 8 meters.

[0110] In one embodiment, the packed tower has 6-10 theoretical trays, preferably 8.

[0111] In one embodiment, the reflux ratio of the packed tower is 2-5, preferably 3-4.

[0112] In one embodiment, the top condensation temperature of the packed tower is -10~25℃, preferably -10~15℃.

[0113] The solvent recovery unit described above is used for distillation to recover washing solvents such as ethanol for recycling. Specifically, since the main byproduct of the prepolymerization reaction is water, it needs to be removed. The solvent recovery unit should recover solvents (such as ethanol) used in the post-treatment washing step, not substances directly produced by the reaction. This process and system integrates the "reaction-post-treatment-solvent recovery" design. The ethanol-impurity mixture collected from the washing and filtration processes is transported to a packed column for distillation recovery. Compared to sieve tray columns, packed columns typically have lower pressure drop and higher separation efficiency, making them more suitable for recovering heat-sensitive solvents (such as ethanol), obtaining higher purity recycled solvents, and ensuring the effectiveness of the next washing cycle.

[0114] In the above system, the final polycondensation reaction unit is connected to a vacuum pumping device, which is selected from one or a combination of molecular pumps or mechanical pumps.

[0115] In one embodiment, the vacuum pumping device is a combination of a molecular pump and a mechanical pump connected in series.

[0116] In the above system, such as Figure 1 As shown, the final polycondensation reaction unit is a double-walled reactor. The final polycondensation reaction unit and the transesterification reaction unit share the same double-walled reactor structure and reaction mechanism.

[0117] In the above system, such as Figure 1 As shown, the final polycondensation reaction unit is equipped with a third online monitoring device, which is selected from one or more combinations of an online melt rheometer, a torque sensor, an online moisture analyzer, and an absolute pressure vacuum gauge. This device enables the final polycondensation reaction unit to achieve its core monitoring objectives: final molecular weight, melt characteristics, absolutely anhydrous environment, and extremely high vacuum.

[0118] The aforementioned absolute pressure vacuum gauge is a high-precision absolute pressure vacuum gauge and is interlocked with temperature.

[0119] The aforementioned first, second, and third online monitoring devices are used to monitor the reaction temperature, pressure, reaction rate, and product molecular weight in real time, and to adjust the reaction conditions in a timely manner to ensure stable product quality.

[0120] The third aspect of the present invention provides a polyoxin glycol ester, which is prepared by the synthesis process of the polyoxin glycol ester provided in the first aspect of the present invention.

[0121] The fourth aspect of this invention provides the use of poly(ethylene oxalate) in industrial application materials.

[0122] In the above-mentioned applications, the industrial application material is selected from at least one of packaging materials, biomedical materials, agricultural materials, or environmentally friendly materials.

[0123] Polyethylene oxalate (PEG) can be used as a biodegradable food packaging material, especially suitable for short-term product packaging. PEG also has good biocompatibility and can be used as a potential biodegradable medical material. Furthermore, PEG can be used as a biodegradable agricultural mulch film to reduce white pollution. PEG can also be blended with biodegradable materials such as PBAT to produce blown films with enhanced mechanical and barrier properties.

[0124] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0125] In the following embodiments, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art.

[0126] Example 1: Synthesis of Bio-based Poly(oxalic acid) Glycol Dimethyl oxalate and ethylene glycol were mixed in a molar ratio of 1:2 and added to a double-walled reactor. Stannous oxalate was used as a catalyst at a rate of 4‰ of the molar amount of dimethyl oxalate. The temperature was increased to 80°C at a rate of 10°C / min and stirred at 30 rpm for 60 minutes. Then, the temperature was increased to 160°C at a rate of 10°C / min. The transesterification reaction was carried out for 290 minutes, with the first drop of small molecule methanol as the zero point of timing, to obtain oligomeric ethylene glycol oxalate and methanol with a molecular weight of 8-12 kDa (weight average molecular weight).

[0127] Oligomeric polyethylene oxalate was placed in a prepolymerization reactor and subjected to a prepolymerization reaction at 130°C and a reaction pressure of 3 kPa absolute for 45 minutes to obtain medium molecular weight polyethylene oxalate with a molecular weight of 20-30 kDa (weight average molecular weight). The medium molecular weight polyethylene oxalate was then washed with ethanol as a low-boiling-point solvent, using three times the amount of ethanol. It was then filtered three times under reduced pressure at 2 kPa absolute, and dried at 60°C under a vacuum of ≤1 kPa for 9 hours, resulting in a moisture content of less than 200 ppm.

[0128] Then, the dried medium-molecular-weight polyethylene oxalate was placed in a double-walled reactor and slowly heated to 185°C at a heating rate of 1°C / min. The reaction pressure was 100 Pa absolute pressure, and the final polycondensation reaction was carried out for 180 minutes with a stirring rate of 40 rpm to obtain high-molecular-weight polyethylene oxalate with a molecular weight of 80-100 kDa (weight average molecular weight).

[0129] In addition, methanol is recovered via a sieve tray column with a reflux ratio of 2.5 times the minimum reflux ratio. The column's top condensation temperature is 10°C, and the recovered methanol has a purity of over 99%, making it recyclable. CO2 generated during the transesterification reaction is absorbed using a 20wt% MEA solution via chemical absorption. The absorbed CO2 is then regenerated in a desorption column with a bottom temperature of 120°C and a top pressure of 0.2 MPa (absolute pressure), achieving a purity of over 99%. The regenerated CO2 is used in the production of food-grade dry ice. Ethanol is recovered via a packed column using polypropylene stepped ring packing. The column is 8 meters high, has 8 theoretical trays, a reflux ratio of 4, and a top condensation temperature of 10°C.

[0130] Example 2: Synthesis of Copolymerized Modified Poly(ethylene Oxalate) Dimethyl oxalate and ethylene glycol were mixed in a 1:1 molar ratio and added to a double-walled reactor. Isosorbide was added as a third monomer, with a molar ratio of isosorbide to dimethyl oxalate of 5%. A rare earth titanate composite solid catalyst (the molar ratio of La to stannous oxalate in La₂O₃ was 1:1, and the molar ratio of titanium in TiO₂ to La in La₂O₃ was 1:1) was used as the catalyst. The amount of stannous oxalate was 4‰ of the molar amount of dimethyl oxalate. The temperature was increased to 80°C at a rate of 10°C / min and stirred at 40 rpm for 60 minutes. Then, the temperature was increased to 160°C at a rate of 10°C / min. The transesterification reaction was carried out for 290 minutes, with the first drop of small molecule methanol as the zero point of timing, to obtain oligomeric ethylene glycol oxalate with a molecular weight of 5-10 kDa (weight average molecular weight) and methanol.

[0131] Oligomeric polyethylene oxalate was placed in a prepolymerization reactor and subjected to a prepolymerization reaction at 120°C and a reaction pressure of 2 kPa absolute for 45 minutes to obtain medium molecular weight polyethylene oxalate with a molecular weight of 20-28 kDa (weight average molecular weight). The medium molecular weight polyethylene oxalate was then washed with ethanol as a low-boiling-point solvent, using three times the amount of ethanol. It was then filtered three times under reduced pressure at 1 kPa absolute, and dried at 70°C under a vacuum of ≤1 kPa for 8 hours, resulting in a moisture content of less than 200 ppm.

[0132] Then, the dried medium-molecular-weight polyethylene oxalate was placed in a double-walled reactor and slowly heated to 190°C at a heating rate of 1°C / min. The reaction pressure was 100Pa absolute pressure, and the final polycondensation reaction was carried out for 180 minutes with a stirring rate of 45 rpm to obtain high-molecular-weight polyethylene oxalate with a molecular weight of 80-100 kDa (weight average molecular weight).

[0133] In addition, methanol is recovered via a sieve tray column with a reflux ratio of 2.5 times the minimum reflux ratio. The column's top condensation temperature is 10°C, and the recovered methanol has a purity of over 99%, making it recyclable. CO2 generated during the transesterification reaction is absorbed using a 25wt% MEA solution via chemical absorption. The absorbed CO2 is then regenerated in a desorption column with a bottom temperature of 115°C and a top pressure of 0.2 MPa (absolute pressure), achieving a purity of over 99%. The regenerated CO2 is used in the production of food-grade dry ice. Ethanol is recovered via a packed column using polypropylene stepped ring packing. The column is 8 meters high, has 8 theoretical trays, a reflux ratio of 4, and a top condensation temperature of 10°C.

[0134] Example 3: Synthesis of Continuous Poly(ethylene oxalate) Dimethyl oxalate and ethylene glycol were mixed in a molar ratio of 1:1 and added to a double-walled reactor. Stannous oxalate was used as a catalyst at a rate of 4‰ of the molar amount of dimethyl oxalate. The temperature was increased to 80°C at a rate of 10°C / min and stirred at 40 rpm for 60 minutes. Then, the temperature was increased to 160°C at a rate of 10°C / min. The transesterification reaction was carried out for 290 minutes, with the first drop of small molecule methanol as the zero point of timing, to obtain oligomeric ethylene glycol oxalate and methanol with a molecular weight of 8-15 kDa (weight average molecular weight).

[0135] Oligomeric ethylene oxalate was placed in a prepolymerization reactor and subjected to a prepolymerization reaction at 130°C and a reaction pressure of 3 kPa absolute for 45 minutes to obtain medium molecular weight polyethylene oxalate with a molecular weight of 25-40 kDa (weight average molecular weight). The medium molecular weight polyethylene oxalate was then washed with ethanol as a low-boiling-point solvent, using three times the amount of ethanol. It was then filtered three times under reduced pressure at 1 kPa absolute, and dried at 70°C under a vacuum of ≤1 kPa for 10 hours, resulting in a moisture content of less than 200 ppm.

[0136] Then, the dried medium-molecular-weight polyethylene oxalate was placed in a double-walled reactor and slowly heated to 185°C at a heating rate of 1°C / min. The reaction pressure was 100 Pa absolute pressure, and the final polycondensation reaction was carried out for 180 minutes with a stirring rate of 40 rpm to obtain high-molecular-weight polyethylene oxalate with a molecular weight of 80-100 kDa (weight average molecular weight).

[0137] In addition, methanol is recovered via a sieve tray column with a reflux ratio of 2.5 times the minimum reflux ratio. The column's top condensation temperature is 10°C, and the recovered methanol has a purity of over 99%, making it recyclable. CO2 generated during the transesterification reaction is absorbed using a 25wt% MEA solution via chemical absorption. The absorbed CO2 is then regenerated in a desorption column with a bottom temperature of 130°C and a top pressure of 0.1 MPa (absolute pressure), achieving a purity of over 99%. The regenerated CO2 is used in the production of food-grade dry ice. Ethanol is recovered via a packed column using polypropylene stepped ring packing. The column is 8 meters high, has 8 theoretical trays, a reflux ratio of 3, and a top condensation temperature of 10°C. The recovered ethanol has a purity of over 99%, making it recyclable.

[0138] As can be seen from the comparison of Examples 1, 2 and 3, the present invention solves the fundamental technical problem by adopting a "three-step" strategy and realizes the controllable preparation of high molecular weight products.

[0139] Specifically, traditional direct polycondensation methods struggle to yield high molecular weight products due to oxalic acid decarboxylation and polymer chain thermal degradation. This invention employs a three-step progressive strategy: transesterification → pre-polymerization → final polycondensation. This approach avoids decarboxylation at the source (using stable dimethyl oxalate) and decomposes the polymerization reaction through stepwise, controllable conditions (temperature, vacuum), maximally suppressing side reactions at each stage. The results of Examples 1-3 demonstrate that this process can stably prepare high molecular weight poly(ethylene oxalate). In Examples 1-3, the final polycondensation was carried out under extreme high vacuum of ≤100 Pa and precise temperature control of ≤1℃ / min. This directly ensured the acquisition of high molecular weight products with high thermal stability (the goal of the examples: 5% thermal decomposition temperature above 240℃). The three-step method laid the foundation for implementing these demanding but necessary final conditions.

[0140] In addition, the specialized reactor design ensures efficient, uniform, and safe reactions. Because the transesterification and final polycondensation utilize a double-walled reactor (with cooling jacket, condenser coil, and optimized stirring), and the pre-polycondensation employs a high-vacuum reactor with a fractionation column, precise control is achieved over the exothermic reaction, byproduct removal, mixing of high-viscosity materials, and temperature uniformity.

[0141] During the transesterification stage, timely removal of methanol (via condenser coils and sieve trays) drives a positive shift in equilibrium; in the pre / final polycondensation stage, high vacuum (3 kPa, 100 Pa) and powerful dehydration significantly improve the conversion rate of each reaction step and reduce unreacted monomer residues. Uniform mixing and temperature control prevent local overheating, effectively suppressing thermal degradation and coking, resulting in polymers with lighter color, narrower molecular weight distribution, and higher thermal stability. Nearly 100% recovery and recycling of key materials significantly reduces production costs. Through an integrated separation and recovery device, the internal circulation of main raw materials and solvents is achieved, significantly reducing unit consumption.

[0142] Specific manifestations (data from Examples 1-3): (1) Methanol recovery: The methanol recovered by the sieve plate tower has a purity of ≥99% and can be directly reused in the transesterification reaction, which can reduce methanol raw material consumption by more than 90%.

[0143] (2) Ethanol solvent recovery: The ethanol recovered by the packed tower has a purity of ≥99% and is recycled for the washing process, which can reduce the consumption of ethanol solvent by more than 95%.

[0144] (3) CO2 resource utilization: The CO2 recovered by the MEA absorption-desorption system has a purity of ≥99% and can be sold as a product (such as food-grade dry ice), turning waste into treasure, creating additional revenue, and saving the cost of waste gas treatment.

[0145] (4) Ethylene glycol reflux: The fractionation column of the prepolymerization reactor separates and refluxes the volatile ethylene glycol monomers, which improves the utilization rate of raw materials.

[0146] (5) Integrated and continuous design improves production efficiency. Unit operations such as reaction, distillation, washing, and recovery are designed as a coherent system (as in the continuous direction of Example 3), reducing material transfer, intermediate storage, and batch processing time. The entire process flow is smooth, the production cycle is shortened, and the equipment utilization rate is improved, laying the foundation for large-scale continuous production, thereby reducing the fixed investment amortization and labor costs per unit product.

[0147] (6) High molecular weight and high thermal stability: As described in the background art, one of the core objectives of this process is to overcome the poor thermal stability of poly(ethylene oxalate). Through strict raw material purification (moisture content <200 ppm after drying), inert atmosphere protection, and extreme conditions (high vacuum, slow heating) in the final polycondensation stage, a product with high thermal stability (5% thermal decomposition temperature above 240°C) was successfully prepared (as described in the objectives of the examples). This is a performance leap that is difficult to achieve with traditional processes, and it greatly expands its application fields.

[0148] (7) Structural designability and product diversification. As shown in Example 2, copolymerized modified polyethylene oxalate can be easily synthesized by introducing a third monomer (such as isosorbide, accounting for 5%). This allows for the introduction of rigid structures or functional groups while maintaining the main chain properties, further adjusting the thermal, mechanical, or degradation properties of the polymer to meet specific high-end application requirements.

[0149] (8) The effects of the synthesis process of this invention are systematic and comprehensive: From a technical perspective, it fundamentally solves the problems of decarboxylation and thermal degradation in the synthesis of polyoxoethylene glycol ester, significantly improving the yield and product quality (molecular weight, thermal stability, color). From an economic perspective, through a near-closed-loop material cycle (methanol, ethanol, CO2), the cost of raw materials and solvents is reduced by 80-95%, by-product resource utilization brings benefits, integrated design improves production efficiency, and the overall production cost is significantly reduced. From an environmental and sustainable perspective, the process achieves green production, with very little waste discharge (mainly water), high atom economy, and meets the sustainable development requirements of modern industry.

[0150] Therefore, this invention not only provides a feasible synthesis route, but also provides an efficient, economical, green industrial solution that can produce high-performance products.

[0151] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any form or substance. It should be noted that those skilled in the art can make various improvements and additions without departing from the method of the present invention, and these improvements and additions should also be considered within the scope of protection of the present invention. Any modifications, alterations, and equivalent changes made by those skilled in the art based on the above-disclosed technical content without departing from the spirit and scope of the present invention are equivalent embodiments of the present invention. Furthermore, any modifications, alterations, and evolutions made to the above embodiments based on the essential technology of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A process for synthesizing polyoxoethylene glycol ester, comprising the following steps: 1) Dimethyl oxalate and ethylene glycol are mixed and then subjected to transesterification under the action of a catalyst to obtain oligomeric ethylene glycol oxalate and methanol; The reaction formula is shown in equation (1): n (COOCH3)2 + n HOCH2CH2OH → n HOCH2CH2COOCCOOH + 2n CH3OH; 4) The oligomeric oxalate glycol ester is subjected to a pre-condensation reaction to obtain medium molecular weight polyoxalate glycol ester. The reaction formula is shown in equation (2): 2n HOCH2CH2COOCCOOH → (COOCH2CH2)2COOCCOOH + n H2O; 7) Medium molecular weight polyethylene oxalate is subjected to a final polycondensation reaction to obtain high molecular weight polyethylene oxalate. The reaction formula is shown in equation (3): (COOCH2CH2)2COOCCOOH → [O-CH2CH2-O-CO-CO-O-CH2CH2-O] n + (n-1) H2O, In formulas (1), (2) or (3), n is a positive integer; the weight-average molecular weight of the oligomeric oxalate glycol ester is 1-15 kDa; the weight-average molecular weight of the medium molecular weight polyoxalate glycol ester is 20-50 kDa; and the weight-average molecular weight of the high molecular weight polyoxalate glycol ester is 80-100 kDa.

2. The synthesis process of polyoxoethylene glycol ester according to claim 1, characterized in that, Includes one or more of the following conditions: A1) In formula (1), (2) or (3), the viscosity of the oligomeric oxalate glycol ester is ≥1.46 Pa·s and <50 Pa·s; the viscosity of the medium molecular weight polyoxalate glycol ester is ≥50 Pa·s and ≤300 Pa·s; the viscosity of the high molecular weight polyoxalate glycol ester is 732 Pa·s-1200 Pa·s; A2) In step 1), the molar ratio of dimethyl oxalate to ethylene glycol is 1:1-2; A3) In step 1), the catalyst is a stannous oxalate or rare earth titanate composite solid catalyst; A4) In step 1), the transesterification reaction further includes the addition of a third monomer, which is isosorbide; A5) In step 1), the reaction temperature of the transesterification reaction is 120-160℃; A6) In step 1), the temperature program for the transesterification reaction is as follows: heat to 70-80°C at a heating rate of 9-11°C / min and keep stirring for 55-65 minutes, then continue heating to 120-160°C at a heating rate of 9-11°C / min. A7) In step 1), the reaction time for the transesterification reaction is 160-290 minutes; A8) In step 2), the reaction temperature of the pre-condensation reaction is 120-130℃; A9) In step 2), the reaction pressure of the pre-condensation reaction is 2-3 kPa absolute pressure; A10) In step 2), the reaction time of the pre-condensation reaction is 30-60 minutes; A11) In step 2), the pre-condensation reaction is followed by washing, filtering, and drying. A12) In step 3), the reaction temperature of the final polycondensation reaction is 185-195℃; A13) In step 3), the heating program for the final polycondensation reaction is: heating to 185-195°C at a heating rate of no more than 1°C / min; A14) In step 3), the final polycondensation reaction is carried out in a vacuum, and the reaction pressure of the final polycondensation reaction is not greater than 100 Pa absolute pressure; A15) In step 3), the reaction time of the final polycondensation reaction is 120-240 minutes; A16) In step 3), the stirring rate during the final polycondensation reaction is 10-50 rpm.

3. The synthesis process of polyoxoethylene glycol ester according to claim 2, characterized in that, Includes one or more of the following conditions: B1) In item A3, the molar amount of stannous oxalate is 3.9-4.1‰ of dimethyl oxalate; B2) In item A3, the rare earth titanate composite solid catalyst comprises a rare earth element compound, a titanium-containing compound, and stannous oxalate. The molar ratio of rare earth element to stannous oxalate in the rare earth element compound is 0.5-2:1; the molar ratio of titanium element to rare earth element in the titanium-containing compound is 0.5-2:1; and the molar amount of stannous oxalate is 3.9-4.1‰ of dimethyl oxalate. B3) In item A4, the molar amount of the third monomer is 4-6% of dimethyl oxalate; B4) In item A6, the stirring rate is 10-50 rpm; B5) In item A11, the solvent used for washing is an organic solvent with a boiling point below 80°C; B6) In item A11, the solvent used for washing is 2-4 times the mass of medium molecular weight poly(ethylene oxalate); B7) In item A11, the filtration is vacuum filtration, and the pressure of vacuum filtration is 1-2 kPa absolute pressure; B8) In item A11, the filtering is repeated no less than 3 times; B9) In item A11, the vacuum degree of the drying process is ≤1 kPa; B10) In item A11, the drying temperature is 50-80℃; B11) In item A11, the drying time is 6-12 hours; B12) In item A11, the drying is carried out until the moisture content is less than 200 ppm.

4. The synthesis process of polyoxoethylene glycol ester according to claim 3, characterized in that, Includes one or more of the following conditions: C1) In item B2, the rare earth element in the compound containing rare earth elements is selected from at least one of lanthanum or cerium, and the rare earth element in the compound is selected from at least one of La2O3, CeO2, La2(C2O4)3 or Ce(C2O4)2. C2) In item B2, the titanium-containing compound is a titanium complex or titanium oxide; Preferably, the titanium complex is a tetraalkyl titanate; Preferably, the titanium oxide is TiO2; C3) In item B5, the solvent used for washing is ethanol.

5. A system for synthesizing polyoxoethylene glycol ester, characterized in that, Along the reaction direction, a mixing device, a transesterification reaction unit, a pre-polymerization reaction unit, a purification unit, and a final polymerization reaction unit are connected in sequence. The transesterification reaction unit is connected to a CO2 treatment device and is also connected to a methanol recovery device to form a circulation loop. The purification unit, along the reaction direction, includes a washing component, a filtering component, and a drying component. The filtering component is connected to a solvent recovery unit and is also connected to the washing component to form a circulation loop.

6. The synthesis system for polyoxoethylene glycol ester according to claim 5, characterized in that, Includes one or more of the following conditions: D1) The transesterification reaction unit is a double-walled reactor; D2) The transesterification reaction unit is equipped with a first online monitoring device, which is selected from any one or more combinations of an online gas chromatograph, an online viscometer, and a distributed temperature sensor. D3) The methanol recovery device is a sieve tray tower; D4) The CO2 treatment device includes a chemical absorption section and a desorption regeneration section in sequence along the CO2 input direction. The chemical absorption section is an absorption tower and the desorption regeneration section is a desorption tower. D5) The prepolymerization reaction unit is a batch reactor, which is equipped with a stirring paddle and a vacuum device. D6) The pre-condensation reaction unit is equipped with a second online monitoring device, which is selected from any one or more combinations of an online moisture analyzer, an online viscometer, a stirring torque sensor, and a high-precision vacuum pressure sensor. D7) The washing component is a stirring washing tank; D8) The filter component is a vacuum filter; D9) The drying component is a vacuum drying oven; D10) The solvent recovery unit is a packed tower; D11) The final polycondensation reaction unit is connected to a vacuum pumping device, which is selected from one or a combination of molecular pumps or mechanical pumps. D12) The final polycondensation reaction unit is a double-walled reactor; D13) The final polycondensation reaction unit is equipped with a third online monitoring device, which is selected from any one or more combinations of an online melt rheometer, a torque sensor, an online moisture analyzer, and an absolute pressure vacuum gauge.

7. The synthesis system for polyoxoethylene glycol ester according to claim 6, characterized in that, Includes one or more of the following conditions: E1) In item D2, the distributed temperature sensor is selected from any one or more combinations of PT100 resistance temperature sensor or thermocouple. E2) In item D3, the condensation temperature at the top of the sieve tray column is -10~70℃; E3) In item D4, the absorbent used in the chemical absorption section is a lean amine solution; Preferably, the amine-deficient solution is an ethanolamine solution, which is an aqueous solution of ethanolamine with a weight percentage concentration of 15-30 wt%. E4) In item D4, in the desorption regeneration section, the bottom temperature of the desorption tower is 110-130℃ and the top pressure is 0.1-0.3MPa absolute pressure. E5) In item D5, the vacuum pumping device is selected from one or a combination of two of molecular pumps or mechanical pumps; E6) In item D10, the packing material in the packed tower is polypropylene stepped ring packing; E7) In item D10, the height of the packed tower is 7-9 meters; E8) In item D10, the theoretical number of trays in the packed tower is 6-10 layers; E9) In item D10, the reflux ratio of the packed tower is 2-5; E10) In item D10, the top condensation temperature of the packed tower is -10~25℃.

8. A polyoxinyl glycol ester, prepared by the synthesis process of polyoxinyl glycol ester according to any one of claims 1-4.

9. Use of the polyoxoethylene glycol ester according to claim 8 in industrial application materials.

10. The use according to claim 9, characterized in that, The industrial application materials are selected from at least one of packaging materials, biomedical materials, agricultural materials, or environmentally friendly materials.

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