Preparation method of high molecular weight poly (alkyl oxalate) homopolymer and copolymer

Abstract

The invention relates to a preparation method of a high molecular weight poly (alkyl oxalate) homopolymer and copolymer, and belongs to the technical field of polymer synthesis. According to the method disclosed by the invention, bulk chemical oxalic acid diester and aliphatic diol are used as raw materials, and a process route of synthesizing an oxalic acid alkyl ester oligomer through polycondensation, preparing an oxalic acid alkyl cyclic lactone monomer through controllable depolymerization and preparing poly (oxalic acid alkyl ester) through ring opening polymerization of the oxalic acid alkyl cyclic lactone monomer is adopted, so that oligomeric oxalic acid alkyl ester can be prepared through polycondensation; a controllable depolymerization process is adopted to efficiently prepare a high-purity alkyl oxalate cyclic lactone monomer, and a high-efficiency catalyst is adopted to realize controllable ring opening polymerization of the alkyl oxalate cyclic lactone monomer to prepare a high-molecular-weight poly (alkyl oxalate) homopolymer. In the ring-opening polymerization process, a chain structure and a sequence structure of a polymer are adjusted by adopting a copolymerization means to prepare the high-molecular-weight poly (alkyl oxalate) copolymer, so that controllable preparation of oxalate-based polyesters with different structures and properties is realized, and the use requirements of different application scenes can be met.

Description

Technical Field

[0001] The invention relates to the technical field of polymer synthesis, and in particular to a method for preparing a high molecular weight polyalkyl oxalate homopolymer and copolymer. Background Art

[0002] Polymer materials have become one of the most important materials in the daily life of human society, but the excessive demand and unreasonable treatment of polymer materials have caused tremendous pressure on resources and the environment. On the one hand, the synthetic raw materials of polymers are heavily dependent on non-renewable fossil resources; on the other hand, most synthetic polymer materials take a long time to completely decompose under natural conditions. The development of bio-based and degradable polymer materials is an effective strategy to solve the above problems. Among them, aliphatic polyesters are a type of degradable polymer material with excellent performance, wide application, and can be synthesized using bio-based raw materials.

[0003] Polyalkyl oxalate is a typical type of degradable aliphatic polyester material. The main chain structure is an alternating arrangement of aliphatic diols and oxalic acid. Polyalkyl oxalate exhibits unique thermal and crystallization properties due to its structure. The melting point of polyalkyl oxalate containing odd-numbered carbon atoms is generally lower than 60°C, while the melting point of polyalkyl oxalate containing even-numbered carbon atoms is higher (70-200°C). This type of polyester material usually has high tensile strength, high modulus and high crystallinity; and studies have found that due to the electron-withdrawing effect of adjacent ester bonds, polyalkyl oxalate shows excellent non-enzymatic hydrolysis ability, can also be rapidly degraded in soil, and has the potential to degrade in seawater. Due to its good biocompatibility, polyalkyl oxalate can be used in medical fields such as absorbable sutures and drug-carrying engineering, and can also be used as metal ion adsorbents, solid lithium battery electrolytes, and agricultural mulch films.

[0004] Polyalkyl oxalates are usually prepared by the polycondensation reaction of oxalic acid compounds and aliphatic diols. Commonly used oxalic acid monomers include oxalic acid, dimethyl oxalate, diethyl oxalate and oxalyl chloride. Oxalic acid and dimethyl oxalate are relatively cheap and are commonly used polycondensation monomers; while oxalyl chloride and diethyl oxalate are relatively expensive and are not suitable for industrial production. Oxalic acid has a wide range of sources. It can be obtained through plant extraction, or it can be prepared by chemical methods such as oxidation of sugar, ethylene glycol or propylene and heating of formate. However, oxalic acid has relatively poor stability. It is easy to decompose into formic acid in ethylene glycol or aqueous solution, and it is also easy to undergo decarboxylation reaction under heating conditions to become formic acid and carbon dioxide. Therefore, it is difficult to apply to high-temperature polycondensation. The polycondensation reaction with oxalic acid and diol as raw materials usually requires a long reaction time, but can only obtain polyalkyl oxalates with a molecular weight of several thousand at a low yield. With the industrialization of the carbon monoxide catalytic coupling method for preparing oxalate esters, the green chemical process for preparing polyalkyl oxalates with oxalate esters as raw materials is more meaningful.

[0005] The domestic research groups of Wei Zhiyong and Zhou Weidong and the foreign research groups of Miller and Shalaby have studied the polycondensation reaction of dimethyl oxalate and diols to prepare polyalkyl oxalates, and have made important progress (Macromolecules 2023, 56, 3149-3159. Angew Chem, 2021, 133 (33), 18483-18491. Polym. Chem., 2014, 5, 955-961. US4140678A). However, this method still has some defects. For example, dimethyl oxalate will slowly decompose at 140°C, causing feeding deviation and affecting the molecular weight of polyester; at the same time, using dimethyl oxalate as a raw material usually requires gradual heating, vacuum conditions and long-term polymerization (> 12 hours), which consumes a lot of energy; and the polycondensation often uses bulk polymerization, which has poor heat and mass transfer effects; these make it difficult to control the molecular weight and dispersibility of polyester in the polycondensation reaction. Higher reaction temperature is conducive to increasing the reaction rate, and longer reaction time is conducive to increasing the molecular weight. However, when the reaction temperature is too high and the reaction time is prolonged, the thermal stability of the monomer and the product must be fully considered. This contradiction is more prominent in the process of preparing polyalkyl oxalate by polycondensation reaction. Moreover, polycondensation reaction cannot form controllable end groups, so it is impossible to synthesize materials such as block copolyesters. Therefore, it is very important to develop new polymerization methods to prepare high molecular weight polyalkyl oxalate.

[0006] Compared with polycondensation, the ring-opening polymerization of cyclic monomers has more advantages. Ring-opening polymerization has good atom economy, and can flexibly choose solution polymerization and bulk polymerization. According to the actual application requirements, highly active metal catalysts and environmentally friendly non-metallic catalysts can be selected, and polyalkyl oxalate can be prepared by ring-opening polymerization quickly under mild conditions. Ring-opening polymerization can better control the chain structure, sequence structure and composition of the product, and can synthesize block copolyesters with clear structures. Therefore, it has good advantages in terms of polymerization activity, controllability, economy and energy consumption.

[0007] High molecular weight, end-group-defined poly(alkyl oxalate) can be obtained by ring-opening polymerization of oxalyl lactone monomers. Its cyclic monomer oxalic acid alkyl cyclic lactone has a structure similar to that of lactide and glycolide, so it can follow the industrial process route for preparing lactide monomers (polycondensation-depolymerization two-step method). The two-step process for synthesizing lactide can improve the purity of lactide and then achieve the preparation of polylactic acid (PLA) with high molecular weight, controllable structure and excellent performance through lactide ring-opening polymerization. It is currently the most widely used method in industry, and the core technology of its strategy lies in the synthesis and purification of lactide. Compared with the polycondensation reaction, one of the difficulties in preparing poly(alkyl oxalate) by ring-opening polymerization is also the efficient and highly selective synthesis of high-purity cyclic monomers, and another difficulty is the controllable ring-opening polymerization of cyclic monomers.

[0008] Our research group conducted a thorough literature and patent background research on the synthesis and ring-opening polymerization of alkyl oxalate cyclic lactone monomers. In 1933, Carothers et al. discovered that linear polyesters can be resolved into cyclic lactone monomers or cyclic dimers under specific conditions (J.Am.Chem.Soc.1933,55(12),5031-5039). In 1979, Alksnis and Deme discovered that the ring-opening polymerization of ethylene glycol oxalate (vinyl oxalate) existed an equilibrium phenomenon between polyester and cyclic lactone. Then, they experimentally depolymerized polyethylene oxalate to obtain hexavalent polyethylene oxalate monomers, and calculated the upper limit temperature of the monomer bulk polymerization reaction to be 234°C (J.Polym.Sci.,Part A:Polym.Chem.1979,15(4),2701-2706). Afterwards et al. imitated the preparation method of lactide (lactic acid condensation to oligomers-oligomeric polylactic acid depolymerization to lactide), first depolymerized the oligomers condensed from ethylene glycol and oxalic acid to hexavalent oxalate ethylene glycol, and then achieved the ring-opening polymerization of the monomer (Polym. Degrad. Stab. 1986, 15 (4), 345-356). In 2012, Sinopec Beijing Chemical Research Institute designed a continuous production process for oxalate cyclic monomers, but the catalyst used was expensive and inefficient, so the yield was not high (CN201210425013.4). According to current reports, the controlled depolymerization of oligomeric oxalate glycol esters is still difficult, resulting in very low purity and yield of the synthesis of hexameric oxalate glycol esters, so that there is no good large-scale monomer source for ring-opening polymerization; at the same time, the types of alkyl oxalate monomers are very single, and current research only focuses on oxalate glycol esters, lacking research on the development, synthesis and ring-opening polymerization of substituted hexameric oxalyl lactones and seven- and eight-membered oxalyl lactones; due to the lack of abundant alkyl oxalate monomers, it is impossible to carry out copolymerization research on such monomers; and the catalyst design for monomer ring-opening polymerization is still blank, lacking the development of high-efficiency catalysts and organic catalysts, resulting in low molecular weight and unclear end group structure of polyester prepared by ring-opening polymerization.

[0009] In summary, the existing methods for preparing polyalkyl oxalates by condensation polymerization have defects such as complicated steps, poor molecular weight controllability, and difficulty in synthesizing copolyesters. The process for preparing polyalkyl oxalates by ring-opening polymerization has the problem of few types of alkyl oxalate monomers, and the prepared polyester has the problems of low molecular weight and unclear end group structure. Therefore, it is urgent to provide a method for preparing high molecular weight polyalkyl oxalates by controlled ring-opening polymerization. Summary of the invention

[0010] In view of one or more technical problems existing in the prior art, the present invention provides a method for preparing a high molecular weight polyalkyl oxalate homopolymer and copolymer. The present invention adopts the process route of "condensation polymerization to synthesize alkyl oxalate oligomers, controlled depolymerization to prepare alkyl oxalate ring lactone monomers, and ring-opening polymerization of alkyl oxalate ring lactone monomers to prepare polyalkyl oxalate", thereby realizing the controllable preparation of oxalic acid-based polyesters with different structures and properties, expanding the types of oxalic acid-based polyesters, improving the performance of oxalic acid-based polyesters, and meeting the use requirements of different application scenarios.

[0011] The present invention provides a method for preparing a high molecular weight polyalkyl oxalate homopolymer, the preparation method comprising:

[0012] S1. subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction, and distillation to obtain an oxalic acid alkyl cyclic lactone monomer;

[0013] S2. subjecting the oxalic acid alkyl cyclic lactone monomer to ring-opening polymerization under the action of an initiator and a first catalyst to obtain a polyalkyl oxalate homopolymer.

[0014] Preferably, step S1 comprises: (i) subjecting an oxalic acid diester compound and an aliphatic diol compound to a condensation reaction to obtain an alkyl oxalate oligomer; the condensation reaction comprises a first stage condensation reaction carried out under normal pressure and a second stage condensation reaction carried out under reduced pressure (vacuum conditions); (ii) subjecting the alkyl oxalate oligomer to a depolymerization reaction and distillation under reduced pressure to obtain an alkyl oxalate cyclic lactone monomer.

[0015] Preferably, step S1 comprises: subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction and distillation under reduced pressure to obtain an oxalic acid alkyl cyclic lactone monomer.

[0016] Preferably, the oxalic acid diester compound has the following structure:

[0017]

[0018] Among them, R 7 is one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, and benzyl;

[0019] The oxalic acid diester compound is preferably one or more of dimethyl oxalate, diethyl oxalate, di-n-propyl oxalate, diisopropyl oxalate, di-n-butyl oxalate, diisobutyl oxalate, di-tert-butyl oxalate, diphenyl oxalate, and dibenzyl oxalate, more preferably dimethyl oxalate.

[0020] Preferably, the aliphatic diol compound has the following structure:

[0021]

[0022] Where x is 0 to 2, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 Each is independently hydrogen, an alkyl group of 1 to 8 carbon atoms, a cycloalkyl group, or a phenyl group;

[0023] Preferably, the aliphatic diol compound is selected from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,2-propylene glycol, 2-methyl-1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, 1,2-butanediol, 1,2-pentanediol and its isomers, 1,2-hexanediol and its isomers, 1,2-heptanediol and its isomers, 1,2-octanediol and its isomers, 1,2-nonanediol and its isomers, 1,2-decanediol and its isomers, 1,3-pentanediol and its isomers, 1,3-hexanediol and its isomers, 1,3 -heptanediol and its isomers, 1,3-octanediol and its isomers, 1,3-nonanediol and its isomers, 1,3-decanediol and its isomers, 1,4-pentanediol and its isomers, 1,4-hexanediol and its isomers, 1,3-heptanediol and its isomers, 1,4-octanediol and its isomers, 1,4-nonanediol and its isomers, 1,4-decanediol and its isomers, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,2-cycloheptanediol, 1,2-cyclooctanediol, 1,2-cyclononanediol, 1,2-cyclodecanediol, phenyl-1,2-ethanediol or one or more thereof.

[0024] Preferably, the amount of the initiator is 0.01 mol% to 10 mol% of the oxalic acid alkyl cyclic lactone monomer; preferably, the initiator is one or more of monohydroxy alcohol, dihydroxy alcohol, polyhydroxy alcohol, phenol, and amino compound; wherein the monohydroxy alcohol is preferably one or more of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, benzyl alcohol, phenylethyl alcohol, phenylpropanol, cyclopentanol, and cyclohexanol; the dihydroxy alcohol is preferably ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, cyclohexanediol, One or more of cyclopentanediol, cyclononanediol, cyclodecanediol, and terephthalic acid; the phenol is preferably one or more of phenol, hydroquinone, and phloroglucinol; the amino compound is preferably one or more of methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, benzylamine, phenylethylamine, amphetamine, cyclopentylamine, cyclohexylamine, aniline, ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, cyclohexanediamine, cyclopentanediamine, cyclononanediamine, cyclodecanediamine, p-phenylenediamine, and p-phenylenediamine; and / or

[0025] The amount of the first catalyst is 0.01 mol% to 10 mol% of the oxalic acid alkyl cyclic lactone monomer; preferably, the first catalyst is one or more of an organic metal catalyst, a rare earth metal catalyst, and an organic catalyst; wherein the metal catalyst is preferably one of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, diethyl zinc, zinc dichloride, Salen-Al catalyst, Porphyrin-Al catalyst, β-diimine-Zn catalyst, Phenolato-Ti catalyst, Tripodal-Fe catalyst, n-butyl lithium, isobutyl lithium, lithium diisopropylamide, sodium methoxide, sodium tert-butoxide, and potassium tert-butoxide. or more; the rare earth catalyst is preferably one or more of β-diketone rare earth metal complexes, cyclopentadienyl rare earth catalysts, bisphenol-based rare earth catalysts, Schiff base rare earth catalysts, sulfonic acid rare earth catalysts, rare earth metal halides, Salen rare earth complexes, and P-SalenY catalysts; the organic catalyst is preferably one or more of methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, boron trifluoride, tri(pentafluorophenyl)boron, triethylboron, camphorsulfonic acid, triethylamine, pyridine, 4-dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, hexamethyldisilazane, and phosphazene bases.

[0026] Preferably, the polycondensation reaction is carried out in the presence of a second catalyst or without a catalyst, the temperature of the polycondensation reaction is not less than 80°C, preferably 100 to 200°C, and the time of the polycondensation reaction is 1 to 12 hours;

[0027] The depolymerization reaction is carried out in the presence of a third catalyst or without a catalyst, the temperature of the depolymerization reaction is 100 to 200° C., the time of the depolymerization reaction is 1 to 12 hours; and / or

[0028] The temperature of the ring-opening polymerization is -80 to 200° C., and the time of the ring-opening polymerization is 0.1 to 24 hours.

[0029] Preferably, the amount of the second catalyst is 0.0001wt% to 10wt% of the oxalic acid diester compound, and the second catalyst is preferably stannous octoate, dibutyltin dilaurate, dibutyltin oxide, tetrabutyl titanate, tetraisopropyl titanate, zinc acetate, magnesium oxide, magnesium hydroxide, magnesium carbonate, tin chloride, ferric chloride, titanium chloride, zinc chloride, aluminum chloride, zinc oxide, tin oxide, ferric oxide, bismuth trifluoromethanesulfonate, zinc trifluoromethanesulfonate, 4-dimethylaminopyridine, nitrogen heterocyclic carbene, p-toluenesulfonic acid, trifluoromethanesulfonic acid, diphenyl phosphate, ionic liquid or more; and / or

[0030] The amount of the third catalyst used is 0.0001wt% to 10.0wt% of the alkyl oxalate oligomer, and the third catalyst is preferably one or more of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, tetrabutyl titanate, tin chloride, ferric chloride, titanium chloride, zinc chloride, aluminum chloride, zinc oxide, tin oxide, ferric oxide, 4-dimethylaminopyridine, p-toluenesulfonic acid, trifluoromethanesulfonic acid, diphenyl phosphate, ionic liquid, sodium glycolate, and sodium acetate.

[0031] The present invention also provides a method for preparing a high molecular weight polyalkyl oxalate copolymer, the preparation method comprising:

[0032] S1. subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction, and distillation to obtain a first oxalic acid alkyl ring lactone monomer;

[0033] S2. subjecting the first oxalic acid alkyl cyclic lactone monomer and the cyclic lactone monomer to ring-opening polymerization under the action of an initiator and a catalyst to obtain a polyalkyl oxalate copolymer.

[0034] Preferably, the cyclic lactone monomer is selected from one or more of lactide, glycolide, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, enantholactone, pentadecalactone, and a second oxalic acid alkyl cyclic lactone monomer.

[0035] Compared with the prior art, the present invention has at least the following beneficial effects:

[0036] The invention uses bulk chemicals oxalic acid diester and aliphatic diol as raw materials, which have wide sources, low costs and diverse structures, thus ensuring the richness of the polyalkyl oxalate structure and the diversity of its properties. The process route of "condensation polymerization to synthesize alkyl oxalate oligomers, controlled depolymerization to prepare alkyl oxalate ring lactone monomers, and ring-opening polymerization of alkyl oxalate ring lactone monomers to prepare polyalkyl oxalate" is adopted, which abandons strict reaction conditions and simplifies the condensation polymerization process. It can prepare oligomeric alkyl oxalate with molecular weight ranging from hundreds to thousands. The controllable depolymerization process can efficiently convert oligomers into high-purity alkyl oxalate ring lactone monomers, optimize the synthesis process of alkyl oxalate ring lactone monomers, and improve the yield and purity of monomers; the controlled ring-opening polymerization of alkyl oxalate ring lactone monomers is achieved by using efficient catalysts to prepare high-molecular-weight polyalkyl oxalate homopolymers, and high-molecular-weight polyalkyl oxalate copolymers are prepared by adjusting the chain structure and sequence structure of the polymer by copolymerization during the ring-opening polymerization process, thereby realizing the controllable preparation of oxalic acid-based polyesters with different structures and properties, expanding the types of oxalic acid-based polyesters, and improving the performance of oxalic acid-based polyesters, which can meet the use requirements of different application scenarios.

[0037] The invention realizes fine control of polymer molecular weight and molecular weight distribution by precise control of reaction conditions and screening of catalysts, and the prepared polyalkyl oxalate has excellent mechanical strength and good thermal stability. By adjusting the type of initiator, linear, cyclic, star-shaped or multi-branched polyalkyl oxalate can be obtained, so that it has richer secondary structure and aggregated structure, and polyalkyl oxalate with corresponding structure and performance can be synthesized according to practical application.

[0038] The present invention uses the prepared oxalic acid alkyl ring lactone monomers with different structures, or the prepared oxalic acid alkyl ring lactone monomers and other cyclic lactone monomers for ring-opening copolymerization, and can achieve accurate regulation of the polyalkyl oxalate chain structure and molecular weight by accurately controlling the order of adding comonomers and the dosage ratio and polymerization conditions, and can adjust the sequence structure and aggregation state of the polymer, thereby changing the melting point, glass transition temperature, mechanical strength, rheology, processability and degradability of the copolyester, and preparing a polymer with a specific structure and performance, which can further expand the structure, performance and application range of the polymer, and provide a broad space for designing high-performance, high-functional new materials. The copolymerization method can not only improve its processability and enhance environmental stability, but also adjust the physicochemical properties of the polymer, ensure that the obtained polymer has excellent physicochemical properties, and meet the needs of specific applications.

[0039] The preparation method of polyalkyl oxalate provided by the present invention has significant advantages in the field of polymer synthesis technology, which include not only improving production efficiency and reducing costs, but also expanding polymer structure, enhancing polymer performance and expanding its application field, thus providing an effective way for the development and application of high-performance polymer materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0041] Figure 1 is the NMR spectrum of ethylene glycol oxalate monomer obtained in Example 3;

[0042] Figure 2 is the NMR spectrum of 1,4-butanediol oxalate monomer obtained in Example 17;

[0043] Figure 3 is the nuclear magnetic spectrum of poly(1,2-propylene glycol oxalate) obtained in Example 13;

[0044] Figure 4 is the nuclear magnetic spectrum of poly(1,4-butylene oxalate) obtained in Example 19;

[0045] Figure 5 is the DSC graph of polyethylene oxalate obtained in Example 8;

[0046] Figure 6 is the DSC graph of poly(1,2-propylene oxalate) obtained in Example 13;

[0047] Figure 7 is the DSC graph of poly(1,3-propylene oxalate) obtained in Example 15;

[0048] Figure 8 The present invention is a schematic diagram of the preparation process of the polyalkyl oxalate homopolymer and the polyalkyl oxalate copolymer. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0050] The present invention provides a method for preparing a high molecular weight polyalkyl oxalate homopolymer, the preparation method comprising:

[0051] S1. subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction, and distillation to obtain an oxalic acid alkyl cyclic lactone monomer;

[0052] S2. subjecting the oxalic acid alkyl cyclic lactone monomer to ring-opening polymerization under the action of an initiator and a first catalyst to obtain a polyalkyl oxalate homopolymer.

[0053] The invention uses bulk chemicals oxalic acid diester and aliphatic diol as raw materials, which have wide sources, low costs and diverse structures, thus ensuring the richness of the polyalkyl oxalate structure and the diversity of its properties. The process route of "condensation polymerization to synthesize alkyl oxalate oligomers, controlled depolymerization to prepare alkyl oxalate ring lactone monomers, and ring-opening polymerization of alkyl oxalate ring lactone monomers to prepare polyalkyl oxalate" is adopted, which abandons strict reaction conditions and simplifies the condensation polymerization process. It can prepare oligomeric alkyl oxalate with molecular weight ranging from hundreds to thousands. The controllable depolymerization process can efficiently convert oligomers into high-purity alkyl oxalate ring lactone monomers, optimize the synthesis process of alkyl oxalate ring lactone monomers, and improve the yield and purity of monomers; the controlled ring-opening polymerization of alkyl oxalate ring lactone monomers is achieved by using efficient catalysts to prepare high-molecular-weight polyalkyl oxalate homopolymers, and high-molecular-weight polyalkyl oxalate copolymers are prepared by adjusting the chain structure and sequence structure of the polymer by copolymerization during the ring-opening polymerization process, thereby realizing the controllable preparation of oxalic acid-based polyesters with different structures and properties, expanding the types of oxalic acid-based polyesters, and improving the performance of oxalic acid-based polyesters, which can meet the use requirements of different application scenarios.

[0054] The invention realizes fine control of polymer molecular weight and molecular weight distribution by precise control of reaction conditions and screening of catalysts, and the prepared polyalkyl oxalate has excellent mechanical strength and good thermal stability. By adjusting the type of initiator, linear, cyclic, star-shaped or multi-branched polyalkyl oxalate can be obtained, so that it has richer secondary structure and aggregated structure, and polyalkyl oxalate with corresponding structure and performance can be synthesized according to practical application.

[0055] The present invention selects bulk chemicals as starting materials, reduces production costs, uses bio-based materials, reduces dependence on petroleum-based resources, has a wide source of raw materials and diverse structures, and ensures the richness of the structure and diversity of the performance of polyalkyl oxalate. At the same time, strict reaction conditions are abandoned, the polycondensation reaction process is simplified, and low-molecular alkyl oxalate with a molecular weight ranging from hundreds to thousands can be prepared, which can meet the subsequent oxalic acid alkyl ring lactone monomer process requirements and simplify the synthesis process.

[0056] According to some preferred embodiments, step S1 comprises: (i) subjecting an oxalic acid diester compound and an aliphatic diol compound to a condensation reaction to obtain an alkyl oxalate oligomer; the condensation reaction comprises a first stage condensation reaction carried out under normal pressure and a second stage condensation reaction carried out under reduced pressure conditions (vacuum conditions); (ii) subjecting the alkyl oxalate oligomer to a depolymerization reaction and distillation under reduced pressure conditions to obtain an alkyl oxalate cyclic lactone monomer. Specifically, step S1 comprises: adding oxalic acid diester compound I and aliphatic diol compound II to a polymerization device, heating to above 80°C to carry out a first-stage polycondensation reaction under high temperature and normal pressure conditions, and then carrying out a second-stage polycondensation reaction under high temperature and reduced pressure conditions, cooling the polymerization device to room temperature after the polymerization is completed, washing the polymer after the reaction with an organic solvent (wherein the organic solvent is preferably at least one of methanol and ether) to remove small molecules and catalysts, and finally vacuum drying to obtain pure oxalic acid alkyl ester oligomer III; stirring the oxalic acid alkyl ester oligomer III under high temperature and reduced pressure conditions to carry out a depolymerization reaction, distilling the system after the depolymerization reaction and collecting the fraction volatilized at 100-200°C, and purifying the collected fraction by vacuum sublimation or reduced pressure distillation to obtain a high-purity oxalic acid alkyl ring lactone monomer IV.

[0057] According to some preferred embodiments, step S1 includes: under reduced pressure, subjecting oxalic acid diester compounds and aliphatic diol compounds to polycondensation reaction, depolymerization reaction, and distillation to obtain oxalic acid alkyl ring lactone monomer. Specifically, step S1 includes: adding oxalic acid diester compound I and aliphatic diol compound II to a polymerization device, heating to above 80°C to fully mix them at high temperature, and then subjecting them to one-pot polycondensation reaction and depolymerization reaction under high temperature and reduced pressure conditions, distilling the system after the depolymerization reaction and collecting the volatilized fraction at 100 to 200°C, and purifying the collected fraction by vacuum sublimation or reduced pressure distillation to obtain high-purity oxalic acid alkyl ring lactone monomer IV;

[0058] Specifically, step S2 includes: adding an initiator and a catalyst to the oxalic acid alkyl cyclic lactone monomer IV, adding a quencher to terminate the reaction after reacting for a period of time under certain conditions, and washing the obtained polyalkyl oxalate homopolymer with methanol. By adjusting the reaction conditions, such as temperature, pressure and catalyst concentration, the molecular weight of the polyester can be further increased, and finally a polyalkyl oxalate with a molecular weight of 2 to 1000 kDa can be prepared, and the molecular weight distribution of the polymer is controlled to ensure that the polyester has excellent mechanical properties and processability; controlling the end group structure and realizing the end group functionalization provides a broad space for subsequent material modification and application.

[0059] According to some preferred embodiments, the oxalic acid diester compound has the following structure:

[0060]

[0061] Among them, R 7 is one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, and benzyl;

[0062] The oxalic acid diester compound is preferably one or more of dimethyl oxalate, diethyl oxalate, di-n-propyl oxalate, diisopropyl oxalate, di-n-butyl oxalate, diisobutyl oxalate, di-tert-butyl oxalate, diphenyl oxalate, and dibenzyl oxalate, more preferably dimethyl oxalate.

[0063] According to some preferred embodiments, the aliphatic diol compound has the following structure:

[0064]

[0065] Where x is 0 to 2, R 1 , R 2 , R 3 , R 4 , R 5 , R 6 Each is independently hydrogen, an alkyl group of 1 to 8 carbon atoms, a cycloalkyl group, or a phenyl group;

[0066] Preferably, the aliphatic diol compound is selected from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,2-propylene glycol, 2-methyl-1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, 1,2-butanediol, 1,2-pentanediol and its isomers, 1,2-hexanediol and its isomers, 1,2-heptanediol and its isomers, 1,2-octanediol and its isomers, 1,2-nonanediol and its isomers, 1,2-decanediol and its isomers, 1,3-pentanediol and its isomers, 1,3-hexanediol and its isomers, 1,3 -heptanediol and its isomers, 1,3-octanediol and its isomers, 1,3-nonanediol and its isomers, 1,3-decanediol and its isomers, 1,4-pentanediol and its isomers, 1,4-hexanediol and its isomers, 1,3-heptanediol and its isomers, 1,4-octanediol and its isomers, 1,4-nonanediol and its isomers, 1,4-decanediol and its isomers, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,2-cycloheptanediol, 1,2-cyclooctanediol, 1,2-cyclononanediol, 1,2-cyclodecanediol, phenyl-1,2-ethanediol or one or more thereof.

[0067] The above-mentioned oxalic acid diester compounds and diol compounds of the present invention can be converted from bulk coal-based chemicals such as methanol, etc., or can be purified by biomass raw materials or synthesized by chemical conversion, which ensures a wide range of raw material sources, low costs, and rich structures, and improves the economy and environmental friendliness of the reaction. Compared with the prior art, the present invention greatly expands the types of substrates by changing the diol compounds, provides rich structures for the subsequent synthesis of monomers and polyesters, and the selected bulk commodities are low in price and widely available, which significantly reduces product costs and realizes the high added value conversion of these low-priced chemicals.

[0068] According to some preferred embodiments, the amount of the initiator is 0.01 mol% to 10 mol% of the oxalic acid alkyl cyclic lactone monomer; preferably, the initiator is one or more of a monohydroxy alcohol, a dihydroxy alcohol, a polyhydroxy alcohol, a phenol, and an amino compound; wherein the monohydroxy alcohol is preferably one or more of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, benzyl alcohol, phenylethyl alcohol, phenylpropanol, cyclopentanol, and cyclohexanol; the dihydroxy alcohol is preferably one or more of ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, cyclopentanol, and cyclohexanol. One or more of hexanediol, cyclopentanediol, cyclononanediol, cyclodecanediol, and terephthalic acid; the phenol is preferably one or more of phenol, hydroquinone, and phloroglucinol; the amino compound is preferably one or more of methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, benzylamine, phenylethylamine, amphetamine, cyclopentylamine, cyclohexylamine, aniline, ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, cyclohexanediamine, cyclopentanediamine, cyclononanediamine, cyclodecanediamine, p-phenylenediamine, and p-phenylenediamine; and / or

[0069] The amount of the first catalyst is 0.01 mol% to 10 mol% of the oxalic acid alkyl cyclic lactone monomer; preferably, the first catalyst is one or more of an organic metal catalyst, a rare earth metal catalyst, and an organic catalyst; wherein the metal catalyst is preferably one of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, diethyl zinc, zinc dichloride, Salen-Al catalyst, Porphyrin-Al catalyst, β-diimine-Zn catalyst, Phenolato-Ti catalyst, Tripodal-Fe catalyst, n-butyl lithium, isobutyl lithium, lithium diisopropylamide, sodium methoxide, sodium tert-butoxide, and potassium tert-butoxide. or more; the rare earth catalyst is preferably one or more of β-diketone rare earth metal complexes, cyclopentadienyl rare earth catalysts, bisphenol-based rare earth catalysts, Schiff base rare earth catalysts, sulfonic acid rare earth catalysts, rare earth metal halides, Salen rare earth complexes, and P-SalenY catalysts; the organic catalyst is preferably one or more of methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, boron trifluoride, tri(pentafluorophenyl)boron, triethylboron, camphorsulfonic acid, triethylamine, pyridine, 4-dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, hexamethyldisilazane, and phosphazene base. The present invention uses an organic catalyst to catalyze ring-opening polymerization to prepare polyalkyl oxalate without metal residue, and the prepared material can be applied to fields with strict requirements on metal residue rate. Polyester prepared by catalytic ring-opening polymerization with an organic catalytic system can be used in fields with strict requirements on metal residues, such as medical fields, food packaging, and electronic packaging, greatly improving the application scenarios of the product.

[0070] According to some preferred embodiments, the polycondensation reaction is carried out under the condition of a second catalyst or without a catalyst, the temperature of the polycondensation reaction is not less than 80°C, preferably 100-200°C, and the time of the polycondensation reaction is 1-12h. The polycondensation reaction of the present invention can be carried out under the condition of no catalyst, but when a trace amount of low-toxicity catalyst (the amount used is 0.0001wt%-10wt% of the oxalic acid diester compound) is introduced, the reaction rate can be significantly accelerated, the reaction yield can be increased, thereby reducing production costs, and the synthetic equipment is not damaged. Whether to add a catalyst can be selected according to actual conditions.

[0071] According to some preferred embodiments, the depolymerization reaction is carried out under a third catalyst or without a catalyst, and the temperature of the depolymerization reaction is 100 to 200°C; the time of the depolymerization reaction is 1 to 12 hours. The depolymerization reaction of the present invention can be carried out without a catalyst, but the addition of a catalyst can accelerate the reaction process, achieve a faster depolymerization rate, and also improve the selectivity of the depolymerization reaction, ensure a high yield of the oxalic acid alkyl ring lactone monomer, and help reduce the cost of monomer preparation. In addition, due to the improvement of the depolymerization selectivity, there are very few by-products, and a high-purity monomer can be obtained only by a purification method of reduced pressure sublimation, and the loss of the product in the purification process is very small, while avoiding the use of organic solvents, improving the environmental protection of the process. Whether to add a catalyst can be selected according to actual conditions.

[0072] The present invention can significantly improve the depolymerization selectivity by using a specific catalyst, ultimately increasing the yield of the monomer, and can obtain high-purity monomers using simple purification methods, thus avoiding the use of organic solvents, reducing the generation of industrial wastewater, and being more suitable for actual industrial production.

[0073] According to some preferred embodiments, the temperature of the ring-opening polymerization is -80 to 200° C., and the time of the ring-opening polymerization is 0.1 to 24 hours.

[0074] According to some preferred embodiments, the amount of the second catalyst is 0.0001wt% to 10wt% of the oxalic acid diester compound, and the second catalyst is preferably one or more of stannous octoate, tetrabutyl titanate, tetraisopropyl titanate, zinc acetate, magnesium oxide, magnesium hydroxide, magnesium carbonate, tin chloride, ferric chloride, titanium chloride, zinc chloride, aluminum chloride, zinc oxide, tin oxide, ferric oxide, bismuth trifluoromethanesulfonate, zinc trifluoromethanesulfonate, 4-dimethylaminopyridine, nitrogen heterocyclic carbene, p-toluenesulfonic acid, trifluoromethanesulfonic acid, diphenyl phosphate, and ionic liquids; and / or

[0075] The dosage of the third catalyst is 0.0001wt% to 10.0wt% of the alkyl oxalate oligomer, and the third catalyst is preferably one or more of stannous octoate, tetrabutyl titanate, tin chloride, ferric chloride, titanium chloride, zinc chloride, aluminum chloride, zinc oxide, tin oxide, ferric oxide, 4-dimethylaminopyridine, p-toluenesulfonic acid, trifluoromethanesulfonic acid, diphenyl phosphate, ionic liquid, sodium glycolate, and sodium acetate.

[0076] The present invention also provides a method for preparing a high molecular weight polyalkyl oxalate copolymer, the preparation method comprising:

[0077] S1. subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction, and distillation to obtain a first oxalic acid alkyl ring lactone monomer;

[0078] S2. subjecting the first oxalic acid alkyl cyclic lactone monomer and the cyclic lactone monomer to ring-opening polymerization under the action of an initiator and a catalyst to obtain a polyalkyl oxalate copolymer.

[0079] It should be noted that in the preparation process of the polyalkyl oxalate homopolymer and the polyalkyl oxalate copolymer of the present invention, a quencher needs to be added after the ring-opening polymerization is carried out for a period of time to terminate the reaction, and then the obtained polyalkyl oxalate homopolymer and the polyalkyl oxalate copolymer are washed in an organic solvent to remove the catalyst and unreacted monomers, and finally the pure polyalkyl oxalate homopolymer and the polyalkyl oxalate copolymer are obtained by drying.

[0080] The present invention further adjusts the comprehensive performance of polyester by copolymerizing a first oxalic acid alkyl cyclic lactone monomer with a cyclic lactone monomer (which may be a second oxalic acid alkyl cyclic lactone monomer having a different molecular structure from the first oxalic acid alkyl cyclic lactone monomer, or one or more of other cyclic lactone monomers), thereby achieving the preparation of high-performance materials and making up for the defects of homopolymers. Specifically, the sequence structure and aggregation state of the polymer are effectively adjusted by copolymerizing an oxalic acid alkyl cyclic lactone monomer with a cyclic lactone monomer (which may be a second oxalic acid alkyl cyclic lactone monomer having a different molecular structure from the first oxalic acid alkyl cyclic lactone monomer, or one or more of other cyclic lactone monomers), thereby changing the melting point, glass transition temperature, mechanical strength, rheology, processability and degradability of the copolyester, greatly enriching the structure of oxalic acid-based polyesters and broadening the application scenarios of polyesters.

[0081] The present invention uses the prepared oxalic acid alkyl ring lactone monomers with different structures, or the prepared oxalic acid alkyl ring lactone monomers and other cyclic lactone monomers for ring-opening copolymerization, and can achieve accurate regulation of the polyalkyl oxalate chain structure and molecular weight by accurately controlling the order of adding comonomers and the dosage ratio and polymerization conditions, and can adjust the sequence structure and aggregation state of the polymer, thereby changing the melting point, glass transition temperature, mechanical strength, rheology, processability and degradability of the copolyester, and preparing a polymer with a specific structure and performance, which can further expand the structure, performance and application range of the polymer, and provide a broad space for designing high-performance, high-functional new materials. The copolymerization method can not only improve its processability and enhance environmental stability, but also adjust the physicochemical properties of the polymer, ensure that the obtained polymer has excellent physicochemical properties, and meet the needs of specific applications.

[0082] The preparation method of polyalkyl oxalate provided by the present invention has significant advantages in the field of polymer synthesis technology, which include not only improving production efficiency and reducing costs, but also expanding polymer structure, enhancing polymer performance and expanding its application field, thus providing an effective way for the development and application of high-performance polymer materials.

[0083] In the preparation process of the polyalkyl oxalate copolymer of the present invention, step S2 can prepare a block copolymer, an alternating copolymer or a random copolymer with controllable structure by controlling the feeding order of the monomers, specifically including the following two situations:

[0084] The first case: a first oxalic acid alkyl cyclic lactone monomer, a cyclic lactone monomer (which may be a second oxalic acid alkyl cyclic lactone monomer having a molecular structure different from the first oxalic acid alkyl cyclic lactone monomer, or one or more other cyclic lactone monomers), an initiator and a catalyst are mixed and ring-opening polymerization is performed to obtain an alternating copolymer or a random copolymer.

[0085] The second case: firstly, the first oxalic acid alkyl cyclic lactone monomer (or cyclic lactone monomer) is subjected to the first ring-opening polymerization under the action of an initiator and a catalyst, and then the cyclic lactone monomer (or the first oxalic acid alkyl cyclic lactone monomer) is added to carry out the second ring-opening polymerization, and then, according to the number of blocks and the molecular structure of the synthesized polymer, the oxalic acid alkyl cyclic lactone monomer or the cyclic lactone monomer can be added to carry out the ring-opening polymerization (third ring-opening polymerization, fourth ring-opening polymerization...), to obtain a polyalkyl oxalate copolymer with a block structure. By screening the monomer structure and regulating the order of adding materials, a controllable block copolymer (two-block, three-block and multi-block copolymer) is prepared, and finally a polyester material such as an elastomer is prepared.

[0086] According to some preferred embodiments, the cyclic lactone monomer is selected from one or more of lactide, glycolide, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, enantholactone, pentadecalactone, and a second oxalic acid alkyl cyclic lactone monomer.

[0087] It should be noted that the difference between the preparation process of the polyalkyl oxalate copolymer of the present invention and the polyalkyl oxalate homopolymer is that the cyclic lactone monomer is introduced in step S2. Except for the cyclic lactone monomer, the types and amounts of other substances involved in the preparation process that are not further limited (oxalic acid diester compounds, aliphatic diol compounds, oxalic acid alkyl cyclic lactone monomers, first catalysts, second catalysts, third catalysts and initiators, etc.), and the process parameters involved in the preparation process (condensation reaction, depolymerization reaction, temperature, time, pressure, etc. of ring-opening polymerization, purification method, etc.) are the same as those of the preparation method of the polyalkyl oxalate homopolymer described above, and will not be elaborated here. In addition, the preparation methods of the second oxalic acid alkyl cyclic lactone monomer in the cyclic lactone monomer and the first oxalic acid alkyl cyclic lactone monomer in step S1 are the same as the preparation method of the oxalic acid alkyl cyclic lactone monomer in the polyalkyl oxalate homopolymer, and the difference between the two (the first oxalic acid alkyl cyclic lactone monomer and the second oxalic acid alkyl cyclic lactone monomer) is only that they have different molecular structures (other oxalic acid alkyl cyclic lactone monomers with different molecular structures from the first oxalic acid alkyl cyclic lactone monomer obtained due to different raw material types, amounts or reaction parameters, etc.), and the use of "first" and "second" here is only to distinguish oxalic acid alkyl cyclic lactone monomers with different molecular structures.

[0088] The schematic diagram of the preparation process of the polyalkyl oxalate homopolymer and the polyalkyl oxalate copolymer of the present invention is as follows Figure 8 As shown, it should be noted that Figure 8 Medium R 8 is an initiator, substituent R 1 , R 2 , R 3 , R 4 , R 5 , R 6 , R 7 The types of initiators are the same as above and are not described one by one here. The condensation polymerization in the figure corresponds to the condensation polymerization reaction above, the high temperature and vacuum corresponds to the high temperature and reduced pressure above, and the depolymerization into rings corresponds to the depolymerization reaction above.

[0089] In order to more clearly illustrate the technical solutions and advantages of the present invention, the present invention is further described below in conjunction with the examples. The present invention does not specifically limit the sources of the reagents used in the examples and comparative examples, and the reagents can be directly purchased or synthesized by themselves.

[0090] A. Preparation of Ethylene Oxalate Monomer without Catalyst

[0091] Example 1

[0092] Preparation of oxalic acid glycol ester oligomer: Add dimethyl oxalate (30g, 0.25mol) and ethylene glycol (19g, 0.30mol) to a 100mL reaction bottle. React at 80°C under normal pressure for 1.5h, heat to 110°C for 1.5h, heat to 140°C for 3h, and heat to 150°C for 1h. At 150°C, gradually reduce the pressure to 10000Pa for 1h, and gradually reduce the pressure to 50Pa for 4h to obtain a low molecular weight polymer. Wash the polymer with ice methanol and vacuum dry to obtain oxalic acid glycol ester oligomer with a yield of 78%.

[0093] Example 2

[0094] Preparation of ethylene glycol oxalate monomer: 10 g of ethylene glycol oxalate oligomer prepared in Example 1 was placed in a bottle and the pressure was reduced to 50-100 Pa. The mixture was reacted at 180° C. for 4 h to obtain a crude ethylene glycol oxalate monomer product. The crude product was subjected to multiple reduced pressure distillations to obtain pure ethylene glycol oxalate monomer in a yield of 65%.

[0095] Example 3

[0096] One-pot method for preparing ethylene glycol oxalate monomer: add dimethyl oxalate (600g, 5.08mol) and ethylene glycol (380g, 6.10mol) to a 3L reaction bottle, react at 80°C under normal pressure for 1.5h, heat to 110°C for 1.5h, heat to 140°C for 3h, heat to 150°C for 1h. At 150°C, gradually reduce the pressure to 10000Pa for 0.5h, gradually reduce the pressure to 50Pa for 1-2h, then heat to 180°C for 2h, and obtain crude ethylene glycol oxalate monomer by vacuum distillation. After the crude product is washed with deionized water and dried, pure ethylene glycol oxalate monomer is obtained by vacuum distillation with a yield of 52%. The nuclear magnetic spectrum is as follows: Figure 1 As shown, it is proved that ethylene glycol oxalate monomer is obtained.

[0097] B. Efficient preparation of ethylene glycol oxalate monomer under catalyst conditions

[0098] Example 4

[0099] Preparation of oxalic acid glycol ester oligomer: Add dimethyl oxalate (60g, 0.508mol), ethylene glycol (38g, 0.610mol) and tetrabutyl titanate (0.018g) to a 250mL reaction bottle. React at 80℃ under normal pressure for 1.5h, heat to 110℃ for 1.5h, heat to 140℃ for 3h, heat to 150℃ for 1h. At 150℃, gradually reduce the pressure to 10000Pa for 0.5h, gradually reduce the pressure to 50Pa for 1-2h to obtain a low molecular weight polymer, wash the polymer with ice methanol, and vacuum dry to obtain oxalic acid glycol ester oligomer with a yield of 95%.

[0100] Example 5

[0101] Preparation of ethylene glycol oxalate monomer: The ethylene glycol oxalate oligomer prepared in Example 4 and sodium glycolate (3 wt %) were mixed in a bottle, the pressure was reduced to 50-100 Pa, and the mixture was reacted at 180° C. for 1 h to obtain a crude product of ethylene glycol oxalate monomer. The crude product was dissolved in dichloromethane and washed with deionized water. The organic phase was dried over anhydrous magnesium sulfate and concentrated, and then purified ethylene glycol oxalate monomer was obtained by vacuum distillation with a yield of 90%.

[0102] Example 6

[0103] Preparation of oxalic acid glycol ester monomer by one-pot method: Add dimethyl oxalate (600g, 5.08mol), ethylene glycol (380g, 6.10mol) and tetrabutyl titanate (0.18g) into a 3L reaction bottle, react at 80℃ under normal pressure for 1.5h, heat to 110℃ for 1.5h; heat to 140℃ for 3h, heat to 150℃ for 1h. At 150℃, gradually reduce the pressure to 10000Pa for 0.5h, gradually reduce the pressure to 50Pa for 1-2h to obtain a low molecular weight polymer. Add stannous octoate (the amount is 3wt% of the low molecular weight polymer), control the pressure in the bottle at 50Pa, heat to 180℃ for 2h to obtain a crude product of oxalic acid glycol ester monomer, wash the crude product with deionized water and dry it, and then distill it under reduced pressure to obtain pure oxalic acid glycol ester monomer with a yield of 85%.

[0104] Example 7

[0105] Preparation of oxalic acid glycol ester monomer by one-pot method: Add dimethyl oxalate (600g, 5.08mol) and ethylene glycol (380g, 6.10mol) to a 3L reaction bottle, react at 80℃ under normal pressure for 1.5h, heat to 110℃ for 1.5h, heat to 140℃ for 3h, heat to 150℃ for 1h. At 150℃, gradually reduce the pressure to 10000Pa for 0.5h, gradually reduce the pressure to 50Pa for 1-2h to obtain a low molecular weight polymer. Add sodium glycolate (the amount is 1wt% of the low molecular weight polymer), control the pressure in the bottle at 50Pa, heat to 180℃ for 2h to obtain a crude product of oxalic acid glycol ester monomer, and obtain pure oxalic acid glycol ester monomer by vacuum distillation of the crude product, with a yield of 81%.

[0106] C. Ring-opening polymerization of ethylene glycol oxalate monomer

[0107] Example 8

[0108] Preparation of polyethylene oxalate by ring-opening polymerization of ethylene glycol oxalate monomer: In a glove box under a nitrogen atmosphere, stannous octoate (0.041 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate (11.6 g, 0.1 mol) prepared in Example 6 were added to a dry bottle, and polymerization was started at 100° C. After the polymerization was completed, the reactant was poured into excess cold methanol and washed three times. Polyethylene oxalate was obtained after vacuum drying with a yield of 91%. The DSC graph of polyethylene oxalate is shown in FIG. Figure 5 As shown, it is proved that the prepared polyethylene oxalate is a highly crystalline polyester with a glass transition temperature of 42°C and a melting point of about 180°C.

[0109] Example 9

[0110] Preparation of polyethylene oxalate by ring-opening polymerization of ethylene oxalate monomer: In a glove box under a nitrogen atmosphere, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (0.014 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene oxalate obtained in Example 6 (11.6 g, 0.1 mol) were added to a dry bottle, and polymerization was started at 25°C. After the polymerization was completed, the reactant was poured into excess cold methanol and washed three times. Polyethylene oxalate was obtained after vacuum drying with a yield of 85%.

[0111] D. Preparation and ring-opening polymerization of propylene glycol oxalate monomer

[0112] Example 10

[0113] Preparation of 1,2-propylene glycol oxalate oligomer: Add dimethyl oxalate (60g, 0.508mol), 1,2-propylene glycol (46g, 0.610mol) and tetrabutyl titanate (0.018g) into a 250mL reaction bottle, react at 80°C for 1.5h; heat to 110°C for 1.5h; heat to 140°C for 3h; heat to 150°C for 1h. Then gradually reduce the pressure to 10000Pa at 150°C for 0.5h; gradually reduce the pressure to 50Pa for 2h, and wash with methanol to obtain a low molecular weight polymer 1,2-propylene glycol oxalate oligomer with a yield of 95%.

[0114] Embodiment 11

[0115] Preparation of 1,2-propylene glycol oxalate monomer: Mix the 1,2-propylene glycol oxalate oligomer obtained in Example 10 and sodium glycolate (the amount used is 3 wt% of the 1,2-propylene glycol oxalate oligomer) in a bottle, reduce the pressure to 50 Pa, and react at 200°C for 1 h to obtain a crude 1,2-propylene glycol oxalate monomer product, wash with deionized water, dry, and then obtain pure 1,2-propylene glycol oxalate monomer by reduced pressure distillation in a yield of 78%.

[0116] Example 12

[0117] Preparation of 1,2-propylene glycol oxalate monomer by one-pot method: Add dimethyl oxalate (600g, 5.08mol), 1,2-propylene glycol (460g, 6.10mol) and tetrabutyl titanate (0.18g) to a 3L reaction bottle. React at 80°C under normal pressure for 1.5h, heat to 110°C for 1.5h, heat to 140°C for 3h, and heat to 150°C for 1h. At 150°C, gradually reduce the pressure to 10000Pa for 0.5h, gradually reduce the pressure to 50Pa for 2h to obtain a low molecular weight polymer. Add stannous octoate (the amount is 3wt% of the low molecular weight polymer), control the pressure in the bottle at 50Pa, heat to 180°C for 2h to obtain a crude product of 1,2-propylene glycol oxalate monomer. The crude product was washed with deionized water and dried, and then purified 1,2-propylene glycol oxalate monomer was obtained by reduced pressure distillation with a yield of 85%.

[0118] Embodiment 13

[0119] Preparation of poly(1,2-propylene glycol oxalate) by ring-opening polymerization of 1,2-propylene glycol oxalate monomer: In a glove box under a nitrogen atmosphere, stannous octoate (0.041 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and 1,2-propylene glycol oxalate (13.0 g, 0.1 mol) prepared in Example 12 were added to a dry bottle, respectively, and polymerized at 100° C. for 1 h. After the polymerization, the reactant was poured into excess cold methanol and washed three times. After vacuum drying, poly(1,2-propylene glycol oxalate) was obtained with a yield of 93%. Its NMR spectrum is shown as follows: Figure 3 As shown, it is proved that poly 1,2-propylene glycol oxalate is obtained, and its DSC diagram is as follows Figure 6 As shown, it is proved that the prepared poly(1,2-propylene oxalate) is a slow crystallizing polyester with a glass transition temperature of -8°C and a melting point of 81°C.

[0120] Embodiment 14

[0121] Preparation of 1,3-propylene glycol oxalate monomer by one-pot method: dimethyl oxalate (600g, 5.08mol), 1,2-propylene glycol (460g, 6.10mol) and tetrabutyl titanate (0.18g) were added to a 3L reaction bottle. React at 80℃ under normal pressure for 1.5h; heat to 110℃ for 1.5h; heat to 140℃ for 3h; heat to 150℃ for 1h. At 150℃, gradually reduce the pressure to 10000Pa for 0.5h, and gradually reduce the pressure to 50Pa for 2h to obtain a low molecular weight polymer. Add stannous octoate (the amount is 3wt% of the low molecular weight polymer), control the pressure in the bottle at 50Pa, heat to 180℃ for 2h to obtain a crude product of propylene glycol oxalate monomer. After the crude product is washed with deionized water and dried, pure 1,3-propylene glycol oxalate monomer is obtained by vacuum distillation with a yield of 77%.

[0122] Embodiment 15

[0123] Preparation of poly(1,3-propylene oxalate) by ring-opening polymerization of 1,3-propylene oxalate monomer: In a glove box under a nitrogen atmosphere, stannous octoate (0.041 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and 1,3-propylene oxalate monomer (13.0 g, 0.1 mol) prepared in Example 14 were added to a dry bottle, and the mixture was polymerized at 100° C. for 1 h. After the polymerization, the reactant was poured into an excess of cold methanol and washed three times. After vacuum drying, poly(1,3-propylene oxalate) was obtained with a yield of 88%. Its DSC graph is shown as follows: Figure 7 As shown, it is proved that the prepared poly(1,3-propylene oxalate) is an amorphous polyester with a glass transition temperature of about 29°C and no crystallization and melting point transition.

[0124] E. Preparation and ring-opening polymerization of 1,4-butanediol oxalate monomer

[0125] Example 16

[0126] Preparation of 1,4-butanediol oxalate oligomer: Dimethyl oxalate (60 g, 0.508 mol), 1,4-butanediol (55 g, 0.610 mol) and tetrabutyl titanate (0.018 g) were added to a 250 mL reaction bottle, reacted at 80°C for 1.5 h, heated to 110°C for 1.5 h, heated to 140°C for 3 h, and heated to 150°C for 1 h. Then, the pressure was gradually reduced to 10000 Pa at 150°C for 0.5 h; the pressure was gradually reduced to 50 Pa for 2 h, and a low molecular weight polymer was obtained after washing with methanol, with a yield of 95%.

[0127] Embodiment 17

[0128] Preparation of 1,4-butylene oxalate monomer: The 1,4-butylene oxalate oligomer prepared in Example 16 and sodium glycolate (the amount used is 3wt% of the 1,4-butylene oxalate oligomer) are mixed in a bottle, the pressure is reduced to 50Pa, and the reaction is carried out at 200°C for 1h to obtain a crude 1,4-butylene oxalate monomer product, which is washed with deionized water, dried, and then distilled under reduced pressure to obtain a pure 1,4-butylene oxalate monomer with a yield of 71%. The NMR spectrum is as follows: Figure 2 As shown, it is proved that 1,4-butanediol oxalate monomer is obtained.

[0129] Embodiment 18

[0130] Preparation of 1,4-butanediol oxalate monomer by one-pot method: Add dimethyl oxalate (600g, 5.08mol), 1,4-butanediol (550g, 6.10mol) and tetrabutyl titanate (0.18g) to a 3L reaction bottle. React at 80°C under normal pressure for 1.5h, heat to 110°C for 1.5h, heat to 140°C for 3h, and heat to 150°C for 1h. At 150°C, gradually reduce the pressure to 10000Pa for 0.5h, gradually reduce the pressure to 50Pa for 2h to obtain a low molecular weight polymer. Add stannous octoate (the amount is 3wt% of the low molecular weight polymer), control the pressure in the bottle at 50Pa, heat to 180°C for 2h to obtain a crude product of 1,4-butanediol oxalate monomer. The crude product was washed with deionized water and dried, and then purified 1,4-butanediol oxalate monomer was obtained by reduced pressure distillation with a yield of 66%.

[0131] Embodiment 19

[0132] Preparation of poly(1,4-butylene oxalate) by ring-opening polymerization of 1,4-butylene oxalate monomer: In a glove box under nitrogen atmosphere, stannous octoate (0.041 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and 1,4-butylene oxalate (13.0 g, 0.1 mol) prepared in Example 18 were added to a dry bottle, and polymerized at 100°C for 1 h. After the polymerization, the reactant was poured into excess cold methanol and washed three times. After vacuum drying, poly(1,4-butylene oxalate) was obtained with a yield of 97%. The NMR spectrum is shown in FIG. Figure 4 As shown, it is proved that poly 1,4-butylene oxalate is prepared.

[0133] F. Catalytic Ring-Opening Homopolymerization of Oxalic Acid Alkyl Cyclolactone Monomers (Preparation of Homopolymers)

[0134] Embodiment 20

[0135] In a glove box under nitrogen atmosphere, diethyl zinc (0.04 mL, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate prepared in Example 6 (11.6 g, 0.1 mol) were added to a dry bottle, and polymerization was started at 100°C. After the polymerization, the reactants were poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate was obtained with a yield of 85%.

[0136] Embodiment 21

[0137] In a glove box with a nitrogen atmosphere, methylaluminum-Salen ligand catalyst (0.062 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate prepared in Example 6 (11.6 g, 0.1 mol) were added into a dry bottle, and polymerization was started at room temperature. After the polymerization was completed, the reactants were poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate was obtained with a yield of 95%.

[0138] Embodiment 22

[0139] In a glove box under nitrogen atmosphere, La[N(SiMe 3 ) 2 ] 3 Catalyst (0.056 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate prepared in Example 6 (11.6 g, 0.1 mol) were polymerized at room temperature. After the polymerization was completed, the reactants were poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate was obtained with a yield of 88%.

[0140] Embodiment 23

[0141] In a glove box under nitrogen atmosphere, Y[N(SiMe 3 ) 2 ] 2 THF 2 Catalyst (0.059 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate prepared in Example 6 (11.6 g, 0.1 mol) were polymerized at room temperature. After the polymerization was completed, the reactants were poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate was obtained with a yield of 90%.

[0142] Embodiment 24

[0143] In a glove box under nitrogen atmosphere, 1,8-diazabicyclo[5.4.0]undec-7-ene (0.015 g, 0.1 mmol) and diethylzinc catalyst (0.04 mL, 0.1 mmol) were added to a dry bottle to form a Lewis acid-base catalytic system, and then benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate prepared in Example 6 (11.6 g, 0.1 mol) were added to the bottle. Polymerization began at room temperature. After the polymerization was completed, the reactant was poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate was obtained with a yield of 90%.

[0144] Embodiment 25

[0145] In a glove box under nitrogen atmosphere, 1,8-diazabicyclo[5.4.0]undec-7-ene (0.015 g, 0.1 mmol) and diphenylurea catalyst (0.021 g, 0.1 mmol) were added to a dry bottle to prepare a binary organic catalyst system, and then benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate prepared in Example 6 (11.6 g, 0.1 mol) were added to the bottle and polymerization was started at room temperature. After the polymerization was completed, the reactants were poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate was obtained with a yield of 85%.

[0146] F. Catalytic Ring-Opening Copolymerization of Oxalic Acid Alkyl Cyclolactone Monomers

[0147] Embodiment 26

[0148] In a glove box under a nitrogen atmosphere, stannous octoate (0.041 g, 0.1 mmol), p-phenylenediol (0.014 g, 0.1 mmol) and ethylene glycol oxalate (11.0 g, 0.1 mol) obtained in Example 6 were added into a dry bottle, and the mixture was polymerized at 100°C for 1 h. After the ethylene glycol oxalate monomer was completely consumed, propylene glycol oxalate (13.0 g, 0.1 mol) obtained in Example 12 was added at 100°C for 1 h. The reactants were poured into excess cold methanol and washed three times. After vacuum drying, poly(ethylene oxalate)-poly(propylene oxalate) block copolymers were obtained.

[0149] Embodiment 27

[0150] In a glove box under nitrogen atmosphere, 1,5,7-triazabicyclo[4.4.0]dec-5-ene (0.014 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol), propylene glycol oxalate prepared in Example 12 (13.0 g, 0.1 mol) and ethylene glycol oxalate prepared in Example 6 (11.0 g, 0.1 mol) were added to a dry bottle and incubated at 100 ° C for 2 h. The reactants were poured into excess cold methanol and washed three times. After vacuum drying, a poly(ethylene oxalate)-poly(propylene oxalate) random copolymer was obtained.

[0151] Embodiment 28

[0152] In a glove box under a nitrogen atmosphere, stannous octoate (0.041 g, 0.1 mmol), benzyl alcohol (0.011 g, 0.1 mmol) and ethylene glycol oxalate (11.0 g, 0.1 mol) obtained in Example 6 were added to a dry bottle and incubated at 100°C for 1 h. Then, L-lactide (14.4 g, 0.1 mmol) was added and incubated at 140°C for 2 h. Finally, the reactants were poured into excess cold methanol and washed three times. After vacuum drying, polyethylene glycol oxalate-polylactide diblock copolymer was obtained.

[0153] The above is only a preferred embodiment of the present invention. It should be pointed out that although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that several improvements and modifications may be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention and do not deviate from the scope defined by the claims of the present invention.

[0154] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a high molecular weight polyalkyl oxalate homopolymer, characterized in that: The preparation method comprises: S1. subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction, and distillation to obtain an oxalic acid alkyl cyclic lactone monomer; S2. subjecting the oxalic acid alkyl cyclic lactone monomer to ring-opening polymerization under the action of an initiator and a first catalyst to obtain a polyalkyl oxalate homopolymer.

2. The preparation method according to claim 1, characterized in that: Step S1 comprises: (i) subjecting an oxalic acid diester compound and an aliphatic diol compound to a condensation reaction to obtain an oxalic acid alkyl ester oligomer; the condensation reaction comprises a first stage condensation reaction carried out under normal pressure and a second stage condensation reaction carried out under reduced pressure; (ii) subjecting the oxalic acid alkyl ester oligomer to a depolymerization reaction and distillation under reduced pressure to obtain an oxalic acid alkyl cyclic lactone monomer.

3. The preparation method according to claim 1, characterized in that: Step S1 comprises: subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction and distillation under reduced pressure to obtain an oxalic acid alkyl cyclic lactone monomer.

4. The preparation method according to claim 1 or 2, characterized in that: The oxalic acid diester compound has the following structure: Wherein, R7 is one or more of methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, and benzyl; The oxalic acid diester compound is preferably one or more of dimethyl oxalate, diethyl oxalate, di-n-propyl oxalate, diisopropyl oxalate, di-n-butyl oxalate, diisobutyl oxalate, di-tert-butyl oxalate, diphenyl oxalate, and dibenzyl oxalate, more preferably dimethyl oxalate.

5. The preparation method according to claim 1 or 2, characterized in that: The aliphatic diol compound has the following structure: Wherein, x is 0 to 2, and R1, R2, R3, R4, R5, and R6 are each independently hydrogen, an alkyl group of 1 to 8 carbon atoms, a cycloalkyl group, or a phenyl group; Preferably, the aliphatic diol compound is selected from ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 2-methyl-1,2-propylene glycol, 2-methyl-1,3-propylene glycol, 1,4-butanediol, 2,3-butanediol, 1,3-butanediol, 1,2-butanediol, 1,2-pentanediol and its isomers, 1,2-hexanediol and its isomers, 1,2-heptanediol and its isomers, 1,2-octanediol and its isomers, 1,2-nonanediol and its isomers, 1,2-decanediol and its isomers, 1,3-pentanediol and its isomers, 1,3-hexanediol and its isomers, 1,3 -heptanediol and its isomers, 1,3-octanediol and its isomers, 1,3-nonanediol and its isomers, 1,3-decanediol and its isomers, 1,4-pentanediol and its isomers, 1,4-hexanediol and its isomers, 1,3-heptanediol and its isomers, 1,4-octanediol and its isomers, 1,4-nonanediol and its isomers, 1,4-decanediol and its isomers, 1,2-cyclopentanediol, 1,2-cyclohexanediol, 1,2-cycloheptanediol, 1,2-cyclooctanediol, 1,2-cyclononanediol, 1,2-cyclodecanediol, phenyl-1,2-ethanediol or one or more thereof.

6. The preparation method according to claim 1 or 2, characterized in that: The amount of the initiator is 0.01 mol% to 10 mol% of the oxalic acid alkyl cyclic lactone monomer; preferably, the initiator is one or more of monohydroxy alcohol, dihydroxy alcohol, polyhydroxy alcohol, phenol, and amino compound; wherein the monohydroxy alcohol is preferably one or more of methanol, ethanol, propanol, butanol, pentanol, hexanol, heptanol, octanol, benzyl alcohol, phenylethyl alcohol, phenylpropanol, cyclopentanol, and cyclohexanol; the dihydroxy alcohol is preferably ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, heptanediol, octanediol, nonanediol, decanediol, cyclohexanediol, cyclopent ... The phenol is preferably one or more of phenol, hydroquinone, and phloroglucinol; the amino compound is preferably one or more of methylamine, ethylamine, propylamine, butylamine, pentylamine, hexylamine, heptylamine, octylamine, benzylamine, phenylethylamine, amphetamine, cyclopentylamine, cyclohexylamine, aniline, ethylenediamine, propylenediamine, butylenediamine, pentanediamine, hexanediamine, heptanediamine, octanediamine, nonanediamine, decanediamine, cyclohexanediamine, cyclopentanediamine, cyclononanediamine, cyclodecanediamine, p-phenylenediamine, and p-phenylenediamine; and / or The amount of the first catalyst is 0.01 mol% to 10 mol% of the oxalic acid alkyl cyclic lactone monomer; preferably, the first catalyst is one or more of an organic metal catalyst, a rare earth metal catalyst, and an organic catalyst; wherein the metal catalyst is preferably one of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, diethyl zinc, zinc dichloride, Salen-Al catalyst, Porphyrin-Al catalyst, β-diimine-Zn catalyst, Phenolato-Ti catalyst, Tripodal-Fe catalyst, n-butyl lithium, isobutyl lithium, lithium diisopropylamide, sodium methoxide, sodium tert-butoxide, and potassium tert-butoxide. or more; the rare earth catalyst is preferably one or more of β-diketone rare earth metal complexes, cyclopentadienyl rare earth catalysts, bisphenol-based rare earth catalysts, Schiff base rare earth catalysts, sulfonic acid rare earth catalysts, rare earth metal halides, Salen rare earth complexes, and P-SalenY catalysts; the organic catalyst is preferably one or more of methanesulfonic acid, trifluoromethanesulfonic acid, p-toluenesulfonic acid, boron trifluoride, tri(pentafluorophenyl)boron, triethylboron, camphorsulfonic acid, triethylamine, pyridine, 4-dimethylaminopyridine, 1,8-diazabicyclo[5.4.0]undec-7-ene, 1,5,7-triazabicyclo[4.4.0]dec-5-ene, hexamethyldisilazane, and phosphazene bases.

7. The preparation method according to claim 1 or 2, characterized in that: The polycondensation reaction is carried out under the condition of a second catalyst or without a catalyst, the temperature of the polycondensation reaction is not less than 80° C., preferably 100 to 200° C., and the time of the polycondensation reaction is 1 to 12 hours; The depolymerization reaction is carried out in the presence of a third catalyst or without a catalyst, the temperature of the depolymerization reaction is 100 to 200° C., the time of the depolymerization reaction is 1 to 12 hours; and / or The temperature of the ring-opening polymerization is -80 to 200° C., and the time of the ring-opening polymerization is 0.1 to 24 hours.

8. The preparation method according to claim 7, characterized in that: The amount of the second catalyst is 0.0001wt% to 10wt% of the oxalic acid diester compound, and the second catalyst is preferably one or more of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, tetrabutyl titanate, tetraisopropyl titanate, zinc acetate, magnesium oxide, magnesium hydroxide, magnesium carbonate, tin chloride, ferric chloride, titanium chloride, zinc chloride, aluminum chloride, zinc oxide, tin oxide, ferric oxide, bismuth trifluoromethanesulfonate, zinc trifluoromethanesulfonate, 4-dimethylaminopyridine, nitrogen heterocyclic carbene, p-toluenesulfonic acid, trifluoromethanesulfonic acid, diphenyl phosphate, and ionic liquids; and / or The amount of the third catalyst used is 0.0001wt% to 10.0wt% of the alkyl oxalate oligomer, and the third catalyst is preferably one or more of stannous octoate, dibutyltin dilaurate, dibutyltin oxide, tetrabutyl titanate, tin chloride, ferric chloride, titanium chloride, zinc chloride, aluminum chloride, zinc oxide, tin oxide, ferric oxide, 4-dimethylaminopyridine, p-toluenesulfonic acid, trifluoromethanesulfonic acid, diphenyl phosphate, ionic liquid, sodium glycolate, and sodium acetate.

9. A method for preparing a high molecular weight polyalkyl oxalate copolymer, characterized in that: The preparation method comprises: S1. subjecting an oxalic acid diester compound and an aliphatic diol compound to polycondensation reaction, depolymerization reaction, and distillation to obtain a first oxalic acid alkyl ring lactone monomer; S2. subjecting the first oxalic acid alkyl cyclic lactone monomer and the cyclic lactone monomer to ring-opening polymerization under the action of an initiator and a first catalyst to obtain a polyalkyl oxalate copolymer.

10. The preparation method according to claim 9, characterized in that: The cyclic lactone monomer is selected from one or more of lactide, glycolide, β-propiolactone, β-butyrolactone, γ-butyrolactone, δ-valerolactone, ε-caprolactone, enantholactone, pentadecalactone, and a second oxalic acid alkyl cyclic lactone monomer.

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