A polyethylene-like degradable copolyester, its preparation method and application

Abstract

The application discloses a polyethylene-like degradable copolyester, a preparation method and application thereof. The structural formula of the polyethylene-like degradable copolyester is shown in the following formula: -R1- is a structural unit of long-chain dibasic acid or ester thereof, -O-R2-O- is a structural unit of long-chain dihydric alcohol, m=1-10, n=1-10, and x=10-100; -R 1‑ The molar ratio of the oxalic acid short-chain oligomer to the long-chain dihydric alcohol is 3:2-19:1. The application solves the problem that the long-chain dihydric alcohol is not easy to remove in the polycondensation by adopting the oxalic acid short-chain oligomer assisted polycondensation method, and the content of the oxalic acid is precisely controlled, the main chain of the prepared polyethylene-like degradable copolyester contains long-chain methylene structure and oxalate bond, the polyethylene-like degradable copolyester not only has excellent mechanical properties and crystallization ability, but also can realize controllable degradation of the controllable polyethylene-like polyester by controlling the length of the methylene and the number of the oxalic acid structure, and can be widely applied to plastic products, and meets the needs of different application scenes for the stability and degradation rate of the degradable material.

Description

Technical Field

[0001] This invention relates to the field of polymer material synthesis technology, specifically to a polyethylene (PE)-like biodegradable copolyester, its preparation method, and its application. Background Technology

[0002] Ethylene production capacity is an important indicator of a country's petrochemical development level. As of 2021, the world's polyethylene (PE) production reached 120 million tons, accounting for one-quarter of total plastic production. Polyethylene is widely used in electronics, military, agriculture, construction, and aerospace due to its odorless and tasteless properties, good low-temperature resistance, high gas barrier properties, and good chemical stability. However, it also has drawbacks such as poor mechanical properties, poor heat resistance, low surface hardness, and extremely slow or even non-degradable degradation rates. With the introduction of "plastic restriction orders" and "plastic bans," management measures to address plastic pollution have been further upgraded. Achieving the biodegradability of PE is one of the important measures to solve "white pollution" under the plastic ban.

[0003] PE-like polyesters are polyesters containing long-chain methylene groups formed by polymerizing long-chain dicarboxylic acids and long-chain diols. Compared to conventional short-chain polyester structures, the ester bond density is significantly reduced. The long-chain methylene structure gives them similar crystallinity and water-blocking properties to PE. However, during the polycondensation process, the high boiling point of the long-chain diol makes it difficult to remove, preventing molecular weight growth. Furthermore, the alcohol-to-acid ratio must be strictly controlled at 1, making the synthesis conditions and ingredient control for PE-like polyesters extremely demanding. Although PE-like polyesters introduce hydrolyzable ester bonds into their structure, they remain hydrophobic materials. The ester bonds are difficult to undergo nucleophilic substitution reactions with water and thus degrade. Therefore, the hydrolysis and composting degradation of PE-like polyesters remain very slow.

[0004] Polyoxalate is a highly hydrophilic polyester, a novel polyester material capable of truly achieving full natural degradation. Introducing the oxalic acid structure into PE-like polyester materials could create biodegradable PE-like polyesters with tunable degradation rates. However, oxalic acid, dimethyl oxalate, or diethyl oxalate have poor thermal stability and struggle to remain stable during high-temperature melt polycondensation, thus preventing their reaction with long-chain diacids and diols to form high-molecular-weight PE-like polyesters. Therefore, the key challenges in synthesizing biodegradable PE-like polyesters lie in how to introduce the oxalic acid structure into them to control the degradation rate, and how to improve the stability of oxalic acid monomers to prevent decomposition during polycondensation with long-chain diacids or their esters while promoting molecular weight growth. Summary of the Invention

[0005] The main objective of this invention is to provide a polyethylene (PE) biodegradable copolyester and its preparation method, so as to overcome the shortcomings of the prior art.

[0006] Another object of the present invention is to provide the application of the aforementioned polyethylene-like biodegradable copolyester.

[0007] To achieve the aforementioned objectives, the technical solution adopted by this invention includes:

[0008] This invention provides a polyethylene-like biodegradable copolyester, the structural formula of which is shown in formula (1):

[0009]

[0010] Wherein, -R1- is a structural unit of a long-chain dicarboxylic acid or its esterified form, -O-R2-O- is a structural unit of a long-chain diol, m, n, and x are all integers, m = 1 to 10, n = 1 to 10, x = 10 to 100; and -R1- and The molar ratio is 3:2 to 19:1.

[0011] In some embodiments, the structural units of the long-chain dicarboxylic acid or its esterified form are selected from at least one of the structures shown in formula (2):

[0012]

[0013] Where a is an integer, a = 10 to 23.

[0014] In some embodiments, the long-chain diol is selected from at least one of the structures shown in formula (3):

[0015]

[0016] Where c is an integer, c = 12 to 25.

[0017] This invention also provides a method for preparing a polyethylene-like biodegradable copolyester, comprising:

[0018] Dimethyl oxalate and / or diethyl oxalate, a first diol and an esterification catalyst are mixed to form a first mixed system. The first mixed system is subjected to a first esterification reaction or a first transesterification reaction to obtain a first esterification product or a first transesterification product. Then, the temperature is lowered to carry out a first pre-condensation reaction to obtain a low-polymerization-degree oxalate prepolymer.

[0019] A second mixed system is formed by mixing a long-chain dicarboxylic acid or its esterified form, a long-chain diol, and an esterification catalyst, and the second mixed system is subjected to a second esterification reaction or a second transesterification reaction to obtain a second esterification product or a second transesterification product.

[0020] The oxalic acid prepolymer, the second esterification product, or the second transesterification product are mixed to form a third mixed system. The third mixed system undergoes a third transesterification reaction under conditions of complete melt melting. Then, the temperature is raised to carry out a second pre-condensation reaction and a final condensation reaction to obtain a polyethylene-like biodegradable copolyester.

[0021] This invention also provides a polyethylene-like biodegradable copolyester prepared by the aforementioned method.

[0022] The embodiments of the present invention also provide the application of the aforementioned polyethylene-like biodegradable copolyester in the preparation of agricultural mulch films, fiber fabrics, telecommunication cables, packaging materials, plastic container products, tissue engineering scaffolds, or drug carriers.

[0023] Compared with the prior art, the present invention has the following beneficial technical effects:

[0024] This invention addresses the challenge of removing long-chain diols during polycondensation by employing oxalic acid short-chain oligomer-assisted polycondensation. By precisely controlling the oxalic acid content, the resulting polyethylene-like biodegradable copolyester contains long-chain methylene structures and oxalate bonds in its main chain. This not only possesses excellent mechanical properties and crystallization ability but also allows for controlled degradation of the polyethylene-like polyester by adjusting the methylene length and the number of oxalic acid unit structures. This effectively addresses plastic pollution and can be widely applied in plastic products, meeting the stability and degradation rate requirements of biodegradable materials in various application scenarios. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0026] Figure 1 The above is a 1H NMR spectrum of the polyethylene-like biodegradable polyester prepared in Example 1 of this invention.

[0027] Figure 2 This is a DSC curve of the polyethylene-like biodegradable polyester prepared in Example 1 of the present invention;

[0028] Figure 3 The stress-strain curve of the polyethylene-like biodegradable polyester prepared in Example 1 of this invention is shown. Detailed Implementation

[0029] In view of the deficiencies of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The main solution is to solve the problem of the difficulty in removing long-chain diols during polycondensation by using oxalic acid short-chain oligomers as an aid in polycondensation, and to precisely control the oxalic acid content. The main chain containing long-chain methylene structures and oxalate bonds not only possesses excellent mechanical properties and crystallization ability, but also allows for the controllable degradation of polyethylene-like polyesters by adjusting the content of the oxalic acid structure. The technical solution of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0030] The following will provide a further explanation of the technical solution, its implementation process, and its principles.

[0031] Specifically, as one aspect of the technical solution of this invention, the structural formula of the polyethylene (PE) biodegradable copolyester involved is shown in formula (1):

[0032]

[0033] Wherein, -R1- is the structural unit of a long-chain dicarboxylic acid or its esterified form, -O-R2-O- is the structural unit of a long-chain diol, and m, n, and x are all integers, m = 1 to 10, n = 1 to 10, x = 10 to 100.

[0034] In some implementations, -R1- is... The molar ratio is 3:2 to 19:1, preferably 4:1 to 19:1.

[0035] In some embodiments, the structural units of the long-chain dicarboxylic acid or its esterified form are selected from at least one of the structures shown in formula (2):

[0036]

[0037] Where a is an integer, a = 10 to 23. Furthermore, the value of a is preferably an even number, for example, a can be preferably 10, 12, 14, 16, 18, 20, 22, etc.

[0038] In some embodiments, the long-chain diol is selected from at least one of the structures shown in formula (3):

[0039]

[0040] Where c is an integer, c = 12 to 25. Furthermore, even numbers are preferred for c, for example, c can be 12, 14, 16, 18, 20, 22, 24, etc.

[0041] Furthermore, the polyethylene-like biodegradable copolyester provided by this invention preferentially selects even-numbered long-chain diacids or their esters and even-numbered long-chain diols to ensure stable comprehensive thermodynamic properties and excellent crystallinity and barrier properties. In addition, this invention, through molecular chain structure design, introduces oxalic acid segments into the main chain of the polyethylene-like biodegradable copolyester to improve its hydrophilicity and degradation ability, thereby increasing the biocompatibility of the polyethylene-like biodegradable copolyester. This expands its application fields from agricultural mulch films, fiber fabrics, telecommunications cables, packaging materials, and plastic container products to tissue engineering scaffolds, drug delivery carriers, and other fields, demonstrating broad application prospects.

[0042] In some embodiments, the polyethylene-like biodegradable copolyester backbone contains The structure is introduced by assisted polycondensation, and the structural unit of the oxalic acid prepolymer, the assisted polycondensation raw material, is selected from at least one of the structures in formula (4):

[0043]

[0044] in, The diol derived from dimethyl oxalate or diethyl oxalate, and the diol from which the -O-R3-O- originates is selected from at least one of ethylene glycol, propylene glycol, and butanediol; b is an integer, b = 1 to 10.

[0045] In some embodiments, the intrinsic viscosity of the PE-like biodegradable copolyester is 1.5 to 2.5 dL / g, and the number-average molecular weight is 80,000 to 160,000 g / mol; according to the L*a*b* color model, the L* value is greater than 80, the absolute value of a* is less than 4, and the absolute value of b* is less than 8.

[0046] In some embodiments, the glass transition temperature of the PE-like biodegradable copolyester is -80 to 65°C, the melting point is 70 to 105°C, the tensile strength is 10 to 40 MPa, the elongation at break is 600 to 1600%, and the water vapor permeability coefficient is 4 × 10⁻⁶. -14 ~10×10 -14 g·cm / cm 2 The mass loss after 60 days of hydrolysis is 30-50%, while that after 60 days of enzymatic degradation is 40-70%, and that after 60 days of seawater degradation is 5-15%.

[0047] In summary, the aforementioned polyethylene-like biodegradable copolyester exhibits excellent thermal and mechanical properties, and its degradation rate can be controlled by adjusting the methylene length and the number of oxalic acid units. This effectively addresses plastic pollution and meets the degradation rate requirements of different application scenarios.

[0048] As another aspect of the technical solution of the present invention, it relates to a method for preparing a polyethylene-like biodegradable copolyester, which includes:

[0049] Dimethyl oxalate and / or diethyl oxalate, a first diol and an esterification catalyst are mixed to form a first mixed system. The first mixed system is subjected to a first esterification reaction or a first transesterification reaction to obtain a first esterification product or a first transesterification product. Then, the temperature is lowered to carry out a first pre-condensation reaction to obtain a low-polymerization-degree oxalate prepolymer.

[0050] A second mixed system is formed by mixing a long-chain dicarboxylic acid or its esterified form, a long-chain diol, and an esterification catalyst, and the second mixed system is subjected to a second esterification reaction or a second transesterification reaction to obtain a second esterification product or a second transesterification product.

[0051] The oxalic acid prepolymer, the second esterification product, or the second transesterification product are mixed to form a third mixed system. The third mixed system undergoes a third transesterification reaction under conditions of complete melt melting. Then, the temperature is raised to carry out a second pre-condensation reaction and a final condensation reaction to obtain a polyethylene-like biodegradable copolyester.

[0052] In some embodiments, the first diol includes at least one of short-chain diols such as ethylene glycol, propylene glycol, and butanediol, but is not limited thereto.

[0053] In some embodiments, the molar ratio of dimethyl oxalate and / or diethyl oxalate to the first diol (ethylene glycol, propylene glycol, or butanediol) is 1:1.2 to 1:1.5.

[0054] In some embodiments, the temperature of the first esterification reaction or the first transesterification reaction is 140–180°C, preferably 140–160°C, and the time is 1–4 h, preferably 2–4 h.

[0055] In some embodiments, the polyethylene-like biodegradable copolyester backbone contains The structure is introduced by assisted polycondensation, and the oxalic acid prepolymer, the assisted polycondensation raw material, has at least one of the structures shown in formula (4):

[0056]

[0057] In the structure of equation (4), The diol derived from dimethyl oxalate or diethyl oxalate, and the diol sourced from -O-R3-O- is selected from at least one of ethylene glycol, propylene glycol, butanediol, etc., with ethylene glycol and butanediol being preferred; b is an integer, b = 1 to 10.

[0058] In some embodiments, the preparation method includes: after the first esterification reaction or the first transesterification reaction is completed, the temperature is lowered to 100-150°C, the reaction system is depressurized to 200-1000 Pa to carry out a first pre-condensation reaction for 0.5-4 hours to obtain a low degree of polymerization oxalic acid prepolymer.

[0059] In some more specific embodiments, the preparation method includes:

[0060] Dimethyl oxalate or diethyl oxalate, ethylene glycol or propylene glycol or butanediol and esterification catalyst are mixed to form a first mixed system. The first mixed system undergoes a first esterification reaction or a first transesterification reaction at 140-180°C. The timing is zero when the first drop of methanol or ethanol falls, and the esterification reaction or transesterification reaction ends when the amount of methanol or ethanol collected as a byproduct is more than 95% of the theoretical value.

[0061] The product from the above steps is cooled to 110–150°C, and the reaction system is depressurized to 200–1000 Pa to carry out the first pre-condensation reaction. The condensation time is 0.5–4 h to obtain a low degree of polymerization oxalic acid prepolymer.

[0062] In some more specific embodiments, the preparation method includes: after the first esterification reaction or the first transesterification reaction is completed, the temperature is lowered to 110-130°C, the reaction system is depressurized to 200-400 Pa to carry out the first pre-condensation reaction for 1-1.5 h, to obtain a low degree of polymerization oxalic acid prepolymer.

[0063] In some embodiments, the molar ratio of the sum of the long-chain dicarboxylic acid or its long-chain dicarboxylic acid ester and the molar amount of the oxalate structure in the oxalic acid prepolymer to the long-chain diol is 1:1 to 1.2:1.

[0064] In some embodiments, the structures of the long-chain dicarboxylic acid or its esterified form, as well as the long-chain diol, are as described above and will not be repeated here.

[0065] In some embodiments, the temperature of the second esterification reaction or the second transesterification reaction is 170–210°C, preferably 170–190°C, and the time is 1–4 h, preferably 2–4 h.

[0066] In some embodiments, the mass fraction of the long-chain dicarboxylic acid or its esterified form in the second mixture is 0.1‰ to 3‰, preferably 0.5‰ to 1‰.

[0067] In some more specific embodiments, the preparation method includes: mixing a long-chain dicarboxylic acid or its esterified form, a long-chain diol, and an esterification catalyst to form a second mixed system, wherein the second mixed system undergoes a second esterification reaction or a second transesterification reaction at 170–210°C, with the timing starting from the first drop of methanol or water and ending when the amount of methanol or water collected as a byproduct is more than 95% of the theoretical value, which is the endpoint of the esterification reaction or transesterification reaction.

[0068] In some embodiments, the esterification catalyst used in the first and second mixed systems includes at least one of antimony-based catalysts and titanium-based catalysts. For example, the antimony-based catalyst may preferably be selected from any one or a combination of two or more of antimony trioxide, antimony acetate, antimony glycolate, and triethyl antimonate; the titanium-based catalyst may preferably be selected from any one or a combination of two or more of titanium isopropoxide, tetrabutyl titanate, and tetraethyl titanate, but is not limited thereto.

[0069] In some more specific embodiments, in the first mixed system, the esterification catalyst accounts for 0.1‰ to 3‰ of the mass of dimethyl oxalate and / or diethyl oxalate, preferably 0.5‰ to 1‰.

[0070] In some more specific embodiments, in the second mixture, the esterification catalyst accounts for 0.1‰ to 3‰ of the mass of the long-chain dicarboxylic acid or its esterified form, preferably 0.5‰ to 1‰.

[0071] In some embodiments, the temperature of the third transesterification reaction is 130–160°C, preferably 140–150°C, and the time is 0.5–2 h, preferably 1–1.5 h.

[0072] In some embodiments, the preparation method includes: gradually heating the reaction system obtained from the third transesterification reaction to 190–240°C, depressurizing the reaction system to 100–500 Pa to carry out a second pre-condensation reaction, the second pre-condensation reaction lasting 0.5–3 h; then depressurizing the reaction system to below 20 Pa to carry out a final condensation reaction, the stable vacuum degree of the final condensation reaction not exceeding 7 Pa, the final condensation reaction lasting 0.5–2 h, to obtain the polyethylene-like biodegradable copolyester.

[0073] In some preferred embodiments, the preparation method specifically includes:

[0074] The oxalic acid prepolymer, the second esterification product, or the product of the second transesterification prepared above are mixed to form a third mixed system. The third mixed system undergoes a third transesterification reaction under the condition of complete melting at 130-160°C for 0.5-2 hours.

[0075] The reaction system obtained from the third transesterification reaction is gradually heated to 190–240°C, and the reaction system is depressurized to 100–500 Pa to carry out a second pre-condensation reaction for 0.5–3 hours. The reaction system is then further depressurized to below 20 Pa to carry out a final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7 Pa, and the final condensation reaction time is 0.5–2 hours, to obtain the degradable copolyester similar to polyethylene.

[0076] In some more preferred embodiments, the preparation method includes: gradually heating the reaction system obtained from the third transesterification reaction to 200-220°C, depressurizing the reaction system to 200-400 Pa to carry out a second pre-condensation reaction, the second pre-condensation reaction lasting 1-1.5 h; then depressurizing the reaction system to below 20 Pa to carry out a final condensation reaction, the stable vacuum degree of the final condensation reaction not exceeding 7 Pa, the final condensation reaction lasting 1-2 h, to obtain the polyethylene-like biodegradable copolyester.

[0077] In some preferred embodiments, the method for preparing the polyethylene (PE)-like biodegradable copolyester of the present invention specifically includes the following steps:

[0078] Step 1: Dimethyl oxalate or diethyl oxalate, ethylene glycol or propylene glycol or butanediol and esterification catalyst are mixed to form a first mixed system. The first mixed system is subjected to a first transesterification reaction or transesterification reaction at 140-160°C, preferably 140-180°C. The timing is zero when the first drop of methanol or ethanol falls, and the endpoint is reached when the amount of methanol or ethanol collected as byproduct is more than 95% of the theoretical value.

[0079] Step 2: Cool the product from Step 1 to 100-150℃, preferably 110-130℃, and depressurize the reaction system to 200-1000Pa, preferably 200-400Pa, to carry out the first pre-condensation reaction. The first pre-condensation reaction takes 0.5-4h, preferably 1-1.5h, to obtain a low degree of polymerization oxalic acid prepolymer.

[0080] The low-polymerization-degree oxalic acid prepolymer obtained by the first pre-condensation reaction in step 2 of the present invention can significantly increase the thermal decomposition temperature of dimethyl oxalate or diethyl oxalate, ensuring that it does not decompose during the melt condensation reaction with long-chain dicarboxylic acids or their esters and long-chain diols.

[0081] Step 3: Mix the long-chain dicarboxylic acid or its esterified product, the long-chain diol and the esterification catalyst to form a second mixed system. The second mixed system is subjected to a second esterification reaction or a second transesterification reaction at 170-210℃, preferably 170-190℃. The timing is from the first drop of methanol or water falling to zero point, and the esterification reaction or transesterification reaction ends when the amount of methanol or water collected as by-products is more than 95% of the theoretical value.

[0082] Step 4: Mix the oxalic acid prepolymer obtained in Step 2 with the product of Step 3 to form a third mixed system. The third mixed system undergoes a third transesterification reaction at 130-160°C, preferably 140-150°C, under conditions of complete melt melting. The time for the third transesterification reaction is 0.5-2 hours, preferably 1-1.5 hours.

[0083] In step 4 of this invention, the oxalic acid prepolymer undergoes a full transesterification reaction with long-chain dicarboxylic acids or their esterifications and long-chain diols, which can almost completely transesterify the ethylene glycol, propylene glycol or butanediol structural units in the oxalic acid prepolymer into long-chain diols. During the pre-condensation process, the ethylene glycol, propylene glycol or butanediol structural units are completely extracted from the polymerization system.

[0084] Step 5: Gradually heat the reaction system from Step 4 to 190–240°C, preferably 200–220°C, and depressurize the reaction system to 100–500 Pa, preferably 200–400 Pa, to carry out a second pre-condensation reaction. The time for the second pre-condensation reaction is 0.5–3 h, preferably 1–1.5 h. Further depressurize the reaction system to below 20 Pa to carry out a final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7 Pa, and the final condensation time is 0.5–2 h, preferably 1–2 h, to obtain the degradable copolyester similar to polyethylene (PE).

[0085] In summary, the preparation method of this invention first synthesizes a low-polymerization-degree oxalic acid prepolymer with an initial thermal decomposition temperature (reaching 5% mass loss) of 240°C, effectively solving the problem of thermal degradation of dimethyl oxalate (initial thermal decomposition temperature 165°C) and diethyl oxalate (initial thermal decomposition temperature 185°C) during melt polycondensation with long-chain dicarboxylic acids or their esters and long-chain diols. On the other hand, the oxalic acid prepolymer uses diols with low boiling points such as ethylene glycol, propylene glycol, or butanediol, which undergo sufficient transesterification reaction during mixing with long-chain dicarboxylic acids or their esters and long-chain diols. During the polycondensation process, the low-boiling-point diols are extracted from the polymerization system. When the amount of oxalic acid prepolymer added is less than 20%, all the low-boiling-point diols in the oxalic acid prepolymer can be extracted from the polymerization system, ensuring the integrity of the polyethylene-like polyester structure. Under the condition that no additional polycondensation catalyst is required, the reaction time is shortened to achieve the increase of molecular weight, reducing the environmental burden of metal catalysts.

[0086] Furthermore, the oxalic acid prepolymer-assisted polycondensation method provides a new polymerization approach for synthesizing high molecular weight polyethylene-like polyesters. By changing the content of oxalic acid in the molecular chain to control the degradation rate, it can be widely used in plastic products, effectively addressing plastic pollution problems and meeting the needs of different application scenarios for the stability and degradation rate of degradable materials.

[0087] As another aspect of the technical solution of the present invention, it relates to a polyethylene-like biodegradable copolyester obtained by the aforementioned method.

[0088] As another aspect of the technical solution of the present invention, it also relates to the application of the aforementioned polyethylene-like biodegradable copolyester in the fields of preparing agricultural mulch films, fiber fabrics, telecommunication cables, packaging materials, plastic container products, tissue engineering scaffolds, or drug carriers.

[0089] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0090] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments or examples only and is not intended to be limiting of the invention.

[0091] In this embodiment, a differential scanning calorimeter (Mettler Toledo DSC) was used to test the thermal performance. The heating rate was 10℃ / min, the temperature range was -80℃ to 200℃, and the measurement was carried out in an N2 atmosphere.

[0092] In this embodiment, a Zwicki 1kN universal testing machine was used to test the mechanical properties. The sample dimensions were 15.0 mm in length, 2.0 mm in width, and 1.0 mm in thickness, and the tensile speed was 20 mm / min.

[0093] In this embodiment, the water vapor barrier performance was tested using a Labthink W3-006. The test was conducted at 38°C and 90% RH by measuring the difference in water vapor evaporation before and after the test. The sample's permeability area was 33 cm². 2 .

[0094] In the example, phosphate buffer solution was used as the degradation solvent, and hydrolysis degradation test was carried out under constant temperature of 37°C. The sample was 10 mm long, 10 mm wide, and 0.5 mm thick.

[0095] In the example, a phosphate buffer solution of 0.1 mg / ml lipase was used as the degradation solvent, and the enzyme degradation test was carried out under constant temperature conditions of 37°C. The sample was 10 mm long, 10 mm wide, and 0.5 mm thick.

[0096] In the example, 35g of sea salt was used for calibration in a 1L volumetric flask, and seawater degradation test was conducted under constant temperature conditions of 37℃. The sample was 10mm long, 10mm wide, and 0.5mm thick.

[0097] Example 1

[0098] 0.063 mol of dimethyl oxalate, 0.088 mol of ethylene glycol, and 0.5‰ (of dimethyl oxalate) of titanium isopropoxide were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150°C, and the first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of methanol fell, and the esterification or transesterification reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 100°C and the pressure of the reaction system was reduced to 200 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree ethylene glycol oxalate prepolymer.

[0099] 0.237 mol of dimethyl dodecanoate, 0.32 mol of 1,12-dodecanediol, and tetrabutyl titanate with a mass fraction of 1‰ (as a percentage of dimethyl dodecanoate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 180°C to carry out the second esterification or transesterification reaction for 2 hours. The timing was stopped when the first drop of methanol or water fell, and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150°C, and the ethylene glycol oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction for 1 hour.

[0100] The system is gradually heated to 210°C and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1 hour. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 2 hours to obtain a light yellow biodegradable copolyester similar to PE.

[0101] The biodegradable copolyester with double bonds in the main chain prepared in this embodiment was subjected to nuclear magnetic resonance hydrogen spectroscopy, DSC, mechanical properties, water vapor barrier properties and degradation performance tests.

[0102] Figure 1 , Figure 2 , Figure 3 The figures show the 1H NMR spectrum, DSC spectrum, and stress-strain curve of the PE-like biodegradable polyester prepared in this embodiment. Figure 1It can be seen that the molecular structure of this biodegradable polyester is clear. In the dicarboxylic acid composition, the molar ratio of dodecanoic acid to oxalic acid is 80.2:19.8, and the residual ethylene glycol content is negligible at 0.8%. From... Figure 2 It is known that the glass transition temperature of this biodegradable polyester is -66.8℃, and its melting point is 79.0℃. From... Figure 3 It is known that the tensile strength of this biodegradable polyester is 17.4 MPa and the elongation at break is 981%.

[0103] Tests showed that the intrinsic viscosity of this type of biodegradable PE copolyester was 1.54 dL / g; the number-average molecular weight was 87,000 g / mol; and according to the L*a*b* color model, the L* value was 85, the a* value was 3.5, and the b* value was 7.3.

[0104] Tests showed that the water vapor permeability coefficient of this type of biodegradable PE copolyester was 9.31 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; Enzymatic degradation resulted in a 65% mass loss within 60 days, hydrolysis resulted in a 46% mass loss within 60 days, and seawater degradation resulted in an 11% mass loss within 60 days.

[0105] Example 2

[0106] 0.033 mol of dimethyl oxalate, 0.046 mol of propylene glycol, and a composite catalyst consisting of tetrabutyl titanate and triethyl antimonate with a mass fraction of 0.5‰ (as a percentage of dimethyl oxalate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150 °C, and the first esterification or transesterification reaction was carried out for 1.5 h. The timing was stopped when the first drop of methanol fell, and the esterification or transesterification reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 120 °C and the pressure of the reaction system was reduced to 200 Pa, and the first pre-polymerization reaction was carried out for 1 h to obtain a low-polymerization degree propylene glycol oxalate prepolymer.

[0107] 0.267 mol of dimethyl tridecanoate, 0.31 mol of 1,13-tridecanodiol, and a composite catalyst consisting of tetrabutyl titanate and titanium glycol (0.6‰ by mass, representing 0.6‰ of dimethyl tridecanoate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 180°C to carry out the second esterification or transesterification reaction for 2 hours. The esterification or transesterification reaction was considered to have ended when the first drop of methanol or water was collected (zero point) and the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 155°C, and the propylene glycol oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction for 1.5 hours.

[0108] The system is gradually heated to 200℃ and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1.5h. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1.5h to obtain a milky white PE-like biodegradable copolyester.

[0109] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of dodecanoic acid to oxalic acid of 90.1:9.9, with a negligible residual ethylene glycol content of 0.4%; an intrinsic viscosity of 1.64 dL / g; a number-average molecular weight of 120,000 g / mol; and, according to the L*a*b* color model, an L* value of 87, an a* value of 3.2, and a b* value of 6.4; a glass transition temperature of -68.3℃ and a melting point of 76.8℃; a tensile strength of 16.9 MPa and an elongation at break of 900%; and a water vapor permeability coefficient of 7.62 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; The mass loss due to enzyme degradation was 63% within 60 days, the mass loss due to hydrolysis was 42% within 60 days, and the mass loss due to seawater degradation was 10% within 60 days.

[0110] Example 3

[0111] 0.018 mol of dimethyl oxalate, 0.025 mol of butanediol, and 0.5‰ (of dimethyl oxalate) of titanium isopropoxide were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150°C, and the first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of methanol or ethanol fell, and the esterification or transesterification reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 125°C and the pressure of the reaction system was reduced to 400 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree butanediol oxalate prepolymer.

[0112] 0.282 mol of dimethyl dodecanoate, 0.32 mol of 1,12-dodecanediol, and 0.8‰ (of dimethyl dodecanoate) of tetrabutyl titanate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 180°C to carry out the second esterification or transesterification reaction for 2 hours. The timing was stopped when the first drop of methanol fell and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 155°C, and the butylene oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction under the condition that the melt was completely melted for 1 hour.

[0113] The system is gradually heated to 210°C and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1 hour. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1 hour to obtain a milky white PE-like biodegradable copolyester.

[0114] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of dodecanoic acid to oxalic acid of 95:5, with negligible ethylene glycol residue at 0.2%; an intrinsic viscosity of 1.94 dL / g; a number-average molecular weight of 138,000 g / mol; and, according to the L*a*b* color model, an L* value of 84, an a* value of 2.9, and a b* value of 4.8; a glass transition temperature of -67.4℃ and a melting point of 82.3℃; a tensile strength of 13.2 MPa and an elongation at break of 1130%; and a water vapor permeability coefficient of 4.92 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; The mass loss due to enzyme degradation was 52% within 60 days, the mass loss due to hydrolysis was 37% within 60 days, and the mass loss due to seawater degradation was 8% within 60 days.

[0115] Example 4

[0116] 0.033 mol of dimethyl oxalate, 0.046 mol of ethylene glycol, and 0.6‰ (of dimethyl oxalate) of antimony trioxide were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150°C. The first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of methanol or ethanol fell, and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 125°C and the pressure of the reaction system was reduced to 300 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree ethylene glycol oxalate prepolymer.

[0117] 0.267 mol of dimethyl octadecanoate, 0.31 mol of 1,18-octadecanediol, and 0.6‰ (of dimethyl octadecanoate) of tetrabutyl titanate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 190°C to carry out the second esterification or transesterification reaction for 1 hour. The timing was stopped when the first drop of methanol fell and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150°C, and the ethylene glycol oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction for 1.5 hours.

[0118] The system is gradually heated to 190°C and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1 hour. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1 hour to obtain a milky white PE-like biodegradable copolyester.

[0119] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of octadecanoic acid to oxalic acid of 90.2:9.8, with negligible ethylene glycol residue of 0.5%; an intrinsic viscosity of 2.31 dL / g; a number-average molecular weight of 148,000 g / mol; and, according to the L*a*b* color model, an L* value of 84, an a* value of 2.9, and a b* value of 5.3; a glass transition temperature of -67.2℃ and a melting point of 84.7℃; a tensile strength of 14.8 MPa and an elongation at break of 850%; and a water vapor permeability coefficient of 8.94 × 10⁻⁶. -14 g·cm / cm 2 The mass loss due to enzyme degradation was 59% within 60 days, the mass loss due to hydrolysis was 46% within 60 days, and the mass loss due to seawater degradation was 12% within 60 days.

[0120] Example 5

[0121] 0.033 mol of dimethyl oxalate, 0.046 mol of ethylene glycol, and antimony acetate with a mass fraction of 0.7‰ (ε-dimethyl oxalate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150°C, and the first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of methanol or ethanol fell, and the esterification or transesterification reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 125°C and the pressure of the reaction system was reduced to 200 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree ethylene glycol oxalate prepolymer.

[0122] 0.267 mol of dimethyl eicosanoate, 0.31 mol of 1,20-eicosanodiol, and 0.6‰ (of dimethyl eicosanoate) of triethyl antimonate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 185 °C to carry out the second esterification or transesterification reaction for 1 hour. The timing was stopped when the first drop of methanol fell and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 155 °C, and the ethylene glycol oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction for 1.5 hours.

[0123] The system is gradually heated to 195°C and depressurized to 200 Pa to carry out the second pre-condensation reaction, which takes 1.5 h. The reaction system is further depressurized to less than 20 Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7 Pa, and the final condensation reaction takes 1 h to obtain a milky white PE-like biodegradable copolyester.

[0124] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of eicosanoic acid to oxalic acid of 90:10, with negligible ethylene glycol residue of 0.4%; an intrinsic viscosity of 2.24 dL / g; a number-average molecular weight of 143,000 g / mol; and, according to the L*a*b* color model, an L* value of 82, an a* value of 3.3, and a b* value of 5.9; a glass transition temperature of -68.4℃ and a melting point of 82.8℃; a tensile strength of 13.2 MPa and an elongation at break of 820%; and a water vapor permeability coefficient of 7.59 × 10⁻⁶. -14 g·cm / cm 2 The mass loss due to enzyme degradation was 48% within 60 days, the mass loss due to hydrolysis was 32% within 60 days, and the mass loss due to seawater degradation was 7% within 60 days.

[0125] Example 6

[0126] 0.123 mol of diethyl oxalate, 0.1722 mol of ethylene glycol, and a composite catalyst consisting of tetrabutyl titanate and antimony acetate with a mass fraction of 0.8‰ (as a percentage of diethyl oxalate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 160°C, and the first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of ethanol fell, and the esterification or transesterification reaction ended when the amount of ethanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 120°C and the pressure of the reaction system was reduced to 200 Pa, and the first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree ethylene glycol oxalate prepolymer.

[0127] 0.177 mol of dimethyl dodecanoate, 0.31 mol of 1,12-dodecanediol, and a composite catalyst consisting of tetrabutyl titanate and antimony acetate with a mass fraction of 1‰ (as a percentage of dimethyl dodecanoate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 185 °C to carry out the second esterification or transesterification reaction for 2 hours. The esterification or transesterification reaction was considered to have ended when the first drop of methanol was recorded as the zero point and the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150 °C, and the propylene glycol oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction for 1.5 hours.

[0128] The system is gradually heated to 200℃ and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1 hour. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1 hour to obtain a milky white PE-like biodegradable copolyester.

[0129] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a dodecanoic acid:oxalic acid molar ratio of 60:40, with a residual ethylene glycol content of 15%; an intrinsic viscosity of 1.44 dL / g; a number-average molecular weight of 119,000 g / mol; an L* value of 80, an a* value of 2.8, and a b* value of 5.7 according to the L*a*b* color model; a glass transition temperature of -64.8℃ and a melting point of 89.2℃; a tensile strength of 13.5 MPa and an elongation at break of 980%; and a water vapor permeability coefficient of 5.11 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; The mass loss due to enzyme degradation was 64% within 60 days, the mass loss due to hydrolysis was 47% within 60 days, and the mass loss due to seawater degradation was 14% within 60 days.

[0130] Example 7

[0131] 0.018 mol of dimethyl oxalate, 0.026 mol of butanediol, and 0.8‰ (of dimethyl oxalate) of tetrabutyl titanate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 180°C, and the first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of methanol fell, and the esterification or transesterification reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150°C and the pressure of the reaction system was reduced to 200 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree butanediol oxalate prepolymer.

[0132] 0.282 mol of dimethyl docosanoate, 0.32 mol of 1,22-docosanediol, and 0.7‰ (of dimethyl docosanoate) of tetrabutyl titanate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 190°C to carry out the second esterification or transesterification reaction for 2 hours. The timing was stopped when the first drop of methanol fell, and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150°C, and the butylene oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction under the condition that the melt was completely melted for 1.5 hours.

[0133] The system is gradually heated to 210°C and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1 hour. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1.5 hours to obtain a milky white PE-like biodegradable copolyester.

[0134] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of docosanoic acid to oxalic acid of 94.4:5:6, with negligible ethylene glycol residue of 0.3%; an intrinsic viscosity of 2.44 dL / g; a number-average molecular weight of 167,000 g / mol; and, according to the L*a*b* color model, an L* value of 87, an a* value of 1.3, and a b* value of 3.5; a glass transition temperature of -69.8℃ and a melting point of 80.5℃; a tensile strength of 11.9 MPa and an elongation at break of 780%; and a water vapor permeability coefficient of 4.33 × 10⁻⁶. -14 g·cm / cm 2 The mass loss due to enzyme degradation was 47% within 60 days, the mass loss due to hydrolysis was 32% within 60 days, and the mass loss due to seawater degradation was 8% within 60 days.

[0135] Example 8

[0136] 0.018 mol of diethyl oxalate, 0.024 mol of butanediol, and 0.5‰ (of diethyl oxalate) of antimony glycol glycolate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150°C, and the first esterification or transesterification reaction was carried out for 1 hour. The timing was stopped when the first drop of ethanol fell, and the esterification or transesterification reaction ended when the amount of ethanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 120°C and the pressure of the reaction system was reduced to 200 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree butanediol oxalate prepolymer.

[0137] 0.282 mol of dimethyl tetradecanoate, 0.32 mol of 1,24-tetradecanoic acid diol, and a mixture of titanium isopropoxide and triethyl antimonate with a mass fraction of 1‰ (accounting for dimethyl tetradecanoate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 190°C to carry out the second esterification reaction or transesterification reaction for 2 hours. The timing was stopped when the first drop of methanol fell and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150°C, and the butylene oxalate prepolymer obtained in the first step was added to carry out the third transesterification reaction under the condition that the melt was completely melted for 1 hour.

[0138] The system is gradually heated to 210°C and depressurized to 200Pa to carry out the second pre-condensation reaction, which takes 1 hour. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1 hour to obtain a milky white PE-like biodegradable copolyester.

[0139] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of 94:6 for tetracosanoic acid to oxalic acid, with a negligible residual ethylene glycol content of 0.3%. The intrinsic viscosity is 1.68 dL / g; the number-average molecular weight is 116,000 g / mol; according to the L*a*b* color model, the L* value is 82, the a* value is 2.4, and the b* value is 3.5; the glass transition temperature is -67.2℃, and the melting point is 80.7℃; the tensile strength is 11.3 MPa, and the elongation at break is 670%; the water vapor permeability coefficient is 4.46 × 10⁻⁶. -14 g·cm / cm 2 The mass loss due to enzyme degradation was 44% within 60 days, the mass loss due to hydrolysis was 30% within 60 days, and the mass loss due to seawater degradation was 6% within 60 days.

[0140] Example 9

[0141] 0.063 mol of diethyl oxalate, 0.0504 mol of butanediol, and 0.1‰ (of diethyl oxalate) of antimony glycol glycolate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 140°C, and the first esterification or transesterification reaction was carried out for 4 hours. The timing was stopped when the first drop of ethanol fell, and the esterification or transesterification reaction ended when the amount of ethanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 110°C and the pressure of the reaction system was reduced to 200 Pa. The first pre-condensation reaction was carried out for 1 hour to obtain a low-polymerization degree butanediol oxalate prepolymer.

[0142] 0.237 mol of dimethyl tetracosanoate, 0.3 mol of 1,24-tetracosanodiol, and a mixture of titanium isopropoxide and triethyl antimonate with a mass fraction of 0.1‰ (as a percentage of dimethyl tetracosanoate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 170°C for a second esterification or transesterification reaction, which lasted for 1 hour. The esterification or transesterification reaction ended when the first drop of methanol was collected (marked as zero point) and the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 160°C, and butylene oxalate prepolymer was added for a third transesterification reaction, which lasted for 1 hour under completely melted conditions. The molar ratio of the sum of the molar amounts of dimethyl tetracosanoate and butylene oxalate prepolymer to 1,24-tetracosanodiol was 1.2:1.

[0143] The system is gradually heated to 220°C and depressurized to 100Pa to carry out the second pre-condensation reaction, which takes 3 hours. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 1 hour to obtain a milky white PE-like biodegradable copolyester.

[0144] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of 80.2:19.8 for tetracosanoic acid to oxalic acid, with a negligible residual ethylene glycol content of 0.9%. The intrinsic viscosity is 1.77 dL / g; the number-average molecular weight is 132,000 g / mol; according to the L*a*b* color model, the L* value is 80, the a* value is 2.2, and the b* value is 3.1; the glass transition temperature is -62.8℃, and the melting point is 83.5℃; the tensile strength is 12.5 MPa, and the elongation at break is 710%; the water vapor permeability coefficient is 4.21 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; Enzymatic degradation resulted in a 40% mass loss within 60 days, hydrolysis resulted in a 24% mass loss within 60 days, and seawater degradation resulted in a 5% mass loss within 60 days.

[0145] Example 10

[0146] 0.048 mol of dimethyl oxalate, 0.0624 mol of ethylene glycol, and antimony acetate with a mass fraction of 3‰ (as a percentage of dimethyl oxalate) were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 140°C, and the first esterification or transesterification reaction was carried out for 3 hours. The timing was stopped when the first drop of methanol or ethanol fell, and the esterification or transesterification reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 110°C and the pressure of the reaction system was reduced to 400 Pa. The first pre-condensation reaction was carried out for 4 hours to obtain a low-polymerization degree ethylene glycol oxalate prepolymer.

[0147] 0.252 mol of dimethyl eicosanoate, 0.3 mol of 1,20-eicosanodiol, and 3‰ (by mass of dimethyl eicosanoate) of triethyl antimonate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 170°C for a second esterification or transesterification reaction, which lasted for 4 hours. The esterification or transesterification reaction was considered complete when the first drop of methanol was recorded as the zero point and when the amount of methanol collected as a byproduct reached more than 95% of the theoretical value. The system was then cooled to 130°C, and ethylene glycol oxalate prepolymer was added for a third transesterification reaction, which lasted for 2 hours. The molar ratio of the sum of the molar amounts of dimethyl eicosanoate and ethylene glycol oxalate prepolymer to 1,20-eicosanodiol was 1.2:1.

[0148] The system is gradually heated to 240℃ and depressurized to 500Pa to carry out the second pre-condensation reaction, which takes 0.5h. The reaction system is further depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the final condensation reaction is less than or equal to 7Pa, and the final condensation reaction takes 0.5h to obtain a milky white PE-like biodegradable copolyester.

[0149] Testing revealed that the dicarboxylic acid composition of this type of biodegradable PE copolyester exhibits a molar ratio of 85.5:14.5 for docosanoic acid and 14.5 for oxalic acid, with a negligible residual ethylene glycol content of 0.7%. The intrinsic viscosity is 1.68 dL / g; the number-average molecular weight is 121,000 g / mol; according to the L*a*b* color model, the L* value is 84, the a* value is 2.7, and the b* value is 3.4; the glass transition temperature is -65.7℃, and the melting point is 82.9℃; the tensile strength is 12.3 MPa, and the elongation at break is 650%; the water vapor permeability coefficient is 4.47 × 10⁻⁶. -14 g·cm / cm 2 The mass loss due to enzyme degradation was 42% within 60 days, the mass loss due to hydrolysis was 28% within 60 days, and the mass loss due to seawater degradation was 7% within 60 days.

[0150] Comparative Example 1

[0151] 0.3 mol of dimethyl dodecanoate, 0.3 mol of 1,12-dodecanediol, and 0.3‰ of tetrabutyl titanate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 180℃ to carry out esterification or transesterification reaction. The reaction was carried out for 3 hours. The timing was stopped when the first drop of methanol fell and the reaction ended when the amount of methanol collected as a byproduct was more than 95% of the theoretical value.

[0152] The system is gradually heated to 210°C and depressurized to 200Pa for pre-polymerization reaction, which takes 1.5 hours. The reaction system is then further depressurized to below 20Pa for final polymerization reaction, where the stable vacuum degree of the final polymerization reaction is less than or equal to 7Pa and the reaction time is 1.5 hours, resulting in a PE-like copolyester.

[0153] Testing revealed that the copolyesters dodecanoic acid and dodecanoic acid glycol of this type of PE exhibit clear structures; the intrinsic viscosity is 2.21 dL / g; the number-average molecular weight is 137,000 g / mol; according to the L*a*b* color model, the L* value is 88, the a* value is 3.5, and the b* value is 4.3; the glass transition temperature is -69.7℃, and the melting point is 84.7℃; the tensile strength is 11.7 MPa, the elongation at break is 1500%, and the water vapor permeability coefficient is 9.48 × 10⁻⁶. -14 g·cm / cm 2•s·Pa; Enzymatic degradation resulted in a 9% mass loss within 60 days, while hydrolysis resulted in no mass degradation within 60 days.

[0154] Comparative Example 2

[0155] 0.063 mol of dimethyl oxalate, 0.237 mol of dimethyl dodecanoate, 0.32 mol of 1,12-dodecanediol, and 0.6‰ of tetrabutyl titanate were added to the reactor. Under nitrogen protection, the temperature was gradually increased to 160℃ and the reaction was carried out for 3 hours. The esterification reaction or transesterification reaction was considered to have ended when the first drop of methanol was dropped and the amount of methanol collected as a byproduct was more than 95% of the theoretical value.

[0156] The system was gradually heated to 200℃ and depressurized to 20Pa to carry out a pre-condensation reaction. A large amount of white solid precipitated in the collection bottle. The melt could not solidify and agglomerate, no torque was generated, and the melt turned black.

[0157] Comparative Example 3

[0158] 0.063 mol dimethyl oxalate, 0.237 mol dimethyl dodecanoate, 0.088 mol ethylene glycol, 0.32 mol 1,12-dodecanoic acid glycol, and a composite catalyst of tetrabutyl titanate and titanium isopropoxide with a mass fraction of 0.8‰ were added to the reactor. Under nitrogen protection, the temperature was gradually increased to 160℃ and the reaction was carried out for 4 hours. The timing was stopped when the first drop of methanol was dropped and the amount of methanol collected as a byproduct reached 70% of the theoretical value and could not be increased further.

[0159] The system is gradually heated to 200℃ and depressurized to 200Pa to carry out a pre-condensation reaction for 2 hours. The reaction system is further depressurized to less than 20Pa to carry out a final condensation reaction. The vacuum degree of the final condensation reaction is less than or equal to 7Pa and the time of the final condensation reaction is 8 hours, resulting in a yellow PE copolyester.

[0160] Tests showed that the molar ratio of dodecanoic acid to oxalic acid in the dicarboxylic acid composition of this type of PE copolyester was 91.4:8.6, the residual ethylene glycol content was 6.4%, the intrinsic viscosity was 0.35 dL / g, and the number average molecular weight was 18000 g / mol.

[0161] Comparative Example 4

[0162] 0.15 mol of dimethyl oxalate, 0.21 mol of ethylene glycol, and 2‰ titanium isopropoxide were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150 °C, and the reaction was carried out for 1.5 h. The esterification or transesterification reaction was considered to have ended when the first drop of methanol was collected and the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 120 °C, the pressure of the reaction system was reduced to 200 Pa, and the reaction was carried out for 1 h to obtain a low-polymerization degree ethylene glycol oxalate prepolymer.

[0163] 0.15 mol of dimethyl dodecanoate, 0.3 mol of 1,12-dodecanediol, and 0.8‰ tetrabutyl titanate were added to a reactor. Under nitrogen protection, the temperature was gradually increased to 180℃ for esterification or transesterification reaction. The reaction was carried out for 2 hours. The timing was stopped when the first drop of methanol fell, and the reaction was considered complete when the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150℃, and ethylene glycol oxalate prepolymer was added for transesterification reaction, which was carried out for 4 hours.

[0164] The system is gradually heated to 210°C and depressurized to 200Pa for pre-polymerization reaction, which takes 2 hours. The reaction system is then further depressurized to below 20Pa for final polymerization reaction, where the stable vacuum degree of the final polymerization reaction is less than or equal to 7Pa and the reaction time is 4 hours, resulting in a yellow PE copolyester.

[0165] Testing revealed that the dicarboxylic acid composition of this type of PE copolyester exhibited a dodecanoic acid:oxalic acid molar ratio of 54:46, with a residual ethylene glycol content of 24.8%; an intrinsic viscosity of 1.32 dL / g; a number-average molecular weight of 107,000 g / mol; an L* value of 75, an a* value of 5.4, and a b* value of 8.9 according to the L*a*b* color model; a glass transition temperature of -64.5℃ and a melting point of 78.8℃; a tensile strength of 10.1 MPa and an elongation at break of 350%; and a water vapor permeability coefficient of 15.3 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; The mass loss due to enzyme degradation was 84% ​​within 60 days, the mass loss due to hydrolysis was 67% within 60 days, and the mass loss due to seawater degradation was 35% within 60 days.

[0166] Comparative Example 5

[0167] 0.063 mol dimethyl oxalate, 0.088 mol ethylene glycol, and 0.32 mol A mixed catalyst consisting of 1,12-dodecanediol, 0.5‰ titanium isopropoxide, and 1‰ tetrabutyl titanate was added to a reactor. Under nitrogen protection, the temperature was gradually increased to 150°C for the first esterification or transesterification reaction for 1 hour. The temperature was then gradually increased to 180°C for the second esterification or transesterification reaction for 2 hours. The esterification or transesterification reaction ended when the first drop of methanol was collected (zero point) and the amount of methanol collected as a byproduct was more than 95% of the theoretical value. The system was then cooled to 150°C and depressurized to 200 Pa for the first pre-polymerization reaction for 1 hour. The system was then gradually heated to 210°C and depressurized to 200 Pa for the second pre-polymerization reaction for 1 hour. The system was then further depressurized to below 20 Pa for the final polycondensation reaction, with a stable vacuum degree of less than or equal to 7 Pa and a final polycondensation time of 2 hours, yielding a PE-like biodegradable copolyester.

[0168] Testing revealed that this type of biodegradable PE copolyester is a dodecyl oxalate homopolymer, with a negligible ethylene glycol residue of 0.9%; its intrinsic viscosity is 1.55 dL / g; its number-average molecular weight is 110,000 g / mol; according to the L*a*b* color model, its L* value is 89, a* value is 2.9, and b* value is 5.8; its glass transition temperature is -54.6℃, and its melting point is 128.6℃; its tensile strength is 18.2 MPa, and its elongation at break is 500%; its water vapor permeability coefficient is 6.33 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; Enzymatic degradation resulted in a mass loss of 85% within 60 days, hydrolysis resulted in a mass loss of 57% within 60 days, and seawater degradation resulted in a mass loss of 21% within 60 days.

[0169] Comparative Example 6

[0170] 0.063 mol of dimethyl oxalate, 0.237 mol of dimethyl dodecanoate, 0.42 mol of ethylene glycol, and a mixed catalyst of 0.5‰ titanium isopropoxide and 1‰ tetrabutyl titanate were added to the reactor. Under nitrogen protection, the temperature was gradually increased to 150°C for the first esterification or transesterification reaction for 1 hour. The temperature was then gradually increased to 180°C for the second esterification or transesterification reaction for 2.5 hours. The timing was stopped from the first drop of methanol until the amount of methanol collected as a byproduct was reached. The theoretical value is more than 95% of the endpoint of the esterification or transesterification reaction; the system is cooled to 150°C and the pressure of the reaction system is reduced to 200 Pa, and the first pre-condensation reaction is carried out for 1 hour; the system is gradually heated to 190°C and the pressure is reduced to 200 Pa to carry out the second pre-condensation reaction, and the second pre-condensation reaction time is 1 hour; the reaction system is further reduced to less than 20 Pa to carry out the final condensation reaction, and the stable vacuum degree of the final condensation reaction is less than or equal to 7 Pa, and the final condensation time is 2 hours, to obtain a PE-like biodegradable copolyester.

[0171] Testing revealed that the molar ratio of dodecanoic acid to oxalic acid in the dicarboxylic acid composition of this type of biodegradable PE copolyester is 85.3:14.7; the intrinsic viscosity is 1.12 dL / g; the number-average molecular weight is 87,000 g / mol; according to the L*a*b* color model, the L* value is 83, the a* value is 2.1, and the b* value is 5.4; the glass transition temperature is -48.4℃, the melting point is 135.8℃; the tensile strength is 17.4 MPa, the elongation at break is 400%; and the water vapor permeability coefficient is 6.18 × 10⁻⁶. -14 g·cm / cm 2 •s·Pa; The mass loss due to enzyme degradation was 87% within 60 days, the mass loss due to hydrolysis was 63% within 60 days, and the mass loss due to seawater degradation was 24% within 60 days.

[0172] As shown in Example 1 and Comparative Example 1, PE-like polyesters without oxalic acid segments in their molecular chains hardly degrade. As shown in Example 1, Comparative Example 2, and Comparative Example 3, directly reacting diethyl oxalate or diethyl oxalate and ethylene glycol with long-chain diacids in a one-pot process results in insufficient esterification, causing the oxalic acid segments to thermally degrade during the polycondensation stage. This prevents the extraction of long-chain diols from the system, hindering molecular weight increase, leading to yellowing or blackening of the PE-like polyester, and even making synthesis impossible. As shown in Example 1 and Comparative Example 4, when the ethylene glycol oxalate prepolymer exceeds 20% in the long-chain diacid system... Even with sufficient transesterification time, ethylene glycol cannot be completely extracted from the reaction system during polycondensation, resulting in excessively high ethylene glycol content in the molecular chain, altering the PE-like polyester structure, and rendering the molecular structure uncontrollable. As shown in Example 1 and Comparative Example 5, when dimethyl dodecanoate was not added, dodecanediol oxalate homopolymer was obtained, and ethylene glycol could be completely extracted with negligible content. As shown in Example 1 and Comparative Example 6, even with reduced polycondensation temperature and without the addition of 1,12-dodecanediol, some ethylene glycol and oxalic acid were extracted from the system, making the product ratio uncontrollable.

[0173] By employing the above technical solution, this invention can effectively synthesize high molecular weight PE-like biodegradable copolyesters through polycondensation by coordinating the length of methylene groups and the content of oxalic acid units in the polyester structure. This ensures that the PE-like biodegradable copolyesters possess good and stable thermal, mechanical, and barrier properties, while also controlling the degradation rate of the copolyesters.

[0174] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0175] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A polyethylene-like biodegradable copolyester, characterized in that, The structural formula of the polyethylene-like biodegradable copolyester is shown in formula (1): ； Equation (1); Wherein, -R1- is a structural unit of a long-chain dicarboxylic acid or its esterified form, -O-R2-O- is a structural unit of a long-chain diol, m, n, and x are all integers, m=1~10, n=1~10, x=10~100; and -R1- and The molar ratio is 3:2 to 19:1; The structural units of the long-chain dicarboxylic acid or its esters are selected from at least one of the structures shown in formula (2): ； Equation (2); Where a is an integer, a = 10~23; The long-chain diol is selected from at least one of the structures shown in formula (3): ； Equation (3); Where c is an integer, c = 12~25.

2. The polyethylene-like biodegradable copolyester according to claim 1, characterized in that: The intrinsic viscosity of the polyethylene-like biodegradable copolyester is 1.5~2.5 dL / g, and the number-average molecular weight is 80000~160000 g / mol; according to the L*a*b* color model, the L* value is greater than 80, the absolute value of a* is less than 4, and the absolute value of b* is less than 8. And / or, the glass transition temperature of the polyethylene-like biodegradable copolyester is -80 to 65°C, the melting point is 70 to 105°C, the tensile strength is 10 to 40 MPa, the elongation at break is 600 to 1600%, and the water vapor permeability coefficient is 4 × 10⁻⁶. -14 ~10×10 -14 g·cm / cm 2 The mass loss after 60 days of hydrolysis is 30-50%, while the mass loss after 60 days of enzymatic degradation is 40-70%, and the mass loss after 60 days of seawater degradation is 5-15%.

3. The method for preparing the polyethylene-like biodegradable copolyester according to any one of claims 1 to 2, characterized in that, include: Dimethyl oxalate and / or diethyl oxalate, a first diol and an esterification catalyst are mixed to form a first mixed system, and the first mixed system is subjected to a first esterification reaction or a first transesterification reaction to obtain a first esterification product or a first transesterification product. The mixture is then cooled to carry out the first pre-condensation reaction, resulting in a low-polymerization-degree oxalic acid prepolymer; the molar ratio of dimethyl oxalate and / or diethyl oxalate to the first diol is 1:1.2 to 1:1.5, and the first diol is selected from at least one of ethylene glycol, propylene glycol, and butanediol. A second mixed system is formed by mixing a long-chain dicarboxylic acid or its esterified form, a long-chain diol, and an esterification catalyst. The second mixed system is then subjected to a second esterification reaction or a second transesterification reaction to obtain a second esterified product or a second transesterification product. The molar ratio of the sum of the molar amounts of the long-chain dicarboxylic acid or its esterified form and the molar amounts of the oxalate ester structure in the oxalic acid prepolymer to the molar amount of the long-chain diol is 1:1 to 1.2:

1. The oxalic acid prepolymer, the second esterification product, or the second transesterification product are mixed to form a third mixed system. The third mixed system undergoes a third transesterification reaction under conditions of complete melt melting. Then, the temperature is raised to carry out a second pre-condensation reaction and a final condensation reaction to obtain a polyethylene-like biodegradable copolyester.

4. The preparation method according to claim 3, characterized in that: The temperature of the first esterification reaction or the first transesterification reaction is 140~180℃, and the time is 1~4h.

5. The preparation method according to claim 3, characterized in that... include: After the first esterification reaction or the first transesterification reaction is completed, the temperature is lowered to 100~150℃, and the reaction system is depressurized to 200~1000Pa to carry out the first pre-condensation reaction for 0.5~4h, to obtain a low degree of polymerization oxalic acid prepolymer.

6. The preparation method according to claim 3, characterized in that, The oxalic acid prepolymer has at least one of the structures shown in formula (4): ； Equation (4) Wherein, the diol from which -O-R3-O- originates is selected from at least one of ethylene glycol, propylene glycol, and butanediol; b is an integer, b=1~10.

7. The preparation method according to claim 3, characterized in that: The structural units of the long-chain dicarboxylic acid or its esters are selected from at least one of the structures shown in formula (2): ； Equation (2); Where a is an integer, a = 10~23.

8. The preparation method according to claim 3, characterized in that, The long-chain diol is selected from at least one of the structures shown in formula (3): ； Equation (3); Where c is an integer, c = 12~25.

9. The preparation method according to claim 3, characterized in that: The temperature for the second esterification reaction or the second transesterification reaction is 170~210℃, and the time is 1~4h.

10. The preparation method according to claim 3, characterized in that: The esterification catalyst includes at least one of antimony-based catalysts and titanium-based catalysts.

11. The preparation method according to claim 3, characterized in that: In the first mixed system, the mass of the esterification catalyst accounts for 0.1‰ to 3‰ of the mass of dimethyl oxalate and / or diethyl oxalate.

12. The preparation method according to claim 3, characterized in that: In the second mixed system, the mass of the esterification catalyst accounts for 0.1‰ to 3‰ of the mass of the long-chain dicarboxylic acid or its esterified form.

13. The preparation method according to claim 4, characterized in that: The temperature of the first esterification reaction or the first transesterification reaction is 140~160℃.

14. The preparation method according to claim 5, characterized in that... include: After the first esterification reaction or the first transesterification reaction is completed, the temperature is lowered to 110~130℃, and the reaction system is depressurized to 200~400Pa to carry out the first pre-condensation reaction for 1~1.5h, to obtain a low degree of polymerization oxalic acid prepolymer.

15. The preparation method according to claim 9, characterized in that: The temperature for the second esterification reaction or the second transesterification reaction is 170~190℃.

16. The preparation method according to claim 3, characterized in that: The third transesterification reaction is carried out at a temperature of 130-160°C for a time of 0.5-2 hours.

17. The preparation method according to claim 10, characterized in that: The antimony-based catalyst includes any one or a combination of two or more of antimony trioxide, antimony acetate, antimony glycol, and triethyl antimonate. And / or, the titanium-based catalyst comprises any one or a combination of two or more of titanium isopropoxide, tetrabutyl titanate, and tetraethyl titanate.

18. The preparation method according to claim 11, characterized in that: In the first mixing system, the mass of the esterification catalyst accounts for 0.5‰ to 1‰ of the mass of dimethyl oxalate and / or diethyl oxalate.

19. The preparation method according to claim 12, characterized in that: In the second mixing system, the mass of the esterification catalyst accounts for 0.5‰ to 1‰ of the mass of the long-chain dicarboxylic acid or its esterified form.

20. The preparation method according to claim 3, characterized in that... include: The reaction system obtained from the third transesterification reaction is gradually heated to 190~240℃, and the reaction system is depressurized to 100~500Pa to carry out the second pre-condensation reaction, which takes 0.5~3h. Then, the reaction system is depressurized to less than 20Pa to carry out the final condensation reaction. The stable vacuum degree of the condensation reaction does not exceed 7Pa, and the condensation reaction takes 0.5~2h to obtain the polyethylene-like biodegradable copolyester.

21. The preparation method according to claim 16, characterized in that: The third transesterification reaction is carried out at a temperature of 140-150°C for 1-1.5 hours.

22. The preparation method according to claim 20, characterized in that... include: The reaction system obtained from the third transesterification reaction is gradually heated to 200-220°C, and the reaction system is depressurized to 200-400 Pa to carry out the second pre-condensation reaction, which takes 1-1.5 h. Then, the reaction system is depressurized to less than 20 Pa to carry out the final condensation reaction, where the stable vacuum degree of the condensation reaction does not exceed 7 Pa and the condensation reaction takes 1-2 h, thus obtaining the polyethylene-like biodegradable copolyester.

23. The use of any one of the polyethylene-like biodegradable copolyesters according to claims 1 to 2 in the preparation of agricultural mulch films, fiber fabrics, telecommunication cables, packaging materials, plastic container products, tissue engineering scaffolds or drug carriers.

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