Monomers containing pyrrolidinone ring, degradable long chain random copolyesters and methods of preparation

Abstract

The application provides a monomer containing a pyrrolidone ring, a degradable long-chain random copolyester and a preparation method. The copolyester has the structure shown in the following formula: wherein R1 comprises an ether bond or a thioether bond, R2 and R3 comprise a linear alkyl group containing 10-30 carbon atoms, x and y are both integers from 1 to 10, and m is an integer from 20 to 100. The degradable long-chain random copolyester provided by the application has a high molecular weight, excellent crystallinity, a high Young's modulus and water vapor gas barrier property, and good hydrolysis sensitivity, and the biodegradation rate can be controlled in a wide range, so that the copolyester can be widely applied to the preparation of agricultural mulching films, shopping bags and other products. Meanwhile, the preparation process is simple, easy to operate, the reaction conditions are mild, and the yield is high.

Description

Technical Field

[0001] This application specifically relates to a monomer containing a pyrrolidone ring, a biodegradable long-chain random copolyester, and a preparation method thereof, belonging to the field of polymer materials technology. Background Technology

[0002] Aliphatic polyesters with 10 or more methylene groups between ester bonds are generally referred to as long-chain aliphatic polyesters or polyethylene-like aliphatic polyesters. As the aliphatic chain length increases, repeating units form stable crystalline regions through van der Waals interactions between methylene segments, and the polyester properties gradually approach those of polyethylene, which has a high melting point, high crystallinity, and high water vapor barrier properties. By selecting the length of the monomer raw materials, the properties of long-chain aliphatic polyesters can be tuned between flexible LDPE and more rigid HDPE to meet different application requirements; the presence of ester bonds also endows long-chain aliphatic polyesters with chemical recyclability. Therefore, these customizable and recyclable long-chain aliphatic polyesters have become one of the most promising alternatives to polyethylene. However, highly crystalline and highly hydrophobic materials are generally difficult to degrade, and the biodegradability of long-chain aliphatic polyesters decreases with the chain length between ester bonds. This leads to a conflict between their application properties and degradation rates, resulting in limited recycling methods and application scenarios. When leaked into the natural environment, the slow degradation rate of long-chain aliphatic polyesters still causes environmental pollution problems due to waste accumulation.

[0003] Introducing hydrophilic units into the polyester structure through copolymerization with polar diacids is beneficial for improving the hydrophilicity of copolyesters and enhancing their biodegradability. Pyrrolidone cyclic diacids can be synthesized via the Michael addition reaction of itaconic acid and aliphatic diamines, and copolymerization can introduce polar CN into the copolyester backbone. However, due to the hydrophobicity of the methylene segment, the hydrophilicity of the pyrrolidone ring structure obtained from aliphatic diamines is limited. Furthermore, the steric hindrance effect of the pyrrolidone ring affects the close packing of the molecular chains; adding too many pyrrolidone units can disrupt the crystallinity of the polyester, affecting its thermal and mechanical properties. Therefore, aliphatic pyrrolidone diacids still cannot effectively enhance the biodegradability of long-chain aliphatic polyesters while maintaining the desired copolyester application performance.

[0004] Long-chain aliphatic polyesters prepared by melt polycondensation require strict control of the alkyd-acid ratio (1:1). Deviations in monomer purity and feed ratio can cause an imbalance in the alkyd-acid ratio, making it difficult to increase the polymer molecular weight. Using an excess of diols, removing as much diol as possible during the polycondensation stage under high temperature and high vacuum conditions can increase the polymer molecular weight. However, long-chain diols have high boiling points, requiring higher polymerization temperatures and reaction times to synthesize high-molecular-weight products. For example, decanediol has a normal boiling point of 297°C, and the boiling point of long-chain diols increases with increasing carbon chain length, making preparation conditions even more demanding. Researchers have proposed introducing low-boiling-point diols into the polymerization system to assist in polyester exchange and solve these problems. Specifically, low-boiling-point ethylene glycol and high-boiling-point hexanediol are first mixed with diester oxalate and esterified to obtain hydroxyl-terminated oligomers. Then, the two oligomers are mixed and further polycondensed at 150–220°C for 0.5–6 hours under reduced pressure to obtain high-molecular-weight polyhexanediol oxalate. This process of low-boiling-point volatile diol-assisted polymerization can obtain high molecular weight polyesters containing long-chain diols at lower polymerization temperatures and shorter polymerization times. However, short-chain ethylene glycols may form diethylene glycol (boiling point of 245℃ at normal pressure) during the reaction, which is difficult to completely remove, resulting in residual chain segments that affect the material properties. Summary of the Invention

[0005] The main objective of this application is to provide a monomer containing a pyrrolidone ring, a biodegradable long-chain random copolyester, its preparation method and application, in order to overcome the shortcomings of the prior art.

[0006] To achieve the above-mentioned objectives, this application adopts the technical solution described below.

[0007] The first aspect of this application provides a monomer containing a pyrrolidone ring, having the structure shown in Formula 1.

[0008]

[0009] R contains either an ether bond or a thioether bond.

[0010] The second aspect of this application provides a method for preparing a monomer containing a pyrrolidone ring, comprising: subjecting itaconic acid and a diamine to a Michael addition reaction to obtain the monomer;

[0011] The monomer has the structure shown in Formula 1, and the diamine has the structure shown in Formula 2.

[0012]

[0013] H2N-R-NH2

[0014] Formula 2

[0015] R contains an ether bond or a thioether bond;

[0016] A third aspect of this application provides a biodegradable long-chain random copolyester having the structure shown in Formula 3.

[0017]

[0018] Wherein, R1 contains ether bonds or thioether bonds, R2 and R3 include straight-chain alkyl groups containing 10-30 carbon atoms, x and y are integers from 1 to 10, m is an integer from 20 to 100, and the molar ratio of R1 to R3 is 1:9-3:7.

[0019] A fourth aspect of this application provides a method for preparing a biodegradable long-chain random copolyester, comprising:

[0020] An intermediate product is obtained by subjecting a first mixed system containing monomer A, monomer B, monomer C, monomer D and an esterification catalyst to an esterification reaction or transesterification reaction.

[0021] The second mixed system containing the intermediate product, polycondensation catalyst, and stabilizer is subjected to a polycondensation reaction to obtain the biodegradable long-chain random copolyester.

[0022] Wherein, monomer A includes an aliphatic dicarboxylic acid or its ester containing R3, monomer B includes a long-chain diol containing R2, monomer C includes the monomer containing the pyrrolidone ring, monomer D includes propylene glycol, and R2 and R3 include alkyl groups containing 10-30 carbon atoms.

[0023] The fifth aspect of this application provides the use of the monomer containing the pyrrolidone ring or the biodegradable long-chain random copolyester in the preparation of film products. These film products include, but are not limited to, agricultural mulch films and shopping bags.

[0024] Compared with the prior art, this application has at least the following beneficial effects:

[0025] (1) The preparation process of the monomer containing pyrrolidone ring and the biodegradable long-chain random copolyester is simple, easy to operate, mild in reaction conditions and high in yield.

[0026] (2) The biodegradable long-chain random copolyester provided has a high molecular weight, not only with excellent crystallinity, high Young's modulus and water vapor barrier properties, but also with good hydrolysis sensitivity and biodegradation rate that can be controlled within a wide range. It can be widely used in the preparation of film products such as agricultural mulch film and shopping bags. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 The 1H NMR spectrum of the SPA monomer containing pyrrolidone prepared in Example 1;

[0029] Figure 2 The infrared spectrum of the SPA monomer containing pyrrolidone prepared in Example 1;

[0030] Figure 3 The infrared spectrum of the biodegradable long-chain random copolyester prepared in Example 1;

[0031] Figure 4 The image shows the DSC secondary heating curve of the biodegradable long-chain random copolyester prepared in Example 1.

[0032] Figure 5 The stress-strain curve of the biodegradable long-chain random copolyester prepared in Example 1 is shown.

[0033] Figure 6 GPC curve of the biodegradable long-chain random copolyester prepared in Example 1;

[0034] Figure 7 This is a schematic diagram of the surface contact angle of the biodegradable long-chain random copolyester prepared in Example 1. Detailed Implementation

[0035] As mentioned above, given the problems of existing long-chain aliphatic polyesters, such as the difficulty in balancing polyethylene-like properties and degradation performance, and the low molecular weight of condensation polymerization, this application provides a monomer containing a pyrrolidone ring, a biodegradable long-chain random copolyester, its preparation method, and its application. This application first uses itaconic acid and a diamine containing an ether or thioether bond as raw materials to synthesize a pyrrolidone-ring dicarboxylic acid, i.e., the monomer containing the pyrrolidone ring, via a Michael addition reaction. Then, the pyrrolidone-ring dicarboxylic acid, an aliphatic dicarboxylic acid or its esterified form, a long-chain diol, propylene glycol, and a catalyst are mixed and reacted to obtain a polyester oligomer. The polyester oligomer is then subjected to a condensation polymerization reaction under high temperature and high vacuum conditions to obtain the biodegradable long-chain random copolyester. This process is simple and easy to operate, with mild reaction conditions and high yield. The prepared copolyester has advantages such as easy crystallization, hydrolysis sensitivity, and adjustable biodegradation rate. Simultaneously, it exhibits a fast crystallization rate, high crystallization enthalpy and melting enthalpy, high modulus, and excellent water vapor barrier properties. The technical solution of this application will be further described below.

[0036] Some embodiments of this application provide a monomer containing a pyrrolidone ring having the structure shown in Formula 1.

[0037]

[0038]

[0039] Some embodiments of this application also provide a method for preparing the monomer containing the pyrrolidone ring, comprising: subjecting itaconic acid and a diamine to a Michael addition reaction to obtain the monomer;

[0040] The monomer has the structure shown in Formula 1, and the diamine has the structure shown in Formula 2.

[0041] H2N-R-NH2.

[0042] Formula 2

[0043] In Formulas 1 and 2 above, R contains an ether bond or a thioether bond.

[0044] Furthermore, R may include at least one of the following structural units:

[0045]

[0046] In one embodiment, the preparation method specifically includes: carrying out the Michael addition reaction of a mixed reaction system containing itaconic acid, a diamine, and water at 130-180°C to obtain the monomer.

[0047] In one embodiment, the reaction time is 24-48 hours.

[0048] In one embodiment, the molar ratio of itaconic acid to diamine is 1.8-2.2:1.

[0049] In a more specific embodiment, the preparation method may include: dissolving itaconic acid and diamine in water, stirring and refluxing at 130°C, removing excess water, precipitating in cold methanol, and washing multiple times to obtain the monomer containing the pyrrolidone ring.

[0050] The method for preparing the monomer containing the pyrrolidone ring provided in this application is simple, has mild conditions, and has a high yield, exceeding 95%.

[0051] Some embodiments of this application also provide a biodegradable long-chain random copolyester having the structure shown in Formula 3.

[0052]

[0053] In this design, R1 contains ether or thioether bonds, while R2 and R3 consist of straight-chain alkyl groups containing 10-30 carbon atoms. x and y are integers from 1 to 10, and m is an integer from 20 to 100. The molar ratio of R1 to R3 is 1:9 to 3:7. If the proportion of R1 is too small, the copolyester will have insufficient hydrophilicity, resulting in a slow degradation rate. As the proportion of R1 increases, the hydrophilicity gradually improves, and the degradation rate accelerates. However, when the R1 proportion exceeds 30%, the copolyester's crystallinity decreases significantly, leading to insufficient mechanical and barrier properties.

[0054] Preferably, R2 and R3 can be selected from long-chain alkyl groups containing 10-30 carbon atoms.

[0055] In one embodiment, R1 may include at least one of the following structural units:

[0056]

[0057] The biodegradable long-chain random copolyester of this application has a high molecular weight, with a weight-average molecular weight higher than 120,000 g / mol, preferably 140,000-200,000 g / mol, a dispersion of 2.0-3.0, and an intrinsic viscosity of 1.15-1.35 dL / g.

[0058] In the biodegradable long-chain random copolyester of this application, by adjusting the molar fraction of repeating units containing aliphatic diacids in the total repeating units to be greater than or equal to 70%, the copolyester exhibits a crystalline structure of long-chain aliphatic polyester. The presence of repeating units containing aliphatic diacids ensures a high melt crystallization enthalpy and melting enthalpy of the copolyester, resulting in a fast crystallization rate and high crystallinity. The high crystallinity also ensures that the copolyester possesses high Young's modulus and water vapor barrier properties. Specifically, the biodegradable long-chain random copolyester has a melt crystallization enthalpy or melting enthalpy above 50 J / g, a melting point above 60°C, a Young's modulus of 200-800 MPa (2-8 times that of commercial PBAT), and a water vapor barrier coefficient of 1.10 × 10⁻⁶. -13 -4.65×10 -14 g·cm / cm 2 ·s·Pa, which can reach 3-8 times that of commercial PBAT.

[0059] Meanwhile, the biodegradable long-chain random copolyester of this application exhibits improved overall hydrophilicity due to the presence of ether / ether-thio ester bonds and pyrrolidone ring structures. Furthermore, the synergistic effect of these two polar structures effectively increases the rate of water molecule diffusion into the copolyester, thereby enhancing the hydrolysis rate of ester bonds and enabling rapid degradation under enzymatic catalysis. Moreover, the hydrophilicity of the polyester can be altered by varying the content of pyrrolidone units containing ether / thioester bonds, thus regulating its biodegradation rate. Specifically, the water contact angle of the biodegradable long-chain random copolyester is 85°-70°, with a mass loss rate of 20%-60% after 6 months of degradation in water, and a mass loss rate of 30%-90% after 30 days of degradation by *Candida antarcticus* lipase b (CALB enzyme).

[0060] In summary, the biodegradable long-chain random copolyester of this application is easily crystallized and has an adjustable degradation rate. It combines excellent degradation performance with physical and mechanical properties similar to polyethylene, including a fast crystallization rate, high crystallization enthalpy and melting enthalpy, high modulus, and excellent water vapor barrier properties. When used in agricultural mulch films and other products, it exhibits better stiffness and moisture retention, while when used in shopping bags and other products, it has higher load-bearing capacity and resistance to deformation. Furthermore, the degradation rate of the biodegradable long-chain random copolyester of this application can be controlled by the type and content of the primary and secondary repeating units, thus broadening its applicability, especially suitable for preparing agricultural mulch films and other products where the degradation rate can be adjusted over a wide range according to the needs of the usage environment.

[0061] Some embodiments of this application provide a method for preparing the biodegradable long-chain random copolyester, wherein the method uses long-chain diols and aliphatic diacids as main monomers, and a small amount of diacids containing pyrrolidone rings as comonomers, and synthesizes the copolyester through esterification-melt polycondensation or transesterification-melt polycondensation reaction.

[0062] In one embodiment, the preparation method specifically includes:

[0063] An intermediate product is obtained by subjecting a first mixed system containing monomer A, monomer B, monomer C, monomer D and an esterification catalyst to an esterification reaction or transesterification reaction.

[0064] The second mixed system containing the intermediate product, polycondensation catalyst, and stabilizer is subjected to a polycondensation reaction to obtain the biodegradable long-chain random copolyester.

[0065] The monomer A comprises an aliphatic diacid containing R3 or its esterification. The role of monomer A is to give the copolyester advantages of rapid crystallization and high crystallinity, and to improve its mechanical properties and gas barrier properties.

[0066] The monomer B includes a long-chain diol containing R2. The introduction of the long-chain diol can further improve the crystallinity of the copolyester, while increasing its hydrophobicity and improving its melting point and water vapor barrier properties.

[0067] The monomer C includes the monomer containing the pyrrolidone ring. Since the longer the chains of aliphatic diacids and diols, the weaker the degradability and the slower the degradation rate of the resulting polyester product, the present application introduces polar pyrrolidone units to regulate the biodegradation rate of the polyester. Furthermore, depending on the length of the aliphatic diacids and diols, different types and amounts of monomers can be selected to adjust their degradation rate to varying degrees, while maintaining other excellent properties as much as possible. Simultaneously, adding polar ether / ether-sulfur bonds between the pyrrolidone rings leverages the synergistic effect of multiple polar structures such as CN and CO / CS, further improving the hydrophilicity of the chain segments. This allows for a rapid improvement in the polyester's degradation performance after the introduction of a small amount of pyrrolidone units.

[0068] The monomer D includes propylene glycol, and R2 and R3 include alkyl groups containing 10-30 carbon atoms. Since long-chain diols have high boiling points and are difficult to remove at lower polymerization temperatures, which is not conducive to the increase of molecular weight, this application adds low-boiling-point, easily removable short-chain diols to the system to assist in the polycondensation process. Compared with ethylene glycol, which also has a low boiling point, propylene glycol does not form difficult-to-remove byproducts at high temperatures. Therefore, this application selects propylene glycol to assist in the melt polycondensation process. This not only facilitates the preparation of high molecular weight polymers, but also ensures that the minimal propylene glycol chain residue does not affect the performance of the copolyester.

[0069] In one embodiment, in the first mixed system, the ratio of the sum of the molar amounts of monomers A and C to the sum of the molar amounts of monomers B and D is 1:m, the molar ratio of monomer A to monomer C is 1:9-3:7, and the molar ratio of monomer B to monomer D is n:(mn), where m = 1.4-1.6 and n = 0.9-1.1.

[0070] In this application, by introducing the monomer containing the pyrrolidone ring and controlling the relative content of it with the aliphatic dicarboxylic acid within the above range, the hydrophilicity and degradation ability of the copolyester can be more precisely controlled and improved with minimal impact on its thermal and mechanical properties, thereby maintaining or improving its excellent degradation ability in water and biological enzyme environments.

[0071] In one embodiment, the esterification or transesterification reaction is carried out under a protective atmosphere and at a temperature of 175-200°C. Excessive temperature can cause the diol to volatilize, leading to a mismatch in the acid-to-alcohol ratio and reaction failure; excessively low temperature will result in low reaction efficiency.

[0072] Furthermore, the protective atmosphere includes an atmosphere formed by inert gases such as argon, nitrogen, or mixtures thereof.

[0073] In one embodiment, the reaction time for the esterification or transesterification reaction is 4-6 hours.

[0074] In one embodiment, the preparation method includes: obtaining the intermediate product when the esterification reaction or transesterification reaction proceeds to a yield of water or methanol as a byproduct greater than or equal to 90% of the theoretical yield.

[0075] In one embodiment, in the first mixed system, the molar ratio of the esterification catalyst to the sum of the molar amounts of monomers A and C is 0.5:1000-2.0:1000. If there is too little catalyst, the esterification efficiency will be low and the reaction will be incomplete; if there is too much catalyst, the product will be yellow in color.

[0076] In a more specific implementation example, the preparation method may include the following steps:

[0077] (1) Esterification stage: Monomers A, B, C, D and esterification catalyst are mixed to form a first mixed system, and the intermediate product is obtained by esterification or transesterification reaction until the yield of by-product water or methanol is at least 90%.

[0078] (2) Polycondensation stage: The intermediate product, polycondensation catalyst and stabilizer are then subjected to vacuum melt polycondensation to obtain the copolyester.

[0079] In one embodiment, the esterification catalyst includes, but is not limited to, any one or a combination of titanium-based catalysts, antimony-based catalysts, tin-based catalysts, acetic acid-based catalysts, etc.

[0080] The titanium-based catalyst includes, but is not limited to, any one or more combinations of tetrabutyl titanate, isopropyl titanate, isobutyl titanate, titanium propylene glycol, and titanium dioxide. The antimony-based catalyst includes, but is not limited to, any one or more combinations of antimony trioxide, antimony acetate, and antimony propylene glycol. The tin-based catalyst includes, but is not limited to, any one or more combinations of butylstannic acid, dibutyltin oxide, stannous isooctanoate, stannous oxalate, dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin oxide. The acetate-based catalyst includes, but is not limited to, any one or more combinations of lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, zinc acetate, cobalt acetate, antimony acetate, lead acetate, and manganese acetate.

[0081] In one embodiment, the molar ratio of the polycondensation catalyst to the sum of the molar amounts of monomers A and C is 0.1:1000 to 0.5:1000.

[0082] In one embodiment, the ratio of the molar amount of the stabilizer to the sum of the molar amounts of monomers A and C is 0.5:1000-2.0:1000. If there is too little stabilizer, the reaction product is prone to thermal degradation, and if there is too much stabilizer, the remaining stabilizer will remain as an impurity, affecting the quality of the final product.

[0083] In one embodiment, the reaction temperature of the polycondensation reaction is 200-230°C. If the temperature is too low, the reaction time will be greatly extended, and if the temperature is too high, side reactions such as pyrolysis may occur.

[0084] In one embodiment, the reaction time of the polycondensation reaction is 8h-24h.

[0085] In one embodiment, the polycondensation reaction is carried out under a vacuum of up to 5 Pa.

[0086] In one embodiment, the polycondensation catalyst includes, but is not limited to, any one or more combinations of titanium-based catalysts, antimony-based catalysts, tin-based catalysts, and acetate-based catalysts. Specifically, the titanium-based catalyst includes, but is not limited to, any one or more combinations of tetrabutyl titanate, isopropyl titanate, isobutyl titanate, titanium propylene glycol, and titanium dioxide. The antimony-based catalyst includes, but is not limited to, any one or more combinations of antimony trioxide, antimony acetate, and antimony propylene glycol. The tin-based catalyst includes, but is not limited to, any one or more combinations of butylstannic acid, dibutyltin oxide, stannous isooctanoate, stannous oxalate, dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin oxide. The acetate-based catalyst includes, but is not limited to, any one or more combinations of lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, zinc acetate, cobalt acetate, antimony acetate, lead acetate, and manganese acetate.

[0087] In one embodiment, the stabilizer can inhibit the breakage of ester bonds, aliphatic chains, etc. during the reaction process, and may include antioxidant 1010, antioxidant 1076, antioxidant 1500, antioxidant 425, heat stabilizer 330, heat stabilizer 1178, heat stabilizer 618, heat stabilizer 626, heat stabilizer 168, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tri(tridecyl) phosphite, tri(octadecyl) phosphite, triphenyl phosphite, tri-p-toluene phosphite, diphenyltridecyl phosphite, etc. The following are any one or more combinations of, but not limited to, tris(2,4-di-tert-butylphenyl) phosphate, di(2,4-di-p-isopropylphenyl) pentaerythritol diphosphite phosphate, pentaerythritol tetraphenyl tridecyl phosphite, pentaerythritol didecyl diphosphite, pentaerythritol diisodecyl diphosphite, tetraphenyl dipropylene glycol diphosphite, phosphoric acid, phosphorous acid, polyphosphoric acid and triethyl phosphonoacetate, light stabilizer 791, light stabilizer 700, light stabilizer 783, light stabilizer 119, light stabilizer 770, light stabilizer 622, light stabilizer 944, and light stabilizer 1164.

[0088] In this application, when the esterification catalyst is a titanium-based catalyst or an antimony-based catalyst, the esterification catalyst can also be used as the polycondensation catalyst. In this case, the esterification product can be directly subjected to subsequent polycondensation reaction. However, considering that the esterification catalyst will be partially deactivated after the esterification reaction, when the esterification catalyst and the polycondensation catalyst are the same, a portion of the esterification catalyst can be added to the esterification product before the polycondensation reaction. The ratio of the added esterification catalyst to the sum of the molar amounts of monomer A and monomer C can be 0.5:1000-1:1000.

[0089] The method for preparing the copolyester provided in this application has the advantages of simple process, mild conditions, and high yield.

[0090] The technical solutions of this application are described in detail below with reference to specific embodiments, so that those skilled in the art can better understand and implement the technical solutions of this application. Specific functional details disclosed herein should not be construed as limiting, but rather as the basis for the claims and as a representative basis for teaching those skilled in the art to employ the application differently in any appropriate detailed embodiment.

[0091] In the following examples and comparative examples, unless otherwise specified, all raw materials are basically commercially available or prepared by conventional methods in the art.

[0092] In the following examples and comparative examples, a phenol and tetrachloroethane mixed solution with a mass ratio of 1:1 was used, and the Ubbelohde viscosity was measured at 25°C. The weight-average molecular weight and dispersity were determined using gel permeation chromatography (Agilent PL-GPC220) according to polystyrene standards. The sample was dissolved in chloroform with a concentration of 1 mM / mL, using chloroform as the mobile phase at a flow rate of 1 mL / min. -1 The temperature is 40℃.

[0093] In the following examples and comparative examples, thermal performance was tested using a differential scanning calorimeter (Mettler Toledo DSC), with a heating rate of 10℃ / min and a temperature range of -20℃ to 250℃, in an N2 atmosphere.

[0094] In the following examples and comparative examples, a Zwicki 1kN universal testing machine was used to test the mechanical properties. The dimensions of the specimen 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.

[0095] In the following examples and comparative examples, the surface contact angle of the samples was tested using an OCA25 contact angle measuring instrument.

[0096] In the following examples and comparative examples, a water vapor transmission rate testing system was used to test the water vapor barrier performance in a constant temperature and humidity chamber at 38°C and 90% relative humidity. The sample's transmission area was 29.2 cm². 2 .

[0097] In the following examples and comparative examples, phosphate buffer solution was used as the degradation solvent, and hydrolysis degradation tests were conducted at a constant temperature of 37°C. The sample was 10 mm long, 10 mm wide, and 0.5 mm thick.

[0098] In the following examples and comparative examples, 0.1 mg / ml lipase phosphate buffer solution 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.

[0099] Example 1 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), comprising the following steps:

[0100] (1) Preparation of a monomer containing a pyrrolidone ring: 2.2 mol of itaconic acid and 1.0 mol of 1,1′-thiobis(methylamine) were dissolved in water, stirred and refluxed at 130 °C for 48 h, then excess water was removed, and the precipitate was obtained in cold methanol. After washing several times, a monomer containing a pyrrolidone ring was obtained and named SPA. The NMR spectrum of this monomer is shown below. Figure 1 As shown, the infrared spectrum is as follows Figure 2 As shown.

[0101] (2) Preparation of polyester oligomers by esterification reaction: 0.1 moles of SPA monomer containing pyrrolidone ring, 0.9 moles of tetradecyl diacid, 1.05 moles of tetradecyl glycol, 0.55 moles of propylene glycol and 170 mg of tetrabutyl titanate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 200°C and reacted for 4 hours until the water content produced exceeded 90% of the theoretical yield, and polyester oligomers as intermediate products were obtained.

[0102] (3) Preparation of copolyester by melt polycondensation reaction: 145 mg of antimony trioxide, a polycondensation catalyst, and 650 mg of diphenyl phosphate, a stabilizer, were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa, and the reaction temperature was maintained at 220℃. After 18 hours, the polymerization reaction was terminated when the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. Its structure was determined by infrared spectroscopy and nuclear magnetic resonance, as shown in Formula 4-1. The infrared spectrum of the copolyester is as follows. Figure 3 As shown.

[0103]

[0104] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 1:9.

[0105] The copolyester was tested and found to have an intrinsic viscosity of 1.26 dL / g, a weight-average molecular weight of 185,500 g / mol, a dispersion of 2.1, a melting peak temperature of 91.4℃, a melting enthalpy of 95.6 J / g, a crystallization peak temperature of 64℃, and a crystallization enthalpy of 95.6 J / g.

[0106] Tests showed that the copolyester had a modulus of 550 MPa, a strength of over 30 MPa, and an elongation at break of over 1000%.

[0107] The DSC secondary heating curve, stress-strain curve, and GPC curve of the copolyester are as follows: Figure 4 , Figure 5 and Figure 6 As shown.

[0108] Tests showed that the copolyester had a surface contact angle of 83° with water and a water vapor barrier coefficient of 4.894 × 10⁻⁶. -14 g·cm / cm 2 The surface contact angle of this copolyester with water is 7 times that of PBAT. Figure 7 As shown.

[0109] Tests showed that the copolyester lost 20% of its mass after 180 days of degradation in deionized water, and 30% of its mass after 30 days of degradation in CALB enzyme-buffered PBS.

[0110] Example 2 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), which includes the following steps:

[0111] (1) Preparation of monomer containing pyrrolidone ring: 1.8 mol itaconic acid and 1.0 mol 2,2'-thiobis(ethylamine) were dissolved in water, stirred and refluxed at 180°C for 24 h, then excess water was removed, precipitated in cold methanol, and washed several times to obtain monomer containing pyrrolidone ring, named ESPA.

[0112] (2) Preparation of polyester oligomers by esterification reaction: First, 0.2 moles of pyrrolidone ring-containing monomer ESPA, 0.8 moles of dodecyl dimethyl ester, 1.03 moles of dodecyl glycol, 0.57 moles of propylene glycol, and 560 mg of isopropyl titanate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 200°C and reacted for 6 hours until the content of the water and methanol mixture produced exceeded 90% of the theoretical value, thus obtaining polyester oligomers.

[0113] (3) Preparation of copolyester by melt polycondensation reaction: 150 mg of antimony acetate, a polycondensation catalyst, and 150 mg of phosphorous acid, a stabilizer, were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa, and the reaction temperature was maintained at 220 °C. After 12 hours, the polymerization reaction was terminated when the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. The structural formula was determined by infrared spectroscopy, nuclear magnetic resonance and other characterization methods as shown in Formula 4-2.

[0114]

[0115] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 2:8.

[0116] The copolyester was tested and found to have an intrinsic viscosity of 1.28 dL / g, a weight-average molecular weight of 156783 g / mol, a dispersion of 2.3, a melting peak temperature of 90.1℃, a melting enthalpy of 83.7 J / g, a crystallization peak temperature of 64.7℃, and a crystallization enthalpy of 83.0 J / g.

[0117] The copolyester was tested and found to have a modulus of 300 MPa, a strength exceeding 15 MPa, and an elongation at break exceeding 700%. The surface contact angle of the copolyester was also tested to be 70°, and its water vapor barrier coefficient was 9.638 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa is 3.6 times that of PBAT.

[0118] Tests showed that the copolyester decreased by 26% in deionized water after 190 days of degradation, and by 40% in CALB enzyme-buffered PBS buffer after 30 days of degradation.

[0119] Example 3 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), which includes the following steps:

[0120] (1) Preparation of monomer containing pyrrolidone ring: 2.0 mol itaconic acid and 1.0 mol 1,8-diamine-3,6-dithiooctane were dissolved in water, stirred and refluxed at 160℃ for 36 h, then excess water was removed, precipitated in cold methanol, and washed several times to obtain monomer containing pyrrolidone ring, named DSPA.

[0121] (2) Preparation of polyester oligomers by esterification reaction: First, 0.3 moles of monomers containing pyrrolidone rings, DSA, 0.7 moles of dimethyl 1,10-sebacate, 1.0 moles of 1,10-decanediol, 0.4 moles of propylene glycol, and 210 mg of stannous isooctanoate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 175°C and reacted for 4 hours until the content of the water and methanol mixture produced exceeded 90% of the theoretical value, thus obtaining polyester oligomers.

[0122] (3) Preparation of copolyester by melt polycondensation reaction: 150 mg of tetrabutyl titanate, a polycondensation catalyst, and 150 mg of triisooctyl phosphite, a stabilizer, were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa and the reaction temperature was maintained at 200 °C. After 8 hours, the polymerization reaction was terminated when the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. Its structural formula was determined by infrared and nuclear magnetic resonance, as shown in Formula 4-3.

[0123]

[0124]

[0125] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 3:7.

[0126] The copolyester was tested and found to have an intrinsic viscosity of 1.28 dL / g, a weight-average molecular weight of 140622 g / mol, a dispersion of 2.5, a melting peak temperature of 69.7℃, a melting enthalpy of 64.3 J / g, a crystallization peak temperature of 53.8℃, and a crystallization enthalpy of 63.4 J / g.

[0127] The copolyester tested showed a modulus of 250 MPa, a strength exceeding 15 MPa, and an elongation at break exceeding 800%. The copolyester also exhibited a surface contact angle of 70° and a water vapor barrier coefficient of 1.10 × 10⁻⁶. -13 g·cm / cm 2 ·s·Pa is 3.1 times that of PBAT.

[0128] Tests showed that the copolyester lost 60% of its mass after 180 days of degradation in deionized water, and 90% of its mass after 30 days of degradation in CALB enzyme-buffered PBS.

[0129] Example 4 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), which includes the following steps:

[0130] (1) Preparation of monomers containing pyrrolidone rings with oxygen ether bonds: 2.1 mol itaconic acid and 1.0 mol 1,1′-oxobis(methylamine) were dissolved in water, stirred and refluxed at 130 °C for 48 h, then excess water was removed, precipitated in cold methanol, and washed several times to obtain monomers containing pyrrolidone rings, named OPA.

[0131] (2) Preparation of polyester oligomers by esterification reaction: 0.2 moles of monomer OPA containing pyrrolidone ring, 0.8 moles of tetradecyl diacid, 0.9 moles of tetradecyl diol, 0.6 moles of propylene glycol, and 360 mg of zinc acetate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 200℃ and reacted for 6 hours until the water content exceeded 90% of the theoretical value, thus obtaining polyester oligomers.

[0132] (3) Preparation of copolyester by melt polycondensation reaction: 125 mg of polycondensation catalyst dibutyltin oxide and 250 mg of stabilizer triisooctyl phosphite were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa. The reaction temperature was maintained at 230 °C. After 24 hours, the polymerization reaction was terminated after the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. Its structural formula 4-4 was determined by infrared spectroscopy, nuclear magnetic resonance and other characterization as follows:

[0133]

[0134] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 2:8;

[0135] The copolyester was tested and found to have an intrinsic viscosity of 1.26 dL / g, a weight-average molecular weight of 198,745 g / mol, a dispersion of 2.3, a melting peak temperature of 90.0℃, a melting enthalpy of 84.2 J / g, a crystallization peak temperature of 62.1℃, and a crystallization enthalpy of 84.0 J / g.

[0136] The copolyester was tested and found to have a modulus of 800 MPa, a strength exceeding 28 MPa, and an elongation at break exceeding 500%. The surface contact angle of the copolyester was also tested to be 85°, and its water vapor barrier coefficient was 4.6493 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa is 8 times that of PBAT.

[0137] Tests showed that the copolyester decreased by 21% in deionized water after 180 days of degradation, and by 30% in CALB enzyme-buffered PBS buffer after 30 days of degradation.

[0138] Example 5 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), which includes the following steps:

[0139] (1) Preparation of monomers containing pyrrolidone rings with oxygen ether bonds: 2.0 mol itaconic acid and 1.0 mol 2,2′-oxobis(ethylamine) were dissolved in water, stirred and refluxed at 180°C for 24 h, then excess water was removed, precipitated in cold methanol, and washed several times to obtain monomers containing pyrrolidone rings, named EOPA.

[0140] (2) Preparation of polyester oligomers by esterification reaction: First, 0.3 moles of monomer EOPA containing pyrrolidone ring, 0.7 moles of octadecyl diacid, 1.03 moles of tetradecyl glycol, 0.37 moles of propylene glycol and 200 mg of stannous oxalate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 190°C and reacted for 6 hours until the water content exceeded 90% of the theoretical value, thus obtaining polyester oligomers.

[0141] (3) Preparation of copolyester by melt polycondensation reaction: 185 mg of zinc acetate, a polycondensation catalyst, and 250 mg of triisooctyl phosphite, a stabilizer, were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa and the reaction temperature was maintained at 210 °C. After 12 hours, the polymerization reaction was terminated when the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. Its structural formula was determined by infrared and nuclear magnetic resonance, as shown in Formula 4-5.

[0142]

[0143] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 3:7;

[0144] The copolyester was tested and found to have an intrinsic viscosity of 1.15 dL / g, a weight-average molecular weight of 141917 / mol, a dispersion of 2.0, a melting peak temperature of 81.7℃, a melting enthalpy of 87.3 J / g, a crystallization peak temperature of 66.8℃, and a crystallization enthalpy of 87.1 J / g.

[0145] The copolyester was tested and found to have a modulus of 300 MPa, a strength exceeding 15 MPa, and an elongation at break exceeding 700%. The surface contact angle of the copolyester was also tested to be 75°, and its water vapor barrier coefficient was 8.023 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa is 4.4 times that of PBAT.

[0146] Tests showed that the copolyester decreased by 26% in weight after 180 days of degradation in deionized water, and by 43% in weight after 30 days of degradation in CALB enzyme-containing PBS buffer.

[0147] Example 6 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), which includes the following steps:

[0148] (1) Preparation of monomers containing pyrrolidone rings with oxygen ether bonds: 1.8 mol itaconic acid and 1.0 mol 1,8-diamino-3,6-dioxaoctane were dissolved in water, stirred and refluxed at 145°C for 40 h, then excess water was removed, precipitated in cold methanol, and washed several times to obtain the diacid monomer of pyrrolidone, named DOPA.

[0149] (2) Preparation of polyester oligomers by esterification reaction: 0.1 moles of DOPA monomer containing pyrrolidone ring, 0.9 moles of eicosyl dimethyl ester, 0.9 moles of dodecyl glycol, 0.7 moles of propylene glycol, and 145 mg of tetraisopropyl titanate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 175°C and reacted for 6 hours until the content of the water and methanol mixture produced exceeded 90% of the theoretical value, thus obtaining polyester oligomers.

[0150] (3) Preparation of copolyester by melt polycondensation reaction: 320 mg of polycondensation catalyst dibutyltin dilaurate and 330 mg of stabilizer triisooctyl phosphite were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa and the reaction temperature was maintained at 200 °C. After 8 hours, the polymerization reaction was terminated after the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. Its structural formula was determined by infrared and nuclear magnetic resonance, as shown in Formula 4-6.

[0151]

[0152] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 1:9;

[0153] The copolyester was tested and found to have an intrinsic viscosity of 1.19 dL / g, a weight-average molecular weight of 168293 / mol, a dispersion of 2.0, a melting peak temperature of 80.2℃, a melting enthalpy of 77.6 J / g, a crystallization peak temperature of 64.7℃, and a crystallization enthalpy of 76.1 J / g.

[0154] The copolyester was tested and found to have a modulus of 400 MPa, a strength exceeding 20 MPa, and an elongation at break exceeding 700%. The surface contact angle of the copolyester was also tested to be 78°, and its water vapor barrier coefficient was 7.061 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa is 5 times that of PBAT.

[0155] Tests showed that the copolyester decreased by 24% in deionized water after 180 days of degradation, and by 41% in CALB enzyme-buffered PBS buffer after 30 days of degradation.

[0156] Example 7 This example provides a method for preparing a biodegradable long-chain random copolyester (hereinafter referred to as copolyester), which includes the following steps:

[0157] (1) Preparation of pyrrolidone ring monomers containing oxygen ether bonds: 1.9 mol itaconic acid and 1.0 mol 1,8-diamino-3,6-dioxane were dissolved in water, stirred and refluxed at 150°C for 40 h, then excess water was removed, precipitated in cold methanol, and washed several times to obtain the diacid monomer of pyrrolidone, named DOPA.

[0158] (2) Preparation of polyester oligomers by esterification reaction: 0.2 moles of DOPA monomer containing pyrrolidone ring, 0.8 moles of eicosyl dimethyl ester, 0.9 moles of dodecyl glycol, 0.7 moles of propylene glycol, and 145 mg of tetraisopropyl titanate were added to the reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 185°C and reacted for 5 hours until the content of the water and methanol mixture produced exceeded 90% of the theoretical value, thus obtaining polyester oligomers.

[0159] (3) Preparation of copolyester by melt polycondensation reaction: 145 mg of tetraisopropyl titanate catalyst and 330 mg of triisooctyl phosphite stabilizer were added to the oligomer obtained in step (2). The pressure was gradually reduced and the temperature was increased. After 30 minutes, the vacuum degree of the reactor reached 5 Pa and the reaction temperature was maintained at 200 °C. After 8 hours, the polymerization reaction was terminated after the rated stirring torque of 200 N·cm was reached, and the copolyester was obtained. Its structural formula was determined by infrared and nuclear magnetic resonance, as shown in Formula 4-7.

[0160]

[0161] Where x and y are integers from 1 to 10, m is an integer from 20 to 100, and x:y = 2:8;

[0162] The copolyester was tested and found to have an intrinsic viscosity of 1.19 dL / g, a weight-average molecular weight of 175610 g / mol, a dispersion of 2.1, a melting peak temperature of 79.1℃, a melting enthalpy of 75.4 J / g, a crystallization peak temperature of 64.5℃, and a crystallization enthalpy of 75.4 J / g.

[0163] The copolyester was tested and found to have a modulus of 400 MPa, a strength exceeding 20 MPa, and an elongation at break exceeding 700%. The surface contact angle of the copolyester was also tested to be 78°, and its water vapor barrier coefficient was 7.059 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa is 5 times that of PBAT.

[0164] Tests showed that the copolyester decreased by 23% in deionized water after 180 days of degradation, and by 40% in CALB enzyme-buffered PBS buffer after 30 days of degradation.

[0165] Comparative Example 1 The preparation method of homopolymer polyester (defined as PTDD, hereinafter referred to as homopolymer polyester) provided in this comparative example includes the following steps:

[0166] (1) 1 mole of tetradecyl diacid, 1.05 mole of tetradecyl glycol, 0.55 mole of propylene glycol and 100 mg of tetrabutyl titanate were added to a reactor. Under the protection of high-purity nitrogen, the temperature was gradually increased to 200°C and reacted for 4 hours until the water content exceeded 90% of the theoretical value, thus obtaining polyester oligomer.

[0167] (2) Add 145 mg of antimony trioxide, a polycondensation catalyst, and 650 mg of diphenyl phosphate, a stabilizer, to the above polyester oligomer. Gradually raise the temperature to 220 °C and gradually lower the vacuum to 5 Pa. React for 18 h to obtain homopolymer PTDD. Characterize it by infrared spectroscopy, nuclear magnetic resonance and other methods to determine its structure as shown in Formula 5-1.

[0168]

[0169] The intrinsic viscosity of this homopolymer was tested to be 1.27 dL / g, the weight-average molecular weight was 153525 g / mol, the dispersion was 2.0, the melting peak temperature was 93.4℃, the melting enthalpy was 95.4 J / g, the crystallization peak temperature was 71.9℃, and the crystallization enthalpy was 95.4 J / g.

[0170] Tests showed that the homopolymer polyester had a modulus of 700 MPa, a strength exceeding 35 MPa, and an elongation at break exceeding 600%. The homopolymer polyester also exhibited a surface contact angle of 95° and a water vapor barrier coefficient of 5.138 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa.

[0171] Tests showed that the homopolymer exhibited almost no mass loss after 180 days of degradation in deionized water, and similarly, almost no mass loss after 30 days of degradation in CALB enzyme-containing PBS buffer.

[0172] Comparative Example 2 The preparation method of a copolyester provided in this comparative example is basically the same as that in Example 1, except that 1,1′-thiobis(methylamine) in step (1) is replaced with 1,3-propanediamine, and finally a copolyester is obtained. Its structure is determined by infrared, nuclear magnetic resonance and other characterization methods as shown in Formula 5-2.

[0173]

[0174] Tests showed that the resulting copolyester had a surface contact angle of 88° with water and a water vapor barrier coefficient of 4.763 × 10⁻⁶. -14 g·cm / cm 2 The ·s·Pa value is 7.4 times that of PBAT. Meanwhile, in deionized water, the copolyester showed a 13% mass decrease after 180 days of degradation, and in CALB enzyme-buffered PBS buffer, the copolyester showed a 15% mass decrease after 30 days of degradation. Compared to Example 1, the synthesized diacid monomer, lacking thioether bonds, exhibited reduced polarity, leading to a larger surface contact angle between the copolyester and water, increased water vapor barrier properties, decreased hydrophilicity, and reduced degradation performance.

[0175] Comparative Example 3 The preparation method of a copolyester provided in this comparative example is basically the same as that in Example 1, except that: 0.1 moles of pyrrolidone ring-containing monomer SPA in step (2) is replaced with thiodiacetic acid, and finally a copolyester is obtained. Its structure is determined by infrared, nuclear magnetic resonance and other characterization methods as shown in Formula 5-3.

[0176]

[0177] The obtained copolyester was tested and found to have a surface contact angle of 87° and a water vapor barrier coefficient of 4.797 × 10⁻⁶. -14 g·cm / cm 2The ·s·Pa value is 7.4 times that of PBAT. Meanwhile, in deionized water, the copolyester showed a 14% mass decrease after 180 days of degradation, and in CALB enzyme-buffered PBS buffer, the copolyester showed a 16% mass decrease after 30 days of degradation. Compared to Example 1, the monomer used in this comparative example contains thioether bonds but not pyrrolidone structures, resulting in reduced polarity. This leads to a larger surface contact angle between the copolyester and water, increased water vapor barrier properties, decreased hydrophilicity of the material, and reduced degradation performance.

[0178] Comparative Example 4 provides a copolyester preparation method that is basically the same as that in Example 1, except that propylene glycol in step (2) is replaced with ethylene glycol, and a copolyester is finally obtained.

[0179] The obtained copolyester was tested and found to have an intrinsic viscosity of 1.0 dL / g, a weight-average molecular weight of 103,540 g / mol, and a dispersion of 1.9. Simultaneously, the copolyester exhibited a modulus of 550 MPa, a strength exceeding 13 MPa, and an elongation at break exceeding 450%. Compared to Example 1, in this comparative example, the low-boiling-point diol was replaced with ethylene glycol instead of propylene glycol. The resulting copolyester showed a decrease in molecular weight and mechanical properties within the same polycondensation time. This is because ethylene glycol at high temperatures generates diethylene glycol, which is difficult to remove and leads to a decrease in polymerization efficiency.

[0180] Comparative Example 5 provides a copolyester preparation method that is basically the same as that in Example 1, except that propylene glycol in step (2) is replaced with butanediol, and finally a copolyester is obtained.

[0181] The obtained copolyester was tested and found to have an intrinsic viscosity of 0.98 dL / g, a weight-average molecular weight of 95460 g / mol, and a dispersion of 1.8. Simultaneously, the copolyester exhibited a modulus of 550 MPa, a strength exceeding 15 MPa, and an elongation at break exceeding 490%. Compared to Example 1, this comparative example replaced the low-boiling-point glycol, propylene glycol, with butanediol. Because butanediol itself has a higher boiling point, it cannot be rapidly removed during polycondensation to assist in molecular chain growth like propylene glycol. Therefore, under the same reaction conditions, a large amount of butanediol remains, making it difficult for the product's molecular weight to increase, thus reducing the material's mechanical properties.

[0182] Comparative Example 6 provides a copolyester preparation method that is basically the same as that in Example 1, except that the feed ratio in step (2) is adjusted to 0.5 moles of SPA monomer containing a pyrrolidone ring, 0.5 moles of tetradecyl diacid, 1.05 moles of tetradecyl diol, and 0.55 moles of propylene glycol. The copolyester is then obtained, and its structure is determined by infrared spectroscopy, nuclear magnetic resonance, etc.

[0183] As shown in Equation 5-4.

[0184]

[0185] The obtained copolyester was tested and found to have an intrinsic viscosity of 1.25 dL / g, a weight-average molecular weight of 176,342 g / mol, a dispersion of 2.0, a melting peak temperature of 55℃, a melting enthalpy of 43.2 J / g, a crystallization peak temperature of 43℃, and a crystallization enthalpy of 46.2 J / g. Furthermore, the copolyester exhibited a modulus of 120 MPa, a strength exceeding 15 MPa, and an elongation at break exceeding 500%.

[0186] Compared to Example 1, this comparative example introduces too many diacid monomers containing pyrrolidone rings, which destroys the crystallization ability of the material and leads to a decrease in thermal, mechanical and barrier properties.

[0187] Comparative Example 7 provides a copolyester preparation method that is basically the same as that in Example 1, except that the feed ratio in step (2) is adjusted to 0.05 moles of SPA monomer containing a pyrrolidone ring, 0.95 moles of tetradecyl diacid, 1.05 moles of tetradecyl diol, and 0.55 moles of propylene glycol, ultimately yielding the copolyester. Its structure was determined by infrared spectroscopy, nuclear magnetic resonance, and other characterization methods, as shown in Formula 5-4.

[0188] The tested copolyester had a surface contact angle of 93° and a water vapor barrier coefficient of 5.127 × 10⁻⁶. -14 g·cm / cm 2 ·s·Pa. Meanwhile, in deionized water, the copolyester showed almost no mass loss after 180 days of degradation, and similarly, in CALB enzyme-containing PBS buffer, it showed almost no mass loss after 30 days of degradation.

[0189] Compared to Example 1, the amount of diacid monomer containing a pyrrolidone ring introduced in this comparative example is too low, resulting in excessively high hydrophilicity of the material and failing to effectively improve the degradation performance of the copolyester.

[0190] In addition, the inventors of this case also conducted experiments with other raw materials, process operations, and process conditions described in this specification, referring to the aforementioned embodiments, and obtained relatively ideal results in all cases.

[0191] All aspects, embodiments, features, and examples of this application are to be regarded as illustrative in all respects and are not intended to limit the application; the scope of this application is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of this application as claimed.

[0192] Although this application has been described with reference to illustrative embodiments, those skilled in the art will understand that various other changes, omissions, and / or additions can be made without departing from the spirit and scope of this application, and that elements of the described embodiments can be substituted with substantially equivalents. Furthermore, many modifications can be made without departing from the scope of this application to adapt particular situations or materials to the teachings of this application. Therefore, this application is not intended to be limited to the specific embodiments disclosed for carrying out this application, but rather is intended to include all embodiments falling within the scope of the appended claims.

Claims

1. A biodegradable long-chain random copolyester, characterized in that: The copolyester has the structure shown in Formula 3. ； Formula 3; R1 is selected from one of the following structural units: 、 、 、 、 、 ； R2 and R3 are selected from straight-chain alkyl groups containing 10-30 carbon atoms, x and y are integers from 1 to 10, m is an integer from 20 to 100, and the molar ratio of R1 to R3 is 1:9-3:

7.

2. The biodegradable long-chain random copolyester according to claim 1, characterized in that: The biodegradable long-chain random copolyester has a weight-average molecular weight higher than 120,000 g / mol, a dispersion of 2.0-3.0, and an intrinsic viscosity of 1.15-1.35 dL / g.

3. The biodegradable long-chain random copolyester according to claim 2, characterized in that: The weight-average molecular weight of the biodegradable long-chain random copolyester is 140,000-200,000 g / mol.

4. The biodegradable long-chain random copolyester according to claim 1, characterized in that: The biodegradable long-chain random copolyester has a melt crystallization enthalpy or melting enthalpy above 50 J / g, a melting point above 60℃, a Young's modulus of 200-800 MPa, and a water vapor barrier coefficient of 1.10 × 10⁻⁶. -13 - 4.65×10 -14 g·cm / cm 2 ·s·Pa; Furthermore, the water contact angle of the biodegradable long-chain random copolyester is 85°-70°, the mass loss rate in water after 6 months of degradation is 20%-60%, and the mass loss rate in Candida antarctica lipase b after 30 days of degradation is 30%-90%.

5. A method for preparing a biodegradable long-chain random copolyester, characterized in that, include: An esterification or transesterification reaction is carried out in a first mixed system containing monomer A, monomer B, monomer C, monomer D and an esterification catalyst. The ratio of the sum of the molar amounts of monomer A and monomer C to the sum of the molar amounts of monomer B and monomer D is 1:m, the molar ratio of monomer A to monomer C is 1:9-3:7, and the molar ratio of monomer B to monomer D is n:(mn), where m=1.4-1.6 and n=0.9-1.

1. The esterification or transesterification reaction is carried out under a protective atmosphere at a reaction temperature of 175-200℃. An intermediate product is obtained when the yield of the byproduct water or methanol is greater than or equal to 90% of the theoretical yield. The second mixture containing the intermediate product, polycondensation catalyst, and stabilizer is subjected to polycondensation reaction under a vacuum of less than 5 Pa, wherein the molar ratio of the stabilizer to the sum of the molar amounts of monomer A and monomer C is 0.5:1000-2.0:1000, and the reaction temperature of the polycondensation reaction is 200-230℃, thereby obtaining the biodegradable long-chain random copolyester. Wherein, monomer A is selected from aliphatic diacids containing R3 or their esters, monomer B is selected from long-chain diols containing R2, and monomer C has the structure shown in Formula 1. ； Formula 1; Where R is selected from at least one of the following structural units: 、 、 、 、 、 ， The monomer D is propylene glycol, and R2 and R3 are selected from alkyl groups containing 10-30 carbon atoms.

6. The preparation method according to claim 5, characterized in that: The reaction time for the esterification or transesterification reaction is 4-6 hours.

7. The preparation method according to claim 5, characterized in that: In the first mixed system, the molar ratio of the esterification catalyst to the sum of the molar amounts of monomers A and C is 0.5:1000-2.0:1000.

8. The preparation method according to claim 5, characterized in that: The esterification catalyst is selected from any one or more combinations of titanium-based catalysts, antimony-based catalysts, tin-based catalysts, and acetic acid-based catalysts. The titanium-based catalyst is selected from any one or more combinations of tetrabutyl titanate, isopropyl titanate, isobutyl titanate, titanium propylene glycol, and titanium dioxide. The antimony-based catalyst is selected from any one or more combinations of antimony trioxide, antimony acetate, and antimony propylene glycol. The tin-based catalyst is selected from any one or more combinations of butylstannic acid, dibutyltin oxide, stannous isooctanoate, stannous oxalate, dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin oxide. The acetic acid-based catalyst is selected from any one or more combinations of lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, zinc acetate, cobalt acetate, antimony acetate, lead acetate, and manganese acetate.

9. The preparation method according to claim 5, characterized in that: The molar ratio of the polycondensation catalyst to the sum of the molar amounts of monomers A and C is 0.1:1000-0.5:1000.

10. The preparation method according to claim 5, characterized in that: The reaction time for the polycondensation reaction is 8h-24h.

11. The preparation method according to claim 5, characterized in that: The polycondensation catalyst is selected from any one or more combinations of titanium-based catalysts, antimony-based catalysts, tin-based catalysts, and acetate-based catalysts. The titanium-based catalyst is selected from any one or more combinations of tetrabutyl titanate, isopropyl titanate, isobutyl titanate, titanium propylene glycol, and titanium dioxide. The antimony-based catalyst is selected from any one or more combinations of antimony trioxide, antimony acetate, and antimony propylene glycol. The tin-based catalyst is selected from any one or more combinations of butylstannic acid, dibutyltin oxide, stannous isooctanoate, stannous oxalate, dibutyltin diacetate, dibutyltin dilaurate, and dioctyltin oxide. The acetate-based catalyst is selected from any one or more combinations of lithium acetate, potassium acetate, calcium acetate, magnesium acetate, barium acetate, zinc acetate, cobalt acetate, antimony acetate, lead acetate, and manganese acetate.

12. The preparation method according to claim 5, characterized in that: The stabilizer is selected from antioxidant 1010, antioxidant 1076, antioxidant 1500, antioxidant 425, heat stabilizer 330, heat stabilizer 1178, heat stabilizer 618, heat stabilizer 626, heat stabilizer 168, trimethyl phosphite, triethyl phosphite, triisooctyl phosphite, triisodecyl phosphite, trilauryl phosphite, tri(tetranyl) phosphite, tri(octadecyl) phosphite, triphenyl phosphite, tri-p-toluene phosphite, diphenyltridecyl phosphite, tri(2,4-di-tert-butylphenyl) phosphite, di(2-) The following are any one or more combinations of the following: (4-di-p-isopropylphenyl) pentaerythritol diphosphite phosphate, pentaerythritol tetraphenyl tridecyl phosphite, pentaerythritol didecyl phosphite, pentaerythritol diisodecyl phosphite, tetraphenyl dipropylene glycol diphosphite, phosphoric acid, phosphorous acid, polyphosphoric acid and triethyl phosphonoacetate, light stabilizer 791, light stabilizer 700, light stabilizer 783, light stabilizer 119, light stabilizer 770, light stabilizer 622, light stabilizer 944, and light stabilizer 1164.

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