Biodegradable polyester material and preparation method thereof

Abstract

The invention relates to the technical field of biomedical materials, in particular to a biodegradable polyester material and a preparation method thereof.The preparation method of the biodegradable polyester material comprises the following steps that a monomer, an initiator and a tin catalyst are subjected to a bulk polymerization reaction, and a crude product is obtained; dissolving the crude product in a first organic solvent to obtain a crude product solution; adding pre-treated iminodiacetic acid type chelating resin into the crude product solution for adsorption; the total exchange capacity chelated copper of the imidodiacetic acid type chelating resin is greater than or equal to 1.95 mmol / g; the use amount of the pretreated iminodiacetic acid type chelating resin is 5-15% of the mass of the crude product. According to the preparation method of the biodegradable polyester material, provided by the invention, the high-quality polyester material with high molecular weight, narrow molecular weight distribution and extremely low tin catalyst residual quantity can be stably obtained while high-efficiency production is ensured.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, and in particular to a biodegradable polyester material and its preparation method. Background Technology

[0002] Biodegradable polyester materials, such as polylactic acid (PLA), polycaprolactone (PCL), polylactic acid-glycolic acid copolymer (PLGA) and its copolymers, have been widely used in biomedical fields such as surgical sutures, orthopedic fixation materials, and drug delivery carriers due to their excellent biocompatibility and biodegradable and absorbable properties.

[0003] Currently, stannous octoate (Sn(Oct)2) is widely used industrially as a catalyst for synthesizing these polyester materials. As a heavy metal catalyst, the residual tin in the final product must be strictly controlled. Especially for medical implant-grade applications, industry standards typically require residual tin levels to be below 150 ppm or even lower. In conventional post-processing, the polymer is usually purified by dissolving the polymerization product and then precipitating it in unsuitable solvents (such as methanol, ethanol, or water). While this method effectively removes unreacted monomers and oligomers, it is extremely ineffective at removing tin catalyst residues that exist in chemically bonded or physically embedded forms.

[0004] To meet the stringent requirements for tin residue in the final product, existing technologies are generally forced to adopt a compromise strategy of source control, that is, to strictly limit the amount of catalyst added at the beginning of the polymerization reaction (for example, the mass ratio of catalyst to monomer is usually controlled at 1 / 10000 or lower). Although this strategy can control the final tin content to a certain extent, it brings a series of serious technical defects to the polymerization process itself: (1) Slow reaction rate: The extremely low catalyst concentration leads to a significant extension of the polymerization reaction time, which directly causes low production efficiency, increased energy consumption and high production costs. (2) Difficulty in increasing molecular weight: Due to the low catalyst concentration, it is difficult to maintain the effective concentration of active centers in the polymerization system, which makes it difficult to grow polymer chains and to stably obtain the required high molecular weight (e.g., weight average molecular weight Mw>200,000) products, thereby limiting the mechanical properties and application range of the materials. (3) Wide molecular weight distribution: At low catalyst concentrations, the competition between side reactions caused by thermal effects or impurities in the system and the main reaction intensifies, which leads to a wider molecular weight distribution of the final polymer product (i.e., an increase in the polydispersity index PDI value). A wide molecular weight distribution can affect the batch stability of material mechanical properties and the uniformity and predictability of degradation rates.

[0005] Therefore, existing technologies present an irreconcilable contradiction between efficiently producing high-quality biodegradable polyesters and controlling catalyst residues in the final product. There is an urgent need in this field for a new technical solution that can achieve efficient polymerization while effectively removing tin residues from the final product, thereby producing high-performance polyester materials that meet medical implantation standards. Summary of the Invention

[0006] This invention provides a biodegradable polyester material and its preparation method, which solves the problem in the prior art that it is difficult to balance high polymerization efficiency and high purity (i.e. low catalyst tin residue) of the final product when preparing medical-grade biodegradable polyester. It achieves the stable acquisition of high-performance medical-grade polyester material with three excellent characteristics: high molecular weight, narrow molecular weight distribution and ultra-low tin residue (<20ppm) while significantly improving the polymerization rate and shortening the production cycle.

[0007] According to a first aspect of the present invention, the present invention provides a method for preparing a biodegradable polyester material, comprising the following steps: The monomer, initiator and tin catalyst were subjected to bulk polymerization to obtain the crude product; The crude product is dissolved in a first organic solvent to obtain a crude product solution; then, a pretreated iminodiacetic acid chelating resin is added to the crude product solution for adsorption; the iminodiacetic acid chelating resin has a total exchange capacity of chelating copper ≥1.95 mmol / g; The amount of the pretreated iminodiacetic acid chelating resin is 5-15% of the mass of the crude product.

[0008] The method for preparing biodegradable polyester materials provided by this invention introduces a highly efficient resin adsorption tin removal step, which decouples the contradiction between polymerization efficiency and tin residue in the final product. This allows for the use of high-concentration tin catalysts during the polymerization stage to increase the reaction rate and product molecular weight. Then, the tin residue is effectively reduced to an extremely low level through subsequent adsorption steps. This ensures both production efficiency and product performance while meeting the stringent requirements for heavy metal residues in medical-grade materials.

[0009] According to the preparation method of the biodegradable polyester material of the present invention, the pretreatment method is as follows: the iminodiacetic acid type chelating resin is first extracted with a second organic solvent as the extraction solvent and refluxed at 70-90℃ for 12-36h, and then extracted with a third organic solvent as the extraction solvent and refluxed at 70-80℃ for 12-36h.

[0010] This invention pretreats the iminodiacetic acid-type chelating resin before adsorption, effectively removing impurities such as pore-forming agents and unreacted monomers remaining from the resin during manufacturing. This not only prevents these impurities from contaminating the polyester product or causing degradation during subsequent adsorption, but more importantly, it activates the chelating sites of the resin, significantly improving its adsorption capacity and efficiency for tin ions.

[0011] Preferably, the second organic solvent is selected from one or more of methanol, ethanol and isopropanol; the third organic solvent is selected from tetrahydrofuran and / or acetone.

[0012] Preferably, the iminodiacetic acid type chelating resin has a styrene-divinylbenzene backbone, comprising 40-50% by mass iminodiacetic acid groups; the iminodiacetic acid type chelating resin has a total exchange capacity of chelated copper ≥ 1.95 mmol / g; the iminodiacetic acid type chelating resin has a volumetric total exchange capacity of chelated copper ≥ 0.60 mmol / ml, a water content of 50-60%, a wet apparent density of 0.70-0.80 g / ml, a wet true density of 1.15-1.25 g / ml, a particle size of 0.4-1.25 mm ≥ 95%, and a uniformity coefficient ≤ 1.6; the iminodiacetic acid type chelating resin...

[0013] According to the preparation method of the biodegradable polyester material of the present invention, the adsorption temperature is 20-30℃, the time is 3-5h, and the stirring speed is 100-300 rpm.

[0014] This invention optimizes the temperature and time of the adsorption process, ensuring efficient tin removal under mild and controllable conditions, effectively avoiding hydrolysis or thermal degradation of polyester materials during purification. Compared to traditional purification methods that require heating or the use of acids and alkalis, these mild conditions maximize the protection of the long-chain structure of the polyester, thereby guaranteeing the high molecular weight and narrow molecular weight distribution of the final product.

[0015] According to the preparation method of biodegradable polyester material of the present invention, the first organic solvent is selected from one or more of dichloromethane, trichloromethane and tetrahydrofuran; in the crude product solution, the mass-volume percentage of the crude product is 10-20%.

[0016] This invention optimizes the mass-volume percentage of the crude product, providing an optimal viscosity range for the adsorption process that balances mass transfer efficiency and processing cost while ensuring complete polymer dissolution. This concentration range avoids the problem of excessively viscous solution hindering the contact between tin ions and resin active sites, while also avoiding the problem of excessive solvent consumption and low production efficiency due to excessively dilute solution, thus achieving a balance between adsorption efficiency and economic benefits.

[0017] According to the preparation method of biodegradable polyester material of the present invention, the amount of tin catalyst added is 0.01-0.05% of the mass of the monomer.

[0018] This invention allows for the use of catalysts at much higher concentrations than conventional processes (typically <150 ppm), which greatly increases the polymerization rate (e.g., reducing reaction time from 48 h to 8 h) and helps to obtain higher polymer molecular weights.

[0019] Preferably, the tin catalyst is selected from one or more of stannous octoate, tri-n-butylmethoxytin, and dioctyltin dilaurate.

[0020] According to the preparation method of the biodegradable polyester material of the present invention, the amount of initiator added is 0.1-1% of the mass of the monomer; preferably, the initiator is selected from one or more of dodecyl alcohol, 1-butanol and glycolic acid.

[0021] According to the preparation method of the biodegradable polyester material of the present invention, the monomer is selected from one or more of D,L-lactide, caprolactone, glycolide, and L-lactide.

[0022] According to the preparation method of the biodegradable polyester material of the present invention, the bulk polymerization reaction temperature is 120-180℃ and the time is 6-10h.

[0023] With the synergistic effect of high-concentration catalysts, this invention can achieve efficient conversion of monomers and full growth of polymer chains in a short time (6-10h), and rapidly obtain crude products with the target molecular weight.

[0024] The method for preparing the biodegradable polyester material according to the present invention further includes the following steps: after adsorption is completed, the chelating resin is separated, and the biodegradable polyester material is extracted from the filtrate using a poor solvent.

[0025] The post-treatment steps of this invention, such as filtration and precipitation, after adsorption, effectively separate the purified high-purity polymer from the tin-loaded chelating resin and solvent, ultimately yielding a dry, pure solid product. The precipitation step not only solidifies the product but also further removes trace amounts of oligomers that may be present in the system, further improving the product's purity.

[0026] Preferably, the unsuitable solvent is selected from one or more of ethanol, methanol, n-heptane, and methyl tert-butyl ether; the volume of the unsuitable solvent is 5-15 times that of the filtrate.

[0027] According to a second aspect of the present invention, the present invention also provides a biodegradable polyester material prepared by the above-described preparation method.

[0028] According to the biodegradable polyester material of the present invention, the residual tin content in the biodegradable polyester material is <20ppm; the weight-average molecular weight of the biodegradable polyester material is 200-500kDa; and the molecular weight distribution (PDI) of the biodegradable polyester material is ≤1.8.

[0029] The present invention provides a method for preparing biodegradable polyester materials. By employing a high-concentration tin catalyst during the bulk polymerization stage to ensure reaction efficiency and product molecular weight, and then, under mild conditions, innovatively using a specially pretreated iminodiacetic acid-type chelating resin to efficiently adsorb and remove tin from the dissolved crude product, the technical contradiction between the polymerization rate and catalyst residue in the final product is successfully resolved. This method not only significantly improves polymerization efficiency and shortens reaction time, solving the problems of low efficiency and high cost of traditional processes, but also enables the stable production of high-quality polyester materials with high molecular weight (200-500 kDa), narrow molecular weight distribution (PDI≤1.8), and extremely low tin catalyst residue (<20 ppm) while ensuring high-efficiency production. The entire purification process is conducted under mild conditions, effectively avoiding product degradation, thereby comprehensively improving the product's mechanical properties, degradation behavior uniformity, and biosafety, enabling it to meet the stringent standards of high-end medical implant devices. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0031] The D401, D402, D402-Ⅱ, and D405 macroporous chelating resins used in the following examples and comparative examples were all purchased from Jiangsu Suqing Water Treatment Engineering Group Co., Ltd.

[0032] Example 1 The iminodiacetic acid-type chelating resin used in this embodiment is the D401 type macroporous chelating resin. The method for pretreating the iminodiacetic acid-type chelating resin is as follows: The iminodiacetic acid chelating resin was loaded into a Soxhlet extractor.

[0033] Using analytical grade methanol as solvent, extraction was performed by reflux at 70°C in a water bath for 24 hours. The solvent was then changed to tetrahydrofuran, and extraction was continued by reflux for another 24 hours.

[0034] The extracted resin was washed three times with ethanol, then dried in a vacuum oven to constant weight and sealed for later use.

[0035] This embodiment provides a method for preparing a biodegradable polyester material PLGA, comprising the following steps: 750g of DL-lactide and 200g of glycolide were added to the reactor. 1.4mL of dodecanol (initiator) and 1.62g of stannous octoate (catalyst) were added (the tin addition was 0.05% of the total monomer mass, i.e., 500ppm, far higher than the conventional 100-150ppm). After three purgings with nitrogen, bulk polymerization was carried out at 150℃. Due to the high catalyst concentration, the reaction reached the preset molecular weight (reaction ended) in only 8 hours. A sample of the crude product was then taken for analysis; the tin content was approximately 485ppm.

[0036] Dissolution and Adsorption: The crude product was dissolved in dichloromethane to prepare a clear solution with a concentration of 10% (w / v). Pretreated iminodiacetic acid-type chelating resin was added to the solution. The amount of resin used was 5% of the mass of the crude product. Adsorption was performed at 25°C (room temperature) with mechanical stirring (200 rpm) for 4 hours.

[0037] Post-processing: Resin was removed by filtration through a G3 sintered glass funnel, yielding a colorless and transparent filtrate. The filtrate was slowly added to 10 times its volume of anhydrous ethanol for precipitation, and the white flocculent precipitate was collected. The precipitate was then vacuum-dried at 40°C for 48 hours to obtain the PLGA product.

[0038] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 3 ppm. GPC analysis showed that the weight-average molecular weight was 245 kDa and the molecular weight distribution coefficient (PDI) was 1.65.

[0039] Example 2 This embodiment provides a method for preparing a biodegradable polyester material PLA, including the following steps: 1000g of DL-lactide, 1.5mL of dodecanol as initiator, and 1.62g of stannous octoate catalyst were added to the reactor (the tin addition amount was 0.05% of the total monomer mass, i.e., 500ppm, which is much higher than the conventional 100-150ppm). After vacuuming and nitrogen purging three times, bulk polymerization was carried out at 150℃ for 8h.

[0040] Dissolution and Adsorption: The obtained crude product was dissolved in dichloromethane to prepare a clear solution with a concentration of 10% (w / v). Pretreated iminodiacetic acid-type chelating resin was added to the solution. The amount of resin used was 5% of the mass of the crude product. Adsorption was performed at 25°C (room temperature) with mechanical stirring (stirring speed of 300 rpm) for 4 hours. The iminodiacetic acid-type chelating resin and its pretreatment method used in this example are the same as in Example 1.

[0041] Post-processing: Resin was removed by filtration through a G3 sintered glass funnel, yielding a colorless and transparent filtrate. The filtrate was slowly added to 10 times its volume of anhydrous ethanol for precipitation, and the white flocculent precipitate was collected. The precipitate was then vacuum-dried at 40°C for 48 hours to obtain the PLLA product.

[0042] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 4 ppm. GPC analysis showed that the weight-average molecular weight was 228 kDa and the molecular weight distribution coefficient (PDI) was 1.51.

[0043] Example 3 This embodiment provides a method for preparing a biodegradable polyester material PCL, comprising the following steps: 1000g of caprolactone, 1.5mL of dodecanol (initiator), and 1.71g of stannous octoate (catalyst) were added to the reactor (the tin addition was 500ppm, much higher than the conventional 100-150ppm). After purging with nitrogen three times, bulk polymerization was carried out at 150℃ for 8 hours.

[0044] Dissolution and Adsorption: The obtained crude product was dissolved in dichloromethane to prepare a clear solution with a concentration of 10% (w / v). Pretreated iminodiacetic acid-type chelating resin was added to the solution. The amount of resin used was 5% of the mass of the crude product. Adsorption was performed at 25°C (room temperature) with mechanical stirring (stirring speed of 100 rpm) for 4 hours. The iminodiacetic acid-type chelating resin and its pretreatment method used in this example are the same as in Example 1.

[0045] Post-processing: Resin was removed by filtration through a G3 sintered glass funnel, yielding a colorless and transparent filtrate. The filtrate was slowly added to 10 times its volume of anhydrous ethanol for precipitation, and the white flocculent precipitate was collected. The precipitate was then vacuum-dried at 40°C for 48 hours to obtain the final PCL product.

[0046] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 5 ppm. GPC analysis showed that the weight-average molecular weight was 211 kDa and the molecular weight distribution coefficient (PDI) was 1.41.

[0047] Example 4 This embodiment provides a method for preparing biodegradable polyester material PLGA, which differs from Embodiment 1 in that the amount of resin used is 10% of the mass of the crude product.

[0048] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 3.8 ppm. GPC analysis showed that the weight-average molecular weight was 247 kDa and the molecular weight distribution coefficient (PDI) was 1.69.

[0049] Example 5 This embodiment provides a method for preparing biodegradable polyester material PLGA, which differs from Embodiment 1 in that the amount of resin used is 15% of the mass of the crude product.

[0050] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 3 ppm. GPC analysis showed that the weight-average molecular weight was 243 kDa and the molecular weight distribution coefficient (PDI) was 1.64.

[0051] Example 6 This embodiment provides a method for preparing biodegradable polyester material PLGA, which differs from Example 1 in that the extraction reflux temperature of the chelating resin is 60°C.

[0052] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 23 ppm. GPC analysis showed that the weight-average molecular weight was 236 kDa and the molecular weight distribution coefficient (PDI) was 1.67.

[0053] Comparative Example 1 This comparative example provides a method for preparing a biodegradable polyester material, comprising the following steps: Polymerization reaction: The raw materials are the same as in Example 1, but in order to control the final tin content, the amount of stannous octoate added is only 0.01% (100 ppm tin). At the same temperature, the reaction needs to proceed for 48 hours to reach the predetermined conversion rate.

[0054] Post-treatment: Without resin adsorption, the product is directly dissolved and then precipitated with ethanol.

[0055] Results: Residual tin content: 85 ppm (still higher than the <20 ppm requirement for some high-end implants). Weight-average molecular weight (Mw): 160 kDa (due to limited catalyst, molecular weight growth is difficult). PDI: 2.11 (long reaction time and thermal degradation lead to a wider distribution).

[0056] Comparative Example 2 This comparative example provides a method for preparing a biodegradable polyester material, comprising the following steps: Polymerization reaction: The raw materials are the same as in Example 1, and the amount of tin used is also 500 ppm. The reaction is carried out at 150°C for 8 hours.

[0057] Post-treatment: The product was dissolved in dichloromethane solution and then directly poured into ethanol for precipitation, without resin adsorption. The dissolution-precipitation process was repeated twice. Results: Residual tin content: 420 ppm (indicating that simple physical precipitation has a negligible effect on the removal of chemically bonded or embedded tin), GPC determination showed a weight-average molecular weight of 238 kDa and a molecular weight distribution coefficient (PDI) of 1.70.

[0058] Conclusion: Although the molecular weight has increased, the heavy metal content is seriously excessive, making it unsuitable as a medical material.

[0059] Comparative Example 3 This comparative example provides a method for preparing a biodegradable polyester material, comprising the following steps: Polymerization reaction: Same as in Example 1.

[0060] Dissolution and Adsorption: The crude product was dissolved in dichloromethane to prepare a 10% (w / v) clear solution. Untreated D401 macroporous chelating resin was added to the solution. The amount of resin used was 5% of the crude product mass. Adsorption was carried out by mechanical stirring at 25°C (room temperature) for 4 hours.

[0061] Results: Residual tin content: 51 ppm. Weight-average molecular weight (Mw): 224 kDa (the molecular weight is slightly lower, possibly due to product degradation caused by impurities remaining in the resin). PDI: 1.64, and impurities in the resin cause the product to have a yellowish color.

[0062] Comparative Example 4 This comparative example provides a method for preparing a biodegradable polyester material, which differs from Example 1 in that: D402 type macroporous chelating resin (total exchange capacity of 1.45 mmol / g) is used instead of D401 type macroporous chelating resin.

[0063] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 48 ppm. GPC analysis showed that the weight-average molecular weight was 243 kDa and the molecular weight distribution coefficient (PDI) was 1.63.

[0064] Comparative Example 5 This comparative example provides a method for preparing a biodegradable polyester material, which differs from Example 1 in that: a D402-Ⅱ type macroporous chelating resin with amino phosphate groups is used instead of a D401 type macroporous chelating resin.

[0065] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 39 ppm. GPC analysis showed that the weight-average molecular weight was 237 kDa and the molecular weight distribution coefficient (PDI) was 1.69.

[0066] Comparative Example 6 This comparative example provides a method for preparing a biodegradable polyester material, which differs from Example 1 in that a D405 type macroporous chelating resin with thiol groups is used instead of a D401 type macroporous chelating resin.

[0067] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 57 ppm. GPC analysis showed that the weight-average molecular weight was 241 kDa and the molecular weight distribution coefficient (PDI) was 1.66.

[0068] Comparative Example 7 This comparative example provides a method for preparing a biodegradable polyester material PLGA, which differs from Example 1 in that the amount of chelating resin used is 2% of the mass of the crude product.

[0069] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 78 ppm. GPC analysis showed that the weight-average molecular weight was 239 kDa and the molecular weight distribution coefficient (PDI) was 1.65.

[0070] Comparative Example 8 This comparative example provides a method for preparing a biodegradable polyester material PLGA, which differs from Example 1 in that the amount of chelating resin used is 20% of the mass of the crude product.

[0071] Results: ICP-MS (Inductively Coupled Plasma Mass Spectrometry) analysis showed that the residual tin content in the finished product was 59 ppm. Excessive chelating resin can cause some resin to break down during stirring, resulting in poor adsorption. GPC analysis showed that the weight-average molecular weight was 246 kDa and the molecular weight distribution index (PDI) was 1.63.

[0072] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a biodegradable polyester material, characterized in that, Includes the following steps: The monomer, initiator and tin catalyst were subjected to bulk polymerization to obtain the crude product; The crude product is dissolved in a first organic solvent to obtain a crude product solution; then, a pretreated iminodiacetic acid chelating resin is added to the crude product solution for adsorption; the iminodiacetic acid chelating resin has a total exchange capacity of chelating copper ≥1.95 mmol / g; The amount of the pretreated iminodiacetic acid chelating resin is 5-15% of the mass of the crude product.

2. The method for preparing the biodegradable polyester material according to claim 1, characterized in that, The pretreatment method is as follows: the iminodiacetic acid type chelating resin is first extracted with a second organic solvent at 70-90℃ for 12-36h by reflux extraction, and then extracted with a third organic solvent at 70-80℃ for 12-36h by reflux extraction. Preferably, the second organic solvent is selected from one or more of methanol, ethanol and isopropanol; the third organic solvent is selected from tetrahydrofuran and / or acetone.

3. The method for preparing the biodegradable polyester material according to claim 1 or 2, characterized in that, The iminodiacetic acid type chelating resin has a styrene-divinylbenzene skeleton, comprising iminodiacetic acid groups at a mass percentage of 40-50%; the iminodiacetic acid type chelating resin has a total volumetric exchange capacity of chelated copper ≥ 0.60 mmol / ml, a water content of 50-60%, a wet apparent density of 0.70-0.80 g / ml, a wet true density of 1.15-1.25 g / ml, a particle size of 0.4-1.25 mm ≥ 95%, and a uniformity coefficient ≤ 1.

6.

4. The method for preparing the biodegradable polyester material according to any one of claims 1-3, characterized in that, The adsorption temperature is 20-30℃, the time is 3-5h, and the stirring speed is 100-300rpm.

5. The method for preparing the biodegradable polyester material according to any one of claims 1-4, characterized in that, The first organic solvent is selected from one or more of dichloromethane, trichloromethane, and tetrahydrofuran; the crude product solution contains 10-20% by mass volume of the crude product.

6. The method for preparing the biodegradable polyester material according to any one of claims 1-5, characterized in that, The amount of tin catalyst added is 0.01-0.05% of the mass of the monomer; Preferably, the tin catalyst is selected from one or more of stannous octoate, tri-n-butylmethoxytin, and dioctyltin dilaurate; And / or, the amount of the initiator added is 0.1-1% of the monomer mass; preferably, the initiator is selected from one or more of dodecyl alcohol, 1-butanol and glycolic acid; And / or, the monomer is selected from one or more of D,L-lactide, caprolactone, glycolide, and L-lactide.

7. The method for preparing the biodegradable polyester material according to any one of claims 1-6, characterized in that, The bulk polymerization reaction is carried out at a temperature of 120-180℃ for 6-10 hours.

8. The method for preparing the biodegradable polyester material according to any one of claims 1-7, characterized in that, The process also includes the following steps: after adsorption is complete, the chelating resin is separated, and the biodegradable polyester material is extracted from the filtrate using a poor solvent; Preferably, the unsuitable solvent is selected from one or more of ethanol, methanol, n-heptane, and methyl tert-butyl ether; the volume of the unsuitable solvent is 5-15 times that of the filtrate.

9. A biodegradable polyester material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The biodegradable polyester material according to claim 9, characterized in that, The biodegradable polyester material has a residual tin content of <20ppm; the weight-average molecular weight of the biodegradable polyester material is 200-500kDa; and the molecular weight distribution (PDI) of the biodegradable polyester material is ≤1.8.