High toughness biaxially oriented polyglycolic acid film and method of making same

Abstract

This application relates to the field of film packaging technology, and particularly to a high-toughness biaxially oriented polyglycolic acid (PGA) film and its preparation method. The film has a three-layer structure: the upper and lower surface layers comprise an anti-sticking masterbatch and a PGA composite resin, and the core layer comprises a PGA composite resin. The composite resin comprises PGA, a PGA toughening agent, a hydroxyl fatty acid ester, a chain extender, and an antioxidant. The PGA toughening agent is a copolymer polymerized from ε-caprolactone, glycolide, succinic acid, and butanediol, and the hydroxyl fatty acid ester is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) with a 3-hydroxyhexanoate unit molar content ≥25%. This application achieves synergistic toughening through the toughening agent and PGA, combined with the chain extender and antioxidant, significantly improving film toughness and processing stability while ensuring high barrier properties, high transparency, and high strength, making it suitable for high-requirement packaging applications.

Description

Technical Field

[0001] This application relates to the field of packaging materials technology, and in particular to a high-toughness biaxially oriented polyglycolic acid film and its preparation method. Background Technology

[0002] Biodegradable polyesters are among the most mature and widely used biodegradable polymers. Polyglycolic acid (PGA), in particular, has gained increasing attention due to its combination of good mechanical properties, gas barrier properties, biodegradability, and biocompatibility. Since its introduction, PGA's high production cost and price have limited its applications, primarily serving as biomedical materials such as surgical sutures and tissue engineering scaffolds. In recent years, with the development of chemical technology, China's total coal-to-ethylene glycol production capacity has increased significantly, providing ample raw material sources for PGA production and promoting its application in food packaging, oil extraction, and agriculture. However, PGA's industrialization process is constrained by its inherent limitations; its poor toughness and rapid degradation rate restrict its application scenarios.

[0003] PGA contains a large number of ester bonds in its molecular chain, making it extremely sensitive to moisture when heated. Even after the raw material is dried, the high temperatures generated during processing can easily trigger thermal degradation and hydrolysis. After degradation, the breakage of the molecular chain leads to uncontrolled material flowability (melt index spikes), a narrowing of the processing window, a significant decrease in the mechanical strength of the finished product, and the potential for darkening of the color.

[0004] In biaxially oriented thin film processes, the resin undergoes complex thermal processing steps, including screw melting, melt pumping, filtering, melt piping, melt adapters, and die heads. It is difficult for PGA resin to remain undegraded under such prolonged thermal conditions. Thermal degradation of the material can lead to serious defects such as uncontrollable thickness or even film breakage during the stretching process of cast sheets.

[0005] Therefore, the market urgently needs to polymerize a PGA resin toughening agent and combine it with melt tackification technology to prepare a polyglycolic acid composite resin that is suitable for biaxial stretching process, in order to meet the demand for biodegradable high-barrier films. Summary of the Invention

[0006] To address the issues mentioned in the background art, such as "the poor toughness and rapid degradation rate of PGA resin limiting its application scenarios, and the easy thermal degradation of PGA resin during biaxial stretching," this application provides a high-toughness biaxially oriented polyglycolic acid film, the technical solution of which is as follows: The high-toughness biaxially oriented polyglycolic acid film provided in this application has a three-layer structure, including an upper surface layer, a core layer and a lower surface layer arranged from top to bottom; By weight, the upper surface layer comprises 1 to 10 parts of anti-sticking masterbatch and 90 to 99 parts of polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 1 to 10 parts of anti-sticking masterbatch and 90 to 99 parts of polyglycolic acid composite resin; The components of the polyglycolic acid composite resin, by weight, include: 40-60 parts of polyglycolic acid (PGA), 40-60 parts of polyglycolic acid toughening agent, 5-12 parts of hydroxy fatty acid ester (PHA), 1-5 parts of chain extender, and 0.1-1 parts of antioxidant. The hydroxy fatty acid ester is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and the molar content of the 3-hydroxyhexanoate unit is ≥25 mol%. The polyglycolic acid toughening agent is a copolymer obtained by polymerization reaction of ε-caprolactone monomer, glycolide, 1,4-succinic acid and 1,4-butanediol.

[0007] In some embodiments, the polyglycolic acid toughening agent is prepared using a method comprising the following steps: S100: By weight, 99.9–99.99 parts of ε-caprolactone monomer (CL monomer) and 0.01–0.1 parts of catalyst are mixed and subjected to microwave irradiation pretreatment for 2–10 min. S200: The pretreated material is stirred and refluxed at 80-110℃ for 1-2 hours to form polycaprolactone prepolymer; S300: Add 30-50 parts of glycolide monomer and 0.01-0.1 parts of catalyst to the polycaprolactone prepolymer, and stir and reflux at 120-180°C for 1-2 hours to form poly(caprolactone-glycolic acid) prepolymer, i.e. PCL prepolymer; S400: Add 3-8 parts of 1,4-succinic acid monomer, 3-8 parts of 1,4-butanediol monomer, 0.01-0.1 parts of catalyst and 0.1-1 parts of chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and stir and polymerize for 30-50 min under vacuum conditions of 170-220℃ and 100-2000 Pa to obtain the polyglycolic acid toughening agent.

[0008] In some embodiments, the catalyst is selected from one or more of stannous octoate, titanium acetylacetonate, monobutyltriisooctoate, and tetrabutyl titanate.

[0009] In some embodiments, the chain control agent is selected from one or more of vinyl acrylate (VA), diisocyanate (such as MDI or TDI), and polyethylene glycol methyl ether (MPEG).

[0010] In some embodiments, the components of the anti-sticking masterbatch, by weight, include: 1 to 5 parts of lubricant, 2 to 10 parts of opening agent, and 85 to 97 parts of polyglycolic acid toughening agent.

[0011] In some embodiments, the opening agent is selected from one or more of silica, calcium carbonate, organosilicon, and acrylic.

[0012] In some embodiments, the lubricant is selected from one or more of PE wax, oleamide, silicone wax, paraffin wax, and erucamide.

[0013] In some embodiments, the molar content of 3-hydroxyhexanoate units in the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) is 25 mol% to 40 mol.

[0014] In some embodiments, the melt index of the polyglycolic acid composite resin under test conditions of 190°C and 2.16 kg is 2-4 g / 10 min.

[0015] In some embodiments, the chain extender is selected from one or more of ethylene-methyl acrylate-glycidyl methacrylate (EMA-GMA or EMAG), styrene and glycidyl acrylate copolymer (ADR chain extender), hexamethylene diisocyanate (HDI), 4,4'-methylene diphenyl isocyanate (MDI), and polycarbodiimide.

[0016] In some embodiments, the antioxidant is selected from one or more of antioxidant 1010, antioxidant 1098, antioxidant 2246, antioxidant 168, antioxidant 330, antioxidant DNP, antioxidant SEED, and phosphite antioxidants.

[0017] In some embodiments, the total thickness of the high-toughness biaxially oriented polyglycolic acid film is 10–40 μm, the thickness of the upper and lower surface layers is 1–3 μm each, and the thickness of the core layer is 4–38 μm.

[0018] This application also provides a method for preparing a high-toughness biaxially oriented polyglycolic acid film as described above, which includes the following steps: S1: Mix the polyglycolic acid, polyglycolic acid toughening agent, hydroxy fatty acid ester, chain extender and antioxidant in the specified amounts evenly, melt-blend, extrude and granulate through a twin-screw extruder to obtain polyglycolic acid composite resin, and dry for later use; S2: Add the formulated amount of anti-sticking masterbatch and polyglycolic acid composite resin to extruder A to prepare the upper surface layer; add the polyglycolic acid composite resin to extruder B to prepare the core layer; add the formulated amount of anti-sticking masterbatch and polyglycolic acid composite resin to extruder C to prepare the lower surface layer; control the temperature of each extruder and T-die to 170~210℃. S3: Using the synchronous stretching method, the melt layers from the second step are co-extruded, cooled on a quenching roller at 30-35℃, pretreated in water at 50-60℃, and then subjected to biaxial stretching at a stretching temperature of 80-110℃ and a setting temperature of 100-150℃, with a stretching ratio of 2.0×2.0 to 5.5×5.5. S4: The biaxially oriented polyglycolic acid film obtained in step 3 is wound up and cut to obtain the final product.

[0019] Compared with existing technologies, the high-toughness biaxially oriented polyglycolic acid film provided in this application has the following advantages: This application proposes a method that significantly improves the toughness of PGA through synergistic modification with toughening agents and specific PHAs, solving the problems of high brittleness and easy film breakage under biaxial tension in pure PGA, enabling stable film formation in industrial applications. Combined with a chain extender and antioxidant system, it effectively inhibits thermal degradation during processing, resulting in stable melt flow and a wider processing window. The modified film retains the inherent high barrier properties of PGA, while exhibiting low haze, high transparency, and excellent mechanical and dimensional stability. The entire composition is fully biodegradable, and the surface anti-stick masterbatch further addresses the issue of easy adhesion in biodegradable films. Attached Figure Description

[0020] Figure 1 This is a layer structure diagram of the high-toughness biaxially oriented polyglycolic acid film provided in the embodiments of this application.

[0021] Among them, 10 is the upper surface layer; 20 is the core layer; and 30 is the lower surface layer. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. The technical features designed in the different implementations of this application described below can be combined with each other as long as they do not conflict with each other. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0023] In the description of this application, it should be noted that all terms used in this application (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains, and should not be construed as limiting this application; it should be further understood that the terms used in this application should be understood to have the same meaning as those in the context of this specification and the relevant field, and should not be understood in an idealized or overly formal sense, except as expressly defined in this application.

[0024] To verify the effectiveness of the proposed solution, the present application provides the following embodiments and comparative examples: Example: Example 1 like Figure 1 As shown, the membrane structure includes an upper surface layer 10, a core layer 20, and a lower surface layer 30 arranged sequentially from top to bottom; By weight, the upper surface layer 10 comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer 20 comprises 100 parts of polyglycolic acid composite resin; The lower surface layer 30 comprises 3 parts of anti-sticking masterbatch and 97 parts of polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 50 parts polyglycolic acid toughening agent, 10 parts P(3HB-co-3HHx), 2 parts ADR chain extender and 0.5 parts antioxidant 1010.

[0025] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0026] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0027] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0028] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0029] Example 2 like Figure 1 As shown, the membrane structure includes an upper surface layer 10, a core layer 20, and a lower surface layer 30 arranged sequentially from top to bottom; By weight, the upper surface layer 10 comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer 20 comprises 100 parts of polyglycolic acid composite resin; The lower surface layer 30 comprises 3 parts of anti-sticking masterbatch and 97 parts of polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 60 parts polyglycolic acid (PGA), 40 parts polyglycolic acid toughening agent, 5 parts P(3HB-co-3HHx), with a 3HHx content of 25 mol%, 1 part ADR chain extender, and 0.1 part antioxidant 1010.

[0030] The content of 3HHx in P(3HB-co-3HHx) is 25 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.99 parts by weight of CL monomer and 0.01 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 2 minutes.

[0031] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 80°C for 1 hour to form a low molecular weight PCL prepolymer.

[0032] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 30 parts by weight of GA monomer and 0.01 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 120°C for 1 hour to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0033] S400, high temperature and high vacuum polymerization: 3 parts by weight of 1,4-succinic acid monomer, 3 parts by weight of 1,4-butanediol monomer, 0.01 parts by weight of tetrabutyl titanate catalyst and 0.1 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent are added to the poly(caprolactone-glycolic acid) prepolymer. Then, the polymerization is carried out under high temperature of 170°C and high vacuum of 100 Pa for 30 min with continuous stirring to obtain the polyglycolic acid toughening agent. Example 3 like Figure 1 As shown, the membrane structure includes an upper surface layer 10, a core layer 20, and a lower surface layer 30 arranged sequentially from top to bottom; By weight, the upper surface layer 10 comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer 20 comprises 100 parts of polyglycolic acid composite resin; The lower surface layer 30 comprises 3 parts of anti-sticking masterbatch and 97 parts of polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 40 parts polyglycolic acid (PGA), 60 parts polyglycolic acid toughening agent, 12 parts P(3HB-co-3HHx), 5 parts ADR chain extender and 1 part antioxidant 1010.

[0034] The content of 3HHx in P(3HB-co-3HHx) is 40 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.9 parts by weight of CL monomer and 0.1 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 10 minutes.

[0035] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 110°C for 2 hours to form a low molecular weight PCL prepolymer.

[0036] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 50 parts by weight of GA monomer and 0.1 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 180°C for 2 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0037] S400, High Temperature and High Vacuum Polymerization: Add 8 parts by weight of 1,4-succinic acid monomer, 8 parts by weight of 1,4-butanediol monomer, 0.1 parts by weight of tetrabutyl titanate catalyst and 1 part by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 50 min at a high temperature of 220°C and a high vacuum of 2000 Pa to obtain the polyglycolic acid toughening agent; Example 4 like Figure 1 As shown, the membrane structure includes an upper surface layer 10, a core layer 20, and a lower surface layer 30 arranged sequentially from top to bottom; By weight, the upper surface layer 10 comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer 20 comprises 100 parts of polyglycolic acid composite resin; The lower surface layer 30 comprises 3 parts of anti-sticking masterbatch and 97 parts of polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 50 parts polyglycolic acid toughening agent, 10 parts P(3HB-co-3HHx), 2 parts EMAG chain extender and 0.5 parts antioxidant 1098.

[0038] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of monobutyltriisooctanoate tin catalyst were mixed and microwave irradiated for 5 minutes.

[0039] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0040] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of monobutyltriisooctanoate tin catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0041] S400, High-Temperature High-Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of titanium acetylacetone catalyst and 0.5 parts by weight of vinyl acrylate (VA) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0042] This application also provides a method for preparing the anti-sticking masterbatch of the above embodiments: Three parts of erucamide, five parts of silica and 92 parts of polyglycolic acid toughening agent were added to a twin-screw extruder and melt-extruded at 160-210℃. The mixture was then stretched, cooled, pelletized and dried to obtain the anti-sticking masterbatch.

[0043] This application also provides a method for preparing the thin film of the above embodiments as follows: Step 1: Polyglycolic acid (PGA), polyglycolic acid toughening agent, hydroxy fatty acid ester (PHA), chain extender and antioxidant are mixed in proportion, melt-blended, extruded and granulated by a twin-screw extruder, and the resulting polyglycolic acid composite resin is dried for later use; Step 2: Add the anti-sticking masterbatch and polyglycolic acid composite resin to extruder A in proportion to make the upper surface layer 10; add the polyglycolic acid composite resin to extruder B to make the core layer 20; add the anti-sticking masterbatch and polyglycolic acid composite resin to extruder C in proportion to make the lower surface layer 30; the temperature of each extruder and T-die is controlled between 170 and 210℃. Step 3: Using the LISIM simultaneous stretching method, the layers from Step 2 are extruded, rapidly cooled and cast on 32°C quenching rollers, pretreated in water at 55°C, and then subjected to biaxial stretching at 90°C and a setting temperature of 130°C, with a stretching ratio of 3.0. 3.0; Step 4: Roll up, slit, and package the biaxially oriented polyglycolic acid film obtained in step 3.

[0044] Comparative example: Comparative Example 1 (Ordinary PGA film) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the upper surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid (PGA) resin; The core layer comprises 100 parts of polyglycolic acid (PGA) resin; The lower surface layer comprises 3 parts of anti-sticking masterbatch and 97 parts of polyglycolic acid (PGA) resin.

[0045] The difference between its preparation method and the example is that the temperature of each extruder and T-die is controlled between 190 and 230°C.

[0046] Comparative Example 2 (Compared to the Example: No PGA toughening agent added) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the upper surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 10 parts P(3HB-co-3HHx), 2 parts ADR chain extender and 0.5 parts antioxidant 1010.

[0047] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The difference between its preparation method and the example is that the temperature of each extruder and T-die is controlled between 190 and 230°C.

[0048] Comparative Example 3 (Compared to the Example: No PHA resin added) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the upper surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 50 parts polyglycolic acid toughening agent, 2 parts ADR chain extender and 0.5 parts antioxidant 1010.

[0049] The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0050] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0051] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0052] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0053] The preparation method is the same as in the examples.

[0054] Comparative Example 4 (Compared to the Example: no chain extender ADR added) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the upper surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 50 parts polyglycolic acid toughening agent, 10 parts P(3HB-co-3HHx) and 0.5 parts antioxidant 1010.

[0055] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0056] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0057] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0058] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0059] The preparation method is the same as in the examples.

[0060] Comparative Example 5 (Compared to Example 1: No antioxidants added) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the upper surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 50 parts polyglycolic acid toughening agent, 10 parts P(3HB-co-3HHx) and 2 parts ADR chain extender.

[0061] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0062] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0063] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0064] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0065] Comparative Example 6 (Compared to the Example: HHx content in PHA is 10 mol%) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the upper surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 50 parts polyglycolic acid toughening agent, 10 parts P(3HB-co-3HHx), 2 parts ADR chain extender and 0.5 parts antioxidant 1010.

[0066] The content of 3HHx in P(3HB-co-3HHx) is 10 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0067] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0068] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0069] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0070] The preparation method is the same as in the examples.

[0071] Comparative Example 7 (lower proportion of adjuvants compared to the Example) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the components of the upper surface layer are: 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The core layer consists of 100 parts of polyglycolic acid composite resin. The components of the lower surface layer are: 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 25 parts polyglycolic acid toughening agent, 3 parts P(3HB-co-3HHx), 0.5 parts ADR chain extender and 0.01 parts antioxidant 1010.

[0072] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0073] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0074] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0075] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0076] The preparation method is the same as in the examples.

[0077] Comparative Example 8 (Higher content of additives compared to the Example) The membrane structure includes an upper surface layer, a core layer, and a lower surface layer arranged sequentially from top to bottom; By weight, the components of the upper surface layer are: 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The core layer consists of 100 parts of polyglycolic acid composite resin. The components of the lower surface layer are: 3 parts anti-sticking masterbatch and 97 parts polyglycolic acid composite resin. The polyglycolic acid composite resin comprises 50 parts polyglycolic acid (PGA), 100 parts polyglycolic acid toughening agent, 30 parts P(3HB-co-3HHx), 6 parts ADR chain extender and 2 parts antioxidant 1010.

[0078] The content of 3HHx in P(3HB-co-3HHx) is 30 mol% The polyglycolic acid toughening agent is prepared by the following steps: S100, Microwave Pretreatment: Before the reaction, 99.95 parts by weight of CL monomer and 0.05 parts by weight of stannous octoate catalyst were mixed and microwave irradiated for 5 minutes.

[0079] S200, PCL prepolymerization: The pretreated material is stirred and refluxed at 105℃ for 1.5 hours to form a low molecular weight PCL prepolymer.

[0080] S300, Poly(caprolactone-glycolic acid) prepolymer: Add 40 parts by weight of GA monomer and 0.05 parts by weight of stannous octoate catalyst to the PCL prepolymer, and then stir and reflux at 160°C for 1.5 hours to form a medium molecular weight poly(caprolactone-glycolic acid) prepolymer.

[0081] S400, High Temperature and High Vacuum Polymerization: Add 5 parts by weight of 1,4-succinic acid monomer, 5 parts by weight of 1,4-butanediol monomer, 0.05 parts by weight of tetrabutyl titanate catalyst and 0.5 parts by weight of polyethylene glycol methyl ether (MPEG) chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and then continuously stir and polymerize for 45 minutes at a high temperature of 210°C and a high vacuum of 1000 Pa to obtain the polyglycolic acid toughening agent.

[0082] The preparation method is the same as in the examples.

[0083] Comparative Example 9 (Compared to the Examples: the polyglycolic acid toughening agent was replaced by an equal mass) The only difference from Example 1 is that poly(lactide-glycolic acid) toughening agent is replaced with an equal mass of poly(lactide-glycolic acid) copolymer (PLGA). All other processes and conditions remain unchanged.

[0084] Comparative Example 10 (Compared to the Examples: the amount of polyglycolic acid toughening agent added is lower) The only difference from Example 1 is that the amount of polyglycolic acid toughening agent added to the polyglycolic acid composite resin is 10 parts. All other processes and conditions remain unchanged.

[0085] Comparative Example 11 (Compared to the Examples: the amount of polyglycolic acid toughening agent added is higher) The only difference from Example 1 is that the amount of polyglycolic acid toughening agent added to the polyglycolic acid composite resin is 100 parts. All other processes and conditions remain unchanged.

[0086] Comparative Example 12 The only difference from Example 1 is that PBAT is used in place of the polyhydroxyalkanoate (PHA) copolymer. All other processes and conditions remain the same.

[0087] The films prepared in the examples and comparative examples were subjected to performance tests: 1. The testing standards or methods are as follows: Thickness: Tested in accordance with GB / T20220-2006 "Average thickness of plastic film and sheet samples, average thickness of rolls and surface area per unit mass"; Haze: Tested according to GB / T2410-2008 "Standard for Determination of Light Transmittance and Haze of Transparent Plastics"; Tensile properties: Tested according to GB / T1040-3 "Determination of tensile properties of plastics - Part 3: Test conditions for thin plastics and sheets"; Heat shrinkage rate: GB / T12027-2004 Test method for dimensional change rate of plastic films and sheets under heat, test temperature is 120℃, test time is 10min.

[0088] Water vapor transmission rate: The water vapor transmission rate of the thin film was tested according to GB / T1037-1988; Oxygen permeability: The oxygen permeability of the membrane was tested according to GB / T1038-2000; the test conditions were 23℃ and 50%RH.

[0089] Film-forming properties of stretched films: No film formation is indicated by X; continuous film breakage during stretching is indicated by... ○ indicates poor film thickness and many crystal points, which does not meet the requirements; ◎ indicates good film thickness and few crystal points, which meets the requirements.

[0090] 2. The test evaluation results are shown in Table 1-4: Table 1

[0091] Table 2

[0092] Table 3

[0093] Table 4

[0094] The data above shows that: (1) Example The high-toughness biaxially oriented polyglycolic acid film prepared in the embodiments of this application has excellent mechanical properties, barrier properties, optical properties, flexibility (low tensile modulus) and dimensional stability (low thermal shrinkage), making it particularly suitable for food packaging, which can extend the shelf life of food and provide more options for biodegradable film materials.

[0095] (2) Comparative examples of missing key components Comparative Example 1 used pure PGA resin without polyglycolic acid composite resin. The processing temperature needed to be increased to 190-230℃, but film formation still failed (evaluation X). This indicates that pure PGA is unsuitable for biaxial orientation stretching process due to its poor toughness and thermal stability. The construction of a composite resin system is a prerequisite for film formation.

[0096] Comparative Example 2 did not add the polyglycolic acid toughening agent specifically synthesized in this application to the composite resin, and was composed only of PGA, PHA, chain extender and antioxidant. It also failed to form a film (evaluation X), proving that the toughening agent of this application is the core component for achieving material toughness and processing stability, and cannot be omitted.

[0097] Comparative Example 3, without the addition of PHA to the composite resin, could barely form a film (evaluation: ○), but its performance was significantly degraded: the elongation at break decreased to 108%, and the tensile modulus increased to 4020 MPa, indicating that the film became brittle and its toughness decreased; the water vapor permeability increased to 25.2 g / m³. 2 • After 24 hours, the barrier properties also decreased. This demonstrates a synergistic toughening effect between PHA and the toughening agent in this application; only by using both together can a balance of high toughness and good barrier properties be achieved.

[0098] Comparative Example 4, which did not add a chain extender to the composite resin, could form a film, but the quality was poor (evaluated as ○). The tensile strength dropped sharply from 284 MPa in Example 1 to 148 MPa, and the elongation at break dropped from 142% to 89%, resulting in a significant decrease in mechanical properties. Furthermore, the film thickness was uneven and contained numerous crystal points. This demonstrates that chain extenders are crucial for improving melt strength, enhancing processing stability, and maintaining mechanical properties.

[0099] Comparative Example 5, without the addition of antioxidants to the composite resin, showed continuous film breakage during stretching (evaluated as...). The tensile strength decreased to 189 MPa, the elongation at break decreased to 94%, the haze increased to 4.15%, and the film showed yellowing. This indicates that antioxidants are indispensable for inhibiting the thermal degradation of PGA during high-temperature processing; the lack of antioxidants will lead to material degradation, performance deterioration, and processing failure.

[0100] (3) Comparative examples of PHA composition deviation Comparative Example 6 reduced the molar content of 3-hydroxyhexanoate (HHx) units in PHA from ≥25 mol% as specified in this application to 10 mol%. Although film formation was achieved (evaluated as ◎), the haze increased dramatically from 1.18% in Example 1 to 11.5%, nearly tenfold. The film exhibited severe whitening and a significant decrease in transparency; the elongation at break decreased to 103%, and the toughness also decreased. This demonstrates that an HHx content of ≥25 mol% is a critical threshold for achieving high transparency. Below this threshold, severe degradation of optical performance occurs due to poor compatibility between PHA and the substrate. This compositional limitation is critical and not a conventional choice in the art.

[0101] (4) Comparative examples of component content deviations Comparative Example 7 reduced the amounts of toughening agent, PHA, chain extender, and antioxidant to below the lower limit of this application (25 parts toughening agent, 3 parts PHA, 0.5 parts chain extender, and 0.01 parts antioxidant). The result was that no film could be formed (evaluation X). This proves that when the content of each component is below the range defined in this application, sufficient toughening effect, melt strength, and thermal stability cannot be obtained. Therefore, the lower limit of the content in this application is necessary.

[0102] Comparative Example 8 increased the amounts of toughening agent, PHA, chain extender, and antioxidant to levels exceeding the limits specified in this application (100 parts toughening agent, 30 parts PHA, 6 parts chain extender, and 2 parts antioxidant). Although film formation was achieved, the quality was poor (evaluated as ○), and performance was severely degraded: oxygen permeability decreased from 0.89 cc / m³ in Example 1. 2 ·day surged to 8.5cc / m 2 • Daily water vapor transmission rate increased 24 times; water vapor permeability increased from 15.2 g / m³. 2 • Increased to 35.4 g / m² in 24 hours 2 • After 24 hours, the temperature increased threefold; tensile strength decreased from 284 MPa to 115 MPa, a decrease of 60%; elongation at break decreased from 142% to 87%; heat shrinkage increased from 1.21% to 6.7%, and dimensional stability decreased significantly. This demonstrates that when the content of each component exceeds the limits specified in this application, not only is it impossible to further improve performance, but it also seriously damages barrier properties, mechanical properties, and dimensional stability. The upper limit of the content in this application is critical.

[0103] (5) Comparative examples of selective substitution of specific components (Comparative Examples 9-12) Comparative Example 9 used poly(lactide-glycolic acid) copolymer (PLGA) in place of the polyglycolic acid toughening agent specifically synthesized in this application. Although film formation was achieved (evaluated as ◎), the oxygen permeability increased to 3.13 cc / m³. 2 • Daily water vapor permeability increased to 45.1 g / m 2 • After 24 hours, the barrier properties decreased significantly; the tensile modulus increased to 4526 MPa, while the elongation at break decreased to 101%, and the film became brittle and its toughness decreased. This indicates that the chemical structure of the toughening agent in this application is irreplaceable and cannot be achieved by PLGA, which is conventionally selected in the art.

[0104] Comparative Example 10 reduced the amount of polyglycolic acid toughening agent to 10 parts (below the lower limit of 40 parts in this application), and the result was that no film could be formed (evaluation X), proving that when the amount of toughening agent is below the range defined in this application, it cannot provide sufficient toughening effect and melt strength, and the lower limit of toughening agent amount in this application is necessary.

[0105] Comparative Example 11 increased the amount of polyglycolic acid toughening agent to 100 parts (exceeding the upper limit of 60 parts in this application). Although film formation was achieved (evaluated as ◎), the oxygen permeability increased to 3.02 cc / m³. 2 • Daily water vapor permeability increased to 30.3 g / m 2 • After 24 hours, the barrier properties decreased; the heat shrinkage rate increased to 5.21%, and the dimensional stability deteriorated significantly. This demonstrates that when the amount of toughening agent exceeds the limits specified in this application, it will damage the barrier properties and dimensional stability of the film. The upper limit of the toughening agent amount in this application is critical.

[0106] Comparative Example 12, which replaced the specific component of PHA (poly(3-hydroxybutyrate-co-3-hydroxyhexanoate)) in this application with PBAT of similar quality, was able to form a film (evaluated as ◎), but the haze increased to 4.5%, the transparency decreased, and the oxygen permeability increased to 5.19 cc / m. 2 • Daily water vapor permeability increased to 34.2 g / m 2 • After 24 hours, the barrier properties deteriorated significantly; the tensile modulus increased to 3550 MPa, the elongation at break decreased to 128%, and the toughness also decreased. This indicates that the specific PHA and its compositional limitations in this application are irreplaceable and cannot be replaced by ordinary biodegradable polyesters (such as PBAT).

[0107] (6) Overall Conclusion Through systematic analysis of the performance data of the embodiments and comparative examples, the following conclusions can be drawn: First, the "polyglycolic acid composite resin" system constructed in this application (containing a specific toughening agent, PHA with HHx ≥ 25 mol%, chain extender, and antioxidant) is the foundation for achieving stable film formation and obtaining excellent comprehensive performance in the biaxial orientation process. The absence of any key component (Comparative Examples 1-5) will result in failure to form a film or a significant decrease in performance.

[0108] Second, the limitation of HHx content in PHA (≥25mol%) in this application is a key threshold for achieving high transparency. Below this threshold, the haze will increase sharply (Comparative Example 6). This technical feature is critical and non-obvious.

[0109] Third, the limits on the content of each component in this application have strict critical thresholds. If the content is below the lower limit (Comparative Example 7), film formation is impossible; if the content is above the upper limit (Comparative Example 8), barrier properties, mechanical properties, and dimensional stability are severely degraded. This indicates that the composition range of this application is not simply a matter of preference, but a necessary condition for achieving excellent overall performance.

[0110] Fourth, this application achieves balanced and excellent performance in six dimensions—film-forming properties, barrier properties, transparency, toughness, strength, and dimensional stability—through the synergistic effect of specific toughening agents and PHA, as well as the combination of chain extenders and antioxidants. This is something that no single comparative example can achieve.

[0111] In summary, the overall technical effect of the technical solution of this application is significantly better than that of the other comparative examples. The combination of its technical features is synergistic and non-obvious, providing sufficient and strong data support for the inventiveness of this application.

[0112] The technical features, design concepts, and beneficial effects of this application can be summarized as follows: Design concept: Addressing the industry pain points of pure polyglycolic acid (PGA), which possesses intrinsic high barrier properties and fully biodegradable characteristics, but also suffers from high brittleness and poor toughness, poor compatibility with traditional toughening agents, easy thermal degradation during processing, and excessively rapid natural degradation rate that limits its application scenarios, this application's overall design concept is as follows: starting from two dimensions, molecular modification and processing compatibility, firstly, a dedicated toughening system adapted to PGA is developed to solve the compatibility and toughening problems, then, the degradation and processing thermal stability issues are solved by synergistic regulation of molecular properties through two components, and finally, melt-bonding technology is used to ensure the stability of industrial production, thus breaking through the application bottleneck of PGA films.

[0113] II. Technical Features Compatible toughening agent design: Self-formulated polyglycolic acid toughening agents overcome the defects of traditional degradable toughening agents and poor compatibility with PGA from the root, and toughening modification can be achieved without destroying the intrinsic properties of PGA.

[0114] Two-component synergistic toughening system: Based on a dedicated toughening agent, it is combined with a weak hydrogen bond, low melting point, amorphous hydroxy fatty acid ester (PHA) copolymer. The two types of components form a synergistic effect, jointly achieving synergistic toughening of PGA resin, with a modification effect far superior to that of a single toughening component.

[0115] Dual-component molecular-level regulation: Two types of toughening components can achieve dual molecular regulation: on the one hand, they can reduce the content of hydroxyl and ester groups in the PGA matrix, weakening chain rigidity and reducing degradation active sites at the molecular level; on the other hand, they can reduce the overall polarity and melting point of PGA, avoiding the risk of processing thermal degradation from the root.

[0116] Melt hardening processing technology: A melt hardening process was developed to enhance the melt strength of PGA composite resin by introducing chain extenders, thus ensuring the stability of the film production process; at the same time, antioxidants were introduced to further block degradation side reactions during thermal processing.

[0117] III. Beneficial Effects The toughening modification process can completely preserve the mechanical properties and high transparency of the PGA film, solving the pain point of traditional toughening solutions that "toughening always sacrifices performance"; The dual-component synergistic toughening can significantly improve the toughness of the PGA matrix, completely solving the problems of high brittleness and easy film breakage under biaxial tension in pure PGA, and enabling stable film formation in industrial applications. The degradation rate of PGA can be controlled to a reasonable range suitable for packaging and other scenarios, while effectively inhibiting thermal degradation during processing, thus solving the problem of limited application scenarios caused by poor toughness, rapid degradation and unstable processing of PGA. Melt adhesion technology can further improve production stability, broaden the processing window, and increase product yield. The final film still retains its fully biodegradable characteristics, which meets the needs of green and environmentally friendly development.

[0118] In summary, this application's solution significantly improves the toughness of PGA through synergistic modification with toughening agents and specific PHAs, solving the problems of high brittleness and easy film breakage under biaxial tension in pure PGA, enabling stable film formation in industrial applications. Combined with a chain extender and antioxidant system, it effectively inhibits thermal degradation during processing, resulting in stable melt flow and a wider processing window. The modified film retains the inherent high barrier properties of PGA, while exhibiting low haze, high transparency, and excellent mechanical and dimensional stability. The overall composition is fully biodegradable, and the surface anti-stick masterbatch further addresses the issue of easy adhesion in biodegradable films.

[0119] It should be noted that: LISIM is an abbreviation for Linear Synchronous Stretching. As the fourth generation of BOPA film technology, LISIM technology is currently the most advanced synchronous stretching technology in the industry. It combines the advantages of step-by-step stretching and mechanical synchronous stretching methods with magnetic levitation technology, and the resulting linear synchronous film combines the advantages of good mechanical strength, good ductility and good uniformity.

[0120] In this article, “~” is used to represent the range of values, and the range of values ​​represented by this expression includes two endpoint values.

[0121] In summary, the specific parameters or some commonly used reagents or raw materials in the above embodiments are specific or preferred embodiments under the concept of this application, and not limitations thereof; where no specific technology or conditions are specified in the embodiments, they shall be carried out in accordance with the technology or conditions described in the literature in this field or in accordance with the product instructions; where the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be obtained commercially.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application 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 or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A high-toughness biaxially oriented polyglycolic acid film, characterized in that, The high-toughness biaxially oriented polyglycolic acid film has a three-layer structure, including an upper surface layer, a core layer, and a lower surface layer arranged from top to bottom. By weight, the upper surface layer comprises 1 to 10 parts of anti-sticking masterbatch and 90 to 99 parts of polyglycolic acid composite resin; The core layer comprises 100 parts of polyglycolic acid composite resin; The lower surface layer comprises 1 to 10 parts of anti-sticking masterbatch and 90 to 99 parts of polyglycolic acid composite resin; The components of the polyglycolic acid composite resin, by weight, include: 40-60 parts of polyglycolic acid, 40-60 parts of polyglycolic acid toughening agent, 5-12 parts of hydroxy fatty acid ester, 1-5 parts of chain extender, and 0.1-1 parts of antioxidant. The hydroxy fatty acid ester is poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), and the molar content of the 3-hydroxyhexanoate unit is ≥25 mol%. The polyglycolic acid toughening agent is a copolymer obtained by polymerization reaction of ε-caprolactone monomer, glycolide, 1,4-succinic acid and 1,4-butanediol.

2. The high-toughness biaxially oriented polyglycolic acid film according to claim 1, characterized in that, The polyglycolic acid toughening agent is prepared using a method comprising the following steps: S100: Mix 99.9 to 99.99 parts by weight of ε-caprolactone monomer and 0.01 to 0.1 parts by weight of catalyst, and pretreat by microwave irradiation for 2 to 10 minutes. S200: The pretreated material is stirred and refluxed at 80-110℃ for 1-2 hours to form polycaprolactone prepolymer; S300: Add 30-50 parts of glycolide monomer and 0.01-0.1 parts of catalyst to the polycaprolactone prepolymer, and stir and reflux at 120-180°C for 1-2 hours to form poly(caprolactone-glycolic acid) prepolymer; S400: Add 3-8 parts of 1,4-succinic acid monomer, 3-8 parts of 1,4-butanediol monomer, 0.01-0.1 parts of catalyst and 0.1-1 parts of chain control agent to the poly(caprolactone-glycolic acid) prepolymer, and stir and polymerize for 30-50 min under vacuum conditions of 170-220℃ and 100-2000 Pa to obtain the polyglycolic acid toughening agent.

3. The high-toughness biaxially oriented polyglycolic acid film according to claim 2, characterized in that, The catalyst is selected from one or more of stannous octoate, titanium acetylacetonate, monobutyltriisooctanoate, and tetrabutyl titanate. The chain control agent is selected from one or more of vinyl acrylate, diisocyanate, and polyethylene glycol methyl ether.

4. The high-toughness biaxially oriented polyglycolic acid film according to claim 1, characterized in that, The components of the anti-sticking masterbatch, by weight, include: 1-5 parts of lubricant, 2-10 parts of opening agent, and 85-97 parts of polyglycolic acid toughening agent.

5. The high-toughness biaxially oriented polyglycolic acid film according to claim 4, characterized in that, The opening agent is selected from one or more of silicon dioxide, calcium carbonate, organosilicon, and acrylic. The lubricant is selected from one or more of PE wax, oleamide, silicone wax, paraffin wax, and erucamide.

6. The high-toughness biaxially oriented polyglycolic acid film according to claim 1, characterized in that, In the poly(3-hydroxybutyrate-co-3-hydroxyhexanoate), the molar content of 3-hydroxyhexanoate units is 25 mol% to 40 mol.

7. The high-toughness biaxially oriented polyglycolic acid film according to claim 1, characterized in that, The melt index of the polyglycolic acid composite resin under test conditions of 190℃ and 2.16kg is 2-4g / 10min.

8. The high-toughness biaxially oriented polyglycolic acid film according to claim 1, characterized in that: The chain extender is selected from one or more of the following: ethylene-methyl acrylate-glycidyl methacrylate copolymer, styrene-glycidyl acrylate copolymer, hexamethylene diisocyanate, 4,4'-methylene diphenyl isocyanate, and polycarbodiimide. The antioxidant is selected from one or more of antioxidants 1010, 1098, 2246, 168, 330, DNP, SEED, and phosphite antioxidants.

9. The high-toughness biaxially oriented polyglycolic acid film according to claim 1, characterized in that, The total thickness of the high-toughness biaxially oriented polyglycolic acid film is 10–40 μm, the thickness of the upper and lower surface layers is 1–3 μm, and the thickness of the core layer is 4–38 μm.

10. A method for preparing a high-toughness biaxially oriented polyglycolic acid film as described in any one of claims 1 to 9, characterized in that, Includes the following steps: S1: Mix the polyglycolic acid, polyglycolic acid toughening agent, hydroxy fatty acid ester, chain extender and antioxidant in the specified amounts evenly, melt-blend, extrude and granulate through a twin-screw extruder to obtain polyglycolic acid composite resin, and dry for later use; S2: Add the formulated amount of anti-sticking masterbatch and polyglycolic acid composite resin to extruder A to prepare the upper surface layer; add the polyglycolic acid composite resin to extruder B to prepare the core layer; add the formulated amount of anti-sticking masterbatch and polyglycolic acid composite resin to extruder C to prepare the lower surface layer; control the temperature of each extruder and T-die to 170~210℃. S3: Using the synchronous stretching method, the melt layers from the second step are co-extruded, cooled on a quenching roller at 30-35℃, pretreated in water at 50-60℃, and then subjected to biaxial stretching at a stretching temperature of 80-110℃ and a setting temperature of 100-150℃, with a stretching ratio of 2.0×2.0 to 5.5×5.

5. S4: The biaxially oriented polyglycolic acid film obtained in step 3 is wound up and cut to obtain the final product.

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