A high-toughness polyglycolide copolymer, and a preparation method and application thereof

Abstract

The application discloses a high-toughness polyglycolide copolymer and a preparation method and application thereof. The polyglycolide copolymer is an A-B diblock copolymer and / or an A-B-A triblock copolymer. Block A is a copolymer segment formed by polyglycolide and a lactide or lactone with more than four carbon atoms except for glycolide, and block B is an aliphatic-aromatic copolyester. The polyglycolide copolymer has high toughness and good strength-modulus-toughness balance. The preparation method directly prepares the block copolymer of the aliphatic-aromatic copolyester and the (polyglycolide and the random copolymer of the lactide or lactone with more than four carbon atoms except for glycolide) through a one-step method, and the preparation method is simpler, the reaction condition is more relaxed, and continuous preparation can be realized.

Description

Technical Field

[0001] This invention relates to a copolymer, and more specifically, to a high-toughness polyglycolic acid copolymer, its preparation method, and its application. Background Technology

[0002] Polyglycolic acid (PGA), also known as polyglycolic acid or polyhydroxyacetic acid, is a fully biodegradable material that can completely degrade under natural conditions within 1-3 months. PGA also possesses excellent mechanical properties, strong O2 and CO2 barrier properties, and is non-toxic, harmless, and environmentally friendly. It has obtained certification as a safe biodegradable plastic material in the United States, the European Union, and Japan. However, PGA not only has a high melting point but also poor toughness at room temperature, which greatly limits its application in a wider range of fields.

[0003] Aliphatic-aromatic copolyesters combine the high toughness and good biodegradability of aliphatic polyesters with the high strength and excellent thermal properties of aromatic polyesters. The most representative and widely used aliphatic-aromatic copolyesters are polybutylene adipate terephthalate (PBAT) and polybutylene terephthalate terephthalate (PBST). The former is a random copolymer of butylene adipate (BA) and butylene terephthalate (BT), while the latter is a random copolymer of butylene succinate (BS) and butylene terephthalate (BT). Driven by environmental policies, PBAT is now widely used in biodegradable shopping bags, packaging, agricultural films, and textiles. Compared to PBAT, PBST possesses equally excellent thermal and mechanical properties. Furthermore, succinic acid can be obtained from bio-based raw materials through fermentation, thus synthesizing partially bio-based PBST, which helps reduce carbon emissions. However, PGA has poor compatibility with PBAT / PBST, and the toughness of PGA materials cannot be improved by simply blending it with PBAT / PBST.

[0004] CN109762143A (Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, 2019.05.17) discloses a hydrolyzable copolyester, which is a random copolymer composed of segments of a difficult-to-hydrolyze polyester (PBS, PBAT, or PBST, etc.) and segments of an easily hydrolyzeable polyester (PGA or PGLA). It exhibits good mechanical and hydrolytic properties, with a tensile strength of 25-45 MPa and an elongation at break of 80-800%. However, its synthesis route involves dehydration polycondensation of monomers such as succinic acid and butanediol, which requires stringent conditions, a complex and time-consuming reaction process, low efficiency, and makes it difficult to obtain high molecular weight copolymers.

[0005] CN 111647144 A (Shanghai Pujing Chemical, 2020.9.11) discloses a method for adjusting the molecular chain structure of polyglycolic acid (PGA). This method alters the molecular structure by adding functional groups (hydrophilic / hydrophobic groups -OH, -COOR, etc.) or chain segments (branching, copolymerization, etc.) with specific performance characteristics, thereby changing the original molecular properties of PGA. One example involves using polyethylene glycol (PEG) as an initiator; however, the PEG used has a low molecular weight, with a maximum of only 12000 g / mol, and the addition amount is only 5%, resulting in minimal performance improvement. Furthermore, the reaction is a low-temperature nitrogen-protected reaction with harsh conditions and a long reaction time (at least 50 minutes). This prolonged reaction time can lead to the thermal decomposition or degradation of PGA, forming colored or odorous byproducts and reducing the quality of the PGA product.

[0006] In summary, there is a persistent need in this field to improve the toughness of polyglycolic acid copolymers. Summary of the Invention

[0007] In view of the existing technical problems, the present invention provides a high-toughness polyglycolic acid copolymer, its preparation method and application. The polyglycolic acid copolymer not only has high toughness, but also has a good strength-modulus-toughness balance.

[0008] One objective of this invention is to provide a polyglycolic acid copolymer, wherein the polyglycolic acid copolymer is an AB diblock copolymer and / or an ABA triblock copolymer; wherein block A is a copolymer segment formed by polyglycolic acid and lactones or lactones of C4 or above other than glycolide, and block B is an aliphatic-aromatic copolyester.

[0009] According to the present invention, the product of the present invention is a polyglycolic acid copolymer that is an AB diblock copolymer and / or an ABA triblock copolymer; rather than a physical blend of the two copolymers. The detection and verification methods include, but are not limited to, 1H NMR spectroscopy (…). 1 H-NMR detection and Fourier transform infrared absorption spectroscopy (FTIR) detection.

[0010] According to the present invention, the selection range of the contents of block A and block B is relatively wide. In a preferred embodiment of the present invention, the content of block A is 50%-92% by mass, preferably 60%-90% by mass, relative to the total mass of block A and block B; and the content of block B is 8%-50% by mass, preferably 10%-40% by mass.

[0011] According to the present invention, preferably, the content of block A is 50%-92% by mass relative to the total mass of block A and block B, preferably 60%-90% by mass, for example, 60%, 70%, 80%, 90% by mass, and any two values ​​or any range.

[0012] According to the present invention, preferably, the content of block B is 8%-50% by mass relative to the total mass of block A and block B, preferably 10%-40% by mass, for example, 10%, 20%, 30%, 40% by mass, and any two values ​​or any range thereof.

[0013] More preferably, by mass, the content of block A is 70%-90% by mass and the content of block B is 10%-30% by mass relative to the total mass of block A and block B.

[0014] In a preferred embodiment of the present invention, block A is a copolymer segment formed by random copolymerization of glycolide and lactones or lactones with a C4 or higher content other than glycolide.

[0015] According to the present invention, the lactones or lactones with C4 or more other than glycolide include, but are not limited to, at least one of lactide, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, δ-caprolactone, and ε-caprolactone, preferably lactide.

[0016] According to the present invention, the polyglycolic acid segment in block A With lactone or lactone segments of C4 or higher, other than glycolide The mass ratio can be selected over a wide range. In a preferred embodiment of the present invention, the polyglycolic acid segment in block A... With lactone or lactone segments of C4 or higher, other than glycolide The mass ratio is (0.1-10):1, preferably (1-5):1. According to the present invention, the block B is an aliphatic-aromatic copolyester, and its selection range is relatively wide. In a preferred embodiment of the present invention, the block B is a copolyester segment formed by polycondensation of an aliphatic diol containing an aliphatic diacid and / or an aromatic diacid.

[0017] Preferably, block B is a copolyester segment formed by condensation of at least one of α,ω-aliphatic diacid and aromatic diacid containing 2-18 main chain carbon atoms with at least one aliphatic diol.

[0018] R is C k H 2k+1t and k are both integers not less than 0, and t and k are not both 0 at the same time.

[0019] In a more preferred embodiment of the present invention, block B is a polybutylene adipate terephthalate (PBAT) segment and / or a polybutylene terephthalate succinate (PBST) segment. More preferably, block B is at least one selected from polybutylene adipate-co-terephthalate, polyethylene adipate-co-terephthalate, polyethylene succinate-co-terephthalate, and polybutylene succinate-co-terephthalate.

[0020] According to the present invention, the selection range of block B is relatively wide. In a preferred embodiment of the present invention, the weight-average molecular weight of block B is 1,000-200,000 g / mol, preferably 20,000-100,000 g / mol, for example, it can be 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, as well as any two values ​​or ranges.

[0021] More preferably, the weight-average molecular weight of block B is 30,000-100,000.

[0022] According to the present invention, the weight-average molecular weight of the polyglycolic acid copolymer has a wide selection range. In a preferred embodiment of the present invention, the weight-average molecular weight of the polyglycolic acid copolymer is 20,000-300,000 g / mol, preferably 80,000-200,000 g / mol. For example, it can be 80,000, 100,000, 120,000, 140,000, 160,000, 180,000, 200,000, or any two values ​​or ranges.

[0023] According to the present invention, the molecular weight distribution coefficient of the polyglycolic acid copolymer has a wide range of selection. In a preferred embodiment of the present invention, the molecular weight distribution coefficient of the polyglycolic acid copolymer is 1.01-3, preferably 1.01-2.

[0024] The content of block A, the content of block B, and the polyglycolic acid segment in block A With lactone or lactone segments of C4 or higher, other than glycolide The mass ratio, type of block B, weight-average molecular weight of block B, weight-average molecular weight of the polyethylene glycol copolymer, and molecular weight distribution coefficient of the polyethylene glycol copolymer can be detected by conventional methods in the art, including but not limited to gel permeation chromatography (GPC). In the embodiments of the present invention, the content of block A, the content of block B, and the polyethylene glycol segment in block A are... With lactone or lactone segments of C4 or higher, other than glycolide The mass ratio, etc., can also be calculated by the amount of material fed.

[0025] In one embodiment of the invention, for example, the block copolymer contains copolymers with structural formulas as shown in formula (I) and / or formula (II): In equations (I) and (II), R1 is independently... or Let m, n, p, q, x, y, and z represent the degree of aggregation. p and q are independent integers ranging from 1 to 1000, preferably from 10 to 500. x, y, and z are independent integers ranging from 50 to 5000, preferably from 1000 to 2000. m and n are independent integers ranging from 50 to 1000, preferably from 300 to 600. R represents C. k H 2k+1 Both t and k are integers not less than 0, and t and k are not both 0. In a preferred embodiment of the present invention, the polyglycolic acid copolymer is prepared by copolymerization of raw materials including glycolide, lactones or lactones of C4 or higher other than glycolide, and aliphatic-aromatic copolyesters.

[0026] According to the present invention, the copolymer of the present invention has a good balance of strength, modulus and toughness. In a preferred embodiment of the present invention, the tensile strength of the copolymer of the present invention is 25-100 MPa, the tensile modulus is 0.6-1.5 GPa, and the elongation at break is 50-600%.

[0027] A second objective of this invention is to provide a method for preparing the polyglycolic acid copolymer as described above, comprising melting copolymerization of raw materials including glycolide, lactones or lactones of C4 or higher other than glycolide, aliphatic-aromatic copolyester, catalyst and optional antioxidant, followed by cooling to obtain the polyglycolic acid copolymer.

[0028] In the above technical solution, the preparation method of polyglycolic acid copolymer includes: using an aliphatic-aromatic copolyester as an initiator, together with the monomer glycolide, and other C4 or higher lactones or lactones, in the presence of a catalyst, to carry out bulk ring-opening polymerization to obtain the high-toughness polyglycolic acid copolymer, that is, a block copolymer of aliphatic-aromatic copolyester and (polyglycolic acid and (other C4 or higher lactones or lactones or lactones)).

[0029] According to the present invention, the mass ratio of glycolide to the total mass of lactones or lactones of C4 or above other than glycolide is selected within a wide range. In a preferred embodiment of the present invention, the mass ratio of glycolide to the total mass of lactones or lactones of C4 or above other than glycolide is (0.1-10):1, preferably (1-5):1.

[0030] According to the present invention, the mass ratio of the total mass of glycolide and other C4 or higher lactones or lactones to the aliphatic-aromatic copolyester is selected within a wide range. In a preferred embodiment of the present invention, the mass ratio of the total mass of glycolide and other C4 or higher lactones or lactones to the aliphatic-aromatic copolyester is (10-1):1, preferably (9-1.5):1.

[0031] According to the present invention, the range of catalyst dosage is relatively wide. In a preferred embodiment of the present invention, the mass ratio of the total mass of glycolide and lactones or lactones of C4 or above other than glycolide to the mass of catalyst is (100-20000):1, preferably (200-10000):1.

[0032] According to the present invention, the selection range of the total mass of antioxidants is relatively wide. In a preferred embodiment of the present invention, the ratio of the total mass of antioxidants to the total mass of glycolide, lactones or lactones of C4 or above other than glycolide and aliphatic-aromatic copolyesters is (0-0.02):1, preferably (0.0001-0.01):1.

[0033] According to the present invention, the weight-average molecular weight of the aliphatic-aromatic copolyester is selected over a wide range. In a preferred embodiment of the present invention, the weight-average molecular weight of the aliphatic-aromatic copolyester is 1,000-200,000 g / mol, preferably 20,000-100,000 g / mol, for example, it can be 20,000, 30,000, 40,000, 50,000, 60,000, 70,000, 80,000, 90,000, 100,000, as well as any two values ​​or ranges.

[0034] More preferably, the weight-average molecular weight of the aliphatic-aromatic copolyester is 30,000-100,000.

[0035] Preferably, the aliphatic-aromatic copolyester is selected from at least one of the following polymers:

[0036] Low molecular weight polymers obtained by alcoholysis of polybutylene terephthalate succinate and / or polybutylene terephthalate succinate; low molecular weight polymers obtained by alcoholysis of at least one of chain-extended modified polybutylene terephthalate succinate, end-group modified polybutylene terephthalate succinate, and polybutylene adipate terephthalate; chain-extended modified polybutylene adipate terephthalate and end-group modified polybutylene adipate terephthalate.

[0037] According to the present invention, the catalyst has a wide range of selection. In a preferred embodiment of the present invention, the catalyst is a salt compound or an organic guanidine compound corresponding to at least one of group IIA-VA metal elements and transition metal elements; preferably, the catalyst is a salt compound corresponding to at least one of Sn, Bi, Mg, Al, Ca, Fe, Mn, Ti and Zn, and more preferably Sn salt.

[0038] According to the present invention, the selection range of antioxidants is relatively wide. In a preferred embodiment of the present invention, the antioxidants are selected from hindered phenolic and / or phosphite antioxidants; including but not limited to 2,6-di-tert-butyl-p-cresol, 1,1,3-tris(2-methyl-4-hydroxy-5-tert-butylphenyl)butane, 2,2′-methylenebis(6-tert-butyl-4-methylphenol), hexanediol bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (such as BASF's antioxidant Irganox 1010), N,N'-bis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine (such as antioxidant 1024). N,N′-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine (e.g., antioxidant 1098), β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate n-octadecyl ester (e.g., BASF's antioxidant Irganox 1076), At least one of 1,3,5-trimethyl-2,4,6-tris(3,5-di-tert-butyl-4-hydroxybenzyl)benzene, triphenyl phosphite, tri(4-nonylphenyl) phosphite, diphenylisooctyl phosphite, diphenylisodecyl phosphite, phenyl di(2-ethylhexyl) phosphite, phenyl diisodecyl phosphite, tri(2-ethylhexyl) phosphite, triisodecyl phosphite, tri(dodecyl) phosphite, pentaerythritol diisodecyl diphosphite, tris[2,4-di-tert-butylphenyl] phosphite (e.g., antioxidant 168), bis(2,4-dicumylphenyl) pentaerythritol diphosphite (e.g., antioxidant 686), and bis(2,4-di-tert-butylphenyl)propionate pentaerythritol diphosphite (e.g., antioxidant 626). According to the present invention, the selection range of conditions for melt copolymerization reaction is relatively wide. In a preferred embodiment of the present invention, the conditions for melt copolymerization reaction include: a temperature of 180-250°C, preferably 200-240°C; and / or a reaction time of 1-20 min.

[0039] In a preferred embodiment of the present invention, the preparation process is carried out in a melt mixing device; preferably, the melt mixing device is a combination of one or more of the following: a batch reactor, a tubular reactor, a mixer, a Farrel continuous mixer, a Banbury mixer, a single-screw extruder, a multi-screw extruder, and a reciprocating single-screw extruder, preferably a mixer or a twin-screw extruder.

[0040] In a preferred embodiment of the present invention, the preparation process is carried out in an internal mixer; preferably, the mixing temperature is 180-250℃, more preferably 200-230℃, the rotation speed is 5-150 rpm, more preferably 20-80 rpm, and the reaction time is 1-20 min, more preferably 3-10 min.

[0041] In a preferred embodiment of the present invention, the preparation process is carried out in a twin-screw extruder; preferably, the processing temperature is 180-250℃, more preferably 210-240℃, the screw speed is 5-300 rpm, more preferably 30-100 rpm, and the length-to-diameter ratio is 30-80, more preferably 40-70.

[0042] The internal mixers applicable to this invention include internal mixers of various designs, such as the PolyLab HAAKE manufactured by Thermo Fisher Scientific in the United States. TM Rheomex OS 567-1000 internal mixer module, etc. Continuous twin-screw extrusion equipment applicable to this invention includes twin-screw extruders of different designs, such as the HAAKE Eurolab16 benchtop parallel co-rotating twin-screw extruder manufactured by Thermo Fisher in the United States, and co-rotating parallel twin-screw extruders such as the ZSK Mcc18 or ZSK 40 manufactured by Coperion in Germany.

[0043] A third objective of this invention is to provide a polyglycolic acid copolymer prepared by the preparation method described above.

[0044] Compared with the prior art, the present invention has the following advantages:

[0045] (1) The present invention directly uses polybutylene terephthalate as an initiator to initiate the ring-opening polymerization of glycolide and other C4 or higher lactones or lactones, and directly prepares block copolymers of aliphatic-aromatic copolyesters and (random copolymers of polyglycolic acid and other C4 or higher lactones or lactones) in one step, which is simpler to prepare.

[0046] (2) Compared with the traditional method of preparing polyglycolic acid, this method has more relaxed reaction conditions, can be prepared under normal pressure without nitrogen protection, and has a shorter reaction time, which reduces the degradation and discoloration of the copolymer, resulting in high-quality copolymer, and can achieve continuous preparation.

[0047] (3) The polyglycolic acid copolymer of the present invention not only has high toughness, but also a better strength-modulus-toughness balance. Through research and verification, the inventors of the present invention have discovered that: compared with simple aliphatic-aromatic copolyester and polyglycolic acid block copolymers, the block copolymer of the present invention introduces lactone or lactone segments with a C4 or higher content other than glycolide. With the introduction of the second monomer (lactolide or lactone with a C4 or higher content other than glycolide), the regularity of the polymer molecular chain is broken, reducing the regularity of the polyglycolic acid segments, thereby significantly reducing the crystallinity of the copolymer, and thus giving the copolymer good toughness at room temperature. Under the preferred content of lactone or lactone with a C4 or higher content other than glycolide in the present invention, the copolymer of the present invention has better toughness. In summary, this invention introduces high-toughness aliphatic-aromatic copolyesters into polyglycolic acid (PEG) on the one hand, and reduces the overall crystallinity by introducing a second monomer (such as lactic acid). PGA and PLA can play a synergistic role, and the synergistic effect of the two polymer segments can significantly improve the toughness of PEG. Compared with PGA-polyester copolymers or PLA-polyester copolymers alone, it has higher toughness and can obtain a new material with better balance of strength, toughness, modulus and degradation rate. The tensile strength is 25-100 MPa, the tensile modulus is 0.6-1.5 GPa, and the elongation at break is 50-600%. Attached Figure Description

[0048] Figure 1 To detect the 1H NMR spectra of the purified products in Example 2 (PGLA-b-PBAT), Comparative Example 1 (PGLA-80 / 20), and Comparative Example 3 (pure PBAT) in Example 1. 1 The ¹H-NMR spectrum shows that the solvent for all samples is deuterated trifluoroacetic acid. Figure 1 As can be seen, after purification, Example 2 still contains characteristic peaks of both PGLA and PBAT, indicating that the preparation method described in this invention does indeed yield a block copolymer of PGLA and PBAT rather than a simple physical blend.

[0049] Figure 2 To detect local (2000-1500 cm⁻¹) Fourier transform infrared absorption spectra (FTIR) of purified Example 2 (PGLA-b-PBAT), Comparative Example 1 (PGLA-80 / 20), and Comparative Example 3 (pure PBAT) in Example 2. -1 )Magnified comparison, sampling method is attenuated total reflection (ATR). By Figure 2As can be seen, the infrared spectrum of the purified Example 2 also shows the characteristic carbonyl absorption peak of PBAT (1700 cm⁻¹). -1 The carbonyl characteristic absorption peak of PGLA (around 1750 cm⁻¹) and PGLA (around 1750 cm⁻¹) -1 (Left and right), which once again verifies that the preparation method described in this invention does indeed yield a block copolymer of PGLA and PBAT rather than a simple physical blend.

[0050] Figure 3 The second heating curves obtained by differential scanning calorimetry (DSC) for Example 1, Example 2, Comparative Example 1 (PGLA-80 / 20) and Comparative Example 3 (pure PBAT) are compared. The convex peaks in the figure are exothermic peaks, and the concave peaks are endothermic peaks.

[0051] Figure 4 To detect typical tensile stress-strain curves of injection molded parts from Examples 1, 2, Comparative Example 1 (PGLA-80 / 20), Comparative Example 2 (PGLA-b-PBAT with low PBAT content), and Comparative Example 3 (pure PBAT) in Example 5. Figure 4 As can be seen, the elongation at break of Examples 1 and 2 is significantly higher than that of Comparative Example 1, while the tensile strength is significantly higher than that of Comparative Example 3. This indicates that the novel block copolymer in this invention combines the advantages of both PGLA and PBAT, possessing good toughness while maintaining high strength. Furthermore, as seen in Comparative Example 2, the formulation in this invention is optimized; when the aliphatic-aromatic copolyester content is too low, the modification effect is not significant, and a product with high toughness cannot be obtained.

[0052] Figure 5 This is a phase diagram comparing the tensile mechanical properties of Examples 1, 2, Comparative Example 1 (PGLA-80 / 20), Comparative Example 2 (PGLA-b-PBAT with low PBAT content), and Comparative Example 3 (pure PBAT). All five materials are compared with Comparative Example 1 (PGLA-80 / 20) as the baseline. The horizontal axis represents the PBAT content; a horizontal axis of 0 corresponds to Comparative Example 1, and a horizontal axis of 1 corresponds to Comparative Example 3. The vertical axes represent tensile strength, tensile modulus, elongation at break, and fracture energy, respectively. The dashed lines in the diagram represent the theoretical properties of the ideal blends of Comparative Example 1 and Comparative Example 3. Points above the curve indicate values ​​greater than the theoretical values, and vice versa. Detailed Implementation

[0053] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0054] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0055] Raw material source:

[0056] All raw materials used in this invention are commercially available.

[0057] Both glycolide and L-lactide were purchased from Shandong Jinan Daigang Biotechnology Co., Ltd., with a purity of ≥99.5%.

[0058] Anhydrous stannous chloride (SnCl2), stannous octoate (Sn(Oct)2), zinc acetate (dihydrate), ethylene glycol, and 1,4-butanediol were purchased from Sinopharm Chemical Reagent Co., Ltd. Anhydrous stannous chloride, stannous octoate, zinc acetate (dihydrate), and ethylene glycol were all AR grade, while 1,4-butanediol was CP grade. Chain extender ADR (… ADR-4468 (epoxy equivalent: 310 g / mol) was purchased from BASF (China) Co., Ltd.

[0059] Unless otherwise specified, the polybutylene terephthalate (PBAT) (weight-average molecular weight approximately 80,000 g / mol) used in the following examples and comparative examples was purchased from BASF (China) Co., Ltd., brand name: F-Blend-C1200; Polybutylene terephthalate (PBST) (weight-average molecular weight approximately 60,000 g / mol), Sinopec Yizheng Chemical Fiber Co., Ltd., grade TS159. Polyglycolic acid (PGA) was purchased from KEBIN-PRAK AB, Netherlands, GMP grade glycolide homopolymer with an average intrinsic viscosity of 1.2 dl / g.

[0060] The performance of this invention was determined according to the following method:

[0061] 1H NMR (1H NMR) spectrum 1 H-NMR: The test was performed on a JNM-ECZ500R / S1 nuclear magnetic resonance spectrometer manufactured by JEOL Ltd., Japan. Deuterated trifluoroacetic acid was used as the solvent.

[0062] Fourier Transform Infrared Spectroscopy (FTIR): The instrument used was a Frontier Fourier Transform Infrared Spectrometer from PerkinElmer, USA. Absorption signals were obtained using an Attenuated Total Refractive Index (ATR) accessory, with each sample ranging from 650 to 4000 cm⁻¹. -1 Scan the area 4 times.

[0063] Gel permeation chromatography (GPC): The test was performed on an Anglienti PL-GPC50 gel permeation chromatograph (USA), and the processing software was GPC offline. During the test, the mobile phase was hexafluoroisopropanol containing 5 mmol / L sodium trifluoroacetate, the flow rate was 1 mL / min, the column temperature was 40℃, the injection volume was 100 μL, the standard was PMMA, and the sample concentration was 1 mg / mL.

[0064] Differential scanning calorimetry (DSC) analysis: The test instrument was a Discovery series scanning calorimeter from TA Instruments (USA). During the test, 5-10 mg of sample was weighed into the sample pan. The test temperature range was 0℃-240℃. All samples underwent a heating process to eliminate thermal history, and the cooling curve was recorded simultaneously. The heating and cooling rates were 10℃ / min, and the plateau time at the highest and lowest temperatures was 2 min. The test atmosphere was nitrogen.

[0065] Injection Molding Method and Tensile Testing: The sample was injection molded into a 5A type tensile specimen (thickness: 2mm) using a HAAKE MiniJet micro-injection molding machine according to GB / T 1040.2-2006. The barrel temperature and mold temperature were 230℃ and 50℃, respectively. The injection pressure and time were 300 bar and 5s, respectively, and the holding pressure and time were 100 bar and 30s, respectively. Then, tensile testing was performed on an Instron 3344 material testing machine with a tensile rate of 20mm / min and a fixture spacing of 50mm.

[0066] The experimental parameters for some of the embodiments and comparative examples are shown in Table 1.

[0067]

Example 1

[0068] Ethylene lactone, L-lactide, anhydrous stannous chloride, and polybutylene terephthalate (PBAT) (weight-average molecular weight approximately 80,000 g / mol) were thoroughly premixed at a mass ratio of 75:15:0.027:10 using PolyLab HAAKE from ThermoFisher Technologies, Inc. TM The polymerization reaction was carried out using a Rheomex OS 567-1000 internal mixer (rotor diameter 35mm, rotor length 50mm). The rotation speed was 50 rpm, the temperature was 215℃, and the reaction time was 5 min. After the reaction, the mixture was directly cooled in air to obtain the PGLA-b-PBAT block copolymer.

[0069]

Example 2

[0070] The synthesis method is the same as in Example 1, except that the ratio of glycolide, L-lactide, anhydrous stannous chloride and polybutylene terephthalate (PBAT) is changed to 65:13:0.0234:22.

[0071]

Example 3

[0072] The synthesis method is the same as in Example 1, except that polybutylene adipate terephthalate (PBAT) is replaced with polybutylene terephthalate succinate (PBST) (weight-average molecular weight is approximately 60,000 g / mol).

[0073]

Example 4

[0074] The synthesis method is the same as in Example 1, except that PBAT is replaced with chain-extended modified PBAT.

[0075] The general preparation process of chain-extended modified PBAT is as follows: PBAT and chain extender ADR-4368 are mixed in a ratio of 1000:3 and then extruded and granulated using a Labtech parallel co-rotating twin-screw extruder (screw diameter: 20 mm, length-to-diameter ratio: 40). The extruder has 11 sections from the feed port to the die, numbered 1-11. Section 1 only serves as the feeding section and is not heated. The temperatures of sections 2-11 of the extruder are 110℃, 160℃, 210℃, 220℃, 220℃, 220℃, 220℃, 220℃, and 210℃, respectively. The weight-average molecular weight of the obtained chain-extended modified PBAT is approximately 90,000 g / mol.

[0076]

Example 5

[0077] The synthesis method is the same as in Example 1, except that PBAT is replaced with PBST that has undergone alcoholysis.

[0078] The general preparation process of alcoholyzed PBST is as follows: PBST, zinc acetate, and ethylene glycol are mixed in a ratio of 1000:4:50 and then extruded and granulated using a Labtech parallel co-rotating twin-screw extruder (screw diameter: 20 mm, length-to-diameter ratio: 40). The extruder has 11 sections from the feed inlet to the die, numbered 1-11. Section 1 only serves as the feeding section and is not heated. The temperatures of sections 2-11 of the extruder are 110℃, 150℃, 190℃, 190℃, 190℃, 190℃, 190℃, 190℃, and 190℃, respectively. The weight-average molecular weight of the obtained alcoholyzed PBST is approximately 20,000 g / mol.

[0079] The PBST obtained by alcoholysis has two terminal hydroxyl groups and can be used to synthesize ABA triblock copolymers (PGLA-b-PBST-b-PGLA).

[0080]

Example 6

[0081] Glycol, L-lactide, stannous octanoate, polybutylene terephthalate (PBAT), antioxidant 1076, and antioxidant 626 were thoroughly premixed at a mass ratio of 75:15:0.09:10:0.2:0.6 and extruded into granules using a HAAKEEurolab16 benchtop parallel co-rotating twin-screw extruder (screw diameter: 16 mm, L / D ratio: 40:1). The extruder has 11 sections from the feed port to the die, numbered 1-11. Section 1 only serves as the feed port and is water-cooled without heating. The temperatures of sections 2-11 are 120℃, 180℃, 240℃, 240℃, 240℃, 240℃, 240℃, 230℃, and 210℃, respectively. The feed rate is 1 kg / h, and the screw speed is 40-50 rpm.

[0082]

Example 7

[0083] PGLA-b-PBAT block copolymers were prepared according to the method of Example 1, except that the ratio of glycolide, L-lactide, anhydrous stannous chloride and polybutylene terephthalate (PBAT) was changed to 55:11:0.0198:34.

[0084]

Example 8

[0085] PGLA-b-PBAT block copolymers were prepared according to the method of Example 1, except that the ratio of glycolide, L-lactide, anhydrous stannous chloride and polybutylene terephthalate (PBAT) was changed to 54:36:0.021:10.

[0086]

Example 9

[0087] PGLA-b-PBAT block copolymers were prepared according to the method of Example 1, except that the ratio of glycolide, L-lactide, anhydrous stannous chloride and polybutylene terephthalate (PBAT) was changed to 42:8:0.015:50.

[0088] Comparative Example 1

[0089] The synthesis method was similar to that in Example 1, but the initiator was changed from polybutylene terephthalate (PBAT) to 1,4-butanediol. The ratio of glycolide, L-lactide, anhydrous stannous chloride, and 1,4-butanediol was 80:20:0.03:0.1. The reaction temperature was 220°C, and the reaction time was 5 min. After the reaction was completed, the mixture was allowed to cool naturally to obtain the random copolymer of GA and LA, PGLA-80 / 20.

[0090] Comparative Example 2

[0091] The synthesis method was the same as in Example 1, except that the ratio of glycolide (GA), L-lactide, anhydrous stannous chloride, and polybutylene terephthalate (PBAT) was changed to 76:17:0.0279:7. Comparative Example 2 synthesized a block copolymer with a lower PBAT content (7%).

[0092] Comparative Example 3

[0093] Commercially available pure PBAT.

[0094] Comparative Example 4

[0095] Commercially available pure PGA.

[0096] Comparative Example 5

[0097] The PGA / PBAT blend was prepared as follows: Polyglycolic acid (Comparative Example 4) and PBAT (Comparative Example 3) were premixed thoroughly at a mass ratio of 80:20 and extruded into granules using a Labtech parallel co-rotating twin-screw extruder (screw diameter: 20 mm, L / D ratio: 40). The extruder consisted of 11 sections from the feed port to the die, numbered 1-11. Section 1 only served as the feeding section and was not heated. The temperatures of sections 2-11 were 200℃, 215℃, 220℃, 220℃, 220℃, 230℃, 230℃, 230℃, 220℃, and 210℃, respectively. The feeding rate was 5 kg / h, and the screw speed was 200 rpm. After extrusion, the mixture was air-cooled to obtain the blend PBAT / PGA-20 / 80.

[0098] Comparative Example 6

[0099] The synthesis method was the same as in Example 2, but without the addition of lactide. The glycolide, anhydrous stannous chloride and polybutylene terephthalate (PBAT) were mixed in a mass ratio of 78:0.0234:22 to obtain the block copolymer PGA-b-PBAT.

[0100] Comparative Example 7

[0101] The synthesis method was the same as that of Comparative Example 6, but the glycolide was replaced with lactide to obtain the block copolymer PLA-b-PBAT.

[0102] Table 1

[0103]

[0104] Detection Example 1

[0105] The methanol precipitates obtained from Example 2 (PGLA-b-PBAT), Comparative Example 1 (PGLA-80 / 20), and Comparative Example 3 (pure PBAT) were purified by dissolving methanol in hexafluoroisopropanol and characterized by 1H NMR spectroscopy. The solvent was deuterated trifluoroacetic acid. The comparison results are shown in the figure below. Figure 1 As shown.

[0106] Detection Example 2

[0107] Infrared characterization was performed on PGLA-b-PBAT of Example 2, PGLA-80 / 20 of Comparative Example 1, and pure PBAT of Comparative Example 3. The sampling method was attenuated total internal reflection (ATR), and the resulting images were in the range of 2000-1500 cm⁻¹. -1 magnified comparison images within the range are as follows Figure 2 As shown.

[0108] Detection Example 3

[0109] The molecular weights of Examples 1, 2, 6, Comparative Examples 1, 2, and 3 were characterized by GPC, and the results are shown in Table 2.

[0110] As can be seen from Table 2, the molecular weight and distribution of the examples are not significantly different from those of Comparative Examples 1 and 2, with the weight-average molecular weight ranging from approximately 100,000 to 160,000 g / mol.

[0111] Table 2

[0112]

[0113] Detection Example 4

[0114] DSC characterization was performed on Examples 1, 2, 6, 1, 2, and 3, and the results are shown in Table 3. The second heating curves for some examples and comparative examples are shown in Table 3. Figure 3 As shown.

[0115] Table 3

[0116]

[0117] T g: Glass transition temperature; T m Melting point; ΔH m Enthalpy of fusion; T c Crystallization temperature

[0118] From Table 3 and Figure 3As can be seen, the block copolymer PGLA-b-PBAT in this invention significantly reduces the melting point, enthalpy of fusion, and crystallization temperature compared to pure PGA (Comparative Example 4), thus significantly improving processability. Simultaneously, compared to Comparative Examples 4 and 5, the block copolymer PGLA-b-PBAT in this invention exhibits a significantly lower enthalpy of fusion, indicating a significant reduction in crystallinity, further verifying the improved toughness of the block copolymer PGLA-b-PBAT in this invention. This may be because the block copolymer PGLA-b-PBAT introduces LA segments; the random PGLA disrupts the regularity of the GA segments, reducing the polymer's crystallinity and improving the material's toughness and processability.

[0119] Case 5

[0120] Mechanical properties were tested on the products in the examples and the comparative examples. The samples were injection molded into 5A type tensile specimens (thickness: 2 mm) using a HAAKE MiniJet micro-injection molding machine according to GB / T1040.2-2006. The barrel temperature and mold temperature were 210℃ (190℃ for Comparative Example 3) and 50℃, respectively. The injection pressure and time were 200 bar and 5 s, respectively, and the holding pressure and time were 100 bar and 10 s, respectively. Tensile tests were then performed on an Instron 3344 material testing machine (USA) at a tensile rate of 20 mm / min and a fixture spacing of 50 mm. Typical stress-strain curves from the tensile tests are shown below. Figure 4 The specific analysis results are shown in Table 4. Figure 5 This is a graph showing the relationship between the mechanical properties of the block copolymer of the present invention and the PBAT content in the block copolymer.

[0121] from Figure 4 As can be seen, the PGLA-b-PBAT block copolymer of the present invention has excellent mechanical properties. Comparative Example 4 (pure PGA), Comparative Example 1 (PGLA), and the block copolymer with low PBAT content (7%) all exhibit brittle fracture behavior, with elongation at break of less than 8.3%. Although Comparative Example 3 (pure PBAT) exhibits ductile fracture behavior, its tensile stress in the commonly used tensile deformation range (50%-450%) is low (approximately 10 MPa to 15 MPa), indicating poor load-bearing capacity. In contrast, Examples 1 and 2 of the present invention both exhibit ductile fracture behavior, but their tensile stress in the commonly used tensile deformation range (50%-450%) is significantly higher than that of PBAT (Comparative Example 3), both exceeding 20 MPa, indicating better load-bearing capacity. Furthermore, the stress-strain curves of Examples 1 and 2 show long yield plateaus, and after yielding, there is a peculiar "stress hardening" phenomenon, i.e., a stress rise stage before fracture, which is a very rare and unexpected finding in copolymers.

[0122] Table 4

[0123]

[0124]

[0125] From Table 4 and Figure 5 As can be seen, on the one hand, compared with pure PGLA (Comparative Example 1) and pure PGA (Comparative Example 4), although the tensile strength and modulus of the embodiments of the present invention are significantly reduced, the elongation at break and the fracture energy are significantly improved. The elongation at break is increased by two orders of magnitude, and the fracture energy is increased by one order of magnitude. That is, compared with PGLA and PGA, the block copolymer of the present invention sacrifices a small amount of strength and modulus, but the toughness is significantly improved. In addition, the strength of the block copolymer of the present invention is still comparable to that of commercially available PBAT (Comparative Example 3). In applications such as disposable packaging, the strength comparable to that of PBAT (Comparative Example 3) is sufficient to meet the application requirements. Moreover, the modulus of pure PBAT (Comparative Example 3) is too low, and the present invention also significantly improves the modulus (by two orders of magnitude) compared with pure PBAT. Therefore, the block copolymer of the present invention achieves a better strength-modulus-toughness balance compared with existing common biodegradable polymers PGLA, PGA and PBAT.

[0126] Meanwhile, as can be seen from Comparative Example 5, under the same ratio of PGA and PBAT, the pure physical blend still exhibits brittleness, with an elongation at break of only 3.5% and a fracture energy of only 0.3 J.

[0127] Furthermore, compared to Comparative Example 6, although the strength and modulus of Example 2 decreased after the introduction of lactide, the elongation at break was significantly increased, and the final fracture energy was also two orders of magnitude higher. As can be seen from Comparative Example 7, if lactide is not added at all (i.e., Comparative Example 7), compared with Example 2, although the strength is only slightly reduced, the modulus and elongation at break are significantly lower, and the final fracture energy is still lower than that of Example 2.

[0128] Furthermore, as can be seen from Comparative Example 2, the PBAT content in the embodiments of the present invention is optimized, resulting in a better toughening effect and suitable strength and modulus.

[0129] The copolymers obtained in Examples 3-9 were tested according to the method in Test Example 5. It was found that the mechanical properties of Examples 4 and 6 were close to those of Example 1 and better than those of Example 2; the mechanical properties of Example 3 were slightly worse than those of Example 1 but better than those of Example 2; the mechanical properties of Example 8 were close to those of Example 2; and the mechanical properties of Examples 5, 7 and 9 were worse than those of Example 2 but better than those of Comparative Example 7.

[0130] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

[0131] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0132] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0133] The endpoints and any values ​​of the ranges disclosed in this application are not limited to the precise ranges or values; such ranges or values ​​should be understood to include values ​​close to them. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In principle, various technical solutions can be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0134] In the context of this specification, except where expressly stated otherwise, any matters or issues not mentioned shall apply directly to those known in the art without any modification.

[0135] Furthermore, any implementation described herein can be freely combined with one or more other implementations described herein, and the resulting technical solutions or technical ideas shall be regarded as part of the original disclosure or original record of the present invention, and should not be regarded as new content not disclosed or anticipated herein, unless those skilled in the art consider the combination to be obviously unreasonable.

Claims

1. A polyglycolic acid copolymer, wherein the polyglycolic acid copolymer is an AB diblock copolymer and / or an ABA triblock copolymer; in, Block A is a copolymer segment formed by random copolymerization of glycolide and lactones or lactones with a C4 or higher content other than glycolide; Block B is an aliphatic-aromatic copolyester, which is a copolyester segment formed by polycondensation of aliphatic diacid and aromatic diacid with aliphatic diol. By mass, relative to the total mass of block A and block B, the content of block A is 50%-92% by mass; and the content of block B is 8%-50% by mass.

2. The polyglycolic acid copolymer according to claim 1, characterized in that: By mass, relative to the total mass of block A and block B, the content of block A is 60%-90% by mass; and the content of block B is 10%-40% by mass.

3. The polyglycolic acid copolymer according to claim 1, characterized in that: The lactones or lactones with a C4 or higher number other than glycolide include at least one of lactide, β-butyrolactone, γ-butyrolactone, γ-valerolactone, δ-valerolactone, γ-caprolactone, δ-caprolactone, and ε-caprolactone; and / or, The polyethylene glycol segment in block A With lactone or lactone segments of C4 or higher, other than glycolide The mass ratio is (0.1-10):1, and R is C. k H 2k+1 t and k are both integers not less than 0, and t and k are not both 0 at the same time.

4. The polyglycolic acid copolymer according to claim 1, characterized in that: The polyethylene glycol segment in block A With lactone or lactone segments of C4 or higher, other than glycolide The mass ratio is (1-5):1, and R is C k H 2k+1 t and k are both integers not less than 0, and t and k are not both 0 at the same time.

5. The polyglycolic acid copolymer according to claim 1, characterized in that: Block B is a copolyester segment formed by the condensation of α,ω-aliphatic diacids and aromatic diacids containing 2-18 main chain carbon atoms with at least one aliphatic diol.

6. The polyglycolic acid copolymer according to claim 1, characterized in that: Block B is a polybutylene adipate terephthalate segment and / or a polybutylene terephthalate succinate segment; and / or... The weight-average molecular weight of block B is 1000-200000 g / mol.

7. The polyglycolic acid copolymer according to claim 1, characterized in that: Block B is poly(adipate)- co -Butyl terephthalate segments, polyadipate- co -Ethylene terephthalate segments, polysuccinic acid- co -Ethylene terephthalate segments, polysuccinic acid- co - at least one of the butylene terephthalate segments; and / or The weight-average molecular weight of block B is 20,000-100,000 g / mol.

8. The polyglycolic acid copolymer according to any one of claims 1-7, characterized in that: The weight-average molecular weight of the polyglycolic acid copolymer is 20,000-300,000 g / mol; and / or, The molecular weight distribution coefficient of the polyglycolic acid copolymer is 1.01-3; and / or, The polyglycolic acid copolymer is prepared by copolymerization of raw materials including glycolide, lactones or lactones with a C4 or higher content other than glycolide, and aliphatic-aromatic copolyesters.

9. The polyglycolic acid copolymer according to any one of claims 1-7, characterized in that: The weight-average molecular weight of the polyglycolic acid copolymer is 80,000-200,000 g / mol; and / or, The molecular weight distribution coefficient of the polyglycolic acid copolymer is 1.01-2.

10. A method for preparing the polyglycolic acid copolymer according to any one of claims 1-9, comprising melting copolymerizing raw materials including glycolide, lactones or lactones of C4 or higher other than glycolide, aliphatic-aromatic copolyester, catalyst and optional antioxidant, and then cooling to obtain the polyglycolic acid copolymer.

11. The preparation method according to claim 10, characterized in that: By mass, the mass ratio of glycolide to other C4 or higher lactones or lactones is (0.1-10):1; and / or, By mass, the total mass ratio of glycolide and other C4 or higher lactones or lactones to the mass ratio of aliphatic-aromatic copolyester is (10-1):1; and / or, The mass ratio of glycolide and other C4 or higher lactones or lactones to the catalyst, by mass, is (100-20000):1; and / or, By mass, the ratio of the total mass of antioxidants to the total mass of glycolide, lactones or lactones of C4 or higher other than glycolide, and aliphatic-aromatic copolyesters is (0-0.02):

1.

12. The preparation method according to claim 10, characterized in that: By mass, the mass ratio of glycolide to other C4 or higher lactones or lactones is (1-5):1; and / or, By mass, the total mass ratio of glycolide and other C4 or higher lactones or lactones to the aliphatic-aromatic copolyester is (9-1.5):1; and / or, The mass ratio of glycolide and other C4 or higher lactones or lactones to the catalyst, by mass, is (200-10000):1; and / or, By mass, the ratio of the total mass of antioxidants to the total mass of glycolide, lactones or lactones of C4 or higher other than glycolide, and aliphatic-aromatic copolyesters is (0.0001-0.01):

1.

13. The preparation method according to claim 10, characterized in that: The aliphatic-aromatic copolyester has a weight-average molecular weight of 1000-200000 g / mol; and / or, The aliphatic-aromatic copolyester is selected from at least one of the following polymers: Polybutylene terephthalate (PBTB), low molecular weight polymers obtained by alcoholysis of PBTB, chain-extended modified PBTB, low molecular weight polymers obtained by alcoholysis of polybutylene adipate (PADI), chain-extended modified PBTB, and polybutylene adipate (PADI).

14. The preparation method according to claim 10, characterized in that: The aliphatic-aromatic copolyester is selected from at least one of the following polymers: End-group modified polybutylene terephthalate succinate, end-group modified polybutylene adipate terephthalate; and / or, The weight-average molecular weight of the aliphatic-aromatic copolyester is 20,000-100,000 g / mol.

15. The preparation method according to claim 10, characterized in that: The catalyst is a salt compound or an organic guanidine compound corresponding to at least one of the group IIA-VA metal elements and transition metal elements; And / or, The antioxidant is selected from hindered phenolic and / or phosphite antioxidants.

16. The preparation method according to claim 10, characterized in that: The catalyst is a salt compound corresponding to at least one of Sn, Bi, Mg, Al, Ca, Fe, Mn, Ti and Zn.

17. The preparation method according to claim 10, characterized in that: The catalyst is a Sn salt.

18. The preparation method according to claim 10, characterized in that: The conditions for melt copolymerization include: The temperature is 180-250℃; and / or, The reaction time is 1-20 min.

19. The preparation method according to claim 10, characterized in that: The conditions for melt copolymerization include: The temperature is 200-240℃.

20. The preparation method according to claim 10, characterized in that: The preparation process is carried out in a melt mixing device.

21. The preparation method according to claim 10, characterized in that: The preparation process is carried out in an internal mixer.

22. The preparation method according to claim 21, characterized in that: The mixing temperature is 180-250℃, the rotation speed is 5-150 rpm, and the reaction time is 1-20 min.

23. The preparation method according to claim 21, characterized in that: The mixing temperature is 200-230℃, the rotation speed is 20-80 rpm, and the reaction time is 3-10 min.

24. The preparation method according to claim 10, characterized in that: The preparation process is carried out in a twin-screw extruder.

25. The preparation method according to claim 24, characterized in that: The processing temperature is 180-250℃, the screw speed is 5-300 rpm, and the length-to-diameter ratio is 30-80.

26. The preparation method according to claim 24, characterized in that: The processing temperature is 210-240℃, the screw speed is 30-100 rpm, and the length-to-diameter ratio is 40-70.

27. A polyglycolic acid copolymer prepared by any one of claims 10-26.

28. The use of a polyglycolic acid copolymer according to any one of claims 1-9, 27 in injection-molded articles of aliphatic-aromatic copolyester and polyglycolic acid blend.

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