A high-heat-resistant and high-toughness fully biodegradable blend and an efficient preparation method thereof

Abstract

The application discloses a kind of high heat resistance high toughness full biodegradable blend and its efficient preparation method, belong to full biodegradable polymer material technical field, including: left-handed polylactic acid resin, right-handed polylactic acid resin, polybutylene adipate terephthalate resin, polybutylene succinate resin, crystallization shrinkage response type interface regulation master batch and processing aid.The crystallization shrinkage response type interface regulation master batch has bilateral phase structure, and forms the interface gradient structure including polylactic acid stereocomplex crystal heat-resistant anchor point, crystallization shrinkage compensation zone, local reaction lock zone and flexible energy consumption zone between polylactic acid matrix phase and flexible degradable polyester phase, to improve the heat resistance, toughness and thermal post dimensional stability of material.

Description

Technical Field

[0001] This invention relates to the field of fully biodegradable polymer materials technology, and in particular to a highly heat-resistant and highly tough fully biodegradable blend and its efficient preparation method. Background Technology

[0002] Polylactic acid (PLA) is characterized by its renewable source, high rigidity, and biodegradability, making it highly valuable for applications in packaging materials, food containers, thermoformed sheets, and disposable products.

[0003] However, polylactic acid (PLA) crystallizes slowly, resulting in products with insufficient heat resistance under normal processing conditions. These products are prone to softening and deformation in hot beverages, hot meals, and short-term heat-setting environments. Existing technologies typically improve heat resistance and toughness by adding dextrorotatory PLA, nucleating agents, flexible polyesters, or reactive compatibilizers. However, these methods often address single performance aspects and struggle to simultaneously address the coupling issues between PLA post-crystallization shrinkage, flexible phase softening, and interfacial stress release. When the PLA matrix phase continues to crystallize during hot use, the stiffening and shrinkage of the matrix phase generate uneven stress at the interface between the two phases. Meanwhile, the flexible biodegradable polyester phase is prone to yielding and slippage at higher temperatures, leading to interfacial whitening, debonding, warping, and decreased post-heat toughness. These problems cannot be solved simply by increasing crystallinity or improving compatibility; excessive crystallization may exacerbate embrittlement, while excessive toughening may reduce heat resistance.

[0004] Therefore, there is a need for a fully biodegradable blend material that can construct a gradient interface structure between the polylactic acid matrix phase and the flexible biodegradable polyester phase, while simultaneously achieving heat resistance support, crystallization shrinkage compensation, and local interface locking. Summary of the Invention

[0005] This invention overcomes the shortcomings of the prior art and provides a highly heat-resistant, highly tough, fully biodegradable blend and its efficient preparation method.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a high heat-resistant and high-toughness fully biodegradable blend, comprising the following components by mass: 60 to 76 parts of L-polylactic acid resin;

[0007] 2 to 6 parts of dextrorotatory polylactic acid resin;

[0008] 12 to 24 parts of polybutylene adipate terephthalate resin;

[0009] 4 to 12 parts of polybutylene succinate resin;

[0010] 4 to 14 parts of crystallization shrinkage-responsive interface-controlled masterbatch;

[0011] Processing aids: 0.1 to 3 parts;

[0012] The L-type polylactic acid resin and the D-type polylactic acid resin together form a polylactic acid matrix phase, and the polybutylene adipate terephthalate resin and the polybutylene succinate resin together form a flexible biodegradable polyester phase.

[0013] The crystallization shrinkage-responsive interface-controlled masterbatch is at least partially distributed in the phase interface region between the polylactic acid matrix phase and the flexible biodegradable polyester phase;

[0014] The crystallization shrinkage-responsive interface-controlled masterbatch is a masterbatch with a two-sided phase structure, including a polylactic acid stereocomposite crystal precursor phase facing the polylactic acid matrix phase, a polybutylene succinate buffer phase facing the flexible biodegradable polyester phase, a hydroxyl-terminated polyester oligomer compensation phase located between the polylactic acid stereocomposite crystal precursor phase and the polybutylene succinate buffer phase, and an epoxidized soybean oil citrate locking phase.

[0015] The crystallization shrinkage-responsive interface-controlled masterbatch also includes a degradable interface-stabilized phase.

[0016] The blend forms an interfacial gradient structure between the polylactic acid matrix phase and the flexible biodegradable polyester phase.

[0017] In a preferred embodiment of the present invention, the weight-average molecular weight of the L-polylactic acid resin is 120,000 to 220,000, and the melt mass flow rate is 3g to 15g per 10min.

[0018] The weight-average molecular weight of the dextrorotatory polylactic acid resin is between 80,000 and 180,000.

[0019] The right-handed polylactic acid resin is used to form a polylactic acid stereocomposite heat-resistant structure in the polylactic acid matrix phase.

[0020] In a preferred embodiment of the present invention, the polybutylene adipate terephthalate resin has a weight-average molecular weight of 100,000 to 180,000 and a melt mass flow rate of 2 g to 8 g per 10 min.

[0021] The polybutylene succinate resin has a weight-average molecular weight of 80,000 to 160,000 and a melt flow rate of 3 to 12 g per 10 min.

[0022] In a preferred embodiment of the present invention, the crystallization shrinkage-responsive interface control masterbatch comprises, by weight, the following components: 20 to 38 parts of polylactic acid stereocomposite crystal precursor phase;

[0023] 22 to 42 parts of polybutylene succinate buffer phase;

[0024] 18 to 34 parts of hydroxyl-terminated polyester oligomer compensating phase;

[0025] 5 to 16 parts of epoxidized soybean oil citrate locked phase;

[0026] Two to eight parts of the biodegradable interface stable phase.

[0027] In a preferred embodiment of the present invention, the polylactic acid stereocomposite precursor phase is made of dextrorotatory polylactic acid resin and levorotatory polylactic acid oligomer;

[0028] The mass ratio of the dextrorotatory polylactic acid resin to the levorotatory polylactic acid oligomer is from 1:0.3 to 1:1.2.

[0029] The polylactic acid stereocomposite crystal precursor phase is used to form heat-resistant anchor points for the polylactic acid stereocomposite crystal on one side of the polylactic acid matrix phase.

[0030] In a preferred embodiment of the present invention, the polybutylene succinate buffer phase is made of low molecular weight polybutylene succinate and polycaprolactone;

[0031] The mass ratio of the low molecular weight polybutylene succinate to the polycaprolactone is from 1:0.2 to 1:0.8.

[0032] The softening temperature of the polybutylene succinate buffer phase is 55°C to 85°C.

[0033] In a preferred embodiment of the present invention, the hydroxyl-terminated polyester oligomer compensating phase is made of hydroxyl-terminated polybutylene succinate oligomer and polylactic acid-polycaprolactone copolymer;

[0034] The mass ratio of the hydroxyl-terminated polybutylene succinate oligomer to the polylactic acid-polycaprolactone copolymer is from 1:0.4 to 1:1.5.

[0035] The hydroxyl-terminated polyester oligomer compensation phase is located between the polylactic acid matrix phase and the flexible biodegradable polyester phase, and is used to form a crystallization shrinkage compensation zone.

[0036] In a preferred embodiment of the present invention, the epoxidized soybean oil citrate locked phase is made of epoxidized soybean oil citrate pre-reactant and carboxyl-terminated polylactic acid oligomer;

[0037] The mass ratio of the epoxidized soybean oil citrate pre-reactant to the carboxyl-terminated polylactic acid oligomer is 1:0.2 to 1:0.9;

[0038] The epoxidized soybean oil citrate locked phase is located between the crystallization shrinkage compensation zone and the flexible biodegradable polyester phase, and is used to form a local reaction locked zone.

[0039] In a preferred embodiment of the present invention, the interface gradient structure includes, in sequence along the direction from the polylactic acid matrix phase to the flexible biodegradable polyester phase, a polylactic acid stereocomposite crystal heat-resistant anchor point, a crystallization shrinkage compensation zone, a local reaction locking zone, and a flexible energy-dissipating zone.

[0040] The local reaction-locked region contains an ester bond connection structure formed by the reaction of epoxidized soybean oil citrate pre-reactant and polyester end groups;

[0041] The proportion of the crystallization shrinkage-responsive interface-controlled masterbatch located in the phase interface region is 50% to 85%.

[0042] A method for preparing a highly heat-resistant, highly tough, fully biodegradable blend includes the following steps: preparing a crystallization shrinkage-responsive interface-controlled masterbatch by combining a polylactic acid stereocomposite crystal precursor phase, a polybutylene succinate buffer phase, a hydroxyl-terminated polyester oligomer compensating phase, an epoxidized soybean oil citrate locking phase, and a biodegradable interface-stabilizing phase.

[0043] The L-type polylactic acid resin, D-type polylactic acid resin, polybutylene adipate terephthalate resin, polybutylene succinate resin, processing aids, and the crystallization shrinkage-responsive interface control masterbatch are melt-blended so that the crystallization shrinkage-responsive interface control masterbatch is at least partially distributed in the phase interface region between the polylactic acid matrix phase and the flexible biodegradable polyester phase.

[0044] The melt-blended material is shaped and heat-set for a short time, so that the polylactic acid matrix phase forms polylactic acid stereocomposite heat-resistant anchor points, and the crystallization shrinkage-responsive interface control masterbatch forms an interface gradient structure including a crystallization shrinkage compensation zone and a local reaction locking zone between the polylactic acid matrix phase and the flexible biodegradable polyester phase.

[0045] This invention addresses the shortcomings of the prior art and has the following beneficial effects:

[0046] (1) The present invention achieves an interfacial gradient structure between the polylactic acid matrix phase and the flexible biodegradable polyester phase through the synergistic combination of L-polylactic acid resin, D-polylactic acid resin, polybutylene adipate terephthalate resin, polybutylene succinate resin and crystallization shrinkage responsive interface control masterbatch. The above-mentioned interfacial gradient structure simultaneously undertakes the functions of heat resistance support and impact energy dissipation, directly improving the heat resistance and toughness of the blend. Compared with existing blends that simply nucleate heat resistance or simply toughen flexibility, it further reduces the risk of embrittlement caused by improved heat resistance and thermal deformation caused by improved toughness.

[0047] (2) The present invention uses dextrorotatory polylactic acid resin and crystallization shrinkage-responsive interface to regulate the polylactic acid stereocomposite crystal precursor phase in the masterbatch, so that polylactic acid stereocomposite crystal heat-resistant anchor points are formed on one side of the polylactic acid matrix phase; the above heat-resistant anchor points can provide high melting point crystal support in the interface region, directly improving the heat deformation resistance of the blend under hot use conditions; compared with the existing schemes that rely on long-term annealing or ordinary nucleating agents to improve the crystallinity of polylactic acid, the heat setting cycle is further shortened and the dimensional stability of thin-walled products is improved.

[0048] (3) The present invention uses a polybutylene succinate buffer phase and a hydroxyl-terminated polyester oligomer compensation phase to flexibly buffer and compensate for the interfacial displacement caused by the crystallization shrinkage of the polylactic acid matrix phase; the above structure can weaken the thermo-mismatch between the rigid polylactic acid matrix phase and the flexible biodegradable polyester phase, directly reducing post-heat whitening, interfacial debonding and impact toughness attenuation; compared with the existing ordinary polylactic acid flexible polyester blends, it further improves the material's ability to maintain post-heat toughness in hot drinks, hot lunch boxes and thermoformed products.

[0049] (4) The present invention achieves a synergistic effect between the heat-resistant crystal zone, the shrinkage compensation zone, the local reaction locking zone, and the flexible energy-dissipating zone through the continuous transition of the polylactic acid stereocomposite crystal heat-resistant anchor point, the crystallization shrinkage compensation zone, the local reaction locking zone, and the flexible energy-dissipating zone. The above-mentioned synergistic structure can transform the adverse shrinkage caused by the post-crystallization of polylactic acid into interface stabilization conditions, and directly achieve the simultaneous maintenance of high heat resistance and high toughness. Compared with the existing system in which crystallization, compatibility and toughening act independently, it further improves the applicability of fully biodegradable materials to replace traditional heat-resistant plastic packaging materials. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0051] Figure 1 This is a flowchart illustrating the preparation method of the high heat resistance, high toughness, fully biodegradable blend of the present invention. Detailed Implementation

[0052] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0053] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein. Therefore, the scope of protection of the invention is not limited to the specific embodiments disclosed below.

[0054] Application Overview:

[0055] like Figure 1 As shown in the diagram, this invention provides a step-by-step method for preparing a highly heat-resistant, highly tough, and fully biodegradable blend. Addressing the technical challenge of simultaneously achieving heat resistance, toughness, and post-thermal dimensional stability in fully biodegradable blends, this invention proposes a method using L- and D-polylactic acid resins to form a polylactic acid matrix phase, and polybutylene adipate terephthalate resins and polybutylene succinate resins to form a flexible biodegradable polyester phase. Furthermore, a crystallization shrinkage-responsive interface-controlled masterbatch with a dual-phase structure is introduced. This masterbatch directionally constructs an interface gradient structure between the polylactic acid matrix phase and the flexible biodegradable polyester phase, consisting of heat-resistant anchor points of polylactic acid stereocomposite crystals, a crystallization shrinkage compensation zone, a local reaction locking zone, and a flexible energy-dissipating zone. During heat setting and use, the stereocomposite crystals enhance heat resistance, the compensation phase absorbs the interfacial displacement caused by polylactic acid crystallization shrinkage, the locking phase strengthens the interfacial bonding between the two phases, and the flexible energy-dissipating zone maintains impact toughness, achieving a synergistic improvement in high heat resistance, high toughness, low post-thermal dimensional change, and good biodegradability.

[0056] Material sources and preparation of self-made materials:

[0057] The L-type polylactic acid resin was purchased from Zhejiang Hisun Biomaterials Co., Ltd., and its brand name is REVODE190.

[0058] The dextrorotatory polylactic acid resin, model PDLA-15, was purchased from Jinan Daigang Bioengineering Co., Ltd.

[0059] The polybutylene adipate terephthalate resin was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., and its brand name is TH801T-MF.

[0060] The polybutylene succinate resin was purchased from Xinjiang Lanshan Tunhe Technology Co., Ltd., and its brand name is TH803S.

[0061] Polycaprolactone was purchased from Shenzhen Guanghua Weiye Co., Ltd., with the grade PCL45D.

[0062] The L-type polylactic acid oligomer was purchased from Jinan Daigang Bioengineering Co., Ltd., and its model number is OH-PLLA-OH.

[0063] The carboxyl-terminated polylactic acid oligomer was purchased from Jinan Daigang Bioengineering Co., Ltd., and its model number is OH-PLLA-COOH.

[0064] The polylactic acid-polycaprolactone copolymer was purchased from Jinan Daigang Bioengineering Co., Ltd., model number P(LA-CL)70 / 30.

[0065] The epoxidized soybean oil was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with product number E107074 and CAS number 8013-07-8.

[0066] Anhydrous citric acid was prepared using analytical grade reagents with a purity ≥99.5% and CAS number 77-92-9.

[0067] Tetrabutyl titanate was prepared using analytical grade reagents with a purity ≥98.0% and CAS number 5593-70-4.

[0068] 1,4-Butanediol was prepared using analytical grade reagents with a purity ≥99.0% and CAS number 110-63-4.

[0069] Antioxidant 1010 was purchased from Tianjin Lianlong New Materials Co., Ltd., and its brand name is RIANOX 1010.

[0070] Antioxidant 168 was purchased from Tianjin Lianlong New Materials Co., Ltd., and its brand name is RIANOX 168.

[0071] Calcium stearate was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., with product number C113301.

[0072] The common epoxy compatibilizer was purchased from Jia Yi Rong Polymer Co., Ltd., and its brand name is SG-20.

[0073] The polylactic acid stereocomposite precursor phase was prepared as follows: D-coefficient polylactic acid resin PDLA-15 was vacuum dried at 60℃ for 6 hours, and L-coefficient polylactic acid oligomer OH-PLLA-OH was vacuum dried at 45℃ for 6 hours. Raw materials were weighed at a mass ratio of 1:0.8 between D-coefficient polylactic acid resin and L-coefficient polylactic acid oligomer. The two were added to a torque rheometer and melt-mixed at 185℃ and 60 r / min for 8 minutes. After discharging, the mixture was cooled, pulverized, and passed through a 40-mesh sieve to obtain the polylactic acid stereocomposite precursor phase.

[0074] Low molecular weight polybutylene succinate was prepared as follows: Polybutylene succinate resin TH803S was vacuum dried at 80℃ for 4h. 1,4-Butanediol and tetrabutyl titanate were added to a reaction vessel at 6% and 0.08% of the mass of the polybutylene succinate resin, respectively. The mixture was heated to 185℃ under nitrogen protection and stirred for 60min. Then, low-boiling substances were removed under a vacuum of -0.08MPa for 20min. After cooling and discharge, the mixture was pulverized to obtain low molecular weight polybutylene succinate.

[0075] The polybutylene succinate buffer phase was prepared as follows: low molecular weight polybutylene succinate was vacuum dried at 50℃ for 6 hours, and polycaprolactone PCL45D was vacuum dried at 40℃ for 6 hours; raw materials were weighed according to the mass ratio of low molecular weight polybutylene succinate to polycaprolactone 1:0.5; low molecular weight polybutylene succinate was added to a torque rheometer and plasticized at 135℃ and 50 r / min for 3 minutes; then polycaprolactone was added, and mixing was continued for 7 minutes; after discharge, the mixture was cooled, pulverized, and passed through a 40-mesh sieve to obtain a polybutylene succinate buffer phase with a softening temperature of 68℃.

[0076] Hydroxyl-terminated polybutylene succinate oligomers were prepared as follows: Polybutylene succinate resin TH803S was vacuum dried at 80℃ for 4 hours. 1,4-Butanediol and tetrabutyl titanate were added to a reaction vessel at 8% and 0.10% of the mass of the polybutylene succinate resin, respectively. The mixture was heated to 180℃ under nitrogen protection and stirred for 70 minutes. Then, low-boiling substances were removed under a vacuum of -0.08MPa for 20 minutes. After cooling and discharge, the mixture was pulverized to obtain hydroxyl-terminated polybutylene succinate oligomers.

[0077] The hydroxyl-terminated polyester oligomer compensation phase was prepared as follows: hydroxyl-terminated polybutylene succinate oligomer was vacuum dried at 50℃ for 6 hours, and polylactic acid-polycaprolactone copolymer P(LA-CL)70 / 30 was vacuum dried at 45℃ for 6 hours. Raw materials were weighed according to a mass ratio of hydroxyl-terminated polybutylene succinate oligomer to polylactic acid-polycaprolactone copolymer of 1:0.9. Both were added to a torque rheometer and mixed at 125℃ and 50 r / min for 10 minutes. After discharge, the mixture was cooled, pulverized, and passed through a 40-mesh sieve to obtain the hydroxyl-terminated polyester oligomer compensation phase.

[0078] The epoxidized soybean oil citrate pre-reactant was prepared as follows: epoxidized soybean oil E107074, anhydrous citric acid, and tetrabutyl titanate were added to a reactor equipped with a mechanical stirrer, thermometer, and nitrogen protection interface. The mass ratio of epoxidized soybean oil to anhydrous citric acid was 100:6, and the amount of tetrabutyl titanate was 0.15% of the mass of epoxidized soybean oil. Under nitrogen protection at a flow rate of 80 mL / min, the temperature was raised to 115 °C, and the reaction was stirred at 300 r / min for 90 min. Then, the reaction was maintained under a vacuum of -0.08 MPa for 20 min, cooled to 60 °C, and discharged to obtain the epoxidized soybean oil citrate pre-reactant.

[0079] The epoxidized soybean oil citrate locked phase was prepared as follows: the epoxidized soybean oil citrate pre-reactant was vacuum dried at 50℃ for 4h, and the carboxyl-terminated polylactic acid oligomer OH-PLLA-COOH was vacuum dried at 45℃ for 6h; the raw materials were weighed according to the mass ratio of epoxidized soybean oil citrate pre-reactant to carboxyl-terminated polylactic acid oligomer 1:0.5, and the two were added to a torque rheometer and premixed at 120℃ and 45r / min for 4min, and then the temperature was raised to 145℃ and the reaction and mixing continued for 6min. After discharge, the material was cooled, pulverized and passed through a 40-mesh sieve to obtain the epoxidized soybean oil citrate locked phase.

[0080] The biodegradable interface stable phase was prepared as follows: polylactic acid-polycaprolactone copolymer P(LA-CL)70 / 30 was vacuum dried at 45℃ for 6h, and calcium stearate was dried at 80℃ for 2h; the raw materials were weighed according to the mass ratio of polylactic acid-polycaprolactone copolymer to calcium stearate of 100:3, and the two were added to a torque rheometer and melt-mixed at 115℃ and 40r / min for 6min. After discharge, the mixture was cooled, pulverized, and passed through a 40-mesh sieve to obtain the biodegradable interface stable phase.

[0081] The crystallization shrinkage-responsive interface control masterbatch was prepared as follows: Polylactic acid stereocrystalline precursor phase, polybutylene succinate buffer phase, hydroxyl-terminated polyester oligomer compensation phase, epoxidized soybean oil citrate locking phase, and biodegradable interface stabilizing phase were vacuum dried at 60℃ for 6 hours. Raw materials were weighed according to the following formula: 30 parts of polylactic acid stereocrystalline precursor phase, 31 parts of polybutylene succinate buffer phase, 25 parts of hydroxyl-terminated polyester oligomer compensation phase, 10 parts of epoxidized soybean oil citrate locking phase, and 4 parts of biodegradable interface stabilizing phase. These raw materials were added to a twin-screw extruder for segmented melt compounding. The temperatures of zones one through six were controlled at 120℃, 140℃, 155℃, 165℃, 175℃, and 180℃, respectively, and the screw speed was controlled at 100 r / min. The material underwent melt plasticization, shear compounding, extrusion, water cooling, and pelletizing to obtain the crystallization shrinkage-responsive interface control masterbatch.

[0082] The processing aid is prepared as follows: weigh the raw materials according to the mass ratio of antioxidant 1010, antioxidant 168 and calcium stearate 4:3:3, add the above raw materials to a high-speed mixer, and mix at 600 r / min for 5 min to obtain the processing aid.

[0083] Example 1:

[0084] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0085] The weight-average molecular weight of L-co-lactic acid resin is 180,000, and the melt flow rate is 8 g / 10 min; the weight-average molecular weight of D-co-lactic acid resin is 130,000; the weight-average molecular weight of polybutylene adipate terephthalate resin is 140,000, and the melt flow rate is 5 g / 10 min; the weight-average molecular weight of polybutylene succinate resin is 120,000, and the melt flow rate is 7 g / 10 min.

[0086] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 30 parts by weight of polylactic acid stereocomposite crystal precursor phase, 31 parts of polybutylene succinate buffer phase, 25 parts of hydroxyl-terminated polyester oligomer compensation phase, 10 parts of epoxidized soybean oil citrate locking phase, and 4 parts of biodegradable interface stabilizing phase.

[0087] The polylactic acid stereocomposite precursor phase is prepared by mixing dextrorotatory polylactic acid resin and levorotatory polylactic acid oligomers at a mass ratio of 1:0.8; the polybutylene succinate buffer phase is prepared by mixing low molecular weight polybutylene succinate and polycaprolactone at a mass ratio of 1:0.5, with a softening temperature of 68℃; the hydroxyl-terminated polyester oligomer compensating phase is prepared by mixing hydroxyl-terminated polybutylene succinate oligomers and polylactic acid-polycaprolactone copolymers at a mass ratio of 1:0.9; and the epoxidized soybean oil citrate locking phase is prepared by mixing epoxidized soybean oil citrate pre-reactant and carboxyl-terminated polylactic acid oligomers at a mass ratio of 1:0.5.

[0088] In preparation, the polylactic acid stereocomposite crystal precursor phase, polybutylene succinate buffer phase, hydroxyl-terminated polyester oligomer compensating phase, epoxidized soybean oil citrate locking phase, and degradable interface stabilizing phase were vacuum dried at 60℃ for 6 hours. After drying, they were added to a twin-screw extruder in the above proportions for segmented melt compounding. The temperatures of zones one to six were controlled at 120℃, 140℃, 155℃, 165℃, 175℃, and 180℃, respectively, and the screw speed was controlled at 100 r / min. The material was melt-plasticized, sheared compounded, extruded, water-cooled, and pelletized to obtain a crystallization shrinkage-responsive interface-controlled masterbatch with a two-sided phase structure.

[0089] L-coated polylactic acid resin, D-coated polylactic acid resin, polybutylene adipate terephthalate resin, polybutylene succinate resin, and processing aids were vacuum dried at 60°C for 8 hours. Crystallization shrinkage-responsive interface-regulating masterbatch was vacuum dried at 50°C for 6 hours. Subsequently, the above materials were added to a twin-screw extruder for melt blending in proportion. The temperatures of zones one to six were controlled at 155°C, 165°C, 175°C, 180°C, 180°C, and 175°C, respectively, and the screw speed was controlled at 160 r / min. The melt was extruded, water-cooled, air-dried, and pelletized to obtain fully biodegradable blended granules.

[0090] The obtained fully biodegradable blend particles were injection molded into standard samples. The injection molding barrel temperature was controlled at 170℃ to 185℃, the mold temperature at 35℃ to 45℃, the holding time at 8s, and the cooling time at 20s. The injection-molded samples were then briefly heat-set at 95℃ for 120s, and then conditioned at 23℃ and 50% relative humidity for 24h to obtain a highly heat-resistant and highly tough fully biodegradable blend.

[0091] Example 2:

[0092] By weight, take 68 parts of L-polylactic acid resin, 2 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0093] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0094] Example 3:

[0095] By weight, take 68 parts of L-polylactic acid resin, 6 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0096] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0097] Example 4:

[0098] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 4 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0099] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0100] Example 5:

[0101] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 14 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0102] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0103] Example 6:

[0104] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 12 parts of polybutylene adipate terephthalate resin, 12 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0105] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0106] Example 7:

[0107] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 24 parts of polybutylene adipate terephthalate resin, 4 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0108] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0109] Example 8:

[0110] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0111] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 20 parts by weight of polylactic acid stereocomposite crystal precursor phase, 42 parts of polybutylene succinate buffer phase, 18 parts of hydroxyl-terminated polyester oligomer compensation phase, 16 parts of epoxidized soybean oil citrate locking phase, and 4 parts of biodegradable interface stabilizing phase.

[0112] The softening temperature of the polybutylene succinate buffer phase is 55°C.

[0113] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0114] Example 9:

[0115] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0116] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 38 parts by weight of polylactic acid stereocomposite crystal precursor phase, 22 parts of polybutylene succinate buffer phase, 33 parts of hydroxyl-terminated polyester oligomer compensation phase, 5 parts of epoxidized soybean oil citrate locking phase, and 2 parts of biodegradable interface stabilizing phase.

[0117] The softening temperature of the polybutylene succinate buffer phase is 85℃.

[0118] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0119] Example 10:

[0120] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0121] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 20 parts by weight of polylactic acid stereocomposite crystal precursor phase, 22 parts of polybutylene succinate buffer phase, 34 parts of hydroxyl-terminated polyester oligomer compensation phase, 16 parts of epoxidized soybean oil citrate locking phase, and 8 parts of biodegradable interface stabilizing phase.

[0122] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0123] Comparative Example 1:

[0124] By weight, take 68 parts of L-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 1 part of ordinary epoxy compatibilizer, and 1.0 part of processing aid.

[0125] The above materials were vacuum dried at 60℃ for 8 hours and then added to a twin-screw extruder for melt blending. The temperatures of zones one through six were controlled at 155℃, 165℃, 175℃, 180℃, 180℃, and 175℃, respectively, and the screw speed was controlled at 160 r / min. The melt was extruded, water-cooled, air-dried, and pelletized to obtain blended granules. The blended granules were injection molded into standard samples and heat-set at 95℃ for 120 seconds to obtain a common PLA / PBAT / PBS blend material.

[0126] Comparative Example 2:

[0127] By weight, take 68 parts of L-polylactic acid resin, 1.8 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0128] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0129] Comparative Example 3:

[0130] By weight, take 68 parts of L-polylactic acid resin, 6.2 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0131] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0132] Comparative Example 4:

[0133] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 3.8 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0134] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0135] Comparative Example 5:

[0136] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 14.2 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0137] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0138] Comparative Example 6:

[0139] By weight, the following components were selected: 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 2.7 parts of polylactic acid stereocomposite crystal precursor phase, 2.79 parts of polybutylene succinate buffer phase, 2.25 parts of hydroxyl-terminated polyester oligomer compensating phase, 0.90 parts of epoxidized soybean oil citrate locking phase, 0.36 parts of biodegradable interface stabilizing phase, and 1.0 part of processing aid.

[0140] The polylactic acid stereocomposite crystal precursor phase, polybutylene succinate buffer phase, hydroxyl-terminated polyester oligomer compensating phase, epoxidized soybean oil citrate locking phase, and degradable interface stabilizing phase are directly melt-blended with L-type polylactic acid resin, D-type polylactic acid resin, polybutylene adipate terephthalate resin, polybutylene succinate resin, and processing aids.

[0141] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0142] Comparative Example 7:

[0143] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0144] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 61 parts by weight of polybutylene succinate buffer phase, 25 parts of hydroxyl-terminated polyester oligomer compensation phase, 10 parts of epoxidized soybean oil citrate locking phase, and 4 parts of biodegradable interface stabilizing phase.

[0145] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0146] Comparative Example 8:

[0147] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0148] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 61 parts by weight of polylactic acid stereocomposite crystal precursor phase, 25 parts of hydroxyl-terminated polyester oligomer compensating phase, 10 parts of epoxidized soybean oil citrate locking phase, and 4 parts of biodegradable interface stabilizing phase.

[0149] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0150] Comparative Example 9:

[0151] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0152] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 30 parts by weight of polylactic acid stereocomposite crystal precursor phase, 56 parts of polybutylene succinate buffer phase, 10 parts of epoxidized soybean oil citrate locking phase, and 4 parts of biodegradable interface-stabilizing phase.

[0153] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0154] Comparative Example 10:

[0155] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0156] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 30 parts by weight of polylactic acid stereocomposite crystal precursor phase, 31 parts of polybutylene succinate buffer phase, 35 parts of hydroxyl-terminated polyester oligomer compensation phase, and 4 parts of degradable interface stabilizing phase.

[0157] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0158] Comparative Example 11:

[0159] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0160] The crystallization shrinkage-responsive interface-controlled masterbatch is composed of 30 parts by weight of polylactic acid stereocomposite crystal precursor phase, 31 parts of polybutylene succinate buffer phase, 29 parts of hydroxyl-terminated polyester oligomer compensation phase, and 10 parts of epoxidized soybean oil citrate locking phase.

[0161] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0162] Comparative Example 12:

[0163] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0164] The polylactic acid stereocomposite precursor phase is prepared by mixing dextrorotatory polylactic acid resin and levorotatory polylactic acid oligomer in a mass ratio of 1:0.25.

[0165] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0166] Comparative Example 13:

[0167] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0168] The polylactic acid stereocomposite precursor phase is prepared by mixing dextrorotatory polylactic acid resin and levorotatory polylactic acid oligomer in a mass ratio of 1:1.25.

[0169] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0170] Comparative Example 14:

[0171] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0172] The polybutylene succinate buffer phase is made of low molecular weight polybutylene succinate and polycaprolactone, and has a softening temperature of 52°C.

[0173] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0174] Comparative Example 15:

[0175] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0176] The polybutylene succinate buffer phase is made of low molecular weight polybutylene succinate and polycaprolactone, and has a softening temperature of 88°C.

[0177] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0178] Comparative Example 16:

[0179] By weight, take 68 parts of L-polylactic acid resin, 4 parts of D-polylactic acid resin, 18 parts of polybutylene adipate terephthalate resin, 8 parts of polybutylene succinate resin, 9 parts of crystallization shrinkage responsive interface control masterbatch, and 1.0 part of processing aid.

[0180] The epoxidized soybean oil citrate locked phase is prepared by epoxidized soybean oil citrate pre-reactant and carboxyl-terminated polylactic acid oligomer at a mass ratio of 1:0.95.

[0181] Except for the above, the remaining components and preparation process are the same as in Example 1.

[0182] Experimental methods:

[0183] After the fully biodegradable blended particles obtained in each embodiment and comparative example were injection molded into standard samples, they were conditioned for 24 hours in an environment of 23°C and 50% relative humidity before performance testing was conducted. The conditioning and testing environment of the samples were carried out in accordance with GB / T 2918-2018 "Standard Environment for Conditioning and Testing of Plastic Samples", which is applicable to the constant environmental conditioning and testing of plastics and their various types of samples.

[0184] The load deformation temperature was determined in accordance with GB / T 1634.1-2025 "Determination of load deformation temperature of plastics - Part 1: General test method" and GB / T 1634.2-2019 "Determination of load deformation temperature of plastics - Part 2: Plastics and hard rubber".

[0185] In the specific test, an injection-molded specimen measuring 80mm × 10mm × 4mm was used, placed sideways on a three-point bending support structure. The bending stress was 0.45MPa, and the heating rate was 120℃ / h. The required loading force was calculated based on the specimen width, thickness, and support span, using the following formula: Where F is the loading force, σ is the bending stress, b is the specimen width, h is the specimen thickness, and L is the support span; when the specimen reaches the standard deflection during the heating process, the corresponding temperature is recorded, which is the load deformation temperature, in °C.

[0186] The impact strength of the notched simply supported beam was determined in accordance with GB / T 1043.1-2008 "Determination of impact properties of simply supported plastic beams - Part 1: Non-instrumental impact test".

[0187] In specific testing, 80mm×10mm×4mm injection-molded specimens were used, with an A-type notch machined in the middle of the specimen. The remaining width at the bottom of the notch was recorded as bN. The impact direction was the back of the notch. At least 5 valid specimens were tested in each group, and the specimen fracture absorption energy Ec was recorded. The impact strength of the notched simply supported beam was calculated according to the formula. Calculation, where Impact strength of a notched simply supported beam, in units of Ec is the energy absorbed during sample fracture, in J; h is the sample thickness, in mm. The remaining width at the notch is in mm. The arithmetic mean of the calculation results of the effective samples is taken as the impact strength of the notched simply supported beam of this group of materials.

[0188] The heat treatment method was GB / T 7141-2008 "Test Method for Heat Aging of Plastics". The notched simply supported beam impact strength was measured before and after heat treatment according to GB / T 1043.1-2008. GB / T 7141-2008 specifies the conditions for plastics to be exposed to hot air. The material properties after heat exposure can be evaluated by the selected mechanical property test method.

[0189] In the specific test, the injection-molded notched impact specimen was heat-treated in a 90℃ forced-air drying oven for 2 hours, and then removed and restored in an environment of 23℃ and 50% relative humidity for 2 hours. Then, the impact strength of the notched simply supported beam was retested according to GB / T 1043.1-2008. The heat treatment impact strength retention rate was calculated according to the formula R=at / a0×100%, where R is the heat treatment impact strength retention rate in %, a0 is the impact strength of the notched simply supported beam before heat treatment, and at is the impact strength of the notched simply supported beam after heat treatment at 90℃.

[0190] The dimensional change rate after heating at 90℃ was determined in accordance with GB / T 12027-2004 "Test Method for Dimensional Change Rate of Plastic Films and Sheets under Heating". This standard is applicable to the determination of longitudinal and transverse dimensional changes of plastic films and plastic sheets with a thickness of less than 1 mm under heating conditions.

[0191] In the specific testing, each group of fully biodegradable blended particles was compressed into sheet samples of 100mm × 100mm × 0.8mm. Initial gauge lengths were marked on both the longitudinal and transverse sides of the samples. The initial longitudinal gauge length was denoted as [insert initial gauge length here]. The initial lateral gauge length is denoted as The sample was placed in a 90℃ forced-air drying oven and heated for 30 minutes. After being removed, it was allowed to recover in an environment of 23℃ and 50% relative humidity for 30 minutes before the longitudinal gauge length was measured. and lateral gauge length The dimensional change rate after heating at 90℃ is calculated according to formula... Calculate, where D is the dimensional change rate after heating at 90℃, in percentage. and These are the longitudinal and transverse gauge lengths before heating, respectively. and These are the longitudinal and transverse gauge lengths after heating, respectively.

[0192] The melting enthalpy of the stereocomposite crystal was determined in accordance with GB / T 19466.3-2004 "Differential Scanning Calorimetry (DSC) for Plastics - Part 3: Determination of Melting and Crystallization Temperatures and Enthalpy".

[0193] In specific testing, 5mg to 8mg samples were cut from each group of samples, placed in an aluminum crucible and sealed. DSC testing was performed under a nitrogen atmosphere with a nitrogen flow rate of 50mL / min, a test temperature range of 30℃ to 250℃, and a heating rate of 10℃ / min. The melting peak of the polylactic acid stereocomposite crystal within the 200℃ to 240℃ range was used for baseline integration to obtain the enthalpy of fusion of the stereocomposite crystal. The enthalpy of fusion of the stereocomposite crystal was calculated according to the formula ΔHsc = A / m, where ΔHsc is the enthalpy of fusion of the stereocomposite crystal, in units of... A represents the integral heat of the melting peak of the stereocomplex crystal, in J, and m represents the sample mass, in g.

[0194] The proportion of the debonded area at the interface was determined by scanning electron microscopy and image area statistics. The magnification of the scanning electron microscope images was calibrated in accordance with GB / T 27788-2020 "Guidelines for Magnification Calibration of Scanning Electron Microscope Images for Microbeam Analysis".

[0195] In the specific testing, the impact fracture samples of each group were subjected to brittle fracture in liquid nitrogen. The fracture surface samples were then sputter-coated with gold and observed under a scanning electron microscope at an accelerating voltage of 5kV. Five cross-sectional areas were randomly selected from each group of samples, and images of each area were acquired at a magnification of 2000x. Image analysis software was used to identify voids, cracks, debonding gaps, and phase interface separation areas at the two-phase interface in the cross-sectional images as interface debonding areas. The observable area of ​​the cross-section was identified as the total statistical area. The proportion of interface debonding area was calculated according to the formula S=Ad / A0×100%, where S is the proportion of interface debonding area in %, Ad is the total area of ​​the interface debonding area, and A0 is the total statistical area of ​​the cross-section. The arithmetic mean of the calculation results of the five fields of view was taken as the proportion of interface debonding area of ​​the material group.

[0196] The 180-day biodegradation rate was determined in accordance with GB / T 19277.1-2025 "Determination of final aerobic biodegradation capacity of materials under controlled composting conditions by means of determination of carbon dioxide released - Part 1: General method".

[0197] In the specific test, each group of materials was crushed to a particle size of less than 2 mm. After determining the total organic carbon content of the samples, the samples were mixed with mature compost inoculum and placed in a controlled composting reaction vessel. The composting degradation test was carried out under the conditions of 58℃±2℃, aerobic and suitable humidity for 180 days. During the test, the amount of carbon dioxide released by the test vessel was measured periodically. At the same time, a blank vessel was set up to deduct the carbon dioxide released by the inoculum itself. The theoretical carbon dioxide release of the sample was calculated according to the formula ThCO2=m×C×44 / 12, where ThCO2 is the theoretical carbon dioxide release, m is the dry basis mass of the added test material, C is the mass fraction of total organic carbon of the test material, and 44 / 12 is the molecular weight conversion factor for carbon to carbon dioxide. The 180-day biodegradation rate was calculated according to the formula B=(CO2t-CO2b) / ThCO2×100%, where B is the 180-day biodegradation rate, CO2t is the cumulative amount of carbon dioxide released by the test vessel within 180 days, CO2b is the cumulative amount of carbon dioxide released by the blank vessel, and ThCO2 is the theoretical carbon dioxide release of the test material.

[0198] The experimental data are shown in the table below:

[0199] Table 1. Experimental parameters for the examples and comparative examples.

[0200] Group Load deformation temperature / ℃ Impact strength of a notched simply supported beam / kJ·m⁻² Post-heat shock strength retention rate / % Dimensional change rate after heating at 90℃ / % Enthalpy of fusion of stereocomplex crystals / J·g⁻¹ Percentage of interface debonding area / % 180d biodegradation rate / % Example 1 110.8 43.7 88.6 0.42 21.8 3.6 91.2 Example 2 99.4 41.5 83.2 0.69 14.6 5.8 90.7 Example 3 113.1 35.9 78.4 0.57 25.3 6.9 90.1 Example 4 101.6 36.8 80.5 0.76 16.2 7.4 91.6 Example 5 109.2 39.6 84.1 0.51 22.6 5.1 89.8 Example 6 108.4 40.8 85.7 0.48 20.9 4.4 90.9 Example 7 104.9 44.2 81.6 0.64 19.5 6.2 90.5 Example 8 102.7 38.9 82.4 0.72 15.8 6.8 91.0 Example 9 112.4 34.7 77.9 0.61 26.1 7.2 89.9 Example 10 107.6 41.3 86.2 0.46 19.7 4.1 90.3 Comparative Example 1 74.9 20.6 53.4 2.38 2.7 24.8 90.6 Comparative Example 2 88.6 34.1 69.5 1.34 9.1 12.9 91.1 Comparative Example 3 114.3 26.7 61.8 0.93 27.4 14.6 89.6 Comparative Example 4 93.5 31.2 68.7 1.21 12.4 13.5 91.4 Comparative Example 5 107.1 28.4 65.2 1.06 22.1 15.3 89.1 Comparative Example 6 91.8 27.9 62.4 1.57 11.6 18.7 90.8 Comparative Example 7 82.7 36.5 71.2 1.45 4.9 13.8 91.3 Comparative Example 8 108.6 22.8 55.6 1.18 21.2 19.5 90.2 Comparative Example 9 106.9 27.4 58.3 1.62 20.5 21.6 90.5 Comparative Example 10 104.3 30.1 60.9 1.38 19.8 22.4 90.7 Comparative Example 11 101.5 32.6 67.5 1.09 18.7 16.2 90.9 Comparative Example 12 93.2 35.8 72.1 1.13 10.8 11.7 91.0 Comparative Example 13 111.2 29.3 64.7 0.94 24.7 15.1 89.8 Comparative Example 14 98.4 34.5 63.8 1.46 18.9 17.5 90.6 Comparative Example 15 106.1 25.9 57.6 1.27 20.3 20.1 90.4 Comparative Example 16 106.5 26.8 59.2 1.31 20.6 19.4 89.7

[0201] Experimental conclusions and analysis:

[0202] As shown in Table 1, Example 1 exhibits the best overall performance, with a load deformation temperature reaching 110.8℃ and an impact strength of 43.7 for the notched simply supported beam. The heat-induced impact strength retention rate reached 88.6%, the dimensional change rate after heating at 90℃ was only 0.42%, and the melting enthalpy of the stereocomposite crystal was 21.8. The debonded area at the interface accounted for only 3.6%, and the biodegradation rate after 180 days still reached 91.2%, indicating that the present invention does not only improve a single heat resistance index, but achieves a good comprehensive balance between heat resistance, toughness, heat recovery toughness retention, dimensional stability and biodegradability.

[0203] Compared to Comparative Example 1, the load deformation temperature of Example 1 increased from 74.9℃ to 110.8℃, and the impact strength of the notched simply supported beam increased from 20.6℃. Increased to 43.7 The heat recovery rate of impact strength retention increased from 53.4% ​​to 88.6%, the dimensional change rate after heating at 90℃ decreased from 2.38% to 0.42%, and the proportion of interface debonding area decreased from 24.8% to 3.6%.

[0204] The above results demonstrate that even with the addition of common epoxy compatibilizers, ordinary PLA, PBAT, and PBS blends cannot simultaneously solve the problems of insufficient polylactic acid crystallization, thermal softening of the flexible phase, interfacial stress concentration, and post-thermal debonding. This invention addresses these issues by forming heat-resistant anchors for the polylactic acid stereocomposite crystals with a dextrorotatory polylactic acid resin and a polylactic acid stereocomposite crystal precursor phase. It also utilizes a polybutylene succinate buffer phase and a hydroxyl-terminated polyester oligomer compensating phase to absorb the interfacial displacement caused by polylactic acid crystallization shrinkage, and an epoxidized soybean oil citrate locking phase to form a localized reaction-locking region. This allows heat-resistant support, shrinkage compensation, and interfacial locking to occur synergistically within the same interfacial region.

[0205] Examples 2 and 3 correspond to the lower and upper limits of the protected range for the amount of dextrorotatory polylactic acid resin used, respectively. The enthalpy of fusion of the stereocomposite crystal in Example 2 is 14.6. The load deformation temperature was 99.4℃, indicating that even with a low dosage of dextrorotatory polylactic acid resin, a certain amount of stereocomposite crystals could still be formed and good impact toughness maintained, but the heat resistance was lower than that of Example 1. The enthalpy of melting of the stereocomposite crystals in Example 3 was increased to 25.3℃. The load deformation temperature increased to 113.1℃, but the impact strength of the notched simply supported beam decreased to 35.9kJ. The heat recovery rate of impact strength decreased to 78.4%, indicating that a higher amount of dextrorotatory polylactic acid resin is beneficial to improve heat resistance, but excessive stereocomposite crystals will increase the rigidity of the matrix and increase the risk of interfacial stress concentration.

[0206] Examples 4 and 5 correspond to the lower and upper limits of the protected range for the amount of masterbatch used in the crystallization shrinkage-responsive interface control, respectively. In Example 4, the load deformation temperature was 101.6℃, and the interface debonding area ratio was 7.4%, indicating that when the masterbatch amount was low, the number of interface gradient structures was insufficient, and the interface compensation and local locking effects were weakened. In Example 5, the load deformation temperature was 109.2℃, and the notched simply supported beam impact strength was 39.6. The debonding area ratio at the interface was 5.1%, indicating that a higher amount of masterbatch can maintain good heat resistance and interfacial stability. However, the impact strength and biodegradability of the material decreased slightly after the content of flexible components and oligomers increased.

[0207] The above data shows that a certain amount of crystallization shrinkage-responsive interface control masterbatch is required to form a continuous and effective interface gradient structure. However, excessive addition will also change the phase structure equilibrium. Therefore, the range of 4 to 14 parts can cover the effective range for achieving the technical effect.

[0208] Examples 6 and 7 show that variations in the ratio of polybutylene adipate terephthalate (PEPA) resin to polybutylene succinate (PBS) resin affect the flexible energy-dissipating zone and post-thermal dimensional stability. In Example 6, the PBS resin content was higher, resulting in a load deformation temperature of 108.4°C and a post-thermal dimensional change rate of 0.48% at 90°C, indicating that increasing the PBS resin content improves post-thermal support and dimensional retention.

[0209] In Example 7, the high content of polybutylene adipate terephthalate resin increased the notched simply supported beam impact strength to 44.2. However, the load deformation temperature decreased to 104.9℃, and the dimensional change rate after heating at 90℃ increased to 0.64%, indicating that when the flexible biodegradable polyester phase is too biased towards PBAT, it is beneficial for impact energy dissipation, but the dimensional stability after heating is slightly weaker. PBAT and PBS together constitute the flexible biodegradable polyester phase, which is more beneficial for balancing toughness and thermal stability than a single flexible toughening system.

[0210] Examples 8 to 10 further verified the rationality of the crystallization shrinkage-responsive interface regulation of the proportion range of each phase inside the masterbatch.

[0211] In Example 8, the polylactic acid stereocomposite crystal precursor phase was at a low level, with a load deformation temperature of 102.7°C and a melting enthalpy of 15.8°C. This indicates that reducing the number of heat-resistant anchor points decreases the material's heat resistance. In Example 9, the polylactic acid stereocomposite crystal precursor phase was relatively high, with a load deformation temperature reaching 112.4℃ and a stereocomposite crystal melting enthalpy reaching 26.1℃. However, the impact strength of the notched simply supported beam decreased to 34.7. This indicates that excessively strong heat-resistant crystals will reduce impact energy dissipation capacity.

[0212] The impact strength of the notched simply supported beam in Example 10 is 41.3. The post-thermal impact strength retention rate was 86.2%, and the interface debonding area ratio was 4.1%, indicating that the functional phases can still maintain a good comprehensive effect after recombination within a limited range. This proves that the protection scope of the present invention is not an isolated single point, but an effective technical range formed around the interface gradient structure.

[0213] Comparative Examples 2 and 3 respectively reflect the effect of deviating from the specified range in the dosage of dextrorotatory polylactic acid resin. The enthalpy of fusion of the stereocomposite crystal in Comparative Example 2 is only 9.1. The load deformation temperature dropped to 88.6℃, indicating that insufficient right-handed polylactic acid resin hinders the formation of sufficient heat-resistant anchor points in the polylactic acid stereocrystalline composite structure. Although the load deformation temperature of Comparative Example 3 reached 114.3℃, the impact strength of the notched simply supported beam decreased to 26.7. The heat-induced impact strength retention rate decreased to 61.8%, and the proportion of interface debonding area increased to 14.6%. This indicates that excessive D-co-polylactic acid resin does not simply bring better results, but will lead to matrix rigidification, excessive crystal concentration and enhanced interface stress. This comparison proves that the amount of D-co-polylactic acid resin used in this invention is not the conventional "the more the better," but needs to form a matching relationship with the flexible polyester phase and interface control masterbatch.

[0214] Comparative Examples 4 and 5 respectively reflect the effects of the amount of crystallization shrinkage-responsive interface-controlled masterbatch deviating from the specified range.

[0215] Comparative Example 4 exhibited a load deformation temperature of 93.5℃, a dimensional change rate of 1.21% after heating at 90℃, and an interfacial debonding area ratio of 13.5%. This indicates that insufficient masterbatch dosage prevents the formation of sufficiently continuous heat-resistant anchor points, crystallization shrinkage compensation zones, and local reaction locking zones at the phase interface. Comparative Example 5 maintained a load deformation temperature of 107.1℃, but the impact strength of the notched simply supported beam decreased to 28.4. The post-heat impact strength retention rate decreased to 65.2%, and the proportion of interface debonding area increased to 15.3%. This indicates that excessive masterbatch will cause enrichment of interface components, local aggregation of oligomers, or disruption of the continuity of flexible phase, which will weaken impact toughness and post-heat stability. This comparison shows that the present invention achieves interface structure balance by limiting the amount of masterbatch, rather than simply increasing the conventional optimization of compatible components.

[0216] Comparative Example 6 directly melt-blended the polylactic acid stereocrystalline precursor phase, polybutylene succinate buffer phase, hydroxyl-terminated polyester oligomer compensating phase, epoxidized soybean oil citrate locking phase, and biodegradable interface stabilizing phase, without first preparing a crystallization shrinkage-responsive interface-controlled masterbatch with a two-sided phase structure. The load deformation temperature of Comparative Example 6 was only 91.8℃, and the notched simply supported beam impact strength was 27.9. The heat-induced impact strength retention rate was 62.4%, the dimensional change rate after heating at 90℃ was 1.57%, and the debonding area at the interface accounted for 18.7%.

[0217] The results show that even when the total amount of each functional component is close to that of Example 1, without a masterbatch-based two-sided phase structure, it is difficult for each component to be directionally distributed in the phase interface region between the polylactic acid matrix phase and the flexible biodegradable polyester phase, and it is impossible to form an interface gradient structure that continuously transitions along the direction from the polylactic acid matrix phase to the flexible biodegradable polyester phase. This demonstrates that the core of this invention is not simply the superposition of formulations, but rather the achievement of interface positioning and functional zoning through a masterbatch structure.

[0218] Comparative Example 7, lacking the polylactic acid stereocomposite crystal precursor phase, experienced a reduced load deformation temperature of 82.7℃ and a stereocomposite crystal melting enthalpy of only 4.9℃. This indicates that the polylactic acid stereocomposite crystal precursor phase is a key factor in forming the heat-resistant anchor points. Comparative Example 8, lacking the polybutylene succinate buffer phase, still achieved a load deformation temperature of 108.6℃, but its notched simply supported beam impact strength was only 22.8. The heat-induced impact strength retention rate was 55.6%, and the interface debonding area accounted for 19.5%. This indicates that although the interface heat resistance support can be partially retained after the lack of a buffer phase, the impact energy cannot be effectively dissipated, and the stress difference between the rigid polylactic acid phase and the flexible biodegradable polyester phase cannot be buffered.

[0219] Comparative Example 9, lacking the hydroxyl-terminated polyester oligomer compensating phase, showed a dimensional change rate of 1.62% after heating at 90℃, and an interfacial debonding area ratio of 21.6%, indicating that the crystallization shrinkage compensation zone has a direct effect on suppressing post-heat warping and interfacial cracking. Comparative Example 10, lacking the epoxidized soybean oil citrate locking phase, showed an interfacial debonding area ratio of 22.4%, and a post-heat impact strength retention rate of only 60.9%, indicating that the local reaction locking zone is key to maintaining the interfacial bonding strength after heating.

[0220] Comparative Example 11 lacked a degradable interfacial stabilizing phase, and its interfacial debonding area ratio increased to 16.2%, indicating that the degradable interfacial stabilizing phase helps improve the dispersion and interfacial positioning stability of the masterbatch.

[0221] The above univariate comparative studies respectively established the direct causal relationship between five types of technical features and their corresponding technical effects: heat-resistant anchoring, flexible buffering, shrinkage compensation, reaction locking, and interface stability.

[0222] Comparative Examples 12 and 13 show that the mass ratio of dextrorotatory polylactic acid resin to levorotatory polylactic acid oligomer in the polylactic acid stereocomposite precursor phase also affects the balance between heat resistance and toughness. The enthalpy of fusion of the stereocomposite crystal in Comparative Example 12 is 10.8. The load deformation temperature was 93.2℃, indicating that when the proportion of L-polylactic acid oligomers is insufficient, the formation efficiency of the stereocomposite crystal precursor phase decreases.

[0223] The enthalpy of fusion of the stereocomposite crystal in Comparative Example 13 is 24.7. The load deformation temperature was 111.2℃, but the impact strength of the notched simply supported beam decreased to 29.3℃. This indicates that when the ratio is too high, local crystallization and rigidity are enhanced, which can easily lead to impact embrittlement and interface debonding. Data shows that the internal ratio of the polylactic acid stereocomposite crystal precursor phase is not arbitrarily adjustable, but needs to be coordinated with the interface compensation zone and the flexible energy dissipation zone.

[0224] Comparative Examples 14 and 15 reflect the effects of the polybutylene succinate buffer phase softening temperature deviating from the specified range. In Comparative Example 14, the polybutylene succinate buffer phase softening temperature was 52°C, and its dimensional change rate after heating to 90°C increased to 1.46%, while the post-heating impact strength retention rate was only 63.8%, indicating that premature softening of the buffer phase leads to insufficient interfacial support under hot operating conditions.

[0225] The softening temperature of the polybutylene succinate buffer phase in Comparative Example 15 was 88°C, and its notched simply supported beam impact strength decreased to 25.9. The post-heat impact strength retention rate was 57.6%, and the interface debonding area accounted for 20.1%. This indicates that when the softening temperature of the buffer phase is too high, the interface buffer phase cannot respond compliantly in time during heat setting and heat use, and cannot release the stress generated by polylactic acid crystallization shrinkage. The softening temperature range of 55℃ to 85℃ can ensure that the buffer phase does not lose support prematurely, and can also play a stress buffering role under heat setting and heat use conditions.

[0226] In Comparative Example 16, the internal proportion of the locked phase of epoxidized soybean oil citrate deviated from the specified range, resulting in a load deformation temperature of 106.5℃, but a notched simply supported beam impact strength of only 26.8℃. The post-heat impact strength retention rate was 59.2%, and the debonding area at the interface accounted for 19.4%.

[0227] The results show that a higher degree of localized locking is not necessarily better. When the proportion of carboxyl-terminated polylactic acid oligomers is too high, the rigidity of the localized reaction zone increases or the reaction structure becomes overly concentrated, which reduces interfacial flexibility and impact energy dissipation capacity. Therefore, this invention limits the mass ratio of epoxidized soybean oil citrate pre-reactant to carboxyl-terminated polylactic acid oligomers to avoid performance losses caused by insufficient or excessive localized locking.

[0228] The above experimental results confirm that the technical effect of this invention is not a conventional linear optimization resulting from changes in the content of a single component. Comparative Examples 3, 8, 9, and 10 all show that while increasing the content of stereocomposite crystals or retaining only a portion of the heat-resistant structure may maintain a higher load deformation temperature, it significantly sacrifices impact toughness, post-thermal impact strength retention, or interfacial stability.

[0229] Example 1 simultaneously achieves higher load deformation temperature, higher impact strength, lower post-thermal dimensional change rate, and lower interface debonding area ratio. This demonstrates that the present invention, through the gradient synergy of polylactic acid stereocomposite crystal heat-resistant anchor point, crystallization shrinkage compensation zone, local reaction locking zone, and flexible energy-dissipating zone, makes the shrinkage generated by post-crystallization of polylactic acid no longer simply manifest as an interface damage factor, but is transformed into interface stabilization conditions by the compensation phase and the locking phase.

[0230] The 180-day biodegradability of all embodiments and comparative examples remained between approximately 89.1% and 91.6%, indicating that the present invention, after introducing a crystallization shrinkage-responsive interface-controlled masterbatch and a local reaction-locking structure, did not significantly sacrifice the material's overall biodegradability. Therefore, the present invention can simultaneously improve heat resistance, toughness, and post-thermal dimensional stability while maintaining biodegradability, solving the problem of simultaneously improving heat resistance and maintaining toughness in ordinary fully biodegradable blends.

[0231] Based on the preferred embodiments of the present invention described above, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A highly heat-resistant, highly tough, fully biodegradable blend, characterized in that, By weight, it includes the following components: 60 to 76 parts of L-polylactic acid resin; 2 to 6 parts of dextrorotatory polylactic acid resin; 12 to 24 parts of polybutylene adipate terephthalate resin; 4 to 12 parts of polybutylene succinate resin; 4 to 14 parts of crystallization shrinkage-responsive interface-controlled masterbatch; Processing aids: 0.1 to 3 parts; The L-type polylactic acid resin and the D-type polylactic acid resin together form a polylactic acid matrix phase, and the polybutylene adipate terephthalate resin and the polybutylene succinate resin together form a flexible biodegradable polyester phase. The crystallization shrinkage-responsive interface-controlled masterbatch is at least partially distributed in the phase interface region between the polylactic acid matrix phase and the flexible biodegradable polyester phase; The crystallization shrinkage-responsive interface-controlled masterbatch is a masterbatch with a two-sided phase structure, including a polylactic acid stereocomposite crystal precursor phase facing the polylactic acid matrix phase, a polybutylene succinate buffer phase facing the flexible biodegradable polyester phase, a hydroxyl-terminated polyester oligomer compensation phase located between the polylactic acid stereocomposite crystal precursor phase and the polybutylene succinate buffer phase, and an epoxidized soybean oil citrate locking phase. The crystallization shrinkage-responsive interface-controlled masterbatch also includes a degradable interface-stabilized phase. The blend forms an interfacial gradient structure between the polylactic acid matrix phase and the flexible biodegradable polyester phase.

2. The high heat resistance, high toughness, fully biodegradable blend according to claim 1, characterized in that, The weight-average molecular weight of the L-type polylactic acid resin is 120,000 to 220,000, and the melt mass flow rate is 3g to 15g per 10min. The weight-average molecular weight of the dextrorotatory polylactic acid resin is between 80,000 and 180,000. The right-handed polylactic acid resin is used to form a polylactic acid stereocomposite heat-resistant structure in the polylactic acid matrix phase.

3. The high heat resistance, high toughness, fully biodegradable blend according to claim 1, characterized in that, The polybutylene adipate terephthalate resin has a weight-average molecular weight of 100,000 to 180,000 and a melt mass flow rate of 2 g to 8 g per 10 min. The polybutylene succinate resin has a weight-average molecular weight of 80,000 to 160,000 and a melt flow rate of 3 to 12 g per 10 min.

4. The high heat resistance, high toughness, fully biodegradable blend according to claim 1, characterized in that, By weight, the crystallization shrinkage-responsive interface-controlled masterbatch comprises the following components: 20 to 38 parts of polylactic acid stereocomposite crystal precursor phase; 22 to 42 parts of polybutylene succinate buffer phase; 18 to 34 parts of hydroxyl-terminated polyester oligomer compensating phase; 5 to 16 parts of epoxidized soybean oil citrate locked phase; Two to eight parts of the biodegradable interface stable phase.

5. The high heat resistance, high toughness, fully biodegradable blend according to claim 4, characterized in that, The polylactic acid stereocomposite crystal precursor phase is made of dextrorotatory polylactic acid resin and levorotatory polylactic acid oligomer; The mass ratio of the dextrorotatory polylactic acid resin to the levorotatory polylactic acid oligomer is from 1:0.3 to 1:1.

2. The polylactic acid stereocomposite crystal precursor phase is used to form heat-resistant anchor points for the polylactic acid stereocomposite crystal on one side of the polylactic acid matrix phase.

6. The high heat resistance, high toughness, fully biodegradable blend according to claim 4, characterized in that, The polybutylene succinate buffer phase is made of low molecular weight polybutylene succinate and polycaprolactone; The mass ratio of the low molecular weight polybutylene succinate to the polycaprolactone is 1:0.2 to 1:0.8; The softening temperature of the polybutylene succinate buffer phase is 55°C to 85°C.

7. The high heat resistance, high toughness, fully biodegradable blend according to claim 4, characterized in that, The hydroxyl-terminated polyester oligomer compensation phase is made of hydroxyl-terminated polybutylene succinate oligomer and polylactic acid polycaprolactone copolymer. The mass ratio of the hydroxyl-terminated polybutylene succinate oligomer to the polylactic acid-polycaprolactone copolymer is from 1:0.4 to 1:1.

5. The hydroxyl-terminated polyester oligomer compensation phase is located between the polylactic acid matrix phase and the flexible biodegradable polyester phase, and is used to form a crystallization shrinkage compensation zone.

8. The high heat resistance, high toughness, fully biodegradable blend according to claim 4, characterized in that, The epoxidized soybean oil citrate locked phase is made of epoxidized soybean oil citrate prereactant and carboxyl-terminated polylactic acid oligomer; The mass ratio of the epoxidized soybean oil citrate pre-reactant to the carboxyl-terminated polylactic acid oligomer is 1:0.2 to 1:0.9; The epoxidized soybean oil citrate locked phase is located between the crystallization shrinkage compensation zone and the flexible biodegradable polyester phase, and is used to form a local reaction locked zone.

9. The high heat resistance, high toughness, fully biodegradable blend according to claim 1, characterized in that, The interface gradient structure, along the direction from the polylactic acid matrix phase to the flexible biodegradable polyester phase, sequentially includes a polylactic acid stereocomposite crystal heat-resistant anchor point, a crystallization shrinkage compensation zone, a local reaction locking zone, and a flexible energy-dissipating zone. The local reaction-locked region contains an ester bond connection structure formed by the reaction of epoxidized soybean oil citrate pre-reactant and polyester end groups; The proportion of the crystallization shrinkage-responsive interface-controlled masterbatch located in the phase interface region is 50% to 85%.

10. A method for preparing a highly heat-resistant, highly tough, fully biodegradable blend as described in any one of claims 1 to 9, characterized in that, The process includes the following steps: preparing a crystallization shrinkage-responsive interface-controlled masterbatch by combining a polylactic acid stereocomposite crystal precursor phase, a polybutylene succinate buffer phase, a hydroxyl-terminated polyester oligomer compensating phase, an epoxidized soybean oil citrate locking phase, and a biodegradable interface-stabilizing phase. The L-type polylactic acid resin, D-type polylactic acid resin, polybutylene adipate terephthalate resin, polybutylene succinate resin, processing aids, and the crystallization shrinkage-responsive interface control masterbatch are melt-blended so that the crystallization shrinkage-responsive interface control masterbatch is at least partially distributed in the phase interface region between the polylactic acid matrix phase and the flexible biodegradable polyester phase. The melt-blended material is shaped and heat-set for a short time, so that the polylactic acid matrix phase forms polylactic acid stereocomposite heat-resistant anchor points, and the crystallization shrinkage-responsive interface control masterbatch forms an interface gradient structure including a crystallization shrinkage compensation zone and a local reaction locking zone between the polylactic acid matrix phase and the flexible biodegradable polyester phase.

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