A fully bio-based PBAT-PLA copolymer, preparation method and application thereof

Abstract

The present application relates to the technical field of bio-based polymer material, and more particularly to a full bio-based PBAT-PLA copolymer, a preparation method and an application thereof, which is prepared by melt mixing bio-based polybutylene adipate terephthalate, bio-based polylactic acid and bio-based multi-epoxy chain extender through a twin-screw extruder, so that the tensile strength of the full bio-based PBAT-PLA copolymer is 31.5-44.3 MPa, and the elongation at break is 85-498%. The bio-based multi-epoxy chain extender prepared by specific selection can simultaneously improve the tensile strength and elongation at break of the full bio-based PBAT-PLA copolymer, and solve the technical problems of poor compatibility of traditional bio-based polylactic acid and non-bio-based polybutylene adipate terephthalate, and the technical problem that the addition of existing chain extenders cannot simultaneously improve the tensile strength and elongation at break of the copolymer.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bio-based high molecular materials, and particularly relates to a full bio-based PBAT-PLA copolymer and a preparation method and application thereof. BACKGROUND

[0002] In recent years, non-petroleum-based degradable materials have attracted more and more attention. Among many biodegradable materials, polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) are the most common biodegradable materials on the market. They each have different characteristics and application scenarios, and occupy an important position in the market.

[0003] Bio-based raw materials, such as bio-based polylactic acid (PLA), are a kind of bio-based degradable materials obtained by fermentation of renewable resources such as corn starch, and have the advantages of high strength and good gloss, but their brittleness is serious, with an elongation at break of only about 5%, which seriously limits the development and application of PLA materials. Polybutylene adipate terephthalate (PBAT) is a degradable material derived from petroleum, which combines the advantages of polybutylene adipate (PBA) and polybutylene terephthalate (PBT), and has good flexibility and elongation at break. By blending PBAT with PLA to prepare PBAT / PLA blends, the toughness of PLA can be improved while the strength of PBAT is improved, thereby preparing PBAT / PLA blended materials with excellent performance. However, the polarity difference between PBAT and PLA is large, and direct blending can easily lead to phase separation and compatibility problems.

[0004] In current research work, most researchers mainly use different types of compatibilizers to modify PBAT-PLA. For example, the author Xia Xuelian et al. published a literature entitled “Reactive compatibilization of PLA / PBAT blends” in the journal “Plastics Industry”, which specifically disclosed the use of maleic anhydride (MAH) and 2,2'- (1,3-phenylene) bisoxazoline (BOZ) as compatibilizers to improve the compatibility of PLA / PBAT system through reactive compatibilization. The results showed that MAH and BOZ reacted with PLA / PBAT, increasing the interaction between PLA and PBAT and improving the comprehensive mechanical properties of the composite material. Compared with PLA / PBAT, the tensile, impact strength and elongation at break of the compatibilized composite material were increased by 13.72%, 139.67% and 122.12%, respectively.

[0005] Or for example, Xiong Kai and other authors published a document titled "Study on Toughening Modification of PLA / PBAT System by E-MA-MAH Triblock Copolymer" in the journal "Guangzhou Chemical Industry". It specifically disclosed the use of ethylene-ethyl acrylate-maleic anhydride triblock copolymer (E-MA-MAH) as a compatibilizer for PLA / PBAT. The results showed that the anhydride functional groups of the compatibilizer reacted with the active functional groups of the PBAT and PLA blend system, increasing the interfacial adhesion and significantly improving the toughness of the blend.

[0006] While the compatibilizers employed in the aforementioned prior art studies have improved the compatibility of PBAT-PLA and achieved a certain degree of improvement in mechanical properties, the PBAT employed is petroleum-based, whose production relies on fossil fuels such as petroleum, a non-renewable resource. Furthermore, conventional preparation methods for all-biobased PBAT-PLA copolymers rely solely on physical blending, which cannot guarantee dispersibility. Furthermore, the compatibilizers used are not biomass-derived. These various factors have limited the research and development of all-biobased PBAT-PLA copolymers.

[0007] CN116968214A discloses a method for improving the compatibility of PLA with other bio-based degradable plastics. The method comprises the following components in parts by weight: 10-60 parts of PLA, 40-90 parts of other bio-based degradable plastics, 0.2-0.35 parts of a modifier, and 0.3-0.5 parts of an antioxidant, wherein the other bio-based degradable plastics are PBAT or PBS. A method for improving the compatibility of the blended material is also disclosed. However, the tensile strength and elongation at break of the product obtained according to this technical solution cannot be simultaneously improved. For example, in Example 3, the tensile strength is 47.2 MPa, but the elongation at break is only 43.3%, or in Example 5, the elongation at break is 497%, but the tensile strength is only 23.4 MPa.

[0008] CN117304665A discloses a method for preparing a PLA / PBAT composite material synergistically modified with a polylactic acid graft copolymer and a bio-based additive. This method involves melt-blending dried polylactic acid (PLA), polybutylene terephthalate-adipate (PBAT), the polylactic acid graft copolymer, and a compatibilizer through a twin-screw extruder. The compatibilizer's epoxy groups react with the hydroxyl groups in the blend to improve compatibility. However, this technical solution still yields unsatisfactory results, with the highest elongation at break being only 165.505%, which still fails to meet the current market demand for bio-based materials with both improved elongation at break and tensile strength.

[0009] Based on the above-mentioned existing technology, there are technical problems in the existing technology that need to be solved urgently, such as the inability to simultaneously improve the tensile strength and elongation at break when preparing PBAT-PLA copolymers using bio-based raw materials, and the poor compatibility between PLA and PBAT. Summary of the Invention

[0010] To solve the above technical problems, the present invention provides a fully bio-based PBAT-PLA copolymer, which is prepared by melt mixing bio-based poly(butylene terephthalate-adipate-butylene terephthalate) (PBAT), bio-based poly(lactic acid) (PLA), and a bio-based multi-epoxy chain extender through a twin-screw extruder;

[0011] The bio-based multi-epoxy chain extender has an epoxy value of ≥0.49 mol / 100 g and an epoxy group number of ≥4 per molecule;

[0012] The all-biobased PBAT-PLA copolymer has a tensile strength of 31.5-44.3 MPa and an elongation at break of 85-498%.

[0013] Furthermore, the test standard for the tensile strength and elongation at break is IOS527-2012.

[0014] Furthermore, in parts by weight, the components and contents of the all-biobased PBAT-PLA copolymer are as follows:

[0015] Bio-based polybutylene terephthalate-adipate (PBAT): 20-80 parts by weight;

[0016] Bio-based polylactic acid (PLA): 20-80 parts by weight;

[0017] Bio-based polyvalent epoxy chain extender: 0.3-2 parts by weight.

[0018] Furthermore, the bio-based polyvalent epoxy chain extender is preferably 0.3 parts by weight.

[0019] Furthermore, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is 70,000-120,000.

[0020] Furthermore, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is preferably 77,000-78,000.

[0021] Furthermore, the weight average molecular weight of the bio-based polylactic acid (PLA) is 100,000-150,000.

[0022] Furthermore, the weight average molecular weight of the bio-based polylactic acid (PLA) is preferably 120,000.

[0023] Furthermore, the bio-based polybutylene terephthalate-adipate (PBAT) is prepared by esterification and polycondensation of bio-based dibasic acid and bio-based diol via a first catalyst.

[0024] Furthermore, the bio-based dibasic acid is bio-based terephthalic acid and bio-based adipic acid.

[0025] Furthermore, the mass ratio of the bio-based terephthalic acid to the bio-based adipic acid is 1:1.

[0026] Furthermore, the bio-based diol is bio-based butanediol.

[0027] Furthermore, the mass ratio of the bio-based dibasic acid to the bio-based diol is 1:(1.4-1.5).

[0028] Furthermore, the mass ratio of the bio-based dibasic acid to the bio-based diol is preferably 1:1.44.

[0029] Furthermore, the first catalyst is tetrabutyl titanate.

[0030] Furthermore, the amount of the first catalyst added is 100-800 ppm of the overall bio-based poly (butylene terephthalate-adipate-butylene terephthalate) (PBAT) raw material.

[0031] Furthermore, the amount of the first catalyst added is 500 ppm of the overall bio-based poly (butylene terephthalate-adipate-butylene terephthalate) (PBAT) raw material.

[0032] Furthermore, the bio-based polyvalent epoxy chain extender is prepared from highly unsaturated vegetable oil, hydroxyl-containing vegetable oil, and auxiliary vegetable oil in a hydrogen peroxide aqueous solution by catalysis of a second catalyst.

[0033] Furthermore, the components and contents of the bio-based multi-epoxy chain extender are as follows:

[0034] Highly unsaturated vegetable oil: 30-45 parts by weight;

[0035] Hydroxyl-containing vegetable oil: 5-15 parts by weight;

[0036] Auxiliary vegetable oil: 5-15 parts by weight;

[0037] Second catalyst: 0.5-2 parts by weight;

[0038] Aqueous hydrogen peroxide solution: 60-90 parts by weight.

[0039] Furthermore, in parts by weight, the components and contents of the bio-based multi-epoxy chain extender are preferably:

[0040] Highly unsaturated vegetable oil: 35 parts by weight;

[0041] Hydroxyl-containing vegetable oil: 10 parts by weight;

[0042] Auxiliary vegetable oil: 10 parts by weight;

[0043] Second catalyst: 0.5 parts by weight;

[0044] Aqueous hydrogen peroxide solution: 60 parts by weight.

[0045] Furthermore, the highly unsaturated vegetable oil is one or more of linseed oil and tung oil.

[0046] Furthermore, the hydroxyl-containing vegetable oil is castor oil.

[0047] Furthermore, the auxiliary vegetable oil is soybean oil.

[0048] Furthermore, the second catalyst is a polymer of vinylbenzenesulfonic acid and divinylbenzene, with a chemical name of Amberlyst 15 and a CAS number of 39389-20-3.

[0049] Furthermore, the volume concentration of the hydrogen peroxide aqueous solution is 30-50%.

[0050] Furthermore, the volume concentration of the hydrogen peroxide aqueous solution is preferably 30-50%.

[0051] The present invention also provides a method for preparing a fully bio-based PBAT-PLA copolymer, comprising the following steps:

[0052] Step 1: Bio-based polylactic acid (PLA) pretreatment: Dry the bio-based polylactic acid for later use;

[0053] Step 2: preparing bio-based poly(butylene terephthalate-adipate) (PBAT): adding the bio-based dibasic acid and the bio-based diol into a reactor, stirring and mixing them uniformly, adding a first catalyst, and causing an esterification reaction. After the esterification reaction is completed, the reactor is heated to carry out a polycondensation reaction. After the polycondensation reaction is completed, a melt of bio-based poly(butylene terephthalate-adipate) (PBAT) is obtained.

[0054] Step 3: preparing a bio-based multi-epoxy chain extender: uniformly mixing a highly unsaturated vegetable oil, a hydroxyl-containing vegetable oil, and an auxiliary vegetable oil to obtain a mixed oil, adding a second catalyst and an aqueous hydrogen peroxide solution to the mixed oil to cause an epoxidation reaction to obtain a bio-based multi-epoxy chain extender;

[0055] Step 4: Evenly mix the bio-based polylactic acid (PLA) obtained in step 1 and the bio-based multi-epoxy chain extender obtained in step 3 to obtain a premix;

[0056] Step 5: The premix obtained in step 4 is fed into a twin-screw extruder through a main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based poly(butylene terephthalate-adipate) (PBAT) obtained in step 3 is fed into the twin-screw extruder through a side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation and drying, the fully bio-based PBAT-PLA copolymer is obtained.

[0057] Furthermore, the drying temperature in step 1 is 70° C. and the drying time is 8 h, which effectively removes moisture and prevents hydrolysis of the bio-based polylactic acid.

[0058] Furthermore, the esterification reaction in step 2 is carried out at a temperature of 170-230° C. and for a time of 2.5-4 hours.

[0059] Furthermore, the temperature of the esterification reaction in step 2 is preferably 230° C., and the time is 3.5 h.

[0060] Furthermore, the heating rate is 0.5-2°C / min.

[0061] Furthermore, the heating rate is preferably 1°C / min.

[0062] Furthermore, the temperature of the polycondensation reaction is 200-240° C., and the time is 2.5-4 hours.

[0063] Furthermore, the polycondensation reaction temperature is preferably 240° C. and the time is 4 hours.

[0064] Furthermore, step 3 also includes dehydrating and removing impurities from the mixed oil.

[0065] Furthermore, the dehydration and impurity removal is performed by vacuum dehydration at 110-120° C. for 2-3 hours, and filtering to remove impurities.

[0066] Furthermore, the epoxidation reaction is carried out at 60-80° C. and 300 rpm for 4-8 hours, and the epoxy value is monitored using the hydrochloric acid-acetone method (GB / T 1677-2008).

[0067] Furthermore, the epoxidation reaction is carried out at 65° C. and 300 rpm with stirring for 5 hours.

[0068] Furthermore, the epoxy value of the bio-based polyvalent epoxy chain extender is preferably 0.49 mol / 100 g, and the number of epoxy groups is preferably 4 per molecule.

[0069] Furthermore, after the epoxidation reaction occurs in step 3, the second catalyst is filtered and recovered, the product is washed with water until neutral, and then distilled under reduced pressure to obtain a bio-based multi-epoxy chain extender.

[0070] Furthermore, the conditions for the reduced pressure distillation are: pressure 0.05-0.1 MPa, temperature 60-90° C., and time 1-3 h.

[0071] Furthermore, the conditions for the reduced pressure distillation are preferably: pressure 0.05 MPa, temperature 60° C., and time 2 h.

[0072] Furthermore, the aspect ratio of the twin-screw extruder in step 5 is 52:1.

[0073] Furthermore, the melt of the bio-based polybutylene terephthalate-adipate (PBAT) is transported to the twin-screw extruder through a melt delivery pipe and a melt metering pump under the action of a melt booster pump.

[0074] Furthermore, the temperatures of each zone of the twin-screw extruder are set to 90-100°C in zone 1, 110-130°C in zone 2, 130-150°C in zone 3, 150-170°C in zone 4, 170-190°C in zone 5, 170-190°C in zone 6, 170-190°C in zone 7, 170-190°C in zone 8, 170-190°C in zone 9, 170-190°C in zone 10, 170-190°C in zone 11, 170-190°C in zone 12, and 170-190°C in zone 13.

[0075] Furthermore, the temperature of each zone of the twin-screw extruder is preferably set to 90°C in zone 1, 110°C in zone 2, 130°C in zone 3, 150°C in zone 4, 170°C in zone 5, 170°C in zone 6, 170°C in zone 7, 170°C in zone 8, 180°C in zone 9, 180°C in zone 10, 185°C in zone 11, 185°C in zone 12, and 190°C in zone 13.

[0076] Furthermore, the screw speed of the twin-screw extruder is 200-300 r / min, and the feeding speed is 10-30 Hz.

[0077] Furthermore, the screw speed of the twin-screw extruder is preferably 220 r / min, and the feeding rate is 20 Hz.

[0078] Furthermore, after extrusion granulation, the drying condition is 70° C. for 8 h.

[0079] The present invention also provides a plastic product, which is prepared by injection molding or blow molding the above-mentioned all-biobased PBAT-PLA copolymer.

[0080] Furthermore, the plastic products are plastic tableware, including but not limited to plastic straws and plastic knives and forks.

[0081] The beneficial effects of the present invention are:

[0082] 1. The all-bio-based PBAT-PLA copolymer of the present invention is prepared by melt mixing bio-based poly(butylene terephthalate-adipate), bio-based poly(lactic acid), and a bio-based poly(epoxy) chain extender through a twin-screw extruder. The copolymer has a tensile strength of 31.5-44.3 MPa and an elongation at break of 85-498%. The copolymer is prepared by specifically selecting a bio-based poly(epoxy) chain extender, i.e., the bio-based poly(epoxy) chain extender has an epoxy value of ≥0.49 mol / 100 g and the number of epoxy groups is ≥4 per molecule. This improves both the tensile strength and elongation at break of the copolymer, thereby resolving the technical issues of poor compatibility between conventional bio-based poly(lactic acid) and non-bio-based poly(butylene terephthalate-adipate), as well as the inability of existing commercially available chain extenders to simultaneously improve both the tensile strength and elongation at break of the copolymer.

[0083] 2. The present invention specifically prepares a bio-based multi-epoxy chain extender. During the preparation of the bio-based multi-epoxy chain extender, the cyclization reaction of the double bond is the main reaction. By controlling the content of each component in the bio-based multi-epoxy chain extender and the preparation conditions, the epoxy value and the number of epoxy groups of the bio-based multi-epoxy chain extender are directionally controlled to prepare the fully bio-based PBAT-PLA copolymer with both high tensile strength and high elongation at break. The epoxy groups can react with the terminal carboxyl groups of PLA and the terminal hydroxyl groups of PBAT to form a chemical bridging structure of PLA-chain extender-PBAT, significantly improving the interfacial bonding strength between the two phases. At the same time, the fully bio-based PBAT-PLA copolymer is prepared by melt-in-line addition of bio-based poly(butylene terephthalate-adipate) (PBAT). In addition, the raw materials used in the preparation are all selected from renewable bio-based raw materials, achieving the fully bio-based preparation of the fully bio-based PBAT-PLA copolymer.

[0084] 3. The present invention ensures that the epoxy value of the prepared bio-based multi-epoxy chain extender is ≥0.49 mol / 100g, which can ensure sufficient reaction sites. Because the terminal group concentration of PBAT and PLA is relatively low, if the epoxy value is too low, the chain extender cannot fully react with the polymer, resulting in insufficient molecular weight increase or limited compatibility improvement. It also ensures rapid ring-opening reaction during the melt extrusion process of the twin-screw extruder at the processing temperature (170-190°C) while avoiding side reactions such as epoxy group self-polymerization.

[0085] The number of epoxy groups is ≥4 per molecule in order to form a stable three-dimensional network structure. The multiple epoxy groups in a single molecule can react simultaneously with multiple PLA or PBAT molecular chains to construct a lightly cross-linked network. Existing commercially available chain extenders, such as BASF's epoxy chain extender ADR, can only achieve linear chain extension. The bio-based multi-epoxy chain extender specifically prepared in this invention has multiple epoxy groups that can achieve both chain extension and branching. This reduces phase separation through chemical bonds, significantly improving tensile strength and elongation at break.

[0086] 4. In the preparation process of the present invention, the bio-based polylactic acid (PLA) and the bio-based multi-epoxy chain extender obtained in step 3 are specifically mixed to obtain a premix, which is then fed into the twin-screw extruder via a main feeding system connected to zone 1 of the twin-screw extruder. A bio-based polybutylene terephthalate-adipate (PBAT) melt is then fed into the twin-screw extruder via a side feeding system connected to zone 3 of the twin-screw extruder. This ensures that the PLA and the chain extender react preferentially, preventing premature consumption of the chain extender by the PBAT melt. PBAT is then introduced into the high-temperature shear zone (zone 3), where the remaining epoxy groups of the chain extender achieve final crosslinking. By precisely controlling the epoxy value and number of epoxy groups of the chain extender, combined with the specific raw material addition process and equipment operating parameters of the twin-screw extruder, the fully bio-based PBAT-PLA copolymer can achieve an optimal balance between toughness, thermal stability, and processability. This copolymer is suitable for producing higher-quality plastic products that require injection molding or blow molding, such as plastic tableware, including but not limited to plastic straws and plastic cutlery. BRIEF DESCRIPTION OF THE DRAWINGS

[0087] Figure 1 This is a graph showing the molecular weight test results of the bio-based poly (butylene terephthalate-adipate) prepared in the present invention;

[0088] Figure 2 The infrared spectra of the fully bio-based PBAT-PLA copolymer of the present invention are compared with pure PBAT and pure PLA;

[0089] Figure 3 This is a scanning electron micrograph of the fully bio-based PBAT-PLA copolymer prepared in Example 1 of the present invention;

[0090] Figure 4 This is a scanning electron micrograph of the copolymer prepared in Comparative Example 2 of the present invention;

[0091] Figure 5 This is a scanning electron microscope image of the copolymer prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0092] Example 1

[0093] This embodiment provides a fully bio-based PBAT-PLA copolymer, which is prepared by melt mixing bio-based polybutylene terephthalate-adipate (PBAT), bio-based polylactic acid (PLA), and a bio-based multi-epoxy chain extender through a twin-screw extruder; the fully bio-based PBAT-PLA copolymer has a tensile strength of 31.5 MPa and an elongation at break of 498%.

[0094] In parts by weight, the components and contents of the all-biobased PBAT-PLA copolymer are as follows:

[0095] Bio-based polybutylene terephthalate-adipate (PBAT): 80 parts by weight;

[0096] Bio-based polylactic acid (PLA): 20 parts by weight;

[0097] Bio-based polyvalent epoxy chain extender: 0.3 parts by weight;

[0098] The preparation method of the all-biobased PBAT-PLA copolymer comprises the following steps:

[0099] Step 1: Pretreatment of bio-based polylactic acid (PLA): Dry the bio-based polylactic acid at 70°C for 8 hours before use to effectively remove moisture and prevent hydrolysis of the bio-based polylactic acid.

[0100] In this embodiment, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120,000; the bio-based polylactic acid (PLA) is purchased from Zhejiang Hisun Biomaterials Co., Ltd.

[0101] In some embodiments, the bio-based polylactic acid is a commercially available bio-based raw material that can be directly purchased;

[0102] Step 2: Preparation of bio-based poly (butylene terephthalate-adipate) (PBAT): Add the bio-based dibasic acid and the bio-based diol into a reactor at a mass ratio of 1:1.44, stir and mix them evenly, add 500 ppm of the first catalyst, and conduct an esterification reaction at 230°C for 3.5 hours. Then, heat the reactor to 240°C at a heating rate of 1°C / min for a polycondensation reaction for 4 hours. Finally, a melt of bio-based poly (butylene terephthalate-adipate) (PBAT) is obtained.

[0103] In this embodiment, the bio-based dibasic acid is bio-based terephthalic acid and bio-based adipic acid in a mass ratio of 1:1, and the bio-based diol is bio-based butanediol;

[0104] The bio-based terephthalic acid was purchased from STORA ENSO OYJ; the bio-based adipic acid was purchased from Toray Industries, Inc.

[0105] The bio-based butanediol was purchased from Yuanli Chemical Group Co., Ltd.

[0106] In some embodiments, the bio-based terephthalic acid, bio-based adipic acid, and bio-based butanediol are all commercially available bio-based raw materials that can be directly purchased;

[0107] In this embodiment, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is 77917, and the molecular weight is measured as follows:

[0108] The results were determined by gel permeation chromatography (GPC) using a Waters model e2695 high performance liquid chromatograph, with the GPC column eluted with tetrahydrofuran at a flow rate of 1 ml / min at 25°C. Figure 1 shown; according to Figure 1 The obtained general peak table is shown in Table 1:

[0109] Table 1 General peak table of bio-based poly (butylene terephthalate-adipate-butylene terephthalate) (PBAT)

[0110]

[0111] Step 3, preparing a bio-based multi-epoxy chain extender: 35 parts by weight of a highly unsaturated vegetable oil, linseed oil, 10 parts by weight of a hydroxyl-containing vegetable oil, castor oil, and 10 parts by weight of an auxiliary vegetable oil, soybean oil, are uniformly mixed to obtain a mixed oil, and the mixed oil is dehydrated and impurity-removed, wherein the dehydration and impurity-removal comprises vacuum dehydration at 110° C. for 2.5 hours, filtering to remove impurities, adding 0.5 parts by weight of a second catalyst, Amberlyst 15, and 60 parts by weight of an aqueous hydrogen peroxide solution (volume concentration of 40%) to the mixed oil, and causing an epoxidation reaction, specifically reacting at 65° C. and stirring at 300 rpm for 5 hours, monitoring the end point by the epoxy value, i.e., the epoxy value of the bio-based multi-epoxy chain extender is 0.49 mol / 100 g, and the number of epoxy groups is 4 / molecule. The second catalyst is then filtered to recover, the product is washed with water until neutral, and subjected to reduced pressure distillation at a pressure of 0.05 MPa and a temperature of 60° C. for 2 hours to obtain a bio-based multi-epoxy chain extender;

[0112] Step 4: uniformly mixing the bio-based polylactic acid (PLA) obtained in step 1 and the bio-based multi-epoxy chain extender obtained in step 3 to obtain a premix;

[0113] Step 5: The premix obtained in step 4 is fed into the twin-screw extruder through the main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based poly(butylene terephthalate-adipate) (PBAT) obtained in step 2 is fed into the twin-screw extruder through the side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation, the mixture is dried at 70° C. for 8 hours to obtain the fully bio-based PBAT-PLA copolymer.

[0114] In this embodiment, the aspect ratio of the twin-screw extruder in step 5 is 52:1.

[0115] The melt of the bio-based polybutylene terephthalate-adipate (PBAT) is transported to the twin-screw extruder through a melt delivery pipe and a melt metering pump under the action of a melt booster pump.

[0116] The temperatures of each zone of the twin-screw extruder are set to 90°C for zone 1, 110°C for zone 2, 130°C for zone 3, 150°C for zone 4, 170°C for zone 5, 170°C for zone 6, 170°C for zone 7, 170°C for zone 8, 180°C for zone 9, 180°C for zone 10, 185°C for zone 11, 185°C for zone 12, and 190°C for zone 13.

[0117] The screw speed of the twin-screw extruder is 220 r / min, and the feeding rate is 20 Hz.

[0118] like Figure 2 As shown, the infrared spectra of the bio-based PBAT-PLA copolymer prepared in this embodiment, pure PBAT and pure PLA were measured by transmission method using a TENSOR-2 Fourier transform infrared spectrometer from BRUKER, Germany, and compared. As can be seen from the figure, pure PLA has a high infrared spectroscopy at 1752 cm -1 The absorption peak near it is the characteristic peak of its ester group. The absorption peak of pure PBAT is at 1715cm -1 The absorption peak near 1752cm is the characteristic peak of its ester group. After copolymerization, PLA and PBAT have a peak at 1752cm -1 and 1715cm -1 The absorption peak near 1757 cm -1 and 1717cm -1 There are absorption peaks near the carbonyl stretching vibration frequency (1717 cm -1 ) with the ester group of PLA (1752 cm -1 ) interact with each other, resulting in a shift in the characteristic peak position of the PBAT-PLA copolymer prepared in this example.

[0119] Example 2

[0120] This embodiment provides a fully bio-based PBAT-PLA copolymer, which is prepared by melt mixing bio-based polybutylene terephthalate-adipate (PBAT), bio-based polylactic acid (PLA), and a bio-based multi-epoxy chain extender through a twin-screw extruder; the fully bio-based PBAT-PLA copolymer has a tensile strength of 44.3 MPa and an elongation at break of 85%.

[0121] In parts by weight, the components and contents of the all-biobased PBAT-PLA copolymer are as follows:

[0122] Bio-based polybutylene terephthalate-adipate (PBAT): 20 parts by weight;

[0123] Bio-based polylactic acid (PLA): 80 parts by weight;

[0124] Bio-based polyvalent epoxy chain extender: 0.3 parts by weight;

[0125] The preparation method of the all-biobased PBAT-PLA copolymer comprises the following steps:

[0126] Step 1: Pretreatment of bio-based polylactic acid (PLA): Dry the bio-based polylactic acid at 70°C for 8 hours before use to effectively remove moisture and prevent hydrolysis of the bio-based polylactic acid.

[0127] In this embodiment, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120,000; the bio-based polylactic acid (PLA) is purchased from Zhejiang Hisun Biomaterials Co., Ltd.

[0128] In some embodiments, the bio-based polylactic acid is a commercially available bio-based raw material that can be directly purchased;

[0129] Step 2: Preparation of bio-based poly (butylene terephthalate-adipate) (PBAT): Add the bio-based dibasic acid and the bio-based diol into a reactor at a mass ratio of 1:1.44, stir and mix them evenly, add 500 ppm of the first catalyst, and conduct an esterification reaction at 230°C for 3.5 hours. Then, heat the reactor to 240°C at a heating rate of 1°C / min for a polycondensation reaction for 4 hours. Finally, a melt of bio-based poly (butylene terephthalate-adipate) (PBAT) is obtained.

[0130] In this embodiment, the bio-based dibasic acid is bio-based terephthalic acid and bio-based adipic acid in a mass ratio of 1:1, and the bio-based diol is bio-based butanediol;

[0131] The bio-based terephthalic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd.; the bio-based adipic acid was purchased from Toray Industries, Inc.;

[0132] The bio-based butanediol was purchased from Yuanli Chemical Group Co., Ltd.

[0133] In some embodiments, the bio-based terephthalic acid, bio-based adipic acid, and bio-based butanediol are all commercially available bio-based raw materials that can be directly purchased;

[0134] In this embodiment, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is 77917, and the molecular weight is measured as follows:

[0135] The results were determined by gel permeation chromatography (GPC) using a Waters model e2695 high performance liquid chromatograph, where the GPC column was eluted with tetrahydrofuran at a flow rate of 1 mL / min at 25 °C;

[0136] Step 3, preparing a bio-based multi-epoxy chain extender: 35 parts by weight of a highly unsaturated vegetable oil, linseed oil, 10 parts by weight of a hydroxyl-containing vegetable oil, castor oil, and 10 parts by weight of an auxiliary vegetable oil, soybean oil, are uniformly mixed to obtain a mixed oil, and the mixed oil is dehydrated and impurity-removed, wherein the dehydration and impurity-removal comprises vacuum dehydration at 110° C. for 2.5 hours, filtering to remove impurities, adding 0.5 parts by weight of a second catalyst, Amberlyst 15, and 60 parts by weight of an aqueous hydrogen peroxide solution (volume concentration of 40%) to the mixed oil, and causing an epoxidation reaction, specifically reacting at 65° C. and stirring at 300 rpm for 5 hours, monitoring the end point by the epoxy value, i.e., the epoxy value of the bio-based multi-epoxy chain extender is 0.49 mol / 100 g, and the number of epoxy groups is 4 / molecule. The second catalyst is then filtered to recover, the product is washed with water until neutral, and subjected to reduced pressure distillation at a pressure of 0.05 MPa and a temperature of 60° C. for 2 hours to obtain a bio-based multi-epoxy chain extender;

[0137] Step 4: uniformly mixing the bio-based polylactic acid (PLA) obtained in step 1 and the bio-based multi-epoxy chain extender obtained in step 3 to obtain a premix;

[0138] Step 5: The premix obtained in step 4 is fed into the twin-screw extruder through the main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based poly(butylene terephthalate-adipate) (PBAT) obtained in step 2 is fed into the twin-screw extruder through the side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation, the mixture is dried at 70° C. for 8 hours to obtain the fully bio-based PBAT-PLA copolymer.

[0139] In this embodiment, the aspect ratio of the twin-screw extruder in step 5 is 52:1.

[0140] The melt of the bio-based polybutylene terephthalate-adipate (PBAT) is transported to the twin-screw extruder through a melt delivery pipe and a melt metering pump under the action of a melt booster pump.

[0141] The temperatures of each zone of the twin-screw extruder are set to 90°C for zone 1, 110°C for zone 2, 130°C for zone 3, 150°C for zone 4, 170°C for zone 5, 170°C for zone 6, 170°C for zone 7, 170°C for zone 8, 180°C for zone 9, 180°C for zone 10, 185°C for zone 11, 185°C for zone 12, and 190°C for zone 13.

[0142] The screw speed of the twin-screw extruder is 220 r / min, and the feeding rate is 20 Hz.

[0143] Example 3

[0144] This embodiment provides a fully bio-based PBAT-PLA copolymer, which is prepared by melt mixing bio-based polybutylene terephthalate-adipate (PBAT), bio-based polylactic acid (PLA), and a bio-based multi-epoxy chain extender through a twin-screw extruder; the fully bio-based PBAT-PLA copolymer has a tensile strength of 36.2 MPa and an elongation at break of 426%.

[0145] In parts by weight, the components and contents of the all-biobased PBAT-PLA copolymer are as follows:

[0146] Bio-based polybutylene terephthalate-adipate (PBAT): 50 parts by weight;

[0147] Bio-based polylactic acid (PLA): 50 parts by weight;

[0148] Bio-based polyvalent epoxy chain extender: 0.3 parts by weight;

[0149] The preparation method of the all-biobased PBAT-PLA copolymer comprises the following steps:

[0150] Step 1: Pretreatment of bio-based polylactic acid (PLA): Dry the bio-based polylactic acid at 70°C for 8 hours before use to effectively remove moisture and prevent hydrolysis of the bio-based polylactic acid.

[0151] In this embodiment, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120,000; the bio-based polylactic acid (PLA) is purchased from Zhejiang Hisun Biomaterials Co., Ltd.

[0152] In some embodiments, the bio-based polylactic acid is a commercially available bio-based raw material that can be directly purchased;

[0153] In this embodiment, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120,000;

[0154] Step 2: Preparation of bio-based poly (butylene terephthalate-adipate) (PBAT): Add the bio-based dibasic acid and the bio-based diol into a reactor at a mass ratio of 1:1.44, stir and mix them evenly, add 500 ppm of the first catalyst, and conduct an esterification reaction at 230°C for 3.5 hours. Then, heat the reactor to 240°C at a heating rate of 1°C / min for a polycondensation reaction for 4 hours. Finally, a melt of bio-based poly (butylene terephthalate-adipate) (PBAT) is obtained.

[0155] In this embodiment, the bio-based dibasic acid is bio-based terephthalic acid and bio-based adipic acid in a mass ratio of 1:1, and the bio-based diol is bio-based butanediol;

[0156] The bio-based terephthalic acid was purchased from Shanghai Yuanye Biotechnology Co., Ltd.; the bio-based adipic acid was purchased from Toray Industries, Inc.;

[0157] The bio-based butanediol was purchased from Yuanli Chemical Group Co., Ltd.

[0158] In some embodiments, the bio-based terephthalic acid, bio-based adipic acid, and bio-based butanediol are all commercially available bio-based raw materials that can be directly purchased;

[0159] In this embodiment, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is 77917, and the molecular weight is measured as follows:

[0160] The results were determined by gel permeation chromatography (GPC) using a Waters model e2695 high performance liquid chromatograph, where the GPC column was eluted with tetrahydrofuran at a flow rate of 1 mL / min at 25 °C;

[0161] Step 3, preparing a bio-based multi-epoxy chain extender: 35 parts by weight of a highly unsaturated vegetable oil, linseed oil, 10 parts by weight of a hydroxyl-containing vegetable oil, castor oil, and 10 parts by weight of an auxiliary vegetable oil, soybean oil, are uniformly mixed to obtain a mixed oil, and the mixed oil is dehydrated and impurity-removed, wherein the dehydration and impurity-removal comprises vacuum dehydration at 110° C. for 2.5 hours, filtering to remove impurities, adding 0.5 parts by weight of a second catalyst, Amberlyst 15, and 60 parts by weight of an aqueous hydrogen peroxide solution (volume concentration of 40%) to the mixed oil, and causing an epoxidation reaction, specifically reacting at 65° C. and stirring at 300 rpm for 5 hours, monitoring the end point by the epoxy value, i.e., the epoxy value of the bio-based multi-epoxy chain extender is 0.49 mol / 100 g, and the number of epoxy groups is 4 / molecule. The second catalyst is then filtered to recover, the product is washed with water until neutral, and subjected to reduced pressure distillation at a pressure of 0.05 MPa and a temperature of 60° C. for 2 hours to obtain a bio-based multi-epoxy chain extender;

[0162] Step 4: uniformly mixing the bio-based polylactic acid (PLA) obtained in step 1 and the bio-based multi-epoxy chain extender obtained in step 3 to obtain a premix;

[0163] Step 5: The premix obtained in step 4 is fed into the twin-screw extruder through the main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based poly(butylene terephthalate-adipate) (PBAT) obtained in step 2 is fed into the twin-screw extruder through the side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation, the mixture is dried at 70° C. for 8 hours to obtain the fully bio-based PBAT-PLA copolymer.

[0164] In this embodiment, the aspect ratio of the twin-screw extruder in step 5 is 52:1.

[0165] The melt of the bio-based polybutylene terephthalate-adipate (PBAT) is transported to the twin-screw extruder through a melt delivery pipe and a melt metering pump under the action of a melt booster pump.

[0166] The temperatures of each zone of the twin-screw extruder are set to 90°C for zone 1, 110°C for zone 2, 130°C for zone 3, 150°C for zone 4, 170°C for zone 5, 170°C for zone 6, 170°C for zone 7, 170°C for zone 8, 180°C for zone 9, 180°C for zone 10, 185°C for zone 11, 185°C for zone 12, and 190°C for zone 13.

[0167] The screw speed of the twin-screw extruder is 220 r / min, and the feeding rate is 20 Hz.

[0168] Comparative Example 1

[0169] This comparative example provides a copolymer. Compared to Example 1, no bio-based polyepoxy chain extender is added. The copolymer is prepared by melt mixing bio-based polybutylene terephthalate adipate (PBAT) and bio-based polylactic acid (PLA) through a twin-screw extruder. The copolymer has a tensile strength of 22.5 MPa and an elongation at break of 402%.

[0170] In parts by weight, the components and contents in the copolymer are as follows:

[0171] Bio-based polybutylene terephthalate-adipate (PBAT): 80 parts by weight;

[0172] Bio-based polylactic acid (PLA): 20 parts by weight;

[0173] The preparation method of the copolymer comprises the following steps:

[0174] Step 1: Pretreatment of bio-based polylactic acid (PLA): Dry the bio-based polylactic acid at 70°C for 8 hours before use to effectively remove moisture and prevent hydrolysis of the bio-based polylactic acid.

[0175] Wherein, in this comparative example, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120,000;

[0176] Step 2: Preparation of bio-based poly (butylene terephthalate-adipate) (PBAT): Add the bio-based dibasic acid and the bio-based diol into a reactor at a mass ratio of 1:1.44, stir and mix them evenly, add 500 ppm of the first catalyst, and conduct an esterification reaction at 230°C for 3.5 hours. Then, heat the reactor to 240°C at a heating rate of 1°C / min for a polycondensation reaction for 4 hours. Finally, a melt of bio-based poly (butylene terephthalate-adipate) (PBAT) is obtained.

[0177] Wherein, in this comparative example, the bio-based dibasic acid is bio-based terephthalic acid and bio-based adipic acid in a mass ratio of 1:1, and the bio-based diol is bio-based butanediol;

[0178] Wherein, in this comparative example, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is 77917;

[0179] Step 3: The dried bio-based polylactic acid obtained in step 1 is fed into the twin-screw extruder through the main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based polybutylene terephthalate-adipate (PBAT) obtained in step 2 is fed into the twin-screw extruder through the side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation, the mixture is dried at 70°C for 8 hours to obtain the copolymer.

[0180] In this comparative example, the aspect ratio of the twin-screw extruder in step 3 is 52:1.

[0181] The melt of the bio-based polybutylene terephthalate-adipate (PBAT) is transported to the twin-screw extruder through a melt delivery pipe and a melt metering pump under the action of a melt booster pump.

[0182] The temperatures of each zone of the twin-screw extruder are set to 90°C for zone 1, 110°C for zone 2, 130°C for zone 3, 150°C for zone 4, 170°C for zone 5, 170°C for zone 6, 170°C for zone 7, 170°C for zone 8, 180°C for zone 9, 180°C for zone 10, 185°C for zone 11, 185°C for zone 12, and 190°C for zone 13.

[0183] The screw speed of the twin-screw extruder is 220 r / min, and the feeding rate is 20 Hz.

[0184] Comparative Example 2

[0185] This comparative example provides a copolymer. Compared to Example 1, the bio-based multi-epoxy chain extender in Example 1 is replaced with an equal amount of commercially available BASF epoxy chain extender ADR. That is, the copolymer in this comparative example is prepared by melt mixing bio-based polybutylene terephthalate-adipate (PBAT), bio-based polylactic acid (PLA), and BASF epoxy chain extender ADR through a twin-screw extruder. The copolymer has a tensile strength of 26.1 MPa and an elongation at break of 357%.

[0186] In parts by weight, the components and contents in the copolymer are as follows:

[0187] Bio-based polybutylene terephthalate-adipate (PBAT): 80 parts by weight;

[0188] Bio-based polylactic acid (PLA): 20 parts by weight;

[0189] Commercially available BASF epoxy chain extender ADR: 0.3 parts by weight;

[0190] The preparation method of the copolymer comprises the following steps:

[0191] Step 1: Pretreatment of bio-based polylactic acid (PLA): Dry the bio-based polylactic acid at 70°C for 8 hours before use to effectively remove moisture and prevent hydrolysis of the bio-based polylactic acid.

[0192] Wherein, in this comparative example, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120,000;

[0193] Step 2: Preparation of bio-based poly (butylene terephthalate-adipate) (PBAT): Add the bio-based dibasic acid and the bio-based diol into a reactor at a mass ratio of 1:1.44, stir and mix them evenly, add 500 ppm of the first catalyst, and conduct an esterification reaction at 230°C for 3.5 hours. Then, heat the reactor to 240°C at a heating rate of 1°C / min for a polycondensation reaction for 4 hours. Finally, a melt of bio-based poly (butylene terephthalate-adipate) (PBAT) is obtained.

[0194] Wherein, in this comparative example, the bio-based dibasic acid is bio-based terephthalic acid and bio-based adipic acid in a mass ratio of 1:1, and the bio-based diol is bio-based butanediol;

[0195] Wherein, in this comparative example, the weight average molecular weight of the bio-based polybutylene terephthalate-adipate (PBAT) is 77917;

[0196] Step 3: Evenly mix the bio-based polylactic acid (PLA) obtained in step 1 and the commercially available BASF epoxy chain extender ADR to obtain a premix;

[0197] Step 4: The premix obtained in step 3 is fed into a twin-screw extruder through a main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based polybutylene terephthalate (PBAT) obtained in step 2 is fed into the twin-screw extruder through a side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation, the mixture is dried at 70° C. for 8 hours to obtain the copolymer.

[0198] In this comparative example, the aspect ratio of the twin-screw extruder in step 4 is 52:1.

[0199] The melt of the bio-based polybutylene terephthalate-adipate (PBAT) is transported to the twin-screw extruder through a melt delivery pipe and a melt metering pump under the action of a melt booster pump.

[0200] The temperatures of each zone of the twin-screw extruder are set to 90°C for zone 1, 110°C for zone 2, 130°C for zone 3, 150°C for zone 4, 170°C for zone 5, 170°C for zone 6, 170°C for zone 7, 170°C for zone 8, 180°C for zone 9, 180°C for zone 10, 185°C for zone 11, 185°C for zone 12, and 190°C for zone 13.

[0201] The screw speed of the twin-screw extruder is 220 r / min, and the feeding rate is 20 Hz.

[0202] Comparative Example 3

[0203] The comparative example provides a copolymer, which is prepared by replacing the bio-based polybutylene adipate terephthalate (PBAT) in Example 1 with petroleum-based polybutylene adipate terephthalate (PBAT) and not using a bio-based polybasic epoxy chain extender, i.e., the copolymer in the comparative example is prepared by melt mixing petroleum-based polybutylene adipate terephthalate (PBAT) and bio-based polylactic acid (PLA) through a twin-screw extruder; the tensile strength of the full bio-based PBAT-PLA copolymer is 22.7 MPa, and the elongation at break is 398%;

[0204] The components in the copolymer and the content are as follows in parts by weight:

[0205] Petroleum-based polybutylene adipate terephthalate (PBAT): 80 parts by weight;

[0206] Bio-based polylactic acid (PLA): 20 parts by weight;

[0207] The preparation method of the copolymer includes the following steps:

[0208] Step 1, bio-based polylactic acid (PLA) pretreatment: the bio-based polylactic acid is dried at 70°C for 8h and then used, effectively removing moisture to avoid hydrolysis of the bio-based polylactic acid;

[0209] In this embodiment, the weight average molecular weight of the bio-based polylactic acid (PLA) is 120000;

[0210] Step 2, the dried bio-based polylactic acid obtained in step 1 is fed into a twin-screw extruder through a main feeding system connected to zone 1 of the twin-screw extruder, and petroleum-based polybutylene adipate terephthalate (PBAT) (weight average molecular weight 78000) is melted and then fed into the twin-screw extruder through a side feeding system connected to zone 3 of the twin-screw extruder, and after extrusion and granulation, the copolymer is obtained by drying at 70°C for 8h.

[0211] In the comparative example, the length-diameter ratio of the twin-screw extruder in step 2 is 52:1.

[0212] The melt of the petroleum-based polybutylene adipate terephthalate (PBAT) is transported into the twin-screw extruder through a melt metering pump by the action of a melt booster pump.

[0213] The temperature of each zone of the twin-screw extruder is set as follows: zone 1 90°C, zone 2 110°C, zone 3 130°C, zone 4 150°C, zone 5 170°C, zone 6 170°C, zone 7 170°C, zone 8 170°C, zone 9 180°C, zone 10 180°C, zone 11 185°C, zone 12 185°C, and zone 13 190°C.

[0214] The screw speed of the twin-screw extruder is 220 r / min, and the feeding rate is 20 Hz.

[0215] The properties of the copolymers prepared in Examples 1-3 and Comparative Examples 1-3 were compared, and the results are shown in Table 2:

[0216] Table 2 Comparative results of the properties of the copolymers prepared in Examples 1-3 and Comparative Examples 1-3

[0217]

[0218] The copolymers prepared in Example 1, Comparative Example 2, and Comparative Example 3 were injection molded using the existing technology. The injection molded specimens were frozen and quenched in liquid nitrogen, and the cross-sections were gold-sprayed. Finally, they were observed using a scanning electron microscope (SEM XL-30 ESEM FEG, FEICo., USA). The obtained scanning electron microscope images are shown in FIG. Figure 3-5 shown.

[0219] from Figure 5 It can be seen that in the copolymer prepared in Comparative Example 3, the interface between PLA and PBAT is very clear. This is because the compatibility between the two phases is poor. With the addition of epoxy chain extender, Figure 3-4 As shown in the figure, the interface becomes blurred, which indicates that the interfacial adhesion between the two phases and the compatibility between the interfaces are significantly enhanced due to the addition of epoxy chain extender. This result is due to the interaction between the interfacial phases of PLA and PBAT, which promotes the formation of compatibility.

[0220] And from Figure 3 and Figure 4 By comparison, it can be seen that the bio-based multi-epoxy chain extender prepared by specific selection in Example 1 of the present invention significantly improves the interfacial bonding strength of the two phases, and its interfacial bonding strength is significantly better than that of the commercially available epoxy chain extender used in Comparative Example 2.

[0221] In summary, the present invention prepares a bio-based polycyclic epoxy chain extender through specific selection. That is, in the process of preparing the bio-based polycyclic epoxy chain extender, the cyclization reaction of the double bond is mainly used. By controlling the content of each component in the bio-based polycyclic epoxy chain extender and the preparation conditions, the epoxy value and the number of epoxy groups of the bio-based polycyclic epoxy chain extender are directionally controlled, so that the tensile strength and elongation at break of the all-bio-based PBAT-PLA copolymer are simultaneously improved, and the technical problem of poor compatibility between traditional bio-based polylactic acid and non-bio-based polybutylene terephthalate-adipate-butylene adipate is solved.

[0222] It should be understood that the present invention is not limited to the above description and that various modifications and changes can be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A fully bio-based PBAT-PLA copolymer, characterized in that: The all-biobased PBAT-PLA copolymer is prepared by melt mixing bio-based poly(butylene terephthalate-adipate-butylene adipate), bio-based polylactic acid, and bio-based multi-epoxy chain extender through a twin-screw extruder; The bio-based multi-epoxy chain extender has an epoxy value of ≥0.49 mol / 100 g and an epoxy group number of ≥4 per molecule; The all-biobased PBAT-PLA copolymer has a tensile strength of 31.5-44.3 MPa and an elongation at break of 85-498%; In parts by weight, the components and contents of the all-biobased PBAT-PLA copolymer are as follows: Bio-based poly (butylene terephthalate-adipate): 20-80 parts by weight; Bio-based polylactic acid: 20-80 parts by weight; Bio-based polyvalent epoxy chain extender: 0.3-2 parts by weight; The bio-based polyvalent epoxy chain extender is prepared from highly unsaturated vegetable oil, hydroxyl-containing vegetable oil, and auxiliary vegetable oil in a hydrogen peroxide aqueous solution by catalysis of a second catalyst; The highly unsaturated vegetable oil is one or more of linseed oil and tung oil; The hydroxyl-containing vegetable oil is castor oil; The auxiliary vegetable oil is soybean oil.

2. The all-biobased PBAT-PLA copolymer according to claim 1, characterized in that: The weight average molecular weight of the bio-based polybutylene terephthalate-adipate ester is 70,000-120,000; The weight average molecular weight of the bio-based polylactic acid is 100,000-150,000.

3. The all-biobased PBAT-PLA copolymer according to claim 2, characterized in that: The bio-based polybutylene terephthalate-adipate ester is prepared by esterification and polycondensation of a bio-based dibasic acid and a bio-based diol via a first catalyst.

4. A method for preparing the all-biobased PBAT-PLA copolymer according to any one of claims 1 to 3, characterized in that: The steps include: Step 1: Pretreatment of bio-based polylactic acid: drying the bio-based polylactic acid for later use; Step 2, preparing bio-based poly (butylene terephthalate-adipate) ester: adding the bio-based dibasic acid and the bio-based diol into a reactor, stirring and mixing them uniformly, adding a first catalyst to cause an esterification reaction, and after the esterification reaction is completed, heating the reactor to carry out a polycondensation reaction. After the polycondensation reaction is completed, a melt of bio-based poly (butylene terephthalate-adipate) ester is obtained; Step 3: preparing a bio-based multi-epoxy chain extender: uniformly mixing a highly unsaturated vegetable oil, a hydroxyl-containing vegetable oil, and an auxiliary vegetable oil to obtain a mixed oil, adding a second catalyst and an aqueous hydrogen peroxide solution to the mixed oil to cause an epoxidation reaction to obtain a bio-based multi-epoxy chain extender; Step 4: uniformly mixing the bio-based polylactic acid obtained in step 1 and the bio-based multi-epoxy chain extender obtained in step 3 to obtain a premix; Step 5: The premix obtained in step 4 is fed into the twin-screw extruder through the main feeding system connected to the first zone of the twin-screw extruder, and the melt of the bio-based poly(butylene terephthalate-adipate) obtained in step 3 is fed into the twin-screw extruder through the side feeding system connected to the third zone of the twin-screw extruder. After extrusion granulation and drying, the fully bio-based PBAT-PLA copolymer is obtained.

5. The method for preparing the all-biobased PBAT-PLA copolymer according to claim 4, characterized in that: The temperature of the esterification reaction in step 2 is 230° C. and the time is 3.5 h.

6. The method for preparing the all-biobased PBAT-PLA copolymer according to claim 4, characterized in that: Step 3 also includes dehydrating and removing impurities from the mixed oil.

7. The method for preparing the all-biobased PBAT-PLA copolymer according to claim 4, characterized in that: The aspect ratio of the twin-screw extruder in step 5 is 52:1; The temperature of each zone of the twin-screw extruder is set to 90-100°C in zone 1, 110-130°C in zone 2, 130-150°C in zone 3, 150-170°C in zone 4, 170-190°C in zone 5, 170-190°C in zone 6, 170-190°C in zone 7, 170-190°C in zone 8, 170-190°C in zone 9, 170-190°C in zone 10, 170-190°C in zone 11, 170-190°C in zone 12, and 170-190°C in zone 13; The screw speed of the twin-screw extruder is 200-300 r / min, and the feeding speed is 10-30 Hz.

8. A plastic product, characterized in that: The plastic product is prepared by injection molding or blow molding of the all-biobased PBAT-PLA copolymer according to any one of claims 1 to 3.

9. The plastic product according to claim 8, characterized in that: The plastic product is plastic tableware.

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