Preparation method of epoxidized castor oil-compatibility-modified PBAT / PLA / CaCO3 composite material

Abstract

The present invention discloses a method for preparing a PBAT / PLA / CaCO3 composite material modified with epoxidized castor oil. Castor oil (CO) is first epoxidized to obtain epoxidized castor oil (ECO), and then the epoxidized castor oil is used to improve the interfacial compatibility of the PBAT / PLA / CaCO3 composite material. The composite material is obtained by mixing PBAT, calcium carbonate, and PLA. A self-made epoxidized castor oil is added as a reactive compatibilizer to improve the compatibility between the different phases. The prepared PBAT / PLA / CaCO3 composite material exhibits enhanced interfacial adhesion and improved interfacial forces. The resulting composite material exhibits good biodegradability, excellent mechanical properties, and overall performance, and is expected to be widely used in the field of biodegradable plastics.

Description

Technical Field

[0001] The present invention belongs to the field of polymer materials, and in particular relates to a method for preparing an epoxidized castor oil-compatibilized PBAT / PLA / CaCO3 composite material. Background Art

[0002] At present, the use and promotion of biodegradable plastics have attracted more and more attention, and there is an urgent need to develop low-cost, degradable composite materials with excellent mechanical properties. Polybutylene terephthalate-adipate (PBAT) is an aromatic polyester with biodegradability and excellent toughness, but its relatively low strength limits its application range. By blending PBAT with polylactic acid (PLA) and calcium carbonate, the cost can be effectively reduced and the strength of the composite material can be increased. At the same time, the mixed system of the three is also a degradable composite material with good biocompatibility.

[0003] During the preparation of composite materials, the compatibility issues between the components will greatly affect the mechanical properties. Since reactive compatibilizers can form chemical bonds between the PBAT matrix and the multi-component filler, they are widely used in PBAT / PLA / CaCO3 composites. However, the preparation process of most reactive compatibilizers is complicated and expensive. Therefore, the development of low-cost, renewable, and environmentally friendly reactive compatibilizers is a current research hotspot. Bio-based active plant oils, such as epoxidized soybean oil (ESO) and its oligomers, have gradually attracted widespread attention. The epoxy groups in ESO are commonly used as compatibilizers for PLA / PBAT composites through reaction with hydroxyl groups. The present invention uses castor oil, which is widely available and inedible, as the matrix, and prepares epoxidized castor oil as a compatibilizer for the composite material through epoxidation reaction. This improves the compatibility of the composite material without affecting its degradability. By exploring the most appropriate addition amount, the overall performance of the composite material is improved. Summary of the Invention

[0004] This invention provides a method for preparing a PBAT / PLA / CaCO3 composite material modified with epoxidized castor oil. This method utilizes PBAT as the primary matrix, PLA and CaCO3 as additives, and epoxidized castor oil as a compatibilizer to improve the interfacial compatibility of the PBAT / PLA / CaCO3 composite. This composite material exhibits biodegradability, good component compatibility, and excellent overall performance, and is expected to find widespread application in disposable plastic products and food packaging.

[0005] The preparation method of the epoxidized castor oil-compatibility-modified PBAT / PLA / CaCO3 composite material of the present invention comprises the following steps:

[0006] Step 1: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added to a three-necked flask in sequence, and the mixture was rapidly stirred and then heated to 50-70°C. 11 g of H2O2 (30 wt%) solution was slowly added dropwise under continuous stirring. After the addition was complete, stirring was continued for 5-6 hours; the reaction mixture was then extracted with ether in a separatory funnel, and the organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid and washed until neutral; finally, the obtained neutral organic phase was subjected to rotary evaporation to remove ether to obtain epoxidized castor oil (ECO) liquid;

[0007] Step 2: Dry PBAT, PLA, and CaCO3 in an electric blast drying oven; Stir the dried CaCO3 and coupling agent in a high-speed mixer to activate the CaCO3; Mix the activated CaCO3, dried PBAT, PLA, and the epoxidized castor oil obtained in step 1, add them to a torque rheometer, and prepare a composite material by mixing.

[0008] In step 1, the oxidant is a hydrogen peroxide solution.

[0009] In step 2, in parts by mass, PBAT is added in an amount of 50 to 90 parts by mass, PLA is added in an amount of 1 to 10 parts by mass, CaCO3 is added in an amount of 10 to 30 parts by mass, and ECO is added in an amount of 1 to 5 parts by mass.

[0010] More preferably, the amount of PBAT added is 60 to 80 parts by mass, the amount of PLA added is 4 to 6 parts by mass, the amount of CaCO3 added is 20 to 30 parts by mass, and the amount of ECO added is 1 to 4 parts by mass.

[0011] More preferably, the feed mass ratio of PBAT, CaCO3 and PLA is 70:25:5.

[0012] The number average molecular weight of the polylactic acid PLA is 5000-50000, preferably 25000-35000. The melt index of the polylactic acid PLA is in the range of 4-10 g / 10 min (190° C. / 2.16 kg).

[0013] The polybutylene adipate-terephthalate (PBAT) has a number average molecular weight of 50,000-100,000, preferably 70,000-80,000. The melt index of PBAT is in the range of 5-10 g / 10 min (190° C. / 2.16 kg).

[0014] In step 2, the coupling agent is one or more of a titanate coupling agent and a silane coupling agent.

[0015] In step 2, the temperature of the high-speed mixer is controlled at 50-100° C. when CaCO 3 is stirred and mixed.

[0016] In step 2, the mixing temperature is controlled at 150-180° C., the screw speed is 40-60 rpm, and the processing time is 10-20 min.

[0017] The beneficial effects of the present invention are embodied in:

[0018] The present invention utilizes homemade epoxidized castor oil to enhance the compatibility of PBAT / PLA / CaCO3 composites, improving their compatibility and mechanical properties. During the mixing process, the epoxidized castor oil acts as a chain extender and compatibilizer, increasing the fluidity of the PBAT and PLA chains, thereby producing a composite material with excellent performance. The present invention utilizes PBAT and calcium carbonate as primary raw materials, and by adding a small amount of polylactic acid to enhance the tensile strength of the material, the material has the advantage of being fully biodegradable. The process is simple, and the resulting composite material exhibits excellent mechanical properties, promising broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is the Fourier infrared spectrum. The modified castor oil spectrum has a wavelength of 848 cm -1 The characteristic absorption peak of epoxy group appeared at , proving the successful formation of epoxy group in epoxidized castor oil.

[0020] Figure 2 The stress-strain curves of PBAT / PLA / CaCO3 composites with different ECO addition amounts.

[0021] Figure 3 This is a microscopic morphology of the PBAT / PLA / CaCO3 composite material of Example 1.

[0022] Figure 4 This is a microscopic morphology of the PBAT / PLA / CaCO3 composite material of Example 3.

[0023] Figure 5 These are the stress-strain curves of the PBAT / PLA / CaCO3 composite materials of Examples 3, 4, 6, and 7.

[0024] Figure 6 These are the stress-strain curves of the PBAT / PLA / CaCO3 composite materials of Examples 4, 8, and 9. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below through specific examples. This example is implemented on the premise of the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following examples.

[0026] In the following examples, the mechanical properties testing method is as follows: a standard dumbbell-shaped specimen is obtained by hot pressing using a flat-plate vulcanizer, and the tensile properties of the PBAT / PLA / CaCO3 composite material are measured on an electronic universal tensile machine at a rate of 50 mm / min in accordance with the national standard GB / T1040.1-2006.

[0027] The PABT used in the following examples was purchased from Xinjiang Lanshan Tunhe Polyester Co., Ltd., model TH801T.

[0028] PLA was purchased from Natureworks, USA, model 4032D.

[0029] CaCO3 was purchased from Cairns Nanomaterials Co., Ltd., model KPR-100H.

[0030] Castor oil (CO) was purchased from Aladdin.

[0031] Epoxidized soybean oil (ESO) was purchased from Maclean.

[0032] Example 1:

[0033] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask. After rapid stirring, the temperature was raised to 60°C. 11 g of a 30 wt% H2O2 solution was slowly added dropwise while stirring continuously. After the addition was complete, the mixture was stirred and reacted for 6 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. The washed neutral organic phase was then subjected to rotary evaporation to remove the ether, yielding epoxidized castor oil (ECO) liquid.

[0034] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8 hours; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10 minutes (first 0.5wt% KH560 was added and stirred at high speed for 5 minutes, and then 0.5wt% titanate coupling agent was added and stirred at high speed for 5 minutes) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3, 70 parts of PBAT and 5 parts of PLA were mixed uniformly and then mixed by a torque rheometer at 170°C and 50 rpm for 10 minutes to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S1.

[0035] Example 2:

[0036] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask, stirred rapidly and uniformly, and then heated to 60°C. 11 g of H2O2 (30 wt%) was slowly added dropwise with continuous stirring. After the addition was complete, the mixture was stirred and reacted for 6 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. The washed neutral organic phase was then subjected to rotary evaporation to remove the ether, obtaining epoxidized castor oil (ECO) liquid.

[0037] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8h; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10min (first 0.5wt% KH560 was added and stirred at high speed for 5min, then 0.5wt% titanate coupling agent was added and stirred at high speed for 5min) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 1 part of ECO were mixed uniformly and mixed by a torque rheometer at 170°C and 50rpm for 10min to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S2.

[0038] Example 3:

[0039] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask, stirred rapidly and uniformly, and then heated to 60°C. 11 g of H2O2 (30 wt%) was slowly added dropwise with continuous stirring. After the addition was complete, the mixture was stirred and reacted for 6 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. The washed neutral organic phase was then subjected to rotary evaporation to remove the ether, obtaining epoxidized castor oil (ECO) liquid.

[0040] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8h; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10min (first 0.5wt% KH560 was added and stirred at high speed for 5min, then 0.5wt% titanate coupling agent was added and stirred at high speed for 5min) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 2 parts of ECO were mixed uniformly and mixed by a torque rheometer at 170°C and 50rpm for 10min to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S3.

[0041] Example 4:

[0042] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask, stirred rapidly and uniformly, and then heated to 60°C. 11 g of H2O2 (30 wt%) was slowly added dropwise with continuous stirring. After the addition was complete, the mixture was stirred and reacted for 6 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. The washed neutral organic phase was then subjected to rotary evaporation to remove the ether, obtaining epoxidized castor oil (ECO) liquid.

[0043] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8 hours; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10 minutes (first 0.5wt% KH560 was added and stirred at high speed for 5 minutes, and then 0.5wt% titanate coupling agent was added and stirred at high speed for 5 minutes) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 3 parts of ECO were mixed uniformly and mixed by a torque rheometer at 170°C and 50rpm for 10 minutes to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S4.

[0044] Example 5:

[0045] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask, stirred rapidly and uniformly, and then heated to 60°C. 11 g of H2O2 (30 wt%) was slowly added dropwise with continuous stirring. After the addition was complete, the mixture was stirred and reacted for 6 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. The washed neutral organic phase was then subjected to rotary evaporation to remove the ether, obtaining epoxidized castor oil (ECO) liquid.

[0046] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8h; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10min (first 0.5wt% KH560 was added and stirred at high speed for 5min, then 0.5wt% titanate coupling agent was added and stirred at high speed for 5min) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 4 parts of ECO were mixed uniformly and mixed by a torque rheometer at 170°C and 50rpm for 10min to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S5.

[0047] Example 6:

[0048] Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8 hours; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10 minutes (first add 0.5wt% KH560 and stir at high speed for 5 minutes, then add 0.5wt% titanate coupling agent and stir at high speed for 5 minutes) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 2 parts of epoxidized soybean oil (ESO) were mixed evenly and mixed by torque rheometer at 170°C and 50rpm for 10 minutes to prepare PBAT / PLA / CaCO3 composite material, which was recorded as S6 sample.

[0049] Example 7:

[0050] Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8 hours; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10 minutes (first add 0.5wt% KH560 and stir at high speed for 5 minutes, then add 0.5wt% titanate coupling agent and stir at high speed for 5 minutes) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 3 parts of epoxidized soybean oil (ESO) were mixed evenly and mixed by torque rheometer at 170°C and 50rpm for 10 minutes to prepare PBAT / PLA / CaCO3 composite material, which was recorded as S7 sample.

[0051] Example 8:

[0052] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask, stirred rapidly and uniformly, and then heated to 60°C. 8 g of H2O2 (30 wt%) was slowly added dropwise with continuous stirring. After the addition was complete, the mixture was stirred and reacted for 6 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. Finally, the washed neutral organic phase was subjected to rotary evaporation to remove the ether, obtaining a low-epoxy content epoxidized castor oil (ECO) liquid.

[0053] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8h; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10min (first 0.5wt% KH560 was added and stirred at high speed for 5min, then 0.5wt% titanate coupling agent was added and stirred at high speed for 5min) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 3 parts of ECO were mixed uniformly and mixed by a torque rheometer at 170°C and 50rpm for 10min to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S8.

[0054] Example 9:

[0055] 1. Preparation of a compatibilizer: 25 g of castor oil (CO), 7.5 g of formic acid (HCOOH), and 1 g of concentrated sulfuric acid (H2SO4) were added sequentially to a three-necked flask, stirred rapidly and uniformly, and then heated to 60°C. 14 g of H2O2 (30 wt%) was slowly added dropwise with continuous stirring. After the addition was complete, the mixture was stirred and reacted for 8 hours. The reaction mixture was then extracted with ether in a separatory funnel. The organic phase was washed with 10 wt% sodium carbonate solution and distilled water to remove free acid until neutral. Finally, the washed neutral organic phase was subjected to rotary evaporation to remove the ether, obtaining a high-epoxy content epoxidized castor oil (ECO) liquid.

[0056] 2. Preparation of PBAT / PLA / CaCO3 composite material: First, PBAT, PLA and CaCO3 were placed in an electric blast drying oven at 80°C and dried for 8h; then the dried CaCO3 and 0.5wt% titanate coupling agent 102 and silane coupling agent KH560 were stirred in a high-speed mixer at 120°C for 10min (first 0.5wt% KH560 was added and stirred at high speed for 5min, then 0.5wt% titanate coupling agent was added and stirred at high speed for 5min) to obtain dry-modified activated CaCO3; finally, 25 parts of activated CaCO3 and 70 parts of PBAT, 5 parts of PLA, and 3 parts of ECO were mixed uniformly and mixed by a torque rheometer at 170°C and 50rpm for 10min to prepare a PBAT / PLA / CaCO3 composite material, which was recorded as sample S9.

[0057] Table 1 shows the mechanical properties test results of the PBAT / PLA / CaCO3 composite. It can be seen that the PBAT / PLA / CaCO3 composite has the best comprehensive performance when 3 parts of ECO are added, and the elongation at break is increased by 51% compared with the blank sample.

[0058] Table 1

[0059]

[0060] Figure 3 、 4 The SEM comparison of PBAT / PLA / CaCO3 composite materials with and without epoxidized castor oil (ECO) added is shown. Figure 3 It can be seen that when ECO is not added, CaCO3 is severely agglomerated and the dispersed PLA is basically invisible. With the introduction of ECO, the agglomeration of CaCO3 is significantly improved and PLA can be seen to be evenly distributed in the matrix of PBAT, indicating that ECO can effectively improve the interfacial compatibility of PBAT / PLA / CaCO3 composites, thereby improving the comprehensive mechanical properties of the composites.

[0061] Figure 5 Figure 2 is the stress-strain curve of PBAT / PLA / CaCO3 composite material with 2 parts of epoxidized castor oil and 3 parts of epoxidized soybean oil added respectively. Figure 5 It can be seen that the mechanical properties of the composite material using ECO as a compatibilizer are improved compared to those using ESO as a compatibilizer. In addition, as a widely available and inedible industrial oil, castor oil has a broader application prospect than edible soybean oil.

[0062] Figure 6 The stress-strain curves of PBAT / PLA / CaCO3 composite materials with different epoxidation rates of ECO can be measured by the hydrochloric acid-acetone method: the epoxidation rate of S4 is 0.07 mol / 100 g, S8 is 0.05 mol / 100 g, and S9 is 0.11 mol / 100 g. Figure 6 It can be seen that with the increase of the epoxidation rate of epoxidized castor oil, the improvement of the mechanical properties of the composite material does not show a positive correlation, indicating that the higher the epoxidation rate of epoxidized castor oil, the better, and its compatibilization effect on PBAT / PLA / CaCO3 composite materials has a certain limit.

[0063] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing an epoxidized castor oil-compatibility-modified PBAT / PLA / CaCO3 composite material, characterized in that: Using PBAT as a matrix, PLA and CaCO3 as additives, and epoxidized castor oil as a compatibilizer, the interfacial compatibility of PBAT / PLA / CaCO3 is improved, including the following steps: Step 1: 25g of castor oil, 7.5g of formic acid, and 1g of concentrated sulfuric acid are added to a reactor in sequence, stirred evenly, and then heated to 50-70°C. An oxidant is added dropwise under continuous stirring, and the reaction is continued with stirring for 5-6 hours after the addition is complete. The reaction mixture is then extracted with ether in a separatory funnel, and the organic phase is washed with 10wt% sodium carbonate solution and distilled water to remove free acid until it is neutral. Finally, the obtained neutral organic phase is subjected to rotary evaporation to remove ether to obtain epoxidized castor oil ECO liquid. Step 2: The dried CaCO3 and the coupling agent are stirred evenly in a high-speed mixer to activate the CaCO3; the activated CaCO3, the dried PBAT, the PLA, and the epoxidized castor oil obtained in step 1 are mixed evenly and added to a torque rheometer, and a composite material is prepared by mixing; The epoxidation rate of the epoxidized castor oil obtained in step 1 is 0.07 mol / 100 g; In step 2, in parts by mass, PBAT is added in an amount of 50 to 90 parts by mass, PLA is added in an amount of 1 to 10 parts by mass, CaCO3 is added in an amount of 10 to 30 parts by mass, and ECO is added in an amount of 1 to 5 parts by mass.

2. The preparation method according to claim 1, wherein: In step 1, the oxidant is a hydrogen peroxide solution with a concentration of 30 wt%.

3. The preparation method according to claim 1, wherein: The addition amount of PBAT is 60~80 parts by mass, the addition amount of PLA is 4~6 parts by mass, the addition amount of CaCO3 is 20~30 parts by mass, and the addition amount of ECO is 1~4 parts by mass.

4. The preparation method according to claim 3, wherein: The feed mass ratio of PBAT, CaCO3 and PLA is 70:25:

5.

5. The preparation method according to claim 1, wherein: In step 2, the coupling agent is a titanate coupling agent, a silane coupling agent, or a combination of several thereof.

6. The preparation method according to claim 1, wherein: In step 2, the temperature of the high-speed mixer is controlled at 50-100° C. when CaCO 3 is stirred and mixed.

7. The preparation method according to claim 1, wherein: In step 2, the mixing temperature is controlled at 150-180° C., the screw speed is 40-60 rpm, and the processing time is 10-20 min.

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