A biodegradable polyester composition, its preparation method and application

Abstract

This invention provides a biodegradable polyester composition, its preparation method, and its application. The biodegradable polyester composition comprises polybutylene adipate / terephthalate, carbon dioxide-propylene oxide copolymer, and polyhydroxyalkanoate, wherein the carbon dioxide-propylene oxide copolymer comprises carbon dioxide-propylene oxide copolymer A and carbon dioxide-propylene oxide copolymer B, and the zinc content of carbon dioxide-propylene oxide copolymer A is greater than that of carbon dioxide-propylene oxide copolymer B. Through the rational combination of the above components, the obtained biodegradable polyester composition has biodegradability and excellent heat preservation and moisture retention functions. At the same time, after being made into a mulch film, it can gradually release organic zinc during the use of the mulch film and during biodegradation, thereby helping to help the growth of crops in zinc-deficient areas.

Description

Technical Field

[0001] This invention belongs to the field of thin film technology, specifically relating to a biodegradable polyester composition, its preparation method, and its application. Background Technology

[0002] In recent years, soil mulching has gradually gained recognition from researchers because mulch has the effect of retaining water and moisture, which can effectively inhibit water evaporation, thereby slowing down the accumulation of salt in the soil on the surface and achieving the effect of improving saline-alkali land.

[0003] Currently, conventional plastic film commonly suffers from poor biodegradability, inadequate heat retention, and poor nutrient absorption by crops when used in areas with poor soil quality, especially in saline-alkali soils and low-temperature areas. On the one hand, traditional polyolefin plastic film has poor degradation performance, and long-term large-scale use of plastic film leads to the accumulation of residual film, resulting in serious pollution problems. On the other hand, long-term use of traditional polyolefin plastic film can easily lead to zinc deficiency and poor heat retention, resulting in bleached seedlings in crops.

[0004] Therefore, in order to address the above-mentioned technical problems, there is an urgent need to develop a biodegradable polyester composition that can release zinc during the crop growth period and to make it into a mulch film. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a biodegradable polyester composition, its preparation method, and its application. The mulch film made from the biodegradable polyester composition is biodegradable, thus avoiding residual film pollution. Furthermore, during use and biodegradation, the zinc it contains is slowly released into the soil, effectively preventing crop bleaching. This makes it suitable for use in areas with poor soil conditions.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides a biodegradable polyester composition comprising polybutylene adipate / terephthalate, carbon dioxide-propylene oxide copolymer, and polyhydroxy fatty acid ester;

[0008] The carbon dioxide-propylene oxide copolymer includes carbon dioxide-propylene oxide copolymer A and carbon dioxide-propylene oxide copolymer B, and the zinc content of carbon dioxide-propylene oxide copolymer A is greater than the zinc content of carbon dioxide-propylene oxide copolymer B.

[0009] The biodegradable polyester composition provided by this invention comprises polybutylene adipate / terephthalate (PBAT), carbon dioxide-propylene oxide copolymer (PPC), and polyhydroxyalkanoate (PHA), and specifies that the PPC includes two PPCs with different zinc contents, namely PPC-A and PPC-B, with PPC-A having a higher zinc content than PPC-B. Firstly, by using the above three materials in combination, the resulting biodegradable polyester composition becomes biodegradable, thus preventing pollution from residual mulch film. Secondly, by adding the zinc-containing PPC, it can be ensured that the mulch film can slowly release its zinc content during use and biodegradation. When placed in the soil, it can effectively prevent crop bleaching. Furthermore, by limiting the PPC to include two types with different zinc contents, PPC-A and PPC-B, the zinc release rate can be effectively controlled. PPC-A, with a relatively higher zinc content, is the main source of zinc supplementation to the soil, while PPC-B, with a relatively lower zinc content, can better maintain a continuous and stable release of zinc, effectively regulating the zinc release rate and ensuring that zinc is released in the early stages of the mulch film's degradation. Finally, by adding the aforementioned PHA, the PHA can accelerate the degradation rate of the mulch film in the soil to a certain extent and further accelerate zinc release in the later stages, thus meeting the zinc supplementation requirements throughout the entire crop growth cycle.

[0010] It should be noted that the zinc in the zinc-containing PPC provided by the present invention all comes from the catalyst used to prepare the PPC, and the zinc content in the final PPC can be controlled by adjusting the amount of catalyst used.

[0011] In this invention, the zinc content of both PPC-A and PPC-B can be obtained by ICP testing according to the experimental method of zinc extraction by water at 38°C.

[0012] Preferably, the biodegradable polyester composition comprises the following components in parts by weight:

[0013] 100 parts by weight of polybutylene adipate / terephthalate;

[0014] 10-40 parts by weight of carbon dioxide-propylene oxide copolymer;

[0015] 1 to 2 parts by weight of polyhydroxy fatty acid ester.

[0016] The amount of the carbon dioxide-propylene oxide copolymer can be 10 parts by weight, 12 parts by weight, 14 parts by weight, 16 parts by weight, 18 parts by weight, 20 parts by weight, 22 parts by weight, 24 parts by weight, 26 parts by weight, 28 parts by weight, 30 parts by weight, 32 parts by weight, 34 parts by weight, 36 parts by weight, 38 parts by weight, or 40 parts by weight, etc.

[0017] The amount of the polyhydroxy fatty acid ester can be 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, or 2 parts by weight, etc.

[0018] Preferably, the melt index of the poly(butylene adipate) / terephthalate is 3-5 g / 10 min, for example 3 g / 10 min, 3.2 g / 10 min, 3.4 g / 10 min, 3.6 g / 10 min, 3.8 g / 10 min, 4 g / 10 min, 4.2 g / 10 min, 4.4 g / 10 min, 4.6 g / 10 min, 4.8 g / 10 min or 5 g / 10 min; the melt index is tested at 190°C with a load of 2.16 kg.

[0019] Preferably, the mass ratio of the carbon dioxide-propylene oxide copolymer A to the carbon dioxide-propylene oxide copolymer B is 100:(1-6), for example, 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5 or 100:6, etc.

[0020] Preferably, the number-average molecular weight of the carbon dioxide-propylene oxide copolymer A is 100–200 kg / mol, such as 100 kg / mol, 110 kg / mol, 120 kg / mol, 130 kg / mol, 140 kg / mol, 150 kg / mol, 160 kg / mol, 170 kg / mol, 180 kg / mol, 190 kg / mol, or 200 kg / mol. Limiting the zinc content of the PPC-A to a relatively high number-average molecular weight ensures that the biodegradable polyester composition possesses superior water vapor composition properties, providing better heat and moisture retention after being made into a mulch film, while also enabling more uniform zinc release.

[0021] Preferably, the molecular weight distribution of the carbon dioxide-propylene oxide copolymer A is 2.2 to 3.2, for example, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3, 3.1 or 3.2.

[0022] Preferably, the zinc content of the carbon dioxide-propylene oxide copolymer A is 2000-10000 ppm, such as 2000 ppm, 2300 ppm, 2500 ppm, 2700 ppm, 2900 ppm, 3100 ppm, 3300 ppm, 3500 ppm, 3700 ppm, 3900 ppm, 4100 ppm, 4300 ppm, 4500 ppm, 4700 ppm, 4900 ppm, 5000 ppm, 6000 ppm, 7000 ppm, 8000 ppm, 9000 ppm, or 10000 ppm.

[0023] Preferably, the number-average molecular weight of the carbon dioxide-propylene oxide copolymer B is 2–2.2 kg / mol, such as 2 kg / mol, 2.02 kg / mol, 2.04 kg / mol, 2.06 kg / mol, 2.08 kg / mol, 2.1 kg / mol, 2.12 kg / mol, 2.14 kg / mol, 2.16 kg / mol, 2.18 kg / mol, or 2.2 kg / mol. Limiting the number-average molecular weight of the PPC-B, which has a relatively low zinc content, better ensures that the mulch film releases zinc in the early stages of use and maintains a continuous and stable release of zinc, effectively controlling the zinc release rate.

[0024] Preferably, the molecular weight distribution of the carbon dioxide-propylene oxide copolymer B is 2 to 4, for example, 2, 2.2, 2.4, 2.6, 2.8, 3, 3.2, 3.4, 3.6, 3.8 or 4.

[0025] In this invention, the number-average molecular weight and molecular weight distribution mentioned above can both be obtained by GPC method.

[0026] Preferably, the zinc content of the carbon dioxide-propylene oxide copolymer B is 50 to 100 ppm, such as 50 ppm, 55 ppm, 60 ppm, 65 ppm, 70 ppm, 75 ppm, 80 ppm, 85 ppm, 90 ppm, 99 ppm or 100 ppm.

[0027] In this invention, the source of PPC-A and PPC-B is not specifically limited, as long as the number average molecular weight, molecular weight distribution and zinc content meet the above requirements. Commercially available products can be purchased directly, or they can be prepared by themselves according to existing methods. For example, PPC-A can be prepared with reference to CN105418907A, and PPC-B can be prepared with reference to CN116836379A.

[0028] Preferably, the number-average molecular weight of the polyhydroxyalkanoate is 50-80 kg / mol, such as 50 kg / mol, 55 kg / mol, 60 kg / mol, 65 kg / mol, 70 kg / mol, 75 kg / mol, or 80 kg / mol.

[0029] Preferably, the molecular weight distribution of the polyhydroxy fatty acid ester is 2 to 2.4, such as 2, 2.05, 2.1, 2.15, 2.2, 2.25, 2.3, 2.35 or 2.4.

[0030] Preferably, the biodegradable polyester composition further includes additives.

[0031] Preferably, the additives include anti-aging additives and / or opening agents.

[0032] Preferably, the content of the anti-aging agent in the biodegradable polyester composition is 0.5 to 2 parts by weight, such as 0.5 parts by weight, 0.7 parts by weight, 0.9 parts by weight, 1.1 parts by weight, 1.3 parts by weight, 1.5 parts by weight, 1.7 parts by weight, 1.9 parts by weight, or 2 parts by weight.

[0033] Preferably, the anti-aging additive includes any one or a combination of at least two of antioxidants, ultraviolet absorbers, or light stabilizers.

[0034] Preferably, the mass ratio of the antioxidant, ultraviolet absorber and light stabilizer is 1:(2-3):(2-3);

[0035] The mass ratio of the antioxidant to the ultraviolet absorber can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8 or 1:3, etc.; the mass ratio of the antioxidant to the light stabilizer can be 1:2, 1:2.2, 1:2.4, 1:2.6, 1:2.8 or 1:3, etc.

[0036] Preferably, the antioxidant includes antioxidant 1010 and / or antioxidant 168.

[0037] Preferably, the ultraviolet absorber includes any one or a combination of at least two of ultraviolet absorber 571, ultraviolet absorber 765, ultraviolet absorber 531 or ultraviolet absorber 234.

[0038] Preferably, the light stabilizer includes any one or a combination of at least two of light stabilizer 944, light stabilizer 622, light stabilizer 770 or light stabilizer 2020.

[0039] Preferably, the content of the opening agent in the biodegradable polyester composition is 1 to 5 parts by weight, such as 1 part by weight, 1.2 parts by weight, 1.4 parts by weight, 1.6 parts by weight, 1.8 parts by weight, 2 parts by weight, 3 parts by weight, 4 parts by weight or 5 parts by weight.

[0040] Preferably, the opening agent comprises any one or a combination of at least two of erucamide, oleamide, calcium carbonate, talc, or silica. In a second aspect, the present invention provides a method for preparing the biodegradable polyester composition as described in the first aspect, the method comprising: mixing polybutylene adipate / terephthalate, carbon dioxide-propylene oxide copolymer, polyhydroxyalkanoate, and optionally additives, followed by granulation to obtain the biodegradable polyester composition.

[0041] Preferably, the granulation is carried out in a twin-screw extruder.

[0042] Preferably, the granulation temperature is 110-160℃, such as 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, 142℃, 144℃, 146℃, 148℃, 150℃, 152℃, 154℃, 156℃, 158℃, or 160℃.

[0043] Thirdly, the present invention provides a biodegradable polyester mulch film, wherein the biodegradable polyester mulch film is obtained by blow molding the biodegradable polyester composition as described in the first aspect.

[0044] Preferably, the thickness of the biodegradable polyester mulch film is 8–15 μm, such as 8 μm, 8.2 μm, 8.4 μm, 8.6 μm, 8.8 μm, 9 μm, 9.2 μm, 9.4 μm, 9.6 μm, 9.8 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, or 15 μm.

[0045] Preferably, the blow molding temperature is 120–170°C, for example, 120°C, 125°C, 130°C, 135°C, 140°C, 142°C, 144°C, 146°C, 148°C, 150°C, 152°C, 154°C, 156°C, 158°C, 160°C, 165°C, or 170°C.

[0046] Fourthly, the present invention provides an application of the biodegradable polyester mulch film as described in the third aspect in areas with soil depletion.

[0047] Compared with the prior art, the present invention has the following beneficial effects:

[0048] The biodegradable polyester composition provided by this invention comprises polybutylene adipate / terephthalate, carbon dioxide-propylene oxide copolymer, and polyhydroxyalkanoate, wherein the carbon dioxide-propylene oxide copolymer comprises carbon dioxide-propylene oxide copolymer A and carbon dioxide-propylene oxide copolymer B, and the zinc content of carbon dioxide-propylene oxide copolymer A is greater than the zinc content of carbon dioxide-propylene oxide copolymer B. Through the reasonable combination of the above components, the biodegradable polyester composition has biodegradability and excellent heat preservation and moisture retention functions, and can gradually release organic zinc during the application of mulch film and biodegradation, thereby helping to help the growth of crops in zinc-deficient areas. Attached Figure Description

[0049] Figure 1 The graphs show the zinc content leaching from the biodegradable polyester mulch films provided in Application Examples 1-2 and Comparative Application Examples 2-3 at different soaking times. Detailed Implementation

[0050] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0051] Unless otherwise specified, the raw materials involved in the following embodiments are all conventional materials in the art, which can be obtained commercially or in-house; in particular, some raw material information is shown below:

[0052] (1) PBAT: melt index of 3.5 g / 10 min (190℃ / 2.16 kg), purchased from Huafeng Group Co., Ltd.

[0053] (2) PHA: Number average molecular weight is 60 kg / mol, molecular weight distribution is 2.3, purchased from Blue Crystal Microbial Company.

[0054] (3) PPC-A:

[0055] PPC-A1: Number average molecular weight is 157 kg / mol, molecular weight distribution is 2.5, and zinc content is 2800 ppm; it was prepared according to the method provided in CN105418907A, and the catalyst used was zinc glutarate catalyst;

[0056] PPC-A2: The number-average molecular weight is 107 kg / mol, the molecular weight distribution is 2.6, and the zinc content is 5647 ppm. It was prepared according to the method provided in CN105418907A, and the catalyst used was zinc glutarate catalyst.

[0057] PPC-A3: The number-average molecular weight is 189 kg / mol, the molecular weight distribution is 3.0, and the zinc content is 8970 ppm. It was prepared according to the method provided in CN105418907A, and the catalyst used was zinc glutarate catalyst.

[0058] PPC-A4: Number average molecular weight is 86 kg / mol, molecular weight distribution is 2.4, zinc content is 2800 ppm, prepared according to the method provided in CN105418907A, using zinc glutarate catalyst.

[0059] (4) PPC-B:

[0060] PPC-B1: The number average molecular weight is 2.2 kg / mol, the molecular weight distribution is 2.9, and the zinc content is 67 ppm. It is prepared and purified according to the method provided in CN116836379A. The catalyst used is a DMC catalyst based on Zn3[Co(CN)6]2.

[0061] PPC-B2: The number average molecular weight is 2.0 kg / mol, the molecular weight distribution is 2.5, and the zinc content is 98 ppm. It is prepared and refined according to the method provided in CN116836379A. The catalyst used is a DMC catalyst based on Zn3[Co(CN)6]2.

[0062] PPC-B3: The number average molecular weight is 2.1 kg / mol, the molecular weight distribution is 2.8, and the zinc content is 52 ppm. It is prepared and purified according to the method provided in CN116836379A. The catalyst used is a DMC catalyst based on Zn3[Co(CN)6]2.

[0063] PPC-B4: The number average molecular weight is 2.5 kg / mol, the molecular weight distribution is 3.1, and the zinc content is 67 ppm. It is prepared and purified according to the method provided in CN116836379A. The catalyst used is a DMC catalyst based on Zn3[Co(CN)6]2.

[0064] (5) Anti-aging additives:

[0065] Antioxidant 168, antioxidant 1010, UV absorber 531, UV absorber 234, light stabilizer 944 and light stabilizer 622 were all purchased from BASF.

[0066] (6) Opening agent:

[0067] Erucamide, commercially available.

[0068] Example 1

[0069] A biodegradable polyester composition comprising, by weight, the following components:

[0070]

[0071] The preparation method of the biodegradable polyester composition provided in this embodiment includes: mixing PBAT, PPC-A1, PPC-B1, PHA, antioxidant 168, antioxidant 1010, ultraviolet absorber 531, ultraviolet absorber 234, light stabilizer 944, light stabilizer 622 and erucamide in a high-speed mixer at a speed of 500 r / min for 3 min, and then granulating by twin-screw extruder with the die head temperature set to 145°C to obtain the biodegradable polyester composition.

[0072] Example 2

[0073] A biodegradable polyester composition comprising, by weight, the following components:

[0074]

[0075]

[0076] The preparation method of the biodegradable polyester composition provided in this embodiment is the same as that in Example 1.

[0077] Example 3

[0078] A biodegradable polyester composition comprising, by weight, the following components:

[0079] The preparation method of the biodegradable polyester composition provided in this embodiment is the same as that in Example 1.

[0080] Example 4

[0081] A biodegradable polyester composition comprising, by weight, the following components:

[0082]

[0083] The preparation method of the biodegradable polyester composition provided in this embodiment is the same as that in Example 1.

[0084] Example 5

[0085] A biodegradable polyester composition differs from Example 1 in that the amount of PPC-A1 is 19.9 parts by weight and the amount of PPC-B1 is 0.1 parts by weight, while the other components, amounts, and preparation methods are the same as in Example 3.

[0086] Example 6

[0087] A biodegradable polyester composition differs from Example 1 in that the amount of PPC-A1 is 18 parts by weight and the amount of PPC-B2 is 2 parts by weight, while the other components, amounts, and preparation methods are the same as in Example 3.

[0088] Example 7

[0089] A biodegradable polyester composition, which differs from Example 1 in that PPC-A4 is used instead of PPC-A1, while the other components, amounts and preparation methods are the same as in Example 1.

[0090] Example 8

[0091] A biodegradable polyester composition differs from Example 1 in that PPC-B4 is used instead of PPC-B1, while the other components, amounts, and preparation methods are the same as in Example 1.

[0092] Example 9

[0093] A biodegradable polyester composition comprising, by weight, the following components:

[0094]

[0095] The preparation method of the biodegradable polyester composition provided in this embodiment includes: mixing PBAT, PPC-A3, PPC-B1, PHA, antioxidant 168, antioxidant 1010, ultraviolet absorber 531, ultraviolet absorber 234, light stabilizer 944, light stabilizer 622, erucamide and calcium carbonate in a high-speed mixer at a speed of 500 r / min for 3 min, and then granulating by twin-screw extruder with the die head temperature set to 145°C to obtain the biodegradable polyester composition.

[0096] Comparative Example 1

[0097] A biodegradable polyester composition differs from Example 1 in that PPC-A1 is not added, PPC-B1 is used in an amount of 20 parts by weight, and the other components, amounts and preparation methods are the same as in Example 1.

[0098] Comparative Example 2

[0099] A biodegradable polyester composition differs from Example 1 in that PPC-B1 is not added, the amount of PPC-A1 is 20 parts by weight, and the other components, amounts, and preparation methods are the same as in Example 1.

[0100] Comparative Example 3

[0101] A biodegradable polyester composition differs from Example 1 in that PHA is not added, while the other components, dosages, and preparation methods are the same as in Example 1.

[0102] Application Examples 1-9 and Comparative Application Examples 1-3

[0103] A biodegradable polyester mulch film, all with a thickness of 10 μm, is prepared by means of: blow molding the biodegradable polyester compositions provided in Examples 1-9 and Comparative Examples 1-3 on a blown film equipment, wherein the blown film machine temperature is set as follows: Zone 1 140℃, Zone 2 145℃, Zone 3 150℃, and the die head 145℃, to obtain the biodegradable polyester mulch film.

[0104] Performance testing:

[0105] (1) Zinc release: Following the experimental method for zinc extraction from water at 38℃, the zinc content released into water by the biodegradable polyester mulch films provided in Application Examples 1-2 and Comparative Application Examples 2-3 at different soaking times was tested using ICP. The resulting curves of zinc release at different soaking times are shown below. Figure 1 As shown;

[0106] from Figure 1 It can be seen that as the soaking time increases, the content of zinc precipitated in the water gradually increases with the increase of the biodegradable polyester mulch provided in Examples 1-2. The release is very uniform throughout the process, indicating that the biodegradable polyester provided in Examples 1-2 can gradually release zinc during the mulching process, which can effectively supplement zinc in zinc-deficient areas.

[0107] In contrast, the biodegradable polyester mulch film provided in Application Example 2, which did not contain PCC-B1, released almost no zinc in the early stage, but began to release a large amount of zinc after more than 40 days. This indicates that the absence of PCC-B1 severely affected the release of zinc content from the mulch film in the early stage, and the total amount of zinc released was also less than that in Application Examples 1 and 2, thus failing to achieve the ideal zinc supplementation effect.

[0108] In contrast, the release of zinc from the biodegradable polyester mulch film provided in Application Example 3 slowed down significantly after 42 days of soaking, and stabilized by 91 days. This indicates that the absence of added PHA will affect the release of zinc from the mulch film in the later stages, and the total amount of zinc released is much less than that in Application Examples 1 and 2, thus failing to achieve the desired zinc supplementation effect.

[0109] In addition, the same tests were performed on other application examples and comparative application examples. The zinc release (zinc content precipitated in water) after soaking for 7 days, 42 days and 84 days was counted and the results are recorded in Table 1.

[0110] Table 1

[0111]

[0112] According to the data in Table 3:

[0113] The biodegradable polyester mulch films provided in Application Examples 1-9 have a certain amount of zinc release in the early stage of soaking. As the soaking time increases, the amount of zinc release gradually increases. The release is very uniform throughout the process, and the final total release is relatively high.

[0114] Comparing the data from Application Example 1 and Comparative Application Examples 1-2, it can be seen that the biodegradable polyester mulch film obtained without the addition of PPC-A (Comparative Application Example 1) has a high zinc release in the initial stage of immersion, but the total release is low, at only 463 ppm; while the biodegradable polyester mulch film obtained without the addition of PPC-B (Comparative Application Example 2) has an extremely low zinc release in the initial stage of immersion, at only 11 ppm, which is also difficult to meet the requirements.

[0115] Comparing the data from Application Example 1 and Comparative Application Example 3, it can be found that the release of zinc from the biodegradable polyester mulch film provided in Comparative Application Example 3 slowed down significantly after 42 days of soaking, and the total zinc release also decreased. This indicates that the absence of PHA will affect the release of zinc from the mulch film in the later stages.

[0116] The applicant declares that this invention illustrates a biodegradable polyester composition, its preparation method, and its application through the above embodiments. However, this invention is not limited to the above embodiments, meaning that this invention does not necessarily rely on the above embodiments for implementation. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of raw materials for the product, addition of auxiliary components, and selection of specific methods, etc., all fall within the protection and disclosure scope of this invention.

Claims

1. A biodegradable polyester composition characterized in that, The biodegradable polyester composition comprises the following components by weight parts: 100 parts by weight of polybutylene adipate terephthalate; 10 to 40 parts by weight of carbon dioxide-propylene oxide copolymer; 1 to 2 parts by weight of polyhydroxyalkanoate; The carbon dioxide-propylene oxide copolymer comprises carbon dioxide-propylene oxide copolymer A and carbon dioxide-propylene oxide copolymer B, and the zinc content of the carbon dioxide-propylene oxide copolymer A is > the zinc content of the carbon dioxide-propylene oxide copolymer B; The mass ratio of the carbon dioxide-propylene oxide copolymer A and the carbon dioxide-propylene oxide copolymer B is 100:(1 to 6); The zinc content of the carbon dioxide-propylene oxide copolymer A is 2000 to 10000 ppm; The zinc content of the carbon dioxide-propylene oxide copolymer B is 50 to 100 ppm.

2. The biodegradable polyester composition according to claim 1, characterized in that, The polybutylene adipate terephthalate has a melt index of 3 to 5 g / 10 min.

3. The biodegradable polyester composition according to claim 1, characterized in that, The carbon dioxide-propylene oxide copolymer A has a number average molecular weight of 100 to 200 kg / mol.

4. The biodegradable polyester composition according to claim 1, characterized in that, The carbon dioxide-propylene oxide copolymer A has a molecular weight distribution of 2.2 to 3.

2.

5. The biodegradable polyester composition according to claim 1, characterized in that, The carbon dioxide-propylene oxide copolymer B has a number average molecular weight of 2 to 2.2 kg / mol.

6. The biodegradable polyester composition according to claim 1, characterized in that, The carbon dioxide-propylene oxide copolymer B has a molecular weight distribution of 2 to 4.

7. The biodegradable polyester composition according to claim 1, characterized in that, The polyhydroxyalkanoate has a number average molecular weight of 50 to 80 kg / mol.

8. The biodegradable polyester composition according to claim 1, characterized in that, The polyhydroxyalkanoate has a molecular weight distribution of 2 to 2.

4.

9. The biodegradable polyester composition according to claim 1, characterized in that, The biodegradable polyester composition further comprises an auxiliary agent.

10. The biodegradable polyester composition according to claim 9, characterized in that, The auxiliary agent comprises an anti-aging auxiliary agent and / or an opening agent.

11. The biodegradable polyester composition according to claim 10, characterized in that, The content of the anti-aging auxiliary agent in the biodegradable polyester composition is 0.5 to 2 parts by weight.

12. The biodegradable polyester composition according to claim 10, characterized in that, The anti-aging auxiliary agent comprises any one or a combination of at least two of an antioxidant, an ultraviolet light absorber or a light stabilizer.

13. The biodegradable polyester composition according to claim 12, characterized in that, The mass ratio of the antioxidant, the ultraviolet light absorber and the light stabilizer is 1:(2 to 3):(2 to 3).

14. The biodegradable polyester composition according to claim 10, characterized in that, The content of the opening agent in the biodegradable polyester composition is 1 to 5 parts by weight.

15. The biodegradable polyester composition according to claim 10, characterized in that, The opening agent comprises any one or a combination of at least two of erucic acid amide, oleic acid amide, calcium carbonate, talc or silicon dioxide.

16. A process for producing the biodegradable polyester composition according to any one of claims 1 to 15, characterized by, The preparation method comprises: mixing polybutylene adipate terephthalate, carbon dioxide-propylene oxide copolymer, polyhydroxyalkanoate and optionally an auxiliary agent, and granulating to obtain the biodegradable polyester composition.

17. The method of claim 16, wherein, The granulation is performed in a twin-screw extruder.

18. The method of claim 16, wherein, The temperature of the granulation is 110 to 160°C.

19. A biodegradable polyester mulch film characterized in that, The biodegradable polyester mulch film is obtained by blow molding the biodegradable polyester composition according to any one of claims 1 to 15.

20. The biodegradable polyester mulch sheet according to claim 19, wherein, The biodegradable polyester mulch film has a thickness of 8 to 15 μm.

21. The biodegradable polyester mulch sheet according to claim 19, wherein, The temperature of the blow molding is 120 to 170°C.

22. Use of the biodegradable polyester mulch film according to any one of claims 19 to 21 in land impoverishment areas.

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