Biodegradable composition having low casting precipitation, and preparation method therefor and use thereof

Abstract

The present invention relates to a biodegradable composition having low casting precipitation, and a preparation method therefor and the use thereof. The biodegradable composition having low casting precipitation comprises the following components in parts by weight: 69-91 parts of polylactic acid, 0-16 parts of a flexible biodegradable polyester, 0-11 parts of a filler, 0.1-3.1 parts of an anti-precipitation agent, and 0.1-3.1 parts of a phosphite antioxidant. In the present invention, the anti-precipitation agent and phosphite antioxidant are added to the biodegradable composition comprising polylactic acid as a main component, thereby effectively improving the casting precipitation problem of the biodegradable composition.

Description

A biodegradable composition with low casting precipitation, its preparation method and application Technical Field

[0001] This invention relates to the field of biodegradable plastics technology, and more specifically, to a low-cast-exudation biodegradable composition, its preparation method, and its application. Background Technology

[0002] Biodegradable materials can decompose in the natural environment through the action of microorganisms, reducing environmental pollution. This is particularly important for addressing the problem of "white pollution" (plastic pollution), as it helps protect soil and water resources. Due to their diverse properties, biodegradable materials can be applied in various fields, including but not limited to flexible and rigid packaging, consumer goods, textiles, agriculture, horticulture, construction, coatings, and electronics.

[0003] One of the main applications of biodegradable materials is the fabrication of thin films, typically achieved through a casting process. Casting is a highly efficient production method that uses melt casting and rapid cooling to produce unstretched, non-oriented flat-extruded films. This process offers high production speed and yield, and the films exhibit excellent transparency, gloss, and thickness uniformity, making it suitable for large-scale production of biodegradable material films.

[0004] One problem with biodegradable materials based on polylactic acid (PLA) resin is that, due to the characteristics of PLA itself, it is easy for PLA to precipitate oligomers and accumulate on the casting roller during the casting process at high temperature (200~220℃) and certain pressure (extrusion pressure 3~5Mpa). The accumulation of precipitates on the casting roller not only affects the quality of subsequent products, but also requires regular cleaning of the casting roller, which increases production costs.

[0005] While it is difficult to completely avoid the precipitation of polylactic acid during the casting process, reducing the precipitation of degradation products during casting can greatly improve the processing stability of materials and the quality of products, increase end-production efficiency, reduce production losses, and bring huge economic benefits. Summary of the Invention

[0006] The primary objective of this invention is to overcome the problem of severe precipitate formation in the casting process of biodegradable materials based on polylactic acid resin in the current technology, and to provide a biodegradable composition with low casting precipitation.

[0007] A further object of the present invention is to provide a method for preparing the above-mentioned low-cast-exudation biodegradable composition.

[0008] A further object of the present invention is to provide the application of the above-described low-casting-exudation biodegradable composition in the preparation of thin films.

[0009] A further object of the present invention is to provide a biodegradable film.

[0010] The above-mentioned objective of the present invention is achieved through the following technical solution:

[0011] A biodegradable composition with low castable precipitation comprises the following components in parts by weight:

[0012] Polylactic acid 69-91 parts,

[0013] 0-16 parts of flexible biodegradable polyester

[0014] 0-11 parts of filler

[0015] Anti-precipitation agent 0.1~3.1 parts,

[0016] Phosphite antioxidants: 0.1-3.1 parts;

[0017] The anti-precipitation agent is a phosphorus compound having the structure shown in Formula I or Formula II;

[0018] Formula I,

[0019] Formula II;

[0020] R1, R2, R3, and R4 are each independently selected from any one of -H, -OH, alkoxy, or -OM; M is selected from alkali metal ions, alkaline earth metal ions, or transition metal ions.

[0021] The total content of titanium and / or tin in the biodegradable composition is 35-100 ppm.

[0022] The inventors of this invention discovered that polylactic acid (PLA) readily generates free radicals under high temperature (200-220°C) and certain pressure (3-5 MPa) conditions during the casting process. These free radicals cause PLA to degrade into oligomers, resulting in precipitation. This invention incorporates phosphite antioxidants, which can react with the free radicals generated from PLA during casting to reduce its decomposition rate, thereby improving the precipitation problem of the biodegradable composition during casting to some extent. However, the improvement in precipitation during casting of the biodegradable composition by adding only phosphite antioxidants is limited.

[0023] Further research by the inventors revealed that the addition of a specific anti-precipitation agent significantly improved the precipitation problem in the casting of biodegradable compositions. This is because polylactic acid (PLA) or other biodegradable polyesters in the biodegradable composition contain trace amounts of tin and / or titanium. Tin and / or titanium not only catalyze the synthesis of PLA or other polyesters but also have a certain catalytic degradation effect on PLA under the high temperature and pressure of the casting process. The addition of the specific anti-precipitation agent can chelate the metal ions of these metal catalysts, preventing the catalytic degradation of PLA by the metal catalysts. The anti-precipitation agent works synergistically with phosphite antioxidants, thereby significantly improving the precipitation problem in the casting of biodegradable compositions.

[0024] In this invention, the total content of titanium and / or tin in the biodegradable composition can be 35, 40, 50, 60, 70, 80, 90 or 100 ppm.

[0025] In this invention, polylactic acid is used as the main resin, and its content accounts for more than 70 wt% of the biodegradable composition.

[0026] Preferably, the phosphorus compound having the structure shown in Formula I is at least one of a phosphate ester compound, a phosphate compound, or a pyrophosphate compound.

[0027] More preferably, the phosphate ester compound includes, but is not limited to, at least one of triethyl phosphate, tripropyl phosphate, or tributyl phosphate; the phosphate compound includes, but is not limited to, at least one of sodium dihydrogen phosphate, potassium dihydrogen phosphate, or zinc dihydrogen phosphate; and the pyrophosphate compound includes, but is not limited to, disodium dihydrogen pyrophosphate. More preferably, it is sodium dihydrogen phosphate.

[0028] Preferably, the phosphite antioxidant is at least one selected from triphenyl phosphite, tris[2,4-di-tert-butylphenyl]phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite, distearate pentaerythritol diphosphite, or bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

[0029] In this invention, polylactic acid can be either commercially available or prepared in-house.

[0030] The process of preparing polylactic acid in-house is as follows:

[0031] Lactide is first reacted in the presence of a catalyst at 130-150°C and 4000-6000 Pa for 2-4 hours, and then reacted at 170-190°C and 80000-12000 Pa for 1-5 hours to obtain polylactic acid.

[0032] Preferably, the polylactic acid molecule is composed of L-lactic acid units and D-lactic acid units.

[0033] Preferably, the amount of titanium and / or tin in the polylactic acid is 40 to 100 ppm; specifically, it can be 40, 50, 60, 70, 75, 80, 90 or 100 ppm.

[0034] Preferably, the content of D-lactic acid units in the polylactic acid is 0.5~6 mol.

[0035] By controlling the content of D-lactic acid units in polylactic acid within this range, the amount of castable exudate of the biodegradable composition is reduced.

[0036] In this invention, the content of D-lactic acid units in polylactic acid can be determined by gas chromatography.

[0037] The molar content of the dextrorotatory D monomer of polylactic acid was obtained by gas chromatography. Specifically, the gas chromatography test was conducted using an Agilent 8860 gas chromatograph with a CP7502 column, an FID detector temperature of 200°C, a hydrogen flow rate of 45 mL / min, an air flow rate of 450 mL / min, and a split ratio of 5:1.

[0038] Preferably, the polylactic acid has a melt flow rate of 3.0~14.0 g / 10min under test conditions of 190°C and 2.16kg.

[0039] In this invention, the melt flow rate of polylactic acid can be measured according to ISO 1133-1:2022.

[0040] The biodegradable composition of the present invention may also incorporate flexible biodegradable polyester to improve the mechanical properties of the biodegradable composition.

[0041] Preferably, the amount of the flexible biodegradable polyester used is 1 to 15 parts.

[0042] Preferably, the melt flow rate of the flexible biodegradable polyester at 190°C and 2.16 kg is 1.0~10.0 g / 10 min.

[0043] In this invention, the melt flow rate of the flexible biodegradable polyester can be measured according to ISO 1133-1:2022.

[0044] Preferably, the content of titanium and / or tin in the flexible biodegradable polyester is 70~120ppm; specifically, it can be 70, 80, 90, 100, 110, or 120ppm.

[0045] More preferably, the flexible biodegradable polyester is a copolymer of a diacid and / or its ester derivatives and a diol.

[0046] In this invention, biodegradable polyester can be commercially available or made in-house.

[0047] More preferably, the dicarboxylic acid is an aliphatic dicarboxylic acid and / or an aromatic dicarboxylic acid.

[0048] More preferably, the aliphatic dicarboxylic acid is at least one selected from succinic acid, adipic acid, pimelic acid, octanoic acid, azelaic acid, sebacic acid, undecanoic acid, or dodecanoic acid.

[0049] More preferably, the aromatic dicarboxylic acid is terephthalic acid.

[0050] More preferably, the diol is at least one of butanediol, propylene glycol, ethylene glycol, or pentanediol.

[0051] More preferably, the flexible biodegradable polyester is at least one of polybutylene adipate terephthalate, polybutylene sebacate terephthalate, polybutylene azelaate terephthalate, polybutylene terephthalate succinate, and polybutylene succinate.

[0052] The biodegradable composition of the present invention may also include fillers to improve the mechanical properties and production cost of the biodegradable composition.

[0053] Preferably, the amount of the filler is 1 to 10 parts.

[0054] Preferably, the particle size D50 of the filler is 2.0~10μm.

[0055] In this invention, the particle size D50 of the filler is determined according to the method in GB / T 19077.1-2008 "Particle size analysis by laser diffraction".

[0056] Preferably, the filler is at least one of calcium carbonate, talc, starch, or kaolin.

[0057] Preferably, the amount of the anti-precipitation agent is 0.1 to 3 parts, specifically 0.1, 0.2, 0.3, 0.5, 0.8, 1.0, 1.2, 1.5, 1.8, 2.0, 2.3, 2.5, 2.8 or 3.0 parts.

[0058] Preferably, the amount of the phosphite antioxidant is 1 to 3 parts; specifically, it can be 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3.0 parts.

[0059] More preferably, the amount of the phosphite antioxidant is 1.5 to 2 parts.

[0060] Preferably, the ratio of the anti-precipitation agent to the phosphite antioxidant is 1:(1.5~2).

[0061] Preferably, the biodegradable material further includes 0.1 to 3 parts of other additives.

[0062] Optionally, the other additives are at least one of lubricants or UV stabilizers.

[0063] Typically, the dosage of other additives is: 0.01 to 0.3 parts by weight for lubricant and 0.1 to 3 parts by weight for UV stabilizer.

[0064] Optionally, the lubricant is at least one of stearamide, ethylene bis-stearamide, oleamide, erucamide, or Fischer-Tropsch wax.

[0065] Optionally, the UV stabilizer is at least one of bis(1-octoxy-2,2,6,6-tetramethyl-4-piperidinyl) sebacate or 2-(2-hydroxy-3-tert-butyl-5-methylphenyl)-5-(2,4-dimethylphenyl)-2H-benzotriazine-4-one.

[0066] The method for preparing the above-mentioned biodegradable composition includes the following steps:

[0067] The components are mixed and melt-extruded to obtain the biodegradable composition.

[0068] Preferably, the temperature of the melt extrusion is 150–240°C.

[0069] The application of the above-mentioned biodegradable composition in the preparation of cast film products is also within the scope of protection of this invention.

[0070] Preferably, the cast film product is a biodegradable film.

[0071] Compared with the prior art, the beneficial effects of the present invention are:

[0072] This invention adds an anti-precipitation agent and a phosphite antioxidant to a biodegradable composition based on polylactic acid, which effectively improves the problem of precipitation during casting of the biodegradable composition. Embodiments of the present invention

[0073] To more clearly and completely describe the technical solution of the present invention, the present invention will be further described in detail below through specific embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention. Various changes can be made within the scope of the claims of the present invention.

[0074] The reagents used in the various embodiments and comparative examples of this invention are described below:

[0075] Polylactic acid 1#: Self-made, prepared as follows: 95 parts by weight of L,L-lactide (L content ≥ 99.5%, the same below) and 5 parts by weight of meso-lactide (D content approximately 50%, the same below) were mixed, and a catalyst (stannous octoate) was added for ring-opening polymerization: first, the reaction was carried out at a reaction temperature of 150℃ and a reaction pressure of 5000Pa for 2 hours, and then at a reaction temperature of 180℃ and a reaction pressure of 10000Pa for 2.6 hours (denoted as time t1); underwater pelletizing, crystallization, and drying were performed to obtain polylactic acid 1#. The melt flow rate of polylactic acid 1# was 8 g / 10 min (2.16 kg, 190℃), the content of D-lactic acid units was 3 mol%, and the tin content was 52 ppm.

[0076] Polylactic acid 2#: Prepared in-house, its preparation method differs from that of polylactic acid 1# in that: the amount of L,L-lactide is 99 parts by weight, the amount of meso-lactide is 1 part by weight, the time t1 is 4.5 hours, and the amount of catalyst added is increased. The melt flow rate of polylactic acid 2# is 3.5 g / 10 min (2.16 kg, 190 °C), the content of D-lactic acid units is 1 mol%, and the content of tin element is 70 ppm.

[0077] Polylactic acid 3#: Prepared in-house, its preparation method differs from that of polylactic acid 1# in that: the amount of L,L-lactide is 91 parts by weight, the amount of meso-lactide is 9 parts by weight, and the time t1 is 1.4 hours. The melt flow rate of polylactic acid 3# is 12 g / 10 min (2.16 kg, 190 °C), the content of D-lactic acid units is 5 mol%, and the content of tin element is 50 ppm.

[0078] Polylactic acid 4#: self-made, its preparation method differs from that of polylactic acid 1# in that: the amount of catalyst added is reduced, and the time t1 is 4.8 hours. The melt flow rate of polylactic acid 3# is 8g / 10min (2.16kg, 190℃), the content of D-lactic acid units is 3mol%, and the content of tin element is 10ppm.

[0079] Polylactic acid 5#: self-made, its preparation method differs from that of polylactic acid 1# in that: the amount of catalyst added is increased, and the time t1 is 1.6 hours. The melt flow rate of polylactic acid 5# is 8g / 10min (2.16kg, 190℃), the content of D-lactic acid units is 3mol%, and the content of tin element is 152ppm.

[0080] The melt flow rate of the polylactic acid was measured according to ISO 1133-1:2022.

[0081] The content of D-lactic acid units in polylactic acid was determined by gas chromatography. The specific process was as follows: (1) Weigh 100±10 mg of ground polylactic acid sample and place it in the inner liner of a 25 mL pressurized container; (2) Add 10 mL of methanol and 1 drop of dilute sulfuric acid; (3) Seal the pressurized container and place it in a 150℃ thermostat for 4 h; (4) Remove the pressurized container and open it after it has cooled to room temperature; (5) After filtering the sample solution through a membrane filter, transfer it to a gas chromatography vial for gas chromatography analysis; (6) Calculate the content of D-lactic acid units in polylactic acid based on the peak area ratio. The instrument used for gas chromatography analysis was an Agilent 8860 gas chromatograph, the column was CP7502, the FID detector temperature was 200℃, the hydrogen flow rate was 45 mL / min, the air flow rate was 450 mL / min, and the split ratio was 5:1.

[0082] Flexible biodegradable polyester 1# (PBAT): Adipic acid, 1,4-butanediol, terephthalic acid, and tetrabutyl titanate are added to a 200L reactor; the molar ratio of adipic acid, 1,4-butanediol, and terephthalic acid is 0.25:0.6:0.25; the mass ratio of adipic acid to tetrabutyl titanate is 2000:1; the reaction temperature is 210℃, the reaction pressure is 50KPa, and the reaction time is 2.8 h, thus obtaining flexible biodegradable polyester 1#. The melt flow rate of flexible biodegradable polyester 1# is 6.0 g / 10min (2.16 kg, 190℃), and the titanium content is 103 ppm.

[0083] Flexible biodegradable polyester 2# (PBS): 1,4-Succinic acid, 1,4-butanediol, and tetrabutyl titanate were added to a 200L reactor; the molar ratio of 1,4-succinic acid to 1,4-butanediol was 1:1.2; the mass ratio of 1,4-succinic acid to tetrabutyl titanate was 3000:1; the reaction temperature was 210℃, the reaction pressure was 50KPa, and the reaction time was 3.6h to obtain flexible biodegradable polyester 2#. The melt flow rate of flexible biodegradable polyester 2# was 3.0g / 10min (2.16kg, 190℃), and the titanium content was 80ppm.

[0084] The tin and / or titanium content in polylactic acid, flexible biodegradable polyester, and the biodegradable compositions of the examples and comparative examples was tested using microwave digestion-ICP-OES. The measurement results are expressed in ppm, where 1 ppm = 0.001‰. Specifically, 0.1 g of the pulverized sample was weighed and placed in a microwave digestion vessel. 5 mL of nitric acid was added to completely submerge the sample. Then, 1.0 mL of hydrogen peroxide was slowly added dropwise. After reacting for 2 min, the vessel was sealed and placed in a microwave digestion furnace for digestion. After cooling to room temperature, the solution in the digestion vessel was filtered through a 0.45 μm filter membrane and transferred to a volumetric flask. The solution was diluted to 50 mL with distilled water and tested using ICP-OES.

[0085] Anti-precipitation agent 1#: Sodium dihydrogen phosphate, MSP2040, Lianyungang Xidu Biochemical;

[0086] Anti-precipitation agent #2: Disodium dihydrogen pyrophosphate, DHPP, Nagase;

[0087] Anti-precipitation agent #3: Triethyl phosphate, Shandong Maofa Chemical Co., Ltd.; TEP.

[0088] Phosphite antioxidant #1: Triphenyl phosphite, Zhejiang Wansheng Co., Ltd.;

[0089] Phosphite antioxidant #2: Tris[2,4-di-tert-butylphenyl]phosphite, Tianjin Lianlong New Material Co., Ltd.;

[0090] Other antioxidant #1: Di(dodecyl)thiodipropionate, commercially available;

[0091] Other antioxidants #2: Hindered phenolic antioxidants, antioxidant 1098, commercially available;

[0092] Filler #1: Talc powder, SL92-10-A, Guangxi Longsheng Huamei Talc Development Co., Ltd., D50 particle size is 7.32μm;

[0093] Filler #2: Talc powder, SD-9462, Liaoning Xinda Talc Group, D50 particle size is 5.87 μm;

[0094] Filler #3: Calcium carbonate, Omya carb5T-JI, D50 particle size is 5.5μm.

[0095] Other additives #1: Lubricant: Ethylene bis-stearamide, commercially available.

[0096] Unless otherwise specified, all components (e.g., other additives 1#) used in the parallel examples and comparative examples are the same commercially available products.

[0097] The biodegradable compositions of the embodiments and comparative examples of the present invention were prepared by the following method:

[0098] Weigh each component according to the formula, mix them evenly, and then put them into a twin-screw extruder. Melt extrusion and granulation are carried out at 150~240℃ to obtain biodegradable materials.

[0099] The biodegradable compositions provided in the embodiments and comparative examples of this invention were subjected to performance testing according to the following test methods:

[0100] Casting precipitation test: The biodegradable composition was dried at 70℃ for 4 hours and then cast in a casting machine. The feed port temperature was fixed at 175℃, and the barrel, melt pump zone, and die head temperatures were all 215℃; the casting roller temperature was 25℃; the screw speed was 90 rpm, and the melt pump speed was 20 rpm. A closed-loop pressure of 4 MPa was applied. The film thickness was 50 micrometers. Before the experiment, a 30-minute transition period was performed, the casting roller was cleaned, casting continued, and the precipitates on the casting roller were collected after 1 hour. The collected precipitates were weighed using an electronic balance. The casting roller speed was fixed at 5 m / min; the casting roller diameter was 25 cm, and the roller side length was 30 cm.

[0101] Examples 1-15

[0102] Examples 1-15 provide a series of biodegradable compositions, the formulations of which are shown in Table 1.

[0103] Table 1. Formulations (parts by weight) for Examples 1-15

[0104]

[0105] Continued from Table 1

[0106]

[0107] Comparative Examples 1-12

[0108] Comparative Examples 1-11 provide a series of biodegradable compositions, the formulations of which are shown in Table 2.

[0109] Table 2 Formulations (parts by weight) for Comparative Examples 1-11

[0110]

[0111] Comparative Example 12

[0112] The difference between Comparative Example 12 and Example 1 is that, based on Example 1, 0.032 parts by weight of stannous octoate were added.

[0113] The performance of the biodegradable compositions of each embodiment and comparative example was determined according to the test methods mentioned above, and the test results are shown in Table 3.

[0114] Table 3 Performance test results of the biodegradable compositions of each example and comparative example

[0115]

[0116] .

[0117] As can be seen from Table 3:

[0118] The amount of precipitation in the casting precipitation test of the biodegradable compositions in Examples 1-15 was all below 0.5g, indicating that the addition of anti-precipitation agents and phosphite antioxidants to the biodegradable compositions of the present invention effectively improved the precipitation problem in the casting of biodegradable compositions.

[0119] Comparative Example 1, without the addition of an anti-precipitation agent, still exhibited severe precipitation problems in the cast-cast biodegradable composition. Comparative Example 2, without the addition of a phosphite antioxidant, also exhibited severe precipitation problems in the cast-cast biodegradable composition. Comparative Example 3, with the addition of an organosulfur antioxidant, still exhibited severe precipitation problems in the cast-cast biodegradable composition. Comparative Example 4, without the addition of either an anti-precipitation agent or a phosphite antioxidant, still exhibited severe precipitation problems in the cast-cast biodegradable composition. Comparative Example 5, without the addition of an anti-precipitation agent but replacing it with an equal amount of a phosphite antioxidant, and Comparative Example 6, without the addition of a phosphite antioxidant but replacing it with an equal amount of an anti-precipitation agent, both failed to effectively improve the precipitation problems in the cast-cast biodegradable composition. Comparative Example 7, with the addition of a hindered phenolic antioxidant, still exhibited severe precipitation problems in the cast-cast biodegradable composition. As can be seen from Comparative Examples 8-11, the problem of cast film precipitation remains severe when the titanium and tin content of the biodegradable composition is outside the specific range, or when the titanium and tin content of the biodegradable composition is outside the specific range and no anti-precipitation agent or phosphite antioxidant is added. For biodegradable compositions with titanium and / or tin content outside the specific range, the effect of adding anti-precipitation agents and phosphite antioxidants on improving the anti-cast film precipitation of the composition is limited. Among them, the cast film precipitation in Comparative Example 8 is still relatively severe, which may be because the tin content in polylactic acid is low, indicating that less tin catalyst was added during its synthesis. Less tin catalyst leads to a higher residual monomer content in polylactic acid, which has a certain impact on the precipitation process. Comparative Example 12 added stannous octoate to the composition based on Example 1, and the cast film precipitation problem of the composition became more severe. It can be seen that the added tin and / or titanium elements in the composition can also affect the cast film precipitation of the composition.

[0120] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A biodegradable composition with low casting precipitation, characterized in that, The components include the following parts by weight: Polylactic acid 69-91 parts, 0-16 parts of flexible biodegradable polyester 0-11 parts of filler Anti-precipitation agent 0.1~3.1 parts, Phosphite antioxidants: 0.1-3.1 parts; The anti-precipitation agent is a phosphorus compound having the structure shown in Formula I or Formula II; Formula I, Formula II; R1, R2, R3, and R4 are each independently selected from any one of -H, -OH, alkoxy, or -OM; M is selected from alkali metal ions, alkaline earth metal ions, or transition metal ions. The biodegradable composition contains 35 to 100 ppm of titanium and / or tin.

2. The biodegradable material according to claim 1, characterized in that, The phosphorus compound is at least one of phosphate esters, phosphates, or pyrophosphates.

3. The biodegradable composition according to claim 1, characterized in that, The phosphite antioxidant is at least one of the following: triphenyl phosphite, tris[2,4-di-tert-butylphenyl]phosphite, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol diphosphite, tetrakis(2,4-di-tert-butylphenol) 4,4'-biphenyl diphosphite, distearate pentaerythritol diphosphite, or bis(2,4-dicumylphenyl)pentaerythritol diphosphite.

4. The biodegradable composition according to claim 1, characterized in that, The polylactic acid exhibits a melt flow rate of 3.0~14.0 g / 10min under test conditions of 190℃ and 2.16kg.

5. The biodegradable composition according to claim 1, characterized in that, The melt flow rate of the flexible biodegradable polyester at 190°C and 2.16 kg was measured to be 1.0~10.0 g / 10 min.

6. The biodegradable composition according to claim 1, characterized in that, The filler is at least one of calcium carbonate, talc, starch, or kaolin.

7. The biodegradable composition according to claim 1, characterized in that, The amount of the phosphite antioxidant is 1 to 3 parts, preferably 1.5 to 2 parts.

8. A method for preparing the biodegradable composition according to any one of claims 1 to 7, characterized in that, Includes the following steps: The components are mixed and melt-extruded to obtain the biodegradable composition.

9. The use of the biodegradable composition described in any one of claims 1 to 7 in the preparation of cast casting products.

10. The application according to claim 9, characterized in that, The cast film products are biodegradable films.

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