Biodegradable composite material and preparation method thereof

Abstract

The invention belongs to the field of high polymer materials, and particularly relates to a biodegradable composite material and a preparation method thereof. The technical problem that an existing biodegradable material product is poor in aging resistance and barrier property is solved. Aromatic-aliphatic copolyester with a side chain is used as a base material, and an esterification-polycondensation process is performed to prepare the polyester. The composite material comprises the following components in parts by weight: 60-90 parts of a copolyester material, 10-30 parts of other blended resin, 20-40 parts of an inorganic filler, 0.5-2 parts of a lubricant and 0.01-2 parts of an epoxy chain extender. The epoxy chain extender is an epoxy chain extender with bio-based aconitic acid as a framework, and the mechanical property and the anti-aging property of the degradable composite material are comprehensively improved based on coordination and cooperation of the base material, the epoxy chain extender and other raw materials. The composite material is expected to be applied to the fields of biodegradable shopping bags, agricultural plastic mulching films, foaming materials and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials. Specifically, it relates to a biodegradable composite material and a preparation method thereof. Background Art

[0002] Under the "dual carbon" strategy and the "plastic ban" policy, biodegradable plastics have attracted much attention due to their excellent biodegradable properties, and the industry has developed rapidly. Among them, biodegradable plastics represented by PBAT (polybutylene adipate terephthalate), PBS (polybutylene succinate), PLA (polylactic acid), and PHA (polyhydroxyalkanoate) have been continuously developed and applied. PBAT is the most commonly used biodegradable plastic and is widely used in products such as shopping bags, packaging bags, and mulch films.

[0003] For biodegradable plastics, how to balance their biodegradable properties and shelf life is one of the key issues of concern in the industry. Traditional biodegradable polyester materials will cause product aging in a humid and hot environment or under ultraviolet light irradiation, seriously affecting their shelf life and service life. At the same time, there are also disadvantages such as poor barrier properties, which limit the popularization and application of such materials in fields such as agricultural films and fruit and vegetable protection bags.

[0004] Therefore, it is necessary to develop new biodegradable composite materials to solve the above problems. Summary of the Invention

[0005] In order to solve the above problems, the present invention provides a biodegradable composite material and a preparation method thereof, aiming to solve technical problems such as poor weather resistance, low barrier properties, and the balance between biodegradable properties and shelf life of existing biodegradable plastics in a humid and hot environment or under ultraviolet light irradiation.

[0006] On the one hand, the present invention provides a biodegradable composite material, which includes: 60 - 90 parts of a copolyester material, 10 - 30 parts of a blend resin material, 20 - 40 parts of an inorganic filler, 0.5 - 2 parts of a lubricant, and 0.01 - 2 parts of an epoxy chain extender.

[0007] Among them, the copolyester material is an aromatic - aliphatic copolyester with side chains; the epoxy chain extender is an epoxy chain extender with a bio - based aconitic acid as the backbone.

[0008] In this application, an aromatic-aliphatic copolyester with side chains, a blend resin, an inorganic filler, a lubricant, and an epoxy chain extender are synergistically compounded in a specific ratio to obtain a biodegradable composite material. Among them, in the aromatic-aliphatic copolyester with side chains, the introduction of the side chain structure increases the space density of the non-crystalline region of the copolyester material, and the composite material obtained by blending with other components has excellent water vapor barrier performance and enhanced aging resistance. However, the unique side chain structure of the aromatic-aliphatic copolyester with side chains makes its compatibility with the blend resin (such as PLA, PBS, PBAT, PPC, etc.) poor, resulting in a decline in the comprehensive performance of the entire composite material. In this application, an epoxy chain extender with an aconitate backbone is used, and its unique double bond structure and epoxy reaction sites can effectively improve the compatibility between the copolyester matrix and the mixed resin, promoting the improvement of the comprehensive performance of the composite material.

[0009] In addition, the biodegradable composite material obtained by compounding the aromatic-aliphatic copolyester matrix material with side chains, the blend resin, the epoxy chain extender with an aconitate backbone and other components can effectively improve its degradation performance while improving the compatibility between the copolyester matrix material and the blend resin due to the introduction of the aconitate backbone and the epoxy structure. The introduction of side chain groups and the blend resin can enable the material to simultaneously have good mechanical properties and weather resistance.

[0010] Optionally, 80-90 parts of the copolyester material, 20-30 parts of the blend resin material, 30-40 parts of the inorganic filler, 1-2 parts of the lubricant, and 1-2 parts of the epoxy chain extender.

[0011] Optionally, the preparation method of the copolyester material includes the following steps:

[0012] Using a fatty dibasic acid with side chains, terephthalic acid, and an aliphatic diol as polymerization monomers, an aromatic-aliphatic copolyester with side chains is prepared by an esterification-polycondensation process;

[0013] Among them, the structural formula of the fatty dibasic acid with side chains is as shown in Formula I, and the structural formula of the aliphatic diol is as shown in Formula II:

[0014]

[0015] Optionally, in Formula I, X in the side chain is an integer from 0 to 4, and Y in the main chain is an integer from 1 to 5; in Formula II, Z in the aliphatic diol is an integer from 0 to 4. For example, the side chain can be one of methyl, ethyl, and n-propyl;

[0016] For example, the aliphatic diol can be one of 1,4-butanediol, ethylene glycol, or 1,3-propanediol;

[0017] Optionally, the preparation method of the copolyester material includes the following steps:

[0018] Add a fatty dibasic acid with a side chain, terephthalic acid, and an aliphatic diol to a reaction kettle, add tetrabutyl titanate as a catalyst, and start the first-stage esterification at a temperature of 150 - 180°C. After 1 - 2 hours of esterification, when the temperature is raised to 210 - 220°C, add tetrabutyl titanate as a catalyst and then start the second-stage esterification. After 2 - 3 hours of esterification, when the water produced reaches 90% of the theoretical water output quality, add tetrabutyl titanate again and raise the temperature to 240 - 250°C to start the polycondensation reaction. When it is found that the torque on the equipment does not change, the polycondensation is completed, and an aromatic-aliphatic copolyester with a side chain is obtained.

[0019] Optionally, the density of the copolyester material is 1.21 g / cm 3 , the tensile strength is 21 - 35 MPa, the elongation at break is 670 - 870%, the melting temperature is 110 - 141°C, and the heat distortion temperature is 90 - 117°C.

[0020] Optionally, the molar ratio of terephthalic acid to the fatty dibasic acid with a side chain is 1:(1 - 5), and the molar ratio of the total amount of acid to the aliphatic diol is 1:(1 - 2).

[0021] Wherein, the total amount of acid is the sum of the fatty dibasic acid with a side chain and terephthalic acid.

[0022] Optionally, the general structural formula of the epoxy chain extender is as shown in Formula III:

[0023]

[0024] Optionally, in Formula III, n is a carbon chain of 1 - 4.

[0025] In an exemplary embodiment of the present invention, the preparation method of the epoxy chain extender includes the following steps:

[0026] (1) React aconitic acid with thionyl chloride at a certain temperature to obtain an acyl chloride intermediate;

[0027] (2) React the acyl chloride intermediate with epoxy alcohol at -10 - 50°C to obtain an epoxy chain extender with a bio-based aconitic acid as the backbone.

[0028] Optionally, in step (1), the certain temperature is 90 - 150°C, and the reaction time is 2 - 10 hours.

[0029] Optionally, in step (1), the certain temperature is 100 - 130°C, and the reaction time is 5 - 8 hours.

[0030] Optionally, the structural formula of the epoxy alcohol is as shown in Formula IV,

[0031]

[0032] Among them, n is an integer from 1 to 4.

[0033] Optionally, the molar ratio of aconitic acid, thionyl chloride and epoxy alcohol is 1:(5 - 8):(3 - 4).

[0034] Optionally, the blend resin material is one or more of PLA, PBS, PBAT or PPC (polypropylene carbonate);

[0035] Optionally, the inorganic filler is one or more of calcium carbonate, talcum powder, silica, titanium dioxide, hydrotalcite or nanocellulose;

[0036] Optionally, the lubricant is one or more of stearic acid, butyl stearate, erucamide, N,N - ethylene bisstearamide.

[0037] The second aspect of the present invention provides a preparation method of a biodegradable composite material, and the preparation method includes the following steps:

[0038] S1: Dry the copolyester material and the blend resin material for later use;

[0039] S2: Mix the epoxy chain extender, inorganic filler, lubricant, dried copolyester material and blend resin material in proportion, and extrude and pelletize to obtain the biodegradable composite material.

[0040] Optionally, in step S1, the drying temperature is 30 - 80 °C and the drying time is 1 - 6 h.

[0041] Optionally, in step S2, the mixing is carried out by a high - speed mixer. The speed of the high - speed mixer is set to stir at a low speed of 150 r / min for 4 - 10 min first, and then stir at a high speed of 1000 r / min for 30 min. The extrusion and pelletizing is carried out by a twin - screw extruder, the main machine temperature is 160 - 200 °C, and the head temperature is 170 - 190 °C.

[0042] Compared with the prior art, the present invention has at least one of the following beneficial effects:

[0043] (1) The biodegradable composite material of the present invention has good mechanical properties, high barrier properties, anti - aging properties and biodegradable properties, and its performance characteristics have broad application prospects in the field of film bag product materials.

[0044] (2) The biodegradable composite material of the present invention uses a copolyester matrix material synthesized with a fatty dibasic acid having a side chain as a polymerization monomer. Due to the existence of its side - chain structure, the space density of the non - crystalline region of the copolyester material increases, and the composite material obtained by blending with other components has excellent water vapor barrier properties. Thanks to its excellent barrier properties, the weather resistance of the composite material is improved.

[0045] (3) The present invention uses an epoxy chain extender based on biobased aconitic acid. With its unique double-bond structure and epoxy reaction sites, it can promote the compatibility between the copolyester matrix material and the blended resin, avoid phase separation, and thus improve the comprehensive performance of the composite material while taking into account the degradation performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] The drawings described herein are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0047] Figure 1 For copolyester 1# in Example 1 1 1H NMR spectrum. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0048] The following describes the present application in detail with reference to the embodiments, but the present application is not limited to these embodiments.

[0049] Unless otherwise specified, the raw materials in the embodiments and comparative examples of the present application are purchased through commercial channels.

[0050] Unless otherwise specified, the methods used in the embodiments and comparative examples of the present application are conventional methods in the prior art.

[0051] Example 1

[0052] The preparation method of the biodegradable composite material includes the following steps:

[0053] 1) Weigh 498 kg of terephthalic acid, 396 kg of methylsuccinic acid, and 758 kg of 1,4-butanediol and add them to a polymerization reactor. Use tetrabutyl titanate as a catalyst to obtain copolyester 1# through an esterification-polycondensation process. Refer to Figure 1 , Figure 1 which shows the 1H NMR spectrum of copolyester 1#.

[0054] 2) Weigh 70 parts of the copolyester 1# prepared above, 20 parts of PLA, 20 parts of calcium carbonate powder, 1 part of erucamide, and 1 part of epoxy chain extender.

[0055] The preparation method of the epoxy chain extender includes the following steps:

[0056] (1) React aconitic acid with thionyl chloride at 120 °C to obtain an acyl chloride intermediate;

[0057] (2) React the acyl chloride intermediate with 2-(oxiran-2-yl)ethanol at 20 °C to obtain epoxy chain extender 1# based on biobased aconitic acid. Among them, the molar ratio of aconitic acid, thionyl chloride, and epoxy alcohol is 1:5:4.

[0058] 3) Add each raw material into a high-speed mixer in a certain order. The addition order is copolyester 1#, PLA, calcium carbonate powder, epoxy chain extender 1#, erucamide. The mixing speed is first low speed for about 4 minutes, and then high speed for about 30 minutes before discharging.

[0059] 4) Add the mixed raw materials into the hopper of a twin-screw extruder. Set the main machine temperature at 180 °C, the head temperature at 190 °C, and the screw rotation speed at 300 r / min. Extrude and pelletize to obtain the biodegradable composite material.

[0060] Example 2

[0061] The preparation method of the biodegradable composite material includes the following steps:

[0062] 1) Weigh 498 kg of terephthalic acid, 396 kg of methylsuccinic acid, and 758 kg of 1,4-butanediol and add them into a polymerization reactor. Use tetrabutyl titanate as the catalyst and obtain copolyester 1# through the esterification-polycondensation process.

[0063] 2) Weigh 60 parts of the copolyester 1# prepared above, 10 parts of PBS, 20 parts of talcum powder, 1 part of butyl stearate, and 1 part of epoxy chain extender.

[0064] Among them, the preparation method of the epoxy chain extender includes the following steps:

[0065] (1) React aconitic acid with thionyl chloride at 90 °C to obtain an acyl chloride intermediate;

[0066] (2) React the acyl chloride intermediate with 2-(oxiran-2-yl)ethanol at 10 °C to obtain an epoxy chain extender 2# with a bio-based aconitic acid skeleton. Among them, the molar ratio of aconitic acid, thionyl chloride, and epoxy alcohol is 1:5:4.

[0067] 3) Add each raw material into a high-speed mixer in a certain order. The addition order is copolyester 1#, PBS, talcum powder, epoxy chain extender 2#, butyl stearate. The mixing speed is first low speed for about 4 minutes, and then high speed for about 30 minutes before discharging.

[0068] 4) Add the mixed raw materials into the hopper of a twin-screw extruder. Set the main machine temperature at 160 °C, the head temperature at 170 °C, and the screw rotation speed at 300 r / min. Extrude and pelletize to obtain the biodegradable composite material.

[0069] Example 3

[0070] The preparation method of the biodegradable composite material includes the following steps:

[0071] 1) Weigh 498 kg of terephthalic acid, 396 kg of methylsuccinic acid, and 758 kg of 1,4-butanediol and add them to the polymerization reactor. Use tetrabutyl titanate as the catalyst, and obtain copolyester 1# through the esterification-polycondensation process. 2) Weigh 90 parts of the copolyester 1# prepared above, 30 parts of PBAT, 30 parts of silica, 2 parts of stearic acid, and 2 parts of epoxy chain extender.

[0072] Among them, the preparation method of the epoxy chain extender includes the following steps:

[0073] (1) React aconitic acid with thionyl chloride at 150 °C to obtain an acyl chloride intermediate;

[0074] (2) React the acyl chloride intermediate with 2-(oxiran-2-yl)ethanol at 50 °C to obtain epoxy chain extender 3# with a bio-based aconitic acid skeleton. Among them, the molar ratio of aconitic acid, thionyl chloride, and epoxy alcohol is 1:5:4.

[0075] 3) Add each raw material to a high-speed mixer in a certain order. The addition order is copolyester 1#, PBAT, silica, epoxy chain extender 3#, and stearic acid in sequence. The mixing speed is first low speed for about 4 minutes, and then high speed for about 30 minutes to discharge.

[0076] 4) Add the mixed raw materials to the hopper of a twin-screw extruder. Set the main machine temperature to 200 °C, the head temperature to 190 °C, and the screw rotation speed to 300 r / min, and extrude and pelletize to obtain the biodegradable composite material.

[0077] Example 4

[0078] Based on Example 1, the main difference is that in step 1), weigh 498 kg of terephthalic acid, 486 kg of ethylsuccinic acid, and 758 kg of 1,4-butanediol and add them to the polymerization reactor. Use tetrabutyl titanate as the catalyst, and obtain copolyester 2# through the esterification-polycondensation process. Prepare the biodegradable composite material with copolyester 2#.

[0079] Example 5

[0080] Based on Example 1, the main difference is that 1) weigh 498 kg of terephthalic acid, 490 kg of propylsuccinic acid, and 758 kg of 1,4-butanediol and add them to the polymerization reactor. Use tetrabutyl titanate as the catalyst, and obtain copolyester 3# through the esterification-polycondensation process. Prepare the biodegradable composite material with copolyester 3#.

[0081] Example 6

[0082] On the basis of Example 1, the main differences are as follows: 1) Weigh 498 kg of terephthalic acid, 522 kg of 2-methyladipic acid, and 758 kg of 1,4-butanediol and add them to a polymerization reactor. Use tetrabutyl titanate as a catalyst and obtain copolyester 4# through an esterification-polycondensation process. Prepare a biodegradable composite material from copolyester 4#.

[0083] Example 7

[0084] On the basis of Example 1, the main differences are as follows: 1) Weigh 498 kg of terephthalic acid, 522 kg of 2-ethyladipic acid, and 758 kg of 1,4-butanediol and add them to a polymerization reactor. Use tetrabutyl titanate as a catalyst and obtain copolyester 5# through an esterification-polycondensation process. Prepare a biodegradable composite material from copolyester 5#.

[0085] Example 8

[0086] On the basis of Example 1, the main differences are as follows: 1) Weigh 498 kg of terephthalic acid, 537 kg of 2-propyladipic acid, and 758 kg of 1,4-butanediol and add them to a polymerization reactor. Use tetrabutyl titanate as a catalyst and obtain copolyester 6# through an esterification-polycondensation process. Prepare a biodegradable composite material from copolyester 6#.

[0087] Example 9

[0088] On the basis of Example 1, the main differences are as follows: 1) React aconitic acid with thionyl chloride at 120 °C to obtain an acyl chloride intermediate; 2) React the acyl chloride intermediate with 1-(oxiran-2-yl)methanol at 20 °C to obtain an epoxy chain extender 4# with a bio-based aconitic acid backbone. Among them, the molar ratio of aconitic acid, thionyl chloride, and epoxy alcohol is 1:10:5. Prepare a biodegradable composite material from epoxy chain extender 4#.

[0089] Comparative Example 1

[0090] On the basis of Example 1, the main difference is that succinic acid is used instead of methylsuccinic acid, and the rest is the same as Example 1.

[0091] Comparative Example 2

[0092] On the basis of Example 5, the main difference is that adipic acid is used instead of 2-methyladipic acid, and the rest is the same as Example 5.

[0093] Comparative Example 3

[0094] On the basis of Example 1, the main difference is that the chain extender is ADR-4468, and the rest is the same as Example 1.

[0095] Comparative Example 4

[0096] On the basis of Example 1, the main difference is that the chain extender is epoxy soybean oil, and the rest is the same as in Example 1.

[0097] Comparative Example 5

[0098] On the basis of Example 1, the main difference is that 120 parts of copolyester 1# are used, and the rest is the same as in Example 1.

[0099] Comparative Example 6

[0100] On the basis of Example 1, the main difference is that 5 parts of epoxy chain extender are used, and the rest is the same as in Example 1.

[0101] Comparative Example 7

[0102] On the basis of Example 1, the main difference is that no blending resin material is added, and the rest is the same as in Example 1.

[0103] Test Example

[0104] The water vapor barrier performance and tensile properties before and after thermal aging of the composite materials prepared in the above examples and comparative examples were tested. The test results are shown in Table 1. The thermal aging was carried out according to GB / T 141-2008 "Test Method for Thermal Aging of Plastics", the tensile property test was carried out according to GB / T 1040-92 "Test Method for Tensile Properties of Plastics", and the shape of the test sample was the type II dumbbell-shaped specimen in the execution standard; the water vapor transmission rate was measured according to GB / T 1037-2021 "Determination of Water Vapor Transmission Performance of Plastic Films and Sheets - Cup Method for Weight Gain and Weight Loss". The biodegradation test method: Refer to the test method of ISO14855, and the CO 2 release amount after 90 days of composting of the material was used as the degradation index.

[0105] Among them, the thermal aging test conditions: The retention rates of tensile strength and elongation at break within 30 days under the conditions of a temperature of 60 °C and a relative humidity of 20% were used to represent.

[0106] Table 1

[0107]

[0108]

[0109] Table 2

[0110] Number <![CDATA[Water vapor transmission rate (g / (m 2 ·24h))]]> Biodegradability Performance (%) Example 1 131 97 Example 2 135 94 Example 3 137 95 Example 4 145 93 Example 5 149 94 Example 6 144 95 Example 7 140 93 Example 8 159 94 Example 9 146 93 Comparative Example 1 539 82 Comparative Example 2 544 85 Comparative Example 3 314 73 Comparative Example 4 208 78 Comparative Example 5 201 72 Comparative Example 6 247 93 Comparative Example 7 321 79

[0111] Referring to the test results in Table 1 above, for the copolyester-based biodegradable composite material of the present application using a dibasic acid with a side chain as the polymerization monomer, the tensile strength before thermal aging is greater than 30 MPa, the elongation at break is not less than 580%, the retention rate of tensile strength after thermal aging is greater than 80%, and the retention rate of elongation at break is greater than 64%. Referring to Comparative Examples 1 and 2, for the copolyester-based composite material using a linear dibasic acid as the polymerization monomer, the tensile strength before thermal aging is less than 30 Mpa, the elongation at break is less than 500%, the retention rate of tensile strength after thermal aging is less than 60%, and the retention rate of elongation at break is less than 50%. It can be seen that the biodegradable composite material of the present application still has good mechanical properties and anti-aging properties after thermal aging.

[0112] Referring to the test results in Table 2, for the copolyester-based biodegradable composite material of the present application using a dibasic acid with a side chain as the polymerization monomer, the water vapor transmission rate is not higher than 160 g / (m 2. 24h), and the biodegradation rate is not less than 90%. It is found that mainly because the introduction of the side chain helps to increase the spatial density of the amorphous region of the copolyester matrix material, which is beneficial to the improvement of the water vapor barrier performance. At the same time, the cooperation of this side chain structure with the epoxy chain extender based on biobased aconitic acid can further improve the degradation performance of the composite material.

[0113] Referring to Examples 1 and Comparative Examples 3-4, 6 for comparison, it can be seen that the type and addition amount of the chain extender affect the comprehensive performance of the biodegradable composite material. By selecting the epoxy chain extender with an aconitic acid ester backbone in the present application, due to the introduction of the aconitic acid ester backbone and epoxy structure, while improving the compatibility between the copolyester matrix material and the blend resin, it can effectively improve its degradation performance and ensure good mechanical properties.

[0114] The above are only the embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A biodegradable composite material, characterized in that: The biodegradable composite material comprises, by weight: 60-90 parts of copolyester material, 10-30 parts of blended resin material, 20-40 parts of inorganic filler, 0.5-2 parts of lubricant, and 0.01-2 parts of epoxy chain extender; The copolyester material is an aromatic-aliphatic copolyester with side chains; and the epoxy chain extender is an epoxy chain extender with bio-based aconitic acid as the skeleton.

2. The biodegradable composite material according to claim 1, characterized in that: The preparation method of the copolyester material comprises the following steps: The side chain modified aromatic-aliphatic copolyester is prepared by using a fatty dibasic acid with side chain, terephthalic acid and aliphatic diol as polymerization monomers through an esterification-polycondensation process; The structural formula of the fatty dibasic acid with a side chain is shown in Formula I, and the structural formula of the aliphatic diol is shown in Formula II: Wherein, in Formula I, X in the side chain is an integer of 0-4, and Y in the main chain is an integer of 1-5; in Formula II, Z in the aliphatic diol is an integer of 0-4.

3. The biodegradable composite material according to claim 2, characterized in that: The molar ratio of terephthalic acid to aliphatic dibasic acid having a side chain is 1:(1-5), and the molar ratio of the total amount of acid to aliphatic diol is 1:(1-2).

4. The biodegradable composite material according to claim 1, characterized in that: The general structural formula of the epoxy chain extender is shown in Formula III: Here, n is an integer from 1 to 4.

5. The biodegradable composite material according to claim 4, characterized in that: The preparation method of the epoxy chain extender comprises the following steps: (1) reacting aconitic acid with thionyl chloride at a certain temperature to obtain an acyl chloride intermediate; (2) reacting the acyl chloride intermediate with epoxy alcohol at -10 to 50° C. to obtain an epoxy chain extender with a bio-based aconitic acid as a skeleton.

6. The biodegradable composite material according to claim 5, characterized in that: The structural formula of epoxy alcohol is shown in Formula IV, Here, n is an integer from 1 to 4.

7. The biodegradable composite material according to claim 5, characterized in that: The molar ratio of aconitic acid, thionyl chloride and epoxy alcohol is 1:(5-10):(3-5).

8. The biodegradable composite material according to claim 1, characterized in that: The blended resin material is one or more of PLA, PBS, PBAT or PPC; and / or the inorganic filler is one or more of calcium carbonate, talc, silicon dioxide, titanium dioxide, hydrotalcite or nanocellulose; And / or the lubricant is one or more of stearic acid, butyl stearate, erucic acid amide, and N,N-ethylene bisstearic acid amide.

9. A method for preparing the biodegradable composite material according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: S1: drying the copolyester material and the blended resin material for standby use; S2: Mix the epoxy chain extender, inorganic filler, lubricant, dried copolyester material and blended resin material in proportion, extrude and granulate to obtain a biodegradable composite material.

10. The preparation method according to claim 9, characterized in that: The extrusion granulation adopts a twin-screw extruder with a main engine temperature of 160-200°C and a head temperature of 170-190°C.

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