Polyvinyl alcohol / polyester degradable composite material as well as preparation method and application thereof

Abstract

The invention discloses a polyvinyl alcohol / polyester degradable composite material and a preparation method and application thereof, and relates to the technical field of degradable composites.The preparation method comprises the steps that succinic acid, 1, 4-butanediol and a modifying agent serve as raw materials, polyester of a special structure is synthesized through an esterification reaction and a condensation polymerization reaction, and then the polyester is added into the polyvinyl alcohol / polyester degradable composite material; the polyving akohol / polyester degradable composite material can be prepared into various types of plastic products through thermoplastic processing, and shows excellent processing performance, mechanical property, barrier property, heat resistance and the like.

Description

Technical Field

[0001] This invention relates to the field of biodegradable composite materials technology, specifically to a polyvinyl alcohol / polyester biodegradable composite material, its preparation method, and its application. Background Technology

[0002] Polyvinyl alcohol (PVA) is an important polymer material that can be industrially produced on a large scale from non-petroleum routes such as coal and natural gas. PVA possesses excellent comprehensive properties, such as superior barrier properties, and its mechanical and heat resistance properties are far superior to polyolefins, comparable to engineering plastics such as polyamide and polycarbonate. Furthermore, PVA is a water-soluble and biodegradable polymer material that can be completely degraded into carbon dioxide and water by microorganisms in the natural environment, exhibiting 100% biodegradability and good biocompatibility. However, the strong hydrogen bonding characteristics of PVA's polyhydroxyl groups make its melting point (226℃) and decomposition temperature (200~250℃) very close, making thermoplastic processing difficult. Achieving thermoplastic processing of PVA would open up new application areas for PVA as a novel plastic, which has significant practical implications. Current methods include solution plasticization, chemical modification, and blending modification with other polymer materials. These methods inhibit PVA crystallization, lower the melting point, increase the thermal decomposition temperature, and obtain a thermoplastic processing window.

[0003] Biodegradable polyester materials are a class of polymers that can be decomposed into harmless substances such as water and carbon dioxide in the natural environment through the action of microorganisms or enzymes. Examples include polylactic acid (PLA), polyglycolic acid (PGA), polybutylene succinate (PBS), polybutylene adipate / terephthalate (PBAT), polycaprolactone (PCL), and polypropylene carbonate (PPC). These materials are prepared through chemical synthesis or bio-fermentation and are widely used in packaging, agriculture, and medical fields.

[0004] The present invention aims to reduce the crystallinity of PVA and increase its glass transition temperature by blending PVA with polyester, thereby enabling thermoplastic processing of PVA and optimizing its processing and application performance. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a polyvinyl alcohol / polyester biodegradable composite material, wherein a novel polyester is synthesized and polyvinyl alcohol is blended and modified, and the prepared polyvinyl alcohol / polyester biodegradable composite material has excellent processing performance and mechanical properties and good thermal stability.

[0006] The technical problem to be solved by the present invention is achieved by the following technical solution: One objective of this invention is to provide a method for preparing a polyvinyl alcohol / polyester biodegradable composite material, comprising the following steps: S1. Using succinic acid, 1,4-butanediol and a modifier as raw materials, esterification, pre-condensation and final condensation reactions are carried out sequentially under the action of a catalyst to obtain polyester. S2. Polyvinyl alcohol, polyester, filler and compatibilizer are blended in a high-speed mixer, then melt-blended in a twin-screw extruder, and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0007] In a further technical solution, the modifier is dimethylsilanediol.

[0008] In a further technical solution, the molar ratio of succinic acid, 1,4-butanediol, and the modifier is 1 : (1.2~1.5) : (0.2~0.3).

[0009] In a further technical solution, the catalyst is a titanate catalyst, including but not limited to at least one of tetraethyl titanate, tetrabutyl titanate, and tetraisopropyl titanate. In some preferred embodiments, the catalyst is composed of a titanate catalyst and bis(n-butylcyclopentadienyl)zirconia dichloride, wherein the mass ratio of the titanate catalyst to bis(n-butylcyclopentadienyl)zirconia dichloride is 9:1.

[0010] In a further technical solution, the amount of the catalyst is 0.1 to 0.5% of the total mass of succinic acid, 1,4-butanediol and dimethylsilanediol.

[0011] In a further technical solution, the reaction temperature of the esterification reaction is 150~200℃.

[0012] In a further technical solution, the reaction temperature of the pre-condensation reaction is 200~250℃, and the reaction pressure is 1~10 kPa.

[0013] In a further technical solution, the reaction temperature of the final polycondensation reaction is 220~280℃, and the reaction pressure is 20~200 Pa.

[0014] In a further technical solution, the weight-average molecular weight of the polyester is between 100,000 and 200,000.

[0015] In a further technical solution, the filler is biomass and / or inorganic minerals. The biomass includes, but is not limited to, at least one of straw powder, starch, and wood flour; the inorganic minerals include, but are not limited to, at least one of talc powder, mica powder, wollastonite powder, calcined kaolin, calcium silicate, and barium sulfate.

[0016] In a further technical solution, the compatibilizer includes, but is not limited to, at least one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, silane coupling agent, and titanate coupling agent.

[0017] In a further technical solution, the mass ratio of polyvinyl alcohol, polyester, filler, and compatibilizer is 100 : (30~50) : (10~30) : (1~5).

[0018] The second objective of this invention is to provide a polyvinyl alcohol / polyester biodegradable composite material obtained by the aforementioned preparation method.

[0019] A third objective of this invention is to provide the application of the aforementioned polyvinyl alcohol / polyester biodegradable composite material in plastic products. Specifically, the plastic products include plastic films, plastic sheets, plastic pipes, plastic filaments, plastic profiles, etc.

[0020] The beneficial effects of this invention are as follows: This invention uses succinic acid, 1,4-butanediol and modifier as raw materials, first synthesizes a polyester with a special structure through esterification and polycondensation reactions, and then uses the polyester to blend and modify polyvinyl alcohol to obtain a polyvinyl alcohol / polyester biodegradable composite material. The polyvinyl alcohol / polyester biodegradable composite material can be thermoplasticized into various types of plastic products and exhibits excellent processing performance, mechanical properties, barrier properties and heat resistance properties. Detailed Implementation

[0021] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0022] The following examples and comparative examples illustrate the sources of raw materials: Polyvinyl alcohol 1788 and polyvinyl alcohol 2099 were purchased from Jiangsu Xinlun Petrochemical Co., Ltd. The corn starch was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd. Talc powder was purchased from Jiangxi Chenxin New Materials Co., Ltd., 1250 mesh; Wollastonite powder, 1250 mesh, was purchased from Jiangxi Chenxin New Materials Co., Ltd. Calcined kaolin was purchased from Hebei Leijiang New Material Technology Co., Ltd., 1250 mesh; Barium sulfate was purchased from Langfang Qianyao Technology Co., Ltd., 1250 mesh; Maleic anhydride-grafted polyethylene was purchased from Shanghai Yonglixin Plastic Co., Ltd. Maleic anhydride-grafted polypropylene was purchased from Dongguan Shenghao Plastic Raw Materials Co., Ltd.

[0023] Example 1 S1. Under nitrogen protection, 1182 g of succinic acid, 1081 g of 1,4-butanediol, 277 g of dimethylsilanediol and 10 g of tetraethyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 180℃ for 6 h. Then, a pre-condensation reaction was carried out at 230℃ and 5 kPa for 1 h, and finally a final condensation reaction was carried out at 250℃ and 100 Pa for 5 h to obtain polyester.

[0024] S2. 100 parts of polyvinyl alcohol 1788, 30 parts of polyester prepared in step S1, 10 parts of corn starch and 1 part of silane coupling agent KH-570 are mixed in a high-speed mixer (speed of 2000 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0025] Example 2 S1. Under nitrogen protection, 1182 g of succinic acid, 1081 g of 1,4-butanediol, 184 g of dimethylsilanediol and 10 g of tetrabutyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 160℃ for 5 h. Then, a pre-condensation reaction was carried out at 200℃ and 10 kPa for 1 h, and finally a final condensation reaction was carried out at 240℃ and 50 Pa for 5 h to obtain polyester.

[0026] S2. 100 parts of polyvinyl alcohol 1788, 40 parts of polyester prepared in step S1, 15 parts of talc powder and 1 part of silane coupling agent KH-550 are mixed in a high-speed mixer (speed of 1000 rpm) for 10 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 250 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0027] Example 3 S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 184 g of dimethylsilanediol and 12 g of tetraisopropyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 160℃ for 5 h. Then, a pre-condensation reaction was carried out at 220℃ and 3 kPa for 1 h, and finally a final condensation reaction was carried out at 250℃ and 200 Pa for 4 h to obtain polyester.

[0028] S2. 100 parts of polyvinyl alcohol 2099, 50 parts of polyester prepared in step S1, 20 parts of wollastonite powder and 2 parts of maleic anhydride grafted polyethylene are mixed in a high-speed mixer (speed of 1500 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 300 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0029] Example 4 S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 277 g of dimethylsilanediol and 12 g of tetrabutyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 150℃ for 4 h. Then, a pre-condensation reaction was carried out at 240℃ and 4 kPa for 1 h, and finally a final condensation reaction was carried out at 250℃ and 100 Pa for 5 h to obtain polyester.

[0030] S2. 100 parts of polyvinyl alcohol 2099, 40 parts of polyester prepared in step S1, 15 parts of calcined kaolin and 3 parts of maleic anhydride grafted polypropylene are mixed in a high-speed mixer (speed of 2000 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0031] Example 5 S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 277 g of dimethylsilanediol and 14 g of tetrabutyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 170℃ for 5 h. Then, a pre-condensation reaction was carried out at 230℃ and 3 kPa for 1 h, and finally a final condensation reaction was carried out at 280℃ and 100 Pa for 3 h to obtain polyester.

[0032] S2. 100 parts of polyvinyl alcohol 2099, 35 parts of polyester prepared in step S1, 10 parts of barium sulfate, 1 part of maleic anhydride grafted polypropylene and 1 part of silane coupling agent KH-550 are mixed in a high-speed mixer (1500 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature 150~190℃, screw speed 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0033] Comparative Example 1 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 4, except that dimethylsilanediol was not added.

[0034] S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol and 12 g of tetrabutyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 150℃ for 4 h. Then, a pre-condensation reaction was carried out at 240℃ and 4 kPa for 1 h, and finally a final condensation reaction was carried out at 250℃ and 100 Pa for 5 h to obtain polyester.

[0035] S2. 100 parts of polyvinyl alcohol 2099, 40 parts of polyester prepared in step S1, 15 parts of calcined kaolin and 3 parts of maleic anhydride grafted polypropylene are mixed in a high-speed mixer (speed of 2000 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0036] Comparative Example 2 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 4, except that dimethylsilanediol was replaced with ethylene glycol.

[0037] S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 186 g of ethylene glycol and 12 g of tetrabutyl titanate were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 150℃ for 4 h. Then, a pre-condensation reaction was carried out at 240℃ and 4 kPa for 1 h, and finally a final condensation reaction was carried out at 250℃ and 100 Pa for 5 h to obtain polyester.

[0038] S2. 100 parts of polyvinyl alcohol 2099, 40 parts of polyester prepared in step S1, 15 parts of calcined kaolin and 3 parts of maleic anhydride grafted polypropylene are mixed in a high-speed mixer (speed of 2000 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0039] Example 6 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 1, except that tetraethyl titanate was replaced with tetraethyl titanate and bis(n-butylcyclopentadienyl)zirconia dichloride in a mass ratio of 9:1.

[0040] S1. Under nitrogen protection, 1182 g of succinic acid, 1081 g of 1,4-butanediol, 277 g of dimethylsilanediol, 9 g of tetraethyl titanate and 1 g of bis(n-butylcyclopentadienyl)zirconia dichloride were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 180℃ for 6 h. Then, a pre-condensation reaction was carried out at 230℃ and 5 kPa for 1 h, and finally a final condensation reaction was carried out at 250℃ and 100 Pa for 5 h to obtain polyester.

[0041] S2. 100 parts of polyvinyl alcohol 1788, 30 parts of polyester prepared in step S1, 10 parts of corn starch and 1 part of silane coupling agent KH-570 are mixed in a high-speed mixer (speed of 2000 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0042] Example 7 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 2, except that tetrabutyl titanate was replaced with tetrabutyl titanate and bis(n-butylcyclopentadienyl)zirconia dichloride in a mass ratio of 9:1.

[0043] S1. Under nitrogen protection, 1182 g of succinic acid, 1081 g of 1,4-butanediol, 184 g of dimethylsilanediol, 9 g of tetrabutyl titanate and 1 g of bis(n-butylcyclopentadienyl)zirconia dichloride were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 160℃ for 5 h. Then, a pre-condensation reaction was carried out at 200℃ and 10 kPa for 1 h, and finally a final condensation reaction was carried out at 240℃ and 50 Pa for 5 h to obtain polyester.

[0044] S2. 100 parts of polyvinyl alcohol 1788, 40 parts of polyester prepared in step S1, 15 parts of talc powder and 1 part of silane coupling agent KH-550 are mixed in a high-speed mixer (speed of 1000 rpm) for 10 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 250 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0045] Example 8 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 3, except that tetraisopropyl titanate was replaced with tetraisopropyl titanate and bis(n-butylcyclopentadienyl)zirconia dichloride in a mass ratio of 9:1.

[0046] S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 184 g of dimethylsilanediol, 10.8 g of tetraisopropyl titanate and 1.2 g of bis(n-butylcyclopentadienyl)zirconia dichloride were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out an esterification reaction at 160 °C for 5 h. Then, a pre-condensation reaction was carried out at 220 °C and 3 kPa for 1 h, and finally, a final condensation reaction was carried out at 250 °C and 200 Pa for 4 h to obtain polyester.

[0047] S2. 100 parts of polyvinyl alcohol 2099, 50 parts of polyester prepared in step S1, 20 parts of wollastonite powder and 2 parts of maleic anhydride grafted polyethylene are mixed in a high-speed mixer (speed of 1500 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 300 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0048] Example 9 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 4, except that tetrabutyl titanate was replaced with tetrabutyl titanate and bis(n-butylcyclopentadienyl)zirconia dichloride in a mass ratio of 9:1.

[0049] S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 277 g of dimethylsilanediol, 10.8 g of tetrabutyl titanate and 1.2 g of bis(n-butylcyclopentadienyl)zirconia dichloride were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 150 °C for 4 h. Then, a pre-condensation reaction was carried out at 240 °C and 4 kPa for 1 h, and finally a final condensation reaction was carried out at 250 °C and 100 Pa for 5 h to obtain polyester.

[0050] S2. 100 parts of polyvinyl alcohol 2099, 40 parts of polyester prepared in step S1, 15 parts of calcined kaolin and 3 parts of maleic anhydride grafted polypropylene are mixed in a high-speed mixer (speed of 2000 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature of 150~190℃, screw speed of 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0051] Example 10 Polyvinyl alcohol / polyester biodegradable composite material was prepared according to the method of Example 5, except that tetrabutyl titanate was replaced with tetrabutyl titanate and bis(n-butylcyclopentadienyl)zirconia dichloride in a mass ratio of 9:1.

[0052] S1. Under nitrogen protection, 1182 g of succinic acid, 1352 g of 1,4-butanediol, 277 g of dimethylsilanediol, 12.6 g of tetrabutyl titanate and 1.4 g of bis(n-butylcyclopentadienyl)zirconia were added to the reactor. The mixture was stirred at room temperature for 30 min, and then heated to carry out esterification reaction at 170℃ for 5 h. Then, a pre-condensation reaction was carried out at 230℃ and 3 kPa for 1 h, and finally a final condensation reaction was carried out at 280℃ and 100 Pa for 3 h to obtain polyester.

[0053] S2. 100 parts of polyvinyl alcohol 2099, 35 parts of polyester prepared in step S1, 10 parts of barium sulfate, 1 part of maleic anhydride grafted polypropylene and 1 part of silane coupling agent KH-550 are mixed in a high-speed mixer (1500 rpm) for 5 min, and then melt-blended in a twin-screw extruder (temperature 150~190℃, screw speed 200 rpm), and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

[0054] The performance of the polyvinyl alcohol / polyester biodegradable composite materials prepared in Examples 1-10 and Comparative Example 2 was tested, and the test results are shown in Table 1.

[0055] The mechanical properties were evaluated by testing tensile strength and elongation at break according to GB / T 1040.1-2018 (23℃, 50%RH, tensile speed 100 mm / min). Thermal stability was evaluated by testing the decomposition temperature using thermogravimetric analysis.

[0056] Table 1 As shown in Table 1, compared with Comparative Examples 1-2, Examples 1-5 enhanced the modification effect of polyester on polyvinyl alcohol by adding dimethylsilanediol as a polyester synthesis monomer, thereby improving the mechanical properties and thermal stability of the composite material. Compared with Examples 1-5, Examples 6-10 improved the reactivity of dimethylsilanediol in polyester synthesis by using a specific ratio of titanate catalyst and bis(n-butylcyclopentadienyl)zirconium dichloride as a polyester synthesis catalyst, further enhancing the modification effect of polyester on polyvinyl alcohol, thereby better improving the mechanical properties and thermal stability of the composite material.

[0057] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a polyvinyl alcohol / polyester biodegradable composite material, characterized in that, The preparation method includes the following steps: S1. Using succinic acid, 1,4-butanediol and a modifier as raw materials, esterification, pre-condensation and final condensation reactions are carried out sequentially under the action of a catalyst to obtain polyester. S2. Polyvinyl alcohol, polyester, filler and compatibilizer are blended in a high-speed mixer, then melt-blended in a twin-screw extruder, and extruded and granulated to obtain a polyvinyl alcohol / polyester biodegradable composite material.

2. The preparation method according to claim 1, characterized in that: The molar ratio of succinic acid, 1,4-butanediol, and modifier is 1 : (1.2~1.5) : (0.2~0.3).

3. The preparation method according to claim 1, characterized in that: The catalyst is a titanate catalyst; Preferably, the amount of catalyst used is 0.1-0.5% of the total mass of succinic acid, 1,4-butanediol, and dimethylsilanediol; Preferably, the titanate catalyst is selected from at least one of tetraethyl titanate, tetra-n-butyl titanate, and tetraisopropyl titanate.

4. The preparation method according to claim 1, characterized in that: The reaction temperature for the esterification reaction is 150~200℃; Preferably, the reaction temperature of the pre-condensation reaction is 200~250℃, and the reaction pressure is 1~10 kPa; Preferably, the reaction temperature of the final polycondensation reaction is 220~280℃, and the reaction pressure is 20~200 Pa.

5. The preparation method according to claim 1, characterized in that: The weight-average molecular weight of the polyester is between 100,000 and 200,000.

6. The preparation method according to claim 1, characterized in that: The filler is biomass and / or inorganic minerals; Preferably, the biomass is selected from at least one of straw powder, starch, and wood powder; Preferably, the inorganic mineral is selected from at least one of talc powder, mica powder, wollastonite powder, calcined kaolin, calcium silicate, and barium sulfate; Preferably, the compatibilizer is selected from at least one of maleic anhydride-grafted polyethylene, maleic anhydride-grafted polypropylene, silane coupling agent, and titanate coupling agent.

7. The preparation method according to claim 1, characterized in that: The modifier is dimethylsilanediol.

8. The preparation method according to claim 1, characterized in that: The mass ratio of polyvinyl alcohol, polyester, filler, and compatibilizer is 100 : (30~50) : (10~30) : (1~5).

9. A polyvinyl alcohol / polyester biodegradable composite material obtained by the preparation method according to any one of claims 1 to 8.

10. The application of the polyvinyl alcohol / polyester biodegradable composite material according to claim 9 in plastic products.

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