Environment-friendly degradable composite plastic and preparation method thereof

Abstract

This invention discloses an environmentally friendly biodegradable composite plastic and its preparation method. It is prepared by reacting modified resin with 1,4-bis(maleimide)butane. When the modified resin and 1,4-bis(maleimide)butane are mixed, the furan groups can undergo a DA reaction with the maleimide groups to form dynamic crosslinks, which makes the prepared composite plastic have excellent mechanical properties. Polylactic acid molecules and polyester molecules are linked by organosilicon segments, and the molecular chains are arranged in a radial pattern similar to snowflakes. The radial structure is connected to multiple branches through a central core to form a three-dimensional network. This structure can effectively disperse stress and improve the overall strength and stiffness of the material. The branches can absorb and disperse external impact energy. Combined with dynamic crosslinking, the mechanical properties of the composite plastic can be further improved.

Description

Technical Field

[0001] This invention relates to the field of biodegradable plastic preparation technology, specifically to an environmentally friendly biodegradable composite plastic and its preparation method. Background Technology

[0002] With the widespread use of plastic products, the environmental problems caused by traditional plastic materials are becoming increasingly serious, especially the impact of single-use plastic products on marine ecosystems, which has attracted widespread attention. Due to their durability and resistance to biodegradation, large amounts of discarded plastic waste are difficult to decompose in the natural environment, leading to pollution of land, water, and other resources, seriously affecting ecological balance and human health. Polylactic acid (PLA), as a widely recognized and applied bio-based biodegradable polymer, can be completely decomposed into carbon dioxide and water, thus causing no form of pollution to the environment. PLA, due to its high strength, good biocompatibility, and biodegradability, is one of the most promising alternatives to traditional petroleum-based polymers; however, its lower impact strength, elongation at break, and brittleness result in mechanical properties far inferior to traditional polymers. Summary of the Invention

[0003] The purpose of this invention is to provide an environmentally friendly and biodegradable composite plastic and its preparation method, which solves the problem of poor mechanical properties of current environmentally friendly and biodegradable composite materials.

[0004] The objective of this invention can be achieved through the following technical solutions:

[0005] A method for preparing an environmentally friendly and biodegradable composite plastic specifically includes the following steps: Step A1: Mix modified polylactic acid, acrylic acid, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 8-10 hours at a speed of 150-200 r / min and a temperature of 70-80℃ to obtain polylactic acid monomer. Step A2: Mix polylactic acid monomer, 1,4-butanediol, adipic acid, terephthalic acid, tetrabutyl titanate and DMF evenly, purge with nitrogen, and react for 8-10 hours at a rotation speed of 120-150 r / min, a temperature of 160-170℃ and a pressure of 2-3 MPa. Then raise the temperature to 240-245℃ and continue the reaction for 3-4 hours at a pressure of 100-150 Pa to obtain the modified resin. Step A3: Mix the modified resin and tetrahydrofuran evenly, stir and add 1,4-bis(maleimide)butane at a speed of 200-300 r / min and a temperature of 40-50℃, and stir for 8-10 h. Then remove the tetrahydrofuran by vacuum distillation to obtain environmentally friendly and biodegradable composite plastic.

[0006] Furthermore, in step A1, the molar ratio of Si-H bonds on the modified polylactic acid to acrylic acid is 1:1, and the amount of chloroplatinic acid used is 1‰ of the mass of acrylic acid.

[0007] Furthermore, in step A2, the ratio of carboxyl groups, 1,4-butanediol, adipic acid, and terephthalic acid on the polylactic acid monomer is 100 mmol: 2.4 mol: 1 mol: 1 mol, and the amount of tetrabutyl titanate is 1% of the sum of the masses of adipic acid and terephthalic acid.

[0008] Furthermore, the mass ratio of the modified resin and 1,4-bis(maleimide)butane described in step A3 is 20:1.

[0009] Furthermore, the modified polylactic acid is prepared by the following steps: Step B1: Mix furfural chloride, ethylene glycolamine, triethylamine and tetrahydrofuran, and react for 3-5 hours at a speed of 200-300 r / min and a temperature of 25-30℃ to obtain a treatment agent. Mix lactic acid and DMF evenly, and react for 3-5 hours at a speed of 120-150 r / min and a temperature of 120-130℃. Raise the temperature to 145-150℃, add stannous chloride, and continue the reaction for 2-3 hours. Raise the temperature to 170-180℃, add the treatment agent, and continue the reaction for 3-5 hours to obtain pretreated polylactic acid. Step B2: Mix pretreated polylactic acid, acrylic acid, p-toluenesulfonic acid and toluene evenly, purge with nitrogen, and react for 1-1.5 h at a speed of 150-200 r / min and a temperature of 115-120℃ to obtain terminal double bond polylactic acid. Mix terminal double bond polylactic acid, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 5-7 h at a speed of 200-150 r / min and a temperature of 70-80℃ to obtain functionalized polylactic acid. Step B3: Mix lithium metal and tetrahydrofuran evenly, purge with nitrogen, stir and add dimethylsilanol at a speed of 60-80 r / min and a temperature of 0-5℃, and react for 2-4 h to obtain lithium dimethylsilanol. Mix lithium dimethylsilanol and tetrahydrofuran evenly, purge with nitrogen, stir and add tetramethylcyclotetrasiloxane at a speed of 120-150 r / min and a temperature of 0-3℃, raise the temperature to 20-25℃, and react for 8-10 h. Then add functionalized polylactic acid and continue the reaction for 1-1.5 h to obtain modified polylactic acid.

[0010] Furthermore, in step B1, the molar ratio of furanoyl chloride, ethylene glycolamine, and triethylamine is 1:1:1.2, the mass ratio of lactic acid to the treatment agent is 10:1, and the amount of stannous chloride used is 5‰ of the mass of lactic acid and the treatment agent.

[0011] Furthermore, in step B2, the molar ratio of pretreated polylactic acid and acrylic acid is 1:2, the amount of p-toluenesulfonic acid is 1% of the mass of acrylic acid, the molar ratio of terminal double-bond polylactic acid and trichlorosilane is 1:2, and the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane.

[0012] Furthermore, in step B3, the molar ratio of lithium metal and dimethylsilanol is 1:1, and the molar ratio of lithium dimethylsilanol, tetramethylcyclotetrasiloxane, and functionalized polylactic acid is 2:4:1.

[0013] The beneficial effects of this invention are as follows: This application discloses an environmentally friendly and biodegradable composite plastic using modified polylactic acid and acrylic acid as raw materials. Under the action of chloroplatinic acid, the Si-H bonds on the modified polylactic acid react with the double bonds on the acrylic acid to obtain polylactic acid monomer. The polylactic acid monomer, 1,4-butanediol, adipic acid and terephthalic acid are esterified and polycondensed to obtain a modified resin. The modified resin is reacted with 1,4-bis(maleimide)butane, so that the furan groups on the modified resin react with the maleimide groups on the 1,4-bis(maleimide)butane to obtain an environmentally friendly and biodegradable composite plastic.

[0014] Modified polylactic acid (PLA) is prepared by reacting furanoyl chloride and ethylene glycolamine with triethylamine to obtain a pretreated PLA. Lactic acid is then polymerized with the hydroxyl groups on the pretreated PLA as reaction endpoints to form PLA segments. Pretreated PLA is then reacted with acrylic acid to esterify the hydroxyl groups on the pretreated PLA and the carboxyl groups on the acrylic acid, resulting in terminal double-bond PLA. Terminal double-bond PLA is then reacted with trichlorosilane with chloroplatinic acid to react the double bonds on the terminal double-bond PLA and the Si-H bonds on the trichlorosilane, resulting in functionalized PLA. Lithium metal and dimethylsilanol are used as raw materials to react the hydroxyl groups on the lithium metal and dimethylsilanol to obtain lithium dimethylsilanol. Lithium dimethylsilanol is then used as an initiator and tetramethylcyclotetrasiloxane as a monomer for ring-opening polymerization. Functionalized PLA is then added to end-cap the polymer to obtain a modified polyester.

[0015] When modified resin and 1,4-bis(maleimide)butane are mixed, the furan group can undergo a DA reaction with the maleimide group to form dynamic crosslinks, resulting in composite plastics with excellent mechanical properties. Polylactic acid molecules and polyester molecules are linked by organosilicon segments, and the molecular chains are arranged in a snowflake-like radial pattern. The radial structure connects multiple branches through a central core to form a three-dimensional network. This structure can effectively disperse stress and improve the overall strength and stiffness of the material. The branches can absorb and disperse external impact energy. Combined with dynamic crosslinking, the mechanical properties of the composite plastics can be further improved. Detailed Implementation

[0016] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0017] Example 1: A method for preparing an environmentally friendly and biodegradable composite plastic, specifically including the following steps: Step A1: Mix modified polylactic acid, acrylic acid, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 8 hours at a speed of 150 r / min and a temperature of 70℃ to obtain polylactic acid monomer. Step A2: Mix polylactic acid monomer, 1,4-butanediol, adipic acid, terephthalic acid, tetrabutyl titanate and DMF evenly, purge with nitrogen, and react for 8 hours at a speed of 120 r / min, a temperature of 160℃ and a pressure of 2 MPa. Then raise the temperature to 240℃ and continue the reaction for 3 hours at a pressure of 100 Pa to obtain the modified resin. Step A3: Mix the modified resin and tetrahydrofuran evenly, stir and add 1,4-bis(maleimide)butane at a speed of 200 r / min and a temperature of 40℃, stir for 8 h, remove tetrahydrofuran by vacuum distillation to obtain environmentally friendly biodegradable composite plastic.

[0018] The molar ratio of Si-H bonds on the modified polylactic acid and acrylic acid in step A1 is 1:1, and the amount of chloroplatinic acid used is 1‰ of the mass of acrylic acid.

[0019] In step A2, the ratio of carboxyl groups on the polylactic acid monomer, 1,4-butanediol, adipic acid, and terephthalic acid is 100 mmol: 2.4 mol: 1 mol: 1 mol, and the amount of tetrabutyl titanate is 1% of the sum of the masses of adipic acid and terephthalic acid.

[0020] The mass ratio of the modified resin and 1,4-bis(maleimide)butane described in step A3 is 20:1.

[0021] The modified polylactic acid is prepared by the following steps: Step B1: Furanoyl chloride, ethylene glycolamine, triethylamine and tetrahydrofuran are mixed and reacted at 200 r / min and 25°C for 3 h to obtain the treatment agent. Lactic acid and DMF are mixed evenly and reacted at 120 r / min and 120°C for 3 h. The temperature is raised to 145°C, stannous chloride is added, and the reaction continues for 2 h. The temperature is raised to 170°C, the treatment agent is added, and the reaction continues for 3 h to obtain pretreated polylactic acid. Step B2: Mix pretreated polylactic acid, acrylic acid, p-toluenesulfonic acid and toluene evenly, purge with nitrogen, and react for 1 hour at 150 r / min and 115°C to obtain terminal double bond polylactic acid. Mix terminal double bond polylactic acid, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 5 hours at 200 r / min and 70°C to obtain functionalized polylactic acid. Step B3: Mix lithium metal and tetrahydrofuran evenly, purge with nitrogen, stir and add dimethylsilanol at 60 r / min and 0℃, and react for 2 h to obtain lithium dimethylsilanol. Mix lithium dimethylsilanol and tetrahydrofuran evenly, purge with nitrogen, stir and add tetramethylcyclotetrasiloxane at 120 r / min and 0℃, heat to 20℃ and react for 8 h. Then add functionalized polylactic acid and continue reacting for 1 h to obtain modified polylactic acid.

[0022] In step B1, the molar ratio of furanoyl chloride, ethylene glycolamine, and triethylamine is 1:1:1.2, the mass ratio of lactic acid to the treatment agent is 10:1, and the amount of stannous chloride used is 5‰ of the mass of lactic acid and the treatment agent.

[0023] In step B2, the pretreatment process involves a 1:2 molar ratio of polylactic acid to acrylic acid, a 1% amount of p-toluenesulfonic acid based on the mass of acrylic acid, a 1:2 molar ratio of terminal double-bond polylactic acid to trichlorosilane, and a 1‰ amount of chloroplatinic acid based on the mass of trichlorosilane.

[0024] In step B3, the molar ratio of lithium metal and dimethylsilanol is 1:1, and the molar ratio of lithium dimethylsilanol, tetramethylcyclotetrasiloxane, and functionalized polylactic acid is 2:4:1.

[0025] Example 2, a method for preparing an environmentally friendly biodegradable composite plastic, specifically includes the following steps: Step A1: Mix modified polylactic acid, acrylic acid, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 9 hours at a speed of 150 r / min and a temperature of 75℃ to obtain polylactic acid monomer. Step A2: Polylactic acid monomer, 1,4-butanediol, adipic acid, terephthalic acid, tetrabutyl titanate and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 9 hours at a speed of 120 r / min, a temperature of 165℃ and a pressure of 3 MPa. Then the temperature is raised to 240℃ and the reaction is continued for 3.5 hours at a pressure of 120 Pa to obtain the modified resin. Step A3: Mix the modified resin and tetrahydrofuran evenly, stir and add 1,4-bis(maleimide)butane at a speed of 200 r / min and a temperature of 45℃, stir for 9 h, remove tetrahydrofuran by vacuum distillation to obtain environmentally friendly biodegradable composite plastic.

[0026] The molar ratio of Si-H bonds on the modified polylactic acid and acrylic acid in step A1 is 1:1, and the amount of chloroplatinic acid used is 1‰ of the mass of acrylic acid.

[0027] In step A2, the ratio of carboxyl groups on the polylactic acid monomer, 1,4-butanediol, adipic acid, and terephthalic acid is 100 mmol: 2.4 mol: 1 mol: 1 mol, and the amount of tetrabutyl titanate is 1% of the sum of the masses of adipic acid and terephthalic acid.

[0028] The mass ratio of the modified resin and 1,4-bis(maleimide)butane described in step A3 is 20:1.

[0029] The modified polylactic acid is prepared by the following steps: Step B1: Furanoyl chloride, ethylene glycolamine, triethylamine and tetrahydrofuran are mixed and reacted at 200 r / min and 30°C for 4 h to obtain the treatment agent. Lactic acid and DMF are mixed evenly and reacted at 120 r / min and 125°C for 4 h. The temperature is raised to 145°C, stannous chloride is added, and the reaction continues for 3 h. The temperature is raised to 175°C, the treatment agent is added, and the reaction continues for 4 h to obtain pretreated polylactic acid. Step B2: Mix pretreated polylactic acid, acrylic acid, p-toluenesulfonic acid and toluene evenly, purge with nitrogen, and react for 1.5 h at a speed of 150 r / min and a temperature of 120 °C to obtain terminal double bond polylactic acid. Mix terminal double bond polylactic acid, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6 h at a speed of 200 r / min and a temperature of 75 °C to obtain functionalized polylactic acid. Step B3: Mix lithium metal and tetrahydrofuran evenly, purge with nitrogen, stir and add dimethylsilanol at 60 r / min and 5°C, and react for 3 h to obtain lithium dimethylsilanol. Mix lithium dimethylsilanol and tetrahydrofuran evenly, purge with nitrogen, stir and add tetramethylcyclotetrasiloxane at 120 r / min and 3°C, raise the temperature to 25°C and react for 9 h. Then add functionalized polylactic acid and continue the reaction for 1.3 h to obtain modified polylactic acid.

[0030] In step B1, the molar ratio of furanoyl chloride, ethylene glycolamine, and triethylamine is 1:1:1.2, the mass ratio of lactic acid to the treatment agent is 10:1, and the amount of stannous chloride used is 5‰ of the mass of lactic acid and the treatment agent.

[0031] In step B2, the pretreatment process involves a 1:2 molar ratio of polylactic acid to acrylic acid, a 1% amount of p-toluenesulfonic acid based on the mass of acrylic acid, a 1:2 molar ratio of terminal double-bond polylactic acid to trichlorosilane, and a 1‰ amount of chloroplatinic acid based on the mass of trichlorosilane.

[0032] In step B3, the molar ratio of lithium metal and dimethylsilanol is 1:1, and the molar ratio of lithium dimethylsilanol, tetramethylcyclotetrasiloxane, and functionalized polylactic acid is 2:4:1.

[0033] Example 3, a method for preparing an environmentally friendly biodegradable composite plastic, specifically includes the following steps: Step A1: Mix modified polylactic acid, acrylic acid, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 10 h at a speed of 200 r / min and a temperature of 80℃ to obtain polylactic acid monomer. Step A2: Mix polylactic acid monomer, 1,4-butanediol, adipic acid, terephthalic acid, tetrabutyl titanate and DMF evenly, purge with nitrogen, and react for 10 hours at a speed of 150 r / min, a temperature of 170℃ and a pressure of 3 MPa. Then raise the temperature to 245℃ and continue the reaction for 4 hours at a pressure of 150 Pa to obtain the modified resin. Step A3: Mix the modified resin and tetrahydrofuran evenly, stir and add 1,4-bis(maleimide)butane at a speed of 300 r / min and a temperature of 50℃, stir for 10 h, remove tetrahydrofuran by vacuum distillation to obtain environmentally friendly biodegradable composite plastic.

[0034] The molar ratio of Si-H bonds on the modified polylactic acid and acrylic acid in step A1 is 1:1, and the amount of chloroplatinic acid used is 1‰ of the mass of acrylic acid.

[0035] In step A2, the ratio of carboxyl groups on the polylactic acid monomer, 1,4-butanediol, adipic acid, and terephthalic acid is 100 mmol: 2.4 mol: 1 mol: 1 mol, and the amount of tetrabutyl titanate is 1% of the sum of the masses of adipic acid and terephthalic acid.

[0036] The mass ratio of the modified resin and 1,4-bis(maleimide)butane described in step A3 is 20:1.

[0037] The modified polylactic acid is prepared by the following steps: Step B1: Furanoyl chloride, ethylene glycolamine, triethylamine and tetrahydrofuran are mixed and reacted at 300 r / min and 30°C for 5 h to obtain the treatment agent. Lactic acid and DMF are mixed evenly and reacted at 150 r / min and 130°C for 5 h. The temperature is raised to 150°C, stannous chloride is added, and the reaction continues for 3 h. The temperature is raised to 180°C, the treatment agent is added, and the reaction continues for 5 h to obtain pretreated polylactic acid. Step B2: Pretreated polylactic acid, acrylic acid, p-toluenesulfonic acid and toluene are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 1.5 h at a speed of 200 r / min and a temperature of 120 °C to obtain terminal double bond polylactic acid. Terminal double bond polylactic acid, trichlorosilane, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 7 h at a speed of 150 r / min and a temperature of 80 °C to obtain functionalized polylactic acid. Step B3: Mix lithium metal and tetrahydrofuran evenly, purge with nitrogen, stir and add dimethylsilanol at 80 r / min and 5°C, and react for 4 h to obtain lithium dimethylsilanol. Mix lithium dimethylsilanol and tetrahydrofuran evenly, purge with nitrogen, stir and add tetramethylcyclotetrasiloxane at 150 r / min and 3°C, raise the temperature to 25°C and react for 10 h. Then add functionalized polylactic acid and continue the reaction for 1.5 h to obtain modified polylactic acid.

[0038] In step B1, the molar ratio of furanoyl chloride, ethylene glycolamine, and triethylamine is 1:1:1.2, the mass ratio of lactic acid to the treatment agent is 10:1, and the amount of stannous chloride used is 5‰ of the mass of lactic acid and the treatment agent.

[0039] In step B2, the pretreatment process involves a 1:2 molar ratio of polylactic acid to acrylic acid, a 1% amount of p-toluenesulfonic acid based on the mass of acrylic acid, a 1:2 molar ratio of terminal double-bond polylactic acid to trichlorosilane, and a 1‰ amount of chloroplatinic acid based on the mass of trichlorosilane.

[0040] In step B3, the molar ratio of lithium metal and dimethylsilanol is 1:1, and the molar ratio of lithium dimethylsilanol, tetramethylcyclotetrasiloxane, and functionalized polylactic acid is 2:4:1.

[0041] Comparative Example 1: This comparative example uses ethylene glycolamine instead of the treatment agent compared to Example 1, but the other steps are the same.

[0042] Comparative Example 2: This comparative example uses pretreated polylactic acid instead of polylactic acid monomers, while the other steps are the same as in Example 1.

[0043] Comparative Example 3: Compared with Example 1, this comparative example uses lactic acid and DMF to mix evenly, and reacts at 120 r / min and 120°C for 3 h. The temperature is then raised to 145°C, stannous chloride is added, and the reaction continues for 2 h. The temperature is then raised to 170°C, and the reaction continues for 3 h. The product obtained replaces the polylactic acid monomer, and the remaining steps are the same.

[0044] The composite plastics obtained in Examples 1-3 and Comparative Examples 1-3 were prepared into Type II specimens according to the standard GB / T1040.1-2018, and the tensile strength was tested at a tensile rate of 50 mm / min. Notched Type A specimens were prepared according to GB / T1843-2008, and the impact strength was tested. The test results are shown in Table 1 below.

[0045] Table 1

[0046] As shown in Table 1, this application has excellent mechanical properties.

[0047] The above description is merely an example and illustration of the concept of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined in the claims, they should all fall within the protection scope of the present invention.

Claims

1. A method for preparing an environmentally friendly biodegradable composite plastic, characterized in that: Specifically, the steps include the following: Step A1: Mix modified polylactic acid, acrylic acid, chloroplatinic acid and DMF evenly, purge with nitrogen gas for protection, and react to obtain polylactic acid monomer; Step A2: Mix polylactic acid monomer, 1,4-butanediol, adipic acid, terephthalic acid, tetrabutyl titanate and DMF evenly, purge with nitrogen gas for protection, and carry out the reaction to obtain the modified resin. Step A3: Mix the modified resin and tetrahydrofuran and add 1,4-bis(maleimide)butane. After stirring, remove the tetrahydrofuran by vacuum distillation to obtain an environmentally friendly and biodegradable composite plastic.

2. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 1, characterized in that: The molar ratio of Si-H bonds on the modified polylactic acid and acrylic acid in step A1 is 1:

1.

3. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 1, characterized in that: The ratio of carboxyl groups, 1,4-butanediol, adipic acid, and terephthalic acid on the polylactic acid monomer described in step A2 is 100 mmol: 2.4 mol: 1 mol: 1 mol.

4. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 1, characterized in that: The mass ratio of the modified resin and 1,4-bis(maleimide)butane described in step A3 is 20:

1.

5. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 1, characterized in that: The modified polylactic acid is prepared by the following steps: Step B1: Mix furanyl chloride, ethylene glycolamine, triethylamine and tetrahydrofuran and react to obtain a treatment agent. Mix lactic acid and DMF and react. Heat and add stannous chloride and continue the reaction. Heat and add the treatment agent and continue the reaction to obtain pretreated polylactic acid. Step B2: Mix pretreated polylactic acid, acrylic acid, p-toluenesulfonic acid and toluene evenly, purge with nitrogen, and react to obtain terminal double bond polylactic acid. Mix terminal double bond polylactic acid, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react to obtain functionalized polylactic acid. Step B3: Mix lithium metal and tetrahydrofuran evenly, purge with nitrogen, stir and add dimethylsilanol to react and obtain lithium dimethylsilanol. Mix lithium dimethylsilanol and tetrahydrofuran evenly, purge with nitrogen, stir and add tetramethylcyclotetrasiloxane, heat and react, then add functionalized polylactic acid and continue the reaction to obtain modified polylactic acid.

6. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 5, characterized in that: The molar ratio of furanoyl chloride, ethylene glycolamine, and triethylamine in step B1 is 1:1:1.2, and the mass ratio of lactic acid to the treatment agent is 10:

1.

7. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 5, characterized in that: In step B2, the molar ratio of pretreated polylactic acid and acrylic acid is 1:2, and the molar ratio of terminal double-bond polylactic acid and trichlorosilane is 1:

2.

8. The method for preparing an environmentally friendly biodegradable composite plastic according to claim 5, characterized in that: In step B3, the molar ratio of lithium metal and dimethylsilanol is 1:1, and the molar ratio of lithium dimethylsilanol, tetramethylcyclotetrasiloxane, and functionalized polylactic acid is 2:4:

1.

9. An environmentally friendly biodegradable composite plastic, characterized in that: Prepared according to any one of the preparation methods described in claims 1-8.

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