Double-layer composite film and manufacturing method thereof

Abstract

The invention discloses a double-layer composite membrane and a manufacturing method thereof, and relates to a double-layer membrane preparation technology, modified resin, zinc oxide, chloroform and DMF are uniformly mixed, electrostatic spinning is performed on the surface of a polylactic acid base membrane, and the double-layer composite membrane is prepared. The modified resin molecule is of a branched structure, and the molecular chain contains a polyester structure and also contains a silicon-oxygen-silicon chain segment, so that the mechanical property of the modified resin is further improved, the problem of high brittleness of polylactic acid is further solved, the double-layer composite film is not easy to damage in the use process, and the service life of the double-layer composite film is prolonged. And a quaternary ammonium salt structure on a modified molecular side chain is matched with a self-branched structure, so that the double-layer composite film has a very good sterilization effect, and meanwhile, zinc oxide in the double-layer composite film can further improve the antibacterial effect and ensure the food freshness.

Description

Technical Field

[0001] This invention relates to the field of composite membrane preparation technology, specifically to a bilayer composite membrane and its preparation method. Background Technology

[0002] In recent years, with the increasing awareness of environmental protection, the application of biodegradable materials in the packaging field has gradually increased. Vegetable packaging, as an indispensable part of daily life, needs to ensure not only the freshness of vegetables but also environmental friendliness and safety. While traditional plastic packaging can effectively maintain the freshness of vegetables, its difficulty in degradation has a significant environmental impact. Meanwhile, polylactic acid (PLA), as an emerging biodegradable material, has received widespread attention for its environmentally friendly characteristics. It is mainly made from renewable resources such as corn starch and can be quickly decomposed by microorganisms in the natural environment, thus reducing the long-term burden on the environment. However, PLA has relatively weak strength and flexibility, and may not meet the mechanical performance requirements of vegetable packaging when used alone. To solve this problem, researchers have been working to develop new composite materials, combining PLA with materials that have better mechanical properties to enhance the overall packaging performance. PBAT is one such material; it has good ductility and toughness, making it suitable for composite with PLA to form excellent packaging films. However, its lack of antibacterial properties limits the use of PLA-PBAT composite double-layer films. Summary of the Invention

[0003] The purpose of this invention is to provide a double-layer composite film and its manufacturing method, which solves the problems of poor mechanical performance and easy bacterial growth that affect the freshness of vegetables in current double-layer composite films.

[0004] The objective of this invention can be achieved through the following technical solutions: A method for manufacturing a double-layer composite membrane specifically includes the following steps: Step A1: Terephthalic acid, oxalic acid, 1,4-butanediol and tetrabutyl titanate are mixed evenly and protected with nitrogen gas. The mixture is reacted at a speed of 120-150 r / min and a temperature of 180-200℃ for 2-4 hours. Then, the modified monomer is added and the reaction continues for 1-2 hours. The temperature is raised to 220-240℃ and the pressure is 180-200 Pa for 2-3 hours. Finally, the temperature is raised to 250-260℃ and the pressure is 60-80 Pa for 1-1.5 hours to obtain the pretreated resin. Step A2: Mix the pretreated resin, triethylamine, and N-methylpyrrolidone evenly, and react them for 20-30 hours at a speed of 200-300 r / min and a temperature of 50-60℃ to obtain a modified resin. Mix the modified resin, polylactic acid, graphene oxide, dichloromethane, and DMF evenly, and electrospin them under the conditions of a voltage of 18-20 kV, a receiving distance of 15-20 cm, and a syringe advance speed of 1.2-1.5 mL / h to obtain a polylactic acid-based film. Step A3: Mix the modified resin, zinc oxide, chloroform and DMF evenly, and stir for 1-1.5 hours at a speed of 300-500 r / min and a temperature of 40-50℃. Then, electrospin the mixture onto the polylactic acid-based membrane surface at a voltage of 20-25 kV, a receiving diameter of 15-20 cm, and a syringe injection speed of 0.8-1.2 mL / h to obtain a double-layer composite membrane.

[0005] Furthermore, the ratio of terephthalic acid, oxalic acid, 1,4-butanediol, tetrabutyl titanate, and modified monomer in step A1 is 2 mol: 2 mol: 3 mol: 5 mmol: 1 mol.

[0006] Furthermore, in step A2, the ratio of the pretreated resin, triethylamine, and N-methylpyrrolidone is 1g:8g:50mL, and the ratio of polylactic acid, graphene oxide, dichloromethane, and DMF is 12g:0.05g:36mL:84mL. The molecular weight of the polylactic acid is 100,000. Furthermore, the ratio of the modified resin, zinc oxide, chloroform, and DMF used in step A3 is 10g:0.3g:30mL:70mL.

[0007] Furthermore, the modified monomer is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride evenly, purge with nitrogen for protection, and react at a speed of 120-150 r / min and a temperature of 90-95℃ for 10-12 h. Then raise the temperature to 105-110℃ and continue the reaction for 2-3 h to obtain polysiloxane. Step B2: Mix polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen for protection, and react for 6-8 hours at a speed of 120-150 r / min and a temperature of 70-80℃ to obtain pretreated polysiloxane. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran evenly, stir and add octamethylcyclotetrasiloxane at a speed of 120-150 r / min and a temperature of 0℃, raise the temperature to 25-30℃ and react for 7-9 hours, then add the pretreated polysiloxane and continue the reaction for 1-1.5 hours to obtain modified polysiloxane. Step B3: Mix the modified polysiloxane, 3-bromo-1-propene, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6-8 hours at a speed of 300-500 r / min and a temperature of 75-85℃ to obtain the pretreated monomer. Mix the pretreated monomer and DMF evenly, stir and add hydrochloric acid solution at a speed of 120-150 r / min and a temperature of 40-45℃, and react for 2-3 hours to obtain the modified monomer.

[0008] Furthermore, the ratio of octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and sulfoxide in step B1 is 4 mol:0.8 mol:6 mol:4 mol:2 L:8 L.

[0009] Furthermore, in step B2, the molar ratio of polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane, and the Si-Cl bond on the pretreated polysiloxane is 1:3:1.

[0010] Furthermore, in step B3, the molar ratio of the modified polysiloxane to 3-bromo-1-propylene is 1:6, the amount of chloroplatinic acid used is 1‰ of the mass of allyl chloride, the ratio of the pretreated monomer to the hydrochloric acid solution is 1g:10mL, and the mass fraction of the hydrochloric acid solution is 18%.

[0011] The beneficial effects of the present invention are as follows: A bilayer composite membrane disclosed in the present invention is prepared by electrospinning on the surface of a polylactic acid-based membrane after uniformly mixing modified resin, zinc oxide, chloroform and DMF. The modified resin is esterified with terephthalic acid, oxalic acid and 1,4-butanediol, and then modified monomers are added and esterification is continued. Finally, the mixture is heated to polycondense to obtain a pretreated resin. The pretreated resin is reacted with triethylamine to form a quaternary ammonium salt structure to obtain the modified resin.

[0012] The modified monomer is prepared by ring-opening octamethylcyclotetrasiloxane as a starting material, followed by hydrolytic condensation with 3-glycidyl etheroxypropylmethyldiethoxysilane, and finally end-capping with tetramethyldivinyldisiloxane to obtain polysiloxane. The polysiloxane is then reacted with trichlorosilane, causing the double bonds on the polysiloxane to react with the Si-H bonds on the trichlorosilane, resulting in a pretreated polysiloxane. Dimethylhydrosilyllithium is used as an initiator, octamethylcyclotetrasiloxane as a polymerization monomer, and the pretreated polysiloxane is added, causing the Si-Cl bonds on the pretreated polysiloxane to react with the lithium silyllithium, resulting in a modified polysiloxane. The modified polysiloxane is then reacted with 3-bromo-1-propene, causing the Si-H bonds on the modified polysiloxane to react with the double bonds on the 3-bromo-1-propene, resulting in a pretreated monomer. The pretreated monomer is then treated with hydrochloric acid, causing the epoxy groups on the pretreated monomer to ring-open, forming a chlorool structure, thus obtaining the modified monomer.

[0013] This bilayer composite film uses polylactic acid and modified resin as substrates, resulting in a bilayer composite film with excellent biodegradability. The modified resin molecules have a branched structure, with polyester structures and silicon-oxygen segments on the molecular chain, which further increases the mechanical properties of the modified resin and compensates for the high brittleness of polylactic acid. This makes the bilayer composite film less prone to damage during use. In addition, the quaternary ammonium salt structure on the side chain of the modified molecule, combined with its own branched structure, gives the bilayer composite film a good bactericidal effect. At the same time, the zinc oxide inside can further enhance the antibacterial effect and ensure the freshness of food. Detailed Implementation

[0014] 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.

[0015] Example 1: A method for manufacturing a double-layer composite film, specifically including the following steps: Step A1: Terephthalic acid, oxalic acid, 1,4-butanediol and tetrabutyl titanate are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 2 hours at a speed of 120 r / min and a temperature of 180℃. Then, the modified monomer is added, and the reaction is continued for 1 hour. The temperature is raised to 220℃ and the reaction is carried out for 2 hours at a pressure of 180 Pa. Finally, the temperature is raised to 250℃ and the reaction is carried out for 1 hour at a pressure of 60 Pa to obtain the pretreated resin. Step A2: The pretreated resin, triethylamine, and N-methylpyrrolidone were mixed evenly and reacted for 20 hours at a speed of 200 r / min and a temperature of 50℃ to obtain the modified resin. The modified resin was then mixed evenly with polylactic acid, graphene oxide, dichloromethane, and DMF. Electrospinning was performed under the conditions of a voltage of 18 kV, a receiving distance of 15 cm, and a syringe injection speed of 1.2 mL / h to obtain a polylactic acid-based film. Step A3: Mix the modified resin, zinc oxide, chloroform and DMF evenly, stir for 1 hour at a speed of 300 r / min and a temperature of 40℃, and then electrospin the mixture onto the polylactic acid-based membrane surface to obtain a double-layer composite membrane.

[0016] The ratio of terephthalic acid, oxalic acid, 1,4-butanediol, tetrabutyl titanate, and modified monomers in step A1 is 2 mol: 2 mol: 3 mol: 5 mmol: 1 mol.

[0017] The ratio of the pretreated resin, triethylamine, and N-methylpyrrolidone used in step A2 is 1g:8g:50mL; the ratio of polylactic acid, graphene oxide, dichloromethane, and DMF is 12g:0.05g:36mL:84mL; and the molecular weight of polylactic acid is 100,000. The ratio of the modified resin, zinc oxide, chloroform and DMF used in step A3 is 10g:0.3g:30mL:70mL.

[0018] The modified monomer is prepared by the following steps: Step B1: Octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted at 120 r / min and 90 °C for 10 h. Then the temperature is raised to 105 °C and the reaction is continued for 2 h to obtain polysiloxane. Step B2: Mix polysiloxane, trichlorosilane, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6 hours at 120 r / min and 70°C to obtain pretreated polysiloxane. Mix lithium dimethylhydrosilyl alcohol and tetrahydrofuran evenly, stir and add octamethylcyclotetrasiloxane at 120 r / min and 0°C, raise the temperature to 25°C and react for 7 hours. Then add the pretreated polysiloxane and continue the reaction for 1 hour to obtain modified polysiloxane. Step B3: Mix the modified polysiloxane, 3-bromo-1-propene, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 6 hours at 300 r / min and 75°C to obtain the pretreated monomer. Mix the pretreated monomer and DMF evenly, stir and add hydrochloric acid solution at 120 r / min and 40°C, and react for 2 hours to obtain the modified monomer.

[0019] The ratio of octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride in step B1 is 4 mol:0.8 mol:6 mol:4 mol:2 L:8 L.

[0020] In step B2, the molar ratio of polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-Cl bond on the pretreated polysiloxane is 1:3:1.

[0021] The molar ratio of the modified polysiloxane and 3-bromo-1-propene in step B3 is 1:6, the amount of chloroplatinic acid is 1‰ of the mass of allyl chloride, the ratio of the pretreated monomer to the hydrochloric acid solution is 1g:10mL, and the mass fraction of the hydrochloric acid solution is 18%.

[0022] Example 2: A method for manufacturing a double-layer composite film, specifically including the following steps: Step A1: Terephthalic acid, oxalic acid, 1,4-butanediol and tetrabutyl titanate are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 3 hours at a speed of 120 r / min and a temperature of 190℃. Then, the modified monomer is added, and the reaction continues for 2 hours. The temperature is raised to 230℃ and the reaction is carried out for 3 hours at a pressure of 190 Pa. Finally, the temperature is raised to 255℃ and the reaction is carried out for 1.3 hours at a pressure of 70 Pa to obtain the pretreated resin. Step A2: The pretreated resin, triethylamine, and N-methylpyrrolidone were mixed evenly and reacted for 25 hours at a speed of 200 r / min and a temperature of 55℃ to obtain the modified resin. The modified resin was then mixed evenly with polylactic acid, graphene oxide, dichloromethane, and DMF. Electrospinning was performed under the conditions of a voltage of 19 kV, a receiving distance of 20 cm, and a syringe advance speed of 1.2 mL / h to obtain a polylactic acid-based film. Step A3: Mix the modified resin, zinc oxide, chloroform and DMF evenly, stir for 1.5 h at a speed of 500 r / min and a temperature of 45℃, and then electrospin the mixture on the surface of the polylactic acid-based membrane to obtain a double-layer composite membrane under the conditions of a voltage of 20 kV, a receiver diameter of 18 cm, and a syringe injection speed of 1 mL / h.

[0023] The ratio of terephthalic acid, oxalic acid, 1,4-butanediol, tetrabutyl titanate, and modified monomers in step A1 is 2 mol: 2 mol: 3 mol: 5 mmol: 1 mol.

[0024] The ratio of the pretreated resin, triethylamine, and N-methylpyrrolidone used in step A2 is 1g:8g:50mL; the ratio of polylactic acid, graphene oxide, dichloromethane, and DMF is 12g:0.05g:36mL:84mL; and the molecular weight of polylactic acid is 100,000. The ratio of the modified resin, zinc oxide, chloroform and DMF used in step A3 is 10g:0.3g:30mL:70mL.

[0025] The modified monomer is prepared by the following steps: Step B1: Octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted at 120 r / min and 95 °C for 11 h. Then the temperature is raised to 108 °C and the reaction is continued for 3 h to obtain polysiloxane. Step B2: Polysiloxane, trichlorosilane, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 7 hours at a speed of 120 r / min and a temperature of 75°C to obtain pretreated polysiloxane. Dimethylhydrosilyl alcohol lithium and tetrahydrofuran are mixed evenly, and octamethylcyclotetrasiloxane is added while stirring at a speed of 120 r / min and a temperature of 0°C. The mixture is heated to 30°C and reacted for 8 hours. Then, the pretreated polysiloxane is added and the reaction is continued for 1.5 hours to obtain modified polysiloxane. Step B3: Mix the modified polysiloxane, 3-bromo-1-propene, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 7 hours at 300 r / min and 80 °C to obtain the pretreated monomer. Mix the pretreated monomer and DMF evenly, stir and add hydrochloric acid solution at 120 r / min and 45 °C, and react for 2 hours to obtain the modified monomer.

[0026] The ratio of octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride in step B1 is 4 mol:0.8 mol:6 mol:4 mol:2 L:8 L.

[0027] In step B2, the molar ratio of polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-Cl bond on the pretreated polysiloxane is 1:3:1.

[0028] The molar ratio of the modified polysiloxane and 3-bromo-1-propene in step B3 is 1:6, the amount of chloroplatinic acid is 1‰ of the mass of allyl chloride, the ratio of the pretreated monomer to the hydrochloric acid solution is 1g:10mL, and the mass fraction of the hydrochloric acid solution is 18%.

[0029] Example 3: A method for manufacturing a double-layer composite film, specifically including the following steps: Step A1: Terephthalic acid, oxalic acid, 1,4-butanediol and tetrabutyl titanate are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 4 hours at a speed of 150 r / min and a temperature of 200℃. Then, the modified monomer is added, and the reaction continues for 2 hours. The temperature is raised to 240℃ and the reaction is carried out for 3 hours at a pressure of 200 Pa. Finally, the temperature is raised to 260℃ and the reaction is carried out for 1.5 hours at a pressure of 80 Pa to obtain the pretreated resin. Step A2: The pretreated resin, triethylamine, and N-methylpyrrolidone were mixed evenly and reacted for 30 hours at a speed of 300 r / min and a temperature of 60℃ to obtain the modified resin. The modified resin was then mixed evenly with polylactic acid, graphene oxide, dichloromethane, and DMF. Electrospinning was performed under the conditions of a voltage of 20 kV, a receiving distance of 20 cm, and a syringe injection speed of 1.5 mL / h to obtain a polylactic acid-based film. Step A3: Mix the modified resin, zinc oxide, chloroform and DMF evenly, stir for 1.5 h at a speed of 500 r / min and a temperature of 50℃, and then electrospin the mixture on the surface of the polylactic acid-based membrane to obtain a double-layer composite membrane under the conditions of a voltage of 25 kV, a receiver diameter of 20 cm, and a syringe injection speed of 1.2 mL / h.

[0030] The ratio of terephthalic acid, oxalic acid, 1,4-butanediol, tetrabutyl titanate, and modified monomers in step A1 is 2 mol: 2 mol: 3 mol: 5 mmol: 1 mol.

[0031] The ratio of the pretreated resin, triethylamine, and N-methylpyrrolidone used in step A2 is 1g:8g:50mL; the ratio of polylactic acid, graphene oxide, dichloromethane, and DMF is 12g:0.05g:36mL:84mL; and the molecular weight of polylactic acid is 100,000. The ratio of the modified resin, zinc oxide, chloroform and DMF used in step A3 is 10g:0.3g:30mL:70mL.

[0032] The modified monomer is prepared by the following steps: Step B1: Octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted at 150 r / min and 95 °C for 12 h. Then the temperature is raised to 110 °C and the reaction is continued for 3 h to obtain polysiloxane. Step B2: Polysiloxane, trichlorosilane, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection. The mixture is reacted for 8 hours at a speed of 150 r / min and a temperature of 80 °C to obtain pretreated polysiloxane. Dimethylhydrosilyl alcohol lithium and tetrahydrofuran are mixed evenly, and octamethylcyclotetrasiloxane is added while stirring at a speed of 150 r / min and a temperature of 0 °C. The mixture is heated to 30 °C and reacted for 9 hours. Then, the pretreated polysiloxane is added and the reaction is continued for 1.5 hours to obtain modified polysiloxane. Step B3: Mix the modified polysiloxane, 3-bromo-1-propene, chloroplatinic acid and DMF evenly, purge with nitrogen, and react for 8 hours at 500 r / min and 85°C to obtain the pretreated monomer. Mix the pretreated monomer and DMF evenly, stir and add hydrochloric acid solution at 150 r / min and 45°C, and react for 3 hours to obtain the modified monomer.

[0033] The ratio of octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and thionyl chloride in step B1 is 4 mol:0.8 mol:6 mol:4 mol:2 L:8 L.

[0034] In step B2, the molar ratio of polysiloxane to trichlorosilane is 1:2, the amount of chloroplatinic acid is 1‰ of the mass of trichlorosilane, and the molar ratio of lithium dimethylhydrosilyl alcohol, octamethylcyclotetrasiloxane and the Si-Cl bond on the pretreated polysiloxane is 1:3:1.

[0035] The molar ratio of the modified polysiloxane and 3-bromo-1-propene in step B3 is 1:6, the amount of chloroplatinic acid is 1‰ of the mass of allyl chloride, the ratio of the pretreated monomer to the hydrochloric acid solution is 1g:10mL, and the mass fraction of the hydrochloric acid solution is 18%.

[0036] Comparative Example 1: This comparative example differs from Example 1 in that 3-glycidyl etheroxypropylmethyldiethoxysilane was not added, but the remaining steps were the same.

[0037] Comparative Example 2: Compared with Example 1, this comparative example uses polysiloxane, 2-mercaptoethanol, chloroplatinic acid and DMF to be mixed evenly, and nitrogen gas is introduced for protection. The reaction is carried out at a speed of 120 r / min and a temperature of 70°C for 6 h. The product obtained replaces the pretreated monomer, and the remaining steps are the same.

[0038] The bilayer composite films prepared in Examples 1-3 and Comparative Examples 1-2 were made into samples with a thickness of 30 μm. The tensile strength was tested according to ISO 1184-1983 standard at a tensile speed of 50 mm / min. The tensile strength was tested according to GB / T 31402-2015 standard. Circular discs with a radius of 0.5 cm were prepared and tested for Escherichia coli and Staphylococcus aureus at a culture temperature of 37℃ for 48 h. The antibacterial rate was tested, and the test results are shown in Table 1 below.

[0039] Table 1

[0040] As shown in Table 1, this application has excellent tensile strength and antibacterial effect.

[0041] 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 manufacturing a double-layer composite membrane, characterized in that: Specifically, the steps include the following: Step A1: Terephthalic acid, oxalic acid, 1,4-butanediol and tetrabutyl titanate are mixed evenly, nitrogen gas is introduced for protection, and the reaction is carried out. Then, the modified monomer is added and the reaction is continued to obtain the pretreated resin. Step A2: Mix the pretreated resin, triethylamine, and N-methylpyrrolidone evenly, and react them for 20-30 hours at a speed of 200-300 r / min and a temperature of 50-60℃ to obtain a modified resin. Mix the modified resin, polylactic acid, graphene oxide, dichloromethane, and DMF evenly, and electrospin them under the conditions of a voltage of 18-20 kV, a receiving distance of 15-20 cm, and a syringe advance speed of 1.2-1.5 mL / h to obtain a polylactic acid-based film. Step A3: Mix the modified resin, zinc oxide, chloroform and DMF evenly, and stir for 1-1.5 hours at a speed of 300-500 r / min and a temperature of 40-50℃. Then, electrospin the mixture onto the polylactic acid-based membrane surface at a voltage of 20-25 kV, a receiving diameter of 15-20 cm, and a syringe injection speed of 0.8-1.2 mL / h to obtain a double-layer composite membrane.

2. The method for manufacturing the double-layer composite membrane according to claim 1, characterized in that: The ratio of terephthalic acid, oxalic acid, 1,4-butanediol, tetrabutyl titanate, and modified monomers in step A1 is 2 mol: 2 mol: 3 mol: 5 mmol: 1 mol.

3. The method for manufacturing the double-layer composite membrane according to claim 1, characterized in that: The ratio of the pretreated resin, triethylamine, and N-methylpyrrolidone used in step A2 is 1g:8g:50mL, and the ratio of polylactic acid, graphene oxide, dichloromethane, and DMF is 12g:0.05g:36mL:84mL.

4. The method for manufacturing a double-layer composite membrane according to claim 1, characterized in that: The ratio of the modified resin, zinc oxide, chloroform and DMF used in step A3 is 10g:0.3g:30mL:70mL.

5. The method for manufacturing a double-layer composite membrane according to claim 1, characterized in that: The modified monomer is prepared by the following steps: Step B1: Mix octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and sulfoxide evenly, and carry out the reaction under nitrogen protection to obtain polysiloxane. The ratio of octamethylcyclotetrasiloxane, 3-glycidyl etheroxypropylmethyldiethoxysilane, tetramethylammonium hydroxide, tetramethyldivinyldisiloxane, deionized water and sulfoxide is 4mol:0.8mol:6mol:4mol:2L:8L. Step B2: Polysiloxane, trichlorosilane, chloroplatinic acid and DMF are mixed evenly, and nitrogen gas is introduced for protection to carry out the reaction to obtain pretreated polysiloxane. Dimethylhydrosilyl alcohol lithium and tetrahydrofuran are mixed and stirred, and octamethylcyclotetrasiloxane is added. After heating and reacting, pretreated polysiloxane is added and the reaction is continued to obtain modified polysiloxane. The molar ratio of polysiloxane to trichlorosilane is 1:2, and the molar ratio of Si-Cl bonds on dimethylhydrosilyl alcohol lithium, octamethylcyclotetrasiloxane and pretreated polysiloxane is 1:3:

1. Step B3: Mix the modified polysiloxane, 3-bromo-1-propene, chloroplatinic acid and DMF evenly, purge with nitrogen for protection, and react to obtain a pretreated monomer. Mix the pretreated monomer and DMF, stir and add hydrochloric acid solution, and react to obtain a modified monomer. The molar ratio of modified polysiloxane to 3-bromo-1-propene is 1:6, and the volume ratio of pretreated monomer to hydrochloric acid solution is 1g:10mL.

6. A double-layer composite membrane, characterized in that: Prepared according to any one of the preparation methods described in claims 1-5.

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