PI / SiO2 modified PET high-temperature-resistant composite release film and preparation method thereof

Abstract

The invention provides a preparation method of a PI / SiO2 modified PET (Polyethylene Terephthalate) high-temperature-resistant composite release film, which comprises the following steps: S1, preparing a polyamide acid fiber film by using a polyamide acid precursor solution as an electrostatic spinning solution and adopting an electrostatic spinning method; s2, applying a drawing force to the polyamide acid fiber membrane at a preset temperature for hot drawing, and then carrying out thermal imidization treatment to obtain a PI nanofiber membrane; s3, adding PET into a mixed solvent of phenol and tetrachloroethane, and stirring until the PET is completely dissolved to obtain a PET solution; s4, adding strawberry-shaped SiO2 gel microspheres into the PET solution, and uniformly stirring to obtain a PET composite solution; and S5, adding the PI nanofiber membrane prepared in the step S2 into a mold, fixedly paving, blade-coating the PI nanofiber membrane with the PET composite solution, and removing the solvent to obtain the high-temperature-resistant release film. According to the invention, the PI electrostatic spinning film is matched with the strawberry-shaped SiO2 gel microspheres, so that the PET release film has better temperature resistance.

Description

Technical Field

[0001] The invention relates to the technical field of release films, and in particular to a PI / SiO2 modified PET high temperature resistant composite release film and a preparation method thereof. Background Art

[0002] High temperature release film is a polymer film with excellent temperature resistance and can work stably in high temperature environment. It is usually made of high temperature resistant polymer and corrosion resistant materials, with excellent chemical resistance and mechanical strength. This film has excellent heat resistance and can be used for a long time under extreme high temperature conditions without embrittlement, deformation or decomposition. In addition, high temperature release film also has low adhesion, which can effectively prevent substances from adhering to the film, reducing the need for cleaning and maintenance. High temperature resistant release film plays an important role in many fields. First, it is widely used in the aerospace industry. In rocket propulsion systems, it is used as a thermal insulation layer to effectively protect engines and thrusters from high temperature gases and flames. Secondly, its application in high temperature processes is also very important. In industries such as oil refining, chemical and metal processing, this film can be used to isolate and protect equipment such as reactors, pipelines and storage tanks. In addition, it can also be used in solar power generation systems to improve the high temperature resistance of solar panels and increase energy efficiency. With the continuous development of science and technology, high temperature resistant release film will continue to be used in more fields. For example, in the electronics industry, it can be used to manufacture high temperature electronic components and circuit boards to provide better performance and reliability. In addition, with the rapid development of the renewable energy industry, it will also play an important role in fields such as wind power generation and geothermal energy utilization. However, the current preparation cost is high, and there are still some technical problems that need to be solved. Therefore, it is necessary to develop more economical, sustainable and high-performance high temperature resistant release film materials. Summary of the invention

[0003] Technical problem to be solved: The purpose of the present invention is to provide a PI / SiO2 modified PET high temperature resistant composite release film, which can provide the PET release film with better temperature resistance by combining PI electrospinning membrane and strawberry-shaped SiO2 gel microspheres.

[0004] Technical solution: A PI / SiO2 modified PET high temperature resistant composite release film, wherein the high temperature resistant release film is composed of PET, a polyimide electrospinning film with an oriented structure and strawberry-shaped SiO2 gel microspheres. The method for preparing the above-mentioned high temperature resistant release film comprises the following steps: S1. Using 18-20wt% polyamic acid precursor solution as electrospinning solution, a polyamic acid fiber membrane is prepared by electrospinning; S2. The polyamic acid fiber membrane is subjected to thermal stretching by applying a stretching force at a preset temperature, and the temperature is increased at a gradient rate of 3-5°C / min, and a thermal imidization treatment is performed according to the procedure of 150-160°C / 1h+180-210°C / 1h+280-300°C / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 10-15wt%; S4. Add strawberry-shaped SiO2 gel microspheres to the PET solution and stir to obtain a PET composite solution; S5. Add the PI nanofiber membrane prepared in step S2 into the mold to fix and flatten it, then scrape the PET composite solution on the PI nanofiber membrane, remove the solvent, and obtain a high temperature resistant release film. Preferably, in step S1, the flow rate of electrospinning is 1-1.5 mL / h, the speed of the receiving roller is 500-800 rpm, the spinning voltage is 16-18 kV, and the receiving distance is 14-16 cm. Preferably, in step S2, the temperature of the hot stretching is 120-140°C, the traction force is 1.0-1.5N, and the traction time is 2-4h. Preferably, in step S4, the mass volume ratio of the strawberry-shaped SiO2 gel microspheres to the PET solution is 1g:10-15mL. The preparation method of the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 50-60°C for 2-4h to obtain a silica sol; S12. The silicone oil microcapsules are added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol is 1g: 8-12mL, and the mixture is stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and vigorously stirred to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 800-1100 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was allowed to stand after stirring to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally SiO2 aerogel balls were prepared by drying at normal pressure. Preferably, the method for preparing the silicone oil microcapsules comprises the following steps: S21. The silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 20-24:15-17:0.25-0.35:120, and stirred to react to obtain a prepolymer; S23. The molten salt is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the molten salt; S24. Add the molten salt prepared in step S23 to the prepolymer prepared in step S22, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 55-60°C, cool and filter, wash, and obtain microcapsule powder. Preferably, the silicone oil is any one of methyl silicone oil, ethyl silicone oil or phenyl silicone oil. Preferably, the molten salt is any one of aluminum nitrate nonahydrate, magnesium nitrate hexahydrate or magnesium chloride hexahydrate, or a combination of two or more thereof. Beneficial effects: The high temperature resistant release film of the present invention has the following advantages: 1. The release film of the present invention is composed of PET, polyimide (PI) electrospinning film with an oriented structure and strawberry-shaped SiO2 gel microspheres. PET, as the base material of the release film, is a high-temperature resistant polymer, unlike PTFE, PEEK, PI and other materials, and its use temperature is as high as 200°C or more. Therefore, PET and PI electrospinning film are used for compounding. The electrospinning film used in the present invention is an oriented spinning film. The PI electrospinning film is heat-stretched when drying. The oriented structure obtained by heat-stretching provides a more direct and continuous conduction path for heat energy. Heat energy can be more effectively transferred through these ordered paths; 2. .The present invention also adds strawberry-shaped SiO2 gel microspheres, which can not only give the release film a good release effect, but also improve the temperature resistance of the release film. The silicone oil microcapsules in the SiO2 gel microspheres have a shell layer of melamine-formaldehyde resin containing molten salt. When the temperature reaches the melting temperature of the molten salt, the molten salt melts, and pores are generated on the surface of the shell layer. The silicone oil in the core layer can flow out through the pores to form a -Si-O- structure on the surface of the release film, which can keep the chemical properties unchanged at high temperatures. At the same time, it has good thermal conductivity and can be used as a heat carrier to transfer heat from a high temperature area to a low temperature area; 3. In the present invention, the PET release film has better temperature resistance by combining the PI electrospinning membrane and the strawberry-shaped SiO2 gel microspheres. DETAILED DESCRIPTION The present invention will be further described below in conjunction with embodiments, which are explanations of the present invention and are not limited to the following embodiments: Example 1 A method for preparing a PI / SiO2 modified PET high temperature resistant composite release film comprises the following steps: S1. Using 18wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1mL / h, the receiving roller speed was 500rpm, the spinning voltage was 16kV, and the receiving distance was 14cm; S2. The polyamic acid fiber membrane was subjected to heat stretching by applying a stretching force at a preset temperature, the heat stretching temperature was 120℃, the traction force was 1.0N, the traction time was 2h, the temperature was increased at a heating rate of 5℃ / min, and the heat imidization treatment was performed according to the procedure of 160℃ / 1h+210℃ / 1h+300℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 10wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 10mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at 50°C for 4h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 8mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 1100 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Methyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 20:15:0.25:120, and stirred to react to obtain a prepolymer; S23. Aluminum nitrate nonahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of aluminum nitrate nonahydrate; S24. Add the aluminum nitrate nonahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to prepolymer being 1:10, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 55°C, cool and filter, wash, and obtain microcapsule powder. Example 2 A method for preparing a PI / SiO2 modified PET high temperature resistant composite release film comprises the following steps: S1. Using 20wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1.5mL / h, the receiving roller speed was 800rpm, the spinning voltage was 18kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was subjected to stretching force at a preset temperature for heat stretching, the heat stretching temperature was 140℃, the traction force was 1.5N, the traction time was 4h, the temperature was increased at a heating rate of 3℃ / min, and the thermal imidization treatment was performed according to the procedure of 150℃ / 1h+180℃ / 1h+280℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 15wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 15mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at 60°C for 2h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 12mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 800 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 24:17:0.35:120, and stirred to react to obtain a prepolymer; S23. The magnesium nitrate hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium nitrate hexahydrate; S24. Add the magnesium nitrate hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer being 1:10, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 60°C, cool and filter, wash, and obtain microcapsule powder. Example 3 A method for preparing a PI / SiO2 modified PET high temperature resistant composite release film comprises the following steps: S1. Using 18.5wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1.2mL / h, the receiving roller speed was 600rpm, the spinning voltage was 17kV, and the receiving distance was 15cm; S2. The polyamic acid fiber membrane was subjected to heat stretching by applying a stretching force at a preset temperature, the heat stretching temperature was 125℃, the traction force was 1.4N, the traction time was 2.5h, the temperature was increased gradually at a heating rate of 4.5℃ / min, and the heat imidization treatment was performed according to the procedure of 150℃ / 1h+190℃ / 1h+300℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 14wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 12mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 55°C for 2.5h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 9mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 900 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 21:15:0.27:120, and stirred to react to obtain a prepolymer; S23. The magnesium chloride hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium chloride hexahydrate; S24. Add the magnesium chloride hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer being 1:10, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 55° C., cool and filter, wash, and obtain microcapsule powder. Example 4 A method for preparing a PI / SiO2 modified PET high temperature resistant composite release film comprises the following steps: S1. Using 19wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1.4mL / h, the receiving roller speed was 700rpm, the spinning voltage was 18kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was subjected to heat stretching by applying a stretching force at a preset temperature, the heat stretching temperature was 135℃, the traction force was 1.2N, the traction time was 3.5h, the temperature was increased at a heating rate of 3.5℃ / min, and the thermal imidization treatment was performed according to the procedure of 160℃ / 1h+200℃ / 1h+290℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1 and stirred until completely dissolved to obtain a PET solution with a concentration of 12 wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 14mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at 60°C for 3.5h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 11mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 1000 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 23:16:0.32:120, and stirred to react to obtain a prepolymer; S23. The magnesium chloride hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium chloride hexahydrate; S24. Add the magnesium chloride hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer is 1:11, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 60°C, cool and filter, wash, and obtain microcapsule powder. Example 5 A method for preparing a PI / SiO2 modified PET high temperature resistant composite release film comprises the following steps: S1. Using 19wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1.3mL / h, the receiving roller speed was 650rpm, the spinning voltage was 17kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was subjected to heat stretching by applying a stretching force at a preset temperature, the heat stretching temperature was 130℃, the traction force was 1.3N, the traction time was 3h, the temperature was increased at a heating rate of 4℃ / min, and the heat imidization treatment was carried out according to the procedure of 155℃ / 1h+195℃ / 1h+295℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 13wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 13mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 55°C for 3h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 10mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 950 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 22:16:0.3:120, stirred and reacted to obtain a prepolymer; S23. The magnesium chloride hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium chloride hexahydrate; S24. Add the magnesium chloride hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer being 1:12, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 60°C, cool and filter, wash, and obtain microcapsule powder. Comparative Example 1 A method for preparing a high temperature resistant release film comprises the following steps: S1. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 13wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 13mL, and stirred to obtain a PET composite solution; S5. Scrape the PET composite solution onto the mold to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 55°C for 3h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 10mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 950 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 22:16:0.3:120, stirred and reacted to obtain a prepolymer; S23. The magnesium chloride hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium chloride hexahydrate; S24. Add the magnesium chloride hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer being 1:12, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 60°C, cool and filter, wash, and obtain microcapsule powder. Comparative Example 2 A method for preparing a high temperature resistant release film comprises the following steps: S1. Using 19wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1.3mL / h, the receiving roller speed was 650rpm, the spinning voltage was 17kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was subjected to heat stretching by applying a stretching force at a preset temperature, the heat stretching temperature was 130℃, the traction force was 1.3N, the traction time was 3h, the temperature was increased at a heating rate of 4℃ / min, and the heat imidization treatment was carried out according to the procedure of 155℃ / 1h+195℃ / 1h+295℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 13wt%; S4. Add the PI nanofiber membrane prepared in step S2 into the mold to fix and flatten it, then scrape the PET solution on the PI nanofiber membrane, remove the solvent, and obtain a high temperature resistant release film. Comparative Example 3 A method for preparing a high temperature resistant release film comprises the following steps: S1. A polyamic acid fiber membrane was prepared by electrospinning using a 19wt% polyamic acid precursor solution as the electrospinning solution. The electrospinning flow rate was 1.3mL / h, the receiving roller speed was 650rpm, the spinning voltage was 17kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was dried at 120°C for 4 h, and the temperature was increased at a gradient rate of 4°C / min, and thermal imidization treatment was performed according to the procedure of 155°C / 1h+195°C / 1h+295°C / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 13wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 13mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 55°C for 3h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 10mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 950 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 22:16:0.3:120, stirred and reacted to obtain a prepolymer; S23. The magnesium chloride hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium chloride hexahydrate; S24. Add the magnesium chloride hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer being 1:12, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 60°C, cool and filter, wash, and obtain microcapsule powder. Comparative Example 4 A method for preparing a high temperature resistant release film comprises the following steps: S1. Using 19wt% polyamic acid precursor solution as electrospinning solution, polyamic acid fiber membrane was prepared by electrospinning method, the electrospinning flow rate was 1.3mL / h, the receiving roller speed was 650rpm, the spinning voltage was 17kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was subjected to heat stretching by applying a stretching force at a preset temperature, the heat stretching temperature was 130℃, the traction force was 1.3N, the traction time was 3h, the temperature was increased at a heating rate of 4℃ / min, and the heat imidization treatment was carried out according to the procedure of 155℃ / 1h+195℃ / 1h+295℃ / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 13wt%; S4. SiO2 gel microspheres were added to the PET solution, the mass volume ratio of SiO2 gel microspheres to the PET solution was 1g: 13mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The preparation method of SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 55°C for 3h to obtain a silica sol; S12. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and vigorously stirred to obtain an oil phase; S13. Silica sol was added to the oil phase and quickly and uniformly dispersed at a stirring speed of 950 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was allowed to stand after stirring to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally SiO2 aerogel spheres were prepared by drying at normal pressure. Comparative Example 5 A method for preparing a high temperature resistant release film comprises the following steps: S1. A polyamic acid fiber membrane was prepared by electrospinning using a 19wt% polyamic acid precursor solution as an electrospinning solution. The electrospinning flow rate was 1.3mL / h, the receiving roller speed was 100rpm, the spinning voltage was 17kV, and the receiving distance was 16cm; S2. The polyamic acid fiber membrane was dried at 120°C for 4 h, and the temperature was increased at a gradient rate of 3.5°C / min, and the imidization treatment was performed according to the procedure of 155°C / 1h+195°C / 1h+300°C / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 13wt%; S4. Strawberry-shaped SiO2 gel microspheres were added to the PET solution, the mass volume ratio of strawberry-shaped SiO2 gel microspheres to the PET solution was 1g: 13mL, and stirred to obtain a PET composite solution; S5. The PI nanofiber membrane prepared in step S2 is added to the mold and fixed and flattened, and then the PET composite solution is scraped on the PI nanofiber membrane to remove the solvent to obtain a high temperature resistant release film; The method for preparing the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 55°C for 3h to obtain a silica sol; S12. The silicone oil microcapsules were added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol was 1g: 10mL, and the mixture was stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80 and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. The composite silica sol was added to the oil phase, and quickly and uniformly dispersed at a stirring speed of 950 rpm, the stirring speed was reduced to 250 rpm, the pH value was adjusted to 6 with NH3·H2O, and the mixture was stirred and allowed to stand to obtain gel particles, the gel particles were placed in anhydrous ethanol, and finally dried at normal pressure to prepare SiO2 aerogel spheres; The preparation method of the silicone oil microcapsules comprises the following steps: S21. Ethyl silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 22:16:0.3:120, stirred and reacted to obtain a prepolymer; S23. The magnesium chloride hexahydrate is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the magnesium chloride hexahydrate; S24. Add the magnesium chloride hexahydrate prepared in step S23 to the prepolymer prepared in step S22, the mass ratio of aluminum nitrate nonahydrate to the prepolymer being 1:10, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 60°C, cool and filter, wash, and obtain microcapsule powder. Table 1 shows the orientation degree of the PI film in Examples 1-5 and Comparative Example 3 / Comparative Example 5 along the stretching direction. Orientation Degree % Example 1 83.5 Example 2 82.1 Example 3 85.2 Example 4 85.5 Example 5 84.0 Comparative Example 3 68.9 Comparative Example 5 54.1 It can be seen from Table 1 that after the thermal imidization treatment, the polyamic acid fiber film is subjected to heat stretching treatment. The PI film subjected to heat stretching treatment has a good orientation along the stretching direction. At the same time, the receiving speed of the roller also affects the orientation of the polyamic acid fiber film. The glass transition temperature T of the double-sided high temperature resistant release film was tested by the comprehensive thermal analyzer DSC. g (℃) and initial decomposition temperature T s (℃); tested using the optical functional film release film method in GB / T 25256-2010, peeling rate / 300mm / min. Table 2 shows the performance indicators of the release film Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A PI / SiO2 modified PET high temperature resistant composite release film, characterized in that: The high temperature resistant release film is composed of PET, a polyimide electrostatic spinning film with an oriented structure and strawberry-shaped SiO2 gel microspheres.

2. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 1, characterized in that: The following steps are involved: S1. Using 18-20wt% polyamic acid precursor solution as electrospinning solution, a polyamic acid fiber membrane was prepared by electrospinning; S2. The polyamic acid fiber membrane is subjected to thermal stretching by applying a stretching force at a preset temperature, the temperature is increased at a gradient rate of 3-5°C / min, and a thermal imidization treatment is performed according to the procedure of 150-160°C / 1h+180-210°C / 1h+280-300°C / 1h to obtain a PI nanofiber membrane; S3. PET was added to a mixed solvent of phenol and tetrachloroethane in a volume ratio of 1:1, and stirred until completely dissolved to obtain a PET solution with a concentration of 10-15wt%; S4. Add strawberry-shaped SiO2 gel microspheres to the PET solution and stir to obtain a PET composite solution; S5. Add the PI nanofiber membrane prepared in step S2 into the mold to fix and flatten it, then scrape the PET composite solution on the PI nanofiber membrane, remove the solvent, and obtain a high temperature resistant release film.

3. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 2, characterized in that: In the step S1, the flow rate of electrospinning is 1-1.5 mL / h, the speed of the receiving roller is 500-800 rpm, the spinning voltage is 16-18 kV, and the receiving distance is 14-16 cm.

4. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 2, characterized in that: The temperature of the hot stretching in step S2 is 120-140° C., the pulling force is 1.0-1.5N, and the pulling time is 2-4h.

5. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 2, characterized in that: The mass volume ratio of the strawberry-shaped SiO2 gel microspheres to the PET solution in step S4 is 1 g:10-15 mL. The preparation method of the strawberry-shaped SiO2 gel microspheres comprises the following steps: S11. TEOS, ethanol and 1 wt% aqueous nitric acid solution were mixed in a mass ratio of 5:8:2 and reacted at a temperature of 50-60°C for 2-4h to obtain a silica sol; S12. The silicone oil microcapsules are added to the silica sol, the mass volume ratio of the silicone oil microcapsules and the silica sol is 1g: 8-12mL, and the mixture is stirred to obtain a composite silica sol; S13. n-heptane, Span 80, Tween 80, and n-butanol were mixed in a mass ratio of 40:1:5:2 and stirred vigorously to obtain an oil phase; S14. Add the composite silica sol to the oil phase, quickly and evenly disperse it at a stirring speed of 800-1100 rpm, reduce the stirring speed to 250 rpm, adjust the pH value to 6 with NH3·H2O, stir and let stand to obtain gel particles, put the gel particles into anhydrous ethanol, and finally dry them at normal pressure to prepare SiO2 aerogel balls.

6. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 5, characterized in that: The preparation method of the silicone oil microcapsules comprises the following steps: S21. The silicone oil, SDBS, emulsifier and water were mixed in a mass ratio of 160:10:3:1600, and mechanically stirred and emulsified to obtain an O / W emulsion; S22. Melamine, formaldehyde solution, triethanolamine and water were mixed in a mass ratio of 20-24:15-17:0.25-0.35:120, and stirred to react to obtain a prepolymer; S23. The molten salt is added to the essential oil, and after stirring, the essential oil is adsorbed on the surface of the molten salt; S24. Add the molten salt prepared in step S23 to the prepolymer prepared in step S22, stir and mix evenly, add to the O / W emulsion prepared in step S21 at a temperature of 55-60°C, cool and filter, wash, and obtain microcapsule powder.

7. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 6, characterized in that: The silicone oil is any one of methyl silicone oil, ethyl silicone oil or phenyl silicone oil.

8. The method for preparing the PI / SiO2 modified PET high temperature resistant composite release film according to claim 6, characterized in that: The molten salt is any one of aluminum nitrate nonahydrate, magnesium nitrate hexahydrate or magnesium chloride hexahydrate, or a combination of two or more thereof.

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